Donor-stabilized silylenes with guanidinato ligands

Article abstract of DOI:10.1002/ejic.201301164

The first donor-stabilized silylenes with guanidinato ligands, compounds 4 and 6, were synthesized and structurally characterized in the solid state and in solution. As demonstrated by single-crystal X-ray diffraction studies, compound 4 contains a bidentate and a monodentate guanidinato ligand of the type [iPrNC(NiPr₂)NiPr]^-, and compound 6 contains the bidentate guanidinato ligand [ArNC(NMe₂)NAr]^- (Ar = 2,6-diisopropylphenyl) and the monodentate amido ligand [(Me₃Si) ₂N]^-. Both silicon(II) complexes exist also in solution. The first donor-stabilized silylenes with guanidinato ligands, compounds I and II, were synthesized and structurally characterized in the solid state and in solution (Ar = 2,6-diisopropylphenyl).

Full text of DOI:10.1002/ejic.201301164

SHORT COMMUNICATION
DOI:10.1002/ejic.201301164
Donor-Stabilized Silylenes with Guanidinato Ligands
Felix M. Mück,[a] Konstantin Junold,[a] Johannes A. Baus,[a]
Christian Burschka,[a] and Reinhold Tacke*[a]
Dedicated to Professor Bernt Krebs on the occasion of his 75th birthday
Keywords: Coordination modes / N ligands / Silicon / Silylenes
The first donor-stabilized silylenes with guanidinato ligands,
compounds 4 and 6, were synthesized and structurally char-
acterized in the solid state and in solution. As demonstrated
by single-crystal X-ray diffraction studies, compound 4 con-
tains a bidentate and a monodentate guanidinato ligand of
the type [iPrNC(NiPr2)NiPr]–, and compound 6 contains the
bidentate guanidinato ligand [ArNC(NMe2)NAr]– (Ar = 2,6-
diisopropylphenyl) and the monodentate amido ligand
[(Me3Si)2N]–. Both silicon(II) complexes exist also in solution.
guanidinato ligands differ in their electronic properties, the
title compounds 4 and 6 were very attractive targets to be
synthesized and to be studied for their reactivity, especially
in comparison with related silylenes that contain amidinato
ligands.
Introduction
The chemistry of stable silylenes is currently one of the
most actively studied fields in silicon chemistry.[1] In this
context, donor-stabilized silicon(II) complexes with amidin-
ato ligands, such as compounds 1 and 2, play an emerging
role.[2] We have now succeeded in synthesizing the first do-
nor-stabilized silylenes that contain guanidinato ligands,
compounds 4 and 6 (Scheme 1). Germylenes, stannylenes,
and plumbylenes with guanidinato ligands have already
been synthesized, starting from suitable germanium(II),
tin(II), or lead(II) precursors.[3,4] However, to the best of
our knowledge, related guanidinatosilicon(II) complexes
have not yet been described in the literature. This is proba-
bly due to the lack of suitable analogous silicon(II) precur-
sors. To overcome this problem, we used a totally different
strategy for the preparation of 4 and 6, a reductive HCl
elimination of six- and five-coordinate silicon(IV) com-
plexes 3 and 5, respectively (Scheme 1). This strategy has
also been successfully used for the synthesis of the amidin-
atosilicon(II) complexes 1 and 2.[2a,2g] As amidinato and
Results and Discussion
Compounds 4 and 6 were synthesized according to
Scheme 1. Treatment of the lithium guanidinate Li[iPrNC-
(NiPr2)NiPr] with trichlorosilane (molar ratio 2:1) in tetra-
hydrofuran afforded the six-coordinate silicon(IV) complex
3 (94% yield), which, upon reaction with potassium bis(tri-
methylsilyl)amide (molar ratio 1:1) in toluene, gave 4 (95%
yield, after crystallization from n-hexane). Treatment of the
lithium guanidinate Li[ArNC(NMe2)NAr] (Ar = 2,6-di-
isopropylphenyl) with one molar equivalent of trichloro-
silane in tetrahydrofuran afforded the five-coordinate sili-
con(IV) complex 5 (81% yield, after crystallization from
acetonitrile), which, upon reaction with two molar equiva-
lents of potassium bis(trimethylsilyl)amide, afforded 6 (75%
yield, after crystallization from n-hexane).
