Trapping Experiments on a Trichlorosilanide Anion: A Key Intermediate of Halogenosilane Chemistry

Article abstract of DOI:10.1021/acs.inorgchem.7b00216

Treatment of Si₂Cl₆ with [Et₄N][BCl₄] in CH₂Cl₂ furnished the known products of a chloride-induced disproportionation reaction of the disilane, such as SiCl₄, [Si(SiCl₃)₃]^-, and [Si₆Cl₁₂·2Cl]^2-. No Si-B-bonded products were detectable. In contrast, the addition of Si₂Cl₆ to [Et₄N][BI₃Cl] afforded the Si-B adduct [Et₄N][I₃SiBI₃]. Thus, a quantitative Cl/I exchange at the silicon atom accompanies the trihalogenosilanide formation. [Et₄N][I₃SiBI₃] was also accessible from a mixture of Si₂I₆, [Et₄N]I, and BI₃. According to X-ray crystallography, the anion [I₃SiBI₃]^- adopts a staggered conformation with an Si-B bond length of 1.977(6) ?. Quantum-chemical calculations revealed a polar covalent Si-B bond with significant contributions from intramolecular I···I dispersion interactions.

Full text of DOI:10.1021/acs.inorgchem.7b00216

This is an open access article published under an ACS AuthorChoice License, which permits
copying and redistribution of the article or any adaptations for non-commercial purposes.
Forum Article
pubs.acs.org/IC
Trapping Experiments on a Trichlorosilanide Anion: a Key
Intermediate of Halogenosilane Chemistry
Julian Teichmann,† Markus Bursch,‡ Benedikt Kostler,† Michael Bolte,† Hans-Wolfram Lerner,†
̈
Stefan Grimme,*,‡ and Matthias Wagner*,†
†Institut fur Anorganische Chemie, Goethe-Universitat Frankfurt am Main, Max-von-Laue-Straße 7, 60438 Frankfurt am Main,
̈
̈
Germany
‡Mulliken Center for Theoretical Chemistry, Institut fur Physikalische und Theoretische Chemie, Universitat Bonn, Beringstraße 4,
̈
̈
53115 Bonn, Germany
S
* Supporting Information
ABSTRACT: Treatment of Si2Cl6 with [Et4N][BCl4] in CH2Cl2 furnished
the known products of a chloride-induced disproportionation reaction of the
disilane, such as SiCl4, [Si(SiCl3)3]−, and [Si6Cl12·2Cl]2−. No Si−B-bonded
products were detectable. In contrast, the addition of Si2Cl6 to [Et4N][BI3Cl]
afforded the Si−B adduct [Et4N][I3SiBI3]. Thus, a quantitative Cl/I
exchange at the silicon atom accompanies the trihalogenosilanide formation.
[Et4N][I3SiBI3] was also accessible from a mixture of Si2I6, [Et4N]I, and BI3.
According to X-ray crystallography, the anion [I3SiBI3]− adopts a staggered conformation with an Si−B bond length of 1.977(6)
Å. Quantum-chemical calculations revealed a polar covalent Si−B bond with significant contributions from intramolecular I···I
dispersion interactions.
One of the simplest Lewis bases that can be employed for the
disproportionation of Si2Cl6 is the chloride ion. Depending on
the reaction temperatures and the molar ratios of the starting
materials, treatment of the disilane with soluble chloride salts
[R4N]Cl in CH2Cl2 leads either to open-chain oligosilane−
chloride adducts, such as [Si3Cl9]− and the branched [Si6Cl15]−,
or to chloride-complexed cyclohexasilanes, such as [Si6Cl12·
2Cl]2− (Figure 1).22 The propensity of the underlying PCSs to
coordinate additional chloride ions not only testifies to the high
Lewis acidity of these species but also facilitates their isolation
and crystallographic characterization. In the case of the
cyclohexasilane diadduct, the two chloride ions can be
conveniently abstracted using AlCl3, which opens up a facile
route for preparing Si6Cl12 on a larger scale.23 In addition to
chainlike and cyclic PCSs, monodisperse silicon cluster
compounds are also readily accessible: Our group has recently
prepared the first Si20 dodecahedrane (“silafullerane”) from
Si2Cl6, [nBu4N]Cl, and nBu3N through a one-step self-assembly
protocol in 27% yield (Figure 1).24 Each silafullerane cage hosts
an endohedral chloride ion and thereby acquires a negative
charge. Moreover, the clusters are decorated regioselectively
with 12 SiCl3 substituents, which may serve as anchor groups to
link individual silafulleranes together.
INTRODUCTION
■
Perchlorinated oligosilanes (PCSs) are valuable precursors for
the deposition of silicon thin films. The PCS sample is either
thermolyzed directly to give elemental silicon in a disproportio-
nation reaction1 or converted to the corresponding perhydro-
genated oligosilanes prior to thermolysis.2,3
Apart from these industrial applications, PCSs are also
attractive in their own right because they exhibit rich molecular
chemistry, which often proceeds via intriguing intermediates to
finally furnish products with sophisticated structural frame-
works. The underlying mechanistic pathways are characterized
by the tendency of covalent Si−Si bonds to undergo
rearrangement reactions, a dynamic behavior that can be
triggered deliberately by the addition of Lewis bases. As one of
the first examples, Urry and co-workers reported that
hexachlorodisilane (Si2Cl6) undergoes quantitative transforma-
tion to perchlorinated neopentasilane Si(SiCl3)4 and SiCl4
upon the catalytic action of various trialkylamines (R3N).4−9
Recent experimental and quantum-chemical studies have
shown that dichlorosilylene adducts R3N−SiCl2 play a decisive
role in the course of this reaction.10−13 Certain diaryl-
methanones can also liberate dichlorosilylenes from Si2Cl6,
albeit only at elevated temperatures. Under these conditions,
the resulting ketone−SiCl2 adducts ultimately lead to the
reductive coupling of carbonyl compounds to afford tetraaryl-
ethylenes (sila-McMurry reaction).14 Reduction reactions have
also successfully been performed on organic nitro compounds,
phosphine oxides, and sulfoxides by means of Si2Cl6 or HSiCl3/
R3N.15−21 In most cases, donor-stabilized SiCl2 has been
proposed as the key intermediate.
A quantum-chemical assessment of the chloride-induced
disproportionation of Si2Cl6 indicates an initial nucleophilic
attack of the chloride ion on one of the silicon atoms with
Special Issue: Advances in Main-Group Inorganic Chemistry
Received: January 24, 2017
© XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.7b00216
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Forum Article
tionate Si2Cl6. We have previously shown that the Lewis acidity
of BCl3 is comparable to that of cyclo-Si6Cl12,23 which made us
confident that the chloride affinity of Si2Cl6 is also sufficiently
high to abstract chloride ions from preformed [BCl4]−
complexes in a dynamic equilibrium. A formal metathesis
reaction could therefore lead from [BCl4]− and Si2Cl6 to
[Cl3SiBCl3]− and SiCl4.
Given these considerations, we first prepared a suspension of
[Et4N][BCl4] in an NMR tube by mixing equimolar solutions
of BCl3 and [Et4N]Cl in CH2Cl2.38 After 1 equiv of neat Si2Cl6
had been added at room temperature, an exothermic reaction
occurred, but the visual appearance of the mixture remained
essentially the same. The sample was vacuum-sealed and
investigated by 11B and 29Si NMR spectroscopy. The 11B NMR
spectrum showed only one resonance, which was assignable to
the [BCl4]− ion (δ = 6.6).39 The 29Si NMR spectrum contained
no signal for residual Si2Cl6 (δ = −6.6),24 but numerous other
resonances with chemical shift values characteristic of SiCl4 (δ
= −18.9),22 [Si(SiCl3)3]− (δ = −137.9 and +29.9),37 and
chloride diadducts of (SiCl3-substituted) cyclohexasilanes (such
as [Si6Cl12·2Cl]2− in Figure 1).22 These observations lead to the
conclusion that disproportionation of Si2Cl6 can indeed be
induced by [BCl4]− ions. However, under the conditions
applied, the vast majority of the generated [SiCl3]−
intermediates further react with yet unconsumed Si2Cl6 rather
than with BCl3. As a consequence, the usually observed
products of the chloride-induced assembly of PCSs are formed
(Scheme 1a).22
Figure 1. X-ray crystallographically determined molecular structures of
the anions [Si3Cl9]− (top left), [Si6Cl15]− (top right), [Si6Cl12·2Cl]2−
(bottom left), and [Si32Cl45]− (bottom right).
subsequent heterolytic cleavage of the Si−Si bond and
formation of SiCl4 and an [SiCl3]− anion.22 [SiCl3]− ions
have previously been proposed as key intermediates of the so-
called “Benkeser reactions”, which employ a HSiCl3/R3N
combination to introduce SiCl3 groups into various different
substrates via a nucleophilic pathway.25−33 In view of these
mechanistic models, [SiCl3]− represents an important link
between the chemistries of Si2Cl6, on the one hand, and
HSiCl3, on the other hand. A second link relates [SiCl3]− to
SiCl2 chemistry because the ion can be viewed as a chloride-
stabilized dichlorosilylene. However, only a small amount of
experimental data have been gathered on [SiCl3]− to date,
despite its importance for preparative (organo)silicon chemistry
and its formal analogy to the well-known [CX3]− ions (X = Cl,
Br, I; compare the Appel,34 Corey−Fuchs,35 and haloform36
reactions).
Scheme 1. Reactions between Si2X6, [R4N]X, and BX3 (X =
Cl, I)
Collision-induced dissociation experiments carried out in a
mass spectrometer on mixtures of Si(SiCl3)4 and [Et4N]Cl in
CH2Cl2 produced a peak at m/z 134.9, which is assignable to
[SiCl3]− and thus indicates that this ion can indeed be
generated in the gas phase.37 Moreover, the above-mentioned
species [Si3Cl9]− can be viewed not only as a chloride adduct of
the trisilane Si3Cl8 but also as the trapping product of [SiCl3]−
by 1 equiv of the starting material Si2Cl6. This latter result
encouraged us to try to trap [SiCl3]− also with other Lewis
acids and thereby to prove its intermediate appearance. In order
to be able to unequivocally distinguish between the trapping
reagent and a coordinating [SiCl3]− ion, the Lewis acid needs
to be silicon-free, which led to our choice of boron trihalides.
Herein, we report on the reactions of Si2X6 with [R4N]X in the
presence of BX3 (X = Cl, I) and on the characterization of the
unique Si−B adduct [I3SiBI3]− by means of X-ray crystallog-
raphy. The electronic structure of the anion was elucidated by
quantum-chemical calculations.
We next repeated the previous experiment but switched from
BCl3 to BI3 for the following reasons: (i) BI3 is a much stronger
Lewis acid than BCl3, (ii) iodinated products should crystallize
more readily than their chlorinated congeners, (iii) the higher
electron count of iodo substituents should facilitate product
analysis by X-ray crystallography and energy-dispersive X-ray
(EDX) spectroscopy. As a downside of this approach, two types
of halogen atoms are now present in the sample such that
various mixed-halogen species are likely to be formed. Indeed,
an 11B NMR spectroscopic investigation of the sample revealed
the presence of all five possible tetrahalogenoborate anions
−
[BClnI4−n
]
(n = 0−4), and the corresponding 29Si NMR
spectrum contained the signals of SiCl4 and SiCl3I (see the
Supporting Information for more details). The NMR tube was
stored at room temperature in the dark in order to avoid
photolysis of iodoborane species. After 24 h, single crystals had
grown on top of an amorphous precipitate, which were
identified as [Et4N][I3SiBI3] by means of X-ray crystallography
(Figure 2). Compound [Et4N][I3SiBI3] represents the desired
borane adduct of an [SiX3]− ion; however, all originally silicon-
bonded chloro substituents have been replaced by iodine
atoms. Improved yields of the adduct should thus be achievable
by employing Si2Cl6 and BI3 in a 1:2 ratio rather than a 1:1
ratio. A corresponding synthesis was subsequently carried out
RESULTS AND DISCUSSION
■
Reactions between Si2X6, [R4N]X, and BX3 (X = Cl, I). In
order to avoid halogen scrambling, we first selected BCl3 to trap
the putative [SiCl3]− ion. A fundamental problem in designing
the experiment lies in the fact that the Lewis acid has to already
be present when the highly reactive [SiCl3]− is generated. Thus,
Si2Cl6 and BCl3 will necessarily compete for the added chloride
ions, and one has to make sure that Cl− will not just neutralize
the boron Lewis acid without getting a chance to dispropor-
B
DOI: 10.1021/acs.inorgchem.7b00216
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Forum Article
(10.33%)], nitrogen [1.60% (1.51%)], iodine [79.7% (81.8%)],
and silicon [3.51% (3.02%)]. According to EDX analysis, the
crystals contained silicon and iodine in a ratio of Si:I = 1:5.7
( 0.04). We note that the experimentally determined carbon/
hydrogen/nitrogen content is slightly too high, while the iodine
content is somewhat too low. A contamination of the sample
with a small amount of [Et4N][BI4] could well account for
these deviations, however, the corresponding 11B resonance
should be detectable by NMR spectroscopy, which is not the
case. Moreover, our EDX measurements do not support the
presence of excess iodine (with respect to silicon). As an
alternative explanation, we propose that the sample contains a
few chloro substituents in place of the iodo substituents: In
addition to the signals assignable to silicon and iodine atoms,
the EDX measurements indeed showed a small signal indicating
the presence of chlorine atoms (cf. the Supporting Information
for a plot of the spectrum). As a conceivable chlorine source,
we identified the solvent CH2Cl2, which undergoes some
halogen exchange with BI3 to furnish small amounts of CH2ICl
and BClI2 (cf. the Supporting Information).
The ultimate proof of the composition of [Et4N][I3SiBI3]
was provided by X-ray crystallography (Figure 2 and Table 1).
The crystal lattice of the compound contains [Et4N]+ cations
and [I3SiBI3]− anions in a 1:1 ratio. The anion can be
interpreted as the adduct between [SiI3]− and BI3 with an Si−B
bond length of 1.977(6) Å [cf. Si−B = 2.018(2) Å in the adduct
between [SiEt3]− and 9H-9-borafluorene42]. As a prominent
structural feature, [I3SiBI3]− adopts an almost perfectly
staggered conformation with the absolute values of the smaller
I−Si−B−I torsion angles ranging from 56.8(3)° to 63.0(3)°.
The average Si−I bond length amounts to 2.454 Å and thus lies
close to that of Si2I6 [2.425(1) Å; Table 1]. The average B−I
bond length also possesses almost the same value as that in the
comparable P−B adduct Cy3PBI3 (2.252 vs 2.241 Å; Cy =
cyclohexyl). Both the silicon and boron centers are fully
pyramidalized, which points toward a strong covalent Si−B
bond.
Figure 2. Solid-state structure of [Et4N][I3SiBI3] (cation omitted for
clarity; Si, blue; B, green): side view of the anion (left) and projection
along the B−Si axis (right). Selected bond lengths [Å] and bond
angles [deg]: Si−B = 1.977(6), Si−I = 2.457(2)/2.454(2)/2.451(2),
B−I = 2.261(6)/2.249(6)/2.246(6); Si−B−I = 108.5(3)/110.8(3)/
109.4(3), B−Si−I = 112.9(2)/112.2(2)/112.3(2), I−B−I = 108.9(2)/
108.9(3)/110.2(3), I−Si−I = 106.8(1)/106.3(1)/105.9(1).
on a preparative scale and furnished crystals of [Et4N][I3SiBI3]
in 44% yield (Scheme 1b).
With the aim of minimizing the number of byproducts from
which [Et4N][I3SiBI3] has to be separated, we finally conducted
the synthesis starting from Si2I6,40 [Et4N]I, and BI3 in a
stoichiometric ratio of 1:1:1 (Scheme 1c). Single crystals of
[Et4N][I3SiBI3] grew upon storage of the mixture in the dark at
room temperature for 10 days. The comparatively long reaction
time is likely due to the poor solubilities of Si2I6 and [Et4N]I in
CH2Cl2. An 11B NMR spectrum recorded on the mother liquor
revealed almost exclusively the resonance of the [BI4]− ion (cf.
the Supporting Information for a plot of the spectrum).41
Consequently, this sample of the Si−B adduct was used for
elemental analysis and EDX spectroscopy. In contrast to
[Et4N][BI4], the target compound [Et4N][I3SiBI3] is only
sparingly soluble in CH2Cl2 as well as all other common inert
solvents. We, nevertheless, noticed a loss of crystalline material
during extensive washing. In parallel, a resonance at δ = −32.4,
which we assign to an unknown decomposition product,
became increasingly apparent in the 11B NMR spectrum of the
washing solution. The yield of the single-crystalline [Et4N]-
[I3SiBI3] left over after repeated rinsing with CH2Cl2 amounted
to 31%.
Characterization of [Et4N][I3SiBI3]. The generally poor
solubility of the adduct [Et4N][I3SiBI3] precluded its character-
ization by solution-phase NMR spectroscopy. Solid-state magic-
angle-spinning NMR spectroscopy also did not provide
interpretable data, likely because the 29Si NMR resonance is
severely broadened due to coupling with the 10B and 11B nuclei
Quantum-Chemical Calculations. In order to obtain
more information about the electronic structure of the
[I3SiBI3]− anion, quantum-chemical calculations were per-
formed to answer the following questions: (i) Is the molecule
mainly bound by a covalent Si−B bond or do intramolecular
dispersion interactions between the six iodo substituents also
play an important role? (ii) What is the driving force behind the
observed Cl/I exchange reaction on the silicon center?
The computational studies were carried out using density
functional theory. Geometry optimizations were conducted
using the D3(BJ) dispersion-corrected45−49 PBE050 hybrid
functional in conjunction with the def2-QZVP51 basis set. Final
gas-phase single-point energies were obtained at the B2PLYP-
3
(S = 3 and /2, respectively). The quadrupolar nature of the
boron nuclei leads to a further broadening of the 29Si NMR
signal and also affects the resolution of the 11B NMR resonance.
The experimental characterization of [Et4N][I3SiBI3] will
therefore be based on elemental analysis, EDX spectroscopy,
and X-ray crystallography.
Elemental analysis of [Et4N][I3SiBI3] gave satisfactory values
for hydrogen [2.32% (requires: 2.17%)], carbon [11.05%
Table 1. Comparison of Experimentally Determined Bond Lengths and Bond Angles of [Et4N][I3SiBI3] with the Corresponding
a
Calculated Values
entry
Si−B [Å]
Si−I (avg) [Å]
B−I (avg) [Å]
Σ(I−Si−I) [deg]
Σ(I−B−I) [deg]
[Et4N]+[I3SiBI3]−
calcd [I3SiBI3]−
[Et3Si(H)BFlu]−
2.018(2)
Cy3PBI3
I3SiSiI3
1.977(6)
2.454
2.011
2.474
2.228
316.8
335.2
2.425(1)
333.3
2.252
2.241
326.7
319.0
328.0
a
Key geometric parameters of three selected literature-known compounds are included for comparison. [Et3Si(H)BFlu]− = adduct between [SiEt3]−
and 9H-9-borafluorene; Cy3P = tricyclohexylphosphane.42−44 Calculated bond lengths obtained at the PBE0-D3/def2-QZVP level of theory.
C
DOI: 10.1021/acs.inorgchem.7b00216
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Forum Article
D3(BJ)52/def2-QZVP//PBE0-D3(BJ)/def2-QZVP level of
theory. Gibbs free energies were obtained by summing the
dispersion-corrected electronic energies, ro-vibrational correc-
tions from a modified harmonic oscillator statistical treatment
based on harmonic frequencies, and solvation corrections
computed by means of the COSMO-RS53 model (2014
parametrization for dichloromethane). All calculations were
conducted with the TURBOMOLE 7.0.2 program package54,55
and COSMOtherm, version C3.0, release 16.01.56 For further
computational details, see the Supporting Information.
that the Cl−/I− exchange starting from [SiCl3]− with BI3 is
overall strongly exergonic (ΔGR = −18.2 kcal/mol). Each
exchange step is exergonic itself until a complete halide
exchange between the silicon and boron fragments has taken
place. We conclude that the strongly exergonic exchange
reactions represent the driving force of the [I3SiBI3]−
formation. The reaction free energy is dominated by the
enthalpic component.
CONCLUSION
■
The solid-state structure of the [I3SiBI3]− anion in a
staggered conformation was reproduced in good accordance
in the gas phase at the PBE0-D3(BJ)/def2-QZVP level of
theory (Table 1). The strongly pyramidalized boron atom
indicates a covalent B−Si bond. This assumption is supported
by analysis of the localized molecular orbitals (LMOs) obtained
at the PBE0/def2-QZVP(-g) level of theory. The LMO
representing the B−Si bond is predominantly of the σ type
with a major localization at the silicon center (populations: Si,
0.748; B, 0.335). The atomic orbitals involved in the B−Si
bond are mainly of s character at the silicon center (s, 75.0%; p,
23.8%) and mainly of p character for the boron atom (s, 40.2%;
p, 61.3%), which matches the expectation of an s-type lone pair
at the [SiI3]− fragment, forming a strong bond with the vacant
pz orbital of the Lewis acid BI3. The calculated dissociation free
energy of ΔGDiss = 24.3 kcal/mol for [I3SiBI3]− further
indicates a relatively strong B−Si bond [B2PLYP-D3(BJ)/def2-
QZVP+COSMO-RS(CH2Cl2)//PBE0-D3(BJ)/def2-QZVP
values].
It has been postulated that the deprotonation of HSiCl3 with
amine bases as well as the chloride-induced disproportionation
of Si2Cl6 result in the formation of [SiCl3]− ions as the primary
intermediates. However, to date, only a small amount of
experimental evidence exists to support this suggestion. We
have now shown that the treatment of Si2Cl6 with [Et4N]Cl in
the presence of BI3 leads to the single-crystalline adduct
[Et4N][I3SiBI3]. The isolation of [Et4N][I3SiBI3] not only
represents the first successful trapping of a trihalogenosilanide
with a boron Lewis acid but also reveals a quantitative Cl/I
exchange reaction at the silicon center under the conditions
applied. The same product was obtained from a mixture of
Si2I6, [Et4N]I, and BI3.
The Si−B bond length amounts to 1.977(6) Å (calculated
value: 2.011 Å); the SiI3 and BI3 fragments are pronouncedly
pyramidalized. These experimental observations, together with
quantum-chemical calculations, point toward a strong, yet
highly polarized covalent bond. The atomic orbitals involved in
bonding possess mainly s character at the silicon center and p
character at the boron center. In addition to the direct Si−B
dative bond, intramolecular dispersion interactions between the
six iodo substituents contribute significantly to the stability of
the [I3SiBI3]− anion (ΔGDiss = 24.3 kcal/mol; D3 dispersion
contribution of 9.1 kcal/mol).
Analysis of the relative energy contributions to the
dissociation free energy (Table 2) indicates that dispersion
Table 2. Dissociation Free Energies and Its Components
[kcal/mol] at the B2PLYP-D3(BJ)/def2-QZVP+COSMO-
a
RS(CH2Cl2)//PBE0-D3(BJ)/def2-QZVP Level of Theory
structure
[I3SiBI3]−
ΔGDiss
ΔEE
ΔGRRHO
−16.5
ΔGsolv
−4.2
ΔED3
ASSOCIATED CONTENT
■
24.3
35.9
9.1
S
* Supporting Information
a
ΔGDiss = dissociation free energy; ΔEE = electronic gas-phase energy
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.7b00216.
difference; ΔGRRHO = ro-vibrational energy correction difference;
ΔGsolv = relative solvation energy correction difference; ΔED3 = D3
dispersion energy difference.
Experimental details, characterization data including
1
plots of H, 11B, and 29Si NMR spectra, EDX data for
interactions (ΔED3 = 9.1 kcal/mol) contribute significantly to
stabilization of the [SiI3]− and BI3 fragments upon bond
formation (for more detailed information on the atom pairwise
dispersion treatment and the corresponding energy compo-
nents in all considered compounds, see the Supporting
Information).
[Et4N][I3Si−BI3], and computational details (PDF)
X-ray crystal structure analysis (CIF)
XYZ plot (XYZ)
AUTHOR INFORMATION
Because the full mechanism of the formation of [I3SiBI3]−
has yet to be elucidated, we investigated the reaction free
energies for a stepwise halide exchange between the [SiX3]−
and BX3 fragments (Scheme 2). This consideration indicates
■
Corresponding Authors
*E-mail: grimme@thch.uni-bonn.de.
*E-mail: Matthias.Wagner@chemie.uni-frankfurt.de.
Scheme 2. Calculated Relative Gibbs Free Energies of the Species Involved in Progressive Halide Exchange between [SiCl3]−
a
and BI3 at the B2PLYP-D3(BJ)/def2-QZVP+COSMO-RS(CH2Cl2)//PBE0-D3(BJ)/def2-QZVP Level of Theory
a
All energies [kcal/mol] are given relative to the corresponding starting compound [SiCl3]− in the context of the given model reaction.
D
DOI: 10.1021/acs.inorgchem.7b00216
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Forum Article
(15) Orlandi, M.; Tosi, F.; Bonsignore, M.; Benaglia, M. Metal-Free
Reduction of Aromatic and Aliphatic Nitro Compounds to Amines: A
HSiCl3-Mediated Reaction of Wide General Applicability. Org. Lett.
2015, 17, 3941−3943.
(16) Orlandi, M.; Benaglia, M.; Tosi, F.; Annunziata, R.; Cozzi, F.
HSiCl3-Mediated Reduction of Nitro-Derivatives to Amines: Is
Tertiary Amine-Stabilized SiCl2 the Actual Reducing Species? J. Org.
Chem. 2016, 81, 3037−3041.
(17) Naumann, K.; Zon, G.; Mislow, K. Perchloropolysilanes: Novel
Reducing Agents for Phosphine Oxides and Other Organic Oxides. J.
Am. Chem. Soc. 1969, 91, 2788−2789.
ORCID
Matthias Wagner: 0000-0001-5806-8276
Author Contributions
J.T. designed and conducted all syntheses (assisted by B.K.)
and collected the X-ray data; M.Bu. carried out all quantum-
chemical calculations; M.Bo. processed the X-ray data and
solved and refined the structure; H.-W.L. was involved in the
study design; M.W. supervised the experimental studies; M.W.,
J.T., M.Bu., and S.G. wrote the paper, and all of the authors
discussed the results and commented on the manuscript.
(18) Zon, G.; DeBruin, E. K.; Naumann, K.; Mislow, K.
Stereospecific Desulfurization of Acyclic Phosphine Sulfides with
Hexachlorodisilane and the Alkaline Hydrolysis of Monoalkoxy- and
Monoalkylmercaptophosphonium Salts. Stereochemistry and Mecha-
nism. J. Am. Chem. Soc. 1969, 91, 7023−7027.
(19) Tsui, F.-P.; Vogel, T. M.; Zon, G. Deoxygenation of Aryl Nitro
Compounds with Disilanes. J. Org. Chem. 1975, 40, 761−766.
(20) Krenske, E. H. Theoretical Investigation of the Mechanisms and
Stereoselectivities of Reductions of Acyclic Phosphine Oxides and
Sulfides by Chlorosilanes. J. Org. Chem. 2012, 77, 3969−3977.
(21) Krenske, E. H. Reductions of Phosphine Oxides and Sulfides by
Perchlorosilanes: Evidence for the Involvement of Donor-Stabilized
Dichlorosilylene. J. Org. Chem. 2012, 77, 1−4.
(22) (a) Tillmann, J.; Meyer, L.; Schweizer, J. I.; Bolte, M.; Lerner,
H.-W.; Wagner, M.; Holthausen, M. C. Chloride-Induced Aufbau of
Perchlorinated Cyclohexasilanes from Si2Cl6: A Mechanistic Scenario.
Chem. - Eur. J. 2014, 20, 9234−9239. The [Si6Cl12·2Cl]2− ion has
previously been prepared by amine-promoted disproportionation of
HSiCl3, and the electronic structure of this diadduct has been
investigated by quantum-chemical calculations: (b) Choi, S.-B.; Kim,
B.-K.; Boudjouk, P.; Grier, D. G. Amine-Promoted Disproportionation
and Redistribution of Trichlorosilane: Formation of Tetradecachlor-
ocyclohexasilane Dianion. J. Am. Chem. Soc. 2001, 123, 8117−8118.
(c) Dai, X.; Choi, S.-B.; Braun, C. W.; Vaidya, P.; Kilina, S.; Ugrinov,
A.; Schulz, D. L.; Boudjouk, P. Halide Coordination of Perhalocyclo-
hexasilane Si6X12 (X = Cl or Br). Inorg. Chem. 2011, 50, 4047−4053.
(d) Pokhodnya, K.; Olson, C.; Dai, X.; Schulz, D. L.; Boudjouk, P.;
Sergeeva, A. P.; Boldyrev, A. I. Flattening a Puckered Cyclohexasilane
Ring by Suppression of the Pseudo-Jahn-Teller Effect. J. Chem. Phys.
2011, 134, 014105.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
The authors are grateful to Prof. Dr. A. Terfort and Thalia
Vavaleskou for recording the EDX spectra. They also thank
■
Prof. Dr. J. Schmedt auf der Gunne and Wenyu Li for solid-
̈
state NMR measurements. This work was supported by the
DFG through the priority program “Control of London
dispersion interactions in molecular chemistry” (SPP 1807).
REFERENCES
■
(1) Auner, N. Verfahren zur Herstellung von Silicium aus
Halogensilanen. DE Patent WO2006125425A1, Nov 30, 2006.
(2) Hammad, A.; Amanatides, E.; Mataras, D.; Rapakoulias, D.
PECVD of Hydrogenated Silicon Thin Films from SiH4+H2+Si2H6
Mixtures. Thin Solid Films 2004, 451−452, 255−258.
(3) Chung, K. H.; Sturm, J. C.; Sanchez, E.; Singh, K. K.; Kuppurao,
S. The High Growth Rate of Epitaxial Silicon−Carbon Alloys by Using
Chemical Vapour Deposition and Neopentasilane. Semicond. Sci.
Technol. 2007, 22, S158−S160.
(4) Kaczmarczyk, A.; Urry, G. A New Synthesis for Hexasilicon
Tetradecachloride, Si6Cl14. J. Am. Chem. Soc. 1960, 82, 751−752.
(5) Kaczmarczyk, A.; Millard, M.; Urry, G. A New Pentasilicon
Dodecachloride, Si5Cl12. J. Inorg. Nucl. Chem. 1961, 17, 186−188.
(6) Nuss, J. W.; Urry, G. On the Structures of Pentasilicon
Dodecachloride, Si5Cl12, and Hexasilicon Tetradecachloride, Si6Cl14. J.
Inorg. Nucl. Chem. 1964, 26, 435−444.
(7) Kaczmarczyk, A.; Millard, M.; Nuss, J. W.; Urry, G. The
Preparation and Some Properties of a New Pentasilicon Dodeca-
chloride, Si5Cl12. J. Inorg. Nucl. Chem. 1964, 26, 421−425.
(8) Urry, G. Systematic Synthesis in the Polysilane Series. Acc. Chem.
Res. 1970, 3, 306−312.
(9) Fleming, D. K. The Crystal and Molecular Structure of
Dodecachloropentasilane Silicon Tetrachloride. Acta Crystallogr., Sect.
B: Struct. Crystallogr. Cryst. Chem. 1972, 28, 1233−1236.
(10) Meyer-Wegner, F.; Nadj, A.; Bolte, M.; Auner, N.; Wagner, M.;
Holthausen, M. C.; Lerner, H.-W. The Perchlorinated Silanes Si2Cl6
and Si3Cl8 as Sources of SiCl2. Chem. - Eur. J. 2011, 17, 4715−4719.
(11) Tillmann, J.; Meyer-Wegner, F.; Nadj, A.; Becker-Baldus, J.;
Sinke, T.; Bolte, M.; Holthausen, M. C.; Wagner, M.; Lerner, H.-W.
Unexpected Disproportionation of Tetramethylethylenediamine-Sup-
ported Perchlorodisilane Cl3SiSiCl3. Inorg. Chem. 2012, 51, 8599−
8606.
(23) Tillmann, J.; Moxter, M.; Bolte, M.; Lerner, H.; Wagner, M.
Lewis Acidity of Si6Cl12 and Its Role as Convenient SiCl2 Source.
Inorg. Chem. 2015, 54, 9611−9618.
(24) Tillmann, J.; Wender, J. H.; Bahr, U.; Bolte, M.; Lerner, H.-W.;
Holthausen, M. C.; Wagner, M. One-Step Synthesis of a [20]-
Silafullerane with an Endohedral Chloride Ion. Angew. Chem., Int. Ed.
2015, 54, 5429−5433.
(25) Benkeser, R.; Hickner, R. A. The Stereochemistry of the
Addition of Silicochloroform to Acetylenes. J. Am. Chem. Soc. 1958, 80,
5298−5300.
(26) Benkeser, R. A.; Smith, W. E. Trichlorosilane-Tertiary Amine
Combinations as Reducing Agents for Polyhalo Compounds. Potential
Analogies with Phosphorus Chemistry. J. Am. Chem. Soc. 1968, 90,
5307−5309.
(27) Benkeser, A.; Gaul, J. M.; Smith, W. E. Silylation of Organic
Halides. A New Method of Forming the Carbon-Silicon Bond. J. Am.
Chem. Soc. 1969, 91, 3666−3667.
(28) Benkeser, R. A. Chemistry of Trichlorosilane-Tertiary Amine
Combinations. Acc. Chem. Res. 1971, 4, 94−100.
(29) Cho, Y. S.; Kang, S.-H.; Han, J. S.; Yoo, B. R.; Jung, I. N. Novel
Phosphonium Chloride-Catalyzed Dehydrohalogenative Si−C Cou-
pling Reaction of Alkyl Halides with Trichlorosilane. J. Am. Chem. Soc.
2001, 123, 5584−5585.
(30) Kang, S. H.; Han, J. S.; Yoo, B. R.; Lee, M. E.; Jung, I. N.
Phosphonium Chloride-Catalyzed Dehydrochlorinative Coupling
Reactions of Alkyl Halides with Hydridochlorosilanes. Organometallics
2003, 22, 529−534.
(12) Schweizer, J. I.; Scheibel, M. G.; Diefenbach, M.; Neumeyer, F.;
Wurtele, C.; Kulminskaya, N.; Linser, R.; Auner, N.; Schneider, S.;
̈
Holthausen, M. C. A Disilene Base Adduct with a Dative Si−Si Single
Bond. Angew. Chem., Int. Ed. 2016, 55, 1782−1786.
(13) Schweizer, J. I.; Meyer, L.; Nadj, A.; Diefenbach, M.;
Holthausen, M. C. Unraveling the Amine-Induced Disproportionation
Reaction of Perchlorinated Silanes - A DFT Study. Chem. - Eur. J.
2016, 22, 14328−14335.
(14) Moxter, M.; Tillmann, J.; Fuser, M.; Bolte, M.; Lerner, H.-W.;
̈
Wagner, M. Tetraarylethylenes from Diarylmethanones and Hexa-
chlorodisilane: The ’Sila-McMurry’ Reaction. Chem. - Eur. J. 2016, 22,
16028−16031.
E
DOI: 10.1021/acs.inorgchem.7b00216
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Forum Article
(31) Jung, D. E.; Kang, S. H.; Han, J. S.; Lim, W. C.; Park, Y. W.;
Yoo, B. R. Si-C Coupling Reaction of Polychloromethanes with
HSiCl3 in the Presence of Bu4PCl: Convenient Synthetic Method for
Bis(chlorosilyl)methanes. J. Organomet. Chem. 2007, 692, 3901−3906.
(32) Hong, S. H.; Hyun, S. I.; Jung, I. N.; Han, W.-S.; Kim, M.-H.;
Yun, H.; Nam, S.-W.; Kang, S. O. Phosphine-Catalyzed Si−C
Coupling of Bissilylmethanes: Preparation of Cyclic (Cl2SiCH2)2
and Linear Cl2Si(CH2SiCl3)2 via Silylene and Silene Intermediates.
Organometallics 2010, 29, 687−691.
(53) Klamt, A. Conductor-like Screening Model for Real Solvents: A
New Approach to the Quantitative Calculation of Solvation
Phenomena. J. Phys. Chem. 1995, 99, 2224−2235.
(54) TURBOMOLE 7.0.2, a development of Universitat Karlsruhe
̈
Forschungszentrum Karlsruhe GmbH, 1989−2007, TURBOMOLE
GmbH, since 2007; available from http//www.turbomole.com.
(55) Furche, F.; Ahlrichs, R.; Hattig, C.; Klopper, W.; Sierka, M.;
̈
Weigend, F. Turbomole. Wiley Interdiscip. Rev. Comput. Mol. Sci. 2014,
4, 91−100.
(56) Eckert, F.; Klamt, A.; Pohler, L. COSMOtherm, version C3.0,
release 16.01; COSMOlogic GmbH Co. KG: Leverkusen, Germany,
2015.
(33) Kolesnikov, S. P.; Maksimov, S. N.; Smolenskii, E. A. Proton-
Donor Properties of HCCl3, HSiCl3, and HGeCl3 Molecules: A
Quantum-Chemical Study. Russ. Chem. Bull. 2001, 50, 740−742.
(34) Appel, R. Tertiares Phosphan/Tetrachlormethan, ein vielseitiges
̈
Reagens zur Chlorierung, Dehydratisierung und PN-Verknupfung.
̈
Angew. Chem. 1975, 87, 863−874.
(35) Corey, E. J.; Fuchs, P. L. A Synthetic Method for Formyl→
Ethynyl Conversion. Tetrahedron Lett. 1972, 13, 3769−3772.
(36) Vollhardt, K. P. C.; Schore, N. E. In Organische Chemie;
Butenschon, H., Ed.; Wiley-VCH: Weinheim, Germany, 2005.
̈
(37) Tillmann, J. C. Chlorid-induzierter Aufbau perchlorierter
Oligosilane ausgehend von Si2Cl6 oder HSiCl3. Ph.D. Thesis,
Goethe-Universitat Frankfurt, Frankfurt (Main), Germany, 2015.
̈
(38) Sheikh, S. U. A Systematic Study of the Thermal Decomposition
of Tetraalkylammonium Haloborates. J. Therm. Anal. 1980, 18, 299−
306.
(39) Noth, H.; Wrackmeyer, B. Nuclear Magnetic Resonance
̈
Spectroscopy of Boron Compounds. In NMRBasic Principles and
Progress; Diehl, P., Fluck, E., Kosfeld, R., Eds.; Springer: Berlin, 1978.
(40) Jansen, M.; Friede, B. Hexaiododisilane. Acta Crystallogr., Sect.
C: Cryst. Struct. Commun. 1996, 52, 1333−1334.
(41) The resonance of the minor component [BI3Cl]− was also
present in the 11B NMR spectrum. It arises from a side reaction of BI3
with the solvent CH2Cl2.
(42) Hubner, A.; Bolte, M.; Lerner, H.-W.; Wagner, M. Extensive
̈
Structural Rearrangements upon Reduction of 9H-9-Borafluorene.
Angew. Chem., Int. Ed. 2014, 53, 10408−10411.
(43) Braunschweig, H.; Radacki, K.; Uttinger, K. Syntheses of Mono-
and Dinuclear Diiodoboryl Complexes of Platinum. Inorg. Chem. 2007,
46, 8796−8800.
(44) Berger, M.; Auner, N.; Bolte, M. Hexabromo- and
Hexaiododisilane: Small and Simple Molecules Showing Completely
Different Crystal Structures. Acta Crystallogr., Sect. C: Struct. Chem.
2014, 70, 1088−1091.
(45) Grimme, S.; Antony, J.; Ehrlich, S.; Krieg, H. A Consistent and
Accurate Ab Initio Parametrization of Density Functional Dispersion
Correction (DFT-D) for the 94 Elements H-Pu. J. Chem. Phys. 2010,
132, 154104.
(46) Grimme, S.; Ehrlich, S.; Goerigk, L. Effect of the Damping
Function in Dispersion Corrected Density Functional Theory. J.
Comput. Chem. 2011, 32, 1456−1465.
(47) Becke, A. D.; Johnson, E. R. A Density-Functional Model of the
Dispersion Interaction. J. Chem. Phys. 2005, 123, 154101.
(48) Johnson, E. R.; Becke, A. D. A Post-Hartree−Fock Model of
Intermolecular Interactions. J. Chem. Phys. 2005, 123, 024101.
(49) Grimme, S.; Hansen, A.; Brandenburg, J. G.; Bannwarth, C.
Dispersion-Corrected Mean-Field Electronic Structure Methods.
Chem. Rev. 2016, 116, 5105−5154.
(50) Adamo, C.; Barone, V. Toward Reliable Density Functional
Methods without Adjustable Parameters: The PBE0 Model. J. Chem.
Phys. 1999, 110, 6158−6170.
(51) Weigend, F.; Ahlrichs, R. Balanced Basis Sets of Split Valence,
Triple Zeta Valence and Quadruple Zeta Valence Quality for H to Rn:
Design and Assessment of Accuracy. Phys. Chem. Chem. Phys. 2005, 7,
3297−3305.
(52) Grimme, S. Semiempirical Hybrid Density Functional with
Perturbative Second-Order Correlation. J. Chem. Phys. 2006, 124,
034108.
F
DOI: 10.1021/acs.inorgchem.7b00216
Inorg. Chem. XXXX, XXX, XXX−XXX