Preparation of aminomethyl functionalised silanes via an α-lithiated amine: From their synthesis, stability and crystal structures to stereochemical issues

Article abstract of DOI:10.1039/c2dt12163h

The preparation of aminomethyl functionalised silanes based on the α-lithiated amine, (1R,2R)-N,N,N′,N′-tetramethylcyclohexane-1, 2-diamine [(R,R)-TMCDA] is reported. This methodology can be applied for the synthesis of mono-aminomethyl substituted systems, but most remarkably also for di- and trifunctionalised compounds. The trapping of the lithiated amine is accompanied by transmetallation reactions resulting in the formation of (silylmethyl)silanes depending on the reaction temperature. The zinc(ii) halide complexes of the mono-functionalised systems show the formation of exclusively one configuration of the stereogenic nitrogen atom, in which the spatially more demanding substituent exhibits the pseudo-equatorial position. The di- and trifunctionalised systems feature high sensitivity towards Si-C bond cleavage under re-formation of the (R,R)-TMCDA fragment. The Royal Society of Chemistry 2012.

Full text of DOI:10.1039/c2dt12163h

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PAPER
Preparation of aminomethyl functionalised silanes via an α-lithiated amine:
From their synthesis, stability and crystal structures to stereochemical issues†
Viktoria H. Gessnera,b and Carsten Strohmann*a
Received 12th November 2011, Accepted 18th December 2011
DOI: 10.1039/c2dt12163h
The preparation of aminomethyl functionalised silanes based on the α-lithiated amine, (1R,2R)-N,N,N′,N′-
tetramethylcyclohexane-1,2-diamine [(R,R)-TMCDA] is reported. This methodology can be applied for
the synthesis of mono-aminomethyl substituted systems, but most remarkably also for di- and
trifunctionalised compounds. The trapping of the lithiated amine is accompanied by transmetallation
reactions resulting in the formation of (silylmethyl)silanes depending on the reaction temperature. The
zinc(II) halide complexes of the mono-functionalised systems show the formation of exclusively one
configuration of the stereogenic nitrogen atom, in which the spatially more demanding substituent
exhibits the pseudo-equatorial position. The di- and trifunctionalised systems feature high sensitivity
towards Si–C bond cleavage under re-formation of the (R,R)-TMCDA fragment.
others, the chiral (1R,2R)-N,N,N′,N′-tetramethylcyclohexane-1,2-
Introduction
diamine [(R,R)-TMCDA, (R,R)-1] and the commonly used
TMEDA (N,N,N′,N′-tetramethylethylenediamine).6 These depro-
α-Functionalised silanes, above all alkoxysilanes, find various
applications in industry such as for surface modification,
adhesion promotion or the crosslinking of silicones.1 Amongst
others, amino, epoxy and glycidoxy, mercapto and sulfido substi-
tuents are used as functional groups. These functionalities are
described to crucially influence the properties of the silane,
which is commonly known as the so-called α-effect.2 One intri-
guing example is the acceleration of the hydrolysis of the alkoxy
functions upon the introduction of an aminomethyl function.3
The preparation of the required α-aminosilanes of type B is
usually accomplished by substitution reaction of a (chloro-
methyl)silane A with the corresponding secondary amine
(Scheme 1, route I).4 This synthetic route, however, lacks the
accessibility of these silanes,5 so that alternative preparation
methodologies, especially via the cheap and in many varieties
available chlorosilanes C, are desired. To accomplish the
preparation of B starting from chlorosilanes α-amino-substituted
carbanions are necessary. Due to the low acidity of the α-hydro-
gen atom and the involved hindered deprotonation this route has
not been considered relevant until now.
tonations occurred in high yields even at room temperature and
on a preparative scale. As such, it was possible to apply the
obtained lithiated building blocks to the introduction of a nitro-
gen function giving way to a series of new ligand systems.7
Motivated by these results we aimed at expanding the applica-
bility of these building blocks for the synthesis of aminomethyl
functionalised silanes starting from simple chlorosilanes. Special
focus was given to the preparation of oligo(aminomethyl) func-
tionalised silanes, as these compounds seem to be difficult to
access via the (chloromethyl)silane (route I, Scheme 1). To the
best of our knowledge, only one example each of a tri- and
tetra(aminomethyl) functionalised silane is known. Interestingly,
while Tacke and coworkers succeeded in the preparation of
silane 2 via route I,8 Karsch proved the synthetic potential of
their dilithiated diamine {[LiCH2N(Me)CH2]2} as functionalised
building block (Fig. 1).9 This synthesis of spiro compound
3 underlines the great potential of α-amino-substituted carba-
nions for such functionalisations. Herein we report on the
preparation of (aminomethyl)silanes on the basis of α-lithiated
In the course of our studies on Lewis base coordinated orga-
nolithium compounds, we recently reported on the direct lithia-
tion of a series of tertiary methylamines, including, amongst
aAnorganische Chemie, Technische Universität Dortmund, Otto-Hahn-
Straße 6, 44263 Dortmund, Germany. E-mail: mail@carsten-strohmann.
de; Fax: (+) 49-231-755-7062; Tel: (+) 49-231-755-3807
bInstitu für Anorganische Chemie, Julius-Maximilians-Universität
Würzburg, Am Hubland, 97074 Würzburg, Germany
†Electronic supplementary information (ESI) available: Crystallographic
details, NMR spectra. CCDC reference numbers 851902–851906. For
ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/c2dt12163h
Scheme 1 General preparation methods of (aminomethyl)silanes of
type B via the (chloromethyl)silane A or the chlorosilane C.
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obtained for the dimethylphenyl and the diphenylmethylsilane
(R,R)-6 and (R,R)-7 by dissolving the corresponding silane in
acetone or acetone/diethyl ether with an equivalent amount of
the metal salt. After slow evaporation of the solvent the zinc
bromide adducts were obtained as colourless crystals. The
crystal structures of both compounds are depicted in Fig. 2. The
zinc complexes are part of systematic studies on the catalysis of
lactide ring-opening polymerisation. Analogous complexes with
TMCDA-based diamine ligands have revealed to be efficient
initiators for this transformation.12
Fig. 1 Reported tri- and tetra(aminomethyl)silanes.8,9
(R,R)-TMCDA. Besides the introduction of one diamine moiety,
the di- and tri-substitution reactions are also presented.
Both complexes (RC,RC,RN)-8 and (RC,RC,RN)-9 crystallise as
monomeric adducts in the monoclinic crystal system, space
group P21. The asymmetric unit of (RC,RC,RN)-9 contains two
molecules, one of which is shown in Fig. 2. For selected bond
lengths and angles, see Table 1; for crystallographic details and
structure refinement, see Table 3 and the supporting infor-
mation.† In both structures, the zinc(II) bromide is coordinated
by the TMCDA side-arm resulting in a distorted tetrahedral
coordination environment of the zinc atom. The angles around
the metal atom range from 87.8(1) to 117.0(1)° and 87.3(2) to
117.1(1)°, respectively, with the smallest angle being the bite
angle to the diamino side-arm. The angles around silicon differ
only slightly from the ideal tetrahedral angle. In both cases the
R,R-configuration of the stereogenic carbon centres of the
diamine is evident. The complexation also in solution is
Results and discussion
Mono-functionalised silanes
To evaluate the potential of lithiated amines for the preparation
of functionalised silanes, (R,R)-TMCDA [(R,R)-1] was first
applied for the synthesis of mono-functionalised systems.
(R,R)-1 is readily available by racemic resolution of a mixture of
all isomers (RR, SS, cis) with L-tartaric acid and subsequent
methylation via Eschweiler–Clarke reaction.10 Note, that also the
racemic mixture of the amine is known to undergo deprotonation
reaction of the N-methyl group.7 However, the enantiomeric pure
compound was chosen to ease analysis of the desired silyl com-
pounds, especially the multiple functionalised systems.
For the preparation of the (aminomethyl)silanes the chiral
diamine was treated with tert-butyllithium in n-pentane at room
temperature for deprotonation of its methyl group. As outlined in
Scheme 2 the thus obtained lithiated amine 4 was in situ reacted
with different chlorosilanes at low reaction temperatures (for
details see the experimental section). After aqueous work-up and
distillation the (aminomethyl)-silanes (R,R)-5, (R,R)-6 and (R,R)-
7 were obtained as colourless oils in only moderate yields of 49
to 62%. The dimethylphenyl compound (R,R)-6 has already
been described before in context of the preparation of Si-chiral
compounds by diastereoselective deprotonation of its diastereo-
topic methyl groups.11 All compounds were characterised by
multinuclear NMR spectroscopy, elemental analysis and mass
spectrometry. It is noteworthy, that due to the chiral side-arm the
phenyl substituents in (R,R)-7 are diastereotopic, so that two sets
of signals are observed in the 1H and 13C NMR spectra.
The stereoinformation of the chiral nitrogen side-arm is
retained during the whole reaction sequence of lithiation and
trapping reaction. This is evidenced by optical rotation measure-
ments and single-crystal X-ray diffraction analyses of the corre-
sponding zinc(II) bromide complexes (see below) in combination
with NMR studies. The zinc(II) bromide complexes were
Scheme 2 Preparation of functionalised silanes 5–7 via α-lithiated
(R,R)-TMCDA, (R,R)-1. (i) tBuLi, pentane, −30 °C → rt; (ii) RR′2SiCl.
Fig. 2 Molecular structure and numbering scheme of the zinc com-
plexes (RC,RC,RN)-8 (top) and (RC,RC,RN)-9 (bottom).
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Table 1 Selected bond lengths (Å) and angles (°) for 8, 9, 12
(RC,RC,RN)-8
Zn–Br(1)
Zn–Br(2)
Si(1)–C(10)
Si(1)–C(11)
2.349(1)
2.358(1)
1.894(4)
1.873(4)
87.8(1)
112.3(1)
110.8(1)
114.4(2)
111.8(2)
Zn–N(1)
Zn–N(2)
Si(1)–C(12)
Si(1)–C(13)
Br(1)–Zn–Br(2)
N(2)–Zn–Br(1)
N(2)–Zn–Br(2)
C(10)–Si–C(13)
C(11)–Si–C(12)
2.088(3)
2.092(3)
1.888(4)
1.890(3)
117.0(1)
113.5(1)
111.9(1)
103.7(2)
109.5(2)
N(1)–Zn–N(2)
N(1)–Zn–Br(1)
N(1)–Zn–Br(2)
C(10)–Si–C(11)
C(10)–Si–C(12)
Scheme 3 Trapping reaction of diphenylmethylchlorosilane to (R,R)-7
and (R,R)-10 via transmetallation; (i) t-BuLi, −30 °C to rt, 4h; (ii)
Ph2MeSiCl, low temperature, aqueous work-up.
(RC,RC,RN)-9a
Zn–Br(1)
Zn–Br(2)
Si(1)–C(10)
Si(1)–C(11)
N(1)–Zn–N(2) 87.3(2) 87.2(2)
N(1)–Zn–Br(1) 110.5(1) 111.5(1) N(2)–Zn–Br(1) 114.1(15) 115.1(1)
N(1)–Zn–Br(2) 109.2(1) 109.6(1) N(2)–Zn–Br(2) 114.6(1) 111.9(2)
C(10)–Si–C(11) 114.9(3) 112.0(3) C(10)–Si–C(18) 105.3(3) 105.3(3)
2.354(1) 2.356(1) Zn–N(1)
2.362(1) 2.367(1) Zn–N(2)
1.873(7) 1.878(6) Si(1)–C(12)
1.849(7) 1.818(7) Si(1)–C(18)
2.065(6) 2.077(6)
2.093(6) 2.100(5)
1.881(7) 1.870(8)
temperature with a decrease of transmetallation α to silicon at
lower trapping temperatures. While at −30 °C compound (R,R)-
10 has been formed in half the amount of the simple trapping
product, only a 4 : 1 mixture has been observed at −70 °C
(Scheme 3). The same side reaction was also observed for the
preparation of silane (R,R)-5, however with smaller amounts of
the corresponding (silylmethyl)silyl compound (R,R)-11. Here,
at −78 °C, only a 9 : 1 mixture was obtained, while at −30 °C a
3 : 1 mixture was obtained.
1.895(6) 1.900(7)
Br(1)–Zn–Br(2) 117.1(1) 117.6(1)
C(10)–Si–C(12) 110.8(3) 112.0(3) —
—
(RC,RC,RN)-12
Zn–Br(1)
Zn–Br(2)
Si(1)–C(10)
Si(1)–C(11)
Si(2)–C(23)
Si(2)–C(24)
N(1)–Zn–N(2)
N(1)–Zn–Br(1)
N(1)–Zn–Br(2)
C(10)–Si(1)–C(11)
C(10)–Si(1)–C(17)
C(23)–Si(2)–C(24)
C(23)–Si(2)–C(31)
2.351(1)
2.362 (1)
1.906(3)
1.873(3)
1.870(2)
1.884(3)
88.0 (1)
112.0(1)
110.0(1)
109.4(1)
103.1(1)
110.3(1)
113.0(1)
Zn–N(1)
Zn–N(2)
2.085(2)
2.100(2)
1.880(3)
1.857(2)
1.882(3)
1.864(2)
116.2(1)
114.9(1)
112.4(1)
113.0(1)
120.2(1)
107.6(1)
—
Si(1)–C(17)
Si(1)–C(23)
Si(2)–C(30)
Si(2)–C(31)
Br(1)–Zn–Br(2)
N(2)–Zn–Br(1)
N(2)–Zn–Br(2)
C(10)–Si(1)–C(23)
Si(1)–C(12)–Si(2)
C(23)–Si(2)–C(30)
—
The observed transmetallation in the α-position is in line with
the well-known anion-stabilizing ability of silyl groups, which is
due to the high polarisability of Si and the presence of low-lying
σ*-SiR orbitals allowing for negative hyperconjugation.14 This
stability of the silyl substituted carbanion corroborates with the
thermodynamic preference observed in experiment. The for-
mation of the transmetallation products (R,R)-10 and (R,R)-11
can be minimized by simple addition of the lithiated amine
(R,R)-4 to the chlorosilane. We have recently used this increased
acidity of the methyl groups bound to silicon in diastereoselec-
tive deprotonation reactions to access Si-chiral compounds.11
Analogously to the simple trapping products (R,R)-6 and
(R,R)-7, the transmetallation product (R,R)-10 was transferred
into the corresponding zinc(II) bromide complex (RC,RC,RN)-12
by slow evaporation of a solution of (R,R)-10 in acetone. (RC,RC,
RN)-12 crystallises in the orthorhombic crystal system, in the
space group P212121. One additional solvent molecule crystal-
lises in the asymmetric unit (not depicted in Fig. 3). For selected
bond lengths and angles, see Table 1; for crystallographic
details and structure refinement, see Table 3 and the supporting
information.† Comparable to (RC,RC,RN)-8 and (RC,RC,RN)-9,
the zinc atom exhibits a distorted tetrahedral coordination by
complexation through the amino side-arm, which again exhibits
R,R-configuration at the stereogenic carbon atoms. The complex
possesses structural features analogous to the presented zinc(II)
bromide complexes (R,R)-8 and (R,R)-9 (Fig. 2).
a Complex 9 contains two molecules in the asymmetric unit. Values for
both molecules are given.
confirmed by NMR spectroscopy of the zinc(II) adducts. Upon
coordination of the metal the configuration of the nitrogen atoms
becomes fixed. As such the methyl groups of the N(CH3)2
moiety become diastereotopic and appear as two singlet reson-
ances in the 1H and 13C NMR spectra (see SI†).
As the lithiation of TMCDA to 4 itself was found to occur
quantitatively,7 the trapping reactions according Scheme 2 were
investigated more carefully to explain the moderate yields (49 to
62%) of the obtained mono-functionalised silanes 5–7. Typically
such substitution reactions of chlorosilanes with organolithium
compounds are known to proceed quantitatively.13 For this
purpose, the treatment of (R,R)-4 with diphenylmethylchlorosi-
lane was accomplished at different reaction temperatures and the
crude product (prior work-up) studied by NMR spectroscopy.
Besides the simple substitution product (R,R)-7 (Scheme 2), the
formation of a second amino-functionalised compound was
observed. The isolation finally revealed the (silylmethyl)silyl
compound (R,R)-10 as by-product of the trapping reaction. This
compound is formed by deprotonation of the methyl group
of the initially formed silane 7 and its subsequent reaction with
still present chlorosilane. As investigated for the diphenylmethyl-
silane, this transmetallation reaction depends on the trapping
An intriguing feature of all isolated zinc(II) bromide com-
plexes is the selective formation of one specific configuration at
the stereogenic nitrogen atom N(2) (see Fig. 2 and 3). Upon
coordination of the zinc salt to the diamino side-arm the silyl
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Fig. 3 Molecular structure of the zinc(II) bromide complex (RC,RC,
RN)-12 of compound 10.
Scheme 4 Preparation of multiple TMCDA functionalised silanes.
Bis- and tris(aminomethyl)-functionalised silanes
To further evaluate the potential of lithiated (R,R)-TMCDA as
building block for the synthesis of organometallic compounds
multiple functionalisations were attempted. The target molecules
were also expected to serve as interesting multidentate ligand
systems with intriguing coordination behaviour. For these
multiple functionalisations the lithiated amine was cautiously
treated with dichlorodimethylsilane and trichloromethylsilane
(Scheme 4). After an aqueous work-up and Kugelrohr distillation
the desired bis- and tris(aminomethyl)-functionalised silanes 13
and 14 were obtained in 68 and 31% yield as colourless oils.
These compounds are rare representatives of oligo-aminomethyl
functionalised silanes.17 Especially, tris(aminomethyl)silanes are
difficult to access by the common synthetic route via (chloro-
methyl)silane and the corresponding secondary amine (route I,
Scheme 1). This is also due to the limited pathways to multiple
chloromethyl substituted silanes.18 To the best of our knowledge,
14 is even the first chiral tris(aminomethyl)silane.
The low yield of 14 can be attributed to the sensitivity of the
compound towards moisture, leading to the Si–C bond cleavage
under re-formation of (R,R)-TMCDA. Due to this reactivity—
which has not been observed for any of the other presented
silanes—the aqueous work-up resulted in the loss of product.
Interestingly, the sensitivity of 14 is only observed in solution.
The compound itself can be stored without any precautions for
weeks.
The decomposition of 14 by Si–C bond cleavage was studied
by NMR spectroscopy in non-dried benzene-d6. We assumed
that under these conditions hydrolysis would be slow enough to
also detect intermediate products of the hydrolysis. Indeed, the
decomposition occurs slow enough to be followed by NMR
spectroscopy. Hydrolysis of 30 mg silane in 0.7 mL C6D6 is
completed after 60 h. Fig. 5 depicts an extract of the NMR
spectra showing the methyl functions at the nitrogen atoms
of silane 14 (blue) and the NMe2 groups of the formed
(R,R)-TMCDA (1) (red). However, no further amine functiona-
lised silanes could be detected during this decomposition
process. This suggests an “auto-catalytic” process, in which the
Fig. 4 Scheme of the preferred configuration at the stereogenic nitro-
gen atom in the ZnBr2 adduct of (RC,RC,RN)-6; arrangement of the
spatially more demanding substituent (red) in pseudo-equatorial
position.
substituted nitrogen atom becomes stereogenic. Most interest-
ingly, all complexes feature R-configuration at the nitrogen. In
this configuration, the sterically more demanding substituent
adopts the pseudo-equatorial position of the five-membered ring,
which is formed upon coordination of the metal salt to the
diamino side-arm (Fig. 4). For a more detailed study, the zinc(II)
chloride complexes of silanes (R,R)-5 and (R,R)-6 were also syn-
thesised (for crystallographic details, bond lengths and ORTEP
plots of these complexes, see ESI†). Comparable to the zinc(II)
bromide complexes (Fig. 2, Fig. 3) the structures of the ZnCl2
adducts feature monomeric compounds, all of which show the
pseudo-equatorial arrangement of the spatially more demanding
silyl substituent and thus one specific configuration of the stereo-
genic nitrogen atom. This selective formation of one configur-
ation may be of interest for asymmetric transformations
employing complexes in transition metal-catalysed reaction such
as the presented zinc(II) adducts. Here, complexes with ligands
based on the cyclohexanediamine framework have already
gained wide applications.10b,15 Especially, diamines with three
different substituents at the nitrogen atom revealed to be more
efficient for the induction of stereoinformation.16 This is attribu-
ted to the closer arrangement of the stereocentre to the active
metal centre compared to complexes with solely ligand chirality.
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Fig. 5 Extract of 1H NMR spectra in C6D6; decomposition of the tris(aminomethyl)-substituted silane 14 via Si–C bond cleavage.
cleavage of the second and also third side-arm occurs faster than
the cleavage of the first Si–C bond, which means that the
initially formed hydroxy species are more prone to decompo-
sition than compound 14 itself.
functionalised silanes towards Si–C bond cleavage. An
analogous crystallization experiment of the tris(aminomethyl)-
functionalised system 14 with ZnBr2 exclusively lead to the
decomposition product ZnBr2·(R,R)-TMCDA resulting from the
cleavage of all Si–C bonds. ZnBr2·(R,R)-TMCDA could be iso-
lated as crystalline solid in 79% yield. The failed isolation of
any intermediate decomposition product as ZnBr2 adduct is in
line with the NMR experiments.
In contrast to 14 the bis(aminomethyl)-functionalised silane
13 was revealed to be stable in solution. However, decompo-
sition was observed during crystallisation attempts of the corre-
sponding zinc(II) bromide complexes. Thereby, a solution of 13
in acetone was treated with an equivalent amount of the metal
salt. In this case no simple adduct comparable to (RC,RC,RN)-8
or (RC,RC,RN)-9 could be isolated. Instead, the stable zinc silano-
late 15—with an Si–O–Zn fragment—as result of the cleavage
of one TMCDA unit could be isolated (Scheme 5).12,19 The
formation of this compound has been described previously by
treatment of the corresponding disiloxane with ZnBr2.20 The for-
mation of 15 underlines the stability of these metallasilanolates,
which have long been supposed to be unstable compounds and
emphasises the increased sensitivity of multiple (aminomethyl)
The observed sensitivities of compound 13 and 14 towards
Si–C bond cleavage is consistent with previous observations of
other groups dealing with aminomethyl substituted silanes.17c,21
Investigations by Moreau and coworkers showed that the
decomposition of a series of (aminomethyl)trialkoxysilanes
during sol–gel applications led—analogous to our systems—to
the corresponding methylamine and silica. The cleavage was a
result of the nucleophilic attack of water and a Si–O−, respect-
ively, at the silicon. Most interestingly, the decomposition was
found to proceed faster the more alkoxy functions that were
present in the silane, i.e. the higher the “electrophilicity” of the
Si atom.21 This is in total agreement with the observed “auto-
catalytic” decomposition of 14. As such, the intermediate di- and
mono-(aminomethyl) functionalised hydroxysilanes should
decompose faster than the still present 14 without hydroxyl
groups bound to the silicon. This also explains the increased sen-
sitivity of the tris(aminomethyl)-functionalised silane 14 com-
pared with 13 or even the mono-substituted systems 5, 6 and 7.
The cleavage of 13 upon treatment with zinc(II) bromide can
thus also be explained by the increased electrophilicity of the Si
atom due to quartenisation of the nitrogen atom upon coordi-
nation of the metal salt.
Scheme 5 Formation of zinc silanolate 15 via Si–C bond cleavage in
13.
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cooling (for temperature, see each compound) the corresponding
chlorosilane (1.4 eq.) was cautiously (partly vigorous reaction!!)
added, the mixture again warmed to rt and stirred for 2 h. After
addition of 10 mL diethyl ether and 10 mL of 2 M HClaq to dis-
solve the formed lithium chloride, the combined organic layers
were extracted 3 times with 20 mL of 2 M HClaq. The aqueous
layers were afterwards set to pH 12 with 2 M NaOH and finally
extracted 3 times with 30 mL of diethyl ether and the combined
organic layers were dried over Na2SO4. After removal of all
volatile compounds in vacuo, the crude product was purified by
Kugelrohr distillation.
Conclusions
In conclusion we reported on the efficient use of the α-lithiated
tertiary amine, (R,R)-TMCDA [(R,R)-1], for the preparation of
(aminomethyl) functionalised silanes. The formation of a series
of mono-functionalised systems proceeds with good yields
accompanied by transmetallation of the initially formed silane
leading to the corresponding (silylmethyl)silanes. Formed
zinc(II) halide complexes of the presented TMCDA functiona-
lised silanes showed the formation of monomeric adducts with
one specific configuration at the stereogenic nitrogen atom.
Thereby, the spatially more demanding substituent adopts the
pseudo-equatorial position of the five-membered ring formed
upon complexation of the metal salt by the diamine side-arm.
Furthermore the potential of α-lithiated tertiary amines for the
formation of multiple (aminomethyl) substituted silanes is
depicted by the syntheses of compound 13 and 14 with two
and three (aminomethyl) functionalities, respectively. These
compounds revealed an increased sensitivity in solution towards
Si–C bond cleavage under reformation of the diamine. This
sensitivity was found to increase with number of (aminomethyl)
substituents in the silane. We are currently looking into the
mechanistic features of this interesting hydrolysis behaviour and
the expansion of the preparation of (aminomethyl) functionalised
silanes via other α-lithiated tertiary amines.
Synthesis of (R,R)-5 and (R,R)-11. Using general procedure A,
3.90 g (22.9 mmol) (R,R)-TMCDA [(R,R)-1] dissolved in
pentane were treated with 17.6 mL (29.9 mmol) t-BuLi. Tri-
methylchlorosilane was added at −30 °C. Kugelrohr distillation
gave (R,R)-5 (oven temperature: 128 °C, 3 × 10−2 mbar; yield:
2.72 g, 11.2 mmol, 49%) and (R,R)-11 (oven temperature
148: °C, 3 × 10−2 mbar; yield: 1.21 g, 3.84 mmol, 17%) in a
3 : 1 ratio as colourless oils. Trapping of the lithiated amine at
−78 °C gave a 8.8 : 1 ratio with an overall yield of 79%. Spectro-
1
scopic data of (R,R)-5 H NMR: (300.1 MHz, C6D6): δ = 0.13
[s, 9H; Si(CH3)3], 1.00–1.14 (m, 4H; 2 CH2, cyclohexyl),
1.68–1.73 (m, 2H; CH2, cyclohexyl), 1.78–1.87 (m, 2H; CH2,
2
cyclohexyl), 1.90 + 2.13 [AB system, JAB = 14.4 Hz, 2H;
N(CH2)Si], 2.26 [s, 3H; N(CH3)CH2Si], 2.27–2.33 [m, 2H;
CHN], 2.31 [s, 6H; N(CH3)2]. {1H}13C NMR: (75.5 MHz,
C6D6): δ = −0.96 [Si(CH3)3], 25.2 + 26.1 + 26.5 + 26.6 (CH2,
cyclohexyl], 40.7 [N(CH3)CH2Si], 41.0 [N(CH3)2], 45.5
[N(CH2)Si], 64.7 (CHN), 67.8 (CHN). 29Si NMR: (59.6 MHz,
C6D6): δ = −0.62. Elemental analysis: Calc. for C13H30N2Si: C
64.39, H 12.47, N 11.55; Found: C 64.48, H 12.20, N 11.15.
GC-MS tR = 11.53 min [80 °C (2 min) − 10 °C min−1 − 280 °C
(5 min)]; m/z (%): 242 (22) (M+), 169 (60) {[M − Si(CH3)3]+},
124 (100) {[C6H9N(CH3)CH2]+}, 73 (45) {[Si(CH3)3]+}, 58
(80) {[N(CH3)2CH2]+}. Spectroscopic data of (R,R)-11: 1H
NMR: (300.1 MHz, CDCl3): δ = −0.27 (s, 2H; SiCH2Si), 0.03
[s, 9H; Si(CH3)3], 0.03 + 0.04 [s, 6H; Si(CH2)CH2Si],
0.97–1.14 (m, 4H; 2 CH2, cyclohexyl), 1.61–1.68 (m, 2H; CH2,
cyclohexyl), 1.8–1.82 (m, 2H; CH2, cyclohexyl), 1.89 + 2.06
Experimental section
General considerations
All experiments were carried out under a dry, oxygen-free argon
atmosphere using standard Schlenk techniques. H2O is distilled
water. The solvents used were dried over sodium and distilled
prior to use. Cyclohexane-1,2-diamine was purchased from
Aldrich, the chlorosilanes and tert-butyl lithium were provided
by Wacker Chemie and Chemetall, respectively. The concen-
tration of tert-butyl lithium was determined by titration against
diphenylacetic acid before use. (R,R)-TMCDA (R,R)-1 and
(R,R)-6 were prepared according to the literature.6c,10 Enantio-
meric purity of 1 was determined according the literature.6e
1H, 13C, 29Si NMR spectra were recorded on DRX-300 and
AMX-500 Bruker spectrometers at 22 °C. Assignment of the
signals was supported by additional DEPT-135 and C,H-COSY
experiments. All values of the chemical shift are in ppm regard-
ing the δ-scale. All spin–spin coupling constants (J) are given in
Hertz (Hz). GC-MS analysis were performed on a ThermoQuest
TRIO-1000 (EI = 70 eV); Column; Zebron, Capillary GC
Column, ZB-1. Optical rotation values were determined on a
Jasco-polarimeter: P-1030 (cell path l = 1.00 dm; temperature:
20.0 °C, wave length λ = 589 nm).
2
[AB system, JAB = 14.5 Hz, 2H; N(CH2)Si], 2.14 [s, 3H;
N(CH3)CH2Si], 2.27–2.33 [m, 2H; CHN], 2.30 [s, 6H;
N(CH3)2]. {1H}13C NMR: (75.5 MHz, C6D6): δ = 0.65
(SiCH2Si), 2.0 [Si(CH3)3], 3.0 (SiCH2Si), 25.6 + 25.7 + 26.1 +
26.6 (CH2, cyclohexyl), 40.8 [N(CH3)CH2Si], 40.9 [N(CH3)2],
46.5 [N(CH2)Si], 64.7 (CHN), 67.7 (CHN). 29Si NMR:
(59.6 MHz, C6D6): δ = −0.11 + 0.45. GC-MS: tR = 15.75 min
[80 °C (2 min) − 10 °C min−1 − 280 °C (5 min)]; m/z (%): 314
(15) (M+), 228 (23) [MH − CH2Si(CH3)3], 169 (100) {[M −
Si(CH3)2CH2Si(CH3)3]+}, 145 (20) {[Si(CH3)2CH2Si(CH3)3]+},
124 (75) {[C6H9N(CH3)CH2]+}, 73 (43) {[Si(CH3)3]+}, 58 (48)
{[N(CH3)2CH2]+}.
A. General procedure for the preparation of aminomethyl
functionalised silanes
(R,R)-TMCDA was dissolved in n-pentane and cooled to
−30 °C. At this temperature tert-butyl lithium (solution in n-
pentane) was added, the mixture allowed to warm to room temp-
erature and stirred for an additional 3–4 h during which the
formed precipitate of (R,R)-TMCDA completely dissolved. After
Synthesis of (R,R)-7 and (R,R)-10. Using general procedure
A, 4.00 g (23.5 mmol) (R,R)-TMCDA in 25 mL pentane were
treated with 20 mL (30.0 mmol) t-BuLi. Diphenylmethylchloro-
silane was added at the temperatures given in Table 2. Kugelrohr
distillation gave (R,R)-7 (oven temperature 225 °C, 6 × 10−42
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Table 2 Obtained product ratios and yields depending on the trapping
temperature
(CH2CHN), 25.4 (CH2CHN), 26.17 + 26.18 [(CH2)2CH2], 40.5
[N(CH3)CH2Si], 40.6 [N(CH3)2], 43.8 [N(CH2)Si], 64.4 (CHN),
67.4 (CHN). 29Si NMR: (99.4 MHz, C6D6): δ = −1.2. Elemental
analysis: Calc. for C22H48N4Si: C 66.60, H 12.19, N 14.12;
Found: C 66.23, H 12.17, N 14.49. [α]2D0 −28.1 (cyclohexane,
0.827 g/100 mL); GC-EI/MS: tR = 11.99 min [80 °C (2 min)
− 10 °C min−1 − 280 °C (5 min)]; m/z (%): 381 (2) [(M − CH3)+],
227 (100) {[M − (C10H21N2)]+}, 170 (15) [(R,R)-TMCDA], 124
(25) {[C6H9N(CH3)CH2]+}, 58 (60) {[N(CH3)2CH2]+}.
Trapping temperature
(R,R)-7
(R,R)-10
Total isolated yield
−30 °C
−50 °C
−70 °C
2.1
3.3
4.2
1
1
1
87%
74%
86%
mbar) and (R,R)-10 (oven temperature 260 °C, 6 × 10−4 mbar)
as colourless, highly viscous oils.
Synthesis of 14. Using general procedure A, 4.00
g
Spectroscopic data of diphenylmethylsilane (R,R)-7: 1H
NMR: (500.1 MHz, d-Tol): δ = 0.66 [s, 3H; Si(CH3)],
(23.5 mmol) (R,R)-TMCDA [(R,R)-1] dissolved in 25 mL
n-pentane were treated with 15 mL (25.5 mmol) t-BuLi. 1.5 g
(10.0 mmol) methyltrichlorosilane was then slowly added at
−70 °C. Caution: extremely exothermic reaction. Kugelrohr dis-
tillation (oven temperature: 290 °C, 4 × 10−4 mbar) gave 14 as a
slightly yellow, highly viscous oil (1.35 g, 2.45 mmol, 31%). 1H
NMR: (400.1 MHz, C6D6): δ = 0.65 [s, 3H; SiCH3], 1.15–1.31
[m, 12H; 6 × CH2CH2], 1.75–1.79 [m, 6H; 3 × CH2CHN],
1.90–1.93 [m, 3H; CH2CHN], 2.05–2.08 [m, 3H; CH2CHN],
0.87–1.05 [m, 4H;
2 × CH2CH2], 1.57–1.62 [m, 2H;
CH2CHN(CH3)CH2], 1.67–1.72 [m, 1H; CH2CHN(CH3)CH2],
1.76–1.80 [m, 1H; CH2CHN(CH3)CH2], 2.19 [s, 3H; N(CH3)
CH2Si], 2.22 [s, 6H; N(CH3)2], 2.24–2.27 [m, 2H; 2 × CHN],
2
2.48 + 2.74 [AB system, JAB = 14.4 Hz, 2H; N(CH2)Si],
7.02–7.22 (m, 6H; Harom), 7.64–7.70 (m, 4H; Harom). {1H}13C
NMR: (125.8 MHz, d-Tol):
δ = −3.6 [Si(CH3)], 24.1
(CH2CHN), 24.7 (CH2CHN), 26.4 [(CH2)2CH2], 26.2
[(CH2)2CH2], 40.3 [N(CH3)2], 40.8 [N(CH3)CH2Si], 42.7
[N(CH2)Si], 64.5 (CHN), 66.9 (CHN), 128.00 + 128.01
(CHmeta), 129.28 + 129.29 (CHpara), 135.1 + 135.2 (CHortho),
138.0 + 138.1 (Cipso). 29Si NMR: (99.4 MHz, d-Tol): δ = −11.2.
Elemental analysis: Calc. for C23H34N2Si: C 75.35, H 9.35, N
7.64; Found: C 75.48, H 9.20, N 7.35. [α]2D0 −6.8 (cyclohexane,
1.057 g/100 mL). GC-MS: tR = 12.14 min [80 °C (2 min) −
10 °C min−1 − 280 °C (5 min)]; m/z (%): 366 (3) [M+], 197 (32)
{[Si(CH3)Ph2]+}, 169 (100) {[M − Si(CH3)Ph2]+}, 124 (58)
{[C6H9N(CH3)CH2]+}, 58 (100) {[N(CH3)2CH2]+}. Spectro-
2
2.41 + 2.62 [AB system, JAB = 14.2 Hz, 6H; N(CH2)Si],
2.41–2.54 [m, 6H; 6 × CHN], 2.49 [s, 18H; N(CH3)2], 2.56
[s, 9H; N(CH3)CH2Si]. {1H}13C NMR: (125.8 MHz, C6D6):
δ = −3.0 [Si(CH3)], 25.0 (2 × CH2CHN), 26.20, 26.24
[(CH2)2CH2], 40.6 [N(CH3)2], 40.8 [N(CH3)CH2Si], 42.7
[N(CH2)Si], 64.5 (CHN), 67.5 (CHN). 29Si NMR: (99.4 MHz,
C6D6): δ = −1.4. Elemental analysis: Calc. for C31H66N6Si:
C 67.58, H 12.07, N 15.25; Found: C 67.17, H 12.59,
N
14.72. [α]2D0 −33.5 (cyclohexane, 0.618 g/100 mL);
GC-MS: tR = 19.26 min [80 °C (2 min) − 10 °C min−1
− 280 °C (5 min)]; m/z (%): 381 (20) {[M – (C10H21N2)]+},
170 (35) [(R,R)-TMCDA], 124 (25) {[C6H9N(CH3)CH2]+},
84 (100) {[N(CH3)2C3H4]+}, 71 (63) [(C4H9N)+], 58 (92)
{[N(CH3)2CH2]+}.
1
scopic data of (R,R)-10: H NMR: (500.1 MHz, CDCl3): δ =
0.23 (s, 3H SiCH3), 0.80–1.04 [m, 4H; CH2, cyclohexyl], 0.96
(s, 2H; SiCH2Si), 1.57–1.70 [m, 3H; CH2, cyclohexyl],
1.79–1.81 [m, 1H; CH2, cyclohexyl], 2.01 [s, 3H; N(CH3)
CH2Si], 2.22 [s, 6H; N(CH3)2], 2.22–2.29 [m, 2H; CHN], 2.34
2
+ 2.54 [AB system, JAB = 14.6 Hz, 2H; N(CH2)Si], 7.27–7.36
B. General procedure for the synthesis of the zinc(II) bromide/
chloride complexes
3
(m, 12H; Harom), 7.37–7.48 (m, 4H; Harom) 7.55 (d, 2H, JHH
=
6.2 Hz; Hortho), 7.64 (d, 2H, JHH = 6.6 Hz; Hortho). {1H}13C
NMR: (125.8 MHz, CDCl3): δ = −2.63 [Si(CH3)], −2.18
(SiCH2Si), 23.0 + 24.9 + 25.3 + 25.6 (CH2 cyclohexyl), 39.9
[N(CH3)CH2Si], 40.3 [N(CH3)2], 43.9 [N(CH2)Si], 63.9 (CHN),
65.8 (CHN), 127.46 + 127.48 + 127.57 + 127.59 (CHmeta),
128.78 + 128.84 +128.98 + 129.02 (CHpara), 134.21 + 134.25 +
135.1 + 135.4 (CHortho), 136.8 (br) + 137.4 + 138.8 (Cipso). 29Si
NMR: (59.6 MHz, d-Tol): δ = −11.10, −8.04.
3
The silane and an equivalent amount of the zinc(II) salt were dis-
solved in acetone or a mixture of acetone/diethyl ether and
stored at room temperature. Upon evaporation of the solvent, col-
ourless crystals of the corresponding adduct are formed, which
were washed with cold diethyl ether.
Synthesis of the zinc(II) bromide/chloride complexes of (R,R)-
6. Using general procedure B, 100 mg (0.33 mmol) of silane
(R,R)-6 and 74 mg, 0.33 mmol zinc(II) bromide (45 mg,
0.33 mmol zinc(II) chloride) gave colourless crystals of (RC,RC,
RN)-8 (161 mg, 30 mmol; 92%) (chloride: 128 mg, 0.29 mmol;
Synthesis of 13. Using general procedure A, 6.00
g
(35.2 mmol) (R,R)-TMCDA [(R,R)-1] dissolved in 25 mL n-
pentane were treated with 29 mL (43.5 mmol) t-BuLi. Trapping
with 6.00 g (47.6 mmol) dimethyldichlorosilane at −50 °C.
Caution: vigorous reaction. Kugelrohr distillation (oven tempera-
ture 200 °C, 4 × 10−4 mbar) gave 13 as a colourless, highly
1
88%). ZnBr2 adduct: H NMR: (300.1 MHz, CDCl3): δ = 0.54
[s, 3H; Si(CH3)], 0.69 [s, 3H; Si(CH3)], 1.10–1.37 (m, 4H; 2
CH2, cyclohexyl), 1.83–1.86 (m, 2H; CH2, cyclohexyl),
2.01–2.16 (m, 2H; CH2, cyclohexyl), 2.33 [s, 3H; N(CH3)], 2.43
[s, 3H; N(CH3)], 2.55–2.57 [m, 2H; CHN], 2.63 [s, 3H;
1
viscous oil (5.82 g, 15.9 mmol, 68%). H NMR: (500.1 MHz,
C6D6): δ = 0.44 [s, 6H; Si(CH3)2], 1.08–1.26 [m, 8H; 4 ×
CH2CH2], 1.73–1.78 [m, 4H; 2 × CH2CHN], 1.89–1.91 [m, 2H;
CH2CHN], 1.98–2.00 [m, 2H; CH2CHN], 2.19 + 2.42 [AB
2
N(CH3)], 2.67 + 2.91 [AB system, JAB = 13.8 Hz, 1H; N(CH2)
Si, D1 + D2], 7.34–7.36 (m, 3H; Harom), 7.57–7.60 (m, 2H;
2
system, JAB = 14.2 Hz, 4H; N(CH2)Si], 2.41–2.47 [m, 4H; 2 ×
H
arom). {1H}13C NMR: (75.7 MHz, CDCl3): δ = −1.68 + −1.89
CHN], 2.45 [s, 12H; N(CH3)2], 2.46 [s, 6H; N(CH3)CH2Si].
[Si(CH3)2], 21.8 + 22.4 + 24.2 + 24.3 (CH2, cyclohexyl), 40.9 +
41.8 + 47.4 [N(CH3)], 49.3 [N(CH2)Si], 64.1 (CHN), 67.6
{1H}13C NMR: (125.8 MHz, C6D6): δ = −2.0 [Si(CH3)], 24.9
3458 | Dalton Trans., 2012, 41, 3452–3460
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Table 3 Crystal data and structure refinement of all zinc(II) bromide complexes
Compound
(RC,RC,RN)-8
(RC,RC,RN)-9
(RC,RC,RN)-12
CCDC No.
Formula
851902
C18H32SiN2ZnBr2
529.74
851903
C23H34SiN2ZnBr2
591.80
851904
C39H52SiN2ZnBr2O
846.20
Formula weight/g mol−1
T/K
173(2)
173(2)
173(2)
Wavelength/Å
Crystal system
Space group
a/Å
b/Å
c/Å
0.71073
Monoclinic
P21 (4)
11.5004(6)
8.3851(4)
11.6141(7)
96.489(5)
1112.80(10)
2
1.581
4.751
536
0.71073
Monoclinic
P21 (4)
12.3467(6)
11.0348(6)
19.5297(14)
106.652(7)
2549.2(3)
0.71073
Orthorhombic
P212121 (19)
12.2947(4)
16.4427(5)
19.7658(6)
—
3995.8(2)
4
1.407
β/°
Volume/Å3
Z
4
Dc/Mg m−3
μ(Mo Kα)/mm−1
F(000)
1.542
4.157
1200
2.706
1744
Crystal dimensions/mm
Theta range/°
Index ranges
0.30 × 0.20 × 0.10
2.36 to 25.00
−13 ≤ h ≤ 13
−9 ≤ k ≤ 9
−13 ≤ l ≤ 13
10 641
3863 [Rint = 0.0310]
Full-matrix least-squares on F2
3868/7/222
1.027
0.40 × 0.40 × 0.10
2.14 to 25.00
−14 ≤ h ≤ 14
−13 ≤ k ≤ 13
−22 ≤ l ≤ 23
23 721
8910 [Rint = 0.0859]
Full-matrix least-squares on F2
8910/1/531
1.006
0.30 × 0.20 × 0.10
2.06 to 25.00
−14 ≤ h ≤ 14
−19 ≤ k ≤ 19
−21 ≤ l ≤ 23
33 648
7038 [Rint = 0.0456]
Full-matrix least-squares on F2
7038/0/430
—
Reflections collected
Independent reflections
Refinement method
Data/restraints/parameter
Goodness-of-fit on F2
1.019
—
—
—
—
Final R indices [2σ(I)]
R1 = 0.0243
R1 = 0.0255
wR2 = 0.0550
R1 = 0.0269
wR2 = 0.0553
−0.001(8)
R1 = 0.0432
—
wR2 = 0.0674
R1 = 0.0649
wR2 = 0.0691
−0.045(8)
wR2 = 0.0392
R1 = 0.0351
wR2 = 0.0397
0.003(5)
R indices (all data)
Absolute structure parameter
(CHN), 127.8 (CHmeta), 129.2 (CHpara), 133.6 (CHortho), 137.4
(Cipso). 29Si NMR: (59.6 MHz, CDCl3): δ = −5.5.
cyclohexyl], 2.01–2.05 [m, 2H; CH2, cyclohexyl], 2.07 + 2.50 +
2.67 [s, 3H; N(CH3)], 2.52–2.62 [m, 2H; CHN], 2.84 + 3.31
[AB system, JAB = 14.0 Hz, 2H; N(CH2)Si], 7.27–7.36 (m,
2
Synthesis of the zinc(II) bromide/chloride complexes of (R,R)-
7. Using general procedure B, 100 mg (0.27 mmol) of (R,R)-7
and 61 mg (0.27 mmol) zinc(II) bromide (36.8 mg, 0.27 mmol
zinc(II) chloride) gave colourless crystals of (RC,RC,RN)-9
(123 mg, 0.21 mmol; 78%) (chloride: 119 mg, 0.24 mmol;
88%). ZnBr2 adduct: 1H NMR: (300.1 MHz, CDCl3): δ =
1.13–1.37 (m, 4H; 2 CH2, cyclohexyl), 1.18 [s, 3H; Si(CH3)],
1.86–1.88 (m, 2H; CH2, cyclohexyl), 2.03–2.07 (m, 2H; CH2,
cyclohexyl), 2.19 + 2.48 + 2.65 [s, 3H; N(CH3)], 2.53–2.61 [m,
12H; Harom), 7.45–7.49 (m, 4H; Harom), 7.52–7.58 (m, 4H;
H
arom). {1H}13C NMR: (75.5 MHz, CDCl3): δ = −2.94 (SiCH3),
−2.47 (SiCH2Si), 21.9 + 22.6 + 24.3 + 24.4 (CH2, cyclohexyl),
41.2 + 42.0 [N(CH3)2], 47.4 [N(CH2)Si], 47.5 [N(CH3)CH2Si],
64.2 (CHN), 67.7 (CHN), 127.5 + 127.9 (br) + 128.2 (CHmeta),
128.7 + 129.6 (br) + 129.8 (CHpara), 134.5 + 134.6 + 134.7 +
134.9 (CHortho), 135.1 +135.3 + 135.4 + 135.6 (Cipso). 29Si
NMR: (59.6 MHz, CDCl3): δ = −8.0, −10.5.
2
2H; CHN], 3.09 + 3.25 [AB system, JAB = 14.3 Hz, 2H;
Formation of zinc silanolate 15. Using general procedure B;
100 mg (0.25 mmol) silane 13 and 56 mg (0.25 mmol) zinc(II)
bromide in 10 mL acetone gave colourless plates of 15 (86 mg,
0.11 mmol; 88%). For spectroscopic details see literature.20
N(CH2)Si, D1 + D2], 7.29–7.35 (m, 3H; Harom), 7.44–7.46 (m,
3H; Harom), 7.55–7.58 (m, 2H; Harom), 7.66–7.70 (m, 2H;
Harom). {1H}13C NMR: (75.5 MHz, CDCl3): δ = −2.97
[Si(CH3)2], 21.9 + 22.6 + 24.3 + 24.4 (CH2, cyclohexyl), 41.3 +
42.0 + 47.3 [N(CH3)], 47.5 [N(CH2)Si], 64.1 (CHN), 67.7
(CHN), 127.8 + 128.2 (CHmeta), 129.5 + 129.7 (CHpara), 134.5
+134.9 (CHortho), 135.0 + 135.33 (Cipso). 29Si NMR: 59.6 MHz,
CDCl3): δ = −10.5.
Formation of (R,R)-TMCDA·ZnBr2 (16). Using general pro-
cedure B; 100 mg (0.18 mmol) silane 14 and 123 mg
(0.54 mmol) zinc(II) bromide in 10 mL acetone gave colourless
plates of 16 (169 mg, 0.43 mmol; 79%). 1H NMR: (500.1 MHz,
CDCl3): δ = 1.16–1.34 (m, 4H, CH2 cyclohexyl), 1.84–1.89 (m,
2H; CH2 cyclohexyl), 2.01–2.05 (m, 2H; CH2 cyclohexyl), 2.42
[s, 6H; N(CH3)2], 2.57–2.60 (m, 2H; CHN), 2.63 [s, 6H;
N(CH3)2]. {1H}13C NMR: (125.8 MHz, CDCl3): δ = 22.3 +
24.2 (CH2 cyclohexyl) 41.1 + 47.1 [N(CH3)2], 64.5 (CHN).
Elemental analysis: Calc. for C10H22N2ZnBr2: C 30.37, H 5.61,
N 7.08; Found: C 30.50, H 5.55, N 7.10.
Synthesis of the zinc(II) bromide complexes of (R,R)-10. Using
general procedure B, 100 mg (0.18 mmol) of (silylmethyl)silane
(R,R)-8 and 40 mg (0.18 mmol) zinc(II) bromide gave colourless
1
plates of (RC,RC,RN)-12 (125 mg, 0.16 mmol; 88%). H NMR:
(300.1 MHz, CDCl3): δ = 0.13 (s, 3H SiCH3), 1.04–1.198
[m, 6H; CH2, cyclohexyl + SiCH2Si], 1.77–1.85 [m, 2H; CH2,
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1992, 70, 1733; (f) L. H. Sommer and J. Rocket, J. Am. Chem. Soc.,
1951, 3, 5130.
Crystallographic details
5 For syntheses of (chloromethyl)silanes, see: (a) J. O. Daiss, K. A. Barth,
C. Burschka, P. Hey, R. Ilg, K. Klemm, I. Richter, S. A. Wagner and
R. Tacke, Organometallics, 2004, 23, 5193; (b) V. I. Handmann,
R. Bertermann, C. Burschka and R. Tacke, J. Organomet. Chem., 2000,
613, 19; (c) T. Kobayashi and K. H. Pannell, Organometallics, 1990, 9,
2201; (d) T. Kobayashi and K. H. Pannell, Organometallics, 1991, 10,
1960; (e) J. L. Speier, J. Am. Chem. Soc., 1951, 73, 824; (f) D. Seyferth
and E. G. Rochow, J. Am. Chem. Soc., 1955, 77, 907;
(g) A. Y. Yakubovich, S. P. Makarov, V. A. Ginsburg, G. I. Gavrilov and
E. N. Merkulova, Dokl. Akad. Nauk SSSR, 1950, 72, 69.
6 (a) C. Strohmann, V. H. Gessner and A. Damme, Chem. Commun., 2008,
3381; (b) C. Strohmann and V. H. Gessner, Angew. Chem., Int. Ed., 2007,
46, 4566; (c) C. Strohmann and V. H. Gessner, Angew. Chem., Int. Ed.,
2007, 46, 8281; (d) C. Strohmann and V. H. Gessner, J. Am. Chem. Soc.,
2007, 129, 5982; (e) C. Strohmann and V. H. Gessner, J. Am. Chem.
Soc., 2008, 130, 11710; (f) V. H. Gessner and C. Strohmann, J. Am.
Chem. Soc., 2008, 130, 14412; (g) V. H. Gessner, C. Däschlein and
C. Strohmann, Chem.–Eur. J., 2009, 15, 3320; (h) C. Strohmann and
V. H. Gessner, Chem.–Asian J., 2008, 3, 1929; (i) V. H. Gessner and
C. Strohmann, Organometallics, 2010, 29, 1858.
Data collection of all compounds was conducted with CrysAlis
CCD, Oxford Diffraction Ltd. CCD (D8 three-circle goni-
ometer), cell determination, refinement and integration with
CrysAlis RED, Oxford Diffraction Ltd., Version 1.171.32.37;
empirical absorption correction with CrysAlis RED using spheri-
cal harmonics, implemented in SCALE3 ABSPACK scaling
algorithm. The crystal structure determinations were effected at
−100 °C (type of radiation: Mo Kα, α = 0.71073 Å). The struc-
tures were solved applying direct and Fourier methods using
SHELXS-97 (G. M. Sheldrick, SHELXS97, University of
Göttingen 1997) and refined with SHELXL-97 (G. M. Sheldrick,
SHELXL97, University of Göttingen 1997). Crystallographic
data (excluding structure factors) have been deposited with the
Cambridge Crystallographic Data (see Table 3 and S1†). Table 3
and Table S1 (SI†) give further information about the data
collection and structure refinement of all α-lithiated silanes.
Further information (ORTEP plots, atomic coordinates and ani-
sotropic displacement parameters) is available in the Supporting
Information.†
7 V. H. Gessner, B. Fröhlich and C. Strohmann, Eur. J. Inorg. Chem.,
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(b) J.-C. Kizirian, N. Cabello, L. Pinchard, J.-C. Caille and A. Alexakis,
Tetrahedron, 2005, 61, 8939.
11 C. Däschlein, V. H. Gessner and C. Strohmann, Chem.–Eur. J., 2010, 16,
4048.
Acknowledgements
This research was supported by the Deutsche Forschungs-
gemeinschaft (DFG) and the Fonds der Chemischen Industrie
(FCI). V.H.G. specially thanks the FCI for the award of a doc-
toral and the Alexander-von-Humbold foundation for a postdoc-
toral fellowship. We gratefully acknowledge Chemetall GmbH
and Wacker Chemie AG for the provision of chemicals.
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3460 | Dalton Trans., 2012, 41, 3452–3460
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