Sequential and selective hydrogenation of the Cα-C/ β and M-Cα double bonds of an allenylidene ligand coordinated to osmium: New reaction patterns between an allenylidene complex and alcohols

Article abstract of DOI:10.1021/ja071972a

Complex [OsH(=C=C=CPh₂)(CH₃CN)₂(P ^/Pr₃)₂]BF₄ (1) reacts with primary and secondary alcohols to give the corresponding dehydrogenated alcohols and the hydride-carbene derivative [OsH(= CHCH=CPh₂)(CH₃CN) ₂(P^/Pr₃)₂]BF₄ (2), as a result of hydrogen transfer reactions from the alcohols to the C _α-C_β double bond of the allenylidene ligand of 1. The reactions with phenol and t-butanol, which do not contain any β-hydrogen, afford the alkoxy-hydride-carbyne complexes [OsH(OR)(=CCH=CPh₂)(CH₃CN)-(P^/Pr ₃)₂]BF₄ (R = Ph (3), ^tBu (4)), as a consequence of the 1,3-addition of the O-H bond of the alcohols to the metallic center and the C_β atom of the allenylidene of 1. On the basis of the reactions of 1 with these tertiary alcohols, deuterium labeling experiments, and DFT calculations, the mechanism of the hydrogenation is proposed. In acetonitrile under reflux, the Os-C double bond of 2 undergoes hydrogenation to give 1,1-diphenylpropene and [Os{CH₂CH(CH ₃)P^/Pr₂(CH₃CN)₃(P ^/Pr₃)]BF₄ (11), containing a metalated phosphine ligand. This reaction is a first-order process with activation parameters of ΔH^? = 89.0 ± 6.3 kJ mol ^-1 and ΔS^? = -43.5 ± 9.6 J moh ^-1 K^-1. The X-ray structures of 2 and 3 are also reported.

Full text of DOI:10.1021/ja071972a

Published on Web 06/20/2007
Sequential and Selective Hydrogenation of the Cr-Câ and
M-Cr Double Bonds of an Allenylidene Ligand Coordinated
to Osmium: New Reaction Patterns between an Allenylidene
Complex and Alcohols
Tamara Bolan˜o, Ricardo Castarlenas, Miguel A. Esteruelas,* and Enrique On˜ate
Contribution from the Departamento de Qu´ımica Inorga´nica, Instituto de Ciencia de Materiales
de Arago´n, UniVersidad de Zaragoza-CSIC, 50009 Zaragoza, Spain
Received March 20, 2007; E-mail: maester@unizar.es
Abstract: Complex [OsH(dCdCdCPh2)(CH3CN)2(PiPr3)2]BF4 (1) reacts with primary and secondary
alcohols to give the corresponding dehydrogenated alcohols and the hydride-carbene derivative [OsH(d
CHCHdCPh2)(CH3CN)2(PiPr3)2]BF4 (2), as a result of hydrogen transfer reactions from the alcohols to the
CR-Câ double bond of the allenylidene ligand of 1. The reactions with phenol and t-butanol, which do not
contain any â-hydrogen, afford the alkoxy-hydride-carbyne complexes [OsH(OR)(tCCHdCPh2)(CH3CN)-
t
(PiPr3)2]BF4 (R ) Ph (3), Bu (4)), as a consequence of the 1,3-addition of the O-H bond of the alcohols
to the metallic center and the Câ atom of the allenylidene of 1. On the basis of the reactions of 1 with these
tertiary alcohols, deuterium labeling experiments, and DFT calculations, the mechanism of the hydrogenation
is proposed. In acetonitrile under reflux, the Os-C double bond of 2 undergoes hydrogenation to give
1,1-diphenylpropene and [Os{CH2CH(CH3)PiPr2(CH3CN)3(PiPr3)]BF4 (11), containing a metalated phosphine
ligand. This reaction is a first-order process with activation parameters of ∆Hq ) 89.0 ( 6.3 kJ mol-1 and
∆Sq ) -43.5 ( 9.6 J mol-1 K-1. The X-ray structures of 2 and 3 are also reported.
quinoline,6 pyridopyridinyl, thiazinyl,7 dihydronapthopyrrolyl,8
etc.9), which require multistep procedures in conventional
organic synthesis.
Introduction
The term “hydrogenation” refers to a chemical reaction in
which one or more hydrogen atoms (and only those) are
incorporated in the product(s) of the reaction. The chemose-
lective hydrogenation of a specific carbon-carbon double
bond in compounds containing several of them is a challenging
problem in synthetic organic and organometallic chemistry.1
The reactivity of the C3-organic unit is a function of the
particular metallic fragment stabilizing the allenylidene ligand.
In agreement with the presence of electrophilic (CR and Cγ)
and nucleophilic (Câ) sites in the C3-chain,10 three types of
behaviors have been observed for the allenylidene
complexes:11 R-electrophilic, γ-electrophilic, and nucleophilic.
The most noticeable feature of the first of them is the formation
of Fischer type alkenylcarbene derivates by addition of RXH
molecules (alcohols, amines, etc.) to the CR-Câ double bond.12
In contrast to the R-electrophilic compounds, the γ-electrophilic
ones do not undergo intermolecular addition of weak nucleo-
philic reagents and the reactions with strong nucleophiles lead
to alkynyl complexes.13 The nucleophilic behavior involves
addition of electrophiles at Câ.12j,14
Transition metal allenylidene complexes are a class of
compounds with three consecutive double bonds: one metal-
carbon and two carbon-carbon. Their chemistry has been
subject of special attention in recent years due to their
potential as organometallic intermediates that may have unusual
reactivity in stoichiometric2 and catalytic reactions.3 The pres-
ence of three reactive centers (unsaturated C3 chain) or more
(unsaturated chain plus substituents) in the η1-carbon ligand
allows one to build, in one or two steps, organic skeletons
(naphthofuranyl,4 pyrazolopyrazolyl,5 azetidine, hexahydro-
(1) Chaloner, P. A.; Esteruelas, M. A.; Joo´, F.; Oro, L. A. Homogeneous
Hydrogenation; Kluwer: Dordrecht, Netherlands, 1994.
(4) (a) Esteruelas, M. A.; Go´mez, A. V.; Lo´pez, A. M.; On˜ate, E.; Ruiz, N.
Organometallics 1998, 17, 2297. (b) Esteruelas, M. A.; Go´mez, A. V.;
Lo´pez, A. M.; Oliva´n, M.; On˜ate, E.; Ruiz, N. Organometallics 2000, 19,
4.
(5) (a) Esteruelas, M. A.; Go´mez, A. V.; Lo´pez, A. M.; On˜ate, E. Organo-
metallics 1998, 17, 3567. (b) Bertolasi, V.; Mantovani, N.; Marvelli, L.;
Rossi, R.; Bianchini, C.; de los Rios, I.; Peruzzini, M.; Akbayeva, D. N.
Inorg. Chim. Acta 2003, 344, 207.
(6) Esteruelas, M. A.; Go´mez, A. V.; Lo´pez, A. M.; On˜ate, E.; Ruiz, N.
Organometallics 1999, 18, 1606.
(7) Bernad, D. J.; Esteruelas, M. A.; Lo´pez, A. M.; Oliva´n, M.; On˜ate, E.;
Puerta, M. C.; Valerga, P. Organometallics 2000, 19, 4327.
(8) Buil, M. L.; Esteruelas, M. A.; Lo´pez, A. M.; On˜ate, E. Organometallics
2003, 22, 162.
(2) (a) Werner, H. Chem. Commun. 1997, 903. (b) Bruce, M. I. Chem. ReV.
1998, 98, 2797. (c) Cadierno, V.; Gamasa, M. P.; Gimeno, J. Eur. J. Inorg.
Chem. 2001, 571. (d) Selegue, J. P. Coord. Chem. ReV. 2004, 248, 1543.
(e) Winter, R. F.; Za´lisˇ, S. Coord. Chem. ReV. 2004, 248, 1565. (f) Cadierno,
V.; Gamasa, M. P.; Gimeno, J. Coord. Chem. ReV. 2004, 248, 1627. (g)
Fischer, H.; Szesni, N. Coord. Chem. ReV. 2004, 248, 1659. (h) Rigaut,
S.; Touchard, D.; Dixneuf, P. H. Coord. Chem. ReV. 2004, 248, 1585.
(3) (a) Castarlenas, R.; Fischmeister, C.; Bruneau, C.; Dixneuf, P. H. J. Mol.
Catal. A: Chem. 2004, 213, 31. (b) Dragutan, I.; Dragutan, V. Platinum
Metals ReV. 2006, 50, 81. (c) Bruneau, C.; Dixneuf, P. H. Angew. Chem.,
Int. Ed. 2006, 45, 2176. (d) Nishibayashi, Y.; Uemura, S. Curr. Org. Chem.
2006, 10, 135.
9
8850
J. AM. CHEM. SOC. 2007, 129, 8850-8859
10.1021/ja071972a CCC: $37.00 © 2007 American Chemical Society

Hydrogenation of CR
−Câ and M−CR Double Bonds
A R T I C L E S
The hydrogenation of allenylidene compounds has received
scarce attention and has been centered on the M-CR and Câ-
Cγ double bonds. As far as we know, the addition of two
hydrogen atoms to the CR-Câ bond has not been achieved.
