Comparative reactivity of triorganosilanes, HSi(OEt)3 and HSiEt3, with IrCl(CO)(PPh3)2. Formation of IrCl(H)2(CO)(PPh3)2 or Ir(H)2(SiEt3)(CO)(PPh3</sub

Article abstract of DOI:10.1016/j.ica.2008.12.033

Reaction of HSi(OEt)₃ with IrCl(CO)(PPh₃)₂ (5:1 molar ratio) at room temperature for 1 h gives IrCl(H){Si(OEt)₃}(CO)(PPh₃)₂ (1), which is observed by the ¹H and ³¹P{

Full text of DOI:10.1016/j.ica.2008.12.033

Inorganica Chimica Acta 362 (2009) 2951–2956
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Note
Comparative reactivity of triorganosilanes, HSi(OEt)3 and HSiEt3, with
IrCl(CO)(PPh3)2. Formation of IrCl(H)2(CO)(PPh3)2 or Ir(H)2(SiEt3)(CO)(PPh3)2
depending on the substituents at Si
b
b
Yasushi Nishihara a, , Miwa Takemura , Kohtaro Osakada
*
a Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka, Okayama 700-8530, Japan
b Chemical Resources Laboratory, Tokyo Institute of Technology, R1-03, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Reaction of HSi(OEt)3 with IrCl(CO)(PPh3)2 (5:1 molar ratio) at room temperature for 1 h gives
IrCl(H){Si(OEt)3}(CO)(PPh3)2 (1), which is observed by the 1H and 31P{1H} NMR spectra of the reaction
mixture. The same reaction, but in 20:1 molar ratio at 50 °C for 24 h produces IrCl(H)2(CO)(PPh3)2 (2)
rather than the expected product Ir(H)2{Si(OEt)3}(CO)(PPh3)2 (3) that was previously reported to be
formed by this reaction. Accompanying formation of Si(OEt)4, (EtO)3SiOSi(OEt)3, and (EtO)2HSiOSi(OEt)3
is observed. On the other hand, trialkylhydrosilane HSiEt3 reacts with IrCl(CO)(PPh3)2 (10:1 molar ratio)
at 80 °C for 84 h to give Ir(H)2(SiEt3)(CO)(PPh3)2 (4) in a high yield, accompanying with a release of
ClSiEt3.
Received 9 September 2008
Accepted 27 December 2008
Available online 14 January 2009
Keywords:
Iridium
Hydrosilanes
Oxidative addition
Hydrido complex
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
concerted reductive elimination of chlorosilanes [14]. In addition,
a kinetic study on the thermal reaction of RhCl(H){Si(OEt)n-
Syntheses of the silyliridium complexes having a thermo-
dynamically stable Ir–Si bond are reported and they are known
to show high reactivities under some conditions [1–7]. Typical
synthetic methods for the silyliridium complexes are the reactions
of hydrosilanes with low-valent iridium complexes, which causes
cleavage of H–Si bond by oxidative addition to form the Ir–Si
bond. For instance, the reaction of HSiR3 with Vaska’s complex
IrCl(CO)(PPh3)2 was reported to produce Ir(H)2(SiR3)(CO)(PPh3)2
via the proposed pathway shown in Scheme 1 [8]. This transforma-
tion involves three steps: the reversible oxidative addition of HSiR3
to the starting Ir(I) complex affording the octahedral silyliridi-
um(III) complex, the irreversible reductive elimination of Cl–SiR3
[9] from the formed Ir(III) intermediate through trans-cis isomeri-
zation [10], and oxidative addition of the second HSiR3 to the in situ
formed IrH(CO)(PPh3)2.
Me3ꢀn}(PPh3)2 (n = 1–3) with a pentacoordinated structure re-
vealed different rates of reductive elimination of chlorosilanes,
depending on the substituents at Si; RhCl(H){Si(OEt)3}(PPh3)2 lib-
erates ClSi(OEt)3 (k = 2.01 ꢁ 10ꢀ5 sꢀ1) at 60 °C much more slowly
than RhCl(H){SiMe2(OEt)}(PPh3)2 (k = 3.7 ꢁ 10ꢀ3 sꢀ1
) [15]. This
slow reductive elimination of ClSi(OEt)3 from the Rh(III) complex
is a sharp contrast with the above reaction in Scheme 1, in which
the apparent double oxidative addition of HSi(OEt)3 to IrCl(CO)-
(PPh3)2 gave rise to the formation of Ir(H)2{Si(OEt)3}(CO)(PPh3)2
via a facile release of ClSi(OEt)3 from the analogous Ir(III) complex
[8b]. The different reactivities between Rh and Ir complexes
bearing the Si(OEt)3 ligand prompted us to investigate the reac-
tions of two different hydrosilanes, HSi(OEt)3 and HSiEt3, with
IrCl(CO)(PPh3)2.
The above reaction has been known to be applicable to prepara-
tion of the analogous Ir(H)2(MR3)(CO)(PPh3)2 (M = Ge and Sn) by
the reactions of triorganogermanes [2,11] and triorganostannanes
[12,13] with IrCl(CO)(PPh3)2.
From a viewpoint of the irreversible reductive elimination of
chlorosilanes Cl–SiR3 in Group 9 transition metals, we have already
reported that a hexacoordinated RhCl(H){Si(C6H5CF3)3}(PMe3)3
with the chloro and silyl ligands at cis position underwent the
2. Results and discussion
An NMR tube experiment of HSi(OEt)3 with IrCl(CO)(PPh3)2 in
5:1 molar ratio at room temperature resulted in the formation of
IrCl(H){Si(OEt)3}(CO)(PPh3)2 (1) in 41% NMR yield (see, Eq. (1)).
The 1H NMR spectrum of the reaction mixture showed a triplet as-
signed to the hydrido ligand of 1 at d ꢀ5.93 (JPH = 15 Hz), indicating
that two equivalent phosphorus atoms are located at cis positions
of the hydrido ligand. The earlier studies by Chalk in 1969 on the
same reaction was reported to give the complex that showed the
* Corresponding author. Tel./fax: +81 86 251 7855.
E-mail address: ynishiha@cc.okayama-u.ac.jp (Y. Nishihara).
1H NMR signal of the hydrido ligand at
a similar position
0020-1693/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2008.12.033

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Y. Nishihara et al. / Inorganica Chimica Acta 362 (2009) 2951–2956
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
Scheme 1.
(d = ꢀ6.1 (JPH = 14 Hz) in benzene) [8b]. Our several attempts to
isolate 1 from the reaction mixture failed due to the reversible
reductive elimination of HSi(OEt)3 from 1 to regenerate the start-
ing IrCl(CO)(PPh3)2 during evaporation under reduced pressure.
This observation is compatible to the reported results; the
HSi(OEt)3 adduct thermally decomposes in vacuo to yield the origi-
nal IrCl(CO)(PPh3)2. Bennett also reported that CO reacted with a
pentacoordinated IrCl(H){Si(OEt)3}(PPh3)2 to generate not 1, but
IrCl(CO)(PPh3)2 and HSi(OEt)3 [16]. This result suggests the tenta-
tive formation of 1, but the spontaneous reductive elimination of
HSi(OEt)3 from the unstable 1 occurs to recover IrCl(CO)(PPh3)2
and HSi(OEt)3.
Fig. 1. ORTEP drawing of IrCl(H)2(CO)(PPh3)2 (2) at the 30% ellipsoid level.
Hydrogen atoms except for the Ir–H hydrogen are omitted for simplicity. Selected
bond distances (Å) and angles (deg): Ir1–Cl1 2.4602(17), Ir1–P1 2.3269(15), Ir1–P2
2.3215(13), Ir1–C1 1.904(7), Ir1–H1 1.536, and Ir1–H2 1.520; Cl1–Ir1-P1 91.84(5),
Cl1–Ir1–P2 87.13(5), Cl1–Ir1–C1 103.4(2), P1–Ir1–P2 168.34(5), P1–Ir1–C1 94.5(2),
P2–Ir1–C1 97.0(2), Cl1–Ir1–H1 176.5, Cl1–Ir1–H2 98.3, P1–Ir1–H1 89.3, P1–Ir1–H2
85.3, P2–Ir1–H1 92.4, P2–Ir1–H2 83.4, C1–Ir1–H1 73.2, C1–Ir1–H2 158.3, and H1–
Ir1–H2 85.1.
method in the literature [20] in order to determine its structure
unequivocally and to compare its detailed NMR data with those of
the complex from the reaction in Eq. (2). Reaction of HSi(OEt)3 (2
equivalents) with IrCl(CO)(PPh3)2 in toluene at 50 °C for 1 h cleanly
formed Ir(H)2{Si(OEt)3}(CO)(PPh3)2 (3) in 72% yield (see, Eq. (3)).
The 1H NMR spectrum of 3 exhibits two Ir–H signals at d ꢀ10.70
(ddd, JPH = 110 Hz, JPH = 19 Hz, and JHH = 5 Hz) and d ꢀ9.55 (ddd,
JPH = 22 Hz, JPH = 15 Hz, and JHH = 5 Hz). A large coupling constant
of the former signal indicates that this hydrogen atom is located
trans to one of the phosphorus atoms. The 31P{1H} NMR spectrum
of 3 shows two doublets at d 3.51 and 7.25, which are assigned to
the two inequivalent PPh3 ligands. The stereochemistry of 3 with
two bulky PPh3 ligands at mutually cis positions is attributed to
the large trans influence of the hydrido and silyl ligands.
ð1Þ
On the contrary, the reaction of a large excess amounts (20 molar
equivalents) of HSi(OEt)3 with IrCl(CO)(PPh3)2 at 50 °C gave the iso-
lable IrCl(H)2(CO)(PPh3)2 (2) in 82% yield (see, Eq. (2)). Complex 2
was identified by comparison of the IR and NMR (1H and 31P{1H})
data with those reported in the literature [17]. GC–MS and
29Si{1H} NMR analyses of the reaction mixture revealed the forma-
tion of Si(OEt)4, (EtO)3SiOSi(OEt)3, and (EtO)2HSiOSi(OEt)3 as organ-
ic by-products. The formation of 2 was also evidenced by the
molecular structure determination by X-ray diffraction. An ORTEP
drawing of 2 is depicted in Fig. 1. Complex 2 has a slightly distorted
octahedral coordination around the Ir center with two trans PPh3 li-
gands and with the chloro and carbonyl ligands at mutually cis
positions. The Ir–Cl bond distance (2.460(2) Å) is within the range
of the bonds reported in hexacoordinate Ir(III)–Cl complexes
(2.367(9)–2.518(1) Å) [18,19].
ð3Þ
In order to compare the reactivity of hydrosilanes bearing different
substituents, reaction of HSiEt3 with IrCl(CO)(PPh3)2 in a 10:1 molar
ratio at 80 °C in toluene yielded Ir(H)2(SiEt3)(CO)(PPh3)2 (4) in 75%
isolated yield and ClSiEt3 in 96% yield, based on Cl, respectively
(see, Eq. (4)). The obtained results are consistent with the reactions
of HSiMe3 and HSiCl3 with IrCl(CO)(PPh3)2 [11c], giving the corre-
sponding complexes Ir(H)2(SiR3)(CO)(PPh3)2 (R = Me and Cl) whose
structures are similar to 4. The structure of 4 was determined unam-
biguously by IR and NMR (1H, 31P{1H}, and 13C{1H}) spectroscopy as
well as elemental analysis. The 1H NMR spectrum of 4 exhibited two
Ir–H signals at d ꢀ10.57 (ddd, JPH = 113 Hz, JPH = 19 Hz, JHH = 5 Hz)
and at d ꢀ9.51 (ddd, JPH = 23 Hz, JPH = 15 Hz, JHH = 5 Hz). These peak
positions and coupling constants are similar to those of 3. Complex 4
showed a characteristic signal of the carbony carbon at d 183.51 in
ð2Þ
Although the reaction of HSi(OEt)3 with IrCl(CO)(PPh3)2 has been
reported to afford Ir(H)2{Si(OEt)3}(CO)(PPh3)2 (3), according to the
reported literature [8b], reaction depicted in Eq. (2) did not form
3 at all. We thus prepared complex 3 according to another synthetic
the 13C{1H} NMR spectrum and IR band at 1956 cmꢀ1
.

Y. Nishihara et al. / Inorganica Chimica Acta 362 (2009) 2951–2956
2953
HSi(OEt)3
or
H2Si(OEt)2
Si(OEt)3
Si(OEt)3
PPh3
O
PPh3
O2
(i)
2
+
(EtO)3SiOSi(OEt)3
or
H
Ir CO
H
Ir CO
Ph3P
Ph3P
Cl
Cl
(EtO)2HSiOSi(OEt)3
1
H2O
+
IrCl(CO)(PPh3)2
2
+
HOSi(OEt)3
(ii)
(EtO)3SiOSi(OEt)3
2 HOSi(OEt)3
+
H2O
Ir cat
+
Si(OEt)4
(iii)
2 HSi(OEt)3
H2Si(OEt)2
Scheme 2. A plausible sequence for the formation of 2, Si(OEt)4, and the disiloxanes.
tion mixture can accelerate the reaction toward the formation of 2,
although no example of reactivities of silyliridium complexes to-
ward water or oxygen has been reported to date.
Another possible reaction pathway for the formation of 2 is a di-
rect hydrogenation of 1. Parish et al. reported that in the Ir-cata-
lyzed condensation of HSi(OEt)3 with R1OH (R1 = Me and Et),
giving (R1O)Si(OEt)3 with a release of H2, the starting IrCl-
(CO)(PPh3)2 converts into a mixture of IrCl(H)2(CO)(PPh3)2 (2),
IrCl2(H)(CO)(PPh3)2, and IrH3(CO)(PPh3)2 [25]. Since neither
IrCl2(H)(CO)(PPh3)2 nor IrH3(CO)(PPh3)2 were contaminated in
the present reaction mixture, the hydrogenation pathway can be
ruled out. Although they also postulated formation of IrH-
(CO)(PPh3)2 and ClSi(OEt)3 during the reaction, their formation
might be attributed to reduction of IrCl(CO)(PPh3)2 by alcohol
and the intermolecular transfer of the Cl ligand, respectively, rather
than the formation of IrH(CO)(PPh3)2 from 1 via elimination of
ClSi(OEt)3. In a sharp contrast, the reaction of HSiEt3 with IrCl-
(CO)(PPh3)2, forming complex 4 and ClSiEt3, follow the reaction
pathway depicted in Scheme 1.
ð4Þ
As described above, both HSi(OEt)3 and HSiEt3 react with IrCl-
(CO)(PPh3)2 to give the Ir(III) intermediates through the initial oxi-
dative addition. The final products of the reactions, however, were
different from each other; complexes IrCl(H)2(CO)(PPh3)2 (2) and
Ir(H)2(SiEt3)(CO)(PPh3)2 (4), respectively. The former reaction did
not involve reductive elimination of ClSi(OEt)3 from 1, which is con-
sistent with the high stability of the Rh [15] and Ir [21] complexes
with the Cl and Si(OEt)3 ligands.
Scheme 2i depicts a plausible reaction pathway for the forma-
tion of 2, Si(OEt)4, and the other ethoxysiloxanes. Conversion of
the Ir–Si(OEt)3 bond in the formed complex 1 into the Ir–O–
Si(OEt)3 bond would be accelerated by the contaminating O2
[22,23], which smoothly reacts with HSi(OEt)3 (or H2Si(OEt)2) to
form ethoxysiloxanes [22] those are detected by the 29Si{1H}
NMR spectrum and GC–MS [24] (see Section 4). On the other hand,
complex 1 might decompose by hydrolysis with the contaminating
water to form 2 and triethoxysilanol, which easily converts into
ethoxysiloxanes via the known condensation, as shown in Scheme
2ii. Accompanying generation of H2Si(OEt)2 and Si(OEt)4 is attrib-
uted to the Ir-catalyzed disproportionation of HSi(OEt)3 (Scheme
2iii) [24].
In order to elucidate a role of O2 or H2O, we carried out several
reactions of HSi(OEt)3 with IrCl(CO)(PPh3)2 in toluene under differ-
ent conditions. In a flame-sealed NMR tube containing carefully
evacuated benzene-d6, the reaction at 50 °C proceeded much more
slowly than that in a standard NMR tube experiment and resulted
in a lower yield of 2 (28%), accompanied with the unreacted 1
(64%) even after 144 h. This results support that complex 1 it self
is rather stable under an Ar atmosphere, but it would suffer from
the contaminating O2 in the reaction mixture to convert into the
postulated silyloxoiridium complex. In addition, the reaction of
HSi(OEt)3 with IrCl(CO)(PPh3)3 in the presence of 20 molar equiv-
alents of water under Ar smoothly generated 2 in 80% yield. In
addition, when 20 molar equivalents of D2O was added to the reac-
tion mixture, again complex 2 was formed in 98% yield with D
incorporation (22% at d ꢀ17.58 and 27% at d ꢀ6.66). On the other
hand, the reaction under an O2 atmosphere without water gave
only 17% of 2 along with some unidentified products. These results
suggest that incorporation of H2O and/or O2 contained in the reac-
3. Summary
This study showed that HSiEt3 reacts with IrH(CO)(PPh3)2 to
give Ir(H)2(SiEt3)(CO)(PPh3)2 (4) and ClSiEt3, in agreement with re-
ports of Chalk et al. in 1969. The reaction of HSi(OEt)3, however,
does not produce an analogous complex Ir(H)2(SiR3)(CO)(PPh3)2
due to a slow reductive elimination of Cl–Si(OEt)3 from the Cl–
Ir–Si(OEt)3 species in complex 1 and causes the formation of 2
and disiloxanes by acceleration of the contaminating oxygen and
water at 50 °C.
4. Experimental
4.1. General
All the reactions were carried out under an Ar atmosphere using
standard Schlenk techniques. Glassware was dried in an oven
(130 °C) and heated under reduced pressure before use. Hexane
and toluene were distilled from sodium and benzophenone prior
to use or purchased from Kanto Chemicals Co. Ltd. Benzene-d6
was dried over MS-4A and deoxygenated by three freeze-thaw
cycles under reduced pressure. HSi(OEt)3 and HSiEt3 were was pur-
chased from Tokyo Chemical Industry Co., Ltd. and used without
further purification. IrCl(CO)(PPh3)2 was prepared according to
published procedure [26].

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Y. Nishihara et al. / Inorganica Chimica Acta 362 (2009) 2951–2956
NMR spectra (1H, 13C{1H}, 29Si{1H}, and 31P{1H}) were recorded
temperature. The reaction mixture was stirred at 50 °C for 1 h to
result in pale yellow suspension. The volatiles were removed and
the residue was washed with hexane (15 mL ꢁ 3 times), and dried
in vacuo to give Ir(H)2{Si(OEt)3}(CO)(PPh3)2 (3) as pale yellow pow-
der (395 mg, 0.55 mmol, 72%). 1H NMR (300 MHz, benzene-d6,
25 °C): d ꢀ10.70 (ddd, JPH = 110 Hz, JPH = 19 Hz, JHH = 5 Hz, 1H),
ꢀ9.55 (ddd, JPH = 22 Hz, J(PH) = 15 Hz, JHH = 5 Hz, 1H), 1.21 (t,
JHH = 7 Hz, 9H), 3.98 (dq, JHH = 7 Hz, JPH = 2 Hz, 6H), 6.82–7.01 (m,
18H, PPh3), 7.25–7.32 (m, 6H, PPh3), 7.59–7.66 (m, 6H, PPh3);
on JEOL EX-400 or Varian Mercury 300 spectrometers. The IR spec-
tra were recorded on a Shimadzu FTIR-8100A spectrometer in KBr.
GC–MS analyses were carried out on a Hitachi M-80 spectrometer
or a Shimadzu QP-5000 GC–MS system. Elemental analyses were
carried out with a Yanaco MT-5 CHN autocorder.
4.2. Synthesis and characterization
4.2.1. Reaction of HSi(OEt)3 with IrCl(CO)(PPh3)2 at room temperature
31P{1H} NMR (121.5 MHz, benzene-d6, 25 °C):
d
3.51 (d,
To a solution of IrCl(CO)(PPh3)2 (31 mg, 0.04 mmol) in 1.0 mL of
benzene-d6 was added HSi(OEt)3 (38 lL, 0.20 mmol) in an NMR
JPP = 16 Hz), 7.25 (d, JPP = 16 Hz); 13C{1H} NMR (100.5 MHz, dichlo-
romethane-d2, 25 °C): d 18.16 (CH3), 57.38 (CH2), 127.81 (d,
JCP = 11.0 Hz, PPh3-ortho), 128.11 (d, JCP = 9.2 Hz, PPh3-ortho),
129.60 (PPh3-para), 129.71 (PPh3-para), 133.95 (d, JCP = 11.0 Hz,
PPh3-meta), 135.30 (dd, JCP = 35.9, JCP = 2.5 Hz, PPh3-ipso), 135.32
(d, JCP = 11.0 Hz, PPh3-meta), 136.83 (dd, JCP = 36.5, JCP = 2.3 Hz,
PPh3-ipso), 185.77 (dd, JCP = 16.5, JCP = 7.1 Hz, CO); IR (KBr, cmꢀ1):
tube at room temperature. After 1 h, the solution became dark yel-
low. 1H and 31P{1H} NMR spectra showed the formation of 1 in 41%
NMR yield and the presence of unreacted IrCl(CO)(PPh3)2. 1: 1H
NMR (300 MHz, benzene-d6, 25 °C): d ꢀ5.93 (t, JPH = 15 Hz, 1H),
0.89 (t, JHH = 7 Hz, 9H), 3.30 (q, JHH = 7 Hz, 6H), 6.99–7.09 (m,
18H, PPh3), 8.05–8.07 (m, 12H, PPh3); 31P{1H} NMR (121.5 MHz,
benzene-d6, 25 °C): d 9.17. Attempts to isolate 1 were unsuccessful
due to its facile conversion into IrCl(CO)(PPh3)2 during evaporation
of volatiles.
1094 (mSi–O), 1968 (mCO), 2080 (mIr–H trans to CO).
4.2.4. Reaction of HSiEt3 with IrCl(CO)(PPh3)2
To a toluene (10 mL) dispersion of IrCl(CO)(PPh3)2 (512 mg,
0.65 mmol) was added HSiEt3 (1.07 mL, 6.7 mmol) at room tem-
perature. The reaction mixture was heated to 80 °C with stirring
for 84 h to result in a dark yellow homogeneous solution. The vol-
atiles were removed and the residue was washed with hexane
(5 mL ꢁ 3 times) and dried in vacuo to give Ir(H)2(SiEt3)-
(CO)(PPh3)2 (4) as pale yellow powder (517 mg, 75%). Data of 4:
1H NMR (300 MHz, benzene-d6, 25 °C): d ꢀ10.57 (ddd, JPH = 113 Hz,
JPH = 19 Hz, JHH = 5 Hz, 1H), ꢀ9.51 (ddd, JPH = 23 Hz, JPH = 15 Hz,
JHH = 5 Hz, 1H), 1.06 (dq, JHH = 7 Hz, JPH = 2 Hz, 6H), 1.25 (t,
JHH = 7 Hz, 9H), 6.86–6.92 (m, 18H, PPh3), 7.35–7.51 (m, 6H,
PPh3), 7.53–7.50 (m, 6H, PPh3); 31P{1H} NMR (121.5 MHz, ben-
4.2.2. Reaction of HSi(OEt)3 with IrCl(CO)(PPh3)2 at 50 °C: formation of
2
To a toluene (10 mL) dispersion of IrCl(CO)(PPh3)2 (500 mg,
0.65 mmol) was added HSi(OEt)3 (2.5 mL, 12.8 mmol) at room
temperature. The reaction mixture was heated to 50 °C with stir-
ring for 24 h to result in the deposition of a pale yellow solid.
The volatiles were removed and washed with hexane (5 mL ꢁ 3
times), and dried in vacuo to give IrCl(H)2(CO)(PPh3)2 (2) as pale
yellow powder (512 mg, 82%). Recrystallization from toluene/hex-
ane afforded dark yellow prisms suitable for X-ray crystallography.
2: 1H NMR (300 MHz, benzene-d6, 25 °C) [17e]: d ꢀ17.58 (dt,
JPH = 15 Hz, JHH = 5 Hz, 1H), ꢀ6.66 (dt, JPH = 18 Hz, JHH = 5 Hz, 1H),
6.92–7.05 (m, 18H, PPh3), 7.87–7.95 (m, 12H, PPh3); 31P{1H} NMR
(121.5 MHz, benzene-d6, 25 °C): d 9.81; 13C{1H} NMR (100.5 MHz,
dichloromethane-d2, 25 °C): d 128.56 (t, JCP = 5.5 Hz, PPh3-ortho),
130.90 (PPh3-para), 135.12 (t, JCP = 27.5 Hz, PPh3-ipso), 135.38 (t,
JCP = 5.5 Hz, PPh3-meta), 177.17 (t, JCP = 5.5 Hz, CO); IR (KBr,
zene-d6, 25 °C):
d 1.21 (d, JPP = 13 Hz), 9.90 (d, JPP = 13 Hz);
13C{1H} NMR (100.5 MHz, dichloromethane-d2, 25 °C): d 5.59
(CH3), 12.76 (dd, JCP = 5.5 Hz, JCP = 3.7 Hz, CH2), 128.01 (PPh3-ortho),
128.09 (PPh3-ortho), 129.55 (PPh3-para), 129.86 (PPh3-para),
133.96 (d, JCP = 10.9 Hz, PPh3-meta), 135.35 (d, JCP = 10.9 Hz, PPh3-
meta), 136.32 (d, JCP = 52.3 Hz, PPh3-ipso), 137.68 (d, JCP = 52.3 Hz,
PPh3-ipso), 183.51 (t, JCP = 3.6 Hz, CO); IR (KBr, cmꢀ1): 1956 (
mCO),
cmꢀ1): 1979 (
mCO), 2106 (mIr–H trans to CO), 2193 (mIr–H trans to
2080 (mIr–H trans to CO), 2126 (mIr–H trans to PPh3). Anal. Calc. for
C43H47OP2SiIr: C, 59.91; H, 5.50. Found: C, 60.08; H, 5.58%. An
NMR tube reaction of IrCl(CO)(PPh3)2 (31 mg, 0.04 mmol) and HSi-
Cl). Anal. Calc. for C37H32ClOPIr: C, 56.81; H, 4.21; Cl, 4.53. Found:
C, 56.99; H, 4.28; Cl, 4.81%.
The reaction of IrCl(CO)(PPh3)2 (3.91 g, 5.0 mmol) and HSi(OEt)3
(18.8 mL, 100 mmol) in toluene (55 mL) was carried out in order to
characterize various tetraethoxysilane and ethoxysiloxanes. GC–
MS of the reaction mixture indicated the presence of the silicon-
containing by-products whose major fragments [m/z (relative
intensity, ion)] are shown below. Si(OEt)4: [208(5, M+), 193(77),
179(34), 163(52, M+ ꢀ OEt), 149(100), 119(24), 79(80), 63(72)].
(EtO)2HSiOSi(OEt)3: [297 (4, M+ ꢀ H), 253 (100, M+ ꢀ OEt), 225
(17), 209 (13), 197 (13), 181 (15), 169 (18), 155 (15), 141 (50),
123 (14)]. (EtO)3SiOSi(OEt)3: [342 (2, M+), 297 (100, M+ ꢀ OEt),
269 (30), 253 (35), 241 (17), 225 (25), 197 (22), 185 (19), 169
(18), 157 (39), 141 (28), 123 (13)] [24].
Et3 (32 lL, 0.20 mmol) in benzene-d6 (0.7 mL) in an NMR tube at
Table 1
Crystal data and details of the structure refinement of 2.
Formula
C37H32ClOP2Ir
Molecular weight
782.28
Crystal system
Space group
a (Å)
orthorhombic
Pbca (No. 61)
21.936(3)
17.782(5)
16.696(3)
6512.4(23)
8
b (Å)
c (Å)
V (Å3)
The 29Si{1H} NMR spectrum of the products after removal of 2
showed the following signals (relative intensity); Si(OEt)4: d
ꢀ82.29 (100); (EtO)2HSiOSi(OEt)3: d ꢀ68.65 (3), ꢀ77.29 (5);
(EtO)3SiOSi(OEt)3: d –88.77 (10). The volatiles were removed and
washed with hexane (5 mL ꢁ 3 times), and distillation of hexane
washings (110 °C/155 Torr) gave Si(OEt)4 (961 mg, 4.62 mmol,
92% yield, based on IrCl(CO)(PPh3)2) as a colorless liquid.
Z
l
(mmꢀ1
)
4.320
F (000)
3088
1.596
0.45 ꢁ 0.25 ꢁ 0.20
5.0-55.0
7474
Dcalcd (g cmꢀ3
)
Crystal size (mm3)
2h range (°)
Number of unique reflections
Number of used reflections
Number of variables
4701
409
R1 (I > 3.00
R
GOF
r
(I))
0.032
0.044
1.002
4.2.3. Reaction of HSi(OEt)3 with IrH(CO)(PPh3)3: preparation of 3
Complex 3 was prepared as modified to the literature [20]. To a
yellow dispersion of IrH(CO)(PPh3)3 (600 mg, 0.60 mmol) in tolu-
ene (12 mL) was added HSi(OEt)3 (2.25 mL, 1.20 mmol) at room
w2a
a
Weighting scheme [r .
(Fo)2]ꢀ1

Y. Nishihara et al. / Inorganica Chimica Acta 362 (2009) 2951–2956
2955
80 °C showed the formation of 1H NMR signals of both 4 and ClSi-
Et3 (96%).
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Single crystals of 2 suitable for X-ray diffraction studies were
obtained by recrystallization from toluene/hexane. Crystallo-
graphic data and details of refinement were summarized in
Table 1. The crystals were sealed in glass capillary tubes and
mounted, and the X-ray data were collected with a Rigaku R-AXIS
RAPID II imaging plate area detector using graphite-monochromat-
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A full-matrix least-squares refinement was used for the non-
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Acknowledgment
(l) E. Gutiérrez-Puebla, A. Monge, M. Paneque, M.L. Poveda, S. Taboada, M.
Trujillo, E. Carmona, J. Am. Chem. Soc. 121 (1999) 346;
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(n) R.S. Simons, J.C. Gallucci, C.A. Tessier, W.J. Youngs, J. Organomet. Chem. 654
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This work was partially supported by a Grant-in-aid for Young
Scientists No. 13740412 from the Ministry of Education, Culture,
Sports, Science and Technology, Japan.
(o) L.D. Field, B.A. Messerle, M. Rehr, L.P. Soler, T.W. Hambley, Organometallics
22 (2003) 2387;
Appendix A. Supplementary material
(p) R.S. Simons, M.J. Panzner, C.A. Tessier, W.J. Youngs, J. Organomet. Chem.
681 (2003) 1;
(q) J.-D. Lee Lee, K.J. Kim, I.-H. Suh, M. Cheong, S.O. Kang, Organometallics 23
(2004) 135;
(r) I. Kownacki, B. Marciniec, K. Szubert, M. Kubicki, Organometallics 24 (2005)
6179;
CCDC 186010 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via http://www.ccdc.
cam.ac.uk/data_request/cif.
(s) T. Saiki, Y. Nishio, T. Ishiyama, N. Miyaura, Organometallics 25 (2006)
6068;
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.ica.2008.12.033.
(t) J. Yang, M. Brookhart, J. Am. Chem. Soc. 129 (2007) 12656.
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