Reduction and C(sp2)-H bond activation of ketones promoted by a cyclopentadienyl-osmium-dihydride-dihydrogen complex

Article abstract of DOI:10.1021/om0508177

The dihydride-dihydrogen complex [OsH₂(η⁵-C ₅H₅)(η²-H₂)(PⁱPr ₃)]BF₄ (2) has been prepared by addition of HBF ₄·OEt₂ to OsH₃H₃(η ⁵-C₅H₅)(PⁱPr₃) (1), and its reactions with benzylideneacetone, methyl vinyl ketone, acetophenone, and benzylideneacetophenone have been studied. The reaction with benzylideneacetone leads initially to [OsH₂(η⁵-C₅H ₅){κ¹-OC(CH₃)CH=CHPh}-(P ⁱPr₃)]BF₄ (3), which in dichloromethane is converted to the hydroxyallyl derivative [OsH-(η⁵-C ₅H₅){η³-CH₂C(OH)CHCH ₂Ph}(PⁱPr₃)]BF₄ (4). Complex 4 releases 4-phenylbutan-2-one, and the resulting metallic fragment activates a C_β(sp²)-H bond of a new molecule of benzylideneacetone to give [OsH(η⁵-C₅H ₅){C(Ph)CHC(O)CH₃}(PⁱPr₃)]BF ₄ (5), which affords Os(η⁵-C₅H ₅){C(Ph)CHC(O)CH₃}(PⁱPr₃) (6) by deprotonation with NaOCH₃. The reaction of 2 with methyl vinyl ketone gives ethyl methyl ketone and [OsH(η⁵-C₅H ₅){CHCHC(O)-CH₃}(PⁱPr₃)]BF ₄ (9). The latter can also be obtained from Os(η⁵- C₅H₅)Cl{η²-CH₂=CHC(O)-CH ₃(PⁱPr₃) (7) via the intermediate [Os(η⁵-C₅H₅){CH₂CHC(O)CH ₃}(PⁱPr₃)]BF₄ (8). Treatment of 9 with NaOCH₃ leads to an equilibrium mixture of Os(η⁵- C₅H₅){CHCHC(O)CH₃}-(PⁱPr ₃) (10) and the hydride-vinylidene OsH(η⁵-C ₅H₅){=C=CHC(O)CH3}(PⁱPr₃) (11). The reaction of 2 with acetophenone gives 1-phenylethanol and the orthometalated derivative [OsH(η⁵-C₅H₅){C ₆H₄C(O)CH₃}(PⁱPr₃)] BF₄ (13), which is deprotonated with NaOCH₃ to give Os(η⁵-C₅H₅){C₆H ₄C(O)CH₃ (14), while the reaction of 2 with benzylideneacetophenone leads to [OsH(η⁵-C₅H ₅){C(Ph)CHC(O)Ph}(PⁱPr₃)]BF₄ (15), which yields Os(η⁵-C₅H₅){C(Ph)CHC(O)Ph} (PⁱPr₃) (16) by deprotonation. Complexes 3, 10, and 13 have been characterized by X-ray diffraction analysis.

Full text of DOI:10.1021/om0508177

Organometallics 2005, 24, 5989-6000
5989
Reduction and C(sp2)-H Bond Activation of Ketones
Promoted by a Cyclopentadienyl-Osmium-
Dihydride-Dihydrogen Complex
Miguel A. Esteruelas,* Yohar A. Herna´ndez, Ana M. Lo´pez,*
Montserrat Oliva´n, and Enrique On˜ate
Departamento de Quı´mica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n,
Universidad de Zaragoza-CSIC, 50009 Zaragoza, Spain
Received September 21, 2005
The dihydride-dihydrogen complex [OsH2(η5-C5H5)(η2-H2)(PiPr3)]BF4 (2) has been prepared
by addition of HBF4‚OEt2 to OsH3(η5-C5H5)(PiPr3) (1), and its reactions with benzylidene-
acetone, methyl vinyl ketone, acetophenone, and benzylideneacetophenone have been studied.
The reaction with benzylideneacetone leads initially to [OsH2(η5-C5H5){κ1-OC(CH3)CHdCHPh}-
(PiPr3)]BF4 (3), which in dichloromethane is converted to the hydroxyallyl derivative [OsH-
(η5-C5H5){η3-CH2C(OH)CHCH2Ph}(PiPr3)]BF4 (4). Complex 4 releases 4-phenylbutan-2-one,
and the resulting metallic fragment activates a Câ(sp2)-H bond of a new molecule of
benzylideneacetone to give [OsH(η5-C5H5){C(Ph)CHC(O)CH3}(PiPr3)]BF4 (5), which affords
Os(η5-C5H5){C(Ph)CHC(O)CH3}(PiPr3) (6) by deprotonation with NaOCH3. The reaction
of 2 with methyl vinyl ketone gives ethyl methyl ketone and [OsH(η5-C5H5){CHCHC(O)-
CH3}(PiPr3)]BF4 (9). The latter can also be obtained from Os(η5-C5H5)Cl{η2-CH2dCHC(O)-
CH3}(PiPr3) (7) via the intermediate [Os(η5-C5H5){CH2CHC(O)CH3}(PiPr3)]BF4 (8). Treat-
ment of 9 with NaOCH3 leads to an equilibrium mixture of Os(η5-C5H5){CHCHC(O)CH3}-
(PiPr3) (10) and the hydride-vinylidene OsH(η5-C5H5){dCdCHC(O)CH3}(PiPr3) (11). The
reaction of 2 with acetophenone gives 1-phenylethanol and the orthometalated deriva-
tive [OsH(η5-C5H5){C6H4C(O)CH3}(PiPr3)]BF4 (13), which is deprotonated with NaOCH3
to give Os(η5-C5H5){C6H4C(O)CH3}(PiPr3) (14), while the reaction of 2 with benzylidene-
acetophenone leads to [OsH(η5-C5H5){C(Ph)CHC(O)Ph}(PiPr3)]BF4 (15), which yields
Os(η5-C5H5){C(Ph)CHC(O)Ph}(PiPr3) (16) by deprotonation. Complexes 3, 10, and 13 have
been characterized by X-ray diffraction analysis.
Introduction
as the key step to the selective formation of the
saturated ketone, while the coordination of the oxygen
atom is thought to be determinant to the hydrogenation
of the carbonyl group (Scheme 1).3 Thus, the selectivity
in the reduction of this type of compounds has been
mainly associated with the steric crowding around the
metal center of the catalyst. In both cases the direct
addition of two hydrogen atoms to the double bond is
proposed to occur.4
A large part of the reactions involving dihydrogen
compounds proceed by loss of molecular hydrogen.1 The
weak binding of the H2 molecule to transition metals
makes this ligand a good leaving group, which stabilizes
unsaturated species without hindering the coordination
of substrates to the metal centers. Several catalytic
systems for the reduction of ketones and R,â-unsatur-
ated ketones, by both hydrogenation and hydrogen
transfer, are based upon this strategy.2
The activation of C(sp2)-H bonds by transition-metal
compounds is another reaction of great importance,5 due
The coordination of the C-C double bond of R,â-
unsaturated ketones to the catalyst has been proposed
(2) (a) Sa´nchez-Delgado, R. A.; Rosales, M.; Esteruelas, M. A.; Oro,
L. A. J. Mol. Catal. A: Chem. 1995, 96, 231. (b) Esteruelas, M. A.;
Oro, L. A. Chem. Rev. 1998, 98, 577. (c) Esteruelas, M. A.; Oro, L. A.
Adv. Organomet. Chem. 2001, 47, 1.
(3) Chaloner, P. A.; Esteruelas, M. A.; Joo´, F.; Oro, L. A. Homoge-
neous Hydrogenation; Kluwer Academic Publishers: Dordrecht, The
Netherlands, 1994.
(4) (a) Bianchini, C.; Peruzzini, M. In Recent Advances in Hydride
Chemistry; Peruzzini, M., Poli, R., Eds.; Elsevier: Amsterdam, 2001;
Chapter 9, pp 271-297. (b) Clapham, S. E.; Hadzovic, A.; Morris, R.
H. Coord. Chem. Rev. 2004, 248, 2201.
(5) (a) Jones, W. D.; Feher, F. J. Acc. Chem. Res. 1989, 22, 91. (b)
Shilov, A. E.; Shul’pin, G. B. Chem. Rev. 1997, 97, 2879.
* To whom correspondence should be addressed. E-mail: maester@
unizar.es; amlopez@unizar.es.
(1) (a) Jessop, P. G.; Morris, R. H. Coord. Chem. Rev. 1992, 121,
155. (b) Heinekey, D. M.; Oldham, W. J., Jr. Chem. Rev. 1993, 93, 913.
(c) Sabo-Etienne, S.; Chaudret, B. Coord. Chem. Rev. 1998, 178-180,
381. (d) Kubas, G. J. Metal Dihydrogen and σ-Bond Complexes:
Structure, Theory and Reactivity; Kluwer: New York, 2001. (e)
McGrady, G. S.; Guilera, G. Chem. Soc. Rev. 2003, 32, 383. (f)
Heinekey, D. M.; Lledo´s, A.; Lluch, J. M. Chem. Soc. Rev. 2004, 33,
175.
10.1021/om0508177 CCC: $30.25 © 2005 American Chemical Society
Publication on Web 10/25/2005

5990 Organometallics, Vol. 24, No. 24, 2005
Esteruelas et al.
Scheme 1
nation with HBF4‚OEt2. Our interest in learning to
rationalize the reactivity of this type of species toward
unsaturated organic molecules13 prompted us to inves-
tigate its reactions with R,â-unsaturated and aromatic
ketones.
This paper reports the preparation of [OsH2(η5-C5H5)-
(η2-H2)(PiPr3)]BF4 and shows the sequence of steps that
leads to the reduction and subsequent C(sp2)-H bond
activation of these substrates, by means of the charac-
terization of intermediates.
Results and Discussion
1. Preparation of [OsH2(η5-C5H5)(η2-H2)(PiPr3)]-
BF4. The addition of 1.2 equiv of HBF4‚OEt2 to a diethyl
ether solution of the trihydride-osmium(IV) complex
OsH3(η5-C5H5)(PiPr3) (1) leads to the dihydride-elon-
gated dihydrogen derivative [OsH2(η5-C5H5)(η2-H2)-
(PiPr3)]BF4 (2), which is isolated as a white solid in 93%
yield, according to eq 1.
to its connection with the addition of vinylic and
aromatic C(sp2)-H bonds to unsaturated hydrocarbons.6
Among the various strategies used, chelate assistance
to promote cyclometalation is considered to be a promis-
ing way. In this context, the study of the behavior of
R,â-unsaturated7 and aromatic ketones8 is of particular
interest.
The C-H bond activation reactions with hydride-
dihydrogen or polyhydride precursors are little studied.9
They compete with the reduction of the substrate, and
the selectivity toward one of the processes is not always
high.10
As a part of our work on the chemistry of the
cyclopentadienyl-osmium moiety,11 we have previously
reported the preparation of the trihydride-osmium(IV)
derivative OsH3(η5-C5H5)(PiPr3).12 Now, we have ob-
served that the latter affords the dihydride-dihydrogen
derivative [OsH2(η5-C5H5)(η2-H2)(PiPr3)]BF4 by proto-
The most noticeable signal in the 1H NMR spectrum
of 2 in dichloromethane-d2 at room temperature is a
doublet at -10.70 ppm, with a H-P coupling constant
of 14.1 Hz, corresponding to the dihydride-elongated
dihydrogen unit. A variable-temperature 300 MHz study
of this resonance gives a T1 value of 950 ( 20 ms at
273 K, which decreases to 106 ( 1 ms at 180 K. In this
temperature range, the T1(min) value was not found.
The reaction of 1 with trifluoromethanesulfonic acid-d1
(DOTf) in dichloromethane-d2 gives the [2-d1]OTf salt,
which shows a H-D coupling constant of 3.6 Hz. This
value is average owing to the exchange process in the
dihydride-elongated dihydrogen unit. Assuming that the
hydride-dihydrogen H-D coupling constants are all
between 0 and 1 Hz,14 then the H-D coupling constant
in the dihydrogen ligand is between 20.6 and 21.6 Hz.
According to the standard Morris’ empirical equation,1a
the calculated H-D coupling constant yields a H-H
separation of about 1.1 Å, which agrees well with that
found in the related pentamethylcyclopentadienyl com-
plex [OsH2(η5-C5Me5)(η2-H2)(PPh3)]BF4 by spectroscopic
methods (1.06-1.08 Å) and a single-crystal neutron
diffraction study (1.014(11) Å).15 A singlet at 43.3
ppm in the 31P{1H} NMR spectrum is also characteristic
of 2.
(6) See for example: (a) Jun, C.-H.; Han, J.-S.; Kang, J.-B.; Kim,
S.-I. J. Organomet. Chem. 1994, 474, 183. (b) Kakiuchi, F.; Tanaka,
Y.; Sato, T.; Chatani, N.; Murai, S. Chem. Lett. 1995, 679. (c) Fujii,
N.; Kakiuchi, F.; Chatani, N.; Murai, S. Chem. Lett. 1996, 939. (d) Fujii,
N.; Kakiuchi, F.; Yamada, A.; Chatani, N.; Murai, S. Bull. Chem. Soc.
Jpn. 1998, 71, 285. (e) Chatani, N.; Ishii, Y.; Ie, Y.; Kakiuchi, F.; Murai,
S. J. Org. Chem. 1998, 63, 5129. (f) Busch, S.; Leitner, W. Chem.
Commun. 1999, 2305. (g) Kakiuchi, F.; Sato, T.; Igi, K.; Chatani, N.;
Murai, S. Chem. Lett. 2001, 386. (h) Kakiuchi, F.; Murai, S. Acc. Chem.
Res. 2002, 35, 826. (i) Baya, M.; Esteruelas, M. A.; Gonza´lez, A. I.;
Lo´pez, A. M.; On˜ate, E. Organometallics 2005, 24, 1225.
(7) See for example: (a) Werner, H.; Dirnberger, T.; Schulz, M.
Angew. Chem., Int. Ed. Engl. 1988, 27, 948. (b) Dirnberger, T.; Werner,
H. Chem. Ber. 1992, 125, 2007. (c) Nu¨rnberg, O.; Werner, H. J.
Organomet. Chem. 1993, 460, 163. (d) Werner, H.; Schulz, M.;
Windmu¨ller, B. Organometallics 1995, 14, 3659. (e) Bleeke, J. R.; New,
P. R.; Blanchard, J. M. B.; Haile, T.; Beatty, A. M. Organometallics
1995, 14, 5127. (f) Steinert, P.; Werner, H. Chem. Ber. 1997, 130, 1591.
(g) Castarlenas, R.; Esteruelas, M. A.; Mart´ın, M.; Oro, L. A. J.
Organomet. Chem. 1998, 564, 241. (h) Li, X.; Appelhans, L. N.; Faller,
J. W.; Crabtree, R. H. Organometallics 2004, 23, 3378. (i) Eguillor, B.;
Esteruelas, M. A.; Oliva´n, M.; On˜ate, E. Organometallics 2005, 24,
1428.
(8) (a) Guari, Y.; Sabo-Etienne, S.; Chaudret, B. J. Am. Chem. Soc.
1998, 120, 4228. (b) Barrio, P.; Castarlenas, R.; Esteruelas, M. A.;
Lledo´s, A.; Maseras, F.; On˜ate, E.; Toma`s, J. Organometallics 2001,
20, 442. (c) Barrio, P.; Esteruelas, M. A.; On˜ate, E. Organometallics
2003, 22, 2472. (d) Esteruelas, M. A.; Lledo´s, A.; Oliva´n, M.; On˜ate,
E.; Tajada, M. A.; Ujaque, G. Organometallics 2003, 22, 3753.
(9) (a) Barea, G.; Esteruelas, M. A.; Lledo´s, A.; Lo´pez, A. M.; On˜ate,
E.; Tolosa, J. I. Organometallics 1998, 17, 4065. (b) Barrio, P.;
Castarlenas, R.; Esteruelas, M. A.; On˜ate, E. Organometallics 2001,
20, 2635. (c) Esteruelas, M. A.; Lledo´s, A.; Maseras, F.; Oliva´n, M.;
On˜ate, E.; Tajada, M. A.; Toma`s, J. Organometallics 2003, 22, 2087.
(d) Barrio, P.; Esteruelas, M. A.; On˜ate, E. Organometallics 2004, 23,
1340. (e) Eguillor, B.; Esteruelas, M. A.; Oliva´n, M.; On˜ate, E.
Organometallics 2004, 23, 6015.
2. Elementary Steps for the C-C Double Bond
Reduction. In the presence of benzylideneacetone,
complex 2 loses a hydrogen molecule and the resulting
unsaturated dihydride coordinates the ketone to afford
[OsH2(η5-C5H5){κ1-OC(CH3)CHdCHPh}(PiPr3)]BF4 (3),
which is isolated as a yellow solid in 79% yield, accord-
ing to Scheme 2.
(13) 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.
(10) Barrio, P.; Esteruelas, M. A.; On˜ate, E. Organometallics 2004,
23, 3627.
(11) Esteruelas, M. A.; Lo´pez, A. M. Organometallics 2005, 15,
3584.
(14) Gusev, D. G.; Kuhlman, R. L.; Renkema, K. B.; Eisenstein, O.;
Caulton, K. G. Inog. Chem. 1996, 35, 6775.
(12) Baya, M.; Crochet, P.; Esteruelas, M. A.; Gutie´rrez-Puebla, E.;
Ruiz, N. Organometallics 1999, 18, 5034.
(15) Gross, C. L.; Young, D. M.; Schultz, A. J.; Girolami, G. S. J.
Chem. Soc., Dalton Trans. 1997, 3081.

Reduction and C(sp2)-H Bond Activation of Ketones
Organometallics, Vol. 24, No. 24, 2005 5991
Scheme 2
the bulky ligands are mutually transoid disposed. The
Os-O(1) bond length of 2.128(2) Å agrees well with the
osmium-oxygen distances found in osmium-ketone
compounds,7i,8b,d,9e,17 whereas the O(1)-C(7) bond length
of 1.247(4) Å is slightly longer than that observed in
free benzylideneacetone (1.2242(13) Å).18 This suggests
a weakening of the C-O double bond of the ketone as a
consequence of the coordination of the oxygen atom to
the metal center. The effect of the coordination is also
evident in the IR spectrum of 3, which shows the ν(CO)
band at 1616 cm-1, shifted 64 cm-1 to lower wavenum-
bers if compared with the free molecule. In agreement
with the coordination of the oxygen atom,19 the carbonyl
resonance in the 13C{1H} NMR spectrum is observed
at 213.6 ppm, shifted 15.5 ppm to lower field with regard
to the resonance of the free benzylideneacetone. As
expected for the transoid disposition of the hydride
ligands, the 1H NMR spectrum contains only one high-
field resonance. It appears as a doublet at -7.6 ppm
with a H-P coupling constant of 32.0 Hz. The 31P{1H}
NMR spectrum shows a singlet at 42.1 ppm, which
under off-resonance conditions is split into a triplet,
as a result of the P-H coupling with two hydride
ligands.
The coordination of benzylideneacetone to the osmium
atom, by the carbonyl group, was proved by an X-ray
diffraction analysis experiment on a single crystal of the
BArF4 salt of 3 (BArF4 ) tetrakis(3,5-bis(trifluorometh-
yl)phenyl)borate). This salt was prepared by reaction
of benzylideneacetone with the BArF salt of 2. Figure
4
1 shows a view of the structure of the cation, whereas
Table 1 collects selected bond distances and angles.
In dichloromethane at room temperature, complex 3
is converted to the hydroxyallyl derivative [OsH(η5-
C5H5){η3-CH2C(OH)CHCH2Ph}(PiPr3)]BF4 (4). After 12
h, this monohydride is isolated as a green solid in 82%
yield.
In the 1H NMR spectrum, the resonance correspond-
ing to the OH group appears at 7.56 ppm, as a broad
signal. The H2C(sp2) hydrogen atoms of the hydroxyallyl
ligand display a doublet at 4.40 ppm, with a H-H
coupling constant of 5.2 Hz, and a multiplet at 2.27 ppm,
whereas the HC(sp2) hydrogen atom gives rise to a
double doublet of doublets at 2.99 ppm, with H-H
coupling constants of 11.2 and 2.2 Hz and a H-P
coupling constant of 11.0 Hz. The resonances due to CH2
protons of the benzyl substituent of the allyl group
appear as the AB part of an ABC spin system with δA
) 3.65, δB ) 3.17, and JAB ) 14.2 Hz. The hydride
resonance appears at -13.63 ppm as a doublet with a
H-P coupling constant of 31.1 Hz. In the 13C{1H} NMR
spectrum, the resonances corresponding to the allyl
carbon atoms are observed at 130.7 (COH), 37.1 (CH),
and 19.5 (CH2) ppm. The 31P{1H} NMR spectrum
contains a singlet at 18.0 ppm, which under off-
resonance conditions is split into a doublet. With the
exception of the chemical shifts of the 1H and 13C COH
resonances, which agree well with those reported for
Figure 1. Molecular diagram of the cation of [OsH2(η5-
C5H5){κ1-OC(CH3)CHdCHPh}(PiPr3)]BArF (3).
4
The distribution of ligands around the osmium atom
can be described as a four-legged piano stool geometry,
with the cyclopentadienyl ring occupying the three-
membered face, while the monodentate ligands lie in
the four-membered face. Although the O(1)-Os-P(1)
angle of 88.77(7)° is noticeably small, like in other
cyclopentadienyl-osmium(IV)-dihydride complexes,12,16
Table 1. Selected Bond Distances (Å) and Angles
(deg) for the Complex [OsH2(η5-C5H5){K1-OC(CH3)-
CHdCHPh}(PiPr3)]BArF (3)
4
Os-O(1)
Os-P(1)
Os-H(01)
Os-H(02)
Os-C(1)
Os-C(2)
2.128(2)
2.3136(9)
1.37(4)
Os-C(3)
Os-C(4)
Os-C(5)
O(1)-C(7)
C(7)-C(8)
C(8)-C(9)
2.232(3)
2.295(3)
2.241(3)
1.247(4)
1.455(5)
1.334(5)
(16) (a) Esteruelas, M. A.; Gutie´rrez-Puebla, E.; Lo´pez, A. M.; On˜ate,
E.; Tolosa, J. I. Organometallics 2000, 19, 275. (b) Esteruelas, M. A.;
Lo´pez, A. M.; Tolosa, J. I.; Vela, N. Organometallics 2000, 19, 4650.
(c) Baya, M.; Crochet, P.; Esteruelas, M. A.; On˜ate, E. Organometallics
2001, 20, 240. (d) Baya, M.; Buil, M. L.; Esteruelas, M. A.; On˜ate, E.
Organometallics 2004, 23, 1416. (e) Esteruelas, M. A.; Lo´pez, A. M.;
On˜ate, E.; Royo, E. Organometallics 2004, 23, 3021. (f) Esteruelas, M.
A.; Lo´pez, A. M.; On˜ate, E.; Royo, E. Organometallics 2004, 23, 5633.
(g) Esteruelas, M. A.; Lo´pez, A. M.; On˜ate, E.; Royo, E. Inorg. Chem,
2005, 44, 4094.
1.52(4)
2.163(3)
2.158(3)
Ma-Os-O(1)
136.6
P(1)-Os-H(02)
H(01)-Os-H(02)
Os-O(1)-C7)
O(1)-C(7)-C(8)
O(1)-C(7)-C(6)
C(6)-C(7)-C(8)
C(7)-C(8)-C(9)
C(8)-C(9)-C(10)
77.8(15)
138(2)
Ma-Os-P(1)
134.6
Ma-Os-H(01)
Ma-Os-H(02)
O(1)-Os-P(1)
O(1)-Os-H(01)
O(1)-Os-H(02)
P(1)-Os-H(01)
113.7
133.6(2)
115.6(3)
121.1(3)
123.3(3)
123.7(4)
126.8(4)
107.1
(17) Barrio, P.; Esteruelas, M. A.; Lledo´s, A.; On˜ate, E.; Toma`s, J.
Organometallics 2004, 23, 3008.
88.77(7)
76.0(17)
80.1(15)
68.3(17)
(18) Degen, A.; Bolte, M. Acta Crystallogr. 1999, C55, IUC9900170.
(19) (a) Esteruelas, M. A.; Go´mez, A. V.; Lahoz, F. J.; Lo´pez, A. M.;
On˜ate, E.; Oro, L. A. Organometallics 1996, 15, 3423. (b) Bohanna,
C.; Esteruelas, M. A.; Go´mez, A. V.; Lo´pez, A. M.; Mart´ınez, M.-P.
Organometallics 1997, 16, 4464.
a M represents the midpoint of the Cp ring.

5992 Organometallics, Vol. 24, No. 24, 2005
Esteruelas et al.
Scheme 3
Scheme 4
D). The 1,2-hydrogen or 1,2-deuterium shift from the
metal to the oxygen atom of the ketone in 3 or 3-d2 could
afford the η1-hydroxyallyl intermediate a, which should
give b by η1-η3 rearrangement. A second hydrogen or
deuterium migration from the metal, now, to the ter-
minal CHPh carbon atom of the η3-hydroxyallyl ligand
of b could lead to the enol species c, which by C(sp3)-H
bond activation of the methyl group should yield 4 or
4-d2.
other hydroxyallyl complexes of late transition metals,20
these spectroscopic data are very similar to those
found for the silylcyclopentadienyl compound [OsH(η5-
C5H4SiPh3){η3-CH2C(Ph)CH2}(PiPr3)]BF4, where the dis-
position of the allyl ligand with regard to the [OsH(η5-
C5H4SiPh3)(PiPr3)]2+ skeleton has been confirmed by
X-ray diffraction analysis.21 In addition, the cisoid
disposition of the hydride and the H2C(sp2) group of the
hydroxyallyl ligand in 4 is proved by the 1H-1H NOESY
NMR spectrum, which shows the cross-peaks between
the hydride resonance and those due to the H2C(sp2)
protons.
To obtain information about the formation of 4, we
prepared [OsD2(η5-C5H5){κ1-OC(CH3)CHdCHPh}(Pi-
Pr3)]BF4 (3-d2), in situ, by reaction of [OsD2(η5-C5H5)-
(η2-D2)(PiPr3)]BF4 (2-d4) with benzylideneacetone. Un-
der the same conditions as 3, complex 3-d2 is selec-
tively transformed into [OsH(η5-C5H5){η3-CH2C(OD)-
CHCHDPh}(PiPr3)]BF4 (4-d2), containing a deuterium
atom at the oxygen atom and the other one at the benzyl
substituent of the allyl ligand (eq 2). The positions of
these atoms are supported by the 2H NMR spectrum of
4-d2, which shows three broad singlets at 7.6, 3.5, and
3.0 ppm with a 1:0.5:0.5 intensity ratio.
In the presence of benzylideneacetone, complex 4
releases 4-phenylbutan-2-one, and the resulting metallic
fragment activates a C(sp2)-H bond of the R,â-unsatur-
ated substrate to give [OsH(η5-C5H5){C(Ph)CHC(O)-
CH3}(PiPr3)]BF4 (5), which is isolated as a yellow solid
in 79% yield, according to Scheme 2. Under the same
conditions, 4-d2 affords 5 and dideuterated saturated
ketone containing one deuterium at position 4, 0.65 at
position 3, and 0.35 at position 1. This deuterium
distribution is consistent with a 1.8:1 mixture of the
ketones shown in eq 3. The formation of both ketones
indicates that 4 and 4-d2 undergo the reversible migra-
tion of the hydride ligand from the metal center to both
terminal carbon atoms of the hydroxyallyl group, to form
the enol species c and d shown in Scheme 3. These
intermediates release the saturated ketone in an ir-
reversible manner. In agreement with this, reaction
between 4-d2 and 4-phenylbutan-2-one is not observed.
According to the deuterium ratio between the positions
3 and 1 of the ketone, the migration to the CH2-terminal
group appears to be favored with regard to the migra-
tion to the terminal CH carbon atom.
Scheme 3 shows a sequence of reactions that allows
to rationalize the formation of 4 (X ) H) and 4-d2 (X )
(20) See for example: (a) Huang, T.-M.; Hsu, R.-H.; Yang, C.-S.;
Chen, J.-T.; Lee, G.-H.; Wang, Y. Organometallics 1994, 13, 3657. (b)
Arndtsen, B. A.; Bergman, R. G. J. Organomet. Chem. 1995, 504, 143.
(c) Casey, C. P.; Nash, J. R.; Yi, C. S.; Selmeczy, A. D.; Chung, S.;
Powell, D. R.; Hayashi, R. K. J. Am. Chem. Soc. 1998, 120, 722.
(21) Baya, M.; Esteruelas, M. A.; On˜ate, E. Organometallics 2001,
20, 4875.
(22) This resonance appears shifted 5.7 and 7.7 ppm, respectively,
to higher field with regard to the chemical shifts observed for the
carbene atoms of the Fischer carbene derivatives OsH(η5-C5H5)-
{dC(OMe)Ph}(PiPr3) (δ 242.6)23 and OsH(η5-C5H5){dC(OMe)Ph}-
{PiPr2[C(CH3)dCH2]} (δ 244.6).24 However, it appears shifted more
than 77 ppm to lower field with regard to the chemical shifts found
for the OsCR resonances of the alkenyl complexes Os(C2Ph){(E)-
CHdCHPh}(tCCH2Ph)(PiPr3)2 (δ 155.7),25 OsH(η5-C5H5){(E)-CHd
CHPh}{P(OMe)3}(PiPr3) (δ 136.9),26 [Os{(E)-CHdCHCy}Cl(dNd
CMe2)(PiPr3)2][CF3SO3] (δ 143.1),27 and [Os{(Z)-CHdC(Ph)NHdCR2}-
Cl(CO)2(PiPr3)2]+ (δ 158-145).28
In the 1H NMR spectrum of 5 the most notice-
able features are the presence of a singlet at 7.33
ppm, corresponding to the CH hydrogen atom of the
five-membered heterometallacycle, and a doublet at
-12.84 ppm with a H-P coupling constant of 34.4 Hz
due to the hydride ligand. The 13C{1H} NMR spec-
trum suggests that for an adequate description of
the bonding situation in 5 the resonance forms shown
in Scheme 4 should be taken into account. Thus, it
shows the resonance due to the metalated carbon

Reduction and C(sp2)-H Bond Activation of Ketones
Organometallics, Vol. 24, No. 24, 2005 5993
atom at 236.9 ppm.22 This chemical shift agrees
with those corresponding to the related resonances of
Scheme 5
the complexes OsCl{CHCHC(O)Ph}(CO)(PiPr3)2 (δ
230.13),29 Os(SnPh2Cl){C4(O)H2C(O)H}(η2-H2)(PiPr3)2
(δ 230.6), Os(SnPh2Cl){C6H8C(O)H}(η2-H2)(PiPr3)2 (δ
242.9),9e Os(SnPh2Cl){CRCHC(O)R′}(η2-H2)(PiPr3)2 (δ
between 233 and 242),7i OsH{CHCHC(O)CH3}(CO)-
(PiPr3)2 (δ 250.8),30 and OsH3{C6H8C(O)CH3}(PiPr3)2 (δ
255.7),9b where bonding situations intermediate between
resonance forms analogous to A and B have been
proposed to exist. The OsCR resonance of 5 is observed
as a doublet with a C-P coupling constant of 4 Hz. This
value strongly supports the transoid disposition of the
metalated carbon atom of the ketone with regard to the
phosphine ligand.16e,21 The 31P{1H} NMR spectrum
shows a singlet at 24.6 ppm, which under off-resonance
conditions is split into a doublet.
tion of benzylideneacetone to the osmium atom, after
the release of the saturated ketone from 4, as a previous
step to the C(sp2)-H bond activation. All attempts to
isolate this intermediate were unsuccessful. To obtain
information about its nature, we note, however, that one
of the phosphine ligands of Os(η5-C5H5)Cl(PiPr3)2 can
be easily displaced by methyl vinyl ketone to afford
Os(η5-C5H5)Cl{η2-CH2dCHC(O)CH3}(PiPr3) (7) in high
yield.31 Treatment at -70 °C of an acetone solution of
7 with 1.3 equiv of TlPF6 produces the abstraction of
the chloride ligand and the intramolecular coordination
of the carbonyl group of the ketone to give the inter-
mediate [Os(η5-C5H5){CH2CHC(O)CH3}(PiPr3)]PF6 (8),
which is isolated as a green solid in 83% yield, according
to Scheme 5.
Complex 5 can be deprotonated by reaction with
sodium methoxide. The addition of this base to a
tetrahydrofuran solution of 5 gives rise to the formation
of the neutral compound Os(η5-C5H5){C(Ph)CHC(O)-
CH3}(PiPr3) (6), as a result of the extraction of the
hydride ligand (eq 4). The reaction is reversible: the
addition of 1.0 equiv of HBF4‚OEt2 to a dichloromethane-
d2 solution of 6 regenerates 5. Complex 6, which is a
brown oil, is isolated in 88% yield.
In the 1H NMR spectrum, the resonances of the
coordinated ketone appear at 5.78 (CH), 3.51 and 1.70
(CH2), and 2.70 (CH3) ppm, whereas in the 13C{1H}
NMR spectrum they are observed at 141.3 (CO), 67.2
(CH), 31.4 (CH2), and 20.4 (CH3). These chemical shifts
are similar to those corresponding to the related atoms
of complexes [OsH{CH2CHC(O)CH3}(CO)(PiPr3)2]BF4,32
Ru{CH2CHC(O)CH3}(triphos) (triphos ) ttp, Cyttp),33
Ru{CH2C(CH3)C(O)H}(CO)(PPh3)2,34 and Ru{CH2CHC-
(O)R}(PEt3)3 (R ) H, CH3).35 It must be pointed out that
the CH hydrogen atom has the same spin coupling with
both hydrogen atoms of the CH2 group. This indicates
that the Karplus angle in both cases is the same, which
suggests a significant contribution of the σ2-π reso-
nance form to the Os-ketone bonding. The 31P{1H}
NMR spectrum shows a singlet at 9.6 ppm.
1
In the H NMR spectrum of 6, the most noticeable
feature is the absence of any hydride resonance. The
CH hydrogen of the heterometallacycle gives rise to a
singlet at 7.51 ppm. The 13C{1H} NMR spectrum reveals
an increase of the contribution of the resonance form B
to the bonding in the five-membered ring, as a conse-
quence of the deprotonation of the metal center. Thus,
the OsCR resonance is observed at 249.0 ppm, shifted
about 12 ppm to lower field with regard to the chemical
shift of 5. This increase of the carbene resonance form
is in agreement with the formal reduction of the metal
center, which increases the back-bonding Os(dπ)fC(pπ)
interaction. The 31P{1H} NMR spectrum shows a singlet
at 22.8 ppm.
In dichloromethane at room temperature, complex 8
is rapidly converted into [OsH(η5-C5H5){CHCHC(O)-
CH3}(PiPr3)]PF6 (9). After 15 min the transformation
is quantitative. If complex 8 is considered a 16-valence-
electron osmium(IV) species, the formation of 9 can be
rationalized as a 1,2-hydrogen shift from the CH2 carbon
atom of the ketone to the unsaturated metal center of
3. Elementary Steps for the C(sp2)-H Bond
Activation. The formation of 5 involves the coordina-
(23) Esteruelas, M. A.; Gonza´lez, A. I.; Lo´pez, A. M.; On˜ate, E.
Organometallics 2003, 22, 414.
(24) Esteruelas, M. A.; Gonza´lez, A. I.; Lo´pez, A. M.; On˜ate, E.
Organometallics 2004, 23, 4858.
(25) Barrio, P.; Esteruelas, M. A.; On˜ate, E. J. Am. Chem. Soc. 2004,
126, 1946.
(31) Esteruelas, M. A.; Lo´pez, A. M.; Ruiz, N.; Tolosa, J. I. Orga-
nometallics 1997, 16, 4657.
(32) Esteruelas, M. A.; Garc´ıa, M. P.; Lo´pez, A. M.; Oro, L. A.; Ruiz,
N.; Schlu¨nken, C.; Valero, C.; Werner, H. Inorg. Chem. 1992, 31, 5580.
(33) Jia, G.; Meek, D. W.; Gallucci, J. C. Organometallics 1990, 9,
2549.
(34) Hiraki, K.; Nonaka, A.; Matsunaga, T.; Kawano, H. J. Orga-
nomet. Chem. 1999, 574, 121.
(35) Kanaya, S.; Imai, Y.; Komine, N.; Hirano, M.; Komiya, S.
Organometallics 2005, 24, 1059.
(26) Baya, M.; Esteruelas, M. A. Organometallics 2002, 21, 2332.
(27) Castarlenas, R.; Esteruelas, M. A.; On˜ate, E. Organometallics
2001, 20, 3283.
(28) Castarlenas, R.; Esteruelas, M. A.; On˜ate, E. Organometallics
2001, 20, 2294.
(29) Esteruelas, M. A.; Lahoz, F. J.; On˜ate, E.; Oro, L. A.; Zeier, B.
Organometallics 1994, 13, 1662.
(30) Edwards, A. J.; Elipe, S.; Esteruelas, M. A.; Lahoz, F. J.; Oro,
L. A.; Valero, C. Organometallics 1997, 16, 3828.

5994 Organometallics, Vol. 24, No. 24, 2005
Esteruelas et al.
Scheme 6
Figure 2. Molecular diagram of Os(η5-C5H5){CHCHC(O)-
CH3}(PiPr3) (10).
Table 2. Selected Bond Distances (Å) and Angles
(deg) for the Complex
Os(η5-C5H5){CHCHC(O)CH3}(PiPr3) (10)
Os-C(1)
Os-O
1.989(4)
2.121(2)
2.3191(9)
2.187(3)
2.285(3)
2.246(3)
Os-C(8)
Os-C(9)
C(1)-C(2)
C(2)-C(3)
C(3)-O
2.229(3)
2.187(3)
1.384(5)
1.396(5)
1.288(4)
Os-P
Os-C(5)
Os-C(6)
Os-C(7)
Ma-Os-C(1)
Ma-Os-O
Ma-Os-P
C(1)-Os-O
C(1)-Os-P
O-Os-P
128.0
Os-C(1)-C(2)
C(1)-C(2)-C(3)
C(2)-C(3)-C(4)
O-C(3)-C(4)
C(2)-C(3)-O
C(3)-O-Os
118.7(3)
113.0(3)
125.6(3)
117.6(3)
116.8(3)
115.8(2)
8. In this context, it should be mentioned that in acetone
the isomerization is significantly slower than in dichlo-
romethane. As expected, the BF4 salt of 9 and ethyl
methyl ketone are obtained from the reaction of 2 with
vinyl methyl ketone (Scheme 5). By this procedure,
complex 9 is isolated as a yellow solid in 73% yield.
129.0
125.5
75.60(12)
93.16(10)
90.75(7)
a M represents the midpoint of the Cp ring.
1
The H, 13C{1H}, and 31P{1H} NMR spectra of 9 are
consistent with those of 5 and with a notable contribu-
tion of the resonance form B (Scheme 4) to its structure.
The OsCH resonance is observed at 12.70 ppm, as a
double doublet of doublets by spin coupling with the
phosphine (1.4 Hz), the hydride ligand (5.1 Hz), and the
CâH-hydrogen atom (7.3 Hz), which gives rise to a
doublet at 7.29 ppm. The hydride resonance appears as
a double doublet at -13.41 ppm, with a H-P coupling
constant of 31.5 Hz. In the 13C{1H} NMR spectrum, the
resonances corresponding to the carbon atoms of the
heterometallacycle are observed at 222.8 (OsC), 214.5
(CO), and 137.2 (CCO) ppm. The 31P{1H} NMR spec-
trum contains a singlet at 30.2 ppm, which under off-
resonance conditions is split into a doublet.
respectively, whereas the C(1)-Os-O bite angle (75.60-
(12)°) of this group strongly deviates from 90°.
The five-membered heterometallacycle is almost
planar (maximum deviation 0.0198(54) Å, C(4)). The
Os-C(1) bond length of 1.989(4) Å agrees well with
the osmium-carbon distances found in the complexes
Os(SnPh2Cl){CHCHC(O)CH3}(η2-H2)(PiPr3)2 (2.035(2)
Å),7i Os{CHCHC(O)Ph}Cl(CO)(PiPr3)2 (1.921(3) Å),29
and Os(SnPh2Cl){C4(O)H2C(O)H}(η2-H2)(PiPr3)2 (2.021-
(4) Å),9c where the resonance forms shown in Scheme 4
have been taken into account to describe the bonding
situation in the metallacycles. In agreement with this,
the C(1)-C(2) and C(2)-C(3) distances of 1.384(5) and
1.396(5) Å, respectively, are between those expected for
single and double carbon-carbon bonds. The Os-O and
C(3)-O bond lengths of 2.121(2) and 1.288(4) Å also
support the metallafuran resonance forms.36
Like 5, complex 9 can be deprotonated with sodium
methoxide. The addition of the base to a tetrahydrofuran
solution of this compound leads to an equilibrium
mixture of Os(η5-C5H5){CHCHC(O)CH3}(PiPr3) (10) and
its hydride-vinylidene isomer OsH(η5-C5H5){dCdCHC-
(O)CH3}(PiPr3) (11), according to Scheme 6. In benzene-
d6 at room temperature the 10:11 molar ratio is 5:1.
The crystallization of the mixture in pentane at -78
°C affords crystals of 10 suitable for an X-ray diffraction
analysis. Figure 2 shows a view of the structure of the
molecule. Selected bond distances and angles are col-
lected in Table 2. The geometry around the osmium
center is close to octahedral, with the cyclopentadienyl
ligand occupying three sites of a face. The angles formed
by the triisopropylphosphine and the C(1) and O atoms
of the metalated ketone are 93.16(10)° and 90.75(7)°,
1
In the H NMR spectrum, the C(1)-H and C(2)-H
resonances appear as doublets at 13.39 and 7.42
ppm, respectively, with a H-H coupling of 7.3 Hz. The
13C{1H} NMR spectrum, in a manner similar to that of
6, makes clear the increase of the contribution of the
resonance form B to the structure of the metallacycle
as a result of the deprotonation of the metal center of
9. Thus, the C(1) resonance is observed at 237.8 ppm,
shifted 15 ppm to lower field with regard to that of
9. This resonance appears as a doublet with a C-P
(36) Stone, K. C.; Jamison, G. M.; White, P. S.; Templeton, J. L.
Organometallics 2003, 22, 3083, and references therein.

Reduction and C(sp2)-H Bond Activation of Ketones
Organometallics, Vol. 24, No. 24, 2005 5995
Scheme 7
coupling constant of 6 Hz, while the C(2) resonance (δ
131.0) is a singlet. The C(3) atom displays a doublet at
203.8 ppm, with a C-P coupling constant of 2 Hz. The
31P{1H} NMR spectrum shows a singlet at 30.4 ppm.
1
In the H NMR spectrum of the hydride-vinylidene
isomer 11, the most noticeable features are a broad
double doublet at 3.00 ppm, corresponding to the Câ-H
of the vinylidene, and the hydride resonance. The latter
is observed at -14.12 ppm as a double doublet by spin
coupling with the Câ-H proton of the vinylidene (2.0
Hz) and the phosphorus of the phosphine (29.2 Hz). In
dichloromethane-d2, these resonances are temperature
invariant between 183 and 298 K, suggesting that the
vinylidene group does not rotate around the double
bonds. The cisoid disposition of the hydride ligand and
the acyl substituent is supported by the 1H-1H NOESY
NMR spectrum, which shows the cross-peaks between
the hydride and CH3CO (δ 2.51) resonances. In the
13C{1H} NMR spectrum, the CR resonance of the vi-
nylidene appears at 289.7 ppm, as a doublet with a C-P
coupling constant of 11 Hz, while the resonance due to
the Câ atom is observed at 118.1 ppm, as a singlet. The
31P{1H} NMR spectrum contains a singlet at 42.9 ppm,
which under off-resonance conditions is split into a
doublet.
The formation of 11 can be rationalized according to
Scheme 6. The decoordination of the oxygen atom in 10
should give an unsaturated alkenyl intermediate e,
which could evolve into the hydride-vinylidene f by 1,2-
hydrogen shift from the η1-carbon donor ligand to the
metal center. The formation of hydride-vinylidene com-
plexes by an R-elimination reaction in alkenyl com-
pounds is a well-known process.37 Finally the rotation
of the vinylidene of f around the Os-vinylidene bond
should afford 11. The driving force for this process must
be the steric hindrance experienced by the acyl sub-
stituent and the isopropyl groups of the phosphine.
observed at 210.0 ppm as a doublet. The value of 14 Hz
for the C-P coupling constant strongly supports the
cisoid disposition of the metalated carbon atom and the
phosphine. In addition, it should be noted that this
resonance is shifted 12.8 ppm toward higher field with
regard to that of 9, suggesting a lower contribution of
the resonance form B to the structure of 12 than to the
structure of 9. The 31P{1H} NMR spectrum shows a
singlet at 21.7 ppm, which under off-resonance condi-
tions is split into a doublet.
4. Olefinic C(sp2)-H versus Aromatic C(sp2)-H
Activation. Treatment of 2 with 3.0 equiv of acetophe-
none produces the loss of a hydrogen molecule from the
starting compound and the formation of 1.0 equiv of
1-phenylethanol and the orthometalated compound
[OsH(η5-C5H5){C6H4C(O)CH3}(PiPr3)]BF4 (13), which is
isolated as a yellow solid in 87% yield, according to
Scheme 7. The reaction of 2-d4 with 3.0 equiv of
acetophenone also affords 13. This indicates that 13 is
a result of ortho-CH bond activation of the ketone by
the [Os(η5-C5H5)(PiPr3)]+ metal fragment.
The deprotonation of 9 is reversible. Thus, the addi-
tion of 1.0 equiv of HBF4‚OEt2 to a dichloromethane
solution of the equilibrium mixture of 10 and 11 initially
leads to a mixture of 9 and its isomer 12 (Scheme 6).
After 30 min, the 9:12 molar ratio is 1:2. After 12 h at
room temperature the quantitative isomerization of 12
into 9 occurs.
A view of the structure of the cation of 13 is shown
in Figure 3. Selected bond distances and angles are
listed in Table 3. The distribution of ligands around the
osmium atom can be described as a four-legged piano
stool geometry with the orthometalated carbon atom
C(1) transoid to the phosphine ligand. The C(1) -Os-P
and O-Os-H(01) angles are 106.24(12)° and 128.2(18)°,
respectively.
The addition of the proton of the acid to 10 can take
place between the phosphine and the oxygen atom or
alternatively between the phosphine and the metalated
carbon atom. The first addition leads to 12, containing
the metalated carbon atom cisoid disposed to the
phosphine, while the second one directly gives 9. Since
complex 12 is the product of kinetic control and 9 is the
product of thermodynamic control, the previously men-
tioned observations indicate that the addition between
the phosphine and the oxygen is kinetically favored,
whereas the transoid disposition of the metalated
carbon atom and the phosphine is thermodynamically
favored.
The orthometalated ketone acts with a bite angle of
76.08(15)°. The Os-C(1) bond length of 2.016(5) Å is
typical for an Os-C(aryl) single bond and agrees well
with the values previously found in other orthometa-
(37) (a) van Asselt, A.; Burger, B. J.; Gibson, V. C.; Bercaw, J. E. J.
Am. Chem. Soc. 1986, 108, 5347. (b) Dziallas, M.; Werner, H. J.
Organomet. Chem. 1987, 333, C29. (c) Beckhaus, R.; Thiele, K.-H.;
Stro¨hl, D. J. Organomet. Chem. 1989, 369, 43. (d) Bell, T. W.;
Haddleton, D. M.; McCamley, A.; Partridge, M. G.; Perutz, R. N.;
Willner, H. J. Am. Chem. Soc. 1990, 112, 9212. (e) Gibson, V. C.;
Parkin, G.; Bercaw, J. E.; Organometallics 1991, 10, 220. (f) Beckhaus,
R. J. Chem. Soc., Dalton Trans. 1997, 1991. (g) Beckhaus, R. Angew.
Chem., Int. Ed. Engl. 1997, 36, 686, (h) Alvarado, Y.; Boutry, O.;
Gutie´rrez, E.; Monge, A.; Nicasio, M. C.; Poveda, M. L.; Pe´rez, P. J.;
Ru´ız, C.; Bianchini, C.; Carmona, E. Chem. Eur. J. 1997, 3, 860. (i)
Oliva´n, M.; Clot, E.; Eisenstein, O.; Caulton, K. G. Organometallics
1998, 17, 3091.
1
In contrast to 9, in the H NMR spectrum of 12, the
OsCH (δ 11.71) and CHCO (δ 7.22) resonances appear
as double doublets with a H-H coupling constant of 7.7
Hz and H-P coupling constants of 1.6 and 2.6 Hz,
respectively. The hydride ligand displays a doublet at
-9.40 ppm, with a H-P coupling constant of 37.4 Hz.
In the 13C{1H} NMR spectrum the OsC resonance is

5996 Organometallics, Vol. 24, No. 24, 2005
Esteruelas et al.
Scheme 8
Figure 3. Molecular diagram of the cation of [OsH(η5-
C5H5){C6H4C(O)CH3}(PiPr3)]BF4 (13).
the absence of any hydride resonance. In the 13C{1H}
NMR spectrum the resonance of the metalated car-
bon atom of the ketone is observed as a doublet at
202.7 ppm, with a C-P coupling constant of 7 Hz. The
31P{1H} NMR spectrum shows a singlet at 23.5 ppm.
We have shown that the metal fragment [Os(η5-
C5H5)(PiPr3)]+ activates a Câ(sp2)-H bond of R,â-
unsaturated ketones and an ortho-CH bond of an
aromatic ketone such as acetophenone. To study the
preference for the olefinic Câ(sp2)-H activation or
aromatic ortho-CH activation, we have also investigated
the reaction of 2 with benzylideneacetophenone. This
substrate contains both functionalities bonded to the
carbonyl unit, a phenyl group and a carbon-carbon
double bond, which could be activated in a competitive
manner. Thus, we have previously observed that the 14-
valence-electron monohydride OsH(SnPh2Cl)(PiPr3)2,
generated from OsH3(SnPh2Cl){[η2-CH2dC(CH3)]-
PiPr2}(PiPr3), activates both the Câ(sp2)-H of the olefinic
moiety and an ortho-CH bond of the phenyl group. The
activation of the Câ(sp2)-H bond of the olefin is kineti-
cally favored with regard to the ortho-CH bond activa-
tion of the phenyl group. However, the orthometalated
product is thermodynamically more stable than that
resulting from the Câ(sp2)-H bond activation.7i
Table 3. Selected Bond Distances (Å) and Angles
(deg) for the Complex
[OsH(η5-C5H5){C6H4C(O)CH3}(PiPr3)]BF4 (13)
Os-O
2.082(3)
2.3470(11)
1.585(10)
2.016(5)
2.168(5)
2.297(5)
Os-C(20)
Os-C(21)
Os-C(22)
O-C(3)
C(1)-C(2)
C(2)-C(3)
2.294(5)
2.229(4)
2.156(4)
1.261(5)
1.432(6)
1.416(6)
Os-P
Os-H(01)
Os-C(1)
Os-C(18)
Os-C(19)
Ma-Os-C(1)
Ma-Os-O
124.4
O-Os-P
82.09(8)
128.2(18)
76.0(18)
117.2(4)
118.1(3)
111.5(4)
115.9
O-Os-H(01)
P-Os-H(01)
O-C(3)-C(2)
C(3)-O-Os
C(1)-C(2)-C(3)
Ma-Os-P
128.6
114.4
76.08(15)
106.24(12)
66.4(18)
Ma-Os-Η
C(1)-Os-O
C(1)-Os-P
C(1)-Os-H(01)
a M represents the midpoint of the Cp ring.
lated osmium compounds.8b,d,9a,e,16a,c,17,21,38 The Os-O
bond length of 2.082(3) Å is about 0.04 Å shorter than
those in 3 and 10, while the O-C(3) distance of 1.261-
(5) Å is about 0.04 Å longer than that found in the free
acetophenone.39
In agreement with the presence of a hydride ligand
in 13, its 1H NMR spectrum contains a doublet at
-13.80 ppm, with a H-P coupling constant of 32.9 ppm.
In the 13C{1H} NMR spectrum the resonance corre-
sponding to the metalated carbon atom of the ketone
appears as a doublet at 179.3 ppm, with a C-P coupling
constant of 3 Hz. The 31P{1H} NMR spectum shows a
singlet at 28.0 ppm, which under off-resonance condi-
tions is split into a doublet.
In contrast to the monohydride OsH(SnPh2Cl)-
(PiPr3)2, complex 2 exclusively activates the Câ(sp2)-H
bond of benzylideneacetophenone. Treatment of this
compound with 3.0 equiv of the R,â-unsaturated ketone
leads to 1.0 equiv of saturated ketone and the complex
[OsH(η5-C5H5){C(Ph)CHC(O)Ph}(PiPr3)]BF4 (15), which
is isolated according to Scheme 8 as a green solid in 88%
yield.
Like 5 and 9, complex 13 can be deprotonated with
sodium methoxide. The addition of 1.6 equiv of the base
to a tetrahydrofuran solution of 13 leads to the neutral
The 1H, 13C{1H}, and 31P{1H} NMR spectra of 15
agree well with those of 5 and 9. In the 1H NMR
spectrum, the hydride resonance appears at -12.50 ppm
as a doublet with a H-P coupling constant of 34.4 Hz.
In the 13C{1H} NMR spectrum, the OsC resonance is
observed as a doublet at 237.4 ppm, with a C-P
coupling constant of 3 Hz. The 31P{1H} NMR spectrum
contains a singlet at 28.5 ppm, which under off-
resonance conditions is split into a doublet.
derivative Os(η5-C5H5){C6H4C(O)CH3}(PiPr3) (14), as a
result of the abstraction of the hydride ligand of 13.
The reaction is reversible. The addition of 1.0 equiv of
HBF4‚OEt2 to a dichloromethane-d2 solution of 14
regenerates 13.
1
In the H NMR spectrum of 14, which is isolated as
The hydride ligand of 15 is also fairly acidic. Thus,
the treatment of 15 with 1.3 equiv of sodium methoxide
in tetrahydrofuran produces its deprotonation and the
a brown oil in 74% yield, the most noticeable feature is
(38) (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) Crochet,
P.; Esteruelas, M. A.; Gutie´rrez-Puebla, E. Organometallics 1998, 17,
3141.
(39) D Search and Research using the Cambridge Structural Data
Base: Allen, F. H.; Kennard, O. Chem. Des. Autom. News 1993, 8, 31.
formation of the neutral derivative Os(η5-C5H5){C(Ph)-
CHC(O)Ph}(PiPr3) (16), which is isolated as a brown oil
in 82% yield. The reaction is reversible. The addition of

Reduction and C(sp2)-H Bond Activation of Ketones
Organometallics, Vol. 24, No. 24, 2005 5997
selective detector interfaced to an Agilent 6890 series gas
chromatograph system. Samples were injected into a 30 m ×
250 µm HP-5MS 5% phenyl methyl siloxane column with a
film thickness of 0.25 µm.
1.0 equiv of HBF4‚OEt2 to a dichloromethane-d2 solution
of 16 regenerates 15. The formation of an isomer of 15
with a stereochemistry as that of 12 is not observed.
In the 13C{1H} NMR spectrum, the metalated carbon
atom of the ketone of 16 gives rise to a doublet at 249.8
ppm with a C-P coupling constant of 4 Hz. The
31P{1H} NMR spectrum shows a singlet at 23.7 ppm.
Preparation of [OsH2(η5-C5H5)(η2-H2)(PiPr3)]BF4 (2). A
brown solution of 1 (290 mg, 0.69 mmol) in 5 mL of diethyl
ether was treated with HBF4‚Et2O (113 µL, 0.83 mmol).
Immediately a grayish white solid appeared. The solid was
separated by decantation, washed with diethyl ether, and
dried in vacuo. Yield: 325 mg (93%). Anal. Calcd for
C14H30BF4OsP: C, 33.21; H, 5.97. Found: C, 33.35; H, 5.59.
IR (Nujol, cm-1): ν(OsH) 2142 (m), 2108 (m). 1H NMR (300
MHz, CD2Cl2, 293 K): δ 5.78 (s, 5H, C5H5), 2.19 (m, 3H, PCH),
Concluding Remarks
This study reveals that, in the presence of R,â-
unsaturated and aromatic ketones, the dihydride-dihy-
drogen complex [OsH2(η5-C5H5)(η2-H2)(PiPr3)]BF4 loses
a hydrogen molecule, subsequently it reduces 1.0 equiv
of substrate, and finally the resulting [Os(η5-C5H5)-
(PiPr3)]+ metal fragment activates a C(sp2)-H bond
3
3
1.18 (dd, JHP ) 15.9, JHH ) 7.2, 18H, PCHCH3), -10.70 (d,
2JHP ) 14.1, 4H, OsH). 31P{1H} NMR (121.42 MHz, CD2Cl2,
293 K): δ 43.3 (s). MS (LSIMS+): m/z 421 (M+). T1 (ms, 300
MHz, CD2Cl2): 950 ( 20 (273 K), 940 ( 20 (263 K), 690 ( 10
(243 K), 420 ( 10 (223 K), 224 ( 2 (203 K), 168 ( 2 (193 K),
106 ( 1 (180 K).
to give [OsH(η5-C5H5){C(R)CHC(O)R′}(PiPr3)]BF4 or
Preparation of 2-d1. An NMR tube containing a brown
solution of 1 (24 mg, 0.06 mmol) in 0.5 mL of dichloromethane-
d2 was treated with trifluoromethanesulfonic acid-d1 (7 µL,
0.08 mmol). The solution color changed from brown to light
[OsH(η5-C5H5){C6H4C(O)R}(PiPr3)]BF4, depending on
the nature of the ketone.
The reduction of R,â-unsaturated ketones affords
saturated ketones. The reactions are initiated with the
coordination of the oxygen atom of the carbonyl group
and involve the transfer of two hydrogen atoms from
the metal center to the oxygen and Câ atoms of the
substrates.
1
orange. H NMR data were identical to those reported for 2
with the exception of the resonance at -10.69 (dt (1:1:1), 2JHP
) 13.8, JHD (average) ) 3.6, 3H, OsH). 31P{1H} NMR (121.42 MHz,
CD2Cl2, 293 K): δ 43.3 (br).
Preparation of [OsD2(η5-C5H5)(η2-D2)(PiPr3)]BF4 (2-d4).
An NMR tube was charged with 2 (20 mg, 0.04 mmol), and
0.2 mL of methanol-d4 was added. After 5 min, the solvent
was removed in vacuo, and the grayish solid was dissolved in
dichloromethane-d2. 1H NMR data were identical to those
reported for 2 with the exception of the absence of the
The Câ(sp2)-H bond activation probably takes place
by means of the initial σ2-π coordination of the R,â-
unsaturated ketone to the metal fragment [Os(η5-
C5H5)(PiPr3)]+ and most likely involves the 1,2-hydrogen
shift from the CHR carbon atom to the metal center
of the intermediates [Os(η5-C5H5){CH(R)CHC(O)R′}-
(PiPr3)]+.
2
resonance at -10.70 ppm. H NMR (61.42 MHz, CH2Cl2, 293
K): δ -10.0 (br). 31P{1H} NMR (121.42 MHz, CD2Cl2, 293 K):
δ 43.3 (br).
Preparation of BArF Salt of 2. A Schlenk flask was
Although the metal fragment [Os(η5-C5H5)(PiPr3)]+
activates a Câ(sp2)-H olefinic bond of R,â-unsaturated
ketones and an ortho-CH bond of aromatic ketones, the
exclusive activation of the olefinic Câ(sp2)-H bond is
observed in substrates such as benzylideneacetophe-
none, which contains both types of organic moieties
bonded to the carbonyl group.
In conclusion, we show the sequence of steps for
the selective carbon-carbon reduction and selective
Câ(sp2)-H bond activation of R,â-unsaturated ketones
promoted by a new dihydride-dihydrogen complex.
4
charged with 2 (200 mg, 0.40 mmol) and NaBArF (318 mg,
4
0.36 mmol). Diethyl ether (5 mL) was added, and the mixture
was stirred for 1 h at room temperature. The resultant light
orange solution was filtered through Celite and concentrated
to ca. 1 mL under reduced pressure. The addition of pentane
(10 mL) caused the formation of a white solid, which was
separated by decantation and dried in vacuo. Yield: 418 mg
1
(91%). The 31P{1H} and H NMR (300 MHz, CD2Cl2, 293 K)
data were identical to those reported for 2 with the exception
of the appearance of the resonances at 7.74 (br s, 8H, o-BArF
and 7.58 (s, 4H, p-BArF4) ppm.
)
4
Preparation of [OsH2(η5-C5H5){K1-OC(CH3)CHdCHPh}-
(PiPr3)]BF4 (3). In a Schlenk flask in a glovebox were added
2 (50 mg, 0.10 mmol) and benzylideneacetone (150 mg, 1.03
mmol). The flask was removed from the glovebox and placed
on a vacuum line under argon. The reaction mixture was
stirred for 5 min under reduced pressure. The resultant orange
slurry was cooled to -70 °C, and cold diethyl ether (20 mL)
was added. Immediately, a light yellow solid appeared, which
was washed with cold diethyl ether (3 × 5 mL), cold toluene
(3 × 5 mL), and then with pentane (3 × 5 mL). The product
was recrystallized from cold dichloromethane (2 mL) and
diethyl ether (20 mL). The light yellow solid was separated
by decantation and dried in vacuo. Yield: 51 mg (79%). Anal.
Calcd for C24H38BF4OOsP: C, 44.31; H, 5.89. Found: C, 44.63;
H, 6.07. IR (Nujol, cm-1): ν(OsH) 2116 (w), ν(CO) 1616 (m).
Experimental Section
General Methods and Instrumentation. 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. H, 31P{1H}, and 13C{1H} NMR spectra were recorded
1
on either a Varian UNITY 300, 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. Spectral assignments were achieved by
1H-1H COSY and NOESY, 1H{31P}, 13C APT, 1H-13C HMQC,
and 1H-13C HMBC experiments. Infrared spectra were run
on a Perkin-Elmer 1730 spectrometer (Nujol mulls on poly-
ethylene sheets). C and H analyses 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.
GC-MS experiments were run on an Agilent 5973 mass
3
1H NMR (400 MHz, CD2Cl2, 223 K): δ 7.71 (d, JHH ) 16.9,
3
1H, PhCH), 7.68 (m, 2H, Ph), 7.54 (m, 3H, Ph), 6.81 (d, JHH
) 16.9, 1H, CHCO), 5.47 (s, 5H, C5H5), 2.43 (s, 3H, CH3), 2.10
3
3
(br, 3H, PCHCH3), 1.24 (dd, JHP ) 14.5, JHH ) 6.6, 18H,
PHCH3), -7.61 (d, JHP ) 32.0, 2H, OsH). 31P{1H} NMR
2
(161.99 MHz, CD2Cl2, 223 K): δ 42.1 (s, t in off-resonance).
13C{1H} NMR (100 MHz, CD2Cl2, 223 K): δ 213.6 (s, CO), 150.0
(s, PhCH), 132.6 (s, CipsoPh), 132.4, 129.1, 129.0 (all s, Ph),

5998 Organometallics, Vol. 24, No. 24, 2005
Esteruelas et al.
124.7 (s, CHCO), 77.9 (d, JCP ) 2, C5H5), 27.5 (br d, JCP ) 32,
PCHCH3), 27.2 (br, CH3), 18.6 (s, PCHCH3).
(400 MHz, CD2Cl2, 293 K) data were identical to those reported
for 3 with the exception of the absence of the resonance at
-7.61 ppm. 2H NMR (61.42 MHz, CH2Cl2, 293 K): δ -7.3 (br
Preparation of BArF Salt of 3. This complex was
4
2
d, JDP ) 4.2, OsD).
prepared as described for 3 starting from 125 mg (0.10 mmol)
of the BArF salt of 2 and benzylideneacetone (150 mg, 1.03
Both samples were stored at room temperature for 2 h.
Then, 1H and 2H NMR were recorded. The 1H NMR (400 MHz,
CD2Cl2, 293 K) data were identical to those reported for 4 with
the exception of the absence of the resonance at 7.56 ppm and
the intensity of the signals at 3.65 (0.5H, CH2Ph) and 3.17
4
mmol), but it was precipitated by addition of pentane. A light
yellow solid was obtained. Yield: 107 mg (75%). Crystals
suitable for the X-ray diffraction were obtained at 233 K by
slow diffusion of pentane into a concentrated solution of the
BArF4 salt of 3 in toluene. The 31P{1H} and 1H NMR (400 MHz,
CD2Cl2, 233 K) data were identical to those reported for 3 with
the exception of the appearance of the resonances at 7.70 (br
s, 8H, o-BArF4) and 7.52 (s, 4H, p-BArF4) ppm.
2
(0.5H, CH2Ph). H NMR (61.42 MHz, CH2Cl2, 293 K): δ 7.6
(br, OD), 3.5 (br, CHDPh), and 3.0 (br, CHDPh).
After 12 h at room temperature, 1H NMR showed the
1
presence of 5 and 4-phenylbutan-2-one-d2. The H NMR (400
MHz, CD2Cl2, 293 K) data were identical to those reported for
5 and 4-phenylbutan-2-one with the exception of the integral
ratio between the resonances at 2.85 (br t, 1H, CHDPh), 2.74
(br t, 1.35H, CHDCO), and 2.10 (br s, 2.65H, CH2D) corre-
sponding to that of 4-phenylbutan-2-one-d2.
Preparation of [OsH(η5-C5H5){η3-CH2C(OH)CHCH2Ph}-
(PiPr3)]BF4 (4). An orange solution of 3 (51 mg, 0.08
mmol) in 4 mL of dichloromethane was stirred at room
temperature for 12 h. The solution was concentrated to ca. 1
mL under reduced pressure. The addition of diethyl ether (10
mL) caused the formation of a light green solid, which was
separated by decantation, washed with diethyl ether (3 × 5
mL), and dried in vacuo. Yield: 42 mg (82%). Anal. Calcd for
C24H38BF4OOsP: C, 44.31; H, 5.89. Found: C, 43.97; H, 5.69.
1H NMR (400 MHz, CD2Cl2, 293 K): δ 7.56 (br, 1H, OH), 7.50
(m, 2H, Ph), 7.36 (m, 2H, Ph), 7.32 (m, 1H, Ph), 5.48 (s, 5H,
C5H5), 4.40 (d, 2JHH ) 5.2, 1H, OsCH2), 3.65 (dd, 2JHH ) 14.2,
Preparation of Os(η5-C5H5){C(Ph)CHC(O)CH3}(PiPr3)
(6). In a flame-dried Schlenk flask in a glovebox were added
113 mg (0.17 mmol) of 5 and sodium methoxide (12 mg, 0.22
mmol). The flask was removed from the glovebox and placed
on a vacuum line under argon. THF (5 mL) was added, and
after 15 min the solvent was removed in vacuo. The product
was extracted in toluene (10 mL) and filtered through Celite.
Then, the solvent was removed, and the resultant oil was
extracted with pentane (10 mL). The solution was concentrated
to dryness, and a dark brown oil was obtained.40 Yield: 86
2
3
3JHH ) 11.2, 1H, CH2Ph), 3.17 (dd, JHH ) 14.2, JHH ) 2.2,
3
3
3
1H, CH2Ph), 2.99 (ddd, JHH )11.2, JHP )11.0, JHH ) 2.2,
1H, CH), 2.27 (br, 1H, OsCH2), 2.16 (m, 3H, PCHCH3), 1.27
(dd, JHP ) 14.6, JHH ) 7.3, 9H, PCHCH3), 1.16 (dd, JHP
3
3
3
)
mg (88%). 1H NMR (400 MHz, C6D6, 293 K): δ 8.02 (d, JHH
)
)
3
2
14.6, JHH ) 7.3, 9H, PCHCH3), -13.63 (d, JHP ) 31.1, 1H,
OsH). 31P{1H} NMR (161.99 MHz, CD2Cl2, 293 K): δ 18.0 (s, d
in off-resonance). 13C{1H} NMR (100 MHz, CD2Cl2, 293 K): δ
141.6 (s, CipsoPh), 130.7 (s, CO), 129.3, 129.0, 128.6 (all s, Ph),
85.9 (d, JCP ) 2, C5H5), 37.9 (s, CH2Ph), 37.1 (d, JCP ) 5, CH),
27.5 (d, JCP ) 29, PCHCH3), 20.0 (s, PCHCH3), 19.6 (d, JCP
2, PCHCH3), 19.5 (s, OsCH2).
3
3
8.0, 2H, o-Ph), 7.51 (s, 1H, CH), 7.33 (dd, JHH ) 8.0, JHH
3
7.3, 2H, m-Ph), 7.17 (t, JHH ) 7.3, 1H, p-Ph), 4.54 (s, 5H,
C5H5), 2.44 (s, 3H, CH3), 1.88 (m, 3H, PCHCH3), 1.11 (dd, 3JHP
3
3
3
) 13.2, JHH ) 7.3, 9H, PCHCH3), 0.92 (dd, JHP ) 13.2, JHH
) 7.3, 9H, PCHCH3). 31P{1H} NMR (161.99 MHz, C6D6, 293
K): δ 22.8 (s). 13C{1H} NMR (100 MHz, C6D6, 293 K): δ 249.0
(d, JCP ) 4, OsC), 203.8 (d, JCP ) 4, CO), 155.5 (s, CipsoPh),
130.0 (d, JCP ) 2, CH), 129.9 (s, o-Ph), 128.9 (s, p-Ph), 128.3
(s, m-Ph), 72.6 (d, JCP ) 2, C5H5), 26.7 (d, JCP ) 25, PCHCH3),
22.3, (d, JCP ) 2, CH3), 20.8 (s, PCHCH3), 20.6 (s, PCHCH3).
MS (LSIMS+): m/z 562 (M+).
)
Preparation of [OsH(η5-C5H5){C(Ph)CHC(O)CH3}
(PiPr3)]BF4 (5). In a Schlenk flask in a glovebox were
added 2 (102 mg, 0.20 mmol) and benzylideneacetone (125
mg, 0.86 mmol). The flask was removed from the glovebox
and placed on a vacuum line under argon. The argon pres-
sure inside the flask was slightly reduced, and then it was
heated to 50 °C. After 2 h, the resulting orange solution was
cooled to -78 °C. The addition of diethyl ether (15 mL) caused
the formation of a light yellow solid, which was washed with
cold diethyl ether and dried in vacuo. Yield: 103 mg (79%).
GC-MS analysis of the mother liquor showed the presence of
benzylideneacetone and 4-phenylbutan-2-one. Anal. Calcd for
C24H36BF4OOsP: C, 44.45; H, 5.60. Found: C, 44.36; H, 5.66.
1H NMR (400 MHz, CD2Cl2, 293 K): δ 7.83 (m, 2H, Ph), 7.49
(m, 3H, Ph), 7.33 (s, 1H, CH), 5.57 (s, 5H, C5H5), 2.65 (s, 3H,
Preparation of [Os(η5-C5H5){CH2CHC(O)CH3}(PiPr3)]-
PF6 (8). A flame-dried Schlenk flask was charged with 7 (148
mg, 0.28 mmol). Acetone (18 mL) was added to the flask, and
it was cooled to -70 °C in a dry ice/2-propanol bath. Then,
thallium(I) hexafluorophosphate (126 mg, 0.36 mmol) was
added, the reaction mixture was stirred for 20 min, and the
solvent was removed in vacuo. The crude reaction mixture was
cooled to -70 °C and extracted with cold dichloromethane (30
mL). The orange slurry was filtered through Celite and
concentrated to ca. 1 mL under reduced pressure. The addition
of cold diethyl ether (15 mL) caused the formation of a light
green solid, which was separated by decantation, washed with
cold diethyl ether (3 × 5 mL), and dried in vacuo. Yield: 149
mg (83%). Anal. Calcd for C18H32F6OOsP2: C, 34.28; H, 5.12.
Found: C, 34.12; H, 4.98. 1H NMR (300 MHz, CD2Cl2, 233 K):
3
3
CH3), 2.42 (m, 3H, PCHCH3), 1.25 (dd, JHP ) 14.6, JHH
)
3
3
7.3, 9H, PCHCH3), 1.14 (dd, JHP ) 14.6, JHH ) 7.3, 9H,
PCHCH3), -12.84 (d, JHP ) 34.4, 1H, OsH). 31P{1H} NMR
2
(161.99 MHz, CD2Cl2, 293 K): δ 24.6 (s, d in off-resonance).
13C{1H} NMR (100 MHz, CD2Cl2, 293 K): δ 236.9 (d, JCP ) 4,
OsC), 214.6 (d, JCP ) 2, CO), 149.7 (s, CipsoPh), 134.6 (s, CH),
131.7 (s, p-Ph), 129.3 (s, o- and m-Ph), 87.3 (d, JCP ) 2, C5H5),
3
3
3
δ 5.78 (ddd, JHH ) 7.5, JHH ) 7.5, JHP ) 2.4, 1H, CH), 5.60
(s, 5H, C5H5), 3.51 (dd, 3JHH ) 7.5, 2JHH ) 1.5, 1H, CH2), 2.70
3
(s, 3H, CH3), 2.62 (m, 3H, PCHCH3), 1.70 (ddd, JHP ) 14.1,
3JHH ) 7.5, 2JHH ) 1.5, 1H, CH2), 1.38 (dd, 3JHP ) 14.1, 3JHH
)
27.7 (d, JCP ) 30, PCHCH3), 23.4, (s, CH3), 20.2 (d, JCP
)
3
3
6.9, 9H, PCHCH3), 1.35 (dd, JHP ) 14.1, JHH ) 6.9, 9H,
PCHCH3). 31P{1H} NMR (121.4 MHz, CD2Cl2, 233 K): δ 9.6
(s, PCHCH3), -144.2 (sept, JFP ) 714, PF6). 13C{1H} NMR (75.4
MHz, CD2Cl2, 233 K): δ 141.3 (s, CO), 79.4 (s, C5H5), 67.2 (s,
CH) 31.4 (d, JCP ) 6, CH2), 26.2 (d, JCP ) 28, PCHCH3), 20.4,
(s, CH3), 19.5 (s, PCHCH3), 19.1 (s, PCHCH3).
2, PCHCH3), 19.3 (d, JCP ) 2, PCHCH3). MS (LSIMS+): m/z
563 (M+).
Reaction of [OsD2(η5-C5H5)(η2-D2)(PiPr3)]BF4 (2-d4) with
Benzylideneacetone: Formation of [OsD2(η5-C5H5){K1-
OC(CH3)CHdCHPh}(PiPr3)]BF4 (3-d2), [OsH(η5-C5H5)-
{η3-CH2C(OD)CHCHDPh}(PiPr3)]BF4 (4-d2), 5, and 4-
Phenylbutan-2-one-d2. Two NMR tubes were charged with
2-d4 (20 mg, 0.04 mmol) and benzylideneacetone (18 mg, 0.12
mmol). To the first NMR tube, 0.5 mL of dichloromethane was
added, and to the second 0.5 mL of dichloromethane-d2 was
added. After that, 1H and 2H NMR were recorded. The 1H NMR
Preparation of [OsH(η5-C5H5){CHCHC(O)CH3}(PiPr3)]A
(9) (A ) PF6, BF4). 9-PF6 Salt. An orange solution of 7 (668
(40) All our attempts to achieve a valid elemental analysis deter-
mination for this complex were unsuccessful due to the presence of
impurity traces (including solvents) in the sample.

Reduction and C(sp2)-H Bond Activation of Ketones
Organometallics, Vol. 24, No. 24, 2005 5999
mg, 1.28 mmol) in 10 mL of acetone was treated with thallium-
(I) hexafluorophosphate (493 mg, 1.41 mmol). The solution was
allowed to react for 15 min at room temperature, the solvent
was removed in vacuo, and the crude reaction mixture was
dissolved in dichloromethane (10 mL). The orange solution was
filtered through Celite and concentrated to ca. 1 mL under
reduced pressure. The addition of diethyl ether (15 mL) caused
the formation of a yellow solid, which was separated by
decantation and dried in vacuo. Yield: 660 mg (82%). Anal.
Calcd for C18H32F6OOsP2: C, 34.28; H, 5.12. Found: C, 34.19;
H, 5.04. 1H NMR (400 MHz, CD2Cl2, 293 K): δ 12.70 (ddd,
) 2.6 1H, OsCHCH), 5.71 (s, 5H, C5H5), 2.68 (s, 3H, CH3), 2.26
3
3
(m, 3H, PCHCH3), 1.22 (dd, JHP ) 14.8, JHH ) 6.6, 9H,
3
3
PCHCH3), 1.20 (dd, JHP ) 14.3, JHH ) 7.2, 9H, PCHCH3),
-9.40 (d, JHP ) 37.4, 1H, OsH). 31P{1H} NMR (121.4 MHz,
2
CD2Cl2, 293 K): δ 21.7 (s, d in off-resonance). 13C{1H} NMR
(75.4 MHz, CD2Cl2, 233 K): δ 217.4 (s, CO), 210.0 (d, JCP
)
14, OsCH), 138.1 (d, JCP ) 3, OsCHCH), 84.4 (s, C5H5), 28.4
(d, JCP ) 33, PCHCH3), 24.5 (s, CH3), 19.7 (s, PCHCH3), 18.9
(d, JCP ) 2, PCHCH3).
The same procedure was followed in all of the reported
protonation reactions starting from the corresponding osmium
derivatives, 6 (24 mg, 0.04 mmol), 14 (30 mg, 0.06 mmol), or
16 (33 mg, 0.05 mmol) and HBF4‚Et2O (5.5 µL, 0.04 mmol;
3JHH ) 7.3, 3JHH ) 5.1, 3JHP ) 1.4, 1H, OsCH), 7.29 (d, 3JHH
7.3, 1H, OsCHCH), 5.63 (s, 5H, C5H5), 2.62 (s, 3H, CH3), 2.24
)
3
3
1
(m, 3H, PCHCH3), 1.23 (dd, JHP ) 14.6, JHH ) 6.6, 9H,
8.2 µL, 0.06 mmol; and 7.3 µL, 0.05 mmol, respectively). H
3
3
and 31P{1H} NMR spectra recorded after 20 min were identical
to those reported for 5, 13, and 15, respectively.
PCHCH3), 1.10 (dd, JHP ) 14.6, JHH ) 6.6, 9H, PCHCH3),
-13.41 (dd, JHP ) 31.5, JHH ) 5.1, 1H, OsH). 31P{1H} NMR
(161.99 MHz, CD2Cl2, 293 K): δ 30.2 (s, d in off-resonance,
iPr3), -144.4 (sept, PF6). 13C{1H} NMR (100 MHz, CD2Cl2, 293
K): δ 222.8 (br, OsCH), 214.5 (d, JCP ) 2, CO), 137.2 (s,
OsCHCH), 86.7 (s, C5H5), 27.0 (d, JCP ) 29, PCHCH3), 23.4,
(s, CH3), 20.0 (d, JCP ) 2, PCHCH3), 19.2 (d, JCP ) 2, PCHCH3).
MS (LSIMS+): m/z 487 (M+).
2
3
Preparation of [OsH(η5-C5H5){C6H4C(O)CH3}(PiPr3)]-
BF4 (13). This complex was prepared as described for 5
starting from 200 mg (0.40 mmol) of 2 and acetophenone
(150 µL, 1.29 mmol). A light yellow solid was obtained.
Yield: 213 mg (87%). GC-MS analysis of the mother liquor
showed the presence of acetophenone and 1-phenyleth-
anol. Anal. Calcd for C22H34BF4OOsP: C, 42.45; H, 5.51.
Found: C, 42.30; H, 5.24. IR (Nujol, cm-1): ν(OsH) 2171 (m),
ν(CO) 1588 (s). 1H NMR (400 MHz, CD2Cl2, 293 K): δ 8.19 (d,
9-BF4 Salt. This complex was prepared as described for 5
starting from 100 mg (0.20 mmol) of 2 and methyl vinyl ketone
(49 µL, 0.59 mmol). A yellow solid was obtained. Yield: 83
mg (73%). Anal. Calcd for C18H32BF4OOsP: C, 37.77; H, 5.63.
Found: C, 37.42; H, 5.36. GC-MS analysis of the mother liquor
showed the presence of methyl vinyl ketone and ethyl methyl
ketone.
3
3JHH ) 8.0, 1H, Ph), 8.00 (d, JHH ) 8.0, 1H, Ph), 7.30 (vt,
3JHH ) 8.0, 1H, Ph), 7.14 (vt, 3JHH ) 8.0, 1H, Ph), 5.66 (s, 5H,
C5H5), 2.91 (s, 3H, CH3), 2.33 (m, 3H, PCHCH3), 1.21 (dd,
3
3
3JHP ) 14.6, JHH ) 7.3, 9H, PCHCH3), 0.98 (dd, JHP ) 13.9,
3JHH ) 7.3, 9H, PCHCH3), -13.80 (d, JHP ) 32.9, 1H, OsH).
2
Reaction of [OsH(η5-C5H5){CHCHC(O)CH3}(PiPr3)]PF6
(9) with Sodium Methoxide: Formation of Os(η5-C5H5)-
31P{1H} NMR (161.99 MHz, CD2Cl2, 293 K): δ 28.0 (s, d in
off-resonance). 13C{1H} NMR (100 MHz, CD2Cl2, 293 K): δ
220.9 (d, JCP ) 3, CO), 179.3 (d, JCP ) 3, OsC), 145.1 (s, Ph),
145.0 (s, CipsoPh), 134.7 (s, Ph), 133.4 (s, Ph), 124.2 (s, Ph),
86.5 (d, JCP ) 2, C5H5), 27.6 (d, JCP ) 29, PCHCH3), 23.5 (s,
CH3), 20.0 (s, PCHCH3), 18.8 (d, JCP ) 3, PCHCH3). MS
(LSIMS+): m/z 537 (M+).
{CHCHC(O)CH3}(PiPr3) (10) and OsH(η5-C5H5)(dCdCHC-
(O)CH3)(PiPr3) (11). A procedure analogous to that described
for 6 was followed starting from 9-PF6 (250 mg, 0.40 mmol)
and sodium methoxide (25 mg, 0.46 mmol). A dark brown thick
oil was obtained. The NMR spectra in C6D6 at room temper-
ature showed the presence of 10 and 11 in a molar ratio 5:1.
Yield of the mixture: 153 mg (80%). Complex 10 could be
isolated pure by crystallization of the mixture from pentane
at -78 °C. Spectroscopic data for 10: 1H NMR (400 MHz, C6D6,
Preparation of Os(η5-C5H5){C6H4C(O)CH3}(PiPr3) (14).
This complex was prepared as described for 6 starting from
113 mg (0.18 mmol) of 13 and sodium methoxide (15 mg, 0.28
mmol). A dark brown oil was obtained.40 Yield: 72 mg (74%).
1H NMR (400 MHz, C6D6, 293 K): δ 8.49 (m, 1H, Ph), 7.55
(m, 1H, Ph), 6.82 (m, 2H, Ph), 4.60 (s, 5H, C5H5), 2.56 (s, 3H,
3
3
293 K): δ 13.39 (d, JHH ) 7.3, 1H, OsCH), 7.42 (d, JHH
)
7.3, 1H, OsCHCH), 4.60 (s, 5H, C5H5), 2.46 (d, JHP ) 2.2, 3H,
3
3
CH3), 1.70 (m, 3H, PCHCH3), 1.02 (dd, JHP ) 13.2, JHH
)
3
3
CH3), 1.70 (m, 3H, PCHCH3), 1.02 (dd, JHP ) 13.0, JHH
)
3
3
7.3, 9H, PCHCH3), 0.98 (dd, JHP ) 13.2, JHH ) 7.3, 9H,
3
3
7.2, 9H, PCHCH3), 0.82 (dd, JHP ) 12.4, JHH ) 7.2, 9H,
PCHCH3). 31P{1H} NMR (161.99 MHz, C6D6, 293 K): δ 30.4
PCHCH3). 31P{1H} NMR (161.99 MHz, C6D6, 293 K): δ 23.5
(s). 13C{1H} NMR (100 MHz, C6D6, 293 K): δ 237.8 (d, JCP
)
(s). 13C{1H} NMR (100 MHz, C6D6, 293 K): δ 214.9 (d, JCP
)
6, OsCH), 203.8 (d, JCP ) 2, CO), 131.0 (s, OsCHCH), 71.9 (d,
JCP ) 2, C5H5), 25.8 (d, JCP ) 26, PCHCH3), 22.3 (s, CH3), 20.6
(s, PCHCH3), 20.5 (s, PCHCH3). Spectroscopic data for 11: 1H
NMR (400 MHz, C6D6, 293 K): δ 4.89 (s, 5H, C5H5), 3.00 (br,
1H, CH), 2.51 (s, 3H, CH3), 1.83 (m, 3H, PCHCH3), 0.85 (dd,
3, CO), 202.7 (d, JCP ) 7, OsC), 145.3 (s, CipsoPh), 143.9, 133.3,
131.1, 117.7 (all s, Ph), 70.7 (d, JCP ) 2, C5H5), 27.0 (d, JCP
)
25, PCHCH3), 22.2 (s, CH3), 20.8 (s, PCHCH3), 19.9 (s,
PCHCH3). MS (LSIMS+): m/z 536 (M+).
3
3
Preparation of [OsH(η5-C5H5){C(Ph)CHC(O)Ph}(PiPr3)]-
BF4 (15). This complex was prepared as described for 5
starting from 160 mg (0.32 mmol) of 2 and benzylideneac-
etophenone (284 mg, 1.37 mmol), but heating the reaction
mixture for 8 h. A green solid was obtained. Yield: 198 mg
(88%). GC-MS analysis of the mother liquor showed the
presence of benzylideneacetonephenone and benzylacetophe-
none. Anal. Calcd for C29H38BF4OOsP: C, 49.02; H, 5.39.
Found: C, 48.98; H, 5.19. 1H NMR (400 MHz, CD2Cl2, 293 K):
δ 8.02 (m, 3H, Ph), 7.91 (m, 2H, Ph), 7.59-7.52 (m, 6H, Ph
plus CH), 5.65 (s, 5H, C5H5), 2.48 (m, 3H, PCHCH3), 1.28 (dd,
3JHP ) 14.0, JHH ) 7.2, 9H, PCHCH3), 0.83 (dd, JHP ) 14.0,
3JHH ) 7.2, 9H, PCHCH3), -14.12 (dd, 2JHP ) 29.2, 4JHH ) 2.0,
1H, OsH). 31P{1H} NMR (161.99 MHz, C6D6, 293 K): δ 42.9
(s, d in off-resonance). 13C{1H} NMR (100 MHz, C6D6, 293 K):
δ 289.7 (d, JCP ) 11, OsC), 191.8 (s, CO), 118.1 (s, CH), 84.5
(d, JCP ) 2, C5H5), 28.5 (d, JCP ) 31, PCHCH3), 28.5, (s, CH3),
20.5 (s, PCHCH3), 20.2 (s, PCHCH3). MS (LSIMS+): m/z 486
(M+).
Reaction of 10 and 11 with HBF4. An NMR tube
containing a dark brown solution of 10 and 11 (24 mg, 0.05
mmol) in 0.5 mL of dichloromethane-d2 was treated with
HBF4‚Et2O (6.6 µL, 0.05 mmol). The solution color changed
immediately from dark brown to light yellow. After 30 min at
room temperature, the NMR spectra at -40 °C showed the
presence of 9 and 12 in a molar ratio of 1:2. After 12 h at room
temperature, 9 was the only isomer observed. Spectroscopic
data for 12: 1H NMR (300 MHz, CD2Cl2, 233 K): δ 11.71 (dd,
3
3
3JHP ) 15.4, JHH ) 6.6, 9H, PCHCH3), 1.14 (dd, JHP ) 14.6,
2
3JHH ) 7.0, 9H, PCHCH3), -12.50 (d, JHP ) 34.4, 1H, OsH).
31P{1H} NMR (161.99 MHz, CD2Cl2, 293 K): δ 28.5 (s, d in
off-resonance). 13C{1H} NMR (100 MHz, CD2Cl2, 293 K): δ
237.4 (d, JCP ) 3, OsC), 205.7 (d, JCP ) 2, CO), 150.5 (s,
CipsoPh), 133.9 (s, CipsoPh), 133.8 (s, CH), 131.9 (s, p-Ph), 131.2
3
3
4
3JHH ) 7.7, JHP ) 1.6, 1H, OsCH), 7.22 (dd, JHH ) 7.7, JHP
(s, p-Ph), 129.6, 129.5, 129.4, 129.3 (all s, o- and m-Ph), 87.6

6000 Organometallics, Vol. 24, No. 24, 2005
Table 4. Crystal Data and Data Collection and Refinement for 3, 10, and 13
10
Esteruelas et al.
3
13
Crystal Data
formula
C
56H50BF24OOsP
C18H31OOsP
484.60
C22H34BF4OOsP
molecular wt
1426.94
622.47
color and habit
yellow, irregular prism
0.30, 0.20, 0.22
triclinic, P1h
12.1960(16)
12.8102(17)
18.322(2)
brown, irregular block
0.18, 0.16, 0.12
triclinic, P1h
9.2950(6)
colorless, irregular block
0.12, 0.08, 0.02
triclinic, P1h
8.9899(8)
11.2125(10)
11.9126(11)
78.686(2)
size, mm
symmetry, space group
a, Å
b, Å
9.3678(6)
c, Å
11.0350(8)
81.6970(10)
77.1260(10)
81.0550(10)
919.28(11)
2
R, deg
â, deg
γ, deg
V, Å3
Z
87.708(2)
82.980(2)
82.2820(10)
78.1240(10)
1146.71(18)
2
88.746(2)
2838.3(6)
2
Dcalc, g cm-3
1.670
1.751
1.803
Data Collection and Refinement
diffractometer
λ(Mo KR), Å
Bruker Smart APEX
0.71073
monochromator
scan type
graphite oriented
ω scans
µ, mm-1
2θ, range deg
temp, K
no. of data collected
no. of unique data
no. of params/restraints
R1a [F2 > 2σ(F2)]
wR2b [all data]
Sc [all data]
2.393
7.020
5.674
3, 57
100.0(2)
12 019
3, 57
3, 57
100.0(2)
37 705
100.0(2)
8579
13 611 (Rint ) 0.0293)
790/24
4192 (Rint ) 0.0204)
205/0
5414 (Rint ) 0.0348)
282/1
0.0347
0.0222
0.0333
0.0832
0.0445
0.0552
1.144
0.990
0.893
2
2
a R1(F) ) ∑||Fo| - |Fc||/∑|Fo|. b wR2(F2) ) {∑[w(Fo2 - Fc )2]/∑[w(Fo2)2]}1/2
.
c Goof ) S ) {∑[Fo2 - Fc )2]/(n - p)}1/2, where n is the number
of reflections and p is the number of refined parameters.
on F2 with SHELXL97,42 was similar for all complexes,
including isotropic and subsequently anisotropic displacement
parameters. The hydrogen atoms were observed or calculated
and refined freely or using a restricted riding model. Hydride
ligands were observed in the difference Fourier maps and
refined as free isotropic atoms (3) or with restrained Os-H
bond length (13, 1.59 Å, CSD). For 3, one of the CF3 groups of
(d, JCP ) 2, C5H5), 27.9 (d, JCP ) 29, PCHCH3), 20.4 (s,
PCHCH3), 19.3 (d, JCP ) 2, PCHCH3). MS (LSIMS+): m/z
625 (M+).
Preparation of [Os(η5-C5H5){C(Ph)CHC(O)Ph}(PiPr3)
(16). This complex was prepared as described for 6 starting
from 148 mg (0.21 mmol) of 15 and sodium methoxide (19 mg,
0.35 mmol). A dark brown oil was obtained.40 Yield: 106 mg
the BArF anion was observed disordered. This group was
4
defined with four moieties, complementary occupancy fac-
tors, isotropic atoms, and restrained geometry. All the
highest electronic residuals were observed in close proximity
of the Os centers and make no chemical sense. Crystal data
and details of the data collection and refinement are given in
Table 4.
1
(82%). H NMR (400 MHz, C6D6, 293 K): δ 8.23 (s, 1H, CH),
8.18 (m, 2H, Ph), 8.06 (m, 2H, Ph), 7.36 (m, 2H, Ph), 7.22-
7.14 (m, 2H, Ph), 7.03 (m, 2H, Ph), 4.58 (s, 5H, C5H5), 1.83
3
3
(m, 3H, PCHCH3), 1.06 (dd, JHP ) 12.9, JHH ) 7.1, 9H,
3
3
PCHCH3), 0.89 (dd, JHP ) 13.1, JHH ) 7.2, 9H, PCHCH3).
31P{1H} NMR (161.99 MHz, C6D6, 293 K): δ 23.7 (s). 13C{1H}
NMR (100 MHz, C6D6, 293 K): δ 249.8 (d, JCP ) 4, OsC), 198.2
(d, JCP ) 3, CO), 156.3 (s, CipsoPh), 137.3 (s, CipsoPh), 130.0,
129.7, 129.1, 128.9, 128.8, 128.5 (all s, Ph), 127.7 (s, CH), 73.3
(d, JCP ) 2, C5H5), 26.6 (d, JCP ) 26, PCHCH3), 20.7 (s,
PCHCH3), 20.5 (s, PCHCH3). MS (LSIMS+): m/z 624 (M+).
Acknowledgment. Financial support from the
MCYT of Spain (Proyect BQU2002-00606) is acknowl-
edged. Y.A.H. thanks the Spanish MCYT for his grant.
Supporting Information Available: CIF files giving
positional and displacement parameters, crystallographic data,
and bond lengths and angles of compounds 3, 10, and 13. This
material is available free of charge via the Internet at
http://pubs.acs.org.
Structural Analysis of Complexes 3, 10, and 13. 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 covering 0.3° in ω. Data were corrected for absorption
by using a multiscan method applied with the SADABS
program.41 The structures of all compounds were solved by the
Patterson method. Refinement, by full-matrix least squares
OM0508177
(41) Blessing, R. H. Acta Crystallogr. 1995, A51, 33. SADABS: Area-
detector absorption correction; Bruker-AXS: Madison, WI, 1996.
(42) SHELXTL Package v. 6.10; Bruker-AXS: Madison, WI, 2000.
Sheldrick, G. M. SHELXS-86 and SHELXL-97; University of Go¨ttin-
gen: Go¨ttingen, Germany, 1997.