Hydride-carbyne to carbene transformation in an osmium-acetate- bis(triisopropylphosphine) system: Influence of the coordination mode of the carboxylate and the reaction solvent

Article abstract of DOI:10.1021/om0611655

The bis-solvato hydride-allenylidene complex [OsH(=C=C=CPh ₂)(CH₃CN)₂(PⁱPr₃) ₂]BF₄ (1) reacts with acetic acid to give the hydride-carbyne [OsH(κ²-O₂CCH

Full text of DOI:10.1021/om0611655

Organometallics 2007, 26, 2037-2041
2037
Hydride-Carbyne to Carbene Transformation in an
Osmium-Acetate-Bis(triisopropylphosphine) System: Influence of
the Coordination Mode of the Carboxylate and the Reaction Solvent
Tamara Bolan˜o, Ricardo Castarlenas, Miguel A. Esteruelas,* 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 December 21, 2006
The bis-solvato hydride-allenylidene complex [OsH(dCdCdCPh2)(CH3CN)2(PiPr3)2]BF4 (1) reacts
with acetic acid to give the hydride-carbyne [OsH(κ2-O2CCH3)(tCCHdCPh2)(PiPr3)2]BF4 (2), which in
1,2-dichloroethane under reflux is stable and does not evolve into its five-coordinate carbene isomer. In
acetonitrile at room temperature, complex 2 is in equilibrium with [OsH{κ1-OC(O)CH3}(tCCHd
CPh2)(CH3CN)(PiPr3)2]BF4 (4; ∆H° ) -6.4 ( 0.3 kcal‚mol-1, ∆S° ) -22.9 ( 1.1 eu). At 353 K,
complex 4 is transformed into the carbene [Os{κ1-OC(O)CH3}(dCHCHdCPh2)(CH3CN)2(PiPr3)2]BF4
(5; 40%), which is obtained in high yield (88%) by reaction of [Os(dCHCHdCPh2)(CH3CN)3(PiPr3)2]-
[BF4]2 with sodium acetate in 2-propanol. The hydride-carbyne to carbene transformation is analyzed by
DFT calculations.
the osmium counterparts to the Grubbs-type carbene-ruthenium
derivatives, RuCl2(dCHR)(PR′3)2.6 In order to rationalize these
findings, one can argue that the migration of the hydride from
the metal center to the carbyne carbon atom (eq 1) involves a
simple intramolecular reductive elimination.7 It is well-known
that 5d metals favor the oxidized species, while the 4d
counterparts protect the reduced ones. In agreement with the
redox character of eq 1, we have recently shown that the position
of the equilibrium and the activation energy from the hydride
migration are governed by the co-ligands, which determine the
electron richness of the metal center.8
Introduction
Rates and equilibrium positions of chemical reactions, includ-
ing intramolecular redox processes, are solvent-dependent.
Responsible for this medium effect is the different solvation of
reactants and products (position of the equilibria) or reactants
and activated species (rates of chemical reactions).1
One of the most relevant redox processes in the organome-
tallic field is the C-H reductive elimination.2 For alkyl and
hydrocarbyl hydride complexes of late transition metals Pt, Ir,
Rh, Os, and Ru, some reactions are proposed to go by direct
elimination, while others require ligand dissociation prior to the
C-H coupling.3 For both cases, the presence of a chelate ligand
trans disposed to the coupled fragments prevents the C-H bond
formation.4
5
Complexes OsHCl2(tCR)(PR′3)2 are stable isomers of the
unknown compounds OsCl2(dCHR)(PR′3)2, which should be
Electron-rich compounds are susceptible to oxidation. In this
context it should be mentioned that there is a class of
allenylidene derivatives, LnMdCdCdCR2, that show the typical
behavior of Lewis base transition metal complexes.9 EHT-MO
* Corresponding author. E-mail: maester@unizar.es.
(1) See for example: (a) Weaver, M. J. Chem. ReV. 1992, 92, 463. (b)
Reichardt, C. Chem. ReV. 1994, 94, 2319.
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(b) Jones, W. D.; Feher, F. J. Acc. Chem. Res. 1989, 22, 91. (c) Koga, N.;
Morokuma, K. Chem. ReV. 1991, 91, 823. (d) Jones, W. D. Acc. Chem.
Res. 2003, 36, 140. (e) Lersch, M.; Tilset, M. Chem. ReV. 2005, 105, 2471.
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G. J. Am. Chem. Soc. 1986, 108, 1537. (b) Harper, T. G. P.; Desrosiers, P.
J.; Flood, T. C. Organometallics 1990, 9, 2523. (c) Deutsch, P. P.; Eisenberg,
R. J. Am. Chem. Soc. 1990, 112, 714. (d) Hartwig, J. F.; Andersen, R. A.;
Bergman, R. G. Organometallics 1991, 10, 1710. (e) Hsu, G. C.; Kosar,
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10.1021/om0611655 CCC: $37.00 © 2007 American Chemical Society
Publication on Web 03/13/2007

2038 Organometallics, Vol. 26, No. 8, 2007
Bolan˜o et al.
calculations indicate that the HOMO orbital of these species is
mainly located at the Câ atom of the unsaturated chain.10 In
accordance with this, the reactions of these compounds with
electrophiles lead to alkenylcarbyne derivatives, which are stable
with electron-rich coligands.11 When some of the R substituents
of the unsaturated chain are phenyl groups and the complex
contains π-acidic ligands, the reduction into the corresponding
metal-indenylidene compound, an isomer of the starting alle-
nylidene, is observed.12
Results and Discussion
The recently reported13 bis-solvento hydride-allenylidene
complex [OsH(dCdCdCPh2)(CH3CN)2(PiPr3)2]BF4 (1) appears
to be a member of the family of electron-rich species, despite
that one should expect an electron-poor character for the metal
center. Thus, in dichloromethane at room temperature, it reacts
with a stoichiometric amount of acetic acid to afford the hydride-
alkenylcarbyne derivative [OsH(κ2-O2CCH3)(tCCHdCPh2)
(PiPr3)2]BF4 (2), containing a chelate acetate ligand (eq 2). This
complex, which is isolated as a pink solid in 93% yield, is the
result of the addition of the proton of the weak acid to the Câ
atom of the allenylidene ligand and the carboxylate group to
the metal center.
Figure 1. Molecular diagram of the cation of 2. Selected bond
lengths (Å) and angles (deg): Os-O(1) 2.228(3), Os-O(2) 2.203-
(3), Os-C(1) 1.740(4), C(1)-C(2) 1.415(5), C(2)-C(3) 1.358(6);
P(1)-Os-P(2) 166.47(4), O(1)-Os-O(2) 58.66(10), O(1)-Os-
C(1) 177.62(15), O(2)-Os-H(01) 153.5(15).
Os-C(1) bond length of 1.740(4) Å is fully consistent with an
Os-C triple bond formulation.5a,8,14 Similarly to other carbyne-
metal compounds15 a slight bending in the Os-C(1)-C(2)
moiety is also present (Os-C(1)-C(2) ) 171.2(3)°). 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 1.415(5) Å, and C(2) and C(3) by
1.358(6) Å, and the angles around C(2) and C(3) are in the
range 111-125°.
The IR spectrum of 2 in dichloromethane shows the νasym
-
(OCO) band at 1535 cm-1 and the νsym(OCO) band at 1471
cm-1. The value of ∆ν (∆ν ) νasym(OCO) - νsym(OCO)) of
64 cm-1 is consistent with the bidentate coordination mode of
the acetate group.16 In agreement with the presence of a hydride
ligand in the complex, its 1H NMR spectrum shows a triplet at
-7.80 ppm with a H-P coupling constant of 15.7 Hz. In the
low-field region of the spectrum, the most noticeable signal is
a singlet at 5.14 ppm corresponding to the C(sp2)-H proton of
the alkenyl substituent of the carbyne ligand. In the 13C{1H}
NMR spectrum the Os-CR resonance appears at 272.7 ppm,
as a triplet with a C-P coupling constant of 8.0 Hz. The 31P-
{1H} NMR spectrum contains a singlet at 42.6 ppm.
Figure 1 shows a view of the geometry of the cation of 2.
The coordination around the osmium atom can be rationalized
as a distorted octahedron with the phosphorus atoms of the
phosphine ligands occupying trans positions (P(1)-Os-P(2)
) 166.47(4)°). The perpendicular plane is formed by the
bidentate ligand, which acts with a bite angle O(1)-Os-O(2)
of 58.66(10)°, the hydride trans disposed to O(2) (O(2)-Os-
H(O1) ) 153.5(15)°) and the carbyne group trans disposed to
O(1) (C(1)-Os-O(1) ) 177.62(15)°). The acetate group
coordinates in an asymmetrical fashion, with the separation
between the metal center and O(2) (2.203(3) Å) being about
0.02 Å shorter than the Os-O(1) distance (2.228(3) Å). The
Complex 2 is stable in 1,2-dichloroethane, even under reflux
for 24 h. It does not undergo reduction into an indenylidene
species by loss of molecular hydrogen, acetic acid, or tetrafluo-
roboric acid, nor is its transformation into a five-coordinate
carbene isomer observed. In agreement with this, DFT calcula-
tions on the model system [Os(HCO2)H(tCCHdCH2)(PMe3)2]+
indicate that the five-coordinate carbene cation [Os(κ2-O2CH)-
(10) (a) Berke, H.; Huttner, G.; Von Seyerl, J. Z. Naturforsch. B 1981,
36, 1277. (b) Cadierno, V.; Gamasa, M. P.; Gimeno, J.; Gonza´lez-Cueva,
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J.; Modrego, J.; Oro, L. A.; Schrickel, J. Organometallics 1996, 15, 3556.
(d) Esteruelas, M. A.; Go´mez, A. V.; Lo´pez, A. M.; Modrego, J.; On˜ate, E.
Organometallics 1997, 16, 5826. (e) Esteruelas, M. A.; Go´mez, A. V.;
Lo´pez, A. M.; Modrego, J.; On˜ate, E. Organometallics 1998, 17, 5434. (f)
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.
(11) See for example: (a) Crochet, P.; Esteruelas, M. A.; Lo´pez, A. M.;
Ruiz, N.; Tolosa, J. I. Organometallics 1998, 17, 3479. (b) Wen, T. B.;
Cheung, Y. K.; Yao, J.; Wong, W.-T., Zhou, Z. Y.; Jia, G. Organometallics
2000, 19, 3803. (c) Jung, S.; Brandt, C. D.; Werner, H. New J. Chem. 2001,
25, 1101. (d) Rigaut, S.; Touchard, D.; Dixneuf, P. H. Organometallics
2003, 22, 3980. (e) Esteruelas, M. A.; Lo´pez, A. M.; On˜ate, E.: Royo, E.
Organometallics 2004, 23, 3021. (f) Pavlik, S.; Mereiter, K.; Puchberger,
M.; Kirchner, K. J. Organomet. Chem. 2005, 690, 5497. (g) Cadierno, V.;
D´ıez, J.; Garc´ıa-Garrido, S. E.; Gimeno, J. Organometallics 2005, 24, 3111.
(h) Bustelo, E.; Jime´nez-Tenorio, M.; Puerta, M. C.; Valerga, P. Organo-
metallics 2006, 25, 4019.
(14) See for example: (a) Esteruelas, M. A.; Oliva´n, M.; On˜ate, E.; Ruiz,
N.; Tajada, M. A. Organometallics 1999, 18, 2953. (b) Castarlenas, R.;
Esteruelas, M. A.; On˜ate, E. Organometallics 2001, 20, 3283. (c) Barrio,
P.; Esteruelas, M. A.; On˜ate, E. Organometallics 2002, 21, 2491. (d) Barrio,
P.; Esteruelas, M. A.; On˜ate, E. J. Am. Chem. Soc. 2004, 126, 1946. (e)
Wen, T. B.; Hung, W. Y.; Zhou, Z. Y.; Lo, M. F.; Williams, I. D.; Jia, G.
Eur. J. Inorg. Chem. 2004, 2837. (f) Lee, J.-H.; Pink, M.; Caulton, K. G.
Organometallics 2006, 25, 802. (g) 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.
(15) See for example: (a) Esteruelas, M. A.; Lo´pez, A. M.; Ruiz, N.;
Tolosa, J. J. Organometallics 1997, 16, 4657. (b) Crochet, P.; Esteruelas,
M. A.; Lo´pez, A. M.; Martinez, M.-P.; Oliva´n, M.; On˜ate, E.; Ruiz, N.
Organometallics 1998, 17, 4500. (c) Bustelo, E.; Jime´nez-Tenorio, M.;
Mereiter, K.; Puerta, M. C.; Valerga, P. Organometallics 2002, 21, 1903.
(d) Wen, T. B.; Zhou, Z. Y.; Lo, M. F.; Williams, I. D.; Jia, G.
Organometallics 2003, 22, 5217.
(12) See for example: (a) Asensio, A.; Buil, M. L.; Esteruelas, M. A.;
On˜ate, E. Organometallics 2004, 23, 5787. (b) Castarlenas, R.; Vovard,
C.; Fischmeister, C.; Dixneuf, P. H. J. Am. Chem. Soc. 2006, 128, 4079.
(c) Esteruelas, M. A.; Lo´pez, A. M. Organometallics 2005, 24, 3584.
(13) Bolan˜o, T.; Castarlenas, R.; Esteruelas, M. A.; On˜ate, E. J. Am.
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(16) Decon, G. B.; Phillips, R. J. Coord. Chem. ReV. 1980, 33, 327.

Hydride-Carbyne to Carbene Transformation
Organometallics, Vol. 26, No. 8, 2007 2039
Figure 3. Molecular diagram of the cation of 5. Selected bond
lengths (Å) and angles (deg): Os-O(1) 2.1750(18), Os-C(1)
1.909(3), O(1)-C(16) 1.275(3), O(2)-C(16) 1.229(3), C(1)-C(2)
1.439(4), C(2)-C(3) 1.355(4); P(1)-Os-P(2) 172.93(2), O(1)-
Os-C(1) 174.21(10), N(1)-Os-N(2) 175.79(9).
Figure 2. Optimized structures and relative energies (kcal‚mol-1
of 2t, TS1, and 3t.
)
provides values of ∆H° ) -6.4 ( 0.3 kcal‚mol-1 and ∆S° )
-22.9 ( 1.1 eu. The value of ∆H° agrees with DFT calcula-
tions, indicating that the formation of the model cation [OsH-
{κ1-OC(O)H}(tCCHdCH2)(CH3CN)(PMe3)2]+ (4t), from 2t
(dCHCHdCH2)(PMe3)2]+ (3t) lies 25.6 kcal‚mol-1 above the
hydride-carbyne [OsH(κ2-O2CH)(tCCHdCH2)(PMe3)2]+ (2t).
Furthermore the activation barrier for the transformation from
3t into 2t via an η2-carbene transition state [Os(κ2-O2CH){d
and acetonitrile, is exothermic by 11.1 kcal‚mol-1
.
Complex 4 has a higher tendency than 2 to undergo reduction
into the carbene form. Thus, the acetonitrile solution of 4 affords
the carbene derivative [Os{κ1-OC(O)CH3}(dCHCHdCPh2)(CH3-
CN)2(PiPr3)2]BF4 (5) in 40% yield, after 12 h at 353 K (eq 4).
In addition to 5, a complex mixture of other unidentified
products without any acetate ligand is also formed. Complex 5
is obtained as a pure yellow solid in 88% yield, by treatment at
room temperature of 2-propanol solutions of the previously
reported carbene compound [Os(dCHCHdCPh2)(CH3CN)3(Pi-
C(CHdCH2)H}(PMe3)2]+ (TS1), similar to those proposed for
related systems containing only monodentate ligands,8 is very
low (0.5 kcal‚mol-1). The η2-coordination mode shown in
Figure 2 for the carbene ligand of TS1 has been observed in
alkylidene complexes of electron-deficient transition metals.17
In acetonitrile, complex 2 is in equilibrium with the solvento
species [OsH{κ1-OC(O)CH3}(tCCHdCPh2)(CH3CN)(PiPr3)2]-
BF4 (4), resulting from the displacement of the oxygen atom of
the carboxylate, trans disposed to the hydride ligand, by a
solvent molecule (eq 3).
8
Pr3)2][BF4]2 with 5.0 equiv of sodium acetate.
Figure 3 shows a view of the geometry of the cation of 5.
The coordination 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)
) 172.93(2)°). The perpendicular plane is formed by the
acetonitrile molecules trans disposed (N(1)-Os-N(2) ) 175.79-
(9)°) and the carbene ligand trans disposed to the monodentate
acetate group (C(1)-Os-O(1)) ) 174.21(10)°). The Os-C(1)
bond length of 1.909(3) Å supports the Os-C double bond
formulation.8,18 In agreement with the sp2 hybridization at C(1),
the angles around this atom are between 110.9(17)° and 129.5-
(2)°. The parameters of the alkenyl moiety agree well with those
of 2. The C(1)-C(2) distance is 1.439(4) Å, whereas the C(2)-
C(3) bond length is 1.355(4) Å, and the angles around C(2)
and C(3) are in the range 112-128°.
The monodentate coordination mode of the carboxylate in 4
is strongly supported by the IR spectrum of this compound in
acetonitrile, which shows the ν(OCO) bands at 1639 and 1310
cm-1 (∆ν ) 329 cm-1). The replacement of the oxygen atom
by the acetonitrile molecule produces slight changes on the
electron density at the metal center, which are evident in the
chemical shifts of the hydride, carbyne carbon atom, and
1
phosphine resonances in the H, 13C{1H}, and 31P{1H} NMR
spectra. These resonances appear at -5.7 (JH-P ) 17.1 Hz),
268.5 (JC-P ) 10.6 Hz), and 28.5 ppm. In comparison with 2,
they are shifted 2.1 ppm toward lower field, 4.2 ppm toward
higher field, and 14.1 ppm toward higher field, respectively.
The constants for the equilibrium shown in eq 3 were
determined, between 233 and 303 K, by integration of the
hydride resonances. A linear-square analysis of ln K versus 1/T
In the IR spectrum of 5 in Nujol the ν(OCO) bands of the
monodentate acetate ligand appear at 1611 and 1324 cm-1 (∆ν
) 287 cm-1). In dichloromethane at room temperature, the
coordination mode of the acetate does not undergo any changes.
Thus, the IR spectrum in this solvent shows the ν(OCO) bands
(17) See for example: (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.; Hoffmann, R.; Jemmis, E. D. J. Am. Chem. Soc. 1980,
102, 7667.

2040 Organometallics, Vol. 26, No. 8, 2007
Bolan˜o et al.
Figure 4. Variable-temperature 1H{31P} NMR spectra in the
acetonitrile region of [Os{κ1-OC(O)CH3}(dCHCHdCPh2)(CH3-
CN)2(PiPr3)2]BF4 (5): experimental (left) and calculated (right).
Figure 5. Optimized structures and relative energies (kcal‚mol-1
of 4t, TS2, and 6t.
)
at the same wavenumbers as in Nujol. In dichloromethane-d2,
(O)H}(dCHCHdCH2)(CH3CN)2(PMe3)2]+ (5t) from the hy-
dride-carbyne 4t takes place via the five-coordinate intermediate
[Os{κ1-OC(O)H}(dCHCHdCH2)(CH3CN)(PMe3)2]+ (6t), which
lies 21.9 kcal‚mol-1 above 4t. The coordination of an acetonitrile
1
the H and 13C{1H} NMR spectra are temperature-dependent.
Figure 4 shows the variable-temperature 1H{31P} NMR spectra
in the acetonitrile region. According to Figure 3, the hydrogen
and alkenyl substituents of the carbene carbon atom lie in the
plane containing the nitrogen atoms. As a result, the acetonitrile
molecules are chemically inequivalent. In agreement with this,
the spectrum at 233 K contains two resonances for the
acetonitrile methyl groups at 3.14 and 2.93 ppm. On raising
the temperature, they coalesce to give only one resonance. This
behavior can be understood as the result of the rotation of the
alkenylcarbene ligand around the Os-C double bond. Line
shape analysis of the acetonitrile methyl resonances allows the
calculation of the rate constants for the rotation process. The
activation parameters obtained from the corresponding Eyring
analysis are ∆Hq ) 12.8 ( 0.5 kcal‚mol-1 and ∆Sq ) -1.0 (
1.1 eu. The value of the activation entropy, near zero, is
consistent with a rotational process, whereas the value of the
activation enthalpy lies within the range reported for other
transition metal complexes.8,19 In addition to the acetonitrile
methyl resonances, those corresponding to the CR-H and Câ-H
protons of the carbene ligand should be mentioned, which appear
at 20.70 and 7.99 ppm as doublets with a H-H coupling
constant of 13.5 Hz. In the 13C{1H} NMR spectrum the Os-
CR resonance is observed at 259.5 ppm, as a triplet with a C-P
coupling constant of 8.7 Hz. The 31P{1H} NMR spectrum
contains a singlet at 0.9 ppm.
molecule to 6t is exothermic by 44.9 kcal‚mol-1
.
The η2-carbene transition state [Os{κ2-OC(O)H}{dC(CHd
CH2)H} (CH3CN)(PMe3)2]+ (TS2) connecting 4t and 6t (Figure
5) is 24.1 kcal above 4t. Since the κ2-κ1 transformation of the
acetate group by addition of acetonitrile to 2t, to form 4t, is
exothermic by 11.1 kcal‚mol-1, and the difference in energy
between TS1 and 2t of 26.1 kcal‚mol-1 is higher than that
between TS2 and 4t, one can assert that the κ2-κ1 transforma-
tion of the acetate group facilitates the hydride-carbyne to
carbene transformation.
In conclusion, for this osmium-acetate-bis(phosphine) system,
the κ2-coordination of the acetate increases the difference in
stability between the stable hydride-carbyne form and the
carbene, while the κ1-coordination facilitates the hydride-carbyne
to carbene transformation, lowering its activation energy. A
coordinating solvent such as acetonitrile stabilizes the carbene
form, by coordination to the five-coordinate intermediate
resulting from the migratory insertion of the carbyne into the
metal-hydride bond.
Experimental Section
The formation of 5 according to eq 4 indicates that, in contrast
to 1,2-dichloroethane, acetonitrile favors the hydride-carbyne
to carbene transformation. DFT calculations shows that the
formation of the six-coordinate carbene cation [Os{κ1-OC-
All reactions were carried out with rigorous exclusion of air using
Schlenk-tube techniques. Solvents were dried by the usual proce-
dures and distilled under argon prior to use. The starting materials
1 and [Os(dCHCHdCPh2)(CH3CN)3(PiPr3)2][BF4]2 were prepared
by published methods.8,13 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.
Preparation of [OsH(κ2-O2CCH3)(tCCHdCPh2)(PiPr3)2]BF4
(2). A solution of 1 (100 mg, 0.114 mmol) in 5 mL of dichlo-
romethane was treated with acetic acid (7 µL, 0.114 mmol). After
stirring the mixture for 30 min at room temperature, it was filtered
through Celite, and the filtrate was evaporated. The addition of
diethyl ether to the resulting residue led to a pink solid, which was
washed with diethyl ether and dried in vacuo. Yield: 89 mg (93%).
Anal. Calcd for C35H57BF4O2OsP2: C 49.53; H 6.77. Found: C
49.36; H 6.33. IR (Nujol, cm-1): ν(OsH) 2179 (m); νasym(OCO)
1530 (s); νsym(OCO) 1465 (s); ν(BF) 1051 (vs). MS: m/z 762 (M)+.
1H NMR (300 MHz, CD2Cl2, 293 K): δ 7.6-7.2 (m, 10H, Ph),
(18) See for example: (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.; Webern-
do¨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. Organometallics 2003, 22, 744. (h) Esteruelas, M. A.; Gonza´lez,
A. I.; Lo´pez, A. M.; On˜ate, E. Organometallics 2004, 23, 4858. (i)
Castarlenas, R.; Esteruelas, M. A.; On˜ate, E. Organometallics 2005, 24,
4343. (j) Esteruelas, M. A.; Ferna´ndez-AÄ lvarez, F. J.; Oliva´n, M.; On˜ate,
E. J. Am. Chem. Soc. 2006, 128, 4596. (k) Esteruelas, M. A.; Ferna´ndez-
AÄ lvarez, F. J.; On˜ate, E. J. Am. Chem. Soc. 2006, 128, 13044.
(19) See for example: (a) Kegley, S. E.; Brookhart, M.; Husk, G. R.
Organometallics 1982, 1, 760. (b) Gunnoe, T. B.; White, P. S.; Templeton,
J. L. Organometallics 1997, 16, 370.

Hydride-Carbyne to Carbene Transformation
Organometallics, Vol. 26, No. 8, 2007 2041
5.14 (s, 1H, dCH-), 2.43 (m, 6H, PCH), 1.79 (s, 3H, O2CCH3),
1.33 (dvt, N ) 14.1, JH-H ) 7.2, 18H, PCHCH3), 1.28 (dvt, N )
15.0, JH-H ) 7.2, 18H, PCHCH3), -7.80 (t, JH-P ) 15.7, 1H, OsH).
31P{1H} NMR (121.4 MHz, CD2Cl2, 293 K): δ 42.6 (s). 19F NMR
(282.3 MHz, CD2Cl2, 293 K): δ -153.6 (br). 13C{1H}-APT NMR
plus HMBC and HSQC (100.5 MHz, CD2Cl2, 293 K): δ 272.7 (t,
JC-P ) 8.0, OstC), 187.2 (t, JC-P ) 2.3, CdO), 162.6 (s, dCPh2),
139.2 and 137.9 (both s, Cipso-Ph), 132.5 (s, -CHd), 132.0, 130.3,
129.5, 129.4, 129.5, and 128.8 (all s, CHPh), 27.1 (vt, N ) 13.5,
PCH), 25.8 (s, O2CCH3), 19.5 and 19.2 (both s, PCHCH3).
Formation and Characterization of [OsH(κ1-O2CCH3)-
(CD3CN)(tCCHdCPh2)(PiPr3)2]BF4 (4). Complex 2 in acetoni-
trile-d3 gave an equilibrium mixture with 4. IR (CH3CN, cm-1):
ν(OsH) 2191 (m); νasym(OCO) 1639 (s); νsym(OCO) 1310 (s); ν-
(BF) 1105 (vs). Spectroscopy data for 4: 1H NMR (300 MHz, CD3-
CN, 233 K): δ 7.8-7.3 (m, 10H, Ph), 5.38 (s, 1H, dCH-), 2.33
to afford a yellow solid. Yield: 127 mg (88%). Anal. Calcd for
C39H63BF4N2O2OsP2: C 47.29; H 6.45; N 2.76. Found: C 47.56;
H 6.13; N 2.77. IR (Nujol, cm-1): ν(CtN) 2327 (w), 2273 (w);
ν
asym(OCO) 1611 (s); νsym(OCO) 1324 (s); ν(BF) 1056 (vs). MS:
m/z 846 [M + H]+, 685 [M - PiPr3]+, 603 [M - PiPr3 - 2CH3-
CN]+. H NMR (300 MHz, CD2Cl2, 233 K): δ 20.70 (d, JH-H
)
1
13.5, 1H, OsdCH), 7.99 (d, JH-H ) 13.5, 1H, -CHd), 7.9-7.1
(m, 10H, Ph), 3.14 and 2.93 (both s, 6H, CH3CN), 2.29 (m, 6H,
PCH), 2.03 (s, 3H, O2CCH3), 1.20 (m, 36H, PCHCH3). 31P{1H}
NMR (121.4 MHz, CD2Cl2, 233 K): δ 0.9 (s). 19F NMR (282.3
MHz, CD2Cl2, 293 K): δ -152.9 (br). 13C{1H}-APT NMR plus
HMBC and HSQC (75.4 MHz, CD2Cl2, 233 K): δ 259.5 (t, JC-P
) 8.7, OsdCH), 179.7 (s, CdO), 149.0 (s, -CHd), 142.3 and
142.1 (both s, Cipso-Ph), 140.6 (s, dCPh2), 129.7, 129.5, 128.5,
128.4, 127.7, and 127.6 (all s, CHPh), 123.7 and 123.2 (both s, CN),
25.3 (s, O2CCH3), 25.2 (vt, N ) 11.8, PCH), 19.1 and 18.8 (both
s, PCHCH3), 5.0 and 4.5 (both s, CH3CN).
(m, 6H, PCH), 1.70 (s, 3H, O2CCH3), 1.31 (dvt, N ) 13.9, JH-H
)
7.0, 18H, PCHCH3), 1.28 (dvt, N ) 13.9, JH-H ) 6.7, 18H,
PCHCH3), -5.7 (t, JH-P ) 17.1, 1H, OsH). 31P{1H} NMR (121.4
MHz, CD2Cl2, 293 K): δ 28.5 (s). 13C{1H}-APT NMR plus HMBC
and HSQC (75.4 MHz, CD3CN, 233 K): δ 268.5 (t, JC-P ) 10.6,
OstC), 173.9 (s, CdO), 162.8 (s, dCPh2), 139.7 and 138.9 (both
s, Cipso-Ph), 135.4 (s, -CHd), 132.2, 132.1, 131.4, 129.9, 129.8,
and 129.7 (all s, CHPh), 118.7 (s, CN), 27.7 (br, PCH), 24.3 (s,
O2CCH3), 20.1 and 18.9 (both s, PCHCH3), 1.24 (CH3CN).
Preparation of [Os(κ1-O2CCH3)(dCHCHdCPh2)(CH3CN)2-
(PiPr3)2]BF4 (5). A solution of [Os(dCHCHdCPh2)(CH3CN)3(Pi-
Pr3)2][BF4]2 (155 mg, 0.155 mmol) in 10 mL of 2-propanol was
treated with sodium acetate (107 mg, 0.775 mmol). After stirring
the mixture for 12 h at room temperature, the solvent was removed
in vacuo. Then, 10 mL of dichloromethane was added, the
suspension was filtered through Celite, and the filtrate was
evaporated to dryness. The residue was washed with diethyl ether
Acknowledgment. Financial support from the MCYT 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: X-ray analysis, compu-
tational details, determination of the rotational barrier of the carbene
ligand on complex 5, determination of thermodynamic parameters
for the equilibrium 2 to 4, orthogonal coordinates of theoretical
structures, and crystal structure determinations, including bond
lengths and angles of compounds 2 and 5. This material is available
free of charge via the Internet at http://pubs.acs.org.
OM0611655