Hard/soft interactions in early transition metal chemistry: Synthesis, properties and structures of thioether and selenoether complexes of titanium(iv)

Article abstract of DOI:10.1039/b002792h

Reaction of TiCl4 with L-L [L-L = MeE(CH2)EMe; E = S or Se, n = 1 or 3, PhE(CH₂)₂EPh or o-C₆H₄(EMe)₂] in anhydrous H-hexane solution under an N₂ atmosphere results in the rapid formation of [TiCl₄(L-L)] as yellow, orange or red solids. Analogous bromo and iodo species, [TiX4(L-L)] [X = Br; L-L = MeE(CH2)EMe or o-C₆H₄(EMe)₂; X = I; L-L = MeSe(CH₂)₂SeMe or o-C₆H₄(SeMe)₂], were obtained as intense orange or red coloured solids by treatment of TiX4 with L-L in CH2C12 solution. Crystallographic studies on [TiCl₄-{MeS(CH₂)₂SMe}], [TiCl₄{MeS(CH₂)₃SMe}], [TiCl₄{MeSe(CH₂)₃SeMe}] and [TiCl₄{o-C₆H₄(SeMe)₂}] reveal a distorted octahedral arrangement with the coordinated group 16 donor ligand adopting the DL form in the first three cases and the meso form in the fourth example. These studies also reveal a trans influence series of Cl > S = Se on Ti(iv). Solution NMR studies show that the chloro-compounds undergo rapid pyramidal inversion at ambient temperature, while the bromo and iodo species also undergo rapid ligand dissociation/chelate ring-opening. At low temperature these processes are slowed significantly, such that in most of the chloro and bromo species it is possible to identify both the meso and DL invertomers, although ligand exchange is still rapid at 200 K for the iodo species. The potential of these compounds as sources of titanium sulfide or titanium selenide phases via controlled decomposition is also discussed briefly. Finally, the dinuclear species, [CI₃Ti{MeS(CH₂)₂SMe}]₂(u-O), formed by partial hydrolysis of [TiCl₄{MeS(CH₂)₂SMe}], has also been identified crystallographically. The Royal Society of Chemistry 2000.

Full text of DOI:10.1039/b002792h

View Article Online / Journal Homepage / Table of Contents for this issue
Hard/soft interactions in early transition metal chemistry:
synthesis, properties and structures of thioether and selenoether
complexes of titanium(IV)
William Levason, Bhavesh Patel, Gillian Reid, Vicki-Anne Tolhurst and Michael Webster
Department of Chemistry, University of Southampton, Highfield, Southampton, UK SO17 1BJ
Received 7th April 2000, Accepted 12th July 2000
Published on the Web 4th August 2000
Reaction of TiCl4 with L–L [L–L = MeE(CH2)nEMe; E = S or Se, n = 2 or 3, PhE(CH2)2EPh or o-C6H4(EMe)2]
in anhydrous n-hexane solution under an N2 atmosphere results in the rapid formation of [TiCl4(L–L)] as yellow,
orange or red solids. Analogous bromo and iodo species, [TiX4(L–L)] [X = Br; L–L = MeE(CH2)nEMe or
o-C6H4(EMe)2; X = I; L–L = MeSe(CH2)2SeMe or o-C6H4(SeMe)2], were obtained as intense orange or red
coloured solids by treatment of TiX4 with L–L in CH2Cl2 solution. Crystallographic studies on [TiCl4-
{MeS(CH2)2SMe}], [TiCl4{MeS(CH2)3SMe}], [TiCl4{MeSe(CH2)3SeMe}] and [TiCl4{o-C6H4(SeMe)2}] reveal a
distorted octahedral arrangement with the coordinated group 16 donor ligand adopting the  form in the first
three cases and the meso form in the fourth example. These studies also reveal a trans influence series of Cl > S ≈ Se
on Ti(). Solution NMR studies show that the chloro-compounds undergo rapid pyramidal inversion at ambient
temperature, while the bromo and iodo species also undergo rapid ligand dissociation/chelate ring-opening. At low
temperature these processes are slowed significantly, such that in most of the chloro and bromo species it is possible
to identify both the meso and  invertomers, although ligand exchange is still rapid at 200 K for the iodo species.
The potential of these compounds as sources of titanium sulfide or titanium selenide phases via controlled
decomposition is also discussed briefly. Finally, the dinuclear species, [Cl3Ti{MeS(CH2)2SMe}]2(µ-O), formed
by partial hydrolysis of [TiCl4{MeS(CH2)2SMe}], has also been identified crystallographically.
position behaviour of this class of compound is expected
Introduction
to vary with halogen. There are very few well characterised
TiI4 complexes in the literature,6 and no thio- or seleno-ether
derivatives. The group 16 donor ligands which we have used
includes a range of C-functionalities since this is expected to
permit some tuning of the deposition characteristics at the
next stage of this work. The crystal structures of [TiCl4-
{MeS(CH2)2SMe}], [TiCl4{MeS(CH2)3SMe}], [TiCl4{MeSe-
(CH2)3SeMe}], [TiCl4{o-C6H4(SeMe)2}] and [{MeS(CH2)2-
SMe}Cl3Ti(µ-O)TiCl3{MeS(CH2)2SMe}] are also described.
The coordination chemistry of thio- and seleno-ether ligands
with transition metal centres is dominated by complexes involv-
ing middle and late transition metals in medium or high oxid-
ation states, although a number of low-valent early transition
metal carbonyl complexes involving seleno- and telluro-ether
ligands have been reported.1,2 We have investigated the synthesis
and properties of group 16 donor ligands and their coordin-
ation to a wide range of transition metal and p-block ions in
order to exploit the versatile nature of these ligands towards
both high and low oxidation state metals. We are particularly
interested in developing the coordination chemistry of the
group 4 and group 5 metals with thio- and seleno-ethers as
potential single source precursors to metal chalcogenide
materials. Transition metal sulfides and selenides represent an
important class of inorganic materials with diverse appli-
cations ranging from, for example, cathode materials in
rechargeable Li batteries, to semiconductors and semimetals.3
The use of single source precursors to these materials is attrac-
tive since applications often require that the materials are
deposited as thin films and these are not easily obtained with
conventional methods. Here we report on our investigation of
the preparation, structural features and properties of Ti() hal-
ide compounds with a range of bidentate thio- and seleno-ether
ligands. There are scattered reports in the literature on Ti()
thio- and seleno-ether compounds, but generally their charac-
terisation is very limited and there have been no systematic
studies of their properties.4 Very recently Winter and co-
workers have structurally characterised some complexes with
monodentate thio- and seleno-ethers, although these were
mainly obtained indirectly as metal-mediated decomposition
products.5 We report here on the preparation and spectroscopic
characterisation of a series of TiX4 (X = Cl, Br or I) complexes
with bidentate thioether or seleno ether ligands. The bromo
and iodo species were included since the volatility and decom-
Results and discussion
Reaction of TiCl4 with L–L [L–L = MeE(CH2)nEMe, E = S or
Se, n = 2 or 3, PhE(CH2)2EPh, o-C6H4(EMe)2] in rigorously
anhydrous n-hexane solution at room temperature results in the
immediate precipitation of a yellow, orange or red solid,
[TiCl4(L–L)]. The bromo and iodo derivatives, [TiBr4(L–L)]
[L–L = MeE(CH2)nEMe or o-C6H4(EMe)2] and [TiI4(L–L)]
[L–L = MeSe(CH2)2SeMe or o-C6H4(SeMe)2], were prepared by
dissolving TiBr4 or TiI4 in rigorously anhydrous CH2Cl2 with
L–L, and precipitating the resulting deep orange or red prod-
ucts with n-hexane. The iodo derivatives proved to be particu-
larly difficult to isolate as powdered solids, and typically the
yields of these products were considerably lower than for the
chloro and bromo species. All of the complexes are extremely
readily hydrolysed, rapidly decolorising and liberating L–L
upon exposure to moist air. Therefore, the compounds were
routinely stored in a dry, N2-purged glove-box and under these
conditions the solids do not exhibit any appreciable decom-
position over a period of a few weeks.
IR spectroscopy reveals up to four bands in the region 420–
370 or 330–290 cmϪ1, tentatively attributed to ν(Ti–Cl) or
ν(Ti–Br) respectively, indicative of cis-[TiX4(L–L)] (theory
2a1 ϩ b1 ϩ b2). These data, together with microanalyses,
DOI: 10.1039/b002792h
J. Chem. Soc., Dalton Trans., 2000, 3001–3006
This journal is © The Royal Society of Chemistry 2000
3001

View Article Online
indicate that the products are cis-[TiX4(L–L)]. Electronic spec-
tra were recorded by diffuse reflectance owing to the extreme
sensitivity of the compounds. The spectra of these d0 Ti()
compounds show several broad and intense charge transfer
(CT) transitions. The bromide species generally show broad,
ill-defined overlapping transitions. This is not surprising
since on electronegativity grounds π(Br) → Ti(t2g) is unlikely
to be very different from π(Se or S) → Ti(t2g). Analysis
of the spectra shows that the π(Cl) → Ti(t2g) transitions
occur at ca. 28500 cmϪ1, π(Br) → Ti(t2g) at ca. 22500 cmϪ1
,
π(S) → Ti(t2g) at ca. 22000 cmϪ1 and π(Se) → Ti(t2g) at
ca. 21000 cmϪ1. These values compare with ca. 28000 and 22000
cmϪ1 for the lowest energy π(X) → Ti(t2g) CT transitions in
[TiX6]2Ϫ for X = Cl and Br respectively,7 and serve to confirm
the donor types present.
The solution behaviour of these species was investigated via
1H, 13C{1H} and 77Se{1H} NMR spectroscopy in chlorocarbon
solvents. The 1H NMR spectra are rather less informative than
either the 13C{1H} or 77Se{1H} spectra, however they confirm
the presence of the dithio- or diseleno-ether ligand. For the
TiCl4 adducts sharp 1H resonances are observed, these broaden
significantly in the TiBr4 adducts, indicating that ligand dissoci-
ation and/or fast pyramidal inversion is occurring at 300 K (see
below). Resonances for the individual invertomers are not
observed at this temperature. At 300 K the 13C{1H} NMR
spectra of the TiCl4/dithioether systems generally show sharp
ligand resonances consistent with the high temperature limiting
case, while those of the selenoether complexes are very much
broader, suggesting that inversion is slower for these species.
Cooling to ca. 220 K reveals sharp resonances associated with
the presence of both the meso and  forms in varying ratios.
Similar behaviour is observed by 77Se{1H} NMR spectroscopy.
Thus, at 300 K no resonances are seen in any of the 77Se{1H}
NMR spectra. However, two resonances of unequal intensity
are clearly observed to high frequency of the free diselenoether
upon cooling to 200 K. Addition of MeS(CH2)2SMe to a solu-
tion of [TiCl4{MeS(CH2)2SMe}] at 300 K results in very broad,
but discrete, 13C{1H} resonances for ‘free’ and coordinated
MeS(CH2)2SMe. Cooling this system to 250 K results in sharp
resonances associated with both constituents and with the same
chemical shifts as the individual species. This result indicates
that intermolecular exchange is slow at 250 K, becoming
detectable (but not fast) at room temperature for this TiCl4 sys-
tem. These results also indicate that eight-coordinate species do
not form under these conditions. The susceptibility of these
compounds to hydrolysis is demonstrated by the observation
that the deliberate addition of wet CH2Cl2 to a sample of
[TiCl4{MeS(CH2)2SMe}] results in an immediate decoloris-
ation and the 13C{1H} NMR spectrum shows resonances
associated with uncoordinated MeS(CH2)2SMe only.
The solution behaviour of the TiBr4/dithioether and TiBr4/
diselenoether systems are more complex. At 300 K only very
broad resonances are observed in the 13C{1H} NMR spectra.
Similarly, no 77Se{1H} resonances are evident at 300 K. 13C{1H}
NMR spectra of [TiBr4{MeE(CH2)2EMe}] and [TiBr4{o-C6-
H4(EMe)2}] at 200 K reveal resonances due to ‘free’ dithioether
or diselenoether, as well as weak resonances attributed to the
meso and  forms of the coordinated ligand. For example, at
200 K the 13C{1H} NMR spectrum of [TiBr4{o-C6H4(SeMe)2}]
shows a ‘free’:coordinated selenoether ratio of ca. 1:2 and a
(coordinated) meso: ratio of ca. 1:1. 77Se{1H} NMR
spectroscopy at 200 K shows that [TiBr4{MeSe(CH2)3SeMe}] is
extensively dissociated in solution, revealing a strong resonance
for free ligand, with no obvious sign of resonances from
coordinated selenoether. The limited solubilities of [TiBr4-
{MeSe(CH2)2SeMe}] and [TiBr4{o-C6H4(SeMe)2}] prevented
us from observing 77Se{1H} NMR resonances even at 200 K.
The iodo complexes show sharp 13C{1H} and 77Se{1H} NMR
resonances to high frequency of the group 16 donor ligand
itself even at 200 K with no evidence for individual invertomers.
Fig.
1
View of the structure of [TiCl4{MeS(CH2)2SMe}] with
the numbering scheme adopted. Ellipsoids are drawn at the 40%
probability level.
