Contributions to the Chemistry of the Cyclopentadienyl Complex [Cp∧RuCl 2 ] 2 (“Cp-roof” = η...

ARTICLE

DOI: 10.1002/zaac.201400048

Contributions to the Chemistry of the Cyclopentadienyl Complex[Cp∧RuCl2]2 (“Cp-roof” = η5-1-Methoxy-2,4-tert-butyl-3-

neopentylcyclopentadienyl)

Julie Risse,[a] Barnali Dutta,[a] Euro Solari,[a] Rosario Scopelliti,[a] and Kay Severin*[a]

Keywords: Bimetallic; Carbenes; Cyclopentadienyl; Ruthenium

Abstract. The dimeric ruthenium complex [Cp∧RuCl2]2 is easily ac-cessible in a one-pot reaction from RuCl3(solv)n and tert-butylacetyl-ene. It features sterically very demanding “Cp-roof” ligands (Cp∧ =η5-1-methoxy-2,4-tert-butyl-3-neopentylcyclopentadienyl), which im-part a unique reactivity. Herein we describe the synthesis and the char-

Introduction

The bimetallic RuIII complex [Cp∧RuCl2]2 (1) (Cp∧ = η5-1-methoxy-2,4-tert-butyl-3-neopentylcyclopentadienyl) can beobtained in a one pot reaction by heating a solution of[RuCl3(solv)n] in methanol with tert-butylacetylene.[1] Advan-tageously, the reaction is performed by using microwave irra-diation, which allows to complete the reaction within 5 min.[2]

Similar to the widely used [Cp*RuCl2]2 (2) (Cp* = pentameth-ylcyclopentadienyl), complex 1 is a useful starting material inorganometallic synthesis and catalysis (Figure 1). A distinctivefeature of complex 1 is the presence of sterically very de-manding Cp∧ (“Cp-roof”) ligands. The highly substituted cy-clopentadienyl ligands impart a good solubility to Cp∧Ru com-plexes. Furthermore, they efficiently shield the central ruth-enium atom. As a result, it is rather easy to isolate electroni-cally unsaturated Cp∧Ru complexes.[1a,3] Cp∧Ru complexeswere also shown to display a unique behavior in catalytic reac-tions[3,4] and in biological assays.[5]

Below, we describe novel reactions of complex 1. We willdetail the syntheses and the structures of complexes with carb-ene, imido, and orthometalated phosphine ligands, as well asthe microwave-assisted syntheses of the bimetallic complexes[Cp∧Ru(μ-Cl)3Ru(p-cymene)] and [Cp∧Ru(μ-Cl)3RhCp*].

Results and Discussion

Cp∧Ru Complexes with Carbene or Imido Ligands

Metal carbene complexes are a popular class of compounds,having found many applications in synthesis and

* Prof. Dr. K. SeverinFax: +41-21-693-9305E-Mail: [email protected]

[a] Institut des Sciences et Ingénierie ChimiquesÉcole Polytechnique Fédérale de Lausanne1015 Lausanne, Switzerland

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Z. Anorg. Allg. Chem. 2014, 640, (7), 1322–13291322

acterization of novel Cp∧Ru complexes bearing a bridging carbeneligand, a linear imido ligand, or an orthometalated phosphine ligand.Furthermore, the microwave-assisted syntheses of the bimetallic com-plexes [Cp∧Ru(μ-Cl)3Ru(p-cymene)] and [Cp∧Ru(μ-Cl)3RhCp*] aredescribed.

Figure 1. The dimeric ruthenium complex [Cp∧RuCl2]2 (1).

catalysis.[6] Ruthenium carbene complexes of the type[RuCl2(CHR)(PR�3)2], developed by Grubbs and co-workers,have attracted much attention given their usefulness in olefinmetathesis.[7] Cyclopentadienyl ruthenium carbene complexesare of interest because of their involvement in catalytic reac-tions.[8] Examples of monomeric cyclopentadienyl rutheniumcarbene complexes,[9] as well as bridging alkylidene com-plexes[10] have been reported. However, complexes synthe-sized by direct reaction of a carbene precursor with a ruth-enium cyclopentadienyl complex are rare.[11,12] Schäfer andco-workers prepared a series of complexes by reaction of[CpRu(μ-NO)]2 with diazoalkanes, but presented no crystallo-graphic analysis.[11b] A fully characterized cyclopentadienylruthenium complex bearing a bridging alkylidene ligand,[Cp*Ru(μ-Cl)2(μ-CHCH=CPh2)RuCp*] (3), was reported byGrubbs et al. in 1992.[12] Complex 3 was obtained by a reac-tion of [Cp*RuCl]4 with the strained olefin 1,1-diphenylcy-clopropene.

When a slight excess (ca. 1.5 equiv.) of trimethylsilyldiazo-methane was added to a solution of the dimer 1 in THF, thecolor of the solution immediately changed from brown to

Chemistry of the Cyclopentadienyl Complex [Cp∧RuCl2]2

violet along with the evolution of a gas. The reaction mixturewas stirred for an additional hour at room temperature. Afterremoval of the solvent, the residue was extracted with pentaneand the analytically pure complex [Cp∧Ru(μ-Cl)2(μ-CHSiMe3)RuCp∧] (4) was obtained as a violet solid in 88 %yield (Scheme 1). The structure of 4 was evidenced by NMRspectroscopy, elemental analysis, and single-crystal X-raycrystallographic analysis (Figure 2).

Scheme 1. Synthesis of complex 4 (only one diastereoisomer of 4 isshown).

Figure 2. Graphical representation of the molecular structure of com-plex 4 in the crystal. Hydrogen atoms are omitted for clarity.

The dinuclear RuII complex 4 contains a bridging carbeneligand and two bridging chloride ligands. The crystallographicanalysis showed that the meso diastereoisomer had crystallized(the Cp∧Ru fragment displays planar chirality). In solution,the presence of two diastereoisomers in a ratio of 10:11 wasdemonstrated by NMR spectroscopy. A peak assignment waspossible by an NMR spectroscopic analysis of the meso dia-stereoisomer isolated by crystallization. It is interesting to notethat the meso isomer slowly interconverted into the other dia-stereoisomer: after 3 d, the initial ratio of 12:1 (“pure” mesodiastereoisomer) had evolved to 2.8:1. After 6 d, the ratio was2.4:1. A dissociative exchange mechanism via monomeric[Cp∧Ru(CHSiMe3)Cl] is probably responsible for thisisomerization process. The 1H and 13C NMR spectra of com-plex 3 show characteristic resonances for the carbene CHgroup at δ = 14.84 and 14.58 ppm for the proton, and 217.7and 213.9 ppm for the carbon atom (signals for the meso com-pound in italics). These values are in agreement with the chem-ical shifts reported for complex 3 (13.32 and 194.9 ppm,respectively).[12]

For comparison, we have also studied the reaction betweentrimethylsilyldiazomethane and the Cp*Ru complex[Cp*RuCl2]2 (2) (Scheme 2). As in the case of 1, the color of

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the solution changed quickly (from brown to green), and theevolution of a gas was observed. However, isolation of a de-fined complex proved to be more difficult than in the case ofcomplex 4. While we were not able to obtain an analyticallypure product on a preparative scale, we managed to obtain afew single crystals from a benzene/hexane solution. A crystal-lographic analysis revealed that a dinuclear complex with abridging carbene ligand 5 had also formed (Scheme 2 and Fig-ure 3). The structure of complex 5 is similar to that of complex4, with the exception of one chloride ligand, which is not coor-dinated in a bridging mode. As a consequence, the planesformed by the Cp* ligands are inclined by an angle of 56.85°,whereas an angle of only 25.6° is observed for complex 4.

Scheme 2. Synthesis of complex 5.


Selected bond lengths and angles for the complexes 4 and 5are reported in Table 1. The reference values for complex 3are also given. The Ru···Ru bond lengths indicate the presenceof a metal–metal interaction. The value for complex 4(2.6780(4) Å) is slightly larger than those observed for the twoother complexes [5: 2.5843(5) Å; 3: 2.621(1) Å]. The Ru–Cland Ru–C bond lengths are within the expected range.

Table 1. Selected bond lengths /Å and angles /° for complexes 3–5.

3[12] 4 5

Ru1···Ru2 2.621(1) 2.6780(4) 2.5843(5)Ru1–Cl1 2.410(1) 2.3776(4) 2.3582(7)Ru1–Cl2 2.509(1) 2.5000(6) –Ru2–Cl1 – 2.3874(6) 2.3992(9)Ru2–Cl2 – 2.5398(4) 2.4224(7)Ru1–C 2.105(2) 2.1091(13) 2.085(2)Ru2–C 2.117(2) 2.1297(13) 2.080(2)Ru1–Cl1–Ru2 62.9(1) 68.390(11) 65.799(19)Ru1–C–Ru2 76.7(1) 78.36(5) 76.69(8)

K. Severin et al.ARTICLEDixneuf and co-workers reported the Ru-catalyzed addition

of diazo compounds to alkynes.[13–16] They were able to pre-pare silylated 1,3-dienes,[14] alkenylbicyclo[x.1.0]alkanes (x =3,4)[15] and alkenyl alkylidene bicyclo[3.1.0]hexane deriva-tives.[16] For all these transformations, the authors proposed amechanism, in which the catalyst reacts first with the diazocompound to give a monomeric ruthenium carbene complex.

The activity of complex 4, [Cp∧RuCl2]2 and [Cp*RuCl2]2

was evaluated for the coupling reaction between phenylacetyl-ene and trimethylsilyldiazomethane (Table 2). In addition, ex-periments were performed with the reference catalyst[Cp*RuCl(cod)] used by Dixneuf et al. Reactions were carriedout in dioxane, with 5 mol % ruthenium, at room temperature.The yields and conversions were determined by 1H NMRanalysis of the reaction mixture after 30 min. A mixture ofregioisomers is formed during the transformation, with the Z,Zisomer being the major one. All isomers were taken into ac-count for the determination of the yield.

Table 2. Catalytic addition of trimethylsilyldiazomethane to phenyl-acetylene.

Entry Catalyst Conversion /% Yield /%

1 [Cp*RuCl(cod)] 100 722 [Cp∧RuCl2]2 100 583 4 100 614 [Cp*RuCl2]2 50 23

A conversion of 100 % and a yield of 72 % was achievedwith [Cp*RuCl(cod)], which is in agreement with the reportedvalue (65 % isolated yield after chromatography).[14] Reactionscatalyzed by the Cp∧Ru complexes [Cp∧RuCl2]2 and 4 alsoresulted in full conversion of phenylacetylene within 30 min.However, the yields of the silylated 1,3-dienes were slightlyinferior: 58 % and 61 %, respectively. For reactions with thesetwo catalysts, one of the important side products detected byGC-MS is the olefin formed by homo-coupling of two carbeneunits. The lowest activity was observed for [Cp*RuCl2]2

(23 % yield).Although [Cp*RuCl(cod)] is the best catalyst for the selec-

tive formation of silylated 1,3-dienes, both Cp∧Ru complexesare active catalysts for this transformation. The fact that 4 isactive suggests that it might be present during the catalytictransformation. Dinuclear complexes such as 4 and 5 couldserve as a reservoir for the catalytically active [(cyclopen-tadienyl)RuCl(CHSiMe3)] complexes.

After the successful synthesis of the first Cp∧Ru carbenecomplex, we investigated the possibility of preparing a nitrene/imido complex. Indirect evidence for a Cp∧Ru imido complexwas obtained during our studies of the Cp∧Ru-catalyzed trans-formation of benzylic azides into hydrobenzamide derivatives,which led to the isolation of mononuclear Ru tetrazene com-

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plexes.[4a] These species are believed to form via imido com-plexes.[17]

The reaction of the RuII complex [Cp∧RuCl]2 (6)[3] with abulky tertiary azide, azidoadamantane, was investigated. Azi-doadamantane was added to a solution of 6 in THF and themixture was stirred at room temperature for 12 h (Scheme 3).Work-up of the reaction mixture gave an air-stable, greenmicrocrystalline material in 53 % yield. The structure of theimido complex [Cp∧Ru(NAd)Cl] (7) was evidenced by X-raycrystallography (Figure 4). The structural analysis revealedthat the imido ligand is coordinated in a nearly linear fashion[Ru–N–C = 169.0(2)°].


Figure 4. Graphical representation of the molecular structure of com-plex 7 in the crystal. Hydrogen atoms and disordered moieties areomitted for clarity. Selected bond lengths /Å and angles /°: Ru–Cl =2.3785(9), Ru–N = 1.718(3), N–C = 1.442(4); Ru–N–C = 169.0(2).

Complex 7 is structurally related to the (arene)Ru complex[(η6-cymene)Ru(NAr*)] (Ar* = 1,3,5-tris-tert-butylphenyl)described by Burrell et al..[18] This complex shows a Ru–Nbond length of 1.751(14) Å [7: 1.718(3) Å] and the imido li-gand is also coordinated in a linear fashion [Ru–N–C =178.5(12)°]. Other ruthenium complexes containing a terminalimido ligand have been reported in the literature[19] and someshow interesting catalytic activity.[20] However, to the best ofour knowledge, complex 7 is the only reported cyclopen-tadienyl ruthenium complex bearing a terminal imido ligand.


A Cp∧Ru Complex with an Orthometalated PPh3 Ligand

So far, Cp∧Ru complexes with ruthenium in the oxidationstates +II and +III are known.[1–5] We wanted to explore ifCp∧Ru(I) complexes could be prepared. Therefore, we investi-gated the reaction of [Cp∧RuCl2]2 (1) with strong reducingagents such as sodium in the absence and presence of ad-ditional ligands. Unfortunately, we were not able to isolateCp∧Ru(I) complexes on a preparative scale. However, in thecase of the reaction of [Cp∧RuCl2]2 with sodium in the pres-ence of PPh3, an interesting Cp∧RuII complex was obtained.Details of this transformation are reported below.

When a THF solution of [Cp∧RuCl2]2 and PPh3 was treatedwith sodium, the color of the solution immediately turned vi-olet, indicating the formation of the known RuII complex[Cp∧RuCl(PPh3)].[1] After two days of stirring, the color ofthe solution turned brown-orange. Complex 8 could be isolatedin moderate yield (41 %) as an orange powder by selectiveprecipitation from a concentrated pentane/diethyl ether solu-tion after a filtration step. Orange crystals were obtainedfrom a cold solution of 8 in pentane/THF and the structure wasdetermined by X-ray crystallography (Figure 5). Thestructural analysis showed that the hydrido complex[Cp∧Ru(PPh2C6H4)H]Na had formed (Scheme 4). The forma-tion of 8 likely proceeds via the known RuII complex[Cp∧RuCl(PPh3)]. Further reduction to a Ru0 complex andsubsequent oxidative addition/orthometalation gives the RuII

complex 8.




The structure of complex 8 possesses a crystallographic in-version center. The unit cell shows two [Cp∧Ru(PPh2C6H4)H]anions linked by two Na+ ions. The latter are coordinated tothe methoxy groups of the Cp∧ ligand [Na–O = 2.265(6) Å]and to the hydride ligands [Na–H = 2.37(7)/2.09(7) Å].Furthermore, one can observe close contacts to the metalatedcarbon atom of the phenyl ring [Na–Cortho = 2.596(7) Å] and tothe two adjacent carbon atoms [Na–C = 2.867(8)/2.745(7) Å].

NMR analysis of complex 8 in [D8]THF revealed the pres-ence of two diastereoisomers in the ratio 11:10. The formationof diastereoisomers is attributed to the presence of a ste-reogenic central ruthenium atom along with the Cp∧ ligandwith planar chirality. The formation of dimers, as observed inthe solid state, appears unlikely in a strongly coordinating sol-vent such as THF. The hydride ligand in 8 gives rise to twodoublets around –10 ppm in the 1H NMR spectrum. The signalof the aromatic proton neighboring the orthometalated carbonatom was shifted upfield to 4.3 ppm.

Complex 8 was found to be highly reactive. It reacts withprotic solvents like ethanol, methanol, and water, as well aswith oxygen. When 8 was dissolved in dichloromethane orchloroform, an immediate transformation to [Cp∧RuCl(PPh3)]was observed (evidenced by 31P NMR and its characteristicviolet color).

Ruthenium complexes containing an orthometalated tri-phenylphosphine have been reported.[21] A rare exampleof a fully characterized cyclopentadienyl ruthenium complexwith an orthometalated triphenylphosphine ligand,[CpRu(PPh2C6H4)PPh3] (9), was described by Bruce and co-workers in 1988.[22] Complex 9 was prepared by thermal de-composition of the corresponding methyl complex[CpRu(PPh3)2Me], through release of CH4 associated with or-thometalation. Table 3 gives a comparison of selected bondlengths and angles for complex 8 and 9.

Table 3. Selected bond lengths /Å and angles /° for complexes 8 and[CpRu(PPh2C6H4)PPh3] (9).

8 [CpRu(PPh2C6H4)PPh3][21] (9)

Ru–H 1.65(7) –Ru–P 2.2737(19) 2.277(5)Ru–Cortho 2.104(8) 2.07(2)C–Cortho 1.429(10) 1.40(2)Cortho–Ru–P 67.55(19) 67.2(5)Ru–Cortho–C 106.9(5) 107(1)P–C–Cortho 97.0(5) 98(1)

Bimetallic Complexes

Bimetallic complexes, in which two different metal frag-ments are connected by two or three halogeno bridges, areinteresting compounds for applications in catalysis. For exam-ple, they have been used as catalysts for ring-opening and ring-closing metathesis reactions,[23] for transfer hydrogenations[24]

and for atom transfer radical reactions.[25] Over the last years,our laboratory has reported several new synthetic routes forthe preparation of LnM(μ-Cl)xM�Ln (x = 2 or 3) complexes.[26]

K. Severin et al.ARTICLEIn continuation of these studies, we wanted to explore the pos-sibility to prepare such complexes with Cp∧Ru fragments.

Initial test reactions indicated that mixed arene-cyclopen-tadienyl Ru complexes could be obtained by heating alcoholicsolutions of [Cp∧RuCl2]2 with [(p-cymene)RuCl2]2. Byscreening reaction conditions, we found that microwave heat-ing can be used advantageously for this reaction. A mixture of[Cp∧RuCl2]2 and [(p-cymene)RuCl2]2 in methanol was heatedfor 5 min at 140 °C. After cooling, the bimetallic complex[Cp∧Ru(μ-Cl)3Ru(p-cymene)] (10) was obtained as a red crys-talline material in 75 % yield (Scheme 5). The utilization of aslight excess of [(p-cymene)RuCl2]2 (1.5 equiv.) was found tobe beneficial for obtaining pure product. Complex 10 is dia-magnetic and shows a single set of NMR signals for the Cp∧

and the p-cymene ligand. The reduction of the Cp∧RuIII start-ing material is likely caused by the solvent.


Single crystals of complex 10 were obtained from aCH2Cl2/MeOH solution at low temperature and its structurewas established by single X-ray analysis (Figure 6). The crys-tallographic analysis confirmed that the fragments Cp∧Ru and(p-cymene)Ru are connected by three chloro bridges. Thestructural features of complex 10 are similar to the knowncomplex [Cp*Ru(μ-Cl)3Ru(p-cymene)].[26b]

Figure 6. Graphical representation of the molecular structure of com-plex 10 in the crystal. Hydrogen atoms are omitted for clarity. Selectedbond lengths /Å and angles /°: Ru–Ru = 3.3673(3), Cp∧Ru–Cl =2.4993(7)–2.5524(7), (p-cymene)Ru–Cl = 2.4134(7)–2.4260(7);Cp∧–arene angle = 2.18.

Next, we investigated whether a heterobimetallic complexcan be synthesized by using [Cp*RhCl2]2 instead of[(p-cymene)RuCl2]2. Indeed, the new complex [Cp∧Ru(μ-Cl)3RhCp*] (11) could be obtained in high yield (87 %) whena solution of [Cp∧RuCl2]2 and [Cp*RhCl2]2 in ethanol washeated in a microwave for 5 min at 160 °C (Scheme 6).



Single crystals were obtained from a CH2Cl2/EtOH mixtureat low temperature and the X-ray analysis confirmed that theCp∧Ru and the Cp*Rh fragments are connected by threechloro bridges (Figure 7). As in the case of 10, we assume thatthe solvent acts as reducing agent during this reaction.

Figure 7. Graphical representation of the molecular structure of com-plex 11 in the crystal. Hydrogen atoms are omitted for clarity. Selectedbond lengths /Å and angles /°: Ru–Rh = 3.3171(14), Ru–Cl =2.5258(19)–2.5877(18), Rh–Cl = 2.4213(18)–2.4497(19); Cp∧–Cp*angle = 7.30.

Conclusions

Novel reactions of the dimers [Cp∧RuCl2]2 (1) and[Cp∧RuCl]2 (6) are presented. A dinuclear Cp∧Ru complexwith a bridging alkylidene ligand (4) was obtained in a reactionof 1 with N2CHSiMe3. Complex 4 was found to be a catalystfor the coupling of N2CHSiMe3 and phenylacetylene. A rareexample of a cyclopentadienyl ruthenium complex with a ter-minal imido ligand (7) was obtained by reaction of 6 withazidoadamantane. Attempts to prepare Cp∧Ru(I) complexeswere not successful, but a highly reactive hydrido complexwith an orthometalated PPh3 ligand (8) was obtained instead.Finally, we have described the rapid microwave-assisted syn-thesis of the bimetallic complexes [Cp∧Ru(μ-Cl)3Ru(p-cy-mene)] (10) and [Cp∧Ru(μ-Cl)3RhCp*] (11). Overall, our re-sults further demonstrate the utility of the “Cp-roof” complex[Cp∧RuCl2]2 as a starting material in organometallic synthesisand catalysis.

Experimental Section

General: All experiments were performed in a glovebox in an atmo-sphere of dinitrogen (� 1 ppm of oxygen), unless otherwise stated.Tetrahydrofuran, diethyl ether, benzene, dioxane, pentane, and hexanewere purified by filtration through activated aluminium oxide columnsunder dinitrogen (InnovativeTechnology solvent purification system).


Dry ethanol and methanol were obtained by distillation overmagnesium. The complexes [Cp∧RuCl2]2 (1),[1] [Cp*RuCl2]2 (2),[2]

[Cp∧RuCl]2 (6),[3] [(p-cymene)RuCl2]2,[2] [Cp*RhCl2]2,[2] and[Cp*RuCl(cod)][28] were synthesized according to reported procedures.Trimethylsilyldiazomethane solutions (2 m in ether or hexane) and azi-doadamantane were purchased from Aldrich. 1H, 13C, and 31P spectrawere recorded with a Bruker Advance DPX 400 spectrometer. Elemen-tal analyses were performed with an EA 1110 CHN instrument. ABiotage Initiator 2.0 microwave synthesizer (400 W) and 20 mL mi-crowave vials equipped with magnetic stirring bars were used for thepreparation of complexes 8 and 9.

[(Cp∧Ru)2(μ-Cl)2(μ-CHSiMe3)] (4): N2CHSiMe3 (2 m in diethylether, 250 μL, 0.5 mmol) was added to a solution of [Cp∧RuCl2]2

(300 mg, 0.33 mmol) in THF (25 mL). The color of the solution ini-tially brown immediately turned dark violet and evolution of a gas wasobserved. After 2 h of stirring at room temperature THF was removedand the residue was dried under vacuum. Subsequent extraction withpentane (30 mL) and removal of the solvent yielded the analyticallypure product as a violet solid (yield 270 mg, 88 %). NMR analysisshowed the presence of two diastereoisomers in a ratio of ca. 10:11.A peak assignment was possible by a separate NMR analysis of themeso diastereoisomer. The signals for the meso diastereoisomer areshown in italics. Single crystals were obtained by slow evaporation ofa solution of 4 in THF/hexane. Ru2O2SiCl2C42H76: calcd. C 55.18 H8.38 %; found C 55.08 H 8.34 %. 1H NMR (600 MHz, C6D6): δ =14.84, 14.58 (s, 1 H, CH–SiMe3), 4.71, 4.50, 4.28 (s, 1 H, H–Cp∧),3.49, 3.46 (d, 2JHH = 16.1 Hz, 1 H, CH2–Cp∧), 3.50, 3.47 (d, 2JHH =16.1 Hz, 1 H, CH2–Cp∧), 3.42, 3.39 (d, 2JHH = 16.1 Hz, 1 H, CH2–Cp∧), 3.48, 3.32 (d, 2JHH = 16.1 Hz, 1 H, CH2–Cp∧), 3.30, 3.20, 3.18(s, 3 H, OCH3), 1.83, 1.59, 1.55, 1.51, 1.49, 1.35, 1.17, 1.16, 1.14 (s,9 H, tBu), 0.73, 0.70 ppm (s, 9 H, SiMe3). 13C NMR (150 MHz,C6D6): δ = 217.7, 213.9 (CH–SiMe3), 133.4, 132.0, 129.4 (C13),104.2, 99.1, 96.2, 94.9, 89.3, 88.7, 84.6, 80.0, 76.8 (C10, C11, C12),59.7, 59.2 (C9), 58.54, 56.1, 55.9 (C8), 40.8, 40.1, 40.0 (C7), 33.5–31.7 (C1, C2, C3, C4, C5, C6), 8.4, 7.6 ppm (Si–Me3).

[Cp*RuCl(μ-Cl)(μ-CHSiMe3)RuCp*] (5): N2CHSiMe3 (2 m in di-ethyl ether, 650 μL, 1.25 mmol) was added to a solution of[Cp*RuCl2]2 (200 mg, 0.32 mmol) in THF (20 mL). The color of theinitially brown solution immediately turned green and evolution of agas was observed. After 2 h, the solution was filtered and the residuewas dried under vacuum. Single crystals were obtained by slow evapo-ration of a solution of THF/C6H6. We were not able to obtain complex5 in pure form on a preparative scale. Further analyses were thereforenot performed.

[Cp∧RuCl(NAd)] (7): Azidoadamantane (86 mg, 0.48 mmol) wasadded to a solution of [Cp∧RuCl]2 (200 mg, 0.24 mmol) in THF(10 mL). The solution was stirred for 12 h at room temp. After removalof the solvent, the residue was purified by filtration through aluminawith AcOEt:hexane (2:1) as solvent. The crude product was re-crys-tallized from AcOEt/pentane to give a green, microcrystalline material(yield 143 mg, 53 %). Single crystals were obtained by slow evapora-tion of a hexane solution. RuOClNC29H48: calcd. C 61.84 H 8.59 N


2.49 %; found C 61.73 H 8.62 N 2.48 %. 1H NMR (400 MHz, C6D6):δ = 4.24 (s, 1 H, H–Cp∧), 3.18 (d, 2JHH = 15.9 Hz, 1 H, CH2–Cp∧),3.13 (s, 3 H, OCH3), 2.58 (d, 2JHH = 15.9 Hz, 1 H, CH2–Cp∧), 2.06–2.13 (m, 6 H, Ad), 1.78 (s, 9 H, tBu), 1.73–1.78 (m, 3 H, Ad), 1.57(s, 9 H, tBu), 1.34–1.42 (m, 6 H, Ad), 1.08 ppm (s, 9 H, tBu). 13CNMR (100 MHz, C6D6): δ = 141.6 (C13), 105.6, 96.6, 94.8 (C10, C11,C12), 78.8 (N–C), 70.1 (C8), 56.5 (C9), 40.1 (C-Ad), 39.8 (C7), 35.9(C–Ad), 33.7, 33.6, 33.0 (C4, C5, C6), 33.2, 32.8, 32.0 (C1, C2, C3),29.2 ppm (C–Ad).

[Cp∧Ru(PPh2C6H4)H]Na (8): Sodium (120 mg) and afterwards[Cp∧RuCl2]2 (400 mg, 0.44 mmol) were added to a solution of PPh3

(470 mg, 1.8 mmol) in THF (25 mL). The color of the solution turnedquickly violet. After 3 d of stirring at room temperature the color ofthe solution was brown-orange. The solvent was removed and the resi-due was dried under vacuum for 24 h. The residue was extracted withpentane (50 mL) and diethyl ether (5 mL). Partial evaporation of thefiltrate led to slow precipitation of the product in the form of a yellow-orange powder, which was filtered and dried (yield 256 mg, 41 %).The product was obtained as a mixture of diastereoisomers in a ratioca. 11:10. Single crystals were obtained by slow evaporation of a solu-tion of 8 in THF/pentane solution. RuC37H48OPNa: calcd. C 66.95 H7.29 %; found C 66.59 H 7.76 %. 1H NMR (400 MHz, [D8]THF): δ= 8.05–8.12, 6.98–7.32, 6.45–6.41, 6.10–6.23, 4.33–4.34 (m, PPh3),3.38, 3.32 (s, OCH3), 2.25 (s, H–Cp∧), 2.18 (d, 2JHH = 16.5 Hz, CH2–Cp∧), 1.88 (d, 2JHH = 16.5 Hz, CH2–Cp∧), 1.31, 1.10, 0.97, 0.85, 0.82(tBu), –10.29 (d, 2JPH = 32.4 Hz, Ru–H), –10.32 (d, 2JPH = 33.4 Hz,Ru–H) ppm. 13C NMR (100 MHz, [D8]THF): δ = 116.3–178.9 (PPh3,C13), 99.4, 93.5, 89.5, 88.7, 88.0, 87.2 (C12, C11, C10), 57.3, 56.1(C9), 56.6 (C-orthometallated), 39.7 (C8), 39.4 (C7), 34.5, 34.2, 32.4,32.1, 31.7, 31.6 (C6, C5, C4), 33.7, 33.5, 33.2, 32.8, 32.2, 32.0 ppm(C3, C2, C1). 31P NMR ([D8]THF): δ = –0.45, –0.87 ppm (PPh3).

[Cp∧Ru(μ-Cl)3Ru(p-cymene)] (10): [Cp∧RuCl2]2 (100 mg,0.11 mmol) was suspended in methanol (10 mL) in a microwave vialand [(p-cymene)RuCl2]2 (100 mg, 0.16 mmol) was added. The closedvial was placed in the microwave instrument and heated with stirringat 140 °C for 5 min. After cooling to room temperature the microcrys-talline red precipitate was isolated by filtration, washed with methanol(3 � 5 mL), and dried under vacuum (120 mg, 75 %). Single crystalswere obtained from a CH2Cl2/MeOH solution at low temperature.Ru2Cl3OC29H47: calcd. C 48.36 H 6.58 %; found C 48.26 H 6.52 %.1H NMR (400 MHz, C6D6): δ = 4.82 (d, 3JHH = 6.2 Hz, 2 H, CH–cymene), 4.47 (d, 3JHH = 6.2 Hz, 2 H, CH–cymene), 3.72 (s, 1 H, H–Cp∧), 3.49 (s, 3 H, OCH3), 3.21, 2.79 (d, 2JHH = 16.4 Hz, 1 H, CH2–Cp∧), 2.58 (hept, 3JHH = 6.9 Hz, 1 H, CH(CH3)2–cymene), 1.88 (s, 9H, tBu), 1.71 (s, 3 H, CH3–cymene), 1.66, 1.11 (s, 9 H, tBu), 1.00,0.99 ppm [d, 3JHH = 6.9 Hz, 3 H, CH(CH3)2–cymene]. 13C NMR(100 MHz, C6D6): δ = 122.3 (C13), 98.0, 93.7, 83.5 (C10, C11, C12),77.6, 76.2 (CH–cymene), 69.6, 69.5 (C–cymene), 55.3 (C9), 37.5 (C8),37.5 (C7), 32.8, 32.0, 30.0 (C4, C5, C6), 31.3, 31.2, 31.1 (C1, C2, C3),29.8 [CH(CH3)2–cymene], 21.0, 20.9 [CH(CH3)2–cymene], 17.4 ppm(CH3–cymene).

[Cp∧Ru(μ-Cl)3RhCp*] (11): [Cp∧RuCl2]2 (100 mg, 0.11 mmol) wassuspended in ethanol (10 mL) in a microwave vial and [Cp*RhCl2]2

(69 mg, 0.11 mmol) was added. The closed vial was placed in the mi-crowave instrument and heated with stirring at 160 °C for 5 min. Aftercooling to room temperature the solution was filtered and the solventremoved. The dried residue was extracted with methanol (10 mL) andfiltered. After removal of the solvent, a dark brown microcrystallinematerial was obtained (yield 140 mg, 87 %). Single crystals wereobtained from a CH2Cl2/EtOH solution at low temperature.RuRhCl3OC29H48: calcd. C 48.17 H 6.69 %; found C 48.07 H 6.62

K. Severin et al.ARTICLE%. 1H NMR (400 MHz, C6D6): δ = 3.77 (s, 1 H, H–Cp∧), 3.55 (s, 3H, OCH3), 3.27, 2.83 (d, 2JHH = 16.5 Hz, 1 H, CH2–Cp∧), 1.92, 1.68,1.13 (s, 9 H, tBu), 1.09 ppm (Cp*). 13C NMR (100 MHz, C6D6): δ =122.8 (C13), 92.0, 84.5, 70.3 (C10, C11, C12), 69.0 (C-Cp*) 56.1(C9), 38.6 (C7), 37.5 (C8), 33.7, 32.9, 30.6 (C4, C5, C6), 32.2, 32.0,32.0 ppm (C1, C2, C3).

Crystallographic Analyses: Intensity data were collected with aBruker APEX II CCD (4, 5, 7, 11) and an Oxford Diffraction KM-4CCD diffractometer (10); whereas in the case of 8, a marμx systemwas employed, using graphite monochromatized Mo-Kα radiation (λ =0.71073 Å) at low temperature. Data reduction was carried out withCrysAlis PRO[29] (10), EvalCCD[30] (4, 5, 7, 11), and automar[31] (8).The solutions and refinements were performed by SHELX.[32] Thecrystal structures were refined using full-matrix least-squares based onF2 with all non hydrogen atoms anisotropically defined. Hydrogenatoms were placed in calculated positions by means of the “riding”model. Disorder problems were encountered during the refinement ofcomplex 4, 7, and 8 and treated by the split model. Additional electrondensity (due to very disordered solvent molecules) was found in thedifference Fourier map of compound 10 and treated by the SQUEEZEalgorithm of PLATON.[33]

Crystallographic data (excluding structure factors) for the structures inthis paper have been deposited with the Cambridge CrystallographicData Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK.Copies of the data can be obtained free of charge on quoting thedepository numbers CCDC-984139, -984140, -984141, -984142,-984143, and CCDC-984144 (Fax: +44-1223-336-033; E-Mail:[email protected], http://www.ccdc.cam.ac.uk).

Acknowledgements

The work was supported by the Swiss National Science Foundationand by the Ecole Polytechnique Fédérale de Lausanne (EPFL).

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Received: January 29, 2014Published Online: March 4, 2014

Contributions to the Chemistry of the Cyclopentadienyl Complex [Cp∧RuCl 2 ] 2 (“Cp-roof” = η...

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