Multiple Si-H bond activations by tBu2PCH 2CH2PtBu2 and tBu 2PCH2PtBu2 Di(phosphine) complexes of rhodium and iridium

Article abstract of DOI:10.1021/om300943e

Reactions of the di(tert-butylphosphino)ethane complex (dtbpe)Rh(CH ₂Ph) with Ph₂SiH₂ and Et₂SiH ₂ resulted in isolation of (dtbpe)Rh(H)₂(SiBnPh ₂) (1; Bn = CH₂Ph) and (dtbpe)Rh(H) ₂(SiBnEt₂) (2), respectively. Both 1 and 2 feature strong interactions between the rhodium hydride and silyl ligands, as indicated by large ²J_SiH values (44.4 and 52.1 Hz). The reaction of (dtbpm)Rh(CH₂Ph) (dtbpm = di(tert-butylphosphino)methane) with Mes₂SiH₂ gave the pseudo-three-coordinate Rh complex (dtbpm)Rh(SiHMes₂) (3), which is stabilized in the solid state by agostic interactions between the rhodium center and two C-H bonds of a methyl substituent on the mesityl group. The analogous germanium compound (dtbpm)Rh(GeHMes₂) (4) is also accessible. Complex 3 readily undergoes reactions with diphenylacetylene, phenylacetylene, and 2-butyne to give the silaallyl complexes (dtbpm)Rh[Si(CPh=CHPh)Mes₂] (5), (dtbpm)Rh[Si(CH=CHPh)Mes₂] (7), and (dtbpm)Rh(Si(CMe=CHMe)Mes ₂) (8) via net insertions into the Si-H bond. The germaallyl complexes (dtbpm)Rh[Ge(CPh=CHPh)Mes₂] (6) and (dtbpm)Rh[Ge(CMe=CHMe) Mes₂] (9) were synthesized under identical conditions starting from 4. The reaction of (dtbpm)Rh(CH₂Ph) with 1 equiv of TripPhSiH ₂ yielded (dtbpm)Rh(H)₂[5,7-diisopropyl-3-methyl-1-phenyl- 2,3-dihydro-1H-silaindenyl-κSi] (11), and catalytic investigations indicate that both (dtbpm)Rh(CH₂Ph) and 11 are competent catalysts for the conversion of TripPhSiH₂ to 5,7-diisopropyl-3-methyl-1- phenyl-2,3-dihydro-1H-silaindole. A dtbpm-supported Ir complex, [(dtbpm)IrCl]₂, was used to access the dinuclear bridging silylene complexes [(dtbpm)IrH](μ-SiPh₂)(μ-Cl)₂[(dtbpm)IrH] (12) and [(dtbpm)IrH](μ-SiMesCl)(μ-Cl)(μ-H)[(dtbpm)IrH] (13). The reaction of [(dtbpm)IrCl]₂ with a sterically bulky primary silane, (dmp)SiH₃ (dmp = 2,6-dimesitylphenyl), allowed isolation of the mononuclear complex (dtbpm)Ir(H)₄(10-chloro-1-mesityl-5,7-dimethyl-9, 10-dihydrosilaphenanthrene-κSi), in which the dmp substituent has undergone C-H activation.

Full text of DOI:10.1021/om300943e

Article
pubs.acs.org/Organometallics
t
Multiple Si−H Bond Activations by Bu2PCH2CH2PtBu2 and
tBu2PCH2PtBu2 Di(phosphine) Complexes of Rhodium and Iridium
Meg E. Fasulo, Elisa Calimano, J. Matthew Buchanan, and T. Don Tilley*
Department of Chemistry, University of California, Berkeley, Berkeley, California 94720-1460, United States
S
* Supporting Information
ABSTRACT: Reactions of the di(tert-butylphosphino)ethane
complex (dtbpe)Rh(CH2Ph) with Ph2SiH2 and Et2SiH2
resulted in isolation of (dtbpe)Rh(H)2(SiBnPh2) (1; Bn =
CH2Ph) and (dtbpe)Rh(H)2(SiBnEt2) (2), respectively. Both
1 and 2 feature strong interactions between the rhodium
hydride and silyl ligands, as indicated by large 2JSiH values (44.4
and 52.1 Hz). The reaction of (dtbpm)Rh(CH2Ph) (dtbpm =
di(tert-butylphosphino)methane) with Mes2SiH2 gave the
pseudo-three-coordinate Rh complex (dtbpm)Rh(SiHMes2)
(3), which is stabilized in the solid state by agostic interactions
between the rhodium center and two C−H bonds of a methyl substituent on the mesityl group. The analogous germanium
compound (dtbpm)Rh(GeHMes2) (4) is also accessible. Complex 3 readily undergoes reactions with diphenylacetylene,
phenylacetylene, and 2-butyne to give the silaallyl complexes (dtbpm)Rh[Si(CPhCHPh)Mes2] (5), (dtbpm)Rh[Si(CH
CHPh)Mes2] (7), and (dtbpm)Rh(Si(CMeCHMe)Mes2) (8) via net insertions into the Si−H bond. The germaallyl
complexes (dtbpm)Rh[Ge(CPhCHPh)Mes2] (6) and (dtbpm)Rh[Ge(CMeCHMe)Mes2] (9) were synthesized under
identical conditions starting from 4. The reaction of (dtbpm)Rh(CH2Ph) with 1 equiv of TripPhSiH2 yielded
(dtbpm)Rh(H)2[5,7-diisopropyl-3-methyl-1-phenyl-2,3-dihydro-1H-silaindenyl-κSi] (11), and catalytic investigations indicate
that both (dtbpm)Rh(CH2Ph) and 11 are competent catalysts for the conversion of TripPhSiH2 to 5,7-diisopropyl-3-methyl-1-
phenyl-2,3-dihydro-1H-silaindole. A dtbpm-supported Ir complex, [(dtbpm)IrCl]2, was used to access the dinuclear bridging
silylene complexes [(dtbpm)IrH](μ-SiPh2)(μ-Cl)2[(dtbpm)IrH] (12) and [(dtbpm)IrH](μ-SiMesCl)(μ-Cl)(μ-H)[(dtbpm)-
IrH] (13). The reaction of [(dtbpm)IrCl]2 with a sterically bulky primary silane, (dmp)SiH3 (dmp = 2,6-dimesitylphenyl),
allowed isolation of the mononuclear complex (dtbpm)Ir(H)4(10-chloro-1-mesityl-5,7-dimethyl-9,10-dihydrosilaphenanthrene-
κSi), in which the dmp substituent has undergone C−H activation.
activations, resulting in terminal hydrides, hydrides that bridge
two rhodium atoms, and hydrides that bridge between rhodium
and silicon. Additionally, transformations catalyzed by this
family of complexes include olefin hydrosilation, redistribution
of substituents at silicon, dehydrocoupling of silanes, and H/D
exchange.9
Although (dippe)Rh complexes display interesting reactivity
toward primary and secondary silanes, the resulting metal−
silicon products are consistently dinuclear and feature bridging
silyl or silylene ligands.9 Given the interesting possibility of
observing and/or isolating related, mononuclear silylene
species, it is reasonable to explore silane activations by more
sterically hindered diphosphine complexes. Rhodium com-
plexes supported by the di(tert-butylphosphino)methane
(dtbpm) ligand, such as [(dtbpm)RhCl]2 and (dtbpm)RhCl-
(PPh3), have previously been reported to be active catalysts for
the hydrosilation of alkynes, and synthesis of the silyl complex
(dtbpm)Rh[Si(OEt)3](PMe3) has been described.10 Despite
these interesting results, the silicon chemistry of such
INTRODUCTION
■
Catalytic transformations involving organosilanes, such as
hydrosilation, are commercially significant,1 and much of this
catalysis involves the activation of a silane at a transition-metal
center.2 Within this context, a thorough understanding of the
fundamental steps in such reactions, such as Si−H bond
activation and Si−C bond formation,3 can be highly valuable in
the design of new catalysts.4
Complexes of rhodium and iridium supported by pincer
ligands display rich chemistry with regard to silane activation
and catalysis.5 However, while related di(phosphine) rhodium
complexes have been implicated as catalysts for a number of
reactions, such as the dehydrocoupling of phosphines,6 CO2
hydrogenation,7 and the hydroboration of alkenes,8 their silicon
chemistry has not been as extensively explored. Promisingly,
complexes supported by the di(isopropylphosphino)ethane
ligand (dippe) have demonstrated both stoichiometric and
catalytic reactivity toward silanes.9 The dinuclear complex
[(dippe)Rh(μ-H)]2 undergoes reactions with primary and
secondary silanes to give complexes such as [(dippe)Rh]2(μ-
SiPh2)2 and [(dippe)Rh]2(μ-η2-SiHMe2)2.9 A number of these
dinuclear complexes also display various Si−H bond
Received: October 8, 2012
Published: February 4, 2013
© 2013 American Chemical Society
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Scheme 1
complexes remains relatively unexplored. Herein we report
investigations that target (dtbpe)Rh and (dtbpm)Rh complexes
and associated activations of silanes and germanes.
RESULTS AND DISCUSSION
■
Reaction of (dtbpe)Rh(CH2Ph) with Secondary Si-
lanes. The mononuclear complex (dtbpe)Rh(CH2Ph)11 was
envisioned as a potentially useful starting material and
precursor to hydrido(silylene) complexes, as outlined in
Scheme 1. Oxidative addition of an Si−H bond to this complex
would give a (dtbpe)RhIII benzyl silyl hydride, which could then
undergo reductive elimination of toluene. This would result in a
reactive three-coordinate (dtbpe)RhI silyl species, and α-
hydrogen migration from the silicon to the rhodium center
could provide a pathway to a (dtbpe)Rh silylene complex.12
Reactions of (dtbpe)Rh(CH2Ph) with secondary silanes were
found to result in conversion to new, isolable products. For
example, a pentane solution of 1 equiv of Ph2SiH2 was added to
a pentane solution of (dtbpe)Rh(CH2Ph) at room temperature,
and after 24 h the resulting orange-red solution was cooled to
−35 °C to give (dtbpe)Rh(H)2(SiBnPh2) (1; Bn = CH2Ph) as
orange crystals in 69% yield (eq 1). The 1H NMR spectrum of
1 displays peaks in the aromatic region corresponding to two
phenyl groups and one benzyl group, and the methylene group
of the benzyl substituent appears as a singlet at 3.28 ppm. Two
equivalent hydrides appear as a multiplet at −5.35 ppm (JPH
=
19.6 Hz, JRhH = 33.8 Hz) and exhibit a large JSiH value of 44.4
Hz, indicating a strong interaction with Si (cf. JSiH values of ca.
200 Hz for free silanes13). The 31P{1H} NMR spectrum
Figure 1. Two views of the molecular structure of 1 displaying thermal
ellipsoids at the 50% probability level. Selected H atoms have been
omitted for clarity. Selected bond lengths (Å): Rh(1)−Si(1) =
2.3536(19), Rh(1)−P(1) = 2.327(2), Rh(1)−P(2) = 2.323(2),
Rh(1)−H(1) = 1.67(4), Rh(1)−H(2) = 1.49(4), Si(1)−H(1) =
1.84(4), Si(1)−H(2) = 1.88(4).
exhibits a single resonance as a doublet at 111.3 ppm (JRhP
=
114 Hz), and the single 29Si NMR peak at −5.6 ppm is
consistent with a silyl group.13 Complex 1 can be stored at
room temperature for 4 weeks before significant decomposition
is observed.
The identity of 1 was confirmed by X-ray crystallography
(Figure 1). The Rh(1), P(1), P(2), H(1), and H(2) atoms are
coplanar ( 0.04 Å), and the Rh−Si bond forms an angle of
22.1° with this plane. The Rh−Si bond length of 2.3536(19) Å
is typical for Rh−Si single bonds,13 and the Rh−P bond lengths
are nearly identical (2.327(2) and 2.323(2) Å). The rhodium
hydride ligands, H(1) and H(2), were located in the Fourier
map, but the difference in the observed Rh(1)−H(1) (1.67(4)
Å) and Rh(1)−H(2) bond distances (1.49(4) Å) may not be
statistically meaningful. The Si−H bonds (1.84(4) and 1.88(4)
Å) are elongated with respect to a typical Si−H bond distance
of ∼1.5 Å.13 The geometry about Si(1) is approximately square
pyramidal (ignoring the Rh atom), with a phenyl group in the
apical position. This type of structure therefore resembles those
of related σ complexes such as [RuH2{(η2-HSiMe2)2C6H4}-
(PCy3)2].14a Like Cp(PiPr2Me)Fe(H2SiR3),14b 1 may be
−
regarded as a [η3-H2SiR3 ] hydrosilicate complex. Alternatively,
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given the short Rh−H and long Si−H bond distances, 1 may be
described as a silyl dihydride complex, with strong intra-
molecular interactions between the hydride ligands and the
silicon atom.13 Thus, Rh(I) and Rh(III) resonance forms may
be considered (eq 1).
spectrum of 3 reveals two resonances, a doublet of doublets at
1
45.9 ppm (2JPP = 17.9 Hz, JRhP = 226.6 Hz) and a doublet of
1
doublets at 10.6 ppm (2JPP = 17.9 Hz, JRhP = 89.7 Hz),
indicating that each P atom of the dtbpm ligand is in a unique
environment. A large difference in Rh−P couplings has
previously been observed for (dtbpm)Rh complexes,15 and
lower coupling is attributed to the presence of a ligand that
displays a strong trans influence.16 The 29Si NMR spectrum
displays a single peak at −12.4 ppm, in the region expected for
The analogous complex (dtbpe)Rh(H)2(SiBnEt2) (2) was
obtained similarly, by reaction of 1 equiv of Et2SiH2 with
(dtbpe)Rh(CH2Ph) in pentane, followed by cooling to −35 °C
to give yellow crystals in 70% yield. The 1H NMR spectrum of
2 is similar to that of 1, and most notably the hydride ligands
appear as one multiplet (−5.63 ppm, JPH = 19.1 Hz, JRhH = 27.3
Hz) and retain a large coupling to Si with a JSiH value of 52.1
Hz. The 31P{1H} NMR spectrum displays a doublet at 114.7
ppm (JRhP = 136 Hz), and the silicon resonance appears at 0.8
ppm in the 29Si NMR spectrum. Complex 2 is much more
thermally sensitive than 1 and decomposes in solution over 2 h.
Complexes 1 and 2 may form via a series of oxidative
addition and reductive elimination steps. Initial oxidative
addition of an Si−H bond to (dtbpe)Rh(CH2Ph) may give
(dtbpe)RhH(CH2Ph)(SiHPh2), which would rapidly undergo
Si−C bond reductive elimination to produce Ph2(CH2Ph)SiH
and a rhodium hydride species. Finally, Ph2(CH2Ph)SiH would
add to [(dtbpe)RhH] to give the product. This mechanism is
supported by several observations. A solution of (dtbpe)Rh-
(CH2Ph) with 1 equiv of Ph2SiH2 in C6D6 was monitored by
multinuclear NMR spectroscopy over the course of the reaction
and was found to contain Ph2(PhCH2)SiH, as compared to an
independently synthesized sample. After 15 min, ca. 0.25 equiv
of Ph2(PhCH2)SiH was present, and this amount remained
constant throughout most of the course of the reaction, until it
was finally consumed in formation of the final product.
However, no organometallic species corresponding to an
intermediate was definitively identified. Additionally, the
reaction of (dtbpe)Rh(CH2Ph) with 0.5 equiv of Ph2SiH2
and 0.5 equiv of Ph2SiD2 in C6D6 resulted in 3
isotopomers(dtbpe)Rh(H)2(SiBnPh2), (dtbpe)Rh-
(D)2(SiBnPh2), and (dtbpe)Rh(H)(D)[SiBnPh2)], as deter-
mined by 1H and 2H NMR spectroscopy. This H/D scrambling
suggests a mechanism in which Ph2(CH2Ph)Si(H/D) leaves
the coordination sphere of a [(dtbpe)Rh(H/D)] species.
Reactions of (dtbpm)Rh(CH2Ph) with Mes2EH2 (E = Si,
Ge). In light of the limited number of clean reactions observed
for hydrosilanes with (dtbpe)Rh(CH2Ph), and on the basis of
the previous successful synthesis of (dtbpm)Rh[Si(OEt)3]-
(PMe3),10 silane and germane activations by the related benzyl
derivative (dtbpm)Rh(CH2Ph)10 were examined. In screening
the reactivity of (dtbpm)Rh(CH2Ph) with a number of primary
and secondary silanes, it was found that certain sterically
hindered secondary silanes provided isolable reaction products,
while primary silanes and other secondary silanes resulted in
complex reaction mixtures. Thus, reaction of 1 equiv of
Mes2SiH2 with (dtbpm)Rh(CH2Ph) gave orange crystals of 3
from pentane, isolated in 81% yield (eq 2). The 31P{1H} NMR
silyl ligands.13 However, the H NMR spectrum of 3 at room
1
temperature is difficult to interpret, since it contains no
observable Si−H resonance but two broad peaks at 2.56 and
2.24 ppm for the methyl groups of the mesityl substituents,
which together integrate to only 15 H. In addition, a singlet at
6.81 ppm integrates for 4 H and arises from the aromatic
protons of the mesityl substituents on Si.
1
The H NMR spectrum of 3 in toluene-d8 solution at −80
°C is more informative, as it contains four aromatic resonances
(7.06−6.74 ppm) and a broad singlet at 6.21 ppm attributed to
the Si−H group. Additionally, there are five singlets in the
methyl region: four that integrate for 3 H each and one that
integrates for 6 H (p-Me groups). No Rh−H coupling is
observed for these methyl resonances. The tert-butyl groups of
the dtbpm ligand are split into four sets of doublets, each
integrating to 9 H. These NMR data indicate that complex 3
may be formulated as (dtbpm)Rh(SiHMes2), possessing a
geometry that renders the P atoms and the mesityl groups
inequivalent.
Single crystals of 3 suitable for X-ray crystallography were
grown by slow evaporation from a pentane solution at −35 °C
(Figure 2). Surprisingly, the structure of 3 was found to involve
agostic interactions, such that two C−H bonds of one mesityl
methyl group interact with the Rh center. The coordination
geometry about Rh is square planar, with C(18) constituting
one corner of the square. The Rh−Si bond length of 2.3777(7)
Å is typical for a Rh−Si single bond.13 The Rh−P(1) bond
Figure 2. Molecular structure of 3 displaying thermal ellipsoids at the
50% probability level. Selected H atoms have been omitted for clarity.
Selected bond lengths (Å): Rh(1)−Si(1) = 2.3777(7), Rh(1)−P(1) =
2.2181(7), Rh(1)−P(2) = 2.3462(7), Rh(1)−H(100) = 2.01(3),
Rh(1)−H(101) = 2.01(3), Si(1)−H(1) = 1.38(3).
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length (2.2181(7) Å) is shorter than that of Rh−P(2)
(2.3462(7) Å), due to the trans influence of Si. The hydrogen
atoms H(1), H(100), H(101), and H(102) were located in the
Fourier map, and the Rh−H(100) and Rh−H(101) distances
are both 2.01(3) Å. The third C−H bond does not interact
with Rh, nor does the Si−H bond, as it is not in an appropriate
position. For comparison, the alkyl complexes (dtbpm)-
17
RhCH2CMe3 and [(dtbpe)NiCH2CMe3][PF6]18 display
very similar geometries but feature a single γ-CH agostic
interaction. The Rh−C(18) distance of 2.377(3) Å is
significantly shorter than the corresponding distance observed
for (dtbpm)RhNp (2.491(4) Å), which is likely due to the
presence of an additional agostic interaction for 3. A weak
absorption at 2728 cm−1 in the infrared spectrum of a
crystalline sample indicates that the agostic interactions remain
present at room temperature.19a
The analogous germyl complex 4 was prepared by reaction of
(dtbpm)Rh(CH2Ph) with Mes2GeH2, and dark red crystals
were isolated in 71% yield from pentane (eq 2). Unlike 3, the
1H NMR spectrum of 4 displays all expected resonances at
room temperature. A singlet at 6.89 ppm is assigned to the
aromatic protons of the mesityl substituents, the resonance for
the Ge−H group appears at 5.98 ppm, and three singlets at
2.71, 2.32, and 2.25 ppm each integrate for 6 H, accounting for
all methyl groups of the mesityl substituents. The peaks
associated with the dtbpm ligand appear as a triplet at 2.97 (JPH
= 7.5 Hz) for the methylene protons and as two doublets at
1.21 (JPH = 13.4 Hz) and 1.17 ppm (JPH = 12.3 Hz). The
methyl(mesityl) resonances for this complex are quite broad at
room temperature, but at −80 °C in toluene-d8 they are
resolved into five sharp singlets, four that integrate as 3 H and
one that integrates as 6 H (p-Me groups). In addition, two
singlets at 7.01 and 6.69 ppm for the aromatic mesityl protons
are observed. The Ge−H resonance changes very little,
remaining as a doublet at 5.94 ppm (J = 14.2 Hz). At room
temperature, the 31P{1H} NMR spectrum reveals two doublets
Figure 3. Molecular structure of 4 displaying thermal ellipsoids at the
50% probability level. Selected H atoms have been omitted for clarity.
Selected bond lengths (Å): Rh(1)−Ge(1) = 2.4433(6), Rh(1)−P(1) =
2.2098(7), Rh(1)−P(2) = 2.3079(8), Rh(1)−H(100) = 1.99(2),
Rh(1)−H(101) = 2.05(2), Ge(1)−H(1) = 1.41(2).
inequivalent mesityl groups, and the tert-butyl resonances for
the dtbpm ligand are present as three broad singlets (18 H:9
H:9 H). A new singlet at 5.36 ppm is attributed to a vinylic
1
CHPh proton, determined by a 2D H,1H NOESY experiment
to be in the cis position relative to the Si atom. No Si−H
resonance appears in this spectrum or in a spectrum of the
sample cooled to −60 °C in toluene-d8. However, at −60 °C
the vinylic resonance at 5.36 ppm appears as a multiplet, likely
due to coupling to Rh and P, indicating coordination of the
vinyl group. Thus, complex 5 may be viewed as the product of
net insertion of the alkyne into the Si−H bond. An infrared
absorption at 1550 cm−1 (Nujol) may reflect weak coordination
of the vinyl group (cf. νCC for free cis-stilbene at 1628
cm−1).19b
at 42.6 (2JPP = 20.9 Hz, 1JRhP = 218.6 Hz) and 9.6 ppm (2JPP
=
1
20.9 Hz, JRhP = 109.1 Hz). The structure of 4 obtained by X-
ray crystallography differs very little from that of 3 (Figure 3).
The infrared spectrum of a crystalline solid sample contains a
weak absorption at 2720 cm−1, consistent with the agostic
interactions.
In an analogous manner, the reaction of diphenylacetylene
with 4 gave (dtbpm)Rh[Ge(CPhCHPh)Mes2] (6) as a dark
1
orange solid. The H NMR spectrum at room temperature
contains a new resonance at 5.62 ppm, corresponding to the
CHPh proton. A resonance associated with a Ge−H bond is
not observed at room temperature or at −60 °C. The
resonance at 5.62 ppm broadens significantly (fwhh = 34 Hz)
upon cooling but does not display a clear splitting from
coupling to Rh or P. The 31P NMR spectrum displays two
Reactions of (dtbpm)Rh(EHMes2) with Alkynes. Re-
actions of 3 and 4 with alkynes were examined, given the
literature precedent for alkyne hydrosilation by (dtbpm)Rh
complexes.10 A solution of 1 equiv of diphenylacetylene in
C6H6 was added to 3 in C6H6 at room temperature to afford
(dtbpm)Rh[Si(CPhCHPh)Mes2] (5) in high yield (eq 3).
1
doublets of doublets at 31.4 (2JPP = 8.2 Hz, JRhP = 136.7 Hz)
1
and 7.8 ppm (2JPP = 8.2 Hz, JRhP = 88.0 Hz). In general, the
spectroscopic properties for complexes 5 and 6 are very similar.
Complex 3 reacted with phenylacetylene under analogous
conditions to yield (dtbpm)Rh[Si(CHCHPh)Mes2] (7) as a
bright orange solid. The arrangement of substituents on the
allyl group was determined by JHH coupling constants. In the
1H NMR spectrum, a doublet at 5.23 ppm and a doublet of
doublets at 4.16 ppm for the vinylic protons are associated with
a relatively large JHH coupling constant (J = 16.2 Hz) consistent
with a trans arrangement.20 The additional splitting of the
resonance at 4.16 ppm (JRhH = 6.7 Hz) arises from an
interaction with Rh. This trans arrangement of vinylic protons
indicates that Si−H addition to the alkyne has occurred in an
anti-Markovnikov manner. Like 5 and 6, the phosphine ligand
of 7 appears as two doublets of doublets at 37.4 (2JPP = 15.9 Hz,
The identity of 5 was determined by multinuclear NMR
spectroscopy. At room temperature, four peaks in the aromatic
region are associated with two phenyl groups and two mesityl
groups (one peak is comprised of overlapping resonances
correlating to both a phenyl group and mesityl group). Five
resonances attributed to methyl protons reflect the presence of
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Scheme 2
1
1JRhP = 187.5 Hz) and 6.8 ppm (2JPP = 15.9 Hz, JRhP = 127.4
Hz) in the 31P{1H} NMR spectrum, and the silyl group is
observed at 0.6 ppm by 29Si NMR spectroscopy. The reaction
of complex 4 with phenylacetylene resulted in an intractable
mixture of products.
terminal vinyl protons of these complexes display coupling to
Rh, which provides evidence for coordination of the vinyl
group. This type of complex has been targeted for a number of
years due to the similarity to the well-known η3-allyl
complexes.22 The synthesis of silaallyl species has typically
relied on the reaction of a suitable metal precursor with a vinyl
silane, such as (dimethylvinyl)dimethylsilane. Thus, the
formation of silaallyl complexes from the addition of alkynes
to a metal silyl species is unprecedented. Additionally,
complexes 6 and 9 represent the first reported germaallyl
complexes. Unfortunately, further structural data could not be
obtained because all efforts to grow X-ray-quality crystals of 5−
9 were unsuccessful.
Two possible routes to complexes 5−9 are outlined in
Scheme 2. In route A, complex 3 first binds the alkyne, and
then the coordinated alkyne inserts into the Rh−Si bond. The
Si−H bond could then add to the rhodium center to produce a
metallacycle, and reductive elimination of the C−H bond
would generate the observed product. Alternatively, as
indicated by route B, α-hydrogen migration to a Rh silylene
complex could be followed by a [2 + 2] cycloaddition with the
alkyne to form the same metallacycle proposed in route A.
Again, reductive elimination would give the silaallyl complex.
Interestingly, the process by which these reactions occur must
be reversible (at least in the case of 2-butyne).
Reactions of complexes 3 and 4 with 2-butyne in benzene
resulted in color changes from orange to dark red. However,
attempts to isolate products from the reaction solutions
resulted only in quantitative recovery of the starting materials,
3 and 4. The products of these reactions were therefore
characterized in situ by NMR spectroscopy as the E−H
insertion products (dtbpm)Rh[Si(CMeCHMe)Mes2] (8)
and (dtbpm)Rh[Ge(CMeCHMe)Mes2] (9). Complex 8
1
displays new H NMR resonances at 3.91 (CHMe), 2.14, and
2.12 ppm (inequivalent methyl groups on the silaallyl moiety),
and all appear as broad singlets at room temperature. At −60
°C, the CHMe proton shifts to 3.47 ppm and appears as a
multiplet due to H−H and Rh−H coupling. The dtbpm ligand
appears as two doublets of doublets in the 31P{1H} NMR
2
1
spectrum (30.2 ppm, JPP = 7.5 Hz, JRhP = 154.9 Hz; 13.95
ppm, JPP = 7.5 Hz, JRhP = 99.4 Hz), and the 29Si NMR
2
1
1
spectrum contains a single peak at 5.2 ppm. The H NMR
spectrum for complex 9 exhibits a broad multiplet at 4.39 ppm
for the CHMe proton, a multiplet at 2.15 ppm for one CH3
group due to couplings to the terminal CH proton, P and Rh,
and a singlet at 2.13 ppm for the other CH3 group. The
31P{1H} NMR spectrum contains two doublets of doublets at
32.6 (2JPP = 9.8 Hz, 1JRhP = 117.4 Hz) and 13.7 ppm (2JPP = 9.8
Hz, 1JRhP = 92.9 Hz). When complexes 8 and 9 were exposed to
vacuum in the solid state, 3 and 4 were regenerated and 2-
To probe which of these possible reaction pathways might be
operative, the reaction between complex 3 and the Lewis base
DMAP (p-dimethylaminopyridine) was examined. This Lewis
base has been observed to interact with a number of silylene
complexes via coordination to silicon,23 and it was hypothesized
that DMAP may act as a trap for a transient silylene complex. A
solution of DMAP in pentane was added to a solution of 3 in
C6H6, and the reaction mixture was cooled to −35 °C to afford
1
butyne was removed (by H NMR spectroscopy).
Silaallyl complexes are quite rare,21 and 5, 7, and 8 appear to
represent the first family of such complexes with rhodium. The
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(dtbpm)Rh(SiHMes2)(DMAP) (10) as yellow crystals (eq 4).
(dtbpm)RhI complex with an [η3-H2SiR3]− ligand (eq 5; one
bonding representation shown). Interestingly, the decomposi-
tion of 11 in C6D6 over 24 h at room temperature gives an
unidentified Rh complex and 5,7-diisopropyl-3-methyl-1-
phenyl-2,3-dihydro-1H-silaindole (vide infra).
The 1H NMR spectrum at room temperature contains
Single-crystal X-ray diffraction confirms the identity of 11
(Figure 4). The Rh−Si distance of 2.3163(15) Å is quite a bit
resonances for DMAP and the dtbpm ligand but none for
the silyl group. However, upon cooling to −60 °C, peaks
corresponding to two mesityl groups and an Si−H group (6.06
ppm) appear. No hydride ligands are observed. The dtbpm
ligand displays two doublets of doublets in the 31P{1H} NMR
spectrum at 39.14 (2JPP = 9.0, JRhP = 169.5 Hz) and 3.63 ppm
(2JPP = 8.9, JRhP = 97.8 Hz). The 29Si NMR resonance at −33.8
ppm confirms the presence of a silyl group.13 Given this result,
the precedents for alkyne insertions into metal−silicon bonds,24
and the limited precedent for 2 + 2 cycloadditions involving
alkynes and silylene complexes,12a,25 we currently favor the
mechanism of route A.
Reaction of (dtbpm)Rh(CH2Ph) with TripPhSiH2. The
benzyl complex (dtbpm)Rh(CH2Ph) was also found to
undergo a clean reaction with TripPhSiH2 (Trip = 2,4,6-
triisopropylphenyl). A pentane solution of 1 equiv of
TripPhSiH2 was added to a pentane solution of (dtbpm)Rh-
(CH2Ph), and cooling the reaction solution to −35 °C afforded
(dtbpm)Rh(H)2[5,7-diisopropyl-3-methyl-1-phenyl-2,3-dihy-
dro-1H-silaindenyl-κSi] (11) as orange crystals in 65% isolated
yield (eq 5). Because complex 11 is not stable at room
temperature in solution, multinuclear NMR experiments were
performed on solutions of 11 cooled to 0 °C in toluene-d8. The
1H NMR spectrum displays typical resonances for the dtbpm
ligand: a triplet at 3.14 ppm (JPH = 6.9 Hz) for the methylene
protons and two doublets at 1.23 (JPH = 12.6 Hz) and 1.10 ppm
(JPH = 12.8 Hz) for inequivalent tert-butyl groups. Three peaks
in the aromatic region correspond to the phenyl substituent on
Si, and one peak corresponds to the aryl protons of the Trip
group. Only five CH3 groups from the Trip substituent are
apparent, indicating C−H activation at one of the methyl
groups, and two resonances at 1.99 and 1.61 ppm correspond
to diastereotopic protons for the new methylene group. No Si−
H group is observed, and two hydrides are present at −7.04
ppm as a complex multiplet, that displays strong coupling to Si
(JSiH = 51.8 Hz). The multiplet arises from the presence of
inequivalent hydrides (due to the chiral silicon center) and
coupling to the Rh and inequivalent P atoms. Unlike complexes
3−10, the 31P{1H} NMR spectrum displays only one doublet at
19.8 (JRhP = 113.9 Hz), presumably due to a rapid dynamic
process. Additionally, the 29Si NMR resonance of 0.89 is typical
for a silyl ligand. Taken together, the NMR data indicate that
activation of one Trip methyl group has occurred to create a
new Si−C bond. The two new rhodium hydride ligands
originate from the activation of Si−H and C−H bonds. Like
complexes 1 and 2, 11 appears to best be represented as a
Figure 4. Molecular structure of 11 displaying thermal ellipsoids at the
50% probability level. H atoms have been omitted for clarity. Selected
bond lengths (Å): Rh(1)−Si(1) = 2.3163(15), Rh(1)−P(1) =
2.3249(13), Rh(1)−P(2) = 2.3381(16), Si(1)−C(24) = 1.901(5),
Si(1)−C(38) = 1.906(5).
shorter than that observed for 3, and the Rh−P bond lengths
are very similar (2.3249(13) and 2.3381(16) Å). Like
complexes 1 and 2, the Si atom is not coplanar with the
dtbpm phosphorus atoms and Rh. The Si−C bonds of the five-
membered ring are nearly identical, with Si(1)−C(24) at
1.901(5) Å and Si(1)−C(38) at 1.906(5) Å. Although the
rhodium hydride ligands were not located, the strong coupling
to Si observed by NMR spectroscopy indicates that the
hydrides likely occupy positions similar to those located for
complex 1.
The proposed formation of 11 is outlined in Scheme 3.
Oxidative addition of TripPhSiH2 followed by reductive
elimination of toluene can result in a (dtbpm)Rh(SiHTripPh)
complex, which can then undergo C−H activation of a methyl
group to give a cyclometalated species. Reductive elimination
from this species would result in a (dtbpm)RhH species and
5,7-diisopropyl-3-methyl-1-phenyl-2,3-dihydro-1H-silaindole.
Finally, the latter compound would add via Si−H oxidative
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Scheme 3
addition to give 11. Note that the related complex (dippe)Rh-
(CH2Ph) (dippe = bis(diisopropylphosphino)ethane) under-
goes a similar reaction with [2,4,6-tri(tert-butyl)phenyl]-
phosphine to afford (dippe)Rh(H)[5,7-di(tert-butyl)-2,3-dihy-
dro-3,3-dimethyl-1H-phosphindole-κP].6b
Scheme 4
The observation of 5,7-diisopropyl-3-methyl-1-phenyl-2,3-
dihydro-1H-silaindole in 15% yield from the decomposition of
11 led to investigations on the catalytic production of this
species. A solution of TripPhSiH2 in benzene-d6 with a 10%
loading of (dtbpm)Rh(CH2Ph) was monitored at room
temperature (eq 6). Over 48 h, a yield of 90% of 5,7-
diisopropyl-3-methyl-1-phenyl-2,3-dihydro-1H-silaindole was
observed, along with the concurrent release of hydrogen (by
1H NMR spectroscopy). Longer reaction times did not increase
the product yield. Complex 11 also acts as a competent catalyst
for this transformation. After 20 h at room temperature with
10% of 11, 49% conversion was observed. For comparison, after
20 h with (dtbpm)Rh(CH2Ph), 55% conversion was observed.
This result suggests that (dtbpm)Rh(CH2Ph) and 11 function
as precatalysts to the same active species. However, further
catalytic studies were hindered by decomposition of the
rhodium complexes in this system.
material. The complex [(dtbpm)IrCl]2 reacted with 2 equiv of
H2SiPh2 in benzene at room temperature over 40 min to give
the bridging silylene complex [(dtbpm)IrH](μ-SiPh2)(μ-
Cl)2[(dtbpm)IrH] (12) as a yellow-orange solid in 89% yield
(eq 7). The identity of 12 was determined by X-ray
A proposed mechanism is outlined in Scheme 4. When
(dtbpm)Rh(CH2Ph) is used as the precatalyst, the reaction of
(dtbpm)Rh(CH2Ph) and TripPhSiH2 can give 11 and enter
into the catalytic cycle by reductive elimination to form
[(dtbpm)RhH] and 5,7-diisopropyl-3-methyl-1-phenyl-2,3-di-
hydro-1H-silaindole. Similarly, 11 would function as a
precatalyst by reductive elimination to form [(dtbpm)RhH]
and 5,7-diisopropyl-3-methyl-1-phenyl-2,3-dihydro-1H-silain-
dole. The [(dtbpm)RhH] species could then oxidatively add
TripPhSiH2 to give a (dtbpm)Rh(H)2(SiHTripPh) complex,
which could then lose 1 equiv of H2 via reductive elimination.
The resulting (dtbpm)Rh(SiHTripPh) could then activate a
methyl C−H bond to form a cyclometalated species. Reductive
elimination of the Si and C groups would release 5,7-
diisopropyl-3-methyl-1-phenyl-2,3-dihydro-1H-silaindole and
re-form [(dtbpm)RhH].
crystallography (Figure 5), with single crystals grown from a
toluene solution at −35 °C. The Ir−Si bond distances of
2.425(2) and 2.427(2) Å are quite long compared to most Ir−
Si single bonds.13 The hydride ligands were not located in the
Fourier map. Neglecting the hydride ligands, the coordination
environment for Ir(1) can be described as an approximate
square pyramid, with P(3), P(4), Si(1), and Cl(1) forming the
square plane. The empty coordination site trans to Cl(2) is
presumed to contain a hydride ligand (see below). In a similar
manner, Ir(2) adopts an octahedral geometry with P(1), P(2),
Si(1), and Cl(2) defining a coordination plane and the
coordination site trans to Cl(1) being occupied by a hydride
Reactions of [(dtbpm)IrCl]2 with Silanes. Silane
activations related to those above were investigated for the
26
(dtbpm)Ir fragment, using [(dtbpm)IrCl]2 as a starting
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bond is not present in the molecule. A triplet of triplets at
−12.59 ppm (JPH = 5.3, 63.3 Hz) arises from a bridging hydride
ligand due to coupling to each dtbpm ligand, and a doublet of
doublets integrating to 2H at −24.66 ppm (JPH = 2.4, 18.0 Hz)
results from the two terminal Ir−H ligands. No JSiH coupling
constant was observed for these hydride ligands. The presence
of terminal hydrides is further supported by infrared spectros-
copy (2391, 2327 cm−1, Nujol mull). In contrast to the
common trend, by 1H NMR spectroscopy the terminal hydride
ligands appear far upfield from the bridging hydride ligand,29
but this is consistent with the hydride ligands observed for 12.
The 31P{1H} NMR spectrum contains doublets at 18.50 and
3.28 ppm (JPP = 14.5 Hz). By 29Si NMR spectroscopy, a
pseudotriplet at 75.0 ppm (JSiP ∼ 150 Hz) is observed for the
bridging silylene ligand. On the basis of previous reports, this
resonance is much further downfield than one would expect for
a bridging SiMesCl moiety.13,27 However, the connectivity of
13 was confirmed by a low-quality X-ray structure. Additionally,
low-valent Ir−Cl and Rh−Cl have been shown to undergo
facile oxidative addition of an Si−H bond, followed by
reductive elimination of an Si−Cl bond in the context of
catalytic hydrosilation of various substrates.30
Figure 5. Molecular structure of 12 displaying thermal ellipsoids at the
50% probability level. H atoms and tert-butyl groups have been
omitted for clarity. Selected bond lengths (Å): Ir(1)−Si(1) =
2.427(2), Ir(1)−P(3) = 2.406(2), Ir(1)−P(4) = 2.233(2), Ir(1)−
Cl(1) = 2.503(2), Ir(1)−Cl(2) = 2.551(2), Ir(2)−Si(1) = 2.425(2),
Ir(2)−P(1) = 2.237(2), Ir(2)−P(2) = 2.412(2), Ir(2)−Cl(1) =
2.555(2), Ir(2)−Cl(2) = 2.502(2).
In an effort to synthesize a mononuclear (dtbpm)Ir silyl
complex, an extremely bulky primary silane was utilized. The
reaction of [(dtbpm)IrCl]2 with 2 equiv of H3Si(dmp) (dmp =
2,6-dimesitylphenyl) in benzene at 55 °C for 18 h afforded
(dtbpm)Ir(H)4(10-chloro-1-mesityl-5,7-dimethyl-9,10-dihydro-
silaphenanthrene-κSi) (14) as a yellow solid in moderate (72%)
isolated yield (eq 9). The identity of 14 was determined by a
ligand. The strong trans influence of Si is manifested in
different Ir−P bond lengths; the Ir(1)−P(4) bond length is
2.233(2) Å, while the Ir(1)−P(3) bond length is significantly
longer at 2.406(2) Å. The same trend is observed for the
Ir(2)−P(1) (2.237(2) Å) and Ir(2)−P(2) (2.412(2) Å) bonds.
The NMR spectroscopic data for 12 are consistent with the
observed X-ray structure. By 1H NMR spectroscopy, two sets of
tBu resonances are observed, as well as resonances associated
with equivalent phenyl groups. Two equivalent hydride ligands
give rise to a doublet at −23.3 ppm, due to splitting by 31P (JPH
= 24.8 Hz). Coupling to the second 31P nucleus is likely too
small to be observed, which is supported by an analogously
small coupling in 14 (vide infra). As discussed above, the
terminal Ir−H ligands are in coordination sites trans to a Cl
atom, and the small coupling to 31P supports a cis arrangement
of the phosphine and hydride ligands. The 31P{1H} spectrum
displays two doublets at 8.9 and −3.7 ppm (JPP = 6.1 Hz), and a
single resonance at −34.4 ppm in the 29Si NMR spectrum is in
a region consistent with a bridging silylene complex of
iridium.13,27 Additionally, two terminal hydride stretches are
observed by infrared spectroscopy (2328, 2288 cm−1, Nujol
mull). Overall, complex 12 can be considered to be the product
of two Si−H oxidative additions across the two Ir centers of
[(dtbpm)IrCl]2, and such complexes are typical products of the
reactivity of binuclear complexes of Rh and Ir with silanes.28
Under analogous conditions, [(dtbpm)IrCl]2 undergoes
clean conversion to a new product with 2 equiv of MesSiH3
(eq 8). The yellow-orange solid, isolated in 90% yield, was
characterized as [(dtbpm)IrH](μ-SiMesCl)(μ-Cl)(μ-H)-
[(dtbpm)IrH] (13) via multinuclear NMR experiments. The
1H NMR spectrum of complex 13 contains resonances
corresponding to one mesityl group and two dtbpm ligands.
There is no resonance at ca. 5 ppm, indicating that an Si−H
combination of X-ray crystallography (Figure 6) and multi-
nuclear NMR spectroscopy. Single crystals of 14 were grown
from a concentrated toluene solution at −35 °C. The Ir−Si
bond length of 2.323(4) Å is in the region expected for Ir silyl
species, and unlike 12, the Ir−P bond lengths are very similar
(2.378(4) and 2.365(4) Å). The Si−Cl bond length (2.142(6)
Å) is normal, and the Si−C bond lengths are very similar
(1.890(15) and 1.868(14) Å). The hydride ligands were not
1
located. The H NMR spectrum at room temperature displays
five distinct methyl groups, correlating to the CH3 groups of
the dmp ligand. Additionally, two new CH2 resonances are
present at 3.64 and 2.64 ppm, each integrating to 1 H. Four
equivalent hydride ligands appear as a triplet at −11.58 ppm
(JPH = 18.0 Hz), and the integration of the hydrides was
confirmed under varying relaxation times. The 29Si NMR
spectrum displays a resonance at −1.96 ppm that is typical for
metal silyl complexes.
The mechanism for the formation of 14 likely involves a
series of oxidative additions and reductive eliminations,
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transformation of TripPhSiH2 to 5,7-diisopropyl-3-methyl-1-
phenyl-2,3-dihydro-1H-silaindole. Like 11, the iridium complex
14 also contains a silacycle produced by an intramolecular Si−
C bond formation.
Another common theme encountered in this study is the
apparent participation of reactive [(diphosphine)MH] species
as key intermediates in many of the observed transformations.
In the proposed mechanisms for the formations of 1, 2, and 11,
the Si−C bond-forming step appears to produce a
[(diphosphine)RhH] species, which can then undergo further
reaction with the released silane. Similarly, the Si−C bond-
forming step in the synthesis of 14 appears to generate a
[(dtbpm)IrH3] species. Several [(diphosphine)MH] complexes
with group 9 metals have been isolated as dinuclear complexes,
9
such as [(dippe)RhH]2 and [(dippe)NiH]2,32 and these are
active catalysts for H/D exchange or the dehydrocoupling of
silanes. Current efforts to synthesize [(dtbpm)RhH]2 and
[(dtbpm)IrH]2 and explore their catalytic reactivity are
underway.
Figure 6. Molecular structure of 14 displaying thermal ellipsoids at the
50% probability level. H atoms have been omitted for clarity. Selected
bond lengths (Å): Ir(1)−Si(1) = 2.323(4), Ir(1)−P(1) = 2.378(4),
Ir(1)−P(2) = 2.365(4), Si(1)−Cl(1) = 2.142(6), Si(1)−C(1) =
1.890(15), Si(1)−C(15) = 1.868(14).
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 then NaHCO3. Pentane was then dried over MgSO4 and
stored over activated 4 Å molecular sieves and dried over alumina.
Thiophene impurities were removed from benzene and toluene by
treatment with H2SO4 and saturated NaHCO3. Benzene and toluene
were then dried over CaCl2 and further dried over alumina.
Tetrahydrofuran, diethyl ether, dichloromethane, and hexanes were
dried over alumina. Benzene-d6 was dried by vacuum distillation from
Na/K alloy. The complexes (dtbpe)Rh(CH2Ph),10 (dtbpm)Rh-
including an intramolecular C−H activation related to that of
Scheme 4. For example, initial addition of the silane followed
by Si−Cl reductive elimination could produce (dtbpm)IrH and
the chlorosilane. These species could then recombine to form
(dtbpm)IrH2(SiHCldmp), which could undergo hydrogen loss
and then intramolecular C−H activation at Ir. Finally, Si−C
reductive elimination of the cyclic silane, followed by Si−H and
H−H oxidative additions, would produce the product. Unlike
11, complex 14 is stable at elevated temperatures and does not
release a silane product upon heating to 80 °C for 18 h. A
similar complex was reported from the reaction of
(Et2PhP)3IrCl with (dmp)SiH3 and was suggested to form
via an Ir silylene complex.31 While both of these postulated
mechanisms are reasonable, the reaction mixture must be
heated to achieve the synthesis of 14, which is not consistent
with conditions typically observed for reactive silylene
intermediates.
26
(CH2Ph),11 and [(dtbpm)IrCl]2 were prepared according to
literature methods. All other chemicals were purchased from
commercial sources and used without further purification.
NMR spectra were recorded using Bruker AV-500 and AV-600
spectrometers equipped with a 5 mm BB probe. Spectra were recorded
at room temperature and referenced to the residual protonated solvent
for 1H unless otherwise noted. 31P{1H} NMR spectra were referenced
relative to 85% H3PO4 external standard (δ = 0). 19F{1H} spectra were
referenced relative to a C6F6 external standard. 13C{1H} NMR spectra
were calibrated internally with the resonance for the solvent relative to
tetramethylsilane. For 13C{1H} NMR spectra, resonances obscured by
the solvent signal are omitted. 29Si NMR spectra were referenced
relative to a tetramethylsilane standard and obtained via 2D H,29Si
CONCLUSION
1
■
HMBC unless specified otherwise. The following abbreviations have
been used to describe peak multiplicities in the reported NMR
spectroscopic data: “m” for complex multiplet, and “br” for broadened
resonances. Infrared spectra for 3 and 4 were collected on a Perkin-
Elmer Spectrum 400 FTIR spectrometer with an attenuated total
reflectance accessory. Infrared spectra for all other complexes were
recorded on a Nicolet Nexus 6700 FTIR spectrometer with a liquid-
nitrogen-cooled MCT-B detector. Measurements were made at a
resolution of 4.0 cm−1. Elemental analyses were performed by the
College of Chemistry Microanalytical Laboratory at the University of
California, Berkeley.
The complexes (dtbpe)Rh(CH2Ph), (dtbpm)Rh(CH2Ph), and
[(dtbpm)IrCl]2 have been shown to undergo reactions with
various organosilanes, and several themes emerge from the
reactivity patterns for these hindered, bis(phosphine)-sup-
ported group 9 metal complexes. Most notable is the
prevalence of Si−C bond formation in these systems. The
complex (dtbpe)Rh(CH2Ph) undergoes reactions with secon-
dary silanes in which the benzyl group is transferred to the
silicon atom to give the tertiary silyl complexes 1 and 2. Benzyl
reagents often lose the benzyl group as toluene (e.g., in the
reaction of (dtbpm)Rh(CH2Ph) with Mes2SiH2). The sila- and
germaallyl complexes 5−9 result from the net insertion of an
alkyne into an E−H bond. Interestingly, this Si−C bond
formation appears to be reversible on the basis of the
conversion of 8 and 9 back to 3 and 4, respectively, under an
applied vacuum. Complex 11 is produced from a C−H bond
activation and subsequent Si−C bond formation to give a
silacycle, and both (dtbpm)Rh(CH2Ph) and 11 have been
demonstrated to catalyze Si−C bond formation in the
(dtbpe)Rh(H)2(SiBnPh2) (1). To a 2 mL pentane solution of
(dtbpe)Rh(CH2Ph) (0.030 g, 0.058 mmol) was added a 1 mL pentane
solution of Ph2SiH2 (0.011 g, 0.060 mmol). The reaction mixture was
allowed to stand for 24 h at room temperature, after which the
resulting orange-red solution was cooled to −35 °C. After 3 days,
1
orange crystals were collected by filtration in 69% yield (0.028 g). H
NMR (C6D6, 500 MHz): δ 7.93 (4H, d, J = 7.0 Hz, ArH), 7.29 (4H, t,
J = 7.5 Hz, ArH), 7.20 (4H, t, J = 7.5 Hz, ArH), 7.08 (2H, t, J = 7.5 Hz,
ArH), 6.98 (1H, t, J = 7.0 Hz, ArH), 3.28 (2H, s, CH2Ar), 1.37 (4H, d,
J = 12.0 Hz, PCH2CH2P), 1.00 (36H, m, PC(CH3)3), −5.35 (2H, m,
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1
JPH = 19.6 Hz, JRhH = 33.8 Hz, JSiH = 44.4 Hz, RhH). 13C{1H} NMR
(C6D6, 150.9 MHz): δ 147.9 (ArC), 143.4 (ArC), 136.1 (ArC), 130.4
(ArC), 127.3 (ArC), 123.8 (ArC), 37.4 (CH2), 35.2 (PC(CH3)3), 35.0
(P(CH2)2P), 30.5 (PC(CH3)3). 31P{1H} NMR (C6D6, 163.0 MHz): δ
111.3 (d, 1JRhP = 114 Hz). 29Si NMR (C6D6, 99.4 MHz): δ −5.6. Anal.
Calcd for C37H59P2RhSi: C, 63.78; H, 8.53. Found: C, 63.39; H, 8.70.
(dtbpe)Rh(H)2(SiBnEt2) (2). To a 2 mL pentane solution of
(dtbpe)Rh(CH2Ph) (0.050 g, 0.098 mmol) was added a 1 mL pentane
solution of Et2SiH2 (0.009 g, 0.10 mmol). The reaction mixture was
cooled to −35 °C. After 3 days, yellow crystals were collected in 70%
yield (0.041 g). 1H NMR (C6D6, 500 MHz): δ 7.36 (2H, d, J = 7.6 Hz,
ArH), 7.22 (2H, t, J = 7.6 Hz, ArH), 7.04 (1H, t, J = 7.6 Hz, ArH),
2.81 (2H, s, CH2), 1.40 (10H, m, CH2CH3), 1.11 (36H, d, J = 12.2 Hz,
orange solid in 85% yield (0.032 g). H NMR (C6D6, 500 MHz): δ
7.52 (4H, d, J = 7.4 Hz, ArH), 6.98 (4H, t, J = 7.4 Hz, ArH), 6.86 (4H,
ov m, ArH), 6.66 (2H, s, ArH), 5.36 (1H, s, CHPh), 3.18 (5H, br s,
ArCH3 + PCH2P), 2.79 (3H, br s, ArCH3), 2.67 (6H, s, ArCH3), 2.20
(3H, s, ArCH3), 2.04 (3H, s, ArCH3), 1.27 (18H, br s, PC(CH3)3),
1
1.10 (9H, br s, PC(CH3)3), 0.92 (9H, br s, PC(CH3)3). H NMR
(−60 °C, toluene-d8, 500 MHz): δ 7.46 (4H, s, ArH), 6.95 (4H, s,
ArH), 6.80 (4H, s, ArH), 6.59 (2H, s, ArH), 5.24 (1H, t, JRhH = 6.3 Hz,
CHPh), 3.11 (5H, br s, ArCH3 + PCH2P), 2.72 (3H, s, ArCH3), 2.59
(6H, s, ArCH3), 2.19 (3H, s, ArCH3), 2.01 (3H, s, ArCH3), 1.21 (18H,
d, J = 11.5 Hz, PC(CH3)3), 1.05 (9H, d, J = 11.3 Hz, PC(CH3)3), 0.95
(9H, d, J = 11.0 Hz, PC(CH3)3). 13C{1H} NMR (C6D6, 150.9 MHz):
δ 145.7 (ArC), 143.8 (ArC), 143.0 (ArC), 136.9 (ArC), 132.0 (ArC),
130.8 (ArC), 125.0 (ArC), 124.3 (ArC), 124.0 (ArC), 90.3 (CPhSi),
83.6 (CHPh), 37.4 (PCH2P), 36.5 (PC(CH3)3), 31.4 (PC(CH3)3),
27.1 (ArCH3), 21.3 (ArCH3), 21.1 (ArCH3). 31P{1H} NMR (C6D6,
163.0 MHz): δ 27.8 (dd, 2JPP = 9.1 Hz, 1JRhP = 145.1 Hz), 7.9 (dd, 2JPP
PC(CH3)3), 0.88 (4H, t, J = 7.0 Hz, PCH2CH2P), −5.63 (2H, m, JPH
=
19.1 Hz, JRhH = 27.3 Hz, JSiH = 52.1 Hz, RhH). 13C{1H} NMR (C6D6,
150.9 MHz): δ 144.3 (ArC), 141.6 (ArC), 139.9 (ArC), 132.5 (ArC),
125.8 (ArC), 123.1 (ArC), 37.8 (CH2), 34.6 (P(CH2)2P), 31.5
(PC(CH3)3), 30.3 (PC(CH3)3), 7.8 (CH2CH3), 2.4 (CH2CH3).
= 9.1 Hz, JRhP = 89.7 Hz). 29Si NMR (C6D6, 99.4 MHz): δ 3.8. IR:
1
1550 cm−1 (ν(CC)). Anal. Calcd for C49H71P2RhSi: C, 68.99; H,
1
31P{1H} NMR (C6D6, 163.0 MHz): δ 114.7 (d, JRhP = 136 Hz).
29Si NMR (C6D6, 99.4 MHz): δ 0.8 ppm. Anal. Calcd for
C29H59P2RhSi: C, 57.98; H, 9.90. Found: C, 57.70; H, 10.36.
8.39. Found: C, 68.38; H, 8.72.
(dtbpm)Rh(Ge(CPhCHPh)Mes2) (6). A solution of diphenyla-
cetylene (0.008 g, 0.04 mmol) in 1 mL of C6H6 was added to a
solution of 4 (0.030 g, 0.04 mmol) in 2 mL of C6H6. The reaction
solution was stirred for 30 min before being filtered through a Celite
plug. The resulting solution was stripped to dryness to give a dark
(dtbpm)Rh(SiHMes2) (3). A solution of Mes2SiH2 (0.040 g, 0.15
mmol) in 2 mL of pentane was added to a solution of (dtbpm)Rh-
(CH2Ph) (0.075 g, 0.15 mmol) in 2 mL of pentane. After 1 h, the
solution was concentrated (to ca. 2 mL) and cooled to −35 °C to
afford orange crystals in 81% yield (0.081 g). 1H NMR (20 °C,
toluene-d8, 500 MHz): δ 6.81 (4H, s, ArH), 3.01 (2H, t, J = 7.5 Hz,
PCH2P), 2.56 (9H, br s, ArCH3), 2.24 (6H, s, ArCH3), 1.21 (36H, d, J
1
orange solid in 83% yield (0.029 g). H NMR (C6D6, 600 MHz): δ
7.52 (4H, d, J = 6.9 Hz, ArH), 6.99 (4H, m, ArH), 6.88 (2H, br s,
ArH), 6.83 (2H, t, J = 7.5 Hz, ArH), 6.70 (2H, br s, ArH), 5.62 (1H, s,
CHPh), 3.19 (2H, br s, PCH2P), 2.94 (6H, br s, ArCH3), 2.47 (6H, br
s, ArCH3), 2.19 (3H, br s, ArCH3), 2.10 (3H, br s, ArCH3), 1.26 (18H,
1
= 15.0 Hz, PC(CH3)3). H NMR (−80 °C, toluene-d8, 500 MHz): δ
7.06 (1H, s, ArH), 6.96 (1H, s, ArH), 6.76 (1H, s, ArH), 6.74 (1H, s,
ArH), 6.81 (1H, br s, SiH), 3.15 (3H, s, ArCH3), 2.77 (5H, s, ArCH3 +
PCH2P), 2.60 (3H, s, ArCH3), 2.34 (3H, s, ArCH3), 2.30 (3H, s,
ArCH3), 1.44 (9H, d, J = 12.5 Hz, PC(CH3)3), 1.18 (9H, d, J = 11.5
Hz, PC(CH3)3), 1.05 (9H, d, J = 11.5 Hz, PC(CH3)3), 0.95 (9H, d, J =
12.5 Hz, PC(CH3)3). 13C{1H} NMR (−80 °C, toluene-d8, 150.9
MHz): δ 144.8 (ArC), 144.2 (ArC), 144.1 (ArC), 143.4 (ArC), 142.8
(ArC), 142.2 (ArC), 136.3 (ArC), 134.9 (ArC), 126.1 (ArC), 36.3
(PC(CH3)3), 36.0 (PC(CH3)3), 34.0 (PC(CH3)3), 33.8 (PC(CH3)3),
31.9 (PCH2P), 31.0 (PC(CH3)3), 30.7 (PC(CH3)3), 30.3 (PC-
(CH3)3), 25.8 (ArCH3), 25.0 (ArCH3), 23.5 (ArCH3), 21.4
(ArCH3), 21.2 (ArCH3). 31P{1H} NMR (C6D6, 163.0 MHz): δ 45.9
1
br s, PC(CH3)3), 1.11 (18H, br s, PC(CH3)3). H NMR (−60 °C,
toluene-d8, 500 MHz): δ 7.31 (2H, t, J = 7.0 Hz, ArH), 7.04 (2H, d, J
= 7.0 Hz, ArH), 6.83 (2H, m, ArH), 6.77 (4H, t, J = 7.0 Hz, ArH), 6.63
(4H, s, ArH), 5.46 (1H, s, CHPh), 3.12 (2H, dd, J = 16.0, 8.1 Hz,
PCH2P), 2.38 (6H, s, ArCH3), 2.04 (12H, s, ArCH3), 1.24 (9H, d, J =
10.0 Hz, PC(CH3)3), 1.13 (9H, d, J = 13.0 Hz, PC(CH3)3), 1.06 (9H,
d, J = 11.7 Hz, PC(CH3)3), 0.93 (9H, d, J = 12.0 Hz, PC(CH3)3).
13C{1H} NMR (C6D6, 150.9 MHz): δ 147.7 (ArC), 143.6 (ArC),
142.3 (ArC), 135.8 (ArC), 130.2 (ArC), 124.9 (ArC), 123.9 (ArC),
91.1 (CHPh), 92.6 (CHPh), 35.9 (PCH2P), 34.6 (PC(CH3)3), 34.0
(PC(CH3)3), 31.5 (PC(CH3)3), 31.3 (PC(CH3)3), 30.9 (PC(CH3)3),
22.6 (ArCH3), 22.3 (ArCH3), 20.7 (ArCH3). 31P{1H} NMR (C6D6,
163.0 MHz): δ 31.4 (dd, 2JPP = 8.2 Hz, 1JRhP = 136.7 Hz), 7.8 (dd, 2JPP
(dd, 2JPP = 17.9 Hz, 1JRhP = 226.6 Hz), 10.6 (dd, 2JPP = 17.9 Hz, 1JRhP
=
89.7 Hz). 29Si NMR (C6D6, 99.4 MHz): δ −12.4. Anal. Calcd for
C35H61P2RhSi: C, 62.30; H, 9.11. Found: C, 61.94; H, 9.30.
1
= 8.2 Hz, JRhP = 88.0 Hz). Anal. Calcd for C49H71GeP2Rh: C, 65.57;
H, 7.97. Found: C, 65.78; H, 8.04.
(dtbpm)Rh(GeHMes2) (4). A solution of Mes2GeH2 (0.047 g, 0.15
mmol) in 2 mL of pentane was added to a solution of (dtbpm)Rh-
(CH2Ph) (0.075 g, 0.15 mmol) in 2 mL of pentane. After 1 h, the
solution was concentrated (ca. 2 mL) and cooled to −35 °C to afford
dark red crystals in 71% yield (0.077 g). 1H NMR (C6D6, 600 MHz):
δ 6.89 (4H, s, ArH), 5.98 (1H, d, J = 14.0 Hz, GeH), 2.97 (2H, t, J =
7.5 Hz, PCH2P), 2.71 (6H, br s, ArCH3), 2.32 (6H, br s, ArCH3), 2.25
(6H, s, ArCH3), 1.21 (18H, d, J = 13.4 Hz, PC(CH3)3), 1.17 (18H, d, J
= 12.3 Hz, PC(CH3)3). 1H NMR (−80 °C, toluene-d8, 500 MHz): δ 7
0.01 (2H, s, ArH), 6.69 (2H, s, ArH), 5.94 (1H, d, J = 14.2 Hz, GeH),
3.05 (3H, s, ArCH3), 2.71 (2H, m, PCH2P), 2.56 (6H, s, ArCH3), 2.28
(3H, s, ArCH3), 2.23 (3H, s, ArCH3), 1.99 (3H, s, ArCH3), 1.33 (9H,
d, J = 12.8 Hz, PC(CH3)3), 1.11 (9H, d, J = 12.2 Hz, PC(CH3)3), 0.99
(9H, d, J = 11.8 Hz, PC(CH3)3), 0.88 (9H, d, J = 13.0 Hz, PC(CH3)3).
13C{1H} NMR (C6D6, 150.9 MHz): δ 146.5 (ArC), 142.5 (ArC),
135.4 (ArC), 37.6 (PCH2P), 36.5 (PC(CH3)3), 34.6 (PC(CH3)3), 34.0
(PC(CH3)3), 31.7 (PC(CH3)3), 30.9 (PC(CH3)3), 22.3 (ArCH3), 20.8
(ArCH3), 13.8 (ArCH3). 31P{1H} NMR (C6D6, 163.0 MHz): δ 42.6
(dtbpm)Rh(Si(CHCHPh)Mes2) (7). An excess of phenyl-
acetylene (ca. 0.1 mL) was added to a solution of 3 (0.030 g, 0.04
mmol) in 1 mL of C6H6. The reaction solution was stirred for 30 min
before being filtered through a Celite plug. The resulting solution was
stripped to dryness to give a bright orange solid in 88% yield (0.030 g).
1H NMR (C6D6, 500 MHz) δ 7.45 (2H, d, J = 7.4 Hz, PhH), 7.06
(2H, t, J = 7.4 Hz, PhH), 6.89 (1H, d, J = 7.4 Hz, PhH), 6.81 (4H, s,
ArH), 5.23 (1H, d, J = 16.2 Hz, =CH), 4.16 (1H, dd, J = 16.2, JRhH
=
6.7 Hz, CH), 3.12 (2H, t, J = 6.8 Hz, PCH2P), 3.01 (6H, br s,
ArCH3), 2.69 (6H, s, ArCH3), 2.18 (3H, s, ArCH3), 2.16 (3H, s,
ArCH3), 1.34 (9H, d, J = 12.2 Hz, C(CH3)3), 1.26 (9H, d, J = 12.0 Hz,
C(CH3)3)), 1.04 (9H, d, J = 12.7 Hz, C(CH3)3), 0.76 (9H, d, J = 11.8
Hz, C(CH3)3). 13C{1H} NMR (C6D6, 150.9 MHz): δ 145.3 (ArC),
144.4 (ArC), 144.0 (ArC), 139.1 (ArC), 131.5 (ArC), 130.6 (ArC),
128.6 (ArC), 127.2 (ArC), 100.7 (CSi), 76.9 (CHPh), 36.1 (PCH2P),
35.4 (PC(CH3)3), 31.6 (PC(CH3)3), 31.0 (PC(CH3)3), 30.8 (PC-
(CH3)3), 30.3 (PC(CH3)3), 26.9 (ArCH3), 23.1 (ArCH3), 20.8
(ArCH3). 31P{1H} NMR (C6D6, 163.0 MHz): δ 37.4 (dd, JPP
=
2
(dd, 2JPP = 20.9 Hz, 1JRhP = 218.6 Hz), 9.6 (dd, 2JPP = 20.9 Hz, 1JRhP
=
15.9 Hz, 1JRhP = 187.5 Hz), 6.8 (dd, 2JPP = 15.9 Hz, 1JRhP = 127.4 Hz).
29Si NMR (C6D6, 99.4 MHz): δ 0.6. Anal. Calcd for C37H59P2RhSi: C,
63.78; H, 8.53. Found: C, 63.39; H, 8.70.
109.1 Hz). Anal. Calcd for C35H61GeP2Rh: C, 58.44; H, 8.55. Found:
C, 58.26; H, 8.78.
(dtbpm)Rh(Si(CPhCHPh)Mes2) (5). A solution of diphenyla-
cetylene (0.008 g, 0.04 mmol) in 1 mL of C6H6 was added to a
solution of 3 (0.030 g, 0.04 mmol) in 2 mL of C6H6. The red reaction
solution was stirred for 30 min before being filtered through a Celite
plug. The resulting solution was stripped to dryness to give a bright
In Situ Formation of (dtbpm)Rh(Si(CMeCHMe)Mes2) (8).
With a 10 μL syringe, 2-butyne (3.1 μL, 0.04 mmol) was added to a
solution of 3 (0.030 g, 0.04 mmol) in 1 mL of C6D6. The reaction
solution was stirred for 30 min before being filtered through a Celite
1025
dx.doi.org/10.1021/om300943e | Organometallics 2013, 32, 1016−1028

Organometallics
Article
1
plug. H NMR (C6D6, 500 MHz): δ 6.81 (4H, s, ArH), 3.91 (1H, s,
CH), 1.99 (1H, dd, J = 13.5, 6.9 Hz, SiCH2), 1.76 (3H, d, J = 6.7 Hz,
CH3), 1.61 (1H, m, SiCH2), 1.50 (3H, d, J = 6.9 Hz, CH3), 1.39 (6H,
d, J = 6.8, CH3), 1.23 (18H, d, J = 12.6 Hz, PC(CH3)3), 1.10 (18H, d, J
= 12.8 Hz, PC(CH3)3), 1.05 (3H, d, J = 6.9 Hz, CH3), −7.04 (2H, m,
JSiH = 51.8 Hz, RhH2). 13C{1H} NMR (0 °C, toluene-d8, 150.9 MHz):
δ 155.5 (ArC), 152.9 (ArC), 148.8 (ArC), 144.5 (ArC), 126.63 (ArC),
120.4 (ArC), 118.9 (ArC), 37.8 (CH2), 35.1 (PCH2P), 34.9
(PC(CH3)3), 34.6 (PC(CH3)3), 33.8 (PC(CH3)3), 32.9 (PC(CH3)3),
30.5 (PC(CH3)3), 30.3 (PC(CH3)3), 25.2 (ArCH3), 24.5 (ArCH3),
24.3 (ArCH3), 23.8 (ArCH3), 22.8 (ArCH3). 31P{1H} NMR (0 °C,
CHMe), 3.10 (2H, s, PCH2P), 2.88 (12H, s, ArCH3), 2.17 (6H, s,
ArCH3), 2.14 (3H, s, CH3), 2.12 (3H, s, CH3), 1.28 (12H, br s,
PC(CH3)3), 1.18 (12H, br s, PC(CH3)3). 1H NMR (−60 °C, toluene-
d8, 500 MHz): δ 6.83 (1H, s, ArH), 6.74 (2H, s, ArH), 6.58 (1H, s,
ArH), 3.47 (1H, m, CHMe), 3.33 (3H, s, ArCH3), 2.99 (2H, m,
PCH2P), 2.81 (6H, s, ArCH3), 2.64 (3H, s, ArCH3), 2.22 (3H, s,
ArCH3), 2.13 (6H, s, ArCH3), 2.10 (3H, s, ArCH3), 1.32 (9H, d, J =
11.5 Hz, PC(CH3)3), 1.17 (9H, d, J = 11.4 Hz, PC(CH3)3), 1.07 (9H,
d, J = 10.8 Hz, PC(CH3)3), 0.94 (9H, d, J = 12.1 Hz, PC(CH3)3).
13C{1H} NMR (C6D6, 150.9 MHz): δ 143.5 (ArC), 136.5 (ArC), 89.8
(CMeSi), 79.9 (CHMe), 37.2 (PCH2P), 36.0 (PC(CH3)3), 34.9
(PC(CH3)3), 31.5 (PC(CH3)3), 31.3 (PC(CH3)3), 27.3 (ArCH3), 23.4
(CHMeCMeSi), 21.1 (ArCH3). 31P{1H} NMR (C6D6, 163.0 MHz):
δ 30.2 (dd, 2JPP = 7.5 Hz, 1JRhP = 154.9 Hz), 13.95 (dd, 2JPP = 7.5 Hz,
1JRhP = 99.4 Hz). 29Si NMR (C6D6, 99.4 MHz): δ 5.2.
1
toluene-d8, 163.0 MHz): δ 19.8 (d, JRhP = 113.9 Hz). 29Si NMR (0
°C, toluene-d8, 99.4 MHz): δ 0.89. Anal. Calcd for C38H67P2RhSi: C,
63.67; H, 9.42. Found: C, 63.73; H, 9.54.
[(dtbpm)IrH](μ-SiPh2)(μ-Cl)2[(dtbpm)IrH] (12). A solution of
H2SiPh2 (0.023 g, 0.12 mmol) in C6H6 was added to a stirred solution
of [(dtbpm)IrCl]2 (0.10 g, 0.09 mmol) in C6H6. The solution was
stirred at room temperature for 40 min. The solvent was removed
under reduced pressure. The resulting yellow-orange solid was washed
twice with 1 mL of cold pentane to remove remaining H2SiPh2.
Further drying gave 12 as a yellow-orange powder in 89% yield (0.102
g). 1H NMR (C6D6, 500 MHz): δ 8.89 (4H, br s, ArH), 7.44 (4H, t, J
= 7.4 Hz, ArH), 7.26 (2H, t, J = 7.4 Hz, ArH), 3.15 (2H, m, PCH2P),
2.85 (2H, m, PCH2P), 1.55 (18H, d, JPH = 11.5 Hz, PC(CH3)3), 1.43
(18, d, JPH = 11.5 Hz, PC(CH3)3), 1.03 (18H, d, JPH = 13.5 Hz,
PC(CH3)3), 0.85 (18H, d, JPH = 13.5 Hz, PC(CH3)3), −23.3 (2H, d,
JPH = 24.8 Hz, IrH). 13C{1H} NMR (C6D6, 150.9 MHz): δ 136.5
(ArC), 135.6 (ArC), 134.5 (ArC), 129.7 (ArC), 128.1 (ArC), 36.0
(PCH2P), 35.3 (PCH2P), 33.3 (PC(CH3)3), 32.3 (PC(CH3)3), 31.1
(PC(CH3)3), 30.9 (PC(CH3)3), 30.3 (PC(CH3)3), 29.1 (PC(CH3)3).
In Situ Formation of (dtbpm)Rh(Ge(CMeCHMe)Mes2) (9).
With a 10 μL syringe, 2-butyne (3.3 μL, 0.04 mmol) was added to a
solution of 4 (0.030 g, 0.04 mmol) in 1 mL of C6D6. The dark red
reaction solution was stirred for 30 min before being filtered through a
1
Celite plug. H NMR (C6D6, 600 MHz): δ 6.83 (4H, s, ArH), 4.39
(1H, br m, CHMe), 3.14 (2H, t, J = 6.6 Hz, PCH2P), 2.80 (12H, s,
ArCH3), 2.18 (6H, s, ArCH3), 2.15 (3H, m, CH3), 2.13 (3H, s, CH3),
1.27 (18H, d, J = 11.4 Hz, PC(CH3)3), 1.19 (18H, d, J = 12.4 Hz,
PC(CH3)3). 13C{1H} NMR (C6D6, 150.9 MHz): δ 142.4 (ArC), 135.5
(ArC), 87.7 (CMeSi), 79.5 (CHMe), 38.2 (PCH2P), 35.4
(PC(CH3)3), 34.8 (PC(CH3)3), 31.5 (PC(CH3)3), 31.1 (PC(CH3)3),
30.8 (PC(CH3)3), 26.4 (ArCH3), 23.6 (CHMeCMeGe), 22.6
(CHMeCMeGe), 20.7 (ArCH3), 18.4 (ArCH3). 31P{1H} NMR
(C6D6, 163.0 MHz): δ 32.6 (dd, 2JPP = 9.8 Hz, 1JRhP = 117.4 Hz), 13.7
2
31P{1H} NMR (C6D6, 202 MHz): δ 8.9 (d, JPP = 6.1 Hz), −3.7 (d,
2JPP = 6.1 Hz). 29Si NMR (C6D6, 99.4 MHz): δ −34.4. IR: 2328, 2288
(ν(Ir−H)). Anal. Calcd for C46Cl2H88Ir2P4Si: C, 44.25; H, 7.10.
Found: C, 44.42; H, 7.08.
2
1
(dd, JPP = 9.8 Hz, JRhP = 92.9 Hz).
(dtbpm)Rh(SiHMes2)(DMAP) (10). A solution of DMAP (0.009
g, 0.07 mmol) in 1 mL of pentane was added to a solution of 3 (0.050
g, 0.07 mmol) in 2 mL of C6H6. After 30 min, the solution was
concentrated (ca. 2 mL) and cooled to −35 °C to afford yellow
[(dtbpm)IrH](μ-SiMesCl)(μ-Cl)(μ-H)[(dtbpm)IrH] (13). A solu-
tion of H3SiMes (0.018 g, 0.12 mmol) in C6H6 was added to a stirred
solution of [(dtbpm)IrCl]2 (0.102 g, 0.096 mmol) in C6H6. The
solution was stirred at room temperature for 40 min. The solvent was
removed under reduced pressure. The resulting yellow-orange solid
was washed twice with 1 mL of cold pentane to remove the remaining
H3SiMes. Further drying under reduced pressure gave 13 as a yellow
1
crystals in 95% yield (0.053 g). H NMR (C6D6, 500 MHz): δ 8.48
(1H, d, J = 5.6 Hz, ArH), 8.10 (1H, d, J = 6.0 Hz, ArH), 6.10 (1H, d, J
= 5.6 Hz, ArH), 5.53 (1H, d, J = 6.0 Hz, ArH), 2.87 (2H, t, J = 6.9 Hz,
PCH2P), 2.23 (3H, s, NCH3), 2.04 (3H, s, NCH3), 1.48 (18H, br s,
1
PC(CH3)3), 1.25 (18H, d, J = 10.0 Hz, PC(CH3)3). H NMR (−60
1
°C, toluene-d8, 500 MHz): δ 8.38 (1H, br s, ArH), 7.59 (1H, br s,
ArH), 7.21 (1H, s, MesH), 6.95 (1H, s, MesH), 6.78 (1H, s, MesH),
6.14 (1H, s, MesH), 6.06 (1H, m, SiH), 5.40 (1H, br s, ArH), 5.15
(1H, br s, ArH), 4.48 (3H, s, MesCH3), 3.20 (3H, s, MesCH3), 2.70
(5H, s, ArCH3 + PCH2P), 2.26 (3H, s, MesCH3), 2.19 (3H, s,
ArCH3), 2.03 (3H, s, ArCH3), 1.76 (9H, d, J = 10.8 Hz, PC(CH3)3),
1.44 (3H, s, MesCH3), 1.38 (9H, d, J = 10.6 Hz, PC(CH3)3), 1.18
(9H, d, J = 11.0 Hz, PC(CH3)3), 0.95 (9H, d, J = 10.6 Hz, PC(CH3)3).
13C{1H} NMR (C6D6, 150.9 MHz): δ 152.3 (ArC), 151.9 (ArC),
105.4 (ArC), 37.8 (PCH2P), 34.0 (PC(CH3)3), 31.1 (PC(CH3)3), 22.3
(PC(CH3)3), 20.9 (ArCH3), 13.9 (ArCH3), 8.6 (ArCH3). 13C{1H}
NMR (−60 °C, toluene-d8, 150.9 MHz): δ 151.9 (ArC), 145.5 (ArC),
145.3 (ArC), 143.5 (ArC), 105.8 (ArC), 105.4 (ArC), 38.5 (ArCH3),
37.6 (PCH2P), 36.1 (PC(CH3)3), 35.6 (PC(CH3)3), 35.1
(PC(CH3)3), 33.9 (PC(CH3)3), 33.3 (PC(CH3)3), 32.3 (PC(CH3)3),
31.3 (PC(CH3)3), 30.8 (PC(CH3)3), 26.5 (ArCH3), 25.8 (ArCH3),
24.8 (ArCH3), 23.7 (ArCH3), 21.9 (ArCH3), 15.2 (ArCH3). 31P{1H}
powder in 90% yield (0.104 g). H NMR (C6D6, 500 MHz): δ 6.92
(1H, s, ArH), 6.83 (1H, s, ArH), 3.72 (2H, m, PCH2P), 3.51 (2H, m,
PCH2P), 3.36 (3H, s, ArCH3), 3.16 (3H, s, ArCH3), 2.17 (3H, s,
ArCH3), 1.51 (18H, d, JPH = 11.9 Hz, PC(CH3)3), 1.41 (18H, d, JPH
=
9.9 Hz, PC(CH3)3), 1.35 (18H, d, JPH = 9.9 Hz, PC(CH3)3), 1.08
(18H, d, JPH = 11.6 Hz, PC(CH3)3), −12.59 (1H, tt, JPH = 5.3, 63.3
Hz, μ-IrH), −24.66 (2H, dd, JPH = 2.4, 18.0 Hz, IrH). 13C{1H} NMR
(C6D6, 150.9 MHz): δ 144.5 (ArC), 139.1 (ArC), 135.6 (ArC), 130.5
(ArC), 37.3 (PCH2P), 35.2 (PCH2P), 32.3 (PC(CH3)3), 31.6
(PC(CH3)3), 30.8 (PC(CH3)3), 30.2 (PC(CH3)3), 29.9 (PC(CH3)3),
29.3 (PC(CH3)3), 26.5 (ArCH3), 24.0 (ArCH3), 22.3 (ArCH3).
31P{1H} NMR (C6D6, 162 MHz): δ 18.5 (d, 2JPP = 14.5), 3.28 (d, 2JPP
= 14.5). 29Si NMR (C6D6, 99.4 MHz): δ 75.0 (t, JSiP ≈ 150 Hz). IR:
2391, 2327 (ν(Ir−H)). Anal. Calcd for C43Cl2H92Ir2P4Si: C, 42.45; H,
7.62. Found: C, 42.69; H, 7.24.
(dtbpm)Ir(H)4(10-chloro-1-mesityl-5,7-dimethyl-9,10-dihy-
drosilaphenanthrene-κSi) (14). A solution of H3Si(dmp) (0.032 g,
0.094 mmol) in C6H6 was added to a stirred solution of
[(dtbpm)IrCl]2 (0.050 g, 0.046 mmol) in C6H6. The solution was
stirred at 55 °C for 18 h. The solvent was removed under reduced
pressure. The resulting yellow-orange solid was washed twice with 1
mL of cold pentane to remove remaining H3Si(dmp). Further drying
under reduced pressure gave 14 as a yellow powder in 72% yield
(0.058 g). 1H NMR (C6D6, 500 MHz): δ 7.34 (1H, s, ArH), 7.25 (1H,
t, J = 7.5 Hz, ArH), 7.06 (1H, s, ArH), 7.01 (1H, d, J = 7.5, ArH), 6.92
(2H, d, J = 7.5 Hz, ArH), 6.79 (1H, s, ArH), 3.64 (1H, d, J = 13.4 Hz,
CH2), 3.13 (2H, t, J = 7.7 Hz, PCH2P), 2.64 (1H, d, J = 13.4 Hz,
CH2), 2.56 (3H, s, ArCH3), 2.46 (3H, s, ArCH3), 2.42 (3H, s, ArCH3),
2.34 (3H, s, ArCH3), 2.20 (3H, s, ArCH3), 1.10 (18H, d, JPH = 13.5
Hz, PC(CH3)3), 1.00 (18H, d, JPH = 13.6 Hz, PC(CH3)3), −11.58
2
1
NMR (C6D6, 163.0 MHz): δ 39.1 (dd, JPP = 9.0, JRhP = 169.5 Hz),
3.63 (dd, 2JPP = 9.0, 1JRhP = 97.8 Hz). 29Si NMR (C6D6, 99.4 MHz): δ
−33.8. Anal. Calcd for C42H71N2P2RhSi: C, 63.30; H, 8.98; N, 3.52.
Found: C, 62.96; H, 9.23; N, 3.24.
(dtbpm)Rh(H)2[5,7-diisopropyl-3-methyl-1-phenyl-2,3-dihy-
dro-1H-silaindenyl-κSi] (11). A solution of TripPhSiH2 (0.032 g,
0.10 mmol) in 2 mL of pentane was added to a solution of
(dtbpm)Rh(CH2Ph) (0.050 g, 0.10 mmol) in 2 mL of pentane. The
solution was immediately cooled to −35 °C to afford orange crystals in
1
65% yield (0.047 g). H NMR (0 °C, toluene-d8, 500 MHz): δ 8.14
(2H, d, J = 6.7 Hz, PhH), 7.26 (2H, m, PhH), 7.08 (1H, s, PhH), 7.03
(2H, s, ArH), 3.76 (1H, sept, J = 6.7 Hz, CH), 3.58 (1H, sextet, J = 6.9
Hz, CH), 3.14 (2H, t, J = 6.9 Hz, PCH2P), 2.96 (1H, sept, J = 6.8 Hz,
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(4H, t, JPH = 15.1 Hz, IrH). 13C{1H} NMR (C6D6, 150.9 MHz): δ
145.6 (ArC), 145.1 (ArC), 142.9 (ArC), 140.6 (ArC), 139.8 (ArC),
138.2 (ArC), 136.4 (ArC), 135.4 (ArC), 135.1 (ArC), 134.9 (ArC),
129.8 (ArC), 129.7 (ArC), 125.6 (ArC), 41.6 (CH2), 37.6 (PCH2P),
33.5 (PC(CH3)3), 32.8 (PC(CH3)3), 31.9 (PC(CH3)3), 30.5
(PC(CH3)3), 29.7 (PC(CH3)3), 24.0 (ArCH3), 23.0 (ArCH3), 22.7
(ArCH3), 21.4 (ArCH3), 21.1 (ArCH3). 31P{1H} NMR (C6D6, 163.0
MHz): δ −2.1. 29Si NMR (C6D6, 99.4 MHz): δ −1.96. Anal. Calcd for
C41H66ClIrP2Si: C, 56.17; H, 7.59. Found: C, 55.86; H, 7.86.
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ASSOCIATED CONTENT
* Supporting Information
■
S
CIF files giving crystallographic data for the crystal structure
studies in the paper. This material is available free of charge via
the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS
Support for this research was provided by The National Science
Foundation under Grant No. CHE-0957106.
■
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