Werner and co-workers have reported the hydrogenation with
molecular hydrogen of the M-C double bonds of MCl{dCd
CdC(R)Ph}(PiPr3)2 to afford the allene derivatives MCl{η2-
CH2dCdC(R)Ph}(PiPr3)2 (M ) Rh,15 Ir16). We have described
theformationofthevinylideneOs(η5-C5H5)Cl(dCdCHCHPh2)(Pi-
Pr3)2 by reduction of the Câ-Cγ bond of the allenylidene ligand
of Os(η5-C5H5)Cl(dCdCdCPh2)(PiPr3)2 with NaBH4 and some
drops of methanol.17 In the same line, Che, Phillips, and co-
workers have observed that complex trans-[Cl(16-TMC)Ru(d
CdCdCPh2)]PF6 (16-TMC ) 1,5,9,13-tetramethyl-1,5,9,13-
tetraazacyclohexadecane) can be converted to trans-[Cl(16-
TMC)Ru(dCdCHCHPh2)]PF6 by treatment with Zn/Hg in
methanol under reflux.18 These Câ-Cγ reductions appear to be
two-step processes: addition of H- to Cγ and H+ to Câ, in
agreement with the respective electrophilic and nucleophilic
character of the carbon atoms. Thus, Dixneuf and co-workers
have shown that complexes [RuCl(dCdCdCR2)(dppm)2]PF6
(dppm ) Ph2PCH2PPh2) react with NaBH4 to give the corre-
sponding alkynyl derivatives RuCl(CtCCHR2)(dppm)2.19 The
addition of H+ to the Câ atom of alkynyl compounds to form
vinylidenes is a well-known process.20
(9) (a) Crochet, P.; Demerseman, B.; Vallejo, M. I.; Gamasa, P.; Gimeno, J.;
Borge, J.; Garc´ıa-Granda, S. Organometallics 1997, 16, 5406. (b) de los
R´ıos, I.; Jime´nez-Tenorio, M.; Puerta, M. C.; Valerga, P. J. Organomet.
Chem. 1997, 549, 221. (c) Esteruelas, M. A.; Go´mez, A. V.; Lo´pez, A.
M.; Puerta, M. C.; Valerga, P. Organometallics 1998, 17, 4959. (d)
Esteruelas, M. A.; Go´mez, A. V.; Lo´pez, A. M.; Modrego, J.; On˜ate, E.
Organometallics 1998, 17, 5434. (e) Roth, G.; Reindl, D.; Gockel, M.;
Troll, C.; Fischer, H. Organometallics 1998, 17, 1393. (f) Buriez, B.; Burns,
I. D.; Hill, A. F.; White, A. J. P.; Williams, D. J.; Wilton-Ely, J. D. E. T.
Organometallics 1999, 18, 1504. (g) Cadierno, V.; Conejero, S.; Gamasa,
M. P.; Gimeno, J.; Pe´rez-Carren˜o, E.; Garc´ıa-Granda, S. Organometallics
2001, 20, 3175. (h) Mantovani, N.; Marvelli, L.; Rossi, R.; Bertolasi, V.;
Bianchini, C.; de los R´ıos, I.; Peruzzini, M. Organometallics 2002, 21,
2382. (i) Cadierno, V.; Conejero, S.; Gamasa, M. P.; Gimeno, J.; Falvello,
L. R.; Llusar, R. M. Organometallics 2002, 21, 3716. (j) Baya, M.; Buil,
M. L.; Esteruelas, M. A.; Lo´pez, A. M.; On˜ate, E.; Rodr´ıguez, J. R.
Organometallics 2002, 21, 1841. (k) Fischer, H.; Szesni, N.; Roth, G.;
Burzlaff, N.; Weibert, B. J. Organomet. Chem. 2003, 683, 301. (l) Buil,
M. L.; Esteruelas, M. A.; Lo´pez, A. M.; On˜ate, E. Organometallics 2003,
22, 5274. (m) Szesni, N.; Weibert, B.; Fischer, H. Inorg. Chim. Acta 2004,
357, 1789. (n) Szesni, N.; Drexler, M.; Weibert, B.; Fischer, H. J.
Organomet. Chem. 2005, 690, 5597. (o) D´ıez, J.; Gamasa, M. P.; Gimeno,
J.; Lastra, E.; Villar, A. Organometallics 2005, 24, 1410. (p) Pavlik, S.;
Mereiter, K.; Puchberger, M.; Kirchner, K. Organometallics 2005, 24, 3561.
(q) Szesni, N.; Weibert, B.; Fischer, H. Inorg. Chim. Acta 2005, 358, 1645.
(r) Drexler, M.; Haas, T.; Yu, S.-M.; Beckmann, H. S. g.; Weibert, B.;
Fischer, H. J. Organomet. Chem. 2005, 690, 3700. (s) Szesni, N.;
Hohberger, C.; Mohamed, G. G.; Burzlaff, N.; Weibert, B.; Fischer, H. J.
Organomet. Chem. 2006, 691, 5753. (t) D´ıez, J.; Gamasa, M. P.; Gimeno,
J.; Lastra, E.; Villar, A. J. Organomet. Chem. 2006, 691, 4092. (u)
Mantovani, N.; Bergamini, P.; Marchi, A.; Marvelli, L.; Rossi, R.; Bertolasi,
V.; Ferretti, V.; de los Rios, I.; Peruzzini, M. Organometallics 2006, 25,
416. (v) Bustelo, E.; Jime´nez-Tenorio, M.; Puerta, M. C.; Valerga, P.
Organometallics 2006, 25, 4019. (w) Szesni, N.; Weibert, B.; Fischer, H.
Inorg. Chim. Acta 2006, 359, 617.
Alcohols have proven to be useful hydrogen donors and an
important alternative to molecular hydrogen for the hydrogena-
tion of unsaturated molecules.21 We have recently reported the
preparation of the bis-solvento hydride-allenylidene complex
[OsH(dCdCdCPh2)(CH3CN)2(PiPr3)2]BF4, which allows us to
assemble the allenylidene ligand with a terminal alkyne and an
acetonitrile molecule to afford osmacyclopentapyrrole deriva-
tives.22 Now, we show that alcohols hydrogenate the CR-Câ
double bond of the allenylidene ligand of this compound to give
a bis-solvento hydride-alkenylcarbene derivative.
In this Article, we report the following: (i) the hydrogenation
of the CR-Câ bond of [OsH(dCdCdCPh2)(CH3CN)2(PiPr3)2]-
BF4, (ii) the mechanism of the hydrogenation, (iii) a theoretical
study on the mechanism, and (iv) the subsequent hydrogenation
of the Os-C double bond to give 1,1-diphenylpropene.
Results and Discussion
(10) (a) Cadierno, V.; Gamasa, M. P.; Gimeno, J.; Gonza´lez-Cueva, M.; Lastra,
E.; Borge, J.; Garc´ıa-Granda, S.; Pe´rez-Carren˜o, E. Organometallics 1996,
15, 2137. (b) Esteruelas, M. A.; Go´mez, A. V.; Lo´pez, A. M.; Modrego,
J.; On˜ate, E. Organometallics 1997, 16, 5826. (c) Auger, N.; Touchard,
D.; Rigaut, S.; Halet, J.-F.; Saillard, J.-Y. Organometallics 2003, 22, 1638.
(11) Baya, M.; Crochet, P.; Esteruelas, M. A.; Gutie´rrez-Puebla, E.; Lo´pez, A.
M.; Modrego, J.; On˜ate, E.; Vela, N. Organometallics 2000, 19, 2585.
(12) (a) Dussel, R.; Pilette, D.; Dixneuf, P. H.; Fehlhammer, W. P. Organo-
metallics 1991, 10, 3287. (b) Pilette, D.; Ouzzine, K.; Le Bozec, H.;
Dixneuf, P. H.; Rickard, C. E. F.; Roper, W. R. Organometallics 1992,
11, 809. (c) Esteruelas, M. A.; Go´mez, A. V.; Lahoz, F. J.; Lo´pez, A. M.;
On˜ate, E.; Oro, L. A. Organometallics 1996, 15, 3423. (d) Gamasa, M.
P.; Gimeno, J.; Gonza´lez-Bernardo, C.; Borge, J.; Garc´ıa-Granda, S.
Organometallics 1997, 16, 2483. (e) Bernard, D. J.; Esteruelas, M. A.;
Lo´pez, A. M.; Modrego, J.; Puerta, M. C.; Valerga, P. Organometallics
1999, 18, 4995. (f) Ulrico, K.; Porhiel, E.; Pe´ron, V.; Ferrand, V.; Le Bozec,
H. J. Organomet. Chem. 2000, 601, 78. (g) Weberndo¨rfer, B.; Werner, H.
J. Chem. Soc., Dalton Trans. 2002, 1479. (h) Ghebreyessus, K. Y.; Nelson,
J. H. Inorg. Chim. Acta 2003, 350, 12. (i) Jime´nez-Tenorio, M.; Palacios,
M. D.; Puerta, M. C.; Valerga, P. J. Organomet. Chem. 2004, 689, 2776.
(j) Asensio, A.; Buil, M. L.; Esteruelas, M. A.; On˜ate, E. Organometallics
2004, 23, 5787.
