Enantioselective Catalysts for the Diels−Alder Reaction betweenMethacrolein and Cyclopentadiene Based on the Chiral Fragment(η5-C5Me5)M(chiral diphosphane) (M = Rh, Ir)Daniel Carmona,* Fernando Viguri, Ainara Asenjo, M. Pilar Lamata, Fernando Lahoz,Pilar Garcıa-Orduna, and L. A. Oro

Instituto de Sıntesis Quımica y Catalisis Homogenea (ISQCH), CSIC - Universidad de Zaragoza, Departamento de QuimicaInorganica, Pedro Cerbuna 12, 50009 Zaragoza, Spain

*S Supporting Information

ABSTRACT: The aqua complexes [(η 5-C5Me5)M(PP*)-(H2O)][SbF6]2 (M = Rh, Ir; PP* = chiral diphosphane) (1−10) are prepared and characterized. These complexes efficientlycatalyze the Diels−Alder reaction between methacrolein andHCp with enantioselectivities of up to 96% e.e. The norphoscomplexes 9 and 10, which are obtained as diastereomericmixtures of the two epimers at the metal, afford the highest e.e. values. The intermediate complexes [(η 5-C5Me5)M(PP*)-(methacrolein)][SbF6]2 (11−20) are also isolated and characterized, including the molecular structure determination of the [(η 5-C5Me5)M(benphos)(methacrolein)][SbF6]2 (M = Rh (13), Ir (14)) derivatives. An NMR study of the reactivity of the metallicintermediates under catalytic conditions explains the high enantioselectivities achieved with the norphos systems.

■ INTRODUCTIONOne of the most powerful strategies for synthesizing enantioenrichedcompounds by asymmetric catalysis involves the use of metal-basedcatalysts. The metal catalyst function is two-fold: it activates thesubstrates with concomitant acceleration of the catalytic process, andsimultaneously, it provides them with the chiral environment capableof generating enantioselectivity.1 Among the wide variety of metal-catalyzed asymmetric processes, the Diels−Alder (DA) reaction isone of the most versatile synthetic transformations for theconstruction of the cyclohexane framework, allowing the formationof up to four contiguous stereocenters in a concerted fashion.2

Recently, one-point-binding half-sandwich complexes of Rh(III),Ir(III), Ru(II), or Os(II) have been developed as catalysts for thisreaction by the groups of Kundig,3 Faller,4 Davies,5 and ourselves.6 Inparticular, we have shown that a chiral rhodium or iridium fragmentcontaining the diphosphane (R)-propane-1,2-diylbis-(diphenylphosphane) ((R)-prophos) (Scheme 1) is well suited for

generating very active and selective catalysts for cycloadditionreactions.6a,j,7 This fragment presents some peculiar features. First,the metal is a stereogenic center. Fortunately, induction from the

enantiopure (R)-prophos ligand renders, in a completely diaste-reoselective manner, only S at the metal derivatives when, forexample, a molecule of water or methacrolein occupies the vacantposition depicted in Scheme 1.7b Moreover, although, in someinstances, epimerization at the metal in half-sandwich complexes is alow-demanding energy process,8 we have not detected changes inthe configuration of the metal from −90 to +20 °C for our fragment.Second, the five-membered metallacycle M−P1−C−C−P2 adopts aλ conformation, this way allowing the methyl group of the (R)-prophos ligand to occupy the less-hindered pseudoequatorialposition (Scheme 2A). This conformation together with the Sconfiguration at the metal determines the chiral bias of the catalystpocket in which catalysis occurs. Third, when methacroleincoordinates at the vacant site, it adopts a planar geometry with anE configuration with respect its CO double bond and an s-transconformation around the single OC−C bond (Scheme 2B). Finally,the methacrolein rotamer around the M−O bond is set, in both thesolid state and solution, by CH/π attractive interactions between theCHO aldehyde proton and the pro-S phenyl ring connected to theP1 phosphorus atom. All these features make the chiral fragment (η 5-C5Me5)M{(R)-prophos} depicted in Scheme 1 a privileged structurefor cycloadditions to methacrolein. In fact, enantioselectivities ≥ 90%e.e. have been achieved in DA reactions between methacrolein andHCp6j as well as in 1,3-dipolar cycloadditions of enals to nitrones.7a−c

With all these concerns in mind, we envisaged the possibility ofextending these studies to other related chiral diphosphanes. Inthis paper, we report on the synthesis and characterization of newrhodium or iridium complexes of the formula [(η 5-C5Me5)M-

Received: September 13, 2011Published: November 21, 2011

Scheme 1. The Chiral Fragment (η 5-C5Me5)M{(R)-prophos)}

Article

pubs.acs.org/Organometallics

© 2011 American Chemical Society 6661 dx.doi.org/10.1021/om200859z |Organometallics 2011, 30, 6661−6673

(PP*)(H2O)][SbF6]2 (M = Rh, Ir), where PP* represents one ofthe chiral diphosphanes outlined in Scheme 3, and on their

application as catalyst precursors for the DA reaction betweenmethacrolein and HCp. The corresponding catalytic intermediatescontaining coordinated methacrolein [(η 5-C5Me5)M(PP*)-(methacrolein)][SbF6]2 are also isolated and characterized,including the molecular structure determination by X-ray diffractionmethods of two of them, namely, (SM,RC)-[(η

5-C5Me5)M-(benphos)(methacrolein)][SbF6]2 (M = Rh, Ir). The origin ofthe high enantioselectivity achieved with the M(norphos) systems(norphos = (1S,2R,3R,4R)-(−)-2,3-bis(diphenylphosphane)-bicyclo[2.2.1]hept-5-ene]) (Scheme 3) is also discussed.

■ RESULTS AND DISCUSSION

The Aqua Compounds [(η 5-C5Me5)M(PP*)(H2O)]-[SbF6]2. Aqua complexes of the general formula [(η 5-C5Me5)-M(PP*)(H2O)][SbF6]2 (M = Rh, Ir) have been prepared bytreating the corresponding dimer9 [{(η 5-C5Me5)MCl}2μ-(Cl)2] in acetone with AgSbF6 and subsequent addition ofthe corresponding diphosphane (eq 1). The intermediatetris(acetone) solvates10 have not been isolated. The presence oftrace amounts of water in the solvent is enough to afford pureaqua complexes 1−10.4e,5c,6e,g,11

During the reaction, the metal becomes a stereogenic center,and therefore, two diastereomers, epimers at the metal, can be

prepared. For complexes 1−8, the reaction is completelydiastereoselective: from −90 °C to RT, only one set of sharpresonances was observed in the 1H, 13C, and 31P NMR spectra.However, the norphos derivatives 9 and 10 are isolated as 79/21 (9) or 76/24 (10) molar ratio mixtures of the two epimersat the metal. As these ratios do not change after several hours indichloromethane solution, we assume that they are thermody-namic equilibrium compositions, in this solvent.Complexes 1−10 were characterized by analytical and

spectroscopic means. Assignment of the NMR signals was verifiedby two-dimensional homonuclear (COSY, NOESY) and hetero-nuclear (13C−1H, 31P−1H) correlations. In particular, the 31PNMR spectra reveal the presence of the coordinate diphosphane.The spectra consist of two doublets of doublets for the rhodiumcompounds (Rh−P and P−P couplings) and of two doublets(only P−P coupling) for the iridium ones. Typical Rh(III)−Pcouplings of about 130 Hz are measured, and as a reflection of thestronger electron-releasing character of the iridium, thephosphorus resonances of the iridium compounds appear around30 ppm shifted to higher energies. Additionally, 31P−1Hcorrelation spectra allow us to assign the downfield resonance tothe phosphorus nucleus nearest to the asymmetric carbon atom,for complexes 1−8. In the 1H NMR spectra, a broad two-protonpeak in the 2.61−4.81 ppm region denotes the presence of watercoordinated to the metal. In complexes 1−8, a NOE correlationbetween the H11 proton (see Scheme 3 for labeling) and the waterprotons indicates an S configuration for the metal12 in a λconformation for the M−P1−C1−C2−P2 metallacycle. Similarly, incomplexes 9 and 10, a NOE correlation of the H2 proton with thewater protons is indicative of an S configuration at the metal forthe major epimers. Finally, one of the methyl groups of the 2-propyl substituent of the valphos complexes 5 and 6 is shiftedabout 1 ppm toward higher field. Most probably, this shift is dueto the shielding of this methyl by the electronic ring current of thepro-R phenyl group bonded to the nearest phosphorus atom.Catalytic Reactions. The water complexes [(η 5-C5Me5)M-

(PP*)(H2O)][SbF6]2 (1−10) efficiently catalyze the Diels−Alderreaction of methacrolein with cyclopentadiene. Table 1 lists aselection of the results together with the reaction conditionsemployed. The collected results are the average of at least twocomparable reaction runs. Catalyst precursors have to be treatedwith methacrolein in the presence of 4 Å MS before the additionof cyclopentadiene. Both rhodium and iridium systems performsimilarly, the iridium system being a little more reactive andenantioselective. Although the catalytic system remains active,Table 1 lists the conversions achieved after reactions werequenched by addition of excess Me4NCl after 1 h of treatment at−20 °C. e.e.'s ≥ 70% for the exo isomer were obtained, the S atthe C2 enantiomer being the most abundant in all cases.13 Inparticular, the Ir/cyphos complex 8 (entry 8) and the M/norphos

Scheme 2. (A) Conformation of the M−P1−C−C−P2 Metallacycle and (B) Geometry of Coordinated Methacrolein

Scheme 3. Chiral Diphosphanes Employed

Organometallics Article

dx.doi.org/10.1021/om200859z |Organometallics 2011, 30, 6661−66736662

complexes 9 and 10 (entries 9 and 10) give e.e.’s greater than90%. These e.e. values are among the highest achieved for one-point-binding catalysts of the half-sandwich type.3−6

The Methacrolein Compounds [(η 5-C5Me5)M(PP*)-(methacrolein)][SbF6]2. Addition of an excess of methacro-lein to dichloromethane solutions of the aqua complexes [(η 5-C5Me5)M(PP*)(H2O)][SbF6]2 affords the correspondingmethacrolein complexes 11−20 (eq 2).

