Rhodium(I) Oxygen Adduct as a Selective Catalyst for One ...

Rhodium(I) Oxygen Adduct as a Selective Catalyst for One-Pot Sequential Alkyne Dimerization-HydrothiolationTandem Reactions

George Kleinhans,a Gregorio Guisado-Barrios,

b* David C. Liles,

a Guy Bertrand

c and Daniela I.

Bezuidenhouta*

An air-stable rhodium(I)-oxygen adduct featuring a CNC-pincer

ligand, based on 1,2,3-triazol-5-ylidenes, catalyzes the homo-

dimerization and hydrothiolation of alkynes, affording the gem-

enyne and α-vinyl sulfide isomers, respectively, with excellent

selectivity. A one-pot stepwise strategy allows the selective

catalytic preparation of non-symmetric bis-vinyl sulfides, as well

as the alkyne dimerization-hydrothiolation tandem reaction.

The structural motifs of conjugated enynes1 and vinyl sulfides

2

render these organic compounds valuable fine chemicals,

resulting to their use in a myriad of applications. Enynes and

vinyl sulfides are accessible through alkyne functionalization

strategies,3 with catalysts developed to this end for increased

atom-economy and milder reaction conditions.4 However,

chemo-, regio-, and stereoselective control remains a major

challenge in both alkyne dimerization and alkyne

hydrothiolation catalysis. Consequently, examples regarding

selective preparation of E-,5 Z-,

6 and particularly gem-enynes

7

(Figure 1a) during catalytic alkyne dimerization reactions are

scarce. The same applies to the alkyne hydrothiolation

reactions; β-E-8 and β-Z-

9 and especially the more valuable

10 α-

vinylsulfides11

(Figure 1b). Herein we disclose the synthesis and

catalytic activity of two air stable Rh(I) oxygen adducts, which

are very active and highly selective towards both the

dimerization and hydrothiolation of alkynes, yielding gem-

enynes and α-vinyl sulfides, respectively. Moreover a

combination of these two processes in one-pot allows for the

preparation of gem-ene-β-E-vinyl sulfides using a single

catalyst at low catalyst loading.

We recently reported an anionic CNC-pincer ligand, featuring

R

R'SH

R SR'

R

R

R

R

R

R

gem E/Z

RS

R'

(a) Head-to-tail homo-dimerization of alkynes

(b) Synthesis of vinyl sulfides

[cat]

[cat]

-E/-Z

Fig. 1 Previously reported products of (a) alkyne dimerization and

(b) alkyne hydrothiolation.

an amido- and two strong sigma-donating 1,2,3-triazol-5-

ylidene moieties,12

for the stabilization of reactive transition

metal complexes.13

It was reasoned that the unique

characteristics of the ligand could yield a metal catalyst that

exerts both steric and electronic control over the site of attack

on an incoming substrate.

Treatment of the cationic ligand precursors, 1a14

and 1b,13

with excess base (5 eq. KHMDS) in the presence of

[Rh(C2H4)2Cl]2 in THF at -78 °C yielded complexes 2a-b in 68

and 55% yield respectively, after exposure to oxygen (Scheme

1).14

1H and

13C NMR spectroscopy as well as mass

spectrometry and elemental analysis confirmed the formation

of the target complexes. Crystals of 2b suitable for X-ray

diffraction analysis were obtained by slow evaporation of a

toluene solution (Figure 2). The molecular structure displays a

square planar geometry around the rhodium(I) metal center,

Scheme 1 Preparation of rhodium(I) CNC-pincer complexes 2

and 314

N

N

NN

N

NN

Ar

Ar Ar

Ar

But tBu

Rh

O O

2a: 68%

13Ccarbene = 167.5

(J = 38.9 Hz)

2b: 55%

13Ccarbene = 168.4

(J = 39.2 Hz)

CO (g)

N

N

NN

N

NN

Ar

Ar Ar

Ar

But tBu

Rh

3a: 33%

v(CO) = 1941 cm-1

3b: 27%

v(CO) = 1955 cm-1

CO

tBu = tert-butyl

1a: Ar = 2,4,6-trimethylphenyl1b: Ar = 2,6-diisopropylphenyl

i) KN[Si(CH3)3]2 [Rh(C2H4)2Cl]2

ii) O2

NH

N

NN

N

NN

Ar

Ar Ar

Ar

But tBu

HH

PF6

Cl

1

mailto:[email protected]

Fig. 2 Frontal (left) and side-on (right) views of crystal structure of

2b. Selected bond lengths (Å): Rh1–O1, 1.974(3); Rh1–O2, 1.979(3);

O1–O2, 1.375(4); Rh1–N1, 1.985(4); Rh1–C1, 2.037(4); Rh1–C3,

2.035(4).

with molecular oxygen coordinating in a side-on fashion,

similar to previously reported rhodium(I) carbene complexes.15

To gain insight into the electronic properties of the complexes,

carbon monoxide gas was bubbled through a hexane solution

of 2a, or a dichloromethane solution of 2b, yielding the

corresponding carbonyl complexes, 3a and 3b, respectively.

The carbonyl stretching frequencies are of low energy (1941

and 1955 cm-1

, respectively), suggesting that the ligands have

strong donor characteristics, although weaker than the NHC

analogue (bimca) (1921 cm-1

).16

The catalytic activity of both 2a and 2b towards the alkyne

homo-dimerization and hydrothiolation was investigated. 1-

hexyne was used as the model substrate for the optimization

of the dimerization reaction conditions (see SI, Table S1). The

mesityl-substituted complex 2a catalyzed the dimerization of

1-hexyne yielding the gem-enyne isomer exclusively, exhibiting

complete conversion in less than an hour at 1 mol % catalyst

loading and 80 °C. On the contrary, 2b, featuring diarylated

triazolylidenes with bulkier 2,6-diisopropylphenyl substituents

around the metal center, was found to be inactive.

Gratifyingly, 2a displayed a high functional group tolerance

whilst retaining the high selectivity (Table 1). More

importantly, the catalyst mediates the reaction without the

use of base, or additive pyridine acting as a directing co-ligand,

in addition to being stable towards atmospheric conditions.7-9

Based on the mechanistic investigations by the group or Oro et

al.,4b

it can be surmised that during the alkyne dimerization

reaction, the molecular oxygen is substituted by the alkyne

substrate, followed by the oxidative addition of the alkyne C-H

to yield the Rh(III)-hydrido-alkynyl intermediate (SI, Scheme

S2). Due to the exclusive yield of the geminal enyne isomer,

only two of the possible four reaction pathways need to be

considered. The first is a 2,1-insertion across the M-H bond,

while the second involves a 1,2-insertion across the M-C bond.

Both pathways subsequently yield the gem-enyne isomer after

reductive elimination, and substitution by another alkyne

substrate.

For alkyne hydrothiolation, reaction conditions were optimized

using the hydrothiolation of 1-hexyne with thiophenol (see SI,

Table S2). Both catalysts 2a-b yielded the α-vinyl sulfide with

more than 90% selectivity at 1 mol% catalyst loading and 80 °C

(no additive required). Again, 2a displayed higher catalytic

Table 1 Homo-dimerization of terminal alkynesa

Entry Substrate t(h) conv.b (Yield

c) gem/E/Z

1 1 >99 (99c) 100/-/-

2

24 72 (11) 89/11/-

3 NH

Boc

24 96 (89) 100/-/-

4 O

TMS

24 69 (62) 100/-/-

5 H2N

24 59 (42) 100/-/-

6 N

5 >99 (99) 100/-/-

7 HO

10 48 (21) 100/-/-

8 Cl

24 77 (11) 100/-/-

aReactions performed at 80 °C, with 1 mol% of 2a in 0.5 mL C6D6,

and 1,4-di-tert-butylbenzene as internal standard. bConversion

based on NMR integration (%).cNMR yield (%).

activity compared to 2b. The catalytic activity of 2a using in

various terminal alkynes with a range of thiols is summarized

Table 2. Excellent selectivity towards the α-vinyl sulfide isomer

was demonstrated during the hydrothiolation of aliphatic

alkynes with aliphatic thiols, and is comparable to the best

catalysts reported to date.11

Lower activities and selectivities

were observed when both an alkyne or thiol with aryl

substituent as substrate, were used, similar to previous

reports.11a

Table 2 Terminal alkyne hydrothiolation

a

R' SH

[2a]R SR' R

SR'R SR'

R

-E -Z

Entry Alkyne Thiol t(h) conv.

b

(Yieldc,d

) α/β-E/β-Z

1

SH

24 81 (74

c, 66

d) 91/6/3

2 N

SH4 10 > 99 (98

c) 100/-/-

3 NH

Boc

SH4 24 > 99 (98

c) 100/-/-

4

SH

24 59 (23

c) 40/19/41

aReactions performed at 80 °C with 1 mol % of 2a, in 0.5 mL C6D6

with 1,4-di-tert-butylbenzene as internal standard. bConversion

based on NMR integration. cNMR calculated yield for α-vinyl sulfide

(%).dIsolated yield (%).

R

R

R

R

R

gem-enyne E-enyne

[2a]

RZ-enyne

R

2

2

Table 3 Bis-hydrothiolation in a sequential one-pot reaction employing a dithiol and various alkynesa

RHS-(CH2)n-SH

[2a] R S SHn

n = 4 or 6[2a]

R''R'R S Sn

n = 4, R' = alkyl, R'' = H

R' or R S Sn

n = 6, R' = R'' = alkyl

R''

R'

bis' bisE

Entry 1

st

Alkyne Dithiol t(h)

IntermediateProduct

conv.

2nd

Alkyne t(h)

Final Product Overall conv.

(Yield)b

1 3

HS SH4

10

S SH43

> 99

16 S S4

N

3

> 99 (88)

2 3

HS SH6

9

S SH63

> 99

38 3

S S6

59 (50)

aReaction performed in 0.5 mL C6D6, with 2 mol % of 2a and 1,4-di-tert-butylbenzene as internal standard.

bNMR calculated overall yield

(%).

For alkyne hydrothiolation, a plausible reaction mechanism

(see SI, Scheme S2) involves substitution of the coordinated

oxygen by a thiol to yield the active starting intermediate. This

is followed by S-H oxidative addition, resulting to the

formation of the rhodium(III)-hydrido-thiolate complex

intermediate. Alkyne coordination occurs trans to the hydride

ligand, resulting to a cis disposition of the alkyne to the

thiolate. The α-vinyl sulfide isomer is obtained as the major

product of the reaction, which means that, according to the

mechanistic studies done by Oro and co-workers,7c

a 1,2-M-S

insertion is the only pathway that can ensue. A 2,1-M-S-

insertion will yield β-E-vinyl sulfides. After reductive

elimination and re-coordination, the α-vinyl sulfide isomer is

obtained, as well as the active starting intermediate. Notably,

since no dimerization product is observed during the

hydrothiolation reaction employing 2a-b it could be concluded

that thiol S-H addition across the metal center is more

favorable than alkyne C-H addition.

Encouraged by this observation, it was decided to explore the

possibility of preparing non-symmetrical bis-α,α’-vinyl sulfides

using 2a as a single catalyst by a sequential bis-hydrothiolation

of two different alkynes with dithiols (Table 3). Therefore, 1

equivalent of alkyne was treated with a dithiol in the presence

of 2a, exclusively yielding the mono α-vinyl sulfide. A different

alkyne was added to the same reaction mixture, without

attempts to exclude air and moisture. Upon completion of the

reaction, non-symmetrical bis-α,α’-vinyl sulfides were

obtained with high selectivity (Entry 1, Table 3). Dithiols have

been previously employed in bis-hydrothiolation of alkynes,

albeit only symmetrical bis-α,α-vinyl sulfides were obtained

due to addition of 2 equivalents of the same alkyne.8b,9b,11c,17

As is evident from Table 3, terminal alkynes give rise to bis-α-

vinyl sulfides upon hydrothiolation, while the use of an internal

alkyne yields the β-E-vinyl sulfide (Entry 2, Table 3).

These results prompted us to use 2a for a one-pot sequential

dimerization and hydrothiolation tandem reaction. After

alkyne dimerization of dimethylaminopropyne, 1-hexanethiol

was added to the reaction mixture under atmospheric

conditions. Syn-addition of the thiol occurred across the

internal alkyne, resulting in the formation of the 1,3- and 1,4-

gem-ene-β-E-vinyl sulfides as the major products (Scheme 2).

The two products are evenly distributed, leading to the

conclusion that discrimination between the sites of attack

across the internal alkyne is not possible. The formation of the

by-product 1,4-gem-ene-β-Z-vinyl sulfide (see SI) presumably

occurs as the result of isomerization, as repeating the reaction

at higher temperatures, and analysis of the reaction mixture

over prolonged periods, result in an increase of the Z-isomer

yield. The geminal alkene was not affected by the thiol during

the reaction. Such a cascade reaction has, to the best of our

knowledge, not been reported to date. A few reports describe

the hydrothiolation of a pre-prepared enyne, but with

diminished selectivity for a specific isomer.8a,11c,18

In addition,

the reported enynes featured terminal alkynes and not the

more challenging internal alkyne.

Scheme 2 Sequential alkyne dimerization and hydrothiolation

catalyzed by 2a

Both the non-symmetrical bis-hydrothiolation reaction (Table

3, Entry 1) and the tandem alkyne dimerization-

hydrothiolation reaction (Scheme 2) could be scaled up tenfold

to illustrate the application of these catalytic processes under

preparative conditions (SI, Sections S8 and S10).

In summary, we have developed an air-stable rhodium(I) CNC-

pincer complex that selectively catalyzes both atom

economical alkyne dimerization and alkyne hydrothiolation

reactions. 1,3-enynes and α-vinyl sulfides, respectively, were

prepared with excellent selectivity. The selectivity was

retained during the first examples of bis-hydrothiolation of a

dithiol with different alkyne substrates, to yield non-

symmetrical bis-α,α’-vinyl sulfides or bis-α,β-E-vinyl sulfides,

[2a] (3.5 mol%)N

N

NSH5

[2a]

N

S5

N

N

N

S5C6D6, 80 oC C6D6, 60 oC 1,3-gem-ene-

-E-vinyl sulfide (29%)1,4-gem-ene--E-vinyl sulfide (29%)

3

respectively, as the main product after the second

hydrothiolation reaction using a different terminal alkyne or

internal alkyne. Moreover, a one-pot catalyzed dimerization

and hydrothiolation yielded the gem-ene-β-E-vinyl sulfide

products.

DIB gratefully acknowledges the National Research

Foundation, South Africa (NRF 87890 and 92521), and Sasol

Technology R&D Pty. Ltd., South Africa for financial support.

GGB thanks the MINECO for a postdoctoral grant (FPDI-2013-

16525) and Generalitat Valenciana for financial support

(GV/2015/097). GB thanks the DOE (DEFG02-13ER16370) for

financial support.

Notes and references

1 For selected examples of conjugated enynes as building blocks, or for use in polymers, biological or photoactive applications, see: (a) Y. Takayama, C. Delas, K. Muraoka, M. Uemura and F. Sato, J. Am. Chem. Soc., 2003, 125, 14163; (b) S. T. Diver and A. J. Giessert, Chem. Rev., 2004, 104, 1317; (c) H. Katayama, M. Nakayama, T. Nakano, C. Wada, K. Akamatsu and F. Ozawa, Macromolecules, 2004, 37, 13; (d) P. Wessig and G. Müller, Chem. Rev., 2008, 108, 2051; (e) W. Zhang, H. Xu, H. Xu and W. Tang, J. Am. Chem. Soc., 2009, 131, 3832; (f) W. Zhang, S. Zheng, N. Liu, J. B. Werness, I. A. Guzei and W. Tang, J. Am. Chem. Soc., 2010, 132, 3664; (g) T. H. Jones, R. M. M. Adams, T. F. Spande, H. M. Garraffo, T. Kaneko and T. R. Schultz, J. Nat. Prod., 2012, 75, 1930; (h) W. P. Forrest, Z. Cao, H. R. Hambrick, B. M. Prentice, P. E. Fanwick, P. S. Wagenknecht and T. Ren, Eur. J. Inorg. Chem., 2012, 5616; (i) O. S. Morozov, A. F. Asachenko, D. V. Antonov, V. S. Kochurov, D. Y. Paraschuk and M. S. Nechaev, Adv. Synth. Catal., 2014, 356, 2671; (j) P. Röse, C. C. M. Garcia, F. Pünner, K. Harms and G. Hilt, J. Org. Chem., 2015, 80, 7311.

2 For selected examples of vinyl sulfides employed as polymers or with biological applications, see: (a) P. Johannesson, G. Lindeberg, A. Johansson, G. V. Nikiforovich, A. Gogoll, B. Synnergren, M. LeGrèves, F. Nyberg, A. Karlén and A. Hallberg, J. Med. Chem., 2002, 45, 1767; (b) Á. Szilágyi, F. Fenyvesi, O. Majercsik, I. F. Pelyvás, I. Bácskay, P. Fehér, J. Váradi, M. Vecsernyés and P. Herczegh, J. Med, Chem., 2006, 49, 5626; (c) J. Liu, J. W. Y. Lam, C. K. W. Jim, J. C. Y. Ng, J. Shi, H. Su, K. F. Yeung, Y. Hong, M. Faisel, Y. Yu, K. S. Wong and B. Z. Tang, Macromolecules 2011, 44, 68; (d) B. Yao, J. Mei, J. Li, J. Wang, H. Wu, J. Z. Sun, A. Qin and B. Z Tang, Macromolecules 2014, 47, 1325.

3 (a) M. Hoshi, Y. Masuda and A. Arase, Bull. Chem. Soc. Jpn., 1985, 58, 1683; (b) R. Singh, D. S. Raghuvanshi and K. N. Singh, Org. Lett., 2013, 15, 4202; (c) L. Crombie and L. J. Rainbow, J. Chem. Soc. Perkin Trans. I, 1994, 673; (d) I. Suzuki, Y. Tsuchiya, A. Shigenaga, H. Nemoto and M. Shibuya, Tetrahedron Lett., 2002, 43, 6779; (e) M. S. Waters, J. A. Cowen, J. C. McWilliams, P. E. Maligres and D. Askin, Tetrahedron Lett., 2000, 41, 141; (f) A. Kondoh, K. Takami, H. Yorimitsu and K. Oshima, J. Org. Chem., 2005, 70, 6468; (g) Y. Liao, S. Chen, P. Jiang, H. Qi and G-J Deng, Eur. J. Org. Chem., 2013, 6878; (h) C. Sun, Y. Zhang, P. Xiao, H. Li, X. Sun and Z. Song, Org. Lett., 2014, 16, 984; (i) G. Liu, L. Kong, J. Shen and G. Zhu, Org. Biomol. Chem., 2014, 12, 2310.

4 For recent reviews and references therein, see: (a) I. P. Beletskaya and V. P. Ananikov, Chem. Rev., 2011, 111, 1596; (b) R. Castarlenas, A. Di Giuseppe, J. J. Pérez-Torrente and L.

A. Oro, Angew. Chem., Int. Ed., 2013, 52, 211; (c) R. Chinchilla and C. Nájera, Chem. Rev., 2014, 114, 1783.

5 (a) W. Weng, C. Guo, R. Çelenligil-Çetin, B. M. Foxman and O. V. Ozerov, Chem. Commun. 2006, 197; (b) T. Katagiri, H. Tsurugi, T. Satoh and M. Miura, Chem. Commun., 2008, 3405; (c) C. Jahier, O. V. Zatolochnaya, N. V. Zvyagintsev, V. P. Ananikov and V. Gevorgyan, Org. Lett., 2012, 14, 2846; (d) A. Coniglio, M. Bassetti, S. E. García-Garrido and J. Gimeno, Adv. Synth.Catal., 2012, 354, 148; (e) S. Ventre, E. Derat, M. Amatore, C. Aubert and M. Petit, Adv. Synth. Catal., 2013, 355, 2584; (f) O. V. Zatolochnaya, E. G. Gordeev, C. Jahier, V. P. Ananikov and V. Gevorgyan, Chem. Eur. J., 2014, 20, 9578; (g) E. Buxaderas, D. A. Alonso and C. Nájera, RSC. Adv. 2014, 4, 46508.

6 (a) X. Chen, P. Xue, H. H. Y. Sung, I. D. Williams, M. Peruzzini, C. Bianchini and G. Jia, Organometallics, 2005, 24, 4331; (b) S. Ge, V. F. Q. Norambuena and B. Hessen, Organometallics, 2007, 26, 6508; (c) R. H. Platel and L. L. Schafer, Chem. Commun., 2012, 48, 10609.

7 (a) B. M. Trost, C. Chan and G. Ruther, J. Am. Chem. Soc., 1987, 109, 3486; (b) M. Yoshida and R. F. Jordan, Organometallics, 1997, 16, 4508; (c) L. Rubio-Pérez, R. Azpíroz, A. Di Giuseppe, V. Polo, R. Castarlenas, J. J. Pérez-Torrente and L. A. Oro, Chem. Eur. J., 2013, 19, 15304; (d) T. Chen, C. Guo, M. Goto and L.-B. Han, Chem. Commun., 2013, 49, 7498; (e) C. Xu, W. Du, Y. Zeng, B. Dai and H. Guo, Org. Lett. 2014, 16, 948.

8 (a) A. Ogawa, T. Ikeda, K. Kimura and T. Hirao, J. Am. Chem. Soc., 1999, 121, 5108; (b) S. Shoai, P. Bichler, B. Kang, H. Buckley and J. A. Love, Organometallics, 2007, 26, 5778.

9 (a) S. Ranjit, Z. Duan, P. Zhang and X. Liu, Org. Lett., 2010, 12, 4134; (b) I. G. Trostyanskaya and I. P. Beletskaya, Synlett, 2012, 23, 535; (c) S. N. Riduan, J. Y. Ying and Y. Zhang, Org. Lett., 2012, 14, 1780; (d) Y. Yang and R. M. Rioux, Green Chem., 2014, 16, 3916.

10 E. Schaumann, Top. Curr.Chem., 2007, 274, 1. 11 (a) C. Cao, L. R. Fraser and J. A. Love, J. Am. Chem. Soc. 2005,

127, 17614; (b) C. J. Weiss, S. D. Wobser and T. J. Marks, J. Am. Chem. Soc. 2009, 131, 2062; (c) A. Di Giuseppe, R. Castarlenas, J. J. Pérez-Torrente, M. Crucianelli, V. Polo, R. Sancho, F. J. Lahoz and L. A. Oro, J. Am. Chem. Soc., 2012, 134, 8171; (d) S. Kankala, S. Nerella, R. Vadde and C. S. Vassam, RSC Adv. 2013, 3, 23582.

12 (a) G. Guisado-Barrios, J. Bouffard, B. Donnadieu and G. Bertrand, Angew. Chem., Int. Ed. 2010, 49, 4759; (b) R. H. Crabtree, Coord. Chem. Rev. 2013, 257, 755 (c) K. F. Donnely, A. Petronilho, M. Albrecht, Chem. Commun., 2013, 49, 1145; (c) K. J. Kilpin, U. S. D. Paul, A-L. Lee, J. D. Crowley, Chem. Commun., 2011, 47, 328; (e) M. Melaimi, M. Soleilhavoup and G. Bertrand, Angew. Chem., Int. Ed. 2010, 49, 8810.

13 D. I. Bezuidenhout, G. Kleinhans, G. Guisado-Barrios, D. C. Liles, G. Ung and G. Bertrand, Chem. Commun., 2014, 50, 2431.

14 See SI for preparation of ligand precursor salt 1a, and metal complexes 2 and 3.

15 (a) J. M. Praetorius, D. P. Allen, R. Wang, J. D. Web, F. Grein, P. Kennepohl and C. M. Crudden, J. Am. Chem. Soc. 2008, 130, 3724; (b) J. Cipot-Wechsler, D. Covelli, J. M. Praetorius, N. Hearns, O. V. Zenkina, E. C. Keske, R. Wang, P. Kennepohl and C. M. Crudden, Organometallics 2012, 31, 7306; (c) E. C. Keske, O. V. Zenkina, A. Asadi, H. Sun, J. M. Praetorius, D. P. Allen, D. Covelli, B. O. Patrick, R. Wang, P. Kennepohl, B. R. James and C. M. Crudden, Dalton Trans. 2013, 42, 7414.

16 M. Moser, B. Wucher, D. Kunz and F. Rominger, Organometallics, 2007, 26, 1024.

17 J. Yang, A. Sabarre, L. R. Fraser, B. O. Patrick and J. A. Love, J. Org. Chem., 2009, 74, 182.

4

S1

Supporting Information

Rhodium(I) Oxygen Adduct as a Selective Catalyst for One-Pot Sequential Alkyne Dimerization-Hydrothiolation Tandem

Reactions

George Kleinhans,a Gregorio Guisado-Barrios,b* David C. Liles,a Guy Bertrandc and Daniela I. Bezuidenhouta*

aChemistry Department, University of Pretoria, Private Bag X20, Hatfield 0028, Pretoria, South Africa

bInstitute of Advance Materials (INAM), Universitat Jaume I, Avenida Vicente Sos Baynat s/n, 12071 Castellon, Spain

cUCSD-CNRS Joint Research Laboratory (UMI 3555), Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0343, USA

S2

Contents

S1. Standard Operating Procedure............................................................................................................3

S2. Ligand Salt and Complex Synthesis and Characterization Data............................................................5

S3. NMR Spectra of Compounds 2a-b and 3a-b.........................................................................................9

S4. Catalytic Dimerization Details.............................................................................................................14

S5. Catalytic Hydrothiolation Details........................................................................................................20

S6. Proposed Reaction Mechanism for Alkyne Dimerisation and Hydrothiolation Promoted by............26

S7. Catalytic Asymmetric Bis-Hydrothiolation Details..............................................................................26

S8. Asymmetric Bis-Hydrothiolation Reaction under Preparative Conditions……………………………………….33

S9. Cascade Catalytic Details....................................................................................................................34

S10. Tandem Alkyne Dimerization-Hydrothiolation Reaction under Preparative Conditions………………..42

S11. Crystal Structure Details....................................................................................................................42

S12. References........................................................................................................................................43

S3

S1. Standard Operating Proceduresa. Method

All synthetic manipulations, unless otherwise stated, were performed under an N2 gas or Ar gas

atmosphere using oven or flame dried glassware and standard Schlenk or vacuum line techniques. Air

sensitive solids where stored and handled in a PureLab HE glove box. Preparation of NMR and

crystallization samples that also require an inert atmosphere were done in the glove box.

b. Materials

Reagent tBuOCl was prepared according to the method of Mintz and Walling.i The precursor compound

3,6-di-tert-butyl-1,8-diethynyl-9H-carbazole and pincer ligand precursor 1b was prepared as previously

reported by us.ii 1,3-bis-(2,4,6-trimethylphenyl)triaz-1-ene was prepared by an adapted procedure, as

reported for the synthesis of 1,3-bis-(2,6-di-iso-propylphenyl)triaz-1-ene.ii All other reagents were

obtained from commercial sources and were used without any further purification.

Unless otherwise stated, only anhydrous solvents were used during experimental procedures.

Anhydrous THF and Et₂O were obtained after distillation over sodium and benzophenone under a N₂ gas

atmosphere. Anhydrous PhMe and hexane were obtained after distillation over sodium under a N₂ gas

atmosphere. Anhydrous CH₂Cl₂ was obtained after distillation over calcium hydride under a N₂ gas

atmosphere. Deuterated benzene was dried over sodium and distilled under an Ar gas atmosphere.

c. Characterisation Techniques

Nuclear magnetic resonance (NMR) spectra were obtained using either a Bruker AVANCE-III-300

operating at 300.13 MHz for 1H, 75.47 MHz for 13C, 121.49 MHz for 31P and 282.40 MHz for 19F; or

AVANCE-III-400 operating at 400.21 MHz for 1H, 100.64 MHz for 13C, 162.01 MHz for 31P and 376.57 MHz

for 19F. 1H Chemical shifts are reported as δ (ppm) values downfield from Me4Si and chemical shifts

where referenced to residual non-deuterated solvents peaks (CD₃CN, 1.94ppm; CDCl₃, 7.26ppm; C₆D₆,

7.16ppm). 13C chemical shifts are also reported as δ (ppm) values downfield from Me4Si and chemical

shifts where referenced to residual non-deuterated solvents peaks (CD₃CN, 1.32 ppm; CDCl₃, 77.16 ppm;

C₆D₆, 128.06 ppm). Proton coupling constants (J) are given in Hz. The spectral coupling patterns are

S4

designated as follows: s/S - singlet; d/D - doublet; t/T - triplet; q/Q - quartet; sept-septet; m - multiplet;

br - broad signal. Quaternary carbons are designated as Cq.

Chemical shift assignment in the 1H NMR spectra is based on first-order analysis and when required

were confirmed by two-dimensional (2D) (1H-1H) homonuclear chemical shift correlation (COSY)

experiments. The 13C shifts were obtained from proton-decoupled 13C NMR spectra. Where necessary,

the multiplicities of the 13C signals were deduced from proton-decoupled DEPT-135 spectra. The

resonances of the proton-bearing carbon atoms were correlated with specific proton resonances using

2D (13C-1H) heteronuclear single-quantum coherence (HSQC) and heteronuclear multiple bond

correlations (HMBC) experiments. Standard Bruker pulse programs were used in the experiments.

Single crystal X-ray diffraction data were collected on a Bruker Apex II-CCD detector using Mo-K

radiation ( = 0.71073 Å). Crystals were selected under oil, mounted on nylon loops then immediately

placed in a cold stream of N2 at 150 K. Structures were solved and refined using Olex2 and SHELXTL. A

satisfactory refinement of the crystal structure of 2a after squeeze methodology was applied in order to

eliminate residual electronic density of the solvent that could be refined otherwise iii-v

Solution IR spectra (ν(CO)) were recorded on a Perkin-Elmer Spectrum RXI FT-IR spectrophotometer in

CH2Cl2 as solvent. The range of absorption measured was from 4000-600 cm-1.

Mass spectral analyses were performed on a Waters Synapt G2 HDMS by direct infusion at 5 μL/min

with positive electron spray as the ionization technique. The m/z values were measured in the range of

400-1500 with acetonitrile as solvent. Prior to analysis, a 5 mM sodium formate solution was used to

calibrate the instrument in resolution mode.

Microanalyses (%C, H, N) were performed using a ThermoScientific Flash 2000 elemental analyser.

Following extensive drying, analyses of complexes 2 and 3 are outside acceptable limits and are ascribed

to the presence of solvent molecules and/or silicon grease. The full 1H and 13C NMR spectra are

therefore included in the SI to attest to the purity of the compounds, supported by HRMS, FT-IR and

single crystal XRD spectroscopic results.

S5

S2. Synthesis details and characterization

a. Synthesis of 1a

NH

H H

KPF6CH2Cl2

tBuOCl NH

N

N N N N

NH H

PF6-

Cl-

NN

N

H

Scheme S1: Synthesis of tridentate CNC pincer ligand precursor 1a

Compound 1a (Scheme S1) was prepared by a similar method as used for the synthesis of 1b.ii A 500 mL,

3-necked round bottom flask was charged with 3,6-di-tert-butyl-1,8-diethynyl-9H-carbazole (8.00 g,

24.4 mmol), 1,3-bis-(2,4,6-trimethylphenyl)triaz-1-ene (22.00 g, 78.2 mmol) and potassium

hexafluorophosphate (15.24 g, 82.8 mmol). The vessel was purged with N2(g). The solids were dissolved

in dry DCM (250 mL) and the solution was cooled down to -78 °C. To the solution was added tert-BuOCl

(9.3 mL, 78.2 mmol) in a drop wise manner with subsequent stirring of the solution at -78 °C for two

hours. After two hours, the solution was left to slowly warm up to room temperature whilst stirring for

20 hours. The white precipitate was filtered from the brown red solution with subsequent evaporation

of the solvent in vacuo. Trituration with hexanes followed by Et₂O yielded 1a as an off-white solid (24.70

g, 23.1 mmol, 95%). Single crystals where obtainable from acetone layered with hexane. For

C60H69N7ClPF6, Anal. Calcd.: C, 67.54; H, 6.51; N, 9.17. Found: C, 67.53; H, 6.56; N, 8.97. 1H NMR (300

MHz, CD3CN) δ 11.51 (br s, 1H, NHcarb), 10.06 (s, 2H, ArHTriazolium), 8.42 (d, J = 1.8 Hz, 2H, ArHcarb), 7.23 (br

s, 4H, ArHMes), 7.19 (br s, 4H, ArHMes), 7.08 (d, J = 1.5 Hz, 2H, ArHcarb), 2.46 (s, 6H, ArCH₃), 2.36 (s, 6H,

ArCH₃), 2.26 (s, 12H, ArCH₃), 2.08 (s, 12H, ArCH₃), 1.16 (s, 18H, C(CH3)3). 13C NMR (75 MHz, CD3CN) δ

145.3 (ArCq), 144.5 (ArCq), 144.2 (ArCq), 142.3 (ArCq), 138.7 (ArCq), 136.1 (ArCq), 135.9 (ArCq), 133.6

(ArCq), 132.5 (ArCq), 131.3 (ArCH), 130.9 (ArCH), 127.2 (ArCq), 125.9 (ArCH), 122.5 (ArCH), 106.9 (ArCq),

35.4 (C(CH₃)₃), 31.5 (C(CH₃)₃), 21.4 (ArCH₃), 21.2 (ArCH₃), 18.1 (ArCH₃), 18.1 (ArCH₃). 19F NMR (282 MHz,

CD3CN) δ -72.90 (d, J = 706.0 Hz, PF₆). 31P NMR (121 MHz, CD3CN) δ -144.6 (sept, J = 706.5 Hz, PF₆).

HRMS (FIA-ESI): Calculated for C60H69N72+ [M]2+: 443.7802, found: 443.7835.

S6

b. Synthesis of 2a

A flame dried Schlenk tube was charged with 1a (200.0 mg, 1.9 x

10-4 mol), [Rh(C2H4)2Cl]2 (58.2 mg, 1.5 x 10-4 mol) and KN[Si(CH₃)₃]₂

(186.7 mg, 9.4 x 10-4 mol). The reaction vessel was evacuated,

purged with N₂ (g), and cooled down to -78 °C. The solids were

dissolved by addition of THF (20 mL) which was also cooled down

to -78 °C. The solution was stirred for one hour at -78 °C. After one

hour, the reaction was slowly heated up to RT whilst stirring

overnight. The solvent was evaporated in vacuo and the product was extracted with hexanes (4 x 15

mL). Hexane was evaporated, in vacuo, yielding a brown residue. The residue was re-dissolved in

oxygenated dry toluene, and left to settle at RT for 48 hours. After 48 hours, the solvent was evaporated

in vacuo to obtain 2a (130.0 mg, 1.3 x 10-4mol, 68 %) as a brown solid. Crystal suitable for X-ray

diffraction could not be obtained. For RhC60H66N7O2, Anal. Calcd.: C, 70.64; H, 6.52; N, 9.61. Found: C,

68.52; H, 6.42; N, 9.01. 1H NMR (300 MHz, C6D6) δ 8.55 (d, J = 1.8 Hz, 2H, ArHcarb), 7.55 (d, J = 1.8 Hz, 2H,

ArHcarb), 6.78 (s, 4H, ArHMes), 6.71 (s, 4H, ArHMes), 2.43 (s, 12H, ArCH3), 2.34 (s, 6H, ArCH3), 2.08 (s, 6H,

ArCH3), 1.77 (s, 12H, ArCH3), 1.25 (s, 18H, C(CH3)3). 13C NMR (75 MHz, C6D6) δ 167.5 (d, J = 39.0 Hz, Rh-

CCarbene), 144.4 (ArCq), 141.1 (ArCq), 140.8 (ArCq), 140.4 (ArCq), 138.3 (ArCq), 137.2 (ArCq), 135.7 (ArCq),

135.7 (ArCq), 134.9 (ArCq), 130.0 (ArCH), 127.2 (ArCH), 118.1 (ArCH), 116.4 (ArCH), 113.9 (ArCq), 113.9

(ArCq), 34.7 (C(CH₃)₃), 31.9 (C(CH₃)₃), 21.4 (ArCH3), 21.3 (ArCH3), 21.0 (ArCH3), 21.0 (ArCH3), 18.4 (ArCH3),

18.4 (ArCH3), 17.2 (ArCH3), 17.2 (ArCH3). HRMS (FIA-ESI): Calculated for C60H66N7RhO22+ [M + CH3CN +

2H]2+: 531.2377, found: 531.2393.

c. Synthesis of 2b

A flame dried Schlenk tube was loaded with 1bii (200.0 mg, 1.6 x 10-4

mol), [Rh(C2H4)2Cl]2 (50.3 mg, 1.3 x 10-4 mol) and KN[Si(CH₃)₃]₂ (161.3

mg, 8.1 x 10-4 mol). The Schlenk tube was evacuated and purged

with N₂ (g). The reaction vessel was cooled down to -78 °C, and the

solids dissolved by addition of THF (20 mL) which was also cooled

down to -78 °C. The solution was stirred for one hour at -78 °C. The

reaction, after one hour, was slowly heated up to RT whilst stirring overnight. The solvents were

evaporated in vacuo and the product was extracted with hexanes (4 x 15 mL). Evaporation of the hexane

solvent, in vacuo, yielded a brown residue. The residue was re-dissolved in oxygenated dry toluene, and

NN

N N N N

NRh

O O

NN

N N N N

NRh

O O

S7

left to settle at RT for 48 hours. After 48 hours, the solvent was evaporated in vacuo to obtain 2b (105.0

mg, 8.8 x 10-5 mol, 55%) as a brown solid. Slow evaporation of a toluene solution yielded single crystals

suitable for XRD analysis. For RhC72H90N7O2, Anal. Calcd.: C, 72.77; H, 6.53; N, 8.25. Found: C, 71.65; H,

7.40; N, 7.76. 1H NMR (400 MHz, C6D6) δ 8.40 (d, J = 2.0 Hz, 2H, ArHcarb), 7.49 (d, J = 2.0 Hz, 2H, ArHcarb),

7.34 (t, J = 7.8 Hz, 2H, ArHDipp), 7.30 (t, J = 7.8 Hz, 2H, ArHDipp), 7.16 (d, 4H, ArHDipp overlaps with C6D6),

7.13 (d, J = 8.0 Hz, 4H, ArHDipp), 2.98 (sept, J = 6.8 Hz, 4H, CH(CH₃)₂), 2.66 (sept, J = 6.8 Hz, 4H, CH(CH₃)₂),

1.65 (d, J = 6.8 Hz, 12H, CH(CH₃)₂), 1.23 (d, J = 7.2 Hz, 12H, CH(CH₃)₂), 1.21 (s, 18H, C(CH3)3), 1.05 (d, J =

6.8 Hz, 12H, CH(CH₃)₂), 0.78 (d, J = 6.8 Hz, 12H, CH(CH₃)₂). 13C NMR (100 MHz, C6D6) δ 168.4 (d, J = 39.2

Hz, Rh-CCarbene), 146.3 (ArCq), 145.4 (ArCq), 144.4 (ArCq), 141.6 (ArCq), 140.6 (ArCq), 137.5 (ArCq), 135.3

(ArCq), 131.7 (ArCH), 129.1 (ArCH), 125.5 (ArCH), 121.6 (ArCH), 119.6 (ArCH), 116.7 (ArCH), 113.2 (ArCq),

34.6 (C(CH₃)₃), 32.0 (C(CH₃)₃), 29.6 (CH(CH₃)₂), 29.1 (CH(CH₃)₂), 26.0 (CH(CH₃)₂), 24.8 (CH(CH₃)₂), 24.3

(CH(CH₃)₂), 23.2 (CH(CH₃)₂). HRMS (FIA-ESI): Calculated for C72H90N7RhO22+ [M]2+: 593.8105, found:

593.8127.

d. Synthesis of 3a

To a flame dried Schlenk tube was added 2a (25.0 mg, 2.5 x 10-5

mol). The reaction vessel was purged with N2 (g). The brown solid

was dissolved by adding hexane (5 mL). Carbon monoxide gas was

bubbled through the solution for 5 minutes, resulting in a colour

change from dark to orange. After filtration, the solvent was

removed in vacuo, yielding 3a (8.3 mg, 8.2 x 10-6 mol, 33%) as an

orange solid. For RhC61H66N7O, Anal. Calcd.: C, 72.10; H, 6.55; N,

9.65. Found: C, 70.37; H, 6.71; N, 9.15. 1H NMR (300 MHz, C6D6) δ 8.67 (d, J = 1.8 Hz, 2H, ArHcarb), 7.42

(d, J = 1.8 Hz, 2H, ArHcarb), 6.84 (s, 4H, ArHMes), 6.73 (s, 4H, ArHMes), 2.40 (s, 12H, ArCH3), 2.31 (s, 6H,

ArCH3), 2.09 (s, 6H, ArCH3), 1.78 (s, 12H, ArCH3), 1.30 (s, 18H, C(CH3)3). 13C NMR (75 MHz, C6D6) δ 194.9

(d, J = 71.6 Hz, Rh-CO), 173.4 (d, J = 41.1 Hz, Rh-CCarbene), 144.9 (ArCq), 141.3 (ArCq), 140.6 (ArCq), 139.1

(ArCq), 138.3 (ArCq), 138.0 (ArCq), 136.1 (ArCq), 135.7 (ArCq), 135.6 (ArCq), 129.9 (ArCH), 129.0 (ArCH),

127.1 (ArCq), 117.9 (ArCH), 116.9 (ArCH), 112.7 (ArCq), 34.6 (C(CH₃)₃), 32.1 (C(CH₃)₃), 21.5 (ArCH3), 21.0

(ArCH3), 18.7 (ArCH3), 17.3 (ArCH3). IR (νCO, CH2Cl2): 1941 cm-1. HRMS (FIA-ESI): Calculated for

C60H66N7RhCO+ [M]+: 1015.4384, found: 1015.4407.

NN

N N N N

NRh

CO

S8

e. Synthesis of 3b

To a Schlenk tube was added 2b (30.0 mg, 2.5 x 10-5 mol), and

dissolved by adding CH2Cl2 (2 mL) resulting in a brown coloured

solution. At room temperature, CO (g) was bubbled through the

solution resulting in a colour change from brown to a yellow-brown.

The solution was filtered and the solvent removed in vacuo yielding

3b (8.0 mg, 6.8 x 10-6 mol, 27%) as a yellow-brown coloured residue.

For RhC73H90N7O, Anal. Calcd.: C, 74.02; H, 7.66; N, 8.28. Found: C, 71.87; H, 7.51; N, 7.87. 1H NMR (300

MHz, C6D6) δ 8.52 (d, J = 1.8 Hz, 2H, ArHcarb), 7.64 (dd, J = 5.7 Hz, 3.3 Hz, 1H, ArHDipp), 7.46 (d, J = 1.5 Hz,

2H, ArHcarb), 7.31 – 7.25 (m, 6H, ArHDipp), 6.93 (dd, J = 5.7 Hz, 3.3 Hz, 1H, ArHDipp), 3.04 (sept, J = 6.8 Hz,

4H, CH(CH₃)₂), 2.62 (sept, J = 6.8 Hz, 4H, CH(CH₃)₂), 1.55 (d, J = 6.9 Hz, 12H, CH(CH₃)₂), 1.25 (s, 18H,

C(CH3)3), 1.16 (d, J = 6.9 Hz, 12H, CH(CH₃)₂), 1.04 (d, J = 6.9 Hz, 12H, CH(CH₃)₂), 0.78 (d, J = 6.9 Hz, 12H,

CH(CH₃)₂). 13C NMR (75 MHz, C6D6) δ 195.4 (d, J = 70.2 Hz, Rh-CO), 173.4 (d, J = 41.6 Hz, Rh-CCarbene),

146.3 (ArCq), 146.1 (ArCq), 144.4 (ArCq), 142.7 (ArCq), 138.2 (ArCq), 137.6 (ArCq), 135.7 (ArCq), 133.4

(ArCq), 131.5 (ArCH), 130.9 (ArCH), 130.8 (ArCH), 129.1 (ArCH), 127.2 (ArCq), 125.4 (ArCH), 124.1 (ArCH),

119.0 (ArCH), 117.1 (ArCH), 111.8 (ArCq), 34.5 (C(CH₃)₃), 32.3 (C(CH₃)₃), 29.3 (CH(CH₃)₂), 29.1 (CH(CH₃)₂),

25.6 (CH(CH₃)₂), 24.8 (CH(CH₃)₂), 24.2 (CH(CH₃)₂), 23.1 (CH(CH₃)₂). IR (νCO, CH2Cl2): 1955 cm-1. HRMS (FIA-

ESI): Calculated for C72H90N7RhCO2+ [M + H]2+: 592.8204, found: 592.8197.

NN

N N N N

NRh

CO

S9

S3. NMR Spectra of Compounds 2a-b and 3a-b

0.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.0f1 (ppm)

-2E+07

0

2E+07

4E+07

6E+07

8E+07

1E+08

1E+08

1E+08

2E+08

2E+08

2E+08

2E+08

2E+08

3E+08

3E+08

3E+08

18.0

6

11.9

6

6.28

6.24

11.5

0

4.05

4.03

2.05

2.00

1.25

1.77

2.08

2.34

2.43

6.71

6.78

7.54

7.55

8.54

8.55

Figure S1. ¹H NMR of 2a in C6D6 solvent

S10

102030405060708090100110120130140150160170180f1 (ppm)

0

2E+06

4E+06

6E+06

8E+06

1E+07

1E+07

1E+07

2E+07

2E+07

2E+07

2E+07

2E+07

3E+0717.2

17.2

18.4

18.4

21.0

21.0

21.3

21.4

31.9

34.7

113.

911

3.9

116.

411

8.1

127.

113

0.0

134.

913

5.7

135.

713

7.2

138.

314

0.4

140.

814

1.1

144.

4

167.

216

7.7

Figure S2. 13C NMR of 2a in C6D6 solvent

0.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.09.5f1 (ppm)

-1E+07

0

1E+07

2E+07

3E+07

4E+07

5E+07

6E+07

7E+07

8E+07

9E+07

1E+08

1E+08

1E+08

13.9

714

.51

17.1

915

.10

13.0

5

4.43

4.40

5.03

2.47

2.54

5.45

1.99

2.00

0.77

0.79

1.04

1.06

1.21

1.24

1.64

1.66

2.61

2.63

2.64

2.66

2.68

2.70

2.71

2.93

2.94

2.96

2.98

3.00

3.01

3.02

7.12

7.14

7.15

7.17

7.28

7.30

7.32

7.34

7.36

7.49

7.49

8.40

8.41

Figure S3. ¹H NMR of 2b in C6D6 solvent

S11

2030405060708090100110120130140150160170180f1 (ppm)

0

5E+06

1E+07

2E+07

2E+07

2E+07

3E+07

4E+07

4E+07

4E+07

5E+07

6E+07

6E+07

6E+07

7E+07

8E+07

8E+0723.2

024

.29

24.7

926

.04

29.1

029

.62

31.9

934

.58

113.

2011

6.73

119.

5612

1.56

125.

4612

9.12

131.

7413

5.32

137.

4514

0.59

141.

6114

4.39

145.

4414

6.30

168.

1616

8.55

Figure S4. 13C NMR of 2b in C6D6 solvent

0.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.09.5f1 (ppm)

-2E+07

0

2E+07

4E+07

6E+07

8E+07

1E+08

1E+08

1E+08

2E+08

2E+08

2E+08

2E+08

2E+08

3E+08

3E+08

3E+08

3E+08

3E+08

4E+08

4E+08

18.7

7

12.0

2

6.17

6.01

12.0

3

4.07

4.00

2.10

2.00

1.30

1.78

2.09

2.31

2.40

6.73

6.84

7.42

7.43

8.67

8.67

Figure S5. ¹H NMR of 3a in C6D6 solvent

S12

102030405060708090100110120130140150160170180190200210f1 (ppm)

0

1E+06

2E+06

3E+06

4E+06

5E+06

6E+06

7E+06

8E+06

9E+06

1E+07

1E+07

1E+07

1E+07

1E+07

2E+07

2E+07

2E+07

2E+07

2E+07

17.2

18.7

21.0

21.5

32.1

34.6

112.

711

6.9

117.

912

7.1

129.

012

9.9

135.

613

5.7

136.

113

8.0

138.

313

9.1

140.

614

1.3

144.

8

173.

117

3.7

194.

419

5.4

Figure S6. 13C NMR of 3a in C6D6 solvent

1.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.0f1 (ppm)

-1E+07

0

1E+07

2E+07

3E+07

4E+07

5E+07

6E+07

7E+07

8E+07

9E+07

1E+08

1E+08

1E+08

1E+08

1E+08

2E+08

2E+08

2E+08

12.8

614

.31

17.3

120

.69

14.0

6

4.70

4.55

1.24

6.04

2.05

0.92

2.00

0.79

1.03

1.05

1.14

1.17

1.25

1.54

1.56

2.53

2.56

2.58

2.60

2.62

2.65

2.67

2.69

2.98

3.00

3.02

3.04

3.07

3.09

3.11

6.91

6.92

6.93

6.94

7.25

7.26

7.27

7.28

7.30

7.31

7.45

7.46

7.63

8.52

8.52

Figure S7. ¹H NMR of 3b in C6D6 solvent

S13

2030405060708090100110120130140150160170180190200f1 (ppm)

0

5E+05

1E+06

2E+06

2E+06

2E+06

3E+06

4E+06

4E+06

4E+06

5E+06

6E+06

6E+06

6E+06

7E+06

8E+06

8E+06

23.1

24.2

24.8

25.6

29.1

29.3

32.2

34.5

39.2

68.1

111.

811

7.1

119.

012

4.1

125.

412

7.2

129.

113

0.8

130.

913

1.5

133.

413

5.7

137.

613

8.2

142.

714

4.4

146.

114

6.3

167.

617

3.2

173.

7

195.

019

5.9

Figure S8. ¹³C NMR of 3b in C6D6 solvent

S14

S4. Catalytic Dimerization Details

a. Optimisation of Catalytic Dimerization of 1-hexyne to (gem)-7-methylene-

undec-5-yne

Standard operating procedure for dimerization reactions: a high pressure NMR tube with a J. Young

valve was charged with one mol % catalyst 2a (3.6 mg, 3.5 x 10-6 mol) or one mol % catalyst 2b (4.1 mg,

3.5 x 10-6 mol) and 0.25 equivalents of internal standard, 1,4-di-tert-butylbenzene (16.6 mg, 8.7 x 10-5

mol). Catalytic amount of base was added as indicated in Table S1. To the mixture was added

deuterated benzene (0.5 mL). One equivalent of 1-hexyne (40 µL, 3.5 x 10-4 mol) was added, and the

NMR tube capped. 1H NMR spectroscopy was performed at time 10 min after addition of the alkyne. The

reaction mixture was heated up to appropriate temperature and reacted for the duration as indicated

(see Table S1). Upon cooling down to room temperature, 1H NMR spectroscopy was performed at the

final time. Conversion and calculated yields where determined from NMR analysis based on integration

of alkyne and product, referenced to the internal standard. Product identity was confirmed by

comparison with previously reported NMR spectra.vi

Table S1. 1-hexyne dimerization promoted by 2.a

Product distributionEntry Catalyst Base(mol %)

T (◦C)

t (h) Conversionb

(%)Yieldc

(%) Gem-enyne

E-enyne

Z-enyne

1 2a K2CO3 (1) 80 > 1 > 99 99 100 - -2 2a K2CO3 (1) 40 > 1 6 4 100 - -3 2a KOtBu (1) 80 > 1 > 99 99 100 - -4 2a Pyridine (3) 80 > 1 88 88 100 - -5 2b K2CO3 (1) 80 > 1 0 0 - - -6 2b K2CO3 (1) 80 20 9 3 100 - -7 2a None 80 > 1 > 99 99 100 - -

aReaction performed in C6D6 (0.5 mL) with internal standard 1,4-di-tert-butylbenzene, 1 mol % catalyst (3.5 x 10-6 mol) and 3.5 x 10-4 mol 1-hexyne. bConversion as determined through NMR integration based on 1-hexyne referenced to 1,4-di-tert-butylbenzene. cYield as determined from NMR integration based on 1-hexyne.

S15

7-methylene-undec-5-yne

54

32

16

78

910

11

12

1H NMR (300 MHz, C6D6) 5.38 (d, J = 2.1 Hz, 1H, C=CH2), 5.09 (m, 1H, C=CH2), 2.16 (m, 8H, H4,8), 1.59 (tt,

J = 7.2 Hz, 7.5 Hz, 7.8 Hz, 2H, H9), 1.43 - 1.23 (m, 6H, H2,3,10 overlaps with -C(CH3)3 of di-tert-

butylbenzene), 0.86 and 0.78 (both t, J = 7.2 Hz, 6H, H1,11).

0.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.0f1 (ppm)

0

1E+07

2E+07

3E+07

4E+07

5E+07

6E+07

7E+07

8E+07

9E+07

1E+08

6.06

6.28

32.2

0

4.57

8.48

2.05

2.06

4.00

0.76

0.78

0.80

0.84

0.86

0.89

1.27

1.30

1.33

1.35

1.59

2.13

2.15

2.16

2.17

2.18

5.08

5.09

5.38

5.38

7.29

Figure S9. Catalytic dimerization reaction of 1-hexyne (blue) to (gem)-7-methylene-undec-5-yne (red) at time 10 min (blue spectrum) and at time after reaction (red spectrum).

S16

b. Catalytic Dimerization of terminal alkynes to gem-enynes catalyzed by 2a

Standard operating procedure for dimerization reactions: a high pressure NMR tube with a J. Young

valve was loaded with one mol % catalyst 2a and 0.25 equivalents of internal standard, 1,4-di-tert-

butylbenzene. To the mixture was added deuterated benzene (0.5 mL). One equivalent of terminal

alkyne was added, and the NMR tube capped. 1H NMR spectroscopy was performed at time 10 min after

addition of the alkyne. The reaction mixture was heated up to 80 °C and reacted for the duration as

indicated (see Article, Table 1). Upon cooling down to room temperature, 1H NMR spectroscopy was

performed at the final time. Conversion and calculated yields where determined from NMR analysis

based on integration of alkyne and product, referenced to the internal standard.

Entry 2, Table 1: Dimerization of Phenylacetylene

Experiments were carried out as described above. Amounts of reagents added are as follows: catalyst 1

mol % (3.7 mg, 3.6 x 10-6 mol); internal standard 0.25 equivalent (17.3 mg, 9.1 x 10-5 mol) and one

equivalent phenylacetylene (40 µL, 3.6 x 10-4 mol). Product identity was confirmed by comparison with

previously reported NMR spectra.vi

1,3-diphenylbut-1-yn-3-ene

o-1

o-2

m-1

p-1

m-2

p-2

1H NMR (300 MHz, C6D6) 7.77 - 7.68 (m, 2H, Ho-1), 7.54 - 7.38 (m, 2H, Ho-2, extensive overlap with

unreacted phenylacetylene, E-enyne, internal standard and residual solvent), 7.09 - 6.87 (m, 6H, Hm and

Hp, extensive overlap with unreacted phenylacetylene, E-enyne and internal standard), 5.75 (d, J = 0.8

Hz, 1H, C=CH2), 5.70 (d, J = 0.7 Hz, 1H, C=CH2).

S17

Entry 3, Table 1: Dimerization of N-Boc-Propargylamine



equivalent N-Boc-propargylamine (40 mg, 2.6 x 10-4 mol). Product identity was confirmed by comparison

with previously reported NMR spectra.vii

N,N-bis(tert-butyloxycarbonyl)-4-methylenepent-2-yne

HN

HN

O

O

O

O

1H NMR (300 MHz, C6D6) 5.26 (br s, 1H, C=CH2), 5.15 (d, J = 1 Hz, 1H, C=CH2), 4.57 (br s, 2H, CH2NH),

3.82 (d, J = 2.8 Hz, 2H, CH2NH), 3.66 (d, J = 5.3 Hz, 2H, CH2NH), 1.42 (s, 9H,-C(CH3)3), 1.39 (s, 9H,-C(CH3)3).

Entry 4, Table 1: Dimerization of trimethylsilyloxypropyne

Experiments were carried out as described above. Amounts of reagents added are as follows:1 mol %

(3.3 mg, 3.3 x 10-6 mol); internal standard 0.25 equivalent (15.5 mg, 8.1 x 10-5 mol) and one equivalent

trimethylsilyloxypropyne (50 µL, 3.3 x 10-4 mol). Product identity was confirmed by comparison with

previously reported NMR spectra.viii

2-trimethylsiloxymethyl-4-trimethylsiloxy-1-penten-3-yne

O

OSi

Si

1H NMR (300 MHz, C6D6) 5.64 (q, J = 2.0 Hz, 1H, C=CH2), 5.51 (d, J = 1.8 Hz, 1H, C=CH2), 4.28 (s, 2H,

OCH2), 4.14 (t, J = 1.8 Hz, 2H, OCH2), 0.12 (s, 9H, Si(CH3)3), 0.06 (s, 9H, Si(CH3)3).

S18

Entry 5, Table 1: Dimerization of propargylamine



equivalent propargylamine (30 µL, 4.7 x 10-4 mol).

4-methylenepent-2-yne-1,5-diamine

H2N

NH2

1H NMR (300 MHz, C6D6) 5.34 (br s, 1H, C=CH2), 5.19 (d, J = 1.7 Hz, 1H, C=CH2), 3.18 (br s, 4H, CH2NH2),

0.75 (br s, 4H, CH2NH2).

Entry 6, Table 1: Dimerization of N,N-dimethylaminopropyne



equivalent N,N-dimethylaminopropyne (40 µL, 3.7 x 10-4 mol). Product identity was confirmed by

comparison with previously reported NMR spectra.vi

N,N,N,N-tetramethyl-4-methylenepent-2-yne-1,5-diamine

N

N

1H NMR (300 MHz, C6D6) 5.50 (d, J = 2.1 Hz, 1H, C=CH2), 5.38 (m, 1H, C=CH2), 3.24 (s, 2H, CH2N(CH3)2),

2.90 (s, 2H, CH2N(CH3)2), 2.19 (s, 6H, CH2N(CH3)2), 2.12 (s, 6H, CH2N(CH3)2).

Entry 7, Table 1: Dimerization of propargyl alcohol



S19

equivalent propargyl alcohol (25 µL, 4.3 x 10-4 mol). Product identity was confirmed by comparison with

previously reported NMR spectra of similar enyne alcohol-type compounds.ix

4-methylenepent-2-yne-1,5-diol

HO

OH

1H NMR (300 MHz, C6D6) 5.37 (br s, 1H, C=CH2), 5.34 (br s, 1H, C=CH2), 4.09 (s, 2H, CH2OH), 3.96 (s, 2H,

CH2OH), 2.05 (br s, 2H, CH2OH).

Entry 8, Table 1: Dimerization of propargyl chloride


mol % (2.8 mg, 2.8 x 10-6 mol); internal standard 0.25 equivalent (13.2 mg, 6.9 x 10-5 mol) and propargyl

chloride, 1 equivalent (20 µL, 2.8 x 10-4 mol). Product identity was confirmed by comparison with

previously reported NMR spectra of similar enyne chloro-type compounds.x

1,5-dichloro-4-methylenepent-2-yne

Cl

Cl

1H NMR (300 MHz, C6D6) 5.64 (t, J = 6.2 Hz, 2H, C=CH2), 4.59 (s, 2H, CH2Cl), 4.57 (s, 2H, CH2Cl).

S20

S5. Catalytic Hydrothiolation Details

a. Optimisation of Catalytic Hydrothiolation of 1-hexyne with thiophenol

Standard operating procedure for hydrothiolation reactions. A high pressure NMR tube with a J. Young

valve was charged with one mol % catalyst 2a (4.0 mg, 3.9 x 10-6 mol) or one mol % catalyst 2b (4.7 mg,

3.9 x 10-6 mol) and 0.25 equivalents of internal standard, 1,4-di-tert-butylbenzene (18.6 mg, 9.8 x 10-5).

Catalytic amount of base was added as indicated in Table S2. To the mixture was added deuterated

benzene (0.5 mL). One equivalent of 1-hexyne (45 µL, 3.9 x 10-4 mol) and one equivalent of thiophenol

(40 µL, 3.9 x 10-4 mol) were added, and the NMR tube capped. 1H NMR spectroscopy was performed at

time 10 min after addition of the substrates. The reaction mixture was heated up to the appropriate

temperature and reacted for the duration as indicated (see Table S2). Upon cooling down to room

temperature, 1H NMR spectroscopy was performed at the final time. Conversion and calculated yields

were determined from NMR analysis based on the integration of substrates and product, referenced to

the internal standard. Product identity was confirmed by comparison with previously reported NMR

spectra.xi

Table S2.Hydrothiolation of 1-hexyne (1 equivalent) with thiophenol (1 equivalent) promoted by 2.a

Product distributionEntry Catalyst Base (mol %) T (°C) t (h) Conversion (%)b

Yield (%)c α-vinyl

sulfideβ-E-vinyl

sulfide

β-Z-vinyl sulfide

1 2a K2CO3 (1) 80 24 77 71 91 d 6 3

2 2a K2CO3 (1) 40 24 14 11 91 d 5 43 2a Pyridine (5) 80 24 74 64 89 d 8 34 2a None 80 24 81 74 91 d 6 35 2b K2CO3 (1) 80 24 58 49 92 d 2 6

aReaction performed in C6D6 (0.5 mL) with internal standard 1,4-di-tert-butylbenzene, 1 mol % catalyst (3.5 x 10-6 mol) and 3.5 x 10-4 mol 1-hexyne. bConversion as determined through NMR integration based on 1-hexyne referenced to 1,4-di-tert-butylbenzene. cYield of α-vinyl sulfide as determined from NMR integration based on 1-hexyne. dPlus unidentified products.

S21

2-Phenylthio-1-hexene

S

1H NMR (300 MHz, C6D6) 7.44 - 7.40 (m, 2H, ArH), 7.05 - 6.96 (m, 3H, ArH overlaps with unreacted

thiophenol), 5.06 (s, 1H, C=CH2), 4.97 (s, 1H, C=CH2), 2.20 (t, J = 7.6 Hz, 2H, CH2), 1.50 (tt, J = 7.6 Hz, 7.5

Hz, 2H, CH2), 1.26 - 1.16 (m, 2H, CH2 overlaps with C(CH3)3 of internal standard), 0.80 (t, J = 7.3 Hz, 3H,

CH3).

0.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.5f1 (ppm)

0

1E+07

2E+07

3E+07

4E+07

5E+07

6E+07

7E+07

8E+07

9E+07

1E+08

1E+08

1E+08

3.17

3.12

6.36

2.10

2.13

1.00

1.01

3.17

1.40

1.84

0.72

0.74

0.77

0.80

0.82

1.16

1.18

1.21

1.23

1.26

1.46

1.47

1.48

1.50

1.50

1.52

1.53

1.56

1.76

1.77

1.78

1.91

1.92

1.94

1.95

1.96

1.97

2.17

2.20

2.22

4.97

5.06

5.88

5.90

5.93

5.95

6.03

6.04

6.08

6.09

6.96

6.97

6.98

6.99

7.00

7.00

7.01

7.02

7.03

7.04

7.04

7.05

7.16

7.29

7.40

7.41

7.41

7.42

7.43

7.44

7.44

Figure S10. Catalytic hydrothiolation reaction of 1-hexyne (blue) with thiophenol (blue) yielding 2-phenylthio-1-hexene (red) at time 10 min (blue spectrum) and at time after reaction (red spectrum).

b. Catalytic Hydrothiolation of terminal alkynes with thiols catalyzed by 2a

Standard operating procedure for hydrothiolation reactions: a high pressure NMR tube with a J. Young

valve was loaded with one mol % catalyst 2a and 0.25 equivalents of internal standard, 1,4-di-tert-

butylbenzene. To the mixture was added deuterated benzene (0.5 mL). One equivalent of terminal

S22

alkyne and thiol was added, and the NMR tube capped. 1H NMR spectroscopy was performed at time 10

min after addition of the substrates. The reaction mixture was heated up to 80 °C and reacted for the

duration as indicated (see Article, Table 2). Upon cooling down to room temperature, 1H NMR

spectroscopy was performed at the final time. Conversion and calculated yields where determined from

NMR analysis based on integration of alkyne and product, referenced to the internal standard.

Entry 2, Table 2: Hydrothiolation of N,N-dimethylaminopropyne with 1-hexanethiol

Experiments were carried out as mentioned. Amounts of reagents added are as follows: 1mol % catalyst

2a (3.2 mg, 3.2 x 10-6 mol); internal standard 0.25 equivalent (15.1 mg, 7.9 x 10-5 mol); one equivalent

N,N-dimethylaminopropyne (34.1 µL, 3.2 x 10-4 mol) and one equivalent 1-hexanethiol (45 µL, 3.2 x 10-4

mol).

N,N-dimethyl-2-hexylthioprop-2-en-1-amine

SN

1H NMR (300 MHz, C6D6) 5.24 (t, J = 1.0 Hz, 1H, C=CH2), 4.78 (s, 1H, C=CH2), 3.00 (s, 2H, CH2N(CH3)2),

2.56 (t, J = 7.3 Hz, 2H, CH2), 2.12 (s, 6H, CH2N(CH3)2), 1.53 (tt, J = 7.5 Hz, 7.2 Hz, 2H, CH2), 1.27 - 1.11 (m,

6H, (CH2)3 overlaps with C(CH3)3 of internal standard), 0.82 (t, J = 0.8 Hz, 3H, CH3). 13C NMR (75 MHz,

C6D6) 145.7, 106.3, 66.3, 45.1, 31.8, 31.0, 29.2, 28.7, 22.9, 14.2.

S23

1.01.52.02.53.03.54.04.55.05.56.06.57.07.58.0f1 (ppm)

0

5E+07

1E+08

2E+08

2E+08

2E+08

3E+08

4E+08

4E+08

4E+08

3.21

5.11

6.37

2.29

6.50

2.05

2.05

0.96

1.00

1.00

0.80

0.82

0.85

1.13

1.14

1.15

1.17

1.20

1.26

1.27

1.53

2.11

2.12

2.54

2.56

2.59

3.00

4.78

5.24

5.24

5.24

7.28

Figure S11. 1H NMR of N,N-dimethyl-2-hexylthioprop-2-en-1-amine

101520253035404550556065707580859095100105110115120125130135140145150f1 (ppm)

0

5E+07

1E+08

2E+08

2E+08

2E+08

3E+08

4E+08

4E+08

4E+08

5E+08

6E+08

14.2

22.9

28.7

29.2

31.0

31.8

45.1

66.3

106.

3

145.

7

Figure S12. 13C NMR of N,N-dimethyl-2-hexylthioprop-2-en-1-amine

S24

Entry 3, Table 2: Hydrothiolation of N-Boc-propargylamine with 1-hexanethiol


2a (3.2 mg, 3.2 x 10-6 mol); internal standard 0.25 equivalent (15.1 mg, 7.9 x 10-5 mol); one equivalent N-

Boc-propargylamine (49.1 mg, 3.2 x 10-4 mol) and one equivalent 1-hexanethiol (45 µL, 3.2 x 10-4 mol).

N-tert-butyloxycarbonyl-2-hexylthioprop-2-en-1-amine

S

HNO

O

1H NMR (300 MHz, C6D6) 5.14 (s, 1H, C=CH2), 4.77 (s, 1H, C=CH2), 4.64 (br s, 1H, CH2NH), 3.82 (d, J = 5.9

Hz, 2H, CH2NH), 2.45 (t, J = 7.3 Hz, 2H, CH2), 1.49 - 1.39 (m, 2H, CH2 overlaps with OC(CH3)3), 1.42 (s, 9H,

OC(CH3)3 overlaps with CH2), 1.25 - 1.05 (m, 6H, (CH2)3 overlaps with C(CH3)3 of internal standard), 0.82

(t, J = 7.0 Hz, 3H, CH3). 13C NMR (75 MHz, C6D6) 155.6, 144.0, 108.0, 79.0, 46.1, 31.7, 31.3, 29.0, 28.7,

28.5, 22.9, 14.2.

0.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.5f1 (ppm)

-1E+07

0

1E+07

2E+07

3E+07

4E+07

5E+07

6E+07

7E+07

8E+07

9E+07

1E+08

1E+08

1E+08

3.28

6.83

5.07

12.4

9

2.06

2.02

0.69

1.00

0.94

1.00

0.80

0.82

0.85

1.10

1.12

1.12

1.14

1.17

1.19

1.21

1.21

1.25

1.42

1.44

1.44

1.46

2.43

2.45

2.48

3.81

3.83

4.64

4.77

5.14

Figure S13. 1H NMR of N-tert-butyloxycarbonyl-2-hexylthioprop-2-en-1-amine

S25

102030405060708090100110120130140150160170f1 (ppm)

0

5E+06

1E+07

2E+07

2E+07

2E+07

3E+07

4E+07

4E+07

4E+07

5E+07

6E+07

6E+07

6E+07

7E+07

8E+07

8E+07

8E+07

14.2

22.9

28.5

28.7

28.9

31.3

31.6

31.7

34.3

46.1

78.9

107.

9

125.

3

144.

0

148.

1

155.

6

Figure S14. 13C NMR of N-tert-butyloxycarbonyl-2-hexylthioprop-2-en-1-amine

Entry 4, Table 2: Hydrothiolation of phenylacetylene with thiophenol


2a (3.5 mg, 3.4 x 10-6 mol); internal standard 0.25 equivalent (16.3 mg, 8.5 x 10-5 mol); one equivalent

phenylacetylene (37.6 µL, 3.4 x 10-4 mol) and one equivalent thiophenol (35 µL, 3.4 x 10-4 mol). Product

identity was confirmed by comparison with previously reported NMR spectra.xi

1-Phenyl-1-phenylthioethene

S

1H NMR (300 MHz, C6D6) 7.63 - 7.57 (m, 2H, ArH overlaps with E- and Z-isomers), 7.42 - 7.27 (m, 4H,

ArH overlaps with ArH of internal standard and with E- and Z-isomers), 7.06 - 6.85 (m, 4H, ArH overlaps

with E- and Z-isomers), 5.50 (s, 1H, C=CH2), 5.30 (s, 1H, C=CH2).

S26

S6. Proposed Reaction Mechanism for Alkyne Dimerisation and Hydrothiolation promoted by 2a

[Rh] OO

H

R[Rh]

H

R

[Rh]H

R

[Rh] R

RH

[Rh]H

R

R

[Rh]

RR

H

[Rh]R

R

H

H

R

R

R

H

H

[Rh] = (CNCMes)Rh

RSH[Rh] S

R

H

[Rh] SR

H

[Rh]H H

SRR'

H

R'

[Rh] S

RH

H R'

H R

1,2-carbometalation

Alkyne hydrothiolation

RSH

R' SR

1,2-metal-thiolateinsertion

2,1-hydrometalation

Alkyne dimerisation

O2O2

Scheme S2. Proposed mechanistic route of alkyne dimerization and hydrothiolation mediated by 2a

S7. Catalytic Asymmetric bis-Hydrothiolation Details

Standard operating procedure for asymmetric bis-hydrothiolation reactions. A high pressure NMR tube

with a J. Young valve was charged with two mol % catalyst 2a and 0.25 equivalents of internal standard,

1,4-di-tert-butylbenzene. To the mixture was added deuterated benzene (0.5 mL). One equivalent of

terminal alkyne and one equivalent of the dithiol were added, followed by the NMR tube being capped. 1H NMR spectroscopy was performed at time 10 min after addition of the substrates. The reaction

mixture was heated up to 80 °C and reacted for the duration as indicated (see Article, Table 3). 1H NMR

spectroscopy confirmed the complete conversion of the substrates to the mono-α-vinyl sulfide product.

To the same reaction mixture, in open atmospheric conditions, was added one equivalent of the second

terminal alkyne. The NMR tube was capped, a 1H NMR experiment performed, and the tube was

subsequently heated up to 80 °C for the duration as indicated in Table 3 (see Article). 1H NMR

spectroscopy confirmed the formation of the unsymmetrical bis-α,α’-vinyl sulfide, or unsymmetrical bis-

α,β-E-vinyl sulfides. Conversion and calculated yields were determined from NMR analysis based on the

integration of alkyne and product, referenced to the internal standard.

S27

Entry 1, Table 3: Bis-Hydrothiolation of 1-hexyne and N,N-dimethylaminopropyne with

1,4-butanedithiol (bis-α,α’-vinyl sulfide)


mol % (6.1 mg, 6.0 x 10-6 mol); internal standard 0.25 equivalent (14.2 mg, 7.5 x 10-5 mol); 1 equivalent

of 1-hexyne (34.3 µL, 3.0 x 10-4 mol) and one equivalent of 1,4-butanedithiol (35 µL, 3.0 x 10-4 mol).

