Preparation of half-sandwich osmium-allyl complexes by consecutive C - C bond formation and C - H bond activation reactions

Article abstract of DOI:10.1021/om050907b

The vinylidene complex Os(η⁵-C₅H ₅)Cl(=C=CHPh)(PⁱPr₃) (1) reacts with MeMgCl to give the osmaindene OsH(η⁵-C₅H₅){C(CH ₃)=CHC₆H₄}(P

Full text of DOI:10.1021/om050907b

Organometallics 2006, 25, 693-705
693
Preparation of Half-Sandwich Osmium-Allyl Complexes by
Consecutive C-C Bond Formation and C-H Bond Activation
Reactions
Miguel A. Esteruelas,* Ana I. Gonza´lez, Ana M. Lo´pez,* Montserrat Oliva´n, and
Enrique On˜ate
Departamento de Qu´ımica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n, UniVersidad de
Zaragoza-CSIC, 50009 Zaragoza, Spain
ReceiVed October 19, 2005
The vinylidene complex Os(η5-C5H5)Cl(dCdCHPh)(PiPr3) (1) reacts with MeMgCl to give the
osmaindene OsH(η5-C5H5){C(CH3)dCHC6H4}(PiPr3) (2), which isomerizes into the exo-allyl compound
Os(η5-C5H5)(η3-CH2CHCHPh)(PiPr3) (3) in refluxing toluene. Treatment of 3 with HBF4‚OEt2 leads to
the endo-d4-allyl derivative [OsH(η5-C5H5){η3-CH2CHCHPh}(PiPr3)]BF4 (4), which can be also obtained
by addition of HBF4‚OEt2 to 2. Complex 4 contains the terminal CHPh group of the allyl cisoid disposed
to the phosphine. In dichloromethane at 40 °C, it isomerizes into an endo-allyl isomer 5 with the terminal
CHPh group cisoid disposed to the hydride. Complex 1 also reacts with EtMgCl. The reaction affords
OsH(η5-C5H5){C(CH2CH3)dCHC6H4}(PiPr3) (6), which in toluene at 70 °C is converted into the exo-
allyl complex Os(η5-C5H5){η3-CH(CH3)CHCHPh}(PiPr3) (7). Treatment of 7 with HBF4‚OEt2 leads to
an equilibrium mixture of exo-d4-allyl derivatives of formula [OsH(η5-C5H5){η3-CH(CH3)CHCHPh}(Pi-
Pr3)]BF4 (8 and 9). The addition of HBF4‚OEt2 to 6 gives an endo-d4-allyl isomer, 10, which is transformed
into the equilibrium mixture of 8 and 9 after 7 days in dichloromethane at 40 °C. Treatment of 1 with
PhMgCl gives rise to OsH(η5-C5H5){C(Ph)dCHC6H4}(PiPr3) (11), which reacts with HBF4‚OEt2 in the
presence of acetonitrile to afford stilbene and the solvento complex [Os(η5-C5H5)(CH3CN)2(PiPr3)]BF4
(12). The X-ray structures of 3, 5, and 8 are also reported.
theoretical5 points of view. Metal-η3-allyl complexes can exist
in different isomers, due to the relative orientations of the allyl
ligands. Knowing the factors controlling the relative energy of
the isomers should help to understand the regio- and stereo-
chemistry of reactions mediated by π-allyl complexes.3c,e,5b-d
In agreement with the tendency shown by Os(η5-C5H5)Cl(Pi-
Pr3)2 to release a phosphine ligand,6 and as a part of our work
Introduction
The design of metallic homogeneous systems that are
effective in the synthesis of functionalized organic molecules
from basic hydrocarbon units is significant and of great interest.1
In this respect, developing systems that consecutively promote
carbon-carbon bond formation and C-H bond activation is
an urgent task.2
(3) See for example: (a) Matsushima, Y.; Onitsuka, K.; Kondo, T.;
Mitsudo, T.; Takahashi, S. J. Am. Chem. Soc. 2001, 123, 10405. (b) Pe´rez,
J.; Riera, V.; Rodr´ıguez, A.; Garc´ıa-Granda, S. Angew. Chem., Int. Ed. 2002,
41, 1427. (c) Trost, B. M.; Crawley, M. L. Chem. ReV. 2003, 103, 2921.
(d) Kacprzynski, M. A.; Hoveyda, A. H. J. Am. Chem. Soc. 2004, 126,
10676. (e) Belda, O.; Moberg, C. Acc. Chem. Res. 2004, 37, 159. (f)
Hermatschweiler, R.; Ferna´ndez, I.; Breher, F.; Pregosin, P. S.; Veiros, L.
F.; Calhorda, M. J. Angew. Chem., Int. Ed. 2005, 44, 4397. (g) Hermatsch-
weiler, R.; Ferna´ndez, I.; Pregosin, P. S.; Watson, E. J.; Albinati, A.; Rizzato,
S.; Veiros, L. F.; Calhorda, M. J. Organometallics 2005, 24, 1809.
(4) See for example: (a) Albers, M. O.; Liles, D. C.; Robinson, D. J.;
Shaver, A.; Singleton, E. Organometallics 1987, 6, 2347. (b) Cosford, N.
D. P.; Liebeskind, L. S. Organometallics 1994, 13, 1498. (c) Hubbard, J.
L.; Zoch, C. R. J. Organomet. Chem. 1995, 487, 65. (d) Mui, H. D.;
Brumaghim, J. L.; Gross, C. L.; Girolami, G. S. Organometallics 1999,
18, 3264. (e) Ng, S. H. K.; Adams, C. S.; Hayton, T. W.; Legzdins, P.;
Patrick, B. O. J. Am. Chem. Soc. 2003, 125, 15210. (f) Cadierno, V.;
Crochet, P.; D´ıez, J.; Garc´ıa-Garrido, S. E.; Gimeno, J. Organometallics
2004, 23, 4836. (g) Norman, D. W.; McDonald, R.; Stryker, J. M.
Organometallics 2005, 24, 4461. (h) Cadierno, V.; D´ıez, J.; Garc´ıa-Garrido,
S. E.; Gimeno, J. Organometallics 2005, 24, 3111. (i) Sa´nchez-Castro, M.
E.; Ram´ırez-Monroy, A.; Paz-Sandoval, M. A. Organometallics 2005, 24,
2875.
Transition-metal allyl complexes are tools of utmost impor-
tance, as they represent real catalysts or reaction intermediates
for a number of highly valuable processes including carbon-
carbon and carbon-heteroatom coupling reactions.3 Thus, they
have attracted much attention from both experimental4 and
* To whom correspondence should be addressed. E-mail: master@
unizar.es; amlopez@unizar.es.
(1) Esteruelas, M. A.; Lo´pez, A. M. In Recent AdVances in Hydride
Chemistry; Peruzzini, M., Poli, R., Eds.; Elsevier: Amsterdam, 2001;
Chapter 7, pp 189-248.
(2) (a) Esteruelas, M. A.; Lahoz, F. J.; On˜ate, E.; Oro, L. A.; Sola, E. J.
Am. Chem. Soc. 1996, 118, 89. (b) Buil, M. L.; Esteruelas, M. A.; Lo´pez,
A. M.; On˜ate, E. Organometallics 1997, 16, 3169. (c) McNeill, K.;
Andersen, R. A.; Bergman, R. G. J. Am. Chem. Soc. 1997, 119, 11244. (d)
Guari, Y.; Sabo-Etienne, S.; Chaudret, B. Eur. J. Inorg. Chem. 1999, 1047.
(e) Dyker, G. Angew. Chem., Int. Ed. 1999, 38, 1698. (f) Jia, G.; Kitamura,
T.; Fujiwara, Y. Acc. Chem. Res. 2001, 34, 633. (g) Kakiuchi, F.; Murai,
S. Acc. Chem. Res. 2002, 35, 826. (h) Ritleng, V.; Sirlin, C.; Pfeffer, M.
Chem. ReV. 2002, 102, 1731. (i) Chin, C. S.; Lee, H.; Noh, S.; Park, H.;
Kim, M. Organometallics 2003, 22, 2119. (j) Grotjahn, D. B.; Hoerter, J.
M.; Hubbard, J. L. J. Am. Chem. Soc. 2004, 126, 8866. (k) Li, X.;
Appelhans, L. N.; Faller, J. W.; Crabtree, R. H. Organometallics 2004, 23,
3378. (l) Yi, C. S.; Yun, S. Y.; Guzei, I. A. J. Am. Chem. Soc. 2005, 127,
5782. (m) Li, X.; Vogel, T.; Incarvito, C. D.; Crabtree, R. H. Organome-
tallics 2005, 24, 62. (n) Cadierno, V.; D´ıez, J.; Garc´ıa-AÄ lvarez, J.; Gimeno,
J. Organometallics 2005, 24, 2801.
(5) See for example: (a) Tobisch, S.; Taube, R. J. Organomet. Chem.
2003, 683, 181. (b) Xue, P.; Bi, S.; Sung, H. H. Y.; Williams, I. D.; Lin,
Z.; Jia, G. Organometallics 2004, 23, 4735. (c) Ariafard, A.; Lin, Z.
Organometallics 2005, 24, 3800. (d) Bi, S.; Ariafard, A.; Jia, G.; Lin, Z.
Organometallics 2005, 24, 680. (e) Ariafard, A.; Bi, S.; Lin, Z. Organo-
metallics 2005, 24, 2241.
10.1021/om050907b CCC: $33.50 © 2006 American Chemical Society
Publication on Web 12/21/2005

