Stoichiometric and catalytic reactions involving Si-H bond activations by Rh and Ir complexes containing a pyridylindolide ligand

Article abstract of DOI:10.1021/om060492+

New rhodium and indium complexes containing the bidentate, monoanionic 2-(2′-pyridyl)indolide (Pylnd) ligand were prepared. The bis(ethylene) complex (PyInd)Rh(C₂H₄)₂ (3) reacted with triethylsilane at 60°C to produce the 16-electron Rh(V) bis(silyl)dihydride complex (PyInd)RhH₂(SiEt₃)₂ (4). Both 3 and 4 catalyzed the chloride transfer reaction of chlorobenzene and Et₃SiH to give Et₃SiCl and benzene in the absence of base. In the presence of LiNⁱPr₂, catalytic C-Si coupling was observed, to produce Et₃SiPh. Analogous Ir complexes of the type (PyInd)IrH ₂(SiR₂)₂, where R₃ = Et₃ (6a), Me₂Ph (6b), Ph₂Me (6c), or Ph₃ (6d), were not catalytically active in this chloride transfer chemistry. The molecular structure of 6c, determined by X-ray crystallography, may be described as having a highly unusual bicapped tetrahedral geometry. DFT calculations indicate that this distortion is associated with the d⁴ electron count and the presence of highly trans-influencing silyl ligands. The reaction of 6a with PMe₃ (5 equiv) produced (PyInd)IrH(SiEt₃)(PMe ₃)₂ (7), while the reaction with PPh₃ (1 equiv) generated a mixture of isomers that was converted to (PyInd)IrH(SiEt ₃)(PPh₃) (8) upon heating in benzene at 80°C. Complexes 7 and 8 exhibit regular octahedral and distorted square pyramidal geometries, respectively.

Full text of DOI:10.1021/om060492+

Organometallics 2006, 25, 4471-4482
4471
Stoichiometric and Catalytic Reactions Involving Si-H Bond
Activations by Rh and Ir Complexes Containing a Pyridylindolide
Ligand
Dmitry Karshtedt,†,‡ Alexis T. Bell,*,§,‡ and T. Don Tilley*,†,‡
Departments of Chemistry and Chemical Engineering, UniVersity of California, Berkeley,
Berkeley, California 94720, and Chemical Sciences DiVision, Lawrence Berkeley National Laboratory,
1 Cyclotron Road, Berkeley, California 94720
ReceiVed June 5, 2006
New rhodium and iridium complexes containing the bidentate, monoanionic 2-(2′-pyridyl)indolide
(PyInd) ligand were prepared. The bis(ethylene) complex (PyInd)Rh(C2H4)2 (3) reacted with triethylsilane
at 60 °C to produce the 16-electron Rh(V) bis(silyl)dihydride complex (PyInd)RhH2(SiEt3)2 (4). Both 3
and 4 catalyzed the chloride transfer reaction of chlorobenzene and Et3SiH to give Et3SiCl and benzene
in the absence of base. In the presence of LiNiPr2, catalytic C-Si coupling was observed, to produce
Et3SiPh. Analogous Ir complexes of the type (PyInd)IrH2(SiR3)2, where R3 ) Et3 (6a), Me2Ph (6b),
Ph2Me (6c), or Ph3 (6d), were not catalytically active in this chloride transfer chemistry. The molecular
structure of 6c, determined by X-ray crystallography, may be described as having a highly unusual bicapped
tetrahedral geometry. DFT calculations indicate that this distortion is associated with the d4 electron
count and the presence of highly trans-influencing silyl ligands. The reaction of 6a with PMe3 (5 equiv)
produced (PyInd)IrH(SiEt3)(PMe3)2 (7), while the reaction with PPh3 (1 equiv) generated a mixture of
isomers that was converted to (PyInd)IrH(SiEt3)(PPh3) (8) upon heating in benzene at 80 °C. Complexes
7 and 8 exhibit regular octahedral and distorted square pyramidal geometries, respectively.
implicated as a key step in Rh- and Pt-catalyzed arylsilane
syntheses via the dehydrogenative coupling of silanes and
arenes6 and in related systems involving silanes and haloarenes.7
Such Si-C coupling reactions are of considerable interest, since
arylsilanes have recently begun to replace their boron- and tin-
containing analogues as substrates for Pd-catalyzed cross-
coupling chemistry.8 Arylsilanes have a number of advantages
over these traditionally employed reagents, since they are
generally more tolerant of functional groups than boronic acids
and less toxic than stannanes.
Introduction
Activation of Si-H bonds by oxidative addition to late
transition metal complexes is a fundamental step in a number
of catalytic transformations involving organosilanes.1 These
include an industrially important Pt-based system for the
hydrosilation of olefins,2 as well as potentially valuable
processes such as dehydrogenative silane polymerization,3 silane
redistribution,4 and silane reduction of haloarenes.5 The oxida-
tive addition of a Si-H bond to a metal center has also been
Complexes of Rh and Ir exhibit particularly rich Si-H bond
activation chemistry due to the ability of these metals to support
mononuclear silyl complexes in a variety of oxidation states.9-14
In addition, these metals are known to form η2-silane complexes,
which can be described as products of incomplete oxidative
addition of a Si-H bond.15 Thus, silane activations by Rh and
Ir continue to attract attention because they offer a variety of
* To whom correspondence should be addressed. E-mail: tdtilley@
berkeley.edu.
† Department of Chemistry, University of California, Berkeley.
§ Department of Chemical Engineering, University of California,
Berkeley.
‡ Lawrence Berkeley National Laboratory.
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10.1021/om060492+ CCC: $33.50 © 2006 American Chemical Society
Publication on Web 08/09/2006

4472 Organometallics, Vol. 25, No. 19, 2006
Karshtedt et al.
strategies for the design of catalytic cycles. While a number of
group 9 complexes containing cyclopentadienyl-6a,10a,b,11,13b,14e
and phosphine-based9,10d-h,12,13d-n,14a-c ligands have been shown
to promote Si-H bond activation, analogous systems with
nitrogen donor ligands remain relatively unexplored.13c,14d The
presence of hard nitrogen donor ligands on soft transition metals
such as Rh or Ir is expected to enable the (NN)Rh and (NN)Ir
fragments to support high oxidation state complexes.16
Recently, bidentate ligands that feature localized neutral and
anionic nitrogen donors have begun to attract interest because
of their ability to support reactive late transition metal species.
For example, platinum complexes of 2-(2′-pyridyl)indolide
(PyInd)17 and the related 2-(N-arylimino)pyrrolide18 ligands have
been observed to mediate catalytic and stoichiometric transfor-
mations of arenes, respectively. While the chemistry of group
9 metals containing such ligands has so far remained unexplored,
their successful application in Pt-promoted hydrocarbon activa-
tions suggests that Rh and Ir complexes of NN* (NN* ) PyInd
or a related ligand) should be reactive toward bond activations
via oxidative addition. Along these lines, the concomitant
activation of silanes and chlorobenzene, generally considered
to be a relatively inert substrate due to the strength of the
aromatic C-Cl bond, represents a particularly interesting goal.19
A possible outcome of a catalyzed reaction between PhCl and
a silane is chloride transfer from carbon to silicon, resulting in
production of benzene and a silyl chloride. In fact, such a
transformation has been realized with triethylsilane, using Pd
or Rh catalysts.5b-d A different reaction pathway, however, can
lead to formation of a C-Si bond, accompanied by the
elimination of HCl. Such a reaction has not been achieved with
PhCl, although analogous Rh-catalyzed processes that utilize
PhBr or PhI in combination with triethoxysilane and stoichio-
metric base have been reported.7 It was envisioned that reactive
(PyInd)M (M ) Rh, Ir) fragments might provide a platform
for examining successive activations of silanes and PhCl and
enable the development of catalytic reactions involving these
substrates.
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B.; Hall, M. B.; Hartwig, J. F. Angew. Chem., Int. Ed. 2004, 43, 5474. (b)
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Duckett, S. B.; Haddleton, D. M.; Jackson, S. A.; Perutz, R. N.; Poliakoff,
M.; Upmacis, R. K. Organometallics 1988, 7, 1526. (d) Fernandez, M.-J.;
Maitlis, P. M. J. Chem. Soc., Dalton Trans. 1984, 2063. (e) Fernandez,
M.-J.; Bailey, P. M.; Bentz, P. O.; Ricci, J. S.; Koetzle, T. F.; Maitlis, P.
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Ogino, H. Chem. Lett. 1998, 69. (b) Aizenberg, M.; Milstein, D. Organo-
metallics 1996, 15, 3317. (c) Okazaki, M.; Tobita, H.; Ogino, H. Organo-
metallics 1996, 15, 2790.
(13) Ir(III): (a) Simons, R. S.; Panzner, M. J.; Tessier, C. A.; Youngs,
W. J. J. Organomet. Chem. 2003, 681, 1. (b) Klei, S. R.; Tilley, T. D.;
Bergman, R. J. Organometallics 2002, 21, 3376. (c) Stradiotto, M.; Fujdala,
K. L.; Tilley, T. D. Chem. Commun. 2001, 1200. (d) Brost, R. D.; Bruce,
G. C.; Joslin, F. L.; Stobart, S. R. Organometallics 1997, 16, 5669. (e)
Okazaki, M.; Tobita, H.; Ogino, H. Chem. Lett. 1997, 437. (f) Esteruelas,
M. A.; Olivan, M.; Oro, L. A. Organometallics 1996, 15, 814. (g) Aizenberg,
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2, 164.
This report describes activations of silanes by PyInd com-
plexes of Rh and Ir. The (PyInd)Rh fragment catalyzes both
the established chloride transfer process that generates Et3SiCl
from PhCl and Et3SiH and the novel base-promoted Ph-Si
coupling between these substrates. These reactions involve an
unusual, isolable 16-electron Rh(V) bis(triethylsilyl)dihydride
species. In contrast, the (PyInd)Ir fragment does not participate
in this catalysis, but provides access to a range of stable Ir(V)
bis(silyl)dihydrides. Structural studies and DFT calculations
demonstrate that these d4 complexes feature a rare, highly
distorted bicapped tetrahedral geometry. This work underscores
the utility of reactive, high-valent intermediates in the develop-
ment of catalytic silane conversions.
Results and Discussion
Synthesis of (PyInd)Rh Complexes. Previous studies dem-
onstrated that the potassium salt K[PyInd] is a convenient
transfer agent for the 2-(2′-pyridyl)indolide ligand.17a Thus,
K[PyInd] was used to prepare several Rh(I) complexes via salt
metathesis with chloride-bridged precursors of the type [L2RhCl]2.
For example, K[PyInd] reacted with [(CO)2RhCl]2 at room
temperature in benzene to give (PyInd)Rh(CO)2 (1) in 76% yield
(eq 1) after extraction with CH2Cl2 and crystallization from a
CH2Cl2/pentane mixture. The IR spectrum of 1 contains two
carbonyl stretching frequencies at 2054 and 1999 cm-1, which
may reflect slightly greater π-back-bonding in this neutral
complex relative to the cationic analogue [(bpy)Rh(CO)2]+ (νCO
at 2080 and 2010 cm-1).20
(15) (a) Schubert, U. AdV. Organomet. Chem. 1990, 30, 151. (b) Bart,
S. C.; Lobkovsky, E.; Chirik, P. J. J. Am. Chem. Soc. 2004, 126, 13794.
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23, 4169. (b) Karshtedt, D.; McBee, J. L.; Bell, A. T.; Tilley, T. D.
Organometallics 2006, 25, 1801.
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Labinger, J. A.; Bercaw, J. E. J. Am. Chem. Soc. 2003, 125, 12674.
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443.

Si-H Bond ActiVations by Rh and Ir Complexes
Organometallics, Vol. 25, No. 19, 2006 4473
of ethylene ligand hydrosilation. Complex 4 is not crystalline,
but it can be isolated in 71% yield as an analytically pure oily
red solid upon lyophilization of the crude product from benzene,
followed by a cold pentane wash to remove SiEt4. The 1H NMR
spectrum of 4 features two hydride resonances at -15.32 ppm
(JRhH ) 28.5 Hz) and -13.88 ppm (JRhH ) 23.5 Hz), while its
29Si{1H} NMR spectrum exhibits only one resonance at 63.0
ppm (JRhSi ) 26.8 Hz). The value of the H-H coupling constant,
9.0 Hz, is typical for an unsymmetrical rhodium cis-dihydride
species.23 In addition, the Si-H coupling constants associated
with the two hydrides, which were observed in the 29Si
Figure 1. ORTEP diagram of the molecular structure of (PyInd)-
Rh(COD) (2), showing one of the two crystallographically inde-
pendent molecules of 2 present in the asymmetric unit (with the
ligand fragments canted at the angle of 11°). Hydrogen atoms were
omitted for clarity. Selected bond lengths (Å): Rh-N1 ) 2.111(5),
Rh-N2 ) 2.058(5), Rh-C14 ) 2.107(6), Rh-C21 ) 2.120(7),
Rh-C17 ) 2.118(6), Rh-C18 ) 2.141(6), C14-C21 ) 1.389(8),
C17-C18 ) 1.393(8). Bond angle (deg): N1-Rh-N2 ) 79.7(2).
1
dimension of the J-resolved H-29Si gradient heteronuclear
multiple bond correlation (gHMBC) spectrum,24 were found to
be 8.1 and 6.2 Hz, respectively. Generally, silyl hydride
complexes with JSiH values below 20 Hz are considered to have
no η2-silane ligand character.1e Thus, the JSiH values suggest
that complex 4 can be viewed as a Rh(V) bis(silyl)dihydride.
Moreover, the unexceptional rhodium-hydride T1 values25,26
(1.1 and 1.2 s, determined at 500 MHz and 25 °C using the
null method) are quite consistent with a classical dihydride
structure, while the bands characteristic of Rh-H bonds (2065,
2090 cm-1) in the IR spectrum also support the presence of
pentavalent rhodium in 4.9c,11d,e,23a The JSiH, T1, and IR data
obtained for 4 are similar to those reported for the analogous
18-electron complex Cp*RhH2(SiEt3)2, for which the oxidation
state of 5 for the Rh center was confirmed by determination of
the hydride positions by neutron diffraction.11e
The diolefin complex (PyInd)Rh(COD) (2) was also prepared
in high yield (93%) via a salt methathesis route, starting from
K[PyInd] and [(COD)RhCl]2 (eq 1). The solid-state structure
of 2 was determined by X-ray crystallography and is shown in
Figure 1. As expected, the PyInd ligand is nearly planar and
the olefinic fragments of the cyclooctadiene ligands are per-
pendicular to the (NN*)Rh plane. The N-Rh-N angle is
approximately 80°, indicating that PyInd enforces a smaller bite
angle than that typically observed in Rh complexes of the related
â-diiminate ligands (approximately 90°), which feature a six-
membered chelate ring.21 Interestingly, two crystallographically
independent molecules of the complex are present in the
asymmetric unit of the primitive monoclinic space group P21/
n. The primary difference between the two molecules is a
rotation of the pyridinyl group with respect to the indolyl group
(dihedral angle of 1° in one rotamer and of 11° in the other
rotamer). This result suggests that the energy barrier to a slight
canting of the PyInd ligand is quite low.
Complex 2 was found to be quite inert toward triethylsilane,
as no changes were observed in the 1H NMR spectrum when a
mixture of 2 and excess Et3SiH (5 equiv) was heated in benzene-
d6 at 130 °C for 12 h. Since this lack of reactivity may be
ascribed to the presence of the chelating, nonlabile cycloocta-
diene ligand, a more reactive Rh(I) precursor was sought. This
was accomplished using [(C2H4)2RhCl]2, which reacted cleanly
with K[PyInd] (eq 1) to yield the (bis)ethylene complex (PyInd)-
Rh(C2H4)2 (3). The 1H NMR spectrum of 3 contains four
distinct, slightly broadened vinylic resonances (1.98, 2.39, 2.75,
and 4.82 ppm). The upfield shift of these resonances relative
to that of free ethylene (5.24 ppm) points to a significant degree
of back-bonding from the Rh(I) center to the carbon-carbon
double bond.22 Presumably, as in complex 2, the olefin ligands
are perpendicular to the (NN*)Rh plane, resulting in chemically
inequivalent environments for the four pairs of vinylic hydro-
gens. The ethylene orientation is further confirmed by the
13C{1H} NMR spectrum of 3, which contains only two
resonances for these ligands at 60.8 (JRhC ) 12.5 Hz) and 63.2
ppm (br).
Complex 4 catalyzed the complete isomerization of 5 equiv
of 1-octene to a mixture of internal octenes (70 °C, 4 h, benzene-
d6), a result that is also consistent with the presence of a hydride
ligand in 4. However, Si-H bond elimination from 4 is facile,
as addition of excess PMe3 to 4 in benzene-d6 at room
temperature resulted in formation of 2 equiv of Et3SiH and a
1
species formulated as (PyInd)Rh(PMe3)2 by H and 31P{1H}
NMR spectroscopy (see Experimental Section). Unfortunately,
this complex could not be isolated, as removal of the solvent
under reduced pressure led to its decomposition. Furthermore,
attempts to synthesize (PyInd)RhH2(SiR3)2 species from silanes
other than Et3SiH did not meet with success. For example, a
reaction of 3 with triphenylsilane appeared to result in a
dihydride species analogous to 4 (as judged by 1H NMR
spectroscopy), but this complex could not be obtained in pure
form.
Catalyzed Reactions of Silanes with PhCl. The observed
chemistry of 3 prompted the examination of this complex as a
catalyst for reactions involving Si-H and Ph-Cl bond activa-
tions. Consistent with expectations, 3 catalyzed the reaction of
10 equiv of Et3SiH with neat PhCl at 80 °C over the course of
(23) (a) Ezhova, M. B.; Patrick, B. O.; Sereviratne, K. N.; James, B. R.;
Waller, F. J.; Ford, M. E. Inorg. Chem. 2005, 44, 1482. (b) Heinrich, H.;
Giernoth, R.; Bargon, J.; Brown, J. M. Chem. Commun. 2001, 1296.
(24) Meissner, A.; Sorensen, O. W. Magn. Reson. Chem. 2001, 39, 49.
(25) (a) Hamilton, D. G.; Crabtree, R. H. J. Am. Chem. Soc. 1988, 110,
4126. (b) Ammann, C.; Isaia, F.; Pregosin, P. S. Magn. Reson. Chem. 1988,
26, 236. (c) Desrosiers, P. J.; Cai, L.; Lin, Z.; Richards, R.; Halpern, J. J.
Am. Chem. Soc. 1991, 113, 4173.
Activation of 4 equiv of Et3SiH by 3 resulted in formation
of the bis(silyl)dihydride complex (PyInd)RhH2(SiEt3)2 (4) upon
heating in benzene at 60 °C over the course of 2 h (eq 2). In
addition, 2 equiv of tetraethylsilane byproduct formed as a result
(21) Willems, S. T. H.; Budzelaar, P. H. M.; Moonen, N. N. P.; de Gelder,
R.; Smits, J. M. M.; Gal, A. W. Chem.--Eur. J. 2002, 8, 1310.
(22) (a) Maire, P.; Breher, F.; Scho¨nberg, H.; Gru¨tzmacher, H. Organo-
metallics 2005, 24, 3207. (b) Hahn, C. Chem.--Eur. J. 2004, 10, 5888.
(26) This method of determining the presence of H-H interactions has
been shown to be somewhat unreliable for a family of osmium polyhydride
complexes; see Desrosiers et al.25c

4474 Organometallics, Vol. 25, No. 19, 2006
Karshtedt et al.
Scheme 1. Proposed Mechanism for the Silylation of
Chlorobenzene
activate PhCl to provide the key hydrido-chloride Rh(V)
intermediate B. Subsequent reductive elimination of Et3SiCl
from B appears to be reasonable because it leads to the formation
of a strong Si-Cl bond. This step may be followed by the
oxidative addition of Et3SiH and loss of benzene, regenerating
intermediate A. While the initiation of a catalytic cycle by
reductive elimination from a 16-electron species may appear
to be unusual, precedent for such a step can be found in the
Ir-pincer alkane dehydrogenation system, where the 14-electron
(PCP)Ir fragment (derived via loss of H2 from (PCP)IrH2) is
thought to be the catalytically active species.28 An alternative
mechanism for chloride transfer catalysis by (PyInd)Rh may
involve a modified associative mechanism. In this pathway, one
of the silyl hydride fragments is converted to an η2-silane ligand,
allowing for oxidative addition of PhCl to form an 18-electron
intermediate. While the formation of such a crowded seven-
coordinate species appears to be less favorable compared to that
of a 14-electron mono(silyl)hydride, neither mechanism can be
ruled out on the basis of the available data. The possibility that
some of the steps in the catalytic cylcle involve σ-bond
metathesis processes, rather than discrete oxidative additions
and reductive eliminations, must also be considered.
20 h to produce Et3SiCl in 77% yield (eq 3). Complex 4 was
To reverse the selectivity of the coupling process to obtain
Et3SiPh rather than Et3SiCl (eq 4), it is necessary to consume
the HCl byproduct that would be generated. If intermediate B
is involved, this can be achieved by a base-promoted reductive
elimination of HCl from the Rh(V) center.29 This type of a
transformation has in fact been realized with a Rh catalyst, using
bromobenzene and triethoxysilane in the presence of a stoichio-
metric amount of a tertiary amine.7c With (EtO)3SiH as a
potential coupling substrate, however, silane redistribution was
the dominant pathway. Thus, when 3 and 10 equiv of (EtO)3SiH,
along with 10 equiv of triethylamine, were heated in PhCl for
16 h at 90 °C, Si(OEt)4 was found to be the major product
(approximately 80% yield), and only traces (<5%) of (EtO)3SiPh
were detected by GC-MS. As a result, Et3SiH, which exhibits
no tendency to undergo redistribution, was utilized in further
attempts to develop Rh-catalyzed dehydrochlorinative couplings
of PhCl with silanes.
the only Rh-containing species observed in solution during the
course of catalysis (by H NMR spectroscopy), as it formed
1
readily under these conditions and persisted until the reaction
was complete. In addition, 2 equiv of SiEt4 were detected by
GC-MS (using tetraphenylsilane as the internal standard),
confirming that the ethylene ligands were removed via hydro-
silation. Isolated complex 4 also catalyzed chloride transfer from
PhCl to yield Et3SiCl, at a rate similar to that obtained with 3
(10 equiv of Et3SiH were consumed at 80 °C in 16 h). This
result demonstrates that 4 is a kinetically competent intermediate
in this transformation.
Et3SiH + PhCl 10 mol % 38 Et3SiCl + PhH
(3)
80 °C, 20 h
The catalytic action of 3 on arylsilanes, under the reaction
conditions similar to those employed with Et3SiH (neat PhCl,
80 °C, 20 h), was dominated by redistribution chemistry at
silicon.27 For example, 3 catalyzed the conversion of Ph2MeSiH
to a mixture of Ph3SiMe, Ph2SiH2, and other silicon-containing
products. The silane Ph3SiMe was observed when the catalytic
reaction was conducted in chorobenzene or cyclohexane,
demonstrating that PhCl was not required to deliver the
additional phenyl group to silicon. Similar results were obtained
with Me2PhSiH, which reacted to give Me2SiPh2, Me2SiH2, and
other silicon-containing products, while Ph3SiH was unreactive
in this system. In contrast, 3 catalyzed the chlorination of 10
Et3SiH + PhCl + base 10 mol % 38 Et3SiPh + base(HCl) (4)
90 °C, 20 h
Initial studies centered on use of alkylamine bases to direct
the catalytic transformation toward C-Si bond formation. This
approach proved promising, as observable amounts of Et3SiPh
(ca. 5% by GC-MS) were formed in the presence of stoichio-
metric triethylamine or diisopropylethylamine (conditions as in
eq 4). It was reasoned, however, that these bases did not remove
HCl efficiently enough to reverse the selectivity of silyl group
transfer. Thus, efforts to improve reaction yields focused on
the utilization of additives that would effect chloride abstraction
or substitution in addition to deprotonation. This was thought
to be necessary because formation of the Si-Cl bond provides
a strong thermodynamic driving force toward the chlorosilane
coupling product. To this end, a number of Lewis/Bronsted base
combinations were screened (Table 1). Although both AlCl3/
iPr2NEt and AlCl3/DBU shifted reaction selectivity from Et3SiCl
to Et3SiPh, only 3 or 4 turnovers could be achieved. This result
may be attributed to the reactive nature of the AlCl3 additive,
t
equiv of Bu2SiH2 in chlorobenzene (80 °C, 40 h) to yield a
t
t
mixture of Bu2HSiCl (67%) and Bu2SiCl2 (9%), and no
products of redistribution of the alkyl groups at silicon were
detected. For all of the substrates other than Et3SiH, complicated
mixtures containing several Rh hydride species were observed
1
by H NMR spectroscopy during the course of catalysis.
Although the mechanism of chloride transfer from PhCl to
Et3SiH is not yet fully understood, we believe that it involves
reductive elimination of Et3SiH from 4 to give a reactive 14-
electron Rh(III) intermediate A (Scheme 1). This species may
(27) Redistribution of arylsilanes is frequently observed as an undesired
side reaction in other Rh-catalyzed silane transformations, but the mechanism
of this process is poorly understood. See, for example: Rosenberg, L.; Davis,
C. W.; Yao, J. J. Am. Chem. Soc. 2001, 123, 5120, and references therein.
Researchers should be cautioned that this process may generate pyrophoric
silane gas as a byproduct.
(28) Renkema, K. B.; Kissin, Y. V.; Goldman, A. S. J. Am. Chem. Soc.
2003, 125, 7770.
(29) Grushin, V. V. Acc. Chem. Res. 1993, 26, 279.

Si-H Bond ActiVations by Rh and Ir Complexes
Organometallics, Vol. 25, No. 19, 2006 4475
Table 1. Effects of Additives on the Catalytic
Dehydrochlorinative Silylation of PhCla
Table 2. Key NMR Data for Ir(V) Complexes 6a-6da
1H (ppm)
29Si (ppm)
JSiH (Hz)
T1 (s)b
yield of
Et3SiPh (%)
yield of
6a
6b
6c
6d
-15.53
-18.04
-14.84
-17.36
-13.87
-16.59
-13.05
-16.06
37.1
6.7
6.4
12.1
9.5
14.2
11.7
17.4
12.5
1.1
1.2
1.2
1.3
1.2
1.3
1.0
1.1
entry
additiveb
iPr2NEt
Et3SiClc (%)
9.6
7.2
9.2
1
2
3
4
5
6
7
8
7
5
14
39
31
0
0
9
35
42
70
84
87
15
5
8
0
NEt3
AlCl3/NEt3
AlCl3/iPr2NEt
AlCl3/DBU
GaCl3/iPr2NEt
AgOTf/iPr2NEt
NBu4I/iPr2NEt
KHMDS
0
a All spectra were obtained in benzene-d6. b Obtained at 500 MHz and
25 °C using the null method.
77
52
48
5
9
10
11
LiHMDS
LDA
29Si chemical shift (37.1 ppm) and the magnitudes of the Si-H
coupling constants for 6a were determined using a J-resolved
1H-29Si gHMBC experiment (vide supra). The JSiH values
obtained for the hydrides in 6a, 6.4 and 6.7 Hz, are close to
those determined for the rhodium analogue 4, and similarly
suggest the lack of η2-silane character in this complex.
Details of the reaction that generates 6a are not known, but
the lack of an observable cyclooctene hydrosilation product
suggests that COE ligands dissociate from the Ir center before
silane oxidative addition. This behavior is different from that
noted in the preparation of 4, in which the olefin ligands are
removed by hydrosilation with excess Et3SiH. The absence of
the requirement for COE hydrosilation suggests that 2 equiv of
the silane are sufficient to prepare 6a, and this is indeed borne
out experimentally (eq 5).
a Conditions as in eq 4. b 1.2 equiv relative to Et3SiH. c Observed as
Et3SiOH or Et3SiOSiEt3 by GC, except for entries 9-11, where Et3SiCl
was converted to the corresponding silylamine in situ.
which appeared to cause rapid decomposition of the Rh
catalyst.30
Alkali metal bases proved to be particularly effective for the
sequestration of chloride (Table 1). Potassium hexamethyldi-
silazide (KHMDS), lithium hexamethyldisilazide (LiHMDS),
and lithium diisopropylamide (LDA) were examined, with LDA
providing the highest selectivity for C-Si coupling (70% yield
of Et3SiPh).31 A relatively small amount of N,N-diisopropyl-
aniline (23%), the product of the reaction between chlorobenzene
and excess lithium amide, was also detected by GC-MS.
Nonetheless, this amine could be easily separated from the
Et3SiPh product on a silica column.
Although this catalysis requires a strong amide base, the
unusual coupling of PhCl with an alkylsilane demonstrates that
the thermodynamically favored Si-Cl bond-forming pathway
can be overcome with the aid of appropriate additives. The
requirement for a stoichiometric amount of LDA limits potential
applications of this system to substrates that contain no acidic
or highly electrophilic functionalities. Nevertheless, it is note-
worthy that the same Rh complex 3 catalyzes both arene
dechlorination and dehydrochlorinative silylation, depending on
the reaction conditions.32
Synthesis and Characterization of Ir(V) Bis(silyl)dihy-
drides. The interesting catalytic and stoichiometric reactivity
of 3 with Et3SiH prompted an investigation of similar species
containing iridium. Initially, these efforts were hampered by
the lack of appropriate Ir(I) precursors. Similar to its Rh
analogue 2, the complex (PyInd)Ir(COD) (5), prepared from
K[PyInd] and [(COD)IrCl]2, was unreactive toward Et3SiH.
Thus, preparation of a (bis)monoolefin Ir(I) complex from
K[PyInd] and [(COE)2IrCl]2 was attempted. This was unsuc-
cessful, as the transiently formed (NN*)Ir(I) species appeared
to activate the cyclooctene ligands to give a mixture of Ir
hydrides. It was found, however, that the direct combination of
K[PyInd], [(COE)2IrCl]2, and 4 equiv of Et3SiH resulted in clean
formation of the bis(triethylsilyl)dihydride (PyInd)IrH2(SiEt3)2
(6a) at room temperature (67% yield). The 1H NMR spectrum
of 6a features two inequivalent hydrides at -18.04 and -15.53
ppm that exhibit small H-H coupling (2J ) 2.0 Hz). Both the
In contrast to its Rh analogue 4, 6a did not catalyze chloride
transfer from chlorobenzene to triethylsilane or promote de-
hydrochlorinative C-Si coupling between these substrates in
the presence of base (LDA). Indeed, 6a remained unchanged
upon heating in chlorobenzene in the presence of 10 equiv of
Et3SiH and 12 equiv of LDA for 40 h at 150 °C, as the amide
became converted to N,N-diisopropylaniline through a direct
aromatic substitution. This lack of reactivity may be attributed
to the fact that 6a is more resistant than its Rh(V) analogue to
reductive elimination of Et3SiH. Moreover, 6a generally exhibits
much greater thermal stability than 4. While 4 underwent
complete decomposition to unidentified species upon heating
in benzene-d6 at 90 °C over the course of 10 h, complex 6
required thermolysis at 190 °C for 20 h (benzene-d6, sealed tube)
before any detectable signs of decomposition were observed
1
by H NMR spectroscopy.
Although 6a was not an active catalyst for chloride transfer
from PhCl, complexes 6a-d were examined as potential
structural models for 4, an isolated intermediate in Rh-catalyzed
C-Si coupling of PhCl and Et3SiH for which an X-ray crystal
structure could not be obtained. To this end, bis(arylsilyl)
complexes 6b, 6c, and 6d were prepared in high yields, as shown
above in eq 5, using 2 equiv of Me2PhSiH, Ph2MeSiH, and
Ph3SiH, respectively, in one-pot reactions with K[PyInd] and
[(COE)2IrCl]2. Key NMR data for complexes 6a-6d are
summarized in Table 2. Although the values of the Si-H
coupling constants for the hydrides in these complexes increase
with an increasing number of phenyl groups on Si, all are
smaller than 20 Hz, indicating that the Si-H bonds have
undergone complete oxidative addition to the Ir center.1e
(30) Direct Friedel-Crafts reactions between arenes and chlorosilanes
mediated by AlCl3 have been observed, but they typically give arylsilane
products in very low yields: Olah, G. A.; Bach, T.; Surya Prakash, G. K.
J. Org. Chem. 1989, 54, 3770.
(31) Resonances in the 1H NMR spectra acquired when this reaction
was monitored were significantly broadened.
(32) Recently, a Pd-based catalytic system was reported for which both
iodoarene silylation and reduction with tertiary silanes were observed,
depending on reaction conditions: Yamanoi, Y. J. Org. Chem. 2005, 70,
9607.

4476 Organometallics, Vol. 25, No. 19, 2006
Karshtedt et al.
Figure 2. ORTEP diagram of the molecular structure of (PyInd)-
IrH2(SiPh2Me)2 (6c). Hydrogen atoms, except for the iridium
hydrides, were omitted for clarity. Selected bond lengths (Å): Ir-
Si1 ) 2.326(1), Ir-Si2 ) 2.338(1), Ir-N1 ) 2.016(3), Ir-N2 )
2.149(3), Ir-H1 ) 1.61(2), Ir-H2 ) 1.60(2). Selected bond angles
(deg): Si1-Ir-Si2 ) 105.71(3), N1-Ir-N2 ) 78.0(1), Si1-Ir-
H1 ) 81(1), Si1-Ir-H2 ) 63(1), Si2-Ir-H1 ) 67(1), Si2-Ir-
H2 ) 55(1).
Figure 3. Top view of the X-ray crystal structure of 6c (hydrogen
atoms and substituents on the silicon atoms were omitted for clarity).
Figure 4. Jaguar representation of the frontier orbitals of 6c, as
determined by a DFT calculation.
Moreover, the T1 values for all of the hydrides are unexceptional,
suggesting the lack of dihydrogen ligand character in these
complexes (Table 2).25,26 Thus, on the basis of these NMR
characterizations, complexes 6a-6d can be viewed as Ir(V)
species with a d4 electron count.
Distortions from octahedral geometry in 6c are expected on
the basis of experimental36 and theoretical37 work on six-
coordinate d4 complexes. To probe the factors that cause this
complex to adopt a bicapped tetrahedral structure, a DFT-
B3LYP approach was used to calculate the frontier orbitals of
6c. The atomic coordinates for 6c were used as a starting point
in the calculations, and an energy minimization was performed
with the aid of the Jaguar software package (see Computational
Details). The geometry of the energy-minimized structure does
not deviate significantly from that of the solid-state structure
of 6c, as determined by X-ray crystallography. The calculated
LUMO features a primarily metal-centered orbital that appears
to be a hybrid between pz and d orbitals (Figure 4) and has
significant M-Si σ* character. This hybrid orbital can also be
derived by an analysis of orbital perturbations caused by a
The solid-state structure of the diphenylmethylsilane deriva-
tive 6c was determined by X-ray crystallography and is shown
in Figure 2. The hydride ligands were located in the Fourier
difference map. The Ir-H distances (Ir-H1 ) 1.60(2) Å, Ir-
H2 ) 1.61(2) Å) are similar to typical bond lengths for iridium
hydrides determined by neutron diffraction (1.58-1.59 Å).33
The molecular structure of 6c features a highly unusual bicapped
tetrahedral geometry, with the tetrahedron defined by the silicon
and nitrogen atoms. Alternatively, this can be viewed as an
extremely distorted octahedral geometry, with the Si-Ir-Si
bond angle involving the “trans” silyl ligands severely com-
pressed to 105.7°. It is also notable that the Si-Ir-Si plane
does not bisect the N-Ir-N angle, as expected in a typical
tetrahedral structure, but “leans” toward the pyridinyl side of
the PyInd ligand (Figure 3). This leaning does not seem to result
from an interaction between the silyl and hydride ligands, since
the Si-H distances are too long (closest Si-H contact: 1.93
Å) to invoke η2-silane complex character in 6c.1e,15d,34 In
addition, the silicon centers are nearly tetrahedral, a fact that
also argues against the presence of an η2-silane ligand.35 Thus,
the origin of this secondary distortion is not fully apparent.
(34) (a) Dioumaev, V. K.; Procopio, L. J.; Carroll, P. J.; Berry, D. H. J.
Am. Chem. Soc. 2003, 125, 8043. (b) Dioumaev, V. K.; Yoo, B. R.;
Procopio, L. J.; Carroll, P. J.; Berry, D. H. J. Am. Chem. Soc. 2003, 125,
8936.
(35) Reinartz, S.; White, P. S.; Brookhart, M.; Templeton, J. L. J. Am.
Chem. Soc. 2001, 123, 6425.
(36) (a) Bernskoetter, W. H.; Lobkovsky, E.; Chirik, P. J. Chem.
Commun. 2004, 764. (b) Yang, S.-Y.; Leung, W.-H.; Lin, Z. Organo-
metallics 2001, 20, 3198. (c) Kamato, M.; Hirotsu, K.; Higuchi, T.; Tatsumi,
K.; Hoffman, R.; Yoshida, T.; Otsuka, S. J. Am. Chem. Soc. 1981, 103,
5772. (d) Templeton, J. L.; Ward, B. C. J. Am. Chem. Soc. 1980, 102,
6568. (e) Chisholm, M. H.; Huffman, J. C.; Kelly, R. L. J. Am. Chem. Soc.
1979, 101, 7615.
(33) Jessop, P. G.; Morris, R. H. Coord. Chem. ReV. 1992, 121, 155.
(37) Kubacek, P.; Hoffman, R. J. Am. Chem. Soc. 1981, 103, 4320.

Si-H Bond ActiVations by Rh and Ir Complexes
Organometallics, Vol. 25, No. 19, 2006 4477
Figure 6. ORTEP diagram of the molecular structure of (PyInd)-
IrH(SiEt3)(PMe3)2 (7). Hydrogen atoms, except for the iridium
hydride, were omitted for clarity. Selected bond lengths (Å): Ir-
P1 ) 2.388(2), Ir-P2 ) 2.249(2), Ir-Si ) 2.416(2), Ir-N1 )
2.079(4), Ir-N2 ) 2.163(4), Ir-H43 ) 1.56(3). Selected bond
angles (deg): P1-Ir-P2 ) 95.13(6), P1-Ir-Si ) 168.49(5), P2-
Ir-Si ) 92.24(6), N1-Ir-N2 ) 76.7(2), P1-Ir-H ) 84(2), P2-
Ir-H ) 81(1), Si-Ir-H1 ) 88(2).
significantly longer than that for the equatorial phosphine, Ir-P
) 2.249(2) Å. Additionally, the fact that the hydride adopts
the position trans to the pyridinyl, rather than the indolyl, can
be rationalized by the expected, greater trans influence of the
indolyl (vs the pyridinyl) group.39
Figure 5. Molecular orbital analysis of the distortion from an
octahedral to a bicapped tetrahedral geometry.
distortion from idealized octahedral geometry to a bicapped
tetrahedral structure via bending of the two axial ligands toward
one another.38 One consequence of this deformation is an
increase in energy for φ2, a molecular orbital derived from the
t
2g set (Figure 5). For a d4 metal complex, this orbital becomes
The 1H NMR spectrum of 7 features a hydride resonance at
-19.82 ppm, which exhibits coupling to the phosphorus atoms
of the two PMe3 ligands (JPH ) 22.5 Hz, JP′H ) 10.5 Hz). A
29Si{1H-INEPT} spectrum of 7 features a resonance at 0.3 ppm
(JSiP ) 151.3 Hz, JSiP ) 14.5 Hz) and is consistent with the
positioning of the phosphines in the solid-state structure.13a The
value of the coupling constant between the hydride and the 29Si
nucleus in this Ir(III) complex, determined by a J-resolved 1H-
29Si gHMBC experiment, is 5.1 Hz, which is not significantly
different form those for the hydrides in the Ir(V) complex 6a
(Table 2).
Complex 6a also reacted with 1 equiv of PPh3 at room
temperature to give 1 equiv of Et3SiH and an 80:20 mixture of
isomers with the formulation (PyInd)IrH(SiEt3)(PPh3), as judged
by 1H and 31P{1H} NMR spectroscopy. Upon heating in benzene
at 80 °C for 2 h, this mixture was completely converted to the
major isomer 8, a monophosphine Ir(III) complex that was
isolated in 91% yield (eq 6). Although the location of the hydride
ligand in the X-ray crystal structure of 7 (Figure 7) was
determined, the estimated standard deviation in the measurement
of the Ir-H distance (1.51(8) Å) is quite large, preventing
meaningful comparisons with Ir-H bond lengths in other
complexes. As with 7, the placement of the hydride trans to
the pyridinyl is consistent with predictions based on the relative
trans influence of the two nitrogen donors of PyInd.
the LUMO, a result that accounts for the fact that the bicapped
tetrahedral geometry is favored for this electron count. Ad-
ditionally, the observed geometry and predicted molecular orbital
structure of 6c are consistent with the high trans influence of
the silyl ligands and the presence of two strongly trans-
influencing hydrides in the equatorial positions. Thus, if the
two axial silyls are at 180° to one another, they must compete
for the electron density in the same metal-based orbital (e.g.,
2
pz and dz ). As these ligands bend away from the z-axis, however,
the orbitals are rehybridized to lower the energies of the bonding
Ir-Si interactions. This results in greatly increased stabilization
of the bonding φ1 orbital (Figure 5). Interestingly, the calculated
HOMO of 6c reflects a high degree of ligand-based character,
suggesting that the distribution of negative charge on the anionic
PyInd ligand dominates the electronic structure of this orbital
(Figure 4).
(PyInd)Ir(III) Complexes. To further understand the effects
of the d-electron count on the structures of (PyInd)Ir complexes,
two Ir(III) derivatives were obtained. Reaction of 6a with excess
PMe3 (5 equiv) at room temperature gave a single isomer of
the d6 complex (PyInd)IrH(SiEt3)(PMe3)2 (7) in 85% yield after
the loss of 1 equiv of Et3SiH (eq 6). The molecular structure of
7 exhibits a regular octahedral geometry (Figure 6), with the
remaining silyl ligand occupying one of the axial positions. The
hydride ligand, which adopts an equatorial rather than an axial
position, was located in the Fourier difference map, and the
Ir-H distance was determined to be 1.56(3) Å. The Ir-P bond
length for the phosphine trans to the silyl group is 2.388(2),
The molecular geometry of 8 can be described as a distorted
square pyramid, featuring four ligands that are all slightly below
the basal plane of the molecule. In addition, the axial silyl group
is bent away from the PyInd ligand, and the Ir-Si bond vector
(38) Albright, T. A.; Burdett, J. K.; Whangbo, M.-H. Orbital Interactions
in Chemistry; Wiley: New York, 1985; pp 289-294.
(39) Lersch, M.; Tilset, M. Chem. ReV. 2005, 105, 2471.

4478 Organometallics, Vol. 25, No. 19, 2006
Karshtedt et al.
activations involving silanes and the C-Cl bond of chlorben-
zene. In addition, utilization of the bidentate, monoanionic ligand
PyInd, rather than more common L2X-type ligands based on
the cyclopentadielyl or tris(pyrazolyl)borate frameworks, leads
to the formation of unusual six-coordinate 16-electron com-
plexes.41 Such species appear to mediate substrate activations
by an unusual process, involving an associative step with a
seven-coordinate intermediate or, alternatively, a dissociative
process requiring reductive elimination from a 16-electron
complex. The results described herein provide impetus for
further synthetic and mechanistic studies of six-coordinate
complexes of the type (NN*)MX4 (M ) Rh, Ir).
Experimental Section
Figure 7. ORTEP diagram of the molecular structure of (PyInd)-
IrH(SiEt3)(PPh3) (8). Hydrogen atoms were omitted for clarity.
Selected bond lengths (Å): Ir-P ) 2.234(2), Ir-Si ) 2.315(2),
Ir-N1 ) 2.037(6), Ir-N2 ) 2.168(6), Ir-H1 ) 1.51(8). Selected
bond angles (deg): P-Ir-Si ) 97.83(7), P-Ir-H1 ) 79(3), Si-
Ir-H1 ) 80(3), N1-Ir-H1 ) 99(3), N2-Ir-H1 ) 176(2), N1-
Ir-N2 ) 77.3(2).
Synthetic Methods. All experiments were conducted under a
nitrogen atmosphere using standard Schlenk techniques or in a
Vacuum Atmospheres drybox, unless otherwise noted. Dry, oxygen-
free solvents were used throughout. Olefin impurities were removed
from pentane by treatment with concentrated H2SO4, 0.5 N KMnO4
in 3 M H2SO4, and saturated NaHCO3. Pentane was then dried over
MgSO4, stored over activated 4 Å molecular sieves, and distilled
over potassium benzophenone ketyl under a nitrogen atmosphere.
Thiophene impurities were removed from benzene by treatment
with H2SO4 and saturated NaHCO3. Benzene was then dried over
MgSO4 and distilled from potassium metal under a nitrogen
atmosphere. Chlorobenzene and dichloromethane were distilled
from CaH2.
forms an angle of approximately 74° with the basal plane. While
the Si-Ir-P angle is approximately 97.8°, the Si-Ir-H1 angle
is significantly smaller (80°), indicating that the silyl ligand
“leans” toward the hydride. Nevertheless, the Si-H distance
of approximately 2.5 Å is too long to invoke η2-silane complex
character in 8.
The 1H NMR spectrum of 8 exhibits a hydride resonance at
-16.76 ppm (JPH ) 21.0 Hz). The 29Si{1H-INEPT} spectrum
of 8, which contains a resonance at 25.9 ppm (JSiP ) 8.8 Hz),
confirms the cis positioning of the triethylsilyl ligand and PPh3,
as indicated by the low value of the Si-P coupling constant.13a
Moreover, the value of the Si-H coupling constant, 6.0 Hz, is
similar to those found for other hydrides described herein. In
general, the successful synthesis of d6 Ir(III) complexes 7 and
8, which feature common octahedral and distorted square
pyramidal geometries, respectively, reinforces the notion that
the d4 electron configuration is an important factor in determin-
ing the unusual structure of the Ir(V) bis(silyl)dihydride 6c.
Deuterated solvents were purchased from Cambridge Isotopes
and dried with appropriate drying agents. Unless otherwise noted,
all reagents were purchased from Aldrich or Gelest Chemicals and
used without further purification. Liquid silanes were stored over
activated molecular sieves, and 1-octene was dried over sodium
metal and then vacuum-transferred onto activated molecular sieves
before use. The compounds K[PyInd],17a [(CO)2RhCl]2,42 [(COD)-
RhCl]2,43 [(C2H4)2RhCl]2,44 and [(COE)2IrCl]2 were prepared
45
according to literature procedures, while [(COD)IrCl]2 was obtained
from Strem Chemicals.
Analytical Methods. Routine NMR spectra were recorded at
room temperature, using a Bruker DRX-500 spectrometer equipped
with a 5 mm BBI probe or a Bruker AV-500 spectrometer equipped
with a 5 mm BB probe. 1H (500.1 MHz) and 13C{1H} (124.7 MHz)
NMR spectra were referenced internally by the residual solvent
signal relative to tetramethylsilane, while 29Si{1H} (99.7 MHz)
NMR spectra were referenced to an external tetramethylsilane
standard and 31P{1H} (202.5 MHz) NMR spectra were referenced
to an external 85% H3PO4 standard. Unless otherwise noted, spectra
for all NMR-active nuclei of a given compound were obtained in
the same solvent. Multiplets that are predicted to be doublets of
doublets but appear as pseudotriplets are denoted as “pt”.
Elemental analyses were performed by the College of Chemistry
Microanalytical Laboratory at the University of California, Berkeley.
FT-infrared spectra were recorded as KBr pellets using a Mattson
FTIR 3000 spectrometer at a resolution of 4 cm-1. Identities of
Conclusions
Rhodium and iridium complexes containing the PyInd ligand
exhibit rich Si-H bond activation chemistry that leads to
interesting catalytic and stoichiometric processes. A (PyInd)-
Rh(I) precursor catalyzes the dehydrochlorinative coupling of
chlorobenzene with triethylsilane, which appears to involve an
unusual Rh(V) bis(silyl)dihydride intermediate. The (PyInd)Ir
fragment provides a platform for the isolation and characteriza-
tion of several pentavalent bis(silyl)dihydrides that are analogous
to the catalytically active rhodium species. Structural charac-
terizations, DFT calculations, and reactivity studies establish
that observed structural distortions are a likely consequence of
the d4 electron count and the presence of strongly trans-
influencing silyl ligands in these complexes.
1
organic products were confirmed by H NMR spectroscopy and
by GC-MS, using an Agilent Technologies 6890N GC system with
an HP-5MS column.
(PyInd)Rh(CO)2 (1). To a stirred suspension of [(CO)2RhCl]2
(0.126 g, 0.323 mmol) in 5 mL of benzene was added K[PyInd]
(0.150 g, 0.646 mmol) as a solid. The reaction mixture was stirred
Studies by other researchers have pointed to the importance
of M(V) (M ) Ir, Rh) silyl or boryl intermediates in catalytic
processes such as dehydrogenative coupling reactions of arenes
with silanes or boranes, respectively.6a,11a,40 The present report
demonstrates that such intermediates also play a role in catalytic
(41) For related work with â-diiminate ligands on Rh and Ir, see:
Bernskoetter, W. H.; Lobkovsky, E.; Chirik, P. J. Organometallics 2005,
24, 4367, and refs 21 and 36a.
(40) (a) Hartwig, J. F.; Cook, K. S.; Hapke, M.; Incarvito, C. D.; Fan,
Y.; Webster, C. E.; Hall, M. B. J. Am. Chem. Soc. 2005, 127, 2538. (b)
Webster, C. E.; Hall, M. B. Coord. Chem. ReV. 2003, 238, 315. (c)
Kawamura, K.; Hartwig, J. F. J. Am. Chem. Soc. 2001, 123, 8422.
(42) McCleverty, J. A.; Wilkinson, G. Inorg. Synth. 1990, 28, 84.
(43) Giordano, G.; Crabtree, R. H. Inorg. Synth. 1990, 28, 88.
(44) Cramer, R. Inorg. Synth. 1990, 28, 86.
(45) van der Ent, A.; Onderdelinden, A. L. Inorg. Synth. 1990, 28, 90.

Si-H Bond ActiVations by Rh and Ir Complexes
Organometallics, Vol. 25, No. 19, 2006 4479
at room temperature for 16 h, and the solvent was removed in vacuo.
The resulting solid was extracted with 10 mL of dichloromethane
and filtered, the solvent volume was reduced to 2 mL, and the
resulting solution was layered with 5 mL of pentane and stored at
-35 °C for 2 days, yielding 1 as a dark green powder (0.173 g,
(PyInd)Ir(COD) (5). To a stirred suspension of [(COD)IrCl]2
(0.289 g, 0.430 mmol) in 8 mL of benzene was added K[PyInd]
(0.200 g, 0.861 mmol) as a solid. The reaction mixture was stirred
at room temperature for 16 h, and the solvent was removed in vacuo.
The resulting solid was extracted with 10 mL of dichloromethane
and filtered, the solvent volume was reduced to 3 mL, and the
resulting solution was layered with 10 mL of pentane and stored
at -35 °C for 2 days, yielding 5 as a red microcrystalline solid
1
76%). H NMR (dichloromethane-d2): δ 6.95 (m, 4H), 7.12 (pt,
3J ) 7.2 Hz, 1H), 7.47 (d, 3J ) 8.5 Hz, 1H), 7.55 (d, 3J ) 7.5 Hz,
3
1H), 7.76 (s, 1H), 8.34 (d, J ) 5.0 Hz, 1H). 13C{1H} NMR: δ
1
103.2, 115.3, 119.0, 120.1, 121.0, 121.4, 123.4, 130.2, 139.2, 146.8,
147.2, 151.4, 157.9. IR (cm-1): 1999 (s, νCO), 2054 (s, νCO). Anal.
Calcd for C15H9N2O2Rh: C, 51.16; H, 2.58; N, 7.95. Found: C,
50.86; H, 2.45; N, 8.26.
(0.391 g, 92%). H NMR (dichloromethane-d2): δ 1.74 (m, 2H,
CH2), 1.92 (m, 2H, CH2), 2.36 (m, 4H, CH2), 3.66 (d, 3J ) 2.5 Hz,
3
2H, CH), 5.23 (d, J ) 3.0 Hz, 2H, CH), 6.92 (m, 2H), 7.03 (m,
3
3H), 7.53 (d, J ) 8.0 Hz, 1H), 7.77 (m, 3H). 13C{1H} NMR: δ
30.4, 32.6, 61.6, 64.3, 103.6, 114.6, 118.8, 119.8, 121.2 (two
overlapping signals), 123.1, 132.3, 138.9, 145.7, 147.5, 149.8, 159.7.
Anal. Calcd for C21H21N2Ir: C, 51.10; H, 4.29; N, 5.67. Found:
C, 50.79; H, 4.36; N, 5.58.
(PyInd)Rh(COD) (2). To a stirred suspension of [(COD)RhCl]2
(0.212 g, 0.430 mmol) in 6 mL of benzene was added K[PyInd]
(0.200 g, 0.861 mmol) as a solid. The reaction mixture was stirred
at room temperature for 16 h, and the solvent was removed in vacuo.
The resulting solid was extracted with 8 mL of dichloromethane
and filtered, the solvent volume was reduced to 3 mL, and the
resulting solution was layered with 10 mL of pentane and stored
at -35 °C for 2 days, yielding 2 as a yellow crystalline solid (0.324
(PyInd)IrH2(SiEt3)2 (6a). To the solids K[PyInd] (0.040 g, 0.172
mmol) and [(COE)2IrCl]2 (0.077 g, 0.086 mmol), which were placed
in a vial, was added a solution of Et3SiH (0.040 g, 55.0 µL, 0.344
mmol) in 5 mL of benzene with rapid stirring. The reaction mixture
was stirred for 30 min and was filtered, and the solvent was then
removed in vacuo. The remaining yellow oil was lyophilized from
benzene, rapidly washed with 2 mL of cold pentane, and dried in
vacuo, resulting in the formation of 6a as an oily, yellow solid
1
g, 93%). H NMR (dichloromethane-d2): δ 1.99 (m, 2H, CH2),
3
2.09 (m, 2H, CH2), 2.54 (m, 4H, CH2), 4.05 (d, J ) 2.0 Hz, 2H,
3
3
CH), 5.47 (d, J ) 2.5 Hz, 2H, CH), 6.87 (pt, J ) 6.8 Hz, 1H),
6.89 (s, 1H), 6.95 (m, 2H), 7.00 (pt, 3J ) 7.0 Hz, 1H), 7.50 (pt, 3J
3
3
1
2
) 6.8 Hz, 2H), 7.67 (d, J ) 7.5 Hz, 1H), 7.73 (d, J ) 8.0 Hz,
1H). 13C{1H} NMR: δ 30.0, 31.5, 78.8 (d, JRhC ) 12.5 Hz), 79.4
(d, JRhC ) 11.3 Hz), 101.8, 114.3, 118.0, 119.9, 120.7, 120.9, 122.1,
131.5, 138.2, 145.6, 147.1, 147.7, 158.7. Anal. Calcd for
C21H21N2Rh: C, 62.38; H, 5.23; N, 6.61. Found: C, 61.99; H, 5.33;
N, 6.61.
(0.070 g, 67%). H NMR (benzene-d6): δ -18.04 ppm (d, J )
2
2.0 Hz, 1H, IrH), -15.53 ppm (d, J ) 2.0 Hz, 1H, IrH), 0.95 (s,
30H, overlapping CH2 and CH3), 6.09 (pt, 3J ) 6.4 Hz, 1H), 6.72
(pt, 3J ) 7.2 Hz, 1H), 6.78 (s, 1H), 7.03 (d, 3J ) 8.0 Hz, 1H), 7.12
3
(m, partially obscured by solvent signal, 1H), 7.37 (pt, J ) 7.6
3
3
Hz, 1H), 7.68 (d, J ) 8.0 Hz, 1H), 7.99 (d, J ) 8.4 Hz, 1H),
8.40 (d, 3J ) 5.6 Hz, 1H). 13C{1H} NMR: δ 8.7, 12.6, 118.9, 119.6,
121.3, 121.5, 121.7, 124.6, 132.3, 138.2, 149.0, 151.2, 154.0, 158.2,
(PyInd)Rh(C2H4)2 (3). To a stirred suspension of [(C2H4)2RhCl]2
(0.251 g, 0.645 mmol) in 5 mL of benzene was added K[PyInd]
(0.300 g, 1.291 mmol) as a solid. The reaction mixture was stirred
at room temperature for 16 h, and the solvent was removed in vacuo.
The resulting solid was extracted with 15 mL of dichloromethane
and filtered, the solvent volume was reduced to 5 mL, and 20 mL
of pentane was added to the resulting solution, yielding a 3 as a
159.5. 29Si NMR (via H-29Si gHMBC): δ 37.1 (JSiH ) 6.4 Hz,
1
JSiH′ ) 6.7 Hz). IR (cm-1): 2094 (br, νIrH), 2162 (br, νIrH). Anal.
Calcd for C25H41N2Si2Ir: C, 48.58; H, 6.69; N, 4.53. Found: C,
48.20; H, 6.73; N, 4.47.
(PyInd)IrH2(SiMe2Ph)2 (6b). To the solids K[PyInd] (0.020 g,
0.086 mmol) and [(COE)2IrCl]2 (0.039 g, 0.043 mmol), which were
placed in a vial, was added a solution of Me2PhSiH (0.023 g, 26.4
µL, 0.172 mmol) in 3 mL of benzene with rapid stirring. The
reaction mixture was stirred for 30 min and was filtered, and the
solvent was then removed in vacuo. The remaining red oil was
then lyophilized from benzene, rapidly washed with 1 mL of cold
pentane, and dried in vacuo, resulting in the formation of 6b as an
oily, orange solid (0.042 g, 75%). 1H NMR (benzene-d6): δ -17.36
1
red-orange powder (0.368 g, 81%). H NMR (dichloromethane-
d2): δ 1.98 (br, 2H, CH), 2.39 (br, 2H, CH), 2.75 (br, 2H, CH),
3
3
4.82 (br, 2H, CH), 5.97 (pt, J ) 6.0 Hz, 1H), 6.61 (pt, J ) 7.0
Hz, 1H), 6.69 (d, 3J ) 6.0 Hz, 1H), 6.79 (s, 1H), 7.00 (d, 3J ) 8.0
Hz, 1H), 7.14 (m, 2H), 7.35 (d, 3J ) 8.5 Hz, 1H), 7.78 (d, 3J ) 7.5
Hz, 1H). 13C{1H} NMR: δ 60.8 (d, JRhC ) 12.5 Hz), 62.6 (br),
103.2, 114.3, 118.8, 119.4, 119.6, 121.6, 123.3, 132.2, 137.3, 142.2,
147.1, 147.8, 159.2. Anal. Calcd for C17H17N2Rh: C, 57.97; H,
4.86; N, 7.95. Found: C, 57.68; H, 4.72; N, 7.73.
2
2
ppm (d, J ) 2.4 Hz, 1H, IrH), -14.84 ppm (d, J ) 2.4 Hz, 1H,
3
IrH), 0.77 (s, 6H, CH3), 0.80 (s, 6H, CH3), 5.80 (pt, J ) 7.2 Hz,
(PyInd)RhH2(SiEt3)2 (4). To a stirred solution of 3 in benzene
(0.080 g, 0.227 mmol) was added 4 equiv of Et3SiH (0.106 g, 145
µL, 0.908 mmol) via syringe. The reaction mixture was stirred for
2 h at 60 °C in a Teflon-sealed flask and allowed to cool to room
temperature, and volatile materials were then removed under
reduced pressure. The resulting red oil was then lyophilized with
benzene, rapidly washed with 3 mL of cold pentane, and dried in
1H), 6.58 (pt, 3J ) 7.6 Hz, 1H), 6.60 (s, 1H), 6.58 (d, 3J ) 7.5 Hz,
3
3
1H), 6.97 (m, 6H, Ph), 7.17 (pt, J ) 7.5 Hz, 1H), 7.37 (pt, J )
8.0 Hz, 1H), 7.41 (m, 4H, Ph), 7.54 (d, 3J ) 5.5 Hz, 1H), 7.65 (pt,
3J ) 8.0 Hz, 1H), 7.85 (d, J ) 8.0 Hz, 1H). 13C{1H} NMR: δ
3
6.8, 7.3, 105.5, 118.9, 119.0, 121.1, 121.2, 121.4, 124.4, 127.6,
128.9, 132.4, 133.2, 137.6, 143.8, 148.6, 150.7, 153.9, 157.6. 29Si
NMR (via H-29Si gHMBC): δ 9.6 (JSiH ) 9.5 Hz, JSiH′ ) 12.1
1
1
vacuo, yielding 4 as an oily, red solid (0.085 g, 71%). H NMR
Hz). IR (cm-1): 2132 (br, νIrH), 2173 (br, νIrH). Anal. Calcd for
C29H31N2Si2Ir: C, 53.10; H, 4.76; N, 4.27. Found: C, 53.33; H,
5.09; N, 4.48.
2
(benzene-d6): δ -15.32 ppm (dd, JRhH ) 28.5 Hz, J ) 9.0 Hz,
1H, RhH), -13.88 ppm (JRhH ) 23.5 Hz, 2J ) 9.0 Hz, 1H, RhH),
3
0.92-1.03 (two overlapping m, 30H, CH2 and CH3), 6.18 (pt, J
3
) 6.0 Hz, 1H), 6.75 (vt, J ) 7.3 Hz, 1H), 6.91 (s, 1H), 7.12 (m,
(PyInd)IrH2(SiPh2Me)2 (6c). To the solids K[PyInd] (0.020 g,
0.086 mmol) and [(COE)2IrCl]2 (0.036 g, 0.043 mmol), which were
placed in a vial, was added a solution of Ph2MeSiH (0.034 g, 34.3
µL, 0.172 mmol) in 3 mL of benzene with rapid stirring. The
reaction mixture was stirred for 30 min and was filtered, and the
volume of the resulting solution was reduced to ca. 1 mL. This
solution was diluted with 5 mL of pentane and stored at -35 °C
for 2 days, leading to the precipitation of 6c as a microcrystalline,
red-orange solid (0.055 g, 82%). 1H NMR (benzene-d6): δ -16.59
3
obscured by solvent signal, 1H), 7.19 (pt, J ) 7.0 Hz, 1H), 7.41
(pt, 3J ) 8.0 Hz, 1H), 7.79 (d, 3J ) 8.0 Hz, 1H), 7.96 (d, 3J ) 8.0
3
Hz, 1H), 8.22 (pt, J ) 5.0 Hz, 1H). 13C{1H} NMR: δ 8.7, 12.7,
103.9, 118.3, 120.0, 120.3, 120.7, 121.6, 123.9, 132.1, 138.3, 148.1,
148.2, 152.3, 158.5. 29Si{1H} NMR: δ 63.0 (JRhSi ) 26.8 Hz).
1
29Si NMR (via H-29Si gHMBC): δ 63.0 (JSiH ) 8.1 Hz, JSiH′
)
6.2 Hz). IR (cm-1): 2065 (br, νRhH), 2090 (br, νRhH). Anal. Calcd
for C25H41N2Si2Rh: C, 56.80; H, 7.82; N, 5.30. Found: C, 56.75;
H, 7.65; N, 5.18.
2
2
ppm (d, J ) 2.5 Hz, 1H, IrH), -13.87 ppm (d, J ) 2.5 Hz, 1H,

4480 Organometallics, Vol. 25, No. 19, 2006
Karshtedt et al.
3
3
IrH), 0.96 (s, 6H, CH3), 5.73 (pt, 3J ) 7.2 Hz, 1H), 6.64 (pt, 3J )
7.5 Hz, 1H), 6.73 (s, 1H), 6.81 (d, 3J ) 8.0 Hz, 1H), 6.91 (m, 6H,
Ph), 7.10 (m, 6H, Ph), 7.18 (m, obscured by solvent signal, 1H),
7.55 (pt, J ) 7.0 Hz, 1H), 7.81 (m, 9H, PPh3), 7.96 (d, J ) 8.0
3
3
Hz, 1H), 8.02 (d, J ) 5.0 Hz, 1H), 8.44 (d, J ) 8.0 Hz, 1H).
13C{1H} NMR: δ 8.7, 10.5, 104.8, 119.7, 119.8, 120.3, 120.6,
121.8, 123.5, 128.8, 130.4, 132.3, 134.3, 134.4, 134.8, 135.2, 137.4,
3
7.26 (pt, J ) 7.5 Hz, 1H), 7.58 (m, 10H, Ph + obscured ligand
resonances), 7.77 (d, 3J ) 8.0 Hz, 1H). 13C{1H} NMR: δ 6.7, 103.9,
116.5, 119.1, 119.2, 121.3, 121.4, 121.6, 124.6, 130.4, 130.7, 132.3,
135.0 (two overlapping signals), 135.1 (two overlapping signals),
149.5, 151.2. 29Si NMR (via 1H-29Si gHMBC): 25.9 ppm (JSiH
)
6.0 Hz). 29Si{1H-INEPT}: δ 25.9 ppm (d, JSiP ) 8.8 Hz). 31P{1H}
NMR: δ 19.3 ppm. IR (cm-1): 2199 (s, νIrH). Anal. Calcd for
C37H40N2PSiIr: C, 58.17; H, 5.28; N, 3.67. Found: C, 57.82; H,
5.15; N, 3.43.
1
140.9, 142.1, 148.2, 151.2, 153.8, 157.2. 29Si NMR (via H-29Si
gHMBC): δ 7.2 (JSiH ) 11.7 Hz, JSiH′ ) 14.2 Hz). IR (cm-1):
2164 (br, νIrH), 2201 (br, νIrH). Anal. Calcd for C39H37N2Si2Ir: C,
59.89; H, 4.77; N, 3.58. Found: C, 60.28; H, 4.88; N, 3.59.
General Procedure for Catalytic Runs. Reactions were con-
ducted in 5 mm Wilmad NMR tubes equipped with a J. Young
Teflon-valve seal, which were heated in temperature-controlled oil
baths. Samples were prepared in a drybox by dissolving the catalyst
and the specified reagents in neat chlorobenzene. Reaction progress
was monitored by 1H NMR spectroscopy (a small amount of
cyclohexane-d12 was added to all samples in order to obtain a lock
signal). Product yields were quantified by GC, using a calculated
response factor to account for the difference in ionization between
the integration standard (tetraphenylsilane) and phenyltriethylsilane.
(PyInd)IrH2(SiPh3)2 (6d). To the solids K[PyInd] (0.020 g,
0.086 mmol) and [(COE)2IrCl]2 (0.036 g, 0.043 mmol), which were
placed in a vial, was added a solution of Ph3SiH (0.045 g, 0.172
mmol) in 3 mL of benzene with rapid stirring. The reaction mixture
was stirred for 30 min and was filtered, and the volume of the
resulting solution was reduced to ca. 1 mL. This solution was
layered with 5 mL of pentane and stored at room temperature for
2 days, leading to the precipitation of 6d as a microcrystalline, red-
1
orange solid (0.062 g, 79%). H NMR (benzene-d6): δ -16.06
Reaction of 4 with 1-Octene. To a sample of 4 (0.010 g, 0.019
mmol) dissolved in 0.5 mL of benzene-d6 was added 5 equiv of
1-octene (0.014 g, 15 µL, 0.095 mmol) via microsyringe in a
drybox. The resulting mixture was transferred to an NMR tube
2
2
ppm (d, J ) 2.8 Hz, 1H, IrH), -13.05 ppm (d, J ) 2.8 Hz, 1H,
3
3
IrH), 5.72 (pt, J ) 7.2 Hz, 1H), 6.52 (pt, J ) 5.6 Hz, 1H), 6.55
(s, 1H), 6.80 (d, 3J ) 8.0 Hz, 1H), 6.98 (m, 18H, Ph), 7.05 (pt, 3J
3
) 6.8 Hz, 1H), 7.55 (pt, J ) 8.6 Hz, 1H), 7.75 (m, 13H, Ph +
1
equipped with a Teflon-valve seal and heated to 70 °C. H NMR
obscured ligand resonance), 7.78 (d, 3J ) 7.0 Hz, 1H), 7.83 (pt, 3J
) 7.2 Hz, 1H). 13C{1H} NMR: δ 104.5, 127.2, 128.4, 128.6, 129.3,
130.1, 133.8, 136.1 (two overlapping signals), 136.2 (two over-
spectra of this reaction mixture were obtained every 30 min,
indicating complete consumption of 1-octene after 4 h. Analysis
of organic reaction products by GC-MS indicated complete conver-
sion of the starting 1-octene to a mixture of internal 1-octenes.
lapping signals), 139.3, 140.0, 142.2, 143.1, 148.2, 153.5, 158.9.
1
29Si NMR (via H-29Si gHMBC): δ 9.2 (JSiH ) 12.5 Hz, JSiH′
)
Reaction of 4 with PMe3. To a sample of 4 (0.010 g, 0.019
mmol) dissolved in 0.5 mL of benzene-d6 was added 10 equiv of
PMe3 (0.0048 g, 20 µL, 0.190 mmol) via microsyringe in a drybox.
The resulting reaction mixture was analyzed by NMR spectroscopy,
indicating liberation of 2 equiv of Et3SiH (by H NMR) and the
formation of a Rh-containing species with the following spectro-
17.4 Hz). IR (cm-1): 2170 (br, νIrH), 2194 (br, νIrH). Anal. Calcd
for C49H41N2Si2Ir: C, 64.73; H, 4.55; N, 3.08. Found: C, 64.71;
H, 4.45; N, 3.38.
(PyInd)IrH(SiEt3)(PMe3)2 (7). To a stirred solution of 6a (0.025
g, 0.040 mmol) in 2 mL of benzene was added 5 equiv of PMe3
(0.015 g, 21.0 µL, 0.202 mmol) via syringe. The reaction mixture
was stirred for 30 min. The reaction volume was then reduced to
ca. 1 mL, and the resulting solution was layered with 5 mL of
pentane and stored for 2 days at room temperature, leading to the
1
1
scopic properties. H NMR: δ 0.77 (br, PMe3, partially obscured
by free PMe3 signal), 1.14 (d, JPH ) 6.4 Hz, 9H, PMe3), 6.78 (pt,
3J ) 6.0 Hz, 1H), 7.4 (m, 3H), 8.12 (d, 3J ) 8.0 Hz, 1H), 8.18 (s,
1H), 8.41 (d, 3J ) 7.6 Hz, 1H), 8.73 (d, 3J ) 4.8 Hz, 1H), 9.88 (d,
3J ) 8.0 Hz, 1H). 31P{1H} NMR: δ -11.4 ppm (br d, JRhP ) 139
Hz), -5.6 ppm (br d, JRhP ) 157 Hz). The presence of a new set
of ligand resonances in the 1H NMR spectrum and the appearance
of two inequivalent Rh-coupled doublets in the 31P{1H} NMR
spectrum, along with the observation of 2 equiv of free Et3SiH,
led to the assignment of the product as (PyInd)Rh(PMe3)2. Removal
of solvent from this reaction mixture resulted in the formation of
intractable materials.
1
precipitation of 7 as a bright yellow powder (0.026 g, 85%). H
NMR (benzene-d6): δ (dd, -19.82 ppm, JPH ) 22.5 Hz, JP′H
)
10.5 Hz, 1H, IrH), 0.33 (d, JPH ) 7.0 Hz, 9H, PMe3), 0.39 (m, 3H,
CH2), 0.65 (m, 3H, CH2), 0.90 (pt, 3J ) 8.0 Hz, 9H, CH3), 1.32 (d,
3
3
JPH ) 8.5 Hz, 9H, PMe3), 6.24 (pt, J ) 6.0 Hz, 1H), 6.93 (pt, J
3
) 7.5 Hz, 1H), 7.17 (pt, J ) 7.5 Hz, 1H), 7.20 (s, 1H), 7.34 (pt,
3J ) 7.5 Hz, 1H), 7.42 (d, 3J ) 8.0 Hz, 1H), 7.74 (d, 3J ) 8.5 Hz,
1H), 7.89 (d, 3J ) 8.0 Hz, 1H), 8.26 (d, 3J ) 6.5 Hz, 1H). 13C{1H}
3
1
NMR: δ 8.1 (d, JPC ) 6.3 Hz), 9.3, 16.7 (d, JPC ) 17.5 Hz),
1
3
General Considerations for X-ray Structure Determinations.
The X-ray analyses of compounds 2, 6c, 7, and 8 were carried out
at the UC Berkeley CHEXRAY crystallographic facility. Measure-
ments were made on a Bruker SMART CCD area detector with
graphite-monochromated Mo KR radiation (λ ) 0.71069 Å). Data
were integrated by the program SAINT and analyzed for agreement
using XPREP. Empirical absorption corrections were made using
SADABS. Structures were solved by direct methods and expanded
using Fourier techniques. All calculations were performed using
the teXsan crystallographic software package. Selected crystal and
structure refinement data are summarized in Table 3.
22.0 (dd, JPC ) 36.3 Hz, JP′C ) 5.0 Hz), 101.5, 118.7, 119.2,
119.6, 119.8, 121.7, 122.1, 130.8, 135.2, 145.7, 146.4, 151.4, 159.5.
29Si NMR (via 1H-29Si gHMBC): 0.3 ppm (JSiH ) 5.1 Hz).
29Si{1H-INEPT}: δ 0.3 ppm (dd, JSiP ) 151.3 Hz, JSiP′ ) 14.5
Hz). 31P{1H} NMR: δ -52.2 ppm (d, JPP ) 11.3 Hz), -41.7 ppm
(d, JPP ) 11.3 Hz). IR (cm-1): 2153 (s, νIrH). Anal. Calcd for
C25H42N2P2SiIr: C, 45.99; H, 6.48; N, 4.29. Found: C, 45.95; H,
6.61; N, 4.13.
(PyInd)IrH(SiEt3)(PPh3) (8). To a stirred solution of 6a (0.025
g, 0.040 mmol) in 2 mL of benzene was added PPh3 (0.011 g, 0.040
mmol) as a solid. The reaction mixture was stirred for 2 h at 80 °C
in a Teflon-sealed flask and allowed to cool to room temperature,
and the reaction volume was then reduced to ca. 1 mL. The resulting
solution was layered with 5 mL of pentane and stored for 2 days
at room temperature, leading to the precipitation of 8 as a yellow-
orange, microcrystalline solid (0.028 g, 91%). 1H NMR (benzene-
d6): δ -16.76 ppm (d, JPH ) 21.0 Hz, 1H, IrH), 0.65-0.73 (two
overlapping m, 12H, CH3 + CH2), 0.80 (m, 3H, CH2), 6.13 (pt, 3J
X-ray Structure Determination of 2. X-ray-quality crystals of
2 formed upon vapor diffusion of diethyl ether into a dichloro-
methane solution at room temperature. There are two crystallo-
graphically independent molecules of the complex in the asymmetric
unit of the primitive monoclinic space group P21/n. The primary
difference between the two molecules is the slight rotation of the
pyridine ring with respect to the indole fragment in one molecule
(dihedral angle of 11°), while in the other molecule the two ligand
fragments are nearly coplanar (dihedral angle of 1°).
3
) 6.0 Hz, 1H), 6.92 (pt, J ) 7.0 Hz, 1H), 7.10 (m, 6H, PPh3),
7.20 (s, 1H), 7.35 (d, 3J ) 7.0 Hz, 1H), 7.42 (d, 3J ) 8.0 Hz, 1H),

Si-H Bond ActiVations by Rh and Ir Complexes
Organometallics, Vol. 25, No. 19, 2006 4481
Table 3. Summary of Crystallographic Data for Compounds 2, 6c, 7, and 8
2
6c
formula
MW
RhN2C21H22
405.32
IrSi2N2C39H22
782.13
cryst color, habit
cryst dimens
cryst syst
orange, tablet
orange, block
0.21 × 0.21 × 0.06 mm
0.16 × 0.16 × 0.05 mm
monoclinic
triclinic
lattice type
primitive
primitive
cell determination (2θ range)
3425 (5.09° < 2θ < 48.88°)
a ) 12.3332(9) Å
b ) 10.7187(8) Å
c ) 24.159(2) Å
5225 (7.00° < 2θ < 52.00°)
a ) 10.7460(7) Å
b ) 11.5942(8) Å
c ) 14.648(1) Å
R ) 98.463(1)°
â ) 98.369(1)°
γ ) 110.232(1)°
V ) 1655.3(2) Å3
P1h (#2)
lattice params
â ) 93.987(1)°
V ) 3186(4) Å3
P21/n (#14)
space group
Z value
Dcalc
µ(Mo KR)
temperature
scan type
8
2
1.690 g/cm3
1.569 g/cm3
10.73 cm-1
41.47 cm-1
-154 °C
ω (0.3° per frame)
total: 13 668
-112 °C
ω (0.3° per frame)
total: 13 575
no. of reflns measd
unique: 5592 (Rint ) 0.062)
Lorentz-polarization
abs (Tmax ) 1.00, Tmin ) 0.61)
direct methods (SIR97)
full-matrix least squares
3336 [I > 3.0σ(I)]
433
unique: 6818 (Rint ) 0.020)
Lorentz-polarization
abs (Tmax ) 1.00, Tmin ) 0.82)
direct methods (SIR97)
full-matrix least squares
5811 [I > 3.0σ(I)]
403
corrections
structure solution
refinement
no. reflns obsd
no. variables
R; Rw; Rall
GOF
max. peak in final diff map
min. peak in final diff map
0.037; 0.039; 0.072
1.27
0.023; 0.027; 0.028
1.16
1.02 e-/Å3
1.18 e-/Å3
-0.94 e-/Å3
-0.47 e-/Å3
7
8
formula
MW
IrP2SiN2C25H42
652.87
IrPSi2N2C37H40
764.02
cryst color, habit
cryst dimens
cryst syst
yellow, blade
red, blocklike
0.20 × 0.08 × 0.01 mm
0.04 × 0.10 × 0.17 mm
monoclinic
orthorhombic
lattice type
primitive
primitive
cell determination (2θ range)
2185 (5.00° < 2θ < 44.00°)
a ) 12.183(1) Å
b ) 14.839(2) Å
c ) 15.701(2) Å
â ) 91.057(2)°
V ) 2838.0(6) Å3
P21/n (#14)
5295 (5.00° < 2θ < 49.00°)
a ) 10.979(1) Å
b ) 15.360(1) Å
c ) 19.484(2) Å
lattice params
V ) 3285.7(5) Å3
P212121 (#19)
space group
Z value
Dcalc
µ(Mo KR)
temperature
scan type
4
4
1.528 g/cm3
1.544 g/cm3
48.87 cm-1
41.88 cm-1
-120 °C
ω (0.3° per frame)
total: 15 929
-130 °C
ω (0.3° per frame)
total: 14 603
no. of reflns measd
unique: 6079 (Rint ) 0.048)
Lorentz-polarization
abs (Tmax ) 1.00, Tmin ) 0.74)
direct methods (SIR97)
full-matrix least squares
3830 [I > 3.0σ(I)]
283
unique: 3408 (Rint ) 0.073)
Lorentz-polarization
abs (Tmax ) 1.00, Tmin ) 0.60)
direct methods (SIR97)
full-matrix least squares
4655 [I > 3.0σ(I)]
364
corrections
structure solution
refinement
no. reflns obsd
no. variables
R; Rw; Rall
GOF
max. peak in final diff map
min. peak in final diff map
0.032; 0.035; 0.062
1.11
0.034; 0.037; 0.046
1.16
1.43 e-/Å3
1.35 e-/Å3
-0.66 e-/Å3
-1.50 e-/Å3
X-ray Structure Determination of 6c. This complex crystallizes
upon vapor diffusion of pentane into a toluene solution at room
temperature. There are two molecules of 6c in the unit cell of the
primitive, triclinic space group P1h. The positions of the hydrides
were observed in the Fourier difference map and were included
with a restrained distance of 1.65 Å to Ir.
temperature. There are four molecules of 7 in the unit cell of the
primitive monoclinic space group P21/n. The iridium center exhibits
a slightly distorted octahedral coordination geometry. The hydride
was located in a difference Fourier map and was included in a
refined position (Ir-H distance ) 1.53 Å).
X-ray Structure Determination of 8. X-ray quality crystals of
complex 8 were obtained by slow evaporation of a dilute benzene
solution. The compound crystallizes in the chiral space group
X-ray Structure Determination of 7. The complex crystallizes
upon vapor diffusion of pentane into a benzene solution at room

4482 Organometallics, Vol. 25, No. 19, 2006
Karshtedt et al.
P212121 with one molecule in the asymmetric unit. The enantio-
morph of the space group and enantiomer of the molecule were
determined by inspection of Friedel pairs of reflections followed
by comparison of least-squares refinements. The results were
unequivocal in favor of the enantiomorph reported. The hydride
was located in a Fourier difference map, and its positional
parameters were refined with a fixed thermal parameter.
gas phase without symmetry constraints. Vibrational frequencies
were calculated to ensure that local minima lacked any negative
frequencies.
Acknowledgment is made to Dr. Herman van Halbeek for
assistance with the 29Si NMR experiments, to Dr. Fred Hollander
and Dr. Allen Oliver for assistance with the X-ray crystal-
lography, and to Dr. Kathy Durkin for training at the Molecular
Graphics Facility. This work was supported by the Director,
Office of Energy Research, Office of Basic Energy Sciences,
Chemical Sciences Division, of the U.S. Department of Energy
under Contract No. DE-AC02-05CH11231.
Computational Details
Method. Quantum mechanical calculations were performed at
the University of California, Berkeley, Molecular Graphics Facility
using a 98 cpu-cluster with 2.8 GHz Xeon processors. The DFT
calculation on 6c was carried out by implementing the B3LYP
exchange-correlation functional46 with the LACVP**++ basis set
using Jaguar 5.5. The geometry of 6c was fully optimized in the
Supporting Information Available: X-ray crystallographic data
for 2, 6c, 7, and 8 (CIF). This material is available free of charge
via the Internet at http://pubs.acs.org.
(46) (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (b) Lee, C.; Yang,
W.; Parr, R. G. Phys. ReV. B 1988, 37, 785.
OM060492+