1. Hydrogenation of the Cr-Câ Double Bond of the
Allenylidene Ligand of [OsH(dCdCdCPh2)(CH3CN)2-
(PiPr3)2]BF4. In contrast to the diphenylallenylidene complexes
of the iron triad with R-electrophilic character, which, in
alcohols, afford R,â-unsaturated alkoxycarbene derivatives, as
a result of the addition of the O-H bond of the alcohols to the
CR-Câ double bond of the C3-chain of the η1-carbon donor
ligand, the hydride-allenylidene complex [OsH(dCdCd
CPh2)(CH3CN)2(PiPr3)2]BF4 (1) in methanol, ethanol, n-pro-
panol, or 2-propanol evolves to the hydride-alkenylcarbene
derivative [OsH(dCHCHdCPh2)(CH3CN)2(PiPr3)2]BF4 (2). The
hydrogenation of the CR-Câ double bond of the allenylidene
ligand of 1 takes place by means of hydrogen transfer from the
alcohols, which undergo dehydrogenation to give the carbonyl
compounds (eq 1). The rates of the hydrogenation depend upon
the nature of the alcohols. While the quantitative reduction with
(13) See, for example: (a) Bohanna, C.; Callejas, B.; Edwards, A. J.; Esteruelas,
M. A.; Lahoz, F. J.; Oro, L. A.; Ruiz, N.; Valero, C. Organometallics 1998,
17, 373. (b) Xia, H. P.; Ng, W. S.; Ye, J. S.; Li, S.-Y.; Wong, W. T.; Lin,
Z.; Yang, C.; Jia, G. Organometallics 1999, 18, 4552. (c) Cadierno, V.;
Conejero, S.; Gamasa, M. P.; Gimeno, J. Organometallics 2002, 21, 3837.
(d) Bustelo, E.; Jime´nez-Tenorio, M.; Mereiter, K.; Puerta, M. C.; Valerga,
P. Organometallics 2002, 21, 1903. (e) Wen, T. B.; Zhou, Z. Y.; Lo, M.
F.; Williams, I. D.; Jia, G. Organometallics 2003, 22, 5217. (f) Venancio,
A. I. F.; Guedes da Silva, M. F. C.; Martins, L. M. D. R. S.; Frau´sto da
Silva, J. J. R.; Pombeiro, A. J. L. Organometallics 2005, 24, 4654.
(14) (a) Wen, T. B.; Cheung, Y. K.; Yao, J.; Wong, W.-T.; Zhou, Z. Y.; Jia, G.
Organometallics 2000, 19, 3803. (b) Jung, S.; Brandt, C. D.; Werner, H.
New J. Chem. 2001, 25, 1101. (c) Rigaut, S.; Touchard, D.; Dixneuf, P. H.
Organometallics 2003, 22, 3980. (d) Esteruelas, M. A.; Lo´pez, A. M.;
On˜ate, E.; Royo, E. Organometallics 2004, 23, 3021. (e) Cadierno, V.;
D´ıez, J.; Garc´ıa-Garrido, S. E.; Gimeno, J. Organometallics 2005, 24, 3111.
(f) Pavlik, S.; Mereiter, K.; Puchberger, M.; Kirchner, K. J. Organomet.
Chem. 2005, 690, 5497. (g) Castarlenas, R.; Vovard, C.; Fischmeister, C.;
Dixneuf, P. H. J. Am. Chem. Soc. 2006, 128, 4079.
(16) Werner, H.; Lass, R. W.; Gevert, O.; Wolf, J. Organometallics 1997, 16,
4077.
(17) Crochet, P.; Esteruelas, M. A.; Lo´pez, A. M.; Ruiz, N.; Tolosa, J. I.
Organometallics 1998, 17, 3479.
(18) Wong, C.-Y.; Che, C.-M.; Chan, M. C. W.; Leung, K.-H.; Phillips, D. L.;
Zhu, N. J. Am. Chem. Soc. 2004, 126, 2501.
(19) Touchard, D.; Pirio, N.; Dixneuf, P. H. Organometallics 1995, 14, 4920.
(20) (a) Bruce, M. I. Chem. ReV. 1991, 91, 197. (b) Puerta, M. C.; Valerga, P.
Coord. Chem. ReV. 1999, 193-195, 977. (c) Esteruelas, M. A.; Lo´pez, A.
M. Organometallics 2005, 24, 3584. (d) Esteruelas, M. A.; Lo´pez, A. M.;
Oliva´n, M. Coord. Chem. ReV. 2007, 251, 795.
(21) Samec, J. S. M.; Ba¨ckvall, J.-E.; Andersson, P. G.; Brandt, P. Chem. Soc.
ReV. 2006, 35, 237.
(22) Bolan˜o, T.; Castarlenas, R.; Esteruelas, M. A.; On˜ate, E. J. Am. Chem.
Soc. 2006, 128, 3965.
(15) Werner, H.; Laubender, M.; Wiedemann, R.; Windmu¨ller, B. Angew. Chem.,
Int. Ed. Engl. 1996, 35, 1237.
9
J. AM. CHEM. SOC. VOL. 129, NO. 28, 2007 8851

A R T I C L E S
Bolan˜o et al.
Scheme 1
corresponding to the Os-H vibration, and the absorption due
to the [BF4]- anion with Td symmetry centered at 1061 cm-1
.
Figure 1. Molecular diagram of the cation of 2. Selected bond lengths
(Å) and angles (deg): Os-N(1) 2.165(6), Os-N(2) 2.132(6), Os-C(1)
1.892(8), C(1)-C(2) 1.472(11); P(1)-Os-P(2) 158.64(7), Os-C(1)-C(2)
129.3(6), N(1)-Os-N(2) 85.5(2), H(01)-Os-N(2) 175(3), C(1)-Os-N(1)
176.5(3).
In the 1H NMR spectrum in dichloromethane-d2, the most
noticeable resonance is that due to the OsdCH proton, which
appears at 21.35 ppm, as a doublet with an H-H coupling
constant of 13.2 Hz. The acetonitrile resonances are observed
at 2.90 and 2.80 ppm as singlets. In the high field region of the
spectrum, the hydride ligand gives rise to a triplet at -16.27
ppm, with an H-P coupling constant of 21.4 Hz. In the 13C-
{1H} NMR spectrum, the OsdC resonance is observed at 265.1
ppm, as a triplet with a C-P coupling constant of 8.1 Hz. In
accordance with the mutually cis disposition of the acetonitrile
molecules, these ligands display two CN resonances at 141.5
and 125.3 ppm. The 31P{1H} NMR spectrum contains a singlet
at 22.4 ppm, which is consistent with the mutually trans
disposition of the phosphine ligands, and with the fact that the
hydrogen and alkenyl substituents of the alkylidene carbon atom
lie in the plane containing the nitrogen atoms.
primary alcohols occurs after 1 h, with 2-propanol 5 h is
necessary to obtain 2 in high yield.
The carbonyl compounds, RR′CO, were characterized by
GC-MS, whereas complex 2, which is isolated as a green solid,
was characterized by elemental analysis, IR, 1H, 31P{1H}, 13C-
{1H} NMR spectroscopy, and by an X-ray crystallographic
study. Figure 1 shows an ORTEP drawing of the cation.
The geometry around the osmium atom can be described as
a distorted octahedron with the phosphorus atoms of the
phosphine ligands occupying trans positions (P(1)-Os-P(2) )
158.64(7)°). The perpendicular plane is formed by the aceto-
nitrile molecules cis disposed (N(1)-Os-N(2) ) 85.5(2)°), the
hydride ligand trans disposed to N(2) (H(01)-Os-N(2) ) 175-
(3)°), and the carbene group trans disposed to N(1) (C(1)-Os-
N(1) ) 176.5(3)°). The Os-C(1) bond length of 1.892(8) Å
supports the Os-C double bond formulation.23 In agreement
with the sp2 hybridization at C(1), the angles around this atom
are between 108(5)° and 129.3(6)°.
2. Mechanism of the Hydrogenation: Reactions with
Phenol and t-Butanol. Although tertiary alcohols can undergo
heterolytic activation of the O-H bond, they are not a suitable
source of hydrogen for the hydrogenation of a C-C double
bond, because they do not contain a geminal hydrogen. Thus,
to obtain information about the first step of the reaction shown
in eq 1, we have also investigated the behavior of 1 in the
presence of phenol and t-butanol (Scheme 1).
Treatment at room temperature of dichloromethane solutions
of 1 with 1.1 equiv of phenol leads to the phenoxy-carbyne
derivative [OsH(OPh)(tCCHdCPh2)(CH3CN)(PiPr3)2]BF4 (3),
as a result of a 1,3-addition of the O-H bond of the alcohol to
the Os-allenylidene unit of 1. Similarly, the stirring of 1 in
t-butanol as solvent affords [OsH(OtBu)(tCCHdCPh2)(CH3-
CN)(PiPr3)2]BF4 (4). The formation of 3 and 4 is in agreement
with the nucleophilic character of the Câ atom of the C3-chain
of the allenylidene and reveals the Lewis base nature of 1, which
is able to undergo the oxidative addition of alcohols.
The IR spectrum of 2 in Nujol shows two ν(CtN) absorp-
tions at 2331 and 2265 cm-1 along with a band at 2172 cm-1
,
(23) (a) Esteruelas, M. A.; Lahoz, F. J.; On˜ate, E.; Oro, L. A.; Zeier, B.
Organometallics 1994, 13, 1662. (b) Esteruelas, M. A.; Lahoz, F. J.; On˜ate,
E.; Oro, L. A.; Valero, C.; Zeier, B. J. Am. Chem. Soc. 1995, 117, 7935.
(c) Brumaghim, J. L.; Girolami, G. S. Chem. Commun. 1999, 953. (d)
Werner, H.; Stu¨er, W.; Wolf, J.; Laubender, M.; Weberndo¨rfer, B.; Herbst-
Irmer, R.; Lehmann, C. Eur. J. Inorg. Chem. 1999, 1889. (e) Castarlenas,
R.; Esteruelas, M. A.; On˜ate, E. Organometallics 2001, 20, 2294. (f) Gusev,
D. G.; Lough, A. J. Organometallics 2002, 21, 2601. (g) Weberndo¨rfer,
B.; Henig, G.; Hockless, D. C. R.; Bennett, M. A.; Werner, H. Organo-
metallics 2003, 22, 744. (h) Esteruelas, M. A.; Gonza´lez, A. I.; Lo´pez, A.
