Reactions of the square-planar compounds Ir(C2Ph)L2(PCy3) (L2 = 2 CO, TFB) with HSiR3 (R = Et, Ph) and Hx+1SiPh3-x (x = 1, 2): Stoichiometric and catalytic formation of Si-C bonds

Article abstract of DOI:10.1021/om950527y

The square-planar cis-dicarbonyl complex Ir(C₂Ph)(CO)₂(PCy₃) (1) reacts with ca. 1 equiv of HSiR₃ to give, in quantitative yield, the corresponding alkynyl-hydrido-silyl derivatives Ir(C₂Ph)(H)(SiR₃)(CO)₂(PCy₃) (SiR₃ = SiEt₃ (2), SiPh₃ (3), SiHPh₂ (4), and SiH₂Ph (5)). The reactivity of the related tetrafluorobenzobarrelene compound Ir(C₂Ph)(TFB)(PCy₃) (6) toward HSiR₃ has been also studied by NMR spectroscopy. The addition of ca. 2 equiv of HSiEt₃ to a benzene-d₆ solution of 6 affords IrH₂(SiEt₃)(TFB)(PCy₃) (7) and PhC=CSiEt₃ in a 1:1 molar ratio, while the reaction of 6 with ca. 1 equiv of HSiPh₃ yields, after 1 h and 30 min, IrH₂-(SiPh₃)(TFB)(PCy₃) (10, 8%), Ir{C(SiPh₃)=CHPh}(TFB)(PCy₃) (11, 52%), and PhC=CSiPh₃ (8%). The addition of ca. 1 equiv of H₂SiPh₂ to a benzene-d₆ solution of 6 leads, after 1 h, to IrH₂{Si(C₂Ph)Ph₂}(TFB)(PCy₃) (12) in 90% yield. The alkynyl compounds 1 and 6 have been found to be active catalysts for the addition of triethylsilane to phenylacetylene. In all experiments, PhCH=CH₂, PhC≡CSiEt₃, cis-PhCH=CH(SiEt₃), trans-PhCH=CH(SiEt₃), and Ph(SiEt₃)C=CH₂ were obtained. On the basis of the results from the stoichiometric reactions together those from the catalytic experiments, reaction pathways for the formation of these silylate products are discussed.

Full text of DOI:10.1021/om950527y

814
Organometallics 1996, 15, 814-822
Rea ction s of th e Squ a r e-P la n a r Com p ou n d s
Ir (C2P h )L2(P Cy3) (L2 ) 2 CO, TF B) w ith HSiR3 (R ) Et,
P h ) a n d Hx+1SiP h 3-x (x ) 1, 2): Stoich iom etr ic a n d
Ca ta lytic F or m a tion of Si-C Bon d s
Miguel A. Esteruelas,* Montserrat Oliva´n, and Luis A. Oro
Departamento de Qu´ımica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n,
Universidad de Zaragoza, CSIC, 50009 Zaragoza, Spain
Received J uly 10, 1995X
The square-planar cis-dicarbonyl complex Ir(C2Ph)(CO)2(PCy3) (1) reacts with ca. 1 equiv
of HSiR3 to give, in quantitative yield, the corresponding alkynyl-hydrido-silyl derivatives
Ir(C2Ph)(H)(SiR3)(CO)2(PCy3) (SiR3 ) SiEt3 (2), SiPh3 (3), SiHPh2 (4), and SiH2Ph (5)). The
reactivity of the related tetrafluorobenzobarrelene compound Ir(C2Ph)(TFB)(PCy3) (6) toward
HSiR3 has been also studied by NMR spectroscopy. The addition of ca. 2 equiv of HSiEt3 to
a benzene-d6 solution of 6 affords IrH2(SiEt3)(TFB)(PCy3) (7) and PhCtCSiEt3 in a 1:1 molar
ratio, while the reaction of 6 with ca. 1 equiv of HSiPh3 yields, after 1 h and 30 min, IrH2-
(SiPh3)(TFB)(PCy3) (10, 8%), Ir{C(SiPh3)dCHPh}(TFB)(PCy3) (11, 52%), and PhCtCSiPh3
(8%). The addition of ca. 1 equiv of H2SiPh2 to a benzene-d6 solution of 6 leads, after 1 h, to
IrH2{Si(C2Ph)Ph2}(TFB)(PCy3) (12) in 90% yield. The alkynyl compounds 1 and 6 have been
found to be active catalysts for the addition of triethylsilane to phenylacetylene. In all
experiments, PhCHdCH2, PhCtCSiEt3, cis-PhCHdCH(SiEt3), trans-PhCHdCH(SiEt3), and
Ph(SiEt3)CdCH2 were obtained. On the basis of the results from the stoichiometric reactions
together those from the catalytic experiments, reaction pathways for the formation of these
silylate products are discussed.
In tr od u ction
and we3p,w have proposed that the anti-addition product
is formed by initial insertion of the unsaturated sub-
strate into a M-Si bond, followed by isomerization of
the (Z)-vinylsilyl intermediate to the less sterically
congested (E)-vinylsilyl isomer (Scheme 1).
Recently, it has been also observed that in the
presence of certain iridium catalysts the hydrosilyla-
tion reaction furthermore produces RCtCSiR′3, accord-
ing to eq 2.4,5
The addition of silanes to alkynes catalyzed by transi-
tion metal complexes is one of the most important
laboratory and industrial methods of forming vinylsi-
lanes,1 which have shown to be versatile intermediates
in organic synthesis.2 In the hydrosilylation of terminal
alkynes, both the normal syn- and the unusual anti-
addition products are formed, as well as the R isomer
(eq 1), and much attention has received in an attempt
to develop highly selective catalysts.3
(3) (a) Benkeser, R. A.; Burrous, M. L.; Nelson, L. E.; Swisher, J . V.
J . Am. Chem. Soc. 1963, 83, 4385. (b) Ojima, I.; Kumagai, M.; Nagai,
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Chem. 1980, 195, 363. (g) Brady, K. A.; Nile, T. A. J . Organomet. Chem.
1981, 206, 299. (h) Lappert, M. F.; Maskell, R. K. J . Organomet. Chem.
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Lii, J .; Tien-Mayr, S.-Y. Organometallics 1988, 7, 2524. (k) Chatani,
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(m) Nagashima, H.; Tatebe, K.; Ishibashi, T.; Sakakibara, J .; Itoh, K.
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Ingallina, P. Organometallics 1990, 9, 3127. (o) Tanke, R. S.; Crabtree,
R. H. J . Am. Chem. Soc. 1990, 112, 7984. (p) Esteruelas, M. A.; Oro,
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C. L.; Clayton, T. W., J r.; Lin J . Organometallics 1991, 10, 1225. (t)
Kopylova, L. I.; Pukhnarevich, V. B.; Voronkov, M. G. Zh. Obshch.
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The formation of the anti-addition product is interest-
ing because the cis isomer is a result of the trans-
addition of the silane to the alkyne. Ojima,3n Crabtree,4
X Abstract published in Advance ACS Abstracts, December 15, 1995.
(1) (a) Noels, A. F.; Hubert, A. J . Industrial Applications of
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15.
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0276-7333/96/2315-0814$12.00/0 © 1996 American Chemical Society

Reactions of Ir(C2Ph)L2(PCy3) Compounds
Organometallics, Vol. 15, No. 2, 1996 815
dicarbonyl compound Ir{η1-OC(O)CH3}(CO)2(PCy3) to-
ward HSiEt3, HSiPh3, H2SiPh2, and H3SiPh was exam-
ined. The study revealed that the cis-dicarbonyl complex
undergoes reactions to give dihydrido-silyl and bis(silyl)
derivatives depending upon the nature of the silane
used. The complexes IrH(SiHPh2)2(CO)2(PCy3) and
IrH(SiH2Ph)2(CO)2(PCy3), which were obtained by reac-
tion of Ir{η1-OC(O)CH3}(CO)2(PCy3) with H2SiPh2 and
H3SiPh, react with alcohols to afford IrH2{Si(OR)-
Ph2}(CO)2(PCy3) and IrH2{Si(OR)2Ph}(CO)2(PCy3), re-
spectively.10 Recently, it has been observed that the
oxidative addition of H2SiPh2 to the complexes Ir(a-
cac)(η2-CH3O2C-CtCCO2CH3)(PR3) (PR3 ) PiPr3, PCy3)
Sch em e 1
Crabtree et al. have suggested that once the (E)-
vinylsilyl intermediate has been formed, â-elimination
of the endo-hydrogen atom of the vinylsilyl group could
afford the silylation product.4 Recently, we have ex-
amined the addition of triethylsilane to phenylacetylene
catalyzed by [Ir(COD)(η2-iPr2PCH2CH2OMe)]BF4.6 This
study has revealed that under the catalytic conditions
both hydrido-alkynyl and hydrido-silyl species are
formed. Hydrido-alkynyl species are the key interme-
diates for the formation of PhCtCSiEt3, while hydrido-
silyl species are the key intermediates for the formation
of cis-PhCHdCH(SiEt3).6b In addition, we note from
some of our previous reports that the formation of the
dehydrogenative silylation product takes place when the
cis-vinylsilane is the major product of the catalytic
reactions.7 Interestingly, in these cases, the catalysts
are alkynyl derivatives or complexes which react with
terminal alkynes to give alkynyl compounds.8 Thus, at
the first glance, one could think that, in some cases, the
formation of transition metal alkynyl compounds, dur-
ing the catalytic hydrosilylation, plays a main role in
the formation of the anti-addition product. In this
respect, the investigation of the reactivity of alkynyl
complexes with silanes is of great interest.
For several years, we have been exploring the reactiv-
ity of square-planar iridium(I) complexes toward silanes.
Eight years ago, we reported that the alkoxy compounds
Ir(OR)(COD)(PR′3) (COD ) 1,5-cyclooctadiene; R ) Me,
PR′3 ) PPh3; R ) Et, PR′3 ) PCy3) react with HSiEt3
and HSiMe2Ph to give ROSiR′′3 (SiR′′3 ) SiEt3, SiMe2-
Ph) and the dihydrido-silyl complexes IrH2(SiR′′3)-
(COD)(PR′3).9 Subsequently, we observed that the
reactions of the acetato complex Ir{η1-OC(O)CH3}(TFB)-
(PR3) (TFB ) tetrafluorobenzobarrelene; PR3 ) PPh3,
PCy3, PiPr3) with HSiR′3 also led to dihydrido-silyl
derivatives of the formula IrH2(SiR′3)(TFB)(PR3) (R′ )
Et, Ph). The same reactions with H2SiPh2 afford IrH2-
{Si[OC(O)CH3]Ph2}(TFB)(PR3), which are the first iri-
dium compounds containing an acetoxysilyl ligand.7a As
a continuation of this work, the reactivity of the cis-
produces Ir(acac){C[CH(OCH3)OSiPh2]dCHCO2CH3}-
(PR3), where the bonding situation in the Ir-Si-O
sequence could be described as an intermediate state
between metal-silylene stabilized by an oxygen base and
a tetrahedral silicon.11
As a continuation of our work in this field, and with
the idea of casting some light on the role of the
transition metal alkynyl compounds in the formation
of cis-RCHdCH(SiR′3) during the catalytic hydrosily-
lation of terminal alkynes, we have now studied the
reactivity of the square-planar alkynyliridium(I) com-
pounds Ir(C2Ph)(CO)2(PCy3) and Ir(C2Ph)(TFB)(PCy3)
toward HSiEt3, HSiPh3, H2SiPh2, and H3SiPh. Al-
though most of the hydridosilyliridium(III) complexes
previously reported have been obtained by oxidative
addition of silanes to square-planar iridium(I) com-
pounds,12 as far as we know, the oxidative addition of
silanes to alkynyl derivatives of this type has not been
previously studied.
In this paper, we report the characterization of the
first alkynyl-hydrido-silyl and dihydrido-alkynylsilyl
derivatives of iridium(III). The catalytic activity of Ir-
(C2Ph)(CO)2(PCy3) and Ir(C2Ph)(TFB)(PCy3) in the ad-
dition of triethylsilane to phenylacetylene is also re-
ported.
Resu lts a n d Discu ssion
Rea ction s of Ir (C2P h )(CO)2(P Cy3) w ith HSiR3.
After 1 h, the addition of ca. 1 equiv of HSiEt3, HSiPh3,
(10) Esteruelas, M. A.; Lahoz, F. J .; Oliva´n, M.; On˜ate, E.; Oro, L.
A. Organometallics 1994, 13, 4246.
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816 Organometallics, Vol. 15, No. 2, 1996
Esteruelas et al.
H2SiPh2, or H3SiPh to yellow benzene-d6 solutions of
Ir(C2Ph)(CO)2(PCy3) (1) does not produce any change
in the solution color. However, the IR spectra, as well
has been recently observed for the oxidative addition
of HSnPh3 and HSnnBu3 to 1.13
Rea ction s of Ir (C2P h )(TF B)(P Cy3) w ith HSiR3.
After 1 h the 1H and 31P{1H} NMR spectra of the
solution formed by addition of ca. 1 equiv of HSiEt3 to
Ir(C2Ph)(TFB)(PCy3) (6) in benzene-d6 show the reso-
nances of 6 and the previously described dihydrido-
silyl derivative IrH2(SiEt3)(TFB)(PCy3) (7)7a in a 1:1
intensity ratio. Analysis by gas chromatography of
the solution also reveals the additional formation of
PhCtCSiEt3, which was characterized by mass spec-
troscopy. The amount of PhCtCSiEt3 formed was
similar to that of 7. The addition of HSiEt3 to the
solution of 6 in a 2:1 molar ratio leads, in quantitative
yield, to a mixture of 7 and PhCtCSiEt3 in a 1:1 molar
ratio. During the reaction, the formation of pheny-
lacetylene was not observed. The above mentioned data
can be rationalized according to Scheme 2. In agree-
ment with eq 3, the reaction could initially involve the
oxidative addition of HSiEt3 to 6, along the olefin-Ir-P
axis (B), to give 8 (SiR3 ) SiEt3), followed by reductive
elimination of PhCtCSiEt3 to give 9. The subsequent
oxidative addition of a second molecule of HSiEt3 to 9
should lead to 7.
1
as the H, 31P{1H}, and 13C{1H} NMR spectra clearly
indicate that the alkynyl-hydrido-silyl derivatives Ir-
(C2Ph)(H)(SiR3)(CO)2(PCy3) have been formed in quan-
titative yield, according to eq 3. In solution, these
compounds are stable up to 24 h if kept under an argon
atmosphere at room temperature.
The presence of two carbonyl ligands mutually cis
disposed and an alkynyl ligand is strongly supported
by the IR and 13C{1H} NMR spectra. The IR spectra
show two ν(CO) absorptions in the terminal carbonyl
region (between 2060 and 1998 cm-1), along with the
ν(CtC) and ν(Ir-H) vibrations between 2120 and 2140
cm-1
. Because the carbonyl ligands are chemically
inequivalent, the 13C{1H} NMR spectra show two dou-
blets at about 172 ppm. With regard to the values of
the P-C coupling constants (about 5 Hz) there is no
doubt about the mutually cis disposition of both carbonyl
groups and the phosphine ligand. The 13C{1H} NMR
spectra also contain the resonances due to the alkynyl
ligand. The CR carbon atoms appear as doublets at
about 73 ppm with coupling constants of about 15 Hz,
while the Câ carbon atoms also appear as doublets at
about 107 ppm, but with P-C coupling constants of
The elimination of PhCtCSiEt3 from 8 merits further
considerations. Due to the facial disposition of the silyl,
hydrido, and alkynyl ligands, three unimolecular reduc-
tive eliminations are possible, leading to HSiEt3,
PhCtCH, or PhCtCSiEt3. The first one again leads
to 6, and it is not our interest. However, of particular
interest is the question of competitive PhCtCH vs
PhCtCSiEt3 reductive elimination. Whereas the re-
ductive elimination of C-H bonds is a well-documented
process,12v,14 there are very few examples for the reduc-
tive elimination of Si-C bonds.12o,15 Milstein et al.12t
have recently studied the possible reductive elimination
from complexes of type fac-IrH(CH3)(SiR3)(PMe3)3. While
both the Si(OEt)3 and SiPh3 derivatives exclusively
liberate CH4 on heating, the SiEt3 derivative gives CH4
+ MeSiEt3 in a 4:1 molar ratio. The different behaviors
of the SiR3 complexes have been attributed to the
different M-Si bond strengths. Electron-donating groups
at the silicon atom weaken the M-Si bond and make
the Si-C elimination competitive with the C-H one.
The intermediate 8 exclusively eliminates PhCtCSiR3,
and the reductive elimination of phenylacetylene does
not occur because of the cis constraint imposed by the
chelating tetrafluorobenzobarrelene ligand and the fact
1
approximately 4 Hz. In the H NMR spectra the most
noticeable resonances are those corresponding to the
hydrido ligands at about -9 ppm, which appear as
doublets with P-H coupling constants between 14.7 and
15.6 Hz. The presence of only one hydrido ligand in
these compounds was inferred from the 31P{1H} NMR
spectra, which contain a singlet between 8.2 and 12.2
ppm which under off-resonance conditions due to P-H
coupling is split into a doublet. The 31P{1H} NMR
spectra also show the satellites due to the 29Si isotope.
The values of the P-Si coupling constants, between 73
and 91 Hz, strongly support the mutually trans disposi-
tion of the silyl and phosphine ligands.
The oxidative addition of silanes to iridium(I) com-
plexes is generally viewed as a diastereoselective con-
certed cis addition process with specific substrate
orientation.12k The exclusive formation of 2-5 is in
agreement with this. Thus, the addition of silanes to 1
seems to occur along the OC-Ir-P axis with the silicon
atom above the carbonyl group (A). The basis of this
(13) Esteruelas, M. A.; Lahoz, F. J .; Oliva´n, M.; On˜ate, E.; Oro, L.
A. Organometallics 1995, 14, 3486.
(14) (a) Halpern, J . Acc. Chem. Res. 1982, 15, 332. (b) Milstein, D.
Acc. Chem. Res. 1984, 17, 221.
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Gladysz, J . Organometallics 1984, 3, 1326. (b) Schubert, U.; Kunz, E.;
Knorr, M.; Mu¨ller, J . Chem. Ber. 1987, 120, 1079. (c) Schubert, U.;
Mu¨ller, C. J . Organomet. Chem. 1989, 373, 165. (d) Thorn, D. L.;
Harlow, R. L. Inorg. Chem. 1990, 29, 2017. (e) Hofmann, P.; Heiss,
H.; Neiteler, P.; Mu¨ller, G.; Lachmann, J . Angew. Chem., Int. Ed. Engl.
1990, 29, 880. (f) Lin, W.; Wilson, S. R.; Girolami, G. S. J . Am. Chem.
Soc. 1993, 115, 3022.
preference is probably steric and involves minimizing
nonbonded interactions between the silyl ligands and
the cyclohexyl groups of the phosphine. The same trend

Reactions of Ir(C2Ph)L2(PCy3) Compounds
Organometallics, Vol. 15, No. 2, 1996 817
Sch em e 2
that in a concerted reductive elimination the ligands
trans to the leaving ligands move into mutually trans
positions in the resulting four-coordinate complex.12v,16
Thus the unfavorable elimination becomes the only
possible alternative.
New Si-C bonds are also formed from the reactions
of 6 with HSiPh3 and H2SiPh2. After 30 min, the 31P-
{1H} NMR spectrum of the solution formed by addition
of ca. 1 equiv of HSiPh3 to 6 in benzene-d6 shows the
singlet of 6 at 23.2 ppm and a new singlet at 17.7 ppm.
Satellites due to the 29Si isotope are not observed, and
the intensity ratio between the two resonances is 6:4.
After 1 h and 30 min, a new singlet at 8.4 appear. This
resonance was assigned to the previously reported
dihydrido-silyl derivative IrH2(SiPh3)(TFB)(PCy3) (10)
by comparison of this spectrum with a pure sample. The
composition of the mixture was ca. 40% of 6, 52% of the
singlet at 17.7 ppm, and 8% of 10. After 2 h and 30
min the new composition of the mixture was ca. 31%,
F igu r e 1. 1H NMR spectrum in the 6.5-2.5 ppm region
of the reaction of Ir(C2Ph)(TFB)(PCy3) (6) with HSiPh3 after
1 h and 30 min of reaction: Ir(C2Ph)(TFB)(PCy3) (2); Ir-
{C(SiPh3)dCHPh}(TFB)(PCy3) (b); IrH2(SiPh3)(TFB)(PCy3)
(*).
coordinated to an iridium atom in a square-planar
arrangement.13 In the APT 13C{1H} NMR spectrum the
resonances of the alkenyl group of this compound appear
as a doublet with negative intensity at 146.16 ppm (J P-C
) 2.7 Hz), assigned to the R-carbon atom, and a singlet
with positive intensity at 124.47 ppm, assigned to the
â-carbon atom. Near the negative doublet the satellites
due to the 29Si isotope appear (J C-Si ) 35 Hz), suggest-
ing that the R-carbon atom of the alkenyl group is
also linked to a triphenylsilyl group. Therefore, the
above spectroscopic data strongly support that the
singlet at 17.7 ppm in the 31P{1H} NMR spectra corre-
sponds to the square-planar alkenylsilyl derivative Ir-
{C(SiPh3)dCHPh}(TFB)(PCy3) (11).
1
50%, and 19%. The H NMR spectra and the analysis
by gas chromatography of the three solutions show the
presence of ca. 60% (30 min), 30% (1 h and 30 min), and
10% (2 h and 30 min) of unreacted HSiPh3. In addition
the formation of PhCtCSiPh3 in similar amounts to
that of 10 was also observed.
1
Figure 1 shows the H NMR spectrum of the solution
Alkenylsilyl derivatives are rare. Eish, Lee, et al.18
have reported that at -20 °C the chloroform solutions
of the titanocene dichloride compound Cp2TiCl2 yield
[Cp2Ti{C(SiMe3)dCHPh}]AlCl4, by treatment with
PhCtCSiMe3 in the presence of CH3AlCl2. Tanaka et
al.19 have observed that alkynes undergo insertion
reactions into the Me3Si-Pt bond of PtBr(SiMe3)(PEt3)2,
to afford the â-alkenylsilyl derivatives PtBr{CRdCR-
(SiMe3)}(PEt3)2. Suzuki et al.20 have found that the
obtained after 1 h and 30 min in the 2.5-6.5 ppm region.
This spectrum contains the olefinic resonances of 6 and
10 along with a singlet at 6.50 (1 H) ppm, and three
broad resonances at 5.31 (2 H), 3.45 (2 H), and 2.74 (2
H). The singlet at 6.50 is characteristic for a â-proton
of an alkenyl group,17 while the broad resonances are
characteristic for a tetrafluorobenzobarrelene ligand,
with chemically inequivalent olefinic bonds which are
(16) (a) Deutsch, P. P.; Eisenberg, R. J . Am. Chem. Soc. 1990, 112,
714. (b) Deutsch, P. P.; Eisenberg, R. Organometallics 1990, 9, 709.
(17) See for example: (a) Andriollo, A.; Esteruelas, M. A.; Meyer,
U.; Oro, L. A.; Sa´nchez-Delgado, R. A.; Sola, E.; Valero, C.; Werner,
H. J . Am. Chem. Soc. 1989, 111, 7431. (b) Esteruelas, M. A.; Garc´ıa,
M. P.; Mart´ın, M.; Nu¨rnberg, O.; Oro, L. A.; Werner, H J . Organomet.
Chem. 1994, 466, 249.
(18) (a) Eisch, J . J .; Piotrowski, A. M.; Brownstein, S. K.; Gabe, E.
J .; Lee, F. L. J . Am. Chem. Soc. 1985, 107, 7219. (b) Brownstein, S.
K.; Gabe, E. J .; Fong Han, N.; Lee, F. L.; Le Page, Y.; Piotrowski, A.
M.; Eisch, J . J . J . Chem. Res. (S) 1992, 214.
(19) Yamashita, H.; Tanaka, M.; Goto, M. Organometallics 1993,
12, 988.

818 Organometallics, Vol. 15, No. 2, 1996
Esteruelas et al.
treatment of the bis(µ-silylene) complex [Cp*Ru(µ-
SiPh2)(µ-H)]2 with acetylene leads to the µ-2,5-1-
disilaruthenacyclopentene complex Cp*Ru(µ-SiPh2-
CHdCHSiPh2)(µ-H)2RuCp* as a result of the insertion
of C2H2 into a Ru-Si bond of [Cp*Ru(µ-SiPh2)(µ-H)]2,
and very recently J ones et al.21 described the synthesis
of Cp*Ru{C(SiHMe2)dCPh2}PR3, which can be viewed
as a 1-silaallene stabilized by both metal ligation and
interaction with a metal-hydrogen bond.
The formation of 11 involves the insertion of
PhCtCSiPh3, formed by reductive elimination from 8
(SiR3 ) SiPh3), into the Ir-H bond of the intermediate
9 (Scheme 2). This reaction could proceed by a con-
certed mechanism involving a four-center intermediate,
or, alternatively, via a vinylidene intermediate. In this
context, it should be noted that Werner et al.22 have
recently observed that not only 1-alkynes HCtCR but
also the trialkylsilyl derivatives RCtCSiR′3 can be
transformed in the coordination sphere of rhodium into
the isomeric disubstituted vinylidenes, :CdC(SiR′3)R.
The position of the triphenylsilyl group at the R-carbon
atom of the alkenyl ligand of 11 rules out the possible
participation of a vinylidene intermediate. In addition,
it should be mentioned that 11 is the kinetically favored
compound from the reaction of 6 with HSiPh3. Fur-
thermore, the dihydrido-silyl complex 11 is formed in
a significant quantity (about 20%) after 2 h and 30 min.
This suggests that in the presence of silane 11 is in
equilibrium with 9 and 10. The deinsertion of the
alkyne from 11 most probably involves the â-elimination
of the endo-hydrogen atom of the alkenylsilyl ligand,
which is in agreement with the previously mentioned
Crabtree proposal.
F igu r e 2. Variable-temperature 1H NMR spectra (toluene-
d8) of IrH2{Si(C2Ph)Ph2}(TFB)(PCy3) (12): (a) 6.5-2.5 ppm
region (signals marked with b correspond to Ir(C2Ph)-
(TFB)(PCy3) (6)) (b) hydride region.
inequivalent, although both olefinic bonds are chemi-
cally equivalent. As would be expected for this arrange-
ment, the spectrum at -60 °C contains four resonances
due to the diolefin, two aliphatic at 5.90 and 4.78 ppm
and two olefinic at 3.95 and 2.92 ppm. This behavior
suggests that 12 has a rigid structure (Scheme 2) only
at low temperature. At room temperature an intramo-
lecular exchange process takes place, which involves the
relative positions of the atoms of the diolefin. This
phenomenon is general for this type of compounds and
is a consequence of the trend that they have to release
the tricyclohexylphophine ligand.7a,10,13
In the 13C{1H} NMR spectrum the most noticeable
resonances are those correspondig to the CR and Câ
carbon atoms of the SiCtCPh group, which appear as
a doublet with a P-C coupling constant of 4.6 Hz at
99.53 and as a singlet at 109.00 ppm, respectively.
Previously, we have reported that the square-planar
compound Ir{η1-OC(O)CH3}(TFB)(PCy3) reacts with H2-
SiPh2 to give the acetoxysilyl derivative IrH2[Si{OC(O)-
CH3}Ph2](TFB)(PCy3). This reaction probably occurs
via the silylene intermediate IrH2{η1-OC(O)CH3}-
(dSiPh2)(TFB), which evolves by nucleophilic attack of
the acetato group at the silicon atom.7a,10 A similar
reaction pathway for the formation of 12 from 6 and
H2SiPh2 is not probable. It is well-known that electronic
structures and reactivities of organic fragments change
when they coordinate to transition metals to form
organometallic complexes. For example, the coordina-
tion of [RCtC]- to a metal center transfers the nucleo-
philicity from the R-carbon atom to the â-carbon atom.23
Therefore, the attack of the CR carbon atom of the
alkynyl group at the silicon atom of a silylene derivative
does not seem likely, given the electrophilicity of both
centers. Hence, it can be proposed that the formation
of 12 from 6 and H2SiPh2 occurs by initial oxidative
addition of H2SiPh2 to 6 to give 8 (SiR3 ) SiHPh2). The
reductive elimination of PhCtCSiHPh2 and subsequent
oxidative addition of the Si-H of PhCtCSiHPh2 to 9
should afford 12 (Scheme 2). A similar mechanism has
been proposed for silane exchange reactions.9b,12d,24
Ad d ition of HSiEt3 to P h CtCH Ca ta lyzed by 1
a n d 6. As expected from eq 3 and Scheme 2, the square
planar alkynyl complexes 1 and 6 catalyze the hydrosi-
lylation of phenylacetylene with triethylsilane. The
The addition of ca. 1 equiv of H2SiPh2 to a benzene-
d6 solution of 6 in an NMR tube leads to the dihydrido-
silyl complex IrH2{Si(C2Ph)Ph2}(TFB)(PCy3) (12) (Scheme
2) in 90% yield, after 1 h. The presence of two hydride
ligands in 12 is strongly supported by the 31P{1H} NMR
spectrum, which shows a singlet at 10.7 ppm, which at
-60 °C, under off-resonance conditions due to the P-H
coupling, is split into a triplet. Near this singlet, the
satellites due to the 29Si isotope appear. The value of
the Si-P coupling constant (60 Hz) is in agreement with
a mutually trans disposition for the tricyclohexylphos-
1
phine ligand and the silyl group. Similarly to the H
1
NMR spectra of 7 and 10, the H NMR spectrum of 12
is temperature-dependent (Figure 2). At room temper-
ature the hydrido ligands appear as a broad resonance
at -14.70 ppm, while the tetrafluorobenzobarrelene
diolefin gives rise to two CH resonances, one aliphatic
at 5.30 ppm and the other olefinic at 3.40 ppm. At -60
°C in toluene-d8, the hydrido ligands appear at -14.80
ppm as a doublet with a P-H coupling constant of 19.9
Hz, suggesting that both hydrido ligands are chemically
equivalent and are disposed cis to the phosphine ligand.
This disposition leads to a situation where the aliphatic
CH protons of the tetrafluorobenzobarrelene diolefin are
chemically inequivalent; furthermore, the protons of
each double carbon-carbon bond are also mutually
(20) Takao, T.; Suzuki, H.; Tanaka, M. Organometallics 1994, 13,
2554.
(21) Yin, J .; Klosin, J .; Abboud, K. A.; J ones, W. M. J . Am. Chem.
Soc. 1995, 117, 3298.
(22) (a) Rappert, T.; Nu¨rnberg, O.; Werner, H. Organometallics 1993,
12, 1359. (b) Werner, H.; Baum, M.; Schneider, D.; Windmu¨ller, B.
Organometallics 1994, 13, 1089. (c) Baum, M.; Windmu¨ller, B.; Werner,
H. Z. Naturforsch. 1994, 49b, 859.
(23) Elschenbroich, Ch.; Salzer, A. Organometallics; VCH Verlags-
gesellschaft: Weinheim, Germany, 1989.
(24) Glockling, F.; Irwin, J . G. Inorg. Chim. Acta 1972, 6, 355.

Reactions of Ir(C2Ph)L2(PCy3) Compounds
Organometallics, Vol. 15, No. 2, 1996 819
Ta ble 1. Hyd r osilyla tion of P h en yla cetylen e Ca ta lyzed by Ir (C2P h )(CO)2(P Cy3) (1)a
[PhCtCH]
[HSiEt3]
(M)
[silylated products]
(M)
[PhCtCSiEt3]
[Ph(SiEt3)CdCH2]
[cis-PhCHdCH(SiEt3)]
[trans-PhCHdCH(SiEt3)]
(M)
(M)
(M)
(M)
(M)
0.24
0.24
0.24
0.24
0.18
0.36
0.48
0.18
0.24
0.36
0.48
0.24
0.24
0.24
0.16
0.18
0.23
0.22
0.16
0.19
0.18
0.022
0.023
0.021
0.018
0.014
0.028
0.029
0.014
0.027
0.049
0.053
0.025
0.016
0.010
0.077
0.075
0.084
0.084
0.076
0.103
0.099
0.047
0.055
0.076
0.065
0.045
0.043
0.042
a
[Catalyst] ) 2.4 × 10-3 M; cyclohexane (0.125 M) was used as an internal standard; solvent 1,2-dichloroethane; argon atmosphere.
The formed amount of PhCHdCH2 is very similar to that of PhCtCSiEt3.
Ta ble 2. Hyd r osilyla tion of P h en yla cetylen e Ca ta lyzed by Ir (C2P h )(TF B)(P Cy3) (6)a
[PhCtCH]
[HSiEt3]
(M)
[silylated products]
(M)
[PhCtCSiEt3]
[Ph(SiEt3)CdCH2]
[cis-PhC HdCH(SiEt3)]
[trans-PhCHdCH(SiEt3)]
(M)
(M)
(M)
(M)
(M)
0.24
0.24
0.24
0.36
0.48
0.72
0.24
0.36
0.48
0.24
0.24
0.24
0.216
0.23
0.22
0.22
0.22
0.22
0.014
0.008
0.003
0.023
0.03
0.002
0.002
0.166
0.151
0.104
0.156
0.145
0.136
0.034
0.069
0.107
0.035
0.042
0.039
0.006
0.003
0.005
0.040
a
[Catalyst] ) 2.4 × 10-3 M; cyclohexane (0.125 M) was used as internal standard; solvent 1,2-dichloroethane; argon atmosphere. The
formed amount of PhCHdCH2 is very similar to that of PhCtCSiEt3.
Sch em e 3
reactions were performed in 1,2-dichloroethane at
60 °C. In all experiments carried out PhCHdCH2,
PhCtCSiEt3, cis-PhCHdCH(SiEt3), trans-PhCHdCH-
(SiEt3), and Ph(SiEt3)CdCH2 were obtained. The quan-
tity of PhCHdCH2 formed is very similar to that of
PhCtCSiEt3. This can be rationalized in terms of a
dehydrogenative silylation (eq 2), along with a normal
hydrosilylation (eq 1). The rate and extent of the
reactions are unaffected by the presence of hydro-
quinone, suggesting that the participation of radical-
like species as catalytic intermediates is not significant.
Hydrosilylation experiments were performed at dif-
ferent concentrations of phenylacetylene and triethyl-
silane, and the results are collected in Tables 1 and 2.
The dicarbonyl complex 1 is a less selective catalyst than
6. In the presence of this complex, the relative amounts
of each reaction product are not very dependent on
phenylacetylene and triethylsilane concentrations and,
in general, they do not show a clear trend. However,
in the presence of the related tetrafluorobenzobarrelene
derivative 6, the relative amount of each reaction
product clearly changes with the initial concentrations
of the phenylacetylene and triethylsilane.
As seen from Table 2, in the initial presence of
0.24 M of triethylsilane, the concentration of trans-
PhCHdCH(SiEt3) is between 0.03 and 0.04 M and only
traces of Ph(SiEt3)CdCH2 are formed. Under these
conditions, the major product in all cases is cis-
PhCHdCH(SiEt3), resulting from the anti-addition of
the silane to the alkyne. The amount of this product
decreases as the phenylacetylene concentration in-
creases. Contrary to this behavior, the amount of
PhCtCSiEt3 rises. Scheme 3 illustrates different reac-
tion sequences that allow us to rationalize the results
recorded in Table 2.
The fact that the quantity of trans-PhCHdCH(SiEt3)
formed is independent of the phenylacetylene concen-
tration and that the decrease of the amount of cis-
PhCHdCH(SiEt3) is similar to the increase of the
amount of PhCtCSiEt3 suggests that the formation of
the syn-addition product is independent of the formation
of cis-PhCHdCH(SiEt3) and PhCtCSiEt3 and, further-
more, suggests that the reaction pathways to afford the
anti-addition product and PhCtCSiEt3 have some com-
mon point, which is sensitive to changes in the pheny-
lacetylene concentration. According to Scheme 2, the
dehydrogenative silylation product can be formed by
reductive elimination from the alkynyl-hydrido-silyl
intermediate 8. The reductive elimination should afford
9, which could inserts PhCtCSiEt3 (path a ) to give an
alkenyl intermediate 13, similar to 11, or alternatively
could react with phenylacetylene to give the styryl
derivative 14 (path b). At high phenylacetylene con-
centrations, both 13 and 14 could afford the correspond-
ing olefins and 6. The formation of olefins and alkynyl

820 Organometallics, Vol. 15, No. 2, 1996
Esteruelas et al.
compounds by reaction of alkenyl complexes and ter-
minal alkynes is a well-known process.25 Because the
paths a and b are competitive and the path b would be
favored with the increase of the phenylacetylene con-
centrations, the increase of this produces an increase
in the amount of PhCtCSiEt3 and a decrease of the
amount of cis-PhCHdCH(SiEt3).
with HSiPh3 and H2SiPh2 leads to Ir{C(SiPh3)dCHPh}-
(TFB)(PCy3) and IrH2{Si(C2Ph)Ph2}(TFB)(PCy3), re-
spectively, which are also the first examples of com-
pounds of these types in iridium chemistry.
The complexes Ir(C2Ph)(CO)2(PCy3) and Ir(C2Ph)-
(TFB)(PCy3) catalyze the addition of HSiEt3 to pheny-
lacetylene to give PhCHdCH2, PhCtCSiEt3, cis-
PhCHdCH(SiEt3), trans-PhCHdCH(SiEt3), and Ph-
(SiEt3)CdCH2. On the basis of the results obtained
from the study of the reactivity of the catalysts toward
HSiR3 and from the catalytic experiments, we conclude
that intermediates of the types M(H)(C2R)(SiR3) and
M{C(SiR3)dCHR} can play a main role in the formation
of the dehydrogenative silylation (RCtCSiR3) and anti-
addition (cis-RCHdCH(SiR3)) products.
Alternatively to the reaction of 13 with phenylacety-
lene to give 6, the intermediate 13 could also react with
triethylsilane to give the silyl intermediate 15, which
could yield the anti-addition product by the Ojima’s
mechanism (path c). This reaction pathway should be
favored at high triethylsilane concentrations and would
produce a decrease in the amount of PhCtCSiEt3. Data
collected in Table 2 show that the amount of dehydro-
genative silylation product decreases as the triethylsi-
lane concentration rises. However, the amount of anti-
addition product also decreases. This decrease of the
amount of cis-PhCHdCH(SiEt3) on increasing the tri-
ethylsilane concentration is accompanied by an increase
in the amount of trans-PhCHdCH(SiEt3) formed. Ac-
cording to the Chalk-Harrod mechanism,26 the syn-
addition product could be formed by reaction of the
styryl intermediate 14 with triethylsilane (path d ), and
its increase should involve a combined decrease of the
amounts of PhCtCSiEt3 and cis-PhCHdCH(SiEt3).
Although this is observed, a decrease in the amount of
trans-PhCHdCH(SiEt3) on increasing the phenylacety-
lene concentration should be also expected, and as it
has been previously mentioned, this does not occur.
Hence, although it can not be rejected that some amount
of trans-PhCHdCH(SiEt3) is formed by path d of
Scheme 3, the contribution of this reaction pathway to
the overall trans-PhCHdCH(SiEt3) is not significant.
Thus, the syn-addition product should be formed by
isomerization of cis-PhCHdCH(SiEt3). In fact, we have
also observed that, at 60 °C in the presence of 6 and
triethylsilane, a mixture of 47% cis-PhCHdCH(SiEt3)
and 53% trans-PhCHdCH(SiEt3) is converted into 4%
cis-PhCHdCH(SiEt3) and 96% trans-PhCHdCH(SiEt3)
after 30 min.
Exp er im en ta l Section
Gen er a l Da ta . All reactions were carried out with the use
of standard Schlenk procedures. Solvents were dried and
purified by known procedures and distilled under argon prior
to use. Elemental analyses were performed with a Perkin-
Elmer 2400 CHNS/O analyzer. 1H, 13C{1H}, and 31P{1H} NMR
spectra were recorded on Varian UNITY 300 spectrometer.
Chemical shifts are expressed in parts per million upfield from
Si(CH3)4 (1H and 13C{1H} NMR spectra) or 85% H3PO4 (31P-
{1H} NMR spectra). Infrared spectra were run on a Perkin-
Elmer 783 spectrophotometer as either solids (Nujol mulls on
polyethylene sheets) or solutions (NaCl cell windows). Mass
spectra analyses were performed with a VG Autospec instru-
ment. In FAB+ mode ions were produced with the standard
Cs+ gun at ca. 30 eV, and 3-nitrobenzyl alcohol (NBA) was
used as the matrix. Electron impact MS (operating at 70 eV)
was used for PhCtCSiEt3 and PhCtCSiPh3. The catalytic
reactions were followed by measuring the silane consumption
as a function of time using cyclohexane as the internal
standard with a 15% â,â′-oxobis(propionitrile) on Chromosorb
W-HP 80/100-mesh column at 40 °C on a Perkin-Elmer 8500
gas chromatograph with a flame ionization detector. Silicon-
containing products were analyzed using a FFAP on Chro-
mosorb GHP 80/100-mesh column at 175 °C. The starting
materials, Ir(C2Ph)(CO)2(PCy3) (1) and Ir(C2Ph)(TFB)(PCy3)
(6), were prepared by published methods.13
Rea ction of 1 w ith HSiEt3. P r ep a r a tion of Ir (C2P h )-
(H)(SiEt3)(CO)2(P Cy3) (2). This reaction was carried out in
an NMR tube (method a) and on preparative scale (method
b).
In summary, on the basis of eq 3 and Scheme 2, the
results collected in Table 2 can be rationalized by
Scheme 3, where the reaction pathways a and c explain
the formation of cis-PhCHdCH(SiEt3) and the reaction
pathway b rationalizes the formation of PhCtCSiEt3.
The syn-addition product, trans-PhCHdCH(SiEt3), is
mainly formed by isomerization of its cis-isomer.
Meth od a . HSiEt3 (10 µL, 0.063 mmol) was added to a
solution of 1 (40 mg, 0.063 mmol) in benzene-d6 (0.5 mL)
1
contained in a 5 mm NMR tube. After 1 h, H, 31P{1H}, and
13C{1H} NMR were recorded. IR (CH2Cl2, cm-1): ν(Ir-H) 2140
(m); ν(CtC) 2130 (m); ν(CO) 2045 (s), 1998 (s). 1H NMR (300
MHz, C6D6, 20 °C): δ 7.52-6.93 (m, 5H, Ph), 2.20-1.10 (m,
33H, PCy3), 0.96-0.50 (m, 15H, -SiEt3), -9.27 (d, 1H, J P-H
) 15.6 Hz, Ir-H). 13C{1H} NMR (75.429 MHz, C6D6): δ 174.52
(d, J P-C ) 4.1 Hz, CO), 173.23 (d, J P-C ) 5.0 Hz, CO), 131.36
(s, Ph), 131.33 (s, Ph), 129.18 (s, Ph), 129.14 (s, Ph), 125.63 (s,
Ph), 106.94 (d, J P-C ) 4.1 Hz, Câ, CtC), 75.05 (d, J P-C ) 16.1
Hz, CR, CtC), 34.38 (d, J P-C ) 18.9 Hz, PCy3), 29.96 (s, PCy3),
29.63 (s, PCy3), 27.73 (d, J P-C ) 10.5 Hz, PCy3), 27.63 (d, J P-C
) 10.6 Hz, PCy3), 26.72 (s, PCy3), 10.81 (d, J P-C ) 4.1 Hz,
SiCH2CH3), 9.60 (d, J P-C ) 1.0 Hz, SiCH2CH3). 31P{1H} NMR
Con clu d in g Rem a r k s
This study has revealed that the cis-dicarbonyl com-
plex Ir(C2Ph)(CO)2(PCy3) reacts with HSiR3 to give
Ir(C2Ph)(H)(SiR3)(CO)2(PCy3), which are the first ex-
amples of compounds of this type in iridium chemistry.
The reactions of the related tetrafluorobenzobarrelene
derivative, Ir(C2Ph)(TFB)(PCy3), with HSiR3 produce
the selective formation of new Si-C bonds. The reaction
with HSiEt3 affords PhCtCSiEt3 and the dihydrido-
silyl complex IrH2(SiEt3)(TFB)(PCy3), while the reaction
29
(121.421 MHz, C6D6): δ 8.2 (s with 29Si satellites, J P- Si ) 73
Hz).
Met h od b. HSiEt3 (25 µL, 0.159 mmol) was added to a
solution of 1 (100 mg, 0.159 mmol) in toluene (5 mL). The
solution was stirred for 1 h at room temperature and concen-
trated to ca. 0.5 mL, and addition of methanol caused the
precipitation of a pale yellow solid. The solution was decanted,
and the solid was washed with methanol and dried in vacuo,
yield 77 mg (65%). Anal. Calcd for C34H54IrO2PSi: C, 54.73;
(25) See for example: (a) Echavarren, A. M.; Lo´pez, J .; Santos, A.;
Romero, A.; Hermoso, J . A.; Vegas, A. Organometallics 1991, 10, 2371.
(b) Santos, A.; Lo´pez, J .; Montoya, J .; Noheda, P.; Romero, A.;
Echavarren, A. M. Organometallics 1994, 13, 3605. (c) Bianchini, C.;
Frediani, P.; Masi, D.; Peruzzini, M.; Zanobini, F. Organometallics
1994, 13, 4616.
(26) Chalk, A. J .; Harrod, F. G. J . Am. Chem. Soc. 1965, 87, 16.

Reactions of Ir(C2Ph)L2(PCy3) Compounds
Organometallics, Vol. 15, No. 2, 1996 821
H, 7.29. Found: C, 55.10; H, 6.43. IR (Nujol, cm-1): ν(Ir-
H), ν(CtC) 2146 (m); ν(CO) 2046 (s), 2004 (s); ν(CdC, Ph) 1599
(m). MS (FAB): m/ e 747 (M+ + 1), 718 (M+ - CO), 528 (M+
- SiEt3 - H - C2Ph).
Rea ction of 1 w ith HSiP h 3. P r ep a r a tion of Ir (C2P h )-
(H)(SiP h 3)(CO)2(P Cy3) (3). This reaction was carried out
analogously as described for 2, by starting from 1 (40 mg, 0.063
mmol) and HSiPh3 (16.5 mg, 0.063 mmol) (method a) and by
starting from 1 (100 mg, 0.159 mmol) and HSiPh3 (41.3 mg,
0.159 mmol) (method b).
Ph), 131.68 (s, Ph), 128.81 (s, Ph), 128.77 (s, Ph), 128.60 (s,
SiPh), 128.24 (s, SiPh), 127.89 (s, SiPh), 125.92 (s, Ph), 107.65
(d, J P-C ) 4.1 Hz, Câ, CtC), 72.21 (d, J P-C ) 14.7 Hz, CR, CtC),
34.47 (d, J P-C ) 20.7 Hz, PCy3), 29.96 (s, PCy3), 29.55 (s, PCy3),
27.61 (d, J P-C ) 10.1 Hz, PCy3), 27.51 (d, J P-C ) 10.6 Hz, PCy3),
26.51 (s, PCy3). 31P{1H} NMR (121.421 MHz, C6D6): δ 12.2 (s
29
with 29Si satellites, J P-
) 91 Hz).
Si
Meth od b. Compound 5 was isolated as a yellow oil. MS
(FAB): m/ e 736 (M+ - 2 H), 603 (M+ - SiH2Ph - CO).
Rea ction of 6 w ith HSiEt3: F or m a tion of Ir H2(SiEt3)-
(TF B)(P Cy3) (7) a n d P h CtCSiEt3. HSiEt3 (8 µL, 0.05
mmol) was added to a solution of 6 (40 mg, 0.05 mmol) in
benzene-d6 (0.5 mL) contained in a 5 mm NMR tube. After 1
h the 1H and 31P{1H} NMR spectra show signals corresponding
to the starting material (6, 50%) and 7 (50%). 31P{1H} NMR
Meth od a . IR (CH2Cl2, cm-1): ν(Ir-H) 2140 (m), ν(CtC)
2130 (m), ν(CO) 2055 (s), 2010 (s). 1H NMR (300 MHz, C6D6,
20 °C): δ 8.10-6.83 (m, 20H, Ph), 2.20-1.00 (m, 33H, PCy3),
-8.71 (d, 1H, J P-H ) 14.8 Hz, Ir-H). 13C{1H} NMR (75.429
MHz, C6D6): δ 173.39 (d, J P-C ) 4.7 Hz, CO), 171.73 (d, J P-C
) 5.1 Hz, CO), 142.74 (d, J P-C ) 4.1 Hz, SiPh3), 136.93 (s,
SiPh3), 131.29 (s, Ph), 131.26 (s, Ph), 130.03 (s, SiPh3), 128.68
(s, Ph), 128.64 (s, Ph), 127.55 (s, SiPh3), 125.77 (s, Ph), 109.23
(d, J P-C ) 4.6 Hz, Câ, CtC), 74.44 (d, J P-C ) 15.7 Hz, CR, CtC),
34.34 (d, J P-C ) 19.8 Hz, PCy3), 29.79 (s, PCy3), 29.62 (s, PCy3),
27.70 (d, J P-C ) 9.6 Hz, PCy3), 27.61 (d, J P-C ) 9.2 Hz, PCy3),
(121.421 MHz, C6D6): δ 23.2 (s, 6), 8.9 (s with 29Si satellites,
29
J P-
) 52 Hz, triplet in off-resonance; 7). MS (EI) analysis
Si
of the mother liquors shows the presence of PhCtCSiEt3. Mass
fragmentation pattern of PhCtCSiEt3 (m/ e): 216 (M+), 187
(M+ - Et), 159 (M+ - 2Et), 131 (M+ - 3Et).
Rea ction of 6 w ith HSiP h 3: F or m a tion of Ir H2(SiP h 3)-
(TF B)(P Cy3) (10), P h CtCSiP h 3, a n d Ir {C(SiP h 3)dCHP h }-
(TF B)(P Cy3) (11). HSiPh3 (13 mg, 0.05 mmol) was added to
a solution of 6 (40 mg, 0.05 mmol) in benzene-d6 (0.5 mL)
contained in a 5 mm NMR tube. The reaction was monitored
by 1H and 31P{1H}. After 30 min the 1H and 31P{1H} show
signals corresponding to 6 (60%) and 11 (40%). After 1 h 30
min the distribution is as follows: 6 (40%), 11 (52%), and 10
(8%). After 2 h 30 min the distribution is as follows: 6 (31%),
11 (50%), and 10 (19%). MS (EI) of the mother liquors shows
the presence of PhCtCSiPh3. Mass fragmentation pattern of
PhCtCSiPh3 (m/ e): 360 (M+), 283 (M+ - Ph), 181 (M+ - Ph
- C2Ph).
Spectroscopic data for Ir{C(SiPh3)dCHPh}(TFB)(PCy3) (11)
are as follows. 1H NMR (300 MHz, C6D6, 20 °C): δ 7.99-6.93
(m, 20H, Ph), 6.50 (s, dCH), 5.31 (br, 2H, -CH TFB), 3.45
(m, 2H, dCH TFB), 2.74 (br, 2H, dCH TFB), 2.00-0.90 (m,
33H, PCy3). 13C{1H} NMR (APT, 75.429 MHz, C6D6): δ 146.16
(d, J P-C ) 2.7 Hz, J C-Si ) 35 Hz, CR), 139.12 (s, SiPh3), 136.29
(s, SiPh3), 130.02 (s, Ph), 128.74 (s, Ph), 127.82 (s, SiPh3),
127.59 (s, SiPh3), 125.71 (s, Ph), 124.25 (s, Câ), 59.82 (d, J P-C
) 12.0 Hz, dCH), 48.22 (s, dCH), 40.73 (s, -CH), 40.70 (s,
-CH), 36.09 (d, J P-C ) 23.9 Hz, PCy3), 30.40 (s, PCy3), 27.87
(d, J P-C ) 10.6 Hz, PCy3), 26.77 (s, PCy3). 31P{1H} NMR
(121.421 MHz, C6D6): δ 17.7 (s).
26.63 (s, PCy3). 31P{1H} NMR (121.421 MHz, C6D6): δ 9.7 (s
29
with 29Si satellites, J P-
) 89 Hz).
Si
Meth od b. Compound 3 was isolated as a pale yellow solid,
yield 99 mg (70%). Anal. Calcd for C46H54IrO2PSi: C, 62.06;
H, 6.11. Found: C, 61.38; H, 5.41. IR (Nujol, cm-1): ν(Ir-
H), ν(CtC) 2135 (m); ν(CO) 2054 (s), 2012 (s); ν(CdC, Ph) 1600
(m). MS (FAB): m/ e 890 (M+), 862 (M+ - CO), 834 (M+ - 2
CO), 527 (M+ - SiPh3 - H - C2Ph).
Rea ction of 1 w ith H2SiP h 2. P r ep a r a tion of Ir (C2P h )-
(H)(SiHP h 2)(CO)2(P Cy3) (4). This reaction was carried out
analogously as described for 2, by starting from 1 (40 mg, 0.063
mmol) and H2SiPh2 (12.5 µL, 0.063 mmol) (method a) and by
starting from 1 (100 mg, 0.159 mmol) and H2SiPh2 (31 µL,
0.159 mmol) (method b).
Meth od a . IR (CH2Cl2, cm-1): ν(Ir-H), ν(Si-H) 2140 (m),
ν(CtC) 2125 (m), ν(CO) 2060 (s), 2015 (s). 1H NMR (300 MHz,
C6D6, 20 °C): δ 8.32-7.00 (m, 15H, Ph), 6.39 (d, 1H, J P-H
)
6.6 Hz, Si-H), 2.20-1.10 (m, 33H, PCy3), -8.95 (d, 1H, J P-H
) 15.1 Hz, Ir-H). 13C{1H} NMR (75.429 MHz, C6D6): δ 172.14
(d, J P-C ) 5.1 Hz, CO), 171.69 (d, J P-C ) 5.0 Hz, CO), 141.66
(d, J P-C ) 3.2 Hz, SiPh2), 141.22 (d, J P-C ) 3.6 Hz, SiPh2),
136.23 (d, J P-C ) 1.4 Hz, SiPh2), 136.15 (d, J P-C ) 0.9 Hz,
SiPh2), 131.52 (s, Ph), 131.49 (s, Ph), 128.77 (s, Ph), 128.74 (s,
Ph), 128.57 (s, SiPh2), 128.41 (s, SiPh2), 128.16 (s, SiPh2),
127.80 (s, SiPh2), 125.85 (s, Ph), 108.28 (d, J P-C ) 4.1 Hz, Câ,
Rea ction of 6 w ith H2SiP h 2. P r ep a r a tion of Ir H2{Si-
(C2P h )P h 2}(TF B)(P Cy3) (12). This reaction was carried out
in an NMR tube (method a) and on a preparative scale (method
b).
CtC), 72.87 (d, J P-C ) 15.6 Hz, CR, CtC), 34.47 (d, J P-C
)
20.2 Hz, PCy3), 29.91 (s, PCy3), 29.62 (s, PCy3), 27.62 (d, J P-C
) 10.1 Hz, PCy3), 27.53 (d, J P-C ) 11.1 Hz, PCy3), 26.56 (s,
Meth od a . H2SiPh2 (9.8 µL, 0.05 mmol) was added to a
solution of 6 (40 mg, 0.05 mmol) in benzene-d6 (0.5 mL)
PCy3). 31P{1H} NMR (121.421 MHz, C6D6): δ 11.6 (s with
29
29Si satellites, J P-
) 87 Hz).
Si
1
contained in a 5 mm NMR tube. After 1 h, H, 31P{1H}, and
Meth od b. Compound 4 was isolated as a pale yellow solid,
yield 88 mg (68%). Anal. Calcd for C40H50IrO2PSi: C, 59.01;
H, 6.19. Found: C, 59.14; H, 5.39. IR (Nujol, cm-1): ν(Ir-
H), ν(Si-H), ν(CtC) 2125 (m), ν(CO) 2057 (s), 2015 (s); ν(CdC,
Ph) 1599 (m). MS (FAB): m/ e 814 (M+).
13C{1H} NMR were recorded. 1H NMR (300 MHz, C6D6, 20
°C): δ 8.22-6.98 (m, 15H, Ph), 5.30 (br, 2H, -CH), 3.40 (br,
4H, dCH), 2.00-1.00 (m, 33H, PCy3), -14.70 (br, 2H, Ir-H).
1H NMR (300 MHz, C7D8, -60 °C): δ 5.90 (s, 1H, -CH), 4.78
(s, 1H, -CH), 3.59 (s, 2H, dCH), 2.92 (s, 2H, dCH), -14.80
(d, 2H, J P-H ) 19.9 Hz, Ir-H). 13C{1H} NMR (75.429 MHz,
C6D6): δ 145.65 (s, SiPh2), 135.31 (s, SiPh2), 132.17 (s, Ph),
128.59 (s, SiPh2), 128.54 (s, Ph), 128.19 (s, SiPh2), 124.88 (s,
Ph), 109.00 (s, Câ, CtC), 99.53 (d, J P-C ) 4.6 Hz, CR, CtC),
39.60 (d, J P-C ) 22.1 Hz, PCy3), 30.12 (s, PCy3), 27.73 (d, J P-C
Rea ction of 1 w ith H3SiP h . P r ep a r a tion of Ir (C2P h )-
(H)(SiH2P h )(CO)2(P Cy3) (5). This reaction was carried out
analogously as described for 2, by starting from 1 (40 mg, 0.063
mmol) and H3SiPh (8 µl, 0.063 mmol) (method a) and by
starting from 1 (100 mg, 0.159 mmol) and H3SiPh (19.5 µL,
0.159 mmol) (method b).
Meth od a . IR (CH2Cl2, cm-1): ν(Ir-H), ν(Si-H) 2135 (m),
ν(CtC) 2120 (m), ν(CO) 2055 (s), 2010 (s). 1H NMR (300 MHz,
C6D6, 20 °C): δ 8.15-6.94 (m, 10H, Ph), 5.43 (m, br, 2H, Si-
H), 2.10-1.00 (m, 33H, PCy3), -9.36 (d, 1H, J P-H ) 14.7 Hz,
Ir-H). 13C{1H} NMR (75.429 MHz, C6D6): δ 171.45 (d, J P-C
) 4.6 Hz, CO), 171.39 (d, J P-C ) 5.5 Hz, CO), 139.49 (d, J P-C
) 2.7 Hz, SiPh), 135.74 (s, SiPh), 135.72 (s, SiPh), 131.71 (s,
) 10.1 Hz, PCy3), 26.82 (s, PCy3). 31P{1H} NMR (121.421 MHz,
29
C6D6): δ 10.7 (s with 29Si satellites, J P-
) 62 Hz, triplet in
Si
off-resonance).
Meth od b. H2SiPh2 (24 µL, 0.125 mmol) was added to a
solution of 6 (100 mg, 0.125 mmol) in toluene (5 mL), and an
immediate color change from red to pale yellow was observed.
This solution was stirred for 5 min at room temperature. The
solution was concentrated to ca. 0.5 mL, and addition of

822 Organometallics, Vol. 15, No. 2, 1996
Esteruelas et al.
methanol caused the precipitation of a white solid. The
solution was decanted, and the solid was washed with metha-
nol and dried in vacuo; yield 76 mg (62%). Anal. Calcd for
The procedure was as follows: Each complex was dissolved
in a 1,2-dichloroethane solution (8 mL) containing HSiEt3,
PhCtCH, and C6H12. The reaction mixture was stirred at 60
°C and monitored by gas chromatography.
C
50H56F4IrPSi: C, 61.01; H, 5.73. Found: C, 60.39; H, 5.36.
IR (Nujol, cm-1): ν(CtC) 2148 (m), ν(Ir-H) 2140 (m), ν(CdC,
Ph) 1596 (m). MS (FAB): m/ e 983 (M+ - H), 883 (M+ - C8H5).
Ca ta lytic Stu d ies. The hydrosilylation reactions were
performed under argon at 60 °C. The reactions were carried
out in a two-necked flask fitted with a condenser and a
magnetic stirring bar. The second neck was capped with a
septum to allow periodical samples to be taken without
opening the system.
Ack n ow led gm en t. We thank the DGICYT (Project
PB92-0092, Programa de Promocio´n General del Cono-
cimiento) and the EU (Project: Selective Processes and
Catalysis involving Small Molecules). M.O. thanks the
Diputacio´n General de Arago´n (DGA) for a grant.
OM950527Y