Again, the norphos complexes 19 and 20 are isolated asdiastereomeric mixtures of both epimers at the metal in a 63/37

(19a/19b) or 67/33 (20a/20b) molar ratio. The newcomplexes were characterized by analytical and spectroscopicmeans (see the Experimental Section). Assignment of the NMRsignals was verified by NOE experiments and by two-dimensional homonuclear and heteronuclear (13C−1H,31P−1H) correlations. The 1H NMR spectra denote the presenceof the C5Me5, PP*, and methacrolein ligands in a 1/1/1 molarratio. In particular, the CHO functionality originates a mediumintensity ν(CO) absorption around 1600 cm−1 in the IR spectraand a 13C resonance at δ = 208−210 ppm. NOE correlationsbetween the H11, H21, or H22 protons of the diphosphane (seeScheme 3) and the CHO, Me (methacrolein), or C5Me5 protonsstrongly suggest an S configuration for the metal in a λconformation for the M−P1−C1−C2−P2 metallacycle forcomplexes 11−18. NOE correlations between the CHO andH2 protons indicate an S configuration at the metal for the mostabundant epimer of compounds 19 and 20. Notably, a generalfeature of compounds 11−20 is that the CHO proton resonatesin the 7.2−8.0 ppm interval, that is, 2.3−1.5 ppm shifted towardhigher energies, with respect to the corresponding free enal. Ithas been previously reported that, for [(η 5-C5Me5)M{(R)-prophos}(enal)]2+ cations, the electronic ring current of the pro-S phenyl group connected to the P1 atom of the diphosphane,related to the existence of CH/π attractive interactions betweenthe CHO proton and this phenyl ring, are in the origin of such astrong shielding.7a−c The molecular structures of the benphosrhodium (13) and iridium (14) complexes reveal a comparableset of interactions in the solid state.Molecular Structures of Compounds 13 and 14. The

molecular structures of complexes 13 and 14 have beendetermined by X-ray diffraction methods.14 Selected bond lengthsand angles are reported in Table 2. Figure 1 shows an ORTEPdiagram of the cation of complex 13 (for a similar view of thecation of 14, see the Supporting Information). Both structuresresulted to be isostructural with analogous structural features.Although we will comment on some structural data of complex14, we are going to center the discussion on complex 13. In bothstructures, the metal atom is pseudotetrahedral, being coordinatedto a C5Me5 ring, to the two phosphorus atoms of the benphoschelate, and to the oxygen atom of the methacrolein ligand. Also,for both complexes, the configuration at the metal is S and thefive-membered metallacycle M−P(1)−C(36)−C(35)−P(2)presents a λ conformation (Cremer and Pople parameters: Q2 =0.579(9) Å and ϕ2 = 75.0(5)° (complex 13) and Q2 = 0.572(4) Å

Table 1. Enantioselective DA Reaction between Methacroleinand Cyclopentadiene Catalyzed by Complexes 1−10a

entry complex diphosphaneconv.b,c

(%)isomer ratioc (exo/

endo) (%)e.e.d

(%)

1 1 (Rh) phenphos 88 98/2 79 (S)2 2 (Ir) phenphos 88 96/4 80 (S)3 3 (Rh) benphos 95 99/1 79 (S)4 4 (Ir) benphos 95 98/2 89 (S)5 5 (Rh) valphos 85 96/4 70 (S)6 6 (Ir) valphos 90 96/4 74 (S)7 7 (Rh) cyphos 85 98/2 88 (S)8 8 (Ir) cyphos 93 98/2 96 (S)9 9 (Rh) norphos 82 98/2 93 (S)10 10 (Ir) norphos 93 98/2 96 (S)

aReaction conditions: catalyst, 0.025 mmol (5 mol %); methacrolein,0.5 mmol; HCp, 3 mmol; 4 mL of CH2Cl2; 100 mg of 4 Å molecularsieves; temperature, −20 °C; reaction time, 1 h. bBased onmethacrolein. cDetermined by GC. dIn the exo isomers. Determinedby 1H NMR with the chiral shift reagent (+)−Eu(hfc)3.

Table 2. Selected Bond Lengths (Å) and Angles (°) for Complexes 13 and 14

13 14 13 14

M−P(1) 2.331(2) 2.320(3) P(1)−C(11) 1.804(9) 1.794(10)M−P(2) 2.360(2) 2.337(3) P(1)−C(17) 1.767(10) 1.810(9)M−O 2.163(2) 2.152(6) P(1)−C(36) 1.848(10) 1.847(11)M−Ga 1.854(9) 1.869(11) P(2)−C(29) 1.825(9) 1.821(10)O−C(38) 1.254(11) 1.259(12) P(2)−C(23) 1.799(10) 1.827(10)C(38)−C(39) 1.396(16) 1.432(16) P(2)−C(35) 1.806(11) 1.797(12)C(39)−C(40) 1.292(17) 1.304(16) C(35)−C(36) 1.552(12) 1.574(14)C(39)−C(41) 1.561(17) 1.436(17) C(36)−C(37) 1.547(14) 1.540(16)P(1)−M−P(2) 83.20(9) 83.2(1) C(37)−C(50) 1.517(13) 1.501(15)P(1)−M−O 85.04(18) 84.9(2) M−O−C(38) 131.2(7) 128.4(6)P(1)−M−Ga 131.3(3) 131.7(3) O−C(38)−C(39) 124.3(10) 121.9(9)P(2)−M−O 86.2(2) 84.6(2) C(38)−C(39)−C(40) 118.2(9) 115(1)P(2)−M−Ga 131.3(3) 131.8(3) C(38)−C(39)−C(41) 116(1) 118(1)O−M−Ga 123.9(3) 124.0(3) C(40)−C(39)−C(41) 125(1) 125(1)

aG represents the centroid of the η 5-C5Me5 ligand.

Organometallics Article

dx.doi.org/10.1021/om200859z |Organometallics 2011, 30, 6661−66736663

and ϕ2 = 77.2(5)° (complex 14)).15 As it has been established thatboth complexes present the same configuration and conformationin solution (see above), it can be concluded that both features areretained on going from the solid state to solution and vice versa.The two M−P distances are slightly different from each other,

specially in the cation of 13 where the Rh−P(1) and Rh−P(2)bond lengths differ by 0.029(2) Å. A similar dissymmetry has beenobserved in other Rh complexes containing (η 5-C5Me5)Rh(PP*)fragments,16,17 which has been associated with the different stericrequirements of dissimilarly substituted P atoms.The methacrolein ligand exhibits a planar s-trans conformation

with an E configuration around the carbonylic double bond, inagreement with related chiral half-sandwich Lewis acid−methacrolein complexes previously reported.3c,6b,7b The partialdelocalization of the π-electron density in the conjugated systemO−C(38)−C(39)−C(40) is evidenced by the shortening of theC(38)−C(39) single bond (1.396(16) Å (13), 1.432(16) Å (14))and the elongation of the O−C(38) double bond (1.254(11) Å(13), 1.259(12) Å (14)) distances, when compared with the meanvalues of these bond distances in related uncoordinated organicsystems (C−C, 1.464(18) Å; OC, 1.192(5) Å).18

From a catalytic point of view, an important feature of thesecomplexes is the conformation of the methacrolein into thechiral pocket generated by the C5Me5 and chiral diphosphaneligands. The G−Rh−O−C(38) torsion angle (G representsthe centroid of the η 5-C5Me5 ligand) characterizes the relativedisposition of the methacrolein and pentamethylcyclopenta-dienyl planes, as well as the rotamer around the Rh−O bond. Avalue of 90° places both planes in a parallel disposition, and

values around 0° or 180° correspond to perpendicular planes.An in-between value of −55.8(9)° has been found for 13,pointing to an intermediate relative orientation. This situation isonly slightly different from that observed in the related prophoscomplex [(η 5-C5Me5)Rh{(R)-prophos}(methacrolein)]-[SbF6]2, where a dihedral angle of −64.6(6)° was found.7b Inthe resulting Rh−O rotamer, the methacrolein plane is almostparallel to the pro-S phenyl ring connected to the P(1) atom(dihedral angle between the mean planes, 14.5(5)°) and quasi-orthogonal to the pro-S phenyl ring connected to the P(2) atom(dihedral angle, 87.5(4)°). This rotamer allows for theestablishment of CH/π interactions (Figure 2) between the

CHO methacrolein proton (H(38)) and the C(17)−C(22) bondof the pro-S phenyl ring of the P(1)Ph2 group, as well as betweena hydrogen of the CH3 group of the methacrolein, H(41A), andthe C(27)−C(28) bond of the pro-S phenyl ring of the P(2)Ph2group. These interactions are characterized by short H···phenylplane ring separations (2.99 and 2.79 Å) and H···C interatomicdistances (2.91−3.08 Å), clearly shorter than the sum of the vander Waals radii (Table 3).19 Notably, these interactions set themethacrolein M−O rotamer and, therefore, are responsible forthe high enantioselectivities achieved in the Diels−Alder reactioninvestigated. In fact, the sign of the enantioselectivity obtained(exo-(S) enantiomer) corresponds to a preferential attack ofHCp to the Re-face of the coordinated methacrolein.Accordingly, in the X-ray structure of the cations of complexes13 and 14, this face is exposed to the attack, whereas the Si-face isshielded by the pro-S phenyl ring of the P(1)Ph2 group.On the Origin of the Enantioselectivity for M/norphos

Systems (M = Rh, Ir). As we stated above, the norphos-containing complexes [(η 5-C5Me5)M(norphos)(H2O)][SbF6]2 (M = Rh (9), Ir (10)) and [(η 5-C5Me5)M(norphos)-(methacrolein)][SbF6]2 (M = Rh (19), Ir (20)) are obtainedas diastereomeric mixtures of both epimers at the metalin molar ratios of SRh-9/RRh-9, 79/21; SIr-10/RIr-10, 76/24;

Figure 1. ORTEP diagram of the cation of complex 13. H atoms areomitted for clarity.

Figure 2. CH/π interactions in complex 13.

Table 3. Selected Structural Parameters (Å, °) Concerning CH/π Interactions for Complex 13a,b

H···G′ H···Ph (plane) γ angle C−H···C C−H···C(Ph)

C(38)−H(38)···C(17)/C(22) 3.160 2.986 19.1 C(17): 3.082 3.453−3.812C(22): 3.059

C(41)−H(41A)···C(27)/C(28) 2.833 2.788 10.2 C(27): 2.913 3.100−3.339C(28): 3.007

aFor the corresponding parameters of the cation of complex 14, see the Supporting Information. bH···G′ represents the distance from the H atom tothe centroid of the phenyl ring of the reported C−H···π interaction. H···Ph is the separation from the H atom to the mean plane of the phenyl ring.γ angle: angle between the H−G′ vector and the normal of the phenyl ring. C−H···C: contact distances between H atom under the assumed criterion(3.05 Å). C−H···C(Ph): separation between H and the rest of the carbon atoms of the phenyl ring.

Organometallics Article

dx.doi.org/10.1021/om200859z |Organometallics 2011, 30, 6661−66736664

SRh-19/RRh-19, 63/37; and SIr-20/RIr-20, 67/33.20 All theremaining related compounds of the formula [(η 5-C5Me5)M-(PP*)(methacrolein)][SbF6]2 (11−18) are obtained as pureSM epimers.In a recent study, we have shown that the two epimers at the

metal of the related nitrile-containing compounds (SM,RC andRM,RC)-[(η

5-C5Me5)M{(R)-prophos}(α ,β-unsaturatednitrile)][SbF6]2 (M = Rh, Ir) induce divergently in the catalytic1,3-dipolar cycloaddition between methacrylonitrile and 3,4-dihydroisoquinoline N-oxide: the SM isomer preferentially givesthe S3C,R5C cycloadduct and the RM, the R3C,S5C one.7d

Taking into account these results, an erosion of theenantioselectivity would be expected when mixtures of epimersat the metal were used as catalysts. However, the e.e. valuescollected in Table 1 show that the opposite is true because thehighest values of enantioselectivity were achieved with thenorphos systems. To try to explain this unexpected catalyticoutcome, we studied, as a model, the reaction betweenmethacrolein and cyclopentadiene catalyzed by the mixture ofiridium epimers SIr-20/RIr-20, generated in situ from thecorresponding aqua complexes SIr-10/RIr-10.At this point, it is useful to remember that (i) in this reaction,

four adducts, namely, exo-(S), exo-(R), endo-(S), and endo-(R),can be formed, as specified in Figure 3, and (ii) the commonly

assumed pathway for this reaction (Figure 4) involves thecyclopentadiene attack to coordinated methacrolein (step 1),

followed by the displacement of the coordinated adduct bymethacrolein (step 2).According to step 1, 31P NMR measurements reveal that the

addition of an equimolar amount of HCp to the methacrolein

complex 20 instantaneously produces the quantitative for-mation of a mixture of new metallic complexes. Thus, the twopairs of doublets assigned to the two epimers of complex 20(trace a, Figure 5) disappear and two new iridium complexes,

labeled as I and II, are formed (trace b). Minute quantities ofsome other complexes are also detected. A Diels−Alder adductwith an exo/endo molar ratio of 98/2 and an e.e. of 96% (exo)was obtained when an excess of NMe4Cl was added to asolution of spectrum b. Figure 5 also reveals that the chemicalshift of the P1 and P2 phosphorus atoms of the RIr-20 and SIr-20isomers, respectively, are much more sensible to the metalenvironment than the two remaining phosphorus nuclei are.For this reason, from now on, we will only show the high-fielddoublet for the complexes we discuss.To ascertain the actual nature of the new species I and II, we

monitored, by 31P NMR, the addition of mixtures of adducts oftwo compositions, A and B21 (see Scheme 4), to a 76/24 = SIr-10/RIr-10 molar ratio mixture of the aqua complex [(η 5-C5Me5)Ir(norphos)(H2O)][SbF6]2, in the presence of 4 Åmolecular sieves as a water scavenger. Under these conditions,the formation of Ir-adduct species is plausible. Mixture A is aracemate with an exo/endo molar ratio of 86/14, and Brepresents a 98/2, exo/endo mixture with 96% e.e. in the majorcomponent (Scheme 4). Addition of an equimolar amount of Ato complex 10 affords four new complexes, labeled I−IV intrace a of Figure 6, together with other minor metallic species.In an independent experiment, an equimolar amount of B wasadded to complex 10, mostly rendering complexes I, II, and IV(Figure 6, trace b).Compounds I and II are formed in the three experiments,

and taking into account the performed reactions, the isomericcompositions of the iridium complexes involved, and thereagents and conditions employed, they have to be the SIr andRIr isomers of the Ir-adduct complex [(η 5-C5Me5)Ir(norphos)-(adduct)]2+ with the exo-(S) adduct coordinated to the metal.

Figure 3. Possible cycloadducts for the DA reaction betweenmethacrolein and cyclopentadiene.

Figure 4. Plausible catalytic cycle.

Figure 5. 31P NMR spectra, in CD2Cl2, at −20 °C, of compound [(η 5-C5Me5)Ir(norphos)(methacrolein)][SbF6]2 (a) and after addition ofHCp (b).

Organometallics Article

dx.doi.org/10.1021/om200859z |Organometallics 2011, 30, 6661−66736665

Formation of almost only I and II from an SIr-20/RIr-20mixture (Figure 5) implies that, with high selectivity, an exoattack through the Re-face of the methacrolein takes place inboth iridium epimers (see Figure 3). That is, both epimers areactive Diels−Alder catalysts for the reaction studied and bothinduce the preferential formation of the same Diels−Alderstereoisomer. Therefore, as a whole, high selectivities areachieved because the stereochemistry of the adducts isgoverned by the configuration of the chiral diphosphane. Theselectivity values obtained with the rhodium system point to asimilar explanation.On the other hand, we assign the resonances III and IV

(Figure 6) to the [(η 5-C5Me5)Ir(norphos)(adduct)]2+ species

in which the exo-(R) adduct is coordinated to the iridium withRIr and SIr configurations, respectively. The remaining minordoublets detected stand for the Ir-adduct complexes with endo-(S) and endo-(R) adducts coordinated to the metal.Finally, taking advantage of the availability of solutions

containing mixtures of Ir-adduct complexes, we studied thedissociation of adducts from them by addition of methacrolein,according to step 2 of the catalytic cycle depicted in Figure 4.Trace a in Figure 7 corresponds to the high-field part of the 31PNMR spectrum, at −40 °C, of the CD2Cl2 solution obtainedafter addition of an equimolar amount of mixture A (Scheme 4)to the aqua complex [(η 5-C5Me5)Ir(norphos)(H2O)][SbF6]2(10). Traces b, c, and d (Figure 7) show the same spectral zoneafter the subsequent addition of 0.3, 0.5, or 0.7 equiv ofmethacrolein. Before the addition of methacrolein (trace a),nine doublets are detected. As we have previously shown,doublets I, II, III, and IV correspond to the four Ir-adductcomplexes in which the exo adducts are coordinated to themetal. We tentatively assign the doublets labeled A, B, C, and Dto the four Ir-adduct complexes with coordinated endo adducts.The remaining doublet, centered at 5.35 ppm, corresponds toresidual aqua complex 10. As methacrolein was added, two

doublets, attributed to the two epimers at the metal of themethac ro l e in complex [(η 5 -C5Me5) I r (norphos) -(methacrolein)][SbF6]2 (20), increased at the expense of theIr-adduct complexes. We have also recorded the spectracorresponding to addition of 0.4, 0.6, and 0.9 equiv ofmethacrolein (spectra not shown in Figure 7). Figure 8 shows

the decreasing of the concentration of the Ir-adducts I−IV withrespect to the amount of methacrolein added. The rate ofdissociation of the exo-(R) adducts from complexes III and IVis greater than that of the exo-(S) adducts from complexes I andII. No equilibria are established between the metallic speciesduring the recording time of the spectra. Therefore, only thepreferential formation of the exo-(S) adducts for both epimersat the metal in step 1 accounts for the observedenantioselectivity. Thus, step 1 is the enantio-determining step.

Scheme 4. Reaction of Complex 10 with Mixtures A and B

Figure 6. Fragments of the 31P NMR spectra, in CD2Cl2, at −70 °C,after addition of equimolar amounts of A (a) or B (b) to complex 10.

Figure 7. High-field 31P NMR resonances, in CD2Cl2, at −40 °C, ofmixtures of Ir-adduct complexes: before methacrolein addition (a) andafter addition of 0.3 (b), 0.5 (c), or 0.7 equiv (d) of methacrolein.

Figure 8. Variation of the concentration of Ir-adduct complexes I−IVwith the addition of methacrolein.

Organometallics Article

dx.doi.org/10.1021/om200859z |Organometallics 2011, 30, 6661−66736666

Finally, Figure 9 shows the relative concentration ofcomplexes SIr-20 and RIr-20 formed by the addition of

methacrolein. Notably, during the addition, the molar ratio ofSIr-20/RIr-20 is almost constant (straight lines) and its value isabout 2. This value is very similar to the 67/33 equilibriumratio attained when these compounds are prepared (see above).Thus, after formation of these stereoisomers from the Ir-adductspecies, the equilibrium composition is achieved by, ifnecessary, instantaneous epimerization at the metal.

■ CONCLUSIONThe new diphosphane complexes [(η 5-C5Me5)M(PP*)-(H2O)][SbF6]2 (M = Rh, Ir) generate very efficient systemsfor the Diels−Alder reaction between methacrolein andcyclopentadiene with an e.e. up to 96%. The stereochemistryof coordinated methacrolein in the metallic intermediates [(η 5-C5Me5)M(PP*)(methacrolein)][SbF6]2 accounts for the en-countered enantioselectivity. The M/norphos complexes areobtained as a mixture of epimers at the metal. However, theygive rise to the most enantioselective systems because thisselectivity is not governed by the configuration at the metal, butby that of the diphosphane ligand.

■ EXPERIMENTAL SECTIONAll solvents were treated in a PS-400-6 Innovative TechnologiesSolvent Purification System (SPS) and degassed prior to use. Allpreparations have been carried out under argon. Infrared spectra wereobtained as net solids with a PerkinElmer Spectrum 100spectrophotometer. Carbon, hydrogen, and nitrogen analyses wereperformed using a PerkinElmer 2400 CHNS/O microanalyzer. ProtonNMR spectra were recorded on Bruker Avance-300 (300.13 MHz),400 (400.16 MHz), or 500 (500.13 MHz) spectrometers. Chemicalshifts are expressed in parts per million upfield from SiMe4 or 85%H3PO4 (

31P). NOEDIFF and 13C, 31P, and 1H correlation spectra wereobtained using standard procedures. Gas chromatography wasperformed on a Hewlet-Packard 3398 gas chromatograph equippedwith a split-mode capillary injection system and a flame ionizationdetector. (R)-phenphos, (R)-benphos, (R)-valphos, and (R)-cyphoswere synthesized from (S)-mandelic acid (Aldrich), L-phenylalanine(Acros), L-valine (Acros) and (S)-hexahydromandelic acid (Fluka),respectively, and NaPPh2 or LiPPh2 according to the literatureprocedures.22 (1S,2R,3R,4R)-norphos was purchased from StremChemical Co.Preparation of the Complexes [(η 5-C5Me5)M(PP*)(H2O)]-

[SbF6]2 (1−10). To a suspension of the appropriate [{(η 5-C5Me5)-MCl}2(μ-Cl)2] dimer (0.400 mmol), in acetone (20 mL), was addedAgSbF6 (551.3 mg, 1.604 mmol). The resulting suspension was stirredat room temperature for 4 h. The mixture was filtered through acannula and the precipitate washed with 3 × 2 mL of acetone. Thefiltrate was concentrated to ca. 10 mL and cooled to −25 °C, and the

corresponding solid PP* ligand (0.800 mmol) was added. Thesolution was stirred at −25 °C for 1 h (3 h when PP* = norphos) andthen vacuum-concentrated to ca. 5 mL. Addition of 20 mL of n-hexanegave orange oils. Vigorous stirring in n-hexane affords orange (Rh)or yellow (Ir) solids. The solutions were poured off and the solidswashed with n-hexane (3 × 10 mL) and then vacuum-dried. The solidswere recrystallized three times, at −25 °C, from CH2Cl2/n-hexane(1/5, v/v).(SRh,RC)-[(η

5-C5Me5)Rh(phenphos)(H2O)][SbF6]2 (1).

Yield: 80%. Anal. Calcd for C42H45F12RhOP2Sb2: C, 42.0; H,3.8. Found: C, 41.9; H, 3.9. IR (solid, cm−1): ν(H2O) 3519(w), ν(SbF6) 650 (s). 1H NMR (400.16 MHz, CD2Cl2,−25 °C): δ = 7.96−6.64 (25H, Ph), 4.18 (m, 1H, H11), 3.44(dt, J = 52.8, 12.9 Hz, 1H, H22), 3.14 (bs, 2H, H2O), 3.01 (ddd,J = 22.3, 15.1, 6.9 Hz, 1H, H21), 1.40 ppm (t, J = 3.1 Hz, 15H,C5Me5).

13C NMR (100.61 MHz, CD2Cl2, −25 °C): δ =135.94−128.47 (30C, Ph), 106.01 (bs, C5Me5), 42.02 (dd,J(P,C) = 24.8, 12.8 Hz, C1), 29.96 (dd, J(P,C) = 35.7, 19.8 Hz,C2), 14.20 ppm (C5Me5).

31P NMR (161.96 MHz, CD2Cl2,−25 °C): δ = 77.74 (dd, J(Rh,P1) = 130.5 Hz, J(P2,P1) =43.6 Hz, P1), 41.52 ppm (dd, J(Rh,P2) = 131.5 Hz, P2).(SIr,RC)-[(η

5-C5Me5)Ir(phenphos)(H2O)][SbF6]2 (2).

Yield: 85%. Anal. Calcd for C42H45F12IrOP2Sb2: C, 39.1; H, 3.5.Found: C, 39.2; H, 3.7. IR (solid, cm−1): ν(H2O) 3497 (w),ν(SbF6) 653 (s). 1H NMR (400.16 MHz, CD2Cl2, −25 °C):δ = 7.96−7.64 (25H, Ph), 4.08 (m, 1H, H11), 3.86 (bs, 2H,H2O), 3.44 (dddd, J = 48.4, 15.7, 11.4, 4.2 Hz, 1H, H22), 2.98(m, 1H, H21), 1.45 ppm (s, 15H, C5Me5).

13C NMR (100.61MHz, CD2Cl2, −25 °C): δ = 135.55−128.37 (30C, Ph), 99.93(s, C5Me5), 42.64 (dd, J(P,C) = 30.4, 9.3 Hz, C1), 30.05 (dd,J(P,C) = 37.7, 16.1 Hz, C2), 8.66 ppm (C5Me5).

31P NMR(161.96 MHz, CD2Cl2, −25 °C): δ = 48.78 (d, J(P2,P1) = 17.1Hz, P1), 17.43 ppm (d, P2).(SRh,RC)-[(η

5-C5Me5)Rh(benphos)(H2O)][SbF6]2 (3).

Yield: 82%. Anal. Calcd for C43H47F12RhOP2Sb2: C, 42.5; H,3.9. Found: C, 42.5; H, 3.7. IR (solid, cm−1): ν(H2O) 3552(w), ν(SbF6) 654 (s). 1H NMR (500.13 MHz, CD2Cl2,−25 °C): δ = 8.00−7.13 (25H, Ph), 3.26 (d, J = 12.3 Hz, 1H, H31),

Figure 9. Relative concentration of the methacrolein epimers SIr-20and RIr-20 with respect to the amount of methacrolein added.

Organometallics Article

dx.doi.org/10.1021/om200859z |Organometallics 2011, 30, 6661−66736667

3.00 (dt, J = 53.4, 14.6 Hz, 1H, H22), 2.86 (m, 1H, H11), 2.61(bs, 2H, H2O), 2.29 (ddd, J = 19.8, 14.5, 5.2 Hz, 1H, H21), 2.00(m, 1H, H32), 1.44 ppm (s, 15H, C5Me5).

13C NMR (125.77MHz, CD2Cl2, −25 °C): δ = 137.92−127.71 (30C, Ph), 105.95(s, C5Me5), 37.36 (dd, J(P,C) = 30.2, 9.5 Hz, C1), 35.66 (d, J =12.3 Hz, C3), 27.60 (dd, J(P,C) = 33.0, 16.7 Hz, C2), 9.20 ppm(C5Me5).

31P NMR (202.48 MHz, CD2Cl2, −25 °C): δ = 70.78(dd, J(Rh,P1) = 131.7 Hz, J(P2,P1) = 41.9 Hz, P1), 44.09 ppm(dd, J(Rh,P2) = 132.6 Hz, P2).(SIr,RC)-[(η

5-C5Me5)Ir(benphos)(H2O)][SbF6]2 (4).

Yield: 77%. Anal. Calcd for C43H47F12IrOP2Sb2: C, 39.4; H, 4.1.Found: C, 39.6; H, 3.6. IR (solid, cm−1): ν(H2O) 3542 (w),ν(SbF6) 653 (s). 1H NMR (500.13 MHz, CD2Cl2, −25 °C):δ = 7.99−7.09 (25H, Ph), 3.25 (d, J = 12.5 Hz, 1H, H31), 3.07(bs, 2H, H2O), 2.98 (m, 1H, H22), 2.78 (m, 1H, H11), 2.27(ddd, J = 21.4, 15.2, 6.1 Hz, 1H, H21), 1.91 (dt, J = 14.2, 6.6 Hz,1H, H32), 1.49 ppm (s, 15H, C5Me5).

13C NMR (125.77 MHz,CD2Cl2, −25 °C): δ = 138.20−127.73 (30C, Ph), 99.71 (s,C5Me5), 37.59 (dd, J(P,C) = 34.1, 8.6 Hz, C1), 34.91 (d, J =16.3 Hz, C3), 27.76 (dd, J(P,C) = 38.3, 15.5 Hz, C2), 8.81 ppm(C5Me5).

31P NMR (202.48 MHz, CD2Cl2, −25 °C): δ = 42.95(d, J(P2,P1) = 14.7 Hz, P1), 19.35 ppm (d, P2).(SRh,RC)-[(η

5-C5Me5)Rh(valphos)(H2O)][SbF6]2 (5).

Yield: 83%. Anal. Calcd for C39H47F12RhOP2Sb2·CH2Cl2: C,38.3; H, 3.9. Found: C, 38.0; H, 3.9. IR (solid, cm−1): ν(H2O)3531 (w), ν(SbF6) 653 (s). 1H NMR (500.13 MHz, CD2Cl2,−25 °C): δ = 7.95−7.29 (20H, Ph), 3.25 (dt, J = 55.5, 13.5 Hz,1H, H22), 2.78 (bs, 2H, H2O), 2.57 (m, 1H, H11), 2.42 (m, 1H,H21), 2.20 (m, 1H, H3), 1.42 (m, 15H, C5Me5), 1.15 (d, J = 6.3Hz, 3H, CH3), 0.13 ppm (d, J = 6.3 Hz, 3H, CH3).

13C NMR(125.77 MHz, CD2Cl2, −25 °C): δ = 134.86−119.68 (24C,Ph), 105.89 (s, C5Me5), 40.55 (dd, J(P,C) = 28.7, 9.7 Hz, C1),27.49 (dd, J = 15.4, 5.3 Hz, C3), 24.48 (d, J = 9.1 Hz, CH3),24.22 (dd, J(P,C) = 34.0, 14.3 Hz, C2), 17.20 (CH3), 9.16 ppm(C5Me5).

31P NMR (202.48 MHz, CD2Cl2, −25 °C): δ = 74.71(dd, J(Rh,P1) = 129.6 Hz, J(P2,P1) = 41.7 Hz, P1), 46.80 ppm(dd, J(Rh,P2) = 133.0 Hz, P2).(SIr,RC)-[(η

5-C5Me5)Ir(valphos)(H2O)][SbF6]2 (6).

Yield: 91%. Anal. Calcd for C39H47F12IrOP2Sb2: C, 37.25;H, 3.8. Found: C, 36.8; H, 3.7. IR (solid, cm−1): ν(H2O)3480 (w), ν(SbF6) 651 (s). 1H NMR (500.13 MHz, CD2Cl2,−25 °C): δ = 7.91−7.23 (20H, Ph), 4.31 (bs, 2H, H2O),3.20 (dt, J = 50.55, 15.1 Hz, 1H, H22), 2.65 (m, 1H, H11),2.40 (m, 1H, H21), 2.21 (m, 1H, H3), 1.45 (s, 15H, C5Me5),1.19 (d, J = 6.5 Hz, 3H, CH3), 0.09 ppm (d, J = 6.3 Hz,3H, CH3).

13C NMR (125.77 MHz, CD2Cl2, −25 °C):δ = 134.80−119.95 (24C, Ph), 99.73 (s, C5Me5), 40.67(dd, J(P,C) = 34.6, 7.0 Hz, C1), 26.47 (dd, J = 14.5, 4.2 Hz,C3), 24.74 (d, J = 10.0 Hz, CH3), 24.17 (dd, J(P,C) = 40.8,12.5 Hz, C2), 17.03 (s, CH3), 8.72 ppm (C5Me5).

31P NMR(202.48 MHz, CD2Cl2, −25 °C): δ = 46.95 (d, J(P2,P1) = 14.2Hz, P1), 22.58 ppm (d, P2).(SRh,RC)-[(η

5-C5Me5)Rh(cyphos)(H2O)][SbF6]2 (7).

Yield: 94%. Anal. Calcd for C42H51F12RhOP2Sb2: C, 41.9;H, 4.75. Found: C, 41.75; H, 4.25. IR (solid, cm−1): ν(H2O)3538 (w), ν(SbF6) 650 (s). 1H NMR (300.13 MHz,CD2Cl2, −25 °C): δ = 7.93−6.97 (20H, Ph), 3.28 (dt,J = 57.3, 13.2 Hz, 1H, H22), 2.75 (bs, 2H, H2O), 2.49 (m,1H, H11), 2.41 (m, 1H, H21), 1.74−0.70 (m, 11H, cy), 1.41ppm (t, J = 3.0 Hz, 15H, C5Me5).

13C NMR (75.48 MHz,CD2Cl2, −25 °C): δ = 134.93−120.70 (24C, Ph), 105.87(s, C5Me5), 40.34 (dd, J(P,C) = 28.1, 9.0 Hz, C1), 37.23−22.94 (6C, cy), 25.00 (m, C2), 9.16 ppm (C5Me5).

31P NMR(121.48 MHz, CD2Cl2, −25 °C): δ = 75.33 (dd, J(Rh,P1) =129.5 Hz, J(P2,P1) = 41.3 Hz, P1), 47.04 ppm (dd, J(Rh,P2) =132.8 Hz, P2).(SIr,RC)-[(η

5-C5Me5)Ir(cyphos)(H2O)][SbF6]2 (8).

Yield: 88%. Anal. Calcd for C42H51F12IrOP2Sb2: C, 38.9; H,4.0. Found: C, 39.1; H, 4.1. IR (solid, cm−1): ν(H2O) 3524(w), ν(SbF6) 652 (s). 1H NMR (500.13 MHz, CD2Cl2,−25 °C): δ = 7.91−7.26 (20H, Ph), 3.99 (bs, 2H, H2O),3.23 (dt, J = 51.6, 11.6 Hz, 1H, H22), 2.52 (m, 1H, H11), 2.39(m, 1H, H21), 1.75−0.70 (11H, cy), 1.44 ppm (s, 15H, C5Me5).13C NMR (125.77 MHz, CD2Cl2, −25 °C): δ = 134.81−119.81(24C, Ph), 99.72 (s, C5Me5), 40.60 (dd, J(P,C) = 33.8, 7.1 Hz,C1), 36.41−22.87 (6C, cy), 25.19 (dd, J(P,C) = 40.8, 12.6 Hz,C2), 8.75 ppm (C5Me5).

31P NMR (202.48 MHz, CD2Cl2,−25 °C): δ = 47.47 (d, J(P2,P1) = 14.2 Hz, P1), 23.22 ppm(d, P2).[(η 5-C5Me5)Rh(norphos}(H2O)][SbF6]2 (9). Yield: 99%. Molar

ratio of S at the metal (9a) to R at the metal (9b) epimer: 79/21. Anal.

Calcd for C41H45F12RhOP2Sb2: C, 41.4; H, 3.8. Found: C, 41.9; H, 3.9.

IR (solid, cm−1): ν(H2O) 3547 (w), ν(SbF6) 653 (s).

Organometallics Article

dx.doi.org/10.1021/om200859z |Organometallics 2011, 30, 6661−66736668

S at Metal Epimer (9a).

1H NMR (500.13 MHz, CD2Cl2, −25 °C): δ = 7.86−7.18(20H, Ph), 6.07 (dd, J = 5.4, 3.2 Hz, 1H, H5), 4.96 (dd, J = 5.5,2.7 Hz, 1H, H6), 3.88 (s, 1H, H1), 3.28 (bs, 2H, H2O), 3.20 (m,1H, H2), 3.11 (s, 1H, H4), 2.96 (m, 1H, H3), 2.03 (bd, 1H,H72), 1.90 (d, J = 9.2 Hz, 1H, H71), 1.43 ppm (t, J = 3.6 Hz,15H, C5Me5).

13C NMR (125.77 MHz, CD2Cl2, −25 °C): δ =140.64 (d, J = 7.0 Hz, C5), 134.68−117.08 (24C, Ph), 130.65(m, C6), 104.61 (d, J = 5.8 Hz, C5Me5), 52.47 (d, J = 9.2 Hz,C7), 49.34 (dd, J = 27.0, 17.6 Hz, C3), 43.64 (d, J = 18.6 Hz,C2), 43.42−42.83 (m, C1), 41.65 (dd, J = 12.7, 7.4 Hz, C4),9.52 ppm (C5Me5).

31P NMR (202.48 MHz, CD2Cl2, −25 °C):δ = 40.14 (dd, J(Rh,P1) = 132.4 Hz, J(P2,P1) = 44.3 Hz, P1),30.91 ppm (dd, J(Rh,P2) = 137.6 Hz, P2).R at Metal Epimer (9b).

1H NMR (500.13 MHz, CD2Cl2, −25 °C): δ = 6.60 (dd, J =5.5, 3.3 Hz, 1H, H5), 6.02 (dd, J = 5.6, 2.5 Hz, 1H, H6), 3.47(bs, 2H, H2O), 3.37 (m, 1H, H2), 3.16 (m, 1H, H1), 2.78 (m,1H, H4), 2.56 (m, 1H, H3), 1.69 (m, 1H, H72), 1.67 (s, 15H,C5Me5), 0.28 ppm (d, J = 8.7 Hz, 1H, H71).

13C NMR (125.77MHz, CD2Cl2, −25 °C): δ = 142.19 (d, J = 6.0 Hz, C5), 132.76(m, C6), 100.49 (d, J = 9.8 Hz, C5Me5), 52.06 (d, J = 12.9 Hz,C7), 8.72 ppm (C5Me5).

31P NMR (202.48 MHz, CD2Cl2,−25 °C): δ = 40.34 (dd, J(Rh,P2) = 131.9 Hz, J(P2,P1) =36.6 Hz, P2), 31.10 ppm (dd, J(Rh,P1) = 147.2 Hz, P1).[(η 5-C5Me5)Ir(norphos}(H2O)][SbF6]2 (10). Yield: 98%. Molar

ratio of S at the metal (10a) to R at the metal (10b) epimer: 76/24.Anal. Calcd for C41H45F12IrOP2Sb2: C, 38.5; H, 3.5. Found: C, 38.6;H, 3.6. IR (solid, cm−1): ν(H2O) 3548 (w), ν(SbF6) 653 (s).S at Metal Epimer (10a).

1H NMR (400.16 MHz, CD2Cl2, −25 °C): δ = 7.19−7.85(20H, Ph), 6.07 (dd, J = 5.0, 3.0 Hz, 1H, H5), 4.91 (dd, J = 5.3,2.6 Hz, 1H, H6), 4.52 (bs, 2H, H2O), 3.28 (s, 1H, H1), 3.24

(m, 1H, H2), 3.11 (s, 1H, H4), 3.08−2.89 (m, 1H, H3), 2.28 (s,1H, H72), 1.96 (bd, J = 9.0 Hz, 1H, H71), 1.46 ppm (s, 15H,C5Me5).

13C NMR (100.61 MHz, CD2Cl2, −25 °C): δ =140.57 (d, J = 7.5 Hz, C5), 134.78−116.04 (24C, Ph), 130.16(d, J = 9.0 Hz, C6), 98.58 (s, C5Me5), 53.11−52.84 (m, C7),49.07 (dd, J(P,C) = 20.0, 1.8 Hz, C3), 42.79−42.57 (m, C1),43.66 (dd, J(P,C) = 42.4, 15.2 Hz, C2), 40.77−40.47 (m, C4),9.07 ppm (C5Me5).

31P NMR (161.96 MHz, CD2Cl2, −25 °C):δ = 12.30 (d, J(P2,P1) = 28.2 Hz, P1), 5.42 ppm (d, P2).R at Metal Epimer (10b).

1H NMR (400.16 MHz, CD2Cl2, −25 °C): δ = 7.19−7.85(20H, Ph), 6.65 (m, 1H, H5), 6.08 (m, 1H, H6), 4.81 (bs, 2H,H2O), 3.41 (m, 1H, H2), 3.23 (s, 1H, H1), 2.75 (s, 1H, H4),2.62 (m, 1H, H3), 1.90 (m, 1H, H72), 1.46 (s, 15H, C5Me5),0.26 ppm (bd, J = 8.9 Hz, 1H, H71).

13C NMR (100.61 MHz,CD2Cl2, −25 °C): δ = 142.08 (m, C5), 132.93 (m, C6), 98.71(s, C5Me5), 52.20 (m, C7), 9.34 ppm (C5Me5).

31P NMR(161.96 MHz, CD2Cl2, −25 °C): δ = 12.44 (d, J(P2,P1) = 27.9Hz, P2), 5.10 ppm (d, P1).Catalytic Procedure. The corresponding metallic complex [(η 5-

C5Me5)M(PP*)(H2O)][SbF6]2 (0.025 mmol, 5 mol %) was dissolvedin 3 mL of dry CH2Cl2 under argon at −20 °C, and 100 mg of4 Å molecular sieves and freshly distilled methacrolein (41.4 μL,0.500 mmol) were added. After 15 min of reaction, cyclopentadiene(247.2 μL, 3.0 mmol) in 1 mL of CH2Cl2 was added. The reaction wasquenched by addition of excess Me4NCl in CH2Cl2, after 1 more hourof reaction, and the conversion and exo/endo ratio were determined byGC. The suspension was then concentrated to ca. 0.3 mL, filteredthrough silica gel, and washed with CH2Cl2/n-hexane (1/1, v/v),before the determination of the enantiomeric purity. Enantiomericexcesses were determined by integration of the aldehyde proton ofboth enantiomers in the NMR spectra, using Eu(hfc)3, in a 0.3 molarratio, as a chiral shift reagent. The absolute configuration of the majoradduct was assigned by comparing the sign of [α]D with that in theliterature.13

Preparation of the Complexes [(η 5-C5Me5)M(PP*)-(methacrolein)][SbF6]2 (11−20). At −25 °C, under argon, to asolution of [(η 5-C5Me5)M(PP*)(H2O)][SbF6]2 (0.120 mmol) inCH2Cl2 (4 mL) were added methacrolein (33.0 μL, 0.395 mmol) and4 Å molecular sieves (200.0 mg). The resulting suspension was stirredfor 20 min and then was filtered through a cannula. The filtrate wasconcentrated to ca. 3 mL. The addition of 20 mL of dry n-hexaneafforded orange (Rh) or yellow (Ir) solids that were filtered off,washed with 3 × 2 mL of dry n-hexane, and vacuum-dried.(SRh,RC)-[(η

5-C5Me5)Rh(phenphos)(methacrolein)][SbF6]2(11).

Organometallics Article

dx.doi.org/10.1021/om200859z |Organometallics 2011, 30, 6661−66736669

Yield: 59%. Anal. Calcd for C46H49F12RhOP2Sb2·CH2Cl2: C,42.15; H, 3.8. Found: C, 41.7; H, 3.9. IR (solid, cm−1):ν(CO) 1620 (m), ν(SbF6) 652 (s). 1H NMR (500.13MHz, CD2Cl2, −25 °C): δ = 7.94−7.08 (25H, Ph), 7.67 (s,1H, CHO), 6.66 (bs, 1H, Hb), 6.13 (bs, 1H, Ha), 3.87(m, 1H, H11), 3.55 (dt, J = 52.55, 12.7 Hz, 1H, H22), 3.18(m, 1H, H21), 1.40 (s, 15H, C5Me5), 1.13 ppm (s, 3H, Me).13C NMR (125.77 MHz, CD2Cl2, −25 °C): δ = 208.56(CHO), 149.41 (C5), 145.06 (C4), 135.15−120.25 (30C,Ph), 106.57 (s, C5Me5), 43.14 (m, C1), 31.78 (dd, J(P,C) =45.8, 24.0 Hz, C2), 13.35 (Me), 9.41 ppm (C5Me5).

31P NMR(202.48 MHz, CD2Cl2, −25 °C): δ = 77.49 (dd, J(Rh,P1) =130.9 Hz, J(P2,P1) = 43.3 Hz, P1), 43.61 ppm (dd, J(Rh,P2) =132.4 Hz, P2).(SIr,RC)-[(η

5-C5Me5)Ir(phenphos)(methacrolein)][SbF6]2 (12).

Yield: 83%. Anal. Calcd for C46H49F12IrOP2Sb2: C, 41.1; H, 3.7.Found: C, 41.1; H, 3.7. IR (solid, cm−1): ν(CO) 1622 (m),ν(SbF6) 654 (s). 1H NMR (400.16 MHz, CD2Cl2, −25 °C):δ = 7.90−6.53 (25H, Ph), 7.75 (s, 1H, CHO), 6.63 (s, 1H, Hb),6.15 (s, 1H, Ha), 3.79 (m, 1H, H11), 3.55 (dddd, J = 48.3, 15.5,11.0, 4.4 Hz, 1H, H22), 3.15 (m, 1H, H21), 1.43 (t, J(P,H) = 2.2Hz, 15H, C5Me5), 1.10 ppm (s, 3H, Me). 13C NMR (100.61MHz, CD2Cl2, −25 °C): δ = 210.13 (CHO), 150.96 (C5),145.45 (C4), 136.93−119.11 (30C, Ph), 100.46 (s, C5Me5),43.32 (dd, J(P,C) = 31.1, 9.0 Hz, C1), 31.40 (dd, J(P,C) =39.3, 14.9 Hz, C2), 13.28 (Me), 8.85 ppm (C5Me5).

31P NMR(161.96 MHz, CD2Cl2, −25 °C): δ = 48.98 (d, J(P2,P1) = 16.3Hz, P1), 20.00 ppm (d, P2).(SRh,RC)-[(η

5-C5Me5)Rh(benphos)(methacrolein)][SbF6]2 (13).

Yield: 90%. Anal. Calcd for C47H51F12RhOP2Sb2: C, 44.5; H,4.05. Found: C, 44.0; H, 3.65. IR (solid, cm−1): ν(CO) 1614(m), ν(SbF6) 653 (s). 1H NMR (500.13 MHz, CD2Cl2,−25 °C): δ = 7.96−7.02 (25H, Ph), 7.28 (s, 1H, CHO), 6.49(s, 1H, Hb), 5.84 (s, 1H, Ha), 3.23 (d, J = 14.9 Hz, 1H, H32),3.16 (dt, J = 52.55, 12.7 Hz, 1H, H22), 2.66 (m, 1H, H11), 2.58(m, 1H, H21), 2.04 (m, 1H, H31), 1.41 (t, J = 2.7 Hz, 15H,C5Me5), 0.98 ppm (s, 3H, Me). 13C NMR (125.77 MHz,CD2Cl2, −25 °C): δ = 207.93 (CHO), 148.73 (C5), 144.65(C4), 135−120 (30C, Ph), 106.71 (s, C5Me5), 37.49 (dd,J(P,C) = 27.7, 11.3 Hz, C1), 36.23 (d, J(P,C) = 15.9 Hz, C3),29.33 (dd, J(P,C) = 35.3, 15.9 Hz, C2), 13.04 (Me), 9.37 ppm(C5Me5).

31P NMR (202.48 MHz, CD2Cl2, −25 °C): δ = 69.85(dd, J(Rh,P1) = 132.4 Hz, J(P2,P1) = 40.7 Hz, P1), 46.46 ppm(dd, J(Rh,P2) = 133.2 Hz, P2).

(SIr,RC)-[(η5-C5Me5)Ir(benphos)(methacrolein)][SbF6]2 (14).

Yield: 82. %. Anal. Calcd for C47H51F12IrOP2Sb2: C, 41.6; H,3.8. Found: C, 42.1; H, 4.1. IR (solid, cm−1): ν(CO) 1600(m), ν(SbF6) 654 (s). 1H NMR (400.16 MHz, CD2Cl2,−25 °C): δ = 7.9−6.9 (25H, Ph), 7.39 (s, 1H, CHO), 6.45 (s,1H, Hb), 5.87 (s, 1H, Ha), 3.22 (d, J = 14.7 Hz, 1H, H32), 3.15(dt, J = 49.3, 13.4 Hz, 1H, H22), 2.62 (m, 1H, H11), 2.53 (m,1H, H21), 2.00 (m, 1H, H31), 1.44 (s, 15H, C5Me5), 0.97 ppm(s, 3H, Me). 13C NMR (100.61 MHz, CD2Cl2, −25 °C): δ =209.51 (CHO), 150.47 (C5), 144.87 (C4), 136.52−119.51(30C, Ph), 100.46 (bs, C5Me5), 37.79 (dd, J(P,C) = 34.2,8.2 Hz, C1), 35.48 (d, J(P,C) = 13.6 Hz, C3), 29.56 (dd,J(P,C) = 41.5, 11.5 Hz, C2), 12.98 (Me), 8.84 ppm (C5Me5).31P NMR (161.96 MHz, CD2Cl2, −25 °C): δ = 42.90 (d,J(P2,P1) = 12.3 Hz, P1), 22.76 ppm (d, P2).(SRh,RC)-[(η

5-C5Me5)Rh(valphos)(methacrolein)][SbF6]2 (15).

Yield: 84%. Anal. Calcd for C43H51F12RhOP2Sb2: C, 42.3; H,4.2. Found: C, 42.3; H, 4.3. IR (solid, cm−1): ν(CO) 1614(m), ν(SbF6) 652 (s). 1H NMR (500.13 MHz, CD2Cl2,−25 °C): δ = 7.93−7.34 (20H, Ph), 7.19 (s, 1H, CHO), 6.45(s, 1H, Hb), 5.79 (s, 1H, Ha), 3.46 (dt, J = 56.0, 13.5 Hz, 1H,H22), 2.61 (m, 1H, H21), 2.33 (m, 1H, H11), 2.12 (m, 1H, H3),1.38 (t, J = 3.1 Hz, 15H, C5Me5), 1.16 (d, J = 6.7 Hz, 3H,CH3), 0.93 (s, 3H, Me), 0.34 ppm (d, J = 6.5 Hz, 3H, CH3).13C NMR (125.77 MHz, CD2Cl2, −25 °C): δ = 207.75(s, CHO), 148.28 (C5), 144.64 (C4), 135−120 (24C, Ph),106.6 (s, C5Me5), 40.67 (dd, J(P,C) = 28.9, 8.6 Hz, C1), 28.49(dd, J(P,C) = 15.1, 5.3 Hz, C3), 26.36 (dd, J(P,C) = 36.9,17.2 Hz, C2), 24.37 (d, J(P,C) = 8.1 Hz, CH3), 17.90 (d,J(P,C) = 8.1 Hz, CH3), 13.14 (Me), 9.31 ppm (C5Me5).

31PNMR (202.48 MHz, CD2Cl2, −25 °C): δ = 74.43 (dd,J(Rh,P1) = 130.4 Hz, J(P2,P1) = 40.7 Hz, P1), 49.16 ppm (dd,J(Rh,P2) = 133.6 Hz, P2).(SIr,RC)-[(η

5-C5Me5)Ir(valphos)(methacrolein)][SbF6]2 (16).

Yield: 60%. Anal. Calcd for C43H51F12IrOP2Sb2: C, 39.4; H, 3.9.Found: C, 39.9; H, 4.2. IR (solid, cm−1): ν(CO) 1588 (m),ν(SbF6) 653 (s). 1H NMR (500.13 MHz, CD2Cl2, −25 °C):δ = 7.91−7.15 (20H, Ph), 7.34 (s, 1H, CHO), 6.41 (s, 1H, Hb),

Organometallics Article

dx.doi.org/10.1021/om200859z |Organometallics 2011, 30, 6661−66736670

5.83 (s, 1H, Ha), 3.40 (ddd, J = 50.1, 14.9, 4.8 Hz, 1H, H22),2.56 (m, 1H, H21), 2.26 (m, 1H, H11), 2.12 (m, 1H, H3), 1.40(s, 15H, C5Me5), 1.19 (d, J = 6.7 Hz, 3H, CH3), 0.91 (s, 3H,Me), 0.31 ppm (d, J = 6.6 Hz, 3H, CH3).

13C NMR (125.77MHz, CD2Cl2, −25 °C): δ = 209.37 (CHO), 150.12 (C5),144.93 (C4), 135.97−119.32 (24C, Ph), 100.56 (s, C5Me5),41.07 (dd, J(P,C) = 34.4, 6.3 Hz, C1), 27.45 (dd, J(P,C) =14.2, 3.9 Hz, C3), 26.29 (dd, J(P,C) = 40.7, 12.2 Hz, C2), 24.69(d, J(P,C) = 8.7 Hz, CH3), 17.71 (CH3), 12.85 (Me), 8.81 ppm(C5Me5).

31P NMR (202.48 MHz, CD2Cl2, −25 °C): δ = 46.84(d, J(P2,P1) = 12.6 Hz, P1), 25.14 ppm (d, P2).(SRh,RC)-[(η

5-C5Me5)Rh(cyphos)(methacrolein)][SbF6]2 (17).

Yield: 97%. Anal. Calcd for C46H55F12RhOP2Sb2: C, 43.8; H,4.4. Found: C, 43.6; H, 4.3. IR (solid, cm−1): ν(CO) 1613(m), ν(SbF6) 653 (s). 1H NMR (500.13 MHz, CD2Cl2, 0 °C):δ = 7.9−7.3 (20H, Ph), 7.23 (s, 1H, CHO), 6.45 (s, 1H, Hb),5.81 (s, 1H, Ha), 3.45 (dt, J = 56.4, 13.9 Hz, 1H, H22), 2.57 (m,1H, H21), 2.23 (m, 1H, H11), 1.53−0.81 (m, 11H, cy), 1.38 (t,J = 3.3 Hz, 15H, C5Me5), 0.89 ppm (s, 3H, Me). 13C NMR(125.77 MHz, CD2Cl2, −25 °C): δ = 207.78 (CHO), 148.34(C5), 144.80 (C4), 134.93−120.68 (24C, Ph), 106.71 (s,C5Me5), 40.84 (dd, J(P,C) = 28.1, 8.8 Hz, C1), 37.33−22.54(6C, cy), 26.70 (dd, J(P,C) = 31.8, 17.8 Hz, C2), 13.01 (Me),9.44 ppm (C5Me5).

31P NMR (202.48 MHz, CD2Cl2, 0 °C):δ = 74.96 (dd, J(Rh,P1) = 130.2 Hz, J(P2,P1) = 40.7 Hz, P1),49.32 ppm (dd, J(Rh,P2) = 133.5 Hz, P2).(SRh,RC)-[(η

5-C5Me5)Ir(cyphos)(methacrolein)][SbF6]2 (18).

Yield: 99%. Anal. Calcd for C46H55F12IrOP2Sb2: C, 40.9; H, 4.1.Found: C, 41.2; H, 4.2. IR (solid, cm−1): ν(CO) 1622 (m),ν(SbF6) 654 (s). 1H NMR (500.13 MHz, CD2Cl2,−25 °C): δ = 7.92−7.29 (20H, Ph), 7.40 (s, 1H, CHO),6.43 (s, 1H, Hb), 5.87 (s, 1H, Ha), 3.40 (dddd, J = 51.8, 15.4,11.9, 4.2 Hz, 1H, H22), 2.53 (m, 1H, H21), 2.16 (m, 1H, H11),1.50−0.84 (m, 11H, cy), 1.42 (t, J = 2.2 Hz, 15H, C5Me5), 0.87ppm (s, 3H, Me). 13C NMR (75.50 MHz, CD2Cl2, −25 °C):δ = 209.83 (CHO), 150.67 (C5), 145.48 (C4), 135.4−129.7(24C, Ph), 100.69 (s, C5Me5), 41.46 (dd, J(P,C) = 33.2, 7.2Hz, C1), 37.43−23.31 (6C, cy), 26.68 (dd, J(P,C) = 19.5, 10.4Hz, C2), 13.30 (Me), 9.25 ppm (C5Me5).

31P NMR (121.48MHz, CD2Cl2, −25 °C): δ = 47.59 (d, J(P2,P1) = 13.6 Hz, P1),25.53 ppm (d, P2).[(η 5-C5Me5)Rh(norphos)(methacrolein)][SbF6]2 (19). Yield:

95%. Molar ratio of S at the metal (19a) to R at the metal (19b)epimer: 63/37. Anal. Calcd for C45H49F12RhOP2Sb2·CH2Cl2: C, 41.6;H, 3.9. Found: C, 41.7; H, 4.2. IR (solid, cm−1): ν(CO) 1599 (m),ν(SbF6) 654 (s).

S at Metal Epimer (19a).

1H NMR (500.13 MHz, CD2Cl2, −25 °C): δ = 7.93−7.29 (20H,Ph), 7.77 (s, 1H, CHO), 6.60 (s, 1H, Hb), 6.18 (dd, J = 5.4, 3.2 Hz,1H, H5), 5.99 (s, 1H, Ha), 4.87 (d, J = 2.3 Hz, 1H, H6), 3.34 (s, 1H,H1), 3.19 (m, 1H, H3), 3.15 (s, 1H, H4), 2.85 (m, 1H, H2), 2.10(bd, J = 10.9 Hz, 1H, H72), 1.96 (d, J = 9.4 Hz, 1H, H71), 1.44 ppm(s, 15H, C5Me5), 1.13 ppm (s, 3H, Me). 13C NMR (125.77 MHz,CD2Cl2, −25 °C): δ = 208.47 (CHO), 149.14 (C10), 145.43 (C9),141.23 (d, J = 7.2 Hz, C5), 137.16−116.77 (24C, Ph), 129.98 (m,C6), 104.54 (s, C5Me5), 52.90 (d, J = 8.8 Hz, C7), 50.07 (dd, J =26.0, 17.5 Hz, C3), 43.69 (d, J = 17.7 Hz, C2), 43.41 (dd, J = 12.7,4.9 Hz, C1), 41.67 (dd, J = 12.7, 7.4 Hz, C4), 13.59 (Me), 9.67 ppm(C5Me5).

31P NMR (121.46 MHz, CD2Cl2, −25 °C): δ = 39.48(dd, J(Rh,P1) = 132.7 Hz, J(P2,P1) = 45.1 Hz, P1), 32.09 ppm (dd,J(Rh,P2) = 136.9 Hz, P2).R at Metal Epimer (19b).

1H NMR (400.16 MHz, CD2Cl2, −25 °C): δ = 7.99 (s, 1H,CHO), 6.73 (s, 1H, Hb), 6.55 (m, 1H, H5), 6.17 (s, 1H, Ha),6.08 (dd, J = 5.3, 2.0 Hz, 1H, H6), 3.49 (m, 1H, H2), 3.30 (s,1H, H1), 2.82 (s, 1H, H4), 2.14 (m, 1H, H3), 1.73 (m, 1H, H72),1.44 (s, 15H, C5Me5), 1.25 (s, 3H, Me), 0.4 ppm (d, J = 8.8 Hz,1H, H71).

13C NMR (125.77 MHz, CD2Cl2, −25 °C): δ =208.70 (CHO), 149.65 (C10), 145.74 (C9), 141.68 (d, J = 6.9Hz, C5), 137.16−116.77 (24C, Ph), 133.20 (m, C6), 104.45 (s,C5Me5), 51.98 (d, J = 10.1 Hz, C7), 47.30 (m, C3), 45.43 (d,J = 26.1 Hz, C2), 43.49 (m, C1), 40.69 (m, C4), 13.59 (Me),9.60 ppm (C5Me5).

31P NMR (202.46 MHz, CD2Cl2, −25 °C):δ = 39.75 (dd, J(Rh,P2) = 131.7 Hz, J(P2,P1) = 46.2 Hz, P2),29.87 ppm (dd, J(Rh,P1) = 136.1 Hz, P1).[(η 5-C5Me5)Ir(norphos)(methacrolein)][SbF6]2 (20). Yield: 77%.

Molar ratio of S at the metal (20a) to R at the metal (20b) epimer: 67/33.Anal. Calcd for C45H49F12IrOP2Sb2: C, 40.6; H, 3.7. Found: C, 40.6; H, 3.9.IR (solid, cm−1): ν(CO) 1583 (m), ν(SbF6) 656 (s).S at Metal Epimer (20a).

Organometallics Article

dx.doi.org/10.1021/om200859z |Organometallics 2011, 30, 6661−66736671

1H NMR (500.13 MHz, CD2Cl2, −25 °C): δ = 7.92−7.30(20H, Ph), 7.76 (s, 1H, CHO), 6.55 (s, 1H, Hb), 6.19 (dd, J =5.4, 3.2 Hz, 1H, H5), 5.98 (s, 1H, Ha), 4.85 (dd, J = 4.9, 2.3 Hz,1H, H6), 3.34 (s, 1H, H1), 3.16 (m, 1H, H3), 3.15 (s, 1H, H4),2.88 (m, 1H, H2), 2.33 (m, 1H, H72), 1.98 (d, J = 9.0 Hz, 1H,H71), 1.45 (s, 15H, C5Me5), 1.13 ppm (s, 3H, Me). 13C NMR(100.61 MHz, CD2Cl2, −25 °C): δ = 209.99 (CHO), 150.75(C10), 145.70 (C9), 141.07 (d, J = 6.5 Hz, C5), 135.93−115.61(24C, Ph), 129.88 (m, C6), 98.74 (s, C5Me5), 52.64 (m, C7),49.80 (m, C3), 43.91 (d, J = 15.3 Hz, C2), 43.11 (m, C1), 40.65(dd, J = 11.8, 6.2 Hz, C4), 14.26 (Me), 9.18 ppm (C5Me5).31P NMR (161.98 MHz, CD2Cl2, −25 °C): δ = 12.41 (d,J(P2,P1) = 28.0 Hz, P1), 6.95 ppm (d, P2).R at Metal Epimer (20b).

1H NMR (400.16 MHz, CD2Cl2, −25 °C): δ = 7.96 (s, 1H,CHO), 7.92−7.30 (20H, Ph), 6.67 (s, 1H, Hb), 6.61 (dd, J =5.5, 3.2 Hz, 1H, H5), 6.19 (s, 1H, Ha), 6.06 (dd, J = 5.5, 2.7 Hz,1H, H6), 3.50 (m, 1H, H2), 3.31 (s, 1H, H1), 2.79 (s, 1H, H4),2.17 (m, 1H, H3), 1.95 (m, 1H, H72), 1.45 (s, 15H, C5Me5),1.26 (s, 3H, Me), 0.38 ppm (d, J = 8.8 Hz, 1H, H71).

13C NMR(100.61 MHz, CD2Cl2, −25 °C): δ = 210.21 (CHO), 151.29(C10), 145.88 (C9), 141.59 (d, J = 7.8 Hz, C5), 133.28 (m, C6),98.67 (s, C5Me5), 52.22 (m, C7), 47.52 (m, C3), 46.01 (m, C2),44.33 (d, J = 15.4 Hz, C1), 39.86 (m, C4), 14.19 (Me), 9.12ppm (C5Me5).

31P NMR (161.98 MHz, CD2Cl2, −20 °C): δ =12.73 (d, J(P2,P1) = 28.6 Hz, P2), 4.36 ppm (d, P1).Structural Analysis of Complexes 13 and 14. The X-ray

diffraction data were collected at 100(2) K on a Bruker SMART APEXCCD area detector diffractometer with graphite-monochromated MoKα radiation (λ = 0.71073 Å) using narrow ω rotations (0.3°).Intensities were integrated with APEX2 and SMART programs andcorrected of absorption effects with SADABS.23 The structures weresolved by direct methods SHELXS-9724 and refined using SHELXL-97.25 Anisotropic displacement parameters were used for all non-Hatoms. Hydrogen atoms were observed in the Fourier difference mapsand refined with a riding model from calculated positions. Addition-ally, to the internal configuration reference of the (R)-benphos ligand,the Flack parameter was refined as a check on the correct absoluteconfiguration determination.26 An analysis of the solvent region hasbeen performed using the SQUEEZE program.27 Complex 14 tends toform twinned crystals, not very appropriate for X-ray diffraction datacollection; unfortunately, several crystals were tested with no success.Finally, a tiny crystal allows us to solve the structure, although thepresence of a high value of the second parameter of the weightingscheme points to the fact that the chosen sample was also twinned.Residual density peaks of 7.22 and 7.19 e·Å−3 were observed at the endof the refinement. Both peaks were located close to the metal atom(closer than 1 Å), at both sides to the Ir atom. They have no chemicalsense.

■ ASSOCIATED CONTENT

*S Supporting InformationX-ray crystallographic information files containing full details ofthe structural analysis of complexes 13 and 14 (CIF format)

and an ORTEP diagram and structural parameters concerningthe CH/π interactions for the cation of 14. This material isavailable free of charge via the Internet at http://pubs.acs.org.

■ ACKNOWLEDGMENTS

We thank the Ministerio de Educacion y Ciencia (Grant CTQ2009-10303/BQU) and Gobierno de Aragon (Grupo Con-solidado: Catalizadores Organometalicos Enantioselectivos) forfinancial support. A.A thanks the IUCH for a grant. P.G.-O.acknowledges financial support from the CSIC, ″JAE-Doc″program, contract cofunded by the ESF.

■ REFERENCES(1) (a) Jacobsen, E. N., Pfaltz, A., Yamamoto, H., Eds. Comprehensive

Asymmetric Catalysis; Springer: New York, 1999; Vol. I−III.(b) Jacobsen, E. N., Pfaltz, A., Yamamoto, H., Eds. ComprehensiveAsymmetric Catalysis: Supplement 1; Springer: New York, 2004.(c) Jacobsen, E. N., Pfaltz, A., Yamamoto, H., Eds. ComprehensiveAsymmetric Catalysis: Supplement 2; Springer: New York, 2004.(d) Ojima, I., Ed. Catalytic Asymmetric Synthesis; VCH: Weinheim,Germany, 2000. (e) Noyori, R. Asymmetric Catalysis in OrganicSynthesis; John Willey and Sons: New York, 1994.(2) (a) Fringuelli, F.; Taticchi, A. The Diels-Alder Reaction. Selected

Practical Methods; Wiley, New York, 2002. (b) Carmona, D.; Lamata,M. P.; Oro, L. A. Coord. Chem. Rev. 2000, 200−202, 717−772.(c) Dias, L. C. J. Braz. Chem. Soc. 1997, 8, 289−332. (d) Hollis, T. K.;Oderdink, W.; Robinson, J. W.; Bosnich, B. Tetrahedron 1993, 49,5415−5430. (e) Kobayashi, S. Pure Appl. Chem. 1998, 70, 1019−1026.(f) Corey, E. J.; Guzman-Perez, A. Angew. Chem., Int. Ed. 1998, 37,389−401. (g) Johannsen, M.; Yao, S.; Graven, A.; Jørgensen, K. A.Pure Appl. Chem. 1998, 70, 1117−1122. (h) Jørgensen, K. A.;Johannsen, M.; Yao, S.; Audrian, H.; Thorhauge, J. Acc. Chem. Res.1999, 32, 605−613.(3) (a) Kundig, E. P.; Bourdin, B.; Bernardinelli, G. Angew. Chem.,

Int. Ed. Engl. 1994, 33, 1856−1858. (b) Bruin, M. E.; Ku ndig, E. P.Chem. Commun. 1998, 2635−2636. (c) Ku ndig, E. P.; Saudan, C. M.;Bernardinelli, G. Angew. Chem., Int. Ed. 1999, 38, 1219−1223.(d) Kundig, E. P.; Saudan, C. M.; Viton, F. Adv. Synth. Catal. 2001,343, 51−56. (e) Kundig, E. P.; Saudan, C. M.; Alezra, V.; Viton, F.;Bernardinelli, G. Angew. Chem., Int. Ed. 2001, 40, 4481−4485.(f) Alezra, V.; Bernardinelli, G.; Corminboeuf, C.; Frey, U.; Ku ndig,E. P.; E. Merbach, A.; Saudan, C. M.; Viton, F.; Weber, J. J. Am. Chem.Soc. 2004, 126, 4843−4853. (g) Anil Kumar, P. G.; Pregosin, P. S.;Vallet, M.; Bernardinelli, G.; Jazzar, R. F.; Viton, F.; Ku ndig, E. P.Organometallics 2004, 23, 5410−5418. (h) Rickerby, J.; Vallet, M.;Bernardinelli, G.; Viton, F.; Ku ndig, E. P. Chem.Eur. J. 2007, 13,3354−3368. (i) Thamapipol, S.; Bernardinelli, G.; Besnard, C.;Kundig, E. P. Org. Lett. 2010, 12, 5604−5607.(4) (a) Faller, J. W.; Parr, J. Organometallics 2000, 19, 1829−1832.

(b) Faller, J. W.; Lavoie, A. J. Organomet. Chem. 2001, 630, 17−22.(c) Faller, J. W.; Parr, J. Organometallics 2001, 20, 697−699. (d) Faller,J. W.; Grimmond, J. B. Organometallics 2001, 20, 2454−2458.(e) Faller, J. W.; Grimmond, J. B.; D’Alliessi, D. G. J. Am. Chem.Soc. 2001, 123, 2525−2529. (f) Faller, J. W.; Lavoie, A. R.; Grimmond,B. J. Organometallics 2002, 21, 1662−1666. (g) Faller, J.; D’Alliessi,D. G. Organometallics 2003, 22, 2749−2757. (h) Faller, J. W.; Fontaine,P. P. Organometallics 2005, 24, 4132−4138.(5) (a) Davies, D. L.; Fawcett, J.; Garratt, S. A.; Russell, D. R. Chem.

Commun. 1997, 1351−1352. (b) Davenport, A. J.; Davies, D. L.;Fawcett, J.; Garratt, S. A.; Lad, L.; Russell, D. R. Chem. Commun. 1997,2347−2348. (c) Davenport, A. J.; Davies, D. L.; Fawcett, J.; Krafczyk,R.; Russell, D. R. J. Chem. Soc., Dalton Trans. 2000, 4432−4441.(d) Davenport, A. J.; Davies, D. L.; Fawcett, J.; Russell, D. R. J. Chem.Soc., Perkin Trans. 1 2001, 1500−1503. (e) Davies, D. L.; Fawcett, J.;Garratt, S. A.; Russell, D. R. Organometallics 2001, 20, 3029−3034.(f) Davies, D. L.; Fawcett, J.; Garratt, S. A.; Russell, D. R. J. Organomet.Chem. 2002, 662, 43−50. (g) Davenport, A. J.; Davies, D. L.; Fawcett,

Organometallics Article

dx.doi.org/10.1021/om200859z |Organometallics 2011, 30, 6661−66736672

J.; Russell, D. R. Dalton Trans. 2004, 1481−1492. (h) Davies, D. L.;Fawcett, J.; Garratt, S. A.; Russell, D. R. Dalton Trans. 2004, 3629−3634. (i) Davenport, A. J.; Davies, D. L.; Fawcett, J.; Russell, D. R.J. Organomet. Chem. 2006, 691, 2221−2227. (j) Davenport, A. J.;Davies, D. L.; Fawcett, J.; Russell, D. R. J. Organomet. Chem. 2006, 691,3445−3450.(6) (a) Carmona, D.; Cativiela, C.; Garcia-Correas, R.; Lahoz, F. J.;

Lamata, M. P.; Lopez, J. A.; Lopez-Ram de Viu, M. P.; Oro, L. A.; SanJose, E.; Viguri, F. Chem. Commun. 1996, 1247−1248. (b) Carmona,D.; Cativiela, C.; Elipe, S.; Lahoz, F. J.; Lamata, M. P.; Lopez-Ramde Viu, M. P.; Oro, L. A.; Vega, C.; Viguri, F. Chem. Commun. 1997,2351−2352. (c) Carmona, D.; Lahoz, F. J.; Elipe, S.; Oro, L. A.;Lamata, M. P.; Viguri, F.; Mir, C.; Cativiela, C.; Lopez-Ram de Viu, M.P. Organometallics 1998, 17, 2986−2995. (d) Carmona, D.; Vega, C.;Cativiela, C.; Lahoz, F. J.; Elipe, S.; Oro, L. A.; Lamata, M. P.; Viguri,F.; Garcia-Correas, R.; Cativiela, C.; Lopez-Ram de Viu, M. P.Organometallics 1999, 18, 3364−3371. (e) Carmona, D.; Lahoz, F. J.;Elipe, S.; Oro, L. A.; Lamata, M. P.; Viguri, F.; Sanchez, F.; Martinez,S.; Cativiela, C.; Lo pez-Ram de Viu, M. P. Organometallics 2002, 21,5100−5114. (f) Brunner, H.; Henning, F.; Weber, M.; Carmona, D.;Lahoz, F. J. Synthesis 2003, 1091−1099. (g) Carmona, D.; Vega, C.;Garcia, N.; Lahoz, F. J.; Elipe, S.; Oro, L. A.; Lamata, M. P.; Viguri, F.;Borao, R. Organometallics 2006, 25, 1592−1606. (h) Barba, C.;Carmona, D.; Garcia, J. I.; Lamata, M. P.; Mayoral, J. A.; Salvatella, L.;Viguri, F. J. Org. Chem. 2006, 71, 9831−9840. (i) Carmona, D.;Lamata, M. P.; Viguri, F.; Rodriguez, R.; Lahoz, F. J.; Dobrinovich, I.;Oro, L. A. Dalton Trans. 2007, 1911−1921. (j) Carmona, D.; Lamata,M. P.; Viguri, F.; Barba, C.; Rodriguez, R.; Lahoz, F. J.; Martin, M. L.;Oro, L. A.; Salvatella, L. Organometallics 2007, 26, 6493−6496.(k) Carmona, D.; Lamata, M. P.; Viguri, F.; Rodriguez, R.; Lahoz, F. J.;Dobrinovich, I.; Oro, L. A. Dalton Trans. 2008, 3328−3338.(7) (a) Carmona, D.; Lamata, M. P.; Viguri, F.; Rodriguez, R.; Oro,

L. A.; Balana, A. I; Lahoz, F. J.; Tejero, T.; Merino, P.; Franco, S.;Montesa, I. J. Am. Chem. Soc. 2004, 126, 2716−2717. (b) Carmona,D.; Lamata, M. P.; Viguri, F.; Rodriguez, R.; Oro, L. A.; Lahoz, F. J.;Balana, A. I.; Tejero, T.; Merino, P. J. Am. Chem. Soc. 2005, 127,13386−13398. (c) Carmona, D.; Lamata, M. P.; Viguri, F.; Rodriguez,R.; Fischer, T.; Lahoz, F. J.; Dobrinovitch, I. T.; Oro, L. A. Adv. Synth.Catal. 2007, 349, 1751−1758. (d) Carmona, D.; Lamata, M. P.; Viguri,F.; Rodriguez, R.; Lahoz, F. J.; Oro, L. A. Chem.Eur. J. 2007, 13,9746−9756. (e) Carmona, D.; Lamata, M. P.; Viguri, F.; Rodriguez,R.; Lahoz, F. J.; Fabra, M. J.; Oro, L. A. Tetrahedron: Asymmetry 2009,20, 1197−1205.(8) Brunner, H. Eur. J. Inorg. Chem. 2001, 905−912.(9) White, C.; Yates, A.; Maitlis, P. M. Inorg. Synth. 1992, 29, 228−

234.(10) White, C.; Thompson, S. J.; Maitlis, P. M. J. Chem. Soc., Dalton

Trans. 1977, 1654−1661.(11) (a) Takahashi, Y.; Hikichi, S.; Akita, M.; Moruoka, Y. Chem.

Commun. 1999, 1491−1492. (b) Therrien, B.; Ward, T. R. Angew.Chem., Int. Ed. 1999, 38, 405−408.(12) Ligand priority sequence, η 5−C5Me5 > P1 > P2 > O: (a) Cahn,

R. S.; Ingold, C.; Prelog, V. Angew. Chem., Int. Ed. Engl. 1966, 5, 385−415. (b) Prelog, V.; Helmchen, G. Angew. Chem., Int. Ed. Engl. 1982,21, 567−583. (c) Lecomte, C.; Dusausoy, Y.; Protas, J.; Tirouflet, J.J. Organomet. Chem. 1974, 73, 67−76. (d) Stanley, K.; Baird, M. C.J. Am. Chem. Soc. 1975, 97, 6598−6599. (e) Sloan, T. E. Top.Stereochem. 1981, 12, 1.(13) Furuta, K.; Shimizu, S.; Miwa, Y.; Yamamoto, H. J. Org. Chem.

1989, 54, 1481−1483.(14) Data for 13: C47H51OP2Rh 2(F6Sb)·2(C6H14), M = 1440.57;

orange block, 0.18 × 0.13 × 0.10 mm3; orthorhombic; P212121; a =11.1778(14) Å, b = 15.922(2) Å, c = 30.769(4) Å; V = 5476.1(12) Å3;Z = 4; Dc = 1.747 g/cm3; μ = 1.419 mm−1; min and max. transmissionfactors, 0.663 and 0.867; 2θ max = 52.80°; 31 927 reflections collected,11 188 unique [Rint = 0.071]; number of data/restrains/parameters,11 188/0/592; final GOF, 1.000; R1 = 0.066 [11 188 reflns, I > 2σ(I)];wR(F 2) = 0.175 for all data; Flack parameter: x = 0.005(34). Data for14: C47H51IrOP2 2(F6Sb)·2(C6H14), M = 1529.9; orange block, 0.16 ×

0.09 × 0.07 mm3; orthorhombic; P212121; a = 11.1076(3) Å, b =15.9002(7) Å, c = 30.7680(10) Å; V = 5434.0(3) Å3; Z = 4; Dc =1.870 g/cm3; μ = 3.561 mm−1; min and max. transmission factors,0.509 and 1.0; 2θmax = 57.88°; 104 944 reflections collected, 13 644unique [Rint = 0.103]; number of data/restrains/parameters, 13 644/0/592; final GOF, 1.100; R1 = 0.069 [13 644 reflns, I > 2 σ(I)];wR(F 2) = 0.156 for all data; Flack parameter: x = 0.034(8).(15) Cremer, D.; Pople, J. A. J. Am. Chem. Soc. 1975, 97, 1354−1358.(16) Totev, D.; Salzer, A.; Carmona, D.; Oro, L. A.; Lahoz, F. J.;

Dobrinovitch, I. T. Inorg. Chim. Acta 2004, 357, 2889−2898.(17) Brunner, H.; Winterm, A.; Breu, J. J. Organomet. Chem. 1998,

553, 285−306.(18) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,

A. G.; Taylor, R. J. Chem. Soc., Perkin Trans. 1987, S1−S19.(19) Takahashi, O.; Kohni, Y.; Nishio, M. Chem. Rev. 2010, 110,

6049−6076.(20) To simplify the stereochemical notation, we will use SM to

denote the (SM,S1C,R2C,R3C,R4C)-[(η5-C5Me5)M(norphos)(ligand)]

[SbF6]2 isomer and RM for the corresponding epimer at the metal(RM,S1C,R2C,R3C,R4C)-[(η

5-C5Me5)M(norphos)(ligand)][SbF6]2; thus,for example, 9a ≡ SRh-9 and 20b ≡ RIr-20.(21) Racemic mixture A was obtained in the reaction between HCp

and methacrolein catalyzed by the achiral complex [(η 5-C5Me5)Ir(dppe)(H2O)][SbF6]2 (dppe = ethane-1,2-diylbis(diphenylphos-phane). Mixture B was obtained according to entry 10, Table 1.(22) (a) King, R. B.; Bakos, J.; Hoff, C. D.; Marko, L. J. Org. Chem.

1979, 44, 1729−1731. (b) Riley, D. P.; Shumate, R. E. J. Org. Chem.1980, 45, 5187−5193. (c) Bergstein, W.; Kleemann, A.; Martens, J.Synthesis 1981, 76−78.(23) Blessing, R. H. Acta Crystallogr. 1995, A51, 33−38.(24) Sheldrick, G. M. Acta Crystallogr. 1997, A46, 467−473.(25) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112−122.(26) Flack, H. D. Acta Crystallogr. 1983, A39, 876−881.(27) der Luis, P. V.; Spek, A. L. Acta Crystallogr. 1990, A46, 194−

201.

Organometallics Article

dx.doi.org/10.1021/om200859z |Organometallics 2011, 30, 6661−66736673