Carbyne and Carbyne(hydrido) Osmium Complexes Containing

Aug 10, 2009 - Synopsis. The fac- and mer-isomers of the carbyne complex [OsCl3(≡CCH═CPh2){iPr2PCH2CH2OMe-κP}2] were prepared from ...
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Organometallics 2009, 28, 5137–5141 DOI: 10.1021/om900507f

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Carbyne and Carbyne(hydrido) Osmium Complexes Containing Hemilabile Phosphines as Ligands† Birgit Richter and Helmut Werner* Institut f€ ur Anorganische Chemie der Universit€ at W€ urzburg, Am Hubland, D-97074 W€ urzburg, Germany Received June 15, 2009

The chetale complex [OsCl2(iPr2PCH2CH2OMe-κ2P,O)2] (1) reacted with the propargylic alcohol HCtCCPh2(OH) to give the vinylidene osmium(II) derivative [OsCl2{dCdCHCPh2(OH)}(iPr2PCH2CH2OMe-κP)(iPr2PCH2CH2OMe-κ2P,O)] (2), which upon treatment with HCl in benzene was transformed to the carbyne complex fac-[OsCl3(tCCHdCPh2){iPr2PCH2CH2OMe-κP}2] (3a). Thermal rearrangement of 3a led to the formation of the mer-isomer 3b. Reactions of either [OsH2Cl2(iPr2PCH2CO2Me-κP)2] (4) or [OsCl2(iPr2PCH2CO2Me-κ2P,O)2] (5) with alkynols HCtCCPh(R)OH (R = Ph, Me, H) gave the vinylcarbyne complexes trans,trans-[OsCl2{tCCHdC(Ph)R}{iPr2PCH2CO2Me-κP}{iPr2PCH2C(dO)O-κ2P,O}] (6-8) by converting one of the phosphinoester ligands into a phosphinoacetate moiety. The six-coordinate carbyne(hydrido) osmium(II) compound [OsHCl2{tCCHdCPh2}(PiPr3){iPr2PCH2CH2NMe2-κP}] (10) was obtained from [OsH2Cl2(PiPr3)(iPr2PCH2CH2NMe2)] (9) and HCtCCPh2(OH).

Introduction In the course of studies on the synthesis and reactivity of osmium(II) and osmium(IV) complexes with phosphinoethers, -esters, and -amines as ligands, we recently reported that the thermal reaction of the octahedral compounds [OsCl2(iPr2PCH2CH2OMe-κ2P,O)2] and [OsCl2(iPr2PCH2CO2R-κ2P,O)2] (R=Me, Et) with phenylacetylene gave the vinylidene complexes [OsCl2(dCdCHPh)(iPr2PCH2CH2OMe-κP)(iPr2PCH2CH2OMe-κ2P,O)] and [OsCl2(dCdCHPh)(iPr2PCH2CO2R-κP)(iPr2PCH2CO2R-κ2P,O)], respectively. They are possibly formed via the isomeric alkyne and alkynyl(hydrido) derivatives as intermediates.1 31P NMR measurements indicated that these osmium(II) vinylidenes exhibit a nonrigid structure in solution at room temperature, which is explained by a rapid exchange in the chelating behavior of the two hemilabile phosphine ligands. The X-ray diffraction analysis of [OsCl2(dCdCHPh)(iPr2PCH2CO2Me-κP)(iPr2PCH2CO2Me-κ2P,O)] revealed an Os-C bond length of 1.802(6) A˚, comparable with the Os-C distance in some other (vinylidene)osmium(II) complexes containing an osmium-carbon double bond.2-5

We report in this paper that, in contrast to the reactions of [OsCl2(iPr2PCH2CH2OMe-κ2P,O)2] (1), [OsCl2(iPr2PCH2CO2Me-κ2P,O)2] (5), and [OsH2Cl2(PiPr3)(iPr2PCH2CH2NMe2-κP)] (9) with HCtCPh, the behavior of 1, 5, and 9 toward alkynols HCtCCPh(R)OH is significantly different. Instead of allenylidene osmium(II) compounds, which were expected to be formed via OH-functionalized vinylidene derivatives,6 carbyne osmium(II) complexes were obtained as the final products. Depending on the type of the hemilabile phosphine ligand, they possess not only a different composition but also a different coordination sphere.

Results and Discussion The dichloro osmium(II) compound 1 reacted with an equimolar amount of HCtCCPh2(OH) in a concentrated solution of benzene to give the red-violet vinylidene complex 2 in good yield (Scheme 1). The 31P NMR spectrum of 2 displays two signals at δ 20.1 and -6.0, which corresponds to an AB spin system. The small 31P-31P coupling constant of 8.7 Hz indicates that the two phosphorus atoms are cisdisposed. Other characteristic spectroscopic features of 2 are (1) the signal of the dCH proton at δ 1.75 in the 1H NMR and (2) the two low-field resonances at δ 298.9 and 124.0 in the 13C NMR spectrum. The latter are assigned to the R-C and the β-C carbon atoms of the vinylidene ligand. Compound 2 was also obtained by treatment of a solution of the dihydrido osmium(IV) derivative [OsH2Cl2(iPr2PCH2CH2OMe-κP)2]1 in benzene with HCtCCPh2(OH) in the molar

† Dedicated to Professor Warren R. Roper in recognition of his outstanding achievements in organoosmium chemistry. *Correponding author. E-mail: [email protected]. (1) Weber, B.; Werner, H. Eur. J. Inorg. Chem. 2007, 2072–2082. (2) Weber, B.; Steinert, P.; Windm€ uller, B.; Wolf, J.; Werner, H. J. Chem. Soc., Chem. Commun. 1994, 2595–2596. (3) Huang, D.; Olivan, M.; Huffman, J. C.; Eisenstein, O.; Caulton, K. G. Organometallics 1998, 17, 4700–4706. (4) Esteruelas, M. A.; Olivan, M.; Onate, E.; Ruiz, N.; Tajada, M. A. Organometallics 1999, 18, 2953–2960. (5) (a) Wen, T. B.; Yang, S.-Y.; Zhou, Z. Y.; Lin, Z.; Lau, C.-P.; Jia, G. Organometallics 2000, 19, 3757–3761. (b) Wen, T. B.; Cheung, Y. K.; Yao, J.; Wong, W.-T.; Zhou, Z. Y.; Jia, G. Organometallics 2000, 19, 3803– 3809. (c) Wen, T. B.; Hung, W. Y.; Zhou, Z. Y.; Lo, M. F.; Williams, I. D.; Jia, G. Eur. J. Inorg. Chem. 2004, 2837–2846.

(6) Selected reviews on metal allenylidenes: (a) Bruce, M. I. Chem. Rev. 1991, 91, 197–257. (b) Werner, H. Chem. Commun. 1997, 903–910. (c) Bruce, M. I. Chem. Rev. 1998, 98, 2797–2859. (d) Cadierno, V.; Gamasa, M. P.; Gimeno, J. Eur. J. Inorg. Chem. 2001, 571–591.

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Richter and Werner

Scheme 1

Scheme 2

assume that in each case a single compound was present, the H NMR spectra of the same samples displayed two sets of signals for the protons of the P-bonded isopropyl groups. We therefore concluded that in the course of the reactions of 4 and 5 with the corresponding alkynols always mixtures of two isomers were formed having either an E- or Z-configuration at the vinylic CdC double bond. The 31P NMR data of 6-8 left no doubt that in the major E-isomer as well as in the minor Z-isomer the PiPr2 moieties were trans-disposed. The Z-isomer, which in each of the mixtures was present in less than 15%, was separated by repeated column chromatography and, owing to the small quantities, finally withdrawn. For 6, the X-ray crystal structure analysis confirmed that the vinyl substituent at the carbyne carbon atom possesses the Econfiguration. It also revealed that the carbyne ligand is in trans position to the carboxylate C(O)O oxygen atom.2 Since the chemical shifts of the signals for the carbyne carbon atom in the 13C NMR spectra of 6-8 are almost the same, we believe that not only in 6 but also in 7 and 8 the carbyne unit is trans to the carboxylate oxygen atom. Moreover, we note that for 7 the E-configuration at the vinylic CdC bond was substantiated by NOE measurements. The reaction of 9, obtained from [OsH2Cl2(PiPr3)2] and iPr2PCH2CH2NMe2 by partial substitution of the PiPr3 ligands,1 afforded the carbyne(hydrido) complex 10 as a moss-green solid, which is significantly more air-sensitive than the related carbyne osmium compounds 6-8 (Scheme 3). In the 1H NMR spectrum of 10, the hydride resonance appears at δ -6.7 as a doublet-of-doublets-ofdoublets, the splitting being due to 31P-1H (twice) and 1 H-1H couplings. The 13C NMR spectrum of 10 displays in the low-field region resonances for the carbyne (δ 253.5) and the vinyl carbon atoms (δ 156.9 and 135.9) with chemical shifts that are very similar to those of the bis(tricyclohexylphosphine) derivative [OsHCl2(tCCHdCMe2)(PCy3)2] (δ 256.0, 162.1, and 135.9). This complex containing trans-disposed PCy3 and cis-disposed chloro ligands was characterized crystallographically.11 The 31P NMR spectrum of 10 shows an AB spin system with two signals δA at 1

ratio of 1:2; albeit in this case the olefin byproduct could not be completely separated from the vinylidene complex. If solutions of compound 2 in benzene or toluene were stored for 24 h at room temperature, a smooth change of color from violet to dark brown occurred. We assume that in the course of this process the six-coordinate allenylidene complex [OsCl2(dCdCdCPh2)(iPr2PCH2CO2Me-κP)(iPr2PCH2CO2Me-κ2P,O)] was generated by elimination of water. However, attempts to isolate this compound by fractional crystallization or column chromatography failed. The reaction of 2 in benzene with an equimolar amount of HCl in benzene also did not lead to the corresponding dichloroosmium(II) allenylidene but gave the light green carbyne derivative 3a instead. If a solution of 3a in benzene was stirred under reflux, a rearrangement to 3b occurred. This thermodynamically more stable isomer was equally formed by treatment of 2 with an excess of HCl. Diagnostic for the osmium(II) carbynes are the singlet resonances at δ -9.0 (3a) and -5.7 (3b) in the 31P NMR spectra, indicating that in both compounds the two PiPr2 units are stereochemically equivalent. The 31P-187Os coupling constant of 164.7 Hz for 3b supports a trans disposition of the phosphorus atoms and predicts a meridional arrangement of the OsCl3 fragment. Similar values for J(31P187Os) were found for all-trans-[OsCl2(CO)2(iPr2PCH2CH2OMe-κP)2] and cis, cis,trans-[OsCl2(CO)2(iPr2PCH2CH2OMe-κP)2], both of which also contain a linear P-Os-P unit.1 The dihydridoosmium(IV) compound 4, which was prepared from [OsH2Cl2(PiPr3)2] and iPr2PCH2CO2Me by ligand displacement,1 reacted with alkynols HCtCCR(Ph)OH (R=Ph, Me, H) to afford the vinylcarbyne complexes 6-8 (Scheme 2). The formation of the carbyne ligand is accompanied by an ester cleavage, thereby converting one of the phosphinoester molecules into a phosphinoacetate moiety. The ester cleavage is possibly initiated by the aluminum oxide, which was deactivated with water and then used to purify the crude reaction product by column chromatography. The mechanism could thus be similar to that of the acid-catalyzed ester cleavage in organic chemistry. A similar conversion (with elimination of methyl chloride) was previously observed by treatment of trans-[IrCl(L)(iPr2PCH2CO2Me-κP)2] (L=CO, CdCHR) with Al2O3.7 Whereas the 31P NMR spectra of samples of 6-8, which were purified once by column chromatography, led us to (7) Steinert, P.; Werner, H. Organometallics 1994, 13, 2677–2681.

(8) (a) Espuelas, J.; Esteruelas, M. A.; Lahoz, F. J.; Oro, L. A.; Ruiz, N. J. Am. Chem. Soc. 1993, 115, 4683–4689. (b) Chrochet, P.; Esteruelas, M. A.; Lopez, A. M.; Martínez, M.-P.; Olivan, M.; Onate, E.; Ruiz, N. Organometallics 1998, 17, 4500–4509. (c) Baya, M.; Chrochet, P.; Esteruelas, M. A.; Gutierrez-Puebla, E.; Lopez, A. M.; Modrego, J.; Onate, E.; Vela, N. Organometallics 2000, 19, 2585–2596. (d) Bolano, T.; Castarlenas, R.; Esteruelas, M. A.; Modrego, F. J.; Onate, E. J. Am. Chem. Soc. 2005, 127, 11184–11195. (e) Bolano, T.; Castarlenas, R.; Esteruelas, M. A.; Onate, E. Organometallics 2007, 26, 2037–2041. (9) (a) Spivak, G. J.; Coalter, J. N.; Olivan, M.; Eisenstein, O.; Caulton, K. G. Organometallics 1998, 17, 999–1001. (b) Lee, J.-H.; Pink, M.; Caulton, K. G. Organometallics 2006, 25, 802–804.

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Organometallics, Vol. 28, No. 17, 2009 Scheme 3

18.6 and δB at 11.9. The large 31P-31P coupling constant of 267.0 Hz is consistent with the proposed trans position of the phosphorus atoms. The results presented in this paper confirm that apart from being useful starting materials for the metal-assisted generation of allenylidene ligands,6 propargylic alcohols of the general composition HCtCCR(R0 )OH also offer the opportunity to obtain carbyne metal complexes by formal elimination of the hydroxyl group. In 2003, Jia et al. reported that the reaction of [OsCl2(PPh3)3] with HCtCCPh2(OH) in benzene at room temperature furnished a mixture of products, from which the fac- and the mer-isomers of the sixcoordinate osmium carbyne complex [OsCl3(tCCHd CPh2)(PPh3)2] could be isolated in low quantities.10 The yield of both isomers could be improved by reacting the same starting materials in the presence of HCl 3 OEt2.12 More recently, the same authors also observed that the reduction of mer-[OsCl3{tCCHdC(2-C6H4Cl)2}(PPh3)2], an analogue of [OsCl3(tCCHdCPh2)(PPh3)2], with zinc in the presence of free triphenylphosphine produced an osmanaphthalyne, which was the first stable compound of this structural type.13 Six-coordinate carbyne(hydrido)osmium complexes, structurally related to 10, were prepared for the first time independently by Oro, Esteruelas, et al.8a and by us.2 In both cases, the starting material was the coordinatively unsaturated dihydridoosmium(IV) compound [OsH2Cl2(PiPr3)2],14 which also opened the gate to an impressive (10) Wen, T. B.; Zhou, Z. Y.; Lo, M. F.; Williams, I. D.; Jia, G. Organometallics 2003, 22, 5217–5225. (11) Werner, H.; Jung, S.; Webernd€ orfer, B.; Wolf, J. Eur. J. Inorg. Chem. 1999, 951–957. (12) Hung, W. Y.; Zhu, J.; Wen, T. B.; Yu, K. P.; Sung, H. H. Y.; Williams, I. D.; Lin, Z.; Jia, G. J. Am. Chem. Soc. 2006, 128, 13742– 13752. (13) He, G.; Zhu, J.; Hung, W. Y.; Wen, T. B.; Sung, H. H. Y.; Williams, I. D.; Lin, Z.; Jia, G. Angew. Chem., Int. Ed. 2007, 46, 9065– 9068. (14) Aracama, M.; Esteruelas, M. A.; Lahoz, F. J.; Lopez, J. A.; Meyer, U.; Oro, L. A.; Werner, H. Inorg. Chem. 1991, 30, 288–293. (15) (a) Esteruelas, M. A.; Lahoz, F. J.; Lopez, J. A.; Oro, L. A.; Schl€ unken, C.; Valero, C.; Werner, H. Organometallics 1992, 11, 2034– 2043. (b) Schl€ unken, C.; Werner, H. J. Organomet. Chem. 1993, 454, 243– 246. (c) Schl€ unken, C.; Esteruelas, M. A.; Lahoz, F. J.; Oro, L. A.; Werner, H. Eur. J. Inorg. Chem. 2004, 2477–2487. (16) Inter alia: (a) Esteruelas, M. A.; Oro, L. A.; Ruiz, N. Organometallics 1994, 13, 1507–1509. (b) Bourgault, M.; Castillo, A.; Esteruelas, M. A.; Onate, E.; Ruiz, N. Organometallics 1997, 16, 636–645. (c) Esteruelas, M. A.; L opez, A. M.; Ruiz, N.; Tolosa, J. I. Organometallics 1997, 16, 4657–4667. (d) Esteruelas, M. A.; Oro, L. A. Chem. Rev. 1998, 98, 577–588. (e) Barea, G.; Esteruelas, M. A.; Lledos, A.; Lopez, A. M.; Tolosa, J. I. Inorg. Chem. 1998, 37, 5033–5035. (f) Buil, M. L.; Eisenstein, O.; Esteruelas, M. A.; García-Yebra, C.; Gutierrez-Puebla, E.; Olivan, M.; Onate, E.; Ruiz, N.; Tajada, M. A. Organometallics 1999, 18, 4949–4959. (g) Castarlenas, R.; Esteruelas, M. A.; Gutierrez-Puebla; Jean, Y.; Lledos, A.; Martín, M.; Onate, E.; Tomas,, J. Organometallics 2000, 19, 3100–3108. (h) Esteruelas, M. A.; Fernandez-Alvarez, F. J.; Onate, E. Organometallics 2008, 27, 6236–6244. (17) (a) Gusev, D. G.; Kuznetsov, V. F.; Eremenko, I. L.; Berke, H. J. Am. Chem. Soc. 1993, 115, 5831–5832. (b) Gusev, D. G.; Kuhlman, R.; Sini, G.; Eisenstein, O.; Caulton, K. G. J. Am. Chem. Soc. 1994, 116, 2685–2686. (c) Spivak, G. J.; Caulton, K. G. Organometallics 1998, 17, 5260–5266. (d) Yandulov, D. V.; Bollinger, J. C.; Streib, W. E.; Caulton, K. G. Organometallics 2001, 20, 2040–2046.

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series of new hydridoosmium(II) and hydridoosmium(IV) derivatives.1,4,8,9,15-18 Finally, it should be kept in mind that the first complexes containing an osmium-carbon triple bond of the general composition [OsCl(tCR)(CO)(PPh3)2] were reported by Roper’s group as early as in 1980, i.e., almost three decades ago.19

Experimental Section All reactions were carried out under an atmosphere of argon by Schlenk techniques. The starting materials 1, 4, 5, and 9 were prepared as described in the literature.1 The propargylic alcohols were commercial products from Aldrich and Messer Griesheim. NMR spectra were recorded on Bruker AC 200 and Bruker AMX 400 instruments at room temperature, if not otherwise stated. IR spectra were recorded on a Perkin-Elmer 1420 infrared spectrometer. Melting points were measured by DTA. Abbreviations used: s, singlet; d, doublet; t, triplet; m, multiplet; br, broadened signal. The term vt indicates a virtual triplet, and N = 3J(P,H) þ 5J(P,H) or 1J(P,C) þ 3J(P,C). The coupling constants JOs,P were determined from the satellites that belongs to the 31P NMR signals.20 Preparation of cis,cis-[OsCl2{dCdCHCPh2(OH)}{iPr2PCH2CH2OMe-KP}{iPr2PCH2CH2OMe-K2P,O}] (2). A solution of 1 (68 mg, 0.11 mmol) in benzene (1 mL) was treated with HCtCCPh2(OH) (23 mg, 0.11 mmol) and slowly stirred for 2 h at room temperature. The solvent was evaporated in vacuo, and pentane (5 mL) was added to the oily residue. The suspension was stirred until a red-violet solid precipitated. The solid was filtered, washed twice with 2 mL portions of pentane, and dried; yield 49 mg (54%). Anal. Calcd for C33H54Cl2O3OsP2: C, 48.23; H, 6.62. Found: C, 48.33; H, 6.85. IR (KBr): ν(OH) 3365 cm-1. 1 H NMR (400 MHz, C6D6): δ 7.80, 7.19, 7.05 (all m, 10 H, C6H5), 3.41, 3.22 (both s, 3 H each, OCH3), 3.61, 3.42, 3.22, 2.92, 2.83, 2.67, 2.56, 2.34, 1.93 (all m, 12 H, PCH2 and OCH2 and PCHCH3), 1.75 [dd, 4JP,H = 4JP’,H =3.5 Hz, 1 H, OsdCdCH], 1.39 [dd, 3JP,H=17.2, 3JH,H =6.8 Hz, 3 H, PCHCH3], 1.35 [dd, 3 JP,H =14.5, 3JH,H =7.0 Hz, 3 H, PCHCH3], 1.24 [dd, 3JP,H = 11.1, 3JH,H = 7.4 Hz, 3 H, PCHCH3], 1.22 [dd, 3JP,H = 10.6, 3 JH,H=7.6 Hz, 3 H, PCHCH3], 1.01 [dd, 3JP,H=14.5, 3JH,H=7.2 Hz, 3 H, PCHCH3], 0.88 [dd, 3JP,H =13.2, 3JH,H =7.3 Hz, 3 H, PCHCH3], 0.84 [dd, 3JP,H=14.8, 3JH,H=6.9 Hz, 3 H, PCHCH3], 0.76 [dd, 3JP,H=13.8, 3JH,H=6.6 Hz, 3 H, PCHCH3]. 13C NMR (50.3 MHz, C6D6): δ 298.9 [dd, 2JP,C = 2JP’,C = 11.4 Hz, OsdCdC], 159.1, 152.1 (both s, ipso-C of C6H5), 128.3, 128.1, 127.7, 127.5, 126.6, 126.5 (all s, C6H5), 124.0 (s, OsdCdC), 73.3 (s, OCH2), 70.6 (s, CPh2), 68.7 [d, 3JP,C =5.1 Hz, OCH2], 60.7, 58.2 (both s, OCH3), 30.1 [d, 1JP,C=33.0 Hz, PCHCH3], 29.5 [d, 1 JP,C=29.1 Hz, PCH2], 28.7 [d, 1JP,C=34.3 Hz, PCHCH3], 27.6 [d, 1JP,C = 29.2 Hz, PCHCH3], 23.8 [d, 1JP,C = 26.7 Hz, PCHCH3], 23.4 [d, 1JP,C = 28.0 Hz, PCH2], 19.9, 19.7, 19.4, 19.2, 19.0, 18.4 (all s, PCHCH3). 31P NMR (81.0 MHz, C6D6): δ 20.1, -6.0 [both d, 2JP,P =8.7 Hz]. Preparation of fac-[OsCl3(tCCHdCPh2){iPr2PCH2CH2OMe-KP}2] (3a). A solution of 2 (72 mg, 0.09 mmol) in benzene (5 mL) was treated dropwise with a saturated solution of HCl in benzene until a change of color from red to dark green occurred. After the reaction mixture was stirred for 5 min at room temperature, the solvent was evaporated in vacuo. To the oily residue was added pentane (5 mL) and the suspension stirred at -78 °C. A light green solid precipitated, which was filtered, (18) Maseras, F.; Eisenstein, O. New J. Chem. 1998, 5–9. (19) (a) Clark, G. R.; Marsden, K.; Roper, W. R.; Wright, L. J. J. Am. Chem. Soc. 1980, 102, 6570–6571. (b) Review: Gallop, M. A.; Roper, W. R. Adv. Organomet. Chem. 1986, 25, 121–198. (20) (a) Benn, R.; Brennecke, H.; Joussen, E.; Lehmkuhl, H.; L opez Ortiz, F. Organometallics 1990, 9, 756–761. (b) Berger, S.; Braun, S.; Kalinowski, H.-O. NMR-Spektroskopie von Nichtmetallen; Georg Thieme Verlag: Stuttgart, 1993; Vol. 3.

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washed twice with 2 mL portions of pentane (0 °C), and dried; yield 60 mg (81%). Anal. Calcd for C33H53Cl3O2OsP2: C, 47.17; H, 6.36. Found: C, 46.89; H, 6.11. 1H NMR (200 MHz, C6D6): δ 8.18, 7.42, 7.20. 7.13 (all m, 10 H, C6H5), 5.46 (br s, 1 H, CHdCPh2), 3.69 (br s, 4 H, OCH2), 3.03 (s, 6 H, OCH3), 2.90 (br m, 4 H, PCH2), 2.39 (m, 4 H, PCHCH3), 1.24 (br s, 24 H, PCHCH3). 13C NMR (50.3 MHz, C6D6): δ 260.2 [t, 2JP,C=13.3 Hz, OstC], 164.3 (s, CHdCPh2), 140.7, 137.5 (both s, ipso-C of C6H5), 135.6 (s, CHdCPh2), 132.0, 131.8, 131.4, 130.0, 129.4, 129.1 (all s, C6H5), 69.5 (s, OCH2), 58.4 (s, OCH3), 28.5, 28.3 [both d, 1JP,C = 28.0 Hz, PCHCH3], 26.0 [d, 1JP,C = 31.8 Hz, PCH2], 20.6, 20.3, 19.9, 19.6 (all s, PCHCH3). 31P NMR (81.0 MHz, C6D6): δ -9.0 (s). Preparation of mer,trans-[OsCl3(tCCHdCPh2){iPr2PCH2CH2OMe-KP}2] (3b). Method a: A stream of carefully dried gaseous HCl was passed through a solution of 2 (77 mg, 0.10 mmol) in benzene (5 mL) for 15 s at room temperature. A change of color from red to green occurred. After the solution was stirred for 5 min, the solvent was evaporated in vacuo and pentane (5 mL) was added to the residue.The suspension was slowly stirred at -78 °C, which led to the formation of a dark green microcrystalline solid. The solid was separated from the mother liquor, washed three times with small amounts of pentane (0 °C), and dried: yield 77 mg (92%). Method b: A solution of 3a (60 mg, 0.07 mmol) in benzene (5 mL) was stirred for 15 h under reflux. After the solution was cooled to room temperature, the solvent was evaporated in vacuo, and the residue worked up analogously to that described for method a: yield 58 mg (97%). Anal. Calcd for C33H53Cl3O2OsP2: C, 47.17; H, 6.36. Found: C, 47.37; H, 6.27. 1H NMR (400 MHz, C6D6): δ 7.61, 7.24 (both m, 2 H each, C6H5), 7.14 (m, 4 H, C6H5), 6.94 (m, 2 H, C6H5), 5.43 [t, 4JP,H = 1,5 Hz, 1 H, CHdCPh2], 3.66 (m, 4 H, OCH2), 3.08 (m, 4 H, PCH2), 3.03 (s, 6 H, OCH3), 2.80 (m, 4 H, PCHCH3), 1.40 [dvt, N = 14.8, 3 JH,H=7.0 Hz, 12 H, PCHCH3], 1.25 [dvt, N=13.8, 3JH,H=7.0 Hz, 12 H, PCHCH3]. 13C NMR (50.3 MHz, C6D6): δ 259.9 [t, 2 JP,C=10.2 Hz, OstC], 158.9 (s, CHdCPh2), 140.4, 138.5 (both s, ipso-C of C6H5), 135.8 (s, CHdCPh2), 130.7, 130.6, 129.9, 129.2, 128.8 (all s, C6H5), 68.6 (s, OCH2), 57.9 (s, OCH3), 25.1 [vt, N=26.7 Hz, PCHCH3], 19.8 [vt, N=25.4 Hz, PCH2], 18.7, 18.6 (both s, PCHCH3). 31P NMR (162.0 MHz, C6D6): δ -5.7 [s, JOs,P =164.7 Hz]. Preparation of trans,trans-[OsCl2(tCCHdCPh2){iPr2PCH2CO2Me-KP}{iPr2PCH2C(dO)O-K2P,O}] (6). Method a: A solution of 4 (80 mg, 0.13 mmol) in benzene (10 mL) was treated with HCtCCPh2(OH) (83 mg, 0.39 mmol) and stirred for 4 h under reflux. A change of color from orange to green occurred. After the solution was cooled to room temperature, the solvent was evaporated in vacuo. The residue was dissolved in benzene (1 mL) and the solution was chromatographed on Al2O3 (neutral, activity grade V, height of column 10 cm). The chromatographic separation was repeated twice. In the final run, the first brown fraction, which was eluted with benzene, was withdrawn. Subsequently, with dichloromethane a green fraction was eluted, which was brought to dryness in vacuo. The residue was recrystallized from diethyl ether/hexane (1:10) to give a green solid; yield 21 mg (21%). Method b: A solution of 5 (81 mg, 0.13 mmol) in benzene (10 mL) was treated with HCtCCPh2(OH) (55 mg, 0.26 mmol) and stirred for 4 h under reflux. The reaction mixture was worked up analogously to that described for method a: yield 18 mg (18%); mp 162 °C dec. Anal. Calcd for C32H46Cl2O4OsP2: C, 47.00; H, 5.67; Os, 23.26. Found: C, 46.73; H, 5.31; Os, 23.05. IR (KBr): ν(CdO) 1720, 1640 cm-1. 1H NMR (400 MHz, CDCl3): δ 7.48, 7.35 (both m, 10 H, C6H5), 5.50 (s, 1 H, CHdCPh2), 3.60 (s, 3 H, OCH3), 3.05, 2.90 (both m, 2 H each, PCHCH3), 3.04, 2.99 [both d, 2JP,H=9.0 Hz, 2 H each, PCH2], 1.35 [dd, 3JP,H=13.4, 3JH,H=7.3 Hz, 6 H, PCHCH3], 1.32 [dd, 3JP,H=12.5, 3JH,H=7.4 Hz, 6 H, PCHCH3], 1.21 [dd, 3JP,H = 15.1, 3JH,H = 7.2 Hz, 6 H, PCHCH3], 1.19 [dd, 3JP,H = 13.8, 3JH,H = 7.3 Hz, 6 H, PCHCH3]. 13C NMR

Richter and Werner (50.3 MHz, CDCl3): δ 276.2 [dd, 2JP,C=2JP’,C=8.9 Hz, OstC], 179.1 [dd, 2JP,C=2JP’,C=9.5 Hz, PCH2C(O)O], 171.1 [d, 2JP,C= 7.6 Hz, PCH2CO2Me], 162.7 (s, CHdCPh2), 139.8, 138.6 (both s, ipso-C of C6H5), 135.5 (s, CHdCPh2), 132.0, 131.7, 130.8, 130.2, 129.8, 129.5 (all s, C6H5), 52.5 (s, CO2CH3), 31.4 [dd, 1 JP,C = 21.1, 3JP’,C = 5.1 Hz, PCH2], 24.0 [d, 1JP,C = 20.3 Hz, PCH2], 23.9 (m, PCHCH3), 19.8, 19.7, 17.5, 17.3 (all s, PCHCH3). 31P NMR (162.0 MHz, CDCl3): AB spin system, δA =15.1 [J(A,B) =265.7, J(Os,P) =158.3 Hz], δB =12.5 [J(A,B) = 265.7, J(Os,P) =168.5 Hz]. Preparation of trans,trans-[OsCl2(tCCHdC(Me)Ph){iPr2PCH2CO2Me-K(P)}{iPr2PCH2C(dO)O-K2P,O}] (7). This compound was prepared analogously to that described for 6, using either 4 (50 mg, 0.08 mmol) and racemic HCtCC(Me)(Ph)OH (53 mg, 0.36 mmol) or 5 (61 mg, 0.10 mmol) and racemic HCtCC(Me)(Ph)OH (28 mg, 0.19 mmol) in benzene (10 mL) as starting materials. The reaction mixture was stirred for 4 h under reflux and then worked up analogously to that described for 6, using diethyl ether as eluant. A pale red microcrystalline solid was obtained: yield 16 mg (18%) with 4 or 17 mg (23%) with 5 as starting material; mp 131 °C dec. Anal. Calcd for C27H44Cl2O4OsP2: C, 42.91; H, 5.87. Found: C, 43.23; H, 6.15. IR (KBr): ν(CdO) 1720, 1645 cm-1. 1H NMR (400 MHz, C6D6): δ 7.10, 7.00, 6.90 (all m, 5 H, C6H5), 5.52 (s, 1 H, CHdC(Me)Ph), 3.84 [vt, N=8.4 Hz, 2 H, PCH2], 3.19 (s, 3 H, OCH3), 2.90 (m, 2 H, PCHCH3), 2.17 (s, 3 H, C(CH3)Ph), 1.46 [dvt, N=16.3, 3JH,H=6.9 Hz, 6 H, PCHCH3], 1.35 [dvt, N=14.5, 3 JH,H =6.8 Hz, 6 H, PCHCH3], 1.22 [dvt, N=16.0, 3JH,H =7.2 Hz, 6 H, PCHCH3], 1.01 [dvt, N = 14.7, 3JH,H = 7.0 Hz, 6 H, PCHCH3]. 13C NMR (100.6 MHz, CDCl3): δ 278.6 [dd, 2JP,C= 2 JP’,C = 8.1 Hz, OstC], 179.3 [dd, 2JP,C = 2JP’,C = 7.2 Hz, PCH2C(O)O], 171.2 (s, PCH2CO2Me), 160.3 (s, CHdC(Me)Ph), 138.5 (s, ipso-C of C6H5), 135.9 (s, CHdC(Me)Ph), 132.3, 130.2, 126.2 (all s, C6H5), 52.7 (s, CO2CH3), 31.3 [dd, 1 JP,C=3JP’,C=13.3 Hz, PCH2], 24.5 [dd, 1JP,C=3JP’,C=12.8 Hz, PCHCH3], 23.6 [dd, 1JP,C = 3JP’,C = 8.9 Hz, PCH2], 23.2 [dd, 1 JP,C = 3JP’,C = 13.0 Hz, PCHCH3], 22.2 (s, C(CH3)Ph), 20.0, 19.8, 17.9, 17.8 (all s, PCHCH3). 31P NMR (162.0 MHz, CDCl3): AB spin system, δA =14.9 [J(A,B) =213.9 Hz, J(Os,P) = 162.6 Hz], δB =13.7 [J(A,B) =213.9 Hz, J(Os,P) =162.6 Hz]. Preparation of trans,trans-[OsCl2(tCCHdCHPh){iPr2PCH2CO2Me-KP}{iPr2PCH2C(dO)O-K2P,O}] (8). This compound was prepared analogously to that described for 6, using either 4 (105 mg, 0.17 mmol) and racemic HCtCCH(Ph)OH (64 μL, 0.51 mmol) or 5 (120 mg, 0.19 mmol) and racemic HCtCCH(Ph)OH (70 μL, 0.56 mmol) in benzene (20 mL) as starting materials. The reaction mixture was stirred for 3 h under reflux and then worked up analogously to that described for 6, using a 1:1 mixture of benzene and diethyl ether as eluant. An olive green microcrystalline solid was obtained: yield 15 mg (12%) with 4 or 14 mg (10%) with 5 as starting material; mp 82 °C dec. Anal. Calcd for C26H42Cl2O4OsP2: C, 42.10; H, 5.71. Found: C, 42.46; H, 5.97. IR (KBr): ν(CdO) 1725, 1645 cm-1. 1 H NMR (400 MHz, CDCl3): δ 7.82 [d, 3JH,H =16.4 Hz, 1 H, CHdCHPh], 7.50, 7.45, 7.30 (all m, 5 H, C6H5), 5.82 [d, 3JH,H= 16.4 Hz, 1 H, CHdCHPh], 3.57 (s, 3 H, OCH3), 3.43 [d, 2JP,H= 9.6 Hz, 2 H, PCH2], 2.99 (m, 4 H, PCHCH3), 2.94 [d, 2JP,H=8.5 Hz, 2 H, PCH2], 1.28 (br m, 24 H, PCHCH3). 13C NMR (100.6 MHz, CDCl3): δ 276.7 [dd, 2JP,C=2JP’,C=8.9 Hz, OstC], 180.1 (br m, PCH2C(O)O], 171.1 [d, 2JP,C = 8.5 Hz, PCH2CO2Me], 148.9 (s, CHdCHPh), 136.1 (s, CHdCHPh), 133.3 (s, ipso-C of C6H5), 133.2, 130.6, 128.5 (all s, C6H5), 52.8 (s, CO2CH3), 30.1 [dd, 1JP,C=3JP’,C=19.5 Hz, PCH2], 24.7 [dd, 1JP,C=24.3, 3JP’,C= 3.8 Hz, PCHCH3], 23.6 [dd, 1JP,C = 21.3, 3JP’,C = 4.4 Hz, PCHCH3], 20.3, 19.8, 18.2, 17.8 (all s, PCHCH3); the signal for the second PCH2 carbon atom had not been observed. 31P NMR (162.0 MHz, CDCl3): AB spin system, δA=17.1, δB=15.9 [J(A,B) =256.3 Hz]. Preparation of [OsHCl2{tCCHdCPh2}(PiPr3){iPr2PCH2CH2NMe2-KP}] (10). A solution of 9 (160 mg, 0.26 mmol) in

Article benzene (15 mL) was treated with HCtCCPh2(OH) (163 mg, 0.78 mmol) and stirred for 3 h under reflux. After the solution was cooled to room temperature, the solvent was evaporated in vacuo. The residue was dissolved in benzene (1 mL) and the solution was chromatographed on Al2O3 (neutral, activity grade V, height of column 10 cm). The first fraction, which was eluted with benzene, was withdrawn. Subsequently, with diethyl ether a dark green fraction was eluted, which was brought to dryness in vacuo. The oily residue was layered with hexane (5 mL), and the suspension was irradiated in an ultrasound bath for 5 min. A moss-green solid was formed, which was filtered and dried in vacuo; yield 23 mg (11%). Anal. Calcd for C34H57Cl2NOsP2: C, 50.86; H, 7.16; N, 1.74. Found: C, 50.97; H, 7.06; N, 1.59. IR (KBr): ν(OsH) 2030 cm-1.1H NMR (400 MHz, C6D6): δ 7.85, 7.35, 7.19, 7.09, 6.95 (all m, 10 H, C6H5), 5.06 [dd, 4JP,H =1.3,

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JH,H=0.9 Hz, 1 H, CHdCPh2], 2.87, 2.74, 2.59, 2.26 (all m, 9 H, PCH2,and NCH2 and PCHCH3), 2.10 (s, 6 H, NCH3), 1.51 [dd, 3 JP,H=14.4, 3JH,H=7.0 Hz, 3 H, PCHCH3], 1.38-1.27 (br m, 24 H, PCHCH3), 1.01 [dd, 3JP,H = 13.6, 3JH,H = 7.2 Hz, 3 H, PCHCH3], -6.72 [ddd, 2JP,H=2JP’,H=16.0, 4JH,H=0.9 Hz, 1 H, OsH]. 13C NMR (100.6 MHz, C6D6): δ 253.5 [dd, 2JP,C=2JP’,C= 11.4 Hz, OstC], 156.9 (s, CHdCPh2), 141.4, 138.0 (both s, ipsoC of C6H5), 135.9 (s, CHdCPh2), 131.2, 130.9, 129.9, 129.8, 129.2, 128.5 (all s, C6H5), 55.0 [d, 2JP,C=3.0 Hz, NCH2], 45.0 (s, NCH3], 28.6 [d, 1JP,C=26.6 Hz, PCHCH3], 27.7 [d, 1JP,C=23.5 Hz, PCHCH3], 24.7 [d, 1JP,C = 27.7 Hz, PCHCH3], 20.1 [d, 1 JP,C =27.9 Hz, PCH2], 20.0, 19.4, 19.3, 19.2, 19.1, 18.8 (all s, PCHCH3). 31P NMR (162.0 MHz, C6D6): AB spin system, δA= 18.6 [J(A,B)=267.0, J(Os,P)=170.1 Hz], δB=11.9 [J(A,B)=267.0, J(Os,P) =175.5 Hz].