C−H Bond Activation of Terminal Allenes: Formation of Hydride

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Organometallics 2010, 29, 4966–4974 DOI: 10.1021/om100192t

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C-H Bond Activation of Terminal Allenes: Formation of Hydride-Alkenylcarbyne-Osmium and Disubstituted Vinylidene-Ruthenium Derivatives Alba Collado,† Miguel A. Esteruelas,*,† Fernando L
opez,§ Jos
e L. Mascare~ nas,*,‡ ,† ‡ Enrique O~ nate,* and Beatriz Trillo †

Departamento de Quı´mica Inorg
anica, Instituto de Ciencia de Materiales de Arag
on, Universidad de Zaragoza-CSIC, 50009 Zaragoza, Spain, ‡Departamento de Quı´mica Org
anica, Universidade de Santiago de Compostela, 15782, Santiago de Compostela, Spain, and § Instituto de Quı´mica Org
anica General-CSIC, Juan de la Cierva 3, 28006, Madrid, Spain Received March 11, 2010

The reactivity of the dihydrides MH2Cl2(PiPr3)2 (M = Os (1), Ru (2)) toward allenes has been studied. Complex 1 reacts with 2 equiv of 3-methyl-1,2-butadiene and 1-methyl-1-(trimethylsilyl)allene to give 1 equiv of olefin and the π-allene derivatives OsCl2(η2-CH2dCdCRMe)(PiPr3)2 (R = Me (3), Me3Si (4)). The X-ray structure of 4 proves the coordination to the metal center of the carbon-carbon double bond of the allene with the lowest steric hindrance. In toluene, complexes 3 and 4 are unstable and evolve into the hydride-alkenylcarbyne derivatives OsHCl2(tCCHdCRMe)(PiPr3)2 (R = Me (5), Me3Si (6)). DFT calculations on the model compound OsCl2(η2-CH2dCdCMe2)(PMe3)2 (3t) suggest that the π-allene to hydride-alkenylcarbyne transformation involves the migration of both hydrogen atoms of the CH2 group of the allene. The first of them occurs between the terminal and central carbon atoms and takes place throught the metal center. The second one is a 1,2-hydrogen shift from the allene terminal carbon to osmium. The reactions of the ruthenium complex 2 with the previously mentioned allenes give olefins and RuCl2(η2CH2dCdCRMe)(PiPr3)2 (R = Me (7), Me3Si (8)), which in dichloromethane and in the presence of allene afford the disubstituted vinylidene complexes RuCl2(dCdCRMe)(PiPr3)2 (R = Me (9), Me3Si (10)). The structure of 10 in the solid state has been determined by X-ray diffraction analysis. DFT calculations show that the formation of 9 and 10 can be rationalized in terms of the initial isomerization of 7 and 8 to alkenylcarbene species, which subsequently undergo metathesis reactions with a second allene molecule.

Introduction

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Allenes are a unique class of organic compounds possessing a 1,2-diene moiety, which is present in many natural products and pharmaceuticals. During the last years, they have shown a nice reactivity. Thus, today, the allene moiety is an established member of the tools utilized in modern organic synthetic chemistry, especially for reactions catalyzed by transition metals.1 Part of the Dietmar Seyferth Festschrift. *Corresponding authors. E-mail: [email protected]; enriqueo@ unizar.es; [email protected]. (1) (a) Zimmer, R.; Dinesh, C. H.; 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) Trillo, B.; Gulías, M.; L
opez, F.; Castedo, L.; Mascare~nas, J. L. Adv. Synth. Catal. 2006, 348, 2381. (g) Ma, S. Aldrichchim. Acta 2007, 40, 91. (h) Jeganmohan, M.; Cheng, C.-H. Chem. Commun. 2008, 3101. (i) Trillo, B.; L
opez, F.; Gulías, M.; Castedo, L.; Mascare~ nas, J. L. Angew. Chem., Int. Ed. 2008, 47, 951. (j) Trillo, B.; L
opez, F.; Montserrat, S.; Ujaque, G.; Castedo, L.; Lled
os, A.; Mascare~nas, J. L. Chem.;Eur. J. 2009, 15, 3336. (k) Alonso, I.; Trillo, B.; L
opez, F.; Montserrat, S.; Ujaque, G.; Castedo, L.; Lled
os, A.; Mascare~nas, J. L. J. Am. Chem. Soc. 2009, 131, 13020. (l) Ma, S. Acc. Chem. Res. 2009, 42, 1679. (m) Alcaide, B.; Almendros, P.; Aragoncillo, C. Chem. Soc. Rev. 2010, 39, 783. (2) (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. (d) Hansen, S. M.; Volland, M. A. O.; Rominger, F.; Eisentr€ager, F.; Hofmann, P. Angew. Chem., Int. Ed. 1999, 38, 1273. pubs.acs.org/Organometallics

Published on Web 04/12/2010

The coordination of one of the carbon-carbon double bonds to a metal center2 produces the activation of the allene, which can then undergo several reactions including insertion into M-R bonds,3 oxidative coupling with other unsaturated substrates,4 (3) (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) Hill, A. F.; Ho, C. T.; WiltonEly, J. D. E. T. Chem. Commun. 1997, 2207. (c) Xia, J.-L.; Wu, X.; Lu, Y.; Chen, G.; Jin, S.; Yu, G.; Liu, S. H. Organometallics 2009, 28, 2701. (d) Bai, T.; Ma, S.; Jia, G. Coord. Chem. Rev. 2009, 253, 423, and references therein. (4) (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.; Sanctus, 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. r 2010 American Chemical Society

