σ-SiH complexes of copper: Experimental evidence and computational analysis

Article abstract of DOI:10.1021/om301211c

Copper and gold complexes 2-4 of the diphosphine-hydrosilane [Ph ₂P(o-C₆H₄)]₂MeSiH ligand 1 have been prepared, and their bonding situation has been analyzed experimentally (NMR, IR, X-ray diffraction) and computationally (geometry optimizations, NBO analyses). The σ-SiH bond remains pendant in the gold complex 4 but engages into a weak side-on coordination to copper. This bonding interaction slightly strengthens when the metal becomes more electron deficient, consistent with essentially pure σ-SiH-to-copper donation. Complexes 2 and 3 provide very rare examples of σ-bond coordination to a coinage metal.

Full text of DOI:10.1021/om301211c

Article
pubs.acs.org/Organometallics
σ‑SiH Complexes of Copper: Experimental Evidence and
Computational Analysis
Maximilian Joost,† Sonia Mallet-Ladeira,‡ Karinne Miqueu,*,§ Abderrahmane Amgoune,*,†
and Didier Bourissou*,†
†University of Toulouse, UPS, LHFA, 118 Route de Narbonne, 31062 Toulouse, France
‡Institut de Chimie de Toulouse (FR 2599), 118 Route de Narbonne, 31062 Toulouse Cedex 9, France
§Institut des Sciences Analytiques et de Physico-Chimie pour l’Environnement et les Mater
́
iaux UMR-CNRS 5254, Universite
́
ident Angot, 64053 Pau Cedex 09, France
́
de Pau
et des Pays de l’Adour, Hel
́
ioparc, 2 Avenue du Pres
S
* Supporting Information
ABSTRACT: Copper and gold complexes 2−4 of the
diphosphine-hydrosilane [Ph2P(o-C6H4)]2MeSiH ligand 1
have been prepared, and their bonding situation has been
analyzed experimentally (NMR, IR, X-ray diffraction) and
computationally (geometry optimizations, NBO analyses).
The σ-SiH bond remains pendant in the gold complex 4 but
engages into a weak side-on coordination to copper. This
bonding interaction slightly strengthens when the metal
becomes more electron deficient, consistent with essentially pure σ-SiH-to-copper donation. Complexes 2 and 3 provide very
rare examples of σ-bond coordination to a coinage metal.
n the past decades, coinage metals have garnered
tremendous interest in catalysis. Cu, Ag, and Au complexes
I
have been applied successfully to a broad range of trans-
formations with very high levels of activity and selectivity.1 In
parallel, fundamental experimental and theoretical studies have
been carried out, and thereby, our knowledge of the properties
and behavior of coinage metal complexes has progressed.2,3
Such organometallic studies are all the more valuable in that the
coinage metals differ markedly from the other transition metals
and that their organometallic chemistry is comparatively much
less known.
Figure 1. Schematic representation of the coordination/activation of
σ-SiSi and σ-SiH bonds at copper and gold.
In this context, we have recently started to explore the ability
of coinage metals to coordinate and activate σ-bonds.4,5 It is
nowadays well-established that σ-bonds can coordinate to
transition metals and σ-complexes are recognized as key
intermediates in the oxidative addition process.6 Over the years,
the side-on coordination of σ-bonds has in fact become a
textbook example of weak metal/ligand interactions,7 and a
variety of σ-complexes have been authenticated experimentally
with H−H,6 H−Si,8 H−B,9 H−C,10 C−C,11 Si−Si,12 etc.,
bonds. However, examples of σ-bond coordination remain
extremely rare with the coinage metals.13,14 Last year, we
reported the first structural characterization of such a complex
upon coordination of a diphosphine-disilane to copper. Weak
side-on coordination of the σ-SiSi bond was identified with
copper,4 whereas oxidative addition was observed in the
corresponding gold complex (Figure 1).5
Hydrosilanes are involved in many transition metal catalyzed
transformations, and as a matter of fact, σ-SiH complexes are
the most studied class of σ-complexes after σ-H2 complexes.8
But very little is known about the coordination of σ-SiH bonds
to the coinage metals, although copper and gold complexes are
very powerful and valuable catalysts for hydrosilylation
reactions and related processes.15
The chelating approach we used to investigate the
coordination of Lewis acids16 and σ-SiSi bonds4,5 was
extrapolated here to σ-SiH bonds (Figure 1).17 For that
purpose, we turned to a diphosphine-hydrosilane ligand,
namely, [Ph2P(o-C6H4)SiH(Me)(o-C6H4)PPh2], 1. This ligand
backbone has recently attracted much interest with group 8 to
10 metals (Ru, Rh, Ir, Ni, Pd, and Pt).18,19 The central σ-SiH
Seeking to determine how general the coordination and
activation of σ-bonds at coinage metals are and to gain more
insight into the underlying factors, we became interested in
studying the interactions of σ-SiH bonds with copper and gold.
Received: December 14, 2012
Published: January 30, 2013
© 2013 American Chemical Society
898
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Article
bond is readily activated by these metals, and the ensuing
diphosphine-silyl pincer complexes were found to possess
versatile reactivity18b,c and interesting catalytic properties.18f
Noteworthily, the σ-SiH complexes en route to the PSiP pincer
complexes have recently been intercepted and characterized
with Ni, Pd, and Pt.18d,g,h Here we report a detailed
experimental and computational study of the coordination of
the diphosphine-hydrosilane 1 to copper and gold. We provide
evidence for the coordination of the σ-SiH bond to copper,
while the hydrosilane remains pendant with gold. The bonding
situation has been analyzed thoroughly, and the electron
density at copper has been varied to see how this affects the
silane coordination.
η2-SiH complexes, albeit with a significantly weaker magnitude
(bands in the range 1650−1800 cm−1 are usually observed).8
To gain further insight into the structure of complex 2,
crystals were grown from a dichloromethane/pentane solution
at −30 °C, and an X-ray diffraction analysis was performed
(Figure 2). The copper center of 2 is surrounded by the two
The diphosphine-hydrosilane ligand 1 was prepared by slight
modification of the reported procedure, coupling two
equivalents of isolated ortho-lithiated triphenylphosphine with
dichloromethylsilane.18a,20 Coordination to copper was
achieved by reacting 1 with CuCl in dichloromethane (addition
at −40 °C and warmup to room temperature over 1 h). The
progress of the reaction is easily followed visually as the initial
suspension of CuCl progressively turns to a clear solution. The
formed complex 2 was isolated as a white solid (68% yield)
after precipitation with pentane (Scheme 1).
Figure 2. X-ray structure of complex 2. Thermal ellipsoids are set at
50% probability; solvent molecules, phenyl substituents at phosphorus,
and hydrogen atoms, except the one at Si, are omitted for clarity.
Scheme 1. Coordination of the Diphosphine-Hydrosilane 1
to Copper Chloride
phosphorus atoms and the chlorine atom, organized in a
trigonal-planar arrangement [PCuP = 115.66(2)°]. Interest-
ingly, the silicon atom also sits close to copper. The Cu−Si
distance [2.997(1) Å] is beyond the sum of the covalent radii
(2.43 Å),22 but well within the sum of the van der Waals radii
(4.10 Å).23 This is consistent with a possible participation of
the σ-SiH bond in the coordination, as suggested by the NMR
and IR data. At this point, it is worth recalling that hydrogen
atoms close to heavy elements, in particular transition metals,
are inherently difficult to locate accurately by X-ray
crystallography even with high-quality measurements. As a
consequence, the margin errors for the associated SiH and MH
distances are large and discussions of these structural
parameters are hardly reliable. Computational studies do not
face the same problem, and density functional theory (DFT)
calculations are most useful in combination with and
complement to X-ray diffraction analyses.24 A theoretical
study of 2 and related complexes has thus been carried out
(vide infra).
Complex 2 displays a single resonance signal at δ = −7.6
ppm in the 31P NMR spectrum, in agreement with the
symmetric coordination of the two phosphorus atoms. The
associated 29Si NMR signal appears as a triplet (JSiP = 23 Hz) at
δ = −30 ppm. These data are very similar to those of the free
ligand 1 (δ = −24 ppm, JSiP = 24 Hz) and indicate the retention
of the hydrosilane motif upon coordination. The slight high-
field shift of the 29Si NMR signal (by 6 ppm) is hardly
informative at this stage. It may result from a weak interaction
of the hydrosilane motif with copper or simply from some
modification of the geometry around silicon upon coordina-
To explore further the coordination of σ-SiH bonds to
copper, we then envisioned increasing the electrophilicity of the
metal and see how this affects the spectroscopic and structural
features of the complex. For that purpose, complex 2 was
reacted with one equivalent of GaCl3 and the new complex 3
was isolated in 80% yield (Scheme 2). The 31P and 29Si NMR
data for 3 (31P: δ −5.0 ppm and 29Si: δ −30 ppm, JSiP = 23 Hz)
very much resemble those of 2, suggesting that the two
complexes adopt similar coordination modes. Notably, the
characteristic features suggesting the presence of a weak
interaction between the σ-SiH bond and the copper center in
tion.21 The H NMR signal for the hydrogen atom bound to
1
silicon is shifted downfield by ∼1.1 ppm compared to that of
the free ligand (from δ = 5.48 ppm in 1 to δ = 6.63 ppm in 2).
1
Most indicative is the associated JSiH coupling constant
1
measured from the 29Si satellites of the H NMR signal. It
decreases from 204 Hz in the free ligand 1 to 180 Hz in
complex 2, suggesting some weakening of the Si−H bond. The
1
decrease of JSiH is a well-established signature for the
coordination of σ-SiH bonds to transition metals.8 Known
silane complexes are associated with coupling constants down
to 40−70 Hz, and usually the more activated the σ-SiH bond is,
the lower the 1JSiH value. Thus, the relatively large 1JSiH coupling
constant of 2 suggests only weak interaction of the σ-SiH bond
with copper. To confirm this bonding picture, we then turned
to infrared spectroscopy, the νSiH stretching frequency being
another useful descriptor.8 The corresponding vibration band is
found at 1996 cm−1 in complex 2, vs 2142 cm−1 in the free
ligand. This variation confirms the weakening of the σ-SiH
bond upon coordination and again follows the usual trend of
1
2 are also met in 3, even to a slightly greater extent: the JSiH
coupling constant is further decreased at 170 Hz and,
concomitantly, the νSiH band is further shifted to lower
frequency at 1973 cm−1 (Table 1). These data may suggest a
slight strengthening of the σ-SiH bond coordination from 2 to
3.
Crystals of 3 were grown from a dichloromethane/pentane
solution at −60 °C, and its molecular structure was elucidated
by X-ray diffraction analysis. Accordingly, the Lewis acid GaCl3
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Scheme 2. Reaction of the Diphosphine-Hydrosilane Copper
Chloride Complex 2 with GaCl3 and X-ray Structure of the
Ensuing Complex 3
Scheme 3. Coordination of the Diphosphine-Hydrosilane 1
to Gold and X-ray Structure of the Ensuing Complex 4
a
a
a
a
Thermal ellipsoids are set at 50% probability; solvent molecules,
Thermal ellipsoids are set at 50% probability; solvent molecules,
phenyl substituents at phosphorus, and hydrogen atoms, except the
one at Si, are omitted for clarity.
phenyl substituents at phosphorus, and hydrogen atoms, except the
one at Si, are omitted for clarity.
gold complex 4 adopts a discrete ion pair structure [(1)-
Table 1. Selected Experimental Data for Ligand 1 and
Complexes 2−4
−
Au+,GaCl4 ] [shortest Au···Cl distance at 3.285(1) Å] with a
a
wide PAuP bite angle [159.92(4)°], but the silicon atom
remains far from gold. Indeed, the AuSi distance in 4 [3.166 (1)
Å] substantially exceeds the CuSi distances in 2 and 3
[2.997(1) and 2.815(1) Å, respectively], although the covalent
radii of gold and copper are very similar (1.36 and 1.32 Å,
respectively).22
The comparison of complexes 2, 3, and 4 provides further
support for the participation of the σ-SiH bond in the
coordination to copper, but not to gold. The bonding situation
in the gold complex 4 contrasts with the oxidative addition
process observed with the σ-SiSi bond and is in fact reminiscent
of that observed in the diphosphine-disilane silver complex.4 In
both cases, the metal center nicely accommodates quasi-linear
bis(phosphine)M+ arrangement. Comparatively, copper is more
Lewis acidic25 and the coordination of the pending σ-SiH or
SiSi bond is favorable. In addition, the fact that the silicon atom
remains remote from gold in complex 4 indicates that the
coordination of the σ-SiH bond to copper in complexes 2 and
3, although favored by the two phosphine anchors, is not
imposed geometrically.
Au+GaCl4
complex 4
−
free
ligand 1
CuCl
complex 2
CuClGaCl3
complex 3
δ
29Si
−23
20
−30
23
−30
23
−37
15
JPSi
1
δ H
1JSiH
5.48
204
2142
6.63
6.44
6.88
180
170
204
νSiH
1996
1973
2141
MSi
PMP
2.997(1)
115.66(2)
2.815(1)
120.13(2)
3.166(1)
159.92(4)
a
NMR chemical shifts in ppm, coupling constants in Hz, νSiH
stretching frequencies in cm−1 (IR), MSi distances in Å, and PMP
bond angles in deg (X-ray).
interacts strongly with the chloride at copper, but without
complete abstraction. The CuCl distance is significantly
elongated [CuCl = 2.359(1) Å in 3 vs 2.229(1) Å in 2], so
that complex 3 can be formally considered as a tight ion pair
[(1)Cu+···ClGaCl3 ]. Here also the silicon atom comes close to
−
copper, at an even shorter distance [CuSi = 2.815(1) Å] than in
complex 2. Since the overall geometry around copper in 3 is
otherwise similar to that of the CuCl complex 2 [trigonal-
planar arrangement, quasi-unchanged PCuP bite angle at
120.13(2)°], the shortening of the CuSi distance most likely
results from electronic rather than geometric factors. The
structural features of 3 are consistent with the spectroscopic
data and suggest indeed a slightly stronger coordination of the
σ-SiH bond upon decreasing the electron density at copper.
We have shown previously that the coordination of
diphosphine-disilane ligands proceeds very differently with
copper and gold: side-on coordination of the σ-SiSi bond was
observed with copper,4 while gold undergoes spontaneous
oxidative addition and forms bis(silyl) gold(III) complexes.5
This prompted us to investigate the influence of the metal
center on the coordination behavior of the diphosphine-
hydrosilane ligand. The gold complex 4 was prepared by
reacting 1 with AuCl(SMe2) and GaCl3 in dichloromethane at
low temperature (Scheme 3). The spectroscopic and crystallo-
graphic data for complex 4 markedly deviate from those of the
copper complexes 2 and 3 and reveal a rather different bonding
A detailed computational study was then carried out in order
to (i) further analyze the structural features of the diphosphine-
silane complexes, (ii) probe the influence of the electron
density at the metal center, and (iii) shed light on the nature of
the σ-SiH/metal interaction. DFT calculations were performed
at the same level of theory as that used previously,4,5,21,26 i.e.,
B3PW91/SDD+f(Cu,Au), 6-31G**(other atoms). The full
substitution pattern of the diphosphine-silane ligand was
retained in order to take reliably into account electronic and
steric factors.
The optimized structure of the CuCl complex 2* nicely
reproduces that determined crystallographically, with deviations
of only 0.03 Å in the CuSi distance and 7° in the PCuP bond
angle (Table 2). Most informative is the localization of the
hydrogen atom at silicon and the associated Si−H bond length.
Accordingly, the σ-SiH bond is predicted to slightly elongate
upon coordination, from 1.484 Å in the free ligand 1* to 1.499
Å in complex 2*.20 The meaningfulness of this variation is
corroborated by comparing copper and gold. Indeed, the σ-SiH
bond length computed for the gold complex 4* (1.481 Å) is
essentially identical to that of the free ligand (and the silicon
atom remains far away from gold at 3.269 Å). This confirms
that the side-on coordination of the σ-SiH bond to copper in
complex 2 is not a geometric artifact but really the result of a
bonding interaction. Besides these structural features, we also
1
situation in the gold complex. Indeed, the JSiH coupling
constant (204 Hz) and νSiH stretching frequency (2141 cm−1)
for 4 are the same as those of the free ligand 1, suggesting that
the σ-SiH bond does not interact with the metal in this case.
This is consistent with the molecular structure of 4 as
determined by single-crystal X-ray diffraction analysis. The
1
looked at spectroscopic data, in particular the JSiH coupling
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Organometallics
Article
of the σ-SiSi bond we reported previously. On the basis of steric
and orbital grounds, the formation of σ-complexes is a priori
less favorable with disilanes than with hydrosilanes,28 but it is
likely that geometric factors also play a role in our systems (the
σ-SiSi bond was included within the chelating ligand backbone,
while the σ-SiH bond is necessarily external).
Finally, as spontaneous oxidative addition of the σ-SiSi bond
had been observed at gold,4,9 we considered theoretically a
similar process with the σ-SiH bond of the copper complex 3*
and gold complex 4*. The structures of the corresponding
Cu(III) and Au(III) complexes were optimized, and oxidative
addition of the σ-SiH bond was found to be strongly disfavored
energetically in both cases (by 34.5 kcal/mol for 3* and 15.9
kcal/mol for 4*), in agreement with our experimental
observations. While σ-SiH coordination is stronger to Cu,
oxidative addition of the σ-SiH bond is easier for Au. This
contrast illustrates that Lewis acidity and a tendency to undergo
oxidative addition are two different aspects of chemistry that do
not necessarily show parallel trends.
Table 2. Selected Theoretical Data for Complexes 2*−5*
a
and Ligand 1*
Cu+
5*
AuGaCl4
‑
ligand
1*
CuCl
2*
CuClGaCl3
3*
4*
Si−H
M−H
M−Si
PMP
1JSiH
1.484
1.499
2.020
3.021
122.40
1.501
1.513
1.966
2.808
154.84
−143
1.481
1.987
2.721
2.972
3.269
128.41
−164.2
155.41
−201.1
−198.6 −176.4
ΔENBO (kcal/mol)
σSiH→
8.4
0.9
12.4
1.1
14.3
Lp*(M)
s(M)→σ*SiH
1.3
0.25
a
1
Bond lengths/distances in Å, bond angles in deg, JSiH coupling
constants in Hz, and NBO delocalization energies in kcal/mol.
1
constant. The values measured experimentally by H NMR for
complexes 2 and 4 as well as the free ligand 1 were nicely
reproduced theoretically using the GIAO method with the
IGLOO II basis set (maximum deviation of only 6 Hz; see
Tables 1 and 2).
This study provides evidence for the coordination of σ-SiH
bonds to copper. The diphosphine-hydrosilane 1 is shown
experimentally and computationally to engage in weak σ-SiH/
Cu interactions. The ensuing copper complexes 2 and 3 stand
as the first σ-SiH complexes involving a coinage metal. The σ-
SiH bond remains pendant in the corresponding gold complex
4. The spectroscopic and geometric features typically associated
with the coordination of σ-SiH bonds to transition metals
The next point was to assess how the electrophilicity of
copper affects its interaction with the σ-SiH bond. For that
purpose, DFT calculations were carried out on complex 3*,
featuring the tight Cu+GaCl4 ion pair structure, and on the
−
cationic complex 5*, featuring a naked copper center (without
counteranion contact).20 Here, the σ-SiH bond length was
found to increase from 1.499 Å in 2* to 1.513 Å in 5*, and
concomitantly, the CuSi distance shortens from 3.021 Å in 2*
to 2.808 Å in 5* (Table 1). It is interesting at this stage to
compare the geometric variations with the spectroscopic data.
A quasi-linear correlation was actually found between the σ-SiH
bond length and the 1JSiH coupling constant (see Figure S1′).27
The two extreme situations are met with the free ligand 1* on
one hand (dSiH = 1.484 Å, 1JSiH = −198.6 Hz) and the cationic
complex 5* one the other hand (dSiH = 1.513 Å, 1JSiH = −143.0
Hz). Although the interaction between the σ-SiH bond and the
copper center is weak in all copper complexes, the structural
and spectroscopic variations observed theoretically along the
series 2* → 3* → 5* clearly indicate a progressive
strengthening of the σ-SiH/Cu interaction upon increasing
the electrophilicity of copper, in agreement with the
experimental observations.
1
(decrease of the JSiH coupling constant and νSiH stretching
frequency, elongation of the SiH bond) are also met here with
copper, albeit with a substantially weaker magnitude. According
to DFT calculations, the coordination of the Si−H bond to
copper arises from weak σ-SiH→Cu donation, and Cu→σ*-
SiH back-donation is negligible. Consistently, the coordination
of the σ-SiH bond slightly strengthens when the electrophilicity
of copper is increased. Future work in our group will seek to
explore further the coordination and activation of σ-bonds at
the coinage metals, with and without chelating assistance.
ASSOCIATED CONTENT
■
S
* Supporting Information
Experimental and computational procedures, characterization,
and coordinates for the optimized structures 2*−5*. CCDC
910791 (2), 910792 (3), and 910793 (4). This material is
available free of charge via the Internet at http://pubs.acs.org.
We then examined in more detail the bonding situation in
complexes 2*−5* via natural bond orbital (NBO) analysis. At
the second-order perturbation level, donor−acceptor inter-
actions from the σ-SiH bond to the metal center were found in
all of the copper complexes 2*, 3*, and 5*, but not in the gold
complex 4*. The associated delocalization energies ΔENBO
increase from 8 kcal/mol in 2* to 12 kcal/mol in 3* and 14
kcal/mol in 5*, providing another confirmation of the gradual
strengthening of the interaction upon increasing the electro-
philicity of the copper center. The relative contributions of Si
and H in the involved σ-SiH bond orbital remain essentially the
same upon coordination and do not vary significantly with the
electron density at copper (36−41% for Si and 58−61% for H).
Noteworthily, only insignificant back-donation from copper to
σ*-SiH was found in 2*, 3*, and 5* (ΔENBO < 1.5 kcal/mol),
indicating that the coordination of the Si−H bond to copper
arises essentially, if not exclusively, from σ-SiH→Cu donation.
According to these NBO analyses, coordination of the σ-SiH
bond to copper is very similar in nature and magnitude to that
AUTHOR INFORMATION
■
Corresponding Author
*Fax: (+33) 5 61 55 82 04 (A.A., D.B.); (+33) 5 59 40 78 62
(K.M.). E-mail: amgoune@chimie.ups-tlse.fr; dbouriss@chimie.
ups-tlse.fr.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
Financial support from the Centre National de la Recherche
Scientifique, the Universite
́
de Toulouse, and the Agence
Nationale de la Recherche (ANR-10-BLAN-070901) is grate-
fully acknowledged. Part of the theoretical work was granted
access to HPC resources of Idris under allocation 2012
(i2012080045) made by GENCI (Grand Equipement National
de Calcul Intensif).
901
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Article
(a) Schubert, U.; Gilges, H. Organometallics 1996, 15, 2373.
(b) Gossage, R. A.; McLennan, G. D.; Stobart, S. R. Inorg. Chem.
1996, 35, 1729. (c) Montiel-Palma, V.; Munoz-Hernandez, M. A.;
Ayed, T.; Barthelat, J. C.; Grellier, M.; Vendier, L.; Sabo-Etienne, S.
Chem. Commun. 2007, 3963. (d) Montiel-Palma, V.; Piechaczyk, O.;
Picot, A.; Auffrant, A.; Vendier, L.; Le Floch, P.; Sabo-Etienne, S. Inorg.
Chem. 2008, 47, 8601.
(18) (a) MacInnis, M. C.; MacLean, D. F.; Lundgren, R. J.;
McDonald, R.; Turculet, L. Organometallics 2007, 26, 6522.
(b) MacLean, D. F.; McDonald, R.; Ferguson, M. J.; Caddell, A. J.;
Turculet, L. Chem. Commun. 2008, 5146. (c) Mitton, S. J.; McDonald,
R.; Turculet, L. Angew. Chem., Int. Ed. 2009, 48, 8568. (d) Mitton, S. J.;
McDonald, R.; Turculet, L. Organometallics 2009, 28, 5122.
(e) Morgan, E.; MacLean, D. F.; McDonald, R.; Turculet, L. J. Am.
Chem. Soc. 2009, 131, 14234. (f) Takaya, J.; Iwasawa, N. Organo-
metallics 2009, 28, 6636. (g) Takaya, J.; Iwasawa, N. J. Am. Chem. Soc.
2008, 130, 15254. (h) Takaya, J.; Iwasawa, N. Dalton Trans. 2011, 40,
8814. (i) Mitton, S. J.; Turculet, L. Chem.Eur. J. 2012, 18, 15258.
(j) Suh, H. W.; Schmeier, T. J.; Hazari, N.; Kemp, R. A.; Takase, M. A.
Organometallics 2012, 31, 8225.
(19) The coordination chemistry of related bis-quinolyl silane to
group 8−10 metals has been developed by Tilley and co-workers; see:
(a) Stradiotto, M.; Fujdala, K. L.; Tilley, T. D. Chem. Commun. 2001,
1200. (b) Sangtrirutnugul, P.; Stradiotto, M.; Tilley, T. D. Organo-
metallics 2006, 25, 1607. (c) Sangtrirutnugul, P.; Tilley, T. D.
Organometallics 2007, 26, 5557. (d) Sangtrirutnugul, P.; Tilley, T. D.
Organometallics 2008, 27, 2223. (e) Yang, J. A.; Del Rosal, I.; Fasulo,
M.; Sangtrirutnugul, P.; Maron, L.; Tilley, T. D. Organometallics 2010,
29, 5544. (f) Yang, J. A.; Fasulo, M.; Tilley, T. D. New J. Chem. 2010,
34, 2528.
REFERENCES
■
(1) For recent reviews, see: (a) “Coinage Metals in Organic
Synthesis” special issue, Chem. Rev., 2008, 108, issue 8. (b) Monnier,
F.; Taillefer, M. Angew. Chem., Int. Ed. 2009, 48, 6954.
(2) For recent reviews on coinage metal catalysis dealing with
mechanistic considerations and isolation of key intermediates, see:
(a) Hashmi, A. S. K. Angew. Chem., Int. Ed. 2010, 49, 5232.
(b) Raubenheimer, H. G.; Schmidbaur, H. Organometallics 2011, 31,
2507. (c) Liu, L. P.; Hammond, G. B. Chem. Soc. Rev. 2012, 41, 3129.
(d) Yoshikai, N.; Nakamura, E. Chem. Rev. 2011, 112, 2339.
(3) For a selection of important recent contributions on coordination
chemistry and reactivity of the coinage metals, see: (a) Casitas, A.;
King, A. E.; Parella, T.; Costas, M.; Stahl, S. S.; Ribas, X. Chem. Sci.
2010, 1, 326. (b) Casitas, A.; Poater, A.; Sola, M.; Stahl, S. S.; Costas,
M.; Ribas, X. Dalton Trans. 2010, 39, 10458. (c) Johnson, M. T.;
Marthinus Janse van Rensburg, J.; Axelsson, M.; Ahlquist, M. S. G.;
Wendt, O. F. Chem. Sci. 2011, 2, 2373. (d) Robinson, P. S. D.;
Khairallah, G. N.; da Silva, G.; Lioe, H.; O’Hair, R. A. J. Angew. Chem.,
Int. Ed. 2012, 51, 3812. (e) Tsui, E.; Muller, P.; Sadighi, J. P. Angew.
̈
Chem., Int. Ed. 2008, 47, 8937. (f) Laitar, D. S.; Tsui, E. Y.; Sadighi, J.
P. Organometallics 2006, 25, 2405. (g) Bachman, R. E.; Bodolosky-
Bettis, S. A.; Pyle, C. J.; Gray, M. A. J. Am. Chem. Soc. 2008, 130,
14303. (h) Rosa, D. A.; Smith, D. A.; Hughes, D. L.; Bochmann, M.
Angew. Chem., Int. Ed. 2012, 51, 10643.
(4) Gualco, P.; Amgoune, A.; Miqueu, K.; Ladeira, S.; Bourissou, D. J.
Am. Chem. Soc. 2011, 133, 4257.
(5) (a) Gualco, P.; Ladeira, S.; Miqueu, K.; Amgoune, A.; Bourissou,
D. Angew. Chem., Int. Ed. 2011, 50, 8320. (b) Gualco, P.; Ladeira, S.;
Miqueu, K.; Amgoune, A.; Bourissou, D. Organometallics 2012, 31,
6001.
(20) See Supporting Informations for details.
(6) Kubas, G. J. Metal Dihydrogen and σ-Bond Complexes; Kluwer
Academic/Plenum: New York, 2001.
(21) A similar high-field shift was observed upon coordination of a
related diphosphine-dimethysilane ligand to gold, without participa-
tion of the silane motif to the coordination; see: Gualco, P.; Mercy,
M.; Ladeira, S.; Coppel, Y.; Maron, L.; Amgoune, A.; Bourissou, D.
Chem.Eur. J. 2010, 16, 10808.
(7) Hartwig, J. F. Organotransition Metal Chemistry: From Bonding to
Catalysis; University Science Books: Sausalito, CA, 2009.
(8) (a) Corey, J. Y. Chem. Rev. 2011, 111, 863. (b) Nikonov, G. I.
Adv. Organomet. Chem. 2005, 53, 217. (c) Lachaize, S.; Sabo-Etienne,
S. Eur. J. Inorg. Chem. 2006, 2006, 2115. (d) Lin, Z. Chem. Soc. Rev.
2002, 31, 239. (e) Schubert, U. Adv. Organomet. Chem. 1990, 30, 151.
(9) Pandey, K. K. Coord. Chem. Rev. 2009, 253, 37.
(10) (a) Brookhart, M.; Green, M. L. H.; Parkin, G. Proc. Natl. Acad.
Sci. 2007, 104, 6908. (b) Bernskoetter, W. H.; Schauer, C. K.;
Goldberg, K. I.; Brookhart, M. Science 2009, 326, 553. (c) Pike, S. D.;
Thompson, A. L.; Algarra, A. G.; Apperley, D. C.; Macgregor, S. A.;
Weller, A. S. Science 2012, 337, 1648.
(11) (a) Brayshaw, S. K.; Sceats, E. L.; Green, J. C.; Weller, A. S. Proc.
Natl. Acad. Sci. 2007, 104, 6921. (b) Chaplin, A. B.; Green, J. C.;
Weller, A. S. J. Am. Chem. Soc. 2011, 133, 13162.
(12) (a) Chen, W.; Shimada, S.; Tanaka, M. Science 2002, 295, 308.
(b) Nikonov, G. I. Angew. Chem., Int. Ed. 2003, 42, 1335.
(13) The coordination of a σ-CH bond has been identified by pulse
electron resonance paramagnetic spectroscopy in a copper(II)
complex of a triazamacrocyclic ligand; see: Ribas, X.; Calle, C.;
Poater, A.; Casitas, A.; Gomez, L.; Xifra, R.; Parella, T.; Benet-
(22) Cordero, B.; Gomez, V.; Platero-Prats, A. E.; Reves, M.;
Echeverria, J.; Cremades, E.; Barragan, F.; Alvarez, S. Dalton Trans.
2008, 2832.
(23) Batsanov, S. S. Inorg. Mater. 2001, 37, 871.
(24) (a) Hieringer, W.; Eppinger, J.; Anwander, R.; Herrmann, W. A.
J. Am. Chem. Soc. 2000, 122, 11983. (b) Lein, M.; Harrison, J. A.;
Nielson, A. J. Dalton Trans. 2011, 40, 10731.
(25) Carvajal, M. A.; Novoa, J. J.; Alvarez, S. J. Am. Chem. Soc. 2004,
126, 1465.
(26) Gualco, P.; Lin, T. P.; Sircoglou, M.; Mercy, M.; Ladeira, S.;
̈
Bouhadir, G.; Perez, L. M.; Amgoune, A.; Maron, L.; Gabbaı, F. P.;
Bourissou, D. Angew. Chem., Int. Ed. 2009, 48, 9892.
(27) A V-type correlation was found between the σ-SiH bond length
1
and the JSiH coupling constant for cationic silane complexes of
ruthenium; see: Gutsulyak, D. V.; Vyboishchikov, S. F.; Nikonov, G. I.
J. Am. Chem. Soc. 2010, 132, 5950.
(28) Bercaw, J. E.; Labinger, J. A. Proc. Natl. Acad. Sci. 2007, 104,
6899.
Buchholz, J.; Schweiger, A.; Mitrikas, G.; Sola,
D. J. Am. Chem. Soc. 2010, 132, 12299.
̀
M.; Llobet, A.; Stack, T.
(14) The ability of coinage metals to activate σ-bonds has been
occasionally investigated computationally; see: (a) de Jong, G. T.;
Bickelhaupt, F. M. Can. J. Chem. 2009, 87, 806. (b) Lillo, V.; Fructos,
M. R.; Ramirez, J.; Braga, A. A. C.; Maseras, F.; Mar, D. R.; Perez, P. J.;
Fernandez, E. Chem.Eur. J. 2007, 13, 2614. (c) Corral, I.; Mo,
́
O.;
Yanez, M. Int. J. Mass Spectrom. 2003, 227, 401.
́
̃
(15) (a) Rendler, S.; Oestreich, M. Angew. Chem., Int. Ed. 2007, 46,
498. (b) Diez-Gonzalez, S.; Nolan, S. P. Acc. Chem. Res. 2008, 41, 349.
(16) (a) Amgoune, A.; Bourissou, D. Chem. Commun. 2011, 47, 859.
(b) Bouhadir, G.; Amgoune, A.; Bourissou, D. Adv. Organomet. Chem.
2010, 58, 1.
̀
(17) U. Schubert, S. R. Stobart, and S. Sabo-Etienne have used
previously a similar strategy and studied the coordination of
phosphine- and diphosphine-hydrosilanes to W, Ru, Ir, and Pt. See:
902
dx.doi.org/10.1021/om301211c | Organometallics 2013, 32, 898−902