M.; On˜ate, E. Organometallics 2004, 23, 4858. (i) Bolan˜o, T.; Castarlenas,
R.; Esteruelas, M. A.; Modrego, F. J.; On˜ate, E. J. Am. Chem. Soc. 2005,
127, 11184. (j) Castarlenas, R.; Esteruelas, M. A.; On˜ate, E. Organome-
tallics 2005, 24, 4343. (k) Esteruelas, M. A.; Ferna´ndez-Alvarez, F. J.;
Oliva´n, M.; On˜ate, E. J. Am. Chem. Soc. 2006, 128, 4596. (l) Esteruelas,
M. A.; Ferna´ndez-Alvarez, F.; On˜ate, E. J. Am. Chem. Soc. 2006, 128,
13044.
Complexes 3 and 4 are isolated as red and brown solids in
90% and 72% yield, respectively, and were characterized by
1
elemental analysis, IR, and H, 13C{1H}, and 31P{1H} NMR
spectroscopy. Complex 3 was further characterized by an X-ray
crystallographic study. An ORTEP drawing of the cation of this
compound is shown in Figure 2.
The coordination around the osmium atom can be rationalized
as a distorted octahedron with the phosphine ligands occupying
trans positions (P(1)-Os-P(2) ) 166.18(5)°). The perpendicu-
lar plane is formed by the phenoxide, acetonitrile, hydride, and
9
8852 J. AM. CHEM. SOC. VOL. 129, NO. 28, 2007

Hydrogenation of CR
−Câ and M−CR Double Bonds
A R T I C L E S
Scheme 2
Figure 2. Molecular diagram of the cation of 3. Selected bond lengths
(Å) and angles (deg): Os-N(1) 2.154(4), Os-O(1) 2.061(3), Os-C(1)
1.740(5), C(1)-C(2) 1.432(6), C(2)-C(3) 1.343(7); P(1)-Os-P(2) 166.18-
(5), Os-C(1)-C(2) 172.9(4), O(1)-Os-C(1) 178.91(19), N(1)-Os-O(1)
79.07(13), N(1)-Os-H(01) 165.7(14), O(1)-Os-H(01) 86.6(14).
carbyne ligands. The phenoxide group lies trans to the carbyne
ligand (O(1)-Os-C(1) ) 178.91(19)°), whereas the hydride
and acetonitrile ligands are also mutually trans disposed (H(01)-
Os-N(1) ) 165.7(14)°). The Os-C(1) bond length of 1.740-
(5)ÅisfullyconsistentwithanOs-Ctriplebondformulation.23i,24
Similarly to other carbyne-metal compounds,13d,e,25 a slight
bending in the Os-C(1)-C(2) moiety is also present (Os-
C(1)-C(2) ) 172.9(4)°). The alkenyl carbyne 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 1.432-
(6) Å and C(2) and C(3) by 1.343(7) Å, and the angles around
C(2) and C(3) are in the range 111-125°. The Os-O(1) distance
of 2.061(3) Å compares well with those found in other alkoxy-
and hydroxy-osmium complexes.26
In the presence of acetonitrile, the n-propanol solutions of 3
and 4 evolve to afford the hydride-carbene complex 2. The
first step of these transformations is the exchange of the
coordinated alkoxy group by reaction with n-propanol, which
acts as solvent. The exchange between the hydrogen-bonded
alcohol and a coordinated alkoxide is a well-known process.27
In agreement with this, we have observed that at -30 °C, the
1H NMR spectra of the freshly prepared solutions of 3 in
2-propanol-d8 contain, in addition to the resonances of 3, a triplet
(JH-P ) 17.7 Hz) at -6.28 ppm and a singlet at 5.38 ppm,
which can be assigned to the hydride ligand and to the Câ-H
hydrogen atom of the alkenyl substituent of the carbyne group
of [OsH{OCD(CD3)2}(tCCHdCPh2)(CH3CN)(PiPr3)2]+ (5-d7).
At temperatures higher than -30 °C, the latter is unstable and
decomposes into a complex mixture of unidentified products.
However, in the presence of acetonitrile the evolution takes place
in a controlled way, and the hydride-carbene 2-d1 is formed.
In agreement with the presence of a hydride ligand in 3 and
1
4, their H NMR spectra in the high field region show triplets
at -6.72(3) and -3.90(4) ppm, with H-P coupling constants
of 16.8 and 17.4 Hz, respectively. In the low field region, the
Câ-H proton of the alkenyl substituent of the carbyne ligands
gives rise to singlets at 5.40 (3) and 5.22 (4) ppm. In the 13C-
{1H} NMR spectra, the Os-CR resonances are observed at 261.0
(3) and 270.7 (4) ppm, as triplets with C-P coupling constants
of 12.3 and 9.0 Hz, respectively. The 31P{1H} NMR spectra
contain singlets at 27.4 (3) and 26.1 (4) ppm.
1
2
Interestingly, the H and H NMR spectra of 2-d1 indicate the
presence of 0.4 deuterium atoms at the CR position and 0.6
deuterium atoms at the hydride position. This deuterium
distribution suggests that 2-d1 is a 4:6 mixture of the isomers
shown in Scheme 2.
Scheme 3 shows a mechanism for the hydrogenation of the
CR-Câ double bond of the allenylidene of 1, which is consistent
with the experimental observations summarized in Schemes 1
and 2. The reactions involve the ruptures of the O-H and
OC-H bonds of the alcohols, and the additions of the hydrogen
atoms to the CR-Câ double bond of the allenylidene. In
accordance with Scheme 1, the 1,3-addition of the O-H bond
of the alcohols to the Os-allenylidene unit should afford alkoxy-
hydride-carbyne intermediates related to 3, 4, and 5-d7. The
composition of 2-d1 indicates that the rupture of the OC-H
bond takes place before the formation of the CR-H one. The
â-hydrogen elimination from the alcoholates should give
dihydride-carbyne intermediates, which could form 2 by migra-
tory insertion of the carbyne ligand into one of the Os-H bonds.
3. Theoretical Calculations on the Mechanism. The mech-
anism for the hydrogenation of the CR-Câ double bond of the
(24) (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.; Oliva´n, M.; On˜ate,
E.; Ruiz, N.; Tajada, M. A. Organometallics 1999, 18, 2953. (c) Castarlenas,
R.; Esteruelas, M. A.; On˜ate, E. Organometallics 2001, 20, 3283. (d) Barrio,
P.; Esteruelas, M. A.; On˜ate, E. Organometallics 2002, 21, 2491. (e)
Esteruelas, M. A.; Gonza´lez, A. I.; Lo´pez, A. M.; On˜ate, E. Organometallics
2003, 22, 414. (f) Barrio, P.; Esteruelas, M. A.; On˜ate, E. J. Am. Chem.
Soc. 2004, 126, 1946. (g) Wen, T. B.; Hung, W. Y.; Zhou, Z. Y.; Lo, M.
F.; Williams, I. D.; Jia, G. Eur. J. Inorg. Chem. 2004, 2837. (h) Lee, J.-H.;
Pink, M.; Caulton, K. G. Organometallics 2006, 25, 802. (i) Hung, W. Y.;
Zhu, J.; Wen, T. B.; Yu, K. P.; Sung, H. H. Y.; Williams, I. D.; Lin, Z.;
Jia, G. J. Am. Chem. Soc. 2006, 128, 13742.
(25) (a) Esteruelas, M. A.; Lo´pez, A. M.; Ruiz, N.; Tolosa, J. I. Organometallics
1997, 16, 4657. (b) Crochet, P.; Esteruelas, M. A.; Lo´pez, A. M.; Mart´ınez,
M.-P.; Oliva´n, M.; On˜ate, E.; Ruiz, N. Organometallics 1998, 17, 4500.
(26) See, for example: (a) Che, C.-M.; Huang, J.-S.; Li, Z.-Y.; Poon, C.-K.;
Tong, W.-F.; Lai, T.-F.; Cheng, M.-C.; Wang, C.-C.; Wang, Y. Inorg.
Chem. 1992, 31, 5220. (b) Edwards, A. J.; Elipe, S.; Esteruelas, M. A.;
Lahoz, F. J.; Oro, L. A.; Valero, C. Organometallics 1997, 16, 3828. (c)
Renkema, K. B.; Huffman, J. C.; Caulton, K. G. Polyhedron 1999, 18,
2575. (d) Bhattacharya, S.; Gupta, P.; Basuli, F.; Pierpont, C. G. Inorg.
Chem. 2002, 41, 5810. (e) Dickinson, P. W.; Girolami, G. S. Inorg. Chem.
2006, 45, 5215. (f) Wu, A.; Dehestani, A.; Saganic, E.; Crevier, T. J.;
Kaminsky, W.; Cohen, D. E.; Mayer, J. M. Inorg. Chim. Acta 2006, 359,
2842.
(27) Esteruelas, M. A.; Oro, L. A. Coord. Chem. ReV. 1999, 193-195, 557 and
references therein.
9
J. AM. CHEM. SOC. VOL. 129, NO. 28, 2007 8853

A R T I C L E S
Scheme 3
Bolan˜o et al.
H(2) atom is transoid with regard to H(1) (H(2)-Os-H(1) )
155.4°) and is separated by 1.754 Å from the osmium atom.
The disposition of H(2) in the transition state determines the
stereochemistry of the resulting dihydride intermediates [OsH2-
(tCCHdCH2){κ1-OC(CH3)2}(PH3)2]+ (7t). The â-elimination
through TS1-a gives the cis-dihydride 7t-a (H(1)-Os-H(2) )
73.2°), while the â-elimination via TS1-b affords the trans-
dihydride 7t-b (H(1)-Os-H(2) ) 157.9°).
There is a noticeable difference in the Os-H bond lengths
of 7t-a, which is consistent with the marked difference in trans
influence between the carbyne and acetone ligands. The distance
between the osmium atom and the hydride ligand trans disposed
to the carbyne group (H(2)) is 0.118 Å longer than the distance
between the metal center and the hydride ligand, H(1), trans
disposed to the acetone molecule (1.724 Å versus 1.606 Å).
The trans influence of a hydride ligand is intermediate between
those of the carbyne and acetone groups. In accordance with
this, the Os-H bond lengths in 7t-b of 1.685 Å (Os-H(1))
and 1.674 Å (Os-H(2)) are intermediate between those of 7t-
a. Both dihydride intermediates are less stable than 5t, the first
allenylidene of 1, by hydrogen transfer from alcohols, has been
analyzed by DFT calculations (B3PW91) using PH3, CCHd
CH2, and (CH3)2CO as models of triisopropylphosphine, alk-
enylcarbyne, and dehydrogenated alcohol, respectively. Because
the alkoxy-hydride-carbyne complexes 3 and 4 have been
isolated and characterized, including the X-ray structure of 3,
the theoretical study is centered on the rupture of the OC-H
bond of the alkoxide ligand and the formation of the CR-H
bond. So, the analysis starts from the model alkoxy-hydride-
carbyne intermediate [OsH{OCH(CH3)2}(tCCHCH2)(CH3CN)-
(PH3)2]+ (5t). The changes in free energy (∆G) have been
computed at 298.15 K and P ) 1 atm. Figure 3 shows the energy
profile, whereas Figure 4 collects the optimized structures and
selected structural parameters.
The â-hydrogen elimination reaction on the alkoxide ligand
of 5t needs a coordination vacancy at the metal center. So,
because 5t is a saturated species, the dissociation of the
acetonitrile molecule should be the first step of the transforma-
tion from 5t into [OsH(dCHCHdCH2)(CH3CN)2(PH3)2]+ (2t).
This release leads to [OsH{OCH(CH3)2}(tCCHdCH2)(PH3)2]+
(6t), which has two minima, a and b. The first of them, 6t-a,
lies 90.7 kJ mol-1 above 5t. The second one, 6t-b, is 13.0 kJ
mol-1 more stable than 6t-a. From a structural point of view,
they show significant differences. The geometry around the
osmium atom of 6t-a can be described as a distorted trigonal
bipyramid with apical phosphines (P-Os-P ) 176.5°) and
inequivalent angles within the Y-shaped equatorial plane (O-
Os-H(1) ) 137.7°, O-Os-C(1) ) 133.2°, and H(1)-Os-
C(1) ) 89.1°), whereas the structure of 6t-b can be rationalized
as a square-pyramidal with the phosphines, mutually trans
disposed (P-Os-P ) 164.5°), the alkoxide and alkenylcarbyne
group (O-Os-C(1) ) 174.7°) occupying the basal sites, and
the hydride ligand located at the apex. The separation between
the â-hydrogen atom H(2) of the alkoxide ligand and the metal
center in 6t-b (1.945 Å) is about 0.16 Å shorter than in 6t-a
(2.111 Å).
of them by 24.2 kJ mol-1 and the second one by 7.1 kJ mol-1
.
The lower stability of 7t-a with regard to 7t-b appears to be a
consequence of the trans disposition of the two ligands with
the highest trans influences of the complex, carbyne and hydride.
The migration of the hydride ligand H(1) to the carbyne group
in 7t-a gives the five-coordinate alkenylcarbene intermediate
[OsH(dCHCHdCH2){κ1-OC(CH3)2}(PH3)2]+ (8t). Similarly,
the migration of H(1) to the carbyne ligand in 7t-b leads to 8t.
The latter, which is 3.3 kJ mol-1 more stable than 7t-a and
13.8 kJ mol-1 less stable than 7t-b, lies 20.9 kJ mol-1 above
5t. Intermediate 8t can be described as a five-coordinate species
with trans phosphines (P-Os-P ) 168.6°) and O-Os-H(1),
O-Os-C(1), and H(1)-Os-C(1) angles of 144.4°, 129.6°, and
85.9°, respectively, within the Y-shaped perpendicular plane.
The activation energy for the insertion has a marked
dependence upon the strength of the bond between the metal
center and the emigrant hydride, which is determined by the
group disposed trans to this hydride, and therefore depends upon
the stereochemistry cis or trans of the dihydrides 7t. The Os-
H(1) distance in the cis-dihydride 7t-a is 0.079 Å shorter than
the Os-H(1) bond length in its trans-dihydride isomer 7t-b. In
agreement with an Os-H(1) bond stronger in 7t-a than in 7t-
b, the activation barrier for the migration of the H(1) hydride
ligand of 7t-a from the metal center to the carbyne carbon atom
(TS2-a) is higher than that (TS2-b) for the migration of the
hydride ligand H(1) of 7t-b (160.1 versus 62.3 kJ mol-1). The
value calculated for the migration of H(1) of 7t-a is also higher
than those previously reported for related processes.23i,28 Ac-
cording to the obtained value, the acetone dissociation should
occur before the migration takes place. The release of acetone
should afford [OsH2(tCCHCH2)(PH3)2]+ species, which lie
between 67 and 100 kJ mol-1 above 5t. Although both TS2-a
and TS2-b can be described as η2-carbene species,29 as expected
from the energy difference between them, the three-membered
The proximity of H(2) and the osmium atom in 6t-b favors
the â-hydrogen elimination reaction. Thus, the activation barrier
for the process in 6t-b (TS1-b) is 81.1 kJ mol-1 above 5t and
26.7 kJ mol-1 lower than in 6t-a (TS1-a; 107.8 kJ mol-1). The
transition states TS1-a and TS1-b are also structurally different.
In TS1-a, the â-hydrogen atom H(2) of the alkoxide group lies
cisoid disposed to the hydride H(1) (H(2)-Os-H(1) ) 73.4°)
and 1.795 Å from the metal center. However, in TS1-b, the
Os-C-H rings are very different. That of TS2-a has Os-H,
Os-C, and C-H distances of 2.089, 1.866, and 1.164 Å,
(28) Bolan˜o, T.; Castarlenas, R.; Esteruelas, M. A.; On˜ate, E. Organometallics
2007, 26, 2037.
(29) (a) Schultz, A. J.; Williams, J. M.; Schrock, R. R.; Rupprecht, 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.
9
8854 J. AM. CHEM. SOC. VOL. 129, NO. 28, 2007

Hydrogenation of CR
−Câ and M−CR Double Bonds
A R T I C L E S
Figure 3. Relative energies (∆G, 298 K, 1 atm; kJ mol-1) for the transformation of 5t to 2t.
respectively, and the triangle angles are between 33.6° and 83.7°.
In TS2-b, not only the three sides of the triangle are similar
(1.774 (Os-H), 1.758 (Os-C), and 1.526 (C-H)) but also the
angles (between 52.5° and 63.2°).
spectroscopically detected. The conversion of 5t into 7t-b is a
combined step, which implies the initial dissociation of aceto-
nitrile to give 6t-b, and the subsequent â-elimination on the
alkoxide ligand. In agreement with the initial dissociation of
acetonitrile, we have also observed that the reaction of 3 with
n-propanol is inhibited in acetonitrile as solvent.
The coordination of acetonitrile to 8t gives [OsH(dCHCHd
CH2){κ1-OC(CH3)2}(CH3CN)(PH3)2]+ (9t). The saturation of
the metal center produces a strong stabilization. Intermediate
9t is 79.8 kJ mol-1 more stable than 5t. It can be described as
an octahedral cis-hydride-carbene intermediate (H(2)-Os-C(1)
) 87.6°) with trans phosphines (P-Os-P ) 171.4°). The
remaining coordination sites involve the acetonitrile molecule
and the carbene group trans disposed (N-Os-C(1) ) 171.1°),
and the acetone molecule and the hydride ligand also trans
disposed (O-Os-H(2) ) 163.9°).
The substitution of the acetone ligand of 9t by a second
acetonitrile molecule gives rise to an additional stabilization of
the system. The formation of 2t, which is 120.8 kJ mol-1 more
stable than 5t, from 9t implies the dissociation of acetone to
afford [OsH(dCHCHdCH2)(CH3CN)(PH3)2]+ (10t) and the
subsequent coordination of acetonitrile to the metal center of
the latter. The acetone dissociation produces a light destabiliza-
tion with regard to 9t. The five-coordinate intermediate 10t is
only 43.0 kJ mol-1 more stable than 5t. In contrast to the acetone
derivative 8t, the structure of 10t can be rationalized as square-
pyramidal with the phosphines mutually trans disposed (P-
Os-P ) 169.0°), the acetonitrile and alkenylcarbene (also trans
disposed; N-Os-C(1) ) 175.5°) occupying the basal sites, and
the hydride ligand located at the apex.
The â-hydrogen elimination in 5t is certainly favored with
regard to the migratory insertion of the carbyne ligand into the
Os-H bond. The energy barrier calculated for the latter of 114.1
kJ mol-1 is higher than that for the â-hydrogen elimination.
Although the resulting alkoxide-carbene is unsaturated, the
â-elimination reaction in this species has also an energy barrier
higher than in 5t. Thus, the transition state for the process lies
94.9 kJ mol-1 above 5t, that is, 13.8 kJ mol-1 above TS1-b.
4. Hydrogenation of the Os-C Double Bond of [OsH(d
CHCHdCPh2)(CH3CN)2(PiPr3)2]BF4. Complex 2 is notable
because it is a rare example of hydride-alkenylcarbene derivative
and by the mutually cis disposition of the hydride and Os-C
double bond. As far as we know, the only hydride-carbene
complexes previously reported in the osmium-chemistry are the
carbonyl derivatives OsHX(CO)(dCHR)(PR′3)2 (X ) Cl, O2-
CCF3; R ) H, Ph, CO2Et, SiMe3; PR′3 ) PiPr3, PMetBu2), with
the hydride and carbene ligands mutually trans disposed.30 In
benzene at 25 °C, complex OsHCl(CO)(dCH2)(PiPr3)2 decom-
poses unselectively to give a mixture of several products.30a On
t
the other hand, the related Bu2MeP derivative OsHCl(CO)(d
CH2)(PMetBu2)2 isomerizes into the five-coordinate methyl
compound Os(CH3)Cl(CO)(PMetBu2)2.30b,d
The visual examination of the energy profile depicted in
Figure 3 shows that the transformation from 5t to 2t through
the pathway b (red) via the trans-dihydride intermediate 7t-b
is strongly favored over the pathway a (blue) via the cis-
dihydride 7t-a. The highest barrier of pathway b is the
â-hydrogen elimination on the alkoxide ligand of 5t and appears
to be the rate-determining step for the reduction. This is
consistent with the previously mentioned dependence of the rate
of the hydrogenation on the nature of the alcohol and with the
moderated stability of the intermediate 5-d7, which can be
The behavior of 2 differs from those previously mentioned.
In acetonitrile under reflux, complex 2 releases 1,1-diphenyl-
(30) (a) Werner, H.; Stu¨er, W.; Laubender, M.; Lehmann, C.; Herbst-Irmer, R.
Organometallics 1997, 16, 2236. (b) Huang, D.; Spivak, G. J.; Caulton,
New J. Chem. 1998, 22, 1023. (c) Werner, H.; Stu¨er, W.; Wolf, J.;
Laubender, M.; Weberndo¨rfer, B.; Herbst-Irmer, R.; Lehmann, C. Eur. J.
Inorg. Chem. 1999, 1889. (d) Ge´rard, H.; Clot, E.; Eisenstein, O. New J.
Chem. 1999, 23, 495. (e) Gandelman, M.; Rybtchinski, B.; Ashkenazi, N.;
Gauvin, R. M.; Milstein, D. J. Am. Chem. Soc. 2001, 123, 5372. (f)
Gondelman, M.; Naing, K. M.; Rybtchinski, B.; Poverenov, E.; Ben-David,
Y.; Ashkenazi, N.; Gauvin, R. M.; Milstein, D. J. Am. Chem. Soc. 2005,
127, 15265.
9
J. AM. CHEM. SOC. VOL. 129, NO. 28, 2007 8855

A R T I C L E S
Bolan˜o et al.
Figure 4. B3PW91 optimized geometries of the intermediates and the transition states for the transformation of 5t to 2t.
propene (eq 2) as a result of the hydrogenation of its Os-C
double bond. The new hydrogen atoms of the olefin come from
the metal center, and from a methyl group of one of the
phosphine ligands, which undergoes metalation with the osmium
metalated carbon atom, which appear at 1.69 and 0.60 ppm. In
the 13C{1H} NMR spectrum, the Os-CH2 and CH signals of
the metalated isopropyl group are observed at -15.6 and 48.4
ppm, respectively. These chemical shifts are similar to those
previously reported for related cyclopentadienyl-14d,25a and
indenyl-osmium compounds.31 The 31P{1H} NMR spectrum
shows two doublets. That corresponding to the metalated
phosphine appears at -27.7 ppm, while the other one is
observed at 3.0 ppm. In agreement with the mutually trans
disposition of these ligands, the P-P coupling constant is 266
Hz.
atom. The reaction affords [Os{CH2CH(CH3)PiPr2(CH3CN)3-
(PiPr3)]BF4 (11) as a brown solid in 83% yield.
The formation of the olefin can be rationalized according to
Scheme 4. The migration of the hydride ligand to the carbene
carbon atom in 2 should lead to an unsaturated σ-allyl
intermediate. Thus, the metal center could promote the C(sp3)-H
bond activation of a methyl group of an isopropyl substituent
of one of the phosphine ligands, to give a hydride-σ-allyl
The presence of a metalated triisopropylphosphine ligand in
11 is strongly supported by its 1H, 13C{1H}, and 31P{1H} NMR
1
spectra in acetonitrile-d3. In the H NMR spectrum, the most
(31) Esteruelas, M. A.; Lo´pez, A. M.; On˜ate, E.; Royo, E. Organometallics 2005,
24, 5780.
noticeable resonances are those due to the CH2-protons of the
9
8856 J. AM. CHEM. SOC. VOL. 129, NO. 28, 2007

Hydrogenation of CR
−Câ and M−CR Double Bonds
A R T I C L E S
Scheme 4
ligand of an alkoxy-carbyne intermediate. The last pattern has
afforded the preparation of the novel hydride-alkenylcarbene
derivative [OsH(dCHCHdCPh2)(CH3CN)2(PiPr3)2]BF4, as a
consequence of the unprecedented hydrogenation of the CR-
Câ double bond of an allenylidene ligand, that of complex [OsH-
(dCdCdCPh2)(CH3CN)2(PiPr3)2]BF4.
Deuterium labeling experiments and theoretical calculations
on this hydrogenation indicate that the â-hydrogen elimination
in the alkoxide ligand of the key intermediates [OsH(OCHR2)-
(tCCHdCPh2)(CH3CN)(PiPr3)2]+ is favored with regard to the
migratory insertion of the carbyne into the Os-H bond.
However, the presence of a hydride co-ligand in the starting
allenylidene complex seems to be determinant for the viability
of the reduction. Because the â-hydrogen elimination is the
favored reaction in the alkoxide-hydride-carbyne intermediate,
the hydrogenation proceeds via a dihydride carbyne species,
and the cis disposition of the carbyne group to both hydride
ligands (trans between them) is essential to the insertion. While
the activation energy for the migratory insertion of the carbyne
intermediate containing a metalated phosphine. The carbon-
hydrogen coupling on the osmium atom should finally afford
the olefin, reducing the metal center.
into an Os-H bond of the trans-dihydride is only 62.3 kJ mol-1
,
it is increased until 160.1 kJ mol-1 in the cis-dihydride isomer.
Complex [OsH(dCHCHdCPh2)(CH3CN)2(PiPr3)2]BF4 is the
unique hydride-carbene known in the osmium-chemistry with
the hydride and carbene ligand mutually cis disposed. Its
behavior also differs from the behavior observed for the
scarce trans-hydride-carbene-osmium complexes reported until
now. In contrast to the latter, it undergoes hydrogenation of
the Os-C double bond. Thus, 1,1-diphenylpropene and the
The reaction shown in eq 2 was followed by 1H NMR
spectroscopy by measuring the disappearance of the CR-H
resonance of the carbene ligand of 2, and the appearance of
both the CHd resonance of the olefin and one of the Os-CH2
resonances of 11. As shown in Figure 5, in acetonitrile-d3, the
decrease of 2 and the increases of the olefin and 11 are
exponential functions of the time, in agreement with first-order
processes. The three first-order rate constants, collected between
40 and 80 °C, have the same value. The activation parameters
obtained from the Eyring analysis are ∆Hq ) 89.0 ( 6.3 kJ
mol-1 and ∆Sq ) -43.5 ( 9.6 J mol-1 K-1. These observations
are consistent with the proposal depicted in Scheme 4 and
suggest that the rate-determining step for the formation of the
olefin is the migratory insertion of the carbene ligand into the
Os-H bond of 2. The negative value of the activation entropy
is similar to that reported for the migration of the hydride ligand
of (PiPr3)2(CO)ClRu{(E)-CHdCH-C(CH2)4-CHdCd}OsHCl-
(CO)(PiPr3)2 from the osmium atom to the CR atom of the
vinylidene group32 and indicates that the insertion occurs by a
concerted mechanism with a geometrically highly oriented
transition state.
complex [Os{CH2CH(CH3)PiPr2(CH3CN)3(PiPr3)]BF4, contain-
ing a metalated phosphine, are formed in acetonitrile.
In conclusion, we report an unprecedented sequential and
selective hydrogenation of a diphenylallenylidene ligand coor-
dinated to osmium and the mechanism of the formation of the
reduced products.
Experimental Section
All reactions were carried out with rigorous exclusion of air using
Schlenk-tube techniques. Solvents were dried by the usual procedures
and distilled under argon prior to use. The starting material [OsH(d
CdCdCPh2)(CH3CN)2(PiPr3)2]BF4 (1) was prepared by the published
method.22 1H, 31P{1H}, 19F, and 13C{1H} NMR spectra were recorded
on either a Varian Gemini 2000, a Bruker AXR 300, a Bruker Avance
400 MHz, or a Bruker Avance 500 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. Infrared spectra were run on a Perkin-Elmer 1730
spectrometer (Nujol mulls on polyethylene sheets). C, H, and N analyses
were carried out in a Perkin-Elmer 2400 CHNS/O analyzer. GC-MS
experiments were run on an Agilent 5973 mass selective detector
interfaced to an Agilent 6890 series gas chromatograph system. Samples
were injected into a 30 m × 250 µm HP-5MS 5% phenyl methyl
siloxane column with a film thickness of 0.25 µm.
Hydrogenation of [OsH(dCdCdCPh2)(CH3CN)2(PiPr3)2]BF4:
Formation of [OsH(dCHCHdCPh2)(CH3CN)2(PiPr3)2]BF4 (2). A
green solution of 1 (569 mg, 0.653 mmol) in 12 mL of n-propanol
was stirred for 1 h. The solvent was removed in vacuo. The addition
of diethyl ether to the resulting residue led to a green solid, which was
washed with diethyl ether and dried in vacuo. Yield: 486 mg (85%).
GC-MS analysis of the mother liquor showed the presence of propanal.
Anal. Calcd for C37H61BF4N2OsP2: C, 50.91; H, 7.04; N, 3.21. Found:
C, 50.66; H, 6.96; N, 3.07. IR (Nujol, cm-1): ν(CtN) 2331 (w), 2265
Concluding Remarks
Until now, the transition metal allenylidenes complexes had
shown two different behaviors with alcohols. Those with
R-electrophilic nature form R,â-unsaturated alkoxycarbene
derivatives, as a result of the 1,2-addition of the O-H bond of
the alcohols to the CR-Câ double bond of the allenylidenes,
while those with γ-electrophilic or nucleophilic nature are inert.
This Article illustrates new reaction patterns. They appear to
be characteristic of very strong nucleophilic species with weak
coordinating co-ligands in the sphere of the metal. One of them,
general for all alcohols, implies the 1,3-addition of the O-H
bond of the alcohols to the metallic center and the Câ atom of
the allenylidene and affords novel alkoxy-carbyne derivatives.
The other one is particular for primary and secondary alcohols,
which can transfer a â-hydrogen to the CR atom of the carbyne
(32) Buil, M. L.; Esteruelas, M. A. Organometallics 1999, 18, 1798.
9
J. AM. CHEM. SOC. VOL. 129, NO. 28, 2007 8857

A R T I C L E S
Bolan˜o et al.
1
Figure 5. Stacked H NMR spectra illustrating the transformation of 2 into 11 and 1,1-diphenylpropene in CD3CN at 313 K.
1
(w); ν(OsH) 2172 (m); ν(CdC) 1538 (m); ν(BF) 1061 (vs). H NMR
(300 MHz, CD2Cl2, 293 K): δ 21.35 (d, JH-H ) 13.2, 1H, OsdCH),
7.6-7.1 (m, 11H, Ph, -CHd), 2.90 and 2.80 (both s, 6H, CH3CN),
2.03 (m, 6H, PCH), 1.26 (dvt, N ) 13.3 Hz, JH-H ) 6.7, 18H,
PCHCH3), 1.15 (dvt, N ) 13.5, JH-H ) 6.9, 18H, PCHCH3), -16.27
(t, JH-P ) 21.4, 1H, OsH). 31P{1H} NMR (121.4 MHz, CD2Cl2, 293
K): δ 22.4 (s). 19F NMR (282.3 MHz, CD2Cl2, 293 K): δ -151.8
(br). 13C{1H}-APT NMR plus HMBC and HSQC (75.4 MHz, CD2Cl2,
293 K): δ 265.1 (t, JC-P ) 8.1, OsdCH), 156.4 (s, -CHd), 143.6
and 142.2 (both s, Cipso-Ph), 141.5 and 125.3 (s, CN), 140.5 (s, d
CPh2), 129.6, 128.5, 128.0, 127.7, 127.5 and 126.9 (all s, CHPh), 27.6
(vt, N ) 12.7, PCH), 18.7 and 18.6 (both s, PCHCH3), 3.6 (s, CH3-
CN).
NMR (300 MHz, CD2Cl2, 293 K): δ 7.7-6.6 (m, 10H, Ph), 5.22 (s,
1H, dCH-), 2.60 (s, 3H, CH3CN), 2.42 (m, 6H, PCH), 1.32 (dvt, N
) 13.6 Hz, JH-H ) 7.0, 18H, PCHCH3), 1.27 (dvt, N ) 14.5, JH-H
)
7.0, 18H, PCHCH3), 1.21 (s, -OC(CH3)3), -3.90 (t, JH-P ) 17.4, 1H,
OsH). 31P{1H} NMR (121.4 MHz, CD2Cl2, 293 K): δ 26.1 (s). 19F
NMR (282.3 MHz, CD2Cl2, 293 K): δ -153.0 (br). 13C{1H}-APT
NMR plus HMBC and HSQC (75.4 MHz, CD2Cl2, 293 K): δ 270.7
(t, JC-P ) 9.0, OstC), 159.1 (s, )CPh2), 139.9 and 138.4 (s, Cipso
-
Ph), 134.1 (s, -CHd), 131.6, 131.3, 130.4, 129.5, 129.4 and 128.7
(all s, CHPh), 127.0 (s, CN), 68.5 (s, -OC(CH3)3), 31.0 (s, -OC(CH3)3),
27.0 (vt, N ) 12.4, PCH), 19.8 and 19.2 (both s, PCHCH3), 3.7 (s,
CH3CN).
Formation of [Os{CH2CH(CH3)PiPr2(CH3CN)3(PiPr3)]BF4 (11).
A green solution of 2 (300 mg, 0.344 mmol) in 12 mL of acetonitrile
was heated under reflux for 3 h. The solution was filtered through Celite,
and the solvent was removed in vacuo. The olefin 1,1-diphenylpropene
was extracted from the resultant brown oil with diethyl ether. The
subsequent addition of n-pentane to the residue led to a brown solid,
which was washed with n-pentane and dried in vacuo. Yield: 225 mg
(83%). Anal. Calcd for C24H47BF4N3OsP2: C, 40.22; H, 6.61; N, 5.86.
Found: C, 40.64; H, 6.83; N, 5.65. IR (Nujol, cm-1): ν(CtN) 2238
(w); ν(BF) 1056 (vs). 1H NMR plus 1H{31P} (500 MHz, CD3CN, 293
K): δ 3.07 (m, 1H, OsCH2CH), 2.59 (s, 6H, CH3CN), 2.47 (s, 3H,
CH3CN), 2.45 (m, 5H, PCH), 1.69 (dddd, JH-P ) 36.5, JH-P ) 4.0,
JH-H ) 9.5, JH-H ) 9.5, 1H, OsCH2), 1.4-1.2 (m, 30H, PCHCH3),
1.45 (dd, JH-P ) 12, JH-H ) 7, 3H, OsCH2CH(CH3)), 0.60 (ddd, JH-H
) 9.5, JH-H ) 9.5, JH-P ) 4.5, 1H, OsCH2). 31P{1H} NMR (202.3
Reaction of [OsH(dCdCdCPh2)(CH3CN)2(PiPr3)2]BF4 with Phe-
nol: Formation of [OsH(OPh)(tCCHdCPh2)(CH3CN)(PiPr3)2]BF4
(3). A green solution of 1 (260 mg, 0.298 mmol) in 10 mL of
dichloromethane was treated with phenol (31 mg, 0.328 mmol). After
the mixture was stirred for 30 min at room temperature, it was filtered
through Celite and the filtrate was evaporated. The addition of diethyl
ether afforded a red solid, which was washed with a mixture of diethyl
ether/pentane (1:3) and dried in vacuo. Yield: 250 mg (90%). Anal.
Calcd for C41H62BF4NOOsP2: C, 53.30; H, 6.76; N, 1.52. Found: C,
53.53; H, 6.59; N, 1.52. IR (Nujol, cm-1): ν(CtN) 2319 (w); ν(OsH)
1
2156 (m); ν(CdC) 1537 (m); ν(BF) 1058 (vs). H NMR (300 MHz,
CD2Cl2, 293 K): δ 7.8-7.2 (m, 10H, Ph), 7.0-6.4 (m, 5H, OPh), 5.40
(s, 1H, dCH-), 2.74 (s, 3H, CH3CN), 2.28 (m, 6H, PCH), 1.28 (dvt,
N ) 13.9 Hz, JH-H ) 7.0, 18H, PCHCH3), 1.27 (dvt, N ) 13.9, JH-H
) 7.0, 18H, PCHCH3), -6.72 (t, JH-P ) 16.8, 1H, OsH). 31P{1H} NMR
(121.4 MHz, CD2Cl2, 293 K): δ 27.4 (s). 19F NMR (282.3 MHz, CD2-
Cl2, 293 K): δ -153.0 (br). 13C{1H}-APT NMR plus HMBC and
HSQC (75.4 MHz, CD2Cl2, 293 K): δ 261.0 (t, JC-P ) 12.3, OstC),
163.1 (t, JC-P ) 8.4, Cipso-OPh), 160.0 (s, dCPh2), 139.5 and 138.6
(s, Cipso-Ph), 135.4 (s, -CHd), 131.8, 131.5, 130.7, 129.5, 129.4 and
128.8 (all s, CHPh), 127.7 (s, CN), 26.9 (vt, N ) 12.5, PCH), 19.9 and
19.3 (both s, PCHCH3), 3.7 (s, CH3CN).
MHz, CD3CN, 293 K): δ 3.0 (d, JP-P ) 266, PiPr3), -27.7 (d, JP-P
)
266, PiPr2CH(CH3)CH2). 19F NMR (282.3 MHz, CD3CN, 293 K): δ
-152.5 (br). 13C{1H}-APT NMR plus HMBC and HSQC (125.6 MHz,
CD3CN, 293 K): δ 121.4, 117.5, and 115.6 (all s, CN), 48.4 (d, JC-P
) 27.0, OsCH2CH(CH3)P), 25.7 (d, JC-P ) 5.3, OsCH2CH(CH3)P),
25.4 (d, JC-P ) 13.2, PCH), 23.2 (dd, JC-P ) 9.9, JC-P ) 3.9, PCH),
20.7 (d, JC-P ) 15.3, PCH), 21.4, 21.1, 20.1, 20.0, 19.6, and 19.3 (all
s, PCHCH3), 4.6, 4.5, and 3.7 (all s, CH3CN), -15.6 (dd, JC-P ) 18.2,
JC-P ) 5.3, OsCH2).
Reaction of [OsH(dCdCdCPh2)(CH3CN)2(PiPr3)2]BF4 with t-
Butanol: Formation of [OsH(OtBu)(tCCHdCPh2)(CH3CN)(PiPr3)2]-
BF4 (4). A green solution of 1 (150 mg, 0.172 mmol) in 12 mL of
t-butanol was stirred for 12 h. The solvent was removed in vacuo. The
addition of diethyl ether to the resulting residue led to a brown solid,
which was washed with diethyl ether and dried in vacuo. Yield: 113
mg (72%). Anal. Calcd for C39H66BF4NOOsP2: C, 51.82; H, 7.35; N,
1.55. Found: C, 51.53; H, 7.27; N, 1.52. IR (Nujol, cm-1): ν(CtN)
1,1-Diphenylpropene. The product was extracted from the residue
obtained during the preparation of 11 with diethyl ether. The solution
was filtered through Celite and concentrated to dryness. An uncolored
1
oil was obtained. This compound was identified by GC-MS and H
and 13C{1H} NMR. 1H NMR (500 MHz, CD3CN, 293 K): δ 7.4-7.1
(m, 10H, Ph), 6.22 (q, JH-H ) 7.0, 1H, dCHCH3), 1.73 (d, JH-H
)
1
2313 (w); ν(OsH) 2178 (m); ν(CdC) 1532 (m); ν(BF) 1055 (vs). H
7.0, 3H, CH3). 13C{1H}-APT NMR plus HMBC and HSQC (125.6
9
8858 J. AM. CHEM. SOC. VOL. 129, NO. 28, 2007

Hydrogenation of CR
−Câ and M−CR Double Bonds
A R T I C L E S
MHz, CD3CN, 293 K): δ 143.9 and 140.9 (s, Cipso-Ph), 143.3 (s,
CPh2), 130.7, 129.2, 129.1, 127.9 and 127.7 (all s, Ph), 125.0 (s, d
CHCH3), 15.8 (CH3).
(000) 2330, T ) 100.0(2) K. Bruker SMART APEX CCD diffracto-
meter equipped with a normal focus, 2.4 kW sealed tube source
(Molybdenum radiation, λ ) 0.71073 Å, µ 2.296 mm-1) operating at
50 kV and 40 mA. 50 743 measured reflections (2θ: 3-55°, ω scans
0.3°), 13 312 unique (Rint ) 0.0732); multiscan absorption correction
applied (SADABS program),35 with min./max.transm.factors 0.750/
0.955. Structure solved by Patterson and difference Fourier maps;
refined using SHELXTL.36 Final agreement factors were R1 ) 0.0668
(8562 observed reflections, I > 2σ(I)) and wR2 ) 0.1735; data/restrains/
parameters 13 312/106/583; GoF ) 1043. Largest peak and hole 2.742
and -0.960 e/Å3. Complex 3: C41H62NP2OOs, BF4‚0.5OC4H10, Mw
960.93, orange, irregular block (0.18 × 0.12 × 0.09 mm), monoclinic,
space group P21/c, a 14.6813(19) Å, b 13.9813(17) Å, c 21.656(3) Å,
â 90.816(2)°, V ) 4444.8(10) Å3, Z ) 4, Dcalc 1.436 g cm-3, F (000)
1964, T ) 100.0(2) K. Bruker SMART APEX CCD diffractometer
equipped with a normal focus, 2.4 kW sealed tube source (Molybdenum
radiation, λ ) 0.71073 Å, µ 2.991 mm-1) operating at 50 kV and 40
mA. 28 234 measured reflections (2θ: 3-56°, ω scans 0.3°), 10 722
unique (Rint ) 0.0544); multiscan absorption correction applied
(SADABS program),35 with min./max.transm.factors 0.621/0.745.
Structure solved by Patterson and difference Fourier maps; refined using
SHELXTL.36 Final agreement factors were R1 ) 0.0453 (7467 observed
reflections, I > 2σ(I)) and wR2 ) 0.0753; data/restrains/parameters
10 722/1/513; GoF ) 0.886. Largest peak and hole 1.847 and -1.421
e/Å3.
Preparation of BPh4 Salt of 2. A green solution of 2 (200 mg,
0.229 mmol) in 10 mL of dichloromethane was treated with NaBPh4
(157 mg, 0.458 mmol). After the mixture was stirred for 1 h at room
temperature, the suspension was filtered through Celite and the filtrate
was evaporated to dryness. The addition of diethyl ether afforded a
green solid, which was washed with diethyl ether and dried in vacuo.
Yield: 225 mg (89%). The 31P{1H} and 1H NMR (300 MHz, CD2Cl2,
293 K) data are identical to those reported for 2 with the exception of
the appearance of the resonance at 7.6-6.9 (m, 30 H, Ph).
Reaction of [OsH(OPh)( dCCHdCPh2)(CH3CN)(PiPr3)2][BF4]
with 2-Propanol-d8. An NMR tube charged with 3 (20 mg, 0.022
mmol) was cooled to -30 °C, and then 0.5 mL of 2-propanol-d8 was
added. At this temperature, the 1H and 31P NMR spectra of the resulting
brown solution showed, in addition to the resonances of 3, the following
i
representative signals: 1H NMR (400 MHz, PrOD, 243 K): δ 5.38
(s, 1H, dCH-), -6.28 (t, JH-P ) 17.7, 1H, OsH). 31P{1H} NMR (161.9
MHz, iPrOD, 243 K): δ 28.7 (s). The solution was led to reach room
1
temperature, and, after addition of 20 µL of CH3CN, the H and 31P
NMR spectra showed the appearance of 2-d1. Next, the solution was
concentrated to dryness, and 0.5 mL of 2-propanol was added. 2H NMR
(61.5 MHz, iPrOH, 293 K): δ 21.35 (br, 0.4D, OsdCD), -16.27 (br,
0.6D, OsD).
Kinetic Analysis for Hydrogenation of the Os-C Double Bond.
The formation of 1,1-diphenylpropene and 11 was followed quantita-
tively by 1H NMR spectroscopy in CD3CN. The decrease of the
intensity of low field carbene-proton was measured automatically at
intervals in a Varian Gemini 2000 spectrometer. Rate constants and
errors were obtained fitting the data to an exponential decay function
using the routine programs of the spectrometer. Activation parameters
∆Hq and ∆Sq were obtained by least-squares fit of the Eyring plot.
Errors were computed by published methods.33
The carbene ligand of complex 2 shows static disorder over the
carbene ligand due to a small rotation of about 10° around the C(2)-
C(3) single bond. This disorder is modeled with two moieties with
complementary occupancy factors (0.23/0.77) and isotropic thermal
parameters due to the proximity of the atoms. The solvent CH2Cl2 and
CH3CH2OCH2CH3 molecules of 2 and 3 were also observed disordered.
Furthermore, the hydride ligands did not refine properly neither for 2
nor for 3. Because of that, the Os-H distances were fixed to 1.59(1)
(average value found in The Cambridge Structural Database).
Computational Details. The calculations have been carried out using
the Gaussian 03 computational package.34 All the structures have been
optimized using DFT and the B3PW91 functional. The 6-31g** basis
set has been used for all the non-hydrogen atoms and hydride ligands
(6-31g for the rest of hydrogens) but the Os, where the LANL2DZ
basis and pseudopotential has been used instead. The transition states
found have been confirmed by frequency calculations, and the con-
nection between the starting and final reactants has been checked by
slightly perturbing the TS geometry toward the minima geometries and
reoptimizing.
CrystalDatafor2and3.Complex2: C37H61N2OsP2,C24H20B‚0.25CH2-
Cl2, Mw 1126.46, green, irregular block (0.10 × 0.8 × 0.02 mm),
monoclinic, space group P2/c, a 18.323(2) Å, b 18.073(2) Å, c 17.688-
(2) Å, â 93.657(2)°, V ) 5845.5(12) Å3, Z ) 4, Dcalc 1.280 g cm-3, F
Acknowledgment. Financial support from the MEC of Spain
(Project CTQ2005-00656) and Diputacio´n General de Arago´n
(E35) is acknowledged. R.C. thanks CSIC and the European
Social Fund for funding through the I3P Program.
Supporting Information Available: Complete ref 34, or-
thogonal coordinates of theoretical structures, and crystal
structure determinations, including bond lengths and angles of
compounds 2 and 3. This material is available free of charge
via the Internet at http://pubs.acs.org.
JA071972A
(35) Blessing, R. H. Acta Crystallogr. 1995, A51, 33-38. SADABS: Area-
detector absorption correction, Bruker-AXS, Madison, WI, 1996.
(36) SHELXTL Package v. 6.10, Bruker-AXS, Madison, WI, 2000. Sheldrick,
G. M. SHELXS-86 and SHELXL-97; University of Go¨ttingen: Go¨ttingen,
Germany, 1997.
(33) Morse, P. M.; Spencer, M. O.; Wilson, S. R.; Girolami, G. S. Organome-
tallics 1994, 13, 1646.
(34) Pople, J. A.; et al. Gaussian 03, revision C.03; Gaussian, Inc.: Wallingford,
CT, 2004.
9
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