Reactions of cationic PNP-supported iridium silylene complexes with polar organic substrates

Article abstract of DOI:10.1021/om901078d

Reactions of PNP-supported silylene complexes [(PNP)(H)Ir-SiRR′] [B(C₆F₅)₄] (R = R′ = Ph (1) and R = H, R′ = Mes (2)) with Lewis bases, carbonyl compounds, alcohols, and amines were investigated. Addition of DMAP (4-dimethylaminopyridine) to 1 and 2 produced base-stabilized silylene complexes [(PNP)(H)IrSiRR′(DMAP)] [B(C₆F₅)₄] (R = R′ = Ph (3) and R = H, R′ = Mes (4)). Reactions of 2 with benzophenone and benzaldehyde afforded the products of stoichiometric hydrosilylation, heteroatom-substituted silylene complexes [(PNP)(H)Ir-SiMes(OCH(Ph)(R))][B(C₆F₅) ₄] (R = Ph (5) and R = H (6)). Complex 1 reacted with DMF or benzophenone, and 2 reacted with DMF, to afford base-stabilized silylene complexes of the type [(PNP)(H)IrSiRR′(B)][B(C₆F ₅)₄] (R = H, R′ = Mes, B = DMF (7); R = R′ = Ph, B = DMF (8) and O-CPh₂ (9)). In contrast, treatment of 1 with acetophenone afforded {(PNPH)IrH[SiPh₂(OC(-CH₂)Ph)]} [B(C₆F₅)₄] (10), from activation of a C-H bond at the α-carbon position of acetophenone. Reactions of alcohols and amines with 1 afforded [(PNPH)IrH(SiPh₂OR)][B(C₆F ₅)₄] (R = 3,5-^tBu₂C ₆H₃ (11), R = Ph (12), R = ⁱPr (13), and R = ^tBu (14)) and [(PNPH)IrH(SiPh₂NHR)][B(C₆F ₅)₄] (R = Ph (15), R = 3,5-(CF₃) ₂C₆H₃ (16)). Exploration of the catalytic activity of iridium silylene complexes with these organic substrates demonstrated that 1 is an effective catalyst for silane alcoholysis and aminolysis and for the hydrosilylation of ketones.

Full text of DOI:10.1021/om901078d

1680 Organometallics 2010, 29, 1680–1692
DOI: 10.1021/om901078d
Reactions of Cationic PNP-Supported Iridium Silylene Complexes
with Polar Organic Substrates
Elisa Calimano and T. Don Tilley*
Department of Chemistry, University of California, Berkeley, California 94720
Received December 16, 2009
Reactions of PNP-supported silylene complexes [(PNP)(H)IrdSiRR0][B(C6F5)4] (R=R0 =Ph(1) and
R = H, R0 = Mes (2)) with Lewis bases, carbonyl compounds, alcohols, and amines were investigated.
Addition of DMAP (4-dimethylaminopyridine) to 1 and 2 produced base-stabilized silylene complexes
[(PNP)(H)IrSiRR0(DMAP)][B(C6F5)4] (R=R0 =Ph(3) andR=H, R0 =Mes(4)). Reactions of 2with
benzophenone and benzaldehyde afforded the products of stoichiometric hydrosilylation, heteroatom-
substituted silylene complexes [(PNP)(H)IrdSiMes(OCH(Ph)(R))][B(C6F5)4] (R = Ph (5) and R = H
(6)). Complex 1 reacted with DMF or benzophenone, and 2 reacted with DMF, to afford base-stabilized
silylene complexes of the type [(PNP)(H)IrSiRR0(B)][B(C6F5)4] (R = H, R0 = Mes, B = DMF (7); R =
R0 = Ph, B = DMF (8) and OdCPh2 (9)). In contrast, treatment of 1 with acetophenone afforded
{(PNPH)IrH[SiPh2(OC(dCH2)Ph)]}[B(C6F5)4] (10), from activation of a C-H bond at the R-carbon
position of acetophenone. Reactions of alcohols and amines with 1 afforded [(PNPH)IrH(SiPh2OR)]-
[B(C6F5)4] (R = 3,5-tBu2C6H3 (11), R = Ph (12), R = iPr (13), and R = tBu (14)) and [(PNPH)IrH-
(SiPh2NHR)][B(C6F5)4] (R = Ph (15), R = 3,5-(CF3)2C6H3 (16)). Exploration of the catalytic activity of
iridium silylene complexes with these organic substrates demonstrated that 1 is an effective catalyst for
silane alcoholysis and aminolysis and for the hydrosilylation of ketones.
Introduction
metal center, has been motivated by their proposed inter-
mediacy in catalytic cycles including silane redistribu-
tion,3 the Direct Process for the synthesis of chlorosilanes,4
silane dehydropolymerization,5 and the hydrosilylation of
alkenes.6
Investigations into the reactivity of silylene complexes
with simple organic substrates have revealed a number of
new stoichiometric transformations at silicon.7 For example,
reactions of chlorinated hydrocarbons with [Cp*(PMe3)2-
OsdSiMe2][B(C6F5)4] and [Cp*(dmpe)(H)2WdSiMe2][B-
(C6F5)4] result in the formation of chlorinated silyl ligands
or free chlorosilanes, in transformations that are significant
as stoichiometric models for the Direct Process.8 Other
notable examples include the reaction of [Cp*(PMe3)2Rud
SiMe2][B(C6F5)4] with isocyanates, resulting in the only known
example of a 1,2-dipolar cycloaddition to a transition-metal
silylene complex.9 Tobita et al. have described reactions of
Investigations of transition-metal complexes featuring
multiple bonds to main group elements are of interest with
respect to the discovery of new reactivity and catalytic
processes. Notable examples of important transformations
promoted by these types of multiply bonded species include
hydroamination by transition-metal imido complexes (Md
NR)1 and olefin metathesis by transition-metal carbene
complexes (MdCR2).2 In this context, transition-metal com-
plexes featuring multiple bonds to silicon have been targeted
as promising compounds for the development of catalytic
transformations of organosilanes. Research into the syn-
thesis and reactivity of transition-metal silylene complexes
(MdSiR2), featuring a double bond between silicon and the
*Corresponding author. E-mail: tdtilley@berkeley.edu.
(1) For group 4 imido complexes and applications into hydroamina-
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R. G. Chem. Rec. 2002, 2, 431–445. (b) Hazari, N.; Mountford, P. Acc.
Chem. Res. 2005, 38, 839–849.
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A. H. Angew. Chem., Int. Ed. 2003, 42, 4592–4633. (b) Trnka, T. M.;
Grubbs, R. H. Acc. Chem. Res. 2001, 34, 18–29.
(5) (a) Tilley, T. D. Comments Inorg. Chem. 1990, 10, 37–51. (b) Toal,
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Organomet. Chem. 2004, 51, 1–52. (d) Gauvin, F.; Harrod, J. F.; Woo, H. G.
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6951–6952.
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Faraday Trans. 1996, 92, 4605–608. (b) Acker, J.; Bohmhammel, K.
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pubs.acs.org/Organometallics
Published on Web 02/26/2010
2010 American Chemical Society

Article
Organometallics, Vol. 29, No. 7, 2010 1681
Cp*(CO)2(H)WdSiH[C(SiMe3)3] with nitriles, epoxides,
and R,β-unsaturated carbonyl compounds, illustrating
a variety of reactivity modes for this silylene complex.10
Similarly, recent reports by the same group have featured
reactions of Cp*(CO)(H)RudSiH[C(SiMe3)3] with nitriles
and carbonyl compounds.11
a resonance at -21.28 ppm, attributed to the hydride
ligand at iridium.
Recent investigations of alkene hydrosilylation by sily-
lene complexes focused on the chemistry of PNP-supported
iridium silylene species of the type [(PNP)(H)IrdSiR2]-
[B(C6F5)4], synthesized via hydride abstraction from
neutral iridium silyl hydride species (eq 1). Previous reports
detailed structural and spectroscopic investigations of this
family of cationic iridium silylene complexes and their
reactions with alkenes in the context of hydrosilyla-
tion catalysis.12 In this contribution, the reactivity of
[(PNP)(H)IrdSiRR0][B(C6F5] (R = R0 = Ph (1) and R =
H, R0 = Mes (2)) toward a variety of organic molecules
including Lewis bases, carbonyl compounds, alcohols, and
amines is described. Furthermore, explorations of catalytic
reactions mediated by PNP-supported iridium silylene
complexes are presented.
Similarly, addition of 1 equiv of DMAP to hydrogen-
substituted silylene complex 2 in C6H5F resulted in a dra-
matic color change from blue green to dark red. A red-violet
solid identified as [(PNP)(H)IrSiMes(H)(DMAP)][B(C6F5)4]
(4) was isolated following analogous procedures to those
employed for 3. The 29Si NMR resonance for 4 appears at
-12.1 ppm, representing a 258 ppm shift from that of the
parent silylene species 2 (246 ppm). The 1H NMR spectrum
of 4 contains a resonance at 6.58 ppm (JSiH 203 Hz), also
shifted upfield from the resonance of the Si-H group for 2
at 10.7 ppm. Interestingly, the phosphorus donors for the
ligand in 4 give rise to two distinct 31P{1H} NMR reso-
nances. The JPP coupling constant of 252 Hz is consistent
with a trans arrangement of the phosphorus atoms. The
inequivalence of phosphorus donors for 4 is attributed to the
presence of three different substituents on the silicon center,
which renders the P atoms diastereotopic.
The first example of a transition-metal silylene catalyst for
the hydrosilylation of alkenes was the base-stabilized ruthe-
nium silylene complex [Cp*(PiPr3)(H)2RudSiH(Ph)(OEt2)]-
[B(C6F5)4], which is a stable precatalyst due to weak binding
between diethyl ether and the silicon center.6 For compari-
son, Stradiotto and co-workers synthesized a base-stabilized
ruthenium silylene species supported by the P,N ligand
2-NMe2-2-PiPr2-indene (the amine on the ligand acts as a
Lewis base to the silicon), which is inactive for the hydro-
silylation of alkenes.14 Addition of 3 equiv of 1-hexene to
DMAP-stabilized silylene complex 4 gave no alkene inser-
tion after 2 days at 65 °C. In contrast, addition of 1-hexene to
[(PNP)(H)IrdSiMes(H)][B(C6F5)4] (2) in fluorobenzene at
ambient temperature results in instantaneous conversion to
[(PNP)(H)IrdSiMes(Hex)][B(C6F5)4].12a Thus, the inertness
of 4 toward reaction with 1-hexene supports the requirement
for kinetic availability of a base-free silylene ligand for
hydrosilylation to proceed.
Reactions of Iridium Silylene Complexes with Carbonyl
Compounds. The observed Lewis acidity of the silylene ligand
prompted investigations of the reactivity of 1 and 2 toward
other polar organic substrates that might be activated via
coordination to the silicon center. Initial efforts focused on
the reaction of hydrogen-substituted silylene 2 with a variety
of carbonyl compounds. To this end, addition of 1 equiv of
benzophenone to a solution of 2 in C6H5F afforded
[(PNP)(H)IrdSiMes(OC(H)Ph2)][B(C6F5)4] (5) as a dark
purple solid isolated in 94% yield (eq 3). This reaction is
analogous to that observed for 2 with alkene substrates to
afford disubstituted silylene ligands.12 Complex 5 exhibits
greater thermal stability than 2, as no decomposition was
observed in bromobenzene-d5 after 24 h at ambient temperature.
Results and Discussion
Reactions of Iridium Silylene Complexes with Lewis Bases.
The coordination of Lewis bases to a Lewis acidic silylene
ligand is a common reaction pathway encountered for
complexes of this type, reflecting considerable electrophilic
character for the silicon center.7 The behavior of 1 and 2
toward Lewis bases was investigated through reactions
with 4-dimethylaminopyridine (DMAP). Addition of
DMAP to 1 in C6H5F at ambient temperature produced
a color change from bright purple to red-violet. The base-
stabilized silylene complex [(PNP)(H)IrSiPh2(DMAP)]-
[B(C6F5)4] (3) was isolated in 82% yield as a red-violet
solid in analytically pure form after washing with pentane
(eq 2). Notably, the 29Si NMR spectrum of 3 contained
a single resonance at 8.7 ppm, over 250 ppm upfield
from that of the parent silylene species 1 (265 ppm).
This difference in chemical shift corresponds to quenc-
hing of the electronic unsaturation at silicon, as the
chemical shift for 3 is in the range usually associated with
a silyl ligand.13 The 1H NMR spectrum of 3 contained
(10) (a) Hashimoto, H.; Ochiai, M.; Tobita, H. J. Organomet. Chem.
2007, 692, 36–43. (b) Watanabe, T.; Hashimoto, H.; Tobita, H. J. Am. Chem.
2006, 128, 2176–2177. (c) Watanabe, T.; Hashimoto, H.; Tobita, H. J. Am.
Chem. Soc. 2007, 129, 11338–11339.
(11) (a) Ochiai, M.; Hashimoto, H.; Tobita, H. Dalton Trans. 2009,
1812–1814. (b) Ochiai, M.; Hashimoto, H.; Tobita, H. Angew. Chem., Int.
Ed. 2007, 46, 8192–8194.
(12) (a) Calimano, E.; Tilley, T. D. J. Am. Chem. Soc. 2008, 130,
9226–9227. (b) Calimano, E.; Tilley, T. D. J. Am. Chem. Soc. 2009, 131,
11161–11173.
(13) Corey, J. Y.; Braddock-Wilking, J. Chem. Rev. 1999, 99, 175–
292.
(14) Rankin, M. A.; MacLean, D. F.; Schatte, G.; McDonald, R.;
Stradiotto, M. J. Am. Chem. Soc. 2007, 129, 15855–15864.

1682 Organometallics, Vol. 29, No. 7, 2010
Calimano and Tilley
Scheme 1
The structure of 5 was confirmed through multinuclear
and 2D NMR experiments. The 1H NMR spectrum reveals a
resonance at 5.79 ppm corresponding to the CHPh2 proton,
corroborated by a correlation in the 2D 1H,13C{1H} HMQC
experiment with a signal at 84.8 ppm in the 13C{1H} NMR
spectrum. Other significant NMR characteristics include the
Ir-H resonance in the 1H NMR at -20.24 ppm, appearing
as a triplet due to couplings to phosphorus, and the silylene
ligand resonance in the 29Si NMR at 161.8 ppm. The upfield
shift of the 29Si NMR resonance of 5 in comparison to parent
complex 2 is consistent with a heteroatom substituent in the
silylene ligand, where π-donation of the oxygen lone pair to
the empty p-orbital on silicon reduces the electronic unsa-
turation at the silylene center.15
purple solid (eq 3). Complex 6 exhibits NMR resonances that
are analogous to those of [(PNP)(H)IrdSiMes(OC(H)Ph2)]-
[B(C6F5)4] (5), including a 1H NMR resonance at 4.48 ppm,
integrating to two protons, attributed to the benzylic group.
Similarly, a 13C{1H} NMR resonance at 72.2 ppm is attri-
buted to the benzylic carbon. The 29Si NMR resonance at
159.3 ppm is consistent with the presence of a heteroatom-
1
substituted silylene ligand. The H NMR spectrum of 6
exhibits an upfield resonance at -20.24 ppm for the iridium
hydride. Interestingly, this reaction requires strict control
of the stoichiometry of the carbonyl substrate, as addition
of 2 equiv of benzaldehyde resulted in a mixture of intract-
able products. In contrast, formation of complex 5 is
independent of the stoichiometry, as addition of 2 equiv
of benzophenone to 2 cleanly yielded only 5. Additionally,
reactions with enolizable carbonyl substrates such as acet-
one or acetophenone produced a mixture of organometallic
products.
The reactivity of PNP-supported iridium silylene complex
2 parallels reactivity previously documented for hydrogen-
substituted ruthenium and tungsten silylene species. The
reaction of hydrogen-substituted silylene complexes with
carbonyl substrates to afford heteroatom-substituted silylene
products has been reported for the reaction of Cp*(CO)2-
(H)WdSiH[C(SiMe3)3] with acetone16 and for reactions of
Cp*(CO)(H)RudSiH[C(SiMe3)3] with benzophenone, benzal-
dehyde, and propionaldehyde.11a
Several pathways are envisioned for reactions of carbonyl
substrates with 2 to give 5 and 6, and three of these
possibilities are depicted in Scheme 1. One pathway involves
direct addition of the carbonyl to the Si-H bond (path A). A
similar process is postulated for the reaction of hydrogen-
substituted silylene complex [Cp*(PiPr3)(H)2RudSiH(Ph)-
(OEt2)][B(C6F5)4] with alkenes, which is supported by
experimental and theoretical investigations.6,17 Note that
the reaction of path A could involve prior coordination
of the carbonyl group to silicon, before insertion into the
Si-H bond. A second path involves a [2þ2] cycloaddition to
Addition of benzophenone to 2 at -20 °C in fluoro-
benzene resulted in an intermediate color change to red-
violet followed by a change to bright purple upon slight
warming. The observation of an intermediate red-violet
color is consistent with the formation a base-stabilized
silylene complex. NMR studies in situ at -20 °C in bromo-
benzene-d5 revealed an intermediate complex containing a
resonance at -21.55 ppm for an Ir-H group. However, a
1
signal for the Si-H group was not identified in the H
NMR spectrum, and signals were not observed at this
temperature for the silylene ligand (in the 2D 1H,29Si
HMBC spectrum) or the PNP ligand (in the 31P NMR
spectrum), precluding further elucidation of the identity of
this intermediate.
Treatment of a solution of 2 in fluorobenzene with 1 equiv
of benzaldehyde resulted in formation of [(PNP)(H)Ird
SiMes(OCH2Ph)][B(C6F5)4] (6), isolated in 89% yield as a
(16) Watanabe, T.; Hashimoto, H.; Tobita, H. Angew. Chem., Int.
Ed. 2004, 43, 218–221.
(17) (a) Beddie, C.; Hall, M. B. J. Am. Chem. Soc. 2004, 126, 13564–
€
13565. (b) Bohme, U. J. Organomet. Chem. 2006, 691, 4400–4410.
(15) Wrackmeyer, B. Annu. Rep. NMR Spectrosc. 2006, 57, 1–49.

Article
Organometallics, Vol. 29, No. 7, 2010 1683
afford an intermediate metallacycle, which could reorganize
via reductive elimination of a C-H bond followed by
R-hydrogen migration (path B). The cycloaddition of a polar
substrate (isocyanates) to a silylene complex has previously
been documented, and experimental observations support a
stepwise addition involving initial formation of a base-
stabilized ruthenium silylene complex.9 A third pathway
involves formation of a base-stabilized silylene complex,
which activates the carbonyl substrate to subsequent reac-
tion with the hydride ligand at iridium, followed by
R-hydrogen migration (path C). Tobita et al. have proposed
pathways B and C for the reaction of Cp*(CO)(H)RudSiH-
[C(SiMe3)3] with ketones and aldehydes and favor path B
due to isolation of an intermediate featuring a Ru-C
bond.11a Furthermore, theoretical investigations for the
reaction of Cp*(CO)2(H)WdSiH[C(SiMe3)3] with acetone
support a mechanism similar to that presented in path C,
involving initial formation of a base-stabilized silylene com-
plex followed by nucleophilic attack of the transition-metal
hydride.18
It was envisioned that obtaining the kinetic isotope effect
for reactions of 2 with carbonyl compounds might aid in
elucidating the mechanism of this transformation. The
reaction of 2 with carbonyl compounds is fast (complete
conversion within 1 min at room temperature), which
makes direct measurements of the rates of reactions of 2
with carbonyl compounds difficult. Another method for
determination of kH/kD involves a competition experiment,
in which the carbonyl compound is allowed to react with
an excess of an equimolar 1:1 mixture of [(PNP)(H)Ird
SiMes(H)][B(C6F5)4] and [(PNP)(D)IrdSiMes(D)][B(C6F5)4].
Interestingly, combining [(PNP)(H)IrdSiMes(H)][B(C6F5)4]
and [(PNP)(D)IrdSiMes(D)][B(C6F5)4] in bromobenzene-d5
resulted in intermolecular scrambling to afford a mixture
of isotopomers within 10 min at ambient temperature. A
similar process for intermolecular redistribution of sub-
stituents between ruthenium silylene and silyl complexes
has previously been reported, but the intermolecular
scrambling of substituents between two silylene complexes
appears to be unknown.19 This rapid H/D scrambling
process precludes determination of a kinetic isotope effect
via a competition experiment.
is shifted to the silyl region. The 13C{1H} NMR spec-
trum reveals a signal for the carbonyl carbon of DMF at
165.2 ppm, confirming retention of the carbonyl moiety.
Thus, the NMR data suggest a saturated and tetrahedral
silicon center (sp3 hybridized) featuring a single bond
to iridium and a positive charge localized on the Lewis
base.
Reactions of the diphenyl-substituted silylene complex 1
toward carbonyl substrates were also explored. Analogous
to the reactivity of [(PNP)(H)IrdSiMes(H)][B(C6F5)4] (2),
treatment of a solution of 1 with 1 equiv of DMF resulted in
a color change to red-violet due to formation of [(PNP)(H)-
IrSiPh2(DMF)][B(C6F5)4] (8) (eq 4). Salient NMR features
for base-stabilized complex 8 include a 29Si NMR resonance
at 29.0 ppm attributed to the Lewis base adduct of the sily-
lene ligand, a 1H NMR resonance at 8.16 ppm for the alde-
hyde proton, a 1H NMR resonance at -19.02 for the
iridium hydride ligand, and a 13C{1H} NMR resonance at
164.9 for the carbonyl carbon. Similarly, addition of 1 equiv
of benzophenone to a solution of 1 in fluorobenzene
afforded [(PNP)(H)IrSiPh2(OCPh2)][B(C6F5)4] (9), isolated
in 93% yield after washing with pentane. The 29Si NMR
resonance for the silylene ligand appears relatively down-
field at 46.8 ppm presumably due to the weaker Lewis
basicity of benzophenone (vs DMAP and DMF). The
13C{1H} NMR spectrum exhibits a signal at 208.2 ppm
for the carbonyl carbon, corroborating the presence of a
carbonyl functionality.
In contrast, addition of 1 equiv of acetophenone to 1 in
fluorobenzene at ambient temperature resulted in a color
change to dark yellow, instead of the red-violet color ob-
served for base-stabilized silylene complexes. A dark yellow
solid identified as {(PNPH)IrH[SiPh2(OC(dCH2)Ph)]}-
[B(C6F5)4] (10) was isolated after precipitation from hexanes
followed by drying under vacuum (eq 5). Complex 10 con-
tains a protonated PNP ligand, an iridium hydride ligand,
and a silyl group that is substituted by the enolate derived
from acetophenone. These structural features were all deter-
mined by multinuclear and multidimensional NMR experi-
ments. The 1H NMR spectrum of 10 exhibits a broad signal
at 7.93 ppm for the NH group on the PNPH ligand, a broad
signal at 4.56 ppm for the alkene CH2 group, and an upfield
resonance at -17.69 for the hydride ligand. The 13C{1H}
NMR spectrum of 10 reveals a signal at 94.6 ppm for the
terminal alkene carbon correlating to the 1H NMR signal at
A series of base-stabilized silylene complexes were isolated
from reactions of 1 and 2 with other carbonyl compounds.
For example, addition of DMF to 2 affords base-stabilized
silylene complex [(PNP)(H)IrdSiMes(H)(DMF)][B(C6F5)4]
(7), instead of the disubstituted silylene complex {(PNP)-
(H)IrdSiMes[OCH2(NMe2)]}[B(C6F5)4] (eq 4). Complex 7
is red-violet, a characteristic color for the DMAP-stabilized
silylene complexes 3 and 4. Similarly, the NMR spectroscopy
for 7 reveals features similar to those of [(PNP)(H)IrSiMes-
1
(H)(DMAP)][B(C6F5)4] (4). The H NMR spectrum con-
tains a resonance at 6.19 ppm attributed to the Si-H group,
as indicated by observation of 29Si satellites (JSiH 207.5 Hz).
Similar to 4, the 31P{1H} NMR spectrum of 7 exhibits two
distinct resonances appearing as doublets for an unsymme-
trical PNP ligand, with a JPP coupling constant of 267 Hz,
consistent with a trans arrangement of the phosphorus
donors about iridium. The 29Si NMR resonance (13.8 ppm)
1
4.56 ppm in a 2D H,13C{1H} HMQC experiment. A 29Si
NMR resonance at -5.7 ppm was observed for the silyl
ligand of 10. In an attempt to determine the mechanism
for the formation of 10, a deuterium labeling experiment
was undertaken involving addition of acetophenone to the
deuterated silylene complex [(PNP)(D)IrdSiPh2][B(C6F5)4]
in bromobenzene-d5 or fluorobenzene. These experiments
resulted in significant deuterium incorporation into the NH,
IrH, and alkene positions for 10 after 10 min at ambient
(18) Zhang, X.-H.; Chung, L.-W.; Lin, Z.; Wu, Y.-D. J. Org. Chem.
2008, 73, 820–829.
(19) Grumbine, S. K.; Tilley, T. D. J. Am. Chem. Soc. 1994, 116,
6951–6952.

1684 Organometallics, Vol. 29, No. 7, 2010
Table 1. Summary of NMR Data for Compounds 11-14
Calimano and Tilley
compound
δ1H (IrH)
δ1H (PNPH)
δ29Si (IrSi)
-3.6
δ31P (PNP)
[(PNPH)IrH(SiPh2OArtBu)][B(C6F5)4]
(ArtBu = 3,5-tBu2C6H3) (11)
-17.36
7.83
48.5
[(PNPH)IrH(SiPh2OPh)][B(C6F5)4] (12)
[(PNPH)IrH(SiPh2OiPr)][B(C6F5)4] (13)
[(PNPH)IrH(SiPh2OtBu)][B(C6F5)4] (14)
-17.45
-17.63
-17.60
7.82
7.56
-3.3
-2.3
-14.8
48.0
47.9
45.5
7.16-7.08a
a Signal obscured by aromatic proton resonances.
temperature. The deuteration of the alkene could result from
reversible alkene insertion into the iridium hydride.
signals between -17.36 and -17.63 ppm for the iridium
hydride ligand and signals between 7.83 and 7.08 ppm for the
amine proton on the pincer ligand. The 29Si NMR resonance
for the alkoxysilyl ligand appears in the region of -14.8 to
-2.3 ppm. Interestingly, formation of the N-H bond could
allow bond activations that might otherwise require access to
high oxidation states, coordination numbers, and/or elec-
tron counts at the iridium center. The participation of this
PNP ligand in the reactivity of iridium complexes has been
previously observed in migratory insertions of silylene12b
and carbonyl ligands to the amido group.21
Reactions of silylene complexes with alcohols have been
documented previously.7b In some cases, such reactions
directly afford silyl ether products, via loss of the silylene
ligand from the metal center.19,22 For example, addition of
alcohols to [Cp*(PMe3)RuSiPh2(NCMe)][BPh4] afforded
the silyl ether product Ph2SiH(OR).19 In other instances,
the controlled addition of an alcohol substrate to a silylene
ligand resulted in OH addition across the MdSi bond to
produce alkoxysilyl and hydride ligands.7b Similar reactivity
has been documented for transition-metal germylene and
stannylene complexes.23
Three possible mechanisms for the reaction of alcohols
with 1 are depicted in Scheme 2. One pathway involves the
concerted addition of the O-H bond across the IrdSi double
bond, followed by migration of the resulting iridium hydride
to the amido group of the PNP ligand (path A). Alterna-
tively, the O-H activation can occur via path B, in which the
alcohol coordinates to the silicon center to form a base-
stabilized silylene complex, followed by deprotonation by
the amido nitrogen. Lastly, a third pathway involves a
process initiated by proton transfer from the alcohol to the
amido group, perhaps with significant, concurrent Si-O
bond formation (path C). In an attempt to distinguish
between these different pathways, deuterated 3,5-di-tert-
butylphenol was employed in this stoichiometric reaction.
NMR studies after 15 min at room temperature in bromo-
benzene-d5 revealed deuterium incorporation into both the
hydride and amine positions (approximately 45:55). Con-
ducting this experiment at -10 °C revealed similar values for
deuteration at the amine and hydride. This pattern is perhaps
most consistent with path A, as migration to the amine could
occur from either of the iridium hydride ligands, whereas
paths B and C would result in deuteration only at the amine
position. However, a separate, rapid scrambling process
could also account for the observed deuterium labeling
results. For example an intramolecular scrambling process,
The formation of 10 by activation of an enolizable ketone has
precedent in past studies of the reactivity of silylene ligands. The
first example of this reactivity described the formation of silyl
enol ethers from the reaction of acetophenone or acetone with
[Cp*(PMe3)2RudSiPh2(NCMe)][BPh4], but in this case an
intermediate adduct was not isolated.20 Furthermore, Tobita
et al. have recently published examples of similar reactions of
transition-metal silylene complexes with enolizable carbonyl
compounds.10c,11a For example, the reaction of Cp*(CO)-
(H)RudSiH[C(SiMe3)3] with acetophenone afforded Cp*-
(CO)(H)2Ru{Si(H)[OC(dCH2)Ph]C(SiMe3)3}, with NMR
characteristics similar to those observed for 10 including a
13C{1H} NMR resonance at 93.1 ppm for the terminal alkene
carbon. It is worth noting that the reaction of acetophenone with
1 results in formation of a N-H bond from participation of the
PNP ligand, whereas in the ruthenium complex the deprotona-
tion of acetophenone results in formation of a hydride ligand.
Reactions of Iridium Silylene Complexes with Alcohols and
Phenol Derivatives. Addition of 1 equiv of EtOH, PhOH, or
3,5-di-tert-butylphenol to 2 at ambient temperature afforded
mixtures of compounds. In contrast, 1 cleanly reacted with
an array of ROH substrates. Treatment of a solution of 1 in
fluorobenzene with 1 equiv of 3,5-di-tert-butylphenol pro-
duced a yellow compound, [(PNPH)IrH(SiPh2OArtBu)]-
[B(C6F5)4] (11, ArtBu = 3,5-tBu2C6H3), isolated in 94%
i
t
yield. Similarly, addition of PhOH, PrOH, or BuOH to
a solution of 1 in fluorobenzene afforded [(PNPH)IrH-
(SiPh2OPh)][B(C6F5)4] (12), [(PNPH)IrH(SiPh2OiPr)][B(C6-
F5)4] (13), and [(PNPH)IrH(SiPh2OtBu)][B(C6F5)4] (14),
respectively, in good yields as yellow solids (eq 6).
(21) Whited, M. T.; Grubbs, R. H. Organometallics 2008, 27, 5737–
5740.
(22) Feldman, J. D.; Mitchell, G. P.; Nolte, J.-N.; Tilley, T. D. J. Am.
The NMR data for complexes 11-14 are summarized in
Chem. Soc. 1998, 120, 11184–11185.
(23) (a) Schager, F.; Seevogel, K.; Porschke, K.-R.; Kessler, M.;
Table 1. The 1H NMR spectra for these compounds contain
€
€
Kruger, C. J. Am. Chem. Soc. 1996, 118, 13075–13076. (b) Hayes, P. G.;
Waterman, R.; Glaser, P. B.; Tilley, T. D. Organometallics 2009, 28, 5082–
5089.
(20) Zhang, C.; Grumbine, S. D.; Tilley, T. D. Polyhedron 1991, 10,
1173–1176.

Article
Organometallics, Vol. 29, No. 7, 2010 1685
Scheme 2
teristic NMR resonances confirm the activation of an N-H
bond of the aniline by 1. The H NMR spectrum for 16
1
reveals resonances at 7.79 and 4.58 ppm for the NH group
of the pincer ligand and anilide group, respectively. The
iridium hydride resonates at -17.99 ppm, with a small
coupling to silicon of 3 Hz, indicating minimal interaction
between the hydride and silylene ligand. Furthermore, the
29Si NMR shift at -16.5 ppm corroborates the formation
of a silyl ligand. Complex 1 was inert toward reaction with
Ph2NH in bromobenzene-d5 after 1 h at ambient tempera-
ture, suggesting a steric limitation to reactions of 1 with
amine substrates.
Catalytic Alcoholysis and Aminolysis of Silanes by
[(PNP)(H)IrdSiPh2][B(C6F5)4] (1). Given the stoichiometric
bond activations described above, it was of interest to
explore related catalytic transformations that might be
mediated by silylene complexes such as 1 and 2. An investi-
gation of catalytic alcoholysis of silanes by silylene com-
plexes focused on complex 1, as 2 did not afford clean
products in stoichiometric reactions with alcohols. Catalytic
runs were performed with 1-2 mol % loading of 1 in
bromobenzene-d5 at ambient temperature with a slight
molar excess of the alcohol substrate (Table 2). Vigorous
evolution of gas, identified as H2 by 1H NMR spectroscopy,
was observed upon combining both substrates with the
catalyst. Catalytic reactions involving Ph2SiH2 and a variety
of alcohol substrates were complete after 4 h at ambient
temperature (eq 8). The nature of the silane products
depended on the alcohol substrate. Only one silane product,
Ph2SiH(OR), was formed when 3,5-di-tert-butylphenol or
tert-butanol was used as substrate (in 92% and 77% yields by
NMR and GC-MS, respectively; entries a and b). With
2-propanol as a substrate, a trace amount of Ph2Si(OiPr)2
was observed by GC-MS in addition to Ph2SiH(OiPr)
(82% yield, entry c). The catalytic coupling of Ph2SiH2 and
methanol yielded a mixture of Ph2SiH(OMe) (70%)
and Ph2Si(OMe)2 (22%) after 3.5 h (entry d). Hence, the
secondary alcoholysis of Ph2SiH(OR) is sensitive to the steric
demands of the alkoxy group.
perhaps mediated by the formation a transient dihydrogen
complex of the type [(PNP)Ir(η2-H2)(SiPh2OR)][B(C6F5)4],
could lead to the observed ratio of N-D and Ir-D. Similar
reversible N-H bond formation has been proposed for
dihydrogen activation24 and in the transfer hydrogenation
of ketones with alcohols25 by transition-metal complexes
supported by similar PNP ligands.
Reactions of Iridium Silylene Complexes with Anilines. The
activation of O-H bonds by complex 1 prompted an in-
vestigation of similar transformations involving N-H
bonds. Treatment of 1 with 1 equiv of aniline afforded the
yellow compound [(PNPH)IrH(SiPh2NHPh)][B(C6F5)4]
1
(15), resulting from N-H activation (eq 7). The H NMR
spectrum of 15 contains a resonance at 7.78 ppm for the
N-H group on the pincer ligand and a resonance at
4.19 ppm for the anilide proton of the silyl ligand. The
iridium hydride resonance appears at -17.96 ppm, as a
broad triplet from coupling to phosphorus. A diagnostic
resonance at -21.9 ppm in the 29Si NMR spectra is consis-
tent with a silyl ligand (and a saturated silicon center).
The ability of tertiary silanes to undergo alcoholysis
was investigated with triphenylsilane and triethylsilane
substrates, in combination with 2-propanol. The reaction
involving triphenylsilane was slower than that of the corres-
ponding reaction with diphenylsilane. Incomplete conver-
sion was observed after 21 h at ambient temperature, to
afford a 45% yield of Ph3Si(OiPr) (entry e). Under the same
conditions, the triethylsilane substrate was completely con-
sumed after 21 h at ambient temperature, to afford Et3Si-
(OiPr) in a high 87% yield, as the only product observed by
NMR spectroscopy (entry f ). The ability of trisubstituted
silanes to act as substrates suggests that a silylene ligand is
not essential in this catalytic reaction. In fact, a 1 mol %
loading of (PNP)IrH(SiHPh2) with 3,5-di-tert-butylphenol
and diphenylsilane also resulted in formation of the alcoho-
lysis product, Ph2SiH(OR), in 96% yield within 23 h at
ambient temperature. However, (PNP)IrH(SiHPh2) is not
as active as 1 and requires longer reaction times for complete
conversion to product.
Similarly, treatment of 1 with 1 equiv of 3,5-(CF3)2C6H3-
NH2 afforded [(PNPH)IrH(SiPh2(NHArF))][B(C6F5)4] (16,
ArF = 3,5-(CF3)2C6H3) isolated in 88% yield. Similar charac-
(24) (a) Fryzuk, M. D.; MacNeil, P. A. Organometallics 1983, 2, 682–
684. (b) Fryzuk, M. D.; MacNeil, P. A.; Rettig, S. J. Organometallics 1985, 4,
1145–1147. (c) Fryzuk, M. D.; MacNeil, P. A.; Rettig, S. J. J. Am. Chem.
Soc. 1987, 109, 2803–2812. (d) Fryzuk, M. D.; Montgomery, C. D.; Rettig,
S. J. Organometallics 1991, 10, 467–473. (e) Ozerov, O. V.; Huffman, J. C.;
€
Watson, L. A.; Caulton, K. G. Organometallics 2003, 2539–2541. (f ) Kass,
M.; Friedrich, A.; Drees, M.; Schneider, S. Angew. Chem., Int. Ed. 2008, 48,
905–907.
(25) (a) Clarke, Z. E.; Maragh, P. T.; Dasgupta, T. P.; Gusev, D. G.;
Lough, A. J.; Abdur-Rashid, K. Organometallics 2006, 25, 4113–4117.
(b) Bi, S.; Xie, Q.; Zhao, X.; Zhao, Y.; Kong, X. J. Organomet. Chem. 2008,
693, 633–638. (c) Chen, X.; Jia, W.; Guo, R.; Graham, T. W.; Gullons, M. A.;
Abdur-Rashid, K. Dalton Trans. 2009, 1407–1410.

1686 Organometallics, Vol. 29, No. 7, 2010
Table 2. Catalytic Results for the Alcoholysis of Silanes by 2
Calimano and Tilley
entry
silane
ROH
[1] mol %
time (h)
products (yield)
a
b
c
H2SiPh2
H2SiPh2
H2SiPh2
R = 3,5-tBu2C6H3
R = tBu
1
1
1
4
4
4
Ph2SiH(OR) (92%)
Ph2SiH(OR) (77%)
Ph2SiH(OR) (84%)
Ph2Si(OR)2 (trace)
Ph2SiH(OR) (70%)
Ph2Si(OR)2 (22%)
Ph3Si(OR) (45%)
Et3Si(OR) (87%)
R = iPr
d
H2SiPh2
R = Me
1
3.5
e
f
HSiPh3
HSiEt3
R = iPr
R = iPr
2
2
21
21
Scheme 3
involves the loss of dihydrogen to form silyl intermediate D,
which could be in equilibrium with silylene complex 1 via a
reversible R-migration. However, as tertiary silanes are
suitable substrates in this process, the silylene intermediate
is not necessary for the reaction with alcohols. Hence, it is
proposed that species D could directly react with alcohols to
produce species of type A. Previous mechanistic studies on
silane alcoholysis by late transition-metal catalysts suggest
that formation of the silyl ether product might proceed via
nucleophilic attack of an alcohol onto an activated silane in
the coordination sphere of the metal.26 Usually the silicon
center is activated toward attack via oxidative addition of the
Si-H bond to the transition-metal center to afford a silyl
hydride intermediate or by the formation of an η2-silane
complex on an electrophilic transition-metal center.26 Thus,
direct reaction of alcohol with species such as D may proceed
via nucleophilic attack of the alcohol onto silicon, and this is
consistent with the conversion of tertiary silanes to R3SiOR
products, and secondary silanes to Ph2Si(OR)2 products. A
similar mechanism may be proposed for the dehydrogenative
coupling of silanes with amines by 1. Interestingly, the
catalytic reaction of H2NArF (ArF = 3,5-(CF3)2C6H3) with
silanes was significantly slower than that of aniline, suggest-
ing that the nucleophilicity of the amine is tied to the reaction
rate of these catalytic processes.
A series of NMR experiments were undertaken to eluci-
date the nature of organometallic species under catalytic
conditions in the coupling of diphenylsilane with 3,5-di-tert-
butylphenol (using 1 to 5 mol % loading of 1). After 1 h at
room temperature in bromobenzene-d5, 31P{1H} NMR spec-
tra of the reaction mixture revealed the presence of an
unidentified species with a resonance at 34.8 ppm. Attempts
to isolate this intermediate by precipitation of the reaction
mixture from hexanes resulted in isolation of a mixture
of organometallic species, containing [(PNPH)IrH(SiPh2-
OArtBu)][B(C6F5)4] (11, ArtBu = 3,5-tBu2C6H3) as the major
species. Similarly, in a separate experiment, the 31P{1H}
NMR spectrum of this catalytic reaction after 4 h revealed
only one species, [(PNPH)IrH(SiPh2OArtBu)][B(C6F5)4] (11,
ArtBu = 3,5-tBu2C6H3) (after complete consumption of
silane product). The 31P{1H} NMR spectra for reactions
with diphenylsilane and other alcohol substrates exhibited
similar resonances appearing between 33 and 37 ppm, for
related organometallic intermediates. Hence, these reactions
have separate intermediates, as indicated by the different
chemical shifts depending on alcohol substrate. These inter-
mediates might arise from the binding of alcohols to tran-
sient species (such as B and D) in the catalytic cycle presented
in Scheme 3.
The catalytic reaction of silanes with anilines using 1 as a
catalyst resulted in formation of silyl amine compounds,
analogous to the formation of silyl ethers via catalytic
alcoholysis. Catalytic runs involved a slight excess of amine
and a 1 mol % loading of 1 in bromobenzene-d5. Upon
combining both substrates with the catalyst, evolution of H2
gas was observed. Catalytic runs with H2NPh were complete
after 5 h and gave Ph2SiH(NHPh) in 85% yield (versus
integration with an internal standard). Catalysis using
H2NArF (ArF = 3,5-(CF3)2C6H3) as a substrate resulted in
slower conversion in comparison to H2NPh. After 5 h at
ambient temperature, a 48% yield of Ph2SiH(NHArF) was
observed, yet high yields of the product (92%) were obtained
after 21 h. This catalytic process is also promoted by
(PNP)IrH(SiHPh2), although slow product formation was
observed with H2SiPh2 and H2NPh substrates (only 27%
yield after 21 h under the same conditions). Thus, in both the
dehydrogenative coupling of silanes with alcohols and
amines, it appears that the silylene ligand is not required.
A simplified mechanism for the alcoholysis of diphenyl-
silane by 1 is depicted in Scheme 3. Addition of alcohol to
silylene complex 1 would afford a complex of the type
[(PNPH)IrH(SiPh2OR)][B(C6F5)4] (A), as described above
for the stoichiometric reaction of 1 with alcohols. The next
step could involve reductive elimination of the silyl ether to
afford hydride intermediate B. However, as complexes 11 to
14 are stable in solution at ambient temperature (>2 weeks),
this product-forming step may proceed through an associa-
tive mechanism via attack of a silane substrate. In support of
this, reaction of 1 equiv of H2SiPh2 with [(PNPH)IrH(SiPh2-
OArtBu)][B(C6F5)4] (ArtBu = 3,5-di-tert-butylphenyl, 11) in
bromobenzene-d5 results in the release of a substoichiometric
amount (52%) of Ph2SiH(OArtBu) after 10 min at ambient
temperature. The next step in the proposed catalytic cycle
involves activation of the silane substrate via oxidative
addition of an Si-H bond, to afford the Ir(V) silyl dihydride
intermediate C. Alternatively, participation of the PNP
ligand in bond activation could provide a lower energy
pathway (compared to that involving the high oxidation
state of intermediate C), to afford instead an Ir(III) complex
of the type [(PNPH)IrH(SiPh2H)][B(C6F5)4]. The next step
(26) (a) Luo, X.-L.; Crabtree, R. H. J. Am. Chem. Soc. 1989, 111,
2527–2535. (b) Doyle, M. P.; High, K. G.; Bagheri, V.; Pieters, R. J.; Lewis,
P. J.; Pearson, M. M. J. Org. Chem. 1990, 6082–6086. (c) Corbin, R. A.;
Ison, E. A.; Abu-Omar, M. M. Dalton Trans. 2009, 2850–2855.

Article
Organometallics, Vol. 29, No. 7, 2010 1687
Table 3. Catalytic Results for the Hydrosilylation of Ketones by 1 and 2a
entry
silane
ketone
catalyst
time (h)
products (yield)
a
b
c
H2SiPh2
H2SiPh2
H2SiPh2
H2SiPh2
benzophenone
benzophenone
benzophenone
acetophenone
2
2
1
1
5
5
4.5
5
Ph2SiH[OC(H)Ph2] (90%)b
Ph2SiH[OC(H)Ph2] (67%)c
Ph2SiH[OC(H)Ph2] (88%)
Ph2SiH[OCH(Me)(Ph)] (48%)
Ph2SiH[OC(dCH2)Ph] (23%)
d
a Catalytic trials conducted with a 1 mol % loading of catalyst in bromobenzene-d5 at room temperature; yields were determined by integration
against an internal standard by 1H NMR spectroscopy. b Order of addition: silane, catalyst, benzophenone, standard. c Order of addition:
benzophenone, catalyst, silane, standard.
Catalytic Ketone Hydrosilylation by [(PNP)(H)IrdSiPh2]-
[B(C6F5)4] (1) and [(PNP)(H)IrdSiMes(H)][B(C6F5)4] (2).
The reaction of 2 with benzophenone and benzaldehyde, to
afford [(PNP)(H)IrdSiMes(OC(H)Ph2)][B(C6F5)4] (5) and
[(PNP)(H)IrdSiMes(OCH2Ph)][B(C6F5)4] (6), motivated
further studies of the ability of silylene complexes to catalyze
the hydrosilylation of carbonyl compounds. Complex 2
was previously studied as a catalyst for the hydrosilylation
of alkenes, and it was of interest to examine the generality
of 2 in hydrosilylation catalysis with other substrates.
Interestingly, complex 2 is not a viable catalyst for the
hydrosilylation of benzaldehyde, as addition of more than
stoichiometric amounts of benzaldehyde to 2 resulted in
decomposition to multiple iridium-containing products
and a color change to yellow-green. Attempts at catalysis
using benzaldehyde as a substrate with equimolar amounts
of H3SiMes and a 1 mol % loading of 2 in bromobenzene-d5
yielded a mixture of silane products, including some inso-
luble material. The mixture of silanes obtained could not be
identified by NMR spectroscopy or GC-MS.
addition of acetophenone gave a mixture of major silane
products after 5 h, identified as Ph2SiH[OCH(Me)(Ph)] and
Ph2SiH[OC(dCH2)Ph] in 48% and 23% yield, respectively
(entry d). Gas evolution was observed upon combining
acetophenone with the silane and catalyst, presumably H2
gas as a byproduct from formation of the Ph2SiH[OC-
(dCH2)Ph] minor product (low concentrations precluded
1
confirmation by H NMR spectroscopy). The catalytic hy-
drosilylation of acetophenone with diphenylsilane to afford
moderate yields of Ph2SiH[OCH(Me)(Ph)] was previously
reported employing the silylene complex [Cp*(PMe3)(H)Ird
SiPh2][B(C6F5)4] as a precatalyst.27 For this ketone hydro-
silylation, (PNP)IrH(SiHPh2) (1 mol %, bromobenzene-d5) is
not a catalyst at room temperature or after heating to 60 °C
for 15 h. However, formation of Ph2SiH[OC(H)Ph2] (23%)
and other unidentified minor products was observed after
heating at 90 °C for 48 h.
Two possible mechanisms for the hydrosilylation of
ketones by 1 are depicted in Scheme 4. In the first step in
the mechanism of route A, R-migration from iridium silylene
complex 1 generates a transient silyl complex (A). Sub-
sequent steps involve the coordination of ketone to an empty
coordination site on iridium (B), followed by insertion into
the Ir-Si bond to generate an iridium alkyl complex (C). The
release of product could then proceed via activation of silane
substrate by Si-H oxidative addition, followed by reduc-
tive elimination of the product, to complete the catalytic
cycle. Similar mechanisms involving insertion of a ketone
into a silyl ligand have been proposed in other transition-
metal-catalyzed hydrosilylation reactions and was first pro-
posed by Ojima et al. for rhodium complexes supported by
chiral phosphine ligands.28
A second possible mechanism, depicted in route B of
Scheme 4, proceeds via a silylene complex and alludes to
the postulated mechanisms for the stoichiometric hydrosily-
lation reactions of hydrogen-substituted silylene complex 1
with carbonyl compounds. As secondary silanes are viable
substrates for this reaction, a mechanism involving the direct
insertion of ketone into the Si-H bond of the silylene ligand
is excluded from this discussion (see Scheme 1, path A). The
first steps involve coordination of the ketone substrate to the
iridium silylene complex to form a base-stabilized silylene
ligand (E). Similar complexes were isolated from the stoi-
chiometric reaction of 1 with DMF and benzophenone to
afford base-stabilized silylene complexes 8 and 9, respec-
tively. Coordination of the ketone to the Lewis basic silylene
ligand could activate the carbonyl substrate to further reac-
tions by rendering the carbonyl carbon more electrophilic.
As a next step in this mechanism, the iridium hydride is
As stoichiometric studies of 2 with benzophenone demon-
strated tolerance to excess benzophenone, it was of interest
to evaluate the viability of 2 as a catalyst for the hydrosilyla-
tion of benzophenone (Table 3). Catalytic trials using ben-
zophenone and MesSiH3 at ambient temperature resulted in
a mixture of silane products after 4.5 h at room temperature.
GC-MS confirmed that one of the silane products is Mes2-
SiH2, from catalytic redistribution, which was previously
documented for this system.12 When employing H2SiPh2 as a
substrate, the catalytic production of one major silane
product, HSiPh2[OC(H)Ph2], was observed in high yield
after 5 h at ambient temperature (90%, entry a). Notably,
the rate of reaction was observed to be dependent on the
order of addition of the silane substrates. When a solution
of benzophenone was first added to 2 followed by silane,
only 67% of the silane product was produced after 5 h at
room temperature, and the remaining H2SiPh2 substrate was
1
observed in the H NMR spectrum (entry b). In contrast,
when a solution of H2SiPh2 was first added to 2 followed
by benzophenone, complete conversion to product was
observed after 5 h at ambient temperature (90% yield, entry a).
The coordination of benzophenone to 1 to form a base-
stabilized silylene complex was also insensitive to addition of
excess benzophenone. It was envisioned that the strong Lewis
acidity of the silylene ligand could activate the carbonyl
substrate upon coordination to the silicon center. To this
end, complex 1 was studied as a catalyst for the hydrosilyla-
tion of ketones. The catalytic trials were conducted at ambient
temperature using a 1 mol % loading of 1 in bromobenzene-d5
with equimolar amounts of diphenylsilane and ketone sub-
strates. The catalytic reaction with benzophenone as a sub-
strate was complete within 4.5 h to afford Ph2SiH[OC(H)Ph2]
(determinedbyNMR andGC-MS, 88%, entry c). Incontrast,
(27) Klei, S. R.; Tilley, T. D.; Bergman, R. G. Organometallics 2002,
21, 4648–4661.
(28) Ojima, I.; Kogure, T.; Kumagai, M.; Horiuchi, S.; Sato, T.
J. Organomet. Chem. 1976, 122, 83–97.

1688 Organometallics, Vol. 29, No. 7, 2010
Calimano and Tilley
Scheme 4
transferred to the carbonyl group via a transition state
containing a five-membered ring (F) to afford a silyl inter-
mediate (H). Alternatively, a [2þ2] cycloaddition of the
carbonyl to produce intermediate G followed by C-H
reductive elimination would afford a silyl intermediate (H).
Subsequent steps include Si-H oxidative addition of diphe-
nylsilane to form disilyl hydride complex I, followed by
Si-H reductive elimination to release product. A final R-
migration regenerates the silylene catalyst and completes the
catalytic cycle. Notably, recent theoretical studies on ketone
hydrosilylation catalyzed by oxazolinylcarbene-rhodium
complexes implicate a mechanism analogous to route B,
which proceeds via the formation of a transient rhodium
silylene complex and hydride transfer through a transition
state analogous to F.29
In order to differentiate between the two mechanisms
proposed, a deuterium labeling experiment was designed
involving [(PNP)(D)IrdSiPh2][B(C6F5)4]. A solution of ben-
zophenone (1 equiv) in bromobenzene-d5 or fluorobenzene
was added to [(PNP)(D)IrdSiPh2][B(C6F5)4] (1 equiv) at
room temperature, and after 2 min the benzophenone was
completely consumed to afford [(PNP)(D)IrSiPh2(OCPh2)]-
[B(C6F5)4] (9-d1). The resulting solution of 9-d1 was then
added to H2SiPh2 (1 equiv). The reaction mixture was
monitored by 1H NMR (for the bromobenzene-d5 solution)
and 2H NMR spectroscopy (for the fluorobenzene solution)
after 10 to 15 min at ambient temperature. It was envisioned
that the product of this reaction would be Ph2SiD[OC(H)Ph2]
if route A was operative or Ph2SiH[OC(D)Ph2] if route B
2
was operative. Interestingly, the H NMR spectra revealed
resonances for both Si-H and C-H groups of the silyl
ether product and the Si-H group of unreacted H2SiPh2
substrate. In addition, scrambling of deuterium into the
2
aliphatic and aromatic regions of the H NMR spectrum
indicates participation of the PNP ligand in this chemistry.
Thus, this labeling experiment does not provide insight
into the mechanism of the hydrosilylation and suggests the
occurrence of additional and/or competitive pathways in
this reaction. Additionally, the organometallic species in
solution under catalytic conditions were monitored by
NMR spectroscopy using a 10 mol % loading of 1 with
diphenylsilane and benzophenone substrates in bromo-
1
benzene-d5. After 10 min at ambient temperature, the H
and 31P{1H} NMR spectra of the reaction mixture revealed
the presence of base-stabilized complex 9 as the major
species, along with an unidentified species containing
a
31P{1H} NMR resonance at 34.4 ppm, and several
other iridium-containing minor products. Note that the
observed coordination of ketone to the silylene center does
not exclude route A, as E could be in equilibrium with silyl
intermediate B (Scheme 4).
Concluding Remarks
With the development of synthetic routes to transition-
metal silylene complexes, research efforts are now targeting
investigations of the stoichiometric and catalytic reactivity
for these species. These studies have established potential
modes of reactivity for these species, and it is clear that the
(29) Schneider, N.; Finger, M.; Haferkemper, C.; Bellemin-Laponnaz,
S.; Hofmann, P.; Gade, L. H. Angew. Chem., Int. Ed. 2009, 48, 1609–1613.

Article
Organometallics, Vol. 29, No. 7, 2010 1689
steric and electronic properties of the metal-based fragment
can play a large role in the observed chemistry of the silylene
ligand. In this contribution, the stoichiometric reactivity
of [(PNP)(H)IrdSiPh2][B(C6F5)4] (1) and [(PNP)(H)Ird
SiMes(H)][B(C6F5)4] (2) toward Lewis bases, alcohols,
amines, and carbonyl compounds was described. The reac-
tion of silylene complexes with Lewis bases has significant
precedence, but there is still much to be learned concerning
the activation of polar substrates by interactions with the
Lewis acidic silicon center of a silylene ligand.
Examination of the catalytic properties of silylene com-
plex 1 with alcohols, amines, and carbonyl compounds
demonstrates potential applications for new transforma-
tions of organosilicon species. In related studies, hydrogen-
substituted complex 2 has been shown to be effective for
alkene hydrosilylations.12b As described here, complex 1
serves as a catalyst for the alcoholysis or aminolysis of silanes
and for the hydrosilylation of ketones. Complexes 1 and 2
contain a Lewis acid functionality (the silylene ligand) and a
Lewis base functionality (the amido nitrogen). Participation of
the amido group of the PNP ligand appears to allow access to
transformations that would otherwise require high oxidation
states and coordination numbers at the iridium center. In
addition, the amido group may serve as a Brønsted base to
activate protic substrates and promote further reactivity at the
silylene center, as proposed for reaction of alcohols and amines
with 1. In summary, a major theme evolving from these studies
is the cooperative participation of silylene and amido ligands in
the activation of substrates in stoichiometric and catalytic
transformations. This theme can help motivate the design of
related transition-metal catalysts that take advantage of the
cooperation of Lewis acidic and Brønsted basic ligand centers
within the coordination sphere of the metal.30
unless specified otherwise. All spectra were recorded at room
temperature unless otherwise noted. Complex multiplets are
noted as “m” and broad resonances as “br”. In 13C{1H} NMR
spectra resonances obscured by the solvent signal are omitted.
Elemental analyses were performed by the College of Chemistry
Microanalytical Laboratory at the University of California,
Berkeley.
[(PNP)(H)IrSiPh2(DMAP)][B(C6F5)4] (3). In the drybox, a
solution of 4-dimethylaminopyridine (DMAP) (0.006 g, 0.047
mmol) in 0.5 mL of C6H5F was added to a solution of 1 (0.070 g,
0.047 mmol) in 0.5 mL of C6H5F. Upon addition of the DMAP,
a color change from purple to red-violet was observed. After
2 min of mixing by taking the fluorobenzene solution into a pipet
and redispensing it into the reaction vessel, the solution was
added to pentane (15 mL) and placed in the -30 °C freezer for
1 h to allow a dark red-violet oil to settle out of the reaction
mixture. A red-violet oil was collected by decanting the super-
natant and dried under vacuum to give a burgundy solid. Yield:
0.062 mg (82%). 1H NMR (C6D5Br, 500 MHz): δ 8.26 (2H, br,
ArH ), 7.60 (4H, d, J = 6.6 Hz, ArH ), 7.56 (2H, d, J = 8.5 Hz,
ArH ), 7.25 (6H, ov m, ArH ), 7.03 (2H, s, ArH ), 6.98 (2H, d, J
= 8.5 Hz, ArH ), 6.04 (2H, d, J = 7.2 Hz), 2.35 (6H, s, NMe2),
2.23 (6H, s, ArMe), 2.19 (2 h, br m, CHMe2), 1.21 (2H, br m,
CHMe2), 0.93 (18H, ov m, CHMe2), 0.60 (6H, m, CHMe2),
2
2
-20.32 (1H, t, JPH = 8.4 Hz, JSiH = 3 Hz, IrH ). 13C{1H}
NMR (C6D5Br, 125.8 MHz): δ 162.1 (t, JCP = 9.7 Hz), 156.3 (s),
150.1 (br m), 148.0 (br m), 140.0 (br m), 137.9 (br m), 136.0 (br
m) 135.7 (s), 132.8 (s), 132.7 (s), 129.3 (br m), 128.2 (s), 123.4 (t,
JCP = 22.5), 116.3 (br m), 106.3 (s) (ArC), 39.2 (s, NMe2),
27.9 (t, JCP = 17.0 Hz), 22.5 (t, JCP = 13.7 Hz), 20.9 (s, ArMe),
20.7 (s, CHMe2), 19.5 (s, CHMe2), 18.8 (s, CHMe2), 17.1 (s,
CHMe2). 31P{1H} NMR (C6D5Br, 202.5 MHz): δ 45.3 (s). 29Si
NMR (C6D5Br, 99.4 MHz): δ 8.7. Anal. Calcd for C69H61N3-
BF20IrP2Si: C, 51.63; H, 3.83; N, 2.62. Found: C, 51.70; H, 3.82;
N, 2.88.
[(PNP)(H)IrSiMes(H)(DMAP)][B(C6F5)4] (4). In the drybox,
a solution of 4-dimethylaminopyridine (DMAP) (0.008 g, 0.069
mmol) in 0.5 mL of C6H5F was added to a solution of 2 (0.100 g,
0.069 mmol) in 0.5 mL of C6H5F. Upon addition of the DMAP,
a color change from blue-green to a violet-red color was
observed. After 2 min of mixing by taking the fluorobenzene
solution into a pipet and redispensing it into the reaction vessel,
the solution was added to pentane (15 mL) and placed in the
-30 °C freezer for 1 h to allow a violet-red oil to settle out of the
reaction mixture. A violet-red oil was collected by decanting the
supernatant and dried under vacuum to give a burgundy solid.
Yield = 0.099 g (91%). 1H NMR (C6D5Br, 500 MHz): δ 8.02
(2H, br s, DMAP), 7.53 (1H, d, J = 7.0 Hz, ArH ), 7.48 (1H, d,
J = 7.1 Hz, ArH ), 7.01 (1H, d, J = 8.4 Hz, ArH ), 6.96 (3H, m,
ArH ), 6.78 (2H, s, ArH ), 6.58 (1H, br s, 1JSiH = 203 Hz, SiH ),
6.01 (2H, d, J = 6.4 Hz, DMAP), 2.38 (6H, s, NMe2), 2.28 (6H,
s, ArMe), 2.24 (3H, s, ArMe), 2.20 (6H, s, ArMe), 2.38-2.20
(3H, under methyl resonances, CHMe2), 2.10 (1H, br, CHMe2),
1.14 (3H, br m, CHMe2), 1.10-0.90 (9H, ov br m, CHMe2),
0.85-0.81 (6H, ov br m, CHMe2), 0.73-0.68 (6H, ov br m,
CHMe2), -21.18 (1H, br s, IrH ). 13C{1H} NMR (C6D5Br,
125.8 MHz): δ 161.8 (br m), 156.1 (s), 150.0 (br m), 148.1 (br m),
145.3 (br m), 143.8 (br m), 140.8 (s), 139.9 (br m), 137.9 (br m),
136.0 (br m), 133.3 (d, JCP = 37.6 Hz), 132.4 (s), 132.0 (s), 128.2
(br m), 118.4 (br m), 113.7 (br m), 107.3 (s) (ArC), 39.2 (s,
Experimental Section
General Considerations. All experiments were carried out
under a nitrogen atmosphere using standard Schlenk techniques
or an inert atmosphere (N2) glovebox. Olefin impurities were
removed from pentane by treatment with concentrated H2SO4,
0.5 N KMnO4 in 3 M H2SO4, and NaHCO3. Pentane was then
˚
dried over MgSO4 and stored over activated 4 A molecular
sieves. Pentane and hexanes were dried by distilling from Na.
Fluorobenzene was dried by vacuum distillation from CaH2.
C6D5Br was refluxed over CaH2 for 20 h and then distilled under
nitrogen. [(PNP)(H)IrdSiMes(H)][B(C6F5)4] (2)12a and [(PNP)-
(H)IrdSiPh2][B(C6F5)4] (1)12b were prepared according to lite-
rature methods. [(PNP)(D)IrdSiPh2][B(C6F5)4] was prepared
by addition of [CPh3][B(C6F5)4] to (PNP)IrD(SiPh2D) follow-
ing analogous procedures detailed for 1. (PNP)IrD(SiPh2D) was
in turn synthesized from the reaction of D2SiPh2 with (PNP)Ir-
(COE).12b DMAP, 3,5-di-tert-butylphenol, and benzophenone
were purified by sublimation. Other alcohol, amine, and carbonyl
reagents were degassed and dried over molecular sieves.
NMR spectra were recorded using Bruker DRX-500,
AV-500, AVB-400, AVQ-400, and AV-600 spectrometers. H
1
NMR spectra were referenced internally to the residual solvent
proton signal relative to tetramethylsilane. 13C{1H} NMR
spectra were referenced internally relative to the 13C signal of
the NMR solvent relative to tetramethylsilane. 31P{1H} spectra
were referenced relative to an 85% H3PO4 external standard.
29Si NMR spectra were referenced relative to a tetramethylsi-
lane external standard and obtained via 2D 1H 29Si HMBC
NMe2), 29.7 (br d, JCP = 28.3 Hz, CHMe2), 25.5 (br d, JCP
=
29.8 Hz, CHMe2), 24.5 (br d, JCP = 33.2 Hz, CHMe2), 23.3
(br m, CHMe2), 21.4 (s, ArMe), 12.4 (br s, under methyl
resonance, CHMe2), 20.9 (s, ArMe), 20.8 (s, ArMe), 19.2 (br s,
CHMe2), 19.0 (s, CHMe2), 18.0 (br s, CHMe2), 17.1 (br s,
CHMe2), 17.0 (br s, CHMe2), 16.9 (br s, CHMe2). 31P{1H}
NMR (C6D5Br, 202.5 MHz): δ 50.8, 49.5, 46.2, 44.8 (AB spin
system, two d, 2JPP = 272 Hz). 29Si NMR (C6D5Br, 99.4 MHz):
δ -12.1. Anal. Calcd for C66H63N3BF20IrP2Si: C, 50.45; H,
4.04; N, 2.67. Found: C, 50.76; H, 3.79; N, 2.84.
(30) For a review of amphoteric ligands containing both Lewis basic
and Lewis acidic sites see: Fontaine, F.-G.; Boudreau, J.; Thibault,
M.-H. Eur. J. Inorg. Chem. 2008, 5439-5454, and references therein.

1690 Organometallics, Vol. 29, No. 7, 2010
Calimano and Tilley
[(PNP)(H)IrdSiMes(OCHPh2)][B(C6F5)4] (5). In the drybox,
a solution of benzophenone (0.009 g, 0.052 mmol) in 0.5 mL of
C6H5F was added to a solution of 2 (0.075 g, 0.052 mmol) in
0.5 mL of C6H5F. Upon addition of benzophenone at ambient
temperature, a color change to bright purple was observed.
After 2 min of mixing by taking the fluorobenzene solution
into a pipet and redispensing it into the reaction vessel, the
solution was added to pentane (10 mL) and placed in the -30 °C
freezer for 1 h to allow a violet oil to separate. The pentane/
fluorobenzene is decanted away, and the remaining oil
was dried under vacuum for 1 h to afford 5 as a purple solid.
Yield = 0.081 g (94%). 1H NMR (C6D5Br, 500 MHz): δ 7.42
(2H, d, J = 8.5 Hz, ArH ), 7.22 (6H, ov m, ArH ), 7.17 (2H, t,
J = 7.7 Hz, ArH), 7.11 (4H, d, J = 6.8 Hz, ArH ), 7.02 (2H, s,
ArH ), 6.91 (2H, J = 8.4 Hz, ArH), 6.67 (2H, s, ArH ), 5.79 (1H,
s, CHPh2), 2.29 (2H, m, CHMe2), 2.24 (6H, s, ArMe), 2.15 (3H,
s, ArMe), 2.14 (6H, brs, ArMe), 2.05 (2H, m, CHMe2), 1.19 (6H,
m, CHMe2), 0.91 (6H, m, CHMe2), 0.74 (6H, m, CHMe2), 0.54
(6H, m, CHMe2), -20.24 (1H, t, 2JPH = 7.8 Hz, IrH ). 13C{1H}
NMR (C6D5Br, 125.8 MHz): δ 162.5 (t, JCP = 10.1 Hz), 150.0
(br m), 148.1 (br m), 144.5 (s), 140.2 (s), 139.9 (br m), 137.9 (br
m), 136.1 (br m), 133.4 (s), 133.3 (s), 132.8 (s), 131.1 (s), 129.4
under vacuum to give a burgundy solid. Yield = 0.10 g (93%). 1H
NMR (C6D5Br, 500 MHz): δ 7.87 (1H, s, HCdO), 7.46 (2H, m,
ArH), 7.05-6.99 (2H, m, ArH ), 6.93 (2H, br d, J=8.4 Hz, ArH),
6.73 (2H, s, ArH ), 6.19 (1H, t, JPH = 5.6 Hz, 1JSiH = 207.5 Hz,
SiH ), 2.69 (3H, s, NMe), 2.38 (9H, br s, NMe þ ArMe), 2.27
(3H, s, ArMe), 2.25 (3H, s, ArMe), 2.08 (3H, s, ArMe), 2.3-2.1
(4H, under methyl resonances, CHMe2), 1.15 (6H, ov dd,
CHMe2), 1.05 (3H, dd, JHH = 6.8 Hz, JPH = 16.6 Hz, CHMe),
0.98-0.85 (9H, ov dd, CHMe2), 0.77 (3H, dd, JHH = 6.7 Hz,
JPH = 16.5 Hz, CHMe2), 0.70 (3H, dd, JHH = 6.7 Hz, JPH = 15.9
Hz, CHMe2), -20.85 (1H, t, 2JPH = 8.5 Hz, IrH). 13C{1H} NMR
(C6D5Br, 125.8 MHz): δ 165.2 (s, HCdO), 162.3 (m), 150.0 (br m),
148.1 (br m), 143.0 (s), 141.1 (s), 139.8 (br m), 138.0 (br m), 136.0 (br
m), 133.2 (d, JCP = 32.5 Hz), 132.4 (d, JCP = 17.0 Hz), 128.7 (d,
JCP = 6.1 Hz), 123.5 (d, JCP = 43.0 Hz), 122.0 (d, JCP = 43.9 Hz),
118.1 (d, JCP = 10.2 Hz), 114.4 (d, JCP = 10.7 Hz) (ArC), 40.2 (s,
NMe), 35.5 (s, NMe), 29.0 (d, JCP = 27.1 Hz, CHMe2), 25.6 (d,
JCP = 23.9 Hz, CHMe2), 24.7 (d, JCP = 32.1 Hz, CHMe2), 23.4 (br
s, ArMe), 22.0 (d, JCP = 23.5 Hz, CHMe2), 21.4 (s, ArMe), 21.3 (d,
CHMe2),20.8(s,ArMe), 19.1 (s, CHMe2), 18.9 (s, CHMe2), 18.8 (d,
CHMe2), 18.7 (d, CHMe2), 17.8(brs, CHMe2), 17.1(brs, CHMe2),
16.7 (d, CHMe2). 31P{1H} NMR (C6D5Br, 202.5 MHz): δ 50.5,
49.1, 47.6, 48.3 (AB spin system, two d, JPP = 267 Hz). 29Si NMR
(C6D5Br, 99.4 MHz): δ13.8. Anal. Calcd for C62H60NBF20IrOP2Si:
C, 48.92; H, 3.97; N, 1.84. Found: C, 48.75; H, 3.95; N, 1.99.
[(PNP)(H)IrSiPh2(DMF)][B(C6F5)4] (8). A Schlenk flask was
loaded with 1 (0.07 g, 0.05 mmol) and 3 mL of fluorobenzene.
Using a 10 μL syringe, dimethylformamide (3.7 μL, 0.05 mmol)
was added to the solution. Upon addition, a color change to red-
violet was observed. After 5 min, all volatile materials were
removed under vacuum. The remaining foam was redissolved
in 1 mL of fluorobenzene. The solution was added to pentane
(10 mL) and placed in the -30 °C freezer for 1 h to allow a red-
violet oil to settle out of the reaction mixture. The red-violet oil
was collected by decantation, and this oil was dried under
vacuum to give a burgundy solid. Yield: 0.06 g (86%). 1H
NMR (C6D5Br, 500 MHz): δ 8.16 (1H, br s, HCdO), 7.57
(4H, m, ArH ), 7.51 (2H, d, J = 8.4 Hz, ArH ), 7.22 (6H, ov m,
ArH ), 7.00 (2H, br s, ArH ), 6.95 (2H, 8.9 Hz, ArH ), 2.76 (3H, s,
NMe), 2.44 (3H, s, NMe), 2.24 (2H, m, CHMe2), 2.23 (6H, s,
ArMe), 1.46 (2H, m, CHMe2), 1.13 (6H, m, CHMe2), 0.92 (12H,
ov m, CHMe2), 0.52 (6H, m, CHMe2), -19.02 (1H, br t, IrH ).
13C{1H} NMR (C6D5Br, 125.8 MHz): δ 164.9 (s, CdO), 161.9
(t, JCP = 10.0 Hz), 150.0 (br m), 148.1 (br m), 140.0 (br m), 139.2
(br s), 138.8 (br m), 136.1 (br m), 134.9 (s), 133.0 (s), 132.8 (s),
130.8 (s), 129.5 (s), 116.2 (br m) (ArC), 49.4 (s, NMe), 35.8 (s,
NMe), 27.9 (br m, CHMe2), 23.3 (br m, CHMe2), 21.1 (s,
CHMe2), 20.8 (s, ArMe), 19.3 (s, CHMe2), 18.0 (s, CHMe2),
17.2 (s, CHMe2). 31P{1H} NMR (C6D5Br, 202.5 MHz): δ 47.6
(s). 29Si NMR (C6D5Br, 99.4 MHz): δ 29.0. Anal. Calcd for
C65H58N2BF20IrOP2Si: C, 50.17; H, 3.76; N, 1.80. Found: C,
50.25; H, 3.73; N, 1.75.
(s), 129.4 (s), 128.3 (t, JCP = 30.4 Hz), 127.2 (s), 121.1 (t, JCP
23.6 Hz), 117.2 (br s) (ArC), 84.8 (s, CHPh2), 27.1 (t, JCP
=
=
16.3 Hz, CHMe2), 24.9 (t, JCP = 15.5 Hz, CHMe2), 24.0 (br,
ArMe), 21.7 (s, ArMe), 21.0 (s, CHMe), 20.8 (s, ArMe), 18.5 (s,
CHMe2), 18.2 (s, CHMe2), 16.8 (s, CHMe2). 31P{1H} NMR
(C6D5Br, 162.0 MHz): δ 52.9 (s). 29Si NMR (C6D5Br, 99.4
MHz): δ 161.8. Anal. Calcd for C73H67NBF20IrOP2Si: C, 53.22;
H, 4.10; N, 0.85. Found: C, 53.31; H, 4.36; N, 0.89.
[(PNP)(H)IrdSiMes(OCH2Ph)][B(C6F5)4] (6). In the drybox,
a solution of benzaldehyde (0.006 g, 0.054 mmol) in 0.5 mL of
C6H5F was added to a solution of 2 (0.080 g, 0.054 mmol) in
0.5 mL of C6H5F. Upon addition of benzophenone, a color
change to bright purple was observed. After 2 min of mixing by
taking the fluorobenzene solution into a pipet and redispensing it
into the reaction vessel, the solution was added to hexanes
(10 mL) and placed in the -30 °C freezer for 1 h to allow a violet
oil to settle out of the reaction mixture. The hexanes/fluorobenzene
was decanted away, and the remaining oil was dried under
vacuum for 1 h to afford 6 as a purple foam. Yield = 0.075 g
1
(89%). H NMR (C6D5Br, 500 MHz): δ 7.40 (2H, br d, J =
8.6 Hz, ArH ), 7.23 (2H, m, ArH ), 7.18 (1H, m, ArH ), 7.03 (2H,
br s, ArH ), 6.95 (2H, m, ArH ), 6.91 (2H, br d, J = 8.1 Hz,
ArH ), 6.72 (2H, s, ArH ), 4.48 (2H, s, OCH2), 2.32 (2H, ov m,
CHMe2), 2.27 (6H, br s, ArMe), 2.24 (6H, s, ArMe), 2.18 (3H, s,
ArMe), 2.11 (2H, m, CHMe2), 1.11 (6H, m, CHMe2), 0.95 (6H,
m, CHMe2), 0.75 (6H, m, CHMe2), 0.63 (6H, m, CHMe2),
2
2
-20.42 (1H, t, JPH = 7.9 Hz, JSiH = 3 Hz, IrH ). 13C{1H}
NMR (C6D5Br, 125.8 MHz): δ 162.4 (t, JCP = 10.2 Hz), 150.1
(br m), 148.2 (br m), 144.4 (s), 139.9 (br m), 137.9 (br m), 136.3
(s), 136.1 (br m), 133.4 (s), 132.8 (s), 129.4 (s), 129.2 (s), 128.9 (s),
127.5 (s), 121.0 (t, JCP = 22.9 Hz), 117.1 (br m) (ArC), 72.2 (s,
OCH2), 26.9 (t, JCP = 17.9 Hz, CHMe2), 24.9 (t, JCP = 14.6 Hz,
CHMe2), 23.7 (br, ArMe), 21.7 (s, ArMe), 20.8 (s, ArMe), 20.6
(s, CHMe2), 18.6 (s, CHMe2), 18.2 (s, CHMe2), 17.0 (s, CHMe2).
31P{1H} NMR (C6D5Br, 202.5 MHz): δ 53.6 (s). 29Si NMR
(C6D5Br, 99.4 MHz): δ 159.3. Anal. Calcd for C66H59NBF20Ir-
OP2Si: C, 50.97; H, 3.82; N, 0.90. Found: C, 51.34; H, 4.11;
N, 0.87.
[(PNP)(H)IrSiPh2(OCPh2)][B(C6F5)4] (9). In the drybox, a
solution of benzophenone (0.012 g, 0.067 mmol) in 0.5 mL of
C6H5F was added to a solution of 1 (0.10 g, 0.067 mmol) in
0.5 mL of C6H5F. Upon addition of benzophenone, a color
change to red-violet was observed. After 2 min of mixing by
taking the fluorobenzene solution into a pipet and redispensing
it into the reaction vessel, the solution was added to pentane
(10 mL), and this mixture was placed in the -30 °C freezer for
1 h to allow a red-violet oil to settle out of the reaction mixture.
A red-violet oil was collected by decanting the supernatant,
and the oil was dried under vacuum to give a burgundy solid.
[(PNP)(H)IrSiMes(H)(DMF)][B(C6F5)4] (7). A Schlenk flask
was loaded with 2 (0.10 g, 0.07 mmol) and 3 mL of fluorobenzene.
Using a 10 μL syringe, dimethylformamide (5.3 μL, 0.07 mmol)
was added to the solution. Upon the addition, a color change to
deep violet-red was observed. After 5 min, all volatile materials
were removed under vacuum. The remaining foam was redissolved
in 1 mL of fluorobenzene. The resulting solution was added to
pentane (15 mL) and placed in the -30 °C freezer for 1 h to allow a
red-violet oil to settle out of the reaction mixture. A dark red-violet
oil was collected by decanting the supernatant, and this was dried
1
Yield = 0.11 g (94%). H NMR (C6D5Br, 500 MHz): δ 7.64
(4H, d, J = 7.1 Hz, ArH ), 7.58 (2H, d, J = 7.9 Hz, ArH ), 7.45
(6H, ov m, ArH ), 7.15-7.07 (10H, ov m, ArH ), 7.01 (4H, ov m,
ArH ), 2.24 (6H, s, ArMe), 2.24 (2H, br m, CHMe2), 1.66 (2H, br
m, CHMe2), 1.13 (6H, m, CHMe2), 0.98 (6H, m, CHMe2), 0.81
(6H, m, CHMe2), 0.60 (6H, m, CHMe2), -19.95 (1H, t, 2JPH
=
8.6 Hz, IrH ). 13C{1H} NMR (C6D5Br, 125.8 MHz): δ 208.19

Article
Organometallics, Vol. 29, No. 7, 2010 1691
(s, CdO), 162.2 (t, JCP = 10.2 Hz), 150.0 (br m), 148.2 (br m),
139.8 (br m), 138.5 (br m), 137.9 (br m), 136.9 (s), 136.0 (br m),
134.5 (s), 133.8 (s), 133.0 (s), 132.6 (s), 129.4 (s), 128.2 (s), 116.2
(br m) (ArC), 27.8 (br m, CHMe2), 23.8 (br m, CHMe2), 20.9 (s,
ArMe), 20.8 (s, CHMe2), 19.4 (s, CHMe2), 18.17 (s, CHMe2),
17.2 (s, CHMe2). 31P{1H} NMR (C6D5Br, 202.5 MHz): δ 49.5
(s). 29Si NMR (C6D5Br, 99.4 MHz): δ 46.8 (s). Anal. Calcd for
C75H60NBF20IrOP2Si: C, 54.13; H, 3.63; N, 0.84. Found: C,
53.75; H, 3.53; N, 0.83.
500 MHz): δ 7.82 (1H, br s, NH ), 7.53 (4H, d, J = 7.0 Hz, ArH),
7.18-7.02 (14H, ov m, ArH), 6.9 (1H, t, J = 8.5 Hz, ArH), 6.78
(2H, d, J = 7.6 Hz, ArH ), 2.32 (4H, br m, CHMe2), 2.26 (6H, s,
ArMe), 1.02 (6H, m, CHMe2), 0.86 (6H, m, CHMe2), 0.73 (6H, m,
2
CHMe2), 0.47 (6H, m, CHMe2), -17.45 (1H, JPH = 10.2 Hz,
IrH). 13C{1H} NMR (C6D5Br, 125.8 MHz): δ 156.1 (s), 150.1 (br
m), 148.1 (br m), 145.5 (t, JCP = 6.7 Hz), 140.9 (s), 139.9 (br m),
138.6 (s), 137.9 (br m), 136.0 (br m), 135.4 (s), 134.5 (s), 134.4 (s),
130.6 (s), 128.3 (s), 125.9 (br m), 122.3 (s), 120.6 (s) (ArC), 26.4 (t,
{(PNPH)IrH[SiPh2(OC(dCH2)Ph)]}[B(C6F5)4] (10). A solu-
tion of acetophenone (0.006 g, 0.05 mmol) in 0.5 mL of
fluorobenzene was added to a solution of 1 (0.080 g, 0.05 mmol)
in 1 mL of C6H5F. An immediate color change to yellow-brown
was observed. After 2 min, the reaction mixture was added to
hexanes (15 mL), and the resulting mixture was placed in the
-20 °C freezer for 1 h. A brown oil was collected by decantation,
and the oil was dried under vacuum to give a light yellow solid.
Yield: 0.077 g (89%). 1H NMR (C6D5Br, 500 MHz): δ 7.93 (1H,
br s, NH ), 7.67 (4H, d, J = 6.9 Hz, ArH ), 7.46 (2H, d, J = 3.6
Hz, ArH ), 7.21-7.16 (13H, ov m, ArH ), 7.04 (2H, br m, ArH ),
4.56 (2H, br s, OC=CH2), 2.31 (2H, br m, CHMe2), 2.24 (6H, s,
ArMe), 2.04 (2H, br m, CHMe2), 0.97 (6H, m, CHMe2), 0.85
(6H, m, CHMe2), 0.69 (6H, m, CHMe2), 0.58 (6H, m, CHMe2),
-17.69 (t, 2JPH = 10.1 Hz, IrH ). 13C{1H} NMR (C6D5Br, 150.9
MHz): δ 156.9 (s), 149.9 (br m), 148.3 (br m), 145.3 (t, JCP = 5.9
Hz), 140.9 (s), 139.6 (br t, JCP = 12.5 Hz), 138.3 (s), 138.0 (s,
SiOC), 137.9 (br m), 136.2 (br m), 136.1 (s), 134.4 (s), 134.3 (s),
130.4 (s), 129.1 (s), 128.8 (s), 128.7 (s) 128.2 (s) (ArC), 94.6
JCP = 16.5 Hz, CHMe2), 25.5 (t, JCP = 15.8 Hz, CHMe2), 21.1 (s,
ArMe), 20.8 (s, CHMe2), 19.6 (s, CHMe2), 17.7 (s, CHMe2), 17.2
(s, CHMe2). 31P{1H} NMR (C6D5Br, 202.5 MHz): δ 48.0 (s). 29Si
NMR (C6D5Br, 99.4 MHz): δ -3.3. Anal. Calcd for C68H57-
NBF20IrOP2Si: C, 51.78; H, 3.64; N, 0.89. Found: C, 52.09; H,
3.30; N, 1.03.
[(PNPH)IrH(SiPh2OiPr)][B(C6F5)4] (13). An excess of
2-propanol (approximately 0.2 mL) was added via cannula to
a solution of 1 (0.080 g, 0.05 mmol) in 1.5 mL of C6H5F. Upon
addition of the alcohol, a color change to light yellow-green was
observed. After 10 min, the reaction mixture was dried under
vacuum. The resulting oil was redissolved in fluorobenzene
(1 mL), and this solution was added to hexanes (10 mL). The
resulting mixture was placed in the -20 °C freezer for 1 h. A
yellow oil was collected by decantation, and then the oil was
dried under vacuum to give a light yellow solid. Yield: 0.067 g
1
(81%). H NMR (C6D5Br, 500 MHz): δ 7.56 (1H, br s, NH ),
7.48 (4H, d, J = 6.9 Hz, ArH ), 7.24 (2H, m, ArH ), 7.18-7.14
(8H, ov m, ArH ), 6.99 (2H, d, J = 8.3 Hz, ArH ), 3.85 (1H, spt,
J = 6 Hz, OCHMe2), 2.36 (4H, br m, CHMe2), 2.25 (6H, s,
ArMe), 1.06 (6H, m, CHMe2), 1.02 (6H, d, J = 6 Hz, OCHMe2),
0.87 (6H, m, CHMe2), 0.74 (6H, m, CHMe2), 0.43 (6H, m,
CHMe2), -17.63 (1H, t, 2JPH = 10.5 Hz, IrH ). 13C{1H} NMR
(C6D5Br, 150.9 MHz): δ 149.9 (br m), 148.3 (br m), 145.8 (t,
JCP = 7.2 Hz), 140.6 (s), 139.7 (br m), 139.5 (s), 137.9 (br m),
136.2 (br m), 135.2 (s), 134.5 (s), 134.1 (s), 130.2 (s), 128.2 (s),
125.8 (s) (ArC), 68.7 (s, OCHMe2), 26.6 (t, JCP = 15.4 Hz,
CHMe2), 25.9 (s, OCHMe2), 25.5 (t, JCP = 14.7 Hz, CHMe2),
21.1 (s, ArMe), 20.8 (s, CHMe2), 20.1 (s, CHMe2), 17.6 (s,
CHMe2), 17.2 (s, CHMe2). 31P{1H} NMR (C6D5Br, 202.5
MHz): δ 47.9 (s). 29Si NMR (C6D5Br, 99.4 MHz): δ -2.3. Anal.
Calcd for C65H59NBF20IrOP2Si: C, 50.59; H, 3.85; N, 0.91.
Found: C, 50.66; H, 3.65; N, 0.99.
(br s, dCH2), 26.3 (t, JCP = 14.2 Hz, CHMe2), 25.4 (t, JCP
=
15.3 Hz, CHMe2), 21.1 (s, ArMe), 21.0 (s, CHMe2), 19.1 (s,
CHMe2), 18.1 (s, CHMe2), 16.9 (s, CHMe2). 31P{1H} NMR
(C6D5Br, 202.5 MHz): δ 47.2 (s). 29Si NMR (C6D5Br, 99.4
MHz): δ -5.7. Anal. Calcd for C70H59NBF20IrOP2Si: C, 52.44;
H, 3.71; N, 0.87. Found: C, 52.77; H, 3.95; N, 1.26.
[(PNPH)IrH(SiPh2OArtBu)][B(C6F5)4] (ArtBu = 3,5-tBu2C6H3)
(11). A solution of 3,5-di-tert-butylphenol (0.011 g, 0.05 mmol)
in 0.5 mL of fluorobenzene was added to a solution of 1 (0.080 g,
0.05 mmol) in 1 mL of C6H5F. Upon addition of the alcohol, a
color change to bright blue was observed initially, followed by
a gradual color change to light yellow-green within 2 min. After
10 min, the reaction mixture was added to hexanes (10 mL), and
the resulting mixture was placed in the -20 °C freezer for 1 h.
A yellow-green oil was collected by decantation, and then the oil
was dried under vacuum to give a light green solid. Yield: 0.079 g
(94%). 1H NMR (C6D5Br, 500 MHz): δ 7.83 (1H, s, NH), 7.53
(4H, d, J = 7.2 Hz, ArH), 7.18 (6H, ov m, ArH), 7.11-7.05 (7H,
ov m, ArH), 6.64 (2H, d, J=0.8Hz, ArH ), 2.36(4H, m, CHMe2),
2.27 (6H, s, ArMe), 1.14 (18 H, s, CMe3), 1.03 (6H, m, CHMe2),
0.87 (6H, m, CHMe2), 0.76 (6H, m, CHMe2), 0.51 (6H, m,
CHMe2), -17.36 (1H, t, 2JPH = 10.5 Hz, IrH). 13C{1H} NMR
(C6D5Br, 150.9 MHz): δ 155.9 (s), 152.3 (s), 149.9 (br m), 148.3 (br
m), 145.6 (t, JCP = 7.3 Hz), 140.8 (s), 139.7 (br m), 138.9 (s), 137.9
(br m), 136.2 (br m), 135.5 (s), 134.6 (s), 134.3 (s), 130.5 (s), 128.3
(s), 125.9 (br), 115.8 (s), 115.1 (s) (ArC), 35.1 (s, CMe3) 31.8 (s,
CMe3), 26.5 (br t, JCP = 16.0 Hz, CHMe2), 25.5 (br t, JCP = 13.6
Hz, CHMe2), 21.1(s, ArMe), 20.7(s, CHMe2), 19.7(brs, CHMe2),
17.6 (s, CHMe2), 17.2 (s, CHMe2). 31P{1H} NMR (C6D5Br, 202.5
MHz): δ 48.5 (s). 29Si NMR (C6D5Br, 99.4 MHz): δ -3.6. Anal.
Calcd for C76H73NBF20IrOP2Si: C, 54.03; H, 4.36; N, 0.83. Found:
C, 54.40; H, 4.35; N, 0.98.
[(PNPH)IrH(SiPh2OtBu)][B(C6F5)4] (14). An excess of tert-
butanol (ca. 0.2 mL) was added via cannula to a solution of 1
(0.080 g, 0.05 mmol) in 1.5 mL of C6H5F. Upon addition of the
alcohol, a color change to light yellow-green was observed. After
10 min, the reaction mixture was dried under vacuum. The
resulting oil was redissolved in fluorobenzene (1 mL), and the
solution was added to hexanes (10 mL). The resulting mixture was
placed in the -20 °C freezer for 1 h. A yellow oil was collected by
decantation, and then the oil was dried under vacuum to give a
light yellow solid. Yield: 0.078 g (93%). 1H NMR (C6D5Br,
500 MHz): δ 7.53 (4H, d, J = 7.1 Hz, ArH), 7.24 (2H, t, J =
7.4 Hz, ArH ), 7.16-7.08 (9H, ov m, ArHþ NH), 6.84 (2H, d, J =
8.3 Hz, ArH ), 2.34 (4H, ov m, CHMe2), 2.24 (6H, s, ArMe), 1.13
t
(9H, BuO), 1.12 (6H, m, CHMe2), 0.88 (6H, m, CHMe2), 0.69
(6H, m, CHMe2), 0.38 (6H, m, CHMe2), -17.60 (1H, t, 2JPH
=
10.6 Hz, IrH). 13C{1H} NMR (C6D5Br, 150.9 MHz): δ 149.9
(br m), 148.3 (br m), 146.1 (t, JCP = 7.1 Hz), 140.8 (s), 140.3 (s),
139.8 (br m), 136.2 (br m), 135.3 (s), 134.2 (s), 133.8 (s), 128.2 (s),
[(PNPH)IrH(SiPh2OPh)][B(C6F5)4] (12). A solution of phenol
(0.006 g, 0.064 mmol) in 0.5 mL of fluorobenzene was added to a
solution of 1(0.080 g, 0.053 mmol) in 1 mL of C6H5F. Within 2 min
after alcohol addition, a color change to light yellow-green was
observed. After 10 min, the reaction mixture was dried under
vacuum. The resulting oil was redissolved in fluorobenzene, this
solution was added to hexanes (10 mL), and the resulting mixture
was placed in the -20 °C freezer for 1 h. A yellow oil was collected
by decantation, and then the oil was dried under vacuum to give
125.4 (br m), 76.5 (s, OCMe3), 32.2 (s, OCMe3), 26.8 (t, JCP =
12.3 Hz, CHMe2), 25.2(t, JCP = 14.2 Hz, CHMe2), 21.1 (s, ArMe),
21.1 (s, CHMe2), 20.1 (s, CHMe2), 18.3 (s, CHMe2), 17.3 (s,
CHMe2). 31P{1H} NMR (C6D5Br, 202.5 MHz): δ 45.5 (s). 29Si
NMR (C6D5Br, 99.4 MHz): δ -14.8. Anal. Calcd for C66H61-
NBF20IrOP2Si: C, 50.91; H, 3.95; N, 0.90. Found: C, 51.05; H,
3.97; N, 0.89.
[(PNPH)IrH(SiPh2NHPh)][B(C6F5)4] (15). Aniline (4.9 μL,
0.05 mmol) was added via syringe to a solution of 1 (0.08 g, 0.05
mmol) in 1 mL of C6H5F. An immediate color change to dark
1
a light yellow solid. Yield: 0.067 g (81%). H NMR (C6D5Br,

1692 Organometallics, Vol. 29, No. 7, 2010
Calimano and Tilley
yellow was observed. After 15 min, the reaction mixture was
added to hexanes (15 mL), and the resulting mixture was placed
in the -20 °C freezer for 18 h. A yellow oil was collected by
decantation, and then the oil was dried under vacuum to give a
light yellow solid. Yield: 0.07 g (86%). 1H NMR (C6D5Br, 500
MHz): δ 7.78 (1H, br s, NH ), 7.64 (4H, d, J = 7.2 Hz, ArH ),
7.20-7.10 (10 H, ov m, ArH ), 6.99 (2H, under solvent signal,
ArH ), 6.97 (2H, d, J = 7.9 Hz, ArH ), 6.66 (1H, t, J = 7.1 Hz,
ArH ), 6.60 (2H, d, J = 7.9 Hz, ArH), 4.19 (1H, s, NH ), 2.31
(2H, m, CHMe2), 2.24 (6H, s, ArMe), 1.86 (2H, m, CHMe2),
0.98 (6H, m, CHMe2), 0.88 (6H, m, CHMe2), 0.67 (6H, m,
CHMe2), 0.53 (6H, m, CHMe2), -17.96 (1H, br t, JPH = 9.3 Hz,
IrH ). 13C{1H} NMR (C6D5Br, 150.9 MHz): δ 149.9 (br m),
148.3 (brm m), 140.9 (br), 139.7 (br m), 137.9 (br m), 136.2 (br
m), 135.5 (s), 134.3 (s), 128.5 (s), 126.4 (br), 119.3 (br), 117.8 (br)
(ArC), 26.5 (t, JCP = 17 Hz, CHMe2), 25.5 (t, JCP = 12 Hz,
CHMe2), 21.1 (s, ArMe), 21.1 (s, CHMe2), 19.5 (s, CHMe2),
18.6 (s, CHMe2), 17.2 (s, CHMe2). 31P{1H} NMR (C6D5Br,
202.5 MHz): δ 45.4 (s). 29Si NMR (C6D5Br, 99.4 MHz): δ -21.9.
Anal. Calcd for C68H58N2BF20IrP2Si: C, 51.82; H, 3.71; N, 1.78.
Found: C, 52.01; H, 3.50; N, 2.11.
CHMe2). 31P{1H} NMR (C6D5Br, 202.5 MHz): δ 46.1 (s). 29Si
NMR (C6D5Br, 99.4 MHz): δ -16.5. 19F{1H} NMR (C6D5Br,
376.5 MHz): δ -61.9 (s, CF3), -130.8 (br s, B(C6F5)4), -161.3 (t,
J = 20.7 Hz, B(C6F5)4), -165.1 (br t, J = 19.3 Hz, B(C6F5)4).
Anal. Calcd for C70H56N2BF26IrP2Si: C, 49.10; H, 3.30; N, 1.64.
Found: C, 49.32; H, 3.04; N, 1.46.
Representative Procedure for Catalytic Alcoholysis Reactions.
In a representative catalytic run, 1 (0.005 g, 0.003 mmol, 1 mol %)
was dissolved in 0.5 mL of bromobenzene-d5, and the resulting
solution was added to bis(p-fluorophenyl)methane (0.0068 g, 0.034
mmol) (as a standard) followed by the silane (0.034 mmol). The
NMR tube was then capped with a rubber septum and taken out of
the drybox, where the alcohol was added by syringe (0.040 mmol)
through the septum. The NMR tube was vented by piercing the
septa with a syringe after 1 h and again after 3 h to release the
buildup of H2 gas. The progress of the reaction was monitored by
1H NMR spectroscopy, and yields were obtained by integration
against a standard. The reaction solution was then opened to air,
diluted with 2 mL of hexanes, filtered through silica gel to remove
any metal species, and analyzed by GC/MS.
Representative Procedure for Catalytic Aminolysis and Hydro-
silylation Reactions. In a representative catalytic run, 1
(0.005 g, 0.003 mmol, 1 mol %) was dissolved in 0.5 mL of
bromobenzene-d5, and the resulting solution was added to
bis( p-fluorophenyl)methane (0.0068 g, 0.034 mmol) (as a
standard), silane (0.034 mmol), and then the aniline or ketone
(0.040 mmol). This solution was then transferred to a Teflon-
capped J. Young NMR tube. The reaction was monitored via 1H
NMR spectroscopy, and yields were obtained by integration
against the internal standard. The reaction solution was then
opened to air, diluted with 2 mL of hexanes, filtered through silica
gel to remove any metal species, and analyzed by GC/MS.
[(PNPH)IrH(SiPh2NHArF)][B(C6F5)4] (ArF =3,5-(CF3)2C6H3)
(16). H2NArF (4.9 μL, 0.05 mmol) was added via syringe to a
solution of 1 (0.08 g, 0.05 mmol) in 1 mL of C6H5F. An immediate
color change to dark yellow was observed. After 15 min, the
reaction mixture was added to hexanes (15 mL), and the resulting
mixture was placed in the -20 °C freezer for 6 h. A yellow oil was
collected by decantation, and then the oil was dried under vacuum
to give a light yellow solid. Yield: 0.08 g (88%). 1H NMR (C6D5Br,
500 MHz): δ 7.79 (1H, br s, NH), 7.55 (4H, d, J = 6.9 Hz, ArH),
7.20-7.10 (11H, ov m, ArH), 7.00-6.97 (4H, ov d þ s, ArH), 4.58
(1H, s, NH), 2.35 (2H, m, CHMe2), 2.24 (6H, s, ArMe), 1.87 (2H,
m, CHMe2), 1.00 (6H, m, CHMe2), 0.88 (6H, m, CHMe2),
0.68 (6H, m, CHMe2), 0.49 (6H, m, CHMe2), -17.99 (1H, t,
Acknowledgment. This work was supported by the
National Science Foundation under Grant No. CHE-
0649583. The authors would also like to thank Drs. Fred
Hollander and Antonio Di Pasquale of the UC Berkeley
CHEXRAY facility for assistance with X-ray crystal-
lography and Rudi Nunlist for assistance with NMR
spectroscopy.
2
JPH = 10.4 Hz, JSiH = 3 Hz, IrH). 13C{1H} NMR (C6D5Br,
150.9 MHz): δ 149.9 (br m), 148.6 (s), 148.2 (br m), 145.3 (t, JCP
7.4 Hz), 141.2 (br m), 139.7 (br m), 137.6 (br m), 137.8 (s), 136.2 (br
=
m), 135.2 (s), 134.7 (s), 134.4 (s), 132.4 (s), 132.2 (s), 131.0 (s), 128.8
(s), 125.9 (s), 124.8 (s), 117.2 (br), 111.8 (br) (ArC), 26.5 (t, JCP =
17.2 Hz, CHMe2), 25.7 (t, JCP = 13.5 Hz, CHMe2), 21.1 (s, ArMe),
21.0 (s, CHMe2), 19.4 (s, CHMe2), 18.4 (s, CHMe2), 17.1 (s,