Activation of Homolytic Si-Zn and Si-Hg Bond Cleavage, Mediated by a Pt0 Complex, via Novel Pt-Zn and Pt-Hg Compounds

Article abstract of DOI:10.1002/anie.201505805

The thermally stable [(tBuMe₂Si)₂M] (M=Zn, Hg) generate R₃Si^. radicals in the presence of [(dmpe)Pt(PEt₃)₂] at 60-80 C. The reaction proceeds via hexacoordinate Pt complexes, (M=Zn (2 a and 2 b), M=Hg (3 a and 3 b)) which were isolated and characterized. Mild warming or photolysis of 2 or 3 lead to homolytic dissociation of the Pt-MSiR₃ bond generating silyl radicals and novel unstable pentacoordinate platinum paramagnetic complexes (M=Zn (5), Hg (6)) whose structures were determined by EPR spectroscopy and DFT calculations. SiM City: The thermally stable [(tBuMe₂Si)₂M] (M=Zn, Hg) generate R₃Si^. radicals in the presence of [(dmpe)Pt(PEt₃)₂]. The enhancing effect of the Pt complex on the homolytic cleavage of the Si-M bonds in [(tBuMe₂Si)₂M] is mediated by formation of octahedral hexacoordinate Pt-M trinuclear complexes.

Full text of DOI:10.1002/anie.201505805

Angewandte
Chemie
International Edition: DOI: 10.1002/anie.201505805
German Edition: DOI: 10.1002/ange.201505805
Bond Cleavage
À
À
Activation of Homolytic Si Zn and Si Hg Bond Cleavage, Mediated
by a Pt Complex, via Novel Pt Zn and Pt Hg Compounds
0
À
À
Yosi Kratish, Gregory Molev, Arseni Kostenko, Dennis Sheberla, Boris Tumanskii,
Mark Botoshansky , Shigeru Shimada, Dmitry Bravo-Zhivotovskii,* and Yitzhak Apeloig*
†
In memory of Paul von RaguØ Schleyer
Abstract: The thermally stable [(tBuMe Si) M] (M = Zn, Hg)
Herein we report that thermally stable SiÀZn and SiÀHg
2
2
0
generate R SiC radicals in the presence of [(dmpe)Pt(PEt ) ] at
bonds are activated towards homolytic cleavage by a Pt
3
3 2
6
0–808C. The reaction proceeds via hexacoordinate Pt com-
complex, [(dmpe)Pt(PEt ) ] (1) dmpe = 1,2-bis(dimethyl-
3
2
plexes, (M = Zn (2a and 2b), M = Hg (3a and 3b)) which
were isolated and characterized. Mild warming or photolysis of
phosphanyl)ethane, yielding hexacoordinate Pt isomers 2a
and 2b (M = Zn) or 3a, 3b (M = Hg), respectively, having
2
or 3 lead to homolytic dissociation of the PtÀMSiR bond
a PtÀMSiR moiety [Eq. (1)]. These novel hexacoordinate
3
3
generating silyl radicals and novel unstable pentacoordinate
platinum paramagnetic complexes (M = Zn (5), Hg (6)) whose
structures were determined by EPR spectroscopy and DFT
calculations.
PtÀMSiR compounds were isolated and characterized by X-
3
ray crystallography and their photolysis and thermolysis is
reported. Photolysis of 2 (i.e., the obtained 63:37 mixture of
2a + 2b, respectively) or of 3 (i.e., the obtained 26:74 mixture
of 3a + 3b, respectively) yields quantitatively the tetracoor-
dinate platinum complex 4 and the EPR spectra of the
intermediate pentacoordinate platinum paramagnetic species,
5 (M = Zn) or 6 (M = Hg), respectively, are observed
[Eq. (2)].
T
he vigorously developing chemistry of heterometallic
complexes containing two or more different metals is of
considerable contemporary interest with a variety of applica-
[
1]
tions in synthesis, catalysis, and materials chemistry. More
specifically, recently heterometallic complexes containing Pt
and Zn atoms attracted attention and several were iso-
Bis(silyl)zincs and bis(silyl)mercuries are good precursors
[
5]
for the photochemical generation of R Si radicals. For
3
[
2–4]
lated.