694 Organometallics, Vol. 25, No. 3, 2006
Esteruelas et al.
Scheme 1
on the chemistry of the osmium-carbon multiple bonds,7,8 we
have previously proved that the treatment of this cyclopenta-
dienyl derivative with phenylacetylene affords the vinylidene
complex Os(η5-C5H5)Cl(dCdCHPh)(PiPr3), via the π-alkyne
intermediate Os(η5-C5H5)Cl(η2-HCtCPh)(PiPr3).9
The reactivity of the vinylidene-metal moieties is dominated
by the electrophilicity and nucleophilicity of the CR and Câ
atoms, respectively. As a result, nucleophiles add to the CR atom,
and the stereoselective coupling of alkyl, aryl, alkenyl, or alkynyl
groups with the vinylidene should be expected.10 The process
may be considered as a counterpart to the coupling of a
hydrocarbyl unit with a Fischer-type carbene moiety, of which
several examples are known.11 In this paper, we report the
coupling between the vinylidene ligand of Os(η5-
C5H5)Cl(dCdCHPh)(PiPr3) and methyl, ethyl, and phenyl
groups, and the transformation of the resulting organic fragments
into allyl ligands by means of H-C(sp3) bond activation
reactions.
(6) (a) Baya, M.; Crochet, P.; Esteruelas, M. A.; Gutie´rrez-Puebla, E.;
Ruiz, N. Organometallics 1999, 18, 5034. (b) Esteruelas, M. A.; Gutie´rrez-
Puebla, E.; Lo´pez, A. M.; On˜ate, E.; Tolosa, J. I. Organometallics 2000,
19, 275. (c) Esteruelas, M. A.; Lo´pez, A. M.; Tolosa, J. I.; Vela, N.
Organometallics 2000, 19, 4650. (d) Carbo´, J. J.; Crochet, P.; Esteruelas,
M. A.; Jean, Y.; Lledo´s, A.; Lo´pez, A. M.; On˜ate, E. Organometallics 2002,
21, 305. (e) Esteruelas, M. A.; Lo´pez, A. M. Organometallics 2005, 24,
3584.
(7) (a) Espuelas, J.; Esteruelas, M. A.; Lahoz, F. J.; Oro, L. A.; Ruiz, N.
J. Am. Chem. Soc. 1993, 115, 4683. (b) Esteruelas, M. A.; Lahoz, F. J.;
On˜ate, E.; Oro, L. A.; Zeier, B. Organometallics 1994, 13, 1662. (c)
Esteruelas, M. A.; Oro, L. A.; Valero, C. Organometallics 1995, 14, 3596.
(d) Esteruelas, M. A.; Lahoz, F. J.; On˜ate, E.; Oro, L. A.; Valero, C.; Zeier,
B. J. Am. Chem. Soc. 1995, 117, 7935. (e) Bourgault, M.; Castillo, A.;
Esteruelas, M. A.; On˜ate, E.; Ruiz, N. Organometallics 1997, 16, 636. (f)
Bohanna, C.; Callejas, B.; Edwards, A. J.; Esteruelas, M. A.; Lahoz, F. J.;
Oro, L. A.; Ruiz, N.; Valero, C. Organometallics 1998, 17, 373. (g) Crochet,
P.; Esteruelas, M. A.; Lo´pez, A. M.; Ruiz, N.; Tolosa, J. I. Organometallics
1998, 19, 3479. (h) 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. (i)
Buil, M. L.; Esteruelas, M. A. Organometallics 1999, 18, 1798. (j)
Esteruelas, M. A.; Oliva´n, M.; On˜ate, E.; Ruiz, N.; Tajada, M. A.
Organometallics 1999, 18, 2953. (k) Buil, M. L.; Eisenstein, O.; Esteruelas,
M. A.; Garc´ıa-Yebra, C.; Gutie´rrez-Puebla, E.; Oliva´n, M.; On˜ate, E.; Ruiz,
N.; Tajada, M. A. Organometallics 1999, 18, 4949. (l) Bohanna, C.; Buil,
M. L.; Esteruelas, M. A.; On˜ate, E.; Valero, C. Organometallics 1999, 18,
5176. (m) Buil, M. L.; Esteruelas, M. A.; Garc´ıa-Yebra, C.; Gutie´rrez-
Puebla, E.; Oliva´n, M. Organometallics 2000, 19, 2184. (n) 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. (o) Esteruelas, M.
A.; Garc´ıa-Yebra, C.; Oliva´n, M.; On˜ate, E.; Tajada, M. A. Organometallics
2000, 19, 5098. (p) Castarlenas, R.; Esteruelas, M. A.; On˜ate, E. Organo-
metallics 2000, 19, 5454. (q) Castarlenas, R.; Esteruelas, M. A.; Gutie´rrez-
Puebla, E.; On˜ate, E. Organometallics 2001, 20, 1545. (r) Castarlenas, R.;
Esteruelas, M. A.; On˜ate, E. Organometallics 2001, 20, 2294. (s) Castar-
lenas, R.; Esteruelas, M. A.; On˜ate, E. Organometallics 2001, 20, 3283. (t)
Baya, M.; Crochet, P.; Esteruelas, M. A.; Lo´pez, A. M.; Modrego, J.; On˜ate,
E. Organometallics 2001, 20, 4291. (u) Baya, M.; Esteruelas, M. A.
Organometallics 2002, 21, 2332. (v) Barrio, P.; Esteruelas, M. A.; On˜ate,
E. Organometallics 2002, 21, 2491. (w) Baya, M.; Esteruelas, M. A.; On˜ate,
E. Organometallics 2002, 21, 5681. (x) Barrio, P.; Esteruelas, M. A.; On˜ate,
E. Organometallics 2003, 22, 2472. (y) Barrio, P.; Esteruelas, M. A.; On˜ate,
E. J. Am. Chem. Soc. 2004, 126, 1946.
Results and Discussion
1. Vinylidene-Methyl Coupling. Treatment at 55 °C of a
tetrahydrofuran solution of Os(η5-C5H5)Cl(dCdCHPh)(PiPr3)
(1) with 1.2 equiv of MeMgCl leads to the osmaindene
derivative OsH(η5-C5H5){C(CH3)dCHC6H4}(PiPr3) (2). Its
formation can be rationalized according to Scheme 1. The
addition of MeMgCl to 1 could initially produce the nucleophilic
substitution of the chloride ligand by a methyl group, to give
a. The subsequent migratory insertion of the vinylidene into
the osmium-methyl bond should afford the unsaturated alkenyl
intermediate b, which could yield 2 by ortho-CH bond activation
of the phenyl substituent at the carbon-carbon double bond.
The formation of b may also occur by direct addition of the
C-donor nucleophile to the CR atom of the vinylidene, followed
by the elimination of chloride from the resulting species c.
Complex 2 was isolated as a yellow solid in 67% yield. In
agreement with the presence of a hydride ligand cisoid disposed
to the phosphine, at 20 °C, the 1H NMR spectrum in benzene-
d6 of this compound shows at -14.56 ppm a doublet with a
H-P coupling constant of 47.2 Hz. In the low-field region of
the spectrum the most noticeable resonance is a singlet at 7.44
(10) (a) Bruce, M. I. Chem. ReV. 1991, 91, 197. (b) Puerta, M. C.;
Valerga, P. Coord. Chem. ReV. 1999, 193-195, 977. (c) Guerchais, V. Eur.
J. Inorg. Chem. 2002, 783. (d) Cadierno, V.; Gamasa, M. P.; Gimeno, J.
Coord. Chem. ReV. 2004, 248, 1627. (e) Werner, H. Coord. Chem. ReV.
2004, 248, 1693. (f) Katayama, H.; Ozawa, F. Coord. Chem. ReV. 2004,
248, 1703.
(11) See for example: (a) Braun, T.; Mu¨nch, G.; Windmu¨ller, B.; Gevert,
O.; Laubender, M.; Werner, H. Chem. Eur. J. 2003, 9, 2516. (b) Esteruelas,
M. A.; Gonza´lez, A. I.; Lo´pez, A. M.; On˜ate, E. Organometallics 2003,
22, 414. (c) Esteruelas, M. A.; Gonza´lez, A. I.; Lo´pez, A. M.; On˜ate, E.
Organometallics 2004, 23, 4858. (d) Werner, H. Organometallics 2005,
24, 1036.
(8) (a) Esteruelas, M. A.; Lo´pez, A. M.; On˜ate, E.; Royo, E. Organo-
metallics 2004, 23, 3021. (b) Asensio, A.; Buil, M. L.; Esteruelas, M. A.;
On˜ate, E. Organometallics 2004, 23, 5787. (c) Baya, M.; Buil, M. L.;
Esteruelas, M. A.; On˜ate, E. Organometallics 2005, 24, 2030. (d) Bolan˜o,
T.; Castarlenas, R.; Esteruelas, M. A.; Modrego, F. J.; On˜ate, E. J. Am.
Chem. Soc. 2005, 127, 11184. (e) Castarlenas, R.; Esteruelas, M. A.; On˜ate,
E. Organometallics 2005, 24, 4343. (f) Baya, M.; Buil, M. L.; Esteruelas,
M. A.; On˜ate, E. Organometallics 2005, 24, 5180.
(9) Esteruelas, M. A.; Lo´pez, A. M.; Ruiz, N.; Tolosa, J. I. Organome-
tallics 1997, 16, 4657.

Half-Sandwich Osmium-Allyl Complexes
Organometallics, Vol. 25, No. 3, 2006 695
Table 2. NOE Experiments Performed on
Complexes 3-5 and 7-10
Figure 1. Molecular diagram of complex Os(η5-C5H5)(η3-
CH2CHCHPh)(PiPr3) (3).
Table 1. Selected Bond Distances (Å) and Angles (deg) for
Complex Os(η5-C5H5)(η3-CH2CHCHPh)(PiPr3) (3)
Os-P
2.3170(7)
2.197(2)
2.115(2)
2.229(2)
2.219(3)
2.229(2)
Os-C(3)
Os-C(4)
Os-C(5)
C(6)-C(7)
C(7)-C(8)
C(8)-C(9)
2.213(2)
2.218(3)
2.216(3)
1.427(3)
1.431(3)
1.485(3)
Os-C(6)
Os-C(7)
Os-C(8)
Os-C(1)
Os-C(2)
Ma-Os-P
124.6
134.2
123.9
130.8
86.30(7)
111.21(7)
95.79(6)
C(6)-Os-C(7)
C(6)-Os-C(8)
C(7)-Os-C(8)
C(6)-C(7)-C(8)
C(7)-C(8)-C(9)
38.59(9)
66.95(9)
38.35(9)
117.4(2)
120.1(2)
Ma-Os-C(6)
Ma-Os-C(7)
Ma-Os-C(8)
P-Os-C(6)
P-Os-C(7)
P-Os-C(8)
a M is the centroid of the C(1)-C(5) Cp ligand.
ppm, corresponding to the vinylic hydrogen of the alkenyl
moiety. In the 13C{1H} NMR spectrum, the resonances due to
the atoms of the alkenyl carbon-carbon double bond are
observed at 142.3 (Câ) and 141.8 (CR) ppm; the first of them
appears as a singlet, while the second one is a doublet with a
C-P coupling constant of 16 Hz. The metalated carbon atom
of the phenyl group gives rise to a doublet at 156.4 ppm with
a C-P coupling constant of 4 Hz. The 31P{1H} NMR spectrum
contains a singlet at 18.5 ppm. These spectroscopic data agree
well with those previously reported for the related compound
tadienyl ligand occupying a face. The structure proves the
formation of the allyl ligand, which is coordinated by the C(6),
C(7), and C(8) carbon atoms, in the exo form with the C(7)-H
unit pointing to the cyclopentadienyl ring. This agrees well with
theoretical results showing that in d6-(η5-C5H5)ML(η3-allyl)
complexes (L ) CO, PR3, NtCR, alkyl, H, halides) the exo
structure form is more stable than the endo one. The exo
structural arrangement of the allyl ligand appears to avoid
repulsive interactions between one pair of d electrons and the
π2 electrons of the allyl ligand and to favor the metal(d)-to-η3-
allyl(π*) back-bonding interactions.5d The phenyl substituent
is syn disposed with regard to C(7)-H, with a C(7)-C(8)-
C(9) angle of 120.1(2)°. The allyl moiety coordinates in an
asymmetrical fashion, with the separation between the central
carbon atom C(7) and the metal (2.115(2) Å) being shorter than
the separation between the metal and the terminal carbon atoms
C(6) (2.197(2) Å) and C(8) (2.229(2) Å). The angles C(6)-
Os-C(8) and C(6)-C(7)-C(8) are 66.95(9)° and 117.4(2)°,
respectively. The carbon-carbon distances within the allylic
moiety, 1.427(3) Å for C(6)-C(7) and 1.431(3) Å for C(7)-
C(8), are in accordance with the values found in Os(η5-C5H5)-
(η3-CH2CHCHCH2Ph)(PiPr3)11b and [OsH(η5-C5H4SiPh3){η3-
CH2C(Ph)CH2}(PiPr3)]BF4.12
OsH(η5-C5H4SiPh3){CHdC(CH3)C6H4}(PiPr3), which has been
characterized by X-ray diffraction analysis.12
In refluxing toluene, complex 2 isomerizes into the allyl
derivative Os(η5-C5H5)(η3-CH2CHCHPh)(PiPr3) (3). After 15
h, the rearrangement is quantitative. Complex 3 is the result of
a methyl-CH bond activation in the alkenyl ligand of b and
the subsequent migratory insertion of the resulting allene into
the osmium-hydride bond of d (Scheme 1).
Since 2 and 3 result from competitive C-H bond activation
processes in the undetected alkenyl intermediate b, the formation
of 2 is in agreement with the kinetic preference of the C-H
arene activation over the C-H alkyl, while the formation of 3
agrees well with the higher stability of a M(η3-allyl) bond with
regard to a M-aryl bond.13
Complex 3 was isolated as a yellow solid in 83% yield. Figure
1 shows a view of its molecular geometry, whereas selected
bond distances and angles are listed in Table 1. The coordination
geometry around the osmium atom can be rationalized as being
derived from a highly distorted octahedron with the cyclopen-
1
In agreement with the structure shown in Figure 1, the H
NMR spectrum in benzene-d6 at room temperature shows four
resonances for the allylic protons at 1.02, 2.58, 2.99, and 4.55
ppm, which were assigned to C(6)H anti to C(7)H, C(8)H,
C(6)H syn to C(7)H, and C(7)H, respectively, on the basis of
1H-1H COSY, 1H-13C HMQC, and NOE experiments (Table
2). The irradiation of the C(8)HPh resonance increases the Ph
(12) Baya, M.; Esteruelas, M. A.; On˜ate, E. Organometallics 2001, 20,
4875.
(13) Jones, W. D.; Feher, F. J. Acc. Chem. Res. 1989, 22, 91.