Upon completion of the first hydrothiolation reaction, one equivalent of the second alkyne, N,N-

dimethylaminopropyne (32.1 µL, 3.0 x 10-4 mol), was added.

bis-α,α’-vinyl sulfide

SS

N

1H NMR (300 MHz, C6D6) 5.20 (d, J = 1.3 Hz, 1H, C=CH2), 4.99 (d, J = 1.4 Hz, 1H, C=CH2), 4.72 (s, 1H,

C=CH2), 4.65 (s, 1H, C=CH2), 2.96 (br s, 2H, CH2N(CH3)2), 2.48 - 2.41 (m, 4H, (CH2)2), 2.20 (tt, J = 7.6 Hz, 4.5

Hz, 2H, CH2), 2.10 (s, 6H, CH2N(CH3)2), 1.58 - 1.46 (m, 6H, (CH2)3), 1.31 - 1.18 (m, 2H, CH2 overlaps with

C(CH3)3 of internal standard), 0.83 (t, J = 7.3 Hz, 3H, CH3). 13C NMR (75 MHz, C6D6) 146.4, 145.2, 106.7,

105.2, 66.3, 45.1, 37.8, 31.4, 30.8, 30.4, 28.0, 27.9, 22.4, 14.1.

S28

0.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.0f1 (ppm)

-2E+07

0

2E+07

4E+07

6E+07

8E+07

1E+08

1E+08

1E+08

2E+08

2E+08

2E+08

2E+08

2E+08

3E+08

3E+08

3E+08

3.17

1.07

11.1

8

2.77

2.28

2.11

2.25

0.98

0.99

1.00

0.82

0.84

0.86

1.22

1.23

1.24

1.26

1.52

1.54

1.54

1.56

1.57

2.01

2.03

2.06

2.19

2.19

2.21

2.21

2.24

2.37

2.39

2.41

2.42

2.43

2.44

2.45

2.45

2.46

4.66

5.00

5.01

5.01

7.28

Figure S15. 1H NMR of α-vinyl sulfide intermediate product

S29

0.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.5f1 (ppm)

0

5E+07

1E+08

2E+08

2E+08

2E+08

3.13

7.47

6.20

6.31

2.38

4.05

2.03

1.00

0.90

1.01

0.94

1.00

0.81

0.83

0.86

1.26

1.53

1.54

1.55

1.56

2.10

2.17

2.20

2.43

2.44

2.46

2.46

2.96

4.65

4.65

4.72

4.99

4.99

5.20

5.21

7.28

Figure S16. 1H NMR of bis-α,α’-vinyl sulfide

102030405060708090100110120130140150f1 (ppm)

0

1E+08

2E+08

3E+08

4E+08

5E+08

6E+08

7E+08

8E+08

9E+08

1E+09

1E+09

14.1

22.4

27.9

28.0

30.4

30.8

31.4

37.8

45.0

66.3

105.

210

6.7

145.

214

6.4

Figure S17. 13C NMR of bis-α,α’-vinyl sulfide

S30

0.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.0f1 (ppm)

1

2

3

Figure S18. Stacked 1H NMR of asymmetric bis-hydrothiolation reaction at initial time (blue spectrum), intermediate step (green spectrum) and final time (red spectrum)

Entry 2, Table 3: Bis-Hydrothiolation of 1-hexyne and 3-hexyne with 1,6-hexanedithiol

(bis-α,β-E-vinyl sulfide)

Experiments were carried out as mentioned. Amounts of reagents added are as follows: catalyst 2 mol %

(5.3 mg, 5.2 x 10-6 mol); internal standard 0.25 equivalent (12.4 mg, 6.5 x 10-5 mol); 1 equivalent of 1-

hexyne (30.1 µL, 2.6 x 10-4 mol) and one equivalent of 1,6-hexanedithiol (40 µL, 2.6 x 10-4 mol). Upon

completion of the first hydrothiolation reaction, one equivalent of the second alkyne, 3-hexyne (29.7 µL,

2.6 x 10-4 mol)), was added.

Bis-α,β-E-vinyl sulfide

SS

S31

1H NMR (300 MHz, C6D6) 5.34 (t, J = 7.3 Hz, 1H, C=CH), 5.02 (d, J = 1.1 Hz, 1H, C=CH2), 4.70 (s, 1H,

C=CH2), 2.51 - 2.44 (m, 4H, (CH2)2), 2.23 (t, J = 7.5 Hz, 2H, CH2), 2.21 - 2.13 (m, 2H, CH2 overlaps with

CH2), 1.98 (t, J = 7.5 Hz, 2H, CH2), 1.61 - 1.50 (m, 2H, CH2), 1.50 - 1.40 (m, 4H, (CH2)2), 1.33 - 1.12 (m, 6H,

(CH2)3 overlaps with C(CH3)3 of internal standard), 1.11 (t, J = 7.5 Hz, 3H, CH3), 0.90 (t, J = 7.5 Hz, 3H,

CH3), 0.84 (t, J = 7.2 Hz, 3H, CH3). 13C NMR (75 MHz, C6D6) 146.8, 136.6, 127.1, 104.9, 37.9, 31.5, 31.4,

31.3, 29.0, 28.9, 28.8, 28.5, 25.4, 22.5, 22.2, 14.8, 14.6, 14.1.

0.00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.0f1 (ppm)

-1E+07

0

1E+07

2E+07

3E+07

4E+07

5E+07

6E+07

7E+07

8E+07

9E+07

1E+08

1E+08

1E+08

1E+08

1E+08

2E+08

2E+08

2E+08

3.11

5.55

9.42

2.42

2.11

2.27

2.12

2.15

0.99

1.00

1.00

0.82

0.85

0.87

1.07

1.08

1.15

1.23

1.24

1.26

1.28

1.30

1.54

1.56

2.09

2.11

2.13

2.15

2.21

2.24

2.26

2.47

2.47

2.49

2.50

2.52

2.52

4.70

4.71

5.02

5.03

7.29

Figure S19. 1H NMR of α-vinyl sulfide intermediate product

S32

0.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.5f1 (ppm)

0

1E+07

2E+07

3E+07

4E+07

5E+07

6E+07

7E+07

8E+07

9E+07

1E+08

1E+08

1E+08

1E+08

1E+08

3.43

2.16

4.36

2.56

8.54

3.21

2.94

3.07

4.64

3.62

1.00

1.04

0.56

1.04

0.82

0.84

0.87

0.88

0.90

0.93

1.04

1.07

1.08

1.11

1.12

1.14

1.15

1.16

1.18

1.19

1.20

1.23

1.26

1.28

1.30

1.33

1.41

1.44

1.44

1.46

1.47

1.50

1.50

1.53

1.56

1.58

1.61

1.96

1.98

1.99

2.01

2.09

2.11

2.11

2.13

2.16

2.18

2.20

2.21

2.23

2.25

2.44

2.44

2.45

2.46

2.49

2.51

4.69

4.70

5.01

5.02

5.02

5.32

5.34

5.37

Figure S20. 1H NMR of bis-α,β-E-vinyl sulfide and unreacted intermediate product

0102030405060708090100110120130140150160f1 (ppm)

0

5E+07

1E+08

2E+08

2E+08

2E+08

3E+08

4E+08

4E+08

4E+08

5E+08

6E+08

6E+08

6E+08

7E+08

8E+08

8E+08

8E+08

14.1

14.6

14.8

22.5

28.5

28.9

28.9

31.3

31.5

37.8

104.

9

127.

1

136.

6

146.

8

Figure S21. 13C NMR of bis-α,β-E-vinyl sulfide and unreacted intermediate product

S33

0.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.5f1 (ppm)

1

2

3

Figure S22. Stacked 1H NMR of asymmetric bis-hydrothiolation reaction at initial time (blue spectrum), intermediate step (green spectrum) and final time (red spectrum)

S8. Sequential bis-hydrothiolation reaction under preparative conditions

The reaction reported in Table 3, Entry 1 was scaled up tenfold. To a Schlenk tube was added 1-hexyne

(343 µL, 2.98 x 10-3 mol ), 1,4-butanedithiol (350 µL, 2.98 x 10-3 mol), catalyst 2a ( 116 mg, 5.97 x 10-5

mol; 2 mol%) and internal standard 1,4-di-tert-butylbenzene (142 mg, 7.46 x 10-4 mol, 0.25 equivalent)

in 4 mL solvent C6D6. The reaction mixture was heated at 80 °C for 14 hours, whereafter the reaction

mixture was allowed to cool down to room temperature. The second alkyne substrate,

dimethylaminopropyne (321 µL, 2.98 x 10-3 mol) was added to the reaction mixture and the reaction

vessel heated for an additional 30 hours at 80 °C. After a total reaction time of 44 hours, NMR analysis

indicated 64% conversion of the substrates, and a calculated overall yield of the bis-α,α’-vinyl sulfide

product of 62%. The reaction mixture was thereafter dry-loaded on an aluminium oxide 90 (neutral,

activated) plug, and the product eluted with hexane:EtOAc (3:1). The purified bis-α,α’-vinyl sulfide

product was isolated with a yield of 406 mg, 47% overall yield.

S34

S9. Cascade Catalytic Details

A high pressure NMR tube with a J. Young valve was loaded with 3.5 mol % of catalyst 2a (11.6 mg, 1.1 x

10-5 mol) and 0.25 equivalents of internal standard, 1,4-di-tert-butylbenzene (15.4 mg, 8.1 x 10-5mol). To

the mixture was added deuterated benzene (0.5 mL). One equivalent of N,N-dimethylaminopropyne (35

µL, 3.3 x 10-4 mol) was added to the solution, and the NMR tube was subsequently capped. 1H NMR

spectroscopy was performed at time 10 min after addition of the alkyne. The reaction mixture was

heated up to 80 °C and left to react for 3 hours. Upon cooling down to room temperature, 1H NMR

spectroscopy confirmed complete conversion of N,N-dimethylaminopropyne to N1,N1,N5,N5-

tetramethyl-4-methylenepent-2-yne-1,5-diamine. To the same reaction mixture, in open atmospheric

conditions, was added 1-hexanethiol (23.1 µL, 1.6 x 10-4 mol). The NMR tube was capped, and a 1H NMR

experiment performed of the resulting mixture. The reaction mixture was heated up to 60 °C for 48

hours. Upon cooling down to room temperature, a 1H NMR experiment was performed on the resulting

mixture. Conversion and calculated yields were determined from NMR analysis based on integration of

substrates and product, referenced to the internal standard. Product identity was determined by

assignments based on 1D (1H, 13C{1H}, 13C-dept 135) and 2D (COSY, HSQC and HMBC) experiments.

2aNN

N

SH

2a

N

S

N

N

N

SC6D6, 80 C3 hours

C6D6, 60 C48 hours

S

HN

N

H

H

a

b

c

Scheme S3: One-pot alkyne dimerization followed by hydrothiolation of the internal alkyne catalyzed by 2a

S35

Table S3. Cascade alkyne dimerization/hydrothiolation to form gem-ene-vinyl sulfides promoted by 2a.a

Step 1b Step 2d

T (◦C) t (h)Conversion

(%)cT (◦C) t (h)

Conversion

(%)cProducts Yield (%)e

Product

Distribution

a 29 44

b 29 4380 3 > 99 60 48 82

c 9 13aReaction performed in 0.5 mL C6D6 with 1,4-di-tert-butylbenzene as internal standard, with catalyst loading 3.5 mol %.bAlkyne homo-dimerization yielding N,N,N,N-tetramethyl-4-methylenepent-2-yne-1,5-diaminecConversion as determined through NMR integration based on substrate and products referenced to 1,4-di-tert-butylbenzene.dHydrothiolation of internal alkyne of enyne formed after step 1, with 1-hexanethiol.eNMR calculated yield.

(a) 1,3-gem-ene-β-E-vinyl-sulfide

N

S

N

H

1

4

26

3

5

1H NMR (300 MHz, C6D6) 6.03 (t, J = 6.8 Hz, 1H, C5-H), 5.44 (dt, J = 1.6 Hz, 1.3 Hz, 1H, C3-H2), 5.06 (dt, J

= 1.3 Hz, 1 Hz, 1H, C3-H2), 3.10 (t, J = 1.3 Hz, 2H, C1-H2), 3.03 (d, J = 6.8 Hz, 2H, C6-H2), 2.18 (s, 6H, C1-

N(CH3)2), 2.13 (s, 6H, C6-N(CH3)2), -S-hexyl moiety (grey scaled) not assigned due to extensive overlap.

