Preparation and characterization of a monocyclopentadienyl osmium - Allenylcarbene complex

Article abstract of DOI:10.1021/om700722e

The dihydride-dihydrogen complex [OsH₂(η⁵-C ₅H₅)(η²-H₂)(PⁱPr ₃)]BF₄ (1) reacts with phenylacetylene to give the allenylcarbene derivative [Os(η⁵-C₅H ₅){=CPh(η²-CH=C=CHPh)}(PⁱPr ₃)]BF₄ (2) via the πr-phenylacetylene intermediate [Os(η⁵-C₅H₅)(η²-PhC=CH) (PⁱPr₃)]BF₄ (3). The reactions of 2 with NaOMe and LiC=CPh afford 3:1 mixtures of two hydride - osmaindene isomers of formula OsH(η⁵C₅H₅)(C(C=CPh)=CHC₆H ₄)(PⁱPr₃) (4 and 5) instead of the expected osmabenzyne complex.

Full text of DOI:10.1021/om700722e

Organometallics 2007, 26, 6009-6013
6009
Preparation and Characterization of a Monocyclopentadienyl
Osmium-Allenylcarbene Complex
Miguel A. Esteruelas,* Yohar A. Herna´ndez, Ana M. Lo´pez,* 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 July 19, 2007
The dihydride-dihydrogen complex [OsH2(η5-C5H5)(η2-H2)(PiPr3)]BF4 (1) reacts with phenylacetylene
to give the allenylcarbene derivative [Os(η5-C5H5){dCPh(η2-CHdCdCHPh)}(PiPr3)]BF4 (2) via the
π-phenylacetylene intermediate [Os(η5-C5H5)(η2-PhCtCH)(PiPr3)]BF4 (3). The reactions of 2 with
NaOMe and LiCtCPh afford 3:1 mixtures of two hydride-osmaindene isomers of formula OsH(η5-
C5H5){C(CtCPh)dCHC6H4}(PiPr3) (4 and 5) instead of the expected osmabenzyne complex.
Scheme 1
Introduction
The reactions of osmium hydride complexes with alkynes
afford a wide range of organometallic compounds. Their nature
depends on both the electronic structure of the starting materials
and the electronic character of the substituents of the alkynes.1
The dihydride-dihydrogen complex [OsH2(η5-C5H5)(η2-
H2)(PiPr3)]BF4 (1) reacts in acetone with 1-phenyl-1-propyne
and 2-butyne to give [OsH(η5-C5H5){κ4-(P,C,C,C)-CH2C-
[CH2C(dCH2)PiPr2]CHR}]BF4 (R ) Ph, CH3) derivatives (e
in Scheme 1), containing a γ-(η3-allyl)-R-alkenylphosphine.
These novel ligands are the result of one-pot dehydrogenative
additions of an isopropyl group of triisopropylphosphine to the
corresponding alkyne.2
These reactions are tandem processes of four steps (Scheme
1). The first of them involves the dissociation of a dihydrogen
ligand from the osmium atom of the starting compound and
the stabilization of the resulting unsaturated dihydride with a
solvent molecule to form [OsH2(η5-C5H5)(κ1-OCMe2)(PiPr3)]-
BF4 (a). During the second one, the displacement of the acetone
molecule by an alkyne and the subsequent reduction of the
hydrocarbon to give allyl derivatives b take place. The third
reaction generates isopropenyldi(isopropyl)phosphine species d
as a consequence of the elimination of Z-olefin from the allyl
intermediate and a hydrogen transfer from an isopropyl sub-
stituent of triisopropylphosphine to a second alkyne molecule
of an undetected species c.3 In the fourth step a third alkyne
displaces the coordinated olefin from the osmium atom, and it
is coupled with the isopropenyl group of the R-alkenylphos-
phine, to afford the γ-(η3-allyl)-R-alkenylphosphine derivatives
e through ene-type reactions via osmacyclopentene intermedi-
ates.4
consequence of this, they quench the third step of the tandem
process shown in Scheme 1. Thus, the treatment at 50 °C of
acetone solutions of 1 with 3.6 equiv of phenylacetylene
for 12 h leads to the allenylcarbene [Os(η5-C5H5){dCPh(η2-
CHdCdCHPh)}(PiPr3)]BF4 (2) instead of a γ-(η3-allyl)-R-
alkenylphosphine derivative. This compound is isolated as a
brown solid in 56% yield (eq 1).
The formation of 2 according to eq 1 is notable. Although
allenylcarbene complexes have been often proposed as key
intermediates for the metal-catalyzed polymerization of terminal
alkynes,6 very few examples of such species have been pre-
viously isolated.7 For osmium, Jia and co-workers8 have reported
Results and Discussion
Terminal alkynes, in contrast to 1-phenyl-1-propyne and 2-
butyne, have the capacity of forming vinylidene species.5 As a
* Corresponding authors. E-mail: maester@unizar.es; amlopez@unizar.es.
(1) (a) 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. (b) Esteruelas, M. A.; Oro, L. A. AdV. Organomet.
Chem. 2001, 47, 1. (c) Esteruelas, M. A.; Lo´pez, A. M. Organometallics
2005, 24, 3584. (d) Esteruelas, M. A.; Lo´pez, A. M.; Oliva´n, M. Coord.
Chem. ReV. 2007, 251, 795.
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On˜ate, E. Organometallics 2007, 26, 2193.
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P. Coord. Chem. ReV. 1999, 193-195, 977. (c) Katayama, H.; Ozawa, F.
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1996, 15, 4731. (b) Ru¨ba, E.; Mereiter, K.; Schmid, R.; Kirchner, K.;
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10.1021/om700722e CCC: $37.00 © 2007 American Chemical Society
Publication on Web 10/25/2007

6010 Organometallics, Vol. 26, No. 24, 2007
Esteruelas et al.
Figure 1. Molecular diagram of 2 (cations A (left) and B (right)), with thermal ellipsoids drawn at the 50% probability level.
respectively, whereas in the 13C{1H} NMR spectrum the three
Table 1. Selected Bond Distances (Å) and Angles (deg) for
Complex 2 and OsCl2{dCPh(η2-CHdCdCHPh)}(PPh3)2
Os-bound carbon signals are observed at 256.9 (C(10)), 142.2
(Jia’s Complex)
(C(1)), and 31.1 (C(9)) ppm. A singlet at 22.2 ppm in the 31P-
cation A
Jia’s complexa
{1H} NMR spectrum is also characteristic of this compound.
The formation of 2 can be rationalized according to Scheme
2. As in the reactions with 1-phenyl-1-propyne and 2-butyne,
the dissociation of a dihydrogen ligand from the starting complex
should afford a. This dihydride-solvento compound could
undergo abstraction of the hydride ligands by action of an alkyne
molecule. The reaction should lead to styrene and a highly
unsaturated metal fragment, which could coordinate an alkyne
molecule to give [Os(η5-C5H5)(η2-PhCtCH)(PiPr3)]BF4 (3).
This species is the phenylacetylene counterpart to those proposed
as intermediates for the formation of complexes e by reaction
of the allyls b with a second molecule of internal alkyne (c in
Scheme 1). In contrast to 1-phenyl-1-propyne and 2-butyne,
where the coordinated alkyne is displaced by Z-CH(CH3)dCHR
or is reduced by the phosphine, intermediate 3 should coordinate
a new phenylacetylene molecule, now as vinylidene, to give f.
Thus, this vinylidene-π-alkyne species could generate 2 via a
Os-C(1)
2.015(16)
2.185(11)
1.962(15)
1.313(18)
1.420(17)
1.419(17)
115.7(10)
74.4(6)
2.067(11)
2.167(11)
1.894(9)
1.316(16)
1.441(15)
1.437(15)
115.9(10)
75.9(4)
Os-C(9)
Os-C(10)
C(1)-C(2)
C(1)-C(9)
C(9)-C(10)
C(1)-C(9)-C(10)
C(1)-Os-C(10)
C(2)-C(1)-C(9)
134.6(13)
139.5(11)
a From ref 8b.
that reaction of the vinylidene starting compound OsCl2(dCd
CHPh)(PPh3)2 with phenylacetylene affords the bisphosphine
derivative OsCl2{dCPh(η2-CHdCdCHPh)}(PPh3)2. Complex
2 is the first example of a monocyclopentadienyl-osmium
compound with an allenylcarbene ligand.
The allenylcarbene derivative 2 was characterized by elemen-
tal analysis, MS, IR, and 1H, 13C{1H}, and 31P{1H} NMR
spectroscopy. Furthermore, its structure was confirmed by X-ray
diffraction analysis. The unit cell contains disordered cations
A and B occupying two alternative orientations in the same
region, each showing the stereochemistry illustrated in Figure
1 with approximate occupancy factors of 57% (enantiomer A)
and 43% (enantiomer B) (see Supporting Information). The
Os-C and C-C distances within the Os-allenylcarbene unit
compare well with those previously reported for Jia’s complex
OsCl2{dCPh(η2-CHdCdCHPh)}(PPh3)2 (Table 1). The Os-
C(10) bond length of 1.962(15) Å supports the Os-C double-
bond formulation.9 The Os-C(9) (2.185(11) Å) and Os-C(1)
(2.015(16) Å) distances agree with those found in osmium-
olefin complexes,10 whereas the C(9)-C(1) bond length (1.420-
(17) Å) lies within the range reported for olefin-transition-
metal derivatives (1.340-1.455 Å).11 The C(9)-C(10) distance
of 1.419(17) Å is similar to the C(1)-C(9) bond length,
indicating the presence of substantial π-electron delocalization
within the Os-C(10)-C(9)-C(1) metallacycle.
(9) (a) Brumaghim, J. L.; Girolami, G. S. Chem. Commun. 1999, 953.
(b) Werner, H.; Stu¨er, W.; Wolf, J.; Laubender, M.; Weberndo¨rfer, B.;
Herbst-Irmer, R.; Lehmann, C. Eur. J. Inorg. Chem. 1999, 1889. (c)
Castarlenas, R.; Esteruelas, M. A.; On˜ate, E. Organometallics 2001, 20,
2294. (d) Gusev, D. G.; Lough, A. J. Organometallics 2002, 21, 2601. (e)
Weberndo¨rfer, B.; Henig, G.; Hockless, D. C. R.; Bennett, M. A.; Werner,
H. Organometallics 2003, 22, 744. (f) Esteruelas, M. A.; Gonza´lez, A. I.;
Lo´pez, A. M.; On˜ate, E. Organometallics 2004, 23, 4858. (g) Castarlenas,
R.; Esteruelas, M. A.; On˜ate, E. Organometallics 2005, 24, 4343. (h) Bolan˜o,
T.; Castarlenas, R.; Esteruelas, M. A.; Modrego, F. J.; On˜ate, E. J. Am.
Chem. Soc. 2005, 127, 11184. (i) Esteruelas, M. A.; Ferna´ndez-Alvarez, F.
J.; Oliva´n, M.; On˜ate, E. J. Am. Chem. Soc. 2006, 128, 4596. (j) Bolan˜o,
T.; Castarlenas, R.; Esteruelas, M. A.; On˜ate, E. Organometallics 2007,
26, 2037. (k) Castarlenas, R.; Esteruelas, M. A.; On˜ate, E. Organometallics
2007, 26, 2129. (l) Castarlenas, R.; Esteruelas, M. A.; On˜ate, E. Organo-
metallics 2007, 26, 3082. (m) Esteruelas, M. A.; Lo´pez, A. M.; On˜ate, E.
Organometallics 2007, 26, 3260.
(10) (a) Johnson, T. J.; Albinati, A.; Koetzle, T. F.; Ricci, J.; Eisenstein,
O.; Huffman, J. C.; Caulton, K. G. Inorg. Chem. 1994, 33, 4966. (b)
Edwards, A. J.; Elipe, S.; Esteruelas, M. A.; Lahoz, F. J.; Oro, L. A.; Valero,
C. Organometallics 1997, 16, 3828. (c) Buil, M. L.; Esteruelas, M. A.;
Garc´ıa-Yebra, C.; Gutie´rrez-Puebla, E.; Oliva´n, M. Organometallics 2000,
19, 2184. (d) Esteruelas, M. A.; Garc´ıa-Yebra, C.; Oliva´n, M.; On˜ate, E.
Organometallics 2000, 19, 3260. (e) Baya, M.; Esteruelas, M. A.; On˜ate,
E. Organometallics 2002, 21, 5681. (f) Esteruelas, M. A.; Gonza´lez, A. I.;
Lo´pez, A. M.; On˜ate, E. Organometallics 2003, 22, 414. (g) Esteruelas,
M. A.; Lledo´s, A.; Maseras, F.; Oliva´n, M.; On˜ate, E.; Tajada, M. A.; Toma`s,
J. Organometallics 2003, 22, 2087. (h) Barrio, P.; Esteruelas, M. A.; On˜ate,
E. Organometallics 2003, 22, 2472. (i) Barrio, P.; Esteruelas, M. A.; On˜ate,
E. Organometallics 2004, 23, 3627. (j) Baya, M.; Buil, M. L.; Esteruelas,
M. A.; On˜ate, E. Organometallics 2005, 24, 5180. (k) Esteruelas, M. A.;
Garc´ıa-Yebra, C.; Oliva´n, M.; On˜ate, E. Inorg. Chem. 2006, 45, 10162.
(11) Allen, F. H.; Davies, J. E.; Galloy, J. J.; Johnson, O.; Kennard, O.;
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G. J. Chem. Inf. Comput. Sci. 1991, 31, 187.
1
The H and 13C{1H} NMR spectra of 2 are consistent with
the structures shown in Figure 1. In the 1H NMR spectrum, the
C(9)-H and C(2)-H resonances appear at 3.34 and 6.76 ppm,
(8) (a) Jia, G. Acc. Chem. Res. 2004, 37, 479. (b) Wen, T. B.; Hung, W.
Y.; Sung, H. H. Y.; Williams, I. D.; Jia, G. J. Am. Chem. Soc. 2005, 127,
2856. (c) 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. (d)
Wen, T. B.; Hung, W. Y.; Sung, H. H.-Y.; Zhou, Z.; Williams, I. D.; Jia,
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251, 2167.

Monocyclopentadienyl Osmium-Allenylcarbene Complex
Organometallics, Vol. 26, No. 24, 2007 6011
Scheme 2
Scheme 3
[2+2] cycloaddition reaction between the C-C triple bond of
the alkyne and the Os-C vinylidene double bond. We note that
Grubbs has previously reported a related process on a ruthenium-
carbene complex, which yields a η3-vinylcarbene derivative.12
Tungsten-η3-vinylcarbene complexes have also been formed
from carbene intermediates upon addition of phenylacetylene.13
A molybdenum η3-iminiumvinylcarbene complex has been ob-
tained via intramolecular reaction of an iminocarbene intermedi-
ate with diphenylacetylene.14 Both the fact that styrene cannot
form an allyl ligand related to those of b and the trend of
phenylacetylene to afford vinylidene complexes can explain the
difference in behavior between the internal and terminal alkynes.
The proposal summarized in Scheme 2 is strongly supported
by the reaction of a with 2.0 equiv of phenylacetylene, in
dichloromethane at 0 °C. Under these conditions, in addition
to styrene, a mixture of the starting dihydride a, 3, and 2 in a
1:5:1 molar ratio is formed after 30 min. As expected the treat-
ment of the mixture with a third alkyne molecule affords 2.
Complex 3 is the first member of the novel [Os(η5-C5H5)-
(η2-RCtCH)(PiPr3)]+ series where the π-alkyne is not an
CHPh)}(PPh3)2 reacts with phenylacetylene in the presence of
triethylamine and with PPh3AuCtCPh in the presence of
[HNEt3]Cl to give, in both cases, the osmabenzyne derivative
OsCl2{tC-C(Ph)dC(CH2Ph)-CHdC(Ph)}(PPh3)2.8b Under
the same conditions, complex 2 affords a 3:1 mixture of two
hydride-osmaindene stereoisomers of formula OsH(η5-C5H5)-
{C(CtCPh)dCHC6H4}(PiPr3) (4 and 5 in Scheme 3), which
are also obtained by treatment of 2 with LiCtCPh or NaOMe
in tetrahydrofuran. The deprotonation is reversible. The addition
of 1.0 equiv of HBF4‚Et2O to a dichloromethane solution of 4
and 5 regenerates 2.
In agreement with the presence of a hydride ligand in 4 and
1
5, the H NMR spectrum of the isomeric mixture in benzene-
d6 at 20 °C shows two doublets at -13.48 (4) and -13.55 (5)
ppm, with H-P coupling constants of 44.9 and 46.7 Hz,
respectively, which support the cisoid disposition of the hydride
and phosphine ligands.18 In the low-field region of the spectrum,
1
alkynol.15 The H and 13C{1H} NMR spectra strongly support
the presence of a π-alkyne group acting as a four-electron donor
the most noticeable resonances are a doublet at 8.03 (JH-P
)
1
ligand16 in the complex. In the H NMR spectrum the most
3.4 Hz; 4) and a singlet at 8.13 (5) ppm, corresponding to the
Câ-H hydrogen atoms of the alkenyl units of the metallacycles.
In the 13C{1H} NMR spectrum, the resonances due to the alkenyl
carbon atoms of 4 appear at 157.0 (Câ) and 119.2 (CR) ppm as
doublets with C-P coupling constants of 4 and 16 Hz,
respectively, which support the cisoid disposition of the phos-
phine to this alkenyl unit.19 The metalated carbon atom of the
phenyl group gives rise to a doublet at 152.7 ppm with a C-P
coupling constant of 4 Hz. The resonances due to the alkenyl
carbon atoms of 5 are observed at 151.6 (Câ) and 127.1 (CR) as
doublets. The values of the C-P coupling constants of 2 and 6
Hz, respectively, are consistent with a transoid disposition
between the phosphine and the alkenyl unit. For this isomer,
the resonance corresponding to the metalated carbon atom of
the phenyl group appears at 145.3 ppm as a doublet with a C-P
coupling constant of 16 Hz. The 31P{1H} NMR spectrum shows
singlets at 18.3 (4) and 18.4 (5) ppm. These spectroscopic data
noticeable resonance is that corresponding to the C(sp)-H
proton, which appears at 10.35 ppm as a doublet with a H-P
coupling constant of 27.8 Hz. In accordance with the chemical
shifts found for other osmium complexes where the alkyne also
acts as a four-electron donor ligand,10h,15,17 the acetylenic reson-
ances in the 13C{1H} NMR spectrum are observed at 167.2
(CPh) and 149.7 (CH) ppm as doublets with C-P coupling
constants of 3 and 19 Hz, respectively. A singlet at 19.7 ppm
in the 31P{1H} NMR spectrum is also characteristic of this
compound.
There is a marked difference in behavior between Jia’s
allenylcarbene and 2. Complex OsCl2{dCPh(η2-CHdCd
(12) Trnka, T. M.; Day, M. W.; Grubbs, R. H. Organometallics 2001,
20, 3845.
(13) Stone, K. C.; Jamison, G. M.; White, P. S.; Templeton, J. L.
Organometallics 2003, 22, 3083.
(14) Adams, C. J.; Anderson, K. M.; Bartlett, I. M.; Connelly, N. G.;
Orpen, A. G.; Paget, T. J. Organometallics 2002, 21, 3454.
(15) Carbo´, J. J.; Crochet, P.; Esteruelas, M. A.; Jean, Y.; Lledo´s, A.;
Lo´pez, A. M.; On˜ate, E. Organometallics 2002, 21, 305.
(16) (a) Templeton, J. L. AdV. Organomet. Chem. 1989, 29, 1, and
references therein. (b) Baker, P. K. AdV. Organomet. Chem. 1996, 40, 45,
and references therein. (c) Frohnapfel, D. S.; Reinartz, S.; White, P. S.;
Templeton, J. L. Organometallics 1998, 17, 3759. (d) Frohnapfel, D. S.;
Enriquez, A. E.; Templeton, J. L. Organometallics 2000, 19, 221.
(17) (a) Espuelas, J.; Esteruelas, M. A.; Lahoz, F. J.; Lo´pez, A. M.; Oro,
L. A.; Valero, C. J. Organomet. Chem. 1994, 468, 223. (b) Bolan˜o, T.;
Castarlenas, R.; Esteruelas, M. A.; On˜ate, E. J. Am. Chem. Soc. 2006, 128,
3965.
(18) See for example: (a) Esteruelas, M. A.; Gutie´rrez-Puebla, E.; Lo´pez,
A. M.; On˜ate, E.; Tolosa, J. I. Organometallics 2000, 19, 275. (b) Baya,
M.; Crochet, P.; Esteruelas, M. A.; On˜ate, E. Organometallics 2001, 20,
240. (c) Esteruelas, M. A.; Lo´pez, A. M.; On˜ate, E.; Royo, E. Organome-
tallics 2004, 23, 3021. (d) Esteruelas, M. A.; Lo´pez, A. M.; On˜ate, E.;
Royo, E. Organometallics 2004, 23, 5633. (e) Baya, M.; Esteruelas, M.
A.; Gonza´lez, A. I.; Lo´pez, A. M.; On˜ate, E. Organometallics 2005, 24,
1225. (f) Esteruelas, M. A.; Lo´pez, A. M.; On˜ate, E.; Royo, E. Inorg. Chem.
2005, 44, 4094. (g) Esteruelas, M. A.; Lo´pez, A. M.; On˜ate, E.; Royo, E.
Organometallics 2005, 24, 5780.
(19) Baya, M.; Esteruelas, M. A. Organometallics 2002, 21, 2332.

6012 Organometallics, Vol. 26, No. 24, 2007
Esteruelas et al.
which was separated by decantation, washed with pentane, and dried
in vacuo. The residue was recrystallized from acetone/diethyl ether.
Yield: 235 mg (56%).
agree well with those previously reported for the related complex
OsH(η5-C5H4SiPh3){CHdC(CH3)C6H4}(PiPr3), where the os-
maindene nature of the metallabicycle has been stablished by
X-ray diffraction analysis.20
Method b. A solution of a (202 mg, 0.36 mmol) in 4 mL of
dichloromethane was treated with phenylacetylene (140 µL, 1.28
mmol). The solution was allowed to react for 30 min at room
temperature, and then, it was concentrated to ca. 1 mL under
reduced pressure. The addition of diethyl ether caused the formation
of a brown solid, which was separated by decantation, washed with
pentane, and dried in vacuo. The solid was redissolved in dichlo-
romethane, and the solution was allowed to react for 30 min at 50
°C. Then, it was concentrated to ca. 1 mL under reduced pressure.
The addition of diethyl ether caused the formation of a brown solid,
which was separated by decantation, washed with pentane, and dried
in vacuo. Yield: 208 mg (82%). GC-MS and 1H NMR analysis of
the mother liquor showed the presence of styrene. Anal. Calcd for
C30H38BF4OsP: C, 50.99; H, 5.42. Found: C, 50.53; H, 5.17. IR
The formation of 4 and 5 instead of an osmabenzyne
derivative appears to be a consequence of the electronic nature
of the metal fragment [Os(η5-C5H5)(PiPr3)]+, which decreases
the pKa of the allenylcarbene ligand with regard to that
coordinated to OsCl2(PPh3)2. The deprotonation of the C(9)
carbon atom of 2 should generate a buta-1,2,3-trien-4-yl ligand,
which could undergo rearrangement into but-1-en-3-yn-2-yl by
a 1,3-shift of the metal (Scheme 3). The equilibrium between
both types of isomers has been proposed as the key step for the
dimerization of terminal alkynes to butatrienes.21 The subsequent
ortho-CH bond activation of the phenyl substituent of the alkenyl
unit of the resulting intermediate h should afford 4 and 5.
The participation of h is strongly supported by the fact that
the isomeric mixture is also formed from the treatment of the
vinylidene complex Os(η5-C5H5)Cl(dCdCHPh)(PiPr3) (6) with
LiCtCPh in tetrahydrofuran, in agreement with our previous
observation that 6 reacts with RMgCl to give the osmaindene
1
(ATR, cm-1): ν(Ph) 1588 (w). H NMR (400 MHz, (CD3)2CO,
298 K): δ 8.65 (d, JH-H ) 7.8, 2H, Ph), 8.11 (t, JH-H ) 7.8, 1H,
Ph), 7.73 (t, JH-H ) 7.8, 2H, Ph), 7.67 (d, JH-H ) 7.8, 2H, Ph),
7.47 (t, JH-H ) 7.8, 2H, Ph), 7.24 (t, JH-H ) 7.8, 1H, Ph), 6.76
(dd, JH-P ) 2.5, JH-H ) 2.5, 1H, )CHPh), 6.09 (s, 5H, C5H5),
3.34 (dd, JH-P ) 2.5, JH-H ) 2.5, 1H, η2-CHdC), 2.68 (m, 3H,
PCH), 1.18 (dd, JH-P ) 15.2, JH-H ) 7.1, 9H, PCHCH3), 1.07
(dd, JH-P ) 14.9, JH-H ) 7.1, 9H, PCHCH3). 31P{1H} NMR (161.99
MHz, (CD3)2CO, 298 K): δ 22.2 (s). 13C{1H} NMR (100.56 MHz,
derivatives OsH(η5-C5H5){C(R)dCHC6H4}(PiPr3) (R ) Me, Et,
Ph) via Os(η5-C5H5){C(R)dCHPh}(PiPr3) intermediates22 re-
lated to h (R ) CtCPh).
(CD3)2CO, 298 K): δ 256.9 (d, JC-P ) 7, OsdCPh), 144.5 (s, Cipso
-
Ph), 142.2 (d, JC-P ) 13, η2-CHdC) 137.8 (s, CipsoPh), 137.3, 136.4,
132.9, 130.4, and 129.2 (all s, Ph), 128.9 (d, JC-P ) 2, dCHPh)
In conclusion, in contrast to 1-phenyl-1-propyne and 2-butyne,
phenylacetylene reacts with the dihydride-dihydrogen complex
[OsH2(η5-C5H5)(η2-H2)(PiPr3)]BF4 to afford an allenylcarbene
derivative via a π-phenylacetylene intermediate, where the
alkyne acts as a four-electron-donor ligand. This novel com-
pound, which is the first monocyclopentadienyl osmium com-
plex with an allenylcarbene group, undergoes deprotonation in
the presence of LiCtCPh to generate a mixture of hydride-
osmaindene isomers instead of giving an osmabenzyne, as is
done by Jia’s previously reported allenylcarbene complex.
128.5 (s, Ph), 89.0 (s, C5H5), 31.1 (s, η2-CHdC), 31.1 (d, JC-P
30, PCH), 21.1 (s, PCHCH3), 20.7 (d, JC-P ) 2, PCHCH3). MS
)
(MALDI-TOF): m/z 621.3 (M+).
Reaction of a with Phenylacetylene: Formation of [Os(η5-
C5H5)(η2-HCtCPh)(PiPr3)]BF4 (3). A solution of a (152 mg, 0.27
mmol) in 4 mL of dichloromethane was cooled to 0 °C, and then,
phenylacetylene (75 µL, 0.68 mmol) was added. The reaction
mixture was stirred for 30 min. After that, the solution was
concentrated to ca. 1 mL under reduced pressure. The resultant
brown solution was cooled to -70 °C, and diethyl ether was added.
Immediately, a brown solid appeared, which was separated by
decantation, washed with pentane, and dried in vacuo. The NMR
spectra showed the presence of a, 3, and 2 in a 1:5:1 molar ratio.
Spectroscopic data for 3: 1H NMR (500 MHz, CD2Cl2, 293 K): δ
10.35 (d, JH-P ) 27.8, 1H, tC-H), 7.75-7.60 (m, 5H, Ph), 5.34
Experimental Section
General Procedures. All reactions were carried out under argon
with rigorous exclusion of air using Schlenk-tube or glovebox
techniques. Solvents were dried by the usual procedures and distilled
under argon prior to use. The starting materials, 1,23 a,2 and 6,24
were prepared by the published methods. In the NMR spectra
chemical shifts (expressed in ppm) are referenced to residual solvent
peaks (1H, 13C) or external H3PO4 (31P). Coupling constants, J, are
given in hertz.
Preparation of [Os(η5-C5H5){dCPh(η2-CHdCdCHPh)}-
(PiPr3)]BF4 (2). Method a. A solution of 1 (300 mg, 0.59 mmol)
in 4 mL of acetone was treated with phenylacetylene (233 µL, 2.12
mmol). The solution was allowed to react for 12 h at 50 °C, and
then, it was concentrated to ca. 1 mL under reduced pressure. The
addition of diethyl ether caused the formation of a brown solid,
(s, 5H, C5H5), 2.84 (m, 3H, PCH), 1.14 (dd, JH-P ) 14.2, JH-H
)
7.1, 18H, PCHCH3). 31P{1H} NMR (121.49 MHz, CD2Cl2, 243
K): δ 38.3 (s). 13C{1H} NMR (75.47 MHz, CD2Cl2, 243 K): δ
167.2 (d, JC-P ) 3, tCPh), 149.7 (d, JC-P ) 19, tCH) 134.3 (s,
CipsoPh), 132.2, 131.5, and 129.6 (all s, Ph), 76.9 (s, C5H5), 28.1
(d, JC-P ) 34, PCH), 19.7 (s, PCHCH3). HRMS m/z 519.182057
(M+), calcd for [C22H32OsP]+: 519.185156.
Preparation of OsH(η5-C5H5){C(CtCPh)dCHC6H4}(PiPr3)
(4 and 5). Method a. THF (5 mL) was added to a mixture of 180
mg (0.26 mmol) of 2 and NaOMe (20 mg, 0.37 mmol) or LiCt
CPh (32 mg, 0.30 mmol). The solution was allowed to react for 12
h at room temperature. Then, the solvent was removed, and the
crude reaction mixture was extracted with pentane and filtered
through Celite. The solution was concentrated to dryness, and a
dark brown solid was obtained. The NMR spectra in C6D6 at room
temperature showed the presence of 4 and 5 in a molar ratio of
3:1. Yield of the mixture: 113 mg (72%).
Method b. The same procedure described in method a was
followed, except that 6 (710 mg, 1.28 mmol) and LiCtCPh (138
mg, 1.28 mmol) were used. Yield: 505 mg (64%). IR (ATR, cm-1):
ν(OsH) and ν(CtC) 2157 (m), 2092 (w), ν(Ph) 1594 (m).
Spectroscopic data for 4: 1H NMR (400 MHz, C6D6, 293 K): δ
8.07 (d, JH-H ) 7.5, 1H, C6H4), 8.03 (d, JH-P ) 3.4, 1H, dCH),
(20) Baya, M.; Esteruelas, M. A.; On˜ate, E. Organometallics 2001, 20,
4875.
(21) (a) Wakatsuki, Y.; Yamazaki, H.; Kumegawa, N.; Satoh, T.; Satoh,
J. Y. J. Am. Chem. Soc. 1991, 113, 9604. (b) Heeres, H. J.; Nijhoff, J.;
Teuben, J. H.; Rogers, R. D. Organometallics 1993, 12, 2609. (c) Ohmura,
T.; Yorozuya, S.; Yamamoto, Y.; Miyaura, N. Organometallics 2000, 19,
365. (d) Esteruelas, M. A.; Herrero, J.; Lo´pez, A. M.; Oliva´n, M.
Organometallics 2001, 20, 3202. (e) Scha¨fer, M.; Wolf, J.; Werner, H.
Dalton Trans. 2005, 1468.
(22) Esteruelas, M. A.; Gonza´lez, A. I.; Lo´pez, A. M.; Oliva´n, M.; On˜ate,
E. Organometallics 2006, 25, 693.
(23) Esteruelas, M. A.; Herna´ndez, Y. A.; Lo´pez, A. M.; Oliva´n, M.;
On˜ate, E. Organometallics 2005, 24, 5989.
(24) Esteruelas, M. A.; Lo´pez, A. M.; Ruiz, N.; Tolosa, J. I. Organo-
metallics 1997, 16, 4657.

Monocyclopentadienyl Osmium-Allenylcarbene Complex
Organometallics, Vol. 26, No. 24, 2007 6013
7.65-7.52 (m, 3H, 1H for C6H4 and 2H for Ph), 7.15-7.00 (m,
4H, 1H for C6H4 and 3H for Ph), 6.87 (t, JH-H ) 7.5, 1H, C6H4),
4.81 (s, 5H, C5H5), 2.31 (m, 3H, PCH), 0.90 (dd, JH-P ) 14.2,
JH-H ) 7.0, 9H, PCHCH3), 0.77 (dd, JH-P ) 12.6, JH-H ) 7.1,
9H, PCHCH3), -13.48 (d, JH-P ) 44.9, 1H, Os-H). 31P{1H} NMR
(161.99 MHz, C6D6, 293 K): δ 18.3 (s). 13C{1H} NMR (100.56
MHz, C6D6, 293 K): δ 160.8 (d, JC-P ) 3, CipsoC6H4), 157.0 (d,
JC-P ) 4, dCH), 152.7 (d, JC-P ) 4, CR in Os-C6H4), 146.4 (s,
C6H4), 131.4, 128.6, and 126.7 (all s, Ph), 124.3, 123.1, and 122.4
K): δ 163.0 (d, JC-P ) 2, CipsoC6H4), 151.6 (d, JC-P ) 2, dCH),
145.3 (d, JC-P ) 16, CR in Os-C6H4), 143.3 (d, JC-P ) 3, C6H4),
131.4 and 128.5 (both s, Ph), 127.1 (d, JC-P ) 6, Os-C(Ct)),
126.7 (s, Ph), 123.5 and 123.0 (both d, JC-P ) 2, C6H4), 121.3 (s,
C6H4), 107.0 (s, Os-C(Ct)), 92.9 (s, tC-Ph), 83.4 (d, JC-P ) 2,
C5H5), 27.5 (d, JC-P ) 30, PCH), 20.7 (s, PCHCH3), 18.7 (d, JC-P
) 3, PCHCH3). CipsoPh could not be assigned. HRMS m/z
621.229558 (M+ + H), calcd for [C30H38OsP]+: 621.232160.
(all s, C6H4), 119.2 (d, JC-P ) 16, Os-C(Ct)), 104.7 (d, JC-P
)
Acknowledgment. Financial support from the MEC of Spain
(Projects CTQ2005-00656 and Consolider Ingenio 2010
CSD2007-00006)) and Diputacio´n General de Arago´n (E35) is
acknowledged. Y.A.H. thanks the Spanish MEC for his grant.
3, Os-C(Ct)), 92.9 (s, tC-Ph), 84.1 (d, JC-P ) 2, C5H5), 28.9
(d, JC-P ) 30, PCH), 21.1 (s, PCHCH3), 19.0 (d, JC-P ) 3,
PCHCH3). CipsoPh could not be assigned. Spectroscopic data for
5: 1H NMR (400 MHz, C6D6, 293 K): δ 8.13 (s, 1H, dCH), 7.65-
7.52 (m, 4H, 2H for C6H4 and 2H for Ph), 7.15-7.00 (m, 4H, 1H
for C6H4 and 3H for Ph), 6.84 (t, JH-H ) 7.6, 1H, C6H4), 4.89 (s,
5H, C5H5), 2.13 (m, 3H, PCH), 0.86 (dd, JH-P ) 14.0, JH-H ) 7.2,
9H, PCHCH3), 0.64 (dd, JH-P ) 12.4, JH-H ) 7.1, 9H, PCHCH3),
-13.55 (d, JH-P ) 46.7, 1H, Os-H). 31P{1H} NMR (161.99 MHz,
C6D6, 293 K): δ 18.4 (s). 13C{1H} NMR (100.56 MHz, C6D6, 293
Supporting Information Available: Crystal structure deter-
mination and CIF file giving crystal data for compound 2. This
material is available free of charge via the Internet at http:
//pubs.acs.org.
OM700722E