Neutral hexacoordinate silicon(IV) complexes with a tridentate dianionic O,N,X ligand (X = O, N, S), bidentate monoanionic X,N ligand (X = O, S), and phenyl ligand: Compounds with a SiO3N2C, SiSO 2N2C, SiO2N3C, SiSON3C, or SiS2ON2C skeleton

Article abstract of DOI:10.1002/ejic.201400083

A series of neutral hexacoordinate silicon(IV) complexes (4a, 4b, 5a, 5b, 6a, and 6b) with a SiO₃N₂C, SiSO₂N ₂C, SiO₂N₃C, SiSON₃C, or SiS ₂ON₂C skeleton have been synthesized and structurally characterized by solid-state and solution NMR spectroscopy and single-crystal X-ray diffraction. These studies were performed with a special emphasis on comparing the respective O/NMe/S analogues 4a/5a/6a and 4b/5b/6b and the O/S pairs 4a/4b, 5a/5b, and 6a/6b with respect to their structures and NMR spectroscopic parameters. A series of neutral hexacoordinate silicon(IV) complexes have been synthesized and structurally characterized by NMR spectroscopy and single-crystal X-ray diffraction. These studies were performed with a special emphasis on comparing the respective O/NMe/S analogues 4a/5a/6a and 4b/5b/6b and the O/S pairs 4a/4b, 5a/5b, and 6a/6b with respect to their structures and NMR spectroscopic parameters. Copyright

Full text of DOI:10.1002/ejic.201400083

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DOI:10.1002/ejic.201400083
Neutral Hexacoordinate Silicon(IV) Complexes with a
Tridentate Dianionic O,N,X Ligand (X = O, N, S),
Bidentate Monoanionic X,N Ligand (X = O, S), and
Phenyl Ligand: Compounds with a SiO3N2C, SiSO2N2C,
SiO2N3C, SiSON3C, or SiS2ON2C Skeleton
Jörg Weiß,[a] Johannes A. Baus,[a] Christian Burschka,[a] and
Reinhold Tacke*[a]
Keywords: Chalcogens / Coordination modes / Main group elements / Silicon / Tridentate ligands
A series of neutral hexacoordinate silicon(IV) complexes (4a,
4b, 5a, 5b, 6a, and 6b) with a SiO3N2C, SiSO2N2C, SiO2N3C,
SiSON3C, or SiS2ON2C skeleton have been synthesized and
structurally characterized by solid-state and solution NMR
spectroscopy and single-crystal X-ray diffraction. These
studies were performed with a special emphasis on compar-
ing the respective O/NMe/S analogues 4a/5a/6a and 4b/5b/
6b and the O/S pairs 4a/4b, 5a/5b, and 6a/6b with respect to
their structures and NMR spectroscopic parameters.
troscopy and single-crystal X-ray diffraction. The studies
reported herein were performed as part of our ongoing sys-
tematic investigations into higher-coordinate silicon(IV)
complexes.[6,7]
Introduction
The past decade has witnessed great advances in the
chemistry of higher-coordinate silicon.[1] A huge variety of
penta- and hexacoordinate silicon(IV) complexes with novel
combinations of different ligand atoms (including soft li-
gand atoms such as sulfur, selenium, tellurium, and iodine)
have been synthesized, structurally characterized, and
studied for their reactivity. In this context, we have demon-
strated the neutral pentacoordinate silicon(IV) complexes
1–3 to be particularly versatile precursors for the synthesis
of new neutral penta- and hexacoordinate silicon(IV) com-
plexes.[2] In continuation of these investigations, we have
now succeeded in synthesizing the neutral hexacoordinate
silicon(IV) complexes 4a, 4b, 5a, 5b, 6a, and 6b. Com-
pounds 4b, 5b, 6a, and 6b, with their novel sulfur-contain-
ing SiSO2N2C, SiSON3C, or SiS2ON2C skeleton, are of
particular interest because only very few hexacoordinate
silicon(IV) complexes with sulfur ligand atoms have been
described in the literature.[2e,3–5] Compounds 4a/5a/6a and
4b/5b/6b represent O/NMe/S analogues, and 4a/4b, 5a/5b,
and 6a/6b are O/S analogues. To gain information on the
effects of the O/NMe/S (4a/5a/6a and 4b/5b/6b) and O/S
exchange (4a/4b, 5a/5b, and 6a/6b) on the structures and
NMR spectroscopic parameters, all these compounds were
characterized by solid-state and solution NMR spec-
Results and Discussion
Compounds 4a, 4b, 5a, 5b, 6a, and 6b were synthesized
by treatment of the corresponding neutral pentacoordinate
chlorosilicon(IV) complexes 1–3 with 8-(trimethylsilyloxy)-
quinoline (7) or 8-(trimethylsilylthio)quinoline (8) using
acetonitrile as the solvent (Scheme 1). The products were
isolated as colored crystalline solids (yield/color: 4a, 94%/
yellow; 4b·0.5CH3CN, 79%/yellow; 5a, 99%/red;
5b·0.5CH3CN, 74%/red; 6a·0.5CH3CN, 74%/orange;
[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/
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201400083.
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6b·0.5CH3CN, 88%/orange). 8-(Trimethylsilyloxy)quinoline
(7) and 8-(trimethylsilylthio)quinoline (8) were synthesized
by treatment of 8-hydroxy- and 8-mercaptoquinoline,
respectively, with an excess of bis(trimethylsilyl)amine and
were isolated as colorless liquids (yield: 7, 91%; 8, 74%).
Figure 2. Molecular structure of 4b in the crystal of 4b·0.5CH3CN
(displacement ellipsoids drawn at the 50% probability level). Se-
lected bond lengths [Å] and angles [°]: Si–S 2.2677(7), Si–O1
1.8007(13), Si–O2 1.7723(13), Si–N1 1.9308(15), Si–N2 2.0720(16),
Si–C1 1.9323(19); S–Si–O1 92.27(5), S–Si–O2 90.45(5), S–Si–N1
171.68(5), S–Si–N2 84.26(5), S–Si–C1 91.84(6), O1–Si–O2
168.55(6), O1–Si–N1 90.81(6), O1–Si–N2 82.64(6), O1–Si–C1
95.47(7), O2–Si–N1 85.06(6), O2–Si–N2 86.57(6), O2–Si–C1
95.56(7), N1–Si–N2 88.48(6), N1–Si–C1 95.55(7), N2–Si–C1
175.58(8).
Scheme 1. Synthesis of compounds 4a, 4b, 5a, 5b, 6a, and 6b.
Compounds 4a, 4b·0.5CH3CN, 5a, 5b·CH3CN, 6a, and
6b·0.5CH3CN were structurally characterized by single-
crystal X-ray diffraction. The crystal data and experimental
parameters used for the crystal structure analyses are given
in Table S1 of the Supporting Information, and the molec-
ular structures of 4a, 4b, 5a, 5b, 6a, and 6b in the crystal
are shown in Figures 1, 2, 3, 4, 5, and 6, respectively; se-
lected bond lengths and angles are given in the respective
figure legends. Compound 6a contains two molecules in the
asymmetric unit, which, as a first approximation, behave as
mirror images.
Figure 3. Molecular structure of 5a in the crystal (displacement
ellipsoids drawn at the 50% probability level). Selected bond
lengths [Å] and angles [°]: Si–O1 1.803(2), Si–O2 1.771(2), Si–N1
1.917(3), Si–N2 2.092(3), Si–N3 1.826(2), Si–C1 1.910(3); O1–Si–
O2 90.35(10), O1–Si–N1 90.10(10), O1–Si–N2 82.72(9), O1–Si–N3
168.72(10), O1–Si–C1 93.05(11), O2–Si–N1 168.54(11), O2–Si–N2
82.00(10), O2–Si–N3 94.58(10), O2–Si–C1 93.56(11), N1–Si–N2
86.69(10), N1–Si–N3 83.07(11), N1–Si–C1 97.86(12), N2–Si–N3
87.91(10), N2–Si–C1 173.82(12), N3–Si–C1 96.75(12).
Figure 1. Molecular structure of 4a in the crystal (displacement
ellipsoids drawn at the 50% probability level). Selected bond
lengths [Å] and angles [°]: Si–O1 1.7915(11), Si–O2 1.7702(11), Si–
O3 1.7564(10), Si–N1 1.9329(13), Si–N2 2.0907(13), Si–C1
1.9107(15); O1–Si–O2 166.89(5), O1–Si–O3 91.26(5), O1–Si–N1
89.70(5), O1–Si–N2 82.72(5), O1–Si–C1 95.69(5), O2–Si–O3
92.23(5), O2–Si–N1 84.94(5), O2–Si–N2 85.21(5), O2–Si–C1
96.80(6), O3–Si–N1 171.10(5), O3–Si–N2 82.55(5), O3–Si–C1
92.31(5), N1–Si–N2 88.80(5), N1–Si–C1 96.40(6), N2–Si–C1
174.56(6).
The silicon coordination polyhedra of 4a, 4b·0.5CH3CN,
5a, 5b·CH3CN, 6a, and 6b·0.5CH3CN are best described as
strongly distorted octahedra, with maximum deviations
from the ideal angles of 90 and 180° ranging from 6.85(11)
to 8.00(9)° and from 9.83(5) to 13.11(5)°, respectively. The
structures of all the compounds studied are very similar,
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Figure 4. Molecular structure of 5b in the crystal of 5b·CH3CN
(displacement ellipsoids drawn at the 50% probability level). Se-
lected bond lengths [Å] and angles [°]: Si–S 2.2981(8), Si–O
1.8013(15), Si–N1 1.9097(18), Si–N2 2.1159(19), Si–N3 1.8365(18),
Si–C1 1.929(2); S–Si–O 90.90(5), S–Si–N1 169.36(6), S–Si–N2
82.06(5), S–Si–N3 94.68(6), S–Si–C1 91.76(7), O–Si–N1 89.69(7),
O–Si–N2 82.60(7), O–Si–N3 167.59(8), O–Si–C1 93.73(8), N1–Si–
N2 87.49(7), N1–Si–N3 82.79(8), N1–Si–C1 98.80(9), N2–Si–N3
87.20(8), N2–Si–C1 172.73(9), N3–Si–C1 97.16(9).
with the tridentate O,N,O, N,N,O, and S,N,O ligands in mer
positions. In all the structures, the imino nitrogen atoms
of these tridentate ligands and the chalcogen atoms of the
bidentate N,X ligands (X = O, S) occupy trans positions,
and the nitrogen atoms of the N,X ligands and the carbon
ligand atoms of the phenyl groups are also found in trans
positions.
As can be seen from Table 1, neither the O/NMe/S nor
O/S exchange significantly affects the bond lengths between
the silicon coordination center and the respective ligand
atoms. The Si–O(enolato) bond lengths are in the range
1.7785(14)–1.803(2) Å, and the Si–C bond lengths range
from 1.910(3) to 1.9323(19) Å. The Si–N(imino) bond
lengths are 1.9097(18)–1.935(3) Å, and the significantly
longer Si–N(quinoline) atom distances are 2.033(3)–
2.1159(19) Å. The respective Si–O [1.754(2)–1.771(2) Å]
and Si–S [2.2677(7)–2.2981(8) Å] bond lengths of the biden-
tate N,X ligands (X = O, S) are also very similar. Likewise,
the O/S exchange in the bidentate ligand does not influence
the Si–O(phenolato) [1.7702(11) and 1.7723(13) Å] and Si–
S [2.2704(9) and 2.2939(15)/2.2862(14) Å] bond lengths of
Figure 5. Molecular structures of the two crystallographically inde-
pendent molecules A and B in the crystal of 6a (displacement ellip-
soids drawn at the 50% probability level). Selected bond lengths
[Å] and angles [°] of molecule A (top): Si1–S1 2.2939(15), Si1–O1
1.798(3), Si1–O2 1.754(2), Si1–N1 1.913(3), Si1–N2 2.039(3), Si1–
C1 1.930(3); S1–Si1–O1 169.88(9), S1–Si1–O2 90.30(9), S1–Si1–N1
85.57(9), S1–Si1–N2 87.48(9), S1–Si1–C1 95.44(11), O1–Si1–O2
92.38(11), O1–Si1–N1 90.51(12), O1–Si1–N2 83.15(11), O1–Si1–C1
94.24(13), O2–Si1–N1 171.82(11), O2–Si1–N2 83.17(11), O2–Si1–
C1 91.66(13), N1–Si1–N2 89.59(12), N1–Si1–C1 95.76(13), N2–
Si1–C1 174.08(13). Selected bond lengths [Å] and angles [°] of mo-
lecule B (bottom): Si2–S2 2.2862(14), Si2–O3 1.794(3), Si2–O4
1.759(2), Si2–N3 1.935(3), Si2–N4 2.033(3), Si2–C27 1.920(4); S2–
Si2–O3 169.86(10), S2–Si2–O4 89.82(9), S2–Si2–N3 85.66(9), S2–
Si2–N4 88.16(9), S2–Si2–C27 95.44(11), O3–Si2–O4 92.51(11), O3–
Si2–N3 90.67(12), O3–Si2–N4 82.32(11), O3–Si2–C27 94.34(13),
O4–Si2–N3 171.13(11), O4–Si2–N4 83.36(11), O4–Si2–C27
91.85(13), N3–Si2–N4 88.87(11), N3–Si2–C27 96.17(13), N4–Si2–
C27 174.01(13).
Table 1. Selected bond lengths of compounds 4a, 4b, 5a, 5b, 6a, and 6b.
Compound (ligands) Si–O(enolato) [Å]
Si–N(imino) [Å]
Si–N(quinoline) [Å] Si–C [Å]
Si–X (tridentate) [Å] Si–X (bidentate) [Å]
(X = O, NMe, S)
(X = O, S)
4a (O,N,O, N,O)
4b (O,N,O, N,S)[a]
5a (N,N,O, N,O)
5b (N,N,O, N,S)[b]
6a (S,N,O, N,O)[c]
1.7915(11)
1.8007(13)
1.803(2)
1.8013(15)
1.798(3)/
1.794(3)
1.9329(13)
1.9308(15)
1.917(3)
1.9097(18)
1.913(3)/
1.935(3)
2.0907(13)
2.0720(16)
2.092(3)
2.1159(19)
2.039(3)/
2.033(3)
1.9107(15)
1.9323(19)
1.910(3)
1.929(2)
1.930(3)/
1.920(4)
1.932(2)
1.7702(11)
1.7723(13)
1.826(2)
1.8365(18)
2.2939(15)/
2.2862(14)
2.2704(9)
1.7564(10)
2.2677(7)
1.771(2)
2.2981(8)
1.754(2)/
1.759(2)
6b (S,N,O, N,S)[d]
1.7785(14)
1.9276(18)
2.0337(19)
2.2834(12)
[a] Solvate 4b·0.5CH3CN. [b] Solvate 5b·CH3CN. [c] Data for two crystallographically independent molecules. [d] Solvate 6b·0.5CH3CN.
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Conclusions
With the synthesis of 4a, 4b, 5a, 5b, 6a, and 6b, we have
succeeded in synthesizing a series of novel hexacoordinate
silicon(IV) complexes that contain a tridentate dianionic
O,N,O, N,N,O, or S,N,O ligand, a bidentate monoanionic
N,X ligand (X = O, S), and a phenyl ligand. These com-
pounds contain a SiO3N2C (4a), SiSO2N2C (4b, 6a),
SiO2N3C (5a), SiSON3C (5b), or SiS2ON2C (6b) skeleton.
The three sulfur-containing skeletons have not previously
been described in the literature. In this context it should be
noted that only a few hexacoordinate silicon(IV) complexes
with sulfur ligand atoms have been synthesized and charac-
terized so far.[2e,3–5] The studies reported herein again em-
phasize the high synthetic potential of the pentacoordinate
chlorosilicon(IV) complexes 1–3 for the targeted synthesis
of novel hexacoordinate silicon(IV) complexes, including
those with soft sulfur ligand atoms.
As shown by crystal structure analyses, the silicon coor-
dination polyhedra of the title compounds are distorted
octahedra, with the tridentate O,N,O, N,N,O or S,N,O li-
gand in mer positions. The imino nitrogen atoms of these
tridentate ligands and the chalcogen atoms of the bidentate
N,X ligands (X = O, S) occupy trans positions, and the ni-
trogen atom of the N,X ligands and the carbon ligand atom
of the phenyl group are also found in trans positions. In
general, the structures of all the compounds studied are
very similar, that is, neither the O/NMe/S nor the O/S ex-
change affects the structures significantly.
Figure 6. Molecular structure of 6b in the crystal of 6b·0.5CH3CN
(displacement ellipsoids drawn at the 50% probability level). Se-
lected bond lengths [Å] and angles [°]: Si–S1 2.2704(9), Si–S2
2.2834(12), Si–O 1.7785(14), Si–N1 1.9276(18), Si–N2 2.0337(19),
Si–C1 1.932(2); S1–Si–S2 88.15(4), S1–Si–O 170.17(5), S1–Si–N1
86.02(6), S1–Si–N2 88.04(5), S1–Si–C1 94.50(7), S2–Si–O 93.28(6),
S2–Si–N1 171.60(6), S2–Si–N2 84.26(7), S2–Si–C1 90.21(8), O–Si–
N1 91.45(7), O–Si–N2 82.43(7), O–Si–C1 95.22(8), N1–Si–N2
89.49(8), N1–Si–C1 96.28(9), N2–Si–C1 173.84(8).
Table 2. Isotropic 29Si chemical shifts of 4a, 4b, 5a, 5b, 6a, and 6b
in the solid state (T = 22 °C) and in solution (T = 23 °C; solvent,
CD2Cl2).
Compound (ligands)
δ29Si (solid state)
[ppm]
δ29Si (solution)
[ppm]
4a (O,N,O, N,O)
4b (O,N,O, N,S)
5a (N,N,O, N,O)
5b (N,N,O, N,S)
6a (S,N,O, N,O)
6b (S,N,O, N,S)
–144.6
–147.2
–138.8
–144.0
–135.8
–141.7
–141.6
As demonstrated by solid-state and solution NMR spec-
troscopic studies, the title compounds also exist in solution,
and it is likely that their structures in the solid state and
in solution are very similar. Interestingly, the isotropic 29Si
chemical shifts of the title compounds are similar [solid
state: δ = –146.9 to –135.3 ppm; solution (CD2Cl2): δ =
–147.2 to –135.8 ppm] and show no systematic trend in
terms of a clear correlation between the chemical shift and
the electronegativity of the ligand atoms.
–140.0[a]
–146.9
–135.3[b]
–146.4[c]
–145.4[d]
[a] Solvate 4b·0.5CH3CN. [b] Solvate 5b·0.5CH3CN. [c] Solvate
6a·0.5CH3CN. [d] Solvate 6b·0.5CH3CN.
the tridentate ligand significantly, whereas the Si–NCH3
distance [1.826(2) and 1.8365(18) Å] is slightly shortened by
the O/S exchange.
Experimental Section
Compounds 4a, 4b·0.5CH3CN, 5a, 5b·0.5CH3CN,
6a·0.5CH3CN, and 6b·0.5CH3CN were also studied by
NMR spectroscopy in the solid state (15N, 29Si) as well as
in solution (1H, 13C, 29Si; solvent, CD2Cl2). The data ob-
General Procedures: All syntheses were carried out under dry ar-
gon. The organic solvents used were dried and purified according
to standard procedures and stored under nitrogen. The solution-
state 1H, 13C, and 29Si NMR spectra were recorded at 23 °C by
tained (see the Exp. Sect.) confirmed the identities of the using a Bruker Avance 500 NMR spectrometer (1H, 500.1 MHz;
13C, 125.8 MHz; 29Si, 99.4 MHz) with CD2Cl2 as the solvent.
compounds studied.
Chemical shifts were determined relative to internal CHDCl2 (1H,
δ = 5.32 ppm), CD2Cl2 (13C, δ = 53.8 ppm), or external TMS (29Si,
δ = 0 ppm). Assignment of the 13C NMR spectroscopic data was
supported by DEPT 135 and 13C,1H correlation experiments. Solid-
state 15N and 29Si VACP/MAS NMR spectra were recorded at
22 °C by using a Bruker DSX-400 NMR spectrometer with bottom
layer rotors of ZrO2 (diameter, 7 mm) containing around 300 mg
of sample [15N, 40.6 MHz; 29Si, 79.5 MHz; external standard, TMS
(29Si, δ = 0 ppm) or glycine (15N, δ = –342.0 ppm); spinning rate,
As can be seen from Table 2, the isotropic 29Si chemical
shifts of 4a, 4b, 5a, 5b, 6a, and 6b in the solid state and
in solution are very similar (maximum deviation, Δδ29Si =
3.8 ppm), which indicates that these neutral hexacoordinate
silicon(IV) compounds also exist in solution. The 29Si
chemical shifts range from δ = –146.9 to –135.3 ppm in the
solid state (Δδ29Si = 11.6 ppm) and from δ = –147.2 to
–135.8 ppm in solution (Δδ29Si = 11.4 ppm). The data ob-
tained do not reveal a clear effect of the O/NMe/S and 5 kHz; contact time, 3 (15N) or 5 ms (29Si); 90° 1H transmitter pulse
O/S exchange in terms of a correlation between the 29Si
length, 3.6 μs; repetition time, 4–7 s].
chemical shifts and the electronegativities of the respective
ligand atoms.
Synthesis of 4a: Compound 7 (316 mg, 1.45 mmol) was added in a
single portion at 20 °C to a stirred solution of 1 (457 mg,
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1.39 mmol) in acetonitrile (60 mL), and the reaction mixture was
then stirred at this temperature for 1 min. The resulting clear solu-
tion was kept undisturbed at 20 °C for 16 h and then at –20 °C for
a further 24 h. The resulting solid was isolated by filtration, washed
with n-pentane (10 mL), and dried in vacuo (20 °C, 1 h, 0.01 mbar)
to give 4a in 94% yield (572 mg, 1.30 mmol) as a yellow crystalline
Synthesis of 5b·0.5CH3CN: Compound 8 (1.03 g, 4.41 mmol) was
added in a single portion at 20 °C to a stirred solution of 2 (1.37 g,
4.00 mmol) in acetonitrile (70 mL), and the reaction mixture was
then stirred at this temperature for 1 min. The resulting clear solu-
tion was kept undisturbed at 20 °C for 16 h. The resulting solid was
isolated by filtration, washed with n-pentane (20 mL), and dried in
solid. 1H NMR (CD2Cl2, 500.1 MHz): δ = 1.77 (s, 3 H, CCH3), vacuo (20 °C, 1 h, 0.01 mbar) to give 5b·0.5CH3CN in 74% yield
2.46 (s, 3 H, CCH3), 5.18 (s, 1 H, CCHC), 6.49–6.52, 6.70–6.74,
(1.44 g, 2.95 mmol) as a red crystalline solid. 1H NMR (CD2Cl2,
6.91–6.96, 7.13–7.16, 7.18–7.21, 7.27–7.36, 7.58–7.65, 8.17–8.20, 500.1 MHz): δ = 1.94 (s, 3 H, CCH3), 1.97 (s, 1.5 H, NϵCCH3),
8.27–8.31 (m, 15 H, C6H4, C6H5, C9H6NO) ppm. 13C NMR 2.32 (s, 3 H, CCH3), 2.49 (s, 3 H, NCH3), 5.23 (s, 1 H, CCHC),
(CD2Cl2, 125.8 MHz): δ = 24.4 (CCH3), 24.9 (CCH3), 103.0
(CCHC), 111.7, 114.4, 115.8, 117.8, 120.6, 121.6, 126.7 (2 C),
126.9, 128.0, 129.4, 130.8, 133.0, 134.5 (2 C), 135.1, 138.9, 141.7,
5.93–5.97, 6.37–6.43, 6.75–6.81, 7.03–7.07, 7.12–7.20, 7.38–7.44,
7.48–7.52, 7.73–7.77, 8.10–8.14, 8.41–8.45 (m, 15 H, C6H4, C6H5,
C9H6NS) ppm. 13C NMR (CD2Cl2, 125.8 MHz):
δ = 2.0
149.8, 154.3, 155.3 (C6H4, C6H5, C9H6NO), 170.5 [C(N)CH3], (NϵCCH3), 23.6 (CCH3), 25.0 (CCH3), 32.7 (NCH3), 103.9
179.7 [C(O)CH3] ppm. 29Si NMR (CD2Cl2, 99.4 MHz): δ =
(CCHC), 116.5 (NϵCCH3), 109.2, 113.2, 120.1, 120.3, 120.6,
–147.2 ppm. 15N VACP/MAS NMR: δ = –186.6 [C(N)CH3], –122.8 126.6, 126.7 (2 C), 127.9, 128.1, 128.3, 134.0 (2 C), 137.1, 139.4,
(C9H6NO) ppm. 29Si VACP/MAS NMR:
C26H22N2O3Si (438.56): calcd. C 71.21, H 5.06, N 6.39; found C
71.0, H 5.2, N 6.5.
δ
=
–144.6 ppm.
140.1, 142.7, 145.0, 148.9, 149.7, 151.8 (C6H4, C6H5, C9H6NS),
170.5 [C(N)CH3], 181.4 [C(O)CH3] ppm. 29Si NMR (CD2Cl2,
99.4 MHz): δ = –135.8 ppm. 15N VACP/MAS NMR:[8] δ = –283.1
(NCH3), –187.9 [C(N)CH3], –114.1 (C9H6NS) ppm. 29Si VACP/
MAS NMR:[8] δ = –135.3 ppm. C28H26.5N3.5OSSi (488.29):[9] calcd.
C 68.89, H 5.47, N 10.04, S 6.57; found C 69.1, H 5.5, N 9.4, S
7.1.
Synthesis of 4b·0.5CH3CN: Compound 8 (810 mg, 3.47 mmol) was
added in a single portion at 20 °C to a stirred solution of 1 (1.14 g,
3.46 mmol) in acetonitrile (70 mL), and the reaction mixture was
then stirred at this temperature for 1 min. The resulting clear solu-
tion was kept undisturbed at 20 °C for 16 h. The resulting solid was
isolated by filtration, washed with n-pentane (20 mL), and dried in
vacuo (20 °C, 1 h, 0.01 mbar) to give 4b·0.5CH3CN in 79% yield
(1.30 g, 2.74 mmol) as a yellow crystalline solid. 1H NMR (CD2Cl2,
500.1 MHz): δ = 1.94 (s, 3 H, CCH3), 1.97 (s, 1.5 H, NϵCCH3),
2.38 (s, 3 H, CCH3), 5.25 (s, 1 H, CCHC), 6.40–6.44, 6.67–6.72,
6.86–6.91, 7.16–7.20, 7.23–7.30, 7.43–7.51, 7.52–7.56, 7.75–7.79,
8.23–8.26, 8.51–8.55 (m, 15 H, C6H4, C6H5, C9H6NS) ppm. 13C
NMR (CD2Cl2, 125.8 MHz): δ = 2.0 (NϵCCH3), 24.1 (CCH3),
25.1 (CCH3), 103.7 (CCHC), 116.9 (NϵCCH3), 115.6, 117.9,
120.5, 120.6, 120.7, 126.9 (2 C), 127.0, 128.1, 128.5, 128.7, 129.8,
132.8, 133.2 (2 C), 139.0, 141.1, 142.6, 146.1, 151.9, 155.0 (C6H4,
C6H5, C9H6NS), 171.1 [C(N)CH3], 180.2 [C(O)CH3] ppm. 29Si
NMR (CD2Cl2, 99.4 MHz): δ = –138.8 ppm. 15N VACP/MAS
Synthesis of 6a·0.5CH3CN: Compound 7 (870 mg, 4.00 mmol) was
added in a single portion at 20 °C to a stirred solution of 3 (1.26 g,
3.64 mmol) in acetonitrile (60 mL), and the reaction mixture was
then stirred at this temperature for 1 min. The resulting clear solu-
tion was kept undisturbed at 20 °C for 16 h. The resulting solid was
isolated by filtration, washed with n-pentane (40 mL), and dried in
vacuo (20 °C, 1 h, 0.01 mbar) to give 6a·0.5CH3CN in 74% yield
(1.28 g, 2.69 mmol) as an orange crystalline solid. 1H NMR
(CD2Cl2, 500.1 MHz): δ = 1.75 (s, 3 H, CCH3), 1.97 (s, 1.5 H,
NϵCCH3), 2.40 (s, 3 H, CCH3), 5.33 (s, 1 H, CCHC), 6.91–7.03,
7.12–7.20, 7.21–7.24, 7.27–7.31, 7.57–7.62, 7.77–7.81, 8.12–8.15,
8.25–8.28 (m, 15 H, C6H4, C6H5, C9H6NO) ppm. 13C NMR
(CD2Cl2, 125.8 MHz): δ = 2.0 (NϵCCH3), 24.63 (CCH3), 24.64
(CCH3), 105.2 (CCHC), 116.9 (NϵCCH3), 112.0, 114.7, 121.2,
122.4, 123.1, 126.1 (2 C), 126.4, 126.9, 129.5, 130.2, 130.7, 134.7,
135.4 (2 C), 139.1, 139.9, 140.5, 141.4, 152.6, 153.7 (C6H4, C6H5,
C9H6NO), 173.6 [C(N)CH3], 181.2 [C(O)CH3] ppm. 29Si NMR
(CD2Cl2, 99.4 MHz): δ = –141.7 ppm. 15N VACP/MAS NMR: δ =
–173.6 [C(N)CH3], –127.8 (NϵCCH3), –122.5 (C9H6NO) ppm. 29Si
VACP/MAS NMR: δ = –146.4 ppm. C27H23.5N2.5O2SSi (475.15):
calcd. C 68.25, H 4.99, N 7.37, S 6.75; found C 68.4, H 5.0, N 7.3,
S 6.7.
NMR:
δ
=
–176.0 [C(N)CH3], –127.3 (NϵCCH3), –120.8
–140.0 ppm.
(C9H6NS) ppm. 29Si VACP/MAS NMR:
δ
=
C27H23.5N2.5O2SSi (475.15): calcd. C 68.25, H 4.99, N 7.37, S 6.75;
found C 68.5, H 5.1, N 7.5, S 6.7.
Synthesis of 5a: Compound 7 (1.05 g, 4.83 mmol) was added in a
single portion at 20 °C to a stirred solution of 2 (1.37 g, 4.00 mmol)
in acetonitrile (70 mL), and the reaction mixture was then stirred
at this temperature for 1 min. The resulting clear solution was kept
undisturbed at 20 °C for 16 h and then at –20 °C for a further 24 h.
The resulting solid was isolated by filtration, washed with n-pent-
ane (20 mL), and dried in vacuo (20 °C, 1 h, 0.01 mbar) to give 5a
in 99% yield (1.79 g, 3.96 mmol) as a red crystalline solid. 1H
Synthesis of 6b·0.5CH3CN: Compound 8 (830 mg, 3.56 mmol) was
added in a single portion at 20 °C to a stirred solution of 3 (1.23 g,
3.56 mmol) in acetonitrile (70 mL), and the reaction mixture was
then stirred at this temperature for 1 min. The resulting clear solu-
tion was kept undisturbed at 20 °C for 16 h. The resulting solid was
NMR (CD2Cl2, 500.1 MHz): δ = 1.76 (s, 3 H, CCH3), 2.26 (s, 3 H, isolated by filtration, washed with n-pentane (15 mL), and dried in
CCH3), 2.37 (s, 3 H, NCH3), 5.10 (s, 1 H, CCHC), 6.02–6.07, 6.40–
6.46, 6.84–6.90, 7.10–7.15, 7.16–7.26, 7.53–7.58, 7.60–7.65, 8.18–
8.22, 8.23–8.27 (m, 15 H, C6H4, C6H5, C9H6NO) ppm. 13C NMR
(CD2Cl2, 125.8 MHz): δ = 24.0 (CCH3), 24.8 (CCH3), 30.9
(NCH3), 103.4 (CCHC), 108.4, 111.4, 112.7, 114.3, 120.3, 121.5,
vacuo (20 °C, 1 h, 0.01 mbar) to give 6b·0.5CH3CN in 88% yield
(1.54 g, 3.14 mmol) as an orange crystalline solid. 1H NMR
(CD2Cl2, 500.1 MHz): δ = 1.91 (s, 3 H, CCH3), 1.97 (s, 1.5 H,
NϵCCH3), 2.33 (s, 3 H, CCH3), 5.36 (s, 1 H, CCHC), 6.84–6.96,
7.06–7.20, 7.40–7.50, 7.72–7.78, 8.20–8.24, 8.36–8.40 (m, 15 H,
126.4 (2 C), 126.5, 127.8, 129.3, 130.4, 130.5, 135.1 (2 C), 135.2, C6H4, C6H5, C9H6NS) ppm. 13C NMR (CD2Cl2, 125.8 MHz): δ =
138.0, 140.6, 148.8, 150.4, 154.5 (C6H4, C6H5, C9H6NO), 170.6 2.1 (NϵCCH3), 24.6 (CCH3), 24.9 (CCH3), 105.8 (CCHC), 119.7
[C(N)CH3], 180.7 [C(O)CH3] ppm. 29Si NMR (CD2Cl2, (NϵCCH3), 121.0, 122.4 (2 C), 123.0, 124.8, 126.3 (2 C), 126.6,
99.4 MHz): δ = –144.0 ppm. 15N VACP/MAS NMR: δ = –288.0
127.2, 128.6, 128.7, 129.4, 130.2, 134.2 (2 C), 137.1, 141.4, 141.8,
(NCH3), –185.3 [C(N)CH3], –118.7 (C9H6NO) ppm. 29Si VACP/ 146.2, 149.7, 155.0 (C6H4, C6H5, C9H6NS), 173.9 [C(N)CH3], 181.4
MAS NMR: δ = –146.9 ppm. C27H25N3O2Si (451.60): calcd. C
71.81, H 5.58, N 9.30; found C 71.8, H 5.6, N 9.4.
[C(O)CH3] ppm. 29Si NMR (CD2Cl2, 99.4 MHz): δ = –141.6 ppm.
15N VACP/MAS NMR: δ = –176.0 [C(N)CH3], –124.2 (NϵCCH3),
Eur. J. Inorg. Chem. 0000, 0–0
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FULL PAPER
–119.8 (C9H6NS) ppm. 29Si VACP/MAS NMR: δ = –145.4 ppm.
C27H23.5N2.5OS2Si (491.22): calcd. C 66.02, H 4.82, N 7.13, S 13.06;
found C 66.1, H 4.8, N 7.0, S 13.0.
Wiley, New York, 2000, p. 97–114; f) R. Tacke, O. Seiler, in:
Silicon Chemistry: From the Atom to Extended Systems (Eds.:
P. Jutzi, U. Schubert), Wiley-VCH, Weinheim, Germany, 2003,
p. 324–337; g) D. Kost, I. Kalikhman, Adv. Organomet. Chem.
2004, 5, 1–106; h) D. Kost, I. Kalikhman, Acc. Chem. Res.
2009, 42, 303–314; i) E. P. A. Couzijn, J. C. Slootweg, A. W.
Ehlers, K. Lammertsma, Z. Anorg. Allg. Chem. 2009, 635,
1273–1278; j) W. Levason, G. Reid, W. Zhang, Coord. Chem.
Rev. 2011, 255, 1319–1341.
a) S. Metz, C. Burschka, D. Platte, R. Tacke, Angew. Chem.
Int. Ed. 2007, 46, 7006–7009; Angew. Chem. 2007, 119, 7136–
7139; b) S. Metz, C. Burschka, R. Tacke, Organometallics 2008,
27, 6032–6034; c) B. Theis, S. Metz, C. Burschka, R. Berter-
mann, S. Maisch, R. Tacke, Chem. Eur. J. 2009, 15, 7329–7338;
d) B. Theis, S. Metz, F. Back, C. Burschka, R. Tacke, Z. Anorg.
Allg. Chem. 2009, 635, 1306–1312; e) S. Metz, C. Burschka, R.
Tacke, Organometallics 2009, 28, 2311–2317; f) S. Metz, B.
Theis, C. Burschka, R. Tacke, Chem. Eur. J. 2010, 16, 6844–
6856; g) J. Weiß, B. Theis, S. Metz, C. Burschka, C. Fon-
seca Guerra, F. M. Bickelhaupt, R. Tacke, Eur. J. Inorg. Chem.
2012, 3216–3228; h) J. Weiß, B. Theis, J. A. Baus, C. Burschka,
R. Bertermann, R. Tacke, Z. Anorg. Allg. Chem. 2014, 640,
300–309; i) J. Weiß, K. Sinner, J. A. Baus, C. Burschka, R.
Tacke, Eur. J. Inorg. Chem. 2014, 475–483.
Synthesis of 7:
A mixture of 8-hydroxyquinoline (9.29 g,
64.0 mmol) and bis(trimethylsilyl)amine (130 mL) was heated un-
der reflux for 2 h. The mixture was then cooled to 20 °C, the sol-
vent was removed in vacuo, and the residue was purified by distil-
lation in vacuo (102–104 °C/0.04 mbar) to give 7 in 91% yield
(12.7 g, 58.4 mmol) as a colorless liquid. 1H NMR (CD2Cl2,
500.1 MHz): δ = 0.36 (s, 9 H, SiCH3), 7.15–7.20, 7.36–7.41, 7.42–
7.45, 8.11–8.15, 8.84–8.88 (m, 6 H, C9H6NO) ppm. 13C NMR
(CD2Cl2, 125.8 MHz): δ = 1.18 (SiCH3), 118.0, 120.8, 121.7, 127.3,
130.2, 136.0, 142.3, 148.9, 152.8 (C9H6NO) ppm. 29Si NMR
(CD2Cl2, 99.4 MHz): δ = 20.0 ppm. C12H15NOSi (217.34): calcd.
C 66.32, H 6.96, N 6.44; found C 66.0, H 7.0, N 6.9.
[2]
Synthesis of 8: A mixture of 8-mercaptoquinoline hydrochloride
(4.83 g, 24.4 mmol) and bis(trimethylsilyl)amine (50 mL) was
heated under reflux for 3 h. The mixture was then cooled to 20 °C,
the solvent was removed in vacuo, and the residue was purified by
distillation in vacuo (106 °C/0.08 mbar) to give 8 in 74% yield
(4.21 g, 18.0 mmol) as a colorless liquid. 1H NMR (CD2Cl2,
500.1 MHz): δ = 0.33 (s, 9 H, SiCH3), 7.39–7.45, 7.68–7.72, 7.89–
7.92, 8.13–8.17, 8.94–8.97 (m, 6 H, C9H6NS) ppm. 13C NMR
(CD2Cl2, 125.8 MHz): δ = 2.0 (SiCH3), 121.7, 126.5, 127.0, 129.4,
134.6, 135.0, 136.8, 148.5, 149.9 (C9H6NS) ppm. 29Si NMR
(CD2Cl2, 99.4 MHz): δ = 16.8 ppm. C12H15NSSi (233.41): calcd. C
61.75, H 6.48, N 6.00, S 13.74; found C 61.5, H 6.5, N 6.1, S 13.8.
[3]
[4]
[5]
S. Metz, C. Burschka, R. Tacke, Eur. J. Inorg. Chem. 2008,
4433–4439.
J. Wagler, E. Brendler, T. Heine, L. Zhechkov, Chem. Eur. J.
2013, 19, 14296–14303.
J. A. Baus, C. Burschka, R. Bertermann, C. Fonseca Guerra,
F. M. Bickelhaupt, R. Tacke, Inorg. Chem. 2013, 52, 10664–
10676.
Crystal Structure Analyses: Suitable single crystals of 4a,
4b·0.5CH3CN, 5a, 5b·CH3CN, and 6b·0.5CH3CN were obtained as
described in the synthesis protocols. Suitable single crystals of 6a
were obtained by slow cooling of a saturated solution in tetra-
hydrofuran from 65 to 20 °C. The 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
[Stoe IPDS (4a, 4b·0.5CH3CN, and 6a; graphite-monochromated
Mo-Kα radiation, λ = 0.71073 Å) or Bruker Nonius KAPPA APEX
II (5a, 5b·CH3CN, and 6b·0.5CH3CN; graphite-monochromated
Mo-Kα radiation, λ = 0.71073 Å)]. All structures were solved by
direct methods (SHELXS-97)[10] and refined by full-matrix least-
squares methods on F2 for all unique reflections (SHELXL-97).[10]
SHELXLE was used as refinement GUI.[11] For the CH hydrogen
atoms, a riding model was employed.
[6]
For selected recent publications of our group dealing with
higher-coordinate silicon(IV) complexes, see: a) K. Junold, C.
Burschka, R. Bertermann, R. Tacke, Dalton Trans. 2011, 40,
9844–9857; b) K. Junold, C. Burschka, R. Tacke, Eur. J. Inorg.
Chem. 2012, 189–193; c) C. Kobelt, C. Burschka, R. Berter-
mann, C. Fonseca Guerra, F. M. Bickelhaupt, R. Tacke, Dalton
Trans. 2012, 41, 2148–2162; d) B. Theis, J. Weiß, W. P. Lippert,
R. Bertermann, C. Burschka, R. Tacke, Chem. Eur. J. 2012, 18,
2202–2206; e) K. Junold, J. A. Baus, C. Burschka, R. Tacke,
Angew. Chem. Int. Ed. 2012, 51, 7020–7023; Angew. Chem.
2012, 124, 7126–7129; f) K. Junold, J. A. Baus, C. Burschka, D.
Auerhammer, R. Tacke, Chem. Eur. J. 2012, 18, 16288–16291.
For selected recent publications of other groups dealing with
higher-coordinate silicon(IV) complexes, see: a) S. Yakubovich,
I. Kalikhman, D. Kost, Dalton Trans. 2010, 39, 9241–9244; b)
P. Bombicz, I. Kovács, L. Nyulászi, D. Szieberth, P. Terleczky,
Organometallics 2010, 29, 1100–1106; c) E. Kertsnus-Banchik,
B. Gostevskii, M. Botoshansky, I. Kalikhman, D. Kost, Orga-
nometallics 2010, 29, 5435–5445; d) R. S. Ghadwal, S. S. Sen,
H. W. Roesky, M. Granitzka, D. Kratzert, S. Merkel, D. Stalke,
Angew. Chem. Int. Ed. 2010, 49, 3952–3955; Angew. Chem.
2010, 122, 4044–4047; e) D. Schöne, D. Gerlach, C. Wiltzsch,
E. Brendler, T. Heine, E. Kroke, J. Wagler, Eur. J. Inorg. Chem.
2010, 461–467; f) A. R. Bassindale, M. Sohail, P. G. Taylor,
A. A. Korlyukov, D. E. Arkhipov, Chem. Commun. 2010, 46,
3274–3276; g) R. S. Ghadwal, K. Pröpper, B. Dittrich, P. G.
Jones, H. W. Roesky, Inorg. Chem. 2011, 50, 358–364; h) S.
Yakubovich, B. Gostevskii, I. Kalikhman, M. Botoshansky,
L. E. Gusel’nikov, V. A. Pestunovich, D. Kost, Organometallics
2011, 30, 405–413; i) S. Muhammad, A. R. Bassindale, P. G.
Taylor, L. Male, S. J. Coles, M. B. Hursthouse, Organometallics
2011, 30, 564–571; j) D. Schwarz, E. Brendler, E. Kroke, J.
Wagler, Z. Anorg. Allg. Chem. 2012, 638, 1768–1775; k) N. A.
Kalashnikova, S. Y. Bylikin, A. A. Korlyukov, A. G. Shipov,
Y. I. Baukov, P. G. Taylor, A. R. Bassindale, Dalton Trans.
2012, 41, 12681–12682; l) M. Sohail, A. R. Bassindale, P. G.
Taylor, A. A. Korlyukov, D. E. Arkhipov, L. Male, S. J. Coles,
M. B. Hursthouse, Organometallics 2013, 32, 1721–1731; er-
ratum: M. Sohail, A. R. Bassindale, P. G. Taylor, A. A. Korlyu-
[7]
CCDC-976253 (for 4a), -976254 (for 4b·0.5CH3CN), -976255 (for
5a), -976256 (for 5b·CH3CN), -976257 (for 6a), and -976258 (for
6b·0.5CH3CN) 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.
Supporting Information (see footnote on the first page of this arti-
cle): Crystallographic data for compounds 4a, 4b·0.5CH3CN, 5a,
5b·CH3CN, 6a, and 6b·0.5CH3CN.
[1] For reviews dealing with higher-coordinate silicon(IV) com-
plexes, see: a) R. R. Holmes, Chem. Rev. 1996, 96, 927–950; b)
V. Pestunovich, S. Kirpichenko, M. Voronkov, in: The Chemis-
try of Organic Silicon Compounds, vol. 2, part 2 (Eds.: Z. Rap-
poport, Y. Apeloig), Wiley, Chichester, UK, 1998, p. 1447–
1537; c) C. Chuit, R. J. P. Corriu, C. Reye, in: Chemistry of
Hypervalent Compounds (Ed.: K.-y. Akiba), Wiley-VCH,
Weinheim, 1999, p. 81–146; d) R. Tacke, M. Pülm, B. Wagner,
Adv. Organomet. Chem. 1999, 44, 221–273; e) M. A. Brook,
Silicon in Organic, Organometallic, and Polymer Chemistry,
Eur. J. Inorg. Chem. 0000, 0–0
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FULL PAPER
kov, D. E. Arkhipov, L. Male, S. J. Coles, M. B. Hursthouse,
Organometallics 2013, 32, 2874; m) M. Sohail, R. Panisch, A.
Bowden, A. R. Bassindale, P. G. Taylor, A. A. Korlyukov, D. E.
Arkhipov, L. Male, S. Cellear, S. J. Coles, M. B. Hursthouse,
R. W. Harrington, W. Clegg, Dalton Trans. 2013, 42, 10971–
10981.
[9] The accuracy of the elemental analysis is affected by partial
loss of acetonitrile (even at storage under standard conditions
of temperature and pressure).
[10] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112–122.
[11] C. B. Hübschle, G. M. Sheldrick, B. Dittrich, J. Appl. Crys-
tallogr. 2011, 44, 1281–1284.
[8] Compound 5b·CH3CN completely loses acetonitrile under
Received: January 23, 2014
MAS conditions.
Published Online: ᭿
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FULL PAPER
Hexacoordinate Silicon
J. Weiß, J. A. Baus, C. Burschka,
R. Tacke* ......................................... 1–8
A series of neutral hexacoordinate sili-
con(IV) complexes have been synthesized
and structurally characterized by NMR
spectroscopy and single-crystal X-ray dif-
fraction. These studies were performed
with a special emphasis on comparing the
respective O/NMe/S analogues 4a/5a/6a
and 4b/5b/6b and the O/S pairs 4a/4b, 5a/
5b, and 6a/6b with respect to their struc-
tures and NMR spectroscopic parameters.
Neutral Hexacoordinate Silicon(IV) Com-
plexes with a Tridentate Dianionic O,N,X
Ligand (X
Monoanionic X,N Ligand (X = O, S), and
Phenyl Ligand: Compounds with
=
O, N, S), Bidentate
a
SiO3N2C, SiSO2N2C, SiO2N3C, SiSON3C,
or SiS2ON2C Skeleton
Keywords: Chalcogens
/
Coordination
modes / Main group elements / Silicon /
Tridentate ligands
Eur. J. Inorg. Chem. 0000, 0–0
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim