Bulky Phenyl Modifications of the Silanide Ligand Si(SiMe3)3 – Synthesis and Reactivity

Article abstract of DOI:10.1002/zaac.201700253

The synthesis and structural characterization of bulkier variations of the very common organometallic compound MSi(SiMe₃)₃, namely MSi(SiMe₃)(SiPh₃)₂ 3 and MSi(SiPh₃)₃ [M = Li (1), K (5)] are presented, which can be synthesized via a step by step exchange of SiMe₃ groups by bulkier SiPh₃ groups. This synthetic route is high selective and is performed in good yields via the silanes Si(SiMe₃)₂(SiPh₃)₂ (2) and Si(SiMe₃)(SiPh₃)₃ (4). Additionally, the corresponding silanes HSi(SiMe₃)(SiPh₃)₂ (6_H) and HSi(SiPh₃)₃ (7_H) are obtained via the reaction of 3 and 5 with aqueous HCl, respectively. Oxidation of 6_H with CCl₄ gives the chlorsilane Cl-Si(SiMe₃)(SiPh₃)₂ (6_Cl). The bulkiest chlorsilane Cl–Si(SiPh₃)₃ (7) is obtained by the reaction of 5 with ECl₂ (E = Sn, Pb).

Full text of DOI:10.1002/zaac.201700253

Journal of Inorganic and General Chemistry
DOI: 10.1002/zaac.201700253
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Bulky Phenyl Modifications of the Silanide Ligand Si(SiMe3)3 –
Synthesis and Reactivity
Patrick Schmidt,[a] Sascha Fietze,[a] Claudio Schrenk,[a] and Andreas Schnepf*[a]
Dedicated to Professor Dieter Fenske on the Occasion of his 75th Birthday
Abstract. The synthesis and structural characterization of bulkier vari-
ations of the very common organometallic compound MSi(SiMe3)3, corresponding silanes HSi(SiMe3)(SiPh3)2 (6H) and HSi(SiPh3)3 (7H)
namely MSi(SiMe3)(SiPh3)2 3 and MSi(SiPh3)3 [M = Li (1), K (5)] are are obtained via the reaction of 3 and 5 with aqueous HCl, respectively.
presented, which can be synthesized via a step by step exchange of Oxidation of 6H with CCl4 gives the chlorsilane Cl-Si(SiMe3)(SiPh3)2
Si(SiMe3)2(SiPh3)2 (2) and Si(SiMe3)(SiPh3)3 (4). Additionally, the
SiMe3 groups by bulkier SiPh3 groups. This synthetic route is
high selective and is performed in good yields via the silanes
(6Cl). The bulkiest chlorsilane Cl–Si(SiPh3)3 (7) is obtained by the
reaction of 5 with ECl2 (E = Sn, Pb).
Introduction
MeLi or Marschner’s route can lead to novel modified silanide
compounds MSi(SiMe3)2SiPh3 (M = Li, K), which were al-
ready used in our group as protecting ligands in group 14
chemistry.[11] Herein we report on further substitution of the
SiMe3 groups in Si(SiMe3)3 by SiPh3 groups, leading thus to
bigger, sterically more demanding silanides.
Protecting ligands and protecting groups are of fundamental
interest in almost all parts of organic and inorganic chemistry,
e.g. giving access to compounds that are not stable without a
protecting ligand.[1] Due to their high reactivity and availabil-
ity of the precursors, anionic silanide ligands used to be ideal
protecting compounds. For example the TMS group (TMS =
SiMe3) is a common protecting group for alcohols and hy-
droxyl groups in organic synthesis.[2] Starting from TMS,
which is sterically less demanding, a huge variety of second
sphere silylated compounds could be invented, e.g. the amide
Results and Discussion
Silanide Modification
The first higher modified silanide compound was formed by
accident as a side product of approx. 20 small red crystals
during the recrystallization process of freshly prepared
LiSi(SiMe3)2(SiPh3) (LiHypPh3). From time to time, these red
crystals could be observed and X-ray crystallography showed,
N(SiMe3)2,[3] the methanides CHn(SiMe3)3–n [4] or the silylated
,
silanide Si(SiMe3)3 (Hypersilyl, Hyp) exhibiting a triply sil-
ylated central silicon atom.[5] Even ligands with modifications
in the outer sphere were synthesized, e.g. the mixed amide
N(SiMe3)Dipp (Dipp = 2,6-diisopropylphenyl).[6] In the 1980s,
a quite simple synthetic procedure of the lithium compound
LiHyp was developed by Gutekunst and Brook by the reaction
of MeLi with the fully substituted silane Si(SiMe3)4.[7] How-
ever, Marschner et al. found a simpler way to synthesize a
potassium silanide in very high yield above 90% by mixing
the silane Si(SiMe3)4 with KOtBu in THF or DME (DME =
1,2-Dimethoxy-ethane).[8] The big advantage of this route is,
that all precursors are air stable compounds. As the potassium
silanide can easily react with R3SiCl (R = Ph, iPr, etc.),[9] it is
possible to introduce different silyl groups, like SiPh3, SiiPr3,
etc. As the cleavage of the Si–Si bond to the TMS group is
strongly favored in Si(SiMe3)3(SiPh3)[10] either the classical
* Prof. Dr. A. Schnepf
Fax: +49-7071-28-2436
E-Mail: andreas.schnepf@uni-tuebingen.de
[a] Chemistry Department
Figure 1. Molecular structure of 1Li in the solid state. The atoms are
presented as thermal ellipsoids with 50% probability (Li, Si) or as
wire model (C, O). Hydrogen atoms are omitted for clarity. Selected
bond lengths /pm and angles /°: Si12-Si1 235.71(7), Si13-Si1
235.56(7), Si1–Si11 235.77(7); Si12–Si1–Si11 103.18(3), Si13–Si1–
Si12 104.01(3), Si13–Si1–Si11 104.38(3).
