Synthesis and structural characterization of silanethiolato complexes having tert-butyldimethylsilyl and trimethylsilyl groups

Article abstract of DOI:10.1039/b316567a

Treatment of cyclotrisilathiane (Me₂SiS)₃ with 3 equiv. of RLi (R = Me, Bu^t) in hexane-Et₂O afforded the lithium silanethiolates LiSSiMe₂R, and the tmeda adduct [(tmeda)LiSSiMe₂Bu^t

Full text of DOI:10.1039/b316567a

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Synthesis and structural characterization of silanethiolato
complexes having tert-butyldimethylsilyl and trimethylsilyl groups
Takashi Komuro,a Tsukasa Matsuo,b Hiroyuki Kawaguchi*b and Kazuyuki Tatsumia
a Research Center for Materials Science, and Department of Chemistry,
Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602,
Japan
b Coordination Chemistry Laboratories, Institute for Molecular Science, Myodaiji,
Okazaki 444-8585, Japan
Received 18th December 2003, Accepted 23rd March 2004
First published as an Advance Article on the web 7th April 2004
Treatment of cyclotrisilathiane (Me2SiS)3 with 3 equiv. of RLi (R = Me, But) in hexane-Et2O afforded the lithium
silanethiolates LiSSiMe2R, and the tmeda adduct [(tmeda)LiSSiMe2But]2 1 (tmeda = N,N,NЈ,NЈ-tetramethylethylene-
diamine) was isolated in the case of R = But. Reaction of Fe(CH3CN)2(CF3SO3)2, CoCl2, and [Cu(CH3CN)4](PF6)
with 1 gave rise to the silanethiolato complexes M(SSiMe2But)2(tmeda) (M = Fe 2, Co 3), and [Cu(SSiMe2But)]4
4, respectively. Complexes (C5H5)2Ti(SSiMe2R)2 (R = Me 5, But 6) and Ni(SSiMe2R)2(dppe) [R = Me 7, But 8;
dppe = 1,2-bis(diphenylphosphino)ethane] were prepared from treatments of (C5H5)2TiCl2 and NiCl2(dppe)
with the corresponding lithium silanethiolates. Complex 7 readily reacted with (C5H5)TiCl3 to produce the
Ti–Ni heterobimetallic compound (C5H5)TiCl(µ-S)2Ni(dppe) 9, in which silicon–sulfur bond cleavage took place.
Characterization of all compounds through spectroscopic techniques and elemental analyses are also described.
X-Ray structural data for compounds 1 and 3–9 are reported.
of lithium, titanium, iron, cobalt, nickel and copper. For nickel
Introduction
silanthiolato complexes, their conversion to the Ti–Ni bi-
Silanethiolato complexes of transition metals represent poten-
metallic compound in the reactions with (C5H5)TiCl3 has been
tial precursors as an entry into homo- and hetero-metallic
investigated.
sulfido clusters (Scheme 1).1–5 These cluster-forming reactions
are promoted by the formation of thermodynamically stable
Results and discussion
Si–X bonds (X = halide, alkoxide, acetate, etc.), in which
silanethiolato complexes serve as the source of the M–SϪ frag-
ment. One of the important advantages of using this system is
the possibility of controlling cluster-forming reactions by the
choice of steric and electronic properties of the substituents on
silicon. This approach has been widely used in organic syn-
theses, where silyl groups have proven to be useful as protecting
agents of functional groups under various conditions.6,7
Preparation of lithium silanethiolates
Lithium salts of the silanethiolato anions Me2RSiSϪ (R = Me,
But) were prepared by the reactions of cyclotrisilathiane
(Me2SiS)3 with 3 equivalents of the corresponding alkyllithium
species RLi (Scheme 2).18 The Et2O solution of LiSSiMe3 pre-
pared in situ was used for the synthesis of trimethylsilane-
thiolato complexes reported here. In the case of R = But, the
colorless product was isolated in 72% yield as the tmeda adduct
[(tmeda)LiSSiMe2But]2 1 (tmeda = N,N,NЈ,NЈ-tetramethyl-
ethylenediamine), and its composition was determined by
NMR and IR spectra.
Scheme 1
Although we previously reported the synthesis of triphenyl-
silanethiolato complexes, these species were found to undergo
low reactivity toward metal acetates and chlorides under mild
conditions.8 Taking steric and/or electronic factors into con-
sideration, it is anticipated that trialkylsilanethiolato complexes
are reactive as compared to triphenylsilanethiolato counter-
parts.6,7 However, trialkylsilanethiolato ligands are less access-
ible relative to aryl-substituted silanethiolato ligands that can
be readily prepared from the corresponding chlorosilanes. The
ease of Si–S bond cleavage reactions makes it difficult to obtain
trialkylsilanethiolato complexes in pure form. In particular,
there were few structurally characterized trimethylsilanethiol-
ato complexes due to their high reactivity.9 Consequently, the
properties of many potential silanethiolato derivatives remain
unexplored.10–17
Scheme 2 R = Me, But. Reagents and conditions: (i) 3 equiv. RLi,
hexane–Et2O, 0 ЊC; (ii) TMEDA, hexane–Et2O, 0 ЊC.
Our entry point to trialkylsilanethiolato chemistry is based
on work carried out by Kraus and Andersh,18 where lithium
trialkylsilanethiolates were prepared in situ from cyclo-
trisilathiane (SSiMe2)3 and alkyllithiums (RLi). Here we
describe the synthesis and characterization of trimethyl-
silanethiolato and tert-butyldimethylsilanethiolato complexes
A single-crystal X-ray diffraction study of 1 was also per-
formed (Fig. 1 and Table 1). The solid-state structure of 1 shows
it to be a dimer, and four nitrogen atoms of tmeda ligands and
two lithium atoms lie on a crystallographic mirror plane. Two
D a l t o n T r a n s . , 2 0 0 4 , 1 6 1 8 – 1 6 2 5
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4
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Table 1 Selected bond distances (Å) and angles (Њ) for 1a
Table 2 Selected bond distances (Å) and angles (Њ) for 3a
Li(1)–S
2.426(4)
2.137(7)
2.173(7)
2.079(1)
Li(2)–S
Li(1)–N(2)
Li(2)–N(4)
2.400(4)
2.125(7)
2.132(7)
Co–S
S–Si
2.2656(9)
2.119(1)
Co–N
2.131(3)
Li(1)–N(1)
Li(2)–N(3)
S–Si
S–Co–S*
S–Co–N
Co–S–Si
125.78(4)
115.14(8)
110.83(4)
N–Co–N*
S–Co–N*
85.0(1)
104.30(8)
S–Li(1)–S*
N(1)–Li(1)–N(2)
Li(1)–S–Si
90.5(2)
85.5(2)
133.0(1)
81.0(2)
S–Li(2)–S*
N(3)–Li(2)–N(4)
Li(2)–S–Si
91.8(2)
86.2(2)
132.6(1)
110.7(1)
a Atoms carrying the asterisk are related to their counterpart by the
symmetry operator [1 Ϫ x, y, 1/2 Ϫ z].
Li(1)–S–Li(2)
S–Si–C(3)
a Atoms carrying the asterisk are related to their counterparts by the
symmetry operator [1 Ϫ x, y, z].
Fig.
1
Structure of [(tmeda)LiSSiMe2But]2 1. One set of the
disordered methylene carbons of the tmeda ligands is shown.
tert-butyldimethylsilyl groups are thus required to have a syn
conformation with respect to the Li(1)–Li(2) vector, in which
the tert-butyl groups point away from the tmeda ligands due to
avoid steric congestion. There is a central puckered Li2S2 ring
(the dihedral angle of 40.1Њ between two Li2S planes), and
Li(1)–S and Li(2)–S distances of 2.426(4) and 2.400(4) Å,
respectively, and angles subtended at Li [90.5(2), 91.8(2)Њ] wider
than at S [81.0(2)Њ]. Each lithium atom adopts a distorted tetra-
hedral geometry with a chelating TMEDA and two bridging
SSiMe2But ligands. Two sulfur atoms are separated by 3.447(1)
Å. The average Li–S distance of 2.413 Å is comparable to those
observed in other lithium thiolates.19
Scheme
3
Reagents and conditions: (i) Fe(CH3CN)2(CF3SO3)2,
CH3CN, rt; (ii) CoCl2, THF, rt; (iii) [Cu(CH3CN)4](PF6), CH3CN, 0 ЊC;
(iv) (C5H5)2TiCl2, Et2O-toluene or THF, 0 ЊC or rt; v) NiCl2(dppe),
Et2O–THF or THF, 0 ЊC; (vi) (C5H5)TiCl3, toluene, rt.
(R = Me 5, But 6) and Ni(SSiMe2R)2(dppe) [R = Me 7, But 8;
dppe = 1,2-bis(diphenylphosphino)ethane] could be prepared in
45–92% isolated yields by the reactions of (C5H5)2TiCl2 and
NiCl2(dppe) with the corresponding lithium silanethiolates.
The spectroscopic data and the combustion analyses data of
these silanethiolato, 2–8, complexes were in agreement with
their formulation. The IR spectra of the silanethiolato com-
plexes all showed characteristic absorptions at approximately
1240 and 830 cmϪ1 attributable to the trialkylsilyl group. Com-
plexes 2 and 3 are paramagnetic and show broad resonances in
Silanethioato complexes of transition metals
The lithium silanethiolates have proven to be useful reagents for
the preparation of a range of transition-metal derivatives. The
reactions of LiSSiMe3 or 1 with transition-metal complexes are
summarized in Scheme 3. This work showed that the products
obtained were strongly dependent on the nature of the silyl
substituents, presumably because of the different lability of
silicon–sulfur bond. The use of the bulky tert-butyldimethyl-
silanethiolato ligand enables us to isolate various metals com-
plexes. For example, we carried out the reactions of Fe(CH3-
CN)2(CF3SO3)2, CoCl2 and [Cu(CH3CN)4](PF6) with 1. In
either case, the reaction proceeded smoothly with the immedi-
ate color change of the reaction mixture to brown for iron,
to dark blue for cobalt, or to orange–brown for copper.
The standard workup afforded silanethiolato complexes, Fe-
(SSiMe2But)2(tmeda) 2 in 77% as colorless crystals, Co-
(SSiMe2But)2(tmeda) 3 in 69% as blue–purple crystals, and
[Cu(SSiMe2But)]4 4 in 49% yield as colorless crystals. During
the formation of 2 and 3, the tmeda ligand was also found to
transfer from Li to Fe and Co, respectively. In contrast, the
analogous reactions with LiSSiMe3 in the presence of tmeda
were not straightforward. Attempts to isolate the trimethyl-
silanethiolato congeners of 2, 3 and 4 have not been successful.
For titanium() and nickel(), trimethylsilanethiolato and tert-
butyldimethylsilanethiolato complexes, (C5H5)2Ti(SSiMe2R)2
1
their H NMR spectra. Solution magnetic moments of 5.0 µB
for 2 and 4.2 µB for 3 were measured by Evans’ NMR method,20
and these values were typical of high-spin iron() and cobalt()
species, respectively.21–23 The H NMR spectroscopic data of
1
4–8 indicated a symmetric or fluxional environment. The tert-
butyldimethylsilanethiolato ligands of 4, 6 and 8 were observed
as two singlets in a 2 : 3 intensity ratio, while the trimethyl-
silanethiolato ligands of 5 and 7 appear as a single peak.
In order to confirm the geometry of these silanethiolato
complexes, X-ray quality crystals of some of these species were
grown. The crystals of 3–8 were found to be suitable for X-ray
crystallography. The solid-state structure of the cobalt complex
3 features a monomeric four-coordinate metal center in a dis-
torted tetrahedral environment analogous to that observed for
Co(SSiPh3)2(tmeda) (Fig. 2 and Table 2).8 The molecule pos-
sesses a crystallographically imposed 2-fold axis through the
cobalt atom that bisects the S–Co–S* angles. The metal–ligand
distances fall within the normal range of high-spin four-co-
ordinated tetrahedral complexes of cobalt().8,23,24 The bond
angles at cobalt vary between 85.0(1) and 125.78(4)Њ, where the
D a l t o n T r a n s . , 2 0 0 4 , 1 6 1 8 – 1 6 2 5
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Table 3 Selected bond distances (Å) and angles (Њ) for 4
Cu(1)–Cu(2)
Cu(2)–Cu(3)
Cu(1)–S(1)
Cu(2)–S(2)
Cu(3)–S(3)
Cu(4)–S(1)
S(1)–Si(1)
2.8128(6)
2.9541(9)
2.168(1)
2.171(1)
2.148(1)
2.177(1)
2.158(1)
2.160(1)
Cu(1)–Cu(4)
Cu(3)–Cu(4)
Cu(1)–S(2)
Cu(2)–S(3)
Cu(3)–S(4)
Cu(4)–S(4)
S(2)–Si(2)
2.9680(9)
2.7413(7)
2.180(1)
2.157(1)
2.151(1)
2.181(1)
2.178(2)
2.152(2)
S(3)–Si(3)
S(4)–Si(4)
Cu(1)–Cu(2)–Cu(3)
Cu(3)–Cu(4)–Cu(1)
S(1)–Cu(1)–S(2)
S(3)–Cu(3)–S(4)
Cu(1)–S(1)–Cu(4)
Cu(2)–S(3)–Cu(3)
Cu(1)–S(1)–Si(1)
Cu(1)–S(2)–Si(2)
Cu(2)–S(3)–Si(3)
Cu(3)–S(4)–Si(4)
90.99(2)
92.12(2)
175.44(4)
175.41(4)
86.15(4)
Cu(2)–Cu(3)–C(4)
88.61(2)
Cu(4)–Cu(1)–Cu(2)
S(2)–Cu(2)–S(3)
S(1)–Cu(4)–S(4)
Cu(1)–S(2)–Cu(2)
Cu(3)–S(4)–Cu(4)
Cu(4)–S(1)–Si(1)
Cu(2)–S(2)–Si(2)
Cu(3)–S(3)–Si(3)
Cu(4)–S(4)–Si(4)
87.00(2)
165.58(5)
173.45(5)
80.54(5)
78.50(5)
104.67(6)
99.80(5)
100.14(6)
112.35(5)
86.65(4)
110.22(7)
106.86(5)
107.83(5)
105.67(6)
Fig. 2 Structure of Co(SSiMe2But)2(tmeda) 3.
N–Co–N* angle of 85.0(1)Њ is the smallest one due to the chel-
ate bite. The S–Si distance of 2.119(1) Å is slightly longer than
the corresponding distances observed in the related triphenyl-
silanethiolato complex Co(SSiPh3)2(tmeda) (average 2.104 Å).8
Complex 4 consists of an eight-membered Cu4S4 core with
adjacent pairs of copper atoms bridged by the sulfur of the
silanethiolato groups [Fig. 3(a) and Table 3]. This thiolato-
bridged M4S4 ring geometry was previously observed for tetra-
meric coinage thiolates.8,12,25,26 Three thiolato substituents
[Si(1), Si(2) and Si(4)] are directed to one side of the Cu4S4
ring, while the fourth substituent [Si(3)] is oriented toward the
opposite side, producing a syn–syn–anti configuration. The
Cu4S4 ring is distinctly folded by 140.59(4)Њ along the S(2)–S(4)
diagonal due to steric congestion. The two-coordinate copper
atoms adopts a geometry considerably distorted from linear,
and the S–Cu–S angles range from 165.58(5) to 175.44(4)Њ. This
deviation from linearity may be attributed to weak metal–metal
interactions. The Cu–Cu distances differs significantly. Two
Cu–Cu distances [Cu(1)–Cu(2), 2.8128(6) Å; Cu(3)–Cu(4),
2.7413(7) Å] are shortened compared to other two [Cu(1)–
Cu(4), 2.9680(9) Å; Cu(2)–Cu(3), 2.9541(9) Å], whereas the
Cu–S–Cu angles at S(2) [80.54(5)Њ] and S(4) [78.50(5)Њ] are
smaller than the corresponding angles at S(1) [86.15(4)Њ] and
S(3) [86.65(4)Њ]. The Cu–S distances average 2.167 Å and are
typical of copper() complexes with bridging thiolato
donors.8,12,25 The average Si–S distance of 2.162 Å is slightly
elongated relative to that of [Cu(SSiPh3)]4 (2.148 Å).8
In the solid-state structure of 4, it should be noted that the
tetramer displays secondary Cu(4)–S(2*) interactions [2.985(1)
Å] with an adjacent molecule to provide the aggregate [{Cu-
t
(SSiMe2 Bu)}4]2 [Fig. 3(b)]. The structural features found in the
aggregate [{Cu(SSiMe2But)}4]2 closely resembles that of the bis-
cyclic structure of [{Ag(SC6H4-2-SiMe3)}4]2.27 This is in con-
trast to the related silanethiolato complexes [Cu(SSiPh3)]4,
which exist as discrete centrosymmetric tetrameric units with a
square plane of copper atoms.8 This difference may arise from
the orientations of the thiolato substituents relative to the
Cu4S4 core. The SiPh3 groups are disposed in an alternate pat-
tern above and below the Cu4S4 ring to give an anti–anti–anti
configuration, in which the phenyl substitutes effectively cover
the Cu4S4 surface. This arrangement prevents close approach of
Cu4S4 units.
Compound 5 crystallizes with two crystallographically
independent molecules in the asymmetric unit. Although the
geometric parameters are somewhat different between two
molecules, their main structural features are practically the
same. Therefore, Fig. 4 shows the structure for only one of
them, while the metric parameters of the two molecules are
compared in Table 4. The structure shows titanium in the
expected tetrahedral environment and the two trimethylsilyl
groups exhibit an anti orientation. The Ti–S distances average
2.426 Å, which is comparable to the corresponding distance of
(C5H5)2Ti(SC6H5)2 (average 2.432 Å).28
Molecules of 7 possess a distorted square planar geometry at
nickel (Fig. 5 and Table 5). The mean deviation for the best
plane defined by the Ni, S(1), S(2), P(1) and P(2) atoms is 0.06
Å. The Ni–S distances (average 2.241 Å) and Ni–P distances
(average 2.163 Å) are comparable to those in the related cis-
bis(thiolato) square-planar nickel complexes, Ni(SC6F5)2-
(dppe) (Ni–S, 2.217 Å; Ni–P, 2.188 Å)29 and Ni(SC6HF4)2-
(dppe) (Ni–S, 2.211 Å; Ni–P, 2.177 Å).30 The average S–Si
Fig. 3 (a) Structure of the tetranuclear core [Cu(SSiMe2But)]4 4.
(b) Fusing of two tetranuclear units via Cu(4)–S(2*) secondary
interactions giving [{Cu(SSiMe2But)}4]2. Carbon atoms are omitted for
clarity. Atoms carrying the asterisk are related to their counterparts by
the symmetry operator [x, y, –1 ϩ z].
D a l t o n T r a n s . , 2 0 0 4 , 1 6 1 8 – 1 6 2 5
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Table 4 Selected bond distances (Å) and angles (Њ) for 5 and 6
Table 6 Selected bond distances (Å) and angles (Њ) for 9
5
Ti–Ni
2.8292(4)
2.2282(7)
2.2182(6)
2.1567(6)
Ti–Cl
2.3381(6)
2.2303(8)
2.2096(7)
2.1649(6)
Ti–S(1)
Ni–S(1)
Ni–P(1)
Ti–S(2)
Ni–S(2)
Ni–P(2)
Molecule A
Molecule B
6
Ti–S(1)
Ti–S(2)
S(1)–Si(1)
S(2)–Si(2)
2.414(1)
2.439(1)
2.132(1)
2.129(2)
2.413(1)
2.436(1)
2.149(1)
2.135(1)
2.4391(9)
2.4443(8)
2.147(1)
2.149(1)
S(1)–Ti–S(2)
Ti–S(1)–Ni
Cl–Ti–S(1)
P(1)–Ni–P(2)
S(1)–Ni–P(2)
S(2)–Ni–P(2)
99.98(3)
79.03(2)
103.21(3)
87.69(2)
171.48(2)
87.29(2)
S(1)–Ni–S(2)
Ti–S(2)–Ni
Cl–Ti–S(2)
S(1)–Ni–P(1)
S(2)–Ni–P(1)
100.93(2)
79.17(3)
104.32(3)
84.02(2)
174.74(3)
S(1)–Ti–S(2)
Ti–S(1)–Si(1)
Ti–S(2)–Si(2)
100.71(4)
123.22(5)
122.14(5)
97.72(4)
120.44(5)
119.56(6)
98.23(3)
120.21(4)
120.41(4)
According to the X-ray analysis, the crystal structures of the
tert-butyldimethylsilanethiolato complexes, 6 and 8, are similar
to their trimethylsilanethiolato congeners. Selected bond dis-
tances and angles of 6 and 8 are listed in the third column of
Table 4 and the second column of the Table 5, respectively.
Comparison between trimethylsilanethiolato (5 and 7) and tert-
butyldimethylsilanethiolato (6 and 8) complexes demonstrates
that the influence of the Si-substituent is not manifested as a
significant perturbation of metal–ligand distances and angles.
It is instructional to compare the Si–S bonds of tri-
alkylsilanethiolato and triphenylsilanethiolato complexes.1,2,8–10
It has been that suggested that the overall order of Si–S dis-
Table 5 Selected bond distances (Å) and angles (Њ) for 7 and 8
7
8
Ni–S(1)
Ni–S(2)
Ni–P(1)
Ni–P(2)
S(1)–Si(1)
S(2)–Si(2)
2.250(1)
2.231(1)
2.162(1)
2.163(2)
2.136(2)
2.115(2)
2.253(2)
2.246(2)
2.166(2)
2.166(2)
2.127(2)
2.131(2)
S(1)–Ni–S(2)
P(1)–Ni–P(2)
S(1)–Ni–P(1)
S(1)–Ni–P(2)
S(2)–Ni–P(1)
S(2)–Ni–P(2)
Ni–S(1)–Si(1)
Ni–S(2)–Si(2)
98.29(6)
86.87(6)
173.31(6)
86.98(5)
88.06(6)
172.93(7)
106.99(8)
107.28(7)
99.67(6)
85.58(6)
174.62(7)
89.82(6)
84.99(6)
170.47(7)
106.39(8)
108.28(8)
tances of silanethiolato ligands is SSiMe2But > SSiMe3
>
SSiPh3, although exceptions to this general hierarchy exist.8,9
Within trialkylsilanethiolato complexes of transition metals,
the Si–S distances of bridging ligands (4, average 2.162 Å) are
lengthened relative to those of terminal ligands (3, 2.119(1) Å;
5, average 2.136 Å; 7, average 2.126 Å). The longest Si–S dis-
tance is observed for the Si(2)–S(2) bond of 4 [2.178(2) Å],
which involves secondary Cu–S interactions found in the aggre-
gate [{Cu(SSiMe2But)}4]2. The reason for this trend presumably
lies in partial ionic character of the silicon–sulfur bond (i.e.,
Siδϩ–SδϪ), in which the electron density on sulfur decreases in
going from terminal to bridging ligands. A similar phenomenon
has been noted in a series of triphenylsilanethiolato complexes
of transition metals.8 Although the silanethiolato ligands in 1
bridge two lithium centers, the Si–S bonds of 1 [2.079(1) Å] are
significantly short compared to those found in silanethiolato
complexes of transition metals. This shortening is probably a
consequence of the more electropositive lithium cation allow-
ing more electron density on sulfur in 1, which in turn gives a
stronger Si–S bond due to pπ–dπ and/or pπ–σ* interaction
between sulfur and silicon.31
Cluster forming reactions
The reactivity of silicon–heteroatom bonds can be tuned by
the substituents on the silicon. To compare the reactivity
of transition metal-bound trimethylsilanethiolates and tert-
butyldimethylsilanethiolates, we carried out the reactions of
Fig. 4 Structure of molecule A in (C5H5)2Ti(SSiMe3)2 5.
t
(dppe)Ni(SSiMe2R)2 (R = Me 7, Bu 8) with (C5H5)TiCl3. The
trimethylsilanethiolato complex 7 was found to react readily
and cleanly with (C5H5)TiCl3 in toluene at room temperature to
generate (C5H5)TiCl(µ-S)2Ni(dppe) 9 in 66% isolated yield. The
1H NMR spectrum and combustion analysis of 9 revealed a
1 : 1 ratio of the C5H5 group to the dppe ligand. The IR spec-
trum indicated the absence of absorptions characteristic of the
SiMe3 group.
The sulfido-bridged heterometallic core of 9 was confirmed
by X-ray crystallography (Fig. 6 and Table 6). The titanium()
and nickel() centers adopt tetrahedral and square planar
geometries, respectively. The structure of 9 closely resembles
that of the related sulfido-bridging Ti/Pd compound (C5H5)TiCl-
(µ-S)2Pd(PEt3)2.4 The TiS2Ni quadrilateral is slightly puckered
with a dihedral angle of 169.0Њ along the S ؒ ؒ ؒ S line. The acute
angles at S(1) [79.03(2)Њ] and S(2) [79.17(3)Њ] and the relatively
short Ti–Ni separation of 2.8292(4) Å suggest a nickel-to-
titanium dative interaction. The observed Ti–Ni distance is
Fig. 5 Structure of Ni(SSiMe3)2(dppe) 7.
distance of 7 (2.126 Å) is slightly long relative to that observed
in the triphenylsilanethiolato complex Ni(SSiPh3)2(tmeda)
(2.105 Å).8
D a l t o n T r a n s . , 2 0 0 4 , 1 6 1 8 – 1 6 2 5
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using standard Schlenk-line techniques. Solvents were dried
and distilled over an appropriate drying agent under an atmos-
phere of dinitrogen. N,N,NЈ,NЈ-tetramethylethylenediamine
1
7
(tmeda) were dried and distilled from CaH2. H, Li, 13C{1H},
31P{1H} and 29Si{1H} NMR spectra were recorded on JEOL
Lambda-500 and JEOL JNM-GX500 spectrometers. Chemical
shifts were reported in ppm. IR samples were recorded as Nujol
mulls between KBr plates using a JASCO FT/IR-410 spectro-
meter. For UV–visible spectra, a JASCO V-560 spectrometer
was used. Solution magnetic susceptibilities were determined by
the Evans’ method20 and corrected for underlying diamagnet-
ism. Elemental analyses were measured using Yanaco MT-6,
22
MSU-32 and LECO-CHNS-932 microanalyzers. (Me2SiS)3
was prepared according to published methods.
Preparations
Synthesis of [Li(tmeda)SSiMe2But]2 1. A solution of Li-
SSiMe2But was prepared by analogous method to literature
procedure.18 To a solution of (Me2SiS)3 (2.9 cm3, 3.6 mmol: 1.24
mol dmϪ3 Et2O solution) in hexane (15 cm3) was added drop-
wise ButLi (6.6 cm3, 11 mmol: 1.62 mol dmϪ3 pentane solution)
at 0 ЊC. The pale yellow solution was stirred for 3 min at 0 ЊC
and treated with tmeda (1.8 cm3, 12 mmol). The solution was
stirred for a further 5 min at 0 ЊC and afforded, after concen-
tration and storage at Ϫ25 ЊC, colorless crystals of 1 (2.09 g,
72%), νmax/cmϪ1 1355m, 1291m, 1239m (SiC), 1234m (SiC),
1178w, 1156w, 1130w, 1065w, 1038m, 1022m, 1013w, 948m,
821s (SiC), 796s, 751m, 665s, 586m, 506m and 434w (Nujol);
δH (500 MHz; C6D6) 2.19 (24 H, s, 8 NCH3), 1.93 (8 H, s,
4 NCH2), 1.28 (18 H, s, 2 SiBut) and 0.43 (12 H, s, 2 SiMe2);
δLi (194.25 MHz; C6D6) 1.05 (s); δC (125.65 MHz; C6D6) 56.9 (s,
NCH2), 47.0 (s, NCH3), 27.6 [s, SiC(CH3)3], 20.2 [s, SiC(CH3)3]
and 2.9 (s, SiMe2); δSi (99.25 MHz, C6D6) 15.3 (s).
Fig. 6 Structure of (C5H5)TiCl(µ-S)2Ni(dppe) 9.
close to that of (C5H5)2Ti(µ-SCH2CH2CH2PPh2)2Ni [2.825(3)
Å]32 and longer than those of [(C5H5)2Ti(µ-SMe)2]2Ni (2.786
34
Å)33 and [(C H ) Ti(µ-SC᎐CPh) ] Ni (2.789 Å). The Ni–S
᎐
᎐
5
5
2
2 2
distances (average 2.214 Å) is short relative to that of 7, and the
S–Ni–S angle of 100.93(2)Њ is increased.
On the other hand, the reaction between the tert-butyl-
dimethylsilanethiolato complex 8 and (C5H5)TiCl3 produced an
inseparable mixture of 9 and ill-defined compound(s). The prob-
lem arose probably from the fact that the Si–S bond of the tert-
butyldimethylsilanethiolato ligand is less reactive compared to
that of the trimethylsilanethiolato ligand, and thus by-products
may be formed as a result of ligand redistribution competition
with Si–S bond cleavage reaction. In fact, as we previously
reported, treatment of the triphenylsilanethiolato complex Fe-
(SSiPh3)2(CH3CN)2 with (NEt4)2[FeCl4] gave (NEt4)2[Fe2-
(SSiPh3)2Cl4], where the ligand transfer was preferred to Si–S
bond rupture.8 This difference in the reactivity between 7 and 8
may be attributed to the steric bulk of the tert-butyl group.
Synthesis of Fe(SSiMe2But)2(tmeda) 2.
A solution of
Fe(CH3CN)2(CF3SO3)2 (0.43 g, 0.99 mmol) in CH3CN (10 cm3)
was treated with 1 (0.45 g, 0.83 mmol) in CH3CN (10 cm3).
After stirring for 5 min at room temperature, the brown solu-
tion was evaporated to dryness. The residue was extracted with
hexane (15 cm3) and centrifuged. Concentration and storage at
Ϫ25 ЊC afforded 2 as a colorless crystalline powder (0.30 g,
77%) (Found: C, 46.11; H, 10.07; N, 5.93; S, 13.66. C18H46-
FeN2S2Si2 requires C, 46.32; H, 9.93; N, 6.00; S, 13.74%);
νmax/cmϪ1 1357m, 1284m, 1246m (SiC), 1238s (SiC), 1123w,
1060w, 1045w, 1023m, 1007m, 951m, 938w, 834s (SiC), 827s,
821s, 795s, 762s, 668m, 585m and 489s (Nujol); δH (500 MHz;
C6D6) 108.5 (4 H, br, ∆ν1/2 710 Hz, 2 NCH2), 78.1 (12 H, br,
∆ν1/2 600 Hz, 4 NCH3), 19.5 (12 H, br, ∆ν1/2 200 Hz, 2 SiMe2) and
12.0 (18 H, br, ∆ν1/2 50 Hz, 2 SiBut); µeff (Evans’ NMR method;
296 K; C6D6) 5.0 µB/Fe.
Summary
In this report, we have described the synthesis of a range of
trimethylsilanethiolato and tert-butyldimethylsilanethiolato
complexes along with some of their solid-state structures. These
trialkylsilanethiolato complexes are readily accessible by salt
metathesis reactions of the corresponding lithium silanethiol-
ates, derived from cyclotrisilathiane and alkyllithiums. Silane-
thiolato complexes obtained are dependent on the nature of
the substituents at silicon. A series of trialkyl- and triphenyl-
silanethiolato complexes allows us the best crystallographic
opportunity to date of investigating the structural influences of
a silanethiolato ligand as a function of the metal center, the
thiolato ligand Si-substituent and the coordination mode of the
thiolato ligand. The potential of silanethiolato species to serve
as precursors for metal–sulfido clusters has been investigated
through the reactions of nickel silanethiolato complexes with
(C5H5)TiCl3. It appears that the cluster forming reactions using
silanethiolato complexes are controlled by the steric and elec-
tronic properties of Si-substituents. Further studies into the
application of silanethiolato complexes in cluster syntheses are
ongoing within the group.
Synthesis of Co(SSiMe2But)2(tmeda) 3. To a suspension of
CoCl2 (0.18 g, 1.4 mmol) in THF (5 cm3) was added a solution
of 1 (0.77 g, 1.4 mmol) in THF (15 cm3) at 0 ЊC. The resulting
dark blue solution was stirred for 10 min at room temperature
and evaporated to dryness. The residue was extracted with tolu-
ene (10 cm3) and centrifuged. After concentration, addition of
hexane (5 cm3), evaporation and washing with hexane (8 cm3),
blue–purple crystals of 3 were obtained (0.45 g, 69%) (Found:
C, 45.66; H, 9.96; N, 5.88; S, 13.48. C18H46CoN2S2Si2 requires
C, 46.02; H, 9.87; N, 5.96; S, 13.65%); λmax/nm (Et2O) 236 (sh)
(ε/dm3 molϪ1 cmϪ1 5800), 289 (sh) (2500), 312 (6500), 369
(3800), 387 (sh) (2400), 570 (220) and 700 (730); νmax/cmϪ1
1356m, 1283m, 1244s (SiC), 1238s (SiC), 1123w, 1056w, 1042w,
1025m, 1004m, 948m, 833s (SiC), 820s, 799s, 759s, 672s, 582m
and 491s (Nujol); δH (500 MHz; C6D6) 84.8 (12 H, br, ∆ν1/2
270 Hz, 4 NCH3), 74.0 (4 H, br, ∆ν1/2 1200 Hz, 2 NCH2), 11.3
(18 H, br, ∆ν1/2 21 Hz, 2 SiBut) and Ϫ6.4 (12 H, br, ∆ν1/2 62 Hz, 2
SiMe2); µeff(Evans’ NMR method; 297 K; C6D6) 4.2 µB/Co.
Experimental
General procedures
All manipulations of air- and/or moisture-sensitive compounds
were carried out under an atmosphere of dinitrogen or argon
D a l t o n T r a n s . , 2 0 0 4 , 1 6 1 8 – 1 6 2 5
1622

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Synthesis of [Cu(SSiMe2But)]4 4. A solution of 1 (0.21 g, 0.39
mmol) in CH3CN (10 cm3) was treated with [Cu(CH3CN)4]-
(PF6) (0.29 g, 0.78 mmol) in CH3CN (10 cm3) at 0 ЊC. After
stirring for 10 min at room temperature, the orange–brown mix-
ture was evaporated to dryness. The residue was extracted with
hexane (15 cm3) and centrifuged. Concentration of the super-
natant and storage at Ϫ30 ЊC gave 4 as colorless crystals (0.08 g,
49%), (Found: C, 33.68; H, 7.21; S, 15.17. C24H60Cu4S4Si4
requires C, 34.17; H, 7.17; S, 15.21%); νmax/cmϪ1 1360m, 1248s
(SiC), 1003w, 937w, 835s (SiC), 819s, 800s, 771s, 674m, 581m
and 466s (Nujol); δH (500 MHz; C6D6) 1.05 (36 H, s, 4 SiBut)
and 0.49 (24 H, s, 4 SiMe2).
Synthesis of Ni(SSiMe2But)2(dppe) 8. Treatment of NiCl2-
(dppe) (0.28 g, 0.53 mmol) in THF (15 cm3) with a solution of 1
(0.29 g, 0.54 mmol) in THF (15 cm3) at 0 ЊC gave a dark purple
solution. After stirring for 10 min at room temperature, the
solvent was removed under vacuum. The residue was extracted
with toluene (7 cm3) and centrifuged. After evaporation of the
supernatant, trituration with hexane (5 cm3) and storage at
Ϫ25 ЊC, a dark purple crystalline powder of 8 was obtained
(0.33 g, 83%), (Found: C, 60.42; H, 7.54; S, 8.25. C38H54-
NiP2S2Si2 requires C, 60.71; H, 7.24; S, 8.53%); λmax/nm (Et2O)
255 (ε/dm3 molϪ1 cmϪ1 23 000), 301 (32 000), 418 (sh) (1700) and
550 (1900); νmax/cmϪ1 3050w, 1437s, 1355w, 1232m (SiC),
1098m, 1025w, 1001w, 874w, 831m (SiC), 819m, 809s, 798s,
764m, 750m, 743m, 709m, 700m, 694s, 671m, 649w, 577w, 532s,
525m, 478s, 444w and 431w (Nujol); δH (500 MHz; C6D6) 7.80
(8 H, br, PC6H5), 7.04–7.08 (12 H, m, PC6H5), 1.50–1.60 (4 H,
br, PCH2), 1.06 (18 H, s, 2 SiBut) and 0.63 (12 H, s, 2 SiMe2).
Synthesis of (C5H5)2Ti(SSiMe3)2 5. To a solution of (Me2SiS)3
(1.0 cm3, 1.1 mmol: 1.11 mol dmϪ3 hexane solution) in Et2O
(15 cm3) was added slowly MeLi (2.7 cm3, 3.1 mmol: 1.14 mol
dmϪ3 Et2O solution) with cooling in an ice bath. After stirring
at 0 ЊC for 5 min, the colorless solution was added to the sus-
pension of (C5H5)2TiCl2 (0.37 g, 1.5 mmol) in toluene (10 cm3).
The dark red–purple mixture was stirred for 15 min at 0 ЊC and
evaporated to dryness. The residue was extracted with hexane
(25 cm3) and centrifuged to remove insoluble solid, followed by
removal of the solvent under vacuum. Recrystallization from
CH3CN afforded 5 as black needles (0.26 g, 45%) (Found: C,
49.05; H, 7.45; S, 16.50. C16H28S2Si2Ti requires C, 49.46; H,
7.26; S, 16.50%); λmax/nm (Et2O) 239 (ε/dm3 molϪ1 cmϪ1 29000),
317 (11000), 437 (2900) and 554 (3600); νmax/cmϪ1 3082w (CH),
1402w, 1239s (SiC), 1027m, 1016m, 836s (SiC), 809s, 752m,
688w, 633s, 476s and 466s (Nujol); δH (499.10 MHz; C6D6) 5.97
(10 H, s, 2 C5H5) and 0.53 (18 H, s, 2 SiMe3).
Synthesis of (C5H5)TiCl(ꢀ-S)2Ni(dppe) 9. Addition of 7
(0.21 g, 0.31 mmol) in toluene (10 cm3) to a solution of (C5H5)-
TiCl3 (0.07 g, 0.32 mmol) in toluene (10 cm3) immediately gave
an orange suspension. After stirring for 2 h at room tem-
perature, the reaction mixture was centrifuged to remove of
supernatant. After washing with Et2O (10 cm3 × 2), a crude
yellow–orange powder was obtained. The resulting solid was
extracted with CH2Cl2 (6 cm3) and Et2O (15 cm3) was layered.
After 12 days, orange crystals were formed and washed with
CH3OH (5 cm3 × 2) and Et2O (5 cm3 × 2). Orange plates of 9
were afforded (0.14 g, 66% based on Ni), (Found: C, 55.30; H,
4.41; S, 9.15. C31H29ClNiP2S2Ti requires C, 55.60; H, 4.36; S,
9.58%); λmax/nm (CH2Cl2) 257 (ε/dm3 molϪ1 cmϪ1 49000), 298
(sh) (28000) and 425 (4700); νmax/cmϪ1 3051w, 1435s, 1308w,
1186w, 1099s, 1015m, 997w, 879w, 817m, 806m, 795s, 750m,
741w, 706s, 697s, 677m, 652w, 532s, 485m, 456s and 438m
(Nujol); δH (500 MHz; CDCl3) 7.70 (4 H, m, PC6H5), 7.57 (4 H,
m, PC6H5), 7.36–7.51 (12 H, m, PC6H5), 6.26 (5 H, s, C5H5),
2.67 (2 H, m, PCHaHb) and 2.41 (2 H, m, PCHaHb); δP (202.35
MHz, CDCl3) 66.6 (s).
Synthesis of (C5H5)2Ti(SSiMe2But)2 6. Treatment of
(C5H5)2TiCl2 (0.24 g, 0.96 mmol) in THF (20 cm3) with 1 (0.53
g, 0.98 mmol) in THF (15 cm3) gave a dark red–purple solution.
After stirring for 10 min at room temperature, the solvent
was removed in vacuo. The residue was extracted with toluene
(17 cm3) and centrifuged to remove insoluble solid. The super-
natant was evaporated to dryness and the resulting solid was
triturated with hexane (5 cm3). After storage at Ϫ25 ЊC over-
night and decantation, dark red crystals of 6 were isolated
(0.37 g, 81%) (Found: C, 55.81; H, 8.49; S, 13.42. C22H40S2Si2Ti
requires C, 55.90; H, 8.53; S, 13.57%); λmax/nm (THF) 241
(ε/dm3 molϪ1 cmϪ1 24000), 322 (12000), 446 (3000) and 550
(4300); νmax/cmϪ1 3073m (CH), 1253m (SiC), 1248m (SiC),
1038w, 1019w, 1004w, 853w, 843w, 834m (SiC), 804s, 797s,
760m, 661w, 577w, 481w and 468m (Nujol); δH (500 MHz;
C6D6) 5.98 (10 H, s, 2 C5H5), 1.13 (18H, s, 2 SiBut) and 0.55
(12 H, s, 2 SiMe2).
Crystallography
Crystallographic data for 1 and 3–9 are summarized in Table 7.
Crystals of these complexes were mounted by a glass fiber (for
1) and by nylon loops (for 3–9), which were set on a Rigaku
Mercury CCD system with graphite-monochromated Mo-Kα
radiation (λ = 0.71070 Å) under a cold nitrogen stream. Data
were collected at 193 K (for 1 and 8), 223 K (for 3), 153 K (for 4,
6 and 7), and 173 K (for 5 and 9). The structures of 3, 5, 6 and 8
were solved by the Patterson method and the other structures
(1, 4, 7 and 9) were solved by direct methods. All structures were
refined on F 2 by the full-matrix least-squares method using
CrystalStructure software package.35 Anisotropic refinement
was applied to all non-hydrogen atoms, and all the hydrogen
atoms except those associated the disordered methylene groups
of 1 were put at calculated positions. Refinement of the Flack
parameter for 1 yielded 0.07(13), confirming the correct polar-
ity.36 In the final difference Fourier syntheses of the nickel
silanethiolato complexes, the residual peaks of 3.11 e ÅϪ3 for 7
and 3.63 e ÅϪ3 for 8 were observed within 0.21 Å of the Ni
atom.
Single crystals of 1 were obtained by crystallization from
hexane. The asymmetric unit consists of one SSiMe2But mole-
cule, two lithium metals, and two tmeda molecules. Thus, the
four nitrogen atoms of tmeda ligands and two lithium atoms lie
on a crystallographic mirror plane. Two CH2CH2 moieties of
each tmeda molecule are disordered around the mirror plane
with occupancy factors of 50 : 50. Single crystals of 3 were
obtained by crystallization from Et2O. A cobalt atom lies on a
crystallographic mirror plane, hence, the asymmetric unit con-
sists of a half-molecule. Single crystals of 4 and 5 were obtained
Synthesis of Ni(SSiMe3)2(dppe) 7. A solution of (Me2SiS)3
(1.2 cm3, 1.3 mmol: 1.11 mol dmϪ3 hexane solution) in Et2O
(15 cm3) was treated with MeLi (3.3 cm3, 3.8 mmol: 1.14 mol
dmϪ3 Et2O solution) with cooling in an ice bath. After stirring
at 0 ЊC for 5 min, the colorless solution was added to a suspen-
sion of NiCl2(dppe) (0.99 g, 1.9 mmol) in THF (5 cm3). After
stirring for 10 min at 0 ЊC THF (10 cm3) was added to this, and
stirred for an additional 15 min at 0 ЊC. The resulting dark
purple solution was evaporated. The residue was extracted with
toluene (18 cm3) and centrifuged to remove an insoluble
material. Concentration of the supernatant and slow addition
of hexane (30 cm3) resulted in formation of a purple solid.
After filtration and washing with hexane (5 cm3 × 3), a purple
crystalline powder of 7 was afforded (1.15 g, 92%) (Found: C,
57.64; H, 6.29; S, 9.25. C32H42NiP2S2Si2 requires C, 57.57; H,
6.34; S, 9.61%); νmax/cmϪ1 3049m, 1483w, 1436s, 1407w, 1242m
(SiC), 1235s (SiC), 1102m, 1026w, 998w, 876w, 830s (SiC),
816m, 745s, 709m, 701s, 694s, 679m, 652w, 632s, 534s, 479s,
472m and 437w (Nujol); δH (500 MHz; C6D6) 7.83 (8 H, br,
PC6H5), 7.07 (12 H, m, PC6H5), 1.60 (2 H, br, PCHaHb), 1.57
(2 H, br, PCHaHb) and 0.53 (18 H, s, 2 SiMe3).
D a l t o n T r a n s . , 2 0 0 4 , 1 6 1 8 – 1 6 2 5
1623

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by crystallization from hexane. For 5, the asymmetric unit
consists of two independent molecules of the complex. Single
crystals of 6 and 9 were obtained by crystallization from tolu-
ene–CH3CN and CH2Cl2–Et2O, respectively. Single crystals of
7 and 8 were obtained by crystallization from toluene–hexane.
CCDC reference numbers 227191–227198.
See http://www.rsc.org/suppdata/dt/b3/b316567a/ for crystal-
lographic data in CIF or other electronic format.
Acknowledgements
This work was supported by a Grant-in-Aid for Scientific
Research [Nos. 14703008 and 14078101 (Priority Areas
“Reaction Control of Dynamic Complexes”)] from Ministry of
Education, Culture, Sports, Science, and Technology, Japan.
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D a l t o n T r a n s . , 2 0 0 4 , 1 6 1 8 – 1 6 2 5
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