Article

electrophilic5 and nucleophilic6 additions, and Hþ abstraction.7 These stoichiometric reactions are the basis of the mechanisms proposed for the catalytic reactions involving allenes. Osmium is more reducing than ruthenium and prefers coordination saturation and redox isomers with more metalcarbon bonds.8 The difference in behavior toward terminal alkynes, RCtCH, between the osmium-dihydride OsH2Cl2(PiPr3)2 and its ruthenium counterpart RuH2Cl2(PiPr3)2 is in agreement with this. While the reactions of the first of them lead to the hydride-carbynes OsHCl2(tCCH2R)(PiPr3)2,9 the second one affords mixtures of the monosubstituted vinylidenes RuCl2(dCdCHR)(PiPr3)2 and the carbenes RuCl2(dCHCH2R)(PiPr3)2.10 Complexes OsHCl2(tCCH2R)(PiPr3)2 are oxidized isomers of the unknown OsCl2(dCHCH2R)(PiPr3)2 compounds, which should be the osmium counterparts to the Grubbs-type carbene-ruthenium derivatives RuCl2(dCHCH2R)(PiPr3)2.11 The reactions of osmium- and ruthenium-hydride complexes with allenes, in contrast to those with alkynes,12 have been rarely studied. They have been focused on monohydride compounds and in all of the cases afford insertion products.13 We have now studied the reactions of the osmium-dihydride OsH2Cl2(PiPr3)2 and its ruthenium counterpart RuH2Cl2(PiPr3)2 with 3-methyl-1,2-butadiene and 1-methyl-1-(trimethylsilyl)allene and have discovered new reaction patterns, involving (5) (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. 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. J. Chem. Soc., Dalton Trans. 2000, 4413. (g) Frohnaptel, D. S.; Enriquez, A. E.; Templeton, J. L. Organometallics 2000, 19, 221. (6) (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. (7) Pu, J.; Peng, T. S.; Arif, A. M.; Gladysz, J. A. Organometallics 1992, 11, 3232. (8) (a) Caulton, K. G. J. Organomet. Chem. 2001, 617-618, 56. (b) Esteruelas, M. A.; L
opez, A. M. Organometallics 2005, 24, 3584. (c) Bola~ no, T.; Castarlenas, R.; Esteruelas., M. A.; Modrego, F. J.; O~nate, E. J. Am. Chem. Soc. 2005, 127, 11184. (d) Bola~no, T.; Castarlenas, R.; Esteruelas, M. A.; O~ nate, E. J. Am. Chem. Soc. 2006, 128, 3965. (e) Esteruelas, M. A.; L
opez, A. M.; Oliv
an, M. Coord. Chem. Rev. 2007, 251, 795. (f) Bola~no, T.; Castarlenas, R.; Esteruelas, M. A.; O~nate, E. Organometallics 2007, 26, 2037. (g) Bola~ no, T.; Castarlenas, R.; Esteruelas, M. A.; O~nate, E. J. Am. Chem. Soc. 2007, 129, 8850. (h) Jia, G. C. Coord. Chem. Rev. 2007, 251, 2167. (i) Bola~no, T.; Castarlenas, R.; Esteruelas, M. A.; O~nate, E. Organometallics 2008, 27, 6367. (j) Bola~ no, T.; Castarlenas, R.; Esteruelas, M. A.; O~nate, E. J. Am. Chem. Soc. 2009, 131, 2064. (9) Espuelas, J.; Esteruelas, M. A.; Lahoz, F. J.; Oro, L. A.; Ruiz, N. J. Am. Chem. Soc. 1993, 115, 4683. (10) (a) Gr€ unwald, C.; Gevert, O.; Wolf, J.; Gonz
alez-Herrero, P.; Werner, H. Organometallics 1996, 15, 1960. (b) Wolf, J.; St€uer, W.; Gr€unwald, C.; Gevert, O.; Laubender, M.; Werner, H. Eur. J. Inorg. Chem. 1998, 1827. (11) (a) Trnka, T. M.; Grubbs, R. H. Acc. Chem. Res. 2001, 34, 18. (b) Grubbs, R. H. Tetrahedron 2004, 60, 7117. (12) Castro-Rodrigo, R.; Esteruelas, M. A.; L
opez, A. M.; O~ nate, E. Organometallics 2008, 27, 3547, and references therein. (13) (a) Nakanishi, S.; Sasabe, H.; Takata, T. Chem. Lett. 2000, 1058. (b) Sasabe, H.; Nakanishi, S.; Takata, T. Inorg. Chem. Commun. 2003, 6, 1140. (c) Xue, P.; Bi, S.; Sung, H. H. Y.; Williams, I. D.; Lin, Z.; Jia, G. Organometallics 2004, 23, 4735. (d) Xue, P.; Zhu, J.; Hung, H. S. Y.; Williams, I. D.; Lin, Z.; Jia, G. Organometallics 2005, 24, 4896. (e) Sasabe, H.; Kihara, N.; Mizuno, K.; Ogawa, A.; Takata, T. Chem. Lett. 2006, 35, 212. (f) Bai, T.; Zhu, J.; Xue, P.; Sung, H. H. Y.; Williams, I. D.; Ma, S.; Lin, Z.; Jia, G. Organometallics 2007, 26, 5581.

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Figure 1. Molecular diagram of 3. Selected bond lengths (A˚) and angles (deg): Os-C(1) 2.156(7), Os-C(2) 2.044(6), C(1)C(2) 1.449(9), C(2)-C(3) 1.322(8), P(1)-Os-P(2) 170.75(5), Cl(1)-Os-Cl(2) 135.09(6), C(1)-C(2)-C(3) 136.8(6), OsC(2)-C(3) 149.1(5).

the C-H bond activation of the terminal CH2 group of the allenes, which leads to two different types of compounds. In agreement with the previously mentioned differences between osmium and ruthenium, while the first of them gives hydridealkenylcarbyne derivatives, the second one affords disubstituted vinylidene compounds. Theoretical calculations on the mechanism of both processes have also been carried out. This paper reports the preparation of hydride-alkenylcarbyne-osmium and disubstituted vinylidene-ruthenium derivatives, starting from the dihydride complexes MH2Cl2(PiPr3)2 (M = Os (1), Ru (2)) and allenes, and the formation pathways of both types of compounds.

Results and Discussion 1. Formation of Hydride-Alkenylcarbyne-Osmium Complexes. Treatment at 313 K of toluene solutions of the osmium complex 1 with either 3.0 equiv of 3-methyl-1,2-butadiene or 1-methyl-1-(trimethylsilyl)allene for 6 h produces the hydrogenation of 1 equiv of allene to give the corresponding olefin; 3-methyl-1-butene in the first case and a mixture of 3-trimethylsilyl-1-butene and 2-trimethylsilyl-2-butene in a 2:1 molar ratio with the second allene;together with the 14-valence-electron metal fragment OsCl2(PiPr3)2, which is trapped by a second equivalent of substrate to afford the π-allene derivatives OsCl2(η2-CH2dCdCRMe)(PiPr3)2 (R = Me (3), Me3Si (4)). Complexes 3 and 4 are isolated as green solids in 74% and 60% yield, respectively, according to eq 1.

Complex 3 has been characterized by X-ray diffraction analysis (Figure 1). The geometry around the osmium atom can be described as a distorted trigonal bipyramid with apical phosphines (P(1)-Os-P(2) = 170.75(5)°) and a Cl(1)-Os-Cl(2) angle of 135.09(6)° within the equatorial plane. The structure proves that the allene is coordinated to the metal center as a η2-ligand through the carbon-carbon double bond with the

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Collado et al.





lowest steric hindrance (C(1)-C(2)). The Os-allene coordination exhibits Os-C(1) and Os-C(2) bond lengths of 2.156(7) and 2.044(6) A˚, which agree well with those found in the complex OsCl{C(Me)dCHCMe3}(η2-CH2dCdCHCMe3)(PPh3)2 (2.122(2) and 2.044(2) A˚), while they are significantly shorter than those reported for OsCl{C(Me)dCHC( O)OEt} (η2CH2dCdCHCO2Et)(PPh3)2 (2.405(3) and 1.367(5) A˚)13d and osmium-olefin compounds (between 2.13 and 2.28 A˚).14 The C(1)-C(2) distance of 1.449(9) A˚, which is about 0.12 A˚ longer than the C(2)-C(3) bond length (1.322(8) A˚), lies on the upper part of the range reported for transition-metal olefin complexes (between 1.340 and 1.445 A˚).15 The angles C(1)-C(2)-C(3) and Os-C(2)-C(3) are 136.8(6)° and 149.1(5)°, respectively. The 1H, 13C{1H}, and 31P{1H} NMR spectra of 3 and 4 are consistent with the structure shown in Figure 1. At room temperature in benzene-d6, the most noticeable resonances in the 1H NMR spectra are those corresponding to the CH2 group of the coordinated allenes, which appear at 4.27 (3) and 4.24 (4) ppm. In the 13C{1H} NMR spectrum of 3 the resonances due to the allene carbon atoms are observed at -6.8 (CH2), 121.0 (CMe2), and 127.0 (C) ppm, whereas in that of 4 they appear at -7.4 (CH2), 127.1 (C), and 146.1 (C(SiMe3)Me) ppm. The 31P{1H} NMR spectra contain singlets at -46.5 (3) and -36.4 (4) ppm, in agreement with the presence of equivalent phosphines. Complexes 3 and 4 are moderately stable in toluene. At 353 K, they evolve to give after 15 h the hydride-alkenylcarbyne derivatives OsHCl2(tCCHdCRMe)(PiPr3)2 (R = Me (5), Me3Si (6)) in quantitative yield, according to eq 2. The formation of these compounds implies the rupture of both C-H bonds of the CH2 group of the allenes. One of the hydrogen atoms migrates to the central carbon atom of the coordinated substrate, while the other one goes to the metal center. This is consistent with previous results of Caulton and co-workers, which have observed that 1 reacts with styrene and propylene to give equimolecular amounts of OsHCl2(tCCH2R)(PiPr3)2 (R = Ph, Me) and the hydrogenated olefin.16