696 Organometallics, Vol. 25, No. 3, 2006
Esteruelas et al.
1
Table 3. Selected H (green) and 13C{1H} (purple) NMR Chemical Shifts (δ, ppm) and Coupling Constants (Hz) for
Complexes 3-5 and 7-10
Scheme 2
(11.4%) and PiPr3 (14.7%) resonances, while the saturation of
the meso C(7)H proton enhances the intensity of the C(6)H syn
(6.5%) and Ph (20%) signals. A NOE effect between C(7)H
and the cyclopentadienyl resonance is not observed. In this
context, it should be noted that exo complexes of this type can
be identified by a NOE effect between the anti protons and the
phosphine, but not by a NOE between the cyclopentadienyl and
the meso proton. The different coupling constants in these
resonances have been deduced by means of the 1H{31P} NMR
spectrum and selective homonuclear irradiation in the 1H NMR
spectrum and are collected in Table 3. In the 13C{1H} NMR
spectrum the most noticeable resonances are a singlet at 50.4
ppm and two doublets at 34.9 and 10.8 ppm with C-P coupling
1
constants of 5 and 7 Hz. On the basis of the H-13C HMQC
spectrum, these resonances were assigned to the C(7), C(8), and
C(6) atoms of the allyl ligand, respectively. The 31P{1H} NMR
spectrum shows a singlet at 20.9 ppm.
and [Ru(η5-C5Me5)(amidinate)(η3-C3H5)]+.16 When L ) CO,
both the exo and endo structural forms have comparable
stability.4b,17
The exo-endo interconversion may proceed by rotation of
the planar π-allyl moiety about the osmium-allyl axis or
alternatively by an η3 f η1 f η3 pathway in which an η1-allyl
intermediate is involved. Density functional theory studies on
d4-Mo(η5-C5H5)(CO)2(η3-C3H5) and d6-M(η5-C5H5)(CO)(η3-
C3H5) (M ) Fe, Ru) complexes show that for the d4-compound
Treatment of 3 in diethyl ether at 0 °C with 1.0 equiv of
HBF4‚OEt2 leads to the d4-allyl derivative [OsH(η5-C5H5){η3-
CH2CHCHPh}(PiPr3)]BF4 (4) as a result of the protonation of
3. The addition of the proton of the acid to the metal center is
accompanied by a change in the coordination form of the allyl
ligand, from exo to endo (Scheme 2). The latter is the preferred
structural form in d4-M(η5-C5R5)L2(η3-allyl) complexes (L *
CO),5d and it has been found in Os(η5-C5Me5)X2(η3-allyl) (X
) Br, Me, H),4d Ru(η5-C5H5)X2(η3-allyl) (X ) Cl, Br),14 Ru-
(η5-C5H5)Cl2(η3-C4H4OMe),4a Ru(η5-C5Me5)(CH2Cl)Cl(η3-
C3H5),4c Ru(η5-C5H5)(R)Br(η3-C3H5) (R ) CH3, CH2SiMe3),15
(16) Kondo, H.; Yamaguchi, Y.; Nagashima, H. Chem. Commun. 2000,
1075.
(17) (a) Faller, J. W.; Incorvia, M. J. Inorg. Chem. 1968, 7, 840. (b)
Faller, J. W.; Chen, C.-C.; Mattina, M. J.; Jakubowski, A. J. Organomet.
Chem. 1973, 52, 361. (c) McCleverty, J. A.; Murray, A. J. Transition Met.
Chem. 1979, 4, 273. (d) Benyunes, S. A.; Binelli, A.; Green, M.; Grimshire,
M. J. J. Chem. Soc. 1991, 895. (e) Liao, M.-F.; Lee, G.-H.; Peng, S.-M.;
Liu, R.-S. Organometallics 1994, 13, 4973. (f) van Staveren. D. R.;
Weyhermu¨ller, T.; Metzler-Nolte, N. Organometallics 2000, 19, 3730.
(14) Nagashima, H.; Mukai, K.; Shiota, Y.; Yamaguchi, K.; Ara, K.-I.;
Fukahori, T.; Suzuki, H.; Akita, M.; Moro-oka, Y.; Itoh, K. Organometallics
1990, 9, 799.
(15) Itoh, K.; Fukahori, T. J. Organomet. Chem. 1988, 349, 227.

Half-Sandwich Osmium-Allyl Complexes
Organometallics, Vol. 25, No. 3, 2006 697
Table 4. Selected Bond Distances (Å) and Angles (deg) for
Complex [OsH(η5-C5H5){η3-CH2CHCHPh}(PiPr3)]BF4 (5)
Os-P
2.3753(10)
2.188(4)
2.180(4)
2.260(5)
2.255(4)
2.254(4)
Os-C(3)
Os-C(4)
Os-C(5)
C(6)-C(7)
C(7)-C(8)
C(8)-C(9)
2.242(4)
2.218(4)
2.238(4)
1.431(7)
1.365(6)
1.505(6)
Os-C(6)
Os-C(7)
Os-C(8)
Os-C(1)
Os-C(2)
Ma-Os-H(1A)
Ma-Os-P
116.2
121.8
121.9
140.9
C(6)-Os-C(7)
C(6)-Os-C(8)
C(7)-Os-C(8)
C(6)-C(7)-C(8)
C(7)-C(8)-C(9)
C(6)-Os-H(1A)
C(7)-Os-H(1A)
C(8)-Os-H(1A)
38.25(18)
64.66(17)
35.75(16)
116.6(5)
125.7(5)
119.7(16)
85.3(16)
80.2(16)
Ma-Os-C(6)
Ma-Os-C(7)
Ma-Os-C(8)
P-Os-H(1A)
P-Os-C(6)
P-Os-C(7)
P-Os-C(8)
112.3
76.5(16)
86.17(13)
93.85(14)
125.89(13)
Figure 2. Molecular diagram for the cation of [OsH(η5-C5H5)-
{η3-CH2CHCHPh}(PiPr3)]BF4 (5).
a M represents the midpoint of the Cp ring.
the rotation of the allyl ligand around the metal-allyl axis
(η3 f η3 f η3 pathway) is intrinsically more favored than the
η3 f η1 f η3 pathway. However, the η3-transition states for
the Fe and Ru complexes are inaccessible and the η3 f η1 f
η3 pathway is more favorable. The reason for this appears to
be that one pair of the six metal d electrons has to occupy a d
orbital having significant M-C5H5 antibonding character in the
transition structure.5e According to these results, in our osmium
system, the mechanism of the exo-endo interconversion could
depend on when the interconversion process takes place, before
the addition of the proton to the metal center or after the
protonation. In the first case, which involves the coexistence in
equilibrium of 3 with no detectable concentrations of its endo
isomer, the η3 f η1 f η3 pathway appears to be a more
reasonable proposal than the rotation of the π-allyl around the
osmium-allyl axis. However, in the second case an inverse
relationship should be expected.
as a four-legged piano-stool geometry, where the allyl ligand
occupies two cisoid positions with a C(6)-Os-C(8) angle of
64.66(17)°. The most noticeable features of the structure are
the cisoid disposition of the substituted C(8) atom with regard
to the hydride ligand, the endo coordination of the allyl, and
the syn disposition of the phenyl group with regard to the meso
carbon atom (C(7)-C(8)-C(9) ) 125.7(5)°). The C3 skeleton
coordinates in an asymmetric fashion. The separation between
the central carbon atom, C(7), and the metal (2.180(4) Å) is
shorter than the separation between the metal and the terminal
carbon atoms C(6) (2.188(4) Å) and C(8) (2.260(5) Å). The
carbon-carbon distances within the allylic skeleton are 1.431-
(7) Å for C(6)-C(7) and 1.365(6) Å for C(7)-C(8). The angle
C(6)-C(7)-C(8) is 116.6(5)°.
1
In agreement with the structure shown in Figure 2, the H
NMR spectrum of 5 in dichloromethane-d2 at 20 °C shows four
resonances for the allylic protons at 4.87 (CHPh), 4.09 (Hmeso),
and 3.13 and 2.93 (CH2) ppm. In the high-field region, the
hydride displays a doublet at -15.31 ppm with a H-P coupling
constant of 34.8 Hz. In the 13C{1H} NMR spectrum, the
resonances corresponding to the allyl carbon atoms are observed
at 73.9 (C(7)), 54.2 (C(8)), and 19.7 (C(6)) ppm. The 31P{1H}
NMR spectrum contains a singlet at 14.0 ppm.
Complex 4 was isolated as a yellow solid in 82% yield. In
agreement with the presence of a hydride ligand in the complex,
the 1H NMR spectrum in dichloromethane-d2 at -20 °C shows
at -15.12 ppm a doublet with a H-P coupling constant of 38.1
Hz. The resonance due to the CHPh-allyl proton (Ha′ in Table
3) appears as a doublet at 5.11 ppm. The value of the Ha′-Hm
coupling constant of 10.8 Hz supports the anti disposition of
this proton with regard to Hm. The resonance corresponding to
the latter is observed at 4.36 ppm, whereas those due to the
CH2 protons appear at 3.13 and 3.45 ppm. The endo disposition
of the allyl with regard to the cyclopentadienyl ligand was
inferred on the basis of NOE experiments (Table 2). The
saturation of the Hm resonance increases the intensity of the Ph
(13.1%), hydride (2.2%), and PiPr3 (2.6%) signals, while a NOE
effect with the cyclopentadienyl resonance is not observed.
However, the saturation of the CHPh-allyl resonance and the
CH2 signal at 3.13 ppm increases the intensity of the Cp
resonance (8.2% and 7.7%, respectively). In the 13C{1H} NMR
spectrum the carbon atoms of the C3 skeleton of the allyl ligand
give rise to singlets at 73.8 (Cmeso), 54.8 (CHPh), and 18.9 (CH2)
ppm. The 31P{1H} NMR spectrum shows a singlet at 17.7 ppm.
Complexes 4 and 5 are diastereoisomers resulting from the
chirality of the osmium atom and the prochirality of the styryl
moiety of the allyl. The isomerization process involves the
decoordination of the styryl moiety from the metal center of 4,
to afford the η1-allyl intermediate e, and the subsequent
coordination of the osmium atom of e to the other face of the
carbon-carbon double bond. The hydride ligand does not play
any role in the transformation. The addition of DBF4‚OD2 to a
dichloromethane solution of 3 affords [OsD(η5-C5H5){η3-
CH2CHCHPh}(PiPr3)]BF4 (4-d1), which isomerizes into the
deuteride derivative 5-d1. Deuterium at the allyl positions of
5-d1 is not observed. The presence of deuterium at the metal
2
center of these compounds is strongly supported by their H
NMR spectra, which show high-field resonances at -15.1 and
-15.3 ppm, respectively.
The cisoid disposition of the CHPh group of the allyl and
the phosphine is unfavorable with regard to that with the CHPh
group cisoid to the hydride, probably as a consequence of
the steric hindrance experienced between the phenyl group and
the isopropyl substituents of the phosphine. Thus, complex 4
isomerizes into the endo-allyl complex 5 (Scheme 2). In
dichloromethane at 40 °C, the transformation is quantitative after
72 h.
Complex 4 can be also obtained from 2. The addition at 0
°C of 1.0 equiv of HBF4‚OEt2 to a diethyl ether solution of the
latter produces the instantaneous precipitation of 4 in 82% yield.
The reaction of 2 with DBF4‚OD2 affords 4a-d1 (eq 1) with the
following deuterium distribution: 0.30 deuterium atom at the
hydride position, 0.15 deuterium atom at the ortho position of
the phenyl group, and 0.55 deuterium atom at the terminal allyl
CPh carbon atom. In dichloromethane-d2, complex 4a-d1 is
transformed into 5a-d1 with the same deuterium distribution as
Figure 2 shows a view of the molecular geometry of 5.
Selected bond distances and angles are listed in Table 4. The
distribution of ligands around the osmium atom can be described

