The donor-stabilized silylene bis[N,N′-diisopropylbenzamidinato(-)] silicon(II): Synthesis, electronic structure, and reactivity

Article abstract of DOI:10.1002/chem.201402483

A convenient and robust synthesis of bis[N,N′- diisopropylbenzamidinato(-)]silicon(II) (1), a donor-stabilized silylene, has been developed (35 g scale). To get further information about the reactivity profile of 1, a series of oxidative addition reactions were studied. Treatment of 1 with PhSe-SePh (Se-Se bond activation), C₆F₆ (C-F activation), and CO₂ (C=O activation/cycloaddition) yielded the neutral six-coordinate silicon(IV) complexes 10, 11, and 13, respectively. Treatment of 1 with N₂O resulted in the formation of the dinuclear five-coordinate silicon(IV) complex 12 (oxidative addition/dimerization), which contains a four-membered Si₂O₂ ring. Compounds 10-13 were characterized by NMR spectroscopic studies in the solid state and in solution and by crystal structure analyses. Silylene 1 is three-coordinate in the solid state (from crystal structure analysis) and exists as the four-coordinate isomer 1′ in benzene solution (from computational studies). Based on state-of-the-art relativistic DFT analyses, the four-coordinate species 1′ was demonstrated to be the thermodynamically favored isomer in benzene solution (favored by ΔG=6.6 kcal mol^-1 over the three-coordinate species 1). The reason for this was studied by bonding analyses of 1 and 1′. Furthermore, the ²⁹Si NMR chemical shifts of 1 and 1′ were computed, and in the case of 1′ it was analyzed how this NMR spectroscopic parameter is affected by solvation. These studies further supported the assumption that the silylene is four-coordinate in solution. Silicon(II)/silicon(IV): The donor-stabilized silylene 1 (three-coordinate in the solid state) was synthesized on a 35 g scale. In benzene solution, the four-coordinate isomer 1′ is the thermodynamically favored species. Treatment of the silylene with PhSeSePh, C₆F₆, N ₂O, and CO₂ yields the respective silicon(IV) complexes 2-5.

Full text of DOI:10.1002/chem.201402483

DOI: 10.1002/chem.201402483
Full Paper
&
Silicon
The Donor-Stabilized Silylene
Bis[N,N’-diisopropylbenzamidinato(ꢀ)]silicon(II):
Synthesis, Electronic Structure, and Reactivity
Konstantin Junold,[a] Marco Nutz,[a] Johannes A. Baus,[a] Christian Burschka,[a]
Cꢀlia Fonseca Guerra,[b] F. Matthias Bickelhaupt,*[b, c] and Reinhold Tacke*[a]
Dedicated to Professor Helmut Werner on the occasion of his 80th birthday
Abstract: A convenient and robust synthesis of bis[N,N’-di-
isopropylbenzamidinato(ꢀ)]silicon(II) (1), a donor-stabilized
silylene, has been developed (35 g scale). To get further in-
formation about the reactivity profile of 1, a series of oxida-
tive addition reactions were studied. Treatment of 1 with
PhSeꢀSePh (SeꢀSe bond activation), C6F6 (CꢀF activation),
and CO2 (C=O activation/cycloaddition) yielded the neutral
six-coordinate silicon(IV) complexes 10, 11, and 13, respec-
tively. Treatment of 1 with N2O resulted in the formation of
the dinuclear five-coordinate silicon(IV) complex 12 (oxida-
tive addition/dimerization), which contains a four-membered
Si2O2 ring. Compounds 10–13 were characterized by NMR
spectroscopic studies in the solid state and in solution and
by crystal structure analyses. Silylene 1 is three-coordinate in
the solid state (from crystal structure analysis) and exists as
the four-coordinate isomer 1’ in benzene solution (from
computational studies). Based on state-of-the-art relativistic
DFT analyses, the four-coordinate species 1’ was demonstrat-
ed to be the thermodynamically favored isomer in benzene
solution (favored by DG=6.6 kcal molꢀ1 over the three-coor-
dinate species 1). The reason for this was studied by bond-
ing analyses of 1 and 1’. Furthermore, the 29Si NMR chemical
shifts of 1 and 1’ were computed, and in the case of 1’ it
was analyzed how this NMR spectroscopic parameter is af-
fected by solvation. These studies further supported the as-
sumption that the silylene is four-coordinate in solution.
this compound.[5,6] According to the crystal structure analysis,
compound 1 is a three-coordinate silylene; however, NMR
spectroscopic studies indicated that in solution the four-coor-
dinate species 1’ may also play a role. Furthermore, in all the
reactions studied so far, compound 1 formally reacted as
a four-coordinate species. For example, treatment of 1 with S8,
Se, Te, or I2 led to the five- or six-coordinate silicon(IV) com-
plexes 2–5 (oxidative additions),[5,6a] and treatment of 1 with
[Fe(CO)5] or [M(CO)6] (M=Cr, Mo, W) yielded the five-coordi-
nate silicon(II) compounds 6–9 (nucleophilic substitutions).[5,6b]
In continuation of these studies, we have now improved the
synthesis of 1 and have investigated a series of further oxida-
tive addition reactions. In addition, we have performed compu-
tational studies on 1 and 1’.
Herein, we report on 1) an improved synthesis of 1 (35 g
scale), 2) the syntheses of compounds 10–13 (formed by treat-
ment of 1 with PhSeSePh, C6F6, N2O, or CO2), and 3) quantum-
chemical studies to elucidate the structure of 1 in solution and
to get information about the bonding situation of 1 and its
four-coordinate isomer 1’. These investigations were per-
formed as part of our systematic studies on higher-coordinate
silicon(II) and silicon(IV) compounds (for recent publications,
see references [5–7]).
Introduction
In the past 2–3 decades, stable silylenes have proven to be
versatile reagents in organosilicon chemistry, which has been
demonstrated quite impressively by Jutzi et al., West et al.,
Heinicke et al., Kira et al., Roesky et al., Driess et al., Filippou
et al., and others.[1–4] In this context, higher-coordinate (donor-
stabilized) silylenes with amidinato ligands are of particular in-
terest because of their relatively easy accessibility and manifold
reactivity.[4] Recently, we have reported on the synthesis of
bis[N,N’-diisopropylbenzamidinato(ꢀ)]silicon(II) (1),
a
new
donor-stabilized silylene,[5] and the first reactivity studies with
[a] K. Junold, M. Nutz, J. A. Baus, Dr. C. Burschka, Prof. Dr. R. Tacke
Universitꢀt Wꢁrzburg, Institut fꢁr Anorganische Chemie
Am Hubland, 97074 Wꢁrzburg (Germany)
Fax: (+49)931-31-84609
E-mail: r.tacke@uni-wuerzburg.de
[b] Dr. C. Fonseca Guerra, Prof. Dr. F. M. Bickelhaupt
VU University Amsterdam, Department of Theoretical Chemistry
Amsterdam Center for Multiscale Modeling (ACMM)
De Boelelaan 1083, 1081 HV Amsterdam (The Netherlands)
E-mail: f.m.bickelhaupt@vu.nl
[c] Prof. Dr. F. M. Bickelhaupt
Radboud University Nijmegen, Institute for Molecules and Materials
Heyendaalseweg 135, 6525 AJ Nijmegen (The Netherlands)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201402483.
Chem. Eur. J. 2014, 20, 1 – 12
1
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
elemental analyses (C, H, N), multinuclear NMR spec-
troscopic studies in the solid state (15N, 29Si, 77Se) and
in solution (1H, 13C, 29Si, 77Se), and crystal structure
analyses (compound 10 was crystallographically char-
acterized as the solvate 10·CH3CN).
The formation of 10–13 can be formally described
in terms of oxidative addition reactions. In the case
of 10 and 11, this reaction implies an activation of
a SeꢀSe and CꢀF bond, respectively. The formation
of 12 and 13 can be rationalized as two-step process-
es (Scheme 2): In the first step, the five-coordinate sil-
icon(IV) complex 12’ (an oxygen analogue of the
stable sulfur, selenium, and tellurium compounds 2–
4) is formed as an intermediate (not detected experi-
mentally; generation of CO monitored as described
in ref. [8]), which then dimerizes to give the dinuclear
five-coordinate silicon(IV) complex 12 or reacts with
a further equivalent of carbon dioxide to give the six-
coordinate silicon(IV) complex 13. Compound 13 rep-
resents the first structurally characterized silicon(IV)
complex with a chelating carbonato(2ꢀ) ligand. The
formation of 13 can be described as a [2+2] cycload-
dition of 12’ and carbon dioxide. In the reactions
Results and Discussion
Syntheses
Compounds 1 and 10–13 were synthesized according to
Scheme 1.
The donor-stabilized silylene 1 was prepared by treatment
of
chlorohydridobis[N,N’-diisopropylbenzamidinato(ꢀ)]sili-
con(IV) (14) with 1.05 molar equivalents of potassium bis(tri-
methylsilyl)amide in benzene at 208C and was isolated in 82%
yield as an orange-colored crystalline solid. The synthetic
method used for the preparation of 1 was the same as de-
scribed earlier;[5] however, modifications concerning the sol-
vent, the molar ratio of the reactants, and the reaction time
were made. The modified method is very convenient and
robust and allows the synthesis of 1 on the 35 g scale. Com-
pound 1 shows a remarkable thermal stability; it melts at
1278C and recrystallizes upon cooling without decomposition.
It is soluble and stable in organic solvents such as benzene,
toluene, n-hexane, THF, and diethyl ether, but decomposes rap-
idly in dichloromethane, DMSO, DMF, and acetonitrile.
The six-coordinate silicon(IV) complexes 10 and 11 were syn-
thesized by treatment of 1 with one molar equivalent of di-
phenyl diselenide or hexafluorobenzene in toluene at 208C.
The dinuclear five-coordinate silicon(IV) complex 12 was ob-
tained by treatment of 1 with an excess of dinitrogen monox-
ide in toluene at ꢀ788C (!208C). The six-coordinate silicon(IV)
complex 13 was synthesized by treatment of 1 with an excess
of carbon dioxide in toluene at 208C. Compound 10 was iso-
lated as a yellow crystalline solid, whereas 11·0.5n-C6H14,
12·C6H5CH3, and 13 were obtained as colorless crystalline
solids (yields: 10, 92; 11·0.5n-C6H14, 87; 12·C6H5CH3, 93; 13,
78%). The identities of these compounds were established by
Scheme 1. Syntheses of compounds 1 and 10–13.
&
&
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
2
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
can be seen from the different
NꢀC bond lengths in these units
(Table 1).
As can be seen from Table 2,
the
SiꢀN(amidinato)
bond
lengths of 10–13 depend on the
coordination mode of the two
amidinato ligands. The SiꢀN dis-
tances of the six-coordinate sili-
con(IV) complexes 10, 11, and
13 (two bidentate amidinato li-
gands) are similar and range
from 1.8711(14) to 1.9744(13) ꢂ.
In the case of the five-coordinate
silicon(IV) complex 12 (one bi-
dentate and one monodentate
Scheme 2. Proposed formation of 12 and 13 via the intermediate 12’.
amidinato ligand at each of the
two silicon atoms), a strong dif-
ferentiation between the SiꢀN
1!10, 1!11, and 1!13, compound 1 formally behaves as
a four-coordinate silylene to give six-coordinate silicon(IV)
complexes. In contrast, in the reaction 1!12, compound 1 for-
mally reacts as a three-coordinate silylene to give a five-coordi-
nate silicon(IV) complex (the formation of the proposed inter-
mediate 12’ formally implies a reaction as a four-coordinate si-
lylene).
bond lengths is observed. The axial SiꢀN distances (2.0966(17)
and 2.0909(16) ꢂ) are significantly longer than the equatorial
ones (1.7569(16)–1.8001(16) ꢂ), and the equatorial SiꢀN bond
distances of the bidentate amidinato ligands (1.7967(15) and
1.8001(16) ꢂ) are somewhat longer than those of the mono-
dentate amidinato ligands (1.7569(16) and 1.7600(15) ꢂ).
Crystal structure analyses
Compounds 10·CH3CN, 11·0.5n-C6H14, 12·C6H5CH3, and 13 were
structurally characterized by single-crystal X-ray diffraction. The
crystal data and the experimental parameters used for the
crystal structure analyses are given in Table S1 (see the Sup-
porting Information). The molecular structures of 10–13 are
shown in Figures 1–4 (hydrogen atoms omitted for clarity); se-
lected bond lengths and angles are given in the corresponding
figure legends.
The silicon coordination polyhedra of the neutral six-coordi-
nate silicon(IV) complexes 10, 11, and 13 are best described as
strongly distorted octahedra, with maximum deviations from
the ideal 90/1808 angles of 21.57/21.57 (10), 22.58/19.07 (11),
and 20.56/18.338 (13). The silicon coordination polyhedra of
the neutral dinuclear five-coordinate silicon(IV) complex 12 are
strongly distorted trigonal bipyramids, with axial OꢀSiꢀN
angles of 159.16(6) and 158.28(6)8. The sum of the equatorial
bond angles amounts to 356.97 and 356.848, and the Berry
distortions[9] were calculated at 33.9 (Si1) and 37.4% (Si2).
The structural features of compounds 10, 11, and 13 are
very similar to what has been found for other six-coordinate
silicon(IV) complexes with two bidentate amidinato ligands
and two monodentate ligands.[5,7c] As observed for the sili-
con(II) complex 1,[5] one bidentate and one monodentate ami-
dinato ligand are bound to each of the two silicon coordina-
tion centers of the five-coordinate silicon(IV) complex 12. The
different coordination modes of the amidinato ligands in 10–
13 (bidentate and/or monodentate) are reflected by different
degrees of electron delocalization in the NC(Ph)N moieties as
Figure 1. Molecular structure of 10 in the crystal of 10·CH3CN (probability
level of displacement ellipsoids 50%). Selected bond lengths [ꢂ] and angles
[8]: SiꢀSe1 2.4470(10), SiꢀSe2 2.4309(11), SiꢀN1 1.888(2), SiꢀN2 1.894(2),
SiꢀN3 1.879(2), SiꢀN4 1.940(2), N1ꢀC1 1.336(3), N2ꢀC1 1.331(3), N3ꢀC14
1.338(3), N4ꢀC14 1.330(3); Se1-Si-Se2 90.07(3), Se1-Si-N1 97.69(8), Se1-Si-N2
165.74(7), Se1-Si-N3 96.08(8), Se1-Si-N4 83.14(7), Se2-Si-N1 97.20(7),
Se2-Si-N2 95.49(7), Se2-Si-N3 99.31(7), Se2-Si-N4 165.11(7), N1-Si-N2
68.63(10), N1-Si-N3 158.43(9), N1-Si-N4 96.83(9), N2-Si-N3 95.96(10), N2-Si-N4
94.23(9), N3-Si-N4 68.43(9), N1-C1-N2 106.1(2), N3-C14-N4 107.3(2).
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
3
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
Figure 3. Molecular structure of 12 in the crystal of 12·C6H5CH3 (probability
level of displacement ellipsoids 50%). Selected bond lengths [ꢂ] and angles
[8]: Si1ꢀO1 1.7205(13), Si1ꢀO2 1.6565(13), Si2ꢀO1 1.6590(13), Si2ꢀO2
1.7199(13), Si1ꢀN1 1.7967(15), Si1ꢀN2 2.0966(17), Si1ꢀN3 1.7569(16), Si2ꢀN5
1.8001(16), Si2ꢀN6 2.0909(16), Si2ꢀN7 1.7600(15), N1ꢀC1 1.349(2), N2ꢀC1
1.309(2), N3ꢀC14 1.400(3), N4ꢀC14 1.284(2), N5ꢀC27 1.351(2), N6ꢀC27
1.311(2), N7ꢀC40 1.396(2), N8ꢀC40 1.279(2); Si1-O1-Si2 93.43(7), Si1-O2-Si2
93.54(7), O1-Si1-O2 86.48(7), O1-Si2-O2 86.42(7), O1-Si1-N1 97.20(7), O1-Si-N2
159.16(6), O1-Si1-N3 104.19(7), O1-Si2-N5 124.82(7), O1-Si2-N6 90.91(6),
O1-Si2-N7 116.46(7), O2-Si1-N1 123.72(7), O2-Si1-N2 91.67(7), O2-Si1-N3
116.71(7), O2-Si2-N5 97.22(7), O2-Si2-N6 158.28(6), O2-Si2-N7 104.79(7),
N1-Si1-N2 66.74(7), N1-Si1-N3 116.54(7), N2-Si1-N3 95.19(7), N5-Si2-N6
66.87(7), N5-Si2-N7 115.56(7), N6-Si2-N7 95.70(7), N1-C1-N2 108.41(16),
N3-C14-N4 121.54(17), N5-C27-N6 108.29(15), N7-C40-N8 120.38(18).
Figure 2. Molecular structure of 11 in the crystal of 11·0.5n-C6H14 (probability
level of displacement ellipsoids 50%). Selected bond lengths [ꢂ] and angles
[8]: SiꢀF1 1.6484(9), SiꢀN1 1.8711(14), SiꢀN2 1.9354(12), SiꢀN3 1.8816(14),
SiꢀN4 1.9744(13), SiꢀC27 2.0042(16), N1ꢀC1 1.3396(18), N2ꢀC1 1.320(2),
N3ꢀC14 1.341(2), N4ꢀC14 1.311(2); F1-Si-N1 94.05(5), F1-Si-N2 160.93(6),
F1-Si-N3 98.58(5), F1-Si-N4 89.54(5), F1-Si-C27 92.31(6), N1-Si-N2 68.12(5),
N1-Si-N3 161.67(6), N1-Si-N4 99.60(6), N1-Si-C27 98.26(6), N2-Si-N3 97.37(6),
N2-Si-N4 86.98(5), N2-Si-C27 96.80(6), N3-Si-N4 67.42(6), N3-Si-C27 94.47(6),
N4-Si-C27 161.87(6), N1-C1-N2 106.59(12), N3-C14-N4 107.70(13).
Table 1. Comparison of the NꢀC bond lengths [ꢂ] of the NC(Ph)N moie-
ties in 10–13.
Compound
N1ꢀC1
N2ꢀC1
N3ꢀC14
N4ꢀC14
lengths of 1.7794(17) and 1.7793(19) ꢂ and an OꢀSiꢀO angle
of 73.54(8)8. The OꢀCꢀO angles (105.7(2), 126.9(2), and
127.4(2)8) reflect the trigonal-planar coordination of the carbo-
nato carbon atom (sum of OꢀCꢀO bond angles is 3608). The
CꢀO bond lengths of the silicon-bound oxygen atoms amount
to 1.338(3) and 1.334(3) ꢂ, whereas the C=O double bond of
the carbonato ligand is significantly shorter (1.219(3) ꢂ).
10
11
12
1.336(3)
1.3396(18)
1.349(2)
1.351(2)[a]
1.331(3)
1.331(3)
1.320(2)
1.309(2)
1.311(2)[b]
1.337(3)
1.338(3)
1.341(2)
1.400(3)
1.396(2)[c]
1.326(3)
1.330(3)
1.311(2)
1.284(2)
1.279(2)[d]
1.335(3)
13
[a] N5ꢀC27. [b] N6ꢀC27. [c] N7ꢀC40. [d] N8ꢀC40.
The SiꢀSe bond lengths of 10 (2.4470(10) and 2.4309(11) ꢂ)
are similar to those observed for the related compound 15
(2.3989(8) and 2.4142(7) ꢂ),[7c] and the SiꢀF distance of 11 is
almost identical with the SiꢀF bond lengths of 16.[7c] The SiꢀC
distance of 11 is 2.0042(16) ꢂ. The tricyclic compound 12 con-
tains a central four-membered Si2O2 ring (SiꢀOꢀSi: 93.43(7)
and 93.54(7)8; OꢀSiꢀO: 86.48(7) and 86.42(7)8). The axial SiꢀO
bond distances (1.7205(13) and 1.7199(13) ꢂ) are somewhat
longer than the equatorial ones (1.6590(13) and 1.6565(13) ꢂ).
Similar structural features have been observed for a series of
related five-coordinate silicon(IV) complexes that also contain
a four-membered Si2O2 ring.[4j,m] Compound 13 contains a four-
membered SiO2C ring formed by the bidentate carbonato
ligand and the silicon coordination center, with SiꢀO bond
NMR spectroscopic studies
Compounds 10–13 were studied by using NMR spectroscopy
in the solid state (15N, 29Si, 77Se; 10, 11·0.5n-C6H14, 12·CH3CN,
13) and in solution (1H, 13C, 29Si, 77Se; solvent, CD2Cl2 (10, 13) or
C6D6 (11, 12)). The data obtained (see the Experimental Sec-
tion) confirm the identities of the compounds studied.
&
&
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
4
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
Table 2. Comparison of selected SiꢀX (X=C, N, O, F, Se) bond lengths [ꢂ]
of 10–13.
Bond
10
11
12
13
SiꢀN1
Si2ꢀN5
SiꢀN2
Si2ꢀN6
SiꢀN3
Si2ꢀN7
SiꢀN4
SiꢀC27
SiꢀO1
Si2ꢀO1
SiꢀO2
Si2ꢀO2
SiꢀF
1.888(2)
1.8711(14)
1.7967(15)[a]
1.8001(16)
2.0966(17)[b]
2.0909(16)
1.7569(16)[c]
1.7600(15)
1.887(2)
1.894(2)
1.879(2)
1.940(2)
1.9354(12)
1.8816(14)
1.873(2)
1.875(2)
1.9744(13)
2.0042(16)
1.8839(19)
1.7794(17)
1.7793(19)
1.7205(13)[d]
1.6590(13)
1.6565(13)[e]
1.7199(13)
1.6484(9)
SiꢀSe1
SiꢀSe2
2.4470(10)
2.4309(11)
[a] Si1ꢀN1. [b] Si1ꢀN2. [c] Si1ꢀN3. [d] Si1ꢀO1. [e] Si1ꢀO2.
Table 3. Comparison of the isotropic 29Si chemical shifts (ppm) of 10–13
in the solid state (T=228C) and in solution (T=238C).
Compound
d29Si (solid state)[a]
d29Si (solution)[b]
10
11
12
13
ꢀ177.3
ꢀ170.0
ꢀ160.5[d]
ꢀ82.9
ꢀ160.0[c]
ꢀ93.0, ꢀ91.9
ꢀ164.4
ꢀ165.9
[a] Compounds 11 and 12 were studied as the solvates 11·0.5n-C6H14 and
12·C6H5CH3. [b] Solvent, CD2Cl2 (10, 13) or C6D6 (11, 12). [c] Doublet,
1J(29Si,19F)=245.5 Hz. [d] Doublet, J(29Si,19F)=250.0 Hz.
1
Figure 4. Molecular structure of 13 in the crystal (probability level of dis-
placement ellipsoids 50%). Selected bond lengths [ꢂ] and angles [8]: SiꢀO1
1.7794(17), SiꢀO2 1.7793(19), SiꢀN1 1.887(2), SiꢀN2 1.873(2), SiꢀN3 1.875(2),
SiꢀN4 1.8839(19), O1ꢀC27 1.338(3), O2ꢀC27 1.334(3), O3ꢀC27 1.219(3),
N1ꢀC1 1.331(3), N2ꢀC1 1.337(3), N3ꢀC14 1.326(3), N4ꢀC14 1.335(3);
O1-Si-O2 73.54(8), O1-Si-N1 96.54(8), O1-Si-N2 96.66(8), O1-Si-N3 96.74(8),
O1-Si-N4 161.67(8), O2-Si-N1 97.53(9), O2-Si-N2 163.11(8), O2-Si-N3 97.76(9),
O2-Si-N4 95.83(9), N1-Si-N2 69.45(9), N1-Si-N3 162.07(10), N1-Si-N4 99.69(7),
N2-Si-N3 97.04(9), N2-Si-N4 96.96(9), N3-Si-N4 69.44(8), O1-C27-O2 105.7(2),
O1-C27-O3 126.9(2), O2-C27-O3 127.4(2), N1-C1-N2 106.82(19), N3-C14-N4
107.17(19).
75 ppm for the two crystallographically independent selenium
sites was observed.
As already observed for other silicon(IV) complexes with two
amidinato ligands,[5,6a,7d] compounds 11 and 12 show a dynamic
1
behavior in solution at 238C. Whereas the H NMR spectra of
10 and 13 (solvent, CD2Cl2) show four doublets and two sep-
tets for the four isopropyl groups, one doublet and one septet
1
are found in the H NMR spectrum of 12 (C6D6) and two dou-
blets and one septet in the H NMR spectrum of 11 (C6D6). Ac-
1
As can be seen from Table 3, the respective isotropic 29Si
chemical shifts of 10–13 in the solid state and in solution are
similar, indicating that these six- and five-coordinate silicon(IV)
complexes also exist in solution. The shift differences observed
for 10 (Dd29Si=7.3 ppm) and 12 (Dd29Si=10.1/9.0 ppm) are
larger than those for 11 (Dd29Si=0.5 ppm) and 13 (Dd29Si=
1.5 ppm) and may reflect somewhat different structures in the
solid state and in solution, however, without changes in the sil-
icon coordination number. For compound 10, also differences
in the isotropic 77Se chemical shifts were observed (solid state:
d77Se=205.2/280.9 ppm; solution: solvent, CD2Cl2; d77Se=
436.6 ppm). These differences could be explained by different
steric arrangements of the two SePh groups in the solid state
and in solution. Generally, the 77Se chemical shift is very sensi-
tive to the surroundings of the 77Se nucleus, and this is also re-
flected by the two different isotropic 77Se chemical shifts of 10
in the solid state, in which a chemical shift difference of
cordingly, one CH3CHCH3 and one CH3CHCH3 resonance signal
are found in the 13C{1H} NMR spectrum of 12, whereas two
CH3CHCH3 signals and one CH3CHCH3 signal are observed for
11. The 13C{1H} NMR spectrum of 10 shows three CH3CHCH3
signals (relative intensities: 1:2:1) and two CH3CHCH3 signals,
and the spectrum of 13 shows four CH3CHCH3 signals and two
CH3CHCH3 signals. These findings can be explained by a rapid
exchange of the amidinato-nitrogen binding sites of 11 and 12
at 238C, whereas such kind of dynamic behavior was not ob-
served for 10 and 13.
As already stated earlier,[5] the 29Si NMR spectra of the sily-
lene 1 suggest that this species is four-coordinate (1’) in solu-
tion ([D8]toluene). This holds true for a wide temperature
range (ꢀ80 to 708C), in which no significant changes in the
29Si chemical shift were observed. This can be interpreted by
the presence of 1’ as a single species rather than an equilibri-
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
5
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
um between 1 and 1’ in solution. This is in excellent agree-
ment with the results of the computational studies.
Table 4. Computed relative energies,[a] SiꢀN distances,[a] and 29Si NMR
chemical shifts[b] for 1 and 1’ in the gas phase and in solution (benzene).
Gas phase
Solution (benzene)
Computational studies
1
1’
1
1’
Relative energies
To elucidate the structure of 1 in solution, we have conducted
theoretical analyses based on relativistic density functional
theory. These calculations include an exploration of the geom-
etry and relative energy of various isomers and aggregates as
well as analyses of the SiꢀN bonding mechanism between
[N,N’-diisopropylbenzamidinato(ꢀ)]silicon(II) (DIBA-Si+) and
a second N,N’-diisopropylbenzamidinato(ꢀ) (DIBAꢀ) ligand to
understand how the preferred structure arises (1 vs. 1’). Fur-
thermore, we have compared the 29Si chemical shifts for the
isomers 1 and 1’ and have studied how this NMR spectroscop-
ic parameter is affected by solvation.
[kcalmolꢀ1
DE
]
0.0
0.0
ꢀ7.4
ꢀ7.1
0.0
0.0
ꢀ6.9
ꢀ6.6
DG298
bond lengths [ꢂ]
SiꢀN1
[c]
[c]
–
2.38
1.88
2.03
1.90
–
2.31
1.88
2.03
1.89
SiꢀN2
1.82
1.96
1.93
1.82
1.94
1.92
Si-N3
Si-N4
29Si chemical shifts [ppm]
no explicit
ꢀ22.3
ꢀ61.1
ꢀ53.0
ꢀ45.9
ꢀ19.7
ꢀ62.7
ꢀ49.5
ꢀ43.0
benzene molecule
one explicit
benzene molecule
two explicit
All calculations were performed with the Amsterdam Density
Functional (ADF) program[10] using relativistic density function-
al theory at the ZORA-BLYP-D3(BJ)/TZ2P level of theory for ge-
ometry optimization and energies.[11–13] The calculations of the
29Si NMR chemical shifts (relative to SiMe4) were performed at
the ZORA-SAOP/ET-pVQZ//ZORA-BLYP-D3(BJ)/TZ2P level of
theory.[14,15] Solvation in benzene was simulated using the con-
ductor-like screening model (COSMO).[16] All stationary points
were verified to be minima on the potential energy surface
through vibrational analysis. The bonding mechanism was ana-
lyzed within the framework of quantitative Kohn–Sham molec-
ular orbital theory in combination with a quantitative energy
decomposition analysis of the interaction energy DEint of se-
lected bonds into classical electrostatic attraction DVelstat, Pauli
repulsion DEPauli between occupied orbitals, stabilizing orbital
interactions DEoi, such as the highest occupied molecular orbi-
tal/lowest unoccupied molecular orbital (HOMO/LUMO) inter-
actions, and dispersion interactions DEdisp (for details, see
ref. [17]).
benzene molecules
[a] Computed at ZORA-BLYP-D3(BJ)/TZ2P by using COSMO to estimate
the effect of solvation. [b] Computed at ZORA-SAOP/ET-pVQZ//ZORA-
BLYP-D3(BJ)/TZ2P relative to SiMe4. [c] Dissociated bond.
The computed relative energies, SiꢀN bond lengths, and
29Si NMR chemical shifts for the three- (1) and four-coordinate
silylene (1’) in the gas phase and in solution (benzene) are
given in Table 4. The calculated molecular structures of 1 and
1’ in solution are shown in Figure 5 and Figure 6. Structure 1’
is characterized by a rather shallow potential energy surface as
a function of SiꢀN distances (e.g., variation in the SiꢀN1 bond
length of 0.1 ꢂ is associated with a change in energy of less
than 0.1 kcalmolꢀ1). As also found experimentally (crystal struc-
ture analysis), the silicon coordination polyhedron of 1 is a dis-
torted Y-tetrahedron, whereas a Y-trigonal-bipyramidal struc-
ture is obtained for 1’, with the lone pair in an equatorial posi-
tion. As can be seen from Table 4, the four-coordinate structure
1’ is clearly more stable than the three-coordinate structure
(1), both in the gas phase (7.4 kcalmolꢀ1) and in solution
(6.9 kcalmolꢀ1); the same holds true in terms of Gibbs free
energy at 298.15 K and 1 atm (DG298). This is in line with the
experimental NMR spectroscopic studies, which suggest the
presence of a four-coordinate species in solution (in this con-
text, see ref. [5]). Table 4 also shows that the respective SiꢀN
distances of 1 and 1’ in the gas phase and in solution are very
similar. Although four-coordinate 1’ is the thermodynamically
Figure 5. Molecular structure of 1 computed at ZORA-BLYP-D3(BJ)/TZ2P in
benzene (COSMO). Selected bond lengths [ꢂ] and angles [8]: SiꢀN2 1.822,
SiꢀN3 1.943, SiꢀN4 1.917, N1ꢀC1 1.288, N2ꢀC1 1.404, N3ꢀC2 1.353, N4ꢀC2
1.342; N2-Si-N3 100.60, N2-Si-N4 99.52, N1-C1-N2 120.70, N3-C2-N4 105.60.
favored species, three-coordinate 1 is found in the crystal. The
reason for this is not yet fully understood.
&
&
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
6
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
Figure 7. Key fragment orbitals of the donor–acceptor interaction between
DIBAꢀ and DIBA-Si+ fragments in the three- (1, left) and four-coordinate sily-
lene (1’, right) as was revealed by Kohn–Sham MO analyses at ZORA-BLYP-
D3(BJ)/TZ2P.
Figure 6. Molecular structure of 1’ computed at ZORA-BLYP-D3(BJ)/TZ2P in
benzene (COSMO). Selected bond lengths [ꢂ] and angles [8]: SiꢀN1 2.313,
SiꢀN2 1.881, SiꢀN3 2.028, SiꢀN4 1.893, N1ꢀC1 1.318, N2ꢀC1 1.361, N3ꢀC2
1.344, N4ꢀC2 1.346; N1-Si-N2 62.72, N1-Si-N3 146.29, N1-Si-N4 90.35,
N2-Si-N3 97.82, N2-Si-N4 104.11, N3-Si-N4 66.82, N1-C1-N2 111.42, N3-C2-N4
106.95.
the DIBA-Si+ LUMO+1 only through one lobe on either side,
for example, lobe a+lobe a along one SiꢀN bond (Figure 7).
At variance, in four-coordinate 1’, two lobes on either side can
build up overlap through two lobes on either side, that is,
lobe a+lobe a and lobe b+lobe b along two SiꢀN bonds.
Thus, the net overlap increases from 0.03 in 1 to 0.14 in 1’, and
the orbital interactions DEoi are reinforced as reflected by the
stronger depopulation and population of the DIBAꢀ HOMOꢀ1
and DIBA-Si+ LUMO+1, respectively (see Table 5). Fragment
orbital energies of DIBAꢀ and DIBA-Si+ are not very different
for 1 and 1’, with differences of only 0.2 eV or less. We con-
clude that it is the enhanced donor–acceptor orbital overlap
through two instead of only one SiꢀN bond, which makes the
four-coordinate 1’ the more stable and thus preferred isomer.
Finally, we have examined how the computed 29Si NMR
chemical shifts of 1 and 1’ compare with the values deter-
mined in the solid state (d=ꢀ15.4 ppm; three-coordinate spe-
cies 1 as demonstrated by crystal structure analysis) and in so-
lution (C6D6, d=ꢀ31.4 ppm). The 29Si NMR chemical shifts com-
puted at the sophisticated ZORA-SAOP/ET-pVQZ//ZORA-BLYP-
D3(BJ)/TZ2P level of theory using COSMO to simulate solvation
in benzene do not match the experimental value of d=
ꢀ31.4 ppm, neither for the three- nor the four-coordinate spe-
cies for which we computed d=ꢀ19.7 (1) and d=ꢀ62.7 ppm
(1’) (Table 4). This seems to be in contradiction with the above-
mentioned finding that 1’ is thermodynamically clearly the fa-
vored isomer. We have carried out extensive and costly explo-
rations to find more stable dimer aggregates of 1 or 1’ in
which the electronic environment of the silicon nucleus gives
rise to the experimentally observed chemical shift. However, all
attempts to find either covalently (Si=Si) or van der Waals-
bound dimers resulted in species that are at significantly, that
is, 10 to 23 kcalmolꢀ1, higher in Gibbs free energy than the
monomers. This can be ascribed to the fact that the silicon
atoms in these species are sterically highly congested by their
Table 5. Bonding analyses for 1 and 1’ in the gas phase.[a]
1
1’
Energy-decomposition
analysis [kcalmolꢀ1
]
DEint
ꢀ168.9
244.0
ꢀ237.0
ꢀ159.9
ꢀ16.0
ꢀ176.2
247.1
ꢀ237.5
ꢀ168.2
ꢀ17.6
DEPauli
DVelstat
DEoi
DEdisp
Gross Mulliken populations [e]
P(HOMOꢀ2 of DIBAꢀ)
1.89
0.12
1.79
0.16
P(LUMO+1 of DIBA-Si+)
<DIBAꢀ j DIBA-Si+ >orbital overlap
<HOMOꢀ1 j LUMOꢀ1>
0.03
0.14
[a] Computed at ZORA-BLYP-D3(BJ)/TZ2P. Energy decomposition analysis:
DEint =DVelstat +DEPauli +DEoi +DEdisp (see ref. [17]).
The results of the bonding analyses are collected in Table 5.
They show that the four-coordinate isomer 1’ is more stable
than the three-coordinate species 1 because of more stabiliz-
ing orbital interaction DEoi between [N,N’-diisopropylbenzami-
dinato(ꢀ)]silicon(II) (DIBA-Si+) and the second N,N’-diisopropyl-
benzamidinato(ꢀ) (DIBAꢀ) ligand. A more detailed Kohn–Sham
molecular orbital (MO) analysis reveals that DEoi mainly arises
from donor–acceptor interactions, such as those between the
HOMOꢀ1 of DIBAꢀ and the LUMO+1 of DIBA-Si+. There are
also other donor–acceptor interactions but this pair is particu-
larly discriminating in favor of the four-coordinate isomer 1’.
The 3D representations of these fragment MOs show that that
in three-coordinate 1, the DIBAꢀ HOMOꢀ1 can overlap with
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
7
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
bulky substituents that prevent the formation of stable silicon–
silicon bonding.
Conclusion
Next, we focused on the fact that the silicon center in the
thermodynamically favored species 1’ is directly exposed to
the solvent and carries a large, outward-oriented lobe of the
HOMO of the system (see Figure 8). In addition, the latter orbi-
We have succeeded in developing a very convenient and
robust method for the synthesis of the donor-stabilized sily-
lene 1 on the 35 g scale. This allows a systematic investigation
of the chemistry of this compound on a broad basis. As shown
for a series of oxidative addition reactions, silylene 1 can for-
mally react as a three- or four-coordinate silicon(II) species. In
the reaction with diphenyl diselenide, hexafluorobenzene, and
carbon dioxide, compound 1 formally behaves as a four-coor-
dinate silylene to give the six-coordinate silicon(IV) complexes
10 (SeꢀSe activation), 11 (CꢀF activation), and 13 (CO2 activa-
tion), respectively. In the reaction with dinitrogen monoxide,
however, compound 1 formally reacts as a three-coordinate si-
lylene to yield the dinuclear five-coordinate silicon(IV) complex
12 (N2O activation). Thus, the unique reactivity profile of 1 is
controlled by the different possible coordination modes of the
two amidinato ligands, which can bind in a mono- and/or bi-
dentate fashion and thereby affect the stability of the sili-
con(IV) compounds formed.
Figure 8. HOMO of the four-coordinate silylene 1’ computed at ZORA-BLYP-
D3(BJ)/TZ2P.
Silylene 1 is three-coordinate in the solid state (crystal struc-
ture analysis) and four-coordinate in solution (isomer 1’; com-
putational studies). Based on state-of-the-art relativistic DFT
analyses, we have shown that the four-coordinate species 1’ is
the thermodynamically favored isomer in benzene solution.
This isomer is favored by DG=6.6 kcalmolꢀ1 over the three-co-
ordinate species 1. The reason is an increased SiꢀN donor–ac-
ceptor overlap in the four-coordinate isomer 1’.
tal is at relatively high energy (ꢀ3.7 eV; not shown in Table 5)
as compared with the HOMO of, for example, SiMe4, which is
much lower in energy (ꢀ6.7 eV). This suggests that the local
electronic environment of the silicon nucleus of 1’ and, thus,
its 29Si NMR chemical shift may be affected more strongly than
usually happens in situations in which the average effect of
a continuum model (such as COSMO) suffices. Indeed, the in-
troduction of discrete solvent molecules into the quantum
chemical description of our model systems moves the 29Si NMR
chemical shift of 1’ strongly into the direction of the experi-
mental value (see Table 4). Thus, coordinating one and two
benzene molecules through one of their CꢀH bonds to 1’
leads to a weak donor–acceptor interaction between the
HOMO of the silylene and the CꢀH antibonding LUMO+2 of
benzene at 0.2 eV (charge transfer of 0.02 electrons), which
pushes the 29Si NMR chemical shift from d=ꢀ62.7 (1’) through
ꢀ49.5 ppm (1’·C6H6) to d=ꢀ43.0 ppm (1’·2C6H6) if we use
COSMO to simulate the remaining bulk solvation in benzene.
The same trend is found in the absence of COSMO as well as
when we use other solvent molecules, such as tetrahydrofuran
(CꢀH antibonding LUMO at 0.0 eV). In the case of SiMe4, the in-
troduction of discrete benzene solvent molecules has no no-
ticeable effect on the 29Si NMR chemical shift, in line with the
notion that strong, local solvent effects as we find for 1’ re-
quire a covalent component in the solute–solvent interaction.
Our analyses show that including discrete solvent molecules in
the quantum chemical treatment brings the computed
29Si NMR chemical shift of 1’ into better agreement with the
experimental value. Full convergence of the computed value
would require both more solvent molecules as well as a sam-
pling of significantly more spatial configurations of the solvent
using statistical methods, such as molecular dynamics (MD) or
Monte Carlo simulations (MC); however, this is beyond the
scope of the present work.
Interestingly, the computed 29Si NMR chemical shift of 1’ de-
pends extremely sensitively on local solute–solvent interactions
between the exposed silicon center and discrete benzene or
tetrahydrofuran solvent molecules. Therefore, to bring the
computed and experimentally determined chemical shift of 1’
into agreement, explicit solvent molecules must be included in
the quantum chemical model system. This is at variance with
the total energy in the present model systems, which is not
much affected by simulating the presence of a solvent environ-
ment by a continuum approach, such as COSMO. Also,
29Si NMR chemical shifts of solute systems with stable, low-
energy closed shells, such as SiMe4, are not so sensitive to dis-
crete solute–solvent interactions and can well be described
with the COSMO approach. The explanation for this is a weak
donor–acceptor interaction between the HOMO of 1’ and the
CꢀH antibonding LUMO+2 of benzene. These findings high-
light once more that continuum approaches for simulating sol-
vent effects should always be used with precaution. Neverthe-
less, these calculations also support the assumption that
isomer 1’ is the more stable species in solution.
Experimental Section
General procedures
All syntheses were carried out under dry argon. The organic sol-
vents used were dried, purified, and deoxygenated according to
1
standard procedures and stored under argon. Solution H, 13C{1H},
15N{1H}, 29Si{1H}, and 77Se{1H} NMR spectra were recorded at 238C
&
&
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
8
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
on a Bruker DRX-300 (1H, 300.1 MHz; 13C, 75.5 MHz; 29Si, 59.6 MHz)
or Bruker Avance 500 NMR spectrometer (1H, 500.1 MHz; 13C,
125.8 MHz; 15N, 50.7 MHz; 29Si, 99.4 MHz; 77Se, 95.4 MHz) using
CD2Cl2 or C6D6 as the solvent. Chemical shifts (d, ppm) were deter-
mined relative to internal CHDCl2 (1H, d=5.32 ppm; CD2Cl2), inter-
nal C6HD5 (1H, d=7.28 ppm; C6D6), internal CD2Cl2 (13C, d=
53.8 ppm; CD2Cl2), internal C6D6 (13C, d=128.0 ppm; C6D6), external
TMS (29Si, d=0 ppm; CD2Cl2, C6D6), external formamide (90% w/w
in DMSO) (15N, d=ꢀ268.0 ppm; C6D6), or external Me2Se (5% w/w
in C6D6) (77Se, d=0 ppm; CD2Cl2). Assignment of the 13C NMR data
was supported by DEPT 135 and 1H,1H and 1H,13C correlation ex-
periments. Solid-state 15N, 29Si, and 77Se VACP/MAS NMR spectra
were recorded at 228C on a Bruker DSX-400 NMR spectrometer
with bottom layer rotors of ZrO2 (diameter, 4 (10) or 7 mm
(11·0.5n-C6H14, 12·C6H5CH3, 13) containing about 80 (4 mm) or
200 mg (7 mm) of sample (15N, 40.6 MHz; 29Si, 79.5 MHz; 77Se,
76.3 MHz; external standard, TMS (13C, 29Si, d=0 ppm), glycine (15N,
d=ꢀ342.0 ppm), or Me2Se (77Se, d=0 ppm); spinning rate, 10
(4 mm) or 7 kHz (7 mm); contact time, 3 (15N) or 5 ms (29Si, 77Se);
2H; o-C6H5), 7.46–7.56 (m, 6H, m- and p-C6H5), 7.60–7.67 ppm (m,
4H; o-SeC6H5); 13C{1H} NMR (CD2Cl2, 125.8 MHz): d=23.0 (2 C; CH3),
23.6 (4 C; CH3), 23.9 (2 C; CH3), 46.9 (2 C; CH3CHCH3), 47.3 (2 C;
CH3CHCH3), 127.1 (br, 2 C; o-C6H5), 127.9 (br, 2 C; o-C6H5), 128.6 (2
C; p-SeC6H5), 128.9 (br, 2 C; m-C6H5), 129.0 (br, 2 C; m-C6H5), 129.7
(4 C; m-SeC6H5), 130.3 (2 C; i-SeC6H5; 77Se satellites could not be
observed), 130.8 (2 C; p-C6H5), 133.1 (2 C; i-C6H5), 133.7 (4 C, 77Se
satellites (2J(13C,77Se)=10.6 Hz); o-SeC6H5), 168.7 ppm (2 C; NCN);
29Si{1H} NMR (CD2Cl2, 99.4 MHz): d=ꢀ170.0 ppm; 77Se{1H} NMR
(CD2Cl2, 95.4 MHz): d=436.6 ppm; 15N VACP/MAS NMR: d=ꢀ200.7,
ꢀ198.0, ꢀ194.9, ꢀ190.6 ppm; 29Si VACP/MAS NMR: d=
ꢀ177.3 ppm (br); 77Se VACP/MAS NMR: d=205.2, 280.9 ppm; ele-
mental analysis calcd (%) for C38H48N4Se2Si (Mr =746.83): C 61.11, H
6.48, N 7.50; found: C 60.7, H 6.5, N 7.6.
Compound
11·0.5n-C6H14:
Hexafluorobenzene
(214 mg,
1.15 mmol) was added at 208C in a single portion to a stirred solu-
tion of 1 (500 mg, 1.15 mmol) in toluene (20 mL), and the reaction
mixture was then stirred at this temperature for 1 h. The volatile
components were removed in vacuo, and n-hexane (2 mL) was
added to the residue. The resulting suspension was heated until
a clear solution was obtained, which was then cooled slowly to
ꢀ208C and kept undisturbed at this temperature for 1 d. The re-
sulting colorless crystalline solid was isolated by filtration and
dried in vacuo (208C, 5 h, 0.01 mbar). Yield: 667 mg (1.00 mmol,
1
908 H transmitter pulse length, 2.6 (4 mm) or 3.6 ms (7 mm); repe-
tition time, 4–7 s).
Syntheses
Compound 1: Benzene (350 mL) was added at 208C in a single
portion to a mixture of chlorohydrido[N,N’-diisopropylbenzamidina-
to(ꢀ)]silicon(IV)[5] (47.1 g, 100 mmol) and potassium bis(trimethylsi-
lyl)amide (21.0 g, 105 mmol), and the reaction mixture was then
stirred at this temperature for 2 h. The resulting precipitate was fil-
tered off, washed with benzene (2ꢃ50 mL), and discarded. The sol-
vent of the filtrate (including the wash solutions) was removed in
vacuo, followed by the addition of n-hexane (50 mL). The resulting
suspension was heated until a clear solution was obtained, which
was then cooled slowly to ꢀ208C and kept undisturbed at this
temperature for 1 d. The resulting orange-colored crystalline solid
was isolated by filtration and dried in vacuo (208C, 6 h, 0.01 mbar).
1
3
87%). H NMR (C6D6, 500.1 MHz): d=1.00 (t, J(1H,1H)=7.0 Hz, 3H;
CH3(CH2)4CH3), 1.24 (d, J(1H,1H)=6.8 Hz, 12H; CH3CHCH3), 1.26 (d,
3
3J(1H,1H)=6.8 Hz, 12H; CH3CHCH3), 1.31–1.42 (m, 4H; CH3-
(CH2)4CH3), 3.63 (br sept, 3J(1H,1H)=6.8 Hz, 4H; CH3CHCH3), 7.17–
7.21 and 7.44–7.49 ppm (m, 10H; C6H5); 13C{1H} NMR (C6D6,
125.8 MHz): d=14.3 (1 C; CH3(CH2)4CH3), 23.0 (1 C; CH3CH2-
(CH2)2CH2CH3), 23.7 (4 C; CH3CHCH3), 24.2 (4 C; CH3CHCH3), 31.9 (1
C; CH3CH2(CH2)2CH2CH3), 46.4 (4 C; CH3CHCH3), 122.6–123.8 (m, 2
C; C6F5), 128.1 (4 C; o-C6H5), 128.5 (4 C; m-C6H5), 129.7 (2 C; p-C6H5),
132.4 (2 C; i-C6H5), 136.2–136.9 (m, 1 C; C6F5), 138.1–139.3 (m, 2 C;
C6F5), 140.7–141.2 (m,
1 C; C6F5), 169.4 ppm (2 C; NCN);
1
29Si{1H} NMR (C6D6, 99.4 MHz): d=ꢀ160.5 ppm (d, 1J(19F,29Si)=
Yield: 35.6 g (81.9 mmol, 82%). H NMR (C6D6, 500.1 MHz): d=1.51
(d, 3J(1H,1H)=6.8 Hz, 24H; CH3), 3.63 (sept, 3J(1H,1H)=6.8 Hz, 4H;
CH3CHCH3), 7.15–7.25 ppm (m, 10H; C6H5); 13C{1H} NMR (C6D6,
125.8 MHz): d=24.9 (8 C; CH3), 47.7 (4 C; CH3CHCH3), 128.3 (br, 4
C; o-C6H5), 128.5 (4 C; m-C6H5), 128.7 (2 C; p-C6H5), 134.4 (2 C;
i-C6H5), 161.1 ppm (2 C; NCN); 15N{1H} NMR (C6D6, 50.7 MHz): d=
ꢀ193.4 ppm; 29Si{1H} NMR (C6D6, 99.4 MHz): d=ꢀ31.4 ppm; 15N
VACP/MAS NMR: d=ꢀ230.4, ꢀ204.4, ꢀ198.9, ꢀ103.0 ppm (NCN);
29Si VACP/MAS NMR: d=ꢀ15.4 ppm; elemental analysis calcd (%)
for C26H38N4Si (Mr =434.70): C 71.84, H 8.81, N 12.89; found: C 70.6,
H 9.1, N 12.5.
250.0 Hz); 15N VACP/MAS NMR: d=ꢀ222.5, ꢀ211.4, ꢀ199.3,
ꢀ188.8 ppm; 29Si VACP/MAS NMR: d=ꢀ160.0 ppm (d, J(19F,29Si)=
1
245.4 Hz); elemental analysis calcd (%) for C35H45F6N4Si (Mr =
663.85): C 63.33, H 6.83, N 8.44; found: C 63.1, H 7.2, N 8.6.
Compound 12·C6H5CH3: Dinitrogen monoxide (ca. 500 mg) was
passed at ꢀ788C within 3 min through a stirred solution of
1 (500 mg, 1.15 mmol) in toluene (20 mL), and the reaction mixture
was then stirred at this temperature for 10 min and then at 208C
for a further 1 h. The resulting solution was concentrated in vacuo
to a volume of 2 mL, cooled slowly to ꢀ208C, and then kept undis-
turbed at this temperature for 2 d. The resulting colorless crystal-
line solid was isolated by filtration, washed with n-pentane (2ꢃ
5 mL), and dried in vacuo (208C, 6 h, 0.01 mbar). Yield: 532 mg
(535 mmol, 93%). 1H NMR (CD2Cl2, 500.1 MHz): d=1.48 (brd,
3J(1H,1H)=6.4 Hz, 48H; CH3CHCH3), 2.24 (s, 3H; C6H5CH3), 3.44 (brs
(FWHH=30.4 Hz), 8H; CH3CHCH3), 7.10–7.32 and 7.41–7.58 ppm
(m, 25H; C6H5 and C6H5CH3); 13C{1H} NMR (CD2Cl2, 125.8 MHz): d=
21.4 (1 C; C6H5CH3), 24.7 (br, 16 C; CH3CHCH3), 48.4 (br, 8 C;
CH3CHCH3), 125.6, 128.0, 128.2, 128.5, 128.9, 129.3, and 136.1 (C6H5
and C6H5CH3; assignment of the aromatic 13C resonance signals
was not possible), 163.6 ppm (br, 4 C; NCN); 29Si{1H} NMR (CD2Cl2,
99.4 MHz): d=ꢀ82.9 ppm; 15N VACP/MAS NMR: d=ꢀ262.2 (1 N),
ꢀ261.2 (1 N), ꢀ253.2 (1 N), ꢀ234.3 (1 N), ꢀ172.9 (1 N), ꢀ171.1 (1
N), ꢀ98.9 ppm (2 N); 29Si VACP/MAS NMR: d=ꢀ91.9, ꢀ93.0 ppm;
elemental analysis calcd (%) for C59H84N8O2Si2 (Mr =993.54): C 71.33,
H 8.52, N 11.28; found: C 70.0, H 8.7, N 11.3.
Compound 10: Toluene (5 mL) was added at 208C in a single por-
tion to a mixture of 1 (300 mg, 690 mmol) and diphenyl diselenide
(215 mg, 689 mmol), and the reaction mixture was then stirred at
this temperature for 16 h. The solvent was removed in vacuo, and
n-pentane (5 mL) was added to the residue. The resulting solid was
isolated by filtration and dried in vacuo (208C, 4 h, 0.01 mbar), fol-
lowed by the addition of acetonitrile (2 mL). The resulting suspen-
sion was heated until a clear solution was obtained, which was
then cooled slowly to ꢀ208C and kept undisturbed at this temper-
ature for 2 d. The resulting yellow crystalline solid was isolated by
filtration, washed with n-pentane (2ꢃ5 mL), and dried in vacuo
(208C, 4 h, 0.01 mbar). Yield: 471 mg (631 mmol, 92%). 1H NMR
3
(CD2Cl2, 500.1 MHz): d=1.17 (d, J(1H,1H)=6.8 Hz, 6H; CH3), 1.22 (d,
3
3J(1H,1H)=6.8 Hz, 6H; CH3), 1.26 (d, J(1H,1H)=6.8 Hz, 6H; CH3), 1.33
(d, 3J(1H,1H)=6.8 Hz, 6H; CH3), 3.48 (sept, 3J(1H,1H)=6.8 Hz, 2H;
3
CH3CHCH3), 3.93 (sept, J(1H,1H)=6.8 Hz, 2H; CH3CHCH3), 7.27–7.33
(m, 2H; o-C6H5), 7.33–7.38 (m, 6H; m- and p-SeC6H5), 7.38–7.44 (m,
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
9
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
Khan, P. P. Samuel, H. W. Roesky, Chem. Sci. 2012, 3, 659–682; f) B.
Blom, M. Stoelzel, M. Driess, Chem. Eur. J. 2013, 19, 40–62.
Compound 13: Carbon dioxide (ca. 500 mg) was passed at 208C
within 5 min through a stirred solution of 1 (500 mg, 1.15 mmol) in
toluene (20 mL), and the reaction mixture was then stirred at this
temperature for 15 min. The resulting suspension was heated until
a clear solution was obtained, which was then cooled slowly to
ꢀ208C and kept undisturbed at this temperature for 1 d. The re-
sulting colorless crystalline solid was isolated by filtration, washed
with n-pentane (2ꢃ5 mL), and dried in vacuo (208C, 4 h,
0.01 mbar). Yield: 444 mg (897 mmol, 78%); 1H NMR (CD2Cl2,
500.1 MHz): d=1.08 (d, 3J(1H,1H)=6.8 Hz, 6H; CH3), 1.13 (d,
[2] For selected publications dealing with stable two-coordinate silicon(II)
compounds, see: a) M. Denk, R. Lennon, R. Hayashi, R. West, A. V. Belja-
kov, H. P. Verne, A. Haaland, M. Wagner, N. Metzler, J. Am. Chem. Soc.
1994, 116, 2691–2692; b) B. Gehrhus, M. F. Lappert, J. Heinicke, R.
Boese, D. Blꢄser, J. Chem. Soc. Chem. Commun. 1995, 1931–1932; c) B.
Gehrhus, P. B. Hitchcock, M. F. Lappert, J. Heinicke, R. Boese, D. Blꢄser, J.
Organomet. Chem. 1996, 521, 211–220; d) R. West, M. Denk, Pure Appl.
Chem. 1996, 68, 785–788; e) J. Heinicke, A. Oprea, M. K. Kindermann, T.
Karpati, L. Nyulꢅszi, T. Veszprꢀmi, Chem. Eur. J. 1998, 4, 541–545; f) M.
Haaf, A. Schmiedl, T. A. Schmedake, D. R. Powell, A. J. Millevolte, M.
Denk, R. West, J. Am. Chem. Soc. 1998, 120, 12714–12719; g) M. Kira, S.
Ishida, T. Iwamoto, C. Kabuto, J. Am. Chem. Soc. 1999, 121, 9722–9723;
h) M. Driess, S. Yao, M. Brym, C. van Wꢆllen, D. Lentz, J. Am. Chem. Soc.
2006, 128, 9628–9629; i) P. Zark, A. Schꢄfer, A. Mitra, D. Haase, W. Saak,
R. West, T. Mꢆller, J. Organomet. Chem. 2010, 695, 398–408; j) Y. Xiong,
S. Yao, M. Driess, Chem. Eur. J. 2012, 18, 3316–3320; k) A. V. Protchenko,
K. H. Birjkumar, D. Dange, A. D. Schwarz, D. Vidovic, C. Jones, N. Kalt-
soyannis, P. Mountford, S. Aldrige, J. Am. Chem. Soc. 2012, 134, 6500–
6503; l) B. D. Rekken, T. M. Brown, J. C. Fettinger, H. M. Tuononen, P. P.
Power, J. Am. Chem. Soc. 2012, 134, 6504–6507.
[3] For selected publications dealing with stable higher-coordinate sili-
con(II) compounds, see: a) P. Jutzi, D. Kanne, C. Krꢆger, Angew. Chem.
1986, 98, 163–164; Angew. Chem. Int. Ed. Engl. 1986, 25, 164–164;
b) H. H. Karsch, U. Keller, S. Gamper, G. Mꢆller, Angew. Chem. 1990, 102,
297–298; Angew. Chem. Int. Ed. Engl. 1990, 29, 295–296; c) P. Jutzi, D.
Eikenberg, A. Mçhrke, B. Neumann, H.-G. Stammler, Organometallics
1996, 15, 753–759; d) P. Jutzi, A. Mix, B. Rummel, W. W. Schoeller, B.
Neumann, H. G. Stammler, Science 2004, 305, 849–851; e) S. Yao, M.
Brym, C. van Wꢆllen, M. Driess, Angew. Chem. 2007, 119, 4237–4240;
3
3J(1H,1H)=6.8 Hz, 6H; CH3), 1.24 (d, J(1H,1H)=6.8 Hz, 6H; CH3), 1.30
(d, 3J(1H,1H)=6.8 Hz, 6H; CH3), 3.50 (sept, 3J(1H,1H)=6.8 Hz, 2H;
3
CH3CHCH3), 3.53 (sept, J(1H,1H)=6.8 Hz, 2H; CH3CHCH3), 7.23–7.29
(m, 2H; o-C6H5), 7.42–7.47 (m, 2H; o-C6H5), 7.49–7.58 ppm (m, 6H;
m- and p-C6H5); 13C{1H} NMR (CD2Cl2, 125.8 MHz): d=22.8 (2 C;
CH3), 23.3 (2 C; CH3), 23.9 (2 C; CH3), 24.0 (2 C; CH3), 46.6 (2 C;
CH3CHCH3), 46.9 (2 C; CH3CHCH3), 127.1 (br, 2 C; o-C6H5), 128.1 (br,
2 C; o-C6H5), 129.15 (br, 2 C; m-C6H5), 129.22 (br, 2 C; m-C6H5), 129.7
(2 C; i-C6H5), 130.7 (2 C; p-C6H5), 159.5 (CO3), 173.6 ppm (2 C; NCN);
29Si{1H} NMR (CD2Cl2, 99.4 MHz): d=ꢀ165.9; 15N VACP/MAS NMR:
d=ꢀ217.6, ꢀ213.1, ꢀ212.1, ꢀ205.0 ppm; 29Si VACP/MAS NMR: d=
ꢀ164.4; elemental analysis calcd (%) for C27H38N4O3Si (494.71): C
65.55, H 7.74, N 11.33; found: C 65.2, H 7.9, N 11.3.
Crystal structure analyses
Suitable single crystals of 10·CH3CN were obtained by slow cooling
of a saturated solution of 10 in CH3CN from 70 to ꢀ208C. Suitable
single crystals of 11·0.5n-C6H14, 12·C6H5CH3, and 13 were obtained
as described in the Experimental Section dealing with the synthe-
ses. The crystals were mounted in inert oil (perfluoropolyalkyl
ether, ABCR) on a glass fiber and then transferred to the cold nitro-
gen gas stream of the diffractometer (Stoe IPDS, graphite-mono-
chromated MoKa radiation, l=0.71073 ꢂ). The structures were
solved by direct methods (SHELXS-97) and refined by full-matrix
least-squares methods on F2 for all unique reflections (SHELXL-
97).[18] SHELXLE was used as refinement GUI.[19] For the CH hydro-
´
Angew. Chem. Int. Ed. 2007, 46, 4159–4162; f) P. Jutzi, K. Leszczynska, B.
Neumann, W. W. Schoeller, H.-G. Stammler, Angew. Chem. 2009, 121,
2634–2637; Angew. Chem. Int. Ed. 2009, 48, 2596–2599; g) R. S. Ghad-
wal, H. W. Roesky, S. Merkel, J. Henn, D. Stalke, Angew. Chem. 2009, 121,
5793–5796; Angew. Chem. Int. Ed. 2009, 48, 5683–5686; h) A. C. Fi-
lippou, O. Chernov, G. Schnakenburg, Angew. Chem. 2009, 121, 5797–
5800; Angew. Chem. Int. Ed. 2009, 48, 5687–5690; i) Y. Xiong, S. Yao, M.
Driess, J. Am. Chem. Soc. 2009, 131, 7562–7563; j) R. S. Ghadwal, H. W.
Roesky, S. Merkel, D. Stalke, Chem. Eur. J. 2010, 16, 85–88; k) Y. Gao, J.
Zhang, H. Hu, C. Cui, Organometallics 2010, 29, 3063–3065; l) J. Li, S.
Merkel, J. Henn, K. Meindl, A. Dçring, H. W. Roesky, R. S. Ghadwal, D.
Stalke, Inorg. Chem. 2010, 49, 775–777; m) A. Meltzer, S. Inoue, C. Prꢄ-
sang, M. Driess, J. Am. Chem. Soc. 2010, 132, 3038–3046; n) A. C. Fi-
lippou, O. Chernov, B. Blom, K. W. Stumpf, G. Schnakenburg, Chem. Eur.
J. 2010, 16, 2866–2872; o) R. Rodriguez, D. Gau, Y. Contie, T. Kato, N.
Saffon-Merceron, A. Baceiredo, Angew. Chem. 2011, 123, 11694–11697;
Angew. Chem. Int. Ed. 2011, 50, 11492–11495; p) W. Wang, S. Inoue, E.
Irran, M. Driess, Angew. Chem. 2012, 124, 3751–3754; Angew. Chem. Int.
gen atoms,
a
riding model was employed. CCDC-983211
(10·CH3CN),
CCDC-983212 (11·0.5n-C6H14), CCDC-983213
(12·C6H5CH3), and CCDC-983214 (13) contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
´
Ed. 2012, 51, 3691–3694; q) K. Leszczynska, K. Abersfelder, A. Mix, B.
Neumann, H.-G. Stammler, M. J. Cowley, P. Jutzi, D. Scheschkewitz,
Angew. Chem. 2012, 124, 6891–6895; Angew. Chem. Int. Ed. 2012, 51,
6785–6788.
Acknowledgements
R.T. thanks the Deutsche Forschungsgemeinschaft for financial
support (TA 75/16–1). C.F.G. and F.M.B. thank the National Re-
search School Combination-Catalysis (NRSC-C) and the Nether-
lands organization for Scientific Research (NWO-CW and NWO-
EW) for financial support and the national supercomputer
center SURFsara in Amsterdam for excellent support.
[4] For selected publications dealing with stable higher-coordinate sili-
con(II) compounds containing amidinato ligands, see: a) C.-W. So, H. W.
Roesky, J. Magull, R. B. Oswald, Angew. Chem. 2006, 118, 4052–4054;
Angew. Chem. Int. Ed. 2006, 45, 3948–3950; b) C.-W. So, H. W. Roesky,
P. M. Gurubasavaraj, R. B. Oswald, M. T. Gamer, P. G. Jones, S. Blaurock, J.
Am. Chem. Soc. 2007, 129, 12049–12054; c) W. Yang, H. Fu, H. Wang, M.
Chen, Y. Ding, H. W. Roesky, A. Jana, Inorg. Chem. 2009, 48, 5058–5060;
d) S. S. Sen, H. W. Roesky, D. Stern, J. Henn, D. Stalke, J. Am. Chem. Soc.
ˇ
2010, 132, 1123–1126; e) G. Tavcar, S. S. Sen, R. Azhakar, A. Thorn, H. W.
Roesky, Inorg. Chem. 2010, 49, 10199–10202; f) S. S. Sen, J. Hey, R.
Herbst-Irmer, H. W. Roesky, D. Stalke, J. Am. Chem. Soc. 2011, 133,
12311–12316; g) A. Jana, D. Leusser, I. Objartel, H. W. Roesky, D. Stalke,
Dalton Trans. 2011, 40, 5458–5463; h) R. Azhakar, S. P. Sarish, H. W.
Roesky, J. Hey, D. Stalke, Inorg. Chem. 2011, 50, 5039–5043; i) R. Azha-
kar, R. S. Ghadwal, H. W. Roesky, H. Wolf, D. Stalke, J. Am. Chem. Soc.
2012, 134, 2423–2428; j) R. Azhakar, R. S. Ghadwal, H. W. Roesky, H.
Wolf, D. Stalke, Chem. Commun. 2012, 48, 4561–4563; k) R. Azhakar,
H. W. Roesky, J. J. Holstein, B. Dittrich, Dalton Trans. 2012, 41, 12096–
Keywords: carbene homologues · chelates · coordination
modes · density functional calculations · silicon
[1] For selected reviews dealing with stable silicon(II) compounds, see:
a) S. Nagendran, H. W. Roesky, Organometallics 2008, 27, 457–492; b) Y.
Mizuhata, T. Sasamori, N. Tokitoh, Chem. Rev. 2009, 109, 3479–3511;
c) M. Asay, C. Jones, M. Driess, Chem. Rev. 2011, 111, 354–396; d) S. Yao,
Y. Xiong, M. Driess, Organometallics 2011, 30, 1748–1767; e) S. S. Sen, S.
&
&
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
10
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
12100; l) P. P. Samuel, R. Azhakar, R. S. Ghadwal, S. S. Sen, H. W. Roesky,
M. Granitzka, J. Matussek, R. Herbst-Irmer, D. Stalke, Inorg. Chem. 2012,
51, 11049–11054; m) R. Azhakar, K. Prçpper, B. Dittrich, H. W. Roesky, Or-
ganometallics 2012, 31, 7586–7590.
Swart, M. Solꢉ, F. M. Bickelhaupt, J. Comput. Chem. 2007, 28, 1551–
1560. See also Ref. [7e].
[11] a) J. C. Slater, Quantum Theory of Molecules and Solids, Vol. 4, McGraw-
Hill, New York, 1974; b) A. D. Becke, Phys. Rev. A 1988, 38, 3098–3100;
c) C. Lee, W. Yang, R. G. Parr, Phys. Rev. B 1988, 37, 785–789; d) B. G.
Johnson, P. M. W. Gill, J. A. Pople, J. Chem. Phys. 1993, 98, 5612–5626;
e) T. V. Russo, R. L. Martin, P. J. Hay, J. Chem. Phys. 1994, 101, 7729–7737;
f) S. Grimme, S. Ehrlich, L. Goerigk, J. Comput. Chem. 2011, 32, 1456–
1465.
[12] a) E. van Lenthe, E. J. Baerends, J. G. Snijders, J. Chem. Phys. 1994, 101,
9783–9792; b) E. van Lenthe, R. van Leeuwen, E. J. Baerends, J. G. Snijd-
ers, Int. J. Quantum Chem. 1996, 57, 281–293.
[13] a) S. Grimme, J. Comput. Chem. 2004, 25, 1463–1473; b) S. Grimme, J.
Comput. Chem. 2006, 27, 1787–1799; c) S. Grimme, J. Antony, S. Ehrlich,
H. Krieg, J. Chem. Phys. 2010, 132, 154104–1–154104–19.
[14] P. R. T. Schipper, O. V. Gritsenko, S. J. V. van Gisbergen, E. J. Baerends, J.
Chem. Phys. 2000, 112, 1344–1352.
[15] G. Schreckenbach, T. Ziegler, J. Phys. Chem. 1995, 99, 606–611.
[16] a) A. Klamt, G. Schꢆꢆrmann, J. Chem. Soc. Perkin Trans. 2 1993, 799–
805; b) A. Klamt, J. Phys. Chem. 1995, 99, 2224–2235; c) C. C. Pye, T.
Ziegler, Theor. Chem. Acc. 1999, 101, 396–408; d) M. Swart, E. Rçsler,
F. M. Bickelhaupt, Eur. J. Inorg. Chem. 2007, 3646–3654.
[5] K. Junold, J. A. Baus, C. Burschka, R. Tacke, Angew. Chem. 2012, 124,
7126–7129; Angew. Chem. Int. Ed. 2012, 51, 7020–7023.
[6] a) K. Junold, J. A. Baus, C. Burschka, D. Auerhammer, R. Tacke, Chem. Eur.
J. 2012, 18, 16288–16291; b) K. Junold, J. A. Baus, C. Burschka, T. Vent-
Schmidt, S. Riedel, R. Tacke, Inorg. Chem. 2013, 52, 11593–11599.
[7] For recent publications dealing with higher-coordinate silicon(IV) com-
pounds, see: a) S. Cota, M. Beyer, R. Bertermann, C. Burschka, K. Gçtz,
M. Kaupp, R. Tacke, Chem. Eur. J. 2010, 16, 6582–6589; b) S. Metz, B.
Theis, C. Burschka, R. Tacke, Chem. Eur. J. 2010, 16, 6844–6856; c) K.
Junold, C. Burschka, R. Bertermann, R. Tacke, Dalton Trans. 2010, 39,
9401–9413; d) K. Junold, C. Burschka, R. Bertermann, R. Tacke, Dalton
Trans. 2011, 40, 9844–9857; e) C. Kobelt, C. Burschka, R. Bertermann, C.
Fonseca Guerra, F. M. Bickelhaupt, R. Tacke, Dalton Trans. 2012, 41,
2148–2162; f) K. Junold, C. Burschka, R. Tacke, Eur. J. Inorg. Chem. 2012,
189–193; g) B. Theis, J. Weiß, W. P. Lippert, R. Bertermann, C. Burschka,
R. Tacke, Chem. Eur. J. 2012, 18, 2202–2206; h) J. Weiß, B. Theis, S. Metz,
C. Burschka, C. Fonseca Guerra, F. M. Bickelhaupt, R. Tacke, Eur. J. Inorg.
Chem. 2012, 3216–3228; i) J. A. Baus, C. Burschka, R. Bertermann, C.
Fonseca Guerra, F. M. Bickelhaupt, R. Tacke, Inorg. Chem. 2013, 52,
10664–10676.
[8] D. Gau, R. Rodriguez, T. Kato, N. Saffon-Merceron, A. de Cꢇzar, F. P.
Cossꢈo, A. Baceiredo, Angew. Chem. 2011, 123, 1124–1128; Angew.
Chem. Int. Ed. 2011, 50, 1092–1096.
[9] The Berry distortions were analyzed with PLATON: A. L. Spek, Acta Crys-
tallogr. Sect. D 2009, 65, 148–155.
[10] a) G. te Velde, F. M. Bickelhaupt, E. J. Baerends, C. Fonseca Guerra, S. J. A.
van Gisbergen, J. G. Snijders, T. Ziegler, J. Comput. Chem. 2001, 22, 931–
967; b) http://www.scm.com. For validation studies, see: c) A. P. Bento,
M. Solꢉ, F. M. Bickelhaupt, J. Comput. Chem. 2005, 26, 1497–1504; d) M.
[17] a) F. M. Bickelhaupt, A. Diefenbach, S. P. de Visser, L. J. de Koning,
N. M. M. Nibbering, J. Phys. Chem. A 1998, 102, 9549–9553; b) F. M.
Bickelhaupt, E. J. Baerends in Reviews in Computational Chemistry,
Vol. 15 (Eds.: K. B. Lipkowitz, D. B. Boyd), Wiley-VCH, New York, 2000,
pp. 1–86.
[18] G. M. Sheldrick, Acta Crystallogr. Sect. A 2008, 64, 112–122.
[19] C. B. Hꢆbschle, G. M. Sheldrick, B. Dittrich, J. Appl. Crystallogr. 2011, 44,
1281–1284.
Received: March 5, 2014
Published online on && &&, 2014
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
11
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
FULL PAPER
&
Silicon
K. Junold, M. Nutz, J. A. Baus,
C. Burschka, C. Fonseca Guerra,
F. M. Bickelhaupt,* R. Tacke*
&& – &&
Silicon(II)/silicon(IV): The donor-stabi-
lized silylene 1 (three-coordinate in the
solid state) was synthesized on the 35 g
scale. In benzene solution, the four-co-
ordinate isomer 1’ is the thermodynami-
cally favored species. Treatment of the
silylene with PhSeSePh, C6F6, N2O, and
CO2 yields the respective silicon(IV)
complexes 2–5.
The Donor-Stabilized Silylene
Bis[N,N’-diisopropylbenz-
amidinato(ꢀ)]silicon(II):
Synthesis, Electronic Structure, and
Reactivity
&
&
Chem. Eur. J. 2014, 20, 1 – 12
www.chemeurj.org
12
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!