C−H Bond Activation Reactions in π-Allene−Osmium

(a) Espuelas , J.; Esteruelas , M. A.; Lahoz , F. J.; Oro , L. A.; Ruiz , N. J. Am. ...... Miguel A. Esteruelas , Ana M. López , Fernando López , Jo...
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Organometallics 2010, 29, 4071–4079 DOI: 10.1021/om100568r

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C-H Bond Activation Reactions in π-Allene-Osmium-Triisopropylphosphine Complexes with Cyclopentadienyl or Hydridotris(pyrazolyl)borate Ligands: Formation of Isopropenyldiisopropylphosphine versus Hydride-Alkenylcarbyne Derivatives Ruth Castro-Rodrigo, Miguel A. Esteruelas,* Ana M. L opez,* Silvia Mozo, and Enrique O~ nate Departamento de Quı´mica Inorg anica, Instituto de Ciencia de Materiales de Arag on, Universidad de Zaragoza-CSIC, 50009 Zaragoza, Spain Received June 9, 2010

The reactions of the bis(solvento) complexes [OsCp(MeCN)2(PiPr3)]PF6 (1; Cp = cyclopentadienyl) and [OsTp(κ1-OCMe2)2(PiPr3)]BF4 (1a; Tp = hydridotris(pyrazolyl)borate) with allenes have been investigated. Complex 1 reacts with 1-methyl-1-(trimethylsilyl)allene and 1,1-dimethylallene to give the π-allene derivatives [OsCp(η2-CH2dCdCRMe)(MeCN)(PiPr3)]PF6 (R = SiMe3 (2), Me (3)). In fluorobenzene at 80 °C, complexes 2 and 3 are moderately stable and evolve into the isopropenyldiisopropylphosphine derivative [OsCp{κ3P,C,C-PiPr2[C(Me)dCH2]}(MeCN)]PF6 (4) by hydrogen transfer from an isopropyl substituent of the phosphine to the coordinated double bond of the allene. Under an ethylene atmosphere the acetonitrile ligand of 4 is displaced by the olefin. The resulting π-ethylene derivative [OsCp(η2-CH2dCH2){κ3P,C,C-PiPr2[C(Me)dCH2]}]PF6 (5) is obtained through a one-pot synthesis procedure by the stirring of 3 in fluorobenzene at 80 °C under 2 atm of ethylene. Treatment of 2 and 3 with dimethyl acetylenedicarboxylate gives [OsCp{η2CH(CO2Me)dCH(CO2Me)}{κ3P,C,C-PiPr2[C(Me)dCH2]PF6 (6). The reaction of 1a with 1,1dimethylallene leads to [OsTp(η2-CH2dCdCMe2)(κ1-OCMe2)(PiPr3)]BF4 (7). In contrast to its Cp counterpart, complex 7 evolves into the hydride-alkenylcarbyne derivative [OsHTp(tCCHdCMe2)(PiPr3)]BF4 (8), by means of a double migration of the hydrogen atoms of the terminal CH2 group of the allene. One of them migrates to the central carbon atom of the allene, and the other one goes to the metal center. The alkenylcarbyne group of 8 is selectively deprotonated in the presence of the hydride ligand to afford the hydride-alkenylvinylidene OsHTp{dCdCHC(Me)dCH2}(PiPr3) (9). The X-ray structures of 2, 5, 8, and 9 are also reported.

Introduction In the search for transition-metal complexes which are efficient in the synthesis of functionalized organic molecules *To whom correspondence should be addressed. E-mail: maester@ unizar.es (M.A.E.); [email protected] (A.M.L.). (1) (a) Esteruelas, M. A.; L opez, A. M. In Recent Advances in Hydride Chemistry; Peruzzini, M., Poli, R., Eds.; Elsevier: Amsterdam, 2001; Chapter 7, pp 189-248. (b) Esteruelas, M. A.; Oro, L. A. Adv. Organomet. Chem. 2001, 47, 1. (c) Esteruelas, M. A.; Lopez, A. M. Organometallics 2005, 24, 3584. (d) Esteruelas, M. A.; Lopez, A. M.; Olivan, M. Coord. Chem. Rev. 2007, 251, 795. (2) (a) Castro-Rodrigo, R.; Esteruelas, M. A.; L opez, A. M.; Olivan, M.; O~ nate, E. Organometallics 2007, 26, 4498. (b) Castro-Rodrigo, R.; Esteruelas, M. A.; L opez, A. M.; O~ nate, E. Organometallics 2008, 27, 3547. (c) CastroRodrigo, R.; Esteruelas, M. A.; Fuertes, S.; Lopez, A. M.; Mozo, S.; O~nate, E. Organometallics 2009, 28, 5941. (d) Castro-Rodrigo, R.; Esteruelas, M. A.; Fuertes, S.; L opez, A. M.; Lopez, F.; Mascare~nas, J. L.; Mozo, S.; O~nate, E.; Saya, L.; Villarino, L. J. Am. Chem. Soc. 2009, 131, 15572. (e) Castro-Rodrigo, R.; Esteruelas, M. A.; L opez, A. M.; Lopez, F.; Mascare~nas, J. L.; Olivan, M.; O~ nate, E.; Saya, L.; Villarino, L. J. Am. Chem. Soc. 2010, 132, 454. (f) Castroopez, A. M.; Lopez, F.; Mascare~nas, J. L.; Rodrigo, R.; Esteruelas, M. A.; L Mozo, S.; O~ nate, E.; Saya, L. Organometallics 2010, 29, 2372. r 2010 American Chemical Society

from basic hydrocarbon units, we have been reporting on the chemistry of the metal fragments OsCp (Cp = cyclopentadienyl) and iPr3P-Os-PiPr3.1 Recently, we have also included the moiety OsTp (Tp = hydridotris(pyrazolyl)borate) in our work,2 since it should bring different findings by combining the fundamental characteristics of the previous systems. Hydridotris(pyrazolyl)borate and cyclopentadienyl are frequently considered similar ligands. This is due mainly to their facial coordination and because both groups are viewed as 5e-donor ligands. 3 However, there are a number of examples which demonstrate that they can exhibit different (3) (a) Tellers, D. M.; Bergman, R. G. J. Am. Chem. Soc. 2000, 122, 954. (b) Tellers, D. M.; Skoog, S. J.; Bergman, R. G.; Gunnoe, T. B.; Harman, W. D. Organometallics 2000, 19, 2428. (c) R€uba, E.; Simanko, W.; Mereiter, K.; Schmid, R.; Kirchner, K. Inorg. Chem. 2000, 39, 382. (d) Tellers, D. M.; Bergman, R. G. Organometallics 2001, 20, 4819. (e) Bergman, R. G.; Cundari, T. R.; Gillespie, A. M.; Gunnoe, T. B.; Harman, W. D.; Klinckman, T. R.; Temple, M. D.; White, D. P. Organometallics 2003, 22, 2331. (f) Dickinson, P. W.; Girolami, G. S. Inorg. Chem. 2006, 45, 5215. (g) Besora, M.; Vyboishchikov, S. F.; Lledos, A.; Maseras, F.; Carmona, E.; Poveda, M. L. Organometallics 2010, 29, 2040. Published on Web 09/01/2010

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behaviors. The Tp ligand enforces conformations allowing L-M-L angles close to 90 and 180°,4 which are typical in complexes containing the iPr3P-Os-PiPr3 skeleton.1b,d These structures favor nonclassical interactions between the hydrogen atoms bonded to the metal center.5 This has a strong influence on the products of the reactions between osmium-hydride compounds and terminal alkynes,6 which depend upon the difference in energy between the dihydrogen and dihydride tautomers.2b The Cp ligand imposes fewer geometrical restrictions than Tp. Thus, reaction pathways requiring high-energy barriers with Tp are possible with Cp. This has been shown to be crucial for the olefin-alkylidene tautomerization equilibrium2c and the metal-mediated ring expansion of alkylidenecyclobutanes.2f Allenes are a unique class of organic compounds possessing a 1,2-diene moiety, which have shown a nice reactivity. Today, the allene unit is an established member of the tools utilized in modern organic synthetic chemistry, in particular for reactions catalyzed by transition metals.7 The coordination of one of the carbon-carbon double bonds to the metal center8 produces the activation of the allene, which can then undergo several (4) Becker, E.; Pavlik, S.; Kirchner, K. Adv. Organomet. Chem. 2008, 56, 155. (5) (a) Moreno, B.; Sabo-Etienne, S.; Chaudret, B.; RodriguezFernandez, A.; Jalon, F.; Trofimenko, S. J. Am. Chem. Soc. 1994, 116, 2635. (b) Moreno, B.; Sabo-Etienne, S.; Chaudret, B.; Rodriguez, A.; Jalon, F.; Trofimenko, S. J. Am. Chem. Soc. 1995, 117, 7441. (c) Chan, W.-C.; Lau, C.-P.; Chen, Y.-Z.; Fang, Y.-Q.; Ng, S.-M.; Jia, G. Organometallics 1997, 16, 34. (d) Oldham, W. J., Jr.; Hinkle, A. S.; Heinekey, D. M. J. Am. Chem. Soc. 1997, 119, 11028. (e) Gelabert, R.; Moreno, M.; Lluch, J. M.; Lledos, A. Organometallics 1997, 16, 3805. (f) Bohanna, C.; Esteruelas, M. A.; Gomez, A. V.; L opez, A. M.; Martínez, M.-P. Organometallics 1997, 16, 4464. (g) Ng, W. S.; Jia, G.; Hung, M. Y.; Lau, C. P.; Wong, K. Y.; Wen, L. Organometallics 1998, 17, 4556. (h) Sabo-Etienne, S.; Chaudret, B. Coord. Chem. Rev. 1998, 178-180, 381. (i) Jia, G.; Lau, C.-P. Coord. Chem. Rev. 1999, 190-192, 83. (j) Jimenez-Tenorio, M.; Palacios, M. D.; Puerta, M. C.; Valerga, P. Organometallics 2005, 24, 3088. (k) Baya, M.; Esteruelas, M. A.; Olivan, M.; O~ nate, E. Inorg. Chem. 2009, 48, 2677. (6) (a) Espuelas, J.; Esteruelas, M. A.; Lahoz, F. J.; Oro, L. A.; Ruiz, N. J. Am. Chem. Soc. 1993, 115, 4683. (b) Esteruelas, M. A.; Lahoz, F. J.; O~ nate, E.; Oro, L. A.; Valero, C.; Zeier, B. J. Am. Chem. Soc. 1995, 117, 7935. (c) Bohanna, C.; Callejas, B.; Edwards, A.; Esteruelas, M. A.; Lahoz, F. J.; Oro, L. A.; Ruiz, N.; Valero, C. Organometallics 1998, 17, 373. (d) Crochet, P.; Esteruelas, M. A.; Lopez, A. M.; Martínez, M.-P.; Olivan, M.; O~ nate, E.; Ruiz, N. Organometallics 1998, 17, 4500. (e) Buil, M. L.; Eisenstein, O.; Esteruelas, M. A.; García-Yebra, C.; Gutierrez-Puebla, E.; Olivan, M.; O~ nate, E.; Ruiz, N.; Tajada, M. A. Organometallics 1999, 18, 4949. (f) Buil, M. L.; Esteruelas, M. A.; García-Yebra, C.; Gutierrez-Puebla, E.; Olivan, M. Organometallics 2000, 19, 2184. (g) Esteruelas, M. A.; García-Yebra, C.; Olivan, M.; O~nate, E.; Tajada, M. A. Organometallics 2000, 19, 5098. (h) Barrio, P.; Esteruelas, M. A.; O~nate, E. Organometallics 2002, 21, 2491. (i) Barrio, P.; Esteruelas, M. A.; O~nate, E. Organometallics 2003, 22, 2472. (j) Barrio, P.; Esteruelas, M. A.; O~nate, E. J. Am. Chem. Soc. 2004, 126, 1946. (k) Bola~no, T.; Castarlenas, R.; Esteruelas, M. A.; Modrego, F. J.; O~ nate, E. J. Am. Chem. Soc. 2005, 127, 11184. (7) (a) Zimmer, R.; Dinesh, C. U.; Nandanan, E.; Khan, F. A. Chem. Rev. 2000, 100, 3067. (b) Bates, R. W.; Satcharoen, V. Chem. Soc. Rev. 2002, 31, 12. (c) Sydnes, L. K. Chem. Rev. 2003, 103, 1133. (d) Ma, S. Acc. Chem. Res. 2003, 36, 701. (e) Ma, S. Chem. Rev. 2005, 105, 2829. (f) Ma, S. Aldrichchim. Acta 2007, 40, 91. (g) Ma, S. Acc. Chem. Res. 2009, 42, 1679. (h) Alcaide, B.; Almendros, P.; Aragoncillo, C. Chem. Soc. Rev. 2010, 39, 783. (8) (a) Shaw, B. L.; Stringer, A. J. Inorg. Chim. Acta Rev. 1973, 7, 1. (b) Bowden, F. L.; Giles, R. Coord. Chem. Rev. 1976, 20, 81. (c) Otsuka, S.; Nakamura, A. Adv. Organomet. Chem. 1976, 14, 245. (9) (a) Hill, A. F.; Ho, C. T.; Wilton-Ely, J. D. E. T. Chem. Commun. 1997, 2207. (b) Nakanishi, S.; Sasabe, H.; Takata, T. Chem. Lett. 2000, 29, 1058. (c) Sasabe, H.; Nakanishi, S.; Takata, T. Inorg. Chem. Commun. 2003, 6, 1140. (d) Xue, P.; Bi, S.; Sung, H. H. Y.; Williams, I. D.; Lin, Z.; Jia, G. Organometallics 2004, 23, 4735. (e) Xue, P.; Zhu, J.; Hung, H. S. Y.; Williams, I. D.; Lin, Z.; Jia, G. Organometallics 2005, 24, 4896. (f) Bai, T.; Zhu, J.; Xue, P.; Sung, H. H.-Y.; Williams, I. D.; Ma, S.; Lin, Z.; Jia, G. Organometallics 2007, 26, 5581. (g) Xia, J.-L.; Wu, X.; Lu, Y.; Chen, G.; Jin, S.; Yu, G.; Liu, S. H. Organometallics 2009, 28, 2701.

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reactions, including insertion into M-H9 and M-R10 bonds, oxidative coupling with other unsaturated substrates,11 electrophilic12 and nucleophilic13 additions, and Hþ abstraction.14 As a part of our work on the chemistry of the iPr3POs-PiPr3 skeleton, we have recently studied the reactions of the complex OsH2Cl2(PiPr3)2 with 1-methyl-1-(trimethylsilyl)allene and 1,1-dimethylallene and proved that disubstituted allene substrates coordinated to the metal fragment OsCl2(PiPr3)2 undergo the unprecedented migration of both hydrogen atoms of the coordinated CH2 group of the allene to afford hydride-carbyne derivatives (eq 1).15 Now, we have investigated the behavior of the bis(solvento) complexes [OsCp(MeCN)2(PiPr3)]PF6 (1) and [OsTp(κ1-OCMe2)2(PiPr3)]BF4 (1a) toward these organic substrates and observed not only that there are marked differences in behavior between 1 and its Tp-counterpart 1a but also that the iPr3P-Os-PiPr3 and OsTp skeletons stabilize the same type of species.

Results and Discussion 1. The OsCp Skeleton. Treatment at room temperature of dichloromethane solutions of the Cp complex 1 with either (10) (a) Tseng, T.-W.; Chen, M.-C.; Keng, R.-S.; Lin, Y.-C.; Lee, G.-H.; Wang, Y. J. Chin. Chem. Soc. 1991, 38, 581. (b) Bai, T.; Ma, S.; Jia, G. Coord. Chem. Rev. 2009, 253, 423 and references therein. (11) (a) Ingrosso, G.; Immirzi, A.; Porri, L. J. Organomet. Chem. 1973, 60, C35. (b) Diversi, P.; Ingrosso, G.; Immirzi, A.; Porzio, W.; Zocchi, M. J. Organomet. Chem. 1977, 125, 253. (c) Borrini, A.; Ingrosso, G. J. Organomet. Chem. 1977, 132, 275. (d) Barker, G. K.; Green, M.; Howard, J. A. K.; Spencer, J. L.; Stone, G. A. J. Chem. Soc., Dalton Trans. 1978, 1839. (e) Duggan, D. M. Inorg. Chem. 1981, 20, 1164. (f) Schmidt, J. R.; Duggan, D. M. Inorg. Chem. 1981, 20, 318. (g) Hoberg, H.; Oster, B. W. J. Organomet. Chem. 1984, 266, 321. (h) Herberhold, M.; Hill, A. F. J. Organomet. Chem. 1990, 395, 315. (i) Chen, M.-C.; Keng, R.-S.; Lin, Y.-C.; Wang, Y.; Cheng, M.-C.; Lee, G.-H. J. Chem. Soc., Chem. Commun. 1990, 1138. (j) Stephan, C.; Munz, C.; Dieck, H. T. J. Organomet. Chem. 1994, 468, 273. (k) Binger, P.; Langhauser, F.; Wedemann, P.; Gabor, B.; Mynott, R.; Kr€uger, C. Chem. Ber. 1994, 127, 39. (l) Matsunaga, P. T.; Mavropoulos, J. C.; Hillhouse, G. L. Polyhedron 1995, 14, 175. (m) Urabe, H.; Takeda, T.; Hideura, D.; Sato, F. J. Am. Chem. Soc. 1997, 119, 11295. (n) Choi, J.-C.; Sarai, S.; Koizumi, T.; Osakada, K.; Yamamoto, T. Organometallics 1998, 17, 2037. (o) Doxsee, K. M.; Juliette, J. J. J. Polyhedron 2000, 19, 879. (p) Arce, A. J.; Chierotti, M.; Sanctis, Y. D.; Deeming, A. J.; Gobetto, R. Inorg. Chim. Acta 2004, 357, 3799. (q) Bayden, A. S.; Brummond, K. M.; Jordan, K. D. Organometallics 2006, 25, 5204. (r) Xue, P.; Zhu, J.; Liu, S. H.; Huang, X.; Ng, W. S.; Sung, H. H. Y.; Williams, I. D.; Lin, Z.; Jia, G. Organometallics 2006, 25, 2344. (12) (a) Pombeiro, A. J. L.; Hughes, D. L.; Richards, R. L.; Silvestre, J.; Hoffmann, R. J. Chem. Soc., Chem. Commun. 1986, 1125. (b) Pombeiro, A. J. L. Polyhedron 1989, 8, 1595. (c) Henderson, R. A.; Pombeiro, A. J. L.; Richards, R. L.; Wang, Y. J. Organomet. Chem. 1993, 447, C11. (d) Casey, C. P.; Brady, J. T.; Boller, T. M.; Weinhold, F.; Hayashi, R. K. J. Am. Chem. Soc. 1998, 120, 12500. (e) Casey, C. P.; Brady, J. T. Organometallics 1998, 17, 4620. (f) Kuznetsov, M. L.; Pombeiro, A. J. L.; Dement'ev, A. I. Dalton Trans. 2000, 4413. (g) Frohnapfel, D. S.; Enriquez, A. E.; Templeton, J. L. Organometallics 2000, 19, 221. (13) (a) Lennon, P.; Madhavarao, M.; Rosan, A.; Rosenblum, M. J. Organomet. Chem. 1976, 108, 93. (b) Benaim, J.; L'Honore, A. J. Organomet. Chem. 1980, 202, C53. (c) De Renzi, A.; Panunzi, A.; Scalone, M.; Vitagliano, A. J. Organomet. Chem. 1980, 192, 129. (d) Manganiello, F. J.; Oon, S. M.; Radcliffe, M. D.; Jones, W. M. Organometallics 1985, 4, 1069. (e) Soriano, E.; Marco-Contelles, J. Organometallics 2006, 25, 4542. (14) Pu, J.; Peng, T. S.; Arif, A. M.; Gladysz, J. A. Organometallics 1992, 11, 3232. (15) Collado, A.; Esteruelas, M. A.; L opez, F.; Mascare~ nas, J. L.; O~ nate, E.; Trillo, B. Organometallics 2010, in press (DOI 10.1021/om100192t).

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Figure 1. Molecular diagram of the cation of 2. Selected bond lengths (A˚) and angles (deg): Os-C(1) = 2.173(11), Os-C(2) = 2.077(9), Os-P(1) = 2.350(2), Os-N(1) = 2.029(6), C(1)-C(2) = 1.376(13), C(2)-C(3) = 1.338(11); P(1)-Os-N(1) = 87.22(18), P(1)-Os-C(1) = 84.8(3), N(1)-Os-C(2) = 83.0(3), Os-C(2)C(3) = 141.2(6), C(1)-C(2)-C(3) = 143.5(9).

1.5 equiv of 1-methyl-1-(trimethylsilyl)allene for 6 h or 1,1dimethylallene for 12 h leads to the corresponding π-allene derivatives [OsCp(η2-CH2dCdCRMe)(MeCN)(PiPr3)]PF6 (R = SiMe3 (2), Me (3)), as a result of the displacement of one of the acetonitrile molecules of 1 by the less sterically hindered carbon-carbon double bond of the allenes. Complexes 2 and 3 are isolated as white solids in 84% and 78% yield, respectively, according to eq 2.

Complex 2 has been characterized by X-ray diffraction analysis. Figure 1 shows a view of the cation of this salt. The structure proves that the allene is coordinated to the metal center as a η2 ligand through the sterically less hindered C(1)-C(2) double bond. According to this, the distribution of ligands around the osmium atom can be described as a four-legged piano-stool geometry with the cyclopentadienyl ring occupying the three-membered face. The coordinated double bond of the allene lies in the four-membered face with C(1) disposed cisoid to the phosphine ligand (16) Wen, T. B.; Hung, W. Y.; Sung, H. H. Y.; Williams, I. D.; Jia, G. J. Am. Chem. Soc. 2005, 127, 2856. (17) Esteruelas, M. A.; Hernandez, Y. A.; L opez, A. M.; O~ nate, E. Organometallics 2007, 26, 6009. (18) (a) Johnson, T. J.; Albinati, A.; Koetzle, T. F.; Ricci, J.; Eisenstein, O.; Huffman, J. C.; Caulton, K. G. Inorg. Chem. 1994, 33, 4966. (b) Edwards, A. J.; Elipe, S.; Esteruelas, M. A.; Lahoz, F. J.; Oro, L. A.; Valero, C. Organometallics 1997, 16, 3828. (c) Esteruelas, M. A.; GarcíaYebra, C.; Olivan, M.; O~nate, E. Organometallics 2000, 19, 3260. (d) Esteruelas, M. A.; Gonzalez, A. I.; Lopez, A. M.; O~nate, E. Organometallics 2003, 22, 414. (e) Barrio, P.; Esteruelas, M. A.; O~nate, E. Organometallics 2004, 23, 3627. (f) Baya, M.; Buil, M. L.; Esteruelas, M. A.; O~nate, E. Organometallics 2005, 24, 2030. (g) Baya, M.; Buil, M. L.; Esteruelas, M. A.; O~ nate, E. Organometallics 2005, 24, 5180. (h) Esteruelas, M. A.; Fernandez-Alvarez, F. J.; Olivan, M.; O~nate, E. J. Am. Chem. Soc. 2006, 128, 4596. (i) Esteruelas, M. A.; García-Yebra, C.; Olivan, M.; O~nate, E. Inorg. Chem. 2006, 45, 10162. (j) Esteruelas, M. A.; Hernandez, Y. A.; Lopez, A. M.; Olivan, M.; Rubio, L. Organometallics 2008, 27, 799. (k) Esteruelas, M. A.; García-Yebra, C.; O~nate, E. Organometallics 2008, 27, 3029. (l) Esteruelas, M. A.; Fuertes, S.; Olivan, M.; O~nate, E. Organometallics 2009, 28, 1582.





and C(2) disposed cisoid to the acetonitrile molecule. The osmium-allene coordination exhibits Os-C(1) and Os-C(2) bond lengths of 2.173(11) and 2.077(9) A˚, which agree well with those found in the complexes OsCl2(η2-CH2dCdCMe2)(PiPr3)2 (2.156(7) and 2.044(6) A˚),15 OsCl{C(Me)dCHCMe3}(η2-CH2dCdCHCMe3)(PPh3)2 (2.122(2) and 2.044(2) A˚),9e OsCl2{dCPh(η2-CH2dCdCHPh)}(PPh3)2 (2.167(11) and 2.067(11) A˚),16 and [OsCp{dCPh(η2-CH2dCdCHPh)}(PiPr3)]BF4 (2.185(11) and 2.015(16) A˚),17 while lie on the lower part of the range reported for the metal-olefin distances in osmium-olefin compounds (between 2.13 and 2.28 A˚),18 and are significantly shorter than those reported for OsCl{C(Me)dCHC( O)OEt}(η2-CH2dCdCHCO2Et)(PPh3)2 (2.405(3) and 2.416(3) A˚).9e The C(1)-C(2) distance of 1.376(13) A˚ is statistically identical with the C(2)-C(3) bond length of 1.338(11) A˚. The angles C(1)-C(2)-C(3) and OsC(2)-C(3) are 143.5(9) and 141.2(6)°, respectively. The 1H, 13C{1H}, and 31P{1H} NMR spectra of 2 and 3 are consistent with the structure shown in Figure 1. At room temperature in dichloromethane-d2 the most noticeable resonances in the 1H NMR spectra are those corresponding to the CH2 group of the coordinated allenes, which appear at 2.68 and 2.28 ppm (2) and at 2.57 and 2.25 ppm (3). In the 13C{1H} NMR spectrum of 2 the resonances due to the allene carbon atoms are observed at -10.3 (CH2), 121.4 (CMe), and 147.3 ppm (C), whereas in that of 3 they appear at -10.0 (CH2), 118.5 (CMe2), and 132.1 ppm (C). The 31P{1H} NMR spectra contains singlets at 7.5 (2) and 7.3 ppm (3) due to the phosphine ligands. Complexes 2 and 3 are moderately stable in fluorobenzene. At 80 °C, they evolve to give after 24 h the isopropenyldiisopropylphosphine derivative [OsCp{κ3P,C,C-PiPr2[C(Me)dCH2]}(MeCN)]PF6 (4) in quantitative yield, according to eq 3. The formation of this complex implies hydrogen transfer reactions from an isopropyl substituent of the phosphine to the coordinated double bond of the allenes. 2-(Trimethylsilyl)-2-butene and 2-methyl-2butene were detected by GC-MS from the reactions of 2 and 3, respectively. Complex 4 was isolated as a yellow solid in 55% yield.

The dehydrogenation of an isopropyl group of the phosphine and the formation of the isopropenyl substituent are strongly supported by the 1H and 13C{1H} NMR spectra of 4. In the 1H NMR spectrum, the olefinic CH2 protons give rise to double doublets at 4.09 (trans to P) and 2.20 (cis to P) ppm, with an H-H coupling constant of 2.8 Hz and H-P coupling constants of 31.2 and 6.8 Hz, respectively. In the 13 C{1H} NMR spectrum, the C(sp2) carbon atoms of the phosphine display doublets at 43.3 (CP) and 31.7 (CH2) ppm, with C-P coupling constants of 17 and 12 Hz, respectively. The 31P{1H} NMR spectrum shows a singlet at 6.3 ppm. These spectroscopic data agree well with those previously reported for other osmium-isopropenyldiisopropylphosphine complexes.19 The acetonitrile ligand of 4 is displaced by an ethylene molecule in fluorobenzene at 80 °C under 2 atm of olefin

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Figure 2. Molecular diagram of the cation of 5. Selected bond lengths (A˚) and angles (deg): Os-C(1) = 2.174(6), Os-C(2) = 2.159(6), Os-C(3) = 2.250(6), Os-C(4) = 2.189(7), Os-P(1) = 2.2855(15), C(1)-C(2) = 1.415(10), C(3)-C(4) = 1.415(9), C(3)P(1) = 1.773(6), C(3)-C(5) = 1.505(8); C(1)-Os-P(1) = 92.9(2), C(2)-Os-P(1) = 115.5(2), P(1)-C(3)-C(4) = 112.8(4), P(1)C(3)-C(5) = 124.1(5), C(4)-C(3)-C(5) = 122.8(5).

(eq 4). The resulting π-ethylene complex [OsCp(η2-CH2dCH2){κ3P,C,C-PiPr2[C(Me)dCH2]}]PF6 (5) can be also obtained starting from 3, through a one-pot synthesis procedure, by means of the stirring of the π-allene precursor in fluorobenzene at 80 °C under 2 atm of ethylene for 2 days.

Complex 5 is isolated as a white solid in 54% yield and has been characterized by X-ray diffraction analysis. Figure 2 shows a view of the cation of the salt. The osmium-ethylene coordination exhibits Os-C distances of 2.174(6) (Os-C(1)) and 2.159(6) A˚ (Os-C(2)), which agree well with those found in other osmium-olefin complexes.18 Similarly, the olefinic bond length C(1)-C(2) of 1.415(10) A˚ is within the range reported for transition-metal olefin complexes (between 1.340 and 1.445 A˚).20 In contrast to the case for ethylene, the olefinic group of the isopropenyldiisopropylphosphine ligand coordinates to the osmium atom in an asymmetrical fashion with Os-C distances of 2.189(7) (Os-C(4)) and 2.250(6) A˚ (Os-C(3)), which are between 0.02 and 0.09 A˚ longer than the Os-ethylene bond lengths. However, the C(3)-C(4) distance of 1.415(9) A˚ is statistically identical with the C(1)-C(2) bond length. The 1H and 13C{1H} NMR spectra of 5 are consistent with the structure shown in Figure 2. In the 1H NMR spectrum, the ethylene signals appear between 2.20 and 2.28 and at 1.31 (19) (a) Edwards, A. J.; Esteruelas, M. A.; Lahoz, F. J.; L opez, A. M.; O~ nate, E.; Oro, L. A.; Tolosa, J. I. Organometallics 1997, 16, 1316. (b) Esteruelas, M. A.; Lledos, A.; Maseras, F.; Olivan, M.; O~nate, E.; Tajada, M. A.; Tomas, J. Organometallics 2003, 22, 2087. (c) Barrio, P.; Esteruelas, M. A.; O~ nate, E. Organometallics 2003, 22, 2472. (d) Baya, M.; Buil, M. L.; Esteruelas, M. A.; O~ nate, E. Organometallics 2004, 23, 1416. (e) Esteruelas, M. A.; Gonzalez, A. I.; Lopez, A. M.; O~nate, E. Organometallics 2004, 23, 4858. (f) Esteruelas, M. A.; Hernandez, Y. A.; Lopez, A. M.; Olivan, M.; O~ nate, E. Organometallics 2007, 26, 2193. (20) Allen, F. H.; Davies, J. E.; Galloy, J. J.; Johnson, O.; Kennard, O.; Macrae, C. F.; Mitchell, E. M.; Mitchell, G. F.; Smith, J. M.; Watson, D. G. J. Chem. Inf. Comput. Sci. 1991, 31, 187.

Castro-Rodrigo et al.

and 0.51 ppm as the ABCD part of an ABCDX (X = 31P) spin system. In agreement with 4, the CH2 resonances of the isopropenyl group of the phosphine are observed at 3.49 (cis to P) and 3.37 ppm (trans to P) with H-P coupling constants of 12 and 32 Hz, respectively. In the 13C{1H} NMR spectrum, the coordinated ethylene molecule displays doublets at 17.6 and 12.8 ppm with C-P coupling constants of 1 and 3 Hz, respectively, whereas the resonances due to the C(sp2) atoms of the isopropenyl substituent of the phosphine appear at 29.2 (CP) and 28.8 ppm (CH2) as doublets with C-P coupling constants of 30 and 7 Hz, respectively. The 31 P{1H} NMR spectrum contains a singlet at 1.6 ppm, due to the phosphine ligand. The allene ligands of 2 and 3 are displaced by dimethyl acetylenedicarboxylate, which is also an efficient hydrogen acceptor for the dehydrogenation of the phosphine. Thus, the reactions of these compounds with the alkyne in fluorobenzene at 80 °C lead to the π-olefin-isopropenyldiisopropylphosphine derivative [OsCp{η2-CH(CO2Me)dCH(CO2Me)}{κ3P,C,C-PiPr2[C(Me)dCH2]}]PF6 (6), as a result of the hydrogen transfer from an isopropyl substituent of the phosphine to the carbon-carbon triple bond of dimethyl acetylenedicarboxylate, and the corresponding allene (eq 5).

Complex 6 is isolated as a cream-colored solid in 92% yield. Its 1H and 13C{1H} NMR spectra are consistent with the asymmetry of the cation. Thus, the 1H NMR spectrum contains two resonances for the olefinic protons of the coordinated olefin at 2.64 and 1.89 ppm. The first of them appears as a double doublet with H-H and H-P coupling constants of 8.8 and 6.6 Hz, respectively, while the second one is observed as a doublet. The olefinic CH2 protons of the isopropenyl group of the phosphine display double doublets at 3.95 (cis to P) and 3.47 (trans to P) ppm, with a H-H coupling constant of 2.6 Hz and H-P coupling constants of 9.0 and 32.6 Hz, respectively. In the 13C{1H} NMR spectrum, the resonances corresponding to the carbon atoms of the olefin appear at 29.6 and 27.8 ppm as doublets with C-P coupling constants of 4 and 2 Hz, respectively, whereas the resonances due to the C(sp2) atoms of the isopropenyl substituent of the phosphine are observed at 67.0 (CP) and 30.9 ppm (CH2), also as doublets but with C-P coupling constants of 21 and 6 Hz, respectively. The 31P{1H} NMR spectrum shows a singlet at 1.7 ppm. 2. The OsTp Skeleton. The Tp complex 1a initially reacts with 1,1-dimethylallene as does the Cp analogue 1. The addition at room temperature of 2.0 equiv of this allene to acetone-d6 solutions of 1a leads to the π-allene derivative [OsTp(η2-CH2dCdCMe2)(κ1-OCMe2)(PiPr3)]BF4 (7), according to eq 6. The coordination of the less sterically hindered carbon-carbon double bond to the metal center is supported by the 1H and 13C{1H} NMR spectra. The 1H NMR spectrum shows the CH2 resonances of the coordinated organic substrate at 5.15 and 3.27 ppm, whereas in the 13C{1H} NMR spectrum the allene resonances appears at 26.9 (CH2), 115.5 (CMe2) and 162.1 ppm (C). The 31 P{1H} NMR spectrum contains a singlet at -19.6 ppm,

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shifted about 15 ppm toward higher field with regard to that of 1a.

Complex 7 is less stable than 3 in solution. In contrast to its Cp counterpart but in agreement with OsCl2(η2-CH2dCd CMe2)(PiPr3)2,15 it evolves into the hydride-alkenylcarbyne [OsHTp(tCCHdCMe2)(PiPr3)]BF4 (8) according to eq 7. Its formation implies the rupture of both C-H bonds of the CH2 group of the allene. One of the hydrogen atoms migrates to the central carbon atom of the coordinated substrate, while the other one goes to the metal center. In acetone at 70 °C, the transformation is quantitative after 6 h. In fluorobenzene at room temperature, the reaction is much more rapid; even intermediate 7 is not detected. In this solvent, the addition of 2.0 equiv of the allene to 1a affords the quantitative formation of the hydride-alkenylcarbyne derivative after 1 h. Complex 8 is isolated as a brown solid in 72% yield.

Figure 3 shows a view of the cation of this compound. The geometry around the osmium atom can be described as a distorted octahedron with the coordinating nitrogen atoms of the Tp ligand in fac sites. The metal coordination sphere is completed by the phosphine ligand disposed trans to N(1) (P(1)-Os-N(1) = 173.21(12)°), the carbyne group disposed trans to N(3) (C(1)-Os-N(3) = 165.4(2)°), and the hydride disposed trans to N(5) (H(01)-Os-N(5) = 169(2)°). The Os-N bond lengths of 2.143(5) (Os-N(1)), 2.179(4) (Os-N(5)), and 2.208(4) A˚ (Os-N(3)) are consistent with the trans influence of the monodentate ligands increasing in the sequence PiPr3 < H < tCCHdCMe2. The Os-C(1) distance of 1.726(6) A˚ agrees well with those found in other (21) See for example: (a) Esteruelas, M. A.; L opez, A. M.; Ruiz, N.; Tolosa, J. I. Organometallics 1997, 16, 4657. (b) Esteruelas, M. A.; Olivan, M.; O~ nate, E.; Ruiz, N.; Tajada, M. A. Organometallics 1999, 18, 2953. (c) Baya, M.; Crochet, P.; Esteruelas, M. A.; Gutierrez-Puebla, E.; Lopez, A. M.; Modrego, J.; O~ nate, E.; Vela, N. Organometallics 2000, 19, 2585. (d) Castarlenas, R.; Esteruelas, M. A.; O~nate, E. Organometallics 2001, 20, 3283. (e) Bola~ no, T.; Castarlenas, R.; Esteruelas, M. A.; O~nate, E. Organometallics 2007, 26, 2037. (f) Castarlenas, R.; Esteruelas, M. A.; O~nate, E. Organometallics 2007, 26, 2129. (g) Castarlenas, R.; Esteruelas, M. A.; Lalrempuia, R.; Olivan, M.; O~nate, E. Organometallics 2008, 27, 795. (h) Buil, M. L.; Esteruelas, M. A.; Garces, K.; Olivan, M.; O~nate, E. Organometallics 2008, 27, 4680. (i) Bola~no, T.; Collado, A.; Esteruelas, M. A.; O~ nate, E. Organometallics 2009, 28, 2107. (j) Buil, M. L.; Esteruelas, M. A.; Garces, K.; O~ nate, E. Organometallics 2009, 28, 5691. (22) Jia, G. Coord. Chem. Rev. 2007, 251, 2167. (23) See for example: (a) Bustelo, E.; Jimenez-Tenorio, M.; Mereiter, K.; Puerta, M. C.; Valerga, P. Organometallics 2002, 21, 1903. (b) Wen, T. B.; Zhou, Z. Y.; Lo, M. F.; Williams, I. D.; Jia, G. Organometallics 2003, 22, 5217. (c) Ozerov, O. V.; Watson, L. A.; Pink, M.; Caulton, K. G. J. Am. Chem. Soc. 2004, 126, 6363. (d) Cadierno, V.; Díez, J.; García-Garrido, S. E.; Gimeno, J. Organometallics 2005, 24, 3111. (e) Caskey, S. R.; Stewart, M. H.; Ahn, Y. J.; Johnson, M. J. A.; Rowsell, J. L. C.; Kampf, J. W. Organometallics 2007, 26, 1912.

Figure 3. Molecular diagram of the cation of 8. Selected bond lengths (A˚) and angles (deg): Os-C(1) = 1.726(6), Os-N(1) = 2.143(5), Os-N(3) = 2.208(4), Os-N(5) = 2.179(4), Os-P = 2.3738(15), Os-H(01) = 1.47(6), C(1)-C(2) = 1.424(8), C(2)C(3) = 1.357(8); N(1)-Os-P = 173.21(12), N(3)-Os-C(1) = 165.4(2), N(5)-Os-H(01) = 169(2), Os-C(1)-C(2) = 168.7(5), C(1)-C(2)-C(3) = 123.2(5), C(2)-C(3)-C(4) = 121.0(6), C(2)C(3)-C(5) = 122.3(5), C(4)-C(3)-C(5) = 116.7(6).

osmium-carbyne derivatives2b,21 and supports the Os-C triple-bond formulation.22 Similarly to other carbyne metal compounds,23 a slight bending in the Os-C(1)-C(2) moiety is also present (Os-C(1)-C(2) = 168.7(5)°). The alkenylcarbyne proposal is supported by the bond lengths and angles within the η1-carbon donor ligand; for example, C(1) and C(2) are separated by 1.424(8) A˚ and C(2) and C(3) by 1.357(8) A˚, and the angles around C(2) and C(3) are in the range 116-124°. The 1H, 13C{1H}, and 31P{1H} NMR spectra of 8 are consistent with the structure shown in Figure 3. In agreement with the presence of a hydride ligand in the complex, the 1H NMR spectrum contains a doublet at -7.17 ppm with an H-P coupling constant of 19.2 Hz. In the low-field region of the spectrum, the most noticeable signal is a singlet at 5.22 ppm corresponding to the C(sp2)-H proton of the alkenyl substituent of the carbyne ligand. In the 13C{1H} NMR spectrum the OsCR resonance appears at 281.9 ppm, as a doublet with a C-P coupling constant of 13 Hz, whereas the C(sp2) resonances corresponding to C(2) and C(3) are observed at 137.5 and 172.1 ppm, respectively, as singlets. The 31 1 P{ H} NMR spectrum shows a singlet at 29.7 ppm, shifted about 50 ppm toward lower field with regard to 7. Despite the expected acidity of the hydride ligand of 8, the treatment at room temperature of tetrahydrofuran solutions of this salt with 1.9 equiv of sodium methoxide for 2 h produces the selective abstraction of a hydrogen atom of one of the methyl substituents of the alkenyl moiety of the alkenylcarbyne ligand. The abstraction of the latter instead of the hydride ligand could be a consequence of the fact that the abstraction of the hydride implies the reduction of the metal center. The deprotonation gives rise to the formation of the neutral hydride-alkenylvinylidene derivative OsHTp{dCdCHC(Me)dCH2}(PiPr3) (9), which is isolated as a brown solid in 57% yield according to eq 8. The behavior of 8 is similar to that of the bis(phosphine)-hydridealkenylcarbyne complex [OsH(tCCHdCPh2 )(MeCN)2(PiPr3)2](BF4)2, which reacts with KOtBu to give the hydrideallenylidene [OsH(dCdCdCPh2)(MeCN)2(PiPr3)2]BF4 as a

Organometallics, Vol. 29, No. 18, 2010

(24) See for example: (a) Huang, D.; Olivan, M.; Huffman, J. C.; Eisenstein, O.; Caulton, K. G. Organometallics 1998, 17, 4700. (b) Bohanna, C.; Buil, M. L.; Esteruelas, M. A.; O~nate, E.; Valero, C. Organometallics 1999, 18, 5176. (c) Castarlenas, R.; Esteruelas, M. A.; O~nate, E. Organometallics 2000, 19, 5454. (d) Castarlenas, R.; Esteruelas, M. A.; Gutierrez-Puebla, E.; O~ nate, E. Organometallics 2001, 20, 1545. (e) Baya, M.; Crochet, P.; Esteruelas, M. A.; Lopez, A. M.; Modrego, J.; O~nate, E. Organometallics 2001, 20, 4291.





dolizine derivative [OsHCp(CHCHC5H4 N)(PiPr3)]PF6 from 

[OsCp(η2-CH2dCHC5H4 N)(PiPr3)]PF6,2c the exo-endo isomerization of the (2-pyridyl)methylenecyclobutane ligand 

of [OsCp{η2-C(CH2CH2CH2)dCH-C5H4N}(PiPr3)]PF6 which j

j



Figure 4 shows a view of 9. The geometry around the osmium atom is similar to that of 8; i.e., it can be described as a distorted octahedron with the coordinating nitrogen atoms of the Tp ligand in fac sites. The metal coordination sphere is completed by the phosphine ligand disposed trans to N(1) (P-Os-N(1) = 176.16(16)°), the C(1) atom of the vinylidene disposed trans to N(3) (C(1)-Os-N(3) = 164.9(3) A˚), and the hydride disposed trans to N(5) (H(01)-Os-N(5) = 170(2)°). As in 8, the coordination of the Tp group is asymmetric as a result of the chirality of the metal center. The Os-N bond lengths of 2.133(6) (Os-N(1)), 2.188(6) (Os-N(5)), and 2.208(6) A˚ (Os-N(3)) are consistent with the trans influence of the alkenylvinylidene group being higher than those of the triisopropylphosphine and hydride ligands. The vinylidene moiety of the alkenylvinylidene ligand is bound to the metal in a nearly linear fashion, with an Os-C(1)-C(2) angle of 173.8(6)°. The Os-C(1) and C(1)-C(2) bond lengths of 1.796(8) and 1.354(10) A˚, respectively, compare well with those found in other osmium-vinylidene complexes2e,24 and support the vinylidene formulation. Bond lengths and angles of the alkenyl substituent are consistent with those of 8. For example,



result of the selective deprotonation of the alkenyl unit of the alkenylcarbyne group in the presence of the hydride ligand.6k

C(2) and C(3) are separated by 1.482(10) A˚ and C(3) and C(4) by 1.379(12) A˚, whereas the angles around C(2) and C(3) are in the range 115-126°. The 1H, 13C{1H}, and 31P{1H} NMR spectra of 9 are consistent with the structure shown in Figure 4. In agreement with the presence of the hydride ligand, the 1H NMR spectrum contains at -9.82 ppm a doublet with a H-P coupling constant of 21.6 Hz. In the 13C{1H} NMR spectrum, the CR and Cβ resonances of the vinylidene appear at 296.3 and 115.2 ppm, respectively, the first of them as a doublet with a C-P coupling constant of 12 Hz, while the second one is observed as a singlet. The C(sp2) atoms of the alkenyl unit display singlets at 133.0 and 101.5 ppm. The 31 P{1H} NMR spectrum contains a singlet at -15.5 ppm. The difference in behavior between 3 and 7 and the similarity between 7 and OsCl2(η2-CH2dCdCMe2)(PiPr3)2 merit further comments. Triisopropylphosphine is a bulky ligand with a large cone angle of 160°.25 As a consequence of its steric requirement, although a few cis-triisopropylphosphine complexes have been reported,24e,26 in bis(phosphine) compounds the usual arrangement of the triisopropylphosphine ligands is mutually trans. Thus, the iPr3P-Os-PiPr3 metal fragment leaves available the region in the plane perpendicular to the P-M-P direction for the entry of the ligands, which are disposed equidistant from the phosphorus atoms, forming with them L-Os-P angles of about 90°. The Tp ligand imposes geometric restrictions to the OsTp metal fragment similar to those of the iPr3-Os-PiPr3 skeleton; the N-Os-N bite angles resulting from the fac coordination of the Tp group are close to 90°, and in the complexes containing the OsTp(PiPr3) skeleton there is always a P-Os-N angle close to 180°.2 The Cp ligand imposes fewer geometrical restrictions than the Tp group or two triisopropylphosphine ligands. Thus, pathways requiring high activation barriers with Tp or two triisopropylphosphine ligands are feasible with Cp. It should be mentioned as examples the C-H activation processes that are responsible for the formation of the hydride-3-osmain-



Figure 4. Molecular diagram of 9. Selected bond lengths (A˚) and angles (deg): Os-C(1) = 1.796(8), Os-N(1) = 2.133(6), Os-N(3) = 2.208(6), Os-N(5) = 2.188(6), Os-P = 2.315(2), Os-H(01) = 1.585(10), C(1)-C(2) = 1.354(10), C(2)-C(3) = 1.482(10), C(3)-C(4) = 1.379(12), C(3)-C(5) = 1.438(10); N(1)-Os-P = 176.16(16), N(3)-Os-C(1) = 164.9(3), N(5)Os-H(01) = 170(2), Os-C(1)-C(2) = 173.8(6), C(1)-C(2)C(3) = 126.0(7), C(2)-C(3)-C(4) = 122.7(7), C(2)-C(3)C(5) = 115.6(7), C(4)-C(3)-C(5) = 121.7(8).

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affords [OsCp{C(dCHCH2CH2)CH2C5H4 N}(PiPr3)]PF6,2f j

j

and the hydrogen transfer from the isopropyl substituent of the phosphine to the coordinated allenes in 2 and 3 that leads to 4. The rigidity of the OsTp(PiPr3) and iPr3P-Os-PiPr3 skeletons prevents the dehydrogenation of their triisopropylphosphine ligands. This allows the double hydrogen migration from the terminal carbon atom of the allenes to afford the hydride-alkenylcarbyne species. DFT calculations on the model complex OsCl2(η2-CH2dCdCMe2)(PMe3)2 suggest that the first migration, which has an activation energy higher than the second, occurs between the terminal and (25) Tolman, C. A. Chem. Rev. 1977, 77, 313. (26) (a) Werner, H.; Sch€afer, M.; N€ urnberg, O.; Wolf, J. Chem. Ber. 1994, 127, 27. (b) Chen, W.; Esteruelas, M. A.; Herrero, J.; Lahoz, F. J.; Martín, M.; O~nate, E.; Oro, L. A. Organometallics 1997, 16, 6010. (c) Esteruelas, M. A.; Lopez, A. M.; O~nate, E.; Royo, E. Inorg. Chem. 2005, 44, 4094. (d) Esteruelas, M. A.; Lopez, A. M.; O~nate, E.; Royo, E. Organometallics 2005, 24, 5780.

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central carbon atoms and takes place through the metal center. The second migration is a 1,2-hydrogen shift from the allene to the osmium atom.15

Concluding Remarks This study has revealed that there are significant differences in behavior between the Cp-π-allene complexes [OsCp(η2-CH2dCdCRMe)(MeCN)(PiPr3)]PF6 (R = SiMe3, Me) and their Tp counterpart [OsTp(η2-CH2dCdCMe2)(κ1-OCMe2)(PiPr3)]BF4, while the latter shows a behavior similar to that of the bis(phosphine) derivatives OsCl2(η2-CH2dCdCRMe)(PiPr3)2 (R = SiMe3, Me). The Cp complexes are moderately stable in solution and evolve into the isopropenyldiisopropylphosphine derivative [OsCp{κ3P,C,C-PiPr2[C(Me)dCH2]}(MeCN)]PF6 by hydrogen transfer from an isopropyl substituent of the phosphine, which is dehydrogenated, to the coordinated double bond of the allenes. The higher geometrical restrictions imposed by the Tp group with regard to the Cp ligand appear to prevent the C-H bond activation reactions that are necessary to the phosphine dehydrogenation. Then, the hydrogen atoms of the terminal CH2 group of the allene of the Tp complex, in a manner similar to that observed for the π-allene-bis(phosphine) compounds, undergo a double migration. One of them migrates to the central carbon atom of the allene, and the second one goes to the metal center. This affords the hydride-carbyne species [OsHTp(tCCHd CMe2)(PiPr3)]BF4. Despite the expected acidity of the hydride ligand of this complex, its alkenylcarbyne ligand can be selectively deprotonated to give the neutral hydridealkenylvinylidene derivative OsHTp{dCdCHC(Me)dCH2}(PiPr3), in a manner similar to that for the bis(phosphine)hydride-alkenylcarbyne complex [OsH(tCCHdCPh2)(MeCN)2(PiPr3)2](BF4)2. In conclusion, although both Cp and Tp coordinate in a fac fashion and are considered five-electron-donor ligands, the allene chemistry of the OsTp(PiPr3) skeleton is noticeably different from that of OsCp(PiPr3). However, it is surprisingly similar to the allene chemistry of the iPr3P-Os-PiPr3 metal fragment.

Experimental Section General Methods and Instrumentation. All reactions were carried out under argon with rigorous exclusion of air using Schlenk tube or glovebox techniques. Solvents were dried by the usual procedures and distilled under argon prior to use or obtained oxygen- and water-free from an MBraun solvent purification apparatus. 1-Methyl-1-(trimethylsilyl)allene and 1,1dimethylallene were obtained from Sigma-Aldrich. The starting materials [OsCp(MeCN)2(PiPr3)]PF6 (1)27 and [OsTp(κ1-OCMe2)2(PiPr3)]BF4 (1a)2a were prepared according to the published methods. 1H, 31P{1H}, and 13C{1H} NMR spectra were recorded on a Varian Gemini 2000, a Bruker ARX 300, a Bruker Avance 300 MHz, or a Bruker Avance 400 MHz instrument. Chemical shifts (expressed in parts per million) are referenced to residual solvent peaks (1H, 13C{1H}) or external H3PO4 (31P{1H}). Coupling constants, J, are given in hertz. Spectral assignments were achieved by 1 H-1H COSY, 1H{31P}, 13C APT, 1H-13C HSQC, and 1H-13C HMBC experiments. Infrared spectra were recorded on a Spectrum One spectrometer as neat solids. C, H, and N analyses were carried out in a Perkin-Elmer 2400 CHNS/O analyzer. High-resolution (27) Esteruelas, M. A.; Gonzalez, A. I.; L opez, A. M.; Olivan, M.; O~ nate, E. Organometallics 2006, 25, 693.

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electrospray mass spectra were acquired using a MicroTOF-Q hybrid quadrupole time-of-flight spectrometer (Bruker Daltonics, Bremen, Germany). Preparation of [OsCp{η2-CH2dCdCMe(SiMe3)}(MeCN)(PiPr3)]PF6 (2). A solution of 1 (237 mg, 0.37 mmol) in 8 mL of dichloromethane was treated with 1-methyl-1-(trimethylsilyl)allene (92 μL, 0.55 mmol). The mixture was stirred for 6 h at room temperature. The yellow solution was filtered through Celite and concentrated to ca. 1 mL under reduced pressure. The addition of diethyl ether (4 mL) caused the formation of a white solid, which was separated by decantation, washed with diethyl ether (2  2 mL), and dried in vacuo. Yield: 229 mg (84%). Anal. Calcd for C23H43NOsSiP2F6: C, 37.95; H, 5.95; N, 1.92. Found: C, 38.26; H, 5.83; N, 1.90. HRMS (electrospray, m/z): calcd for C21H40OsSiP [M - MeCN]þ 543.2245, found 543.2287; calcd for C16H29NOsP [M - {CH2dCdCMe(SiMe3)}]þ 458.1647, found 458.1707. IR (ATR, cm-1): ν(CtN) 2287(w), ν(CdCdC) 1717 (s), ν(CH2) 1470 (s), ν(PF6) 827 (s). 1H NMR (400 MHz, CD2Cl2, 298 K): δ 5.37 (s, 5H, Cp), 2.70 (d, JH-P = 1.6, 3H, NCCH3), 2.68 (m, 1H, CH2), 2.50 (m, 3H, PCHCH3), 2.28 (ddq, JH-P = 13.2, JH-H = 6.5, JH-H = 2.0, 1H, CH2), 2.10 (t, JH-H = 2, 3H, dCCH3), 1.20 (dd, JH-P = 13.6, JH-H = 7.2, 9H, PCHCH3), 1.17 (dd, JH-P = 14.0, JH-H = 7.2, 9H, PCHCH3), 0.10 (s, 9H, Si(CH3)3). 31P{1H} NMR (121.49 MHz, CD2Cl2, 298 K): δ 7.5 (s), -144.3 (sept, JP-F = 710, PF6). 13C{1H} NMR (75.48 MHz, CD2Cl2, 298 K): δ 147.3 (d, JC-P = 3, dCd), 127.1 (d, JC-P = 2, NCCH3), 121.4 (d, JC-P = 2, dCCH3), 82.6 (s, Cp), 27.7 (d, JC-P = 29, PCHCH3), 20.1 (s, PCHCH3), 19.6 (d, JC-P = 2, PCHCH3), 18.9 (d, JC-P = 1, dCCH3), 4.1 (s, NCCH3), -1.4 (s, SiC), -10.3 (d, JC-P = 7, CH2). Preparation of [OsCp{η2-CH2dCdCMe2}(MeCN)(PiPr3)]PF6 (3). A solution of 1 (260 mg, 0.40 mmol) in 8 mL of dichloromethane was treated with 1,1-dimethylallene (59 μL, 0.60 mmol). The mixture was stirred for 12 h at room temperature. The yellow solution was filtered through Celite and concentrated to ca. 1 mL under reduced pressure. The addition of diethyl ether (4 mL) caused the formation of a white solid, which was separated by decantation, washed with diethyl ether (2  2 mL), and dried in vacuo. Yield: 208 mg (78%). Anal. Calcd for C21H37NOsP2F6: C, 37.66; H, 5.57; N, 2.09. Found: C, 37.32; H, 5.42; N, 2.30. HRMS (electrospray, m/z): calcd for C19H34OsP [M - MeCN]þ 485.2008, found 485.2018; calcd for C16H29NOsP [M - CH2dCdC(CH3)2]þ 458.1647, found 458.1656. IR (ATR, cm-1): ν(CtN) 2270 (w), ν(CH2) 1464 (s), ν(PF6) 841 (s). 1H NMR (400 MHz, CD2Cl2, 298 K): δ 5.38 (s, 5H, Cp), 2.71 (d, JH-P = 1.6, 3H, NCCH3), 2.57 (m, 1H, CH2), 2.48 (m, 3H, PCHCH3), 2.29 (s, 3H, dCCH3), 2.25 (m, 1H, CH2), 2.03 (t, JH-H = 2, 3H, dCCH3), 1.19 (dd, JH-P = 13.6, JH-H = 7.2, 9H, PCHCH3), 1.16 (dd, JH-P = 14, JH-H = 7.2, 9H, PCHCH3). 31P{1H} NMR (121.49 MHz, CD2Cl2, 298 K): δ 7.3 (s), -144.3 (sept, JP-F = 710, PF6). 13C{1H} NMR (100.63 MHz, CD2Cl2, 298 K): 132.1 (d, JC-P = 3, dCd), 126.6 (s, NCCH3), 118.5 (s, =C(CH3)2), 82.7 (s, Cp), 28.5 (s, dCCH3), 27.7 (d, JC-P = 29, PCHCH3), 21.3 (s, dCCH3), 20.0 (s, PCHCH3), 19.6 (d, JC-P = 2, PCHCH3), 4.1 (s, NCCH3), -10.0 (d, JC-P = 7, CH2). Preparation of [OsCp{K3P,C,C-PiPr2[C(Me)dCH2]}(MeCN)]PF6 (4). A solution of 2 (160 mg, 0.22 mmol) or 3 (150 mg, 0.22 mmol) in 8 mL of fluorobenzene was stirred for 1 day at 353 K. GC-MS analysis of an aliquot of the crude reaction mixtures showed the presence of 2-(trimethylsilyl)-2-butene and 2-methyl-2butene, respectively. The resulting yellow solution was filtered and vacuum-dried. The addition of dichloromethane (0.5 mL) and diethyl ether (8 mL) afforded a light yellow solid, which was washed with diethyl ether and dried in vacuo. Yield: 74 mg (55%). Anal. Calcd for C16H27NOsP2F6: C, 32.05; H, 4.54; N, 2.34. Found: C, 32.40; H, 4.67; N, 2.69. HRMS (electrospray, m/z): calcd for C16H27NOsP [M]þ 456.1491, found 456.1510. IR (ATR, cm-1): ν(CtN) 2276 (w), ν(PF6) 839 (s). 1H NMR (400 MHz, CD2Cl2, 298 K): δ 5.12 (s, 5H, Cp), 4.09 (dd, JH-P = 31.2, JH-H = 2.8, 1H, dCHHtrans to P), 2.65 (d, JH-P = 2, 3H, NCCH3), 2.23 (m, 1H, PCHCH3), 2.20 (dd, JH-P = 6.8, JH-H = 2.8, 1H, dCHHcis to P),

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1.73 (m, 1H, PCHCH3), 1.68 (d, JH-P = 7.6, 3H, PC(CH3)d), 1.61 (dd, JH-P = 18.8, JH-H = 7.6, 3H, PCHCH3), 1.57 (dd, JH-P = 15.2, JH-H = 7.2, 3H, PCHCH3), 1.44 (dd, JH-P = 15.6, JH-H = 7.2, 3H, PCHCH3), 1.24 (dd, JH-P = 18.8, JH-H = 7.6, 3H, PCHCH3). 31P{1H} NMR (121.49 MHz, CD2Cl2, 298 K): δ 6.3 (s), -144.4 (sept, JP-F = 711, PF6). 13C{1H} NMR (100.63 MHz, CD2Cl2, 298 K): 127.6 (d, JC-P = 8, NCCH3), 79.4 (s, Cp), 43.3 (d, JC-P = 17, PCd), 31.7 (d, JC-P = 12, dCH2), 29.1 (d, JC-P = 33, PCHCH3), 23.9 (d, JC-P = 3, PC(CH3)d), 23.1 (d, JC-P = 5, PCHCH3), 21.6 (d, JC-P = 5, PCHCH3), 20.2 (d, JC-P = 3, PCHCH3), 20.1 (d, JC-P = 21, PCHCH3), 18.8 (d, JC-P = 2, PCHCH3). Preparation of [OsCp(η2-CH 2dCH 2){K3P,C,C-Pi Pr 2[C(Me)dCH2]}]PF6 (5). Method a. A Fischer-Porter bottle was charged with a yellow solution of 3 (150 mg, 0.22 mmol) in 10 mL of fluorobenzene by cannula. The bottle was pressurized to 2 atm of ethylene, the solution was stirred for 2 days at 353 K, and during this time the colored solution became clearer. The resulting light yellow solution was filtered and vacuum-dried. The addition of dichloromethane and diethyl ether afforded a white solid, which was washed with diethyl ether and dried in vacuo. Yield: 70 mg (54%). Method b. A Fischer-Porter bottle was charged with a yellow solution of 4 (100 mg, 0.17 mmol) in 5 mL of fluorobenzene by cannula. The bottle was pressurized to 2 atm of ethylene, and the solution was stirred for 6 h at 353 K. The resulting solution was filtered and vacuum-dried. The addition of dichloromethane (0.5 mL) and diethyl ether (8 mL) afforded a white solid, which was washed with diethyl ether and dried in vacuo. Yield: 78 mg (76%). Anal. Calcd for C16H28OsP2F6: C, 32.76; H, 4.81. Found: C, 32.46; H, 5.28. HRMS (electrospray, m/z): calcd for C16H28OsP [M]þ 443.1538, found 443.1553. IR (ATR, cm-1): ν(PF6) 819 (s). 1 H NMR (400 MHz, CD2Cl2, 298 K): δ 5.39 (s, 5H, Cp), 3.49 (d, JH-P = 12, 1H, dCHHcis to P), 3.37 (dd, JH-P = 32, JH-H = 4, 1H, dCHHtrans to P), 2.57 (m, 1H, PCHCH3), 2.28-2.20 (2H, CHHdCHH), 1.65 (m, 1H, PCHCH3), 1.63 (dd, JH-P = 19, JH-H = 7.4, 3H, PCHCH3), 1.61 (dd, JH-P = 16, JH-H = 7.2, 3H, PCHCH3), 1.49 (d, JH-P = 7.6, 3H, PC(CH3)d), 1.48 (dd, JH-P = 16.8, JH-H = 7.2, 3H, PCHCH3), 1.38 (dd, JH-P = 19.8, JH-H = 7.4, 3H, PCHCH3), 1.31, 0.51 (both m, 1H each, CHHdCHH). 31P{1H} NMR (121.49 MHz, CD2Cl2, 298 K): 1.6 (s), -144.3 (sept, JP-F = 711, PF6). 13C{1H} NMR (100.63 MHz, CD2Cl2, 298 K): 84.1 (s, Cp), 60.7 (d, JC-P = 20, PC(CH3)d), 29.2 (d, JC-P = 30, PCHCH3), 28.8 (d, JC-P = 7, dCH2), 25.1 (d, JC-P = 6, PCHCH3), 24.3 (d, JC-P = 32, PCHCH3), 20.7 (d, JC-P = 2, PCHCH3), 20.5 (d, JC-P = 6, PCHCH3), 18.4 (s, PCHCH3), 17.6 (d, JC-P = 1, CH2dCH2), 12.8 (d, JC-P = 3, CH2dCH2), 10.1 (d, JC-P = 4, PC(CH3)d). Preparation of [OsCp{η2-CH(CO2Me)dCH(CO2Me)}{PiPr2[C(Me)dCH2]}]PF6 (6). A solution of 2 (185 mg, 0.25 mmol) or 3 (167 mg, 0.25 mmol) in 8 mL of fluorobenzene was treated with dimethyl acetylenedicarboxylate (62 μL, 0.51 mmol). The mixture was stirred for 15 h at 353 K. GC-MS analysis of an aliquot of the crude reaction mixture from the reaction of 2 showed the presence of 1-methyl-1-(trimethylsilyl)allene. The resulting yellow solution was filtered and vacuum-dried. The addition of dichloromethane (0.5 mL) and diethyl ether (10 mL) afforded a cream-colored solid, which was washed with diethyl ether and dried in vacuo. Yield: 162 mg (92%). Anal. Calcd for C20H32O4OsP2F6: C, 34.19; H, 4.59. Found: C, 34.24; H, 4.79. HRMS (electrospray, m/z): calcd for C14H24OsP [M - CH(CO2Me)dCH(CO2Me)]þ 415.1225, found 415.1244. IR (ATR, cm-1): ν(PF6) 832 (s), ν(CdO) 1722, 1708 (s). 1 H NMR (400 MHz, CD2Cl2, 298 K): 5.61 (s, 5H, Cp), 3.95 (dd, JH-P = 9.0, JH-H = 2.6, 1H, dCHHcis to P), 3.66 (s, 3H, CO2CH3), 3.65 (s, 3H, CO2CH3), 3.47 (dd, JH-P = 32.6, JH-H = 2.6, 1H, dCHHtrans to P), 2.68 (m, 1H, PCHCH3), 2.64 (dd, JH-H = 8.8, JH-P = 6.6, 1H, dCH), 1.89 (d, JH-H = 8.8, 1H, dCH), 1.79 (m, 1H, PCHCH3), 1.66 (dd, JH-P = 16.6, JH-H = 7.4, 3H, PCHCH3), 1.65 (dd, JH-P = 19.6, JH-H = 7.6, 3H, PCHCH3), 1.59 (d, JH-P = 8.4, 3H, PC(CH3)d), 1.56 (dd, JH-P = 17.6,

Castro-Rodrigo et al. JH-H = 7.2, 3H, PCHCH3), 1.49 (dd, JH-P = 18.8, JH-H = 7.6, 3H, PCHCH3). 31P{1H} NMR (121.49 MHz, CD2Cl2, 298 K): 1.7 (s), -143.9 (sept, JP-F = 711, PF6). 13C{1H} NMR (75.42 MHz, CD2Cl2, 298 K): 174.5 (s, CO2CH3), 172.1 (s, CO2CH3), 89.3 (s, Cp), 67.0 (d, JC-P = 21, PC(CH3)d), 52.7 (s, CO2CH3), 52.4 (s, CO2CH3), 31.2 (d, JC-P = 29, PCHCH3), 30.9 (d, JC-P = 6, dCH2), 29.6 (d, JC-P = 4, dCH), 27.8 (d, JC-P = 2, dCH), 26.0 (d, JC-P = 7, PCHCH3), 24.8 (d, JC-P = 30, PCHCH3), 20.6 (d, JC-P = 5, PCHCH3), 20.3 (d, JC-P = 2, PCHCH3), 18.4 (s, PCHCH3), 9.9 (d, JC-P = 3, PC(CH3)d). Reaction of [OsTp(K1-OCMe2)2(PiPr3)]BF4 (1a) with 1,1-Dimethylallene: Formation of OsTp{η2-CH2dCdCMe2}(κ1-OCMe2)(PiPr3)]BF4 (7). An NMR tube containing an orange solution of 1a (16 mg, 0.021 mmol) in 0.5 mL of acetone-d6 was treated with 1,1dimethylallene (4.1 μL, 0.042 mmol). After 1 h at 25 °C, the NMR spectra showed the presence of 7 as a major species. 1H NMR (400 MHz, CD3COCD3, 263 K): 8.34 (d, 1H, Tp), 8.15 (d, 1H, Tp), 8.09 (d, 1H, Tp) 8.06 (d, 1H, Tp), 7.40 (d, 1H, Tp), 7.33 (d, 1H, Tp), 6.66 (t, 1H, Tp), 6.41 (m, 2H, Tp), 5.15 (br, 1H, CH2), 3.27 (br, 1H, CH2), 2.76 (m, 3H, PCH), 2.28 (s, 3H, dCCH3), 2.17 (s, 6H, (CH3)2CO), 1.40 (br, 9H, PCHCH3), 1.24 (br dd, JH-P = 9.6, JH-H = 6.8, 9H, PCHCH3), 0.14 (s, 3H, dCCH3); all coupling constants for the pyrazolyl proton resonances were about 2 Hz. 31P{1H} NMR (161.98 MHz, CD3COCD3, 263 K): -19.6 (s). 13C{1H} NMR (100.63 MHz, CD3COCD3, 263 K): 208.6 (s, (CH3)2CO), 162.1 (s, dCd), 152.1, 145.2, 144.3, 138.9, 138.6, 138.4 (all s, Tp), 115.5 (s, =C(CH3)2), 108.8, 108.2, 108.1 (all s, Tp), 32.2 (s, dCCH3), 31.1 (s, (CH3)2CO), 26.9 (d, JC-P = 4, dCH2), 25.7 (d, JC-P = 26, PCH), 21.5 (s, PCHCH3), 20.5 (s, PCHCH3), 16.1 (s, dCCH3). After the tube was heated for 6 h at 70 °C, the spectra showed quantitative conversion to 8. Preparation of [OsHTp{tCCHdCMe2}(PiPr3)]BF4 (8). 1,1Dimethylallene (52 μL, 0.53 mmol) was added to a solution of 1a (205 mg, 0.27 mmol) in 10 mL of fluorobenzene. After 1 h the solvent was evaporated. The addition of 0.5 mL of dichloromethane and 6 mL of diethyl ether caused the appearance of an oil, which was washed with diethyl ether (2  6 mL) and dried in vacuo. Light brown solid. Yield: 138 mg (72%). Anal. Calcd for C23H39B2F4N6OsP: C, 38.45; H, 5.47; N, 11.70. Found: C, 38.89; H, 5.43; N, 11.80. HRMS (electrospray, m/z): calcd for C23H39BN6OsP [M]þ 633.2681, found 633.2707. IR (ATR, cm-1): ν(BH) 2516 (w), ν(OsH) 2104 (w), ν(BF4) 1048 (s). 1H NMR (400 MHz, CD2Cl2, 298 K): 7.95 (s, 1H, Tp), 7.92 (d, 1H, Tp), 7.75 (d, 1H, Tp), 7.71 (s, 1H, Tp), 7.68 (s, 2H, Tp), 6.51 (t, 1H, Tp), 6.28 (m, 2H, Tp), 5.22 (s, 1H, dCH), 2.50 (m, 3H, PCH), 1.88 (s, 3H, dCCH3), 1.80 (s, 3H, dCCH3), 1.39 (dd, JH-P = 13.0, JH-H = 7.0, 9H, PCHCH3), 0.98 (dd, JH-P = 15.8, JH-H = 7.0, 9H, PCHCH3), -7.17 (d, JH-P = 19.2, OsH); all coupling constants for the pyrazolyl proton resonances were about 2 Hz. 31P{1H} NMR (161.98 MHz, CD2Cl2, 298 K): 29.7 (s). 13C{1H} NMR (100.63 MHz, CD2Cl2, 298 K): 281.9 (d, JC-P = 13, OsC), 172.1 (s, dC(CH3)2), 145.9 (s, 2 Tp), 144.8, 137.7 (both s, Tp), 137.5 (s, dCH), 136.2, 135.9, 108.0, 107.4, 107.0 (all s, Tp), 27.3 (s, dCCH3), 24.8 (d, JC-P = 30, PCH), 23.0 (s, dCCH3), 20.5 (s, PCHCH3), 18.9 (d, JC-P = 4, PCHCH3). Preparation of the BPh4 Salt of 8. A mixture of 8 (80 mg, 0.11 mmol) and NaBPh4 (76 mg, 0.22 mmol) in 7 mL of acetone was stirred for 3 h. After this time, the solvent was evaporated and 8 mL of dichloromethane was added. The suspension was filtered through Celite and the solvent removed by evaporation. The oily residue was washed with diethyl ether (5  8 mL) and vacuum-dried. Light brown solid. Yield: 63 mg (60%). The 1H and 31P{1H} NMR data were identical with those reported for 8, except for the additional 1H signals of BPh4-. Preparation of OsHTp{dCdCHC(Me)dCH2}(PiPr3) (9). 8 (133 mg, 0.19 mmol) and NaOMe (20 mg, 0.37 mmol) were dissolved in 10 mL of THF. The resulting suspension was stirred for 2 h. The solvent was then removed in vacuo, and the residue was dissolved in diethyl ether (5 mL) and filtered through Celite.

Article Diethyl ether was evaporated. The addition of pentane (3 mL) at -75 °C caused the precipitation of a brown solid, which was separated by decantation and vacuum-dried. Yield: 67 mg (57%). Anal. Calcd for C23H38BN6OsP: C, 43.81; H, 6.07; N, 13.33. Found: C, 44.01; H, 5.88; N, 13.72. HRMS (electrospray, m/z): calcd for C23H39BN6OsP [M þ H]þ 633.2681, found 633.2704. IR (ATR, cm-1): ν(BH) 2471 (w), ν(OsH) 2073 (w), ν(CdC) 1605 (m). 1H NMR (300 MHz, C6D6, 298 K): 8.34 (d, 1H, Tp), 7.86 (d, 1H, Tp), 7.77 (d, 1H, Tp), 7.44 (d, 1H, Tp), 7.41 (d, 1H, Tp), 7.32 (d, 1H, Tp), 5.91 (t, 1H, Tp), 5.81 (t, 2H, Tp), 4.84 (d, JH-H = 2.4, 1H, CH2), 4.18 (dd, JH-H = 2.4, JH-H = 1.4, 1H, CH2), 2.73 (d, JH-H = 1.4, dCH), 2.25 (m, 3H, PCH), 1.98 (s, 3H, CH3), 1.13 (dd, JH-P = 12.0, JH-H = 7.2, 9H, PCHCH3), 1.04 (dd, JH-P = 13.7, JH-H = 7.2, 9H, PCHCH3), -9.82 (d, JH-P = 21.6, 1H, OsH). 31P{1H} NMR (121.49 MHz, C6D6, 298 K): -15.5 (s). 13C{1H} NMR (75.48 MHz, C6D6, 298 K): 296.3 (d, JC-P = 12, OsC), 145.5, 145.3 (both s, Tp), 144.3 (d, JC-P = 1, Tp), 135.3, 135.2, 133.5 (all s, Tp), 133.0 (s, CdCH2), 115.2 (s, CH), 106.0, 105.9 (both s, Tp), 105.6 (d, JC-P = 2, Tp), 101.5 (s, dCH2), 25.8 (d, JC-P = 27, PCH), 23.0 (s, CH3), 20.3 (s, PCHCH3), 19.4 (d, JC-P = 2, PCHCH3). Structural Analysis of Complexes 2, 5, 8, and 9. X-ray data were collected on Bruker Smart APEX CCD (5, 8, 9) and Oxford Diffraction Xcalibur TS instruments (2) using graphitemonochromated Mo KR radiation (λ = 0.710 73 A˚). Data were collected over the complete sphere and were corrected for absorption by using a multiscan method applied with the CrysAlys RED package28 for complex 2, and with the SADABS program for 5, 8, and 9.29 The structures were solved by direct methods. Refinement of complexes was performed by full-matrix least squares on F2 with SHELXL97, 30 including isotropic and subsequently anisotropic displacement parameters. For 9, the hydride ligand was observed in the difference Fourier maps but could not be refined properly; therefore, the osmium-hydride distance was fixed in the refinement (1.59 A˚, CSD). Crystal Data for 2: C23H43NOsPSi 3 PF6 3 CH2Cl2, MW 812.74, plate, colorless (0.11  0.04  0.02), triclinic, space group P1, a = 10.3264(15) A˚, b = 12.0488(6) A˚, c = 13.6302(15) A˚, R = 89.589(6)°, β = 72.938(11)°, γ = 87.127(7)°, V = 1619.2(3) A˚3, Z = 2, Dcalcd = 1.667 g cm-3, F(000) = 808, T = 150(2) K, μ = 4.289 mm-1, 33 636 measured reflections (2θ = 3-58°, ω scans 1.0°), 7375 unique reflections (Rint = 0.1633), minimum/maximum (28) CrysAlis RED, A program for Xcalibur CCD System X-ray Diffraction Data Reduction; Oxford Diffraction Ltd., Oxford, U.K., 2008. (29) Blessing, R. H. Acta Crystallogr. 1995, A51, 33. SADABS: AreaDetector Absorption Correction; Bruker-AXS, Madison, WI, 1996. (30) SHELXTL Package v. 6.10; Bruker-AXS, Madison, WI, 2000. Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112.

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transmission factors 0.65/0.92, final agreement factors R1 = 0.0538 (3519 observed reflections, I > 2σ(I)) and wR2 = 0.0830, 7375/0/ 351 data/restraints/parameters, GOF = 0.702, largest peak and hole 1.284 and -1.001 e/A˚3. Crystal Data for 5: C16H28OsP 3 PF6, Mw 586.52, irregular block, colorless (0.22  0.10  0.03), monoclinic, space group P21/c, a = 15.859(2) A˚, b = 7.4122(11) A˚, c = 17.417(3) A˚, β = 103.397(3)°, V = 1991.6(5) A˚3, Z = 4, Dcalcd = 1.956 g cm-3, F(000) = 1136, T = 100(2) K, μ = 6.614 mm-1, 23 500 measured reflections (2θ= 3-58°, ω scans 0.3°), 4883 unique reflections (Rint = 0.0746), minimum/maximum transmission factors 0.48/0.82, final agreement factors R1 = 0.0378 (3742 observed reflections, I > 2σ(I)) and wR2 = 0.0869, 4883/5/270 data/ restraints/parameters, GOF = 0.884, largest peak and hole 1.329 and -1.031 e/A˚3. Crystal Data for 8: C23H39BN6OsP 3 C24H20B 3 CH2Cl2, Mw 1035.72, irregular block, orange (0.10  0.08  0.06), triclinic, space group P1, a = 11.8045(9) A˚, b = 14.2611(11) A˚, c = 16.1953(12) A˚, R = 67.6380(10)°, β = 71.9150(10)°, γ = 74.2260(10)°, V = 2359.9(3) A˚3, Z = 2, Dcalcd = 1.458 g cm-3, F(000) = 1052, T = 100(2) K, μ = 2.889 mm-1, 29 199 measured reflections (2θ = 3-58°, ω scans 0.3°), 11 294 unique reflections (Rint = 0.0556), minimum/maximum transmission factors 0.73/0.93, final agreement factors R1 = 0.0478 (8916 observed reflections, I > 2σ(I)) and wR2 = 0.1330, 11 294/0/ 546 data/restraints/parameters, GOF = 0.920, largest peak and hole 1.497 and -2.568 e/A˚3. Crystal Data for 9: C23H38BN6OsP, Mw 630.57, irregular block, orange (0.10  0.08  0.06), triclinic, space group P1, a = 8.2181(15) A˚, b = 8.7108(15) A˚, c = 19.098(4) A˚, R = 89.467(5)°, β = 77.641(3)°, γ = 78.370(3)°, V = 1307.3(4) A˚3, Z = 2, Dcalcd = 1.602 g cm-3, F(000) = 628, T = 100(2) K, μ = 4.960 mm-1, 17 539 measured reflections (2θ = 3-58°, ω scans 0.3°), 6231 unique reflections (Rint = 0.0856), minimum/maximum transmission factors 0.60/0.75, final agreement factors R1 = 0.0487 (4848 observed reflections, I > 2σ(I)) and wR2 = 0.1004, 6231/1/311 data/restraints/parameters, GOF = 0.960, largest peak and hole 1.493 and -1.446 e/A˚3.

Acknowledgment. Financial support from the Spanish MICINN (Projects CTQ2008-00810 and Consolider Ingenio 2010 (CSD2007-00006)), the Diputaci on General de Arag on (E35) and the European Social Fund is acknowledged. Supporting Information Available: CIF files giving positional and displacement parameters, crystallographic data, and bond lengths and angles for compounds 2, 5, 8, and 9. This material is available free of charge via the Internet at http://pubs.acs.org.