Hypervalent silicon compounds by coordination of diphosphine-silanes to gold

Article abstract of DOI:10.1002/chem.201001281

Coordination of ambiphilic diphosphine-silane ligands [o-(iPr ₂P)C₆H₄]₂Si(R)F (R = F, Ph, Me) to AuCl affords pentacoordinate neutral silicon compounds in which the metal atom acts as a Lewis base. X-ray diffraction analyses, NMR spectroscopy, and DFT calculations substantiate the presence of Au → Si interactions in these complexes, which result in trigonal-bipyramidal geometries around silicon. The presence of a single electronwithdrawing fluorine atom is sufficient to observe coordination of the silane as a σ-acceptor ligand, provided it is positioned trans to gold. The nature of the second substituent at silicon (R = F, Ph, Me) has very little influence on the magnitude of the Au → Si interaction, in marked contrast to N→ Si adducts. According to variable-temperature and 2D EXSYNMR experiments, the apical/equatorial positions around silicon exchange in the slow regime of the NMR timescale. The two forms, with the fluorine atom in trans or cis position to gold, were characterized spectroscopically and the activation barrier for their interconversion was estimated. The bonding and relative stability of the two isomeric structures were assessed by DFT calculations.

Full text of DOI:10.1002/chem.201001281

DOI: 10.1002/chem.201001281
Hypervalent Silicon Compounds by Coordination of Diphosphine–Silanes
to Gold
Pauline Gualco,[a] Maxime Mercy,[b] Sonia Ladeira,[c] Yannick Coppel,[d]
Laurent Maron,*[b] Abderrahmane Amgoune,*[a] and Didier Bourissou*[a]
Abstract: Coordination of ambiphilic
diphosphine–silane ligands [o-
to observe coordination of the silane as
a s-acceptor ligand, provided it is posi-
tioned trans to gold. The nature of the
second substituent at silicon (R=F, Ph,
Me) has very little influence on the
magnitude of the Au!Si interaction,
in marked contrast to N!Si adducts.
According to variable-temperature and
2D EXSY NMR experiments, the
apical/equatorial positions around sili-
con exchange in the slow regime of the
NMR timescale. The two forms, with
the fluorine atom in trans or cis posi-
tion to gold, were characterized spec-
troscopically and the activation barrier
for their interconversion was estimated.
The bonding and relative stability of
the two isomeric structures were as-
sessed by DFT calculations.
(iPr2P)C6H4]2Si(R)F (R=F, Ph, Me) to
AuCl affords pentacoordinate neutral
silicon compounds in which the metal
atom acts as a Lewis base. X-ray dif-
fraction analyses, NMR spectroscopy,
and DFT calculations substantiate the
presence of Au!Si interactions in
these complexes, which result in trigo-
nal-bipyramidal geometries around sili-
con. The presence of a single electron-
withdrawing fluorine atom is sufficient
Keywords: gold · hypervalent com-
pounds · sigma-acceptor ligands ·
silicon · substituent effects
Introduction
tion-metal complexes of boranes, alanes, and gallanes have
given more insight into unusual M!ER3 interactions (E=
B, Al, Ga).[2–3] Here, the combination of donor and acceptor
moieties within the same ligand architecture, so-called ambi-
philic ligands, proved particularly efficient. This approach
provides straightforward access to complexes featuring coor-
dinated Lewis acids, and the geometric constraints can be
largely modulated by varying the number of donor buttress-
es and the nature of the spacers between the donor and ac-
ceptor sites.[4]
The ability of Lewis acids to act as s-acceptor ligands[1] has
attracted growing interest over the past decade. The increas-
ing number and variety of structurally authenticated transi-
[a] P. Gualco, Dr. A. Amgoune, Dr. D. Bourissou
University of Toulouse, UPS, LHFA
CNRS, LHFA UMR 5069, 118 route de Narbonne
31062 Toulouse (France)
The scope of s-acceptor ligands nowadays appears signifi-
cantly broader than initially believed, and a great variety of
complexes are in fact susceptible to such metal!Lewis acid
interactions.[5] To assess to which extent the Lewis acidity of
the s-acceptor site can be decreased while retaining substan-
tial interaction with the metal, we recently became interest-
ed in the coordination of saturated compounds of heavier
Group 14 elements ER4 (E=Si, Sn, …) to transition metals.
The targeted metal!ER4 interactions would arise from
donation of an occupied d orbital at the metal to a vacant
low-lying s* orbital centered at silicon or tin. Pentacoordi-
nate adducts of silanes and stannanes have been well docu-
mented with organic Lewis bases (N, O, S, …) in both intra-
and intermolecular versions,[6] but related adducts with a
transition metal acting as a Lewis base have scarcely been
Fax : (+33)5-6155-8204
E-mail: amgoune@chimie.ups-tlse.fr
dbouriss@chimie.ups-tlse.fr
[b] Dr. M. Mercy, Dr. L. Maron
University of Toulouse, INSA, UPS, LPCNO
CNRS, LPCNO UMR 5215, 135 avenue de Rangueil
31077 Toulouse (France)
Fax : (+33)5-6155-9697
E-mail: laurent.maron@irsamc.ups-tlse.fr
[c] S. Ladeira
Structure Fꢀdꢀrative Toulousaine en Chimie Molꢀculaire, FR 2599
118 route de Narbonne, 31062 Toulouse cedex 9 (France)
[d] Dr. Y. Coppel
Laboratoire de Chimie de Coordination, UPR8241 CNRS
205 route de Narbonne, 31077 Toulouse (France)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201001281.
10808
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 10808 – 10817

FULL PAPER
studied. Grobe and co-workers prepared nickel and palladi-
Results and Discussion
um cage complexes of type A,[7] but X-ray diffraction analy-
ꢀ
ses revealed long M Si distances and tetrahedral geometries
Diphosphine–silane ligands 1–3 were prepared by treating
two equivalents of o-lithiated diisopropylphenylphosphine
with the trichlorosilane RSiCl3 (R=Ph, Cl, Me) in toluene
at ꢀ788C, and then with HF·collidine (collidine=2,4,6-tri-
methylpyridine) to achieve chlorine to fluorine exchange.
The desired complexes 4–6 were obtained as analytically
pure, white solids (ca. 88% yield) by treating 1–3 with
around silicon, suggesting little, if any, M!Si interaction. In
addition, the existence of donor–acceptor M!Si and M!
Sn interactions has been invoked in silicon- and tin-bridged
[1]ferrocenophanes B[8] as well as in silacyclotriyne nickel
complexes C,[9] in which relatively short M Si distances are
imposed geometrically.
ꢀ
[AuCl
N
Scheme 1. Synthesis and coordination of diphosphine–silane ligands 1–3.
Recently, the ability of silanes and stannanes to behave as
s-acceptor ligands towards electron-rich transition metals
was unambiguously substantiated by two independent stud-
ies. Wagler et al. isolated complexes of type I on reaction of
tetramethimazolylsilanes and -stannanes with MCl2 precur-
sors (M=Pd or Pt).[10] Coordination is accompanied by the
shift of a chlorine atom from the metal to the Group 14 ele-
ment, and the transannular M!E (E=Si, Sn) interaction is
supported by four methimazolyl buttresses, resulting in a
lanternlike structure. Starting from diphosphine–silanes and
stannanes, we prepared gold complexes of general formula
II.[11] Here, the Au!E (E=Si, Sn) interaction is supported
by only two phosphorus buttresses, and the heavier
Group 14 element adopts a trigonal-bipyramidal arrange-
ment. These preliminary results prompted us to explore the
influence of the substitution pattern at silicon on the coordi-
nation of silanes as s-acceptor ligands, and here we report a
comprehensive study on a series of diphosphine–silane gold
complexes [({o-(iPr2P)C6H4}2Si(R)X)AuCl] (R=F, Ph, Me,
X=F, Me). The presence and magnitude of the Au!Si in-
teraction were assessed spectroscopically, structurally and
theoretically.
Complex 4 was shown by X-ray diffraction analysis to fea-
ture an unusual Au!Si interaction, as discussed in a pre-
liminary report.[11] The most diagnostic features are the
ꢀ
short Au Si distance of 3.090(2) ꢂ, a geometry around the
silicon center that only deviates slightly from trigonal-bipyr-
ꢀ
amidal, and the noticeable elongation of the Si F bond
(from 1.599(7) ꢂ in free ligand 1 to 1.635(3) ꢂ in complex
4). The pentacoordinate character of silicon in 4 was also
apparent from NMR spectroscopic studies. In the solid state,
the 29Si NMR signal is shifted upfield on coordination, from
d=ꢀ5 ppm in 1 to ꢀ23 ppm in complex 4. Surprisingly, 19F,
31P, and 29Si NMR analyses indicated the presence of two
species in 60/40 ratio when the crystals of 4 were dissolved
in CDCl3. Based on the similarity of the 29Si NMR chemical
shifts, the major compound in solution (d=ꢀ21.4 ppm) was
assigned to the structure observed in the solid state, with the
fluorine atom trans to gold (4trans). The 29Si NMR chemical
shift of the minor product (d=ꢀ3.9 ppm) differs significant-
ly from that of 4trans, and is found in the same region as that
of the free ligand. This suggests that the Au!Si interaction,
if still present, is significantly weaker in this form. Another
conspicuous feature of the minor species is the presence of a
substantial P–F coupling constant (22.5 Hz). All these data
are consistent with the minor species corresponding to the
cis form 4cis in which the fluorine atom is cis to gold
(Scheme 2).
Scheme 2. Interconversion of the two isomeric forms 4trans (major) and 4cis
(minor) in solution.
Chem. Eur. J. 2010, 16, 10808 – 10817
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
10809

L. Maron, A. Amgoune, D. Bourissou et al.
Variable-temperature 19F and 31P NMR studies were car-
ried out to gain more insight into the interconversion of
4trans and 4cis in solution. The ratio between the two isomeric
forms does not vary significantly from ꢀ20 to 608C, but dy-
namic exchange between 4trans and 4cis was apparent from
broadening of the signals upon heating. However, decompo-
sition occurred before coalescence, and as a result the acti-
vation barrier could not be readily estimated by using a
modified Eyring equation.[12] We thus turned to 2D
EXSY NMR experiments[13,14] to further substantiate the
isomerization process around silicon, and to estimate the as-
sociated activation barrier. The cross-peaks observed be-
tween the resonance signals in the 2D 31P{1H} EXSY NMR
spectrum (Figure 1) unambiguously indicate the presence of
Figure 2. Optimized geometries of the two isomeric forms 4trans (left) and
4cis (right).
Table 1. Geometric data (bond lengths [ꢂ] and angles [8]) determined
crystallographically for complex 4trans and optimized computationally for
actual complexes 4cis* and 4trans*.
4trans XRD
4trans* DFT
4cis* DFT
ꢀ
Au Si
ꢀ
Si F
3.089(13)
1.635(3)
1.880(5)
166.11(12)
353.4(6)
3.131
1.663
1.890
171.86
356.86
3.452
1.634
1.892
144.08
341.33
ꢀ
Si CPh
Au-Si-Xap
ꢀSiabasal
consistent with the 29Si NMR data and further supports
weakening or even annihilation of the Au!Si interaction
from 4trans to 4cis.
The presence and magnitude of Au!Si interactions in
the two isomeric forms of complex 4 were assessed by natu-
ral bond orbital (NBO) and atom in molecules (AIM) anal-
yses. At the second-order perturbation level, a donor–ac-
ceptor interaction from gold to silicon was found in 4trans
*
Figure 1. Contour plot of the 2D 31P{1H} EXSY NMR spectrum recorded
for complex 4 at 277 K in CDCl3 with a mixing time tm =300 ms.
with
a
delocalization energy DENBO of 7.6 kcalmolꢀ1
(Figure 3). In addition, the AIM electron density map of
dynamic exchange between the two species. The rate con-
stant associated with the exchange process was calculated
from the intensities of the cross-peaks according to the
method of Perrin, Dwyer, and Gipe.[13,15] Accordingly, the
activation barrier for the interconversion between 4trans and
4cis was estimated to be 14.9 kcalmolꢀ1 at 277 K.
To gain some insight into the structure of 4cis, DFT calcu-
lations were carried out at the B3PW91/SDDACHTUNGTRENN(UNG Au,P,Cl), 6-
31G**(Si,F,C,H) level of theory. In agreement with the ex-
ACHTUNGTRENNUNG
perimental observations, two minima associated with the
two arrangements around silicon were located at about the
same energy on the potential surface (DG=2.4 kcalmolꢀ1 in
favor of 4trans* at 258C; Figure 2).
Figure 3. Molekel plots for the donor NBO (left) and acceptor NBO
(right) associated with the Au!Si interaction in 4trans
.
The optimized structure of 4trans* nicely reproduces that
determined crystallographically (Table 1). The geometric
data computed for the cis isomer 4cis* differ significantly
4
trans* shows the presence of a bond path between Au and Si
with an electron density 1(r) of 2.13ꢃ10ꢀ2 ebohrꢀ3 at the
bond critical point (BCP). None of these features are ob-
served for the isomer 4cis*, that is, significant Au!Si inter-
action is absent in this form.
ꢀ
from those of 4trans*: the Au Si distance is much longer
(3.45 ꢂ in 4cis* vs. 3.13 ꢂ 4trans*) and the geometry around
the silicon center tends to tetrahedral rather than trigonal-
bipyramidal (SSiabasal =341.38 and Au-Si-CPh 144.18 in 4cis*
vs. SSiabasal =356.98 and Au-Si-F 171.98 in 4trans*). This is
Comparison of the bonding situation in 4trans and 4cis sub-
stantiates the key role of the fluorine atom in the formation
10810
www.chemeurj.org
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 10808 – 10817

Hypervalent Silicon Compounds
FULL PAPER
of the Au!Si interaction, and draws some parallel with that
known for neutral pentacoordinate adducts of silanes with
organic bases. The s*SiF orbital is substantially lower in
energy than the s*SiPh orbital. Consequently, coordination of
the silane moiety as a s-acceptor ligand is more favorable
when the fluorine atom, rather than the phenyl group, is
trans to gold (4trans rather than 4cis). These results also point
out that the presence of the Au!Si interaction in 4trans, al-
though supported by the two phosphorus buttresses, is not
geometrically imposed by the structure of the ligand, since
the silicon center moves away when the relative positions of
the phenyl group and fluorine atom at silicon are ex-
changed.
To further investigate the influence of the substituents at
silicon on the magnitude of metal!silane interactions, we
then replaced the phenyl group by another electron-with-
drawing fluorine atom. The solid-state structure of the ensu-
ing complex 5 was elucidated by X-ray diffraction analysis
(Figure 4). The silicon atom comes close to the metal center.
other fluorine atom, referred to as Feq, sits in the equatorial
ꢀ
plane, cis to gold (Feq-Si-Au 66.62(7)8). The apical Si F
ꢀ
bond (Si Fap 1.612(2) ꢂ) is slightly elongated compared to
ꢀ
the equatorial one (Si Feq 1.588(2) ꢂ), in line with what is
typically observed in difluorosilane adducts with organic
bases.[18]
According to multinuclear NMR analyses, the Au!Si in-
teraction is also present in solution. The 29Si NMR chemical
shift for 5 (d=ꢀ37.3 ppm) falls in the same range as those
reported for pentacoordinate difluoroACTHNUTRGNE(NUG diaryl)silicon deriva-
tives featuring an intramolecular N!Si bond.[18a] The modi-
fication of the geometry around silicon upon coordination is
also apparent from the 19F NMR data. A single signal was
observed at d=ꢀ131.1 ppm for free ligand 2, but the two
fluorine atoms are magnetically inequivalent in complex 5
2
(d=ꢀ108.1 and ꢀ125.4 ppm, J
(F,F)=26 Hz). The 19F NMR
ACHTUNGTRENNUNG
chemical shifts observed for 4cis (d=ꢀ114.9 ppm) and 4trans
(d=ꢀ135.8 ppm) support the following assignment for 5:
ꢀ108.1 ppm (Feq) and ꢀ125.4 ppm (Fap). Accordingly, only
the fluorine atom in cis position to gold would exhibit a J-
ꢀ
The Au Si distance (3.108(1) ꢂ) is in between the sum of
the covalent radii (2.47 ꢂ)[16] and the sum of van der Waals
radii (4.20 ꢂ),[17] and actually very similar to that of 4. The
presence of a gold!silane interaction in 5 is further sup-
ported by the slightly distorted trigonal-bipyramidal geome-
try around silicon (SSiabasal =352.68). As a result, the two
fluorine atoms become inequivalent. One fluorine atom, re-
ferred to as Fap, occupies an apical position and is located
approximately trans to gold (Fap-Si-Au 164.38(8)8), while the
ACHTUNGTREN(NUNG P,F) coupling constant (14.7 Hz), in line with that observed
ꢀ
for 4cis/4trans. The elongation of the Si Fap bond as a result of
d(Au)!s*(SiFap) donation is probably responsible for the
AHCTUNGTRENNUNG
absence of P–F coupling for the fluorine atom trans to gold.
The assignment of the 19F NMR resonance signals of 5 was
further confirmed by solid-state 2D HETCOR 31P-19F NMR
spectroscopy. Here, the intensities of the cross-peaks due to
31P–19F dipolar coupling are directly related to the spatial
proximity between the nuclei. For complex 5, cross-peaks
were observed for both 19F NMR signals, with significantly
higher intensity for that at ꢀ108.1 ppm.[19] This nicely agrees
ꢀ
with the shorter distances observed in the solid state for P
ꢀ
Feq (3.556 and 3.649 ꢂ) versus P Fap (4.882 and 4.979 ꢂ). In
addition, variable-temperature 19F NMR experiments re-
vealed dynamic exchange of Fap and Feq in solution. The ex-
change proceeds in the slow regime of the NMR timescale
up to temperatures at which decomposition occurs. The cor-
responding activation barrier, as estimated by 2D 19F
EXSY NMR spectroscopy (DG° =14.0 kcalmolꢀ1 at 283 K),
is slightly lower than that determined for interconversion
between 4cis and 4trans
.
Density functional theory (DFT) calculations were carried
out on complex 5* to shed more light into the Au!Si inter-
action. The optimized structure of 5* nicely matches that de-
termined experimentally for 5 (Figure 4), and NBO and
AIM analyses further confirmed the presence of the Au!Si
donor–acceptor interaction. The corresponding delocaliza-
tion energy (DENBO =8.1 kcalmolꢀ1) and electron density
1(r) at the BCP (2.34ꢃ10ꢀ2 ebohrꢀ3) were found to be only
slightly higher than those of 4trans, in agreement with the geo-
metric data.
The structure of complex 5 confirms the propensity of di-
phosphine–silane ligands to engage in Au!Si interaction,
and suggests that the silicon substituent in the equatorial po-
sition has minimal influence on the magnitude of the inter-
action. This behavior is in marked contrast with that of ni-
trogen adducts of fluorosilanes. Indeed, the strength of in-
Figure 4. Top: Molecular view of 5 in the solid state (thermal ellipsoids
ꢀ
set at 30% probability). Selected bond lengths [ꢂ] and angles [8]: Au Cl
ꢀ
ꢀ
ꢀ
2.600(1), Si Feq 1.588(2), Si Fap 1.612(2), Au Si 3.108(1); P1-Au-P2
153.28(3), Cl-Au-Si 140.85(3), Au-Si-Fap 164.38(8). Bottom: Optimized
structure of 5*. In both cases, hydrogen atoms are omitted for clarity.
Chem. Eur. J. 2010, 16, 10808 – 10817
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
10811

L. Maron, A. Amgoune, D. Bourissou et al.
tramolecular N!Si interactions typically increases with the
number of fluorine atoms at silicon (SiFPh2 <SiF2Ph<SiF3),
ly, was also found as a minimum on the potential-energy sur-
face, about 4.1 kcalmolꢀ1 higher in energy than 6trans
*
as apparent from a significant shortening of the correspond-
(Figure 6). Similar to 4cis*, the geometric features computed
[18a]
ꢀ
ing N Si bond lengths.
To further assess the influence of the silicon substituents
on the magnitude of the Au!Si interaction, complex 6 fea-
turing a fluorine atom and a methyl group at silicon was
then investigated. As previously observed, the coordination
of the silane as a s-acceptor ligand was unambiguously es-
ꢀ
tablished by X-ray diffraction analysis (Figure 5). The Au Si
Figure 5. Molecular view of 6 in the solid state (thermal ellipsoids set at
50% probability and hydrogen atoms omitted for clarity). Selected bond
ꢀ
ꢀ
ꢀ
lengths [ꢂ] and angles [8]: Au Cl 2.627(3), Si F 1.639(7), Si C1
ꢀ
1.873(11), Au Si 3.089(3); P1-Au-P2 151.55(9), Cl-Au-Si 136.19(10), Au-
Si-F 168.5(3).
Figure 6. Optimized geometries of the two isomeric forms 6trans (top) and
6cis (bottom).
distance is short (3.089(3) ꢂ) and the environment around
silicon
tends
to
trigonal-bipyramidal
(SACTHNGUTERN(UNG C-Si-C)=
354.20(15)8). The fluorine atom occupies an apical position
trans to gold (F-Si-Au 168.5(3)8), while the methyl group
sits in the equatorial plane. Similarly to 4, complex 6 adopts
the 6trans form in the solid state. However, 6trans is the only
species observed in solution in this case. The 29Si NMR
signal is shifted upfield by 16.5 ppm on coordination (from
d=6.0 ppm in the free ligand 3 to d=ꢀ10.5 ppm in 6trans),
for 6cis* substantiate the remoteness of the silicon atom
ꢀ
from the gold center (the Au Si distance is 3.425 ꢂ and the
environment around silicon tends to tetrahedral with SSia =
342.58). Furthermore, while the presence of an Au!Si inter-
action with similar magnitude to those of complexes 4trans
and
5 was confirmed for 6trans by NBO (DENBO =
6.0 kcalmolꢀ1) and AIM analyses (1(r)=1.89ꢃ10ꢀ2 ebohrꢀ3
at the bond critical point), such donor–acceptor interaction
was not observed for 6cis*.
and the 19F NMR resonance appears as a singlet (no J
coupling constant) at d=ꢀ141.5 ppm.
ACHTUNGTNER(NUNG P,F)
DFT calculations were carried out on this complex as well
to gain insight into the other conceivable form 6cis* (featur-
ing the fluorine atom in cis position to gold) and to compare
the bonding situations in the two isomers. The optimized ge-
ometry of 6trans* fits closely with that determined experimen-
tally (Table 2). The 6cis* isomer, not observed experimental-
These results further confirm that the nature of the equa-
torial substituent at silicon has little, if any, influence on the
magnitude of the Au!Si interaction in diphosphine–silane
gold complexes such as 4, 5, and 6. A single electron-with-
drawing fluorine atom at silicon is enough to observe coor-
dination of the silane as a s-acceptor ligand, but its position
plays a key role. Significant Au!Si interaction is only ob-
served when the fluorine atom is positioned trans to the
donor gold center and thus optimizes the overlap between
the low-lying accepting orbital centered at silicon (s*SiF) and
the occupied donating d orbital at gold.
Table 2. Geometric data (bond lengths [ꢂ] and angles [8]) determined
crystallographically and optimized computationally for complex 6.
6trans XRD
6trans* DFT
6cis* DFT
Finally, to confirm the necessity of an electron-withdraw-
ing substituent to observe the coordination of the silane
moiety as a s-acceptor ligand, we sought to prepare and
characterize a complex without fluorine at silicon. Diphos-
phine–silane ligand 7, featuring two methyl substituents, was
ꢀ
Au Si
ꢀ
Si F
3.089(3)
1.639(7)
1.873(11)
168.5(3)
354.20(15)
3.061
1.703
1.893
170.54
357.57
3.425
1.665
1.893
156.65
342.47
ꢀ
Si CMe
Au-Si-Xap
ꢀSiabasal
10812
www.chemeurj.org
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 10808 – 10817

Hypervalent Silicon Compounds
FULL PAPER
prepared and coordinated to gold under similar conditions
to the related fluorinated systems (Scheme 3).
cal calculations. The key geometric features determined
crystallographically were nicely reproduced computationally,
and no sign of significant Au!Si interaction was found by
NBO and AIM analyses.
Conclusion
Diphosphine–silane gold complexes 4–6 have been shown
experimentally and theoretically to feature donor–acceptor
Au!Si interactions. This study provides a comprehensive
picture of the factors influencing the formation of penta-
coordinate silicon derivatives in which a metal center acts as
a Lewis base. In this series, the presence of a single elec-
tron-withdrawing fluorine atom is enough to observe coordi-
nation of the silane as a s-acceptor ligand. The nature of the
second substituent at silicon (R=F, Ph, Me) has very little
influence on the magnitude of the Au!Si interaction, in
marked contrast with that observed for related N!Si ad-
ducts.
The apical/equatorial positions around silicon were found
to exchange in the slow regime of the NMR timescale, and
the two isomeric forms of complex 4, with the fluorine atom
in trans or cis position to gold, were characterized spectro-
scopically.
Scheme 3. Synthesis and coordination of diphosphine–silane ligand 7.
Colorless crystals of complex 8 were obtained at ꢀ308C
from dichloromethane/pentane, and an X-ray diffraction
analysis was carried out (Figure 7). In contrast to complexes
ꢀ
4–6, the solid-state structure of 8 exhibits a long Au Si dis-
tance (3.345(1) ꢂ), and the geometry around silicon remains
essentially tetrahedral. The 29Si NMR resonance signal is
only slightly shifted upon coordination (from d=ꢀ7.0 ppm
in free ligand 7 to d=ꢀ12.4 ppm in complex 8), and falls in
the same range as that observed in 4cis. Moreover, the two
methyl substituents at silicon remain magnetically equiva-
1
lent in complex 8 (both in H and 13C NMR). All of these
experimental data indicate that the silane moiety of 7 does
not participate in coordination. The absence of Au!Si in-
teraction in complex 8 was further substantiated by theoreti-
These results extend the concept of s-acceptor ligands
beyond highly electron deficient moieties (such as Group 13
Lewis acids), and further increase the variety of bonding sit-
uations achievable with heavier Group 14 elements. Spectac-
ular developments have been reported over the last decade
[20]
[21]
ꢀ
ꢀ
for complexes featuring side-on Si H
and Si Si
s
bonds, strongly donating SiR3 groups,[22] and M Si double-
and triple-bond character.23] Coordination of silanes as s-ac-
ceptor ligands offers a further possibility. The variety of
complexes prepared in the past few years from the same di-
phosphine–silane ligand architecture [o-(R2P)C6H4]2SiR’R’’
nicely illustrates this versatility (Scheme 4).[24]
ꢀ
Scheme 4. Schematic representation of the various types of complexes
prepared from diphosphine–silane ligands featuring o-phenylene back-
bones.
Figure 7. Top: molecular view of 8 in the solid state (thermal ellipsoids
ꢀ
set at 50% probability). Selected bond lengths [ꢂ] and angles [8]: Au Cl
ꢀ
ꢀ
ꢀ
2.691(9), Si C1 1.895(4), Si C2 1.877(4), Au Si 3.345(1); P1-Au-P2
148.33(3)8; Cl-Au-Si 136.15 (3)8; Au-Si-C1 164.52(14)8. Bottom: opti-
mized structure of 8*. In both cases, hydrogen atoms are omitted for
clarity.
Chem. Eur. J. 2010, 16, 10808 – 10817
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
10813

L. Maron, A. Amgoune, D. Bourissou et al.
stored at ꢀ308C overnight. 2 was isolated as a white powder (393 mg,
48% yield). Colorless crystals suitable for X-ray crystallography were ob-
tained from pentane solution at ꢀ308C (see Figure S2, Supporting Infor-
Experimental Section
All reactions and manipulations were carried out under an atmosphere
of dry argon by using standard Schlenk techniques. Dry, oxygen-free sol-
vents were employed. Solid-state 1H, 13C, 31P, 19F, 29Si and 2D HETCOR
31P, 19F NMR spectra were recorded on a Bruker Avance 400WB spec-
mation). 31P{1H} NMR (C6D6, 202.5 MHz, 298 K): d=5.9 (t, 4J
ACHTUNGTRENNUNG
48 Hz); 29Si NMR (C6D6, 99.4 MHz, 298 K): d=ꢀ33.1 (t, 1J
ACHTUNGTRENNUNG
1
288 Hz); 19F{1H} NMR (C6D6, 282.5 MHz, 298 K): d=ꢀ131.1 (t, J
ACHTUNGTRENNUNG(F,Si)=
ACTHNUTRGNEUNG
288 Hz, 4J(F,P)=48 Hz); 1H NMR (C6D6, 500 MHz; 298 K): d=8.41 (d,
trometer. Solution H, 13C, 31P, 19F, 29Si, 31P, and 19F 2D EXSY NMR spec-
1
3J
(m, 2H; Harom), 7.14 (m, 2H; Harom), 1.83 (sept d, 2J
3J(H,H)=7.0 Hz, 4H; CHCH3), 1.00 (dd, 3J(H,P)=14.3 Hz, 3J
7.0 Hz, 12H; CHCH3), 0.71 (dd, 3J(H,P)=12.3 Hz, 3J
(H,H)=7.0 Hz,
(H,H)=7.4 Hz, 2H; Harom), 7.26 (d, 3J
ACHUTGTNRENNUG CAHTUNGTRENNUNG
tra were recorded on Bruker Avance 300, 400, or 500 spectrometers.
AHCTUNGTRENNUNG
1
Chemical shifts are expressed in parts per million, relative to residual H
A
R
ACHTUNGTRENNUNG
and 13C solvent signals, 80% H3PO4, CFCl3, or SiMe4. The N values cor-
A
ACHTUNGTRENNUNG
responding to 1= [J(AX)+J
ACTHUNTGRENNG(U A’X)] are provided when second-order
12H; CHCH3); 13C{1H} NMR (C6D6, 125.8 MHz, 301 K): d=144.3 (d,
2
AA’X systems are observed in the 13C NMR spectra.[25] Mass spectra
were recorded on a Waters LCT apparatus. o-Lithiated diisopropylphe-
nylphosphine was prepared by a previously described procedure.[4g] SiCl4
and Me2SiCl2 were purchased from Aldrich and distilled before use.
MeSiCl3 (anhydrous beads, 97%) and PhSiCl3 (anhydrous beads, 97%)
were purchased from Aldrich and used as received. 2,4,6-Trimethylpyridi-
ne·2HF (HF·collidine) was purchased from Alfa Aesar and used as re-
ceived.
2J
4J
U
(C,P)=48.0 Hz, 2J
ACHUTGTNRENNUG ACHUTTGNREN(NUGN C,F)=16.1 Hz,
A
CHCH3), 20.2 (d, 2J(C,P)=17.8 Hz; CHCH3), 20.1 (d, 2J
ACTHNUGTRENNUGN ACHTUNGTRENNNUG
CHCH3); HRMS (ESI+) calcd for [M+H]+ =C24H37P2F2Si+: 453.2133,
found: 453.2108.
Synthesis of 3: A solution of SiMeCl3 (137 mL, 1.17 mmol) in toluene
(5 mL) was added dropwise to a solution of o-lithiated diisopropylphe-
nylphosphine (621 mg, 2.46 mmol) in toluene (5 mL) at ꢀ788C. The solu-
tion was allowed to warm slowly to room temperature during 4 h, after
which the volatile substances were removed under vacuum. Then the
ligand was extracted from the salts with dichloromethane (10 mL). A so-
lution of HF·collidine (91 mg, 1.17 mmol) in dichloromethane (5 mL) was
added to a solution of the above product in dichloromethane (10 mL) at
room temperature, and the mixture was allowed to stir for 30 min. Then,
the solution was pumped to dryness, and the residue was extracted with
n-pentane (3ꢃ5 mL). The filtrate was concentrated to 5 mL and stored at
ꢀ308C overnight. 3 was isolated as a white powder (173 mg, 33% yield).
Synthesis of diphosphine–silane 1:
A solution of SiPhCl3 (186 mL,
1.16 mmol) in toluene (5 mL) was added dropwise to a solution of o-lithi-
ated diisopropylphenylphosphine (616 mg, 2.44 mmol) in toluene (5 mL)
at ꢀ788C. The solution was allowed to warm slowly to room temperature
over 4 h, after which the volatile substances were removed under
vacuum, and the product was extracted from the salts with dichlorome-
thane (10 mL) and directly used in the second-step reaction. A solution
of HF·collidine (90 mg, 1.16 mmol) in dichloromethane (5 mL) was
added to the product in dichloromethane (10 mL) at room temperature,
and the mixture was allowed to stir for 30 min. Then, the solution was
pumped to dryness and the residue extracted with n-pentane (3ꢃ5 mL).
The filtrate was concentrated to 5 mL, stored at ꢀ308C overnight, and
the resulting white precipitate washed with pentane (2ꢃ1 mL). 1 was iso-
lated as a white powder (216.5 mg, 37% yield). 31P{1H} NMR (CDCl3,
31P{1H} NMR (CDCl3, 202.5 MHz, 298 K): d=2.8 (d, 4J
ACHTUNGTRENNUNG
29Si NMR (CDCl3, 99.4 MHz, 298 K): d=6.0 (d, 1J
ACHTUNGTRENNUNG
19F{1H} NMR (CDCl3, 282.2 MHz, 298 K): d=ꢀ151 (d, 4J
ACHTUNGTRENNUNG
1H NMR (CDCl3, 500 MHz, 298 K): d=7.89 (m, 2H; Harom), 7.46 (m,
202.5 MHz, 298 K): d=3.62 (d, 4J
ACHTUNGTRENNUNG
(P,F)=86.8 Hz); 29Si NMR (CDCl3,
2
3
2H; Harom), 7.34 (m, 4H; Harom), 2.00 (sept d, J
6.9 Hz, 2H; CHCH3), 1.88 (sept d, 2J(H,P)=3.2 Hz, 3J
2H; CHCH3), 1.06 (dd, 3J(H,P)=14.0 Hz, 3J
(H,H)=6.9 Hz, 6H;
CHCH3), 1.03 (dt, 3J(H,F)=8.1 Hz, 5J
(H,P)=2.5 Hz, 3H; SiCH3), 0.98
(dd, 3J(H,P)=13.6 Hz, 3J
(H,H)=6.9 Hz, 6H; CHCH3), 0.70 (dd,
3J(H,P)=14.8 Hz, 3J(H,H)=7.3 Hz, 6H; CHCH3), 0.69 (dd, 3J
(H,P)=
14.5 Hz, 3J(H,H)=7.3 Hz, 6H; CHCH3); 13C{1H} NMR (CDCl3,
125.8 MHz, 301 K): d=145.9 (dd, J
Cipso), 143.9 (d, 1J
(C,P)=18.0 Hz; PCipso), 137.1 (m, Carom), 131.6 (d,
A
ACHTUNGTRENNUNG(H,H)=
99.4 MHz, 298 K): d=ꢀ5.2 (d, 1J
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
282.2 MHz, 298 K): d=ꢀ144 (d, 4J
(F,P)=87 Hz); 1H NMR (CDCl3,
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
500 MHz, 298 K): d=7.59 (d, 3J
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
3J
7.5 Hz, 2H;
3J
(H,H)=7.4 Hz, 1H; Ho Ph), 7.31 (t, J
(t, 3J(H,H)=7.4 Hz, 2H; Harom), 2.09 (sept, 3J
CHCH3), 1.94 (sept, 3J(H,H)=7.0 Hz, 2H; CHCH3), 1.05 (dd, 3J
7.1 Hz, 3J(H,H)=6.9 Hz, 6H; CHCH3), 1.04 (dd, 3J
(H,P)=6.4 Hz,
3J(H,H)=6.9 Hz, 6H; CHCH3), 0.83 (dd, 3J(H,P)=5.2 Hz, 3J
(H,H)=
7.1 Hz, 6H; CHCH3), 0.75 (dd, 3J(H,P)=5.5 Hz, 3J
(H,H)=7.1 Hz, 6H;
CHCH3); 13C{1H} NMR (CDCl3, 125.8 MHz, 298 K): d=145.0 (d,
1J(C,P)=19 Hz; PCipso), 144.0 (dd, 2J(C,P)=45.0 Hz, 2J
(C,F)=13.5 Hz;
SiCipso), 137.5 (td, 2J(C,P)=15.6 Hz, 4J
(C,F)=2.8 Hz; Carom), 135.6 (s; Cm
Ph), 132.1 (s; Carom), 129.5 (s; Co Ph), 129.3 (s; Carom), 127.6 (s; Carom),
G
ACHTUNGTRENNUNG ACHTUNGTRENNUNG
(H,H)=8.1 Hz, 2H; Hm Ph), 7.46 (d, 3J
A
ACHTUNGTRENNUNG
H
ACHTUNGTRENNUNG
A
U
ACHTUNGTRENNUNG
3
E
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
2
3
G
ACHTUNGTRENNUNG
ACHUTNGREN(NUG C,F)=13.9 Hz, JHCATUNGTREN(NUGN C,P)=44.5 Hz; Si-
G
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
3J
CAHTUNGTRNEUN(NG C,P)=2.1 Hz; Carom), 129.1 (s; Carom), 127.6 (s; Carom), 25.5 (d, JACHTUNGTRENNUNG
1
G
ACHTUNGTRENNUNG
14.0 Hz; CHCH3), 25.0 (d, 1J
G
N
N
T
ACHTUNGTRENNUNG
2
(C,P)=18.3 Hz; CHCH3), 20.2 (d, 2J
ACHTUNGTRENNUNG
E
ACHTUNGTRENNUNG
13.1 Hz; CHCH3), 20.2 (d, J
12.3 Hz; CHCH3), 19.8 (d, 2J
16.3 Hz, 4J
N
ACHTUNGTRENNUNG
N
A
ACHTUNGTRENNUNG
U
=
G
ACHTUNGTRENNUNG
127.4 (s; Cp Ph), 25.3 (d, 1J
G
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
14.5 Hz; CHCH3), 20.2 (d, 2J
G
ACHTUNGTRENNUNG
0.15 mmol) in dichloromethane (1 mL) at ꢀ788C. After warming to
room temperature, the solution was pumped to dryness and complex 4
was isolated as a white powder (98 mg, 88%). Two isomers are observed
in NMR spectra: 4trans and the 4cis with the fluorine atom positioned trans
and cis to gold, respectively. Colorless crystals suitable for X-ray crystal-
lography were obtained from dichloromethane/pentane at room tempera-
18.9 Hz; CHCH3), 20.2 (d, 2J(C,P)=10.8 Hz; CHCH3), 19.6 (d, 2J
16.0 Hz; CHCH3); HRMS (ESI+) calcd for [M+H]+ =C30H40P2FSi+:
511.2515, found: 511.2533.
Synthesis of 2: A solution of SiCl4 (209 mL, 1.82 mmol) in toluene (5 mL)
was added dropwise to a solution of o-lithiated diisopropylphenylphos-
phine (939 mg, 3.72 mmol) in toluene (10 mL) at ꢀ788C.The solution was
allowed to warm slowly to room temperature over 4 h, after which the
volatile substances were removed under vacuum, and the product was ex-
ture. 4trans
:
31P{1H} NMR (CDCl3, 202.5 MHz, 263 K): d=57.1 (s);
29Si NMR (CDCl3, 99.4 MHz, 263 K): d=ꢀ21.4 (d, 1J
ACHTUNGTREN(NGNU Si,F)=259 Hz);
19F{1H} NMR (CDCl3, 376.3 MHz, 213 K): d=ꢀ135.8 (s); 1H NMR
(CDCl3, 500 MHz, 263 K): d=8.26 (d, 3J
ACHTNUGTRNEG(UN H,H)=7.5 Hz, 2H; Harom), 7.80
tracted with dichloromethane (15 mL).
A solution of HF·collidine
(d, 3J(H,H)=6.9 Hz, 2H; Ho Ph), 7.59 (d, 3J
ACHTNUGTRENNUG AHCTUNGTRENN(GUN H,H)=8.2 Hz, 2H; Harom),
(284 mg, 3.64 mmol) in dichloromethane (5 mL) was added to the solu-
tion of the above product in dichloromethane (15 mL) at room tempera-
ture, the mixture was allowed to stir for 30 min. Then, the solution was
pumped to dryness and the residue extracted with n-pentane (3ꢃ10 mL).
Residual phosphonium salt was deprotonated with 1,8-diazabicyclo-
[5.4.0]undec-7-ene (97 mL, 0.65 mmol) in dichloromethane (5 mL). The
solution was pumped to dryness and the solid extracted with n-pentane
(3ꢃ5 mL). Filtrates were combined and concentrated to 10 mL and
7.52 (m, 4H; Harom), 7.35 (m, 3H; Hm and Hp Ph), 2.70 (m, 2H; CHCH3),
2.61 (m, 2H; CHCH3), 1.42 (m, 6H; CHCH3), 1.13 (m, 6H; CHCH3),
0.93 (m, 12H, CHCH3); 13C{1H} NMR (CDCl3, 125.8 MHz, 263 K): d=
144.1 (dt, 2J
9.0 Hz, 3J
(s; Cm Ph), 135.1 (d, 2J
(s; Carom), 130.2 (s; Carom), 129.6 (s; C4), 128.1 (s; Cp Ph), 28.4 (AA’X, N=
(C,F)=19.5 Hz, 2J(C,P)=15 Hz; SiCipso), 137.4 (dd, 3J
ACHTUNGTRNEUNGN ACHTNUGTRENNUNG ACHTUNGTRENNUNG
G
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
10814
www.chemeurj.org
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 10808 – 10817

Hypervalent Silicon Compounds
FULL PAPER
14.0 Hz; CHCH3), 25.4 (AA’X, N=12.9 Hz; CHCH3), 19.4 (AA’X, N=
99.4 MHz, 301 K): d=ꢀ7.0 (s); 1H NMR (C6D6, 500 MHz, 301 K): d=
2.4 Hz; CHCH3),18.3 (s; CHCH3), 16.4 (s; CHCH3). 4cis:
31P{1H} NMR
7.96 (m, 2H; Harom), 7.49 (m, 2H; Harom), 7.28 (m, 4H; Harom), 1.93 (sept
d, 2J(H,P)=4.3 Hz, 3J(H,H)=7.0 Hz, 4H; CHCH3), 1.20 (t, 5J
ACHTUNGTRNEUNNG ACHUTNGTENRNUG ACHTUNGTRENNUNG
(CDCl3, 202.5 MHz, 263 K): d=59.6 (d, 4J
ACHTUNGTRENNUNG
1.6 Hz, 6H; Si
N
(H,P)=13.2 Hz, 3J
ACHUTGTNRENNUG CAHTUNGTRENNUNG
(CDCl3,99.4 MHz, 263 K): d=ꢀ3.9 (d, 1J
AHCTUNGTRENNUNG
12H; CHCH3), 0.92 (dd, 3J
(H,P)=12.9 Hz, 3J
ACHTUNGTRENNUNG
(CDCl3, 376.3 MHz, 213 K): d=ꢀ114.9 (d, 4J
(F,P)=20 Hz); 1H NMR
ACHTUNGTRENNUNG
(CDCl3, 500 MHz, 263 K): d=7.97 (d, 3J
ACHTUNGTRENNUNG
(m, 2H; Harom), 7.52 (m, 3H; Ho Ph et Harom), 7.46 (t, 3J
ACHTUNGTRENNUNG
A
R
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
2H; Harom), 7.33 (m, 4H; Hm et Hp Ph), 3.00 (m, 2H, CHCH3), 2.77 (m,
2H, CHCH3), 1.58 (m, 6H; CHCH3), 1.27 (m, 12H; CHCH3), 1.00 (m,
6H; CHCH3).13C{1H} NMR (CDCl3, 125.8 MHz, 263 K): d=141.3 (dd,
AHCTUNGTRENNUNG
G
ACHTUNGTRENNUNG
2J
N
G
ACHTUNGTRENNUNG
T
ACHTUNGTRENNUNG
arom), 137.7 (t, 1J
A
AHCTUNGTRENNUNG
C
445.2609, found: 445.2613.
SiCPh), 132.6 (s; Carom), 130.0 (s; Co Ph), 129.6 (s; Carom), 128.8 (s; Carom),
127.8 (s; Cp and Cm Ph), 27.0 (AA’X, N=13.3 Hz; CHCH3), 24.8 (AA’X,
Synthesis of complex 8: A solution of 7 (120 mg, 0.27 mmol) in dichloro-
N=14.1 Hz; CHCH3), 20.0ACTHUNTRGNE(NUG s; CHCH3), 18.9 (AA’X, N=4.2 Hz;
methane (1 mL) was added to a suspension of AuClACTHNUGTRENUNG(SMe2) (79.2 mg,
CHCH3),18.7 (s; CHCH3), 17.8 (s; CHCH3); HRMS (ESI+) calcd for
C30H41P2FSiAuCl: 707.2102, found: 707.2113.
0.27 mmol) in dichloromethane (1 mL) at ꢀ788C. After warming to
room temperature, the solution was pumped to dryness and complex 8
was isolated as a white powder (157.8 mg, 86%). Colorless crystals suita-
ble for X-ray crystallography were obtained from dichloromethane/pen-
tane at room temperature. 31P{1H} NMR (C6D6, 121.4 MHz, 298 K): d=
53.98 (s); 29Si NMR (CDCl3, 59.6 MHz, 298 K): d=ꢀ12.4 (s); 1H NMR
(CDCl3, 300 MHz, 298 K): d=7.79 (m, 2H; Harom), 7.05 (m, 6H; Harom),
Synthesis of complex 5: A solution of 2 (150 mg, 0.33 mmol) in dichloro-
methane (4 mL) was added to a suspension of AuClACTHNUGTRENUNG(SMe2) (100 mg,
0.34 mmol) in dichloromethane (2 mL) at ꢀ788C. After warming to
room temperature, the solution was pumped to dryness and complex 5
was isolated as a white powder (201 mg, 88%). Colorless crystals suitable
for X-ray crystallography were obtained from dichloromethane/diethyl
ether at ꢀ308C. 31P{1H} NMR (CDCl3, 202.5 MHz, 278 K): d=63.2 (d,
2.41 (sept d, 2J
3J(H,P)=15.2 Hz, 3J
15.6 Hz, 3J
ACHTNUTRGENNUG(H,H)=8.2 Hz, 12H; CHCH3), 0.98 (s; 6H; SiACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
A
R
ACHTUNGTRENNUNG
4J
1J
ACHTUNGTRENNUNG
13C{1H} NMR (CDCl3, 75.4 MHz, 298 K): d=147.7 (AA’X, N=15.1 Hz;
Cipso), 139.1 (AA’X, N=18.0 Hz; Cipso), 137.3 (AA’X, N=7.9 Hz; Carom),
ACHTUNGTRENNUNG
(td, 3J
G
E
ACHTUNGTRENNUNG
131.7 (s; Carom), 129.0 (s; Carom), 128.2
ACHTNUGTNERN(NUG s; Carom), 27.7 (AA’X, N=12.5 Hz;
Fap), 1H NMR (CDCl3, 500 MHz, 278 K): d=8.29 (d, 3J
ACHTUNGTRENNUNG
CHCH3), 19.5 (AA’X, N=2.6 Hz; CHCH3), 18.8 (AA’X, N=2.8 Hz;
2H; Harom), 7.57 (m, 6H; Harom), 2.99 (m, 2H; CHCH3), 2.90 (m, 2H;
CHCH3), 1.60 (m, 6H; CHCH3), 1.26 (m, 12H; CHCH3), 0.97 (m, 6H;
CHCH3) 13C{1H} NMR (CDCl3, 125.8 MHz, 278 K): d=142.1 (m, SiCipso),
CHCH3), 8.6 (t, 4J
ACHTNUGTRNNEUG(C,P)=2.3 Hz; SiAHCTUNGTREN(NUGN CH3)2); HRMS (ESI+) calcd for
[MꢀCl]+ =C26H42P2SiAu+: 641.2197, found: 641.2222.
EXSY experiments: 2D 31P{1H} EXSY spectra were recorded in CDCl3
at 277 K for complex 4, and 2D 19F EXSY spectra in CDCl3 at 223, 243,
273, 283 and 303 K for complex 5, with a phase sensitive pulse sequence
from the Bruker pulse library NOESYTP. The EXSY measurements
were repeated with a series of mixing times tm =20 ms and 0.3 s at 277 K
for 4, and tm =10 ms, 0.3 s, and 0.5 s at 223, 243, 273, 283 and 303 K for
complex 5. The diagonal and cross-peak volumes were integrated with
Bruker 2D WINNMR software. Site-to-site rate constants were deter-
mined by using the EXSY CALC software from Mestrelab Research. Ac-
tivation barriers were then calculated by using the Eyring equation.
137.9 (AA’X, N=12.2 Hz; Carom), 136.5 (t, 3J(C,P)=20.4 Hz, 3J
ACTHNUTRGENNUG AHCUTNGTREN(NUGN C,F)=
1.4 Hz; PCipso), 132.4 (s; Carom), 130.6 (s; Carom), 130.5 (s; Carom), 26.6
(AA’X, N=14.1 Hz; CHCH3), 25.3 (AA’X, N=14.7 Hz; CHCH3), 19.9
(s; CHCH3), 18.9 (s; CHCH3), 18.9 (s; CHCH3), 17.5 (s; CHCH3);
HRMS (ESI+) calcd for [MꢀCl]+ =C24H36P2F2SiAu+: 649.1682, found:
649.1695.
Synthesis of complex 6: A solution of 3 (100 mg, 0.22 mmol) in dichloro-
methane (4 mL) was added to a suspension of AuClACTHNUGTRENUNG(SMe2) (64 mg,
0.22 mmol) in dichloromethane (2 mL) at ꢀ788C. After warming to
room temperature, the solution was pumped to dryness and the complex
3 was isolated as a white powder (131 mg, 87%). Colorless crystals suita-
ble for X-ray crystallography were obtained from THF/pentane solution
at ꢀ308C. 31P{1H} NMR (CDCl3, 202.5 MHz, 298 K): d=60.1 (s);
Crystal structure determinations: The X-ray diffraction structures of 1
and 4 were reported in a preliminary communication.[11]
Crystallographic data were collected on Bruker-Kappa APEX-II diffrac-
tometer (for 5 and 6) and Bruker-AXS APEX-II diffractometer (for 2
and 8) with MoKa radiation (l=0.71073 ꢂ) at 180(2) K for 5, 100(2) K
for 6, and 193(2) K for 2 and 8. In all cases, a suitable crystal was mount-
ed on a glass fiber or nylon loop and shock-cooled on the goniometer
head. Semi-empirical absorption corrections were employed.[26] The struc-
tures were solved by direct methods (SHELXS-97),[27] and refined using
the least-squares method on F2.[28]
29Si NMR (CDCl3,99.4 MHz, 298 K): d=ꢀ10.2 (s, 1J
ACHTUNGTREN(NGNU Si,F)=267 Hz);
19F{1H} NMR (CDCl3, 376.3 MHz, 213 K): d=ꢀ141.5 (s); 1H NMR
(CDCl3, 500 MHz, 298 K): d=8.25 (d, 3J
ACHTNUGTRNEG(UN H,H)=7.1 Hz, 2H; Harom), 7.51
(m, 4H; Harom), 7.43 (t, 2H, 3J
CHCH3), 2.80 (m, 2H; CHCH3), 1.51 (m, 6H; CHCH3), 1.45 (d,
3J(H,F)=11.4 Hz, 3H; SiCH3), 1.41 (dd, 3J(H,P)=7.8 Hz, 3J
(H,H)=
ACHTUGNRTNE(NUNG H,H)=7.0 Hz; Harom), 2.89 (m, 2H;
A
U
ACHTUNGTRENNUNG
6.5 Hz, 6H; CHCH3), 1.41 (m, 6H; CHCH3), 1.32 (m, 6H; CHCH3), 0.88
(m, 6H; CHCH3); 13C{1H} NMR (CDCl3, 125.8 MHz, 298 K): d=146.9
Crystal data for 2: C24H36F2P2Si, M=452.56, monoclinic, space group C2,
a=11.8945(7), b=12.2407(5), c=9.2210(5) ꢂ, a=90, b=109.374(3), g=
(dd, 2J
ACHTUNGTRENNUNG ACHTUNGTRENNUNG ACTUHNGTRENNUGN
(C,F)=15.6 Hz, 2J(C,P)=6.4 Hz; SiCipso), 136.8 (q, 4J
ACHTUNGTRENNUNG ACHTUNGTRENNUNG
90, V=1266.53(11) ꢂ3, Z=2, 1calcd =1.187 gcmꢀ3
, FACHTUNGTNRUEGN(000)=484, T=
10.5 Hz, 2J(C,P)=8.6 Hz; Carom), 136.2 (t, 3J
193(2) K, crystal size 0.40ꢃ0.20ꢃ0.02 mm3, 3772 reflections collected
(2329 independent, Rint =0.0389), 2qꢁ26.378, 136 parameters, R1 [I>
2s(I)]=0.0461, wR2 (all data)=0.0595, largest diff. peak and hole: 0.225
(s; Carom), 130.2 (s; Carom), 129.2 (s; Carom), 28.1 (AA’X, N=13.5 Hz;
CHCH3), 25.5 (AA’X, N=13.8 Hz; CHCH3), 19.8 (s; CHCH3), 19.4 (s;
CHCH3), 18.7 (s; CHCH3), 18.4 (s; CHCH3), 9.9 (d, JACHTNUTRGNE(NUG C,F)=24.2 Hz;
and ꢀ0.189 eꢂꢀ3
.
SiCH3); HRMS (ESI+) calcd for [MꢀCl]+ =C25H39P2FSiAu+: 645.1924,
found: 645.1946.
Crystal data for 5: C24H36AuClF2P2Si, M=684.98, monoclinic, space
group P21/c, a=11.5749(6), b=15.0010(8), c=31.6610(17) ꢂ, a=90, b=
Synthesis of 7: A solution of Me2SiCl2 (115 mL, 0.94 mmol) in toluene
(5 mL) was added dropwise to a solution of o-lithiated diisopropylphe-
nylphosphine (475 mg, 1.88 mmol) in toluene (5 mL) at ꢀ788C. The solu-
tion was allowed to warm slowly to room temperature overnight, after
which the volatile substances were removed under vacuum, and ligand 7
was extracted from the salts with dichloromethane (10 mL). Then, the so-
lution was pumped to dryness, and the residue crystallized from n-pen-
tane (5 mL). 7 was isolated as a white powder (177.7 mg, 42% yield).
31P{1H} NMR (C6D6, 202.5 MHz, 301 K): d=1.3 (s); 29Si NMR (C6D6,
98.240(2), g=90, V=5440.7(5) ꢂ3, Z=8, 1calcd =1.672 gcmꢀ3, F
ACHTUNGTRENNUNG(000)=
2704, T=180(2) K, crystal size 0.283ꢃ0.113ꢃ0.03 mm3, 77767 reflections
collected (13085 independent, Rint =0.0864), 2qꢁ27.888, 577 parameters,
R1 [I>2s(I)]=0.0660, wR2 (all data)=0.1418, largest diff. peak and
hole: 2.927 and ꢀ3.708 eꢂꢀ3
.
Crystal data for 6: C25H39AuClFP2Si, M=681.01, monoclinic, space group
P21/c, a=11.5556(3), b=14.9979(4), c=31.9588(8) ꢂ, a=90, b=
97.3890(10), g=908, V=5492.8(2) ꢂ3, Z=8, 1calcd =1.647 gcmꢀ3, F
ACHTUNGTRENNUNG(000)=
Chem. Eur. J. 2010, 16, 10808 – 10817
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
10815

L. Maron, A. Amgoune, D. Bourissou et al.
2704, T=100(2) K, crystal size 0.23ꢃ0.08ꢃ0.03 mm3, 13085 reflections
collected (12960 independent, Rint =0.0864), 2qꢁ27.888, 577 parameters,
R1 [I>2s(I)]=0.0999, wR2 (all data)=0.1418, largest diff. peak and
D. Bourissou, Angew. Chem. 2008, 120, 1503–1506; Angew. Chem.
Int. Ed. 2008, 47, 1481–1484; g) M. Sircoglou, S. Bontemps, G. Bou-
hadir, N. Saffon, K. Miqueu, W. Gu, M. Mercy, C.-H. Chen, B. M.
Foxman, L. Maron, O. V. Ozerov, D. Bourissou, J. Am. Chem. Soc.
2008, 130, 16729–16738; h) M. Sircoglou, M. Mercy, N. Saffon, Y.
Coppel, G. Bouhadir, L. Maron, D. Bourissou, Angew. Chem. 2009,
121, 3506–3509; Angew. Chem. Int. Ed. 2009, 48, 3454–3457.
[5] In addition to h1-coordination of boranes as acceptor ligands, multi-
center h3-BCC and h2-BC interactions involving a p system at boron
have been also evidenced: a) S. R. Oakley, K. D. Parker, D. J. H.
Emslie, I. Vargas-Baca, C. M. Robertson, L. E. Harrington, J. F. Brit-
ten, Organometallics 2006, 25, 5835–5838; b) D. J. H. Emslie, L. E.
Harrington, H. A. Jenkins, C. M. Robertson, J. F. Britten, Organo-
metallics 2008, 27, 5317–5325; c) K. B. Kolpin, D. J. H. Emslie,
Angew. Chem. 2010, 122, 2776–2779; Angew. Chem. Int. Ed. 2010,
49, 2716–2719; d) M. Sircoglou, S. Bontemps, M. Mercy, K. Miqueu,
S. Ladeira, N. Saffon, L. Maron, G. Bouhadir, D. Bourissou, Inorg.
Chem. 2010, 49, 3983–3990; e) X. Zhao, E. Otten, D. Song, D. W.
Stephan, Chem. Eur. J. 2010, 16, 2040–2044.
[6] a) D. Kost, I. Kalikhman in The Chemistry of Organic Silicon Com-
pounds, Vol. 2, Part 2 (Eds.: Z. Rappoport, Y. Apeloig),Wiley, New
York, 1998, pp. 1339–1445; b) Chemistry of Hypervalent Com-
pounds, (Ed.: K.-y. Akiba), Wiley-VCH, Weinheim, 1999; c) Y. I.
Baukov, S. N. Tandura in The Chemistry of Organic Germanium, Tin
and Lead Compounds, Vol. 2 (Ed.: Z. Rappoport), Wiley, New
York, 2002, pp. 961–1239; d) R. R. Holmes, Chem. Rev. 1996, 96,
927–950; e) C. Chuit, R. J. P. Corriu, C. Reye, J. Colin Young,
Chem. Rev. 1993, 93, 1371–1448.
[7] a) J. Grobe, N. Krummen, R. Wehmschulte, B. Krebs, M. Laege, Z.
Anorg. Allg. Chem. 1994, 620, 1645–1658; b) J. Grobe, R. Wehm-
schulte, B. Krebs, M. Laege, Z. Anorg. Allg. Chem. 1995, 621, 583–
596; c) J. Grobe, K. Luetke-Brochtrup, B. Krebs, M. Laege, H. H.
Niemeyer, E. U. Wuerthwein, Z. Naturforsch. B 2007, 62, 55–65.
[8] a) J. Silver, J. Chem. Soc. Dalton Trans. 1990, 3513–3516; b) R.
Rulkens, A. J. Lough, I. Manners, Angew. Chem. 1996, 108, 1929–
1931; Angew. Chem. Int. Ed. Engl. 1996, 35, 1805–1807; c) D. L.
Zechel, K. C. Hultzsch, R. Rulkens, D. Balaishis, Y. Ni, J. K. Pudel-
ski, A. J. Lough, I. Manners, Organometallics 1996, 15, 1972–1978.
[9] a) L. Guo, J. D. Bradshaw, C. A. Tessier, W. J. Youngs, Organometal-
lics 1995, 14, 586–588; b) L. Guo, J. D. Bradshaw, D. B. McConville,
C. A. Tessier, W. J. Youngs, Organometallics 1997, 16, 1685–1692.
[10] a) J. Wagler, A. F. Hill, T. Heine, Eur. J. Inorg. Chem. 2008, 4225–
4229; b) J. Wagler, E. Brendler, Angew. Chem. 2010, 122, 634–637;
Angew. Chem. Int. Ed. 2010, 49, 624–627.
hole: 2.927 and ꢀ3.708 eꢂꢀ3
.
Crystal data for 8: C26H42AuClP2Si, M=705.1, orthorhombic, space group
P21 21 21, a=8.9619(1), b=12.0314(2), c=29.6707(4) ꢂ, a=90, b=90,
g=908, V=3199.22(8) ꢂ3, Z=4, 1calcd =1.582 gcmꢀ3
FACHTNGUTERN(UNG 000)=1520, T=
180(2) K, crystal size 0.22ꢃ0.08ꢃ0.06 mm3, 49291 reflections collected
(9725 independent, Rint =0.0458), 2qꢁ30.498, 318 parameters, R1 [I>
2s(I)]=0.0276, wR2 (all data)=0.0525, largest diff. peak and hole: 1.264
and ꢀ1.050 eꢂꢀ3
.
CCDC-776015 (2), 776016 (5), 776017 (6), and 776018 (8) contain the
supplementary crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
Computational details: Calculations were carried out on the actual com-
plexes 4, 5, 6, and 8. Au, P, and Cl were treated with a Stuttgart–Dresden
pseudopotential in combination with their adapted basis set.[29–31] In all
cases, the basis set was augmented by a set of polarization function (f for
Au, d for P and Cl).[32] C, H, Si and F atoms were described with a 6-31G-
ACHTUNGTRENNUNG
(d,p) double-z basis set.[33] Calculations were carried out at the DFT
level of theory with the hybrid functional B3PW91.[34–35] Geometry opti-
mizations were carried out without any symmetry restrictions, the nature
of the extrema was verified with analytical frequency calculations. All
computations were performed with the Gaussian 03[36] suite of programs.
The electronic structure of the complexes was studied by Natural Bond
Orbital (NBO) analysis (NBO 3.1 program),[37–38] second-order perturba-
tion theory being particularly adapted to the description of metal!Lewis
acid interactions. The electron density of the optimized structures of
complexes 4, 5, 6 and 8 was subjected to an Atoms In Molecules analy-
sis[39] with AIM2000.[40]
Acknowledgements
Financial support from the Centre National de la Recherche Scientifique,
the Pꢄle de Recherche et dꢅEnseignement Supꢀrieur of the Universitꢀ de
Toulouse (fellowship to P.G.) and the COST action CM0802 PhoSciNet is
gratefully acknowledged. We thank the Unidade de RaiosX of the Uni-
versidade de Santiago de Compostela for the X-ray diffraction analysis of
6, Pierre Lavedan for the 2D 19F EXSY NMR experiments on complex 5,
and FranÅois Gabbaꢆ for helpful discussions. L.M. thanks the Institut
Universitaire de France.
[11] P. Gualco, T. P. Lin, M. Sircoglou, M. Mercy, S. Ladeira, G. Bouha-
dir, L. M. Perez, A. Amgoune, L. Maron, F. P. Gabbai, D. Bourissou,
Angew. Chem. 2009, 121, 10076–10079; Angew. Chem. Int. Ed.
2009, 48, 9892–9895.
[1] a) R. B. King, Adv. Chem. Ser. 1967, 62, 203–220; b) M. L. H.
Green, J. Organomet. Chem. 1995, 500, 127–148.
[12] The free energy of activation at coalescence temperature is typically
[2] a) H. Braunschweig, C. Kollann, D. Rais, Angew. Chem. 2006, 118,
5380–5400; Angew. Chem. Int. Ed. 2006, 45, 5254–5274; b) F. G.
Fontaine, J. Boudreau, M. H. Thibault, Eur. J. Inorg. Chem. 2008,
5439–5454; c) I. Kuzu, I. Krummenacher, J. Meyer, F. Armbruster,
F. Breher, Dalton Trans. 2008, 5836–5865; d) H. Braunschweig,
R. D. Dewhurst, A. Schneider, Chem. Rev. 2010, 110, 3924–3957.
[3] For a dative Pt!Be, see: a) H. Braunschweig, K. Gruss, K. Radacki,
Angew. Chem. 2009, 121, 4303–4305; Angew. Chem. Int. Ed. 2009,
48, 4239–4241.
[4] a) S. Bontemps, H. Gornitzka, G. Bouhadir, K. Miqueu, D. Bouris-
sou, Angew. Chem. 2006, 118, 1641–1644; Angew. Chem. Int. Ed.
2006, 45, 1611–1614; b) S. Bontemps, G. Bouhadir, K. Miqueu, D.
Bourissou, J. Am. Chem. Soc. 2006, 128, 12056–12057; c) S. Bon-
temps, G. Bouhadir, P. W. Dyer, K. Miqueu, D. Bourissou, Inorg.
Chem. 2007, 46, 5149–5151; d) M. Sircoglou, S. Bontemps, M.
Mercy, N. Saffon, M. Takahashi, G. Bouhadir, L. Maron, D. Bouris-
sou, Angew. Chem. 2007, 119, 8737–8740; Angew. Chem. Int. Ed.
2007, 46, 8583–8586; e) S. Bontemps, M. Sircoglou, G. Bouhadir, H.
Puschmann, J. A. K. Howard, P. W. Dyer, K. Miqueu, D. Bourissou,
Chem. Eur. J. 2008, 14, 731–740; f) S. Bontemps, G. Bouhadir, W.
Gu, M. Mercy, C.-H. Chen, B. M. Foxman, L. Maron, O. V. Ozerov,
p
estimated through the following formula: DG° =RTc ln
ACHTUNGTRENNUNG[RTc 2/
(pNAhjnAꢀnB j)] with R (gas constant), Tc (coalescence tempera-
ture), NA (Avogadroꢅs number), h (Planckꢅs constant) and jnAꢀnB j
(chemical shift difference): L. M. Jackman, Dyn. Mass Spectrom.
1975, 203–252.
[13] a) K. G. Orrell, Annu. Rep. NMR Spectrosc. 1999, 37, 1–74; b) C. L.
Perrin, T. J. Dwyer, Chem. Rev. 1990, 90, 935–967.
[14] M. Gromova, O. Jarjayes, S. Hamman, R. Nardin, C. Bꢀguin, R.
Willem, Eur. J. Inorg. Chem. 2000, 545–550.
[15] C. L. Perrin, R. K. Gipe, J. Am. Chem. Soc. 1984, 106, 4036–4038.
[16] B. Cordero, V. Gꢇmez, A. E. Pletro-Prats, M. Revꢀs, J. Echeverrꢈa,
E. Cremades, F. Barragꢉn, S. Alvarez, Dalton Trans. 2008, 2832–
2838.
[17] S. S. Batsanov, Inorg. Mater. 2001, 37, 871–885.
[18] a) N. Kano, F. Komatsu, M. Yamamura, T. Kawashima, J. Am.
Chem. Soc. 2006, 128, 7097–7109; b) F. Carrꢀ, R. J. P. Corriu, A.
Kpoton, M. Poirier, G. Royo, J. C. Young, C. Belin, J. Organomet.
Chem. 1994, 470, 43–57; c) K. Gerhard, H. Karl, F. Hartmut, Chem.
Ber. 1983, 116, 3125–3132.
[19] See the Supporting Information.
10816
www.chemeurj.org
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 10808 – 10817

Hypervalent Silicon Compounds
FULL PAPER
[20] a) G. I. Nikonov, Adv. Organomet. Chem. 2005, 53, 217–309; b) M.
Brookhart, M. L. H. Green, G. Parkin, Proc. Natl. Acad. Sci. USA
2007, 104, 6908–6914; c) D. V. Gutsulyak, S. F. Vyboishchikov, G. I.
Nikonov, J. Am. Chem. Soc. 2010, 132, 5950–5951; d) S. Lachaize, S.
Sabo-Etienne, Eur. J. Inorg. Chem. 2006, 2115–2127; e) Z. Lin,
Chem. Soc. Rev. 2002, 31, 239–245.
[21] a) W. Chen, S. Shimada, M. Tanaka, Science 2002, 295, 308–310;
b) R. H. Crabtree, Science 2002, 295, 288–289; c) E. C. Sherer, C. R.
Kinsinger, B. L. Kormos, J. D. Thompson, C. J. Cramer, Angew.
Chem. 2002, 114, 2033–2036; Angew. Chem. Int. Ed. 2002, 41, 1953–
1956; d) G. Aullꢇn, A. Lledos, S. Alvarez, Angew. Chem. 2002, 114,
2036–2039; Angew. Chem. Int. Ed. 2002, 41, 1956–1959; e) G. I. Ni-
konov, Angew. Chem. 2003, 115, 1375–1377; Angew. Chem. Int. Ed.
2003, 42, 1335–1337.
[22] J. Y. Corey, J. Braddock-Wilking, Chem. Rev. 1999, 99, 175–292.
[23] a) G. Balꢉzs, L. J. Gregoriades, M. Scheer, Organometallics 2007, 26,
3058–3075; b) R. Waterman, P. G. Hayes, T. D. Tilley, Acc. Chem.
Res. 2007, 40, 712–719; c) A. C. Filippou, C. Oleg, K. W. Stumpf, G.
Schnakenburg, Angew. Chem. 2010, 122, 3368–3372; Angew. Chem.
Int. Ed. 2010, 49, 3296–3300.
[24] a) M. C. MacInnis, D. F. MacLean, R. J. Lundgren, R. McDonald, L.
Turculet, Organometallics 2007, 26, 6522–66525; b) S. J. Mitton, R.
MacDonald, L. Turculet, Organometallics 2009, 28, 5122–5136;
c) S. J. Mitton, R. McDonald, L. Turculet, Angew. Chem. 2009, 121,
8720–8723; Angew. Chem. Int. Ed. 2009, 48, 8568–8571; d) E.
Morgan, D. F. MacLean, R. McDonald, L. Turculet, J. Am. Chem.
Soc. 2009, 131, 14234–14236; e) J. Takaya, N. Iwasawa, J. Am.
Chem. Soc. 2008, 130, 15254–15255; f) J. Takaya, N. Iwasawa, Orga-
nometallics 2009, 28, 6636–6638.
[29] B. Metz, H. Stoll, M. Dolg, J. Chem. Phys. 2000, 113, 2563–2569.
[30] D. Andrae, U. Haeussermann, M. Dolg, H. Stoll, H. Preuss, Theor.
Chim. Acta 1990, 77, 123–141.
[31] A. Bergner, M. Dolg, W. Kuechle, H. Stoll, H. Preuss, Mol. Phys.
1993, 80, 1431–1441.
[32] A. W. Ehlers, M. Bçhme, S. Dapprich, A. Gobbi, A. Hçllwarth, V.
Jonas, K. F. Kçhler, R. Stegmann, A. Veldkamp, G. Frenking, Chem.
Phys. Lett. 1993, 208, 111–114.
[33] P. C. Hariharan, J. A. Pople, Theor. Chim. Acta 1973, 28, 213–222.
[34] A. D. Becke, J. Chem. Phys. 1993, 98, 5648–5652.
[35] K. Burke, J. P. Perdew, W. Yang, Electronic Density Functional
Theory: Recent Progress and New Directions (Eds.: J. F. Dobson, G.
Vignale, M. P. Das), Springer, Heidelberg, 1998.
[36] Gaussian 03, Revision C.02, M. J. Frisch, G. W. Trucks, H. B. Schle-
gel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, V. G. Zakrzewski,
J. A. Montgomery, Jr., R. E. Stratman, J. C. Burant, S. Dapprich,
J. M. Millam, A. D. Daniels, K. N. Kudin, M. C. Strain, O. Farkas, J.
Tomasi, V. Barone, M. Cossi, R. Cammi, B. Mennucci, C. Pomelli,
C. Adamo, S. Clifford, J. Ochterski, G. A. Petersson, P. Y. Ayala, Q.
Cui, K. Morokuma, D. K. Malick, A. D. Rabuck, K. Raghavachari,
J. B. Foresman, J. Cioslowswi, J. V. Ortiz, A. G. Baboul, B. B. Stefa-
nov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. Gomperts,
R. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Na-
nayakkara, C. Gonzalez, M. Challacombe, P. M. W. Gill, B. Jonhson,
W. Chen, M. W. Wong, J. L. Andres, M. Head-Gordon, E. S. Replo-
gle, J. A. Pople, Pittsburgh PA, 2006.
[37] NBO version 3.1, E. D. Glendening, A. E. Reed, J. E. Carpenter, F.
Weinhold.
[38] A. E. Reed, L. A. Curtiss, F. Weinhold, Chem. Rev. 1988, 88, 899–
926.
[39] R. F. W. Bader, Atoms in Molecules: A Quantum Theory, Oxford
University Press, Oxford, 1994.
[25] a) Nuclear Magnetic Resonance Spectroscopy, (Ed.: F. A. Bovey),
Academic Press, New York, 1969; b) R. J. Abraham, H. Berstein,
Can. J. Chem. 1961, 39, 216–230.
[26] SADABS, Program for data correction, Bruker-AXS.
[27] G. M. Sheldrick, Acta Crystallogr. Sect. A 1990, 46, 467–473.
[28] SHELXL-97, Program for Crystal Structure Refinement, G. M.
Sheldrick, University of Gçttingen (Germany), 1997.
[40] F. B. Konig, J. Schonbohm, D. Bayles, J. Comput. Chem. 2001, 22,
545–559.
Received: May 12, 2010
Published online: July 30, 2010
Chem. Eur. J. 2010, 16, 10808 – 10817
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
10817