Complexes 5 and 6 are isolated as brown and gray solids in 62% and 80% yield, respectively. Complex 5 has been (14) (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) Buil, M. L.; Esteruelas, M. A.; GarcíaYebra, C.; Gutierrez-Puebla, E.; Olivan, M. Organometallics 2000, 19, 2184. (d) Esteruelas, M. A.; García-Yebra, C.; Oliv
an, M.; O~nate, E. Organometallics 2000, 19, 3260. (e) Baya, M.; Esteruelas, M. A.; O~nate, E. Organometallics 2002, 21, 5681. (f) Esteruelas, M. A.; Gonz
alez, A. I.; L
opez, A. M.; O~nate, E. Organometallics 2003, 22, 414. (g) Baya, M.; Buil, M. L.; Esteruelas, M. A.; O~ nate, E. Organometallics 2004, 23, 1416. (h) Baya, M.; Buil, M. L.; Esteruelas, M. A.; O~ nate, E. Organometallics 2005, 24, 2030. (i) Esteruelas, M. A.;
Fern
andez-Alvarez, F. J.; Oliv
an, M.; O~nate, E. J. Am. Chem. Soc. 2006, 128, 4596. (j) Esteruelas, M. A.; Hern
andez, Y. A.; L
opez, A. M.; Oliv
an, M.; Rubio, L. Organometallics 2008, 27, 799. (k) Castro-Rodrigo, R.; Esteruelas, M. A.; L
opez, A. M.; L
opez, F.; Mascare~nas, J. L.; Oliv
an, M.; O~nate, E.; Saya, L.; Villarino, L. J. Am. Chem. Soc. 2010, 132, 454. (15) Allen, F. H.; Davies, J. E.; Galloy, J. J.; Johnson, O.; Kennard, O.; Macrae, C. F.; Mitchell, G. F.; Smith, J. M.; Watson, D. G. J. Chem. Inf. Comput. Sci. 1991, 31, 187. (16) Spivak, G.; Coalter, J. N.; Oliv
an, M.; Eisenstein, O.; Caulton, K. G. Organometallics 1998, 17, 999.

Figure 2. Relative energies (ΔGtoluene; kcal 3 mol-1) for the transformation of 3t into 5t.

previously prepared by reaction of 1 with 2-methyl-1-buten-3yne. The 1H, 13C{1H}, and 31P{1H} NMR spectrum of 6 agrees well with that of 5.9 According to the presence of a hydride ligand in these complexes, the 1H NMR spectrum of 6 contains at -7.11 ppm a triplet with a H-P coupling constant of 16.4 Hz. In the low-field region of the spectrum, the most noticeable resonance is a singlet at 4.95 ppm, assigned to the C(sp2)-H proton of the alkenyl substituent of the carbyne ligand. The cis disposition of the latter and the Me3Si group (δ, -0.23) at the C-C double bond was inferred from a NOESY 1H NMR experiment. In the 13C{1H} NMR spectrum, the OsC resonance appears at 254.9 ppm as a triplet with a C-P coupling constant of 11 Hz, whereas the C(sp2) resonances of the alkenyl substituent are observed at 167.1 and 144.8 ppm as singlets. The 31 1 P{ H} NMR spectrum shows a singlet at 18.3 ppm. 2. Theoretical Calculations on the π-Allene to HydrideAlkenylcarbyne Transformation. In an effort to gain insight into the mechanistic details of the π-allene to hydridealkenylcarbyne transformation, we have carried out DFT calculations (B3PW91) on the process using PMe3 and 3methyl-1,2-butadiene as models of PiPr3 and allene. The changes in free energy ΔG have been computed at 298.15 K and P = 1 atm and corrected using toluene as solvent. Figure 2 shows the energy profile for the transformation, whereas Chart 1 collects the optimized structures and selected structural parameters. The transformation implies a double hydrogen migration, as previously mentioned. The first of them occurs between the terminal and central carbon atoms of the allene (from C1 to C2), whereas the second one is a 1,2-hydrogen shift from the coordinated terminal carbon atom to the metal (from C1 to Os). The hydrogen migration between the central and terminal carbon atoms of the allene takes place via the metal center (C1fOsfC2). Thus, it is initiated by a 1,2-hydrogen shift from the coordinated CH2 group of the allene to the osmium atom. It affords the intermediate 3ta, which is 11.6 kcal 3 mol-1 less stable than 3t. This species can be described as a hydrideosmacyclopropene derivative with the C1-C2 bond of the metallacycle almost perpendicular to the P-Os-P direction. The Os-C1, Os-C2, and C1-C2 bond lengths of 1.908, 2.096, and 1.356 A˚, respectively, compare well with those found by X-ray diffraction analysis for reported osmacyclopropene complexes.17 This hydrogen shift takes place via the transition (17) (a) Buil, M. L.; Eisenstein, O.; Esteruelas, M. A.; Garcı´ a-Yebra, C.; Guti
errez-Puebla, E.; Oliv
an, M.; O~ nate, E.; Ruiz, N.; Tajada, M. A. Organometallics 1999, 18, 4949. (b) Barrio, P.; Esteruelas, M. A.; O~nate, E. Organometallics 2003, 22, 2472.

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trigonal-pyramidal species with trans-phosphines (P-OsP = 170.5°) and the carbene in the foot of the Y (Cl-OsCl = 144.6°; Cl-Os-C = 107.7°). The Os-C1 bond length of 1.878 A˚ supports the Os-C double-bond formulation.18 The OsfC2 hydrogen migration occurs through the transition state TS3, which is 20.1 kcal 3 mol-1 above 3t. It results from the approach of the hydride ligand of 3tb to the central carbon atom of the coordinated organic fragment. Once the C1fC2 hydrogen migration has taken place, the C1fOs hydrogen migration occurs. In agreement with the osmium preference for coordination saturation and the redox isomers with more metal-carbon bonds, the 16-valence electron alkenyl-carbene intermediate 3tc evolves into the 18valence electron hydride-carbyne 5ta, by means of a 1,2-hydrogen shift from the C1 carbene carbon atom to the metal center. Complex 5ta is 10.8 kcal 3 mol-1 more stable than 3t. The transition state TS4 connecting 3tc and 5ta lies 20.2 kcal 3 mol-1 above 3t. It results from the approach of the C1H-hydrogen to the osmium atom. As a consequence of the approach process, 

Chart 1

state TS1, which lies 28.3 kcal 3 mol-1 above 3t. It results from the approach of one of the C-H bonds of the coordinated CH2 group to the osmium atom. The transoid disposition of the hydride ligand and the central carbon atom C2 of the coordinated organic fragment in 3ta prevents the OsfC2 hydrogen migration. Thus, the rotation of the coordinated organic fragment around an Os-(C1-C2 bond) axis is necessary before the migration. The rotation leads to 3tb, with the hydride ligand cisoid disposed to C2. This hydride-osmacyclopropene isomer of 3tb (Os-C1 =1.900 A˚, Os-C2 =2.079 A˚, C1-C2 =1.358 A˚), with the C1-C2 bond also almost perpendicular to the P-Os-P direction, is 7.5 kcal 3 mol-1 less stable than 3t, i.e., 4.1 kcal 3 mol-1 more stable than 3ta. The rotation barrier is 28.9 kcal 3 mol-1. The transition state TS2 connecting 3ta and 3tb can be described as a hydride-osmacyclopropene with the C1-C2 bond almost parallel to the P-Os-P direction (Os-C1 = 1.896 A˚, Os-C2 = 2.143 A˚, C1-C2 = 1.352 A˚). The cisoid disposition of the hydride ligand and C2 in 3tb allows the OsfC2 hydrogen migration, which leads to 3tc. This alkenylcarbene intermediate is 5.3 kcal 3 mol-1 more stable than 3t. It can be described as a five-coordinate (18) See for example: (a) Asensio, A.; Buil, M. L.; Esteruelas, M. A.; O~ nate, E. Organometallics 2004, 23, 5787. (b) Castarlenas, R.; Esteruelas, M. A.; O~ nate, E. Organometallics 2005, 24, 4343. (c) Castarlenas, R.; Esteruelas, M. A.; O~ nate, E. Organometallics 2007, 26, 2129. (d) Castarlenas, R.; Esteruelas, M. A.; O~nate, E. Organometallics 2007, 26, 3082. (e) Esteruelas, M. A.; L
opez, A. M.; O~nate, E. Organometallics 2007, 26, 3260. (f) Castro-Rodrigo, R.; Esteruelas, M. A.; Fuertes, S.; L
opez, A. M.; Mozo, S.; O~ nate, E. Organometallics 2009, 28, 5941. (g) Castro-Rodrigo, R.; Esteruelas, M. A.; Fuertes, S.; L
opez, A. M.; L
opez, F.; Mascare~nas, J. L.; Mozo, S.; O~ nate, E.; Saya, L.; Villarino, L. J. Am. Chem. Soc. 2009, 131, 15572.

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the osmium-carbene unit forms an OsdC(R) H system. The Os-C1 distance of 1.810 A˚ is 0.068 A˚ shorter than in 3tc and 0.068 A˚ longer than in 5ta (Os-C1 = 1.742 A˚). The Os-H and C1-H distances are 2.052 and 1.194 A˚, respectively, whereas the C1-Os-H angle is 35.3°. This distorted η2-coordination mode has been observed in alkylidene complexes of electron-deficient transition metals.19 Finally, the alkenyl substituent of the carbyne ligand of 5ta rotates around the C1-C2 bond to afford the reaction product 5t, which is 12.3 kcal 3 mol-1 more stable than 3t. The activation barrier for the C1fOs hydrogen migration is significantly lower than that for the C1fC2 hydrogen migration (20.2 versus 28.9 kcal 3 mol-1). This suggests that the latter is the rate-determining step for this π-allene to hydride-alkenylcarbyne transformation promoted by the osmium fragment OsCl2(PiPr3)2. 3. Formation of Disubstituted Vinylidene-Ruthenium Derivatives. In consonance with the behavior of the osmium complex 1, the reactions of the ruthenium counterpart 2 with allenes in a first instance lead to olefins and π-allene derivatives. Thus, the treatment at room temperature of toluene solutions of this compound with 3.0 equiv of 3-methyl-1,2-butadiene and 1-methyl-1-(trimethylsilyl)allene for 20 min gives 1 equiv of olefin and the π-allene complexes RuCl2(η2-CH2dCdCRMe)(PiPr3)2 (R = Me (7), Me3Si (8)) in quantitative yield20 (eq 3).

The 1H, 13C{1H}, and 31P{1H} NMR spectra of 7 and 8 are consistent with those of their osmium counterparts 3 and 4. In the 1H spectra in benzene-d6 at room temperature, the CH2 resonance of the coordinated allene is observed at 3.04 ppm for both compounds. In the 13C{1H} NMR spectrum of 7 the allene resonances appear at 6.7 (CH2), 120.6 (C), and 142.3 (CMe2) ppm, whereas in that of 8 they are observed at 4.9 (CH2), (19) (a) Schultz, A. J.; Williams, J. M.; Schrock, R. R.; Rupprencht, G. A.; Fellmann, J. D. J. Am. Chem. Soc. 1979, 101, 1593. (b) Goddard, R. J.; Hoffman, R.; Jemmis, E. D. J. Am. Chem. Soc. 1980, 102, 7667. (20) These compounds were isolated as brown (7) and violet (8) solids in only moderate yields (30% and 42%, respectively) due to their high solubility in all conventional organic solvents.

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126.5 (C), and 164.3 (C(SiMe3)Me) ppm. The 31P{1H} NMR spectra show singlets at 14.0 (7) and 15.3 (8) ppm. Complexes 7 and 8, as their osmium counterparts, are moderately stable in solution. In dichloromethane at room temperature, they slowly evolve into a complex mixture of compounds, containing the disubstituted vinylidene derivatives RuCl2(dCdCRMe)(PiPr3)2 (R = Me (9), Me3Si (10)). In the presence of 30 equiv of allene, these compounds are formed in about 80% yield after 24 h. 4-(Trimethylsilyl)-1,3pentadiene was detected by 1H NMR spectroscopy in the mixture resulting from the decomposition of 8 in the presence of 1-methyl-1-(trimethylsilyl)allene. The formation of this diene suggests that complexes 9 and 10 are generated as a consequence of metathesis reactions between the allenes and five-coordinate alkenylcarbene species related to 3tc (eq 4). The metathesis reaction between 1,2-propadiene and RuCl2(dCHPh)(PCy3)2, to afford RuCl2(dCdCH2)(PCy3)2, has been previously observed by Grubbs and co-workers.21 Figure 3. Molecular diagram of 10. Selected bond lengths (A˚) and angles (deg): Ru-C(1) 1.787(5), C(1)-C(2) 1.308(8), P-Ru-P(0A) 168.40(4), Cl-Ru-Cl(A) 160.68(5), RuC(1)-C(2) 178.4(9).

Several distinct methods have been applied successfully for the synthesis of vinylidene complexes.8e,22 The majority of the routes use terminal alkynes, RCtCH, as starting material. The organic substrate undergoes a low-energy tautomerization process on the coordination sphere of a transition metal,23 which also stabilizes the resulting tautomer by coordination. Heteroatom-substituted alkynes such as silyl-,24 stannyl-,25 thio-,26 and iodoalkynes,27 as well as acylalkynes,28 are also known to undergo similar rearrangement. In contrast, 1,2-migration of alkyl and aryl substituents has been observed only once.29 The known carbon-disubstituted vinylidene complexes have been generally prepared by electrophilic addition to neutral alkynyl compounds, and they are usually cationic species.22,30 The neutral carbon-disubstituted vinylidene derivatives are extremely (21) Schwab, P.; Grubbs, R. H.; Ziller, J. W. J. Am. Chem. Soc. 1996, 118, 100. (22) (a) Bruce, M. I. Chem. Rev. 1991, 91, 197. (b) Puerta, M. C.; Valerga, P. Coord. Chem. Rev. 1999, 193-195, 977. (23) Kunz, D. Angew. Chem., Int. Ed. 2007, 46, 3405. (24) See for examples: (a) Werner, H.; Baum, M.; Schneider, D.; Windm€ uller, B. Organometallics 1994, 13, 1089. (b) Connelly, N. G.; Geiger, W. E.; Lagunas, M. C.; Metz, B.; Rieger, A. L.; Rieger, P. H.; Shaw, M. J. J. Am. Chem. Soc. 1995, 117, 12202. (c) Katayama, H.; Onitsuka, K.; Ozawa, F. Organometallics 1996, 15, 4642. (d) Werner, H.; Lass, R. W.; Gevert, O.; Wolf, J. Organometallics 1997, 16, 4077. (e) Ilg, K.; Paneque, M.; Poveda, M. L.; Rend
on, N.; Santos, L. L.; Carmona, E.; Mereiter, K. Organometallics 2006, 25, 2230. (25) (a) Venkatesan, K.; Blacque, O.; Fox, T.; Alfonso, M.; Schmalle, H. W.; Kheradmandan, S.; Berke, H. Organometallics 2005, 24, 920. (b) Venkatesan, K.; Fox, T.; Schmalle, H. W.; Berke, H. Eur. J. Inorg. Chem. 2005, 901. (26) Miller, D. C.; Angelici, R. J. Organometallics 1991, 10, 79. (27) Miura, T.; Iwasawa, N. J. Am. Chem. Soc. 2002, 124, 518. (28) (a) King, P. J.; Knox, S. A. R.; Legge, M. S.; Orpen, A. G.; Wilkinson, J. N.; Hill, E. A. J. Chem. Soc., Dalton Trans. 2000, 1547. (b) Shaw, M. J.; Bryant, S. W.; Rath, N. Eur. J. Inorg. Chem. 2007, 3943. (29) Ikeda, Y.; Yamaguchi, T.; Kanao, K.; Kimura, K.; Kamimura, S.; Mutoh, Y.; Tanabe, Y.; Ishii, Y. J. Am. Chem. Soc. 2008, 130, 16856. (30) (a) Ting, P.-C.; Lin, Y.-C.; Lee, G.-H.; Cheng, M.-C.; Wang, Y. J. Am. Chem. Soc. 1996, 118, 6433. (b) Lo, Y.-H.; Lin, Y.-C.; Lee, G.-H.; Wang, Y. Organometallics 1999, 18, 982. (c) Liu, C.-W.; Lin, Y.-C.; Huang, S. -L.; Cheng, C.-W.; Liu, Y.-H.; Wang, Y. Organometallics 2007, 26, 3431. (31) (a) Gamble, A. S.; Birdwhistell, K. R.; Templeton, J. L. Organometallics 1988, 7, 1046. (b) Crochet, P.; Esteruelas, M. A.; L
opez, A. M.; Ruiz, N.; Tolosa, J. I. Organometallics 1998, 17, 3479.

scare and have alkenyl or allenyl substituents.31 Complex 9 is a rare example of this type of species with alkyl substituents. Complexes 9 and 10 were isolated as brown (9) and pink (10) solids in 56% and 48% yield, respectively, and characterized by elemental analysis, IR, and 1H, 13C{1H}, and 31 P{1H} NMR spectroscopy. Complex 10 was further characterized by an X-ray crystallographic study. Figure 3 shows a view of the molecular geometry of this compound. The geometry around the ruthenium atom can be described as a distorted square pyramid with the vinylidene ligand at the apical position and the P-Ru-P(0A) (168.40(4)°) and Cl-RuCl(A) (160.68(5)°) axes bent away from the carbon donor ligand. In agreement with other ruthenium-vinylidene complexes,10,32 the vinylidene is bound to the metal in a nearly linear fashion with an Ru-C(1)-C(2) angle of 178.4(9)° and RuC(1) and C(1)-C(2) bond lengths of 1.787(5) and 1.308(8) A˚, respectively. The 13C{1H} and 31P{1H} NMR spectra of 9 and 10 in benzene-d6 at room temperature are consistent with the structure shown in Figure 3. In the 13C{1H} NMR spectra, the carbon atoms of the unsaturated chains display triplets at 337.1 and 102.8 (9) and 322.4 and 95.9 (10) ppm with C-P coupling constants of 16 and 5 (9) Hz and 14 and 3 (10) Hz, respectively. The 31P{1H} NMR spectra show singlets at 27.1 (9) and 28.4 (10) ppm, in accordance with the presence of equivalent phosphines in the complexes. 4. Theoretical Calculations on the Formation of the Disubstituted Vinylidene-Ruthenium Derivatives. The formation of the disubstituted vinylidene complexes 9 and 10 has also been studied by DFT calculations (B3PW91) using PMe3 and 3-methyl-1,2-butadiene as models of PiPr3 and allene. The process has been divided into two parts, the formation of (32) See for example: (a) Katayama, H.; Ozawa, F. Organometallics 1998, 17, 5190. (b) Jim
enez-Tenorio, M. A.; Jim
enez-Tenorio, M.; Puerta, M. C.; Valerga, P. Organometallics 2000, 19, 1333. (c) Baya, M.; Buil, M. L.; Esteruelas, M. A.; L
opez, A. M.; O~nate, E.; Rodríguez, J. R. Organometallics 2002, 21, 1841. (d) Aneetha, H.; Jim
enez-Tenorio, M.; Puerta, M. C.; Valerga, P.; Mereiter, K. Organometallics 2003, 22, 2001. (e) Bustelo, E.; Carb
o, J. J.; Lled
os, A.; Mereiter, K.; Puerta, M. C.; Valerga, P. J. Am. Chem. Soc. 2003, 125, 3311. (f) Field, L. D.; Magill, A. M.; Jensen, P. Organometallics 2008, 27, 6539.

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Figure 4. Relative energies (ΔGdichloromethane; kcal 3 mol-1) for the transformation of 7t into 7tb.

Figure 5. Relative energies (ΔGdichloromethane; kcal 3 mol-1) for the transformation of 7tb into 9t.

Chart 2

lower energy than the migration via the metal center. Figure 4 shows the energy profile for this process, whereas Chart 2 collects the optimized structures and selected structural parameters for intermediates and transition states. The changes in free energy, ΔG, have been computed at 298.15 K and P = 1 atm and corrected using dichloromethane as solvent. The slippage of the ruthenium atom from the C1-C2 double bond of the allene to one of the C1-H bonds gives rise to the intermediate 7ta, which is 26.2 kcal 3 mol-1 less stable than 7t. This species can be described as a σ-(C-H)-allene derivative, with Ru-C1, Ru-H, and C1-H bond lengths of 2.153, 1.672, and 1.239 A˚, respectively. The metal slide takes place via the transition state TS5, which lies 28.6 kcal 3 mol-1 above 7t. The σ-(C-H)-allene intermediate subsequently undergoes a 1,2hydrogen shift from C1 to C2 to afford 7tb, with an activation barrier of 37.8 kcal 3 mol-1. In the transition state TS6, connecting 7ta and 7tb, the coordinated hydrogen atom approaches both C2 (C2-H = 2.002 A˚) and the Cl1 chloride ligand. The Cl1-H separation of 2.032 A˚ is significantly shorter than the sum of the van der Waals radii of hydrogen and chloride (2.95 A˚)33 and supports a strong Cl 3 3 3 H interaction. Once 7tb has been formed, the metathesis with the allene could afford the disubstituted vinylidene, as has been previously mentioned. In this context it should be pointed out that a large number of DFT calculations on several mechanistic aspects of the metathesis reactions have previously appeared in the literature34 and that it is not the aim of this paper to discuss the metathesis mechanism but to corroborate our proposal. In fact, a dissociative pathway with the allene trans disposed to the phosphine in the five-coordinate key Ru-allene intermediate allows the formation of the disubstituted vinylidene (Figure 5, Chart 3), with an energy requirement lower than that for the formation of 7tb.

the alkenylcarbene intermediate RuCl2(dCHCHdCMe2)(PMe3)2 (7tb) and the allene-metathesis reaction. The formation of 7tb by C1-C2 hydrogen migration via the metal center (C1fRufC2) is an unfavorable process from an energy point of view. Not only do all elemental steps of the migration have activation barriers higher than those for the formation of 3tc and all intermediate species are less stable than the corresponding ones for osmium, but also the barrier for the change in orientation of the ruthenacyclopropene unit with regard to the hydride ligand has a value too high to be consistent with the observed reaction rates to form 9 and 10 (see Supporting Information). As expected in agreement with a lower reducing character of ruthenium with regard to osmium, in contrast to the latter, the alkenylcarbene intermediate 7tb is 12.3 kcal 3 mol-1 more stable than its hydride-alkenylcarbyne isomer RuHCl2(tCCHdCMe2)(PMe3)2. The formation of 7tb through a C1fC2 concerted hydrogen migration assisted by one of the chloride ligands is a pathway of

(33) Barrio, P.; Esteruelas, M. A.; Lled
os, A.; O~ nate, E.; Tom
as, J. Organometallics 2004, 23, 3008. (34) See for example: (a) Cavallo, L. J. Am. Chem. Soc. 2002, 124, 8965. (b) Adlhart, C.; Chen, P. Angew. Chem., Int. Ed. 2002, 41, 4484. (c) Vyboishchikov, S. F.; B€uhl, M.; Thiel, W. Chem.;Eur. J. 2002, 8, 3962. (d) Bernardi, F.; Bottoni, A.; Miscione, G. P. Organometallics 2003, 22, 940. (e) Fomine, S.; Vargas, M. S.; Tlenkopatchev, M. A. Organometallics 2003, 22, 93. (f) Adlhart, C.; Chen, P. J. Am. Chem. Soc. 2004, 126, 3496. (g) Costabile, C.; Cavallo, L. J. Am. Chem. Soc. 2004, 126, 9592. (h) Suresh, C. H.; Koga, N. Organometallics 2004, 23, 76. (i) van Rensburg, W. J.; Steynberg, P. J.; Meyer, W. H.; Kirk, M. M.; Forman, G. S. J. Am. Chem. Soc. 2004, 126, 14332. (j) Tsipis, A. C.; Orpen, A. G.; Harvey, J. N. Dalton Trans. 2005, 2849. (k) Straub, B. F. Angew. Chem., Int. Ed. 2005, 44, 5974. (l) Lippstreu, J. J.; Straub, B. F. J. Am. Chem. Soc. 2005, 127, 7444. (m) Correa, A.; Cavallo, L. J. Am. Chem. Soc. 2006, 128, 13352. (n) Occhipinti, G.; Bjørsvik, H.-R.; Jensen, V. R. J. Am. Chem. Soc. 2006, 128, 6952. (o) Getty, K.; Delgado-Jaime, M. U.; Kennepohl, P. J. Am. Chem. Soc. 2007, 129, 15774. (p) Webster, C. E. J. Am. Chem. Soc. 2007, 129, 7490. (q) Mathew, J.; Koga, N.; Suresh, C. H. Organometallics 2008, 27, 4666.

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prefers coordination saturation and redox isomers with more metal-carbon bonds.

Experimental Section

Concluding Remarks This study has revealed two new reaction patterns between transition-metal complexes and allenes that involve the C-H bond activation of the allene terminus. The transformations produce relevant classes of organometallic complexes, namely, hydride-alkenylcarbyne-osmium and disubstituted vinylidene-ruthenium compounds. In addition to the new synthetic routes to prepare these types of compounds, they open new possibilities for devising catalytic methods relying on the successful trapping of such species. The dihydride-osmium complex OsH2Cl2(PiPr3)2 reacts with 3-methyl-1,2-butadiene and 1-methyl-1-(trimethylsilyl)allene to afford initially the π-allene derivatives OsCl2(η2-CH2dCdCRMe)(PiPr3)2, which evolve into the hydride-alkenylcarbyne compounds OsHCl2(tCCHdCRMe)(PiPr3)2 (R=Me, Me3Si). The transformations involve the migration of both hydrogen atoms of the coordinated CH2 group of the allene. The first of them, which has an activation energy higher than the second one, occurs between the terminal and central carbon atoms of the coordinated allene and takes place through the metal center. The second migration is a 1,2-hydrogen shift from the allene to the osmium atom. The dihydride-ruthenium counterpart RuH2Cl2(PiPr3)2 also reacts with the previously mentioned allenes to afford the π-allene derivatives RuCl2(η2-CH2dCdCRMe)(PiPr3)2. However in this case, they evolve to the disubstituted vinylidene compounds RuCl2(dCdCRMe)(PiPr3)2 (R = Me, Me3Si) via the alkenylcarbene intermediates RuCl2(dCHCHdCRMe)(PiPr3)2, which undergo a metathesis reaction with a second molecule of allene. DFT calculations suggest that the alkenylcarbene intermediate is generated by means of a concerted 1,2hydrogen shift from the terminal to the central carbon atom of the coordinated allene of the π-allene species. The migration is assisted by one of the chloride ligands. The difference in behavior between the osmium and ruthenium starting dihydrides is an elegant and new evidence of the fact that osmium is more reducing than ruthenium and

All reactions were carried out with rigorous exclusion of air using Schlenk-tube techniques. Solvents were dried by standard procedures and distilled under argon prior to use. The starting materials OsH2Cl2(PiPr3)2 (1) and RuH2Cl2(PiPr3)2 (2) were prepared by the published methods.10,35 1H, 31P{1H}, and 13C{1H} NMR spectra were recorded on either a Varian Gemini 2000, 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 and N, are given in hertz. Spectral assignments were achieved by 1H-1H COSY, 13C APT, 1H-13C HSQC, and 1H-13C HMBC experiments. Attenuated total reflection infrared spectra (ATR-IR) of solid samples were run on a Perkin-Elmer Spectrum 100 FT-IR spectrometer. C and H analyses were carried out in a Perkin-Elmer 2400 CHNS/O analyzer. High-resolution electrospray mass spectra were acquired using a MicroTOF-Q hybrid quadrupole time-of-flight spectrometer (Bruker Daltonics, Bremen, Germany). Preparation of OsCl2(η2-CH2dCdCMe2)(PiPr3)2 (3). A brown suspension of 1 (350 mg, 0.600 mmol) in 7 mL of toluene was treated with 3-methyl-1,2-butadiene (186 μL, 1.800 mmol). The mixture was stirred for 6 h at 313 K, and the resulting solution was filtered through Celite. The solvent was removed in vacuo. The residue was solved in n-pentane, filtered, and vacuum-dried. A green solid was obtained. Yield: 286 mg (74%). Anal. Calcd for C23H50OsCl2P2: C 42.45; H 7.75. Found: C 42.74; H 7.75. MS: m/z 615 [M - Cl]þ, 547 [M - Cl - C5H8]þ. IR (cm-1): ν(CH2) 1454(s). 1 H NMR (300 MHz, C6D6, 293 K): δ 4.27 (s, 2H, CH2), 3.54 and 3.19 (both s, 6H, CH3), 2.72 (m, 6H, PCH), 1.31 (dvt, N = 13.0, JH-H = 6.9, 18H, PCHCH3), 1.25 (dvt, N = 12.7, JH-H = 6.6, 18H, PCHCH3). 31P{1H} NMR (121.4 MHz, C6D6, 293 K): δ -46.5 (s). 13C{1H}-APT NMR plus HMBC and HSQC (75.4 MHz, C6D6, 293 K): δ 127.0 (t, JC-P = 2, dCd), 121.0 (t, JC-P = 4, dC(CH3)2), 29.1 and 21.2 (both s, CH3), 24.9 (vt, N = 22, PCH), 20.3 and 19.8 (both s, PCHCH3), -6.8 (t, JC-P = 1, CH2). When the reaction was carried out in an NMR tube, the formation of 3-methyl-1-butene was observed by 1H NMR spectroscopy. Preparation of OsCl2{η2-CH2dCdCMe(SiMe3)}(PiPr3)2 (4). A brown solution of 1 (350 mg, 0.600 mmol) in 7 mL of toluene was treated with 1-methyl-1-(trimethylsilyl)allene (300 μL, 1.800 mmol). The mixture was stirred for 6 h at 313 K, and the resulting solution was filtered through Celite. The solvent was removed in vacuo. The residue was solved in n-pentane, filtered, and vacuumdried. A green solid was obtained. Yield: 253 mg (60%). Anal. Calcd for C25H56OsSiCl2P2: C 42.42; H 7.97. Found: C 42.32; H 8.35. MS: m/z 673 [M - Cl]þ, 547 [M - Cl - C7H14Si]þ. IR (cm-1): ν(dCd) 1658(s), ν(CH2) 1452(s). 1H NMR (300 MHz, C6D6, 293 K): δ 4.24 (s, 2H, CH2), 2.94 (s, 3H, CCH3), 2.67 (m, 6H, PCH), 1.28 (dvt, N = 12.9, JH-H = 6.0, 18H, PCHCH3), 1.23 (dvt, N = 13.5, JH-H = 6.9, 18H, PCHCH3), 0.19 (s, 9H, (SiCH3)3)). 31 1 P{ H} NMR (121.4 MHz, C6D6, 293 K): δ -36.4 (s). 13C{1H}APT NMR plus HMBC and HSQC (75.4 MHz, C6D6, 293 K): δ 146.1 (t, JC-P = 3, dCCH3), 127.11 (t, JC-P = 2, dCd), 24.3 (vt, N = 22, PCH), 21.8 (s, CCH3), 20.3 and 20.0 (both s, PCHCH3), -7.4 (s, CH2). When the reaction was carried out in an NMR tube, the formation of a mixture of 3-trimethylsilyl-1-butene and 2trimethylsilyl-2-butene in a 2:1 molar ratio was observed by 1H NMR spectroscopy. Preparation of OsHCl2(tCCHdCMe2)(PiPr3)2 (5). A green solution of 2 (200 mg, 0.308 mmol) in 7 mL of toluene was heated for 15 h at 353 K. The solvent was removed in vacuo, and n-pentane was added to afford a brown solid, which was washed (35) Aracama, M.; Esteruelas, M. A.; Lahoz, F. J.; L
opez, J. A.; Meyer, U.; Oro, L. A.; Werner, H. Inorg. Chem. 1991, 30, 288.

Article with n-pentane and dried in vacuo. Yield: 142 mg (62%). This complex has been previously prepared and reported by a different method.9 Preparation of OsHCl2{tCCHdCMe(SiMe3)}(PiPr3)2 (6). A green solution of 3 (109 mg, 0.187 mmol) in 7 mL of toluene was heated at 353 K. After 15 h the solution was filtered through Celite and the solvent was removed in vacuo. The addition of n-pentane to the residue led to a gray solid, which was washed with n-pentane and dried in vacuo. Yield: 87 mg (80%). Anal. Calcd for C25H56OsSiCl2P2: C 42.42; H 7.97. Found: C 42.57; H 8.23. MS: m/ z 673 [M - Cl]þ, 547 [M - Cl - C7H14Si]þ. IR (cm-1): ν(Os-H) 2170(m). 1H NMR (400 MHz, C6D6, 293 K): δ 4.95 (s, 1H, CH), 2.71 (m, 6H, PCH), 2.06 (br, 3H, CCH3), 1.44 (dvt, N = 13.5, JH-H=6.9, 18H, PCHCH3), 1.34 (dvt, N=13.8, JH-H=6.9, 18H, PCHCH3), -0.23 (s, 9H, (SiCH3)3)), -7.11 (t, JP-H =16.4, 1H, OsH). 31P{1H} NMR (121.4 MHz, C6D6, 243 K): δ 18.3 (s). 13 C{1H}-APT NMR plus HMBC and HSQC (100.5 MHz, C6D6, 293 K): δ 254.9 (t, JC-P = 11, tC), 167.1 (s, dCCH3), 144.8 (s, CH), 26.7 (vt, N = 26, PCH), 21.2 (s, CCH3), 20.0 and 19.8 (both s, PCHCH3), -3.4 (s, SiC). Preparation of RuCl2(η2-CH2dCdCMe2)(PiPr3)2 (7). A brown solution of 2 (200 mg, 0.404 mmol) in 7 mL of toluene was treated with 3-methyl-1,2-butadiene (125 μL, 1.212 mmol). The mixture was stirred for 20 min at room temperature, and the solvent was removed in vacuo. The addition of methanol at 243 K gave rise to a brown solid, which was washed with methanol and dried in vacuo. Yield: 68 mg (30%). Anal. Calcd for C23H50RuCl2P2: C 49.28; H 8.99. Found: C 48.93; H 8.80. IR (cm-1): ν(CH2) 1453(s). 1 H NMR (400 MHz, C7D8, 253 K): δ 3.04 (br, 2H, CH2), 2.53 and 2.50 (both s, 6H, CH3), 2.38 (m, 6H, PCH), 1.21 (dvt, N=12.8, JH-H=6.4, 18H, PCHCH3), 1.12 (dvt, N=12.4, JH-H=6.4, 18H, PCHCH3). 31P{1H} NMR (161.9 MHz, C7D8, 253 K): δ 14.0 (s). 13 C{1H}-APT NMR plus HMBC and HSQC (100.5 MHz, C7D8, 253 K): δ 142.3 (t, JC-P = 6, dC(CH3)2), 120.6 (s, dCd), 29.9 and 24.6 (both s, CH3), 22.9 (vt, N = 17, PCH), 19.9 and 19.5 (both s, PCHCH3), 6.7 (s, CH2). When the reaction was carried out in an NMR tube, the formation of a complex mixture of olefins was observed by 1H NMR spectroscopy. Preparation of RuCl2{η2-CH2dCdCMe(SiMe3)}(PiPr3)2 (8). A brown solution of 2 (200 mg, 0.404 mmol) in 7 mL of toluene was treated with 1-methyl-1-(trimethylsilyl)allene (202 μL, 1.212 mmol). The mixture was stirred for 20 min at room temperature, and the solvent was removed in vacuo. The addition of methanol at 243 K gave rise to a violet solid, which was washed with methanol and dried in vacuo. Yield: 105 mg (42%). Anal. Calcd for C25H56RuSiCl2P2: C 48.53; H 9.13. Found: C 48.13; H 9.63. IR (cm-1): ν(dCd) 1682(s), ν(CH2) 1452(s). 1H NMR (400 MHz, C6D6, 293 K): δ 3.04 (br, 2H, CH2), 2.56 (s, 3H, CH3), 2.45 (m, 6H, PCH), 1.20 (dvt, N = 12.8, JH-H = 6.4, 18H, PCHCH3), 1.16 (dvt, N = 12.8, JH-H = 6.8, 18H, PCHCH3), 0.23 (s, 9H, Si(CH3)3). 31P{1H} NMR (161.9 MHz, C6D6, 293 K): δ 15.3 (s). 13C{1H}-APT NMR plus HMBC and HSQC (100.5 MHz, C6D6, 293 K): δ 164.3 (t, JC-P = 4, dCCH3), 126.5 (s, dCd), 24.0 (s, CH3), 23.2 (vt, N=16, PCH), 20.2 and 20.0 (both s, PCHCH3), 4.9 (s, CH2), -0.32 (s, SiC). When the reaction was carried out in an NMR tube, the formation of a mixture of 3-trimethylsilyl-1-butene and 2-trimethylsilyl-2-butene in a 2:7 molar ratio was observed by 1H NMR spectroscopy. Preparation of RuCl2(dCdCMe2)(PiPr3)2 (9). A solution of 7 (130 mg, 0.232 mmol) in 5 mL of dichloromethane was treated with 3-methyl-1,2-butadiene (717 μL, 6.958 mmol). After 24 h at room temperature, the 31P{1H} NMR spectrum of the reaction mixture showed a conversion of 90%. Then the solvent was removed in vacuo. The addition of methanol at 243 K gave rise to a brown solid, which was washed with methanol and dried in vacuo. Yield: 71 mg (56%). Anal. Calcd for C22H48RuCl2P2: C 48.34; H 8.86. Found: C 47.97; H 8.37. IR (cm-1): ν(CdC) 1674(s). 1H NMR (300 MHz, C6D6, 293 K): δ 2.72 (m, 6H, PCH), 1.81 (t, JH-P = 2.3, 6H, CH3), 1.31 (dvt, N = 13.5, JH-H = 7.2, 36H, PCHCH3). 31P{1H} NMR (121.4 MHz, C6D6, 293 K): δ 27.1 (s). 13C{1H}-APT NMR plus

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HMBC and HSQC (75.4 MHz, C6D6, 293 K): δ 337.1 (t, JC-P = 16, RudC), 102.8 (t, JC-P = 5, dCCH3), 23.1 (vt, N = 18, PCH), 20.1 (s, PCHCH3), 10.7 (t, JC-P = 2, CH3). Preparation of RuCl2{dCdCMe(SiMe3)}(PiPr3)2 (10). A solution of 8 (130 mg, 0.210 mmol) in 5 mL of dichloromethane was treated with 1-methyl-1-(trimethylsilyl)allene (1048 μL, 6.303 mmol). After 24 h at room temperature, the 31P{1H} NMR spectrum of the reaction mixture showed a conversion of 81%. Then, the solvent was removed in vacuo. The addition of methanol at 243 K gave rise to a pink solid, which was washed with methanol and dried in vacuo. Yield: 61 mg (48%). Anal. Calcd for C24H54RuSiCl2P2: C 47.67; H 9.01. Found: C 47.23; H 9.40. IR (cm-1): ν(CdC) 1629(s). 1H NMR (300 MHz, C6D6, 293 K): δ 2.84 (m, 6H, PCH), 1.85 (br, 3H, CH3), 1.33 (dvt, N = 12.9, JH-H = 6.9, 36H, PCHCH3), 0.28 and 0.25 (both s, 9H, SiCH3). 31P{1H} NMR (121.4 MHz, C6D6, 293 K): δ 28.4 (s). 13 C{1H}-APT NMR plus HMBC and HSQC (75.4 MHz, C6D6, 293 K): δ 322.4 (t, JC-P=14, RudC), 95.9 (t, JC-P=3, dCCH3), 23.2 (vt, N=19, PCH), 20.3 (s, PCHCH3), 5.6 (s, CH3), 1.4 and -0.1 (both s, SiC). When the reaction was carried out in an NMR tube, the formation of 4-(trimethylsilyl)-1,3-pentadiene was detected by 1H NMR spectroscopy. Structural Analysis of Complex 3 and 10. X-ray data were collected on a Bruker Smart APEX CCD diffractometer equipped with a normal focus, 2.4 kW sealed tube source (Mo radiation, λ = 0.71073 A˚) operating at 50 kV and 30 (3)/40 (10) mA. Data were collected over the complete sphere by a combination of four sets. Each frame exposure time was 20 s covering 0.3° in ω. Data were corrected for absorption by using a multiscan method applied with the SADABS program.36 The structures were solved by the Patterson method. Refinement of both complexes was performed by full-matrix least-squares on F2 with SHELXL97,37 including isotropic and subsequently anisotropic displacement parameters. For b, the vinylidene ligand was observed disordered about a pseudo-2-fold axes containing the ruthenium atom. Crystal data for 3:. C23H50Cl2OsP2, Mw 649.67, irregular block, orange (0.10  0.04  0.02), monoclinic, space group P1, a = 8.5698(14) A˚, b=11.1789(18) A˚, c=15.860(3) A˚, R=98.265(3)°, β=94.965(3)°, γ = 112.038(3)°, V = 1377.3(4) A˚3, Z = 2, Dcalc = 1.567 g cm-3, F(000) = 656, T=100(2) K, μ = 4.948 mm-1; 17 168 measured reflections (2θ: 3-58°, ω scans 0.3°), 6557 unique (Rint= 0.0652); min./max. transmn factors 0.451/0.570. Final agreement factors were R1=0.0361 (2013 observed reflections, I > 2σ(I)) and wR2=0.0938; data/restraints/parameters 2163/18/135; GoF=1.086. Largest peak and hole: 1.617 and -1.420 e/A˚3. Crystal data for 10:. C24H54Cl2P2RuSi, Mw 604.67, irregular block, dark orange (0.24  0.04  0.04), monoclinic, space group C2/c, a = 19.498(7) A˚, b = 12.003(4) A˚, c = 15.441(6) A˚, β = 120.064(6)°, V=3128(2) A˚3, Z=4, Dcalc = 1.284 g cm-3, F(000)= 1280, T = 100(2) K, μ = 0.823 mm-1; 18 724 measured reflections (2θ: 3-58°, ω scans 0.3°), 3854 unique (Rint = 0.0724); min./max. transmn factors 0.850/0.960. Final agreement factors were R1 = 0.0449 (2992 observed reflections, I > 2σ(I)) and wR2 = 0.0937; data/restraints/parameters 3854/34/202; GoF=1.034. Largest peak and hole: 0.619 and -0.710 e/A˚3. Computational Details and Orthogonal Coordinates of the Model Complexes. The theoretical calculations were carried out on the model complexes by optimizing the structures at the b3pw91-DFT levels with the Gaussian 03 program.38,39 The basis sets used were LANL2DZ basis and pseudopotentials for Os and 6-31G(d,p) for the rest of atoms. The transition states (36) Blessing, R. H. Acta Crystallogr. 1995, A51, 33. SADABS: Areadetector absorption correction; Bruker-AXS: Madison, WI, 1996. (37) SHELXTL Package v. 6.10; Bruker-AXS: Madison, WI, 2000. Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112. (38) They were performed using Gaussian 03 software: Frisch, M. J.; et al. Gaussian 03, revision C.02; Gaussian, Inc.: Pittsburgh, PA, 2003. (39) Ochterski, J. W. Thermochemistry in Gaussian; Gaussian, Inc.: Pittsburgh, PA, 2000.

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have been found by carrying out potential energy surfaces of the processes following the reaction coordinates and optimizing the maxima and were confirmed by frequency calculations. The connections between the starting and final reactants have been checked by slightly perturbing the TS geometry toward the minima geometries and reoptimizing. The numerical values shown in the schemes correspond to calculated enthalpies in the gas phase corrected for solvent effects,38,39 ΔGsolvent (ΔGsolvent = ΔGgas þ ΔΔGsolv). The solvation free energies (Gsolv) were obtained from the single-point calculations combined with the PCM models.

Collado et al.

Acknowledgment. Financial support from the Spanish MICINN (projects CTQ2008-00810 and Consolider Ingenio 2010 CSD2007-00006) and the DGA (E35) is acknowledged. A.C. thanks the CSIC for her JAE grant. Supporting Information Available: X-ray analysis, computational details, orthogonal coordinates of theorical structures, and crystal structure determination, including a CIF file giving crystal data for compounds 3 and 10. This material is available free of charge via the Internet at http://pubs.acs.org.