Several methodologies are available for their syn-
example, upon day-light exposure for 30 min [(tBuMe Si) Zn]
2
2
thesis. One involves the formation of PtÀZn heteronuclear
(7) or [(tBuMe Si) Hg] (8) undergo quantitative demetalla-
2 2
dative linkages from Lewis basic and Lewis acidic metals
tion forming short-lived [tBuMe Si]C radicals which dimerize
2
[1a]
(
termed metal-only Lewis pairs (MOLPs)). For example,
to disilane 9 (95%) or abstract an hydrogen (5%) to form
recently a MOLP PtÀZn complex was isolated from the
silane 10 [Eq. (3)].
[
2]
reaction of [Pt(PCy ) ] (Cy = cyclohexyl) and ZnBr .
In contrast to their facile photolysis, bis(silyl)zincs and
bis(silyl)mercuries are generally thermally stable; for exam-
ple no decomposition of [(tBuMe Si) Zn] (7), [(tBu-
3
2
2
Fischer et al. reported a number of novel {PtÀZnCp*}
(
Cp* = pentamethylcyclopentadienyl) complexes in which
2
2
[3]
a divalent zinc is bonded directly to platinum. Complexes
in which Pt and Zn are bridged by ligands were also isolated
and characterized.
Me Si) Hg] (8), [(tBu MeSi) Zn] (11), or [(tBu MeSi) Hg]
2 2 2 2 2 2
(12) is observed after their heating at 1208C for several days.
However, in the presence of a stoichiometric amount of
[
4]
[
(dmpe)Pt(PEt ) ] (1), 7 and 8 undergo dezincation (at 808C)
3 2
or demercuration (at 608C) respectively, producing silane 10
(90%) and disilane 9 (10%) [Eq. (4)]. In contrast, the more
[
+]
[+]
[
*] Y. Kratish, Dr. G. Molev, A. Kostenko, Dr. D. Sheberla,
Dr. B. Tumanskii, Dr. M. Botoshansky, Dr. D. Bravo-Zhivotovskii,
Prof. Dr. Y. Apeloig
sterically crowded [(tBu MeSi) Zn] (11) and [(tBu MeSi) Hg]
2
2
2
2
(12) are thermally stable in the presence of 1 even at 1408C. It
is reasonable to assume that in Equation (4), 10 and 9 are
Schulich Faculty of Chemistry and the Lise Meitner-Minerva Center
for Computational Quantum Chemistry
Technion-Israel Institute of Technology
Haifa 32000 (Israel)
formed from R SiC radicals by hydrogen abstraction or
3
dimerization, respectively. The same products are also
obtained in the photolysis of 7 and 8, but the 10:9 ratio of
E-mail: chrbrzh@tx.technion.ac.il
5
:95 [Eq. (3)] is nearly inverse to that obtained in Equa-
apeloig@technion.ac.il
[6]
tion (4). Formation of 9 + 10 from 7 or 8 in the presence of
indicates that 1 activates the formation of R SiC radicals. This
Dr. S. Shimada
1
Interdisciplinary Research Center for Catalytic Chemistry, National
Institute of Advanced Industrial Science and Technology (AIST)
Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan)
3
suggestion is supported by the fact that addition of 1 lowers
the temperature required for silyl radical formation in the
thermolysis reactions of ([tBuMe Si) Zn] (7) or [(tBu-
+
[
] These authors contributed equally to this work.
2
2
[
7]
[
†] Deceased.
Me Si) Hg] (8) in the presence of (Me Si) SiH.
2
2
3
3
To probe the presence of silyl radicals in the reaction in
Equation (4) we used TEMPO ((2,2,6,6-tetramethyl-piperi-
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201505805.
Angew. Chem. Int. Ed. 2015, 54, 11817 –11821
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
11817

.
Angewandte
Communications
However, analogy with 8 supports
the generation of silyl radicals in
reaction 4 also for 7.
To understand how 1 generates
silyl radicals in thermolysis of
[
(R Si) M] we studied their reac-
3 2
tions in more detail. Addition of
mole equivalent of 1 to 2 mole
equivalents of [(tBuMe Si) Zn] (7)
1
2
2
at room temperature in hexane
yields instantaneously and quanti-
tatively two isomeric hexacoordi-
IV[8]
nate octahedral Pt
complexes,
2
a and 2b, in a 63:37 ratio [Eq. (1),
M = Zn]. Colorless crystals
of the major isomer 2a,
which has two equatorial
ZnSiR ligands (the equato-
3
rial plane is defined by the
dmpe ligand and the two
ligands trans to it), were
isolated and its structure
was determined by X-ray
crystallography
ure 1a). Similarly 1 reacts
with 8 yielding the analo-
(Fig-
[
9]
gous PtÀHg isomeric complexes 3a and 3b
in a ratio of 26:74, a nearly reversed
isomeric ratio compared to the reaction
[10]
with 7 [Eq. (1), M = Hg].
The brown-
orange crystals of the major isomer 3b,
which has one axial and one equatorial
HgSiR ligand, were isolated from hexane
3
and analyzed by X-ray crystallography
[
9]
(
Figure 1b). Compounds 2 and 3 are
formally products of a double insertion of the
{
(dmpe)Pt} fragment into the SiÀZn and Si < C- < Hg
bonds of 7 and 8, respectively, yielding octahedral
IV
hexacoordinate Pt complexes. Compounds 2a and 3b
have regular bond lengths and bond angles and their
detailed structures are given in the Supporting Infor-
mation.
Compounds 2 and 3 undergo complete thermal (60–808C,
2
.5 h) and photolytic (l > 300 nm, 258C, 0.5 h) conversion
II
into a mixture of the tetracoordinate Pt complex 4,
tBuMe SiH (10), tBuMe Si-SiMe tBu (9), and metallic zinc
2
2
2
or mercury, respectively. Thermolysis or photolysis of mer-
cury species 3 in the presence of 2 mole equivalent of
TEMPO yields the silyl-TEMPO adduct 13 in 92% yield,
indicating that tBuMe Si· radicals are generated from 3. The
2
absence of 9 and 10 in the presence of TEMPO indicates that
din-1-yl)oxyl) as a silyl-radical scavenger. [(tBuMe Si) Hg] (8)
the tBuMe SiC radicals produced from 3 are trapped faster by
2
2
2
reacts relatively slowly with TEMPO yielding only 20% of
the expected radical adduct 13 after 2 h at 608C. However, in
the presence of 1, 8 produces 13 in 92% yield indicating that
TEMPO than they dimerizes or abstract a hydrogen atom.
Additional strong support for the suggestion that 2 and 3
fragment to give radical intermediates is the observation by
EPR spectroscopy of paramagnetic species. When a hexane
solution at 258C of 2 or 3 is irradiated (l > 300 nm) within the
EPR spectrometer cavity, metallic zinc or mercury precip-
itates and an intensive broad EPR signals (line-width
1
enhances the production of silyl radicals. Unfortunately
TEMPO reacts instantaneously (even at room temperature)
with 7 yielding 13, thus, precluding its use to probe the
presence of silyl radicals in Equation (4), with M = Zn.
1
1818 www.angewandte.org
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2015, 54, 11817 –11821

Angewandte
Chemie
Figure 2. EPR spectra of 5 in hexane solution: a) at 258C; b) at
À1438C (frozen solution); EPR spectra of 6 in hexane solution: c) at
1
95
2
58C; d) at À1438C (frozen solution). Arrows indicate the Pt
satellites.
coupling constants and g-factors for 5a and 6a are in good
agreement with the experimental values for 5 and 6,
respectively; the maximal experimental–calculated deviation
Figure 1. a) ORTEP drawing of the molecular structure of 2a.
b) ORTEP drawing of the molecular structure of 3b. Thermal ellipsoids
are set at 20% probability and hydrogen atoms are omitted for
[14b]
in the g factor values is 1.4%.
The zinc-substituted Pt radical 5 is persistent at 258C (t1/2
15 h) while the analogous mercury-substituted Pt radical 6
[
9]
clarity.
ꢀ
has a t1 of only 20 min at 258C. The observed first-order
/2
[18]
decay of 5 and 6, suggests that it occurs by cleavage of the
ꢀ
50.0 G) with giso values of 2.061 for 2 (Figure 2a) and 2.055
equatorial R SiMÀPt bond to yield 4 [Eq. (2)]. The decay
3
for 3 (Figure 2c) are observed. These g-factors are strongly
shifted to low field relative to a free electron (g = 2.002),
which is typical for heavy-element-centered radicals owing to
rates of 5 and 6 as a function of temperature, yield activation
À1
À1
[18]
energies of 32.0 kcalmol for 5 and 24.1 kcalmol for 6.
The calculated R SiMÀPt dissociation energies, at ZORA
3
[
11]
[14b,c]
À1
strong spin-orbit coupling.
solutions these EPR spectra exhibit a three-axis anisotropy
In frozen hexane or toluene
B3LYP-D3/TZVP,
mol for 6a, in particular the difference of 7.3 kcalmol
(7.9 kcalmol , exp.) are in good agreement with the exper-
of 35.9 kcalmol for 5a and 28.6 kcal
À1
À1
[12]
À1
(
Figure 2b,d), indicating a rhombic molecular symmetry.
We conclude that the observed paramagnetic intermediates
are Pt complexes 5 (M = Zn) and 6 (M = Hg), having
imental values.
III
Thermolysis
of
the
more
bulky
substituted
a square-pyramidal geometry formed by cleavage of one of
[(tBu MeSi) M] (M = Zn (11), 808C, M = Hg (12), 1308C)
2
2
the PtÀMSiR bonds [Eq. (2)]. Analysis of the EPR spectra of
with [(dmpe)Pt(PEt ) ] (1) [Eq. (5)], yields the corresponding
3 2
3
II
[19]
5
and 6 (a detailed analysis is presented in the Supporting
square-planar Pt ÀM complexes 14 and 15, respectively.
Information) leads to the conclusion that most of the spin is
localized on the Pt atom. This situation is in contrast to that in
However, in contrast to Equation (1) octahedral complexes
similar to 2 and 3 are not observed with 11 or 12.
III
most other Pt complexes in which most of the spin is
The tetracoordinate 14 and 15 are thermally and photo-
lytically highly stable in contrast to the thermally and
photochemically reactive hexacoordinate 2 and 3. The
[13]
delocalized to the ligands. The good agreement between
[14a,b]
the simulated EPR spectra
and the experimental spec-
trum strongly support the proposed square-pyramidal struc-
higher thermal and photolytic reactivity of 2 and 3 (R Si =
3
[15]
tures of radicals 5 and 6.
The square-pyramidal
structure of radicals 5 and 6 is also supported by
[
14b,c]
quantum mechanics calculations
(
at the ZORA
[16]
[17]
zero order regular approximation) B3LYP /TZVP
level of theory for model systems in which the tBuMe Si
2
groups in 5 and 6 are substituted by Me Si groups
3
(
referred to as 5a and 6a, respectively). The calculated
Angew. Chem. Int. Ed. 2015, 54, 11817 –11821
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org 11819

.
Angewandte
Communications
tBuMe Si) compared to 14 and 15 (R Si = tBu MeSi) reflects
the different stability of the Pt and Pt radical species which
are grateful to the Ministry of Immigrant Absorption, State of
Israel, for a Kamea fellowship.
2
3
2
III
I
result from cleavage of one of their PtÀMSiR bonds. Thus,
3
[
20]
DFT calculations (at ZORA B3LYP-D3 /TZVP, data at
Keywords: mercury · platinum · silyl radicals ·
2
98.15 K) show that cleavage of the PtÀMSiR bond (for
trinuclear complexes · zinc
3
model compounds in which the SiR and dmpe groups were
3
IV
How to cite: Angew. Chem. Int. Ed. 2015, 54, 11817–11821
Angew. Chem. 2015, 127, 11983–11987
substituted by SiH and PH groups, respectively) of a Pt
3
3
III
complex to form a Pt paramagnetic species (Scheme 1,
À1
À1
reaction a) require 6.0 kcalmol (M = Zn) and 4.4 kcalmol
(
M = Hg) less energy than cleavage of the PtÀMSiR bond in
3
[
1] a) J. Bauer, H. Braunschweig, R. D. Dewhurst, Chem. Rev. 2012,
12, 4329 – 4346; b) X. Zhang, G. Liu, G. Gantefçr, K. H. Bowen,
I
I
I
a Pt complex to form a Pt paramagnetic species (Scheme 1,
reaction b).
1
A. N. Alexandrova, J. Phys. Chem. Lett. 2014, 5, 1596 – 1601;
c) S. K. Mandal, H. W. Roesky, Acc. Chem. Res. 2010, 43, 248 –
2
59; d) Y. Ishii, M. Hidai, Catal.
Today 2001, 66, 53 – 61; e) L. H.
Gade, Angew. Chem. Int. Ed.
2
000, 39, 2658 – 2678; Angew.
Chem. 2000, 112, 2768 – 2789;
f) E. K. van den Beuken, B. L.
Feringa, Tetrahedron 1998, 54,
1
2985 – 13011; g) M. Sawamura,
M. Sudoh, Y. Ito, J. Am. Chem.
Soc. 1996, 118, 3309 – 3310;
h) L. B. Flieds, E. N. Jacobsen,
Tetrahedron 1993, 4, 2229 – 2240.
2] M. Ma, A. Sidiropoulos, L. Ralte,
A. Stasch, C. Jones, Chem.
Commun. 2013, 49, 48 – 50.
[
[
3] a) M. Molon, C. Gemel, R. A.
Fischer, Dalton Trans. 2014, 43,
3
114 – 3120; b) T. Bollermann, C.
Gemel, R. A. Fischer, Coord.
Chem. Rev. 2012, 256, 537 – 555;
c) T. Bollermann, K. Freitag, C.
Gemel, R. W. Seidel, R. A.
Fischer, Organometallics 2011,
Scheme 1.
In conclusion, the SiÀM (M = Zn, Hg) bonds in
3
0, 4123 – 4127; d) T. Bollermann, K. Freitag, C. Gemel, R. W.
Seidel, M. von Hopffgarten, G. Frenking, R. A. Fischer, Angew.
Chem. Int. Ed. 2011, 50, 772 – 776; Angew. Chem. 2011, 123, 798 –
02; e) T. Cadenbach, T. Bollermann, C. Gemel, M. Tombul, I.
Fernandez, M. V. Hopffgatren, G. Frenking, R. A. Fischer, J.
Am. Chem. Soc. 2009, 131, 16063 – 16077.
[
(R Si) M], with the relatively non-bulky tBuMe Si substitu-
3 2 2
0
ents, are thermally activated by Pt complex 1 to generate
under mild conditions, tBuMe Si radicals. In contrast, the
2
8
bulkier [(tBu MeSi) M], (M = Zn, Hg) do not undergo SiÀM
2
2
bond activation. The enhancing effect of 1 on the homolytic
cleavage of the MÀSi bonds in [(tBuMe Si) M] is mediated by
[4] a) J. H. Bridson, W. Henderson, B. K. Nicholson, T. S. A. Hor,
Inorg. Chim. Acta 2006, 359, 680 – 684; b) W. Chen, F. Liu, T.
Nishioka, K. Matsumoto, Eur. J. Inorg. Chem. 2003, 4234 – 4243;
c) J. A. R. Navarro, E. Freisinger, B. Lippert, Eur. J. Inorg.
Chem. 2000, 147 – 151; d) H. Schçllhorn, U. Thewalt, B. Lippert,
Inorg. Chim. Acta 1985, 108, 77 – 81.
5] a) D. Bravo-Zhivotovskii, I. Ruderfer, M. Yuzefovich, M. Kosa,
M. Botoshansky, B. Tumanskii, Y. Apeloig, Organometallics
2005, 24, 2698 – 2704; b) D. Bravo-Zhivotovskii, M. Yuzefovich,
N. Sigal, G. Korogodsky, K. Klinkhammer, B. Tumanskii, A.
Shames, Y. Apeloig, Angew. Chem. Int. Ed. 2002, 41, 649 – 651;
Angew. Chem. 2002, 114, 671 – 673; c) N. Wiberg, K. Amelunxen,
H. W. Lerner, H. Noth, A. Appel, J. Knizek, K. Polborn, Z.
Anorg. Allg. Chem. 1997, 623, 1861 – 1870; d) S. W. Bennett, C.
Eaborn, R. A. Jackson, J. Organomet. Chem. 1970, 21, 79 – 81;
e) W. P. Neumann, F. Werner, Chem. Ber. 1978, 111, 3904 – 3911.
6] A possible explanation for the different 9:10 ratio in photolysis
and thermolysis is the presence of the alkyl phosphine ligands on
2
2
formation of octahedral hexacoordinate PtÀM bimetallic
complexes 2 (for Zn) and 3 (for Hg) which dissociate under
mild warming or under photolysis to yield R SiC radicals and
novel square-pyramidal paramagnetic Pt species, character-
ized by EPR spectroscopy and DFT calculations. The
3
III
[
reported activation of the SiÀM bonds in [(tBuMe Si) M]
2
2
(
M = Zn, Hg) occurs in the presence of stoichiometric
amounts of [(dmpe)Pt(PEt ) ] (1). We are now searching for
3
2
0
Pt complexes and metallosilanes for the creation of a catalytic
system based on Pt-mediated homolytic (radical) activation
of R SiÀM bonds which may be an interesting alternative to
3
classic Pt-catalyzed or radical initiated reactions such as those
[21]
used in hydrosilylation.
[
1
which act as an effective hydrogen source for the produced silyl
Acknowledgements
radicals, thus, inverting the 9:10 ratio in Equation (4) compared
to Equation (3). Another explanation, suggested by a referee, is
that in photolysis (Equation (3)) two silyl radicals may be
produced nearly simultaneously in a solvent cage, enhancing the
relative amount of the disilane.
This research was supported by the Israel Science Foundation,
the Fund for the Promotion of Research at the Technion and
the Minerva Foundation in Munich. D.B.-Z., B.T., and M.B.
1
1820 www.angewandte.org
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2015, 54, 11817 –11821

Angewandte
Chemie
[
[
7] R. Dobrovetsky, Y. Kratish, B. Tumanskii, M. Botoshansky, D.
calculated geometries and the simulated spectra are given in the
Bravo-Zhivotovskii, Y. Apeloig, Angew. Chem. Int. Ed. 2012, 51,
Supporting Information; c) The calculations were carried out
using the ORCA 2.9 software. F. Neese, ORCA, version 2.9, an
ab initio, density functional and semi-empirical program pack-
age (Max Planck Institute for Bioinorganic Chemistry: Mülheim
an der Ruhr, Germany, 2012).
4
671 – 4675; Angew. Chem. 2012, 124, 4749 – 4753.
8] The denoted oxidation states are formal and do not indicate the
actual charge on the Pt atom, in particular as the Pauling
electronegativity of Zn (1.65), Hg (1.9), and Si (1.90) are lower
than those of Pt (2.2).
[15] a) In principle, radicals 5 and 6 can also exist having the two SiR3
[
9] The supplementary crystallographic data for 2a is given in
CCDC 1023697 and for 3b in CCDC-1023671. These data can be
obtained free of charge from The Cambridge Crystallographic
Data Centre.
groups in the equatorial positions and the MSiR group in the
3
axial position. According to the DFT calculations these two
À1
isomers are close in energy, within 1.2 kcalmol , and can easily
interconvert by a Berry pseudo-rotation. However, the observed
EPR spectra fit only the calculated spectra of 5 and 6; other
isomers of 5 and 6 have significantly different calculated spectra;
b) Isomers of 5 and 6 with a triangular-bipyramid structure
having the spin pointing to an equatorial position are not
observed and according to the DFT calculations these isomers
are not in a local minimum on the potential-energy surface
collapsing to isomers with the spin pointing to the axial position
as in 5 and 6.
[
10] a) According to DFT calculations at ZORA B3LYP-D3/TZVP
for details see Supporting Information) of model systems in
which the tBuMe Si-groups are substituted by Me Si groups,
(
2
3
a possible explanation for the almost inverse product regiose-
lectivity obtained from bis(silyl)zinc and bis(silyl)mercury lies in
À1
the relative stability of the isomers. Thus, 2a is by 1.2 kcalmol
À1
lower in energy than 2b and 3a is by 1.5 kcalmol higher in
energy than 3b; b) The stereoisomer of 2 with two silylzinc
groups trans to each other is not detected by NMR spectroscopy
[16] a) A. D. Becke, J. Chem. Phys. 1993, 98, 5648 – 5652; b) C. Lee,
W. Yang, R. G. Parr, Phys. Rev. B 1988, 37, 785 – 789; c) S. H.
Vosko, L. Wilk, M. Nusair, Can. J. Phys. 1980, 58, 1200 – 1211.
[17] a) D. A. Pantazis, X. Y. Chen, C. R. Landis, F. Neese, J. Chem.
Theory Comput. 2008, 4, 908; b) A. Schäfer, C. Huber, R.
Ahlrichs, J. Chem. Phys. 1994, 100, 5829 – 5835; c) A. Schäfer, H.
Horn, R. Ahlrichs, J. Chem. Phys. 1992, 97, 2571 – 2577.
[18] Detailed information about the kinetic measurements for 5 and
6 is given in the Supporting Information.
[19] Compounds 14 and 15 were isolated and their X-ray crystallog-
raphy structures are given in the Supporting Information; for 14
in CCDC 1023684 and for 15 in CCDC-1023698. These data can
be obtained free of charge from The Cambridge
Crystallographic Data Centre.
À1
probably because it is 5.8 kcalmol higher in energy than 2a.
Also for the mercury species 3 this isomer is not detected by
NMR (see Supporting Information for more details) even
À1
though, it is only 0.9 kcalmol higher in energy than 3b.
[
[
11] a) B. de Bruin, D. G. H. Hetterscheid, A. J. J. Koekkoek, H.
Grutzmacher, Prog. Inorg. Chem. 2007, 55, 247 – 355; b) A. L.
Rieger, P. H. Rieger, Organometallics 2004, 23, 154 – 162.
12] J. A. Weil, J. R. Bolton, Electron Paramagnetic Resonance:
Elementary Theory and Practical Applications, 2nd ed., John
Wiley & Sons, Inc., Hoboken, NJ, USA, 2007, Chap. 4, pp. 85 –
1
17.
[
13] a) J. S. Pap, F. L. Benedito, E. Bothe, E. Bill, S. D. George, T.
Weyhermüller, K. Wieghardt, Inorg. Chem. 2007, 46, 4187 –
4
196; b) D. Herebian, E. Bothe, F. Neese, T. Weyhermuller, K.
[20] S. Grimme, J. Antony, S. Ehrlich, H. Krieg, J. Chem. Phys. 2010,
132, 154104.
[21] a) B. Marciniec, Comprehensive Handbook on hydrosilylation,
Pergamon Press, Oxford, 1992; b) L. N. Lewis, K. G. Sy, G. L.
Bryant, P. E. Donahue, Organometallics 1991, 10, 3750 – 3759.
Wieghardt, J. Am. Chem. Soc. 2003, 125, 9116; c) E. Mçller, R.
Kirmse, Inorg. Chim. Acta 1997, 257, 273 – 276; Example for Pt
III
complexes in which the spin is localized mainly on the platinum
atom: d) O. Rivada-Wheelaghan, M. A. OrtuÇo, S. E. García-
Garrido, J. Díez, P. J. Alonso, A. Lledós, S. Conejero, Chem.
Commun. 2014, 50, 1299 – 1301; e) O. Rivada-Wheelaghan,
M. A. OrtuÇo, J. Díez, S. E. García-Garrido, C. Maya, A.
Lledós, S. Conejero, J. Am. Chem. Soc. 2012, 134, 15261 – 15264.
14] a) The simulations were performed using the SimFonia software;
b) Additional details of the calculations including the optimized
[
Received: June 24, 2015
Published online: August 18, 2015
Angew. Chem. Int. Ed. 2015, 54, 11817 –11821
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org 11821