The identities of 3–6 were established by elemental analy-
sis, NMR spectroscopic studies in the solid state and in
solution,[5] and crystal structure analysis.[6] The molecular
structures of 3–6 are depicted in Figures 1–4.
The silicon coordination polyhedron of 3 (Figure 1) is a
strongly distorted octahedron, with the chlorido and hy-
drido ligand in cis positions. The distortion mainly results
from the two highly strained four-membered SiN2C chelate
rings formed by the silicon coordination center and the bi-
dentate guanidinato ligands, with N–Si–N angles ranging
from 68.40(6) to 68.70(6)°.
[a] Universität Würzburg, Institut für Anorganische Chemie,
Am Hubland, 97074 Würzburg, Germany
E-mail: r.tacke@uni-wuerzburg.de
http://www-anorganik.chemie.uni-wuerzburg.de/
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SHORT COMMUNICATION
and 1.8901(18) Å], clearly reflecting the different coordina-
tion modes of the two guanidinato ligands. Furthermore,
the significant difference between the two N–C distances in
the monodentate ligand [1.433(3) vs. 1.284(3) Å] indicates
the higher degree of localization of the N=C double bond
compared to the bidentate ligand [1.334(3) vs. 1.344(2) Å].
Generally, the structural features of 4 are very similar to
those of compound 2.
Figure 2. Molecular structure of 4 in the crystal (ellipsoids set at
50% probability; hydrogen atoms omitted for clarity). Selected
bond lengths [Å] and angles [°]: Si–N1 1.9220(17), Si–N2
1.8901(18), Si–N4 1.7633(18), N1–C1 1.334(3), N2–C1 1.344(2),
N3–C1 1.402(3), N4–C14 1.433(3), N5–C14 1.284(3), N6–C14
1.400(3); N1–Si–N2 68.37(7), N1–Si–N4 104.71(8), N2–Si–N4
102.98(8), Si–N1–C1 91.05(12), Si–N2–C1 92.14(13), Si–N4–C14
117.77(12), N1–C1–N2 106.23(17), N1–C1–N3 125.28(17), N2–
C1–N3 128.32(19), N4–C14–N5 125.40(19), N4–C14–N6
115.58(16), N5–C14–N6 118.99(18).
Scheme 1. Syntheses of compounds 3–6.
The silicon coordination polyhedron of 5 (Figure 3) is a
strongly distorted trigonal bipyramid, with the chlorine
atom Cl1 and the nitrogen atom N2 at the axial positions.
The Berry distortion (transition from trigonal bipyramid to
square pyramid) amounts to 33.4%.[8]
Figure 1. Molecular structure of 3 in the crystal (ellipsoids set at
50% probability; hydrogen atoms apart from H1 omitted for clar-
ity).[7] Selected bond lengths [Å] and angles [°]: Si–Cl 2.2742(8), Si–
N1 1.9305(16), Si–N2 1.8920(15), Si–N4 1.9304(15), Si–N5
1.8797(14), N1–C1 1.326(2), N2–C1 1.347(2), N3–C1 1.390(2), N4–
C14 1.323(2), N5–C14 1.344(2), N6–C14 1.386(2); Cl–Si–N1
164.74(5), Cl–Si–N2 96.07(5), Cl–Si–N4 86.08(5), Cl–Si–N5
95.39(5), N1–Si–N2 68.70(6), N1–Si–N4 94.96(7), N1–Si–N5
99.14(6), N2–Si–N4 98.15(7), N2–Si–N5 161.65(7), N4–Si–N5
68.40(6), Si–N1–C1 91.16(11), Si–N2–C1 92.19(10), Si–N4–C14
91.29(11), Si–N5–C14 92.87(10), N1–C1–N2 107.59(14), N1–C1–
N3 126.80(16), N2–C1–N3 125.61(15), N4–C14–N5 106.87(14),
N4–C14–N6 128.18(16), N5–C14–N6 124.94(15).
Figure 3. Molecular structure of 5 in the crystal (ellipsoids set at
50% probability; hydrogen atoms apart from H1 omitted for clar-
ity). Selected bond lengths [Å] and angles [°]: Si–Cl1 2.1590(8), Si–
Cl2 2.0821(7), Si–N1 1.8006(15), Si–N2 1.9113(15), Si–H1
1.382(19), N1–C1 1.369(2), N2–C1 1.335(2), N3–C1 1.330(2); Cl1–
Si–Cl2 93.47(3), Cl1–Si–N1 93.31(5), Cl1–Si–N2 162.71(5), Cl1–Si–
H1 95.7(8), Cl2–Si–N1 128.93(5), Cl2–Si–N2 93.26(5), Cl2–Si–H1
110.8(8), N1–Si–N2 70.16(6), N1–Si–H1 118.8(8), N2–Si–H1
96.8(8), Si–N1–C1 94.44(11), Si–N2–C1 90.71(10), N1–C1–N2
104.33(15), N1–C1–N3 127.69(16), N2–C1–N3 127.94(15).
The silicon coordination polyhedron of 4 (Figure 2) is
The silicon coordination polyhedron of 6 (Figure 4) is
best described as a distorted pseudo-tetrahedron, with the best described as a distorted pseudo-tetrahedron, with the
lone pair as the fourth ligand. The three N–Si–N angles lone pair as the fourth ligand. The three N–Si–N bond
amount to 68.37(7), 102.98(8), and 104.71(8)°. The Si–N angles [67.83(6), 108.72(6), and 113.09(6)°] are similar to
distance of the monodentate ligand [1.7633(18) Å] is signifi- those observed for 4. Also, the Si–N distance of the mono-
cantly shorter than those of the bidentate ligand [1.9220(17) dentate ligand [1.7745(14) Å] is significantly shorter than
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SHORT COMMUNICATION
those of the bidentate ligand [1.9433(14) and 1.9384(15) Å]. nor-stabilized silylenes 2, 4, and 6 reflect different electronic
The latter two distances are somewhat longer than the anal- properties at the silicon atom, which are expected to affect
ogous Si–N distances of 4 [1.9220(17) and 1.8901(18) Å], the reactivity profiles of these silicon(II) species. We have
probably because of the steric demand of the two bulky aryl started a program to investigate the reactivities of 2, 4, and
groups.
6 systematically.
Table 1. Isotropic 29Si chemical shifts [ppm] of the silicon coordina-
tion centers of 3–6 in the solid state (T = 22 °C) and in solution
(C6D6, T = 23 °C).
Compound δ29Si (solid state) δ29Si (solution) |Δδ| Skeleton
3
4
5
6
–186.2
–20.6
–99.6
6.8
–186.5
–25.6
–96.2
14.9
0.3 SiN4ClH
5.0 SiN3
3.4 SiN2Cl2H
8.1 SiN3
Experimental Section
The syntheses were carried out under a dry argon atmosphere in
oven-dried glassware by using standard Schlenk techniques. The
solvents were dried, purified, and deoxygenated according to stan-
dard procedures.
Figure 4. Molecular structure of 6 in the crystal (ellipsoids set at
50% probability; hydrogen atoms omitted for clarity). Selected
bond lengths [Å] and angles [°]: Si1–N1 1.9433(14), Si1–N2
1.9384(15), Si1–N4 1.7745(14), Si2–N4 1.7522(15), Si3–N4
1.7538(14), N1–C1 1.350(2), N2–C1 1.342(2), N3–C1 1.361(2); N1–
Compound 3: Trichlorosilane (26.9 g, 199 mmol) was added in a
single portion at –20 °C to a stirred solution of Li[iPrNC(NiPr2)-
Si1–N2 67.83(6), N1–Si1–N4 113.09(6), N2–Si–N4 108.72(6), Si1– NiPr]–THF[9] (121.3 g, 397 mmol) in tetrahydrofuran (1.5 L), and
N1–C1 89.99(10), Si1–N2–C1 90.44(10), Si1–N4–Si2 112.61(7),
Si1–N4–Si3 127.44(9), Si2–N4–Si3 119.31(8), N1–C1–N2
107.18(14), N1–C1–N3 126.40(15), N2–C1–N3 126.18(15).
the stirred reaction mixture was then warmed to 20 °C over 16 h.
The solvent was removed in vacuo, dichloromethane (500 mL) was
added to the residue, and the remaining solid was filtered off and
discarded. The solvent of the filtrate was removed in vacuo, fol-
lowed by the addition of tetrahydrofuran (100 mL). The resulting
suspension was heated until a clear solution was obtained, which
was then cooled slowly to –30 °C and kept undisturbed at this tem-
perature for 1 d. The resulting colorless crystalline solid was iso-
lated by filtration, washed with cold (–30 °C) n-pentane (2ϫ
Compounds 3–6 were studied by NMR spectroscopy in
the solid state (15N, 29Si) and in solution (1H, 13C, 29Si).
The isotropic 29Si chemical shifts of 3–6 in the solid state
and in solution (Table 1) are similar (Δδ29Si = 0.3–8.1 ppm),
indicating that these compounds also exist in solution. The
isotropic chemical shifts of guanidinatosilicon(II) complex 200 mL), and dried in vacuo (20 °C, 6 h, 0.01 mbar). Yield: 96.5 g
3
(187 mmol, 94%). 1H NMR (C6D6, 23 °C): δ = 1.10 (d, JH,H
=
4 [solid state: δ = –20.6 ppm; solution (C6D6): δ =
–25.6 ppm] and the related amidinatosilicon(II) complex 2
3
6.9 Hz, 12 H, CH3), 1.14 (d, JH,H = 6.9 Hz, 12 H, CH3), 1.24 (d,
3JH,H = 6.7 Hz, 6 H, CH3), 1.50 (d, JH,H = 6.7 Hz, 6 H, CH3),
3
[solid state:
δ = –15.4 ppm; solution (C6D6): δ =
3
3
1.63 (d, JH,H = 6.7 Hz, 6 H, CH3), 1.89 (d, JH,H = 6.7 Hz, 6 H,
–31.4 ppm][2g] differ significantly. The same holds true for
the difference in chemical shift between the solid state and
solution (2, Δδ29Si = 16.0 ppm; 4, Δδ29Si = 5.0 ppm), which
is much more pronounced for 2. In the case of 2, this differ-
ence in shift has been interpreted in terms of a rapid ex-
change of the four nitrogen sites, possibly involving a four-
3
CH3), 3.50 (sept., JH,H = 6.9 Hz, 4 H, CH3CHCH3), 3.74 (sept.,
3JH,H = 6.7 Hz, 2 H, CH3CHCH3), 3.82 (sept., JH,H = 6.7 Hz, 2
3
H, CH3CHCH3), 5.57 (s, 1 H, SiH; 29Si satellites, JH,Si = 296 Hz)
1
ppm. 13C{1H} NMR (C6D6, 23 °C): δ = 22.8 (2 C), 22.9 (4 C),
23.70 (2 C), 23.72 (2 C), 24.8 (2 C), 25.0 (4 C) (CH3), 45.4 (2 C),
47.2 (2 C), 50.1 (4 C) (CH3CHCH3), 166.8 (2 C, N3C) ppm.
coordinate silicon(II) species with two bidentate amidinato 29Si{1H} NMR (C6D6, 23 °C): δ = –186.5 ppm. 15N VACP/MAS
NMR: δ = –235.0, – 233.3, –230.3, –229.2, –213.2, –206.1 ppm. 29Si
ligands. An analogous process can also be assumed for 4;
however, the four-coordinate species does not seem to play
VACP/MAS NMR: δ = –186.2 ppm. C26H57ClN6Si (517.32): calcd.
C 60.37, H 11.11, N 16.25; found C 60.1, H 11.0, N 16.1.
as important a role as in the case of 2. The dynamic behav-
ior of 4 in solution is strongly supported by the 1H and 13
C
Compound 4: Toluene (20 mL) was added at 20 °C in a single por-
tion to a mixture of 3 (5.00 g, 9.67 mmol) and potassium bis(tri-
methylsilyl)amide (2.21 g, 11.1 mmol), and the reaction mixture
was stirred at this temperature for 3 h. The resulting precipitate was
filtered off and discarded, and the solvent of the filtrate was re-
moved in vacuo, followed by the addition of n-hexane (5 mL). The
resulting suspension was heated until a clear solution was obtained,
which was then cooled slowly to –30 °C and kept undisturbed at
this temperature for 2 d. The resulting colorless crystalline solid
was isolated by filtration and dried in vacuo (20 °C, 6 h,
0.01 mbar). Yield: 4.40 g (9.15 mmol, 95%). 1H NMR ([D8]toluene,
NMR spectra at room temperature, which show very broad
resonance signals but well-resolved peaks at –70 °C. The 1H
and 13C NMR spectra of 6 at room temperature do not
indicate a dynamic behavior. The difference in chemical
shift observed in the solid-state and solution 29Si NMR
spectra of 6 (Δδ29Si = 8.1 ppm) is not fully understood. The
same holds true for the significantly different isotropic 29Si
chemical shifts of the two guanidinatosilicon(II) species 4
and 6, both of which contain an SiN3 skeleton. Neverthe-
less, the different 29Si NMR spectroscopic data of the do- –70 °C): δ = 0.72 (d, JH,H = 6.1 Hz, 3 H, CH3), 0.75 (d, JH,H
=
3
3
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SHORT COMMUNICATION
3
3
6.1 Hz, 3 H, CH3), 0.80 (d, JH,H = 6.3 Hz, 3 H, CH3), 0.88 (d,
6 H, CH3), 1.47 (d, JH,H = 6.7 Hz, 6 H, CH3), 2.01 [s, 6 H,
3JH,H = 6.3 Hz, 3 H, CH3), 1.15 (d, JH,H = 6.4 Hz, 3 H, CH3),
1.16 (d, JH,H = 6.6 Hz, 6 H, CH3), 1.22 (d, JH,H = 6.4 Hz, 3 H,
CH3), 1.30 (d, JH,H = 6.7 Hz, 3 H, CH3), 1.34 (d, JH,H = 6.4 Hz,
N(CH3)2], 3.78 (sept., JH,H = 6.7 Hz, 2 H, CH3CHCH3), 3.98
3
3
(sept., 3JH,H = 6.7 Hz, 2 H, CH3CHCH3), 7.05–7.14 (m, 6 H, C6H3)
ppm. 13C{1H} NMR (C6D6): δ = 5.9 [Si(CH3)3], 23.7 (2 C), 23.8
(2 C) (CH3CHCH3), 25.9 (2 C), 27.1 (2 C), 28.3 (2 C), 29.2 (2 C)
(CH3), 38.6 [2 C, N(CH3)2], 124.0 (2 C), 124.4 (2 C, o-C6H3), 126.3
(2 C, i-C6H3), 138.5 (2 C, p-C6H3), 145.0 (2 C), 145.0 (2 C) (m-
C6H3), 152.3 (N3C) ppm. 29Si{1H} NMR (C6D6): δ = –0.3
3
3
3
3
3
3
6 H, CH3), 1.38 (d, JH,H = 6.7 Hz, 3 H, CH3), 1.52 (d, JH,H
=
3
6.0 Hz, 3 H, CH3), 1.71 (d, JH,H = 6.6 Hz, 3 H, CH3), 1.75 (d,
3JH,H = 6.0 Hz, 3 H, CH3), 1.96 (d, JH,H = 6.6 Hz, 3 H, CH3),
3
2.88 (sept., 3JH,H = 6.1 Hz, 1 H, CH3CHCH3), 2.93 (sept., JH,H
=
3
6.3 Hz, 1 H, CH3CHCH3), 3.40 (sept., JH,H = 6.6 Hz, 1 H, [Si(CH3)3], 14.9 (SiN3) ppm. 15N VACP/MAS NMR: δ = –321.1,
3
CH3CHCH3), 3.47 (sept., JH,H = 6.7 Hz, 1 H, CH3CHCH3), 3.64 –289.8, –232.5, –229.6 ppm. 29Si VACP/MAS NMR: δ = 0.9
3
3
3
(sept., JH,H = 6.4 Hz, 2 H, CH3CHCH3), 4.20 (sept., JH,H
=
[Si(CH3)3], 6.8 (SiN3) ppm. C33H58N4Si3 (595.11): calcd. C 66.60,
3
6.0 Hz, 1 H, CH3CHCH3), 4.57 (sept., JH,H = 6.6 Hz, 1 H, H 9.82, N 9.41; found C 66.4, H 9.8, N 9.4.
CH3CHCH3) ppm. 13C{1H} NMR ([D8]toluene, –70 °C): δ = 21.5,
21.6, 22.2, 22.3, 22.4, 23.0, 23.1, 23.6, 23.9, 24.7, 25.5, 25.6, 25.8,
Acknowledgments
26.3, 27.8, 28.0 (CH3), 45.6, 45.7, 46.0, 47.5, 48.1, 48.2, 49.3, 49.4
(CH3CHCH3), 150.9, 155.5 (N3C) ppm. 29Si{1H} NMR ([D8]tolu-
ene, –70 °C): δ = –26.0 ppm. 29Si{1H} NMR (C6D6, 23 °C): δ =
–25.6 ppm. 15N VACP/MAS NMR: δ = –308.3, –279.6, –269.6,
R. T. thanks the Deutsche Forschungsgemeinschaft (TA 75/16-1)
for financial support.
–208.7, –204.6, –117.1 ppm. 29Si VACP/MAS NMR:
δ =
–20.6 ppm. C26H56N6Si (480.86): calcd. C 64.94, H 11.74, N 17.48;
found C 64.9, H 11.6, N 17.3.
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Compound 5:
A solution of lithium dimethylamide (1.89 g,
37.0 mmol) in tetrahydrofuran (60 mL) was added within 10 min at
–78 °C to a stirred solution of bis(2,6-diisopropylphenyl)carbodii-
mide (13.4 g, 37.0 mmol) in tetrahydrofuran (250 mL), and the
stirred reaction mixture was warmed to 20 °C over 2 h. The solu-
tion was cooled to –78 °C, and trichlorosilane (5.01 g, 37.0 mmol)
was added in a single portion. The stirred reaction mixture was
then warmed to 20 °C over 16 h. The solvent was removed in
vacuo, dichloromethane (150 mL) was added to the residue, and
the remaining solid was filtered off and discarded. The solvent of
the filtrate was removed in vacuo, followed by the addition of
acetonitrile (500 mL). The resulting suspension was heated until a
clear solution was obtained, which was then cooled slowly to
–30 °C and kept undisturbed at this temperature for 1 d. The re-
sulting colorless crystalline solid was isolated by filtration, washed
with cold (–30 °C) n-pentane (2ϫ 100 mL), and dried in vacuo
1
(20 °C, 6 h, 0.01 mbar). Yield: 15.1 g (29.8 mmol, 81%). H NMR
3
(CD2Cl2, 23 °C): δ = 1.24 (d, JH,H = 6.9 Hz, 12 H, CH3), 1.31 (d,
3JH,H = 6.9 Hz, 12 H, CH3), 2.41 [s, 6 H, N(CH3)2], 3.35 (sept.,
3JH,H = 6.9 Hz, 4 H, CH3CHCH3), 6.16 (s, 1 H, SiH; 29Si satellites,
1JH,Si = 352 Hz), 7.18–7.21 (m, 4 H, m-C6H3), 7.27–7.32 (m, 2 H,
p-C6H3) ppm. 13C{1H} NMR (CD2Cl2, 23 °C): δ = 23.5 (4 C)
(CH3CHCH3), 25.1 (4 C), 29.0 (4 C) (CH3), 39.7 [2 C, N(CH3)2],
124.4 (4 C, o-C6H3), 127.9 (2 C, i-C6H3), 134.8 (2 C, p-C6H3), 146.6
(4 C, m-C6H3), 160.7 (N3C) ppm. 29Si{1H} NMR (CD2Cl2, 23 °C):
δ = –97.7 ppm. 29Si{1H} NMR (C6D6, 23 °C): δ = –96.2 ppm. 15N
VACP/MAS NMR: δ = –304.3, –250.1, –238.0 ppm. 29Si VACP/
MAS NMR: δ = –99.6 ppm. C27H41Cl2N3Si (506.63): calcd. C
64.01, H 8.16, N 8.29; found C 64.0, H 8.2, N 8.3.
Compound 6: Toluene (200 mL) was added at 20 °C in a single por-
tion to a mixture of 5 (11.8 g, 23.3 mmol) and potassium bis(trime-
thylsilyl)amide (8.82 g, 44.2 mmol), and the reaction mixture was
stirred at this temperature for 18 h. The resulting precipitate was
filtered off and discarded, and the solvent of the filtrate was re-
moved in vacuo, followed by the addition of toluene (15 mL). The
resulting suspension was heated until a clear solution was obtained,
which was then cooled slowly to –30 °C and kept undisturbed at
this temperature for 2 d. The resulting colorless crystalline solid
was isolated by filtration and dried in vacuo (20 °C, 6 h,
0.01 mbar). Yield: 10.4 g (17.5 mmol, 75%). 1H NMR (C6D6,
h) T. Chlupatý, Z. Padeˇlková, F. DeProft, R. Willem, A. Ru˚z-
ˇ
icˇka, Organometallics 2012, 31, 2203–2211.
[4] For a review dealing with stable compounds with low-oxi-
dation-state group 2, 13, 14, or 15 elements containing guanidin-
ato ligands, see: C. Jones, Coord. Chem. Rev. 2010, 254, 1273–
1289.
[5] Solution 1H, 13C{1H}, and 29Si{1H} NMR spectra were re-
corded at 23 °C with a Bruker Avance 500 NMR spectrometer
(1H, 500.1 MHz; 13C, 125.8 MHz; 29Si, 99.4 MHz). C6D6,
CD2Cl2, or [D8]toluene were used as the solvent. Chemical
shifts were determined relative to internal C6HD5 (1H, δ =
3
23 °C): δ = 0.31 [s, 18 H, Si(CH3)3], 1.19 (d, JH,H = 6.7 Hz, 6 H,
3
3
CH3), 1.21 (d, JH,H = 6.7 Hz, 6 H, CH3), 1.33 (d, JH,H = 6.7 Hz,
Eur. J. Inorg. Chem. 2013, 5821–5825
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© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
SHORT COMMUNICATION
7.28 ppm, C6D6), CHDCl2 (1H, δ = 5.32 ppm, CD2Cl2), [D7]-
toluene (1H, δ = 2.09 ppm, [D8]toluene), C6D6 (13C, δ =
128.0 ppm, C6D6), CD2Cl2 (13C, δ = 53.8 ppm, CD2Cl2), [D8]-
toluene (13C, δ = 20.4 ppm, [D8]toluene), or external TMS
(29Si, δ = 0 ppm; C6D6, CD2Cl2, [D8]toluene). Assignment of
the 1H and 13C NMR spectroscopic data was supported by
0.6ϫ0.45ϫ0.25 mm obtained by crystallization from Et2O at
–20 °C, C26H56N6Si, Mr = 480.86, analysis at 173(2) K, mono-
clinic, space group P21/n (no. 14), a = 12.261(2) Å, b =
14.798(3) Å, c = 17.362(3) Å, β = 99.56(2)°, V = 3106.4(9) Å3,
Z = 4, ρcalcd. = 1.028 gcm–3, μ = 0.098 mm–1, F(000) = 1072,
2θmax = 52.04°, 28743 collected reflections, 5813 unique reflec-
tions (Rint = 0.0786), 314 parameters, S = 1.121, R1 = 0.0588
[IϾ2σ(I)], wR2 (all data) = 0.1547, max./min. residual electron
density = +0.821/–0.323 eÅ–3. Selected data for 5: single crystal
of dimensions 0.5ϫ0.4ϫ0.1 mm obtained by crystallization
from acetonitrile at –20 °C, C27H41Cl2N3Si, Mr = 506.62,
analysis at 173(2) K, monoclinic, space group P21/n (no. 14), a
= 10.0989(18) Å, b = 15.9344(19) Å, c = 18.029(4) Å, β =
90.70(2)°, V = 2901.0(9) Å3, Z = 4, ρcalcd. = 1.160 gcm–3, μ =
0.284 mm–1, F(000) = 1088, 2θmax = 52.74°, 22447 collected
reflections, 5816 unique reflections (Rint = 0.0551), 312 param-
eters, S = 0.952, R1 = 0.0374 [IϾ2σ(I)], wR2 (all data) =
1
1H,1H and H,13C correlation experiments and DEPT 135 ex-
periments. Compound 4 was additionally studied by VT NMR
spectroscopic experiments. The thermocouple used with the
probe for these studies was calibrated for lower temperatures
according to ref.[10] by using a 4% solution of MeOH in
[D4]MeOH containing a trace of HCl. Solid-state 15N and 29Si
VACP/MAS NMR spectra were recorded at 22 °C with a
Bruker DSX-400 NMR spectrometer with bottom layer rotors
of ZrO2 (diameter: 7 mm) containing ca. 200 mg of sample
[15N, 40.6 MHz; 29Si, 79.5 MHz; external standard: TMS (13C,
29Si, δ = 0 ppm) or glycine (15N, δ = –342.0 ppm); spinning
rate: 7 kHz; contact time: 3 ms (15N) or 5 ms (29Si); 90° 1H
transmitter pulse length: 3.6 μs; repetition time: 7 s].
0.0974, max./min. residual electron density
= +0.292/
–0.291 eÅ–3. Selected data for 6: single crystal of dimensions
0.55ϫ0.35ϫ0.35 mm obtained by crystallization from toluene
at –20 °C, C33H58N4Si3, Mr = 595.10, analysis at 173(2) K, or-
thorhombic, space group Pbca (no. 61), a = 17.5441(19) Å, b
= 18.4142(18) Å, c = 22.757(3) Å, V = 7351.9(15) Å3, Z = 8,
[6] Crystal structure analyses of 3–6: Suitable single crystals were
mounted in inert oil (perfluoropolyalkyl ether, ABCR) on a
glass fiber and then transferred to the cold nitrogen gas stream
of the diffractometer (3, Bruker X8-APEX II, graphite-mono-
chromated Mo-Kα radiation, λ = 0.71073 Å; 4–6, Stoe IPDS,
graphite-monochromated Mo-Kα radiation, λ = 0.71073 Å).
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).[11] SHELXLE was used as
refinement GUI.[12] For the CH hydrogen atoms, a riding
model was employed. CCDC-955561, -955562, -955563, and
-955564 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. Selected data for 3: single crystal of di-
mensions 0.97ϫ0.76ϫ0.25 mm obtained by crystallization
from THF at –30 °C, C26H57ClN6Si, Mr = 517.32, analysis at
ρcalcd. = 1.075 gcm–3, μ = 0.155 mm–1, F(000) = 2608, 2θmax
=
52.04°, 38082 collected reflections, 7204 unique reflections (Rint
= 0.0508), 377 parameters, S = 0.982, R1 = 0.0401 [IϾ2σ(I)],
wR2 (all data) = 0.1084, max./min. residual electron density =
+0.271/–0.248 eÅ–3.
Due to partial disorder, the position of the SiH hydrogen atom
could not be determined reliably from the X-ray diffraction
data.
The Berry distortion was analyzed by using the PLATON Pro-
gram system: A. L. Spek, Acta Crystallogr., Sect. D 2009, 65,
148–155.
X.-A. Pang, Y.-M. Yao, J.-F. Wang, Q. Shen, Chin. J. Chem.
2005, 23, 1193–1197.
[7]
[8]
[9]
100(2) K, monoclinic, space group P21/n (no. 14),
14.128(3) Å, b = 13.784(5) Å, c = 16.312(3) Å, β = 102.15(2)°,
a =
[10] S. Berger, S. Braun, 200 and More NMR Experiments, Wiley-
VCH, Weinheim, 2004, pp. 141–144.
[11] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112–122.
[12] C. B. Hübschle, G. M. Sheldrick, B. Dittrich, J. Appl. Crys-
tallogr. 2011, 44, 1281–1284.
V
= Z = 4, ρcalcd. = μ =
3105.4(14) Å3, 1.106 gcm–3,
0.186 mm–1, F(000) = 1144, 2θmax = 52.04°, 19052 collected
reflections, 6018 unique reflections (Rint = 0.0296), 326 param-
eters, S = 1.062, R1 = 0.0428 [IϾ2σ(I)], wR2 (all data) =
Received: September 9, 2013
Published Online: October 31, 2013
0.0951, max./min. residual electron density
= +0.511/
–0.402 eÅ–3. Selected data for 4: single crystal of dimensions
Eur. J. Inorg. Chem. 2013, 5821–5825
5825
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim