Reactions of Ir(acac)(cyclooctene)(PCy3) with H2, HC≡CR, HSiR3, and HSnPh3: The acetylacetonato ligand as a stabilizer for iridium(I), iridium(III), and iridium(V) derivatives

Article abstract of DOI:10.1021/om950628w

The acetylacetonato complex Ir(acac)(cyclooctene)(PCy₃) (1) reacts with molecular hydrogen in the presence of 1 equiv of PCy₃ to give Ir(acac)H₂(PCy₃)₂ (2). The addition of 1 equiv of PhC≡CH to a benzene-d₆ solution of 1 causes the displacement of the coordinated olefin and the formation of Ir(acac)(η²-PhC≡CH)(PCy₃) (3). The addition of hexane to this solution reverses the reaction and precipitates 1. The treatment of 1 with 3 equiv of PhC≡CH affords Ir{κ³-CH=C(Ph)CH[C(O)CH₃]₂}(C ₂Ph)(CPh=CH₂)(PCy₃) (4), which is a result of the oxidative addition of the HC≡ bond of an alkyne, the insertion of a second alkyne into an Ir-C³(acac) bond, and the subsequent insertion of a third alkyne into the Ir-H bond, previously formed. The structure of 4 was determined by an X-ray investigation. The coordination geometry around the iridium atom can be rationalized as a distorted octahedron with the bicyclic ligand occupying three coordination sites of a octahedral face. In the presence of PCy₃ the reaction of 1 and PhC≡CH leads to Ir(acac)H(C₂Ph)(PCy₃)₂ (5). Under the same conditions, CyC=CH and Me₃SiC≡CH afford the corresponding hydrido-alkynyl derivatives Ir(acac)H-(C₂R)(PCy₃)₂ (R = Cy (6), Me₃Si (7)). The addition of silanes HSiR₃ to 1 gives Ir(acac)H-(SiR₃)(PCy₃) (SiR₃ = SiEt₃ (8), SiPh₃ (9), SiHPh₂ (10)). The structure of 8 was also determined by an X-ray analysis. The coordination geometry around the metallic center of 8 can be rationalized as a square pyramid with the triethylsilyl group located at the apex. In the presence of PCy₃, the reactions of 1 with silanes lead to Ir(acac)H(SiR₃)(PCy₃)₂ (SiR₃ = SiEt₃ (11), SiHPh₂ (12), SiH₂Ph (13)). Complex 1 also reacts with HSnPh₃. In the absence of PCy₃ the reaction product is Ir(acac)H(SnPh₃)(PCy₃) (14), while in the presence of PCy₃ the six-coordinate derivative Ir(acac)H(SnPh₃)(PCy₃)₂ (15) is obtained. Under atmospheric pressure of hydrogen, complex 8 is converted into the trihydrido-silyl-iridium(V) derivative Ir(acac)H₃(SiEt₃)(PCy₃) (32). In solution, this complex is fluxional with values of ΔH^# and ΔS^# of 12.23 (± 0.76) kcal mol^-1 and 1.45 (± 1.84) cal K^-1 mol^-1, respectively. Complex 8 has also been found to be an active catalyst for the addition of HSiEt₃ to PhC≡CH. In all experiments, PhCH=CH₂, PhC≡CSiEt₃, cis-PhCH=CH(SiEt₃), trans-PhCH=CH(SiEt₃), and Ph(SiEt₃)C=CH₂ were obtained. The major product in all cases is the thermodynamically less stable cis-PhCH=CH(SiEt₃), resulting from the anti-addition of the silane to the alkyne. This product is selectively formed in approximately 70% yield.

Full text of DOI:10.1021/om950628w

Organometallics 1996, 15, 823-834
823
Rea ction s of Ir (a ca c)(cycloocten e)(P Cy3) w ith H2,
HCtCR, HSiR3, a n d HSn P h 3: Th e Acetyla ceton a to
Liga n d a s a Sta bilizer for Ir id iu m (I), Ir id iu m (III), a n d
Ir id iu m (V) Der iva tives
Miguel A. Esteruelas,* Fernando J . Lahoz, Enrique On˜ate, Luis A. Oro, and
Laura Rodr´ıguez
Departamento de Quı´mica Inorga´nica, Instituto de Ciencias de Materiales de Arago´n,
Universidad de Zaragoza-CSIC, 50009 Zaragoza, Spain
Received August 9, 1995X
The acetylacetonato complex Ir(acac)(cyclooctene)(PCy3) (1) reacts with molecular hydrogen
in the presence of 1 equiv of PCy3 to give Ir(acac)H2(PCy3)2 (2). The addition of 1 equiv of
PhCtCH to a benzene-d6 solution of 1 causes the displacement of the coordinated olefin
and the formation of Ir(acac)(η2-PhCtCH)(PCy3) (3). The addition of hexane to this solution
reverses the reaction and precipitates 1. The treatment of 1 with 3 equiv of PhCtCH affords
Ir{κ3-CHdC(Ph)CH[C(O)CH3]2}(C2Ph)(CPhdCH2)(PCy3) (4), which is a result of the oxidative
addition of the HCt bond of an alkyne, the insertion of a second alkyne into an Ir-C3(acac)
bond, and the subsequent insertion of a third alkyne into the Ir-H bond, previously formed.
The structure of 4 was determined by an X-ray investigation. The coordination geometry
around the iridium atom can be rationalized as a distorted octahedron with the bicyclic
ligand occupying three coordination sites of a octahedral face. In the presence of PCy3 the
reaction of 1 and PhCtCH leads to Ir(acac)H(C2Ph)(PCy3)2 (5). Under the same conditions,
CyCtCH and Me3SiCtCH afford the corresponding hydrido-alkynyl derivatives Ir(acac)H-
(C2R)(PCy3)2 (R ) Cy (6), Me3Si (7)). The addition of silanes HSiR3 to 1 gives Ir(acac)H-
(SiR3)(PCy3) (SiR3 ) SiEt3 (8), SiPh3 (9), SiHPh2 (10)). The structure of 8 was also determined
by an X-ray analysis. The coordination geometry around the metallic center of 8 can be
rationalized as a square pyramid with the triethylsilyl group located at the apex. In the
presence of PCy3, the reactions of 1 with silanes lead to Ir(acac)H(SiR3)(PCy3)2 (SiR3 ) SiEt3
(11), SiHPh2 (12), SiH2Ph (13)). Complex 1 also reacts with HSnPh3. In the absence of
PCy3 the reaction product is Ir(acac)H(SnPh3)(PCy3) (14), while in the presence of PCy3 the
six-coordinate derivative Ir(acac)H(SnPh3)(PCy3)2 (15) is obtained. Under atmospheric
pressure of hydrogen, complex 8 is converted into the trihydrido-silyl-iridium(V) derivative
Ir(acac)H3(SiEt3)(PCy3) (32). In solution, this complex is fluxional with values of ∆Hq and
∆Sq of 12.23 (( 0.76) kcal mol-1 and 1.45 (( 1.84) cal K-1 mol-1, respectively. Complex 8
has also been found to be an active catalyst for the addition of HSiEt3 to PhCtCH. In all
experiments, PhCHdCH2, PhCtCSiEt3, cis-PhCHdCH(SiEt3), trans-PhCHdCH(SiEt3), and
Ph(SiEt3)CdCH2 were obtained. The major product in all cases is the thermodynamically
less stable cis-PhCHdCH(SiEt3), resulting from the anti-addition of the silane to the alkyne.
This product is selectively formed in approximately 70% yield.
In tr od u ction
One reason for the relative scarcity of studies on
complexes containing Rh-O and Ir-O bonds is that
such linkages are characteristically weak due to a
mismatch of these hard basic ligands with the soft late
transition metal centers.3 However, the interest in how
the properties of organometallic compounds change on
moving from the more common P- and N-donor has led
to an increase in the number of studies on these
systems. As a result, species stabilized by O-donor
ligands with interesting catalytic properties in reactions
such as hydrogen transfer,4 hydrosilylation,5 and hy-
droboration6 have been recently reported.
The catalytic properties of rhodium and iridium
complexes containing P- and N-donors ligands have
been intensely studied for many years.1 However, the
analogous chemistry with related O-donors has received
less attention, even though metal crystallites and or-
ganometallic precursors supported on metal oxide sur-
faces are often catalytically active.2
X Abstract published in Advance ACS Abstracts, December 15, 1995.
(1) (a) Pignolet, L. H. Homogeneous Catalysis with Metal Phosphine
Complexes; Plenum Press: New York, 1983. (b) Dickson, R. S.
Homogeneous Catalysis with compounds of Rhodium and Iridium;
Reidel Publishing Co.: Dordrecht, The Netherlands, 1985. (c) Chaloner,
P. A.; Esteruelas, M. A.; J oo´, F.; Oro, L. A. Homogeneous Hydrogena-
tion; Kluwer Academic Publishers: Dordrecht, The Netherlands, 1994.
(2) (a) Ballard, D. G. H. Adv. Catal. 1973, 23, 263. (b) Yermarkov,
Yu. Y.; Kuznetsov, B. N.; Zakharov, V. Catalysis by Supported
Complexes, Elsevier: Amsterdam, 1981. (c) Schwartz, J . Acc. Chem.
Res. 1985, 18, 302. (d) Gates, B. C.; Lamb, H. H. J . Mol. Catal. 1989,
52, 1.
(3) (a) Pearson, R. G. J . Am. Chem. Soc. 1963, 85, 3533. (b) Pearson,
R. G. J . Chem. Educ. 1968, 45, 643.
(4) Uson, R.; Oro, L. A.; Ciriano, M. A.; Lahoz, F. J . J . Organomet.
Chem. 1982, 240, 429.
(5) (a) Tanke, R. S.; Crabtree, R. H. J . Chem. Soc., Chem. Commun.
1990, 1056. (b) Tanke, R. S.; Crabtree, R. H. J . Am. Chem. Soc. 1990,
112, 7984. (c) Tanke, R. S.; Crabtree, R. H. Organometallics 1991, 10,
415.
0276-7333/96/2315-0823$12.00/0 © 1996 American Chemical Society

824 Organometallics, Vol. 15, No. 2, 1996
Ta ble 1. 1H NMR Da ta for Com p lexes 2, a n d 5-15a
Esteruelas et al.
complex
PCy3
acac
X
Ir-H
2
5
6
7
8
2.21-1.26 (Cy) 1.30 (s, CH3); 5.28 (s, CH)
-27.90 (t, J P-H ) 16 Hz)
-25.00 (t, J P-H ) 15 Hz)
-25.92 (t, J P-H ) 15 Hz)
-29.50 (t, J P-H ) 15 Hz)
-23.43 (d, J P-H ) 19 Hz)
-22.81 (d, J P-H ) 17 Hz)
-22.70 (d, J P-H ) 19 Hz)
2.32-1.12 (Cy) 1.86, 1.96 (both s, CH3); 5.21 (s, CH) 7.69-6.95 (Ph)
2.25-1.14 (Cy) 1.75, 1.60 (both s, CH3); 5.14 (s, CH) 2.25-1.14 (Cy)
2.25-1.20 (Cy) 1.65, 1.70 (both s, CH3); 5.12 (s, CH) 1.20 (CH3Si)
2.17-1.00 (Cy) 1.72(s, CH3); 5.41(s, CH)
2.20-0.95 (Cy) 1.78(s, CH3); 5.21(s, CH)
2.25-1.22 (Cy) 1.73 (s, CH3); 5.22 (s, CH)
2.25-0.89 (Cy) 1.89 (s, CH3); 5.2 (s, CH)
2.20-0.85 (Cy) 1.76, 1.99 (both s, CH3); 5.44 (s, CH) 8.08-7.21(Ph); 5.30 (t, J P-H ) 8 Hz, Si-H)
2.36-1.00 (Cy) 1.70, 1.92 (both s, CH3); 5.35 (s, CH) 8.35-7.21(Ph); 4.22 (t, J P-H ) 5 Hz, Si-H2)
b; 0.86 (q, J H-H ) 7 Hz, CH2)
8.06-7.16 (Ph)
9
10
11
12
13
14
15
8.19-7.12 (Ph); 7.75 (d, J P-H ) 7 Hz, Si-H)
1.35 (t, J H-H ) 7 Hz, CH3); 1.25 (q, J H-H ) 7 Hz, CH2) -25.48 (t, J P-H ) 16 Hz)
-25.44 (t, J P-H ) 16 Hz)
-25.93 (t, J P-H ) 16 Hz)
-24.40 (dc, J P-H ) 17 Hz)
-27.13 (t, J P-H ) 16 Hz)
2.07-0.90 (Cy) 1.61 (s, CH3); 5.31 (s, CH)
2.12-1.11 (Cy) 1.61, 1.89 (both s, CH3); 5.46 (s, CH) 8.05-7.12 (Ph)
7.92-7.12 (Ph)
a
δ in ppm. Solvents: benzene-d6 (2, 8-15), chloroform-d1 (5-7). Abbreviations used: s ) singlet, d ) doublet, t ) triplet, q ) quartet.
The CH3 resonance is masked by the cyclohexyl signals. c With tin satellites, J Sn-H ) 88 Hz.
b
The design of a new catalyst requires a basic knowl-
olefin is not hydrogenated. A similar behavior has been
observed for the ethylene derivative Ir(acac)(C2H4)(Pi-
Pr3).11
edge of the principal components of the catalytic cycles.
In this respect, the oxidative additions of molecular
hydrogen, terminal alkynes, and group 14 element
hydrido compounds to unsaturated transition metal
centers are reactions of considerable interest in connec-
tion with important homogeneous catalytic processes,
including hydrogenation of unsaturated organic sub-
strates,1c oligomerization of alkynes,7 hydrosilylation,8
and hydrostannation9 of olefins and alkynes.
We recently reported the synthesis of the acetylac-
etonato complex Ir(acac)(cyclooctene)(PCy3), which re-
acts with acetylenedicarboxylic methyl ester to give
Ir(acac)(η2-CH3O2CCtCCO2CH3)(PCy3). The reaction
Complex 2 was isolated as an air-stable powder in
89% yield and characterized by elemental analysis, IR,
1
and H and 31P{1H} NMR spectroscopies. In agreement
with the cis dispositions of the hydrido ligands, the IR
spectrum in Nujol shows two strong absorptions at 2240
of this complex with H2SiPh2 leads to Ir(acac){C[CH-
1
and 2175 cm-1. while in the H NMR spectrum these
ligands appear at -27.80 ppm as a triplet with a P-H
coupling constant of 16 Hz (Table 1). The 31P{1H} NMR
spectrum contains a singlet at 15.8 ppm, indicating that
the phosphine ligands are equivalent and mutually
trans disposed. Under off-resonance conditions, the
singlet is split into a triplet due to the P-H coupling.
2. Rea ction s of Ir (a ca c)(cycloocten e)(P Cy3) w ith
P h en yla cetylen e. The 31P{1H} NMR spectrum of 1
in benzene-d6 shows a singlet at 1.4 ppm.10 The
addition of ca. 1 equiv of phenylacetylene to this solution
(OCH3)OSiPh2]dCHCO2CH3}(PCy3), which is a result
of a net transformation involving addition of one Si-H
bond across the CdO and another across the alkyne
triple bond.10 As a continuation of our work in this field,
we have now studied the reactivity of the acetylaceto-
nato complex Ir(acac)(cyclooctene)(PCy3) toward molec-
ular hydrogen, terminal alkynes, and group 14 element
hydrido compounds.
In this paper we report the results of this study, the
X-ray structure of the hydrido-silyl complex Ir(acac)H-
(SiEt3)(PCy3) and its catalytic activity in the hydrosi-
lylation of phenylacetylene. In addition, the synthesis
and X-ray structure of the unusual complex Ir{κ3-
CHdC(Ph)CH[C(O)CH3]2}(C2Ph)(CPhdCH2)(PCy3) are
also reported.
1
causes the singlet to shift to 7.5 ppm. In the H NMR
spectrum, the most noticeable resonances of the new
solution are the corresponding olefinic protons of the
free cyclooctene olefin at 5.56 ppm and three singlets
at 4.10 (HCt), 1.90 (CH3), and 1.50 (CH3) ppm, with
1:3:3 intensity ratio, which are consistent with the
formation of the π-alkyne derivative Ir(acac)(η2-
PhCtCH)(PCy3) (3) according to eq 2. Attempts to
Resu lts a n d Discu ssion
(6) Westcott, S. A.; Blom, H. P.; Marder, T. B.; Baker, R. T. J . Am.
Chem. Soc. 1992, 114, 8863.
1. Rea ction of Ir (a ca c)(cycloocten e)(P Cy3) w ith
Molecu la r Hyd r ogen . On treatment with PCy3, the
bis(cyclooctene)iridium(I) complex Ir(acac)(cyclooctene)2
affords the phosphine derivative Ir(acac)(cyclooctene)-
(PCy3) (1). The reaction proceeds at room temperature
and does not lead to the displacement of the second
olefin ligand, even in the presence of excess PCy3.10
Complex 1 is a yellow air-sensitive solid, which is stable
under argon and hydrogen atmospheres in the solid
state and in benzene-d6 solution. While complex 1 does
not react with PCy3 or molecular hydrogen individually,
the dihydrido compound Ir(acac)H2(PCy3)2 (2) is easily
formed by passing a slow stream of hydrogen through
a solution of 1 in the presence of 1 equiv of PCy3 (eq 1).
Interestingly, under these conditions the cyclooctene
(7) (a) Scha¨fer, M.; Mahr, N.; Wolf, J .; Werner, H. Angew. Chem.,
Int. Ed. Engl. 1993, 32, 1315. (b) Bianchini, C.; Caulton, K. G.;
Chardon, C.; Doublet, M.; Eisenstein, O.; J ackson, S. A.; J ohnson, T.
J .; Meli, A.; Peruzzini, M.; Streib, W. E.; Vacca, A.; Vizza, F. Organo-
metallics 1994, 13, 2010. (c) Werner, H.; Scha¨fer, M.; Wolf, J .; Peters,
K.; von Schnering, H. G. Angew. Chem., Int. Ed. Engl. 1995, 34, 191.
(8) (a) Ojima, I. The Chemistry of Organic Silicom Compounds;
Patai, S., Rappoport, Z., Eds.; Wiley: New York, 1989; Chapter 25, p
1479. (b) Marciniec, B.; Gulinsky, J .; Urbaniak, W.; Kornetka, Z. W.
Comprehensive Handbook on Hydrosililation; Marciniec, B., Ed.;
Pergamon: Oxford, U.K., 1992; p 758. (c) Marciniec, B.; Gulinsky, J .
J . Organomet. Chem. 1993, 446, 15.
(9) (a) Kikukawa, K.; Umekawa, H.; Wada, F.; Matsuda, T. Chem.
Lett. 1988, 881. (b) Esteruelas, M. A.; Lahoz, F. J .; Oliva´n, M.; On˜ate,
E.; Oro, L. A. Organometallics 1995, 14, 3486.
(10) Esteruelas, M. A.; Lahoz, F. J .; On˜ate, E.; Oro, L. A.; Rodr´ıguez,
L. Organometallics 1995, 14, 263.
(11) Papenfuhs, B.; Mahr, N.; Werner, H. Organometallics 1993, 12,
4244.

Reactions of Ir(acac)(cyclooctene)(PCy3)
Organometallics, Vol. 15, No. 2, 1996 825
Ta ble 2. Bon d Dista n ces (Å) a n d An gles (d eg) for
th e Com p ou n d Ir {K3-CHdC(P h )CH[C(O)CH3]2-
(C2P h )[CP h dCH2](P Cy3) (4)
Ir-P
2.423(2)
2.204(8)
2.222(8)
2.030(9)
1.897(11)
2.017(10)
1.243(12)
1.445(17)
1.523(14)
1.528(18)
C(3)-C(7)
1.545(15)
1.493(15)
1.219(14)
1.318(15)
1.495(14)
1.371(15)
1.542(16)
1.268(16)
1.408(17)
Ir-O(1)
C(4)-C(5)
Ir-O(2)
Ir-C(6)
O(2)-C(4)
C(6)-C(7)
C(7)-C(8)
C(22)-C(23)
C(22)-C(24)
C(14)-C(15)
C(15)-C(16)
Ir-C(14)
Ir-C(22)
O(1)-C(1)
C(1)-C(2)
C(1)-C(3)
C(3)-C(4)
P-Ir-O(1)
95.9(2)
88.3(2)
171.6(3)
93.6(3)
94.9(3)
81.1(3)
85.0(3)
170.1(3)
93.0(4)
83.7(3)
96.3(4)
173.6(4)
85.2(4)
93.4(4)
89.1(4)
119.7(6)
120(1)
C(2)-C(1)-C(3)
C(1)-C(3)-C(4)
C(1)-C(3)-C(7)
C(4)-C(3)-C(7)
C(3)-C(4)-C(5)
O(2)-C(4)-C(3)
O(2)-C(4)-C(5)
Ir-O(2)-C(4)
121(1)
109.2(8)
110.7(8)
119.2(9)
118(1)
120.0(9)
122(1)
119.2(8)
122.5(8)
126(1)
116.9(9)
117.2(9)
176.4(9)
179(1)
126.5(9)
119.3(7)
114.2(9)
P-Ir-O(2)
P-Ir-C(6)
P-Ir-C(14)
P-Ir-C(22)
O(1)-Ir-O(2)
O(1)-Ir-C(6)
O(1)-Ir-C(14)
O(1)-Ir-C(22)
O(2)-Ir-C(6)
O(2)-Ir-C(14)
O(2)-Ir-C(22)
C(6)-Ir-C(14)
C(6)-Ir-C(22)
C(14)-Ir-C(22)
Ir-O(1)-C(1)
O(1)-C(1)-C(2)
O(1)-C(1)-C(3)
Ir-C(6)-C(7)
C(6)-C(7)-C(8)
C(3)-C(7)-C(6)
C(3)-C(7)-C(8)
Ir-C(14)-C(15)
C(14)-C(15)-C(16)
Ir-C(22)-C(23)
Ir-C(22)-C(24)
C(23)-C(22)-C(24)
F igu r e 1. Molecular structure diagram of the complex Ir-
{κ3-CHdC(Ph)CH[C(O)CH3]2}(C2Ph)(CPhdCH2)(PCy3) (4).
isolate 3 remained unsuccessful. Thus, the addition of
hexane to the benzene-d6 solution of 3 and cyclooctene
reverses the reaction and precipitates 1.
119(1)
tricyclohexylphosphine ligand (P-Ir-C(6) ) 171.6(3)°),
while the O(1) and O(2) oxygen atoms are situated trans
to the alkynyl (O(1)-Ir-C(14) ) 170.1(3)°) and alkenyl
(O(2)-Ir-C(22) ) 173.6(4)°) groups, respectively.
The geometry of the κ3-CHdC(Ph)CH[C(O)CH3]2 ligand
is similar to that previously reported for κ3-C(CF3)dC-
(CF3)CH[C(O)CH3]2.12 As expected the C(1)-O(1)
(1.243(12) Å) and C(4)-O(2) (1.219(14) Å) bond lengths
are about 0.8 Å shorter than those observed in delocal-
ized acetylacetonato ligands coordinated to iridium(III)
fragments (mean value 2.082 Å),13 while the C(1)-C(3)
(1.523(14) Å) and C(3)-C(4) (1.528(18) Å) distances are
about 0.15 Å longer (mean 1.383 Å).13 The C(6)-C(7)
(1.318(15) Å) and C(3)-C(7) (1.545(15) Å) bond lengths
compare well with the values of carbon-carbon double
bonds (1.32 Å) and carbon-carbon single bonds (1.53
Å),14 respectively. The Ir-O(1) (2.204(8) Å) and Ir-O(2)
(2.222(8) Å) distances are statistically identical and
significatively longer than the mean of the Ir-O dis-
tances previously reported (2.088 Å).13 Ir-C(6) (2.030(9)
Å) and Ir-C(22) (2.017(10) Å) are also statistically
identical and shorter than the Ir-C bond lengths found
in the alkenyliridium(III) complexes IrH(CHdCH2)-
Cl(CO)(PiPr3)2 (2.059(6) Å)15 and IrH(CHdCH2)(η5-C5-
Me5)(PMe3) (2.054(4) Å).16 However, they are almost
Treatment of 1 with ca. 3 equiv of phenylacetylene
in benzene leads, after 1 h at room temperature, to an
orange solution from which the compound Ir{κ3-CHd
C(Ph)CH[C(O)CH3]2}(C2Ph)(CPhdCH2)(PCy3) (4) (eq 3)
was separated as an orange crystalline solid in 73%
yield, by addition of hexane.
Complex 4 was fully characterized by elemental
1
analysis, IR and H, 31P{1H}, and 13C{1H} NMR spec-
troscopic data, and X-ray diffraction. A drawing of the
molecular structure is shown in Figure 1. Selected bond
distances and angles are listed in Table 2.
The single crystal X-ray diffraction analysis of 4
reveals the presence of the unusual κ3-CHdC(Ph)CH-
[C(O)CH3]2 ligand, which is a result of the 1,4-addition
of a phenylacetylene across the â-ketoenolate-iridium
ring. We note that examples illustrating the 1,4-
addition of activate internal alkynes across the â-ke-
toenolato-iridium and -rhodium rings have been pre-
viously described.12 However, nothing is known about
this reaction with nonactivating terminal alkynes. The
bicyclic system occupies three coordination sites to form
a face of the octahedral environment around the iridium
atom. The C(6) carbon atom is disposed trans to the
identical with those of the complexes [IrH{C(COOC-
H3)dCH2}(Hpz)(PPh3)2]BF4 (Hpz ) pyrazole; 2.02(2)
Å)17 and IrH(acac)(CHdCH2)(PiPr3)2 (2.02(1) Å).11 The
Ir-C(14) length (1.897(11) Å) is consistent with a single
(13) Allen, F. H.; Davies, J . E.; Galloy, J . J .; J ohnson, O.; Kennard,
O.; Macrae, C. F.; Mitchell, E. M.; Mitchell, G. F.; Smith, J . M.; Watson,
D. G. J . Chem. Info. Comput. Sci. 1991, 31, 187.
(14) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,
G.; Taylor, R. J . Chem. Soc., Perkin Trans. 1987, S1.
(15) Schulz, M.; Werner, H. Organometallics 1992, 11, 2790.
(16) (a) Stoutland, P. O.; Bergman, R. G. J . Am. Chem. Soc. 1985,
107, 5481. (b) Stoutland, P. O.; Bergman, R. G. J . Am. Chem. Soc. 1988,
110, 5732.
(12) (a) Russell, D. R.; Tucker, P. A. J . Chem. Soc., Dalton Trans.
1975, 1749. (b) Barlow, J . H.; Clark, G. R.; Curl, M. G.; Howden, M.
E.; Kemmitt, R. D. W.; Russell, D. R. J . Organomet. Chem. 1978, 144,
C47. (c) J arvis, A. C.; Kemmitt, R. D. W.; Russell, D. R.; Tucker, P. A.
J . Organomet. Chem. 1978, 159, 341.
(17) Esteruelas, M. A.; Garcı´a, M. P.; Mart´ın, M.; Nu¨rnberg, O.; Oro,
L. A.; Werner, H. J . Organomet. Chem. 1994, 466, 247.

826 Organometallics, Vol. 15, No. 2, 1996
Esteruelas et al.
bond from Ir(III) to a C(sp) atom and indicates a low
degree of metal-to-ligand back-bonding.18 The C(14)-
C(15) bond length and C(14)-C(15)-C(16) angle are
1.268(16) Å and 179(1)°, respectively; a slight bending
in the Ir-C(14)-C(15) moiety is present (Ir-C(14)-C(15)
) 176.4(9)°); similar values have been found for related
complexes containing terminal alkynyl groups.19
In agreement with the structure shown in Figure 1,
reported have the formula IrHX(SiR3)(PR3)2, and they
have been prepared by oxidative addition of silanes to
IrX(olefin)(PR3)2 (X ) Cl, Br)20,21 and by reaction of IrH5-
(PR3)2 with chlorosilanes in the presence of olefins.22
the 13C{1H} NMR spectrum of 4 in chloroform-d shows
four doublets at 166.93 (J P-C ) 92 Hz), 141.71 (J P-C
)
6 Hz), 125.81 (J P-C ) 4 Hz), and 119.99 (J P-C ) 4 Hz)
ppm and two singlets at 153.92 and 131.13 ppm, which
were assigned to the carbon atoms C(6), C(7), C(14),
Complex 8 was isolated as a yellow crystalline solid
in 93% yield and characterized by elemental analysis,
1
C(22), C(23) and C(15), respectively. In the H NMR
1
IR and H (Table 1) and 31P{1H} spectroscopic data, and
spectrum the most noticeable resonances are a singlet
at 9.15 ppm, assigned to Ir-CHd proton and two virtual
triplets at 5.69 and 5.19 ppm, with H-H and P-H
coupling constants of 3 Hz, which were assigned to the
dCH2 protons. The 31P{1H} NMR spectrum contains a
singlet at -2.5 ppm.
Similarly to the reaction shown in eq 1, complex 1
reacts with phenylacetylene in the presence of 1 equiv
of tricyclohexylphosphine to afford the hydrido-alkynyl
complex Ir(acac)H(C2Ph)(PCy3)2 (5). Under the same
conditions the treatment of 1 with cyclohexylacetylene
and (trimethylsilyl)acetylene leads to the corresponding
hydrido-alkynyl derivatives Ir(acac)H(C2R)(PCy3)2 (R
) Cy (6), SiMe3 (7)) (eq 4).
X-ray diffraction. A drawing of the molecular structure
is presented in Figure 2. Selected bond distances and
angles are listed in Table 3.
The geometry can be rationalized as a square pyramid
with the triethylsilyl group located at the apex. The
four atoms O(1), O(2), P, and H(1) forming the base are
approximately coplanar, whereas the iridium atom is
located 0.2394(4) Å above this plane toward the apical
position. We note that the molecular structures of the
five-coordinate complexes IrHCl(SiiPr2OH)(PEt3)221 and
22
IrHCl(SiCl2CH3)(PiPr3)2 have been previously deter-
mined by X-ray diffraction. In contrast to 8, they show
trigonal bipyramidal arrangements of the ligands around
the metallic center.
The Ir-Si distance of 2.307(1) Å is significantly
shorter than those determined previously for the six-
coordinate iridium(III) complexes IrH2(SiEt3)(COD)-
(AsPh3) (2.414(2) Å),23 IrH2(SiMe2Ph)(CO){P(p-tol)3}2
(2.414(2) Å),24 IrH(SiMe2Cl)(CO)(dppe) (dppe ) 1,2-bis-
(diphenylphosphino)ethane) (2.396(2) Å), IrH(SiEtF2)2-
(CO)(dppe) (2.360(10) Å),25 and IrH{Si(C6H4)Ph2}(PMe3)3
(2.404(3) Å).26 However, it is similar to that found in
the pentacoordinated complex IrHCl(SiiPr2OH)(PEt3)2
(2.313(6) Å)21 and in the six-coordinate complex IrCl2-
(SiMeCl2)(PMe3)3 (2.299(5) Å)27 and longer that those
found in the other five-coordinate derivatives IrHCl-
Complexes 5-7 were isolated as white or pale yellow
solids in about 50% yield. In the IR spectra in Nujol
the most noticeable absorptions are two bands between
2300 and 2000 cm-1, which were assigned to the ν(Ir-
H) and ν(CtC) vibrations. The presence of an alkynyl
ligand is also supported by the 13C{1H} NMR spectra.
The CR carbon atoms appear at about 128 ppm as
triplets with P-C coupling constants between 8 and 13
Hz, while the Câ carbon atoms display singlets at about
(SiMe2Cl2)(PiPr3)2 (2.235(5) Å)22 and Ir(acac){C[CH-
(OCH3)OSiPh2]dCHCO2CH3}(PCy3) (2.264(2) Å).10
1
130 ppm. In the H NMR spectra (Table 1) the hydrido
It should be also mentioned that the Ir-O(2) bond
distance (2.073(3) Å; O trans to P) is significantly
shorter than the Ir-O(1) bond distance (2.121(2) Å; O
trans to H), possibly due to the different trans influences
of the phosphine and hydrido ligands. The O(1)-C(1)
(1.298(5) Å), C(1)-C(3) (1.382(6) Å), C(3)-C(4) (1.394(6)
Å), and C(4)-O(2) (1.267(5) Å) distances compare well
with those found in the delocalized acetylacetonato
ligand coordinated to other Ir(III) fragments.11,13 The
ligands appear between -25 and -29 ppm, as triplets
with P-H coupling constants of 15 Hz. The presence
of only one hydrido ligand in these compounds was
inferred from the 31P{1H} NMR spectra, which contain,
in agreement with the mutually trans disposition of the
phosphine ligands, singlets at about 15 ppm that under
off-resonance conditions due to P-H coupling are split
into doublets.
3. Rea ction s of Ir (a ca c)(cycloocten e)(P Cy3) w ith
HSiR3. The addition of ca. 1 equiv of HSiEt3, HSiPh3,
and H2SiPh2 to solutions of 1 in benzene leads after 30
min to the corresponding five-coordinate hydrido-silyl
complexes Ir(acac)H(SiR3)(PCy3) (SiR3 ) SiEt3 (8), SiPh3
(9), SiHPh2 (10)), according to eq 5. Five-coordinate
hydrido-silyl-iridium(III) compounds are rare, as far
as we know, the derivatives of this type previously
(20) Blackburn, S. N.; Haszeldine, R. N.; Parish, R. V.; Setchfield,
J . H. J . Chem. Res. (S) 1980, 170.
(21) Goikhman, R.; Aizenberg, M.; Kraatz, H. B.; Milstein, D. J . Am.
Chem. Soc. 1995, 117, 5865.
(22) Yamashita, H.; Kawamoto, A. M.; Tanaka, M.; Goto, M. Chem.
Lett. 1990, 2107.
(23) Ferna´ndez, M. J .; Esteruelas, M. A.; Oro, L. A.; Apreda, M. C.;
Foces-Foces, C.; Cano, F. H. Organometallics 1987, 6, 1751.
(24) Rappoli, B. J .; J anik, T. C.; Churchill, M. R.; Thompson, J . S.;
Atwood, J . D. Organometallics 1988, 7, 1939.
(25) Hays, M. K.; Eisenberg, R. Inorg. Chem. 1991, 30, 2623.
(26) Aizenberg, N.; Milstein, D. Angew. Chem., Int. Ed. Engl. 1994,
33, 317.
(18) Bruce, M. I.; Hambley, T. W.; Snow, N. R.; Swincer, A. G. J .
Organomet. Chem. 1982, 235, 105.
(19) (a) Nast, R. Coord. Chem. Rev. 1982, 47, 89. (b) Ferna´ndez, M.
J .; Esteruelas, M. A.; Covarrubias, M.; Oro, L. A.; Apreda, M. C.; Foces-
Foces, C.; Cano, F. H. Organometallics 1989, 8, 1158.
(27) Zlota, A. A.; Frolow, F.; Milstein, D. J . Chem. Soc., Chem.
Commun. 1989, 1826.

Reactions of Ir(acac)(cyclooctene)(PCy3)
Organometallics, Vol. 15, No. 2, 1996 827
The most noticeable absorptions in the IR spectra in
Nujol of 11-13 are those corresponding to the ν(Ir-H)
vibrations, which appear between 2240 and 2210 cm-1
.
1
In the H NMR spectra (Table 1) the hydrido ligands
display triplets at about -25.5 ppm, with P-H coupling
constants of 16 Hz. The 31P{1H} NMR spectra show
singlets between 9.4 and 15.9 ppm, which under off-
resonance conditions due to P-H coupling are split into
doublets.
F igu r e 2. Molecular structure diagram of the complex Ir-
(acac)H(SiEt3)(PCy3) (8).
4. Rea ction s of Ir (a ca c)(cycloocten e)(P Cy3) w ith
HSn P h 3. The addition of ca. 1 equiv of HSnPh3 to a
benzene-d6 solution of 1 leads after 5 min to the five-
coordinate hydrido-stannyl complex Ir(acac)H(SnPh3)-
(PCy3) (14), according to eq 7.
Ta ble 3. Bon d Dista n ces (Å) a n d An gles (d eg) for
th e Com p ou n d Ir (a ca c)H(SiEt3)(P Cy3) (8)
Ir-P
2.235(1)
2.307(1)
2.121(2)
2.073(3)
1.44(4)
C(1)-C(2)
C(1)-C(3)
C(3)-C(4)
O(2)-C(4)
C(4)-C(5)
1.509(6)
1.382(6)
1.394(6)
1.267(5)
1.518(6)
Ir-Si
Ir-O(1)
Ir-O(2)
Ir-H(1)
O(1)-C(1)
1.298(5)
P-Ir-Si
101.19(4)
91.38(8)
167.19(8)
90(1)
122.52(8)
90.04(8)
69(1)
87.7(1)
168(1)
88(1)
Ir-O(1)-C(1)
125.7(2)
114.8(3)
126.2(4)
119.0(4)
126.5(4)
119.7(4)
126.5(4)
113.8(4)
127.4(3)
P-Ir-O(1)
P-Ir-O(2)
P-Ir-H(1)
Si-Ir-O(1)
Si-Ir-O(2)
Si-Ir-H(1)
O(1)-Ir-O(2)
O(1)-Ir-H(1)
O(2)-Ir-H(1)
O(1)-C(1)-C(2)
O(1)-C(1)-C(3)
C(2)-C(1)-C(3)
C(1)-C(3)-C(4)
C(3)-C(4)-C(5)
O(2)-C(4)-C(3)
O(2)-C(4)-C(5)
Ir-O(2)-C(4)
The 1H and 31P{1H} NMR spectra of 14 strongly
support the structure shown in eq 7. The 1H NMR
spectrum (Table 1) contains in the high-field region a
doublet at -24.44 ppm, with a P-H coupling constant
of 17 Hz. The satellites due to the Sn isotopes are also
observed near to this resonance. The value of the Sn-H
coupling constant, 88 Hz, is in agreement with the cis
situation of the triphenylstannyl group and the hydrido
ligand. The 31P{1H} NMR spectrum shows a singlet at
7.6 ppm, along with the satellites corresponding to the
tin active isotopes. The value of the P-Sn coupling
constant, 44 Hz, also agrees well with the mutually cis
disposition of the SnPh3 and PCy3 groups. Under off-
resonance conditions due to P-H coupling the singlet
is split into a doublet.
Ir-P (2.235(1) Å) bond length is also in the expected
range and deserves no further comment.
The 1H and 31P{1H} spectra of 8 are temperature
invariant, suggesting that although 8 is a five-coordi-
nate derivative, it has a rigid structure in solution. In
agreement with the structure shown in Figure 2, the
hydrido ligand appears in the 1H NMR spectrum at
-23.47 ppm as a doublet with a P-H coupling of 19
Hz. Similar chemical shifts have been observed for the
hydrido ligands of the acetato complexes IrH2{η2-O2CR}-
(PPh3)2, where the hydridos also are disposed trans to
an O-donor ligand.28 As the 1H NMR spectrum of 8,
the 1H NMR spectra of 9 and 10 contain doublets at
-22.81 (9) and -22.70 (10) ppm with P-H coupling
constants of 17 and 19 Hz, respectively. The 31P{1H}
NMR spectra of the three compounds show singlets
between 6 and 12 ppm, which under off-resonance
conditions due to P-H coupling are split into doublets,
in accordance with the presence of only one hydrido
ligand in these compounds.
Similary to 8, complex 14 does not react with tricy-
clohexylphosphine. However, the addition of ca. 1 equiv
of HSnPh3 to a toluene solution of 1 in the presence of
1 equiv of phosphine leads to the six-coordinate hy-
drido-stannyl derivative Ir(acac)H(SnPh3)(PCy3)2 (15),
according to eq 8.
Complex 15 was isolated as a pale yellow solid in 61%
yield. In the IR spectrum in Nujol, the most noticeable
absorption is that corresponding to the ν(Ir-H) vibra-
The complexes 8 and 10 do not react with tricyclo-
hexylphosphine. However, the addition of ca. 1 equiv
of HSiEt3, H2SiPh2, and H3SiPh to toluene solutions of
1 in the presence of 1 equiv of tricyclohexylphosphine
affords the six-coordinate hydrido-silyl derivatives Ir-
(acac)H(SiR3)(PCy3)2 (SiR3 ) SiEt3 (11), SiHPh2 (12),
SiH2Ph (13)), which were isolated as white solids in 40-
60% yield (eq 6).
tion, which appears at 2225 cm-1
.
In the 1H NMR
spectrum (Table 1) the hydrido ligand gives rise to a
triplet at -27.13 ppm with a P-H coupling constant of
16 Hz. The 31P{1H} NMR spectrum contains a singlet
at 7.6 ppm, along with the satellites due to the 117Sn
and 119Sn isotopes. In agreement with the structure
shown in eq 8, the value of the P-119Sn coupling
constant is 142 Hz, while the value the P-117Sn coupling
(28) Esteruelas, M. A.; Garc´ıa, M. P.; Lahoz, F. J .; Mart´ın, M.;
Modrego, J .; On˜ate, E.; Oro, L. A. Inorg. Chem. 1994, 33, 3473.

828 Organometallics, Vol. 15, No. 2, 1996
Esteruelas et al.
Sch em e 1
constant is 113 Hz. Under off-resonance conditions due
to P-H coupling the singlet is split into a doublet.
5. Com m en ts on th e F or m a tion of th e Six-
Coor d in a te Com p lexes Ir (a ca c)HX(P Cy3)2. The
oxidative addition of molecular hydrogen and group 14
element hydrido compounds to iridium(I) complexes is
generally viewed as a concerted cis addition.29 Fur-
thermore, J ohnson and Eisenberg30 have proved that
the addition of HSiR3 to iridium(I) cis-phosphine com-
plexes, IrX(CO)(dppe) (X ) Br, CN), is a diasteroselec-
tive process with specific substrate orientation. We
have recently observed that the oxidative addition of
HSnR3 to Ir(C2Ph)(L2)(PCy3) (L2 ) 2 CO, tetrafluo-
robenzobarrelene (TFB)) is also a diasteroselective cis
addition process with specific substrate orientation.9b
According to this, Scheme 1 shows three different
reaction pathways which allow the formation of 2, 5-7,
11-13, and 15 to be rationalized. These compounds are
formed by reaction of 1 with the substrate HX in the
presence of 1 equiv of tricyclohexylphosphine (eqs 1, 4,
6, and 8). Therefore, the reactions could initially involve
the interaction of 1 with the substrate HX (pathway a )
or alternatively with the phosphine (pathways b and
c).
tion of the compounds of the type Ir(acac)HX(PCy3)2
according to pathway a involves the initial formation
of the derivatives 18 and its subsequent reaction with
the phosphine ligand. This pathway can be totally ruled
out. Since, we have previously mentioned that the
derivatives 8-10 do not react with tricyclohexylphos-
phine.
According to pathway b, the reactions shown in the
eqs 1, 4, 6, and 8 involve the initial formation of the
bis(phosphine) intermediate 21. The oxidative addition
of the substrate HX must initially lead to six-coordinate
derivatives, containing the phosphine ligands mutually
cis disposed. The isomerization of these intermediates
could yield the reaction products. However, it should
be noted that this isomerization occurs by disociation
of phosphine and, therefore, via five-coordinate mono-
(phosphine) derivatives, which do not recoordinate
phosphine. At first glance, one could think that the
isomerization of 23 and/or 25 into the reactions product
involves five-coordinate intermediates containing the
acetylacetonato ligand coordinated in an η1-fashion. This
does not seem likely due to the low tendency shown by
the d6 ions to afford unsaturated compounds containing
η1-chelate ligands. Furthermore, it should be noted that
these five-coordinate intermediates should also be ac-
cesible from Ir(acac)HX(PCy3)2 by reaction with phos-
phine, which does not occur.
The d8 ions show a higher tendency than the d6 ions
to afford unsaturated species. Thus, the addition of
phosphine to the solutions of 1 could give the unsatur-
ated square-planar intermediate 27 (pathway c) con-
taining the acetylacetonato coordinate in a η1-C3-
fashion. In iridium there is precedent for this reaction,
as we have previously reported that the addition of
N-donor ligands to Ir(acac)(diolefin) leads to the corre-
sponding Ir(η1-C3-acac) derivatives.31 The oxidative
addition of the substrate HX along of the olefin-Ir-C3-
(acac) axis should give 29 or 31. The subsequent η1-C3
According to pathway a , the oxidative addition of HX
to 1 along the olefin-Ir-O(acac) axis yields a six-
coordinate intermediate 17, which by subsequent diso-
ciation of cyclooctene affords 18, isolated for X ) SiEt3,
SiPh3, SiHPh2, and SnPh3. The isomerization of these
five-coordinate derivatives followed by the coordination
of the phosphine, which is present in the reaction,
should lead to the reaction products. Hence, the forma-
(29) (a) Sommer, L. H.; Lyons, J . E.; Fujimoto, H. J . J . Am. Chem.
Soc. 1969, 91, 7051. (b) Harrod, F. J .; Smith, C. A.; Thank, K. A. J .
Am. Chem. Soc. 1972, 94, 8321. (c) Fawcett, J . P.; Harrod, J . F. J .
Organomet. Chem. 1976, 113, 245. (d) Benett, M. A.; Charles, R.;
Fraser, P. J . Aust. J . Chem. 1977, 30, 1201. (e) J ohnson, C. E.; Fisher,
B. J .; Eisenberg, R. J . Am. Chem. Soc. 1983, 105, 7772. (f) J ohnson,
C. E.; Eisenberg, R. J . Am. Chem. Soc. 1985, 107, 3148.
(30) J ohnson, C. E.; Eisenberg, R. J . Am. Chem. Soc. 1985, 107,
6531.

Reactions of Ir(acac)(cyclooctene)(PCy3)
Organometallics, Vol. 15, No. 2, 1996 829
Sch em e 2
f η2-O,O′ conversion of the acetylacetonato ligand
together with the displacement of the olefin could afford
the reactions products. The synthesis of complex 4
according to eq 3 is strong evidence in favor of pathway
c. Scheme 2 shows a plausible reaction pathway for the
formation of this compound, which involves the oxida-
tive addition of the HCt bond of an alkyne, the
insertion of a second alkyne into a Ir-η1-C3(acac) bond,
and insertion of a third alkyne into a Ir-H bond. As
far as we know, these three reactions sequential on the
same metallic center have no precedent.
F igu r e 3. Experimental (left) and computed (right) high-
field region of the variable-temperature H NMR spectra
1
In addition, it should be mentioned the high stability
of the six-coordinate derivatives 2, 5-7, 11-13, and 15
toward the reductive elimination of HX can be related
to the cis constraint imposed by the chelating acetylac-
etonato ligand and the fact that in a concerted reductive
elimination the ligands trans to the leaving groups move
into mutually trans positions in the resulting four-
coordinate complex.32
of 32 (toluene-d8, 300 MHz).
6. Rea ction of Ir (a ca c)H(SiEt3)(P Cy3) w ith Mo-
lecu la r Hyd r ogen . Under atmospheric pressure of
hydrogen, complex 8 is converted into the trihydrido-
silyl-iridium(V) derivative Ir(acac)H3(SiEt3)(PCy3) (32).
Figure 3 shows the 1H NMR spectrum of this compound,
in the hydrido region, as a function of the temperature.
At 295 K the spectrum contains a broad resonance at
about -24 ppm, which is converted into the AM2 part
F igu r e 4. Eyring plot of the dynamic process of 32 as
deduced from line shape analysis of the variable-temper-
1
ature H NMR spectra.
of an AM2X spin system at 230 K. The position (δA
)
-3.64 and δM ) -23.26) and the values of the coupling
constants (J A-M ) 0, J A-X ) 119.0 and J M-X ) 19.9 Hz)
strongly support the structure shown in eq 9.
agreement with an intramolecular process. Further-
more, it should be mentioned that the reaction shown
in the eq 9 is completely reversible under vacuum at
room temperature. This suggests that the exchange
process could take place by dihydrogen intermediates.
A plausible mechanism for fluxionality which accounts
for the observations is shown in Scheme 3.
Trihydrido-silyl complexes are rare;33 indeed 32 is
the only example with an O-donor ligand. Apart from
32, the only other trihydrido-silyl complexes examples
are the derivatives Ir(η5-C5Me5)H3(SiMe3)34 and IrH3(η2-
R2SiXSiR2)(PPh3)2 (X ) C6H4, R ) Me; X ) O, R ) iPr).35
Complex 32 is also significant because it proves that
the acetylacetonato ligand not only stabilizes Ir(I) and
Ir(III) but also Ir(V). The only O-donor ligand efficient
to stabilize Ir(I), Ir(III), and Ir(V), previously reported,
is the tridentate tris(diphenyloxophosphoranyl)meth-
anide.5c
The 31P{1H} NMR spectrum of 32 shows a singlet at
21.8 ppm which is temperature invariant, suggesting
that the fluxional process only involves the relative
positions of the hydrido ligands. Linear least-squares
analysis of the Eyring plot for the kinetic data (Figure
4) provides values of ∆Hq and ∆Sq of 12.23(( 0.76) kcal
mol-1 and -1.45((1.84) cal K-1 mol-1, respectively. The
value of the entropy of activation, close to zero, is in
7. Ad d ition of HSiEt3 to P h CtCH Ca ta lyzed by
Ir (a ca c)H (SiE t 3)(P Cy3). The addition of silanes to
(31) (a) Oro, L. A.; Carmona, D.; Esteruelas, M. A.; Foces-Foces, C.;
Cano, F. H. J . Organomet. Chem. 1983, 258, 357. (b) Oro, L. A.;
Carmona, D.; Esteruelas, M. A.; Foces-Foces, C.; Cano, F. H. J .
Organomet. Chem. 1986, 307, 83.
(32) (a) Deutsch, P. P.; Eisemberg, R. J . Am. Chem. Soc. 1990, 112,
714. (b) Deutsch, P. P.; Eisenberg, R. Organometallics 1990, 9, 709.
(c) Cleary, B. P.; Mehta, R.; Eisenberg, R. Organometallics 1995, 14,
2297.
(33) Hlatky, G. G.; Crabtree, R. H. Coord. Chem. Rev. 1985, 65, 1.
(34) Gilbert, T. M.; Hollander, F. J .; Bergman, R. G. J . Am. Chem.
Soc. 1985, 107, 3508.
(35) Loza, M.; Faller, J . W.; Crabtree, R. H. Inorg. Chem. 1995, 34,
2937.

830 Organometallics, Vol. 15, No. 2, 1996
Esteruelas et al.
Ta ble 4. Hyd r osilyla tion of P h en yla cetylen e Ca ta lyzed by Ir (a ca c)H(P Cy3)(SiEt3)
product ratios
T, °C
[PhCtCH], M
[HSiEt3], M
PhCtCSiEt3
PhSiEt3CdCH2
cis-PhCHdCH(SiEt3)
trans-PhCHdCH(SiEt3)
23
34
60
60
60
60
60
60
0.24
0.24
0.24
0.24
0.24
0.12
0.18
0.36
0.24
0.24
0.24
0.12
0.18
0.24
0.24
0.24
0.101
0.080
0.054
0.136
0.086
0.014
0.022
0.071
0.070
0.040
0.015
0.058
0.035
0.004
0.010
0.016
0.629
0.690
0.718
0.652
0.692
0.671
0.677
0.766
0.200
0.190
0.213
0.154
0.187
0.311
0.291
0.147
Sch em e 3
alkynes catalyzed by transition metal complexes is one
of the most important laboratory and industrial methods
of forming vinylsilanes,36 which have shown to be
versatile intermediates in organic synthesis.37 Complex
8 catalyzes the hydrosilylation of phenylacetylene with
triethylsilane. The reactions were performed in 1,2-
dichloroethane solutions, and the results are listed in
Table 4. 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 10), along with a normal
hydrosilylation (eq 11). 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.
catalyst OsHCl(CO)(PiPr3)2.38 Raising temperature also
increases the yield of the cis isomer. This agrees with
the behavior of OsHCl(CO)(PiPr3)2 but is in contrast
with that observed in the presence of the complexes
IrH2(SiEt3)(TFB)(PR3) (PR3 ) PPh3, PiPr3, PCy3)39 and
[IrH(H2O)(bq)(PPh3)2]SbF6 (bq ) 7,8-benzoquinolato),40
where raising the temperature favors the syn-addition,
resulting in the trans-isomer.
The mechanisms previously proposed5b,38,41 for the
formation of the anti-addition product involve the initial
insertion of the alkyne into a M-Si bond to give a (Z)-
silylvinyl intermediate, which isomerizes to the less
sterically congested E-isomer via a zwitterionic carbene
complex. In addition â-elimination of the endo-hydrogen
atom of the (E)-silylvinyl group could lead to the
dehydrogenative silylation product PhCtCSiEt3. The
results collected in Table 4 can be rationalized according
to this proposal, although the participation of alkynyl
intermediates cannot be completely rejected. In this
context, it should be mentioned that a recent study on
the addition of triethylsilane to phenylacetylene cata-
lyzed by [Ir(COD)(η2-iPr2CH2CH2OMe)]BF4 has revealed
that under the catalytic conditions both hydrido-
alkynyl and hydrido-silyl intermediates are formed.42
The major product in all cases is the thermodynami-
cally less stable cis-PhCHdCH(SiEt3), resulting from
the anti-addition of the silane to the alkyne. Contact
with the catalyst in the presence of silane leads to
isomerization to the more stable trans-isomer. Table 4
shows that lowering the triethylsilane concentration or
increasing the phenylacetylene concentration increases
the relative amount of cis-PhCHdCH(SiEt3). The same
behavior has been previously observed for the osmium
Con clu d in g Rem a r k s
The complex Ir(acac)(cyclooctene)(PCy3) reacts with
HER3 to give the five-coordinate derivatives Ir(acac)H-
(ER3)(PCy3) (E ) Si, Sn). The determination of the
structure of Ir(acac)H(SiEt3)(PCy3) by X-ray diffraction
(38) Esteruelas, M. A.; Oro, L. A.; Valero, C. Organometallics 1991,
10, 462.
(36) Noels, A. F.; Hubert, A. J . Industrial Aplications of Homoge-
neous Catalysis, Mortreux, A., Petit, F., Eds.; D. Reidel Publishing
Co.: Boston, MA, 1988; Chapter 3.1.3.
(37) (a) Hudrlik, P. F. New Applications of Organometallic Reagents
in Organic Synthesis; Seyferth, D., Ed.; Elsevier: Amsterdam, 1976;
p 127. (b) Chan. T. H. Acc. Chem. Res. 1977, 10, 442. (c) Cook, F.;
Moerch, J .; Schwindeman, J .; Magnus, P. J . Org. Chem. 1980, 45, 1406.
(d) Fleming, I.; Dunogues, J .; Swithers, R. H. Org. React. 1989, 37,
57.
(39) Esteruelas, M. A.; Nu¨rnberg, O.; Oliva´n, M.; Oro, L. A.; Werner,
H. Organometallics 1993, 12, 3264.
(40) J un, C. H.; Crabtree, R. H. J . Organomet. Chem. 1993, 447,
177.
(41) (a) Ojima, I.; Clos, N.; Donovan, R. J .; Ingallina, P. Organome-
tallics 1990, 9, 3127. (b) Esteruelas, M. A.; Herrero, J .; Oro, L. A.
Organometallics 1993, 12, 2377.
(42) Esteruelas, M. A.; Oliva´n, M.: Oro, L. A.; Tolosa, J . I. J .
Organomet. Chem. 1995, 487, 143.

Reactions of Ir(acac)(cyclooctene)(PCy3)
Organometallics, Vol. 15, No. 2, 1996 831
Found: C, 57.40; H, 8.99. IR (Nujol cm-1): ν(Ir-H) 2240,
2175; ν(acac) 1590, 1520. 31P{1H} NMR (80 MHz, C6D6) δ 15.8
(s).
has revealed that these compounds have a square
pyramidal arrangement of ligands around the metallic
center, in contrast to that observed for related five-
coordinate compounds containing only monodentate
ligand, where the arrangement of ligands around the
iridium atom is trigonal bipyramidal.
In the presence of triyclohexylphosphine the complex
Ir(acac)(cyclooctene)(PCy3) reacts not only with silanes
and stannanes but also with terminal alkynes and
molecular hydrogen, to afford the six-coordinate com-
plexes Ir(acac)HX(PCy3)2 (X ) Si, Sn, C2R, H). These
reactions most probably involve reaction intermediates
where the acetylacetonato ligand is coordinated in a η1-
C3(acac) fashion.
An especially interesting reaction takes places when
the complex Ir(acac)(cyclooctene)(PCy3) is treated with
3 equiv of phenylacetylene. Under these conditions the
unusual Ir{κ3-CHdC(Ph)CH[C(O)CH3]2}(C2Ph)(CPhd
CH2)(PCy3) complex is obtained. The formation of this
compound involves the oxidative addition of the HCt
bond of an alkyne, the insertion of a second alkyne into
a Ir-η1-C3(acac) bond, and the insertion of a third alkyne
into a Ir-H bond, on the same metallic center. The
three reactions together on the same metallic atom have
no precedent. Furthermore, it should be noted that,
although, the 1,4-addition of activate alkynes across the
â-ketoenolato-iridium and -rhodium rings have been
previously described, nothing was known about this
reaction with nonactivating terminal alkynes.
Under atmospheric presence of hydrogen, the complex
Ir(acac)H(SiEt3)(PCy3) affords the trihydrido-silyl de-
rivative Ir(acac)H3(SiEt3)(PCy3), which is the only ex-
ample of compound of this type with an O-donor ligand.
Under argon atmosphere the complex Ir(acac)H(SiEt3)-
(PCy3) also catalyzes the addition of triethylsilane to
phenylacetylene to give cis-PhCHdCH(SiEt3) with se-
lectivities of about 70%.
P r ep a r a tion of Ir (a ca c)(η2-HCtCP h )(P Cy3) (3). A solu-
tion of 1 (30 mg, 0.04 mmol) in benzene-d6 (0.6 mL) contained
in a 5-mm NMR tube was treated with HCtCPh (5 µL, 0.04
mmol). After 5 min the 1H and 31P{1H} NMR show signals
corresponding to 3 and free cyclooctene. 1H NMR (300 MHz,
C6D6, 295 K) (δ): 8.20-7.00 (m, 5 H, Ph); 5.60 (m, 2 H, free
coe), 5.22 (s, 1 H, CH of acac), 4.10 (s, 1 H, HCtCPh); 2.25-
1.22 (m, 45 H, Cy and free coe); 1.85 and 1.50 (both s, 6 H,
CH3 of acac). 31P{1H} NMR (121.45 MHz, C6D6): δ 7.5 (s).
P r ep a r a tion of Ir {K3-CHdC(P h )CH[C(O)CH3]2}(C2P h )-
(CP h dCH2)(P Cy3) (4). PhCtCH (46 µL, 0.42 mmol) was
added to a orange solution of 1 (98 mg, 0.14 mmol) in toluene
(10 mL). The resulting red solution was stirred for 1 h at room
temperature and the solvent removed in vacuo. Addition of
hexane caused the precipitated an orange solid. The solvent
was decanted, and the solid was twice washed with hexane
and then dried in vacuo, yield 90 mg (73%). Anal. Calcd for
C
47H58IrO2P: C, 64.42; H, 6.44. Found: C, 64.26: H, 6.29. IR
(Nujol, cm-1): ν(CtC) 2106; ν(CO) 1658, 1593; ν(CdC) 1548.
1H NMR (300 MHz, CDCl3) (δ): 9.15 (s, 1 H, HCdCPh); 7.44-
6.81 (m, 15 H, Ph); 5.79 (s, 1 H, CH of acac); 5.69 and 5.19
(both t, 2 H, J P-H ) 5 Hz, J H-H ) 3 Hz, PhCdCH2); 2.58 and
2.26 (both s, 6 H, CH3); 2.54-1.00 (m, 33 H, Cy). 13C{1H} NMR
(75.45 MHz, CDCl3, 295 K) (δ): 209.38 and 207.37 (both s,
CO); 166.93 (d, J P-C ) 92 Hz, HCdCPh); 153.92 (s, PhCdCH2);
141.71 (d, J P-C ) 6 Hz, HCdCPh); 131.55 (s, Ph); 131.13 (s,
CtCPh); 128.78 (s, Ph); 128.02 (s, Ph); 127.63 (s, Ph); 126.51
(s, Ph); 126.46 (s, Ph); 125.81 (d, J P-C ) 4 Hz, CtCPh); 125.63
(s, Ph); 124.17 (s, Ph); 123.79 (s, Ph); 119.99 (d, J P-C ) 4 Hz,
PhCdCH2); 75.06 (s, CH of acac); 33.99 (d, J P-C ) 18 Hz,
PCHCH2); 33.02 and 32.42 (both s, CH3); 29.59 and 29.45 (both
s, CH2); 28.30 and 28.18 (both d, J P-C ) 10 Hz, PCHCH2); 27.22
(s, CH2). 31P{1H} NMR (80 MHz, CDCl3): δ -2.53 (s).
P r ep a r a tion of Ir (a ca c)H(CtCP h )(P Cy3)2 (5). A solu-
tion of 1 (98 mg, 0.14 mmol) in toluene (10 mL) was treated
with PCy3 (40 mg, 0.14 mmol) and PhCtCH (16 µL, 0.14
mmol). The resulting solution was stirred for 6 h at room
temperature and filtered through Kieselguhr. The filtrate was
concentrated to ca. 0.1 mL; addition of methanol caused the
precipitation of a white solid. The solvent was decanted, and
the solid was twice washed with methanol and dried in vacuo,
yield 69 mg (52%). Anal. Calcd for C49H79IrO2P2: C, 61.67;
H, 8.33. Found: C, 61.96; H, 8.20. IR (Nujol, cm-1): ν(Ir-H)
2260; ν(CtC) 2120; ν(acac) 1580, 1520. 13C{1H} NMR (75.45
MHz, CDCl3, 295 K) (δ): 187.52 and 182.39 (both s, CO of
acac); 130.96 (s, CtCPh); 129.56 (s, Co-Ph); 127.26 (s, Cm-Ph);
127.26 (t, J P-C ) 11 Hz, CtCPh); 125.77 (s, Cp-Ph); 101.08 (s,
CH of acac); 31.15 (d, J P-C ) 15 Hz, PCHCH2); 28.15 and
228.96 (both s, CH2); 27.52 (d, J P-C ) 10 Hz, PCHCH2); 23.75
(s, CH3 of acac); 26.08 (s, CH2). 31P{1H} NMR (80 MHz,
CDCl3): δ 29.8 (s).
In conclusion, this study has revealed that the acetyl-
acetonato ligand stabilizes not only iridium(I) and
iridium(III) but also iridium(V) derivatives. Further-
more, it promotes catalytic activity in the selective anti-
addition of triethylsilane to phenylacetylene. The only
O-donor ligand previously reported with a similar
behavior is the tridentate tris(diphenyloxophosphora-
nyl)methanide.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All reactions were carried out
under an argon atmosphere using Schlenk tube techniques.
Solvents were dried and purified by known procedures and
distilled under argon prior to use. The starting complex Ir-
(acac)(cyclooctene)(PCy3) (1) was prepared by a published
method.10 Elemental analyses were performed with a Perkin-
Elmer 240 XL microanalyzer. NMR spectra were recorded on
a Varian 200 XL or on a Varian UNITY 300. Chemical shifts
are expressed in parts per million, upfield from Si(CH3)4
(13C{1H}, 1H) and 85% H3PO4 (31P{1H}). Infrared spectra were
run on a Perkin-Elmer 783 instrument.
P r ep a r a tion of Ir (a ca c)H 2(P Cy3)2 (2). A solution of 1
(110 mg, 0.16 mmol) in toluene (10 mL) was treated with PCy3
(45 mg, 0.16 mmol), and a slow stream of H2 was passed
through the solution for 30 min at room temperature. The
resulting solution was filtered through Kieselguhr, and the
filtrate was concentrated to ca. 0.1 mL; addition of hexane
precipitated a white solid. The solvent was decanted, and the
solid was twice washed with hexane and dried in vacuo, yield
89 mg (65%). Anal. Calcd for C41H75IrO2P2: C, 57.65; H, 8.84.
P r ep a r a tion of Ir (a ca c)H(CtCCy)(P Cy3)2 (6). The com-
plex was prepared using the procedure described for 5, starting
from 1 (110 mg, 0.16 mmol), PCy3 (45 mg, 0.16 mmol), and
CyCtCH (20 µL, 0.16 mmol). Complex 6 was isolated as a
pale yellow solid, yield 76 mg (50%). Anal. Calcd for
C
49H85IrO2P2: C, 61.29; H, 8.91. Found: C, 61.57; H, 8.96.
IR (Nujol, cm-1): ν(Ir-H) 2263; ν(CtC) 2165; ν(acac) 1595,
1515. 13C{1H} NMR (75.45 MHz, CDCl3) (δ): 185.33 and
181.64 (both s, CO of acac); 129.99 (s, CtCCy); 128.00 (t, J P-C
) 13 Hz, CtCCy); 101.32 (s, CH of acac); 32.90 and 32.58 (both
d, J P-C ) 13 Hz, PCHCH2); 28.06 (s, Cy); 28.87 and 28.64 (both
s, CH2); 28.01 (s br, PCHCH2); 26.86 (s, Cy); 26.00 (s, Cy); 25.83
(s, CH3 of acac); 25.67 (s, Cy); 25.32 (s, CH2). 31P{1H} NMR
(121.45 MHz, CDCl3): δ 14.7 (s).
P r ep a r a tion of Ir (a ca c)H(CtCSiMe3)(P Cy3)2 (7). The
complex was prepared using the procedure described for 5,
starting from 1 (100 mg, 0.15 mmol), PCy3 (41 mg, 0.15 mmol),
and Me3SiCtCH (21 µL, 0.15 mmol). Complex 7 was isolated

832 Organometallics, Vol. 15, No. 2, 1996
Esteruelas et al.
Ta ble 5. Atom ic Coor d in a tes (×104; ×105 for Ir a n d
P Atom s) a n d Equ iva len t Isotr op ic Disp la cem en t
Coefficien ts (Å2 × 103; Å2 × 104 for Ir a n d P Atom s)
for th e Com p ou n d Ir {K3-CHdC(P h )CH[C(O)(CH3]2}-
(C2P h )(CP h dCH2)(P Cy3) (4)
Ta ble 6. Atom ic Coor d in a tes (×104; ×105 for Ir , P ,
a n d Si) a n d Equ iva len t Isotr op ic Disp la cem en t
Coefficien ts (Å2 × 103; Å2 × 104 for Ir , P , a n d Si
Atom s) for th e Com p ou n d Ir (a ca c)H(SiEt3)-
(P Cy3)(8)
b
a
atom
x/ a
y/ b
z/ c
Ueqa/Uiso
atom
x/ a
y/ b
z/ c
Ueq
Ir
P
O(1)
O(2)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
61074(2)
63357(14)
6872(4)
7216(5)
7341(6)
7755(6)
7420(7)
7654(5)
8421(7)
6038(6)
6645(6)
6651(6)
6135(8)
6089(9)
6530(8)
7029(8)
7100(8)
5462(6)
5046(7)
4596(7)
4433(9)
3994(10)
3693(8)
3836(11)
4285(11)
5154(6)
4442(6)
5198(6)
5411(7)
5456(12)
5264(11)
5056(11)
5023(9)
6980(6)
7228(7)
7885(7)
7662(8)
7397(7)
6717(7)
5469(5)
5568(6)
4788(6)
4376(7)
4270(10)
5059(7)
6908(5)
6460(6)
6892(8)
7704(8)
8143(6)
7744(6)
5088(3)
5150(8)
4422(4)
8908(4)
8119(8)
8192(12)
8541(13)
7258(9)
6435(11)
6628(10)
6873(9)
6805(32)
6434(21)
29465(3)
39631(21)
1561(7)
3613(6)
1214(11)
204(9)
1822(10)
3008(11)
3392(12)
2235(8)
1809(8)
1318(9)
1765(9)
1277(11)
359(11)
-72(12)
411(11)
0
199(1)
193(5)
24(2)
28(2)
27(3)
40(3)
31(3)
28(2)
40(3)
24(2)
25(2)
25(2)
36(2)
44(3)
42(3)
45(3)
42(3)
25(2)
32(3)
30(2)
51(4)
76(6)
88(8)
88(7)
47(5)
24(2)
34(3)
31(2)
50(3)
84(8)
84(6)
74(6)
52(4)
27(2)
32(2)
40(3)
44(3)
41(3)
29(2)
18(2)
28(2)
31(2)
42(3)
42(4)
28(2)
20(2)
30(2)
40(3)
44(3)
34(3)
27(2)
80(2)
59(4)
121(3)
100(2)
95(7)
86(5)
95(5)
111(4)
76(9)
120(5)
75(4)
87(15)
185(16)
Ir
P
Si
O(1)
O(2)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
12161(1)
10496(4)
8244(4)
2021(1)
1369(1)
2369(2)
2915(2)
2283(2)
1806(2)
1780(2)
670(1)
110075(1)
125203(8)
96323(9)
11321(2)
9856(2)
10820(3)
11189(4)
9999(3)
9579(3)
8690(4)
8385(3)
7414(3)
0
115(1)
117(2)
149(2)
16(1)
17(1)
17(1)
22(1)
18(1)
17(1)
27(1)
19(1)
24(1)
25(1)
36(1)
19(1)
23(1)
15(1)
16(1)
17(1)
21(1)
23(1)
18(1)
14(1)
19(1)
22(1)
24(1)
24(1)
20(1)
12(1)
18(1)
22(1)
24(1)
26(1)
21(1)
8383(9)
207(3)
-321(3)
-140(3)
-41(9)
12691(11)
12917(11)
87(4)
-1538(3)
-634(4)
-347(4)
-1605(4)
-2013(4)
-3124(5)
150(6)
-682(4)
-570(4)
-777(5)
-751(4)
-1000(4)
-1562(4)
-1965(4)
-2482(4)
-2604(5)
-2230(5)
-1698(5)
-305(4)
-538(4)
-796(5)
-541(5)
-797(9)
-1299(9)
-1568(8)
-1321(7)
281(4)
405(2)
925(4)
C(9)
1296(2)
1824(2)
204(2)
-264(2)
1290(1)
1861(1)
2064(2)
1749(2)
1185(2)
978(2)
9072(4)
8766(5)
9948(4)
2600(5)
2002(6)
2222(4)
1289(5)
3061(4)
3166(4)
4619(4)
5700(4)
5593(5)
4141(4)
1377(4)
-36(6)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
C(30)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
C(37)
C(38)
C(39)
C(40)
C(41)
C(42)
C(43)
C(44)
C(45)
C(46)
C(47)
C1(1)
C(80)
Cl(2)
Cl(3)
C(81)
Cl(4A)b
Cl(4B)b
Cl(5A)b
C(82A)b
Cl(6A)b
Cl(5B)b
C(82B)b
Cl(6B)b
10149(4)
12654(3)
12317(3)
12533(3)
11908(4)
12241(4)
12014(3)
12965(3)
13165(3)
13345(3)
14296(4)
14099(4)
13951(3)
13648(3)
13591(4)
14323(4)
15518(4)
15580(4)
14844(3)
4048(9)
4766(11)
5579(10)
6550(13)
7379(14)
7223(21)
6245(21)
5409(17)
2175(9)
2637(10)
943(10)
204(9)
-917(12)
-1294(14)
-549(14)
597(12)
366(1)
126(1)
-458(1)
-588(2)
-350(2)
235(2)
1425(2)
1390(2)
1803(2)
1777(2)
1790(2)
1378(2)
51(7)
1004(4)
2422(5)
2313(4)
390(4)
-1174(4)
-1828(4)
-1340(4)
250(5)
373(4)
419(5)
-5(11)
135(9)
659(10)
1066(8)
926(6)
5165(9)
5854(9)
6630(11)
7339(10)
6662(10)
5910(9)
692(4)
899(4)
1177(4)
1028(5)
527(5)
56(7)
218(4)
1233(4)
1838(4)
2115(4)
1825(5)
1210(7)
947(4)
1370(4)
1536(4)
2000(5)
1829(5)
1653(5)
1203(4)
-2420(2)
-1782(6)
-1727(3)
-2180(2)
-2549(6)
-3043(5)
-3114(5)
-1731(5)
-1478(13)
-1497(7)
-1813(5)
-1251(9)
-1456(15)
a
Equivalent isotropic U defined as one-third of the trace of the
orthogonalized Uij tensor.
CtCSiMe3); 127.08 (s, CtCSiMe3); 99.95 (s, CH of acac); 29.95
(d, J P-C ) 28 Hz, PCHCH2); 29.15 and 28.96 (both s, CH2);
26.56 (d, J P-C ) 10 Hz, PCHCH2); 25.9 (s, CH3 of acac); 24.99
(s, CH2); 0.53 (s, SiCH3). 31P{1H} NMR (121.45 MHz, CDCl3):
δ 14.9 (s).
P r ep a r a tion of Ir (a ca c)H(SiEt3)(P Cy3) (8). HSiEt3 (24
µL, 0.15 mmol) was added to a solution of 1 (102 mg, 0.15
mmol) in toluene (15 mL). The resulting light yellow solution
was stirred for 30 min at room temperature and filtered
through Kieselguhr. The filtrate was concentrated to ca. 0.1
mL and the oily residue which formed dissolved in 5 mL of
acetone and cooled at -20 °C for 12 h. Complex 8 was isolated
as a yellow microcristalline solid, yield 96 mg (93%). Anal.
Calcd for C29H56IrO2PSi: C, 50.63; H, 8.20. Found: C, 50.61;
H, 8.34. IR (Nujol, cm-1): ν(Ir-H) 2210; ν(acac) 1575, 1520.
31P{1H} NMR (121.45 MHz, C6D6): δ 9.2 (s).
P r ep a r a tion of Ir (a ca c)H(SiP h 3)(P Cy3) (9). The com-
plex was prepared using the procedure described for 8, starting
from 1 (100 mg, 0.15 mmol) and HSiPh3 (39 mg, 0.15 mmol).
Complex 9 was isolated as a light yellow solid, yield 68 mg
(55%). Anal. Calcd for C41H56IrO2P2Si: C, 59.17; H, 6.78.
Found: C, 58.96; H, 6.85. IR (Nujol, cm-1): ν(Ir-H) 2202;
ν(acac) 1565, 1523. 1H NMR (300 MHz, C6D6, 295 K) (δ):
8.06-7.16 (m, 15 H, Ph); 5.21 (s, 1 H, CH of acac); 2.20-0.95
(m, 33 H, Cy); 1.78 (s, 6 H, CH3 of acac); -22.81 (d, 1 H, J P-H
) 17 Hz, Ir-H). 31P{1H} NMR (121.45 MHz, C6D6): δ 6.0 (s).
P r ep a r a tion of Ir (a ca c)H(SiHP h 2)(P Cy3) (10). A solu-
tion of 1 (20 mg, 0.03 mmol) in benzene-d6 (0.6 mL) contained
in a 5-mm NMR tube was treated with H2SiPh2 (6 µL, 0.03
mmol). After 5 min the 1H and 31P{1H} NMR show signals
corresponding to 10 and free cyclooctene. 31P{1H} NMR
(121.45 MHz, C6D6): δ 11.9 (s).
4420(8)
4681(10)
4947(10)
5879(11)
5626(15)
5398(9)
3218(8)
2167(10)
1562(11)
1292(12)
2326(10)
2950(10)
8229(5)
8917(16)
9888(5)
2144(5)
2578(15)
3512(10)
3372(11)
4887(11)
5570(14)
6983(12)
4553(11)
5433(24)
6701(19)
a
Equivalent isotropic U defined as one-third of the trace of the
b
orthogonalized Uij tensor. Atoms involved in solvent disorder.
as
a white solid, yield 69 mg (48%). Anal. Calcd for
C
46H83IrO2P2Si: C, 58.11; H, 8.84. Found: C, 58.90: H; 9.20.
IR (Nujol cm-1): ν(Ir-H) 2275; ν(CtC) 2040; ν(acac) 1595,
1513. 13C{1H} NMR (75.45 MHz, CDCl3, 295 K) (δ): 184.25
and 181.92 (both s, CO of acac); 129.81 (t, J P-C ) 8 Hz,

Reactions of Ir(acac)(cyclooctene)(PCy3)
Organometallics, Vol. 15, No. 2, 1996 833
Ta ble 7. Cr ysta l Da ta a n d Da ta Collection a n d Refin em en t for
Ir {K3-CHdC(P h )CH[C(O)CH3]2}(C2P h )(CP h dCH2)(P Cy3) (4) a n d Ir (a ca c)H(SiEt3)(P Cy3) (8).
4
8
Crystal Data
C47H58IrO2P‚3CH2Cl2
1132.97
formula
mol wt
C29H56IrO2PSi
688.04
color and habit
cryst size, mm
cryst syst
space group
a, Å
orange, prismatic bloc
0.28 × 0.38 × 0.64
orthorhombic
Pna21 (No. 33)
17.260(2)
yellow, prismatic bloc
0.36 × 0.36 × 0.38
orthorhombic
Pna21 (No. 33)
25.909(5)
b, Å
12.207(2)
11.984(2)
c, Å
24.376(2)
9.721(2)
Z
4
4
D(calcd), g cm-1
1.465
1.514
Data Collection and Refinement
four-circle Siemens-P4
diffractometer
λ(Mo KR), Å; technique
monochromator
µ, mm-1
four-circle Siemens-STOE AED-2
0.710 73; bisecting geometry
graphite oriented
2.97
ω
2 e 2θ e 50
173
4.52
ω/2θ
3 e 2θ e 50
120
scan type
2θ range, deg
temp, K
no. of data collcd
no. of unique data
no. of params refined
11 192
9025 (Rint ) 0.0580)
542
0.0453
0.1148
1.450
9424
5333 (Rint ) 0.0267)
312
0.0198
0.050
0.995
R1 [F2 > 2σ(F2)]
a
wR2b [all data]
Sc
Flack param
-0.03(1)
-0.028(6)
a
b
2
2
R1(F) ) ∑||Fo| - |Fc||/∑|Fo|. wR2(F2) ) [∑[w(Fo - Fc2)2]/∑[w(Fo2)2]]1/2
.
c Goof ) S ) [∑[w((Fo - Fc2)2]/(n - p)]1/2
.
P r ep a r a tion of Ir (a ca c)H(SiEt3)(P Cy3)2 (11). The com-
plex was prepared using the procedure described for 5, starting
from 1 (102 mg, 0.15 mmol), PCy3 (47 mg, 0.17 mmol), and
HSiEt3 (27 µL, 0.17 mmol). Complex 11 was isolated as a
white solid, yield 96 mg (66%). Anal. Calcd for C47H89IrO2P2-
Si: C, 58.29; H, 9.26. Found: C, 58.05; H, 9.21. IR (Nujol,
cm-1): ν(Ir-H) 2228; ν(acac) 1590, 1510. 31P{1H} NMR
(121.45 MHz, C6D6): δ 13.9 (s).
mmol) in benzene-d6 (0.6 mL) contained in a 5-mm NMR tube.
After 15 min the 1H and 31P{1H} NMR show signals corre-
sponding to 16. 1H NMR (300 MHz, C6D6, 295 K) (δ): 5.21 (s,
1 H, CH of acac); 2.22-1.11 (m, 48 H, Cy and CH2CH3); 1.89
(s, 6 H, CH3 of acac); -24.00 (br, 3 H, Ir-H). 1H NMR (300
MHz, C6D6, 230 K): AM2 part of an AM2X spin system δA
-3.64 and δM 23.26 (J A-M ) 0, J A-X ) 119.0, J M-X ) 19.9).
31P{1H} NMR (121.45 MHz, C6D6): δ 21.80 (s).
P r ep a r a tion of Ir (a ca c)H(SiHP h 2)(P Cy3)2 (12). The
complex was prepared using the procedure described for 5,
starting from 1 (100 mg, 0.15 mmol), PCy3 (42 mg, 0.15 mmol),
and H2SiPh2 (27 µL, 0.15 mmol). Complex 12 was isolated as
a white solid, yield 86 mg (55%). Anal. Calcd for C53H85IrO2P2-
Si: C, 61.42; H, 8.26. Found: C, 61.28; H, 8.34. IR (Nujol,
cm-1): ν(Ir-H) 2210; ν(Si-H) 2065; ν(acac) 1587, 1512. 31P-
{1H} NMR (121.45 MHz, C6D6): δ 9.4 (s).
P r ep a r a tion of Ir (a ca c)(SiH2P h )H(P Cy3)2 (13). The
complex was prepared using the procedure described for 5,
starting from 1 (105 mg, 0.15 mmol), PCy3 (43 mg, 0.15 mmol),
and H3SiPh (18 µL, 0.15 mmol). Complex 13 was isolated as
a white solid, yield 60 mg (39%). Anal. Calcd for C47H81IrO2P2-
Si: C, 58.79; H, 8.49. Found: C, 58.44; H, 7.95. IR (Nujol,
cm-1): ν(Ir-H) 2240; ν(Si-H) 2048, 2090; ν(acac) 1593, 1514.
31P{1H} NMR (121.45 MHz, C6D6): δ 15.9 (s).
P r ep a r a tion of Ir (a ca c)H(Sn P h 3)(P Cy3) (14). A solution
of 1 (20 mg, 0.03 mmol) in benzene-d6 (0.6 mL) contained in a
5-mm NMR tube was treated with HSnPh3 (11 mg, 0.03 mmol).
After 5 min the 1H and 31P{1H} NMR show signals corre-
sponding to 14 and free cyclooctene. 31P{1H} NMR (121.45
MHz, C6D6): δ 7.58 (s, with tin satellites J Sn-P ) 44 Hz)
P r ep a r a tion of Ir (a ca c)H(Sn P h 3)(P Cy3)2 (15). The com-
plex was prepared using the procedure described for 5, starting
from 1 (100 mg, 0.15 mmol), PCy3 (41 mg, 0.15 mmol), and
HSnPh3 (51.4 mg, 0.15 mmol). Complex 15 was isolated as a
pale yellow solid, yield 110 mg (61%). Anal. Calcd for
Ca ta lytic Stu d ies. The hydrosilylation reactions were
performed under argon at 60 or 20 °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
Suba seal to allow samples to be removed by syringe without
opening the system. In a typical procedure, the complex Ir-
(acac)H(SiEt3)(PCy3)2 were dissolved in a 1,2-dicloroethane
solution (4.8 × 10-3 M) containing HSiEt3, PhCtCH, and
C6H12. The flask was then immersed in a bath at 60 °C, and
the reaction mixture was magnetically stirred. The reactions
were followed by measuring the silane consumption as a
function of time using C6H12 as the internal standard with a
15% â,â′-oxobis(propionitrile) on Chromosorb W-HP 80/10-
mesh column at 40 °C on a Perkin-Elmer 8500 gas chromato-
graph with a flame ionization detector. Silicon-containing
products were analyzed using a FFAP on Chromosorb GHP
80/10-mesh column a 175 °C. Silicon-containig products were
isolated by column chromatography (silica gel 70-230 mesh;
1
hexane) and characterized by H NMR spectroscopy.42
X-r a y Str u ctu r e An a lysis of Com p lexes Ir {K3-CHdC-
(P h )CH[C(O)CH3]2} (C2P h )(CP h dCH2)(P Cy3) (4) a n d Ir -
(a ca c)H(SiEt3)(P Cy3) (8). A summary of crystal data and
refinement parameters is reported in Table 7. Atomic coor-
dinates are listed in Tables 5 and 6. Data were collected on
Siemens P4 (4) or Siemens-Stoe AED-2 (8) diffractometers,
with graphite-monochromated Mo KR radiation (λ ) 0.710 73
Å) by the ω (4) or ω/2θ (8) scan methods. Three standard
reflections were monitored at periodic intervals throughout
data collection; no significant variations were observed. All
data were corrected for absorption using an semiempirical43
C
59H89IrO2P2Sn: C, 58.92; H, 7.45. Found: C, 58.81; H, 7.34.
IR (Nujol, cm-1): ν(Ir-H) 2225; ν(acac) 1590, 1515. 31P{1H}
NMR (121.45 MHz, C6D6): δ 7.62 (s, with tin satellites J 117
Sn-P
) 113 Hz and J 119
) 142 Hz).
Sn-P
P r ep a r a tion of Ir (a ca c)H3(SiEt3)(P Cy3) (16). A slow
stream of H2 was passed through a solution of 11 (20 mg, 0.03
(43) North, A. C. T.; Phillips, D. C.; Matthews, S. F. Acta Crystal-
logr., Sect. A 1968, 24, 351.

834 Organometallics, Vol. 15, No. 2, 1996
Esteruelas et al.
(4) or empirical44 (8) method. All structures were solved by
Patterson (iridium atoms) and conventional Fourier techniques
and refined by full-matrix least-squares on F2 (SHELX-93).45
Da ta for 8. Crystals suitable for the X-ray diffraction study
were obtained from a toluene-acetone solution. A prismatic
block of approximate dimensions 0.36 × 0.36 × 0.38 mm was
indexed to orthorhombic symmetry. A group of 56 reflections
in the range 20 e 2θ e 30° were carefully centered and used
to obtain by least-squares methods the unit cell dimensions.
The hydrogen atoms were localized in a difference map or
calculated (C-H ) 0.96 Å) and refined riding on carbon atoms
with a common isotropic thermal parameter. The hydride
atom were refined free from its observed position. The
refinement converged to R1 ) 0.0198 [F2 > 2σ(F2)] and wR2 )
0.050 (all data), with weighting parameters x ) 0.03 and y )
2.0. The flack parameter refined to -0.028(6).
2
The function minimized was ∑[w(Fo - Fc2)2] with the weight
2
defined as w-1 ) [σ2(Fo2) + (xP)2 + yP] (P ) (Fo + 2Fo2)/3).
For 4 an empirical extinction correction was applied. Atomic
scattering factors, corrected for anomalous dispersion, were
used as implemented in the refinement program.
Da ta for 4. Crystals suitable for the X-ray diffraction study
were obtained from slow diffusion of hexane into a saturated
CH2Cl2 solution of the compound. An orange prismatic bloc
of approximate dimensions 0.28 × 0.38 × 0.64 mm was indexed
to orthorhombic symmetry. A group of 54 reflections in the
range 10 e 2θ e 30° were carefully centered and used to obtain
by least-squares methods the unit cell dimensions. The
hydrogen atoms were calculated (C-H ) 0.96 Å) and refined
riding on carbon atoms with a common isotropic thermal
parameter. Solvent molecules of dichoromethane were ob-
served severely disordered. This molecules exhibit static
disorder in three different spatial regions: Cl(1), C(81), and
Cl(2); Cl(3), C(82), and Cl(4) (two sites for Cl(4)); Cl(5a)‚‚Cl-
(6b), with two sites for all atoms. The refinement converged
to R1 ) 0.0453 [F2 > 2σ(F2)] and wR2 ) 0.1148 (all data), with
weighting parameters x ) 0.070400 and y ) 0 and with an
extinction coefficient of 0.000 073. The flack parameter refined
to -0.03(1) as an indication of a correct determination of the
absolute structure.
Ack n ow led gm en t. We thank the DGICYT (Projet
PB 92-0092, Programa de Promocio´n General del Cono-
cimiento, and EU Projet Selective Processes and Cataly-
sis Involving Small Molecules) for financial suport. E.O.
thanks the DGA (Diputacio´n General de Arago´n) for a
grant. L.R. thanks the Spanish Government for a grant
(Programa de Formacio´n Cient´ıfica para Iberoame´rica).
Su p p or tin g In for m a tion Ava ila ble: Tables of anisotro-
pic thermal parameters, atomic coordinates and thermal
parameters for hydrogen atoms, experimental details of the
X-ray study, bond distances and angles, and selected least-
squares planes and interatomic distances (22 pages). Ordering
information is given on any current masthead page.
(44) Walker, N.; Stuart, D. Acta Crystallogr., Sect. A 1983, 39, 158.
(45) Sheldrick, G. M. J . Appl. Crystallogr., manuscript in prepara-
tion.
OM950628W