13C NMR (100 MHz, C6D6) 143.8 (C2), 138.6 (C4), 129.9 (C5), 116.9 (C3), 63.8 (C1), 58.7 (C6), N(CH3)2 not

assigned due to extensive carbon overlap.

S36

(b) 1,4-gem-ene-β-E-vinyl-sulfide

N

N

S H

2

4

3

1

5

6

1H NMR (300 MHz, C6D6) 6.03 (s, 1H, C4-H), 5.20 (dt, J = 1.3 Hz, 1.2 Hz, 1H, C3-H2), 5.13 (d, J = 1.5 Hz,

1H, C3-H2), 3.35 (d, J = 1 Hz, 2H, C6-H2), 2.86 (br s, 2H, C1-H2), 2.21 (s, 6H, C6-N(CH3)2), 2.10 (s, 6H, C1-

N(CH3)2), -S-hexyl moiety (grey scaled) not assigned due to extensive overlap. 13C NMR (100 MHz, C6D6)

143.6 (C2), 140.4 (C5), 123.3 (C4), 115.9 (C3), 67.1 (C1), 61.2 (C6), N(CH3)2 not assigned due to extensive

carbon overlap.

(c) 1,4-gem-ene-β-Z-vinyl-sulfide

S

HN

N

12

3

45

6

1H NMR (300 MHz, C6D6) 6.36 (br s, 1H, C4-H), 5.12 (d, J = 1.3 Hz, 1H, C3-H), 5.08 (s, 1H, C3-H), 3.23 (s,

2H, C6-H), 3.00 (d, J = 1.3 Hz, 2H, C1-H), 2.16 (s, 6H, C6-N(CH3)2), 2.14 (s, 6H, C1-N(CH3)2), -S-hexyl moiety

(grey scaled) not assigned due to extensive overlap. 13C NMR (100 MHz, C6D6) 141.9 (C2), 141.7 (C5),

128.6 (C4), 110.1 (C3), 64.1 (C1), 57.9 (C6), N(CH3)2 not assigned due to extensive carbon overlap.

S37

0.51.01.52.02.53.03.54.04.55.05.56.06.57.07.5f1 (ppm)

-5E+06

0

5E+06

1E+07

2E+07

2E+07

2E+07

3E+07

4E+07

4E+07

4E+07

5E+07

6E+07

6E+07

6E+07

5.70

34.4

5

4.50

3.87

2.32

3.69

2.34

1.42

5.38

3.58

1.58

1.43

0.65

1.16

0.72

0.44

0.65

0.60

1.23

1.09

1.17

0.59

0.15

0.72

0.54

0.33

0.56

0.29

1.10

0.13

4.00

0.79

0.81

0.84

0.86

1.10

1.12

1.13

1.18

1.19

1.22

1.26

1.47

1.50

1.53

1.54

1.56

1.59

2.10

2.11

2.13

2.14

2.16

2.18

2.18

2.21

2.46

2.48

2.51

2.59

2.62

2.64

2.68

2.86

2.89

3.00

3.02

3.05

3.10

3.23

3.35

5.06

5.06

5.07

5.08

5.13

5.13

5.20

5.20

5.21

5.37

5.37

5.43

5.43

5.43

5.44

5.44

5.50

6.00

6.03

6.05

6.36

Figure S23. 1H NMR spectrum of products obtained after one-pot catalyzed alkyne dimerization followed by hydrothiolation of the internal alkyne by 2a

S38

1520253035404550556065707580859095100105110115120125130135140145150f1 (ppm)

0

1E+07

2E+07

3E+07

4E+07

5E+07

6E+07

7E+07

8E+07

9E+07

1E+08

1E+08

1E+08

1E+08

1E+08

2E+08

2E+08

2E+08

2E+08

2E+08

2E+08

2E+0814.3

14.3

22.9

22.9

23.0

28.8

29.6

31.8

32.4

44.2

45.4

45.4

45.4

45.7

45.8

45.9

57.9

58.6

61.2

63.8

64.1

67.1

110.

0

115.

911

6.9

123.

312

5.3

127.

012

8.6

129.

913

8.6

140.

314

1.7

141.

914

3.3

143.

614

3.8

144.

2

Figure S24. 13C NMR spectrum of products obtained after one-pot catalyzed alkyne dimerization followed by hydrothiolation of the internal alkyne by 2a

S39

2.82.93.03.13.23.33.45.05.15.25.35.45.55.65.75.85.96.06.16.26.36.46.5f1 (ppm)

-2E+06

0

2E+06

4E+06

6E+06

8E+06

1E+07

1E+07

1E+07

2E+07

2E+07

2E+07

2E+07

2E+07

3E+07

3E+07

3E+07

3E+07

3E+07

4E+07

4E+07

1.16

0.72

0.44

0.65

0.60

1.23

1.09

1.17

0.59

0.15

0.72

0.54

0.33

0.56

0.29

1.10

0.13

2.86

2.89

3.00

3.02

3.05

3.10

3.23

3.35

5.06

5.06

5.07

5.08

5.13

5.13

5.20

5.20

5.21

5.36

5.37

5.37

5.43

5.43

5.43

5.44

5.44

5.50

6.00

6.03

6.05

6.36

Figure S25. Selected regions of 1H NMR spectrum of products obtained after one-pot catalyzed alkyne dimerization followed by hydrothiolation (* denotes unreacted gem-enyne intermediate product)

S40

565860626466110112114116118120122124126128130132134136138140142144f1 (ppm)

0

1E+07

2E+07

3E+07

4E+07

5E+07

6E+07

7E+07

8E+07

9E+07

1E+08

1E+08

1E+08

1E+08

1E+08

2E+08

57.9

58.6

61.2

63.8

64.1

65.3

67.1

110.

0

115.

911

6.9

122.

1

123.

3

125.

3

128.

612

9.9

130.

1

138.

6

140.

314

1.7

141.

9

143.

614

3.8

Figure S26. Selected regions of 13C NMR spectrum of products obtained after one-pot catalyzed alkyne dimerization followed by hydrothiolation (* denotes unreacted gem-enyne intermediate product)

S41

0.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.0f1 (ppm)

1

2

3

Figure S27. Stacked 1H NMR spectra of one-pot catalyzed alkyne dimerization followed by hydrothiolation at initial time (blue spectrum), intermediate step (green spectrum) and final time (red spectrum)

S42

S10. Tandem Alkyne Dimerization-Hydrothiolation Reaction under Preparative

Conditions

The reaction reported in the manuscript Scheme 2 was scaled up tenfold. To a Schlenk tube was added

dimethylaminopropyne (350 µL; 3.25 x 10-3 mol), catalyst 2a (116 mg; 1.14 x 10-4 mol; 3.5 mol%) and

internal standard 1,4-di-tert-butylbenzene (154 mg, 8.13 x 10-4 mol, 0.25 equivalent) in 4 mL solvent

C6D6. The reaction was heated at 80 °C for 5 hours, whereafter it was allowed to cool to room

temperature. 1-hexanethiol (231 µL; 1.63 x 10-3 mol; 0.5 equivalent) was added to the reaction mixture,

and the reaction vessel then heated at 60 °C for an additional 48 hours. NMR analysis revealed 60 %

conversion of the substrates, with calculated yields for the different gem-ene-vinyl sulfide product

isomers as follows: 1,3-gem-ene-β-E-vinyl sulfide, 28%; 1,4-gem-ene-β-E-vinyl sulfide, 19%; and 1,4-

gem-ene-β-Z-vinyl sulfide, 9%, with product distribution: 1,3-gem-ene-β-E-vinyl sulfide: 1,4-gem-ene-β-

E-vinyl sulfide: 1,4-gem-ene-β-Z-vinyl sulfide = 50 : 34 : 16.

The products were purified by gradient elution with hexane and ethyl actetate after dry loading on an

aluminium oxide 90 (neutral, activated) plug to yield all three gem-ene-vinyl sulfide products, with an

overall crude isolated yield of 180 mg, 6.33 x 10-4 mol, 39% yield.

S11. Crystal Structure Details

X-ray structure and crystal data for 1a and 2b:

Figure 1: X-ray structure of the salt precursor 1a with thermal ellipsoids at the 50 %probability level. H atoms except for H1 and H13, and the PF6 counteranion were omitted for clarity. Selected bond lengths (Å): H1-Cl1 2.203 (5), H1A-Cl1 2.446 (5).

S43

Crystal Data for 1a: C60H69N7ClF6P (M =1068.64 g/mol): monoclinic, space group P21/c (no. 14), a = 16.2214(4) Å, b = 24.0518(5) Å, c = 15.2494(3) Å, β = 108.8560(9)°, V = 5630.3(2) Å3, Z = 4, T = 150.15 K, μ(CuKα) = 1.404 mm-1, Dcalc = 1.261 g/cm3, 198184 reflections measured (5.756° ≤ 2Θ ≤ 144.494°), 11093 unique (Rint = 0.0378, Rsigma = 0.0120) which were used in all calculations. The final R1 was 0.0430 (I > 2σ(I)) and wR2 was 0.1137 (all data).

Figure 2: X-ray structure of the salt precursor 2b with thermal ellipsoids at the 50 %probability level. H atoms were omitted for clarity. Selected bond lengths (Å) and angles (o): Rh1-N1 1.986(3), Rh1-C1 2.035(4), Rh1-C3 2.036(4), Rh1-O1 1.976(3), Rh1-O2 1.980(3), O1-O2 1.389 (7); O1-Rh1-N1 160.91(13), N1-Rh1-C1 89.65 (13), N1-Rh1-C3 89.09 (13), C1-Rh1 C3 178.57(14), O1-Rh1-O2 40.74(11), O1-Rh1-C1 90.21(13).

Crystal Data for 2b: C72H84N7O2Rh (M =1182.37 g/mol): triclinic, space group P-1 (no. 2), a = 10.8323(5) Å, b = 15.4988(8) Å, c = 24.8410(13) Å, α = 103.4480(14)°, β = 97.0590(13)°, γ = 107.0370(13)°, V = 3795.4(3) Å3, Z = 2, T = 150.15 K, μ(MoKα) = 0.267 mm-1, Dcalc = 1.035 g/cm3, 84650 reflections measured (4.428° ≤ 2Θ ≤ 51.56°), 14487 unique (Rint = 0.1099, Rsigma = 0.0978) which were used in all calculations. The final R1 was 0.0610 (I > 2σ(I)) and wR2 was 0.1727 (all data).

S12. References

i Mintz, M. J.; Walling, C. Organic Synthesis, Coll. 1973, 5, 184.ii Bezuidenhout, D. I.; Kleinhans, G.; Guisado-Barrios, G.; Liles, D. C.; Ung, G.; Bertrand, G. Chem. Commun. 2014, 50, 2431.iii Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A. K.; Puschmann, H. J. Appl. Cryst. 2009, 42, 339.iv Burla, M.C.; Caliandro, R.; Camalli, M.; Carrozzini, B.; Cascarano, G.L.; De Caro, L.; Giacovazzo, C.; Polidori, G.; Siliqi, D.; Spagna, R. J. Appl. Cryst. 2007, 40, 609-613.v Sheldrick, G.M. Acta Cryst. 2008, A64, 112-122.vi Rubio-Pérez, L.; Azpíroz, R.; Di Giuseppe, A.; Polo, V.; Castarlenas, R.; Pérez-Torrente, J. J.; Oro, L. A. Chem. Eur. J. 2013, 19, 15304.vii Peng, H. M.; Zhao, J.; Li, X. Adv. Synth. Catal. 2009, 351, 1371. viii Akita, M.; Yasuda, H.; Nakamura, A. Bull. Chem. Soc. Jpn. 1984, 57, 480.ix Xu, H.-D.; Zhang, R.-W.; Li, X.; Huang, S.; Tang, W.; Hu, W.-H. Org. Lett. 2013, 15, 840.x Nishimura, A.; Tamai, E.; Ohashi, M.; Ogoshi, S. Chem. Eur. J. 2014, 20, 6613.xi Silveira, C. C.; Santos, P. C. S.; Mendes, S. R.; Braga, A. L. J. Organomet. Chem. 2008, 693, 3787.

Rhodium(I) Oxygen Adduct as a Selective Catalyst for One ...

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