University Tübingen
Auf der Morgenstelle 18
72076 Tübingen, Germany
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201700253 or from the au-
thor.
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that it is the fully modified silanide Li(THF)3(Et2O)Si(SiPh3)3
Starting from 2 we tried a further modification by changing
(LiHypPh9) (1Li) (Figure 1).
one of the remaining SiMe3 groups by a SiPh3 group. There-
fore we started working on Marschner’s route of preparing a
potassium silanide by reaction with KOtBu, which shows an
ongoing reaction in monitoring NMR experiments. From the
crude reaction solution, single crystals of the expected
KSi(SiMe3)(SiPh3)2 (3) (KHypPh6) are obtained after adding
the complexing reagent 18-crown-6 and layering the solution
with pentane.
The compound crystallizes in the monoclinic space group
P21/c with four molecules per unit cell. In 1Li an ion separation
is present, where the Li cation is fully coordinated by four
solvent molecules. This is in contrast to the previously reported
LiHypPh3, where the lithium cation is coordinated by the silan-
ide and three solvent molecules, leading to an overall non-
charged molecule. This difference might be a consequence of
the higher steric influence of the phenyl rings. Even if these
crystals are formed by accident, a rational synthesis via a step
by step modification of Si(SiMe3)4 should be possible, as out-
lined in Scheme 1 and discussed in the following.
¯
3crown crystallizes in the triclinic space group P1 with one
ion pair in the unit cell. Therefore, all K atoms are located on
crystallographic inversion centers leading to half a K(18-
crown-6)+ cation and half a [HypPh6–K(18-crown-6)–HypPh6 –
]
anion in the asymmetric unit. Interestingly, 3 crystallizes as an
ion separated dimer [K(18-crown-6)]+ [HypPh6–K(18-crown-
6)–HypPh6]– (3crown) (Figure 3). This is in contrast to the less
bulky derivative K(18-crown-6)HypPh3, which crystallizes as a
monomeric compound, where the potassium cation is coordi-
nated to the silanide and to a crown ether molecule.[11] The
K–Si distances of the potassium cation K1 in 3crown is with
356.4 pm similar to the Si–K distance found in K(18-crown-
6)HypPh3 (356.3 pm), indicating that a similar interaction is
Scheme 1. General concept of the step by step modification of the Hyp
ligand (n = 2, 3, 4; m = 4 – n).
Rational Synthesis of Silanides
Starting from KHypPh3, which is available in good yield, the present being mostly electrostatic in nature. Consequently, the
second modification could be achieved by the reaction with most probable explanation of the structural differences be-
Ph3SiCl, to give after work-up procedures small colorless
tween 3crown and K(18-crown-6)HypPh3 are packing effects in
the solid state.[12]
plate-like single crystals of Si(SiMe3)2(SiPh3)2 (2), suitable for
X-ray crystallography (Figure 2). 2 crystallizes in a monoclinic
unit cell in space group P21/n and is stable against air and
moisture and is available in good yield of 75%. The sterically
more demanding SiPh3 groups with respect to the SiMe3
groups lead to a distortion of the tetrahedral arrangement of
the central silicon atom Si1. Thereby the Si–Si–Si angles in-
cluding both silicon atoms from the SiPh3 groups are 113.8°.
Beside this, the angle including the Si atoms from the SiMe3
groups amounts to 103.0°.
Figure 3.: Molecular structure of 3crown in the solid state. The atoms
are presented as thermal ellipsoids with 50% probability (K, Si, O) or
as wire model (C). Hydrogen atoms are omitted for clarity. Selected
bond lengths /pm and angles /°: K1–Si1 356.43(6), K2–O101
276.90(14), K2–O104 282.49(14), K2–O1072 280.31(15), Si1–Si2
234.38(8), Si1–Si3 235.47(8), Si1–Si4 233.51(8); Si4–Si1–Si3
106.82(3), O101–K2–O107 118.51(4), Si4–Si1–Si2 107.82(3).
Having the potassium salt 3 in hand, a further salt metathesis
reaction to introduce a third SiPh3 group is possible to get
the highly phenylated silane Si(SiMe3)(SiPh3)3 (4). Thereby
compound 4 has a decreased solubility in aliphatic or aromatic
solvents with respect to the lower modified derivative 2. Single
crystals suitable for X-ray measurements could only be ob-
tained from ether, THF, or hot ethanol (Figure 4).
Figure 2. Molecular structure of 2 in the solid state. The atoms are
presented as thermal ellipsoids with 50% probability (K, Si) or as wire
model (C, O). Hydrogen atoms are omitted for clarity. Selected bond
lengths /pm and angles /°: Si4–Si1 238.76(5), Si2–Si1 238.55(5), Si1–
Si5 239.39(5), Si1–Si3 237.54(5); Si4–Si1–Si5 112.657(19), Si2–Si1–
Si4 113.850(18), Si2–Si1–Si5 110.322(19), Si3–Si1–Si4 107.024(19),
Si3–Si1–Si2 109.305(19), Si3–Si1–Si5 103.018(18).
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In the silanide 5, the maximum steric overload in the HypPhx
system (x = 3, 6, 9) is reached. The molecule crystallizes in a
monoclinic lattice in space group P21/c. Interestingly we found
a new structural motif for the cation coordination in the HypPhx
system. In all previously presented examples, the potassium
cation is either attached to the central Si atom of the silanide
or completely surrounded by chelating agents or solvent mol-
ecules. Within 5, the potassium cation is now attached to the
silanide at the phenyl rings and not to the central Si atom. This
circumstance might be caused by the steric demand of HypPh9
and by the better interaction of the phenyl π-system with the
soft Lewis acid K+.
Silanide Halogenation
Figure 4. Molecular structure of 4 in the solid state. The atoms are
presented as thermal ellipsoids with 50% probability (K, Si) or as
wire model (C). Hydrogen atoms are omitted for clarity. Selected bond
lengths [pm] and angles (°): Si1–Si2 240.14(11), Si1–Si3 240.68(11),
Si1–Si4 241.80(11), Si1–Si5 242.39(10); Si2–Si1–Si3 106.34(4), Si2–
Si1–Si4 104.19(4), Si2–Si1–Si5 110.18(4), Si3–Si1–Si4 115.18(4),
Si3–Si1–Si5 106.11(4), Si4–Si1–Si5 114.55(4).
During the modification procedure, we were able to isolate
the negatively charged silyl compounds 3 and 5 in good yield.
These silanides can be easily introduced in organometallic
chemistry and even in cluster chemistry applying salt metathe-
sis reactions, what is part of ongoing research in our lab. How-
ever, in some cases the introduction via a halogenated com-
pound is also useful, as, for example, shown by Sevov and Li
with the rational synthesis of the metalloid cluster
[Ge9(Hyp3)]– by the reaction of the Zintl phase K4Ge9 with
Hyp-Cl.[13] Before this approach, the metalloid cluster
[Ge9(Hyp3)]– was only available by a reaction of LiHyp with
a metastable emulsion of oily donor stabilized GeBr[14] in
The sterically highly demanding silane 4 crystallizes in a
monoclinic crystal system in space group P21/c. Due to the
steric overload at the central silicon atom, the Si–Si bond
lengths in 4 are increased to an average value of 241 pm with
respect to the less crowded compound 2, where average Si–Si
distances of 238 pm are found. By obtaining 4 via this rational
synthesis there should be only one more step to obtain the
previously accidentally formed silanide [Si(SiPh3)3]– (HypPh9).
However, we were not able to get a crystalline product of
LiHypPh9 from a reaction of 4 with MeLi because of the very
low reaction speed, i.e. after two weeks, only 5% conversion
could be observed in monitoring NMR experiments. However,
reaction of 4 with KOtBu is possible by increasing the reaction
time from a few hours up to three days. Single crystalline
KHypPh9 (5) (Figure 5) could be achieved by layering the THF
mother liquor with pentane.
moderate yields.[15] Sevov’s synthetic concept could be also
[16]
applied to other halides, like ClSniPr3
and smaller ClSiR3
groups (R = Et, iPr, iBu), as used by Fässler et al.[17] and even
larger groups like ClHypPh3, as introduced by our group[18]
could be used to obtain metalloid [Ge9R3]– clusters.
To get a full library of precursors for the HypPhx chemistry,
we tried to synthesize and characterize the HypPhx halides.
Thereby, we used the same reaction pathway previously de-
scribed for the synthesis of Hyp-Cl[19] starting from hydrolysis
of the lithium or potassium salt of the silanide to give the
silane HHypPhx (Scheme 2).
Scheme 2. General reaction pathway of the chlorination of silanides
(R = SiMe3, SiPh3).
The so obtained silane should be chlorinated by stirring in
CCl4 to give Cl-HypPhx and HCCl3, which works in the case
of the non-modified Hyp-H in almost quantitative yield. Ad-
ditionally, increasing the number of SiPh3 groups in the silane
leads to an increase of the melting point,[18] i.e. crystallization
of the crude silane should be possible, as well.
In case of HypPh6, hydrolysis and chlorination works as pre-
dicted, but an extension of the reaction time for the chlorina-
tion from one day to at least one week is necessary as indicated
by daily monitoring NMR experiments. The silane HHypPh6
(6H) (see Supporting Information) and the chlorosilane
ClHypPh6 (6Cl) (Figure 6) could be crystallized and structurally
characterized.
Figure 5. Molecular structure of 5 in the solid state. The atoms are
presented as thermal ellipsoids with 50% probability (K, Si) or as wire
model (C, O). Hydrogens are omitted for clarity. Selected bond
lengths /pm and angles /°: Si1–Si2 235.53(4), Si1–Si4 235.02(4), Si1–
Si3 236.28(4); Si2–Si1–Si3 103.544(16), Si4–Si1–Si2 102.419(16),
Si4–Si1–Si3 101.998(16).
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Figure 6. Molecular structure of 6Cl in the solid state. The atoms are
presented as thermal ellipsoids with 50% probability (Cl, Si) or as
wire model (C). Hydrogen atoms are omitted for clarity. Selected bond
lengths /pm and angles /°: Cl1–Si1 211.94(5), Si1–Si2 237.37(5), Si1–
Si3 237.74(5), Si1–Si4 237.89(5); Cl1–Si1–Si2 103.41(2), Cl1–Si1–
Si3 102.57(2), Cl1–Si1–Si4 102.99(2), Si2–Si1–Si3 110.86(2), Si2–
Si1–Si4 113.34(2), Si3–Si1–Si4 121.04(2).
Figure 7. Molecular structure of 7Cl in the solid state. The atoms are
presented as thermal ellipsoids with 50% probability (Cl, Si) or as
wire model (C). Hydrogen atoms are omitted for clarity. Selected bond
lengths /pm and angles /°: Cl1–Si1 213.24(8), Si1–Si2’ 239.11(4);
Cl1–Si1–Si2 102.118(17); Si2–Si1–Si2’ 115.714(12).
further experiments, if this reaction can be used for the synthe-
sis of clusters that are formed on the way to the element. Ad-
ditionally, a different reaction pathway or different reaction
conditions have to be found to introduce the bulkiest ligand of
the presented series in group 14 chemistry.
The chlorosilane 6Cl crystallizes in the monoclinic space
group P21/c with four molecules in the unit cell. The Si–Si
bond lengths of 237 pm are in line with previously
presented Si–Si bonds in tetrasubstituted silanes, like
Si(SiMe3)2(SiPh3)2 (2). The steric influence of the bulky
phenyl rings results in a shrinking of all Si–Si–Cl angles from
the ideal tetrahedral angle of 109° to 102–103°, whereas all
Si–Si–Si angles are widened up to 110–120°.
Conclusions
An equivalent reaction starting from the hydrolysis of
KHypPh9 (5) was promising at first, as the silane HHypPh9 (7H)
could be isolated and characterized via NMR spectroscopy (see
Supporting Information) but the subsequent chlorination reac-
tion with CCl4 failed. Monitoring NMR experiments showed
that no reaction takes place over three weeks, as only 7H could
be detected, showing a massively different reactivity with re-
spect to the other silanes. Nevertheless, we were able to syn-
thesize ClHypPh9 (7Cl), but not via the common way: During
the attempt to introduce HypPh9 in group 14 chemistry we re-
acted MCl2 (M = Sn, Pb) with KHypPh9 (5) to obtain a com-
We showed that further modification of the hypersilyl ligand
Si(SiMe3)3 by bulkier phenyl groups is possible leading at the
end to the superbulky compound Si(SiPh3)3(HypPh9), which
can be now used in organometallic chemistry as silanide sub-
stituents, e.g. via the potassium compound KHypPh6 (3) or via
the chlorosilane Cl-HypPh6 (6Cl). Furthermore, we found a
change in reactivity with increasing number of SiPh3 groups
in a way that the silane HHypPh9 (7H) could not be chlorinated
by the reaction with CCl4 in contrast to the lower modified
ClHypPh6 (6Cl) or ClHypPh3. However, ClHypPh9 (7Cl) is ob-
tained via a salt metathesis reaction of KHypPh9 (5) with the
group 14 halides SnCl2 and PbCl2 implying the preference of
redox chemistry with increasing number of SiPh3 groups com-
pared to classical salt metathesis reactions.
[20]
pound like M(HypPh9)2, the modified analogue of MHyp2
or at least a KCl adduct of it, like KM(HypPh9)2Cl, as found
in similar reactions with KHypPh3 [11]
However, what we ob-
.
served in both cases is the precipitation of a gray solid to give
a colorless solution. From both solutions, we could isolate col-
orless crystals of the chlorosilane 7Cl (Figure 7), which crys-
tallizes in contrast to all other presented compounds in a highly
symmetric hexagonal crystal lattice in space group P63.
Experimental Section
General Considerations: All experiments were done in an inert gas
atmosphere by using standard Schlenk techniques. All organic solvents
This result directly shows that in case of 5 a different reac- were dried with sodium and purificated via distillation. All solids were
stored in a glovebox in an argon atmosphere. NMR measurements
were done with a Bruker DRX-250. The chemical shifts are given in
ppm against external standard SiMe4 (1H, 13C, 29Si). C6D6 and
[D8]THF were dried with 3 Å molecular sieves. Elemental analyses
were performed with a varioMICROcube in the CHNS mode.
tion pathway is opened, which might be due to the steric over-
load of this silanide ligand. Herein not only a simple metathe-
sis reaction takes place but a redox reaction to give 7Cl and a
gray solid, which is most probable elemental tin or lead.[21]
The reaction might proceed via two steps, where first a meta-
thesis reaction gives HypPh9MCl, which then reductively elim-
General Procedure for the Synthesis of KHypPhx: One equivalent
inates 7Cl to give the element Sn or Pb. It has to be proven by of Si(SiMe3)n(SiPh3)m (m = 1, 2, 3; n + m = 4) was mixed with 1.05
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equivalents of KOtBu. This mixture was dissolved in THF and stirred
tion by layering with pentane. 1H NMR (250 MHz, [D8]THF): δ =
at room temperature for at least 10 h. All volatile compounds were
evaporated and the yellow to orange residue was recrystallized from
Et2O, if necessary.
1.79 (m, 6 H, 3THF), 3.63 (m, 6 H, 3THF), 6.75 (m, 18 H, SiPh3),
6.92 (m, 9 H, SiPh3), 7.17 (m, 18 H, SiPh3); 13C{1H} NMR
(62.5 MHz, [D8]THF): δ = 26.2 (s, THF), 68.1 (s, THF), 126.2 (s),
126.5 (s), 137.5 (s), 140.0 (S, all SiPh3). 29Si{1H} NMR (50 MHz,
[D8]THF): δ = –0.5 (s, SiPh3). C73H77KO3Si4: found (calcd.): C 75.3
(75.9), H 6.26% (6.73)%.
General Procedure for the Synthesis of Si(SiMe3)n(SiPh3)m (m = 2,
3; n + m = 4): One equivalent of KHypPhx was dissolved in THF and
cooled to –78 °C. A solution of 1.05 equiv. of ClSiPh3, dissolved in
approx. 50 mL toluene was added. The mixture was allowed to warm
to room temperature within 10 h, whereby the former yellow color
disappeared. When the solution became completely colorless, the reac-
tion was finished. The mixture was quenched with 100 mL of diluted
aqueous HCl. The liquid phases were separated and the aqueous phase
was extracted three times with 100 mL Et2O. All organic phases were
combined, dried with Na2SO4, and all solvents were evaporated. The
remaining off-white waxy residue could be recrystallized from hot eth-
anol leading to single crystals of Si(SiMe3)n(SiPh3)m (m = 2, 3; n + m
= 4)
Synthesis of HSi(SiMe3)(SiPh3)2 [HHypPh6] (6H): KHypPh6 (3, 10 g,
15,1 mmol) was dissolved in THF. The orange mixture was quenched
with 100 mL of diluted aqueous HCl. The liquid phases were separated
and the aqueous phase was extracted three times with 100 mL Et2O.
All organic phases were combined and dried with Na2SO4. Afterwards,
all solvents were evaporated. The remaining residue was recrystallized
from hot ethanol leading to single crystalline HSi(SiMe3)(SiPh3)2 6H
in 77% yield (7.2 g, 11.6 mmol). 1H NMR (250 MHz, C6D6): δ = 0.00
(s, 9 H, SiMe3), 7.07 (m, 18 H, SiPh3), 7.54 (m, 12 H, SiPh3); 13C{1H}
NMR (62.5 MHz, C6D6): δ = 2.0 (s, SiMe3), 128.1 (s), 129.4 (s), 136.2
(s), 136.7 (s, all SiPh3); 29Si NMR (50 MHz, C6D6): δ = –10.3 (decet,
SiMe3), –12.4 (s, SiPh3), –116.1 (d, SiH). EA: found (calcd.): C 74.8
(75.4), H 6.49% (6.43%).
Synthesis of LiSi(SiPh3)3 [LiHypPh9] (1): Compound 1 was formed
accidentally during the synthesis of LiHypPh3, as described in the lit-
erature[11] in very small amounts of approx. 20 crystals per 100 mmol
LiHypPh3, i.e. further characterization was not possible.
Synthesis of ClSi(SiMe3)(SiPh3)2 [ClHypPh6
HHypPh6
H (7 g, 11.2 mmol) in CCl4 and stirring at room temperature
] (6Cl): Dissolving
6
for one week resulted in NMR pure ClHypPh3 (6Cl) (yield 7 g,
10.8 mmol, 96%) after evaporating all volatile components, which
could be recrystallized from Et2O to get X-ray suitable single crystals.
1H NMR (250 MHz, C6D6): δ = 0.05 (s, 9H SiMe3), 7.07 (m, 18 H,
SiPh3), 7.59 (m, 12 H, SiPh3); 13C{1H} NMR (62.5 MHz, C6D6): δ =
0.0 (s, SiMe3), 128.3 (s), 129.7 (s), 134.6 (s), 137.0 (s, all SiPh3);
29Si{1H} NMR (50 MHz, C6D6): δ = –8.5 (s, SiMe3), –13.5 (s,
Sicentral), –18.5 (s, SiPh3). C46H47ClSi4: found (calculated): C 71.9
(71.4), H 5.89% (6.00%).
Synthesis of Si(SiMe3)2(SiPh3)2 (2): Following the general procedure,
Si(SiMe3)2(SiPh3)2 (2) could be obtained as air and moisture stable
colorless crystals from hot ethanol in yields of 21 g (75%) starting
1
from KHypPh3 (20 g, 42 mmol). H NMR (250 MHz, [D8]THF): δ =
0.09 (s, 18 H, SiMe3), 7.23 (m, 30H SiPh3); 13C{1H} NMR
(62.5 MHz, [D8]THF): δ = 4.0 (s, SiMe3), 128.3 (s), 129.7 (s), 137.3
(s), 137.6 (s, all SiPh3); 29Si{1H} NMR (50 MHz, [D8]THF): δ = –9.2
(s, SiMe3), –10.0 (s, SiPh3), –126.7 (s, Sicentral) C42H48Si5: found
(calcd.): C 72.9 (72.7), H 6.87% (6.98%).
Synthesis of ClSi(SiPh3)3 [ClHypPh9] (7Cl): A solution of KHypPh9
(5, 1.7 g, 2 mmol) in THF was added to a solution of 190 mg (1 mmol)
SnCl2 in THF at –78 °C. The color of the solution immediately turned
red. The mixture was allowed to reach room temperature over a period
of 12 h. After that, a grey precipitate appeared and the color of the
solution changed to light yellow. The solution was filtered and stored
without further purification at –28 °C to get colorless single crystals of
Synthesis of KSi(SiMe3)(SiPh3)2 [KHypPh6] (3): Following the gene-
ral procedure, Si(SiMe3)2(SiPh3)2 (2, 10 g, 14.4 mmol) and KOtBu
(1.7 g, 15.1 mmol) were used leading to 3 (yield 9.3 g, 13 mmol,
92%). Single crystals could be obtained by changing the solvent to
toluene and adding 1 equiv. of 18-crown-6. Layering the solution with
pentane resulted in single crystals of 3crown.
1H NMR (250 MHz,
C6D6): δ = –0.29 (s, 9 H, SiMe3), 3.59 (s, 18 H, 18-crown-6), 6.93 (m,
18 H, SiPh3), 7.46 (m, 12 H, SiPh3); 13C{1H} NMR (62.5 MHz,
C6D6): δ = 7.0 (s, SiMe3), 71.1 (s, 18-crown-6), 126.5 (s), 126.7 (s),
137.7 (s), 146.2 (s, all SiPh3); 29Si{1H} NMR (50 MHz, C6D6): δ = 0.8
(s, SiMe3), –7.3 (s, SiPh3), –185.8 (s, Sicentral). C45H51KO3Si4: found
(calcd.): C 67.7 (68.3), H 6.42% (5.50%).
1
ClHypPh9 (7Cl) (yield 600 mg, 0.7 mmol, 35%). H NMR (250 MHz,
[D8]THF): δ = 7.02 (m, 18 H, SiPh3), 7.12 (m, 18 H, SiPh3), 7.26 (m,
18 H, SiPh3). 13C{1H} NMR (62.5 MHz, [D8]THF): δ = 128.3 (s),
129.9 (s), 134.4 (s), 137.7 (s); 29Si{1H} NMR (50 MHz, [D8]THF): δ =
–17.2 (s, SiPh3). C54H45ClSi4: found (calcd.): C 77.4 (77.0), H 5.54%
(5.39%).
Synthesis of Si(SiMe3)(SiPh3)3 (4): Following the general procedure,
KHypPh6 (3, 8 g, 12.1 mmol) and ClSiPh3 (3.8 g, 13 mmol) were used
leading to Si(SiMe3)(SiPh3)3 (4) (yield 8.1 g, 9.7 mmol, 81%). X-ray
suitable single crystals could be obtained via a second recrystallization
step from Et2O at 4 °C.[22] 1H NMR (250 MHz, [D8]THF): δ = 0.13
(s, 9H SiMe3), 7.04 (m, 36 H, SiPh3), 7.28 (m, 9 H, SiPh3); 13C{1H}
NMR (62.5 MHz, [D8]THF): δ = 5.3 (s, SiMe3), 128.0 (s), 129.6 (s),
137.2 (s), 138.1 (s, all SiPh3); 29Si NMR (50 MHz, [D8]THF): δ = –8.1
(SiMe3), –9.4 (SiPh3), –121.0 (Sicentral). C61H64OSi5: found (calcd.): C
74.9 (74.8), H 6.28% (6.39)%.
X-ray Crystallography: Table 1 contains the crystal data and details
of the X-ray structure determination for all crystallized compounds.
The data were collected at 150 K with a Bruker APEXII microsource
diffractometer employing monochromated Mo-Kα (λ = 0.71073 Å) ra-
diation and equipped with an Oxford Cryosystems cryostat. A semi-
empirical absorption correction was applied using SADABS. The
structures were solved by direct methods and refined by full-matrix
least-square techniques (Programs used: Olex2 program package,
SHELXS and SHELXL).[23] The non-hydrogen atoms were refined
anisotropically and the hydrogen atoms were calculated using a riding
model. The coordination of the Li cation in 1Li is best described as a
disorder model of 60% Li(THF)3(Et2O) and 40% Li(THF)4, whereby
all carbon atoms in the minor part are refined isotropically. In com-
Synthesis of KSi(SiPh3)3 [KHypPh9] (5): Following the general pro-
cedure, Si(SiMe3)(SiPh3)3 (4, 5 g, 5.7 mmol) and KOtBu (0.7 g,
6.5 mmol) were used leading to 5 (yield 3.6 g, 4.3 mmol, 75%) Single pound 4 and 6Cl, additional solvent molecules could be identified and
crystals could be obtained over two weeks directly from a THF solu-
refined: in case of 4 one diethyl ether molecule and in case of 6Cl one
Z. Anorg. Allg. Chem. 2017, 1759–1765
www.zaac.wiley-vch.de 1763
© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Table 1. Crystal data and details of structural determinations.
1Li 3crown
C70H78.2LiO4Si4 C42H48Si5 C45H51KO3Si4 C61H64OSi5
2
4
5
6Cl
7Cl
Formula
Formula wt.
T /K
C73H77KO3Si4 C46H47ClSi4
1153.80
150
C54H45ClSi4
841.71
150
1102.83
150
693.25
150
791.31
150
953.57
150
747.64
150
Crystal system
Space group
a /Å
b /Å
c /Å
monoclinic
P21/c
18.9660(10)
18.5491(10)
18.7665(19)
90
110.811(3)
90
6171.4(6)
4
monoclinic
P21/n
10.9419(5)
21.5934(11)
16.5871(8)
90
92.1460(10)
90
3916.3(3)
4
triclinic
P1
monoclinic
P21/c
24.4476(8)
10.9900(4)
39.6879(13)
90
91.193(2)
90
10661.0(6)
8
monoclinic
P21/c
18.9638(3)
17.9510(3)
18.8246(3)
90
93.0690(10)
90
6399.06(18)
4
monoclinic
P21/n
19.4084(4)
10.1884(2)
21.4625(4)
90
104.3740(10)
90
4111.15(14)
4
hexagonal
P63
18.6937(6)
18.6937(6)
10.0792(4)
90
90
120
3050.3(2)
2
0.168
¯
13.3724(10)
13.5189(11)
13.8914(11)
117.893(2)
95.463(2)
93.948(2)
2191.0(3)
2
0.268
1.199
24770
8912
α /°
β /°
γ /°
V /Å3
Z
μ /mm–1
ρ /g·cm–3
Reflns. meas.
Independent
Reflns.
0.144
1.187
163867
12685
0.211
1.176
79251
9654
0.174
1.188
182083
20950
0.205
1.198
283191
24327
0.241
1.208
61340
12584
0.916
114494
6290
R(int.)
Goof
0.0630
1.030
0.0461
1.030
0.0432
1.020
0.0570
1.130
0.0460
1.022
0.0449
1.044
0.0499
1.036
R1 (I Ͼ 2σ)
wR2 (all data)
0.0469
0.1231
0.0332
0.0853
0.0418
0.0911
0.0619
0.1477
0.0475
0.1372
0.0413
0.1045
0.0279
0.0736
[3] H. Bürger, U. Wannagat, Monatsh. Chem. 1963, 94, 761–771.
[4] a) M. A. Cook, C. Eaborn, A. E. Jukes, D. R. M. Walton, J. Or-
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[5] SitBu3, a silanide with a similar steric demand is also available
and is called “supersilyl”: N. Wiberg, K. Amelunxen, H.-W. Ler-
ner, H. Schuster, H. Nöth, I. Krossing, M. Schmidt-Amelunxen,
T. Seifert, J. Organomet. Chem. 1997, 542, 1–18.
[6] B. Luo, V. G. Young, W. J. Gladfelter, J. Organomet. Chem. 2002,
648, 268–275.
toluene molecule. However, in case of 7Cl solvent molecules are
heavily disordered, which could not be reasonably modeled, therefore
SQUEEZE[24] was used to refine the structure (void: 1009 Å3, elec-
trons: 277, solvent: 7 THF).
Crystallographic data (excluding structure factors) for the structures in
this paper have been deposited with the Cambridge Crystallographic
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK. Copies
of the data can be obtained free of charge on quoting the depository
numbers CCDC-1563723 (1Li), CCDC-1563720 (2), CCDC-1563718
(3crown), CCDC-1563721 (4), CCDC-1563726 (5), CCDC-1563725,
(6Cl) and CCDC-1563722 (7Cl) (Fax: +44-1223-336-033; E-Mail:
deposit@ccdc.cam.ac.uk, http://www.ccdc.cam.ac.uk)
[7] H. Gilman, C. L. Smith, J. Organomet. Chem. 1967, 8, 245–253;
G. Gutekunst, A. G. Brook, J. Organomet. Chem. 1982, 225,
1–3.
Supporting Information (see footnote on the first page of this article):
Synthesis and molecular structure of donor free KHypPh6 and HHypPh6
and proton NMR spectra of all compounds.
[8] C. Marschner, Eur. J. Inorg. Chem. 1998, 1998, 221–226.
[9] C. Kayser, R. Fischer, J. Baumgartner, C. Marschner, Organome-
tallics 2002, 21, 1023–1030.
[10] C. Marschner, Organometallics 2006, 25, 2110–2125.
[11] R. Klink, C. Schrenk, A. Schnepf, Dalton Trans. 2014, 43,
16097–16104.
[12] During the recrystallization process we were able to isolate a
second polymorph of 3, which is also dimeric, but this time with-
out a chelating crown ether molecule. The crystal structure of
this second polymorph is shown and discussed in the Supporting
Information.
[13] F. Li, S. C. Sevov, Inorg. Chem. 2012, 51, 2706–2708.
[14] A. Schnepf, R. Köppe, Z. Anorg. Allg. Chem. 2002, 628, 2914–
2918.
Acknowledgements
We thank the Deutsche Forschungsgemeinschaft (DFG) for financial
support.
[15] A. Schnepf, Angew. Chem. 2003, 115, 2728–2729; Angew. Chem.
Int. Ed. 2003, 42, 2624–2625.
Keywords: Chlorsilane; Silanes; Silanide ligand
[16] L. G. Perla, S. C. Sevov, J. Am. Chem. Soc. 2016, 138, 9795–
9798.
[17] L. J. Schiegerl, F. S. Geitner, C. Fischer, W. Klein, T. F. Fässler,
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Z. Anorg. Allg. Chem. 2017, 1759–1765
www.zaac.wiley-vch.de 1764
© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
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Received: July 28, 2017
Published Online: October 16, 2017
Z. Anorg. Allg. Chem. 2017, 1759–1765
www.zaac.wiley-vch.de 1765
© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim