Rhodium complexes containing a tridentate bis(8-quinolyl)methylsilyl ligand: Synthesis and reactivity

Article abstract of DOI:10.1021/om050859v

Synthesis of a series of rhodium complexes bearing a tridentate bis(8-quinolyl)methylsilyl (NSiN) ligand is reported. Bis(8-quinolyl) methylsilane (1) reacted with (PPh₃)₃RhCl via oxidative addition at the Si-H bond to afford (NSiN)Rh(H)Cl(PPh₃) (2). Several coordinatively unsaturated, 16-electron complexes were synthesized, including the cationic complex [(NSiN)Rh(H)(PPh₃)][B(C₆F ₅)₄] (3) and the neutral complex (NSiN)Rh(CH ₂Ph)₂ (12). The X-ray structures of 3 and 12 reveal a square-pyramidal geometry about the Rh center, with the silyl group occupying an apical position. The dicationic complex [(NSiN)Rh(CH₃CN) ₃][OTf]₂ (11), synthesized by reaction of [(NSiN)RhCl ₂]₂ (10) with 2 equiv of AgOTf in acetonitrile, exhibits moderate activity as a catalyst for alkene hydrogenation and for H/Cl exchange between Ph₃SiH and CH₂Cl₂. Complex 2 reacts with 2 equiv of PhCH₂MgCl in benzene to afford (NSiN)-Rh(CH ₂Ph)Cl(PPh₃) (6). Chlorination of 2 by DBU in CH ₂Cl₂ afforded the solvent-activated Rh(III) product (NSiN)RhCl₂(PPh₃) (8). Similarly, with PMe ₃/CH₂Cl₂ as the chlorinating reagent, [(NSiN)Rh-(PMe₃)₂Cl]Cl (9) was obtained. The low-valent complex (NSiN)Rh(COD) (14; COD = 1,5-cyclooctadiene) was synthesized via the reaction of 1 with (CQD)Rh(η³-CH₂Ph) in benzene. The COD ligand was replaced by the phosphine-based dppe ligand, resulting in the thermally more stable complex (NSiN)Rh(dppe) (18; dppe = Ph₂PCH ₂CH₂PPh₂).

Full text of DOI:10.1021/om050859v

Organometallics 2006, 25, 1607-1617
1607
Rhodium Complexes Containing a Tridentate
Bis(8-quinolyl)methylsilyl Ligand: Synthesis and Reactivity
Preeyanuch Sangtrirutnugul, Mark Stradiotto,† and T. Don Tilley*
Department of Chemistry and Center for New Directions in Organic Synthesis (CNDOS),
UniVersity of California, Berkeley, Berkeley, California 94720
ReceiVed October 5, 2005
Synthesis of a series of rhodium complexes bearing a tridentate bis(8-quinolyl)methylsilyl (NSiN)
ligand is reported. Bis(8-quinolyl)methylsilane (1) reacted with (PPh3)3RhCl via oxidative addition at
the Si-H bond to afford (NSiN)Rh(H)Cl(PPh3) (2). Several coordinatively unsaturated, 16-electron
complexes were synthesized, including the cationic complex [(NSiN)Rh(H)(PPh3)][B(C6F5)4] (3) and
the neutral complex (NSiN)Rh(CH2Ph)2 (12). The X-ray structures of 3 and 12 reveal a square-pyramidal
geometry about the Rh center, with the silyl group occupying an apical position. The dicationic complex
[(NSiN)Rh(CH3CN)3][OTf]2 (11), synthesized by reaction of [(NSiN)RhCl2]2 (10) with 2 equiv of AgOTf
in acetonitrile, exhibits moderate activity as a catalyst for alkene hydrogenation and for H/Cl exchange
between Ph3SiH and CH2Cl2. Complex 2 reacts with 2 equiv of PhCH2MgCl in benzene to afford (NSiN)-
Rh(CH2Ph)Cl(PPh3) (6). Chlorination of 2 by DBU in CH2Cl2 afforded the solvent-activated Rh(III)
product (NSiN)RhCl2(PPh3) (8). Similarly, with PMe3/CH2Cl2 as the chlorinating reagent, [(NSiN)Rh-
(PMe3)2Cl]Cl (9) was obtained. The low-valent complex (NSiN)Rh(COD) (14; COD ) 1,5-cyclooctadiene)
was synthesized via the reaction of 1 with (COD)Rh(η3-CH2Ph) in benzene. The COD ligand was replaced
by the phosphine-based dppe ligand, resulting in the thermally more stable complex (NSiN)Rh(dppe)
(18; dppe ) Ph2PCH2CH2PPh2).
and co-workers have synthesized via oxidative addition of a
Si-H bond.6 This method represents a general synthetic route
to metal complexes supported by Si-containing multidentate
ligands.
Introduction
Multidentate ligands with a rigid geometry have been found
to support late-transition-metal complexes that mediate interest-
ing chemical transformations, such as the dehydrogenation of
alkanes and C-H bond activation.2-4 Such observations have
generated considerable interest in the development and explora-
tion of metal complexes containing “pincer ligands.” Despite
this activity, however, only a few chelating ligand systems
containing Si as a donor atom have been developed. The
incorporation of a silyl group as part of the ligand framework
could result in a number of interesting and useful properties
for a metal complex.5 For example, the electron-donating
character of Si can give rise to an electron-rich metal center. In
addition, the strong trans-labilizing ability of Si can promote
the generation of coordinatively unsaturated complexes that may
be useful as catalysts. Examples of chelating ancillary ligands
containing the silyl group include those with a tridentate PSiP
framework (e. g., M[SiMe(CH2CH2CH2PPh2)2]), which Stobart
We have employed a related strategy to prepare complexes
of a new tridentate ligand based on the bis(8-quinolyl)silyl
(NSiN) framework. This method was used to synthesize a
(NSiN)IrIII complex, (NSiN)Ir(H)Cl(COE),7 which possesses a
distorted-octahedral geometry with the NSiN ligand bound to
the Ir center in a facial manner. Preliminary reactivity studies
indicate that the (NSiN)Ir fragment is chemically robust, and
this presumably results from the presence of two chelate rings
which stabilize the NSiN complexes against loss of the ligand.
As a formally five-electron donor, the bis(8-quinolyl)silyl
ligand may be compared to more well-known ligands such as
pentamethylcyclopentadienyl (Cp*), tris(pyrazolyl)borate (Tp),
and 2,6-(tBu2PCH2)2C6H3 (a PCP-based pincer ligand). Rhodium
and iridium complexes of the last three ligands are known to
engage in a number of novel bond activation processes. Thus,
it should be of interest to compare the chemistry of Cp*M,4
TpM,2 and (PCP)M1 (M ) Rh, Ir) derivatives with that of related
(NSiN)M fragments. In addition, the novel set of donor atoms
associated with the NSiN ligand may provide new reaction
pathways. Hard, nitrogen-based ligands, in combination with
soft transition metals such as platinum and rhodium, are known
to participate in a number of C-H activation processes.2-4,8
Furthermore, it should be possible to readily access coordina-
* To whom correspondence should be addressed. E-mail:
tdtilley@berkeley.edu.
† Current address: Department of Chemistry, Dalhousie University,
Halifax, Nova Scotia B3H 4J3, Canada.
(1) (a) Gupta, M.; Hagen, C.; Flesher, R. J.; Kaska, W. C.; Jensen, C.
M. Chem. Commun. 1996, 2083. (b) Gupta, M.; Hagen, C.; Kaska, W. C.;
Cramer, R. E.; Jensen, C. M. J. Am. Chem. Soc. 1997, 119, 840. (c)
Brookhart, M.; Go¨ttker-Schnetmann, I. J. Am. Chem. Soc. 2004, 126, 9330.
(2) (a) Jones, W. D.; Hessell, E. T. J. Am. Chem. Soc. 1992, 114, 6087.
(b) Jones, W. D.; Vetter, A. J. Polyhedron 2004, 23, 413. (c) Jones, W. D.;
Wick, D. D. Organometallics 1999, 18, 495. (d) Jones, W. D.; Hessell, E.
T. J. Am. Chem. Soc. 1993, 115, 554.
(3) Graham, W. A. G.; Ghosh, C. K. J. Am. Chem. Soc. 1987, 109, 4726.
(4) (a) Arndtsen, B. A.; Bergman, R. G. Science 1995, 270, 1970. (b)
Golden, J. T.; Richard, R. A.; Bergman, R. G. J. Am. Chem. Soc. 2001,
123, 5837. (c) Bergman, R. G.; Burger, P. J. Am. Chem. Soc. 1993, 115,
10462.
(6) (a) Stobart, S. R.; Joslin, F. L. Inorg. Chem. 1993, 32, 2221. (b)
Stobart, S. R.; Gossage, R. A.; McLennan, G. D. Inorg. Chem. 1996, 35,
1729 and references therein.
(7) Stradiotto, M.; Fujdala, K. L.; Tilley, T. D. Chem. Commun. 2001,
1200.
(8) (a) Goldberg, K. I.; Fekl, U. J. Am. Chem. Soc. 2002, 124, 6804. (b)
Goldberg, K. I.; Jensen, M. P.; Wick, D. D.; Reinartz, S.; White, P. S.;
Templeton, J. L. J. Am. Chem. Soc. 2003, 125, 8614.
(5) Tilley, T. D. In The Silicon-Heteroatom Bond; Rappoport, Z., Patai,
S., Eds.; Wiley: New York, 1991.
10.1021/om050859v CCC: $33.50 © 2006 American Chemical Society
Publication on Web 02/24/2006

1608 Organometallics, Vol. 25, No. 7, 2006
Sangtrirutnugul et al.
Scheme 1
tively unsaturated metal species (due to the presence of the trans-
labilizing silyl substituent) that feature a nitrogen-based ligand
set.
Especially given the prominent role of Rh complexes in
homogeneous catalysis, it is of interest to explore the chemistry
of (NSiN)Rh complexes. Initial investigations were directed
toward defining the structures that result from introduction of
hydride and carbon-based ligands into the coordination sphere
of such complexes. The synthetic studies reported here targeted
potentially reactive hydrocarbyl hydride complexes of the type
(NSiN)Rh(L)(H)(R) and coordinatively unsaturated, 16-electron
complexes of the types (NSiN)RhH2 and (NSiN)RhR2.
Figure 1. ORTEP diagram of the cationic complex 3 with thermal
ellipsoids shown at the 50% probability level. Hydrogen atoms
(except Rh-H), the B(C6F5)4 counterion, one of the phenyl rings,
and the solvent of crystallization are omitted for clarity.
complex,7 the formation of 2 is stereoselective, in that a chloride
ligand adopts a coordination site trans to the strong trans-
influencing silyl group.
Reactivity Studies of 2. In an attempt to generate a
coordinatively unsaturated Rh(III) complex, 2 was treated with
1 equiv of LiB(C6F5)4‚2.5Et2O11 in dichloromethane at room
temperature. The corresponding cationic complex, [(NSiN)Rh-
(H)(PPh3)][B(C6F5)4] (3), was isolated in 96% yield from vapor
diffusion of diethyl ether into a dichloromethane solution of 3
(Scheme 1). The Rh-H group is observed as an apparent triplet
at δ -13.7 in the 1H NMR spectrum (dichloromethane-d2) and
a medium-intensity band at 2022 cm-1 in the IR spectrum.
Results and Discussion
Ligand Synthesis. Bis(8-quinolyl)methylsilane (1) was pre-
pared via the lithiation of 8-bromoquinoline13 by n-BuLi,
followed by the addition of 0.5 equiv of dichloromethylsilane
(eq 1). Recrystallization from toluene at -30 °C provided bis-
(8-quinolyl)methylsilane (1) as yellow crystals in 48% yield.
For comparison, the previously reported reaction of (NSiN)-
Ir(H)Cl(COE) with either 0.5 or 1.0 equiv of LiB(C6F5)4‚2.5Et2O
produced the cationic, dinuclear complex {[(NSiN)IrH(COE)]2-
(µ2-Cl)}[B(C6F5)4].7 The mononuclear nature of 3 was estab-
lished by X-ray crystallography, which revealed a square-
pyramidal coordination geometry (Figure 1). As a result of its
strong trans-labilizing property, the Si atom adopts the apical
position, trans to an empty coordination site. The rhodium
hydride ligand was located in a difference Fourier map, and its
positional parameters were refined. The Rh-Si bond distance
(2.237(4) Å) falls within the expected range for Rh silyl
complexes (2.21-2.38 Å).12 As observed for (NSiN)Ir com-
plexes, significant geometric distortions at the Si center are
reflected in Rh-Si-C(8) and Rh-Si-C(19) bond angles of
98.4(5) and 128.4(5)°, respectively. The other Rh-Si-C bond
angles are in the range expected for an sp3 center.
Synthesis of (NSiN)Rh(H)Cl(PPh3) (2). Treatment of 1 with
Wilkinson’s catalyst, (PPh3)3RhCl,10 in dichloromethane resulted
in oxidative addition at the Si-H bond to give the 18-electron
complex (NSiN)Rh(H)Cl(PPh3) (2; Scheme 1). Complex 2 was
isolated via crystallization from 1/1 dichloromethane/diethyl
ether as a yellow crystalline solid in 82% yield. The 31P{1H}
NMR spectrum of 2 exhibits a doublet at δ 59.1 (1JRhP ) 150
Hz), and the Rh-H stretch appears at 2030 cm-1 in the IR
The 16-electron, cationic complex 3 is surprisingly inert, as
indicated by its stability in the presence of H2, C6H6, or Ph3-
SiH in 1:1 PhF/benzene-d6 solvent at 80 °C over 1 week.
However, complex 3 did react in dichloromethane solvent at
80 °C to quantitatively produce the cationic complex [(NSiN)-
Rh(Cl)(PPh3)][B(C6F5)4] (4) via H/Cl exchange. Complex 4 was
1
spectrum. The H NMR spectrum of 2 in dichloromethane-d2
contains two sets of quinolyl protons and a hydride resonance
2
(a doublet of doublets) at δ -15.9 (1JRhH ) 17 Hz, JPH ) 24
Hz). These NMR results suggest an octahedral geometry of 2
with C1 symmetry. As with the analogous (NSiN)Ir(H)Cl(PPh3)
(9) Butler, J. L.; Gordon, M. J. Heterocycl. Chem. 1975, 12, 1015.
(10) Wilkinson, G.; Osborn, J. A. Inorg. Synth. 1990, 28, 77.
(11) Massey, A. G.; Park, A. J. J. Organomet. Chem. 1964, 2, 245.
(12) Corey, J. Y.; Braddock-Wilking, J. Chem. ReV. 1999, 99, 175.

Rh Complexes with a Bis(8-quinolyl)methylsilyl Ligand
Organometallics, Vol. 25, No. 7, 2006 1609
Scheme 2
Complex 6 reacts with Me3SiOTf in benzene to give [(NSiN)-
Rh(η3-CH2Ph)(PPh3)]OTf (7), as an orange microcrystalline
precipitate in 58% yield. Once isolated, complex 7 is sparingly
soluble in benzene and only partially dissolves in THF. In THF-
d8, the 1H NMR spectrum of 7 contains a broad singlet peak at
δ 5.63, which can be assigned to the benzyl group. A 2D 13C-
1H HMQC NMR experiment correlated these benzyl CH2
protons to a 13C{1H} NMR resonance at δ 108.6 (br m). Both
1H and 13C{1H} NMR peaks are consistent with a structure
containing an η3-benzyl group.14 In addition, complex 7
underwent an anionic exchange with PPNCl in benzene,
resulting in an analytically pure sample of 6 (Scheme 2). The
process by which 2 is alkylated to form 6 is clearly unusual
and is not fully understood. In addition, successful alkylation
of 2 is limited to PhCH2MgCl. Intractable products were
obtained from reactions between 2 and other alkylating reagents
such as MeLi and PhMgCl, under the same conditions.
Hopefully, further investigations of this system will reveal
mechanistic information concerning the formation of 6.
isolated in 92% yield via vapor diffusion of diethyl ether into
a dichloromethane solution of 4.
In an attempt to render the rhodium center of 3 more reactive,
the synthesis of [(NSiN)Rh(H)(PMe3)][B(C6F5)4], which should
be more electron rich and less sterically crowded, was targeted.
Treatment of bis(8-quinolyl)methylsilane (1) with (COD)Rh-
(PMe3)Cl13 gave the complex (NSiN)Rh(H)Cl(PMe3) (5) in 59%
yield. Complex 5 was isolated from concentrated THF solution
as a yellow powder. The Rh-H resonance of 5 appears in the
1H NMR spectrum (dichloromethane-d2) as a doublet of doublets
at δ -16.6 (1JRhH ) 22 Hz, 2JPH ) 29 Hz). In the IR spectrum,
Another possible synthetic route to (NSiN)Rh(PPh3) involves
dehydrochlorination of 2 with a base. Refluxing 2 in the
presence of 1 equiv of DBU in dichloromethane resulted in an
1
elimination of HCl, as the H NMR spectrum of the crude
reaction mixture indicated the formation of DBU‚HCl. However,
the rhodium-containing product, crystallized from a mixture of
dichloromethane and diethyl ether in 68% yield, was character-
ized as (NSiN)RhCl2(PPh3) (8), the presumed product of
dichloromethane activation (eq 2). The 1H NMR spectrum of 8
the Rh-H group gives rise to a band at 2045 cm-1
.
Chloride abstraction from 5 using LiB(C6F5)4‚2.5Et2O in
dichloromethane-d2 resulted in a mixture of products. Interest-
1
ingly, the H NMR spectum of the reaction mixture did not
contain a hydride resonance that could be assigned to a Rh-H
species. On the basis of results described below, it seems
possible that, upon chloride abstraction, PMe3 dissociates and
acts as a dehydrohalogenation reagent, to remove the rhodium
hydride ligand (vide infra).
Alkyl hydride complexes of the type (NSiN)RhH(R)(PPh3)
were targeted, as such complexes were expected to exhibit a
rich reaction chemistry. These compounds could potentially
eliminate RH to generate the unsaturated species (NSiN)Rh-
(PPh3) and should provide information regarding the stability
of C-H activation products derived from (NSiN)Rh(PPh3). The
addition of 1 equiv of PhCH2MgCl to 2 in benzene resulted in
partial conversion to a new product. To obtain complete
conversion, 2 equiv of PhCH2MgCl was required, and this gave
the neutral complex (NSiN)Rh(CH2Ph)(Cl)(PPh3) (6). The
contains two sets of quinolyl protons, suggesting C1 symmetry.
This chlorination of 2 does not occur in nonhalogenated solvents
under comparable conditions. For example, no reaction was
observed when 2 and 1 equiv of DBU was refluxed in benzene
or THF, over 2 days. This result supports the involvement of
dichloromethane as a reagent in the reaction of eq 2. The
crystallographically determined structure of 8 is shown in Figure
2. As expected, the Rh-Cl bond trans to the silyl group (2.640-
(2) Å) is significantly longer than the bond trans to the quinolyl
N atom (2.356(2) Å).
1
reaction is quantitative by H NMR spectroscopy (using Si-
(SiMe3)4 as standard) and produces 1 equiv of toluene and 1
equiv of 6 (Scheme 2). The 1H NMR spectrum of 6 in benzene-
d6 exhibits two apparent triplets at δ 2.20 and 1.77, assigned as
diastereotopic hydrogens of the benzyl group. On a preparative
scale, 6 was obtained as a somewhat impure, crystalline material
in approximately 50% yield. From this reaction, an analytically
pure sample of 6 could not be obtained, as recrystallizations
invariably yielded product that was contaminated by small
amounts of MgCl2. In one particular sample, 0.89% of Mg was
present according to Mg analysis. However, FAB-MS allowed
observation of a m/z+ peak at 755.3, which corresponds to the
(NSiN)Rh(CH2Ph)(PPh3)+ fragment. Further confirmation of the
identity of 6 comes from the reaction chemistry described below.
In addition to DBU/CH2Cl2, PMe3/CH2Cl2 acts as a chlorinat-
ing reagent for complex 2. Reaction of 2 with an excess of PMe3
(3 equiv) in dichloromethane at room temperature afforded the
dichloromethane-activated Rh(III) product [(NSiN)Rh(PMe3)2-
(14) (a) Fryzuk, M. D.; McConville, D. H.; Rettig, S. J. J. Organomet.
Chem. 1993, 445, 245. (b) Gatti, G.; Lopez, J. A.; Mealli, C.; Musco, A. J.
Organomet. Chem. 1994, 483, 77. (c) Crascall, L. E.; Spencer, J. L. J. Chem.
Soc., Dalton Trans. 1992, 24, 3445.
(13) Andersen, R. A.; Kulzick, M. A.; Price, R. T.; Muetterties, E. L. J.
Organomet. Chem. 1987, 333, 105.

1610 Organometallics, Vol. 25, No. 7, 2006
Sangtrirutnugul et al.
Scheme 3
1
The H NMR spectrum (dichloromethane-d2) of the crude
reaction mixture reveals the presence of HCl‚NEt3 as a side
product. Complex 10 exhibits poor solubility in most organic
1
solvents, including dichloromethane and chloroform. The H
NMR spectrum of 10 in DMSO-d6 contains one set of quinolyl
protons, suggesting that, in solution, complex 10 possesses
mirror symmetry. Drawing a comparison with related species
containing the Tp′ (HB(3,5-Me2pz)3) and Cp* ligands, [Tp′RhCl2]2
and [Cp*RhCl2]2,16,17 it is reasonable to assume that 6 also exists
as a dimer.
Figure 2. ORTEP diagram of complex 8 with thermal ellipsoids
shown at the 50% probability level. Hydrogen atoms, one of the
phenyl rings, and the dichloromethane molecule are omitted for
clarity.
Treatment of complex 10 with 2 equiv of AgOTf in
dichloromethane afforded an off-white, insoluble precipitate
believed to be the bis(triflate) complex (NSiN)Rh(OTf)2.
Subsequent addition of acetonitrile to this precipitate resulted
in formation of the dicationic complex [(NSiN)Rh(CH3CN)3]-
[OTf]2 (11) in 68% isolated yield (Scheme 3). X-ray crystal-
lographic analysis of 11 revealed a distorted-octahedral geom-
etry, in which the Rh-NCCH3 bond distance trans to the silyl
group is approximately 0.3 Å longer than those associated with
the cis-acetonitrile ligands (2.035(6), 2.011(6) Å) (Figure 3).
The 1H NMR spectrum of 11 in acetonitrile-d3 indicates the
presence of only two molecules of bound acetonitrile, as a singlet
at δ 1.97. The absence of a 1H resonance corresponding to the
acetonitrile ligand trans to the strongly trans-labilizing silyl
group suggests a rapid exchange between this acetonitrile ligand
and the acetonitrile-d3 solvent. When complex 11 was dissolved
in dichloromethane-d2, the acetonitrile group trans to the silyl
Cl][Cl] (9), which was crystallized from dichloromethane in
54% yield (eq 3). The H NMR resonances corresponding to
1
1
group appeared as free acetonitrile in the H NMR spectrum.
The IR spectrum of 11 (KBr pellet) contains two medium-
intensity bands at 2304 and 2332 cm-1, which can be assigned
to the nitrile ligands.
It is of interest to compare the reactivity of the dicationic
complex 11 with that of well-known, related species such as
[Cp*Rh(CH3CN)3][X]2 (X ) PF6, BF4).17 For the Cp*Rh
complexes, partial or complete displacement of the coordinated
acetonitrile ligands can be readily achieved with soft donor
ligands (e.g., arene and alkene), thus making [Cp*Rh(CH3CN)3]-
[X]2 convenient precursors to a range of complexes containing
the Cp*RhIII fragment.18 In contrast, no reaction was observed
two PMe3 groups appear at δ 1.26, and a single set of quinolyl
resonances in the 1H NMR spectrum indicates Cs symmetry for
the molecule.
Synthesis and Reactivity of 16-Electron (NSiN)RhX2
Complexes. For previously described complexes, the NSiN
ligand was introduced via Si-H oxidative addition to a low-
valent Rh(I) center. To develop synthetic routes employing more
readily available starting materials, the reaction of RhCl3(CH3-
15
CN)3 with 1 was examined, in the presence of NEt3 as a
(16) Powell, J.; Reinsalu, P.; May, S. Inorg. Chem. 1980, 19, 1582.
(17) Maitlis, P. M.; Yates, A.; White, C. Inorg. Synth. 1992, 29, 228.
(18) (a) Raithby, P. R.; Clegg, W.; Feeder, N.; Castro, A. M. M.; Nahar,
S.; Shields, G. P.; Teat, S. J. J. Organomet. Chem. 1999, 573, 237. (b)
Sheldrick, W. S.; Herebian, D. A.; Schmidt, C. S.; van Wullen, C. Eur. J.
Inorg. Chem. 1998, 1991.
scavenger of HCl. In dichloromethane, this reaction gave a
yellow precipitate with the empirical formula (NSiN)RhCl2 (10)
(Scheme 3).
(15) Catsikis, B.; Good, M. L. J. Inorg. Nucl. Chem. 1968, 4, 529.

Rh Complexes with a Bis(8-quinolyl)methylsilyl Ligand
Organometallics, Vol. 25, No. 7, 2006 1611
Figure 4. ORTEP diagram of complex 12 with thermal ellipsoids
shown at the 50% probability level. Hydrogen atoms are omitted
for clarity.
Figure 3. ORTEP diagram of the dicationic complex 11 with
thermal ellipsoids shown at the 50% probability level. Hydrogen
atoms and two OTf counterions are omitted for clarity.
A related type of 16-electron complex, which is expected to
exhibit a rich reaction chemistry and possibly serve as a
precursor to (NSiN)RhH2, is a dialkylrhodium(III) complex
supported by the NSiN ligand. Thus, it was found that the
reaction of 10 with 2 equiv of PhCH2MgCl in benzene generated
the 16-electron, neutral complex (NSiN)Rh(CH2Ph)2 (12). The
1H NMR spectrum of 12 in THF-d8 exhibits one set of quinolyl
protons, indicative of Cs symmetry. The diastereotopic protons
of the methylene groups of the benzyl rings are observed as
two distinct doublet of doublets at δ 2.47 (2JHH ) 9.0 Hz, 2JRhH
) 3.0 Hz) and 2.11 (2JHH ) 9.0 Hz, 2JRhH ) 1.0 Hz). The Rh-
CH2 resonance in the 13C{1H} NMR spectrum appears as a
doublet at δ 23.30 (1JRhC ) 12.5 Hz).
Complex 12 crystallized from a 3/2 mixture of THF and
diethyl ether as yellow crystals, and the X-ray structure reveals
a square-pyramidal geometry about the Rh center with a THF
molecule located near the Rh atom and trans to the silyl group
(Figure 4). However, the Rh-O distance of 4.384(4) Å is too
long to represent a bonding interaction. The Rh-C bond
distances (2.093(4) and 2.079(4) Å) fall within the expected
range for such Rh-C(benzyl) bonds.20
The possibility that the coordinatively unsaturated, 16-electron
dibenzyl complex 12 might participate in bond activations with
small molecules led us to examine the reactivity of 12 with H2,
benzene-d6, and Et3SiH. However, at 80 °C, no reaction of 12
with either H2 or Et3SiH was observed in benzene-d6 after 3
days. Complex 12 began to decompose at 120 °C in benzene-
d6, to give a black precipitate and toluene as products. Attempts
to generate an 18-electron complex by treating 12 with two-
electron donors, such as PPh3 and CO, were also unsuccessful.
We attribute this unusual stability of the 16-electron complex
when 11 was treated with a variety of soft donors, including
ethylene, (trimethylsilyl)acetylene, and benzophenone, even at
80 °C in dichloromethane-d2. One possible explanation for this
inactivity is that the harder ligand of the (NSiN)Rh fragment
gives rise to a hard Rh center. Thus, complex 11 exhibits a
higher affinity for hard ligands such as acetonitrile, and
displacement of this ligand by softer ligands is more difficult
than for [Cp*Rh(CH3CN)3][X]2 (X ) PF6, BF4).
Previous studies have shown that dicationic complexes of the
type [Cp*Rh(CH3CN)3][BF4]2 act as a catalyst for alkene and
arene hydrogenation.19 Similarly, catalytic studies reveal that
the dicationic (NSiN)Rh complex 11 is moderately active as a
catalyst for alkene hydrogenations. When 5 mol % of complex
11 was combined with either cyclooctene or 1-hexene under
1-2 atm of H2, a quantitative yield of the hydrogenated product
1
was obtained after 1 day at 70 °C, as monitored by H NMR
spectroscopy. In addition, 5 mol % of complex 11 catalyzed
H/Cl exchange between Ph3SiH and dichloromethane solvent
at 70 °C, resulting in the quantitative production of Ph3SiCl
and CH3Cl after 1 day.
The 16-electron complex (NSiN)RhH2 is of significant interest
as a potential catalyst. Notably, a related Rh(III) species
containing the 2,6-(tBu2PCH2)2C6H3 (PCP) pincer ligand, (PCP)-
RhH2, is an active catalyst for the water-gas shift reaction and
for alkane dehydrogenation.1 However, attempts to synthesize
(NSiN)RhH2 have so far been unsuccessful. Reactions of 10
with 2 equiv of LiBEt3H in THF, with or without an atmosphere
of H2, under various reaction conditions, gave mixtures of
products. The use of other hydride donors, such as KH and
LiBH4, also resulted in intractable mixtures.
(20) (a) Dorta, R.; Shimon, L. J. W.; Rozenberg, H.; Milstein, D. Eur.
J. Inorg. Chem. 2002, 1827. (b) Mason, R.; Towl, A. D. C. J. Chem. Soc.
A 1970, 1601. (c) Chan, K. T. K.; Spencer, L. P.; Masuda, J. D.; McCahill,
J. S. J.; Wei, P.; Stephan, D. W. Organometallics 2004, 23, 381. (d) Mak,
K. W.; Xue, F.; Mak, T. C. W.; Chan, K. S. J. Chem. Soc., Dalton Trans.
1999, 3333.
(19) (a) Fish, R. H.; Baralt, E.; Smith, S. J. Organometallics 1991, 10,
54. (b) Baralt, E.; Smith, S. J.; Hurwitz, J.; Horvath, I. T.; Fish, R. H. J.
Am. Chem. Soc. 1992, 114, 5187.

1612 Organometallics, Vol. 25, No. 7, 2006
Sangtrirutnugul et al.
Scheme 4
protons and broad singlets at δ 5.25 and δ 3.32 (for bound
COD), indicating mirror symmetry for the molecule. The 13C-
{1H} NMR spectrum reveals two olefinic carbon resonances at
δ 106.3 and 46.1, both of which couple to 103Rh with J values
of 3.8 and 17 Hz, respectively. These coupling constants suggest
that, in solution, both olefinic groups of the COD ligand are
bound to the Rh center, resulting in a five-coordinate Rh(I)
complex.
Examples of 18-electron, five-coordinate Rh(I) complexes
have been characterized both in solution21 and in the solid state.22
The crystal structures of these compounds reveal a trigonal-
bipyramidal geometry at the Rh center. In observed chemistry
based on TpRh(LL) complexes, both 16- and 18-electron
complexes are known. In the solid state, (κ2-Tp)Rh(NBD) (NBD
) norbornadiene) and (κ2-Tp)Rh(COD) exist as 16-electron
complexes, while (κ3-Tp)Rh(DQ) (DQ ) duroquinone) is
assigned as an 18-electron, 5-coordinate species.22a In addition,
recent studies have shown that complexes of the type TpMeRh-
(LL) (LL ) 2CO, NBD, COD) display κ2-κ3 isomerism of the
TpMe ligand in solution.23 Therefore, to investigate any κ2-κ3
12 to the strong trans-labilizing silyl group of the NSiN ligand.
One of the benzyl groups in 12 was abstracted by 1 equiv of
[Ph3C][PF6] in acetonitrile to afford the 16-electron, cationic
Rh(III) complex [(NSiN)Rh(CH2Ph)(CH3CN)][PF6] (13) in 69%
yield (eq 4). The 1H NMR spectrum (dichloromethane-d2)
1
isomerism for the NSiN ligand in 14, variable-temperature H
NMR experiments of a toluene-d8 solution of 14 were per-
formed. These studies revealed no decoalescence of the 1H NMR
resonances at temperatures as low as -80 °C.
Complex 14 is thermally unstable in solution and decomposes
within a few hours at 70 °C in benzene-d6. It reacts immediately
with H2 (1 atm) in benzene-d6 to produce cyclooctene and a
black precipitate. Neither (NSiN)RhH2 nor (NSiN)RhH2(COE)
was observed by NMR spectroscopy. However, the reaction with
Ph3SiH (1 equiv, benzene-d6, room temperature) immediately
resulted in the clean formation of (NSiN)Rh(H)(SiPh3) (15), as
indicated by a hydride resonance at δ 13.2 (d, 1JRhH ) 28 Hz),
with the elimination of COD. On the basis of 1H NMR
spectroscopy, complex 15 is unstable in benzene solution and
reacted further with COD to yield the olefin-insertion product
(NSiN)Rh(η1-C8H13)(SiPh3) (16) (Scheme 4).
An analogous olefin-insertion product was also obtained from
reaction of 14 with HSi(OSiMe3)3 in benzene, which gave the
neutral Rh(III) complex (NSiN)Rh(η1-C8H13)[Si(OSiMe3)3] (17)
(Scheme 4). However, the olefin insertion step is more rapid
and the rhodium hydride intermediate (NSiN)Rh(H)[Si(O-
SiMe3)3] could not be observed during the course of the reaction.
To investigate the potential hydrosilylation catalytic activity of
14, 10 mol % of 14 was combined with Ph3SiH and COD in
benzene and the mixture heated to 50 °C. After 18 h, several
isomers of the hydrosilylation product C8H13SiPh3 were ob-
served (>90% yield) by GC/MS.
contains two diastereotopic protons for the benzyl group as two
doublets of doublets at δ 3.02 (2JHH′ ) 8.5 Hz, 2JRhH ) 2.5 Hz)
and 2.15 (2JH′H ) 8.5 Hz, 2JRhH′ ) 1.5 Hz). Similar to complex
11, the acetonitrile ligand trans to the quinolyl N atom binds
strongly to the Rh(III) center (vide supra). Treatment of 13 with
1-2 atm of ethylene, diphenylacetylene, or benzophenone in
benzene-d6 did not result in displacement of acetonitrile at 80
°C after 2 days.
The reaction chemistry of 13 was briefly explored. At room
temperature, a benzene-d6 solution of 13 and 1 equiv of Ph3-
SiH yielded no reaction. When the reaction mixture was heated
to 50 °C for 12 h, the 1H NMR spectrum indicated the formation
of toluene and a complex mixture of products. Similar results
were observed for the interactions of 13 with 1-pentyne,
phenylacetylene, and hydrogen (1 atm). In each case, no reaction
was observed at room temperature in benzene-d6, and heating
the reaction mixture to 60 °C resulted in formation of a black
precipitate. Heating a benzene-d6 solution of 13 to 80 °C, with
or without NEt3, resulted in formation of toluene-d after 1 day,
In an attempt to generate more thermally stable Rh(I)
complexes, phosphine derivatives of the type (NSiN)Rh(PR3)n
were targeted. Treatment of 14 with 1 equiv of 1,2-bis-
(diphenylphosphino)ethane (dppe) gave the corresponding Rh-
(I) complex (NSiN)Rh(dppe) (18) in a quantitative yield on the
1
basis of H NMR spectroscopy. The 31P{1H} NMR spectrum
of 18 contains two doublet of doublets at δ 70.6 (1JRhP ) 190
1
according to H NMR spectroscopy. This result indicates that
2
2
Hz, JPP′ ) 15 Hz) and δ 43.3 (1JRhP′ ) 125 Hz, JP′P ) 15
an activation of benzene-d6 occurred; however, other products
from this reaction were not identifiable by NMR spectroscopy.
Neutral (NSiN)RhI Complexes. The investigations described
above suggest that (NSiN)RhI complexes do not form readily
and may be reactive in nature. Therefore, an additional attempt
was made to synthesize an isolable (NSiN)RhI complex, directly
from a Rh(I) reagent. Reaction of (COD)Rh(η3-CH2Ph)17 with
1 equiv of 1 quantitatively produced toluene and (NSiN)Rh-
(21) Cocivera, M.; Ferguson, G.; Lalor, F. J.; Szczecinski, P. Organo-
metallics 1982, 1, 1139.
(22) (a) Cocivera, M.; Ferguson, G.; Kaitner, B.; Lalor, F. J.; O’Sullivan,
D. J.; Parvez, M.; Ruhl, B. Organometallics 1982, 1, 1132. (b) Ryan, R.
R.; Schaeffer, R.; Clark, P.; Hartwell, G. Inorg. Chem. 1975, 14, 3039. (c)
de Bruin, B.; Smits, J. M. M.; Hetterscheid, D. G. H. Organometallics 2004,
23, 4236.
(23) (a) Bucher, U. E.; Currao, A.; Nesper, R.; Ruegger, H.; Venanzi,
L. M.; Younger, E. Inorg. Chem. 1995, 34, 66. (b) Ball, R. G.; Ghosh, C.
K.; Hoyano, J. K.; McMaster, A. D.; Graham, W. A. G. J. Chem. Soc.,
Chem. Commun. 1989, 341.
1
(COD) (14) as a dark brown solid (Scheme 4). The H NMR
spectrum of 14 in benzene-d6 contains one set of quinolyl

Rh Complexes with a Bis(8-quinolyl)methylsilyl Ligand
Organometallics, Vol. 25, No. 7, 2006 1613
(Cambridge Isotopes) were dried with appropriate drying agents
and vacuum transferred prior to use. The reagents 8-bromoquino-
line,9 (PPh3)3RhCl,10 (COD)RhCl(PMe3),13 (COD)Rh(η3-CH2Ph),14a
RhCl3(CH3CN)3,15 Mg(CH2Ph)2(THF)2,24 and LiB(C6F5)4‚2.5Et2O11
were prepared according to literature procedures. Me(H)SiCl2
(Gelest) was distilled under N2 and degassed before use. All other
chemicals were purchased from Aldrich or Gelest and used without
further purification. Ethylene (Air Gas) and dihydrogen (Praxair)
were used as received. The NMR spectra were recorded at 500
MHz (1H), 202 MHz (31P{1H}), 125 MHz (13C{1H}), 376.5 MHz
(19F), or 99 MHz (29Si{1H}) on Bruker DRX-500 and AVQ-400
spectrometers at ambient temperature, with chemical shifts reported
in ppm downfield of tetramethylsilane (1H, 13C, and 29Si), CFCl3
(19F), and 85% H3PO4 (31P). Elemental analyses were performed
by the Micro-Mass Facility in the College of Chemistry at the
University of California, Berkeley. Infrared spectra were recorded
as KBr pellets on a Mattson FTIR 3000 instrument.
Hz). These results indicate that both phosphine groups bind to
the Rh center, as evidenced by the large Rh-P coupling
constants, and are consistent with a trigonal-bipyramidal or a
distorted-square-pyramidal structure. Complex 18 was thermally
stable in benzene-d6 solution and inactive toward Ph3SiH and
H2, even at 80 °C over 3 days.
Conclusions
This paper describes synthetic pathways to various rhodium
complexes containing a tridentate NSiN ligand and initial
reactivity studies for (NSiN)Rh compounds. Reliable methods
for introduction of the NSiN ligand are based on oxidative
addition of the Si-H bond of bis(8-quinolyl)methylsilane, as
employed in the synthesis of (NSiN)Rh(H)(Cl)(PPh3) (2) from
the silane and (PPh3)3RhCl. A related process, involving reaction
of RhCl3(CH3CN)3 with the silane 1 in the presence of NEt3,
provided the useful starting material [(NSiN)RhCl2]2 (10). The
reactivity studies completed thus far indicate that the (NSiN)-
RhIII fragment is rather chemically robust.
Investigations with the (NSiN)RhIII fragment have produced
several coordinatively unsaturated 16-electron complexes, in-
cluding [(NSiN)RhH(PPh3)][B(C6F5)4] (3) and (NSiN)Rh(CH2-
Ph)2 (12). Despite their coordinative unsaturation, these com-
plexes are thermally stable and chemically inert. This stability
may result, in part, from the strong trans effect of Si, which
prevents the binding of molecular substrates trans to the silyl
group.
Similarities between the NSiN ligand and the more well-
known Cp* and Tp ligands are reflected in the formation of
complexes such as [(NSiN)RhCl2]2 (10) and [(NSiN)Rh-
(MeCN)3][OTf]2 (11). However, the chemical behaviors of the
(NSiN)Rh complexes are quite distinct from those of their
Cp*Rh and TpRh counterparts. For example, although [Cp*Rh-
(MeCN)3][OTf]2 possesses highly labile acetonitrile ligands, the
analogous [(NSiN)Rh(MeCN)3][OTf]2 (11) is inert toward
substitution of its acetonitrile ligands by soft donors such as
arenes and alkenes. Nonetheless, like its Cp*Rh analogue,
complex 11 exhibits moderate activity as a catalyst for alkene
hydrogenation. Interestingly, 11 catalyzes H/Cl exchange be-
tween Ph3SiH and CD2Cl2, to quantitatively give Ph3SiCl and
CD2HCl.
Reactive Rh(I) complexes bearing the NSiN ligand were
obtained via the (COD)Rh(η3-CH2Ph) starting material, to
initially give (NSiN)Rh(COD) (14), which is thermally unstable
in solution at 70 °C. In general, the isolation and characterization
of additional (NSiN)RhI complexes has proven difficult, due to
their lack of thermal stability. A notable aspect of this chemistry
concerns the predominance of 5-coordinate Rh(I) complexes,
which is apparently enforced by the tripodal nature of the NSiN
ligand. The Rh(I) complex 14 activates the Si-H group of Ph3-
SiH to give the Rh(III) intermediate (NSiN)Rh(H)(SiPh3) (15),
which then undergoes COD insertion to produce (NSiN)Rh-
(η1-C8H13)(SiPh3) (16). This chemistry is undoubtedly related
to the behavior of 14 as a hydrosilylation catalyst.
Qn2SiHMe (1). This synthesis represents an improvement over
that previously described in the literature. n-Butyllithium (1.6 M
in hexane, 13.5 mL, 21.6 mmol) was added dropwise to a
magnetically stirred solution of 8-bromoquinoline (4.32 g, 20.8
mmol) in 70 mL of THF at -78 °C over 5 min, and stirring was
continued for an additional 5 min at this temperature. Me(H)SiCl2
(1.13 mL, 10.8 mmol) was then slowly added dropwise, causing a
color change from light brown to yellow. The resulting mixture
was stirred at room temperature for 12 h. After removal of the
solvent and other volatile materials in vacuo, the yellow residue
was redissolved in toluene (120 mL) and cannula-filtered. The
remaining off-white solid was washed with 2 × 15 mL of toluene.
The extracts were combined and concentrated to 50 mL, at which
point an off-white solid (LiCl) started to form. The toluene solution
was filtered again, and the filtrate was concentrated to approximately
30 mL and stored under N2 at -30 °C for 48 h. Compound 1 was
obtained as pale yellow crystals in 48% yield (1.50 g, 4.99 mmol).
1H NMR (C6D6, 500 MHz): δ 8.64 (d, JHH ) 4.1 Hz, of d, JHH
)
1.8 Hz, 2 H, Ar H), 7.99 (d, JHH ) 6.7 Hz, of d, JHH ) 1.5 Hz, 2
H, Ar H), 7.47 (d, JHH ) 8.2 Hz, of d, JHH ) 1.8 Hz, 2 H, Ar H),
7.39 (d, JHH ) 8.2 Hz, of d, JHH ) 1.5 Hz, 2 H, Ar H), 7.13 (d,
JHH ) 8.2 Hz, of d, JHH ) 6.7 Hz, 2 H, Ar H), 6.67 (d, JHH ) 8.2
Hz, of d, JHH ) 4.1 Hz, 2 H, Ar H), 6.34 (q, JHH ) 3.8 Hz, 1 H,
SiH), 1.32 (d, JHH ) 3.8 Hz, 3 H, SiCH3). 13C{1H} NMR (C6D6,
125 MHz): δ 153.3, 149.5, 139.1, 138.6, 135.9, 129.5, 127.9, 126.4,
120.8 (aryl carbons), -2.7 (SiCH3). 29Si{1H} NMR (C6D6, 99
MHz): δ -18.9. Anal. Calcd for C19H16N2Si: C, 75.96; H, 5.37;
N, 9.32. Found: C, 75.63; H, 5.50; N, 9.24. IR (cm-1): νSiH 2131
s.
(NSiN)Rh(H)(Cl)(PPh3) (2). To a stirred solution of 1 (0.0650
g, 0.216 mmol) in 10 mL of CH2Cl2 was added a solution of Rh-
(PPh3)3Cl (0.200 g, 0.216 mmol) in 10 mL of CH2Cl2 at room
temperature. After 18 h of stirring, the solvent was removed in
vacuo. The yellow residue was washed with pentane (2 × 10 mL),
and then it was taken up in 15 mL of CH2Cl2; this solution was
filtered through Celite and concentrated to a volume of 7 mL. Vapor
diffusion of diethyl ether into this solution at room temperature
for 48 h produced 2 as yellow crystals in 82% yield (0.135 g, 0.177
1
mmol). H NMR (CD2Cl2, 500 MHz): δ 10.79 (m, 1 H, Ar H),
10.00 (m, 1 H, Ar H), 8.10 (d, JHH ) 8.0 Hz, 1 H, Ar H), 8.00 (d,
JHH ) 6.4 Hz, 1 H, Ar H), 7.83 (d, JHH ) 19 Hz, of d, JHH ) 6.6
Hz, 2 H, Ar H), 7.68 (d, JHH ) 7.2 Hz, 1 H, Ar H), 7.54-7.51 (m,
8 H, Ar H), 7.40 (m, 2 H, Ar H), 7.13-7.05 (m, 10 H, Ar H),
0.419 (s, 3 H, SiCH3), -15.9 (d, JRhH ) 24 Hz, of d, JPH ) 17 Hz,
1 H, RhH). 13C{1H} NMR (CD2Cl2, 125 MHz): δ 155.4, 154.3,
153.3, 152.7, 148.3, 147.8, 137.9, 137.3, 135.1, 134.8, 134.6, 134.5,
133.8 (d, J ) 11.2 Hz), 129.4 (d, J ) 2.5 Hz), 129.1, 128.9, 128.5
(d, J ) 17.5 Hz), 127.7 (d, J ) 10.0 Hz), 127.5, 127.0, 122.2 (d,
J ) 3.8 Hz), 121.8 (aryl carbons), -2.48 (d, J ) 1.0 Hz, SiCH3).
Future investigations will focus on stoichiometric and catalytic
transformations of substrates containing hard donor atoms (e.g.,
O and N) at (NSiN)RhIII centers.
Experimental Section
General Procedures. All manipulations were conducted under
an N2 atmosphere using standard Schlenk or glovebox techniques.
In general, solvents were distilled under N2 from appropriate drying
agents and stored in PTFE-valved flasks. Deuterated solvents
(24) Schrock, R. R. J. Organomet. Chem. 1976, 122, 209.

1614 Organometallics, Vol. 25, No. 7, 2006
Sangtrirutnugul et al.
29Si{1H} NMR (CD2Cl2, 99 MHz): δ 40.3 (m). 31P{1H} NMR
(CD2Cl2, 162 MHz): δ 59.1 (d, JRhP ) 150 Hz). Anal. Calcd for
C37H31N2SiPClRh: C, 63.39; H, 4.46; N, 4.00. Found: C, 63.02;
H, 4.43; N, 3.78. IR (cm-1): ν 2030 (m, Rh-H).
(d JHH ) 8.0 Hz, of d JHH ) 1.0 Hz, 1 H, Ar H), 7.65 (d JHH ) 8.0
Hz, of d JHH ) 1.0 Hz, 1 H, Ar H), 7.54-7.49 (m, 2 H, Ar H),
7.40 (d JHH ) 8.2 Hz, of d JHH ) 4.8 Hz, 1 H, Ar H), 7.36 (m, 1
H, Ar H), 1.21 (d JPH ) 10 Hz, of d JRhH ) 1.5 Hz, 9 H, Ar H),
1.18 (s, 3 H, SiCH3), -16.6 (d JRhH ) 29 Hz, of d JPH ) 22 Hz,
1 H, RhH). 13C{1H} NMR (CD2Cl2, 125 MHz): δ 155.0, 154.2,
153.4, 153.2, 148.4, 147.9, 137.9, 137.6, 135.1, 134.9, 129.2, 129.0,
128.7, 128.5, 127.4, 127.3, 122.1, 122.0 (d, J ) 3.8 Hz) (aryl
carbons), 20.1 (d 1JPC ) 35 Hz, of d 2JRhC ) 2.5 Hz, PCH3), -1.58
[(NSiN)Rh(H)(PPh3)][B(C6F5)4] (3). A solution of 2 (0.150 g,
0.214 mmol) in 10 mL of CH2Cl2 was added dropwise to a stirred
solution of Li(OEt2)2.5B(C6F5)4 (0.185 g, 0.212 mmol) in 10 mL
of CH2Cl2 at room temperature. The stirring was continued for 1 h
before all volatiles were removed under vacuum. The remaining
yellow solid was redissolved in diethyl ether and filtered through
Celite. Vapor diffusion of pentane into the concentrated diethyl
ether solution gave pale yellow crystals in 96% yield (0.305 g, 0.204
(d, 2JRhC ) 3.9 Hz, SiCH3). 29Si{1H} NMR (CD2Cl2, 99 MHz): δ
1
38.6 (m). 31P{1H} NMR (CD2Cl2, 162 MHz): δ 6.80 (d, JRhP
)
138 Hz). Anal. Calcd for C22H25N2SiPClRh: C, 51.32; H, 4.89; N,
5.44. Found: C, 51.58; H, 4.96; N, 5.52. IR (cm-1): ν 1986 (m,
Rh-H).
1
mmol). H NMR (CD2Cl2, 500 MHz): δ 9.21 (m, 1 H, Ar H),
8.73 (d, JHH ) 5.0 Hz, 1 H, Ar H), 8.39 (d, JHH ) 8.0 Hz, of d,
JHH ) 1.0 Hz 1 H, Ar H), 8.12 (d, JHH ) 11.0 Hz, of d, JHH ) 1.0
Hz, 1 H, Ar H), 8.05 (d, JHH ) 8.2 Hz of, d, JHH ) 1.2 Hz, 1 H,
Ar H), 7.93 (d, JHH ) 6.0 Hz, of d, JHH ) 1.5 Hz, 1 H, Ar H), 7.90
(NSiN)Rh(CH2Ph)Cl(PPh3) (6). (1) To a stirred slurry of 2
(0.155 g, 0.221 mmol) in 10 mL of benzene was added a 1.0 M
diethyl ether solution of PhCH2MgCl (0.24 mL, 0.240 mmol). The
reaction mixture was stirred at room temperature for 20 min, after
which it became homogeneous and dark red. The resulting solution
was filtered through Celite, and the benzene solvent was slowly
removed under vacuum. When the solvent volume reached ap-
proximately 3 mL, a yellow microcrystalline solid was obtained.
The solid was washed with 2 × 3 mL of cold toluene to afford the
crude product in 48% yield (0.087 g, 0.106 mmol).
(d, JHH ) 7.5 Hz, 1 H, Ar H), 7.69 (m, 2 H, Ar H), 7.57 (d, JHH
)
8.0 Hz, of d JHH ) 5.0 Hz, 1 H, Ar H), 7.52 (d, JHH ) 7.5 Hz, of
d JHH ) 6.5 Hz 1 H, Ar H), 7.40-7.36 (m, 9 H, Ar H), 7.28-7.22
(m, 7 H, Ar H), 3.46 (q, JHH ) 7.0 Hz, 8 H, OCH2CH3), 1.18 (t,
JHH ) 7.0 Hz, 12 H, OCH2CH3), 0.88 (s, 3 H, SiCH3), -13.5 (t,
JRhH ) JPH ) 22 Hz, 1 H, RhH). 13C{1H} NMR (CD2Cl2, 125
MHz): δ 154.4, 150.4, 150.0, 149.7, 148.1 (br d, JCF ) 241 Hz,
B(C6F5)4), 142.9, 142.3, 139.2, 138.7, 138.2 (br d, JCF ) 248 Hz,
B(C6F5)4), 136.2 (br d, JCF ) 239 Hz, B(C6F5)4), 135.8, 135.6, 132.6
(d, JCP ) 11.0 Hz), 131.2 (d, J ) 2.5 Hz), 129.9, 129.7, 129.6,
129.2 (d, JCP ) 81 Hz), 128.9 (d, JCP ) 7.5 Hz), 128.8, 128.3,
127.7, 125-122 (v br, B-C), 122.0 (d, J ) 2.5 Hz), 121.8 (aryl
carbons), 65.9 (s, OCH2CH3), 14.7 (s, OCH2CH3), -2.0 (s, SiCH3).
19F NMR (CD2Cl2, 376.5 MHz): δ -130.8 (t, JFF ) 18.0 Hz, 8 F,
o-F), -161.6 (t, JFF ) 20.0 Hz, 4 F, p-F), -165.9 (br s, 8 F, m-F).
29Si{1H} NMR (CD2Cl2, 99 MHz): δ 52.95 (d, 1JSiRh ) 40 Hz, of
(2) Complex 6 can also be generated by adding 10 mL of benzene
to a solid mixture of 7 (0.075 g, 0.082 mmol) and PPNCl (0.049 g,
0.085 mmol). The reaction slurry was stirred at room temperature
for 8 h, after which it became more homogeneous. The reaction
mixture was filtered through Celite, and the orange filtrate was
concentrated to approximately 2 mL, at which point a yellow solid
started to form. Slow evaporation of benzene further yielded
1
analytically pure 6 in 22% yield (0.014 g, 0.018 mmol). H NMR
(C6D6, 500 MHz): δ 9.74 (d JHH ) 4.5 Hz, of d JHH ) 2.0 Hz, 1
H, Ar H), 9.68 (d JHH ) 4.8 Hz, of d JHH ) 1.8 Hz, 1 H, Ar H),
8.16 (d, JHH ) 7.0 Hz, 1 H, Ar H), 7.78 (d JHH ) 6.2 Hz, of d JHH
) 2.2 Hz, 1 H, Ar H), 7.36 (m, 6 H, Ar H), 7.19 (m, 2 H, Ar H),
7.08 (m, 3 H, Ar H), 6.84 (m, 2 H, Ar H), 6.76 (m, 9 H, Ar H),
6.64 (m, 1 H, Ar H), 6.52 (d JHH ) 8.2 Hz, of d JHH ) 5.2 Hz, 1
2
d JSiP ) 11 Hz). 31P{1H} NMR (CD2Cl2, 162 MHz): δ 50.8 (d,
1JRhP ) 144 Hz). Anal. Calcd for C69H51N2SiPBO2F20Rh: C, 55.51;
H, 3.44; N, 1.88. Found: C, 55.71; H, 3.05; N, 1.96. IR (cm-1):
ν 2022 (w, Rh-H).
[(NSiN)Rh(Cl)(PPh3)][B(C6F5)4] (4). A CD2Cl2 solution of 3
was heated to 50 °C for 48 h. The reaction was quantitative on the
H, Ar H), 6.44 (d JHH ) 8.2 Hz, of d JHH ) 4.8 Hz, 2 H, Ar H),
1
1
2
basis of H NMR spectroscopy. H NMR (CD2Cl2, 400 MHz): δ
10.1 (m, 1 H, Ar H), 9.34 (d, JHH ) 5.0 Hz, 1 H, Ar H), 8.16 (d,
JHH ) 11.6 Hz, of d JHH ) 6.8 Hz, 2 H, Ar H), 8.04 (d, JHH ) 6.4
6.35 (m, 2 H, Ar H), 3.59 (m, 4 H, THF), 2.20 (t, 2JRhH ≈ JHH′
≈
2
2
6.0 Hz, 1 H, RhCHH′), 1.77 (t, JRhH′ ≈ JH′H ≈ 6.0 Hz, 1 H,
RhCH′H), 1.40 (m, 4 H, THF), 1.15 (s, 3 H, SiCH3). 13C{1H} NMR
(C6D6, 125 MHz): δ 150.6, 150.0, 149.7, 145.9, 140.4, 139.9, 137.9
(d, J ) 32.5 Hz), 137.3, 135.3, 135.0, 135.3, 135.0, 134.1, 133.9
(d, J ) 12.5 Hz), 130.3, 129.5, 129.2, 128.9, 128.4, 127.5, 127.2
(d, J ) 8.8 Hz), 127.0, 126.9, 122.0, 120.1, 119.4 (aryl carbons),
33.3 (d, 2JPC ) 36.5 Hz, of d 1JRhC ) 11.3 Hz, RhCH2Ph) 4.41 (s,
Hz, 1 H, Ar H), 7.86 (d, JHH ) 8.0 Hz, 1 H, Ar H), 7.81 (d, JHH
)
8.0 Hz, 1 H, Ar H), 7.65-7.55 (m, 9 H, Ar H), 7.50 (m, 1 H, Ar
H), 7.33 (m, 3 H, Ar H), 7.16 (m, 6 H, Ar H), 6.86 (m, 1 H, Ar H),
0.96 (s, 3 H, SiCH3). 13C{1H} (CD2Cl2, 125 MHz): 153.0, 152.4,
151.4, 151.0, 148.6 (br d, JCF ) 239 Hz), 142.4, 141.9, 140.3, 139.8,
138.7 (br d, JCF ) 251 Hz), 136.9, 136.7 (br d, JCF ) 243 Hz),
136.4, 134.1 (d, J ) 10 Hz), 131.9 (d, J ) 2.5 Hz), 130.6, 130.4,
129.8, 129.7, 129.3, 129.1 (d, JPC ) 10 Hz), 128.8 (d, JPC ) 52.8
Hz), 128.8, 124.9 (v br, B-C), 123.0 (d, J ) 4.5 Hz), 122.8 (aryl
carbons), -1.29 (s, SiCH3). 19F NMR (CD2Cl2, 376.5 MHz): δ
-131.3 (t, JFF ) 23 Hz, 8 F, o-F), -162.1 (t, JFF ) 23 Hz, 4 F,
p-F), -166.3 (br s, 8 F, m-F). 29Si{1H} NMR (CD2Cl2, 99 MHz):
SiCH3). 29Si{1H} NMR (C6D6, 99 MHz): δ 4.0 (d, JRhSi ) 74
1
Hz, of d 2JSiP ) 15 Hz). 31P{1H} NMR (C6D6, 162 MHz): δ 43.4
(d, 1JRhP ) 167 Hz). Anal. Calcd for C44H37N2SiPRhCl: C, 66.42;
H, 4.69; N, 3.52. Found: C, 66.21; H, 4.33; N, 3.48.
[(NSiN)Rh(η3-CH2Ph)(PPh3)][OTf] (7). At ambient tempera-
ture, 1 equiv of neat TMSOTf (0.030 g, 0.135 mmol) was added
to a stirred 15 mL benzene suspension of 6 (0.100 g, 0.122 mmol).
The reaction mixture became homogeneous within 10 min. After
2 h, the dark red mixture was concentrated to 5 mL. An orange
microcrystalline solid precipitated from solution after 24 h. The
supernatant was decanted, and the remaining precipitate was washed
with 2 × 3 mL of benzene. The product 7 was isolated in 58%
1
2
δ 64.6 (d, JSiRh ) 29.5 Hz, of d JSiP ) 10.0 Hz). 31P{1H} NMR
1
(CD2Cl2, 162 MHz): δ 26.4 (d, JRhP ) 126 Hz). Anal. Calcd for
C61H30N2SiPBClF20Rh: C, 53.12; H, 2.19; N, 2.03. Found: C,
53.42; H, 2.54; N, 2.37.
(NSiN)Rh(H)(Cl)(PMe3) (5). A 150 mL Schlenk flask equipped
with a stir bar was charged with 1 (0.600 g, 2.00 mmol) and (COD)-
Rh(PMe3)Cl (0.612 g, 1.90 mmol). To this solid mixture was added
50 mL of C6H6, and the reaction mixture was stirred at room
temperature for 12 h. Then, all volatiles were removed in vacuo to
produce a yellow solid. Recrystallization from a concentrated THF
solution of 5 at -30 °C resulted in a yellow powder in 59% yield
(0.576 g, 1.12 mmol). 1H NMR (CD2Cl2, 500 MHz): δ 10.56 (m,
1 H, Ar H), 10.15 (m, 1 H, Ar H), 8.12-8.05 (m, 4 H, Ar H), 7.69
1
yield (0.066 g, 0.0708 mmol). H NMR (THF-d8, 500 MHz): δ
9.06 (d JHH ) 5.0 Hz, of d JHH ) 1.5 Hz, 1 H, Ar H), 8.97 (d JHH
) 5.0 Hz, of d JHH ) 2.0 Hz, 1 H, Ar H), 8.43 (d JHH ) 8.5 Hz,
of d JHH ) 1.5 Hz, 1 H, Ar H), 8.20 (d JHH ) 8.0 Hz, of d JHH
1.5 Hz, 1 H, Ar H), 8.10 (d JHH ) 7.0 Hz, of d JHH ) 1.0 Hz, 1 H,
Ar H), 7.77 (m, 2 H, Ar H), 7.55 (m, 4 H, Ar H), 7.25 (t, JHH
)
)
7.5 Hz, 1 H, Ar H), 6.98 (m, 9 H, Ar H), 6.92 (m, 6 H, Ar H), 6.38
(br s, 1 H, Ar H), 6.27 (t, JHH ) 7.5 Hz, 1 H, Ar H), 6.21 (br s, 1

Rh Complexes with a Bis(8-quinolyl)methylsilyl Ligand
Organometallics, Vol. 25, No. 7, 2006 1615
2
2
H, Ar H), 5.63 (br s, 1 H, Ar H), 1.50 (t, JRhH ≈ JHH′ ≈ 5.0 Hz,
δ 10.50 (m, 2 H, Ar H), 8.50 (d JHH ) 20 Hz, of d JHH ) 7.5 Hz,
2 H, Ar H), 8.32 (d JHH ) 18 Hz, of d JHH ) 6.0 Hz, 2 H, Ar H),
7.95 (t, JHH ) 9.0 Hz, 2 H, Ar H), 7.68 (m, 4 H, Ar H), 1.36 (s, 3
H, SiCH3). 13C{1H} NMR (DMSO-d6, 125 MHz): δ 157.7, 155.4,
154.4, 152.5, 146.9, 146.2, 138.7, 138.1, 135.6, 135.4, 134.9 (d, J
) 8.8 Hz), 137.7, 133.3, 130.0 (d, J ) 2.5 Hz), 129.7 (d, J ) 2.5
Hz), 129.3, 129.2, 127.8 (d, J ) 3.8 Hz), 127.9, 127.8, 122.5, 122.4
(aryl carbons), -5.27 (s, SiCH3). 29Si{1H} NMR (DMSO-d6, 99
1 H, RhCH2), 1.17 (t, 2JRhH′ ≈ JH′H ≈ 5.0 Hz, 1 H, RhCH2), 0.87
2
(s, 3 H, SiCH3). 13C{1H} NMR (THF-d8, 125 MHz): δ 150.3,
150.2, 150.1, 150.0, 149.5, 148.9, 144.5 (d, J ) 3.0 Hz), 142.6,
142.1, 138.7, 138.0, 137.7, 136.0, 134.1 (d, J ) 13.8 Hz), 130.8,
130.4, 129.2, 129.1, 128.3 (d, J ) 64 Hz), 127.9 (d, J ) 8.8 Hz),
122.5, 121.6, 121.5, 120.6 (m), 119.3 (m), 108.6 (br m) (aryl
carbons), 31.3 (d 2JPC ) 37.5 Hz, of d 1JRhC ) 11.3 Hz, RhCH2Ph)
4.47 (d, J ) 3.8 Hz, SiCH3). 19F NMR (THF-d8, 376.5 MHz): δ
MHz): δ 51.6 (d, JSiRh ) 22.0 Hz). Anal. Calcd for C19H15N2-
1
-78.02 (s). 29Si{1H} NMR (THF-d8, 99 MHz): δ 4.1 (d JRhSi
)
SiCl2Rh: C, 48.22; H, 3.20; N, 5.92. Found: C, 47.89; H, 3.40;
N, 5.89.
1
70 Hz, of d 2JSiP ) 15 Hz). 31P{1H} NMR (THF-d8, 162 MHz): δ
1
41.2 (d, JRhP ) 167 Hz). Anal. Calcd for C45H37N2SiPO3F3SRh:
C, 59.73; H, 4.12; N, 3.10. Found: C, 59.37; H, 4.03; N, 2.83.
[(NSiN)Rh(CH3CN)3][OTf]2 (11). A 200 mL Schlenk flask,
covered with aluminum foil, was charged with [(NSiN)RhCl2]2
(0.500 g, 0.528 mmol) and AgOTf (0.570 g, 2.22 mmol). To this
was added 50 mL of CH2Cl2, and the reaction mixture was stirred
at ambient temperature for 8 h. After the reaction suspension was
allowed to settle, the yellow filtrate was removed by cannula
filtration to leave an off-white precipitate, to which 30 mL of CH3-
CN was added. The CH3CN solution was stirred for 3 h, at which
point the solution became yellow as a fluffy white precipitate (AgCl)
formed. The reaction solution was concentrated to 5 mL, and vapor
diffusion of diethyl ether into this solution at room temperature
produced 11 as colorless crystals in 68% yield (0.591 g, 0.718
(NSiN)RhCl2(PPh3) (8). A 250 mL two-neck round-bottom flask
was equipped with a stir bar and a reflux condenser. Under N2, 2
(0.400 g, 0.570 mmol) and 50 mL of CH2Cl2 were added, followed
by neat DBU (0.100 mL, 0.669 mmol). The reaction mixture was
refluxed for 12 h at 65 °C, at which point all volatile materials
were removed under reduced pressure. The remaining yellow
residue was then redissolved in 25 mL of CH2Cl2, and filtration
provided a yellow filtrate. Recrystallization from a 1/1 mixture of
CH2Cl2 and diethyl ether (20 mL in total) afforded the desired
1
product in 68% yield (0.312 g, 0.388 mmol). H NMR (CD2Cl2,
1
500 MHz): δ 10.98 (m, 1 H, Ar H), 10.18 (d, JHH ) 5.0 Hz, 1 H,
Ar H), 8.13 (d JHH ) 8.0 Hz, of d JHH ) 1.5 Hz, 1 H, Ar H), 8.04
(d JHH ) 7.0 Hz, of d JHH ) 1.5 Hz, 1 H, Ar H), 8.00 (d JHH ) 6.5
Hz, of d JHH ) 1.5 Hz, 1 H, Ar H), 7.78 (d JHH ) 8.0 Hz, of d JHH
) 1.5 Hz, 1 H, Ar H), 7.72 (d JHH ) 8.0 Hz, 1 H, Ar H), 7.63-
7.59 (m, 7 H, Ar H), 7.53 (q, JHH ) 7.0 Hz, 2 H, Ar H), 7.45 (m,
1 H, Ar H), 7.24-7.22 (m, 3 H, Ar H), 7.10-7.06 (m, 6 H, Ar H),
6.79 (d JHH ) 8.5 Hz, of d JHH ) 5.5 Hz, 1 H, Ar H), 0.45 (s, 3 H,
SiCH3). 13C{1H} NMR (CD2Cl2, 125 MHz): δ 157.7, 155.4, 154.4,
152.5, 146.9, 146.2, 138.7, 138.1, 135.6, 135.4, 134.9 (d, J ) 8.8
Hz), 137.7, 133.3, 130.0 (d, J ) 2.5 Hz), 129.7 (d, J ) 2.5 Hz),
129.3, 129.2, 127.8 (d, J ) 38 Hz), 127.9, 127.8, 122.5, 122.4 (aryl
carbons), -5.27 (SiCH3). 29Si{1H} NMR (CD2Cl2, 99 MHz): δ
mmol). H NMR (CD3CN, 500 MHz): δ 9.63 (d, JHH ) 5 Hz, 2
H, Ar H), 8.48 (d JHH ) 1.5 Hz, of t JHH ) 7 Hz, 4 H, Ar H), 8.00
(d JHH ) 8 Hz, of d JHH ) 1.5 Hz, 2 H, Ar H), 7.78 (d JHH ) 8 Hz,
of d JHH ) 7 Hz, 2 H, Ar H), 7.66 (d JHH ) 8.5 Hz, of d JHH ) 5.5
Hz, 2 H, Ar H), 1.97 (s, 6 H, CH3CN), 1.61 (s, 3 H, SiCH3). 13C-
{1H} NMR (CD3CN, 125 MHz): δ 157.0, 154.4, 142.2, 140.6,
138.6, 131.7, 130.5, 129.7, 124.1 (aryl carbons), 126.2 (CH3CN),
1.8 (CH3CN), -3.9 (SiCH3). 19F NMR (CD3CN, 376.5 MHz): δ
-79.7 (s). 29Si{1H} NMR (CD2Cl2, 99 MHz): δ 63.1 (d, 1JRhSi
)
20.3 Hz). Anal. Calcd for C33H29N2O6S2F6SiRh: C, 39.37; H, 2.94;
N, 8.50, S, 7.78. Found: C, 39.42; H, 2.58; N, 8.31, S, 7.67. IR
(cm-1): ν(CN) 2332, 2304.
(NSiN)Rh(CH2Ph)2 (12). To a solid mixture of 10 (0.250 g,
0.264 mmol) and Mg(CH2Ph)2(THF)2 (0.143 g, 0.550 mmol) was
added 30 mL of C6H6 at room temperature. After 18 h of stirring,
the reaction mixture was taken to dryness under reduced pressure.
The remaining brownish yellow residue was dissolved in 20 mL
of THF and filtered through Celite. Recrystallization from a 1/1
mixture of THF:diethyl ether (6 mL in total) at -30 °C produced
45.1 (d, JSiRh ) 24.2 Hz, of d JSiP ) 11.4 Hz). 31P{1H} NMR
(CD2Cl2, 202.5 MHz): δ 24.2 (d, JRhP ) 128 Hz). Anal. Calcd
for C37H30N2SiPCl2Rh‚CH2Cl2: C, 55.62; H, 3.93; N, 3.47.
1
2
1
Found: C, 55.44; H, 3.97; N, 3.49.
[(NSiN)Rh(PMe3)2(Cl)][Cl] (9). To a 20 mL solution of CH2-
Cl2 solution of 2 (0.200 g, 0.285 mmol) was added 0.3 mL of neat
PMe3 (2.90 mmol). After 8 h, the yellow reaction mixture was
cannula-filtered and the filtrate was dried in vacuo. Recrystallization
from a 1/1 mixture of CH2Cl2 and diethyl ether (20 mL in total)
resulted in colorless crystals in 54% yield (0.096 g, 0.154 mmol).
1H NMR (CD2Cl2, 500 MHz): δ 10.36 (m, 2 H, Ar H), 8.37 (d
JHH ) 8.0 Hz, of d JHH ) 1.5 Hz, 2 H, Ar H), 8.19 (d JHH ) 7.0
Hz, of d JHH ) 1.5 Hz, 2 H, Ar H), 7.89 (d JHH ) 7.5 Hz, of d JHH
) 1.2 Hz, 2 H, Ar H), 7.68 (d JHH ) 8.0 Hz, of d JHH ) 6.5 Hz,
2 H, Ar H), 7.56 (d JHH ) 8.2 Hz, of d JHH ) 5.0 Hz, 2 H, Ar H),
1.41 (s, 3 H, SiCH3), 1.26 (m, 18 H, P(CH3)3). 13C{1H} NMR (CD2-
Cl2, 125 MHz): δ 154.7, 152.4 (d, 2JRhC ) 1.4 Hz), 143.4, 140.4,
136.9, 130.3, 129.6, 128.7, 123.1 (aryl carbons), 17.5 (m, P(CH3)3),
1
a yellow powder in 66% yield (0.203 g, 0.348 mmol). H NMR
(THF-d8, 500 MHz): δ 8.47 (d JHH ) 4.5 Hz, of d JHH ) 1.5 Hz,
2 H, Ar H), 8.07 (d JHH ) 4.5 Hz, of d JHH ) 1.5 Hz, 2 H, Ar H),
7.99 (d JHH ) 8.5 Hz, of d JHH ) 1.5 Hz, 2 H, Ar H), 7.64 (d JHH
) 8 Hz, of d JHH ) 1 Hz, 2 H, Ar H), 7.44 (d JHH ) 8 Hz, of d JHH
) 7 Hz, 2 H, Ar H), 7.06 (d JHH ) 7.5 Hz, of d JHH ) 5 Hz, 2 H,
Ar H), 6.63 (m, 6 H, Ar′ H), 6.42 (m, 4 H, Ar′ H), 2.47 (d JHH
)
9 Hz, of d JRhH ) 3 Hz, 2 H, CH2Ar′), 2.11 (d JHH ) 9 Hz, of d
JRhH ) 1 Hz, 2 H, CH2Ar′), 1.11 (s, 3 H, SiCH3). 13C{1H} NMR
(THF-d8, 125 MHz): δ 153.5, 152.7, 152.6, 152.3, 147.8, 136.5,
134.8, 129.5, 129.1, 128.8, 127.9, 127.5, 127.4, 122.0, 121.2 (aryl
carbons), 23.3 (d, JRhC ) 12.5 Hz, RhCH2), -5.5 (d, JRhC ) 3.8
-2.81 (d, JRhC ) 2.3 Hz, SiCH3). 29Si{1H} NMR (CD2Cl2, 99
Hz, SiCH3). 29Si{1H} NMR (CD2Cl2, 99 MHz): δ 43.7 (d, JRhSi
)
3
MHz): δ 46.1 (d JSiRh ) 28 Hz, of t JSiP ) 12 Hz). 31P{1H}
60.3 Hz). Anal. Calcd for C33H29N2SiRh: C, 67.80; H, 5.00; N,
4.79. Found: C, 67.84; H, 5.08; N, 4.49.
1
2
1
NMR (CD2Cl2, 202.5 MHz): δ 2.44 (d, JPRh ) 117 Hz). Anal.
Calcd for C25H33N2SiP2RhCl2: C, 48.01; H, 5.32; N, 4.48. Found:
C, 47.65; H, 5.30; N, 4.14.
[(NSiN)Rh(CH2Ph)(CH3CN)][PF6] (13). To a 5 mL CH3CN
solution of 8 (0.150 g, 0.273 mmol) was added a 5 mL CH3CN
solution of Ph3CPF6 (0.112 g, 0.288 mmol). The reaction mixture
was stirred at room temperature for 24 h to produce a milky yellow
solution. The resulting mixture was filtered through Celite, and the
yellow precipitate was extracted with 2 × 10 mL of CH3CN. The
clear yellow filtrate was dried under vacuum. Recrystallization by
vapor diffusion of diethyl ether into a concentrated THF solution
(3 mL) of the product produced a yellow crystalline solid in 69%
yield (0.128 g, 0.188 mmol). 1H NMR (CD2Cl2, 500 MHz): δ 9.23
[(NSiN)RhCl2]2 (10). To a solid mixture of 1 (0.650 g, 2.16
mmol) and RhCl3(CH3CN)3 (0.720 g, 2.16 mmol) was added CH2-
Cl2 (75 mL), followed by 0.35 mL of neat NEt3 (2.51 mmol). After
18 h, the resulting orange suspension was allowed to settle. Then,
the orange filtrate was removed via cannula filtration to leave a
yellow precipitate. The yellow residue was washed with CH2Cl2
(2 × 20 mL) and dried in vacuo to give the desired product in
62% yield (0.630 g, 1.33 mmol). 1H NMR (DMSO-d6, 500 MHz):

1616 Organometallics, Vol. 25, No. 7, 2006
Sangtrirutnugul et al.
(d JHH ) 5.0 Hz, of d JHH ) 1.5 Hz, 1 H, Ar H), 8.38 (d JHH ) 5.5
Hz, of t JHH ) 1.0 Hz, 1 H, Ar H), 8.37 (m, 1 H, Ar H), 8.27 (d
JHH ) 8.0 Hz, of d JHH ) 1.5 Hz, 1 H, Ar H), 8.22 (d JHH ) 6.8
Hz, of d JHH ) 1.2 Hz, 1 H, Ar H), 8.19 (d JHH ) 6.8 Hz, of d JHH
) 1.2 Hz, 1 H, Ar H), 8.14 (d JHH ) 8.0 Hz, of d JHH ) 1.5 Hz,
1 H, Ar H), 7.87 (d JHH ) 8.0 Hz, of d JHH ) 1.5 Hz, 1 H, Ar H),
7.79 (d JHH ) 8.2 Hz, of d JHH ) 1.2 Hz, 1 H, Ar H), 7.64 (m, 2
H, Ar H), 7.53 (d JHH ) 8.2 Hz, of d JHH ) 4.8 Hz, 1 H, Ar H),
7.27 (d JHH ) 8.2 Hz, of d JHH ) 5.2 Hz, 1 H, Ar H), 7.06 (m, 3
H, Ar H), 6.72 (m, 2 H, Ar H), 3.02 (d 2JRhH ) 2.5 Hz, of d 2JHH′
) 8.5 Hz, 1 H, RhCH2), 2.20 (s, 3 H, CH3CN), 2.14 (d 2JRhH ) 1.5
Hz, of d 2JHH′ ) 8.5 Hz, 1 H, RhCH2), 1.34 (d, 3JRhH ) 0.5 Hz, 3
1.5 Hz, 2 H, Ar H), 7.61 (d JHH ) 7.5 Hz, of d JHH ) 2.0 Hz, 10
H, Ar H), 7.46 (d, JHH ) 6.0 Hz, 12 H, Ar H), 7.13 (m, 2 H, Ar
H), 6.94 (m, 15 H, Ar H), 6.85 (t, JHH ) 3.0 Hz, 2 H, Ar H), 6.73
(d, JHH ) 7.5 Hz, 2 H, Ar H), 6.37 (d JHH ) 8.0 Hz, of d JHH
)
5.0 Hz, 2 H, Ar H), 5.83 (m, 1 H, CHdCH of COD), 5.53 (m, 1
H, CHdCH of COD), 2.69 (m, 1 H, CHH of COD), 2.21 (m, 1 H,
CHH of COD), 2.16 (m, 1 H, CHH of COD), 2.08 (m, 1 H, CHH
of COD), 1.58 (m, 1 H, CHH of COD), 1.51 (m, 1 H, CHH of
COD), 1.28 (s, 3 H, SiCH3), 1.26-1.19 (m, 3 H, CHH of COD),
0.84 (m, 1 H, CHH of COD), 0.21 (m, 1 H, CHH of COD). 13C-
{1H} NMR (C6D6, 125 MHz): δ 150.7, 149.8, 149.6, 144.5, 137.1,
136.8, 136.4 (d, JRhC ) 2.5 Hz), 136.2, 133.8, 128.6, 128.5, 126.9,
126.8, 126.6, 120.9 (aryl carbons), 34.4, 29.5, 27.0, 26.1 (d, 1JRhC
2
H, SiCH3). 13C{1H} NMR (CD2Cl2, 125 MHz): δ 153.4 (d, JRhC
3
) 84 Hz), 22.7, 14.2, 1.02 (d, JRhC ) 6.2 Hz, SiCH3). 29Si{1H}
) 2.5 Hz), 152.8, 152.7, 152.5, 152.0, 145.0, 142.5, 142.4, 142.3,
1
139.1, 138.5, 136.0, 135.9, 130.1, 129.8, 129.4, 129.0, 128.5, 128.1,
NMR (C6D6, 99 MHz): δ 35.5 (d, JSiRh ) 65 Hz, SiCH3), 11.7
2
1
127.9, 124.2, 122.7, 122.2 (aryl carbons), 128.9 (d, JRhC ) 1.8
(d, JSiRh ) 45 Hz, SiPh3).
Hz, CH3CN), 20.0 (d, 1JRhC ) 20.4 Hz, RhCH2), 4.18 (s, CH3CN),
(NSiN)Rh(η1-C8H13)[(Si(OSiMe3)3)] (17). Compound 17 was
generated from 14 (0.100 g, 0.196 mmol) and HSi(OSiMe3)3 (0.060
g, 0.202 mmol) in 0.5 mL of C6D6. The dark red reaction mixture
3
-4.01 (d, JRhC ) 2.4 Hz, SiCH3). 19F NMR (CD2Cl2, 376.5
1
MHz): δ 73.4 (d, JFP ) 43.3 Hz). 29Si{1H} NMR (CD2Cl2, 99
MHz): δ 57.3 (d, JSiRh ) 40 Hz). 31P{1H} NMR (CD2Cl2, 162
MHz): δ -145.1 (septet, 1JPF ) 711 Hz). Anal. Calcd for C28H25N3-
SiPRhF6: C, 49.49; H, 3.71; N, 6.18. Found: C, 49.30; H, 3.58;
N, 5.99.
1
yielded product 17 within 15 min at room temperature. H NMR
spectroscopy shows 17 to be the major (>95%) product in solution.
The reaction solution was vacuum-dried, leaving a dark yellow
solid, which was washed with 2 × 5 mL of hexanes. The
analytically pure compound was obtained in 42% yield (0.066 g,
(NSiN)Rh(COD) (14). A 5 mL C6H6 solution of 1 (0.163 g,
0.542 mmol) was added dropwise to a 8 mL C6H6 solution of
(COD)Rh(η3-CH2Ph) (0.172 g, 0.569 mmol) at ambient temperature.
The reaction mixture was stirred for 4 h, when it was filtered
through Celite. The dark brown filtrate was reduced to dryness
under vacuum. The resulting dark brown solid was washed with
pentane (2 × 5 mL) and dried in vacuo. Product 16 was obtained
1
0.082 mmol). H NMR (C6D6, 500 MHz): δ 9.31 (d JHH ) 5.0
Hz, of d JHH ) 1.5 Hz, 1 H, Ar H), 8.48 (d JHH ) 5.0 Hz, of d JHH
) 1.5 Hz, 1 H, Ar H), 8.02 (d JHH ) 6.5 Hz, of d JHH ) 1.5 Hz,
1 H, Ar H), 7.89 (d JHH ) 6.5 Hz, of d JHH ) 1.5 Hz, 1 H, Ar H),
7.31 (d JHH ) 8.0 Hz, of d JHH ) 1.5 Hz, 1 H, Ar H), 7.17 (m, 1
H, Ar H), 7.03 (m, 4 H, Ar H), 6.67 (d JHH ) 8.0 Hz, of d JHH
)
1
in 92% yield (0.254 g, 0.499 mmol). H NMR (C6D6, 500 MHz):
5.0 Hz, 1 H, Ar H), 6.47 (d JHH ) 8.0 Hz, of d JHH ) 5.0 Hz, 1 H,
Ar H), 5.61 (m, 2 H, CHdCH of COD), 2.89 (m, 1 H, CHH of
COD), 2.36-2.06 (m, 5 H, CHH of COD), 1.72 (m, 1 H, CHH of
COD), 1.56 (m, 1 H, CHH of COD), 1.46 (d, JHH ) 1.5 Hz, 3 H,
SiCH3), 1.34 (m, 2 H, CHH of COD), 0.18 (s, 27 H, OSiCH3),
-0.14 (m, 1 H, CHH of COD). 13C{1H} NMR (C6D6, 125 MHz):
δ 153.5, 152.8, 151.9, 151.6, 151.0, 150.1, 136.8, 136.4, 134.8,
134.7, 132.7 (C)C of COD), 128.8, 128.6, 128.53 (CdC of COD),
128.50, 127.4, 127.2, 127.0, 120.6, 120.3 (aryl carbons), 38.7, 28.7
(d, JRhC ) 1.0 Hz), 28.5 (d, JRhC ) 44 Hz), 27.6 (d, JRhC ) 20 Hz),
24.6 (d, JRhC ) 1.2 Hz), 3.01 (s, OSiCH3), 2.86 (d, JRhC ) 7.5 Hz,
δ 8.99 (d JHH ) 4.5 Hz, of d JHH ) 1.5 Hz, 2 H, Ar H), 7.99 (d
JHH ) 6.5 Hz, of d JHH ) 1.5 Hz, 2 H, Ar H), 7.27 (d JHH ) 8.0
Hz, of d JHH ) 1.5 Hz, 2 H, Ar H), 7.12 (d JHH ) 8.0 Hz, of d JHH
) 6.5 Hz, 2 H, Ar H), 7.06 (d JHH ) 8.0 Hz, of d JHH ) 1.5 Hz,
2 H, Ar H), 6.59 (d JHH ) 8.0 Hz, of d JHH ) 4.5 Hz, 2 H, Ar H),
5.25 (br s, 2 H, HCdCH), 3.56 (br s, 2 H, HCdCH), 2.46 (m, 4
H, CH2 of COD), 2.34 (m, 2 H, CH2 of COD), 2.27 (m, 2 H, CH2
of COD), 1.05 (s, 3 H, SiCH3). 13C{1H} NMR (C6D6, 125 MHz):
2
δ 155.2 (d, JRhC ) 2.5 Hz), 152.3, 150.3, 135.7, 134.5, 129.0,
2
128.5, 127.4, 126.9, 121.0 (aryl carbons), 106.3 (d, JRhC ) 3.8
Hz, CdC of COD), 46.1 (d, 2JRhC ) 16.8 Hz, CdC of COD), 36.7,
1
SiCH3). 29Si{1H} NMR (C6D6, 99 MHz): δ 36.7 (d, JSiRh ) 69
28.9 (s, CH2 of COD), -6.5 (d, 3JRhC ) 3.2 Hz, SiCH3). 29Si{1H}
1
Hz, SiCH3), -0.32 (d, JSiRh ) 86 Hz, Si(OSiCH3)3), -0.66 (s,
1
NMR (C6D6, 99 MHz): δ 35.2 (d, JSiRh ) 33 Hz). Anal. Calcd
Si(OSiCH3)3). Anal. Calcd for C36H55N2Si5O3Rh: C, 53.45; H, 6.81;
for C27H27N2SiRh: C, 63.52; H, 5.33; N, 5.49. Found: C, 63.32;
H, 5.40; N, 5.67.
N, 3.47. Found: C, 53.08; H, 6.63; N, 3.85.
(NSiN)Rh(dppe) (18). To a stirred solution of 14 (0.100 g, 0.196
mmol) in 10 mL of benzene was added 1,2-bis(diphenylphosphino)-
ethane (0.081 g, 0.203 mmol) in 5 mL of benzene at ambient
temperature. After 12 h, the reaction mixture was filtered through
Celite, and the light brown filtrate was taken to dryness under
vacuum. The yellowish brown residue was washed with 5 mL of
pentane and vacuum dried, giving the product in 89% yield (0.141
g, 0.174 mmol). 1H NMR (C6D6, 500 MHz): δ 8.97 (d, JHH ) 4.5
(NSiN)Rh(H)(SiPh3) (15). Compound 15 was generated in situ
by combining 14 (9 mg, 0.0176 mmol) and Ph3SiH (5 mg, 0.0192
mmol) in 0.5 mL of C6D6. The reaction mixture immediately turned
from dark brown to brownish yellow. Complex 15 was observed
1
as an intermediate in the formation of 16. H NMR (C6D6, 500
MHz): δ 8.42 (d, JHH ) 4.5 Hz, 2 H, Ar H), 7.76 (br s, 6 H, Ar
H), 7.70 (br s, 2 H, Ar H), 7.20 (d, JHH ) 2.5 Hz, 2 H, Ar H), 7.11
(m, 9 H, Ar H), 7.03 (m, 4 H, Ar H), 6.45 (d JHH ) 7.5 Hz, of d
JHH ) 4.5 Hz, 2 H, Ar H), 5.57 (s, 4 H, CH2dCH2 of free COD),
2.20 (s, 8 H, CH2 of free COD), 1.00 (d, JHH ) 1.0 Hz, 3 H, SiCH3),
-13.2 (d, JRhH ) 28 Hz, 1 H, RhH). 13C{1H} NMR (C6D6, 125
MHz): δ 152.4, 149.6, 148.5, 137.4, 136.2, 136.1, 134.3, 130.3,
129.3, 128.8, 127.6, 127.3, 127.0, 120.8 (aryl carbons), 28.3 (s,
CH2 of free COD), 1.40 (d, 3JRhC ) 7.5 Hz, SiCH3). 29Si{1H} NMR
(C6D6, 99 MHz): δ 36.6 (d, 1JSiRh ) 55 Hz, SiCH3), 18.1 (d, 1JSiRh
) 55 Hz, SiPh3).
Hz, 2 H, Ar H), 8.01 (t, JHH ) 7.0 Hz, 4 H, Ar H), 7.76 (d JHH
)
7.0 Hz, of d JHH ) 1.5 Hz, 2 H, Ar H), 7.67 (t, JHH ) 9.0 Hz, 4 H,
Ar H), 7.46 (d JHH ) 8.7 Hz, of d JHH ) 1.8 Hz, 2 H, Ar H), 7.23
(d JHH ) 8.0 Hz, of d JHH ) 1.0 Hz, 2 H, Ar H), 7.08 (m, 8 H,
PPh2), 6.93 (t, JHH ) 8.0 Hz, 2 H, Ar H), 6.85 (t, JHH ) 7.0 Hz, 4
H, Ar H), 6.50 (d JHH ) 8.5 Hz, of d JHH ) 4.5 Hz, 2 H, Ar H),
1.98 (m, 2 H, PCH2), 1.85 (m, 2 H, PCH2), 0.83 (d, JHP ) 2.0 Hz,
3 H, SiCH3). 13C{1H} NMR (C6D6, 125 MHz): δ 154.9, 154.0 (d,
JRhC ) 1.8 Hz), 152.6 (d, JRhC ) 8.5 Hz), 138.5 (d, JRhC ) 13.8
Hz), 138.2 (d, JRhC ) 53 Hz), 137.8, 136.2, 136.1, 134.2 (d, JRhC
) 13.8 Hz), 134.0 (d, JRhC ) 11.2 Hz), 129.0, 127.3 (d, JRhC ) 8.8
Hz), 126.6 (d, JRhC ) 43.8 Hz), 119.8 (aryl carbons), 33.2 (m, PCH2-
CH2P′), 27.8 (m, PCH2CH2P′), 2.20 (SiCH3). 29Si{1H} NMR (C6D6,
(NSiN)Rh(η1-C8H13)(SiPh3) (16). After a reaction mixture
containing 15 and 1,5-cyclooctadiene in C6D6 was left at room
1
temperature for 1 day, the solution became dark red. H NMR
spectroscopy reveals 16 to be the major (>95%) product in solution.
1H NMR (C6D6, 500 MHz): δ 8.55 (d JHH ) 5.0 Hz, of d JHH
)
79.5 MHz): δ 22.6 (d JSiRh ) 145 Hz, of d JSiP ) 38 Hz, of d
1
2

Rh Complexes with a Bis(8-quinolyl)methylsilyl Ligand
Organometallics, Vol. 25, No. 7, 2006 1617
2JSiP′ ) 26 Hz, SiCH3). 31P{1H} NMR (C6D6, 202.5 MHz): δ 70.6
(d 1JPRh ) 190 Hz, of d 2JPP′ ) 15 Hz, PCH2CH2P′), 43.3 (d 1JP′Rh
expanded using Fourier techniques.31 Due to a rapid decrease in
the intensity of reflections with increasing (sin θ)/λ, the structure
of 3 was refined to an acceptable R value with all carbon atoms
set to refine isotropically and all other non-hydrogen atoms were
refined with anisotropic thermal parameters. In addition, the Rh-H
atom of 3 was located in the difference Fourier map and its
positional parameters were refined. For 8, 11, and 12, all non-
hydrogen atoms were refined anisotropically. Unless stated other-
wise, all hydrogen atoms were placed in calculated positions and
not refined. All calculations were performed using the teXsan
crystallographic software package.32
2
) 125 Hz, of d JP′P ) 15 Hz, PCH2CH2P′). Anal. Calcd for
C45H39N2SiP2Rh: C, 67.50; H, 4.91; N, 3.50. Found: C, 67.72; H,
4.82; N, 3.54.
X-ray Crystallography. General Considerations. The single-
crystal X-ray analyses of compounds 3, 8, 11, and 12 were carried
out at the UC Berkeley CHEXRAY crystallographic facility.25 All
measurements were made on a Bruker SMART26 CCD area detector
with graphite-monochromated Mo KR radiation (λ ) 0.710 69 Å).
Crystals were mounted on capillaries with Paratone-N hydrocarbon
oil and held in a low-temperature N2 stream during data collection.
Frames were collected using ω scans at 0.3° increments, using
exposures of 10 s (8, 11, 12) or 15 s (3). Data were integrated by
the program SAINT27 and corrected for Lorentz and polarization
effects. Data were analyzed for agreement and possible absorption
using XPREP.28 Empirical absorption corrections based on com-
parison of redundant and equivalent reflections were applied using
SADABS.29 Structures were solved by direct methods30 and
Acknowledgment. We thank Dr. Fred Hollander and Dr.
Alan Oliver of the UC Berkeley CHEXRAY facility for
assistance with X-ray crystallography, Dr. Urs Burchkhardt and
Dr. Herman van Halbeek for implementation of 29Si NMR
experiments, and Dr. Ulla Andersen for carrying out mass
spectroscopy measurements. This work was supported by the
National Science Foundation under Grant No. 0132099.
Supporting Information Available: CIF files giving crystal-
lographic data for 3, 8, 11, and 12. This material is available free
of charge via the Internet at http://pubs.acs.org.
(25) http://xray.cchem.berkeley.edu.
(26) SMART: Area-Detector Software Package; Molecular Structure
Corp., The Woodlands, TX, 1985 and 1992.
(27) SAINT: SAX Area-Detector Software Package; Siemens Industrial
Automation, Inc., Madison, WI 1995.
OM050859V
(28) XPREP v. 5.03: Part of the SHELXTL Crystal Determination
Package; Siemens Industrial Automation, Inc., Madison, WI, 1995.
(29) Sheldrick, G. M. SADABS: Siemens Area Detector Absorption
Correction Program; 1996 (advance copy, private communication).
(30) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G.; Giacovazzo,
C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna, R. SIR97. J.
Appl. Crystallogr. 1999, 32, 115.
(31) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garcia-Granda, S.; Gould, R. O.; Smits, J. M. M.; Smykalla, C.
DIRDIF92: The DIRDIF Program System; Technical Report of the
Crystallography Laboratory; University of Nijmegen, Nijmegen, The
Netherlands, 1993.
(32) teXsan: Crystal Structure Analysis Package; Molecular Structure
Corp., The Woodlands, TX, 1985 and 1992.