Nickel complexes with bis(8-quinolyl)silyl ligands. An unusual Ni 3Si2 cluster containing six-coordinate silicon

Article abstract of DOI:10.1021/om1004622

Efforts to install the bis(8-quinolyl)methylsilyl (Me-NSiN; 1 = Me-NSiNH) and bis(8-quinolyl)phenylsilyl (Ph-NSiN; 2 = Ph-NSiNH) ligands onto nickel are described. Reaction of 1 with NiCl₂(DME) and NⁱPr ₂Et afforded [(

Full text of DOI:10.1021/om1004622

5544 Organometallics 2010, 29, 5544–5550
DOI: 10.1021/om1004622
Nickel Complexes with Bis(8-quinolyl)silyl Ligands. An Unusual Ni3Si2
Cluster Containing Six-Coordinate Silicon†
Jian Yang,‡ Iker Del Rosal,§ Meg Fasulo,‡ Preeyanuch Sangtrirutnugul,‡ Laurent Maron,*,§
and T. Don Tilley*,‡
‡Department of Chemistry, University of California, Berkeley, California 94720, and
§
ꢀ
Universite de Toulouse, INSA, UPS, LPCNO, 135 Avenue de Rangueil, F-31077 Toulouse, France, and
CNRS, LPCNO, F-31077 Toulouse, France
Received May 14, 2010
Efforts to install the bis(8-quinolyl)methylsilyl (Me-NSiN; 1=Me-NSiNH) and bis(8-quinolyl)-
phenylsilyl (Ph-NSiN; 2 = Ph-NSiNH) ligands onto nickel are described. Reaction of 1 with
NiCl2(DME) and NiPr2Et afforded [(iPr2EtNH)2Cl][(QnH)NiCl3] (3; Qn=quinolyl) via degrada-
tion of the silane. Reaction of 2 with Ni(COD)2 in chlorobenzene yielded [Ph-NSiN]2Ni3Cl2 (5), which is
a rare example of a silylnickel cluster with a [Ni3Si2] core. An X-ray structure determination reveals
the presence of a triangular Ni3 core with two face-capping silyl groups: one that is bonded
symmetrically to the three nickel atoms, while the other is unsymmetrically bound. The bonding in
5 has been investigated by computational methods to obtain descriptions of the molecular orbitals.
The unsymmetrical bonding of Si(1) results from a two-electron bonding interaction with Ni(1), and
this explains the short Si(1)-Ni(1) contact (2.2688(6) A). The symmetrical bonding of Si(2) appears
to result from its interaction with a delocalized Ni3 skeletal orbital. Complex 5 slowly decomposes in
dichloromethane-d2 to (PhClSiQn2)NiCl (6), a Ni(I) chloride complex in which the phenyl group is
bonded to the nickel with an intramolecularly coordinated (silyl)arene ligand. The η2-coordination of
the aryl group involves interaction of ipso and ortho carbon atoms with the metal center. Theoretical
studies of 6 support a very weak Ni-Si interaction (2-3 kcal/mol at the NBO level) that is supported
by the arene coordination. The strength of the η2-coordination of the arene was estimated at the
second-order donor-acceptor NBO level to be 25 kcal/mol.
Introduction
late transition metal complexes.2 A less studied type of
multidentate ligand involves incorporation of a silicon donor
atom.3-5 Such ligands might be expected to provide several
useful functions, including strong electron donation from the
silicon donor to afford an electron-rich metal center. In
addition, the strong trans influence of silicon should promote
coordinative unsaturation at a metal and facilitate substrate
activation processes. Along these lines, we have reported
use of the bis(8-quinolyl)methylsilyl (Me-NSiN) ligand in
new chemical transformations with rhodium, iridium, and
platinum.4 This rigid tridentate silyl ligand strongly prefers
facial coordination to transition metals and stabilizes a series
of Pt(IV) alkyl and hydrido derivatives.4d
Multidentate ligands have gained increasing popularity
over the last few decades, since they have been found to
impart stability and unprecedented reactivity to their organo-
metallic complexes. Examples include PCP pincer ligands
with a central aryl donor group, which have been found to
support alkane dehydrogenation catalysts,1 and PNP ligands
with a central amido donor, which support both early and
† Part of the Dietmar Seyferth Festschrift. Dedicated to Professor Dietmar
Seyferth, in recognition of his many contributions to chemistry and his
tireless service to the oganometallic community.
*To whom correspondence should be addressed. E-mail: laurent.maron@
irsamc.ups-tlse.fr; tdtilley@berkeley.edu.
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r
pubs.acs.org/Organometallics
Published on Web 08/02/2010
2010 American Chemical Society

Article
Given results from previous studies on complexes contain-
Organometallics, Vol. 29, No. 21, 2010 5545
ing multidentate ligands with silicon donor atoms, it is of
interest to explore their use in new chemical transformations
for the first-row transition metals,5c-f especially since there is
considerable interest in development of new catalysts based
on the more abundant, and less expensive, transition metals.6
Within this context, the studies reported here were initiated
to examine the coordination chemistry of NSiN ligands with
nickel. Of particular interest is the influence of a silicon
donor atom on chemical properties of a nickel center.
Relatively few nickel silyl complexes have been isolated;7,8
however, the potentially analogous platinum-silicon chem-
istry is quite rich, with numerous platinum silyl complexes
being described in the literature.8 Of course, platinum silyl
complexes play important roles in homogeneous catalysis,
especially in the area of hydrosilylation.9 In this contribu-
tion, we describe initial efforts to obtain nickel complexes of
the bis(8-quinolyl)methylsilyl (Me-NSiN) and bis(8-quino-
lyl)phenylsilyl (Ph-NSiN) ligands. These studies have led to
isolation of several structurally unusual nickel complexes
including a silicon-nickel cluster with an unusual [Ni3Si2]
core and six-coordinate silicon.
Figure 1. Molecular structures of 3 with thermal ellipsoids
drawn at the 50% probability level. Key bond distances (A)
and angles (deg): Ni(1)-N(1)=2.029(3), Ni(1)-Cl(3)= 2.245(1),
Ni(1)-Cl(4) = 2.231(1), Cl(1) H(1) = 2.336(6), H(1)
3 3 3
3 3 3
Cl(1) H(1) = 130.4(15).
3 3 3
results from C(sp2)-Si cleavage of the NSiN ligand by a protic
species generated by interaction of the silane with a Ni-Cl bond.
Results and Discussion
Ligand Synthesis. To examine possible electronic and steric
effects in NSiN ligands, both methylsilyl and phenylsilyl
derivatives were investigated. Following a previously described
procedure for bis(8-quinolyl)methylsilane (Me-NSiNH, 1),4a,b
bis(8-quinolyl)phenylsilane (Ph-NSiNH, 2) was obtained in
39% yield via lithiation of 8-bromoquinoline followed by
addition of 0.5 equiv of dichlorophenylsilane (eq 1).
-
As shown in Figure 1, the (QnH)NiCl3 anion adopts a
tetrahedral geometry about the Ni center, with the Ni(II)
atom coordinated by quinoline and three chlorides. In the
[(iPr2EtNH)2Cl]þ complex cation, two iPr2EtNHþ units are
symmetrically hydrogen-bonded to a chloride anion, with
crystallographically equivalent H Cl distances of 2.336(6)
3 3 3
A and an H Cl H angle of 130.4(15)°. A similar struc-
3 3 3 3 3 3
ture, in which two R3NHþ cations are bound via hydrogen
bonds to one chloride ion, was previously proposed for
[(nOct3NH)2Cl][FeCl4] on the basis of infrared spectroscopy.
The H Cl H arrangement in this structure was sug-
3 3 3 3 3 3
gested to have a linear geometry.10
Reaction of 1 with (tmeda)NiPhCl. The complex (tmeda)-
NiPhCl11 (tmeda = tetramethylethylenediamine) was en-
visioned as a potential precursor to (R-NSiN)NiCl complexes,
as it was anticipated that Si-H oxidative addition followed
by reductive elimination of C6H6 would lead to formation of
the desired (R-NSiN)NiCl complex. Reaction of 1 with
(tmeda)NiPhCl in 1,2-dichloroethane (or dichloromethane)
Isolation of [(iPr2EtNH)2Cl][(QnH)NiCl3] (3). Treatment
of 1 with NiCl2(DME) and excess NiPr2Et in refluxing THF
did not afford the desired chelate-assisted, Si-H bond
activation product (NSiN)NiCl. Instead, an unexpected
product was isolated in low yield (11%) by crystallization
from THF/pentane, and single-crystal X-ray crystallography
established this compound as [(iPr2EtNH)2Cl][(QnH)-
NiCl3] (3; Qn=quinolyl; eq 2). This Ni(II) product likely
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5546 Organometallics, Vol. 29, No. 21, 2010
Yang et al.
at room temperature afforded an off-white solid (74% yield),
which was characterized by multinuclear NMR spectroscopy
and GC-MS as bis(8-quinolyl)methylphenyl silane (4). This
reaction also provided green crystals from dichloromethane/
pentane, identified by single-crystal X-ray diffraction as
[(tmeda)3Ni3Cl5]2[NiCl4]12 (46% yield). Presumably, this re-
action proceeds by a chelate-assisted, Si-H bond oxidative
addition of 1, followed by C-Si reductive elimination of 4
(eq 3). This C-Si bond formation is likely driven by the
eventual formation of the trinuclear nickel species [(tmeda)3-
Ni3Cl5]2[NiCl4].
Figure 2. Molecular structure of 5 with thermal ellipsoids
drawn at the 50% probability level (hydrogens omitted). Key
bond distances (A): Ni(1)-Ni(2) = 2.3947(4), Ni(1)-Ni(3) =
2.3847(4), Ni(2)-Ni(3) = 2.3203(4), Si(1)-Ni(1) = 2.2688(6),
Si(1)-Ni(2) = 2.4592(6), Si(1)-Ni(3) = 2.5769(6), Si(2)-
Ni(1) = 2.3496(6), Si(2)-Ni(2) = 2.4011(6), Si(2)-Ni(3) =
2.3563(6).
Synthesis of (Ph-NSiN)2Ni3Cl2 (5). An additional ap-
proach to the synthesis of an NSiN-Ni complex utilized
COD as a leaving group and was based on the known reac-
tion of PhCl, Ni(COD)2, and a bidentate N,N-ligand (NN)
such as tmeda or 2,20-bipyridyl to form a (NN)Ni(Ph)Cl
complex.11 It was reasoned that a nickel-phenyl derivative
formed in solution might then react via Si-H oxidative
addition followed by C-H reductive elimination to install
the NSiN ligand onto nickel. Indeed, treatment of silane 2
with Ni(COD)2 and excess PhCl resulted in isolation of a new
nickel silyl species, 5 (eq 4). Further purification by crystallization
longer than those typically associated with Ni-Si bonds
(2.14-2.30 A13,7).
Complex 5 represents a rare example of a structurally
characterized silicon-transition metal cluster containing
six-coordinate silicon. Indeed, clusters that incorporate
more than two metal atoms and bridging Si ligands have
only a few precedents, most of which involve metal carbonyl
fragments.14-19 For example, a series of pseudo-octahedral
Co4Si2 clusters incorporating five-coordinate silicon have
1
afforded 5 as dark red crystals in 38% yield. The H NMR
spectrum of 5in dichloromethane-d2 contains four different sets of
quinolyl protons, suggesting an unsymmetrical structure. The 29Si
NMR spectrum of 5 exhibits two signals at 11.1 and 9.0 ppm,
corresponding to inequivalent silicon environments.
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J. Am. Chem. Soc. 2004, 126, 8072.
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Mackay, K. M.; Nicholson, B. K.; Robinson, B. H.; Van Tiel, M. L.
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Nicholson, B. K. J. Organomet. Chem. 1987, 326, C101. (c) Anema, S. G.;
Lee, S. K.; Mackay, K. M.; Nicholson, B. K. J. Organomet. Chem. 1993,
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95.
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M. V. Organometallics 1990, 9, 2436. (b) Hirotsu, M.; Nishida, T.; Sasaki,
H.; Muraoka, T.; Yoshimura, T.; Ueno, K. Organometallics 2007, 26, 2495.
(16) (a) Heine, A.; Herbst-lrmer, R.; Stalke, D. J . Chem. Soc., Chem.
Commun. 1993, 1729. (b) For another copper complex, [(Me3Si)3SiCu]3:
Klett, J.; Klinkhammer, K. W.; Niemeyer, M. Chem.;Eur. J. 1999, 5, 2531.
(17) (a) Braddock-Wilking, J.; Corey, J. Y.; Dill, K.; Rath, N. P.
Organometallics 2002, 21, 5467. (b) Braddock-Wilking, J.; Corey, J. Y.;
French, L. M.; Choi, E.; Speedie, V. J.; Rutherford, M. F.; Yao, S.; Xu, H.;
Rath, N. P. Organometallics 2006, 25, 3974. (c) Osakada, K.; Tanabe, M.;
Tanase, T. Angew. Chem., Int. Ed. 2000, 39, 4053. (d) Chen, W.; Shimada,
S.; Tanaka, M. Science2002, 295, 308. (e) Yamada, T.; Mawatari, A.; Tanabe,
M.; Osakada, K.; Tanase, T. Angew. Chem., Int. Ed. 2009, 48, 568. (f) Arii,
H.; Takahashi, M.; Nanjo, M.; Mochida, K. Organometallics 2009, 28, 4629.
(g) Shimada, S.; Yong-Hua, Li, Y.-H.; Choe, Y.-K.; Tanaka, M.; Bao, M.;
Uchimaru, T. Proc. Natl. Acad. Sci. U. S. A. 2007, 104, 7758.
(18) Brookes, A.; Knox, S. A. R.; Stone, F. G. A. J. Chem. Soc. A
1971, 3469.
X-ray quality crystals of 5 were obtained by layering
pentane onto a solution of 5 in 1,2-dichloroethane at room
temperature. The ORTEP diagram of 5 is shown in Figure 2.
The three Ni atoms form a triangle, and the central Ni3Cl2
moiety is capped by two bis(8-quinolyl)phenylsilyl groups to
form an unusual [Ni3Si2] core. The Ni(2)-Ni(3) distance
(involving the Ni atoms with Ni-Cl bonds) is 2.3203(4) A,
while the other two Ni-Ni distances are slightly longer,
averaging ca. 2.39 A. One silyl group is primarily bonded to
Ni(1), as indicated by a Ni(1)-Si(1) distance (2.2688(6) A)
that is shorter than the other two Ni-Si(1) distances (av 2.52
A). The other silyl group is bound more symmetrically to the
Ni3 triangle and exhibits roughly equivalent Ni-Si(2) bond
distances, which average 2.37 A. Note that this distance is
(19) (a) Metal-Metal Bonds and Clusters in Chemistry and Catalysis;
Fackler, J. P., Eds.; Plenum: New York, 1990. (b) Clusters and Colloids,
Schmid, G., Eds.; VCH: Weinheim, 1994. (c) Admas, D. A.; Cotton, F. A.
Catalysis by Di- and Polynuclear Metal Cluster Complexes; Wiley:
New York, 1998.
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2001, 314, 1.

Article
Organometallics, Vol. 29, No. 21, 2010 5547
Figure 4. Ni3 skeletal orbital that ensures the symmetrical co-
ordination with Si.
shell singlet, leading to a diamagnetic complex as observed
by NMR experiments.
Figure 3. Optimized DFT structure of 5.
The bonding in 5 may be analyzed by inspection of the mole-
cular orbitals derived from the calculation. Orbitals corresponding
to the Ni-Cl bonds are readily apparent, as are three Ni-Ni
bonding orbitals and two-center, two-electron Ni-N bonds. The
unsymmetrical bonding of Si(1) appears to result from a strong
two-electron bonding interaction with Ni(1), which results in the
short Si(1)-Ni(1) contact. The symmetrical bonding of Si(2) to
the trinickel core can be understood according to the Wade-
Mingos rules for metal clusters.20 These rules indicate that a facial
coordination of a ligand is possible, as one of the Ni3 skeletal
orbitals (formed by a combination of d orbitals) is oriented toward
the silicon center (Figure 4). Moreover, there is only one orbital of
this type for a triangle, so that only one bridging ligand may be
accommodated in this way. Thus, all other ligands must bind to the
cluster in terminal positions, as edge coordination appears to be
disfavored for both steric and electronic factors.
Degradation of 5. Complex 5slowly decomposes in dichloro-
methane-d2 to give a new paramagnetic species (6) over several days
at room temperature (eq 5). A mixture of 5and 6was also obtained
from the reaction of 2 with allyl nickel chloride in dichloromethane
(eq 6). Analysis of the crude products by 1H NMR spectroscopy
suggested a ∼1:3 ratio of 5and 6. Species 6was separated from 5by
successive crystallizations from dichloromethane/pentane and was
structurally characterized as an unusual Ni(I) chloride complex
with an intramolecularly coordinated (silyl)arene ligand.
˚
Table 1. Selected Bond Lengths of 5 in A
optimized
structure
bond
X-ray
Ni2-Ni3
Ni1-Ni3
Ni1-Ni2
Si1-Ni2
Si1-Ni3
Si1-Ni1
Si2-Ni2
Si2-Ni3
Si2-Ni1
Cl1-Ni2
Cl2-Ni3
N1-Ni2
N4-Ni3
N3-Ni1
N2-Ni1
2.310
2.361
2.412
2.524
2.549
2.248
2.357
2.341
2.396
2.228
2.239
1.971
1.927
2.000
1.988
2.320
2.385
2.395
2.459
2.577
2.269
2.401
2.356
2.350
2.240
2.213
1.957
1.940
1.981
1.951
been synthesized via oxidative additions of hydrosilanes to
Co2(CO)8.14 An Fe3Si2 cluster involving four-coordinate
silicon, [(μ3-Si{Fe(CO)2Cp}]2Fe3(CO)9, has been prepared
by reaction of SiH4, Fe(CO)5, and [CpFe(CO)2]2 under harsh
conditions.15a A somewhat related copper complex contain-
ing a bridging silyl ligand, Cu2[Si(SiMe3)3]2BrLi(THF)3,
was synthesized by reaction of (Me3Si)3SiLi(THF)3 with
CuBr.16a Trinuclear M3 complexes (M=Pd, Pt)17 as well as
dinuclear nickel complexes7d with edge-bridged silylene li-
gands have also been reported.
Computational Studies of 5. In order to gain better insight
into the bonding in this unusual nickel-silicon cluster, a
theoretical investigation of 5 at the DFT(B3PW91/SDD(Ni,
Si,Cl), 6-31G(d,p) for the other atoms) level was undertaken.
First of all, the geometry was successfully optimized without
symmetry restrictions (Figure 3).
The comparison between the experimental and theoretical
bond lengths is excellent (Table 1), which demonstrates the
ability of the computational method to model the complex.
The electronic ground state was determined to be a closed-
Crystallographic data for 6 revealed a roughly tetrahedral
geometry about the Ni center (Figure 5). The reaction

5548 Organometallics, Vol. 29, No. 21, 2010
Yang et al.
out in order to further characterize the interaction between
the Ni center and the SiPh fragment. A bond critical point
was located between Ni and Si (F = 0.052), which is closer
to Si (0.72 A) than Ni (1.98 A). Another bond critical point
was located (F=0.072) at a position equidistant between
C(19) (1.04 A) and Ni (1.06 A). The density at the bond
critical point is higher in the latter case, which is consistent
with the NBO analysis. Drawings of molecular orbitals
corresponding to the Ni-phenyl and Ni-Si interactions
are provided in the Supporting Information. A similar
bonding situation has been reported very recently for
{[o-iPr2P(C6H4)BPh2]Cu(μ-Cl)}2,24,25 in which a weak Cuf
B interaction supported by arene coordination has been
thoroughly studied by NMR spectroscopy, X-ray crystallo-
graphy, and DFT calculations.
Conclusion
Reactions of the bis(8-quinolyl)silanes 1 and 2 with simple
nickel complexes have led to unusual coordination com-
plexes of nickel rather than simple mononuclear, four-
coordinate species of the type (R-NSiN)NiX. Addition of 2 to
Ni(COD)2 in the presence of PhCl results in incorporation of
the Ph-NSiN ligand into a nickel complex, the silylnickel
cluster 5. Bonding analysis by inspection of the molecular
orbitals suggests that one silyl ligand plays a central role in
stabilizing the trinickel core, by functioning as a triply brid-
ging ligand bonding symmetrically to a metal cluster skeletal
orbital that is bonding with respect to the three nickel atoms.
This unusual cluster with a [Ni3Si2] core and silicon atoms with
expanded coordination spheres suggests a new role for NSiN
ligands in the assembly of multinuclear metal complexes. The
NSiN ligands also appear to have the potential to allow access
to low-valent nickel species such as 6. The mechanisms of the
reactions providing nickel cluster 5 and the nickel(I) complex 6
are currently unknown, but they may involve the intermediacy
of simple divalent (Ph-NSiN)NiX species. Thus, compounds
of the latter type may be highly reactive and represent inter-
esting targets for future synthetic studies.
Figure 5. Molecular structures of 6 with thermal ellipsoids
drawn at the 50% probability level (hydrogens omitted). Key
bond distances (A) and angles (deg): Ni(1)-C(19) = 2.068(3),
Ni(1)-C(24) = 2.369(3), Ni(1)-Cl(1) = 2.3307(8), Si(1)...Ni-
(1) = 2.6772(10), Si(1)-Cl(2) = 2.1142(11), C(19)-Si(1) =
1.839(3), C(19)-C(24) = 1.429(4), C(20)-C(21) = 1.380(5),
C(22)-C(23) = 1.376(5), Ni(1) Si(1)-Cl(2) = 156.00(4).
3 3 3
involves conversion of the Si-H group of 2 to a Si-Cl group.
The resulting bis(8-quinolyl)phenylchlorosilane lig-
and is bonded to the Ni(I) center in a chelated fashion thr-
ough two N donors of the quinolyl groups and a π inter-
action with the (silyl)phenyl ring. The latter interaction
results in Ni-C(19) and Ni-C(24) distances of 2.068(3)
and 2.369(3) A, respectively, and the C(19)-C(24) distance
(1.429(4) A) is significantly longer than the C(20)-C(21)
(1.380(5) A) and C(22)-C(23) (1.376(5) A) distances, sug-
gesting an η2-coordination of the phenyl ring. The Ni Si
3 3 3
distance of 2.677(1) A is much less than the sum of the van
der Waals radii of Ni and Si (4.1 A),21 but is greater than the
sum of the covalent radii (2.35 A).22 The geometry about the
silicon atom (including Ni as a substituent) may be described
as a distorted trigonal bipyramid ( (C-Si-C) = 342.8°
P
Experimental Section
and Ni Si-Cl = 156.00(4)°), and the Si-Cl distance
General Considerations. All manipulations were carried out
using Schlenk techniques under a purified N2 atmosphere or in a
Vacuum Atmospheres drybox. Solvents were distilled under N2
from appropriate drying agents and stored in Straus flasks.
Benzene-d6 was dried by vacuum distillation from Na/K alloy.
Dichloromethane-d2 was dried with CaH2 and vacuum trans-
ferred prior to use. Ethyldiisopropylamine, tetramethylethylene
diamine (tmeda), 1,2-dichloroethane, dichloromethylsilane,
and dichlorophenylsilane were dried over CaH2 and vacuum
transferred to a sealed storage flask. All other reagents were
3 3 3
(2.114(1) A) is longer than that of a typical Si-Cl bond
(e.g., that of Ph3SiCl is 2.077(1) A23). These findings suggest
the presence of a weak NifSi donor interaction.
To provide insight into the bonding characteristics of 6,
DFT studies were performed on the real complex. A Ni-Si
interaction of 2-3 kcal/mol was found at the NBO level. This
interaction is quite small and has to be supported by the arene
coordination. The strength of the η2-coordination of the
arene can be estimated at the second-order donor-acceptor
NBO level and is much higher than that of the Ni-Si inter-
action (25 vs 2-3 kcal/mol). An AIM analysis was carried
(24) Sircoglou, M.; Bontemps, S.; Mercy, M.; Miqueu, K.; Ladeira,
S.; Saffon, N.; Maron, L.; Bouhadir, G.; Bourissou, D. Inorg. Chem.
2010, 49, 3983.
(25) Examples of metal complexes with M to Si interactions: (a) Wagler,
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Prentice Hall: Englewood Cliffs, NJ, 1990.
J.; Brendler, E. Angew. Chem., Int. Ed. 2010, 49, 624. (b) Gualco, P.; Lin, T.-P.;
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Sircoglou, M.; Mercy, M.; Ladeira, S.; Bouhadir, G.; Perez, L. M.; Amgoune, A.;
(21) Batsanov, S. S. Inorg. Mater. 2001, 37, 871.
(22) Cordero, B.; Gomez, V.; Pletro-Prats, A. E.; Reves, M.;
Maron, L.; Gabbaï, F. P.; Bourissou, D. Angew. Chem., Int. Ed. 2009, 48, 9892.
(c) Guo, L.; Bradshaw, J. D.; McConville, D. B.; Tessier, C. A.; Youngs, W. J.
Organometallics 1997, 16, 1685. (d) Guo, L.; Bradshaw, J. D.; Tessier, C. A.;
Youngs, W. J. Organometallics 1995, 14, 586. (e) Grobe, J.; L€utke-Brochtrup, K.;
ꢀ
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Echeverrıa, J.; Cremades, E.; Barragan, F.; Alvarez, S. Dalton Trans.
´
2008, 2832.
€
(23) (a) Lobkovskii, E’.B.; Fokin, V. N.; Semenenko, K. N. J. Struct.
Chem. 1981, 22, 603. (b) MacLachlan, M. J.; Zheng, J.; Thieme, K.; Lough,
A. J.; Manners, I.; Mordas, C.; LeSuer, R.; Geiger, W. E.; Liable-Sands,
L. M.; Rheingold, A. L. Polyhedron 2000, 19, 275.
Krebs, B.; Lage, M.; Niemeyer, H.-H.; W€urthwein, E.-U. Z. Naturforsch. B
€
2007, 62, 55. (f) Grobe, J.; Wehmschulte, R.; Krebs, B.; Lage, M. Z. Anorg. Allg.
Chem. 1995, 621, 583. (g) Grobe, J.; Krummen, N.; Wehmschulte, R.; Krebs, B.;
Lage, M. Z. Anorg. Allg. Chem. 1994, 620, 1645.
€

Article
Organometallics, Vol. 29, No. 21, 2010 5549
purchased from Aldrich, Strem, or Gelest and used as received.
Allyl nickel chloride dimer,26 (tmeda)NiPhCl,11a and 8-bromo-
quinoline27 were prepared according to literature procedures.
Bis(8-quinolyl)methylsilane (1) was synthesized as previously
described.4a,b NMR spectra were recorded on Bruker AV-600,
DRX-500, AV-500, AVB-400, AVQ-400, and AV-300 spectro-
meters at room temperature. 1H NMR spectra were referenced
to residual protio solvent peaks. 13C{1H} NMR spectra were
referenced to solvent resonances (δ 128.39 for C6D6, δ 54.00 for
CD2Cl2, δ 43.6 for ClCD2CD2Cl). 29Si chemical shifts were
referenced to internal (CH3)4Si. Elemental analyses were carried
out by the College of Chemistry Microanalytical Labo-
ratory at the University of California, Berkeley. GC-MS ana-
lysis was performed on an Agilent Technologies 6890N GC
system with an HP-5MS column.
Complex 4 was characterized by NMR spectroscopy and GC-
MS. 1H NMR (C6D6, 600.13 MHz): δ 8.51 (d, JHH = 4.2 Hz, of
d, JHH = 1.8 Hz, 2H), 7.81 (m, 4H), 7.51 (d, JHH = 7.8 Hz, of d,
J
HH = 1.8 Hz, 2H), 7.44 (d, JHH = 7.8 Hz, of d, JHH = 1.2 Hz,
2H), 7.22-7.10 (m, 5H), 6.65 (d, JHH = 7.8 Hz, of d, JHH = 4.2
Hz, 2H) (aryl hydrogens, total 17H), 1.80 (s, 3H, SiCH3).
13C{1H} NMR (CD2Cl2, 125.8 MHz): δ 153.16, 149.56,
139.50, 139.47, 139.28, 136.63, 135.85, 129.95, 129.03, 128.36,
127.95, 126.51, 121.26 (aryl carbons), -0.49 (Si-CH3). 29Si{1H}
NMR (CD2Cl2, 119.23 MHz): δ -9.0. GC-MS: m/z 376 (Mþ),
361, 299, 248.
Synthesis of (Ph-NSiN)2Ni3Cl2 (5). A slurry of 2 (0.120 g,
0.33 mmol) in chlorobenzene (3 mL) was added to Ni(COD)2
(0.084 g, 0.31 mmol) with stirring. The reaction mixture was
stirred at room temperature for 1 day. The reaction mixture was
then concentrated to ca. 1.5 mL, and pentane (10 mL) was added
to precipitate crude 5 a dark brown solid. The solid was washed
with pentane (2 mL ꢀ 3) and redissolved in 1,2-dichloroethane
(ca. 5 mL). This solution was filtered through Celite and a glass
fiber filter and layered with pentane (ca. 15 mL). At -30 °C, 5
was obtained as dark red blocks in 38% yield (0.040 g, 0.039
mmol). 1H NMR (CD2Cl2, 500.13 MHz): δ 9.74 (m, 1H), 9.08
(b, 2H), 8.88 (b, 2H), 8.76 (m, 2H), 8.51 (d, JHH = 6.5 Hz, of d,
JHH = 1.5 Hz, 1H), 8.17 (m, 1H), 8.03 (m, 1H), 7.94-7.86 (m,
3H), 7.83-7.75 (m, 3H), 7.67 (m, 1H), 7.56-7.49 (m, 5H), 7.42
Synthesis of Bis(8-quinolyl)phenylsilane (Ph-NSiNH, 2). N-
Butyllithium (1.6 M in hexanes, 6.5 mL, 10.4 mmol) was added
dropwise to a stirred solution of 8-bromoquinoline (2.05 g,
9.9 mmol) in THF (50 mL) at -78 °C. The mixture was stirred
for 10 min at this temperature before phenyldichlorosilane (neat,
0.74 mL, 5.1 mmol) was added via syringe. The reaction mixture
was stirred for another 15 min at -78 °C before being warmed to
room temperature and stirred for an additional 19 h. All volatile
materials were removed in vacuo, and the resulting residue was
extracted with toluene (100 mL). The yellow extract was concen-
trated to about 25 mL and filtered. The filtrate was stored at -30 °C
for 2 days to give the product as a pale yellow solid in 39%
yield (0.7 g, 1.93 mmol). 1H NMR (CD2Cl2, 300.13 MHz): δ 8.80
(d, JHH = 4.2Hz, ofd, JHH = 1.8Hz, 2H), 8.19 (d, JHH = 8.1Hz,
of d, JHH = 1.8 Hz, 2H), 7.92 (d, JHH = 8.1 Hz, of d, JHH = 1.5
Hz, 2H), 7.70 (d, JHH = 6.9 Hz, of d, JHH = 1.5 Hz, 2H), 7.65 (m,
2H), 7.47 (m, 2H), 7.41-7.30 (m, 5H) (aryl hydrogens, total
17H), 6.32 (s, 1H, SiH). 13C{1H} NMR (CD2Cl2, 125.77 MHz): δ
153.02, 150.12, 139.76, 136.75, 136.71, 136.54, 136.14, 130.42,
129.57, 128.30, 128.17, 126.76, 121.59. 29Si{1H} NMR (CD2Cl2,
119.23 MHz): δ -23.8. Anal. Calcd (%) for C24H18N2Si (362.50):
C, 79.52, H, 5.00, N, 7.73. Found: C, 79.66, H, 4.80, N, 7.34.
Isolation of [(iPr2EtNH)2Cl][(QnH)NiCl3] (3). A PTFE-
valved sealable reaction flask was charged with NiCl2(DME)
(0.088 g, 0.40 mmol). A solution of 1 (0.120 g, 0.40 mmol) and
ethyldiisopropylamine (0.25 mL, 1.51 mmol) in THF (10 mL)
was added. The flask was sealed and stirred at 70 °C for 37 h. The
mixture was filtered to give a clear green solution, which was
layered with pentane (10 mL). At -30 °C, blue crystals were
obtained in 11% yield (0.025 g, 0.0424 mmol). Anal. Calcd (%)
for C25H47N3Cl4Ni (590.16): C, 50.88, H, 8.03, N, 7.12. Found:
C, 51.18, H, 8.90, N, 7.10. A crystalline sample of 3 (blue needle
0.30 ꢀ 0.05 ꢀ 0.05 mm3) was used for X-ray crystallographic analysis.
Reaction of 1 with (tmeda)NiPhCl in 1,2-Dichloroethane. A
solution of 1 (0.032 g, 0.107 mmol) in 1,2-dichloroethane (3 mL)
was added to (tmeda)NiPhCl (0.031 g, 0.108 mmol) with
stirring. The resulting solution was stirred at room temperature
for 18 h. All volatile materials were removed in vacuo, and the
resulting residue was extracted with benzene (4 mL). The
benzene solution was filtered through Celite and a glass fiber
filter, and the solvent was then removed under vacuum to yield
crude 4 as a pale orange powder (0.039 g). Crude 4 was exposed
to air and extracted into benzene (3 mL). The benzene solution
was filtered through silica gel, and then the solvent was removed
under vacuum to give spectroscopically pure 4 as an off-white
solid in 74% yield (0.030 g, 0.080 mmol). A byproduct from this
reaction, crystallized from CH2Cl2/pentane, was identified by
single-crystal X-ray analysis as the previously known compound
(m, 1H), 7.33 (m, 1H), 7.28 (m, 1H), 7.13 (m, 2H), 7.09 (d, JHH
=
8.0 Hz, of d, JHH = 5.0 Hz, 1H), 7.05 (d, JHH = 5.0 Hz, of d,
JHH = 2.0 Hz, 1H), 6.82 (d, JHH = 8.0 Hz, of d, JHH = 4.5 Hz,
1H), 6.40 (d, JHH = 8.0 Hz, of d, JHH = 5.0 Hz, 1H), 6.30 (d,
J
HH = 5.0 Hz, of d, JHH = 1.5 Hz, 1H), 6.11 (d, JHH = 8.0 Hz,
of d, JHH = 4.5 Hz, 1H), 5.87 (d, JHH = 5.0 Hz, of d, JHH
=
1.5 Hz, 1H) (aryl hydrogens, total 34 H). 13C{1H} NMR
(ClCD2CD2Cl, 150.9 MHz): δ 155.9 (br), 155.3 (br), 153.9
(br), 153.4 (br), 152.7 (br), 150.9 (br), 150.3 (br), 147.6 (br),
147.2 (br), 144.2 (br), 141.4 (br), 139.8 (br), 139.4 (br), 139.3 (br),
138.3 (br), 138.2 (br), 138.0 (br), 137.2 (br), 137.1 (br), 137.0 (br),
136.7 (br), 136.4 (br), 129.1-126.7 (broad overlapping reso-
nances), 121.1 (br), 120.9 (br), 120.5 (br), 120.3 (br). The
broad resonances observed in the 13C{1H} NMR spectrum are
likely due to the slow decomposition of 5. 29Si{1H} NMR
(CD2Cl2, 119.23 MHz): δ 11.1, 9.0. Anal. Calcd (%) for
C48H34N4Si2Ni3Cl2 (ClCH2CH2Cl)0.5 (1019.45): C, 57.73, H,
3
3.56, N, 5.50. Found: C, 58.06, H, 3.45, N, 5.33. Crystals suitable
for X-ray analysis were grown from layering pentane onto a 1,2-
dichloroethane solution of 5 at room temperature.
Isolation of (PhClSiQn2)NiCl (6). A slurry of 2 (0.080 g, 0.22
mmol) in CH2Cl2 (2 mL) was added dropwise to an allyl nickel
chloride dimer (0.036 g, 0.13 mmol) solution in CH2Cl2 (2 mL).
The reaction mixture was stirred at room temperature for 10 min
and filtered. The dark red solution was then layered with pentane
(10 mL) at room temperature for 1 day to give a brown crystalline
solid as a ca. 1:3 mixture of 5 and 6 (0.073 g). The solid was
redissolved in CH2Cl2 (ca. 7 mL), filtered, and layered with pentane
(8 mL). At room temperature an analytically pure sample of
6 (CH2Cl2) was obtained as dark brown crystals in 12% yield
3
(0.015 g, 0.026 mmol). 1H NMR (CD2Cl2, 400.13 MHz): δ 23.5,
18.1, 15.6, 13.4, 5.0. Anal. Calcd (%) for C24H17N2SiCl2Ni -
3
(CH2Cl2) (576.02): C, 52.13, H, 3.32, N, 4.86. Found: C, 52.46,
H, 3.31, N, 5.02. A crystalline sample of 6 (brown plate, 0.10 ꢀ 0.08
ꢀ 0.04 mm) was used for X-ray crystallographic analysis.
X-ray Structure Determination. The X-ray analyses of com-
pounds 3, 5, and 6 were carried out at the UC Berkeley
CHEXRAY crystallographic facility. All measurements were
made on a Bruker SMART, APEX, or MicroStar CCD area
detector with graphite-monochromated Mo or Cu KR radia-
tion. The data were integrated using the Bruker SAINT software
program and scaled using the SADABS software program.
Solution by direct methods (SIR-2004) produced a complete
heavy-atom phasing model consistent with the proposed struc-
ture. All non-hydrogen atoms were refined anisotropically by
[(tmeda)3Ni3Cl5]2[NiCl4] CH2Cl212 (0.012 g, 0.0071 mmol, 46%
3
yield).
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5550 Organometallics, Vol. 29, No. 21, 2010
Yang et al.
full-matrix least-squares (SHELXL-97). All hydrogen atoms
were placed using a riding model. Their positions were con-
strained relative to their parent atom using the appropriate
HFIX command in SHELXL-97.
Computational Details. All the calculations were performed
with the Gaussian 0328 suite of programs. Nickel, silicon, and
chlorine were treated with a Stuttgart-Dresden pseudopotential
in combination with their adapted basis set.29,30 The basis set has
been augmented by a set of f polarization functions31,32 for the
nickel atom and by a set of d polarization functions for the
silicon and chlorine atoms. Carbon, nitrogen, and hydrogen
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any symmetry restrictions, and the nature of the extremum
(minimum) was verified with analytical frequency calculations.
The calculations were carried out in the gas phase. The electron
density has been analyzed using the natural bonding analysis
(NBO).35
Acknowledgment. Dow Corning is gratefully acknow-
ledged for financial support of this research. The authors
wish to acknowledge the National Science Foundation
for partial support, and Richard Taylor, Binh Nguyen,
and Misha Tzou (Dow Corning) are thanked for valuable
discussions. We also thank Dr. Antonio Di Pasquale
for assistance with X-ray crystallography. CALMIP
(Toulouse) and Cines (CNRS, Montpellier) are acknow-
ledged for grant of computing time. L.M. is member of the
Institut Universitaire de France.
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