698 Organometallics, Vol. 25, No. 3, 2006
Esteruelas et al.
favor the reductive elimination of the olefin.12,19 Thus, the C-H
bond activation of the methyl substituent of the olefin could
finally give 4a-d1 containing a deuterium atom at an ortho
position of the phenyl group.
Scheme 3
The electrophilic addition of D+ to the alkenyl ligand of b
should yield a benzyl-methyl-carbene intermediate, containing
a deuterium atom at the C(sp3) atom of the benzyl substituent.
This species could evolve by a â-hydrogen elimination reaction
on the methyl substituent into an unsaturated hydride-alkenyl
intermediate. Thus, the reductive elimination of olefin and the
subsequent C-H or C-D bond activation of the benzyl
substituent of the olefin could give 4a-d1 containing a deuterium
at the terminal-allyl CPh carbon atom or at the hydride position,
respectively.
2. Vinylidene-Ethyl Coupling. Similarly to the reaction of
1 with MeMgCl, the treatment at 55 °C of 1 with EtMgCl in
tetrahydrofuran leads to the osmaindene derivative OsH(η5-
C5H5){C(CH2CH3)dCHC6H4}(PiPr3) (6). In this case, the
metallacycle contains an ethyl substituent at the CR atom of the
carbon-carbon double bond (eq 2). Its formation should involve
the same sequence of elemental steps as the formation of 2,
with ethyl instead of methyl.
4a-d1, in agreement with an isomerization process via the η1-
allyl intermediate e (Scheme 2) and without the hydride
participation. The above-mentioned deuterium distribution is
2
1
strongly supported by the H and H NMR spectra of 4a-d1
2
and 5a-d1. The H NMR spectra in dichloromethane contain
Complex 6 was isolated as a yellow solid in 74% yield. In
agreement with 2, the hydride resonance in the 1H NMR
spectrum of 6 appears at -14.44 ppm as a doublet with a H-P
coupling constant of 47.4 Hz. In the low-field region, the vinylic
hydrogen of the alkenyl unit of the metallacycle gives rise to a
singlet at 7.51 ppm. In the 13C{1H} NMR spectrum, the
resonances due to the atoms of the alkenyl carbon-carbon
double bond are observed at 141.1 (CR) and 138.6 (Câ) ppm.
The first of them appears as a doublet with a C-P coupling
constant of 17 Hz, while the second one is a singlet. The
metalated carbon atom of the phenyl group gives rise to a
doublet at 162.8 ppm, with a C-P coupling constant of 4 Hz.
The 31P{1H} NMR spectrum shows a singlet at 18.6 ppm.
In toluene at 70 °C, complex 6 isomerizes into the allyl
derivative Os(η5-C5H5){η3-CH(CH3)CHCHPh}(PiPr3) (7), which
was isolated after 72 h as a yellow solid in 82% yield, according
to Scheme 4. Its formation can be rationalized as the formation
of 3. A â-hydrogen elimination reaction on the ethyl substituent
CH2 group of the alkenyl ligand of an unsaturated Os(η5-C5H5)-
{(Ε)-C(Et)dCHPh}(PiPr3) intermediate should afford a hydride-
allene species, which could give 7 by insertion of the allene
into the osmium-hydride bond.
resonances at 7.4, 5.1, and -15.1 (4a-d1) and 7.4, 4.9, and -15.1
(5a-d1) ppm in a 0.15:0.55:0.30 intensity ratio, whereas in the
1H NMR spectra in dichloromethane-d2 the intensity ratio of
the resonances at 7.33, 5.11, and -15.12 (4) and 7.26, 4.87,
and -15.31 (5) ppm is 4.85:0.45:0.70.
The results summarized in eq 1 can be rationalized according
to Scheme 3. The presence of deuterium at the ortho position
of the phenyl group appears to be a consequence of the
protonation of the orthometalated carbon atom of 2 (pathway
3a), whereas the presence of deuterium at the hydride position
and at the terminal-allyl CPh carbon atom appears to be the
result of the protonation of the Câ atom of the alkenyl ligand
of intermediate b (pathway 3b). In this context, it should be
noted that alkenyl ligands of electron-rich metals are nucleo-
philic at the Câ atom and their reactions with electrophiles lead
to carbene complexes.7l,18
1
In the H NMR spectrum of 7 in benzene-d6 at 20 °C, the
allylic resonances are observed at 4.54 (Hmeso), 2.51 (CHPh),
and 1.57 (CHMe) ppm. The value of the Hmeso-H coupling
constants of 7.2 Hz is in accordance with the syn disposition of
2a,b,11c,20
the phenyl and methyl substituents with regard to Hmeso
.
The electrophilic addition of D+ to the orthometalated carbon
atom of 2 should afford a hydride-alkenyl intermediate with a
deuterium atom at one of the ortho positions of the phenyl
substituent of the alkenyl ligand. Its unsaturated character should
This disposition seems to be sterically favored, being that
(19) (a) Bohanna, C.; Esteruelas, M. A.; Lahoz, F. J.; On˜ate, E.; Oro, L.
A.; Sola, E. Organometallics 1995, 14, 4825. (b) Albe´niz, M. J.; Esteruelas,
M. A.; Lledo´s, A.; Maseras, F.; On˜ate, E.; Oro, L. A.; Sola, E.; Zeier, B.
J. Chem. Soc., Dalton Trans. 1997, 181.
(18) See for example: Bohanna, C.; Esteruelas, M. A.; Lahoz, F. J.;
On˜ate, E.; Oro, L. A. Organometallics 1995, 14, 4685, and references
therein.
(20) See for example: (a) Clark, H. C.; Hampden-Smith, M. J.; Ruegger,
H. Organometallics 1988, 7, 2085. (b) Krivykh, V. V.; Gusev, O. V.;
Petrovskii, P. V.; Rybinskaya, M. I. J. Organomet. Chem. 1989, 366, 129.

Half-Sandwich Osmium-Allyl Complexes
Organometallics, Vol. 25, No. 3, 2006 699
Scheme 4
Table 5. Selected Bond Distances (Å) and Angles (deg) for
generally observed in reported complexes structurally character-
ized by X-ray diffraction.21 In agreement with the d6-(η5-C5H5)-
ML(η3-allyl) character of 7, the allyl ligand is disposed exo with
regard to the cyclopentadienyl ligand. The orientation was
inferred on the basis of a NOE experiment (Table 2). The
saturation of the allylic CHPh resonance increases the intensity
of the Ph (9.3%), CHMe (4.0%), and PiPr3 (11.0%) resonances,
while a NOE effect with the cyclopentadienyl signal is not
observed. In the 13C{1H} NMR spectrum, the most noticeable
resonances are three doublets at 57.4, 32.4, and 26.0 ppm with
C-P coupling constants of 2, 5, and 6 Hz, which were assigned,
on the basis of the 1H-13C HMQC spectrum, to the Cmeso, CPh,
and CMe allylic carbon atoms, respectively. The 31P{1H} NMR
spectrum shows a singlet at 19.5 ppm.
Complex [OsH(η5-C5H5){η3-CH(CH3)CHCHPh}(PiPr3)]BPh4
(8)
Os-P
2.361(3)
Os-C(14)
Os-C(15)
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
2.197(10)
2.238(10)
1.543(13)
1.394(13)
1.371(13)
1.516(13)
Os-C(2)
Os-C(3)
Os-C(4)
Os-C(11)
Os-C(12)
Os-C(13)
2.213(11)
2.079(11)
2.284(11)
2.279(10)
2.331(10)
2.278(11)
Ma-Os-H(01)
Ma-Os-P
110.8
124.7
125.4
117.9
131.1
76.1
83.7(3)
112.4(3)
103.0(3)
C(2)-Os-C(3)
C(2)-Os-C(4)
C(3)-Os-C(4)
C(2)-C(3)-C(4)
C(1)-C(2)-C(3)
C(3)-C(4)-C(5)
C(2)-Os-H(01)
C(3)-Os-H(01)
C(4)-Os-H(01)
37.8(4)
64.5(4)
36.2(4)
120.3(11)
120.5(10)
124.0(11)
121.6
Ma-Os-C(2)
Ma-Os-C(3)
Ma-Os-C(4)
P-Os-H(01)
P-Os-C(2)
P-Os-C(3)
P-Os-C(4)
In a manner similar to 3, complex 7 reacts with HBF4.
However, in this case, the oxidation of the metal center does
not produce the exo-endo transformation of the allyl ligand.
Treatment at 20 °C of a dichloromethane solution of 7 with 1.0
equiv of HBF4‚OEt2 leads to a 5:2 equilibrium mixture of the
exo-d4-allyl derivatives 8 and 9 ([OsH(η5-C5H5){η3-CH(CH3)-
CHCHPh}(PiPr3)]BF4), according to Scheme 4.
104.0
67.8
a M represents the midpoint of the Cp ring.
-
All attempts to get single crystals of the BF4 salt of the
thermodynamically favored isomer 8 were unsuccessful. The
-
-
exchange of BF4 by BPh4 allowed the crystallization of the
salt. Figure 3 shows a view of the molecular geometry of the
cation of 8. Selected bond distances and angles are listed in
Table 5.
The distribution of ligands around the osmium atom can be
described as a four-legged piano-stool geometry, where the allyl
ligand occupies two cisoid positions (C(2)-Os-C(4) ) 64.5-
(4)°), with the terminal CMe carbon atom (C(2)) cisoid disposed
to the phosphine and the terminal CPh carbon atom (C(4)) cisoid
disposed to the hydride ligand. The structure proves the exo
coordination of the allyl ligand and the syn disposition of both
substituents, the phenyl and methyl groups, with regard to the
meso carbon atom C(3). The C(1)-C(2)-C(3) and C(3)-C(4)-
C(5) angles are 120.5(10)° and 124.0(11)°, respectively. As in
3 and 5, the C3 skeleton coordinates in an asymmetrical fashion.
The separation between C(3) and the metal (2.079(11) Å) is
about 0.2 Å shorter than the separation between the metal and
C(4) (2.284(11) Å) and C(2) (2.213(11) Å). The carbon-carbon
distances within the C3 skeleton are 1.394(13) Å for C(2)-
C(3) and 1.371(13) Å for C(3)-C(4), whereas the C(2)-C(3)-
C(4) angle is 120.3(11)°.
Figure 3. Molecular diagram of the cation [OsH(η5-C5H5){η3-
CH(CH3)CHCHPh}(PiPr3)]+ (8).
1
In the H NMR spectrum of 8 in dichloromethane-d2 at 20
°C, the hydride resonance appears at -13.30 ppm as a doublet
with a H-P coupling constant of 32.7 Hz, in agreement with
the cisoid disposition of the hydride and phosphine ligands.22
(22) See for example: (a) Wilczewski, T. J. Organomet. Chem. 1986,
317, 307. (b) Rottink, M. K.; Angelici, R. J. J. Am. Chem. Soc. 1993, 115,
7267. (c) Jia, G.; Ng, W. S.; Yao, J.; Lau, C.-P.; Chen, Y. Organometallics
1996, 15, 5039. (d) Esteruelas, M. A.; Go´mez, A. V.; Lo´pez, A. M.; Oro,
L. A. Organometallics 1996, 15, 878. (e) Jia, G.; Lau, C.-P. J. Organomet.
Chem. 1998, 565, 37. (f) Baya, M.; Crochet, P.; Esteruelas, M. A.; On˜ate,
E. Organometallics 2001, 20, 240. (g) Baya, M.; Buil, M. L.; Esteruelas,
M. A.; On˜ate, E. Organometallics 2004, 23, 1416. (h) Esteruelas, M. A.;
Lo´pez, A. M.; On˜ate, E.; Royo, E. Organometallics 2004, 23, 5633. (i)
Baya, M.; Esteruelas, M. A.; Gonza´lez, A. I.; Lo´pez, A. M.; On˜ate, E.
Organometallics 2005, 24, 1225. (j) Esteruelas, M. A.; Lo´pez, A. M.; On˜ate,
E.; Royo, E. Inorg. Chem. 2005, 44, 4094.
(21) See for example: (a) Tulip, T. H.; Ibers, J. A. J. Am. Chem. Soc.
1979, 101, 4201. (b) Murrall, N. W.; Welch, A. J. J. Organomet. Chem.
1986, 301, 109. (c) Henly, T. J.; Wilson, S. R.; Shapley, J. R. Inorg. Chem.
1988, 27, 2551. (d) Faller, J. W.; Lambert, C.; Mazzieri, M. R. J. Organomet.
Chem. 1990, 383, 161.

700 Organometallics, Vol. 25, No. 3, 2006
Esteruelas et al.
The allylic resonances are observed at 5.51 (Hmeso), 3.59 (CHPh),
and 2.63 (CHMe) ppm. As for 7, the value of the Hmeso-H
coupling constants is 7.5 Hz. The cisoid disposition of C(4)
and the hydride ligand is consistent with the results of the NOE
experiments carried out on 8 (Table 2). Thus, the saturation of
the hydride resonance produces an enhancement of 4.2% of the
intensity of the signal at 3.59 ppm, while a NOE effect with
the resonance at 2.63 ppm is not observed. In the 13C{1H} NMR
spectrum, the most noticeable resonances are three singlets at
69.9, 53.3, and 38.0 ppm, which were assigned to C(3), C(4),
in the CHDPh substituent of the olefin should be similarly
feasible. The presence of deuterium at CPh and its absence at
the hydride position suggests that the Câ atom of the alkenyl
unit of the osmaindene of 6 undergoes reversible protonation.
Thus, the addition of D+ and the subsequent dissociation of
H+ should afford 6-d1, containing a deuterium atom at Câ of
the alkenyl moiety of the metallacycle (Scheme 5), which could
evolve into the allyl derivative via a process similar to that
shown in pathway 3a. The presence of deuterium at the CPh
carbon atom of 4 is significantly higher than the presence at
the hydride position (0.55 versus 0.30). This suggests that, in
addition to pathways 3a and 3b of Scheme 3, the Câ atom of
the alkenyl unit of 2 also undergoes addition of D+ and
subsequent dissociation of H+.
Complex 10 is structurally similar to 5, which is the most
stable allyl species resulting from the vinylidene-methyl
coupling. However, although the endo structural form seems
to be preferred in half-sandwich d4-allyl complexes and the
cisoid disposition of the hydride ligand and the terminal CHPh
group is favored with regard to the cisoid disposition of the
phosphine and the CHPh group, complex 10 is less stable than
9 despite that the latter contains an exo-allyl ligand and a CHPh
group cisoid disposed to the phosphine. Thus, in dichlo-
romethane at 20 °C, complex 10 isomerizes into 9 in quantitative
yield after 24 h. After 7 days in dichloromethane-d2 at 40 °C,
complex 9 reaches equilibrium with 8.
1
and C(2), respectively, on the basis of the H-13C HMQC
spectrum. The 31P{1H} NMR spectrum shows a singlet at 20.7
ppm.
1
In the H NMR spectrum of 9, the hydride resonance is
observed at -13.76 ppm as a double quartet by spin coupling
with the phosphorus atom of the phosphine (33.6 Hz) and the
hydrogen atoms of the methyl substituent of the allyl ligand
1
(2.1 Hz). The latter was confirmed by a H-1H COSY NMR
spectrum, which shows the cross signals between both reso-
nances. The allylic resonances appear at 5.82 (Hmeso), 3.70
(CHPh), and 3.38 (CHMe) ppm, with Hmeso-H coupling
constants of 9.3 Hz. In agreement with the cisoid disposition
of the terminal allylic CHMe group and the hydride ligand, the
saturation of the allylic signal at 3.38 ppm produces an
enhancement of the hydride resonance of 9.3%. In the 13C{1H}
NMR spectrum, the allylic carbon atoms give rise to singlets at
69.3 (Cmeso), 51.8 (CMe), and 42.5 (CPh) ppm. The 31P{1H}
NMR spectrum shows a singlet at 20.2 ppm.
In a manner similar to 2, complex 6 reacts with HBF4‚OEt2.
The addition at 0 °C of 1.0 equiv of the acid to a diethyl ether
solution of 6 gives rise to the precipitation of the d4-allyl
derivative 10 (Scheme 4), which is an endo isomer of 8 and 9.
Complex 10 was isolated as a white solid in 91% yield. The
1H NMR spectrum in dichloromethane-d2 at -20 °C shows the
hydride resonance at -15.10 ppm, as a doublet with a H-P
coupling constant of 40.5 Hz. Spin coupling between the hydride
and the hydrogen atoms of the methyl substituent of the allyl is
not observed, in agreement with the transoid disposition of the
hydride ligand and the terminal CHMe group. The allylic
resonances are observed at 4.89 (CHPh), 4.21 (Hmeso), and 3.97
(CHMe) ppm, with Hmeso-H coupling constants of 9.5 Hz. In
accordance with the endo coordination of the allyl ligand, the
saturation of the allyl resonances at 4.89 and 3.97 ppm produces
increases of 8.2% and 7.3%, respectively, of the cyclopentadi-
enyl resonance (Table 2). In the 13C{1H} NMR spectrum the
carbon atoms of the C3 skeleton of the allyl ligand give rise to
singlets at 76.3 (Cmeso), 47.1 (CPh), and 42.5 (CMe) ppm. The
31P{1H} NMR spectrum shows a singlet at 13.4 ppm.
The hydride ligand does not play any role in the isomerization
processes from 10 to 9 and from 9 to 8. In agreement with this,
we have observed that the isomerization of 10a-d1 into 8a-d1
via 9a-d1 does not produces any change in the deuterium
distribution of the allyl ligand. Like 4 and 5, complexes 9 and
8 are diastereoisomers resulting from the chirality of the osmium
atom and the prochirality of the CHdCHR (R ) CH3, Ph)
moieties of the allyl ligand. In a manner similar to the
isomerization from 4 to 5, the transformation of 9 into 8 should
occur by decoordination of the styryl moiety from the osmium
atom of 9, to afford the η1-allyl intermediate [OsH(η5-C5H5)-
{η1-C(CH3)HCHdCHPh}(PiPr3)]+, and the subsequent coor-
dination of the metal center of this species to the other face of
the carbon-carbon double bond. This intermediate as well as
e (Scheme 2) should be favored with regard to those containing
an η1-CH(Ph)CHdCHR (R ) H, CH3) allyl ligand due to the
smaller size of H or CH3 with regard to Ph.
The transformation of 10 into 9 seems to occur via rotation
of the allyl ligand around the metal-allyl axis, not only because
the η3 f η3 f η3 pathway is intrinsically more favored than
the η3 f η1 f η3 pathway in d4 compounds of this type, but
also because the formation of an η1-intermediate should give a
less stable diastereomer with an anti substituent.23
The relative stability of 4 and 5 and 8-10 indicates that the
syn substituents at the η3-allyl ligand play an important role in
determining the relative stability of the exo and endo coordina-
The reaction of 6 with DBF4‚OD2 affords 10a-d1 with 0.35
deuterium atom at the ortho position of the phenyl group and
0.65 deuterium atom at the terminal allyl CPh carbon atom (eq
3). Deuterium at the hydride position is not observed. This
2
1
deuterium distribution is supported by the H and H NMR
2
spectra of 10a-d1. The H NMR spectrum in dichloromethane
contains broad singlets at 7.4 and 4.9 ppm in a 0.35:0.65
1
intensity ratio, whereas in the H NMR spectrum in dichlo-
romethane-d2 the intensity ratio of the resonances at 7.3 and
4.89 ppm is 4.6:0.3.
The presence of deuterium at the phenyl substituent of the
allyl ligand can be rationalized according to pathway 3a of
Scheme 3. However, pathway 3b does not justify the presence
of the deuterium at the terminal allyl CPh carbon atom and at
the same time its absence in the hydride position, since from a
statistical point of view, the C-D and C-H bond activations
(23) (a) Faller, J. W.; Thomsen, M. E.; Mattina, M. J. J. Am. Chem.
Soc. 1971, 93, 2642. (b) Faller, J. W.; Tully, M. T. J. Am. Chem. Soc.
1972, 94, 2676. (c) Ward, Y. D.; Villanueva, L. A.; Allred, G. D.; Payne,
S. C.; Semones, M. A.; Liebeskind, L. S. Organometallics 1995, 14, 4132.
(d) Villanueva, L. A.; Ward, Y. D.; Lachicotte, R.; Liebeskind, L. S.
Organometallics 1996, 15, 4190.

Half-Sandwich Osmium-Allyl Complexes
Organometallics, Vol. 25, No. 3, 2006 701
Scheme 5
prevents the transformation of 11 into an allyl derivative. Thus,
the addition of HBF4‚OEt2 to 11 gives rise to E-stilbene and
the metallic fragment [Os(η5-C5H5)(PiPr3)]+, which is trapped
with acetonitrile to afford the solvento complex [Os(η5-
C5H5)(CH3CN)2(PiPr3)]BF4 (12).25
Complex 12 is isolated as a yellow solid in 72% yield. In
the 1H NMR spectrum, the most noticeable resonance is a
doublet at 2.62 ppm, with a H-P coupling constant of 1.2 Hz,
corresponding to the methyl groups of the acetonitrile molecules.
In the 13C{1H} NMR spectrum, these ligands give rise to singlets
at 123.3 (C(sp)) and 4.0 (C(sp3)) ppm. The 31P{1H} NMR
spectrum shows a singlet at 18.3 ppm.
Concluding Remarks
This study reveals that the metal fragment [Os(η5-C5H5)(Pi-
Pr3)]+ is a useful template to promote the formation of d6- and
d4-allyl species, by initial carbon-carbon coupling between a
vinylidene ligand and carbon nucleophiles, containing hydrogen
atoms at the donor atom, and subsequent CH bond activation.
Complex Os(η5-C5H5)Cl(dCdCHPh)(PiPr3) reacts with or-
ganomagnesium compounds, RMgCl (R ) Me, Et, Ph), to give
Scheme 6
initially hydride-osmaindene derivatives, OsH(η5-C5H5){C(R)d
CHC6H4}(PiPr3), as a consequence of the addition of the
nucleophile to the CR atom of the vinylidene followed by ortho-
CH bond activation of the phenyl substituent at the Câ atom.
When R is Me and Et, the hydride-osmaindene moiety
rearranges to afford d6-exo-allyl derivatives, Os(η5-C5H5){η3-
CH(R′)CHCHPh}(PiPr3) (R′ ) H, Me). The transformation
involves the reductive elimination of phenyl in the metallacycle
and a 1,2-hydrogen shift, through the metal center, from the
alkyl substituent to the CR atom of the resulting unsaturated
alkenyl intermediate.
Complexes Os(η5-C5H5){η3-CH(R′)CHCHPh}(PiPr3) generate
hydride-d4-allyl derivatives [OsH(η5-C5H5){η3-CH(R′)CHCHPh}-
(PiPr3)]BF4 by protonation with HBF4. The allyl ligands in these
compounds coordinate in both exo and endo forms. The relative
stability of the resulting isomers depends on the R′ substituent
tion forms in half-sandwich d4-η3-allyl complexes. Faller has
observed that the exo-endo relative stability is also dependent
on the meso- and anti-substitution.17a,b,24 Jia and co-workers have
reported that for Ru(η3-allyl)Cl(CO)(PR3)2 complexes, an anti
substituent at one of the terminal carbons destabilizes the endo
isomer, while a syn substituent has a negligible effect.5b
3. Vinylidene-Phenyl Coupling. Treatment at 55 °C of 1
of the allyl ligand, which is syn disposed with regard to Hmeso
.
with 1.2 equiv of PhMgCl in tetrahydrofuran leads to OsH(η5-
When R′ is H, the endo coordination is thermodynamically
favored. Thus, only endo derivatives have been isolated and
characterized. However, when R′ is Me the exo coordination is
the most stable, and although an endo isomer has been isolated
and characterized, it isomerizes into an equilibrium mixture of
exo species.
In conclusion, half-sandwich osmium-allyl derivatives can
be systematically prepared by reaction of vinylidene complexes
with organomagnesium compounds containing hydrogen atoms
at the CR atom of the organic fragment. The coordination form
of the allyl ligand depends on both the electronic structure of
C5H5){C(Ph)dCHC6H4}(PiPr3) (11), according to Scheme 6.
Its formation should involve the same sequence of elemental
steps as the formation of 2 and 6, with phenyl instead of an
alkyl group.
Complex 11 was isolated as a yellow solid in 64% yield. In
agreement with the presence of a hydride ligand in the
compound, its 1H NMR spectrum in benzene-d6 at 20 °C
contains a doublet at -13.52 ppm with a H-P coupling constant
of 48.0 Hz. In the low-field region of the spectrum, the most
noticeable resonance is a singlet at 7.88 ppm, corresponding to
the Câ-H hydrogen atom of the alkenyl unit of the metallacycle.
In the 13C{1H} NMR spectrum, the resonances due to the alkenyl
carbon atoms appear at 144.4 (Câ) and 142.5 (CR) ppm. The
first of them is observed as a singlet, whereas the second one
is a doublet with a C-P coupling constant of 17 Hz. The
metalated carbon atom of the phenyl group gives rise to a
doublet at 156.6 ppm, with a C-P coupling constant of 5 Hz.
The 31P{1H} NMR spectrum shows a singlet at 17.7 ppm.
The absence of a hydrogen atom at the phenyl carbon atom
bonded to the CR atom of the alkenyl unit of the metallacycle
the metal center and the substituents of the allyl syn to Hmeso
.
While the d6 ion favors the exo coordination, the relative stability
of the exo and endo isomers in d4-species is governed by the
syn substituents.
Experimental Section
General Procedures. 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
(24) (a) Faller, J. W.; Rosan, A. M. J. Am. Chem. Soc. 1976, 98, 3388.
(b) Faller, J. W.; Shvo, Y.; Murray, H. H. J. Organomet. Chem. 1982, 226,
251. (c) Faller, J. W.; Whitmore, B. C. Organometallics 1986, 5, 752.
(25) A related indenyl derivative has been recently reported; see:
Esteruelas, M. A.; Lo´pez, A. M.; On˜ate, E.; Royo, E. Organometallics 2005,
24, 5780.

702 Organometallics, Vol. 25, No. 3, 2006
Esteruelas et al.
starting material Os(η5-C5H5)Cl(dCdCHPh)(PiPr3) was prepared
by the published method.9
(110 mg, 0.21 mmol) in 7 mL of diethyl ether at 0 °C was treated
with HBF4‚Et2O (28 µL, 0.21 mmol). Immediately, a yellow solid
appeared, which was separated by decantation, washed with diethyl
ether (2 × 2 mL), and dried in vacuo. Yield: 98 mg (76%). (b)
The same procedure was followed starting from 3 (108 mg, 0.21
mmol). Yield: 105 mg (82%). Anal. Calcd for C23H36BF4OsP: C,
44.52; H, 5.85. Found: C, 44.51; H, 5.38. IR (Nujol, cm-1): ν-
NMR spectra were recorded on either a Varian Gemini 2000, a
Bruker ARX 300, a Bruker Avance 300 MHz, or a Bruker Avance
400 MHz instrument. Chemical shifts (expressed in parts per
million) are referenced to residual solvent peaks (1H, 13C{1H}) or
external H3PO4 (31P{1H}). Coupling constants, J, are given in hertz.
Infrared spectra were run on a Perkin-Elmer 1730 spectrometer
(Nujol mulls on polyethylene sheets). C, H, and N analysis were
carried out in a Perkin-Elmer 2400 CHNS/O analyzer. Mass spectra
analyses were performed with a VG Austospec instrument. In
LSIMS+ mode, ions were produced with the standard Cs+ gun at
ca. 30 kV, and 3-nitrobenzyl alcohol (NBA) was used in the matrix.
For stilbene, GC-MS analysis was run on an Agilent 5973 mass
selective detector interfaced to an Agilent 6890 series gas chro-
matograph system. Sample was injected into a 30 m × 250 µm
HP-5MS 5% phenyl methyl siloxane column with a film thickness
of 0.25 µm (Agilent). The GC oven temperature was programmed
as follows: 35 °C for 6 min, 35 to 280 °C at 25°/min, 280° for 4
min. The carrier gas was helium at a flow rate of 1 mL/min.
1
(OsH) 2135 (w), ν(Ph) 1598 (m), ν(BF4) 1079 (s). H NMR (300
MHz, CD2Cl2, 253 K, plus COSY): δ 7.40-7.25 (m, 5H, Ph),
5.72 (s, 5H, C5H5), 5.11 (d, JH-Hm ) 10.8, 1H, CHPh), 4.36 (dddd,
JH-P ) 3.8, JH-Ha′ ) 10.8, JH-Ha ) 7.9, JH-Hs ) 5.5, 1H, Hmeso),
3.45 (dd, JH-Hm ) 5.5, Jgem ) 1.8, 1H, Hs), 3.13 (dd, JH-Hm ) 7.9,
Jgem ) 1.8, 1H, Hanti), 1.77 (m, 3H, PCH), 1.02 (dd, JH-P ) 13.3,
JH-H ) 7.1, 9H, PCHCH3), 0.83 (dd, JH-P ) 15.4, JH-H ) 7.1,
9H, PCHCH3), -15.12 (d, JH-P ) 38.1, 1H, Os-H). 31P{1H} NMR
(121.42 MHz, CD2Cl2, 253 K): δ 17.7 (s). 13C{1H} NMR (75.42
MHz, CD2Cl2, 253 K, plus APT, plus HSQC): δ 137.6 (s, Cipso
-
Ph), 128.7, 128.7, and 128.6 (all s, Ph), 85.3 (s, Cp), 73.8 (s, Cmeso),
54.8 (s, CHPh), 28.1 (d, JC-P ) 29, PCH), 20.5 (s, PCHCH3), 19.0
(d, JC-P ) 3, PCHCH3), 18.9 (s, CH2).
Preparation of [OsD(η5-C5H5){η3-CH2CHCHPh}(PiPr3)]BF4
(4-d1). An NMR tube containing a yellow solution of 3 (12 mg,
0.02 mmol) in 0.5 mL of dichloromethane-d2 was treated with
DBF4‚OD2 (6.1 µL, 0.02 mmol) at -20 °C. DBF4‚OD2 was
prepared by adding D2O (1 mL, 50 mmol) to a commercial solution
of HBF4‚OEt2 (1 mL, 7.35 mmol). The NMR spectra at -20 °C
showed the presence of 4-d1. 1H NMR (300 MHz, CD2Cl2, 253 K)
data were identical to those reported for 4 with the exception of
the resonance at -15.12, which was missing. 2H NMR (61.5 MHz,
CH2Cl2, 253 K): δ -5.1 (d, JD-P ) 6, OsD).
Preparation of OsH(η5-C5H5){C(CH3)dCHC6H4}(PiPr3) (2).
A red solution of 1 (270 mg, 0.49 mmol) in 8 mL of tetrahydrofuran
was treated with methylmagnesium chloride (195 µL, 0.58 mmol,
3 M in tetrahydrofuran). The solution was allowed to react for 15
h at 55 °C, and the solvent was removed. The product was extracted
from the resultant brown oil with toluene (7 mL), which was filtered
through Kieselguhr. The solution was concentrated to dryness, and
the addition of 2 mL of methanol caused the precipitation of a
yellow solid. The solid was separated by decantation, washed with
cold methanol (2 × 1 mL), and dried in vacuo. Yield: 174 mg
(67%). Anal. Calcd for C23H35OsP: C, 51.85; H, 6.62. Found: C,
51.76; H, 6.82. IR (Nujol, cm-1): ν(OsH) 2133 (w), ν(Ph) 1574
(m). 1H NMR (400 MHz, C6D6, 293 K): δ 7.59 and 7.51 (both d,
JH-H ) 7.6, each 1H, C6H4), 7.44 (s, 1H, dCH), 7.22 and 6.82
(both t, JH-H ) 7.6, each 1H, C6H4), 4.67 (s, 5H, C5H5), 3.02 (s,
3H, CH3), 2.14 (m, 3H, PCH), 0.81 (dd, JH-P ) 14.6, JH-H ) 7.2,
9H, PCHCH3), 0.63 (dd, JH-P ) 12.0, JH-H ) 7.2, 9H, PCHCH3),
-14.56 (d, JH-P ) 47.2, 1H, Os-H). 31P{1H} NMR (161.89 MHz,
C6D6, 293 K): δ 18.5 (s). 13C{1H} NMR (100.56 MHz, C6D6, 293
K, plus APT, plus HSQC, plus HMBC): δ 164.2 (s, CipsoC6H4),
156.4 (d, JC-P ) 4, CR in Os-C6H4), 143.1 (s, C6H4), 142.3 (s,
dCH), 141.8 (d, JC-P ) 16, Os-C(CH3)), 123.2, 120.4, and 119.6
(all s, C6H4), 82.7 (s, Cp), 42.7 (s, OsC(CH3)), 27.5 (d, JC-P ) 30,
PCH), 20.9 and 18.7 (both s, PCHCH3). MS (LSIMS+): m/z 533
Preparation of 4a-d1. An NMR tube was charged with 2 (30
mg, 0.06 mmol) and 0.5 mL of dichloromethane-d2, the sample
was cooled to -20 °C, and DBF4‚OD2 (15.4 µL, 0.06 mmol) was
added. 1H NMR (300 MHz, CD2Cl2, 253 K) data were identical to
those reported for 4 with the exception of the resonances at 7.33
(m, 4.85H, Ph), 5.11 (d, JH-Hm ) 10.8, 0.45H, CHPh), and -15.12
2
(d, JH-P ) 38.1, 0.70H, Os-H). H NMR (61.5 MHz, CH2Cl2,
253 K): δ 7.4 (br, 0.15D, o-Ph), 5.1 (br, 0.55D, CDPh), -15.1 (d,
JD-P ) 6, 0.30D, OsD).
Isomerization of 4 into 5. A brown solution of 4 (105 mg, 0.17
mmol) in 7 mL of dichloromethane was heated at 40 °C for 72 h.
The resultant brown solution was concentrated to ca. 0.5 mL, and
diethyl ether (5 mL) was added. A yellow solid precipitated, which
was separated by decantation, washed with 2 × 2 mL of diethyl
ether, and dried in vacuo. Yield: 94 mg (89%). Anal. Calcd for
C23H36BF4OsP: C, 44.52; H, 5.85. Found: C, 44.73; H, 5.90. IR
(Nujol, cm-1): ν(OsH) 2109 (w), ν(Ph) 1599 (m), ν(BF4) 1083
i
(M+); 489 (M+ - Pr).
Preparation of Os(η5-C5H5)(η3-CH2CHCHPh)(PiPr3) (3). A
yellow solution of 2 (150 mg, 0.28 mmol) in 10 mL of toluene
was heated under reflux for 15 h. After that period of time, the
resultant solution was cooled to room temperature and the solvent
was removed. The addition of 2 mL of cold pentane caused the
appearance of a yellow solid, which was washed with pentane (2
× 2 mL) and dried in vacuo. Yield: 124 mg (83%). Anal. Calcd
for C23H35OsP: C, 51.85; H, 6.62. Found: C, 51.54; H, 6.66. IR
1
(s). H NMR (400 MHz, CD2Cl2, 293 K, plus COSY): δ 7.34-
7.18 (m, 5H, Ph), 5.67 (s, 5H, C5H5), 4.87 (dd, JH-P ) 2.2, JH-Hm
) 9.2, 1H, CHPh), 4.09 (dddd, JH-P ) 4.6, JH-Ha′ ) 9.2, JH-Ha
)
8.8, JH-Hs ) 5.6, 1H, Hmeso), 3.13 (ddd, JH-P ) 5.6, JH-Hm ) 5.6,
Jgem ) 2.0, 1H, Hsyn), 2.93 (dd, JH-Hm ) 8.8, Jgem ) 2.0, 1H, Hanti),
2.15 (m, 3H, PCH), 1.13 and 1.12 (both dd, JH-P ) 14.2, JH-H
)
7.0, each 9H, PCHCH3), -15.31 (d, JH-P ) 34.8, 1H, Os-H). 31P-
{1H} NMR (161.89 MHz, CD2Cl2, 293 K): δ 14.0 (s). 13C{1H}
NMR (100.56 MHz, CD2Cl2, 293 K, plus APT, plus HSQC): δ
140.8 (s, CipsoPh), 129.1, 128.2, and 127.1 (all s, Ph), 86.1 (s, Cp),
73.9 (s, Cmeso), 54.2 (s, CHPh), 28.1 (d, JC-P ) 30, PCH), 19.7 (s,
CH2), 19.6 (s, PCHCH3), 19.6 (d, JC-P ) 4, PCHCH3). MS
(LSIMS+): m/z 534 (M+).
1
(Nujol, cm-1): ν(Ph) 1594 (m). H NMR (400 MHz, C6D6, 293
K, plus COSY): δ 7.35-7.01 (m, 5H, Ph), 4.55 (dddd, JH-P
)
2.2, JH-Hs ) 6.0, JH-Ha ) 7.7, JH-Ha′ ) 7.8, 1H, Hmeso), 4.32 (s,
5H, C5H5), 2.99 (dd, JH-Hm ) 6.0, Jgem ) 1.8, 1H, Hsyn), 2.58 (dd,
JH-P ) 12.0, JH-Hm ) 7.8, 1H, CHPh), 1.84 (m, 3H, PCH), 1.02
(dd, JH-P ) 12.2, JH-H ) 7.4, 10H, PCHCH3 + Ha), 1.00 (dd,
JH-P ) 12.0, JH-H ) 7.2, 9H, PCHCH3). 31P{1H} NMR (161.89
MHz, C6D6, 293 K): δ 20.9 (s). 13C{1H} NMR (100.56 MHz, C6D6,
293 K, plus APT, plus HMQC): δ 151.3 (s, CipsoPh), 128.4, 125.5,
Preparation of [OsD(η5-C5H5){η3-CH2CHCHPh}(PiPr3)]BF4
(5-d1). An NMR tube containing a brown solution of 4-d1 in
dichloromethane-d2 was heated at 40 °C for 72 h. The NMR spectra
at room temperature show the presence of 5-d1. 1H NMR (300 MHz,
CD2Cl2, 293 K) data were identical to those reported for 5 with
and 122.8 (all s, Ph), 73.0 (s, Cp), 50.4 (s, Cmeso), 34.9 (d, JC-P
)
5, CHPh), 27.1 (d, JC-P ) 25, PCH), 20.8 and 20.1 (both s,
PCHCH3), 10.8 (d, JC-P ) 7, CH2). MS (LSIMS+): m/z 533 (M+).
Preparation of [OsH(η5-C5H5){η3-CH2CHCHPh}(PiPr3)]BF4
(4). Two different methods were used: (a) A yellow solution of 2
2
the exception of the resonance at -15.31, which was missing. H
NMR (61.5 MHz, CH2Cl2, 293 K): δ -15.3 (d, JD-P ) 6, OsD).

Half-Sandwich Osmium-Allyl Complexes
Organometallics, Vol. 25, No. 3, 2006 703
Preparation of 5a-d1. An NMR tube containing a brown solution
of 4a-d1 in dichloromethane-d2 was heated at 40 °C for 72 h. H
22.3 (s, CHCH3), 19.7 and 19.7 (both s, PCHCH3). MS
(LSIMS+): m/z 548 (M+)
1
NMR (300 MHz, CD2Cl2, 293 K) data were identical to those
reported for 5 with the exception of the resonances at 7.26 (m,
4.85H, Ph), 4.87 (d, JH-Hm ) 10.8, 0.45H, CHPh), and -15.31 (d,
Reaction of OsH(η5-C5H5){C(CH2CH3)dCHC6H4}(PiPr3) (6)
with HBF4: Preparation of [OsH(η5-C5H5){η3-CH(CH3)-
CHCHPh}(PiPr3)]BF4 (10). A yellow solution of 6 (140 mg, 0.26
mmol) in 7 mL of diethyl ether at 0 °C was treated with HBF4‚
Et2O (35 µL, 0.26 mmol). Immediately, a white solid appeared,
which was separated by decantation, washed with diethyl ether (2
× 2 mL), and dried in vacuo. Yield: 123 mg (91%). Anal. Calcd
for C24H38BF4OsP: C, 45.43; H, 6.04. Found: C, 45.56; H, 6.12.
IR (Nujol, cm-1): ν(OsH) 2196 (w), ν(Ph) 1598 (m), ν(BF4) 1053
2
JH-P ) 38.1, 0.70H, Os-H). H NMR (61.5 MHz, CH2Cl2, 293
K): δ 7.4 (br, 0.15D, o-Ph), 4.9 (br, 0.55D, CDPh), -15.1 (d, JD-P
) 6, 0.30D, OsD).
Preparation of OsH(η5-C5H5){C(CH2CH3)dCHC6H4}(PiPr3)
(6). The same procedure described for 2 was followed starting from
1 (200 mg, 0.36 mmol) and ethylmagnesium chloride (217 µL, 0.43
mmol, 2 M in tetrahydrofuran). The product was isolated as a yellow
solid. Yield: 196 mg (74%). Anal. Calcd for C24H37OsP: C, 52.72;
H, 6.82. Found: C, 52.93; H, 7.03. IR (Nujol, cm-1): ν(OsH) 2097
(w), ν(Ph) 1573 (m). 1H NMR (300 MHz, C6D6, 293 K): δ 7.61-
7.53 (m, 2H, C6H4), 7.51 (s, 1H, dCH), 7.24-6.84 (m, 2H, C6H4),
4.68 (s, 5H, C5H5), 3.30-3.17 (m, 1H, CH2), 3.09-2.95 (m, 1H,
CH2), 2.15 (m, 3H, PCH), 1.48 (dd, JH-H ) 7.5, JH-H ) 7.5, 3H,
-CH2CH3), 0.80 (dd, JH-P ) 14.2, JH-H ) 7.0, 9H, PCHCH3),
0.64 (dd, JH-P ) 12.1, JH-H ) 7.0, 9H, PCHCH3), -14.44 (d, JH-P
) 47.4, 1H, Os-H). 31P{1H} NMR (121.42 MHz, C6D6, 293 K):
δ 18.6 (s). 13C{1H} NMR (75.42 MHz, C6D6, 293 K, plus APT,
plus HSQC): δ 164.6 (s, CipsoC6H4), 162.8 (d, JC-P ) 4, CR in
Os-C6H4), 143.1 (s, C6H4), 141.1 (d, JC-P ) 17, Os-C(CH2CH3)),
138.6 (s, dCH), 123.1, 120.7, and 119.6 (all s, C6H4), 82.5 (s, Cp),
47.9 (s, CH2), 27.2 (d, JC-P ) 30, PCH), 20.6 (s, PCHCH3), 18.6
(d, JC-P ) 3, PCHCH3), 15.7 (s, CH2CH3). MS (LSIMS+): m/z
547 (M+).
1
(s). H NMR (300 MHz, CD2Cl2, 253 K, plus COSY): δ 7.35-
7.28 (m, 5H, Ph), 5.71 (s, 5H, C5H5), 4.89 (d, JH-Hm ) 9.5, 1H,
CHPh), 4.21 (ddd, JH-P ) 4.7, JH-Ha ) JH-Ha′ ) 9.5, 1H, Hmeso),
3.97 (ddq, JH-P ) 2.7, JH-Hm ) 9.5, JH-HMe ) 6.1, 1H, CHCH3),
2.09 (d, JH-H ) 6.1, 3H, CHCH3), 1.77 (m, 3H, PCH), 1.05 (dd,
JH-P ) 13.3, JH-H ) 7.0, 9H, PCHCH3), 0.84 (dd, JH-P ) 15.0,
JH-H ) 6.9, 9H, PCHCH3), -15.10 (d, JH-P ) 40.5, 1H, Os-H).
31P{1H} NMR (121.42 MHz, CD2Cl2, 253 K): δ 13.4 (s). 13C-
{1H} NMR (75.42 MHz, CD2Cl2, 253 K, plus APT, plus HSQC):
δ 137.8 (s, CipsoPh), 128.5, 128.5, and 128.0 (all s, Ph), 85.4 (s,
Cp), 76.3 (s, Cmeso), 47.1 (s, CHPh), 42.5 (s, CHCH3), 27.5 (d,
JC-P ) 29, PCH), 23.0 (s, CHCH3), 20.1 (s, PCHCH3), 19.0 (d,
JC-P ) 3, PCHCH3).
Preparation of 10a-d1. An NMR tube containing a yellow
solution of 6 (21 mg, 0.04 mmol) in 0.5 mL of dichloromethane-
d2 was treated with DBF4‚OD2 (10.3 µL, 0.04 mmol) at -20 °C.
1
The NMR spectra at -20 °C show the presence of 10a-d1. H
Preparation of Os(η5-C5H5){η3-CH(CH3)CHCHPh}(PiPr3)
(7). A yellow solution of 6 (147 mg, 0.27 mmol) in 10 mL of
toluene was stirred at 70 °C for 72 h. The resultant solution was
concentrated to dryness, pentane was added (3 mL), and the product
appeared as a yellow solid. The solid was washed with pentane (2
× 2 mL) and dried in vacuo. Yield: 120 mg (82%). Anal. Calcd
for C24H37OsP: C, 52.72; H, 6.82. Found: C, 53.03; H, 6.95. IR
NMR (300 MHz, CD2Cl2, 253 K) data were identical to those
reported for 10 with the exception of the resonances at 7.31 (m,
2
4.65H, Ph) and 4.89 (d, JH-Hm ) 9.5, 0.35H, CHPh). H NMR
(61.5 MHz, CH2Cl2, 253 K): δ 7.4 (br, 0.35D, Ph) and 4.9 (br,
0.65D, CDPh).
Preparation of BPh4 Salt of 10. A yellow solution of 10 (235
mg, 0.37 mmol) in 8 mL of dichloromethane at -20 °C was treated
with NaBPh4 (127 mg, 0.37 mmol). After 2 h, the solution was
filtered through Kieselguhr and concentrated to almost dryness. The
addition of 4 mL of diethyl ether caused the precipitation of a white
solid, which was separated by decantation and dried in vacuo.
Yield: 324 mg (89%). The 31P{1H} and 1H NMR (300 MHz, CD2-
Cl2, 253 K) data were identical to those reported for 10 with the
exception of the appearance of the resonance at 7.37-6.92 (m, 25H,
Ph).
1
(Nujol, cm-1): ν(Ph) 1597 (m). H NMR (400 MHz, C6D6, 293
K, plus COSY): δ 7.32-7.04 (m, 5H, Ph), 4.54 (ddd, JH-P ) 2.8,
JH-Ha ) JH-Ha′ ) 7.2, 1H, Hmeso), 4.32 (s, 5H, C5H5), 2.51 (dd,
JH-P ) 12.4, JH-Hm ) 7.2, 1H, CHPh), 1.88 (m, 3H, PCH), 1.79
(d, JH-H ) 5.6, 3H, CHCH3), 1.57 (ddq, JH-P ) 14.2, JH-Hm
7.2, JH-HMe ) 5.6, 1H, CHCH3), 1.02 (dd, JH-P ) 12.0, JH-H
)
)
7.2, 9H, PCHCH3), 1.00 (dd, JH-P ) 12.0, JH-H ) 7.5, 9H,
PCHCH3). 31P{1H} NMR (161.89 MHz, C6D6, 293 K): δ 19.5 (s).
13C{1H} NMR (100.56 MHz, C6D6, 293 K, plus APT, plus
HSQC): δ 151.4 (s, CipsoPh), 128.3, 125.5, and 122.7 (all s, Ph),
73.6 (s, Cp), 57.4 (d, JC-P ) 2, Cmeso), 32.4 (d, JC-P ) 5, CHPh),
27.3 (d, JC-P ) 25, PCH), 26.0 (d, JC-P ) 6, CHCH3), 24.8 (s,
CHCH3), 20.6 and 20.3 (both s, PCHCH3). MS (LSIMS+): m/z
547 (M+).
Reaction of Os(η5-C5H5){η3-CH(CH3)CHCHPh}(PiPr3) (7)
with HBF4: Formation of [OsH(η5-C5H5){η3-CH(CH3)CHCHPh}-
(PiPr3)]BF4 (8 and 9). An NMR tube containing an orange solution
of 7 (19 mg, 0.03 mmol) in 0.5 mL of dichloromethane-d2 was
treated with HBF4‚Et2O (5 µL, 0.03 mmol). Immediately, the color
of the solution changed from orange to light brown and the NMR
spectra, after 7 days, showed the presence of 8 and 9 in a 5:2 molar
ratio. Spectroscopic data for 8: 1H NMR (300 MHz, CD2Cl2, 293
K, plus COSY): δ 7.38-7.28 (m, 5H, Ph), 5.51 (s, 6H, C5H5 +
Isomerization of 10 into 9 and 8. A brown solution of 10 (123
mg, 0.19 mmol) in 7 mL of dichloromethane was stirred at room
temperature for 24 h. The solution was concentrated to ca. 0.5 mL
and cooled to 0 °C. Addition of diethyl ether (5 mL) caused the
precipitation of 9 as a white solid. The product was separated by
decantation, washed with 2 × 2 mL of diethyl ether, and dried in
vacuo. Yield: 112 mg (91%). Anal. Calcd for C24H38BF4OsP: C,
45.43; H, 6.04. Found: C, 45.47; H, 5.94. IR (Nujol, cm-1): ν-
1
(OsH) 2197 (w), ν(Ph) 1598 (m), ν(BF4) 1022 (s). H NMR (300
MHz, CD2Cl2, 293 K, plus COSY): δ 7.60-7.48 (m, 5H, Ph),
5.82 (dd, JH-Ha ) JH-Ha′ ) 9.3, 1H, Hmeso), 5.62 (s, 5H, C5H5),
3.70 (dd, JH-P ) 12.3, JH-Hm ) 9.3, 1H, CHPh), 3.38 (ddq, JH-P
) 3.0, JH-Hm ) 9.3, JH-HMe ) 6.0, 1H, CHCH3), 2.74 (m, 3H,
PCH), 2.40 (dd, JH-H ) 6.0, JH-Ηhyd ) 2.1, 3H, CHCH3), 1.49
(dd, JH-P ) 13.0, JH-H ) 7.0, 9H, PCHCH3), 1.43 (dd, JH-P
)
H
meso), 3.59 (dd, JH-P ) 2.1, JH-Hm ) 7.5, 1H, CHPh), 2.63 (ddq,
15.0, JH-H ) 7.2, 9H, PCHCH3), -13.76 (dq, JH-P ) 33.6, JH-H
) 2.1, 1H, Os-H). 31P{1H} NMR (121.42 MHz, CD2Cl2, 293 K):
δ 20.2 (s). 13C{1H} NMR (75.42 MHz, CD2Cl2, 293 K, plus APT,
plus HSQC): δ 140.1 (s, CipsoPh), 129.4, 127.4, and 126.4 (all s,
Ph), 85.8 (s, Cp), 69.3 (s, Cmeso), 51.8 (s, CHCH3), 42.5 (s, CHPh),
28.8 (d, JC-P ) 29, PCH), 22.6 (s, CHCH3), 20.7 (s, PCHCH3),
19.7 (d, JC-P ) 3, PCHCH3). MS (LSIMS+): m/z 548 (M+). A
brown solution of 9 (27 mg, 0.04 mmol) in 0.5 mL of dichlo-
JH-P ) 15.0, JH-Hm ) 7.5, JH-HMe ) 6.0, 1H, CHCH3), 2.37 (m,
3H, PCH), 1.91 (d, JH-H ) 6.0, 3H, CHCH3), 1.36 (dd, JH-P
13.8, JH-H ) 7.2, 9H, PCHCH3), 1.32 (dd, JH-P ) 15.0, JH-H
)
)
7.0, 9H, PCHCH3), - 13.30 (d, JH-P ) 32.7, 1H, Os-H). 31P{1H}
NMR (121.42 MHz, CD2Cl2, 293 K): δ 20.7 (s). 13C{1H} NMR
(75.42 MHz, CD2Cl2, 293 K, plus APT, plus HSQC): δ 139.9 (s,
CipsoPh), 129.2, 127.6, and 126.4 (all s, Ph), 85.8 (s, Cp), 69.9 (s,
Cmeso), 55.3 (s, CHPh), 38.0 (s, CHCH3), 28.2 (d, JC-P ) 30, PCH),

704 Organometallics, Vol. 25, No. 3, 2006
Table 6. Crystal Data and Data Collection and Refinement for 3, 5, and 8
Esteruelas et al.
3
5
8
Crystal Data
formula
C23H35OsP
532.68
C23H36BF4OsP
620.50
C48H58BOsP‚1/2CH2Cl2
909.39
colorless, irregular block
0.38,0.02,0.01
triclinic, P1h
9.615(2)
13.811(3)
17.423(4)
85.988(4)
75.399(5)
molecular wt
color and habit
size, mm
symmetry, space group
a, Å
yellow, prism
0.22,0.20,0.18
triclinic, P1h
9.0672(14)
10.3723(16)
11.6987(18)
99.221(2)
95.381(2)
105.264(2)
1037.0(3)
2
red, prism
0.16,0.10,0.10
monoclinic, P2(1)/n
10.2094(13)
12.8248(17)
17.944(2)
90.00
96.363(2)
90.00
2334.9(5)
4
b, Å
c, Å
R, deg
â, deg
γ, deg
78.292(5)
2191.8(8)
2
V, Å 3
Z
D calc, g cm-3
1.706
1.765
1.378
Data Collection and Refinement
Bruker Smart APEX
diffractometer
λ(Mo KR), Å
monochromator
scan type
0.71073
graphite oriented
ω scans
µ, mm-1
6.229
3, 57
100.0(2)
13 064
5.569
4, 57
100.0(2)
28 678
3.038
4, 57
100.0(2)
25 962
10 249 (Rint ) 0.1627)
494/82
0.0598
0.1464
2θ, range deg
temp, K
no. of data collect
no. of unique data
no. of params/restraints
R1a [F2 > 2σ(F2)]
wR2b [all data]
Sc [all data]
4967 (Rint ) 0.0193)
5787 (Rint ) 0.0325)
291/18
248/0
0.0174
0.0421
1.110
0.0271
0.0608
0.974
0.664
2
2
2
2
2
a R1(F) ) ∑||Fo| - |Fc||/∑|Fo|. b wR2(F2) ) {∑[w(Fo - Fc )2]/∑[w(Fo )2]}1/2
.
c Goodness of fit ) S ) {∑[Fo - Fc )2]/(n - p)}1/2, where n is the
number of reflections and p is the number of refined parameters.
romethane-d2 was heated at 40 °C. After 7 days, the NMR spectra
showed the presence of 8 and 9 in a 5:2 molar ratio.
Preparation of OsH(η5-C5H5){C(Ph)dCHC6H4}(PiPr3) (11).
The same procedure described for 2 was followed starting from 1
(200 mg, 0.36 mmol) and phenylmagnesium chloride (217 µL, 0.43
mmol, 2 M in tetrahydrofuran). The product was isolated as a yellow
solid. Yield: 137 mg (64%). Anal. Calcd for C28H37OsP: C, 56.54;
H, 6.27. Found: C, 56.22; H, 6.43. IR (Nujol, cm-1): ν(OsH) 2189
Preparation of 9a-d1. An NMR tube containing a brown solution
of 10a-d1 in 0.5 mL of dichloromethane-d2 was kept at room
1
temperature for 24 h. H NMR (300 MHz, CD2Cl2, 293 K) data
were identical to those reported for 9 with the exception of the
resonances at 7.5 (m, 4.65H, Ph) and 3.7 (d, JH-Hm ) 10.8, 0.35H,
1
(w), ν(Ph) 1590 (m). H NMR (400 MHz, C6D6, 293 K): δ 7.92
2
CHPh). H NMR (61.5 MHz, CH2Cl2, 293 K): δ 7.5 (br, 0.35D,
(m, 2H, Ph), 7.88 (s, 1H, dCH), 7.62-6.86 (m, 7H, Ph), 4.65 (s,
5H, C5H5), 2.15 (m, 3H, PCH), 0.79 (dd, JH-P ) 14.8, JH-H ) 7.0,
9H, PCHCH3), 0.62 (dd, JH-P ) 12.2, JH-H ) 7.0, 9H, PCHCH3),
-13.52 (d, JH-P ) 48.0, 1H, Os-H). 31P{1H} NMR (161.89 MHz,
C6D6, 293K): δ 17.7 (s). 13C{1H} NMR (100.56 MHz, C6D6, 293K,
plus APT, plus HSQC): δ 164.5 and 156.7 (both s, CipsoPh), 156.6
(d, JC-P ) 5, CR in Os-C6H4), 144.4 (s, dCH), 143.0 (s, Ph), 142.5
(d, JC-P ) 17, Os-C(Ph)), 128.4, 127.9, 125.2, 123.2, 122.3, and
120.6 (all s, Ph), 83.3 (s, Cp), 27.5 (d, JC-P ) 31, PCH), 21.1 (s,
PCHCH3), 18.8 (d, JC-P ) 3, PCHCH3). MS (LSIMS+): m/z 595
(M+); 435 (M+ - PiPr3).
o-Ph) and 3.7 (br, 0.65D, CDPh).
Preparation of BPh4 Salt of 9. A yellow solution of 10-BPh4
(115 mg, 0.15 mmol) in 7 mL of dichloromethane was stirred at
room temperature for 24 h. Then, the solution was concentrated to
about dryness and diethyl ether (3 mL) was added. Immediately, a
white solid appeared, which was separated by decantation, washed
with 2 mL of diethyl ether, and dried in vacuo. Yield: 101 mg
(88%). The 31P{1H} and 1H NMR (300 MHz, CD2Cl2, 293 K) data
were identical to those reported for 9 with the exception of the
appearance of the resonance at 7.35-6.98 (m, 25H, Ph).
Formation of 8a-d1. An NMR tube containing a brown solution
of 9a-d1 in 0.5 mL of dichloromethane-d2 was heated at 40 °C.
After 7 days, the NMR spectra showed the presence of 8a-d1 and
Reaction of OsH(η5-C5H5){C(Ph)dCHC6H4}(PiPr3) (11) with
HBF4: Preparation of [Os(η5-C5H5)(CH3CN)2(PiPr3)]BF4 (12).
An orange solution of 11 (150 mg, 0.25 mmol) in 7 mL of
acetonitrile was treated with HBF4‚Et2O (45 µL, 0.33 mmol). The
color of the solution changed immediately from orange to brown.
After 30 min, the solvent was removed and the addition of diethyl
ether (2 mL) to the resultant brown oil caused the appearance of a
yellow solid. The solid was separated by decantation, washed with
diethyl ether (2 × 2 mL), and dried in vacuo. GC-MS analysis of
mother liquors showed the presence of stilbene. Yield: 113 mg
(77%). Anal. Calcd for C18H32BF4N2OsP: C, 36.99; H, 5.52; N,
4.79. Found: C, 37.03; H, 5.53; N, 5.09. IR (Nujol, cm-1): ν(CN)
1
9a-d1 in a molar ratio 5:2. H NMR (300 MHz, CD2Cl2, 293 K)
data were identical to those reported for 8 with the exception of
the resonances at 7.33 (m, 4.65H, Ph) and 3.59 (d, JH-Hm ) 9.5,
2
0.35H, CHPh). H NMR (61.5 MHz, CH2Cl2, 293 K): δ 7.3 (br,
0.35D, Ph) and 3.6 (br, 0.65D, CDPh).
Formation of BPh4 Salt of 8. A yellow solution of 9-BPh4 (123
mg, 0.16 mmol) in dichloromethane (7 mL) was heated at 40 °C
for 7 days. Then, the solution was concentrated to about dryness
and diethyl ether (4 mL) was added. Immediately, a white solid
appeared, which was separated by decantation, washed with 2 mL
of diethyl ether, and dried in vacuo. The NMR spectra showed the
presence of 8-BPh4 and 9-BPh4 in a molar ratio 5:2. The 31P{1H}
1
2273 (m), ν(BF4) 1025 (s). H NMR (300 MHz, CD2Cl2, 293 K):
δ 4.80 (s, 5H, C5H5), 2.62 (d, JH-P ) 1.2, 6H, CH3CN), 2.40 (m,
3H, PCH), 1.20 (dd, JH-P ) 13.5, JH-H ) 7.2, 18H, PCHCH3).
31P{1H} NMR (121.42 MHz, CD2Cl2, 293 K): δ 18.3 (s). 13C-
{1H} NMR (75.42 MHz, CD2Cl2, 293 K): δ 123.3 (s, CH3CN),
1
and H NMR (300 MHz, CD2Cl2, 293 K) data were identical to
those reported for 8 with the exception of the appearance of the
resonance at 7.38-6.92 (m, 25H, Ph).

Half-Sandwich Osmium-Allyl Complexes
Organometallics, Vol. 25, No. 3, 2006 705
71.4 (s, Cp), 27.0 (d, JC-P ) 26, PCH), 19.4 (s, PCHCH3), 4.0 (s,
CH3CN). MS (LSIMS+): m/z 457 (M+ - CH3CN).
of them supported a free refinement of these atoms and a restrained
geometry was used in the last cycles of refinement. Hydrogen atoms
(except those corresponding to the allylic carbon atoms, which were
observed in the difference Fourier maps and refined as free isotropic
atoms) were included in calculated positions and refined riding on
their respective carbon atoms with the thermal parameter related
to the bonded atoms. For 5, the BF4 anion was observed disordered.
The anion was defined with four moieties, complementary oc-
cupancy factors, isotropic atoms, and restrained geometry. In the
last cycles of refinement 8 showed an improper refinement of the
thermal parameters of some allyl, Cp, and dichloromethane atoms
probably due to the small intensity of the measured reflections
(mean (I/σ) ) 2.1). However the poor thermal displacements could
be improved by the use of SIMU and DELU restraints (or even
ISOR, or combinations thereof). DELU is used to equalize each
anisotropic vector parallel to the bond and SIMU was used to atoms
that are nonbonded but near in space. All the highest electronic
residuals were observed in close proximity of the Os centers and
make no chemical sense. A summary of crystal data and data
collection and refinement details is reported in Table 6.
Structural Analysis of Complexes 3, 5, and 8. Crystals suitable
for the X-ray diffraction were obtained by cooling at 4 °C a solution
of 3 in pentane, by slow diffusion of diethyl ether into a
concentrated solution of 5 in dichloromethane, and by slow diffusion
of diethyl ether into a concentrated solution of a mixture of the
-
BPh4 salts of 8 and 9 in dichloromethane. X-ray data were
collected for all complexes on a Bruker Smart APEX CCD
diffractometer equipped with a normal focus, 2.4 kW sealed tube
source (Mo radiation, λ ) 0.71073 Å) operating at 50 kV and 30
mA. Data were collected over the complete sphere by a combination
of four sets. Each frame exposure time was 10 s (30 s for 8)
covering 0.3° in ω. Data were corrected for absorption by using a
multiscan method applied with the SADABS program.26 The
structures of all compounds were solved by the Patterson method.
Refinement, by full-matrix least squares on F2 with SHELXL97,27
was similar for all complexes, including isotropic and subsequently
anisotropic displacement parameters. The high quality and extended
range of diffraction data allowed location of the hydride ligands in
5 and 8 in the difference Fourier maps. However, we observed short
Os-H distances due to the well-known behavior of the X-ray
experiments that usually show shorter M-H distances than those
based on neutron diffraction, a radiation much more appropriate
for the precise localization of lighter elements. Unfortunately, none
Acknowledgment. Financial support from the MEC of
Spain (Proyect CTQ2005-00656) is acknowledged.
Supporting Information Available: Detailed X-ray crystal-
lographic data (bond distances, bond angles, and anisotropic
parameters) for 3, 5, and 8 in CIF format. This material is available
free of charge via the Internet at http://pubs.acs.org.
(26) Blessing, R. H. Acta Crystallogr. 1995, A51, 33. SADABS: Area-
detector absorption correction; Bruker- AXS: Madison, WI, 1996.
(27) SHELXTL Package v. 6.1; Bruker-AXS: Madison, WI, 2000.
Sheldrick, G. M. SHELXS-86 and SHELXL-97; University of Go¨ttingen:
Go¨ttingen, Germany, 1997.
OM050907B