Disilane Cleavage with Selected Alkali and Alkaline Earth Metal Salts

Article abstract of DOI:10.1002/chem.201902722

The industry-scale production of methylchloromonosilanes in the Müller–Rochow Direct Process is accompanied by the formation of a residue, the direct process residue (DPR), comprised of disilanes Me_nSi₂Cl_6-n (n=1–6). Great research efforts have been devoted to the recycling of these disilanes into monosilanes to allow reintroduction into the siloxane production chain. In this work, disilane cleavage by using alkali and alkaline earth metal salts is reported. The reaction with metal hydrides, in particular lithium hydride (LiH), leads to efficient reduction of chlorine containing disilanes but also induces disproportionation into mono- and oligosilanes. Alkali and alkaline earth chlorides, formed in the course of the reduction, specifically induce disproportionation of highly chlorinated disilanes, whereas highly methylated disilanes (n>3) remain unreacted. Nearly quantitative DPR conversion into monosilanes was achieved by using concentrated HCl/ether solutions in the presence of lithium chloride.

Full text of DOI:10.1002/chem.201902722

A Journal of
Accepted Article
Title: Disilane Cleavage with Selected Alkali and Alkaline Earth Metal
Salts
Authors: Tobias Santowski, Alexander G. Sturm, Kenrick M. Lewis,
Thorsten Felder, Max C. Holthausen, and Norbert Auner
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Disilane Cleavage with Selected Alkali and
Alkaline Earth Metal Salts
Tobias Santowski[a], Alexander G. Sturm[a], Kenrick M. Lewis[b], Thorsten
Felder[c], Max C. Holthausen*[a], Norbert Auner*[a]
[a] Institut für Anorganische und Analytische Chemie, Goethe-Universität, Max-von-Laue-Straße
7, 60438 Frankfurt/Main (Germany), max.holthausen@chemie.uni-frankfurt.de,
auner@chemie.uni-frankfurt.de
[b] Momentive Performance Materials Inc., 769 Old Saw Mill River Rd, Tarrytown, NY 10591
(United States)
[c] Momentive Performance Materials GmbH, Chempark, 51368 Leverkusen (Germany)
Abstract: The industry-scale production of methylchloromonosilanes in the Müller–Rochow Direct
Process is accompanied by the formation of a residue, the direct process residue (DPR), comprised of
disilanes MenSi2Cl6–n (n = 1–6). Great research efforts have been devoted to the recycling of these
disilanes into monosilanes so as to allow reintroduction into the siloxane production chain. Herein we
report on disilane cleavage using alkali and alkaline earth metal salts. The reaction with metal hydrides,
in particular lithium hydride (LiH), leads to efficient reduction of chlorine containing disilanes but also
induces disproportionation into mono- and oligosilanes. Alkali and alkaline earth chlorides, formed in the
course of the reduction, specifically induce disproportionation of highly chlorinated disilanes, while
highly methylated disilanes (n > 3) remain unreacted. Nearly quantitative DPR conversion into
monosilanes was achieved using concentrated HCl/ether solutions in the presence of lithium chloride.
Introduction
Methylchlorosilanes MenSiCl4-n (n = 1–3) are produced in the Direct Process (DP)[1] at large scales
by reaction of elemental silicon with chloromethane. The production of the main product
Me2SiCl2,[2] however, is accompanied by formation of an unwanted residue (the DPR) comprised
of methylchlorodisilanes, MenSi2Cl6-n (n = 1–6) and, in minor amounts, of carbodisilanes that
accumulate in tens of thousands of tons annually.[3] Owing to the fact that enormous amounts of
silicon are consumed for DPR formation, great efforts have been spent in the past to devise
4]
preparative protocols for the conversion of the DPR into the corresponding monosilanes.[3a,
Specifically, the Lewis-base induced disproportionation of disilanes under moderate reaction
conditions and disilane splitting can be achieved by use of catalytic amounts of phosphines,[5]
amines,[6] as well as phosphonium or ammonium chlorides.[7] These reactions afford
transformation of the DPR constituents into silane monomers along with oligo- or polysilanes as
9]
side products.[8] Based on suggestions put forth in the literature[6a,
the course of disilane
cleavage involves nucleophilic attack of the Lewis-base at the disilane moiety with subsequent
extrusion of a Lewis-base stabilized silylene and formation of a monosilane. Silylene insertion into
a second disilane equivalent gives rise to trisilane formation. Reiteration of this step results in high
molecular weight, in some cases insoluble, polysilanes.[9b] To reduce oligosilane formation,
hydrogen chloride (HCl) is usually added as in situ trapping agent for the silylenes formed.[10] In
any case, the workup of these oligosilanes, or their disposal by incineration, reduces the
economic benefit of the overall DP significantly.
Recently we reported on the competitive chlorination and cleavage of methylhydridodisilanes with
ether/HCl solutions to yield bifunctional monosilanes in excellent yields.[11] The
methylhydridodisilanes used there were synthesized by reduction of the corresponding chloro
1
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substituted precursors with LiAlH4 as hydrogenation agent. In search of alternative hydride
sources, we reacted methylchlorodisilane mixtures mimicking the DPR with lithium hydride. To our
surprise we found that most disilanes are efficiently cleaved, resulting in formation of mostly
bifunctional monosilanes in high yields (see below). These findings prompted us to conduct
further investigations on the disilane hydrogenation and cleavage reactions with alkali- and
alkaline earth hydrides. The results of these studies are reported in the following.
A number of earlier studies by others showed that hydrogenation of chlorosilanes can efficiently
[13]
be achieved using complex reducing agents, such as LiAlH4[12], NaBH4 and LiBH4[14]. Also the
[17]
alkali metal hydrides LiH[15] and NaH[16] as well as alkaline earth metal hydrides such as MgH2
have been used for chlorosilane reduction. Polyether solvents were often used to activate LiBH4
and NaBH4 for reduction of, e.g., SiCl4, Me2SiCl2 or GeCl4.[18] Chlorosilane reductions are
generally performed at ambient temperatures (20–25°C) as temperatures above 100°C often
cause decomposition of the reducing agents or the desired product.[18] Moreover, calcium and
[20]
titanium hydrides[19], or mixtures of NaH/NaBH4
have been found effective in reduction
reactions, but all synthetic routes reported thus far are lacking selectivity and yield the perhydrido
substituted derivatives as main products.
Bifunctional monosilanes represent fundamentally important building blocks in silicone
technology. Utilizing (i) the Si-H functionality for hydrosilylation reactions to create silicon-carbon
bonds[21] and (ii) the Si-Cl functions for hydrolysis or alcoholysis, provides access to the
corresponding silanols or alkoxysilanes employed in condensation reactions to form the siloxane
22]
Si-O-Si bonding motif.[4k,
For the synthesis of bifunctional monosilanes, some preparative
protocols have been reported: As shown by D´Errico and Sharp for a variety of halosilanes, the
selective reduction of a single Si–Cl bond is possible using alkyltin hydrides.[23] Further, the
Roewer group converted Me2SiCl2 to Me2SiHCl with organotin hydrides in the presence of
phosphonium chlorides or amine bases.[24] More recently, Ir-mediated synthetic protocols utilizing
H2 as hydrogen source have been reported.[25] Alternatively, efficient access to monosilanes
R2SiHCl and RSiHCl2 has been established by selective chlorination of hydridomonosilanes with
HCl in the presence of catalytic amounts of Lewis acids[26] or Lewis-bases such as ethers,[27]
The efficient cleavage of silicon-silicon bonds with alkali metal salts was first reported by Ring and
coworkers.[28] This group studied reactions of Si2H6 with alkali metal chlorides and hydrides to
yield SiH4, -(SiH2)n- polymers and metal silanides,[29] and also the cleavage of some alkyldisilanes
was investigated.[30] Further, the pertinent patent literature reports on metal salt catalyzed
cleavage of different disilanes present in the DPR and disclosed alkali metal halides to form
complexes with various tertiary amines, that are effective in cleavage reactions.[31] We here report
on cleavage reactions of different methylchlorodisilanes with alkali and alkaline earth metal salts
to give monosilanes in high yields. We focus in particular on the synthesis of bifunctional
monosilanes, bearing both hydrido and chloro substituents, formed by simultaneous cleavage and
reduction of the disilanes present in the DPR.[28-30]
Results and Discussion
Highly chlorinated disilanes such as Cl2MeSi–SiMeCl2 (1, 50-75 wt% of the DPR) and ClMe2Si–
SiMeCl2 (2, 20-40 wt%) are referred to in the literature as ‘cleavable fraction’ of the DPR, because
they can be thermally cleaved by amine catalyzed reaction with HCl.[10a] In contrast, the term
‘uncleavable fraction’ has been coined for the highly methylated disilanes ClMe2Si–SiMe2Cl (3, 4-
10 wt%), Me3Si–SiMeCl2 (4, 2-4 wt%), Me3Si–SiMe2Cl (5, 3-6 wt%) and Me3Si–SiMe3 (6, 0-1 wt%)
as their cleavage requires harsh conditions.[3b, 3c, 4a, 4c, 32] Only recently cleavage of these disilanes
has been reported but yields of bifunctional monosilanes were low.[4a] In principle, the
‘uncleavable’ fraction of the DPR can be transformed into ‘cleavables’ by high temperature Si-
Cl/Si-Me redistribution reactions with HCl in the presence of AlCl3,[33] but clearly this process is
cumbersome.
2
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Table 1 lists the numbering scheme of starting materials and products relevant in this study,
procedures as well as NMR spectroscopic data are provided as Supporting Information. Disilanes
were separated from authentic industrial DPR samples and hydridodisilanes and
hydridocarbodisilanes were obtained by reduction of chlorinated precursors with LiAlH4
maintaining the Si–Si and the Si–C–Si backbone.
Table 1: Numbering scheme of silanes reacted and reaction products formed.
No.
Compounds
No.
Compounds
Me3SiCl
No.
Compounds
1
Cl2MeSi-SiMeCl2
ClMe2Si-SiMeCl2
ClMe2Si-SiMe2Cl
Me3Si-SiMeCl2
Me3Si-SiMe2Cl
Me3Si-SiMe3
MeSiCl3
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
Cl2MeSi-SiMe2H
2
Me3SiH
ClMe2Si-SiMeH2
3
H2MeSi-SiMeH2
HMe2Si-SiMeH2
HMe2Si-SiMe2H
Me3Si-SiMeH2
Me3Si-SiMe2H
ClMe2Si-SiMe2H
Cl2MeSi-SiMeClH
HClMeSi-SiMeClH
Cl2MeSi-SiMeH2
HClMeSi-SiMeH2
ClMe2Si-SiMeClH
HMe2Si-SiMeClH
4
Cl2MeSi-CH2-SiMeCl2
ClMe2Si-CH2-SiMeCl2
ClMe2Si-CH2-SiMe2Cl
Me3Si-CH2-SiMeCl2
Me3Si-CH2-SiMe2Cl
Me3Si-CH2-SiMe3
5
6
7
8
MeSiHCl2
9
MeSiH2Cl
10
11
12
13
MeSiH3
Me3Si-CH2-SiMe2H
HMe2Si-CH2-SiMe2H
HMe2Si-CH2-SiMeH2
H2MeSi-CH2-SiMeH2
Me2SiCl2
Me2SiHCl
Me2SiH2
To study the reduction and cleavage of disilanes with lithium hydride we chose
tetramethyldichlorodisilane (3) as a representative model compound for the “uncleavable” fraction
of the DPR. 3 was quantitatively reduced at room temperature (r.t.) to tetramethyldisilane 18 with
two equivalents of lithium hydride (eq. 1).
ClMe2Si–SiMe2Cl + 2 LiH → HMe2Si–SiMe2H + 2 LiCl (1)
Increase of the reaction temperature to 140 °C with excess of LiH led to cleavage of 18 to form
dimethylsilane (94 %) together with the NMR-detectable oligosilanes HMe2Si–(SiMe2)n–SiMe2H (n
= 1–3, 6%, cf. the SI).[34] In contrast to the mechanistic picture recently established[35] we found
that lithium chloride does not afford disilane cleavage: In a set of NMR experiments, no reaction
with lithium chloride was observed for disilanes 16[36] and 18 even at elevated temperatures. Also
in contrast to earlier reports,[28a, 30] both disilanes were efficiently cleaved into silane monomers
with lithium hydride. Already at r.t. the reaction with 16 afforded MeSiH3 (44 %) along with
oligosilanes (4 %), 52 % of disilane 16 remained uncleaved. Upon increasing the reaction
temperature to 60 °C, only MeSiH3 was identified by 29Si NMR spectroscopy. The reaction of 18
with excess LiH was studied further in variable-temperature NMR experiments: Me2SiH2 was,
apart from traces of oligosilanes, the only product detectable up to 140°C.[37]
3
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Scheme 1: Suggested mechanism of the LiH induced formation of HMe2Si (A) and Me2SiH2 with concomitant aufbau
of higher oligosilanes. The inset shows the transition state structure TS– computed for the proton abstraction step with
selected structural parameters.
Based on earlier detailed studies on the chloride-induced aufbau of higher perchlorinated
oligosilanes from Si2Cl6,[35] we devised a tentative reaction mechanism for the cleavage of disilane
18 (Scheme 1). As initial step we assume formation of a silicate DH– by attachment of a hydride
ion, released from the LiH solid, to one of the silicon centers in disilane 18 (D), which
subsequently undergoes Si–Si bond cleavage to give Me2SiH2 (M) and the silanide anion HMe2Si–
(A–).[35a, 38] The silanide A– can then abstract a proton[39] from another equivalent of D to yield
–
monosilane Me2SiH2 (M) along with the higher silanide anion HMe2Si–SiMe2 (B–). A quantum
chemical assessment of this step at the SMD(THF)-M062X/6-31+G(d,p) level reveals a moderate
exoergicity (∆RG = –4 kcal mol–1) and an activation barrier of ∆‡G = 28 kcal mol–1 (Scheme 1),
which is in line with a reaction efficiently taking place only at elevated temperature. Alternatively,
A– can add to D to yield the higher silicate T–. This species can then either undergo hydride
migration to the terminal silyl group followed by Si–Si bond cleavage to yield M and B–, or release
a hydride ion back to the LiH solid, which results in formation of the trisilane T. With T undergoing
the same reaction cascade the formation of higher oligosilanes HMe2Si–(SiMe2)n–SiMe2H results,
which eventually become insoluble and escape NMR spectroscopic identification (for
characterized species with n = 1–4 see Supporting Information). Overall, this scenario is in line
with former work[30] of Ring et al. who showed that disilane cleavage with lithium hydride results in
monosilanes, oligosilanes and/or lithium silanides. At variance with Ring’s experiments conducted
at r.t. we do observe, however, cleavage of multiply methylated disilanes with lithium hydride at
elevated reaction temperatures. We note in passing that neither 3 nor 18 react with LiCl, even at
temperatures as high as 220 °C.
Much to our surprise, dimethyltetrachlorodisilane (1), chosen as representative model for the
‘cleavable’ fraction of the DPR, does not form dimethyltetrahydridodisilane 16 upon reaction with
4 equiv. LiH but undergoes quantitative cleavage into monosilanes. Most notably, the industrially
important bifunctional silanes MeSiHCl2 and MeSiH2Cl comprise almost 80% of the product
mixture obtained at r.t. We optimized their yield by using substoichiometric amounts of LiH: The
reaction with 1.3 equiv. LiH yields 8 and 9 in almost 90 %, with 8 in significant excess (Table 2).
4
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Table 2: Reaction products from Cl2MeSi-SiMeCl2 (1) and different molar amounts of LiH (mol%).
1.3 equiv.
LiH
1.3 equiv.
LiH
2.7 equiv.
LiH
2.7 equiv.
LiH
4.0 equiv.
LiH
4.0 equiv.
Compound
LiH
r.t.
60 °C
r.t.
60 °C
r.t.
60 °C
MeSiCl3 (7)
MeSiHCl2 (8)
MeSiH2Cl (9)
MeSiH3 (10)
11
74
15
-
1
2
-
1
-
49
40
10
47
40
11
15
44
41
32
46
21
8
35
57
In contrast to our observations for 18 detailed above, the analogous reduction of disilane 1 to
yield 16 is not possible with LiH. Instead, Si–Si bond cleavage interferes and 1 is quantitatively
converted into monosilanes already at r.t. (Table 2; oligosilanes necessarily formed in this
process are not NMR visible). Evidently, partial reduction of 1 has taken place already with 1.3
equiv. LiH at r.t. giving rise to the formation of LiCl, which might trigger chloride-induced disilane
disproportionation under these conditions.[35] This supposition was corroborated in further
experiments: Treatment of 1 with catalytic amounts of LiCl at r.t. in polar solvents such as glymes,
THF or 1,4-dioxane resulted in MeSiCl3 formation, comprising 50 % of the reaction mixture along
with unreacted 1 and oligosilanes according to 29Si NMR. Full consumption of 1 is observed at
longer reaction times and higher temperatures (Table 3).[34d] This observation contrasts the
inability of LiCl to induce cleavage of highly methylated disilane 3; also the fully reduced
dimethyldisilane 16 shows no sign of Si–Si bond cleavage in the presence of LiCl (cf. the SI).
Table 3: Cleavage reactions of Cl2MeSi-SiMeCl2 (1) with LiCl at different temperatures (mol%).
r.t.
(30 h)
Compound
r.t. (60 h)
60°C (2 h)
80°C (2 h)
100°C (2 h)
120°C (2 h)
220°C (6h)
Cl2MeSi-SiMeCl2 (1)
MeSiCl3 (7)
44
28
66
6
21
69
10
5
87
8
4
91
5
2
93
5
1
96
3
50
6
Oligosilanes
We thus conclude that reaction of disilane 1 with LiH initially leads to partial reduction and
kinetically favored Si–Si bond cleavage sets in once sufficient amounts of LiCl are formed. The
resulting monosilanes, in turn, are then partially reduced by LiH to yield the bifunctional
monosilanes observed in the experiments. These findings complement our related study on the
disilane cleavage with phosphonium chloride salts[40] and will be addressed again in the next
section.
For further scrutiny we investigated the reaction of an authentic sample of a highly chlorinated
DPR fraction, comprised of 1 (69 mol%), 2 (26%), 3 (4%), and 4 (1%) dissolved in diglyme, with
LiH (50 mol% with reference to the total chlorine content of the mixture). After about 30 min at
60 °C disilanes were almost quantitatively consumed and the bifunctional monosilanes MeSiH2Cl
(33 %), MeSiHCl2 (21 %), and Me2SiHCl (9 %) were formed along with MeSiCl3, Me2SiCl2, and
Me3SiCl (together 23 %) and MeSiH3 (13 %). As detailed in the Supporting Information, use of
substoichiometric amounts of LiH leads to predominant formation of bifunctional monosilanes in
up to 70%, whereas use of 400 mol% LiH results in complete reduction to Me2SiH2 (6%) and
MeSiH3 (78%) together with formation of hydridodisilanes 16–19 (16%) that remained stable
under the reaction conditions. Treatment of a mixture of the highly methylated chlorodisilanes 3–4
with different molar amounts of LiH, in turn, led to partial disilane reduction while cleavage
5
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reactions were not detected in significant amounts in most cases. Only the reaction with a high
excess of LiH (350 mol%) led to 50% disilane cleavage at 140 °C (cf. Table S10).
Generally, the disilane fraction of the DPR is contaminated with carbodisilanes. A representative
mixture of 30 (45%), 31 (31%), 32 (14%), 34 (10%) and 35 (1%) was reacted with excess LiH
(suspended in diglyme in a sealed NMR tube, cf. section 6 in the Supporting Information). Heating
the sample to 180°C led to carbodisilane reduction and Si–C cleavage to give MeSiH3 (37%) and
Me2SiH2 (31%) as main products, along with the hydridocarbodisilanes 36–39 (32%).[41] Scheme
3 illustrates a tentative mechanistic suggestion that involves initial hydride-induced Si–C bond
cleavage resulting in formation of methylsilanes together with lithium silanides. The latter undergo
coupling with chlorinated monosilanes to form disilanes,[42] which are subsequently cleaved in the
presence of excess LiH.[43]
Scheme 3: Proposed reaction pathway for the cleavage of carbodisilanes to yield disilanes that are subsequently
cleaved by LiH.
The suitability of other alkali- and alkaline earth metal chlorides to induce disilane
disproportionation was investigated in reactions with an industrial DPR mixture (cf. Table S29):
While disilane conversion was found most effective with LiCl in diglyme, the use of NaCl, KCl,
CaCl2, and MgCl2 is impeded by their lower solubility. Acceptable reaction rates, however, were
found in tetraglyme at 140 °C and above. In exemplary reactions performed at a preparative scale
with both, LiCl and KCl, the DPR mixture was efficiently converted: with a maximum theoretical
yield of 50% the disproportionation led to 42% monosilanes (predominantly MeSiCl3 and
Me2SiCl2, cf. Supporting Information). The residue remaining after distillation of the monosilanes
consists of highly methylated disilanes, carbodisilanes and oligosilanes. A broad signal at
+35 ppm in the 29Si NMR spectrum of the sample was assigned to branched oligosilanes with
terminal Cl2MeSi groups. Slightly higher conversion ratios were obtained with LiCl at 220 °C.[44]
In summary, we have shown that chlorosilane reduction is possible with lithium hydride, which
thereby is established as economically favorable alternative to LiAlH4. We have further shown that
LiCl, formed in the course of the reduction of chlorinated disilanes with LiH, acts as an efficient
catalyst to trigger disproportionation of disilanes bearing SiMeX2 groups (X = H, Cl) into the
corresponding mono- and higher oligosilanes.[45] Si–Si bond cleavage of highly methylated as well
as perhydrogenated disilanes was not observed with lithium chloride. We found, however, that
lithium hydride efficiently triggers disproportionation of perhydrogenated disilanes into MeSiH3,
Me2SiH2, and Me3SiH and oligosilanes.
Experimental
General procedure for disilane cleavage reactions: For the elucidation of the reaction conditions, disilanes
MenSi2Cl6-n (n=2-6) were isolated from the DPR by fractional distillation and investigated as pure model
compounds or in complex mixtures. The reactants e.g. HCl/ether solutions, catalysts and solvents were placed
in an NMR tube under nitrogen atmosphere and cooled to -196°C, subsequently the disilanes were added and
frozen. Then the NMR tube was evacuated (at -196 °C) and sealed in vacuo to avoid losses of low boiling
monosilanes, such as MeSiH3 (b.p. -58 °C), Me2SiH2 (b.p. -20 °C), MeSiH2Cl (b.p. -46 °C), MeSiHCl2 (b.p.
41 °C) and Me2SiHCl (b.p. 35 °C). After warming the mixture to r.t. the reaction temperatures were increased,
6
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10.1002/chem.201902722
Chemistry - A European Journal
and the course of reaction was followed by NMR spectroscopy, especially by 29Si-NMR. The molar ratios of
products formed were determined by integration of product specific NMR signals in the resulting mixtures.
According to the optimum reaction conditions evaluated from the NMR investigations, upscaling was performed
with larger amounts of starting materials in closed reaction ampules. Filling of reactants was similar as
described for the experiments in sealed NMR tubes. Alternatively, upscaling was performed in open systems.
This procedure is described in the Supporting Information.[40]
Acknowledgements
We thank Momentive Performance Materials, Leverkusen, Deutschland, for financial support and
generous gifts of chlorosilanes.
Keywords: Disilane Cleavage; Monosilanes; Alkali and Alkaline Earth Metal Salts; Lithium
Chloride; Lithium Hydride.
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Obtained from reduction fo disilane 1 with LiAlH4.
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8
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10.1002/chem.201902722
Chemistry - A European Journal
[43]
The general applicability of the procedure was demonstrated for an authentic industrial DPR mixture
representing the conventionally ‘uncleavable’ fraction as detailed in the Supporting nformation. lternative
hydride donors such as sodium or calcium hydride require higher temperatures to induce the same
reactivity.
[44]
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In case LiH was used for oligosilane cleavage at 180 °C, MeSiH3 (10) was formed in 52%, MeSiH2Cl (9) in
28% as NMR detectable thermolysis products. The oligosilanes were cleaved as indicated by the
disappearance of the corresponding 29Si NMR signal of the sample (SI 9.).
We have shown in earlier work that highly chlorinated disilanes can efficiently be cleaved with with
concentrated ether/HCl solutions in the presence of catalytic amounts of phosphines and phosphonium
chlorides.[40] In the present context, we have found that this cleavage reaction can be catalysed by LiCl
instead of phosphonium chlorides with equal efficiency: Reaction of a disilane mixture mainly consisting of
1 (50%) and 2 (33%) with a 12M diglyme/HCl solution (1:1 molar ratio disilanes/HCl) in the presence of
catalytic amounts of LiCl led to nearly quantitative monosilane formation (97%, 80°C). The corresponding
reaction with KCl yielded monosilanes was less efficient (70% conversion to monosilanes, 100°C; cf. SI 12
and 13).
9
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10.1002/chem.201902722
Chemistry - A European Journal
FULL PAPER
Tobias Santowski, Alexander G. Sturm,
Kenrick M. Lewis, Thorsten Felder, Max
C. Holthausen*, Norbert Auner*
Page No. – Page No.
Disilane Cleavage with Selected Alkali
and Alkaline Earth Metal Salts
Too valuable for disposal or incineration: Simple recycling of the Müller-Rochow
Direct Process Residue with LiH yields monosilanes suitable for reintroduction into the
silicone production chain.
10
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