Activations of silanes with [PhB(CH2PPh2)3]Ir(H)(η3-C8 H13). Formation of iridium silylene complexes via the extrusion of silylenes from secondary silanes R2SiH2

Article abstract of DOI:10.1021/om020389u

The abstraction of methide from (Me₃P)₃Ir(SiHMes₂)(Me)(H) (1) with B(C₆F₅)₃ gave the silylene complex [fac-(Me₃P)₃(H)₂Ir(SiMes₂)][MeB(C ₆

Full text of DOI:10.1021/om020389u

Organometallics 2002, 21, 4065-4075
4065
Activa tion s of Sila n es w ith
[P h B(CH2P P h 2)3]Ir (H)(η3-C8H13). F or m a tion of Ir id iu m
Silylen e Com p lexes via th e Extr u sion of Silylen es fr om
Secon d a r y Sila n es R2SiH2
J ay D. Feldman, J onas C. Peters,† and T. Don Tilley*
Department of Chemistry, University of California at Berkeley,
Berkeley, California 94720-1460
Received May 13, 2002
The abstraction of methide from (Me3P)3Ir(SiHMes2)(Me)(H) (1) with B(C6F5)3 gave the
silylene complex [fac-(Me3P)3(H)2Ir(SiMes2)][MeB(C6F5)3] (2) via 1,2-hydrogen migration.
Secondary silanes (H2SiR2) reacted with [PhBP3]Ir(H)(η3-C8H13) (3) (where [PhBP3] )
-
PhB(CH2PPh2)3 ) to give silylene complexes of the type [PhBP3](H)2IrdSiR2 (R ) 2,4,6-
trimethylphenyl (Mes), 4a ; R ) Ph, 4b; R ) Et, 4c; R ) Me, 4d ), with loss of cyclooctene.
Analogously, the germylene complex [PhBP3](H)2IrdGeMes2 was obtained via the reaction
of 3 with Mes2GeH2. Primary silanes (H3SiR) reacted with 3 to give [PhBP3](H)2IrdSi(R)-
(c-C8H15) (R ) Mes, 8a ; R ) 2,4,6-triisopropylphenyl (Trip), 8b) via an intermediate silylene
complex with an Si-H bond, [PhBP3](H)2IrdSi(R)(H). With tertiary silanes (R3SiH), silyl-
capped trihydride complexes of the type [PhBP3]IrH3(SiR3) (R ) Et, 7a ; R ) Me, 7b) and
1,3-cyclooctadiene were produced. The mechanisms of these processes are discussed.
In tr od u ction
sition metals (eq 2), and the induced migration of H from
Si to Pt upon abstraction of Me- from (dippe)Pt(Me)-
(SiHMes2) (eq 3; dippe ) Pr2PCH2CH2PiPr2, Mes )
Transition-metal silylene chemistry has evolved sig-
nificantly since the first silylene complexes were re-
ported in 1990.1 This class of compounds is important
to the development of organosilicon chemistry, as nu-
merous reactions of organosilanes are thought to occur
via intermediate silylene complexes.2-7 Furthermore,
since carbene complexes are useful in organic synthesis,
it is possible that analogous silylene complexes may be
valuable as catalysts and synthetic intermediates in
organosilicon chemistry.
i
2,4,6-trimethylphenyl).19 The last process, based on 1,2-
migration, is of interest because silylene-containing
intermediates produced in this way have often been
proposed to account for rearrangements in metal silyl
complexes.2-7,20-30 In addition, the participation of
silylene complexes in catalytic cycles would seem to
require a two-step activation of the silane substrate,
involving initial oxidative addition of the silane followed
by a 1,2-migration to produce the silylene ligand (eq 4).
Synthetic approaches to silylene complexes include
triflate1,8-11 or chloride12 abstraction from silicon to yield
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+
cationic complexes of the type LnMdSiR2 (eq 1), the
coordination of free silylenes (as stable diamide com-
pounds13-17 or as generated photochemically18) to tran-
† Current address: Division of Chemistry and Chemical Engineer-
ing, California Institute of Technology, Pasadena, CA 91125.
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1990, 112, 7801.
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poport, Z., Eds.; Wiley: New York, 1991; pp 245, 309.
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10.1021/om020389u CCC: $22.00 © 2002 American Chemical Society
Publication on Web 08/31/2002

4066 Organometallics, Vol. 21, No. 20, 2002
Feldman et al.
Resu lts a n d Discu ssion
An Ir id iu m Silylen e Com p lex via 1,2-Hyd r ogen
Migr a tion . Our strategy for the generation of iridium
silylene complexes via migration chemistry targeted a
5-coordinate, 16-electron Ir-SiHR2 derivative. It was
envisioned that such a species might be available by
methide abstraction, and a suitable starting material
proved to be (Me3P)3Ir(SiHMes2)(Me)(H) (1), prepared
by addition of Mes2SiH2 to (Me3P)4IrMe.44 Upon addition
of B(C6F5)3 to 1 in CH2Cl2, the reaction solution changed
from colorless to yellow, and NMR spectroscopy indi-
cated quantitative formation of a new product (2). For
2, a resonance attributed to H3C-B(C6F5)3 (δ 0.52) and
an IrH resonance which is integrated as two hydrogens
2
(δ -11.02, J HP(trans) ) 84 Hz) were observed. This
suggested that abstraction of Me- had occurred, fol-
lowed by a 1,2-H migration from silicon to iridium to
form the silylene complex [fac-(Me3P)3(H)2Ir(SiMes2)]-
[MeB(C6F5)3] (2; eq 5). This was verified by the 29Si-
Given the potential for 1,2-migrations to produce
reactive silylene complexes that may mediate new
chemical transformations, we have sought to develop
reaction systems for which this migration is facile. One
approach is based on extension of the induced-migration
method used to form the four-coordinate Pt(II) silylene
complex shown in eq 3 to other metal systems and
coordination geometries. An initial goal targeted migra-
tions that would generate stable octahedral complexes,
and for this purpose we have focused on d6 Ir(III). In
related work, it has been shown that addition of H2-
SiMes2 to Cp*(PMe3)IrMe(OTf) (where OTf ) OSO2CF3)
produces the silylene complex [Cp*(PMe3)(H)IrdSiMes2]-
[OTf], and mechanistic studies suggested that this
transformation occurs via 1,2-migration of hydrogen in
the intermediate [Cp*(PMe3)IrSiHMes2][OTf].31
{1H} NMR spectrum of 2, which contains a large
downfield chemical shift (δ 241, dt, 2J SiP(trans) ) 172 Hz,
2J SiP(cis) ) 4 Hz), characteristic of sp2-hybridized sili-
con.1,8-12,18,19 Presumably Me- abstraction generated the
unsaturated, five-coordinate intermediate [fac-(Me3P)3-
(H)Ir(SiHMes2)][MeB(C6F5)3], prior to 1,2-H migration
to form the coordinatively saturated silylene complex.
Formation of the silylene complex upon addition of
B(C6F5)3 is rapid (<5 min), and no intermediates were
observed at room temperature when the reaction was
monitored by 31P NMR spectroscopy.
In this contribution we describe migrations that
produce octahedral iridium silylene complexes and a
general chemical process that involves the facile extru-
sion of silylenes and germylenes from secondary silanes
and germanes (R2EH2: E ) Si, Ge). As discussed below,
this chemistry appears to involve 1,2-migrations be-
tween iridium and silicon (or germanium). Some of these
results have been communicated previously.32 Extru-
sions of this general type are potentially useful in
catalysis and have been identified in a few other cases.
For example, extrusions of carbenes from organic sub-
strates have been observed at electron-rich metal
centers.33-41 In addition, the extrusion of a germylene
from a germane42,43 has been reported by Banaszak
Holl.
Although analytically pure 2 was easily obtained in
powder form by removing the CH2Cl2 used in its
preparation, we have been unable to crystallize it under
a variety of conditions. In general, we have found that
crystallizations are often problematic for ionic complexes
such as 2, which contain a fluorocarbon-based anion,
MeB(C6F5)3-, and a hydrocarbon-based cation. In an
effort to obtain a neutral analogue of 2, we studied the
reactivity of hydrosilanes in a related iridium system
32
based on [PhBP3]Ir(H)(η3-C8H13
)
(3), where [PhBP3]
) PhB(CH2PPh2)3-. This complex contains three facially
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1999, 121, 9871.
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Norton, M. C.; Shaw, B. L.; Weeks, B. Chem. Commun. 1977, 589.
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Poveda, M. L.; Carmona, E. Chem. Eur. J . 1998, 4, 2225.
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Commun. 2001, 213.
(42) Litz, K. E.; Bender, J . E.; Kampf, J . W.; Banaszak Holl, M. M.
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M. Organometallics 1995, 14, 5008.
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Formation of Iridium Silylene Complexes
Organometallics, Vol. 21, No. 20, 2002 4067
Sch em e 1
Ta ble 1. 29Si NMR Sh ifts for th e Silylen e
Com p lexes [P h BP 3](H)2Ir dSiR2
R2
29Si NMR, δ
R2
29Si NMR, δ
Mes2
Ph2
Et2
241
327
307
Me2
Mes(C8H15
Trip(C8H15
311
274
317
)
)
coordinated phosphines but is zwitterionic, with a borate
incorporated into the ligand backbone.
Silylen e Extr u sion fr om Secon dar y Silan es. Com-
plex 3 reacts with secondary silanes (H2SiR2, with R )
Mes, Ph, Et, Me) in benzene to give silylene dihydride
complexes of the type [PhBP3](H)2IrdSiR2 (eq 6: R )
Mes, 4a ; R ) Ph, 4b; R ) Et, 4c; R ) Me, 4d ), with
concomitant loss of cyclooctene (COE). Formation of the
F igu r e 1. ORTEP diagram of [PhBP3](H)2IrdSiMes2 (4a ).
Interestingly, the related parent allyl complex [PhBP3]-
Ir(H)(η3-C3H5)45 did not react with R2SiH2 (R ) Mes,
Et, or Me) under forcing conditions (benzene-d6, 80 °C,
1 week). The inertness of this complex relative to 3 may
reflect a reduced tendency for it to undergo a change in
hapticity (η3 to η1; Scheme 1) which would allow
oxidative addition to the metal center. It is also note-
46
worthy that the related complexes TpIr(H)(η3-C8H13
)
and TpMe Ir(H)(η -C4H7) (where Tp ) hydridotris-
3
46
2
(pyrazolyl)borate and TpMe ) hydridotris(3,5-dimeth-
2
ylpyrazolyl)borate), which are less electron-rich and less
sterically demanding than 3,45 fail to react with H2-
SiMes2 (benzene-d6, 92 °C, 24 h).
The dimesitylsilylene complex [PhBP3](H)2IrdSiMes2
(4a ) was precipitated by the addition of pentane to a
toluene solution of 4a (67% yield). The molecular
structure of 4a (Figure 1) features a dimesitylsilylene
ligand which is planar at silicon (sum of the angles
about Si 359.0(6)°). Notably, the IrdSi bond distance of
2.260(3) Å is 5% shorter than the average of previously
observed Ir-Si distances (2.39 Å).47 The [PhBP3] ligand
is facially coordinated to iridium with P-Ir-P angles
silylene complex was confirmed by 29Si{1H} NMR
spectroscopy, as all the complexes exhibit resonances
downfield of 200 ppm (Table 1). The required reaction
conditions varied depending on the steric bulk of the
silane. For example, in benzene-d6, formation of [Ph-
BP3](H)2IrdSiMes2 required heating at 95 °C for 24 h
while [PhBP3](H)2IrdSiMe2 formed after heating at 80
°C for 2 min. Furthermore, formation of the silylene
complex is nearly complete in each case (>85% by NMR
spectroscopy). This transformation is exceptional in that
the direct conversion of secondary silanes to silylene
complexes was previously unknown.
(45) Feldman, J . D.; Peters, J . C.; Tilley, T. D. Organometallics, in
press.
(46) Alvarado, Y.; Boutry, O.; Gutierrez, E.; Monge, A.; Nicasio, M.
C.; Poveda, M. L.; Perez, P. J .; Ruiz, C.; Bianchini, C.; Carmona, E.
Chem. Eur. J . 1997, 3, 860.
(47) Corey, J . Y.; Braddock-Wilking, J . Chem. Rev. 1999, 99, 175.

4068 Organometallics, Vol. 21, No. 20, 2002
Feldman et al.
Ta ble 2. Cr ysta llogr a p h ic Da ta for 4a , 5, a n d 6
4a
5
6
empirical formula
fw
cryst size (mm)
cryst syst
space group
a (Å)
b (Å)
c (Å)
C
72H71BP3IrOSi
C47H49BP3IrOSi2
1837.76
0.12 × 0.10 × 0.02
monoclinic
P21/n
15.956(1)
28.838(2)
18.279(1)
90
92.025(1)
90
C75H75BP3IrGe
1344.99
0.34 × 0.10 × 0.03
monoclinic
P1h
13.2680(7)
14.1823(7)
19.105(1)
88.229(1)
73.711(2)
66.383(2)
3148.1(3)
2730, 3.0-46.0
2
1268.39
0.05 × 0.21 × 0.30
monoclinic
P21/c
11.5877(2)
19.6433(2)
27.2469(5)
90
91.569(1)
90
6199.6(2)
6753, 3.0-45.0
4
R (deg)
â (deg)
γ (deg)
V (Å3)
8406(2)
4517, 3.0-46.0
8
orientation rflns: no., 2θ range (deg)
Z
Dcalcd (g/cm3)
1.359
1.552
1.269
diffractometer
radiation
temp (K)
SMART
Mo KR (λ ) 0.710 69 Å), graphite monochromated
167(1)
ω (0.3° per frame)
10.0
49.4
140(1)
51.2
155(1)
51.3
scan type
scan rate (s/frame)
data collected, 2θmax (deg)
no. of rflns measd
total
unique
Rint
10 766
5890
0.075
38 028
14 426
15 973
10 012
0.062
0.100
structure soln
no. of obsd data (I > 3σ(I))
no. of params refined
direct methods (SIR92)
4956
534
0.034; 0.032; 0.034
0.82
5890
665
0.047; 0.049; 0.106
1.54
4392
350
0.041; 0.040; 0.111
0.89
a
final residuals: R; Rw; Rall
goodness of fit indicatorb
max. shift/error final cycle
0.04
1.63, -1.15
0.08
0.97, -0.63
0.01
1.27, -0.88
max and min peaks, final diff map (e/Å3)
a
2 1/2 b
R ) ∑||Fo| - |Fc||/∑|Fo|; Rw ) [∑w(|Fo| - |Fc|)2/∑wFo
]
.
Goodness of fit ) [∑w(|Fo| - |Fc|)2/(Nobservns - Nparams)]1/2
.
Ta ble 3. Selected Bon d Dista n ces (Å) a n d
An gles (d eg) for 4a
plexes are thermally unstable. For 4b-4d , removal of
the solvent in vacuo resulted in significant decomposi-
tion (>50%) to mixtures of products. For [PhBP3](H)2-
IrdSiMe2 (4d ) an apparent hydrolysis product was
observed when crystals were grown over several weeks
from a toluene solution which had been layered with
Et2O. Analysis of these crystals by X-ray crystallography
revealed the bimetallic complex {[PhBP3](H)3Ir(SiMe2)}O
(5, Figure 2 and Table 4), which is assumed to be the
result of slow diffusion of adventitious water into the
solution of 4d (eq 7). Attempts to prepare 5 via the
(a) Bond Distances
Ir1-P1
Ir1-P2
2.345(3)
2.329(3)
Ir1-P3
Ir1-Si1
2.408(2)
2.260(3)
(b) Bond Angles
P1-Ir1-P2
P1-Ir1-P3
P2-Ir1-P3
90.84(9)
89.11(8)
86.17(9)
P1-Ir1-Si1
P2-Ir1-Si1
P3-Ir1-Si1
141.5(1)
120.9(1)
112.32(9)
F igu r e 2. ORTEP diagram of {[PhBP3](H)3IrSiMe2}2O (5).
of 86-91°, but otherwise the iridium center is distorted
from ideal octahedral geometry. Significant steric in-
teractions between dimesitylsilylene and the bulky
[PhBP3] ligand presumably give rise to the Si-Ir-P
angles of 141.5(1), 120.9(1), and 112.3(1)° (vs 180, 90,
and 90° for an ideal octahedron). Selected bond dis-
tances and angles for 4a are listed in Table 3.
stoichiometric addition of H2O to 4d in benzene-d6 gave
a mixture of products.
Ger m ylen e Extr u sion fr om a Ger m a n e. Given the
generality of the transformation shown in eq 6, we
attempted to extend this method to the formation of
germylene complexes from secondary germanes. The
reaction of Mes2GeH2 with 3 (benzene, 83 °C, 36 h) gave
Except for 4a , which possesses the most sterically
demanding substituents at silicon, these silylene com-

Formation of Iridium Silylene Complexes
Organometallics, Vol. 21, No. 20, 2002 4069
complexes containing Ge-Ir bonds are (Ph3P)2(CO)(H)2-
48
IrGeMe3 and the germylene complexes A and B.49
F igu r e 3. ORTEP diagram of [PhBP3](H)2IrdGeMes2 (6).
Ta ble 4. Selected Bon d Dista n ces (Å) a n d
An gles (d eg) for 5
(a) Bond Distances
Among these structures, the Ge-Ir distances range
from 2.32 to 2.47 Å, with the shorter distances corre-
sponding to germylene-iridium contacts.
Ir1-P1
Ir1-P2
Ir1-P3
2.353(3)
2.358(3)
2.358(3)
Ir1-Si1
Si1-O1
Si2-O1
2.408(4)
1.637(8)
1.646(8)
Mech a n istic Con sid er a tion s for Silylen e Extr u -
sion fr om Secon d a r y Sila n es. Two possible mecha-
nisms for silylene (or germylene) formation from the
reactions of H2SiR2 (or H2GeR2) with [PhBP3]Ir(H)(η3-
C8H13) are shown in Scheme 1. In path A, an η1-allyl
complex is in equilibrium with an η2-COE complex, and
addition of an Si-H bond followed by loss of cyclooctene
would yield the 16-electron silyl intermediate D. This
unsaturated intermediate would then undergo 1,2-H
migration to form the observed silylene product, in
which iridium is coordinatively and electronically satu-
rated. Alternatively, as shown in path B, 3 could be in
equilibrium with an η1-allyl complex, which then un-
dergoes oxidative addition of H2SiR2 to give an Ir(V)
intermediate (C). From this intermediate, reductive
elimination of COE and 1,2-H migration would produce
the final product.
In an effort to determine which mechanism is opera-
tive, the reaction of 3 with D2SiMes2 was monitored by
NMR spectroscopy. While path A would yield a product
with two iridium deuterides, [PhBP3](D)2IrdSiMes2,
path B would give a mixture of deuteride and hydride
ligands in the iridium product, with some of the
deuterium label being incorporated into cyclooctene. To
our surprise, this labeling study did not lead to products
consistent with path A or B but instead revealed the
presence of a [PhBP3] ligand metalation process.
During the course of a reaction of D2SiMes2 with 3
(benzene, 80 °C, 3 h) the deuterium label was incorpo-
rated into the ortho position of the P-phenyl substituent
of [PhBP3] as well as various positions of the C8H13 ring
of 3 prior to product formation (by 1H, 2H{1H}, and 31P-
{1H} NMR spectroscopy). This observation indicates
that silane addition to [PhBP3]Ir(H)(η3-C8H13) is revers-
ible (D2SiMes2 is converted to H2SiMes2 prior to forma-
tion of the silylene complex), that ortho metalation of
the ligand P-phenyl groups is a rapid, reversible process,
(b) Bond Angles
P1-Ir1-Si1
P2-Ir1-Si1
P3-Ir1-Si1
Ir1-Si1-O1
Si1-O1-Si2
133.4(1)
117.3(1)
124.8(1)
112.8(3)
148.6(6)
P3-Ir2-Si2
P4-Ir2-Si2
P5-Ir2-Si2
Ir2-Si2-O1
124.8(1)
125.8(1)
126.6(1)
111.9(3)
Ta ble 5. Selected Bon d Dista n ces (Å) a n d
An gles (d eg) for 6
(a) Bond Distances
Ir1-P1
Ir1-P2
2.362(3)
2.329(3)
Ir1-P3
Ir1-Ge1
2.310(3)
2.339(1)
(b) Bond Angles
P1-Ir1-P2
P1-Ir1-P3
P2-Ir1-P3
91.9(1)
88.1(1)
90.2(1)
P1-Ir1-Ge1
P2-Ir1-Ge1
P3-Ir1-Ge1
111.02(7)
113.59(8)
147.96(8)
[PhBP3](H)2IrdGeMes2 (6), which was isolated in 76%
yield. Like the analogous silylene complexes, the 31P-
{1H} NMR spectrum of 6 consists of two coupled
resonances (benzene-d6, δ 6.12, 3.61, 2J PP ) 19 Hz), and
the 1H NMR spectrum features an IrH resonance (δ
-9.68, dm, 2J HPtrans ) 83 Hz) which is integrated as two
hydrogens. Complex 3 did not give analogous stannylene
or carbene complexes upon addition of secondary stan-
nanes or alkanes; H2CR2 (R ) Ph, Mes) failed to react
with 3 in benzene-d6 after heating at 95 °C for 2 weeks,
and Mes2SnH2 reacted immediately with 3 in benzene-
d6 at room temperature to give a variety of iridium
products, H2, and several Sn-H-containing compounds
1
(by H NMR spectroscopy).
X-ray-quality crystals of 6 were grown via the slow
evaporation of a benzene-d6 solution; an ORTEP dia-
gram is shown in Figure 3, and selected bond distances
and angles are given in Table 5. Germylene complex 6
is structurally similar to its silylene analogue (4a ). The
dimesitylgermylene substituent is bent away from the
bulky [PhBP3] phosphine groups, resulting in Ge-Ir-P
angles of 147.96(8), 113.59(8), and 111.02(7)°. The
germanium coordination plane (Ir, Ge, C, C) is nearly
trigonal planar, with the sum of the angles about Ge
being 355.7(6)°, and the IrdGe bond distance is 2.339-
(1) Å. The only other crystallographically characterized
(48) Bell, N. A.; Glockling, F.; Schneider, M. L.; Shearer, H. M. M.;
Wibley, M. D. Acta Crystallogr. Sect. C: Cryst. Struct. Commun. 1984,
40, 625.
(49) Hawkins, S. M.; Hitchcock, P. B.; Lappert, M. F.; Rai, A. K.
Chem. Commun. 1986, 1689.

4070 Organometallics, Vol. 21, No. 20, 2002
Feldman et al.
and that exchange of iridium-bound and cyclooctenyl-
bound hydrogens occurs rapidly (eq 8).50 The metalation
process is consistent with our recent observation of the
ortho-metalation product {PhB[(CH2PPh2)2(CH2PPh-
C6H4)]}Ir(H)(PMe3), which forms upon addition of PMe3
to 3.45
F igu r e 4. ORTEP diagram of one of the two crystallo-
graphically independent molecules of [PhBP3]IrH3(SiMe3)
(7b). One of the phenyl groups on P2 has been omitted for
clarity.
We have observed evidence to suggest that the hy-
dride ligands readily migrate back to silicon. For
example, the addition of excess CO to 4a (benzene-d6,
92 °C, 24 h) produced Mes2SiH2 and [PhBP3]Ir(CO)2
(quantitative by 31P{1H} NMR spectroscopy). Addition-
ally, a C-H activation process was observed upon
reaction of propene with 4a (1 atm, benzene-d6, 80 °C).
After 7 days at 80 °C, 40% conversion to Mes2SiH2 and
[PhBP3]Ir(H)(η3-C3H5) was observed (eq 9). This first
example of a C-H activation by a transition silylene
complex suggests that silylene complexes derived from
[PhBP3]Ir may possess a rich reaction chemistry.
Activa tion of Ter tia r y Sila n es. Both mechanisms
in Scheme 1 involve a rearrangement of the 16-electron
silyl intermediate D to an 18-electron silylene species
via 1,2-H migration from silicon to iridium. This migra-
tion should be less favorable for substituents other than
H, and thus we studied the reactions of tertiary silanes
(HSiR3) with [PhBP3]Ir(H)(η3-C8H13) (3) in an effort to
observe silyl complexes analogous to the proposed
intermediates C and D. However, as described below,
reactions of 3 with tertiary silanes are not analogous
to those with secondary silanes. For example, thermoly-
sis of 3 with 1 equiv of HSiEt3 (benzene-d6, 60 °C, 20 h)
led to formation of 1,3-cyclooctadiene (by GC/MS), and
by 1H NMR spectroscopy an IrH resonance which is
byproduct, as in the reactions with secondary silanes)
or as a source of “[PhBP3]IrH2” (with elimination of 1,3-
COD, as in the reactions with tertiary silanes). This
difference has also been observed in reactions of 3 with
phosphines.45 As yet, we do not fully understand the
factors that influence this reactivity.
Under an atmosphere of HSiMe3 3 reacts (benzene,
75 °C, 6 days) to give the corresponding trimethylsilyl
product [PhBP3]IrH3(SiMe3) (7b), which was isolated in
66% yield. The NMR data for 7b are quite similar to
those of 7a , which suggests that the complexes are
isostructural in solution. The solid-state structure of 7b
was determined by X-ray crystallography (Figure 4) and
confirms the geometry of this complex, which may be
described as a distorted, silyl-capped octahedron. Two
structurally similar molecules are in the asymmetric
unit. In both molecules all P-Ir-P angles are ap-
proximately 90°, while the P-Ir-Si angles range from
119 to 129°. Selected bond distances and angles for 7b
are given in Table 7. Overall, the coordination geometry
for iridium is similar to that in the related complex
2
integrated as three hydrogens (δ -10.6, J HP ) 81 Hz)
and a triethylsilyl substituent are observed. Addition-
ally, the phosphine ligands are equivalent by 31P{1H}
NMR spectroscopy (δ -3.81). These data are consistent
with the symmetrical, silyl-capped Ir(V) species [PhBP3]-
IrH3(SiEt3) (7a , eq 10). This reaction was quantitative
by 1H and 31P{1H} NMR spectroscopy; the isolated yield
of 7a was 38%. It is interesting to note that, depending
on reaction conditions, complex 3 may behave as a
source of “[PhBP3]Ir” (with elimination of COE as a
TpMe IrH3(SiEt3).51 However, it contrasts with the struc-
2
tures of related Cp* complexes, including Cp*IrH3(ER3)
(where ER3 ) SiMe3, SnMe3, SnPh3)52 and Cp*IrH2-
(SiEt3)2,53 which may be described as four-legged piano
stools.
(50) Two reversible processes to account for this are feasible:
insertion of COE into the Ir-H bond, or â-H elimination to form
[PhBP3]Ir(H)2(COD), where COD ) 1,3-cyclooctadiene.
(51) Gutierrez-Puebla, E.; Monge, A.; Paneque, M.; Poveda, M. L.;
Taboada, S.; Trujillo, M.; Carmona, E. J . Am. Chem. Soc. 1999, 121,
346.

Formation of Iridium Silylene Complexes
Organometallics, Vol. 21, No. 20, 2002 4071
Ta ble 6. Cr ysta llogr a p h ic Da ta for 7b a n d 8a
7b
8a
empirical formula
fw
C
48H50BP3IrSi
C62H69BP3IrSi
985.98
994.05
cryst size (mm)
cryst syst
space group
a (Å)
b (Å)
c (Å)
0.19 × 0.16 × 0.07 0.30 × 0.25 × 0.07
triclinic
monoclinic
P21/c
P1h
13.3907(3)
17.3646(4)
20.4662(3)
65.825(1)
86.788(2)
89.680(2)
4333.9(2)
3923, 3.0-45.0
16.9431(4)
14.9301(1)
21.3674(4)
90
99.521(1)
90
R (deg)
â (deg)
γ (deg)
V (Å3)
5330.7(2)
6301, 3.0-45.0
orientation rflns:
no., 2θ range (deg)
Z
4
4
Dcalcd (g/cm3)
diffractometer
radiation
1.523
1.228
SMART
Mo KR (λ ) 0.710 69 Å),
graphite monochromated
F igu r e 5. ORTEP diagram of [PhBP3](H)2IrdSi(Mes)(c-
C8H15) (8a ). The cyclooctyl ring bound to silicon is highly
disordered, and several partial-occupancy carbon atoms are
displayed.
temp (K)
scan type
154(1)
ω (0.3° per frame)
10.0
scan rate (s/frame)
no. of data collected,
2θmax (deg)
no. of rflns measd
total
46.5
Ta ble 8. Selected Bon d Dista n ces (Å) a n d
An gles (d eg) for 8a
25 520
14 104
0.056
24 769
7975
0.100
(a) Bond Distances
unique
Rint
Ir1-P1
Ir1-P2
2.377(2)
2.333(2)
Ir1-P3
Ir1-Si1
2.328(2)
2.250(3)
structure soln
no. of obsd data
(I > 3σ(I))
no. of params refined
final residuals:
direct methods (SIR92)
4387
5626
(b) Bond Angles
P1-Ir1-P2
P1-Ir1-P3
P2-Ir1-P3
87.98(8)
88.51(8)
90.43(8)
P1-Ir1-Si1
P2-Ir1-Si1
P3-Ir1-Si1
115.3(1)
140.7(1)
119.7(1)
483
592
0.035; 0.035;
0.108
0.037; 0.038;
0.081
a
R; Rw; Rall
goodness of fit indicatorb 0.84
1.34
0.01
Sch em e 2
max shift/error
final cycle
0.00
max and min peaks,
1.47, -0.53
0.67, -0.39
final diff map (e/Å3)
a
2 1/2
R ) ∑||Fo| - |Fc||/∑|Fo|; Rw ) [∑w(|Fo| - |Fc|)2/∑wFo
] .
Goodness of fit ) [∑w(|Fo| - |Fc|)2/(Nobservns - Nparams)]1/2
.
b
Ta ble 7. Selected Bon d Dista n ces (Å) a n d
An gles (d eg) for 7b
(a) Bond Distances
Ir1-P1
Ir1-P2
2.367(3)
2.363(3)
Ir1-P3
Ir1-Si1
2.375(3)
2.437(3)
(b) Bond Angles
P1-Ir1-P2
P1-Ir1-P3
P2-Ir1-P3
89.7(1)
91.6(1)
88.9(1)
P1-Ir1-Si1
P2-Ir1-Si1
P3-Ir1-Si1
128.5(1)
128.1(1)
118.7(1)
29Si{1H} NMR shift of δ 274, consistent with the
formation of a silylene complex. However, by H NMR
Silylen e Com p lexes Der ived fr om P r im a r y Si-
1
la n es. Given the ease with which silylenes are extruded
from secondary silanes using 3, we sought to prepare
complexes with a hydrogen substituent on the silylene
ligand, [PhBP3](H)2IrdSiH(R), from the reaction of 3
with primary silanes. Such species are expected to be
quite reactive, given the presence of a Si-H bond and
the relatively low steric protection for the silylene
center. Recently a silylene complex of this type,
[(Et3P)3(H)2IrdSiH(C6H3Mes2-2,6)][B(C6F5)], was re-
ported.54
spectroscopy no resonances consistent with COE or the
presence of a Si-H bond were observed. Instead, several
methylene resonances (δ 1.73-2.03) were observed,
suggesting the possibility of a cyclooctyl substituent on
silicon and a silylene complex of the type [PhBP3](H)2-
IrdSi(Mes)(c-C8H15) (8a ). Such a product could result
(formally) from the hydrosilylation of COE by the
anticipated silylene complex, [PhBP3](H)2IrdSiH(Mes).
An X-ray diffraction study of complex 8a confirmed
its structure (Figure 5), which is similar to that of 4a .
The IrdSi bond distance of 2.250(3) Å is the shortest
Ir-Si contact reported to date.55 The geometry at
iridium is a distorted octahedron, with P-Ir-P angles
ranging from 88 to 90° and P-Ir-Si angles of 140.7(1),
The reaction of MesSiH3 with 3 (benzene-d6, 25 °C,
24 h) did in fact cleanly produce a new species with a
(52) Gilbert, T. M.; Hollander, F. J .; Bergman, R. G. J . Am. Chem.
Soc. 1985, 107, 3508.
(53) Ricci, J . S., J r.; Koetzle, T. F.; Fernandez, M. J .; Maitlis, P. M.;
Green, J . C. J . Organomet. Chem. 1986, 299, 383.
(54) Simmons, R. S.; Gallucci, J . C.; Tessier, C. A.; Youngs, W. J . J .
Organomet. Chem. 2002, 654, 224.
(55) Based on a search of the Cambridge Structural Database, April
2002.

4072 Organometallics, Vol. 21, No. 20, 2002
Feldman et al.
Sch em e 3
119.7(1), and 115.3(1)°. Significantly, the crystallo-
graphic data are consistent with the presence of a
cyclooctyl substituent on the silylene moiety, which
confirms that activation of all three Si-H bonds of
MesSiH3 has taken place. Additional bond distances and
angles for 8a are listed in Table 8.
As outlined in Scheme 3, there are three mechanisms
whereby the intermediate [PhBP3](H)2IrdSiH(Trip) (9)
can react with COE to give the final product [PhBP3](H)2-
IrdSiH(Trip) (8b). First, 1,2-H migration from silicon
to iridium followed by COE coordination, and migratory
insertion would generate five-coordinate [PhBP3]Ir(c-
C8H15)(SiH2Trip) (E). Intermediate E could undergo
reductive elimination to give H2Si(Trip)(c-C8H15) and
“[PhBP3]Ir”,59 which could then form the product si-
lylene complex 9 via double Si-H activation. Alterna-
tively, intermediate E could undergo a series of 1,2-
migrations to give silylene complex F and silyl complex
G prior to product formation. Finally, silylene complex
9 could undergo 2 + 2 cycloaddition to give the iridasi-
lacycle H; C-H reductive elimination would then gener-
ate [PhBP3](H)Ir(c-C8H15)(SiHTrip) (G), and a 1,2-
migration would yield 8b. Although no 2 + 2 cycloaddi-
tions between alkenes and silylene complexes have been
reported, products apparently derived from alkyne
cycloaddition with silylene complexes have been ob-
served.2,3,60-65
In a reaction of the more sterically congested 2,4,6-
triisopropylphenylsilane (TripSiH3) with 3 (toluene,
room temperature, 2.5 days), an intermediate was
observed in the course of an analogous triple Si-H bond
activation. As in the case above, a cyclooctylsilylene
complex, [PhBP3](H)2IrdSi(Trip)(c-C8H15) (8b ), is the
final product with a 29Si{1H} NMR resonance of δ 317.
However, when the reaction was monitored by NMR
spectroscopy, intermediate formation of COE and a
species consistent with [PhBP3](H)2IrdSiH(Trip) (9) was
observed (Scheme 2). The concentration of 9 did not
build up significantly (<20%), but it was observed in
the presence of COE and was completely converted to
8b once all of the COE had been consumed. For 9, two
coupled resonances are observed by 31P{1H} NMR
2
spectroscopy (δ 2.87 and 1.86, J PP ) 18 Hz). The 1H
(57) Guggenberger, L. J .; Schrock, R. R. J . Am. Chem. Soc. 1975,
97, 6578.
(58) Schwab, P.; Grubbs, R. H.; Ziller, J . W. J . Am. Chem. Soc. 1996,
118, 100.
(59) “[PhBP3]Ir” would more likely exist as a metalated isomer.
(60) Yamamoto, K.; Okinoshi, H.; Kumada, M. J . Organomet. Chem.
1971, 27, C31.
(61) Yamashita, H.; Tanaka, M.; Goto, M. Organometallics 1992,
11, 3227.
(62) Seyferth, D.; Shannon, M. L.; Vick, S. C.; Lim, T. F. O.
Organometallics 1985, 4, 57.
(63) Okinoshi. H.; Yamamoto, K.; Kumada, M. J . Am. Chem. Soc.
1972, 94, 9263.
NMR spectrum for silylene 9 features an IrH resonance
at δ -9.34 (2J HPtrans ) 75 Hz) and, significantly, a SiH
resonance at δ 11.16 (3J HP ) 20 Hz). This downfield shift
for the silylene SiH is consistent with [(Et3P)3(H)2Ird
SiH(C6H3Mes2-2,6)][B(C6F5)]54 and other SiH silylene
complexes prepared in our group56 and is reminiscent
1
of the downfield H NMR shifts that have been observed
for hydrogen-substituted carbene complexes of the type
LnMdCHR.57,58
(56) Several silylene complexes with Si-H bonds have been pre-
pared in our laboratory. These fully characterized complexes exhibit
downfield SiH shifts by 1H NMR spectroscopy (δ 10-13). Glaser, P.
B.; Mork, B. V.; Tilley, T. D. Manuscripts in preparation.
(64) Sakurai, H.; Kamiyama, Y.; Nakadaira, Y. J . Am. Chem. Soc.
1977, 99, 3879.
(65) Tanaka, Y.; Yamashita, H.; Tanaka, M. Organometallics 1995,
14, 530.

Formation of Iridium Silylene Complexes
Organometallics, Vol. 21, No. 20, 2002 4073
Laboratory in the College of Chemistry at the University of
California, Berkeley. FT-infrared spectra were recorded on a
Mattson FTIR 3000 instrument.
Con clu sion
In the study described here, migration chemistry in
iridium silyl complexes was exploited to produce stable,
isolable silylene complexes. The synthetic routes em-
ployed have targeted silylene complexes with the most
stable coordination geometry for Ir(III), which is de-
signed to form via 1,2-H migration in a reactive,
5-coordinate intermediate. The viability of this approach
was first demonstrated by a reaction scheme that
appears to generate the 16-electron intermediate (Me3P)3-
(H)Ir-SiHMes2+, which rapidly converts to the 6-coor-
dinate silylene complex (Me3P)3(H)2IrdSiMes2+ (2). This
result, along with those reported earlier for the plati-
num system of eq 3,19 emphasizes the importance of
changes in the metal’s coordination geometry in influ-
encing migration chemistry. Evidently, 1,2-migrations
are not favored in square-planar Pt(II) silyl com-
plexes18,19 or in octahedral Rh(III) silyl complexes.66
However, reaction schemes that produce less stable
coordination geometries (e.g., 3-coordinate Pt(II) or
5-coordinate Ir(III)) can lead to migrations of this type.
Such low-coordinate intermediate species may result
from ligand abstractions, as reported here and else-
where,19,31 but may also form via ligand dissociation
processes. This latter possibility is yet to be demon-
strated, however.
Further development of this migration chemistry
might lead to useful catalytic transformations involving
reactive silylene complexes as intermediates. Significant
progress in this direction has been made with identifi-
cation of reactions that involve the facile extrusion of
silylene ligands from simple secondary and primary
silanes. Notably, this chemistry resulted from investiga-
tion of a new iridium-based fragment involving the
anionic triphosphine ligand [PhBP3]. With development
of new chemical transformations for silylene complexes,
it may prove possible to design catalytic cycles that
involve silylene extrusions. In this context, it is worth
noting the propene reaction of eq 9, which represents
the first example of a C-H activation mediated by a
transition metal silylene complex. Currently, the mech-
anism of this conversion is not known. Future efforts
will address this issue and the reactivity of silylene
complexes toward various organic compounds.
NMR Mea su r em en ts. Routine 1H, 31P{1H}, and 13C{1H}
NMR spectra were recorded at 298 K on a Bruker DRX-500
instrument equipped with a 5 mm broad band probe and
operating at 500.13 MHz (1H), 125.77 MHz (13C), 99.36 MHz
(29Si), and 202.45 MHz (31P). The 29Si NMR data were obtained
using 1H-29Si HMQC experiments. Chemical shifts are re-
ported in ppm downfield from internal SiMe4 (1H, 13C, 29Si),
and external 85% H3PO4 (31P); coupling constants are given
in Hz. Bruker XWINNMR software was used for all processing.
X-r a y Cr ysta llogr a p h y. Gen er a l Con sid er a tion s. The
single-crystal analyses were carried out at the UC Berkeley
CHEXRAY crystallographic facility. Measurements were made
on
a Bruker SMART CCD area detector with graphite-
monochromated Mo KR radiation (λ ) 0.710 69 Å). Data were
integrated by the program SAINT, corrected for Lorentz and
polarization effects, and analyzed for agreement and possible
absorption using XPREP. Empirical absorption corrections
were made using SADABS. Structures were solved by direct
methods and expanded using Fourier techniques. The quantity
minimized by the least-squares program was ∑w(|Fo| - |Fc|),70
where w is the weight of a given observation. The analytical
forms of the scattering factor tables for the neutral atoms were
used, and all scattering factors were corrected for both the real
and the imaginary components of anomalous dispersion. All
calculations were performed using the teXsan crystallographic
software package. Selected crystal and structure refinement
data are summarized in Tables 2 and 6. All crystals were
mounted on a glass fiber using Paratone N hydrocarbon oil.
Con sid er a tion s for 4a . Crystallization via slow diffusion
of pentane into a toluene/THF solution of 4a provided X-ray-
quality crystals. The molecule packs in the unit cell with one
moderately well-defined molecule of toluene and a poorly
defined mass of electron density that might correspond to one
tetrahydrofuran per two molecules of 4a . This was assumed
in determining the unit cell contents for the purposes of
calculating F000 and the density. The model for the disordered
solvent was five half-occupancy carbon atoms, since there was
no way to assign one of them as a likely oxygen atom. All non-
hydrogen atoms were refined anisotropically, except for boron
and the carbon atoms of the solvent molecule. Hydrogen atom
positions were calculated but not refined.
Con sid er a tion s for 5. Crystals suitable for X-ray diffrac-
tion studies were grown over several days from a toluene
solution that had been layered with ether. There are two
unique molecules (which are structurally similar) in the
asymmetric unit. The iridium, phosphorus, and silicon atoms
were refined anisotropically. Methylene (CH2) and methyl
(CH3) carbon atoms were refined anisotropically, while the
phenyl (CH) carbon atoms were refined isotropically, and the
hydrogen atom positions were calculated but not refined.
Con sid er a tion s for 6. Crystals suitable for X-ray diffrac-
tion studies were grown over several days by the slow
evaporation of a benzene solution of 6. The iridium, phospho-
rus, and germanium atoms were refined anisotropically, the
carbon and boron atoms were refined isotropically, and all
hydrogen positions were calculated but not refined.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All experiments were performed
under dry nitrogen using standard Schlenk or drybox tech-
niques. Solvents were distilled under nitrogen from sodium
benzophenone ketyl, and dichloromethane was distilled from
CaH2. To remove olefin impurities, pentane and benzene were
pretreated with concentrated H2SO4, 0.5 N KMnO4 in 3 M H2-
SO4, NaHCO3, and then anhydrous MgSO4. Benzene-d6 and
THF-d8 were distilled from Na/K alloy. Other chemicals were
obtained from commercial suppliers and were used as received.
[PhBP3]Ir(η3-C8H13)(H),32 (PMe3)4IrMe,44 Mes2SiH2,67 and Mes2-
Con sid er a tion s for 7b. Crystals suitable for X-ray dif-
fraction studies were grown over several days by the slow
cooling of a toluene/ether solution to -35 °C. The iridium,
phosphorus, and silicon atoms were refined anisotropically, the
carbon and boron atoms were refined isotropically, and all
hydrogen positions were calculated but not refined.
68
GeH2 were prepared according to literature procedures.
TripSiH3 was prepared by reaction of TripSiCl369 with LiAlH4.
Elemental analyses were performed by the Microanalytical
Con sid er a tion s for 8a . Crystals suitable for X-ray diffrac-
tion were grown over several days by the slow cooling of a
toluene solution to -35 °C. The iridium, phosphorus, silicon,
(66) Mitchell, G. P.; Tilley, T. D. Organometallics 1998, 17, 2912.
(67) Braddock-Wilking, J .; Schieser, M.; Brammer, L.; Huhmann,
J .; Shaltout, R. J . Organomet. Chem. 1995, 499, 89.
(68) Cooke, J . A.; Dixon, C. E.; Netherton, M. R.; Kollegger, G. M.;
Baines, R. M. Synth. React. Inorg. Met.-Org. Chem. 1996, 26, 1205.
(69) Smit, C. N.; Bickelhaupt, F. Organometallics 1987, 6, 1156.
(70) SAINT: SAX Area-Detector Integration Program, version 4.024;
Bruker Inc., Madison, WI, 1995.

4074 Organometallics, Vol. 21, No. 20, 2002
Feldman et al.
and carbon atoms were refined anisotropically, with the
exception of the carbon atoms of the disordered cyclooctyl ring.
The cyclooctyl ring was modeled as 14 partial-occupancy
carbon atoms. The positions and occupancies of these carbon
atoms were refined, while the Biso value for each atom was
fixed at 9.5. The sum of the occupancies for these carbon atoms
is 8. The boron atom was refined isotropically, and the
hydrogen atom positions were calculated but not refined.
fa c-(Me3P )3Ir (SiHMes2)(Me)(H) (1). A Schlenk tube con-
taining a magnetic stir bar was charged with (Me3P)4IrMe
(0.658 g, 1.29 mmol) and H2SiMes2 (0.368 g, 1.37 mmol).
Diethyl ether (20 mL) was added, and the resulting reaction
solution was stirred rapidly. After 2-3 min 1 began to
precipitate. The mixture was stirred for 7.5 h, filtered, and
evaporated to dryness to give 0.558 g of analytically pure 1.
The filtrate was concentrated slightly and stored for 3 days
at room temperature. An additional 0.104 g of crystalline 1
was then isolated by filtration (total yield 73%). 1H NMR
(benzene-d6): δ 6.85 (s, 4 H, aryl), 5.93 (m, 1 H, SiH), 2.89 (br
s, 12 H, ortho 2,4,6-Me3C6H2), 2.21 (s, 6 H, para 2,4,6-Me3C6H2),
1.14 (d, J HP ) 70 Hz, 9 H, PMe3), 1.11 (d, J HP ) 76 Hz, 9 H,
PMe3), 1.06 (d, J HP ) 71 Hz, 9 H, PMe3), 0.09 (m, 3 H, IrMe),
H, para 2,4,6-Me3C6H2), 1.93 (m, 4 H, PhB(CH′2PPh2)(CH2-
PPh2)2), 1.83 (m, 2 H, PhB(CH′2PPh2)(CH2PPh2)2), -9.47 (m,
2J HP(trans) ) 70 Hz, 2 H, IrH). 29Si{1H} NMR (benzene-d6): δ
241.2 (dt, 2J SiP(trans) ) 172.4 Hz, 2J SiP(cis) ) 4 Hz). 31P{1H} NMR
(benzene-d6): δ 3.44 (t, J PP ) 18 Hz), 2.24 (d, J PP ) 18 Hz).
13C{1H} NMR (THF-d8): δ 140.5 (aryl), 139.7 (aryl), 133.2
(aryl), 133.1 (aryl), 132.6 (aryl), 132.4 (aryl), 129.8 (aryl), 129.2
(aryl), 129.1 (aryl), 128.9 (aryl), 124.5 (aryl), 24.5 (ortho 2,4,6-
Me3C6H2), 21.4 (para 2,4,6-Me3C6H2), 18.0 (br, BCH2P). IR
(Nujol, cm-1): 3055 m, 2958 m, 2923 m, 2122 m, 2060 m (IrH),
1064 w, 1482 m, 1417 s, 1262 w, 1159 m, 1096 s, 1027 m, 924
m, 862 w, 803 w, 740 m, 697 s, 517 m. Anal. Calcd for C63H65
BIrP3Si: C, 66.01; H, 5.72. Found: C, 65.76; H, 5.90.
-
Obser va tion s of [P h BP 3](H)2Ir dSiR2. F or R ) P h (4b).
An NMR tube containing a benzene-d6 solution of 3 (0.024 g,
0.024 mmol) and Ph2SiH2 (0.005 g, 0.03 mmol) was heated at
80 °C for 24 h. Analysis of the reaction mixture by 1H, 31P-
{1H), and 29Si{1H} NMR spectroscopy revealed nearly complete
conversion (ca. 85%) to [PhBP3](H)2IrdSiPh2 and COE. 1H
NMR (benzene-d6): δ 8.11, 7.98, 7.76, 7.66, 7.41, 7.05, 6.67,
6.65 (aryl), 1.97 (m, 4 H, PhB(CH′2PPh2)(CH2PPh2)2), 1.85 (m,
2 H, PhB(CH′2PPh2)(CH2PPh2)2), -9.46 (dm, 2J HP(trans) ) 75 Hz,
2
2 H, IrH). 31P{1H} NMR (benzene-d6): δ 5.41 (d, J PP ) 19
2
2
-11.47 (dt, J HP(trans) ) 128 Hz, J HP(cis) ) 17 Hz, 1 H, IrH).
2
31P{1H} NMR (benzene-d6): δ -63.3 (dd, 2J PP ) 19 Hz, 2J PP
)
Hz, 2 P, trans to H), 3.50 (t, J PP ) 19 Hz, 1 P, trans to Si).
29Si{1H} (benzene-d6): δ 327.5.
2
2
14 Hz), -64.1 (dd, J PP ) 19 Hz, J PP ) 14 Hz), -64.7 (br).
1
29Si{1H} NMR (benzene-d6): δ -46.7 (d, J SiH ) 151 Hz). 13C-
F or R ) Et (4c). An NMR tube containing a benzene-d6
solution of 3 (0.017 g, 0.017 mmol) and Et2SiH2 (0.005 g, 0.05
mmol) was allowed to sit at room temperature for 12 h.
Analysis by 1H, 31P{1H}, and 29Si{1H}NMR spectroscopy
revealed nearly complete conversion to [PhBP3](H)2IrdSiEt2
and COE. 1H NMR (benzene-d6): δ 8.13, 7.78, 7.68, 7.57, 7.43,
7.12, 7.00, 6.81 (aryl), 1.92 (m, 4 H, PhB(CH′2PPh2)(CH2-
PPh2)2), 1.80 (m, 2 H, PhB(CH′2PPh2)(CH2PPh2)2), -10.13 (dm,
2J HP(trans) ) 76 Hz, 2 H, IrH). 31P{1H} NMR (benzene-d6): δ
{1H} NMR (toluene-d8): δ 144.1 (Si-C), 135.1 (aryl), 134.6
(2,4,6-Me3C6H2), 129.1 (2,4,6-Me3C6H2), 24.8 (2,4,6-Me3C6H2),
20.7 (2,4,6-Me3C6H2), 23.0 (dm, 1J CP ) 28 Hz, PMe3), 21.2 (dm,
1J CP ) 27 Hz, PMe3), 17.8 (dm, 1J CP ) 29 Hz, PMe3). IR (Nujol,
cm-1): 2133 m (IrH), 2075 m (SiH). Anal. Calcd for C28H54
-
IrP3Si: C, 47.77; H, 7.73. Found: C, 47.44; H, 7.53. Mp: 124-
127 °C.
[fa c-(Me3P )3(H)2Ir dSiMes2][MeB(C6F 5)3] (2). A CH2Cl2
solution (10 mL) of B(C6F5)3 (0.314 g, 6.13 mmol) was added
via cannula to 1 (0.428 g, 6.08 mmol) in CH2Cl2 (10 mL) to
give a yellow solution, which was stirred for 5 min. Removal
of solvent under reduced pressure resulted in formation of a
yellow powder which was analytically pure. Yield: 0.652 g
2
2
6.23 (d, J PP ) 19 Hz, 2 P, trans to H), 2.21 (t, J PP ) 19 Hz,
1 P, trans to Si). 29Si{1H}(benzene-d6): δ 307.4.
F or R ) Me (4d ). A PTFE-capped NMR tube containing a
benzene-d6 solution of 3 (0.018 g, 0.018 mmol) was degassed
by two freeze-pump-thaw cycles, and an atmosphere of Me2-
SiH2 was introduced. The tube was then sealed, and the
solution was heated at 80 °C for 2 min. Analysis by 1H, 31P-
{1H}, and 29Si{1H} NMR spectroscopy revealed nearly complete
conversion (ca. 90%) to [PhBP3](H)2IrdSiMe2 and COE. 1H
NMR (benzene-d6): δ 7.71-6.76 (35 H, aryl), 0.35 (s, 9 H,
SiMe3), -10.17 (dm, 2J HP(trans) ) 69 Hz, 2 H, IrH). 31P{1H} NMR
(benzene-d6): δ 4.76 (d, 2J PP ) 20 Hz, 2 P, trans to H), 2.59 (t,
2J PP ) 20 Hz, 1 P, trans to Si). 29Si{1H}(benzene-d6): δ 311.2.
[P h BP 3](H)2Ir dGeMes2 (6). In a PTFE-sealed reaction
vessel, a 4 mL benzene solution of [PhBP3]Ir(η3-C8H13)H (0.102
g, 0.103 mmol) and Mes2GeH2 (0.031 g, 0.099 mmol) was
stirred at 83 °C for 36 h. The solvent was removed in vacuo to
give a yellow oil, which was triturated with 4 mL of benzene
to yield an orange powder. The powder was crystallized by
layering a 2 mL toluene solution with 3 mL of Et2O and storing
at -35 °C; from this, yellow crystals were obtained (0.084 g,
76%). 1H NMR (benzene-d6): δ 8.01-6.73 (35 H, [PhBP3] aryl),
6.66 (s, 4 H, ortho 2,4,6-Me3C6H2), 2.54 (s, 12 H, ortho 2,4,6-
Me3C6H2), 2.15 (s, 6 H, para 2,4,6-Me3C6H2), 1.89 (br, 2 H
B(CH2P)2(CH′2P′)), 1.82 (br, 2 H B(CH2P)2(CH′2P′)), -9.68 (dm,
2J HP ) 83 Hz, 2 H, IrH). 31P{1H} NMR (benzene-d6): δ 6.12 (t,
2J PP ) 19 Hz, 2 P, trans to H), 3.61 (d, 2J PP ) 19 Hz, 1 P, trans
to Ge). 13C{1H} NMR (benzene-d6): δ 138.8 (aryl), 133.2 (aryl),
132.3 (aryl), 131.9 (aryl), 129.8 (aryl), 129.7 (aryl), 128.5 (aryl),
127.3 (aryl), 125.6 (aryl), 124.2 (aryl), 23.1 (ortho 2,4,6-
Me3C6H2), 21.0 (para 2,4,6-Me3C6H2), 17.6 (br, BCH2P). IR
(KBr, cm-1): 3052 m, 2917 m, 2061 br m (IrH), 1618 m, 1434
1
(88%). H NMR (CD2Cl2): δ 6.85 (s, 4 H, 2,4,6-Me3C6H2), 2.53
(s, 12 H, ortho 2,4,6-Me3C6H2), 2.28 (s, 6 H, para 2,4,6-
2
Me3C6H2), 1.78 (d, J HP ) 9 Hz, 9 H, PMe3[trans to SiMes2]),
1.62 (d, 2J HP ) 8 Hz, 18 H, PMe3), 0.52 (br, 3 H, B-Me), -11.02
2
(dm, J HP(trans) ) 84 Hz, 2 H, IrH). 31P{1H} NMR (CD2Cl2): δ
-63.0 (m), -63.8 (m), -64.4 (m). 29Si{1H} NMR (CD2Cl2): δ
2
254.1 (d, J SiP ) 168 Hz). 13C{1H} NMR (CD2Cl2): δ 149.9
(aryl), 148.0 (aryl), 135.8 (m, C-F), 145.3 (Si-C), 141.8 (aryl),
1
140.0 (aryl), 129.9 (Mes aryl), 24.88 (dm, J CP ) 30 Hz PMe3),
24.5 (ortho 2,4,6-Me3C6H2), 23.7 (m, PMe3), 21.3 (para 2,4,6-
Me3C6H2). IR (Nujol, cm-1): 2357 m (IrH). Anal. Calcd for
C
46H54BF15IrP3Si: C, 45.44; H, 4.48. Found: C, 45.38; H, 4.29.
Mp: 64-69 °C dec.
[P h BP 3](H)2Ir dSiMes2 (4a ). [PhBP3]Ir(η3-C8H13)(H) (0.225
g, 0.228 mmol) was dissolved in benzene (5 mL). This solution
was then transferred into a vessel containing dimesitylsilane,
H2SiMes2 (0.0611 g, 0.228 mmol). The resulting colorless,
homogeneous solution was then warmed to 95 °C, and it
gradually turned yellow within 4-5 h. After 24 h the volatile
materials were removed under reduced pressure. Extraction
with toluene (5 mL) and filtration removed a light yellow
precipitate and afforded a deep yellow filtrate. This filtrate,
which was dried in vacuo, contained yellow 4a (0.221 g) as
1
the only product identified by H and 31P{1H} NMR spectros-
copy. High-yield crystallization of this crude powder was
difficult. However, analytically and spectroscopically pure
material was precipitated via pentane addition to a toluene
solution of 4a , yielding 0.176 g (67%). A crystal suitable for
an X-ray diffraction study was obtained by slow diffusion of
s, 1330 s, 1090 s, 924 m, 812 s, 697 s. Anal. Calcd for C63H65
-
BIrP3Ge: C, 63.55; H, 5.50. Found: C, 63.83; H, 5.67. Mp:
134-137 °C dec.
1
pentane into a toluene/THF mixture (10:1) at 25 °C. H NMR
(benzene-d6): δ 8.10-6.7 (m, 35 H, PhBP3 aryl), 6.63 (s, 2 H,
2,4,6-Me3C6H2), 2.50 (s, 12 H, ortho 2,4,6-Me3C6H2), 2.08 (s, 6
[P h BP 3]Ir H3(SiEt3) (7a ). In a PTFE-sealed reaction vessel,
[PhBP3]Ir(η3-C8H13)H (0.091 g, 0.092 mmol) and Et3SiH (0.011

Formation of Iridium Silylene Complexes
Organometallics, Vol. 21, No. 20, 2002 4075
g, 0.092 mmol) were combined with 4 mL of benzene. The
reaction mixture was stirred and heated at 50 °C for 2 days.
Removal of the volatile materials yielded an oily solid, which
was triturated with 4 mL of pentane to give a yellow solid
(0.035 g, 38%). 1H NMR (benzene-d6): δ 8.23-6.84 (35 H,
[PhBP3] aryl), 1.93 (br, 6 H, BCH2P), 1.37 (q, J ) 8 Hz, 6 H,
SiCH2CH3), 1.08 (t, J ) 8 Hz, 9 H, SiCH2CH3), -11.0 (dm,
2J HP(trans) ) 64 Hz, 3 H, IrH). 31P{1H} NMR (benzene-d6): δ
-5.52 (s). 13C{1H} NMR (benzene-d6): δ 140.1 (aryl), 133.3
(aryl), 132.7 (aryl), 129.4 (aryl), 129.1 (aryl), 128.3 (aryl), 124.9
141.4 (aryl), 140.5 (aryl), 139.1 (aryl), 139.0 (aryl), 133.1 (aryl),
132.8 (aryl), 132.5 (aryl), 129.5 (aryl), 129.1 (aryl), 127.8 (aryl),
124.7 (aryl), 45.9 (d, 3J CP ) 7 Hz, SiCH assigned using a DEPT
90 experiment), 30.0 (cyclooctyl CH2), 28.3 (cyclooctyl CH2),
27.8 (cyclooctyl CH2), 25.9 (cyclooctyl CH2), 22.8 (ortho 2,4,6-
Me3C6H2), 21.5 (para 2,4,6-Me3C6H2), 17.1 (br, BCH2P). IR
(KBr, cm-1): 3055 m, 2917 s, 2851 m, 2090 m (IrH), 1482 m,
1433 s, 1159 w, 1091 s, 921 m, 890 w, 864 w, 790 w, 749 s,
738 s, 696 s, 518 s, 478 w, 421 w. Anal. Calcd for C62H69
-
SiBIrP3: C, 65.42; H, 6.11. Found: C, 65.15; H, 6.31. Mp: 240-
244 °C dec.
3
(aryl), 17.5 (q, J CP ) 2 Hz, SiCH2CH3), 16.5 (br, BCH2P), 9.2
(SiCH2CH3). IR (KBr, cm-1): 3056 m, 2904 m, 2871 m, 2081
br m (IrH), 1482 m, 1434 s, 1159 w, 1091 s, 1002 w, 923 m,
891 w, 861 w, 738 s, 694 w, 516 s, 480 m. Anal. Calcd for
[P h BP 3](H)2Ir dSi(Tr ip )(C8H15) (8b). A 4 mL toluene
solution containing 3 (0.170 g, 0.172 mmol) and TripSiH3
(0.040 g, 0.171 mmol) was stirred for 3 days. The reaction
mixture was concentrated under reduced pressure to ca. 1.5
mL. The slow diffusion of pentane into the resulting toluene
solution (room temperature) afforded yellow, crystalline 8b
(0.097 g, 47%), which was isolated by filtration and washed
C
51H59SiBP3: C, 61.50; H, 5.97. Found: C, 61.78; H, 6.00.
Mp: 207-216 °C dec, 216-219 °C (melt).
[P h BP 3]Ir H3(SiMe3) (7b). In a PTFE-sealed reaction ves-
sel, a 4 mL benzene solution of [PhBP3]Ir(η3-C8H13)H (0.212
g, 0.214 mmol) was degassed by three freeze-pump-thaw
cycles, and an atmosphere of Me3SiH was introduced. The
vessel was then placed in an oil bath maintained at 75 °C for
6 days, after which time the solvent was removed in vacuo.
The resulting oil was washed with pentane (3 × 5 mL) to give
a tan powder (0.135 g, 66%). 1H NMR (benzene-d6): δ 8.13 (d,
J ) 7 Hz, 2 H, aryl), 7.68 (t, J ) 7 Hz, 2 H, aryl), 7.46 (m, 13
H, aryl), 6.78 (m, 18 H, aryl), 1.83 (m, 6 H, BCH2P), 1.06 (s, 9
1
with pentane (2 × 1 mL). H NMR (benzene-d6): δ 8.18-6.68
(37 H, aryl), 3.67 (sept, J ) 6 Hz, 2 H, ortho CHMe2), 2.97
(sept, J ) 6 Hz, 1 H, para CHMe2), 2.38 (br, 6 H, BCH2P),
2.03-1.76 (m, 15 H, cyclooctyl), 1.27 (d, J ) 6 Hz, 12 H, ortho
CHMe2), 1.19 (d, J ) 6 Hz, 6 H, para CHMe2), -10.12 (dm,
2J HP ) 71 Hz, 2 H, IrH). 31P{1H} NMR (benzene-d6): δ 2.80 (t,
2
2J PP ) 18 Hz, 1 P, trans to Si), 1.77 (d, J PP ) 18 Hz, 2 P,
trans to H). 29Si{1H} NMR (benzene-d6): δ 317.1. 13C{1H} NMR
(benzene-d6): 151.4, 150.8, 141.7, 133.6, 132.7, 129.7, 126.0,
124.8, 124.6, 122.1, 121.8 (aryl), 39.2 (SiCH), 31.1 (cyclooctyl
CH2), 29.8 (cyclooctyl CH2), 28.9 (cyclooctyl CH2), 26.9 (cy-
clooctyl CH2), 22.9 (Trip Me), 21.8 (Trip Me), 18.3 (br, BCH2P).
IR (KBr, cm-1): 3056 m, 2955 m, 2918 m, 2137 br m (IrH),
1482 m, 1434 s, 1159 w, 1089 s, 925 m, 863 w, 739 s, 695 s,
519 s, 482 m. Anal. Calcd for C68H81SiBIrSiP3: C, 66.81; H,
6.68. Found: C, 66.95; H, 6.30. Mp: 189-193 dec.
2
H, SiMe3), -10.6 (dm, J HP(trans) ) 81 Hz, 3 H, IrH). 31P{1H}
NMR (benzene-d6): δ -3.81. 29Si{1H} NMR (benzene-d6): δ
-21.4. 13C{1H} NMR (benzene-d6): δ 140.1 (d, J ) 50 Hz, aryl),
132.8 (s, aryl), 132.6 (m, aryl), 129.3 (s, aryl), 128.2 (m, aryl),
3
16.6 (br, BCH2P), 16.4 (q, J CP ) 3 Hz). IR (KBr, cm-1): 3055
m, 2941 w, 2889 w, 2091 br m (IrH), 1483 m, 1433 s, 1259 m,
1159 m, 1092 s, 922 s, 827 s, 739 s, 694 s, 628 m. Anal. Calcd
for C48H53BSiIrP3: C, 60.43; H, 5.60. Found: C, 60.11; H, 5.57.
Mp: 191-197 °C dec, 213-220 °C (melt).
[P h BP 3](H)2Ir dSi(Mes)(C8H15) (8a ). A 1 mL benzene
solution of MesSiH3 was added to a 5 mL benzene solution of
3, and the reaction mixture was stirred at room temperature
for 24 h. The solvent was removed under reduced pressure to
give a yellow oil. This was dissolved in 1 mL of THF, and slow
diffusion of Et2O at -35 °C yielded tan crystals of 8a (0.158 g,
75%). 1H NMR (benzene-d6): δ 8.80-6.52 (35 H, aryl), 2.43
(br, 6 H, BCH2P), 2.19 (s, 6 H, ortho 2,4,6-Me3C6H2), 2.03 (s, 3
H, para 2,4,6-Me3C6H2), 2.03-1.76 (m, 15 H, cyclooctyl), -10.00
Ack n ow led gm en t is made to the National Science
Foundation for their generous support of this work. We
than Dr. Fred Hollander of the UC Berkeley CHEXRAY
facility for assistance with the X-ray structure deter-
minations and for solving the structures for 4a and 8b.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal,
data collection, and refinement parameters, bond distances
and angles, and anisotropic displacement parameters for 4a ,
5, 6, 7b, and 8b. This material is available free of charge via
the Internet at http://pubs.acs.org.
2
(dm, J HP(trans) ) 76 Hz, 2 H, IrH). 31P{1H} NMR (benzene-d6):
2
δ 2.20 (t, 2J PP ) 19 Hz, 1 P, trans to Si), 1.41 (d, J PP ) 19 Hz,
2 P, trans to H). 29Si{1H} NMR (benzene-d6): δ 274.2 (d,
2J SiP(trans) ) 158 Hz). 13C{1H} NMR (benzene-d6): 145.7 (aryl),
OM020389U