This is consistent with ligand exchange still occurring rapidly
even under these low temperature conditions.
The NMR data indicate the relative Lewis acid ability of the
Ti() tetrahalides as TiCl4 > TiBr4 > TiI4. Thus, while the
TiCl4 adducts are undergoing fast inversion at room temper-
ature on the NMR timescale, dissociation is slow (see above);
inversion is slow at low temperature. In contrast for the TiBr4
derivatives, both ligand dissociation and pyramidal inversion
are fast at room temperature. Both of these dynamic processes
are slowed considerably at 200 K, but for those systems at the
low temperature limit, a mixture of [TiBr4(L–L)], L–L and
TiBr4 are present in varying amounts (see above). The iodide
complexes undergo rapid exchange even at 200 K.
Unfortunately, unlike in our previous studies on SnX4 com-
plexes with group 16 donor ligands,8 where 119Sn NMR spectra
proved very useful in understanding the solution behaviour of
the new compounds, we were unable to observe the metal
nucleus (in this case 47/49Ti†) NMR spectra for the compounds in
this work. We were easily able to observe 47/49Ti NMR reson-
ances for [(η5-C5H5)2TiCl2] in CH2Cl2 at 300 K. Cooling this
solution resulted in significant broadening and eventual loss of
the signal, presumably due to the quadrupole. Since for the
thio- and seleno-ether systems we were unable to observe 47/49Ti
NMR spectra either at room temperature or on cooling, and as
these nuclei have similar receptivities to 13C (although both are
lower frequency and quadrupolar), the absence of 47/49Ti reson-
ances is consistent with the occurrence of dynamic processes in
solution (see above).
In view of the paucity of well characterised thio- and seleno-
ether complexes of Ti() and in order to establish unequivo-
cally the coordination geometry at Ti(), single crystal X-ray
structure analyses were undertaken on [TiCl4{MeS(CH2)2-
SMe}], [TiCl4{MeS(CH2)3SMe}], [TiCl4{MeSe(CH2)3SeMe}]
and [TiCl4{o-C6H4(SeMe)2}]. Crystals were obtained by slow
evaporation from CH2Cl2 solutions of the complexes. The
structure of [TiCl4{MeS(CH2)2SMe}] shows (Fig. 1, Table 1) a
distorted octahedral geometry at Ti() derived from four
chloro ligands and two mutually cis S-donors from a chelating
dithioether in the  form. The two mutually trans Cl ligands
lean towards the dithioether ligand [Cl(1)–Ti(1)–Cl(2)
162.91(3)Њ]. A similar arrangement was observed previously for
Sn()–tetrahalo derivatives incorporating bidentate dithio-,
† Unusually both 47Ti and 49Ti resonances occur within the same
spectral range.
3002
J. Chem. Soc., Dalton Trans., 2000, 3001–3006

View Article Online
Table 1 Selected bond lengths (Å) and angles (Њ) for [TiCl4{MeS-
(CH2)2SMe}]
Table 3 Selected bond lengths (Å) and angles (Њ) for [TiCl4{MeSe-
(CH2)3SeMe)]
Ti(1)–Cl(1)
Ti(1)–Cl(2)
Ti(1)–Cl(3)
2.2907(8)
2.2926(8)
2.2358(8)
Ti(1)–Cl(4)
Ti(1)–S(1)
Ti(1)–S(2)
2.2253(9)
2.6106(9)
2.6010(8)
Ti(1)–Cl(1)
Ti(1)–Cl(2)
2.278(3)
2.247(4)
Ti(1)–Se(1)
2.755(3)
Cl(2)–Ti(1)–Cl(2*)
Cl(2)–Ti(1)–Cl(1)
Cl(2)–Ti(1)–Cl(1*)
Cl(1)–Ti(1)–Cl(1*)
Cl(2)–Ti(1)–Se(1*)
104.1(2)
Cl(2)–Ti(1)–Se(1)
Cl(1)–Ti(1)–Se(1)
Cl(1)–Ti(1)–Se(1*)
Se(1)–Ti(1)–Se(1*)
87.50(11)
81.58(11)
86.07(11)
81.12(12)
Cl(1)–Ti(1)–Cl(2)
Cl(1)–Ti(1)–Cl(3)
Cl(1)–Ti(1)–Cl(4)
Cl(1)–Ti(1)–S(1)
Cl(2)–Ti(1)–Cl(3)
Cl(2)–Ti(1)–S(1)
Cl(3)–Ti(1)–Cl(4)
Cl(3)–Ti(1)–S(2)
162.91(3)
95.68(3)
94.75(3)
80.02(3)
95.20(3)
87.58(3)
105.66(3)
165.73(3)
Cl(4)–Ti(1)–S(1)
Cl(4)–Ti(1)–S(2)
S(1)–Ti(1)–S(2)
Cl(1)–Ti(1)–S(2)
Cl(2)–Ti(1)–Cl(4)
Cl(2)–Ti(1)–S(2)
Cl(3)–Ti(1)–S(1)
167.45(3)
88.03(3)
80.34(3)
86.98(3)
94.95(3)
79.33(3)
86.30(3)
94.19(14)
95.79(13)
163.7(2)
168.09(14)
Table 2 Selected bond lengths (Å) and angles (Њ) for [TiCl4{MeS-
(CH2)3SMe}]
Ti(1)–Cl(1)
Ti(1)–S(1)
2.235(2)
2.644(2)
Ti(1)–Cl(2)
2.285(2)
Cl(1)–Ti(1)–Cl(1*)
Cl(1)–Ti(1)–Cl(2)
Cl(1)–Ti(1)–Cl(2*)
Cl(1)–Ti(1)–S(1*)
Cl(2)–Ti(1)–Cl(2*)
102.8(1)
96.53(9)
92.73(9)
168.3(1)
165.1(1)
Cl(2)–Ti(1)–S(1)
Cl(2)–Ti(1)–S(1*)
Cl(1)–Ti(1)–S(1)
S(1)–Ti(1)–S(1*)
82.24(9)
86.44(9)
88.37(7)
80.8(1)
Fig. 3 View of the structure of [TiCl4{MeSe(CH2)3SeMe)] with
the numbering scheme adopted. Ellipsoids are drawn at the 40%
probability level.
Fig.
2
View of the structure of [TiCl4{MeS(CH2)3SMe}] with
the numbering scheme adopted. Ellipsoids are drawn at the 40%
probability level.
diseleno- and ditelluro-ether ligands, which are also derived
from a tetrahedral metal precursor, in this case SnX4.8 Indeed,
all of the Cl–Ti–S bond angles are less than the 90Њ expected for
a regular octahedron. The Ti–S bond distances of 2.6106(9)
and 2.6010(8) Å in this complex are similar to those observed in
the disulfide species [TiCl4(H8C4SSC4H8)], 2.626(7), 2.625(7)
Å,5 and are only slightly longer than those in the imido species,
[TiCl2(NBut)([9]aneS3)] ([9]aneS3 = 1,4,7-trithiacyclononane),
Ti–StransCl = 2.575(1), 2.591(1), Ti–StransN = 2.750(1) Å.9 The
Ti–CltransS bond distances, 2.2358(8) and 2.2253(9) Å, are sig-
nificantly shorter than those for the mutually trans Cl ligands,
2.2907(8), 2.2926(8) Å, consistent with the preference of the
hard Ti() centre for hard Cl ligands. This suggests a trans
influence order on Ti() of Cl > S. [TiCl4{MeS(CH2)3SMe}]
(Fig. 2, Table 2) adopts a similar structure, with the dithioether
adopting the  configuration and the Cl ligands cis to the S
atoms tilted towards the dithioether [Cl(2)–Ti(1)–Cl(2*)
165.1(1)Њ]. The Ti–S and Ti–Cl bond distances are comparable
with, and exhibit the same trends as, those in [TiCl4{MeS-
(CH2)2SMe}] above. The selenoether complex [TiCl4{MeSe-
(CH2)3SeMe}] (Fig. 3, Table 3) is not isomorphous, but adopts
a very similar molecular structure to [TiCl4{MeS(CH2)3SMe}]
above, although the structure of the former was obtained from
Fig.
4
View of the structure of [TiCl4{o-C6H4(SeMe)2}] with
the numbering scheme adopted. Ellipsoids are drawn at the 40%
probability level.
a twinned crystal (see Experimental section). Thus, this species
adopts a distorted octahedral geometry with the diselenoether
ligand chelating and in the  form. The compound has
crystallographic two-fold symmetry, with Ti–Cl 2.278(3),
2.247(4) Å and Ti–Se 2.755(3) Å. The Ti–Se distances are
longer than d(Ti–S) in the thioether species above as expected,
and comparable with those in cis-[TiCl4(SeR2)2] [R = Me, Ti–Se
2.777(4), 2.743(4); R = Et, Ti–Se 2.740(2), 2.763(2) Å] and
similar also to those in the diselenide complex [TiCl4(Et-
SeSeEt)] [2.796(2) Å].5 The complex [TiCl4{o-C6H4(SeMe)2}]
(Fig. 4, Table 4) shows similar Ti–Cl and Ti–Se bond distances,
although this species adopts the meso form, with both Se-
bound Me groups lying on the same side of the TiCl2Se2
plane.
During our initial attempts to obtain crystals of [TiCl4-
{MeS(CH2)2SMe}] we grew crystals of the dinuclear species,
J. Chem. Soc., Dalton Trans., 2000, 3001–3006
3003

View Article Online
Table 4 Selected bond lengths (Å) and angles (Њ) for [TiCl4{o-C6H4-
(SeMe)2}]
longer than those observed in the mononuclear species above.
Related oxo-bridged dinuclear Ti species are known, e.g.
[PPh4]2[{TiCl3(NCMe)2}2(µ-O)]] (µ-O occupies an inversion
centre), [Mg(MeCN)6][{TiCl4(MeCN)}2(µ-O)]ؒ4MeCN [Ti–O–
Ti 174.7(3)Њ] and [{(η5-C5H5)TiCl2}2(µ-O)] (µ-O occupies an
inversion centre).10 The EI mass spectrum of [{MeS(CH2)2-
SMe}Cl3Ti(µ-O)TiCl3{MeS(CH2)2SMe}] shows major peaks
with the correct isotopic distributions corresponding to the
dicationic species [Ti2Cl5O{MeS(CH2)2SMe}2]2ϩ, together with
fragments corresponding to sequential loss of halide. Micro-
analytical data confirm that the dinuclear species identified
crystallographically is representative of the bulk sample
recrystallised in this way.
Se(1)–Ti(1)
Ti(1)–Cl(4)
Ti(1)–Cl(1)
2.727(1)
2.239(2)
2.267(2)
Ti(1)–Cl(3)
Se(2)–Ti(1)
Ti(1)–Cl(2)
2.308(2)
2.744(1)
2.231(2)
Cl(1)–Ti(1)–Cl(3)
Cl(2)–Ti(1)–Cl(3)
Cl(3)–Ti(1)–Cl(4)
Se(1)–Ti(1)–Cl(1)
Se(1)–Ti(1)–Cl(3)
Se(2)–Ti(1)–Cl(1)
Se(2)–Ti(1)–Cl(3)
Cl(1)–Ti(1)–Cl(2)
163.11(7)
93.14(6)
94.87(6)
87.20(5)
80.74(5)
84.41(5)
81.00(4)
94.94(6)
Cl(1)–Ti(1)–Cl(4)
Cl(2)–Ti(1)–Cl(4)
Se(1)–Ti(1)–Se(2)
Se(1)–Ti(1)–Cl(2)
Se(1)–Ti(1)–Cl(4)
Se(2)–Ti(1)–Cl(2)
Se(2)–Ti(1)–Cl(4)
96.42(7)
109.28(7)
74.42(3)
162.48(6)
87.69(5)
88.46(5)
162.05(6)
Table 5 Selected bond lengths (Å) and angles (Њ) for [{MeS(CH2)2-
SMe}Cl3Ti(µ-O)TiCl3{MeS(CH2)2SMe}]
Conclusions
These results show that thioether and selenoether ligands
involving different C-functionalities (terminal substituents and
interdonor linkages) readily form complexes with Ti()
tetrahalides, to yield intensely coloured species that are highly
hydrolytically unstable. Several of the complexes have been
crystallographically authenticated, and these studies have also
revealed an unusual oxo-bridged dinuclear species formed by
partial hydrolysis. NMR spectroscopic studies reveal that the
Lewis acidity of TiX4 increases in the order X = I < Br < Cl,
and that both ligand dissociation and pyramidal inversion are
slowed significantly at ca. 200 K. Also, the thioether species are
less dissociated than the selenoether complexes; a similar trend
to that seen for the Sn() (hard acid) adducts.8
Ti(1)–S(1)
Ti(1)–S(2)
Ti(1)–Cl(2)
2.653(2)
2.624(2)
2.300(2)
Ti(1)–Cl(3)
Ti(1)–Cl(5)
Ti(1)–O(1)
2.295(2)
2.255(2)
1.788(1)
Cl(2)–Ti(1)–Cl(3)
Cl(2)–Ti(1)–Cl(5)
Cl(2)–Ti(1)–S(1)
Cl(2)–Ti(1)–S(2)
Cl(3)–Ti(1)–Cl(5)
Cl(3)–Ti(1)–S(2)
Cl(5)–Ti(1)–S(1)
Cl(5)–Ti(1)–S(2)
160.80(7)
96.79(7)
77.82(6)
87.94(6)
94.12(7)
78.80(6)
90.92(6)
169.18(7)
S(1)–Ti(1)–S(2)
S(1)–Ti(1)–O(1)
S(2)–Ti(1)–O(1)
Cl(2)–Ti(1)–O(1)
Cl(3)–Ti(1)–S(1)
Cl(3)–Ti(1)–O(1)
80.54(6)
165.39(7)
86.40(5)
95.27(6)
86.28(6)
97.66(6)
Ti(1)–O(1)–Ti(1*) 180.00
Cl(5)–Ti(1)–O(1) 102.77(6)
Detailed studies of the decomposition behaviour of these
compounds will be the basis of a later paper, however, pre-
liminary studies show that the aliphatic derivatives are volatile
in high vacuum and may be sublimed with minimal decom-
position. Dealkylation is also shown to occur readily for some
compounds in solution (e.g. [TiCl4{PhSe(CH2)2SePh}] under-
goes elimination in anhydrous CHCl3 solution upon standing,
to yield PhSeSePh as shown by 13C{1H} and 77Se{1H} NMR
studies) and more generally on passing the vaporised material
through a hot tube.
Experimental
IR were measured as Nujol mulls using a Perkin-Elmer 983G
spectrometer over the range 200–4000 cmϪ1. Mass spectra were
run by electron impact (EI) using a VG Analytical 70–250-SE
Normal Geometry Double Focusing Mass Spectrometer. UV–
visible spectra were recorded by diffuse reflectance using BaSO4
as dilutant on a Perkin Elmer Lambda19 UV/visible spec-
1
trometer. H NMR spectra were recorded in CDCl3 using a
Bruker AM300 spectrometer operating at 300 MHz. 13C{1H}
and 77Se{1H} NMR spectra were obtained using a Bruker
AM360 spectrometer operating at 90.6 and 68.7 MHz and are
referenced to SiMe4 and external neat SeMe2 respectively. The
thioether and selenoether ligands were prepared by the liter-
ature methods.11–14 TiX4 were used as received from Aldrich.
Fig.
5
View of the structure of [{MeS(CH2)2SMe}Cl3Ti(µ-O)-
TiCl3{MeS(CH2)SMe)] with the numbering scheme adopted. Ellipsoids
are drawn at the 40% probability level. Atoms marked * are related by a
crystallographic inversion centre.
Preparations
All preparations were conducted using standard Schlenk tech-
niques under a dinitrogen atmosphere and rigorously dry
solvents. One representative synthesis of a TiCl4, TiBr4 and
TiI4 complex is detailed.
[{MeS(CH2)2SMe}Cl3Ti(µ-O)TiCl3{MeS(CH2)2SMe}], obvi-
ously formed by partial hydrolysis of [TiCl4{MeS(CH2)2SMe}]
in ‘wet’ CH2Cl2–hexane. The structure of this species shows
(Fig. 5, Table 5) two distorted octahedral Ti() centres linked
by a bridging oxo-ligand which occupies a crystallographic
inversion centre, and hence imposes a 180Њ angle for the
Ti–O–Ti unit. Once again the dithioether ligands adopt the 
form. In this species all three Cl ligands bend away from
the oxo-ligand, O–Ti–Cl 95.27(6)–102.77(6)Њ. The Ti–S dis-
tances in this dinuclear species, 2.653(2), 2.624(2) Å, are
[TiCl4{MeS(CH2)2SMe}]. To a solution of MeS(CH2)2SMe
(0.11 g, 0.91 mmol) in dry, degassed hexane (20 cm3) was added
TiCl4 (0.10 cm3, 0.91 mmol) via syringe. This resulted in the
immediate precipitation of a bright yellow solid which was
filtered in vacuo, washed with hexane and dried in vacuo. Yield
0.26 g, 91%. Calc. for C4H10Cl4S2Ti: C, 15.4; H, 3.2. Found: C,
15.3; H, 3.2%. 1H NMR: δ 2.92 (br s, CH2, 4 H), 2.38 (br s, CH3,
3004
J. Chem. Soc., Dalton Trans., 2000, 3001–3006

View Article Online
6H). 13C{1H} NMR (300 K): δ 38.9 (CH2), 23.2 (CH3); (200 K):
39.4, 39.1 (CH2), 23.5, 22.2 (CH3). IR (νTiCl)/cmϪ1: 420, 406,
397, 383. Electronic spectrum (10Ϫ3 νmax/cmϪ1): 23.8, 29.5 (sh),
33.3 (sh).
ing to room temperature MeS(CH2)2SMe (0.11 g, 0.84 mmol)
was added. The resulting red solution was stirred for ca. 30 min
then concentrated in vacuo to ca. 5 cm3. Dry hexane (20 cm3)
was then added to afford an orange red solid which was filtered
off and dried in vacuo. Yield 0.24 g, 58%. Required for
C4H10Br4S2Ti: C, 9.8; H, 2.1. Found: C, 10.1; H, 2.0%. 1H
[TiCl3{MeS(CH2)2SMe}]2(ꢀ-O). Method as above, but using
‘wet’ CH2Cl2–hexane. Yellow crystals. Required for C8H20-
Cl6OS4Ti2: C, 12.7; H, 2.7. Found: C, 13.0; H, 2.8%. EI mass
spectrum: found m/z 342, 325, 267, 249; calc. for [48Ti235Cl3O-
{MeS(CH2)2SMe}]ϩ m/z 339, [48Ti235Cl6O]ϩ m/z 322, [48Ti2-
35Cl5O{MeS(CH2)2SMe}2]2ϩ m/z 265.5, [48Ti235Cl4O{MeS-
(CH2)2SMe}2]2ϩ m/z 248.
NMR: δ 2.8 (s, CH2, 4H), 2.2 (s, CH3, 6H). IR (νTiBr)/cmϪ1: 332,
Ϫ3
325, 319, 311. Electronic spectrum (10
33.0 (sh).
ν
/cmϪ1): 22.2 (v br),
max
[TiBr4{MeS(CH2)3SMe}]. Bright red solid. Yield 61%.
Required for C5H12Br4S2Ti: C, 11.9; H, 2.4. Found: C, 12.2; H,
1
2.5%. H NMR: δ 2.76 (s, SCH2, 4H), 2.27 (s, CH3, 6H), 1.95
(m, CH2, 2H). IR (νTiBr)/cmϪ1: 325, 321, 317, 311. Electronic
[TiCl4{MeS(CH2)3SMe}]. Orange solid. Yield 88%. Required
for C5H12Cl4S2Ti: C, 18.4; H, 3.7. Found: C, 17.9; H, 3.6%. 1H
NMR: δ 3.10 (t, SCH2, 4H), 2.53 (s, CH3, 6H), 2.24 (qnt, CH2,
2H). 13C{1H} NMR (300 K): δ 36.4 (SCH2), 24.0 (CH3), 22.0
(CH3); (200 K): 37.6, 35.1 (SCH2), 24.4 (CH2), 22.8, 22.0 (CH3).
IR (νTiCl)/cmϪ1: 408, 398, 387, 378. Electronic spectrum (10Ϫ3
νmax/cmϪ1): 22.5, 27.0 (sh), 31.3 (sh).
Ϫ3
spectrum (10
ν
/cmϪ1): 20.4, 22.5 (sh), 31.5 (sh).
max
[TiBr4{o-C6H4(SMe)2}]. Orange solid. Yield 64%. Required
for C8H10Br4S2Ti: C, 17.9; H, 1.9. Found: C, 18.2; H, 2.2%. 1H
NMR: δ 7.29–7.44 (m, o-C6H4, 4H), 2.73 (s, CH3, 6H). IR
Ϫ3
(νTiBr)/cmϪ1: 327, 317, 310, 304. Electronic spectrum (10
ν
/
max
cmϪ1): 23.3.
[TiCl4{PhS(CH2)2SPh}]. Red solid. Yield 85%. Required for
1
[TiBr4{MeSe(CH2)2SeMe}]. Red solid. Yield 51%. Required
C14H14Cl4S2Ti: C, 38.6; H, 3.2. Found: C, 38.2; H, 3.5%. H
1
NMR: δ 7.32–7.46 (m, Ph, 10H), 3.58 (s, CH2, 4H). 13C{1H}
NMR (300 K): δ 127–130 (Ph), 34.6 (CH2); (200 K): 126–132
for C4H10Br4Se2Ti: C, 8.2; H, 1.7. Found: C, 8.6; H, 1.9%. H
NMR: δ 2.86 (s, CH2, 4H), 2.10 (s, Me, 6H). 13C{1H} NMR
(300 K): no spectrum; (200 K): δ 35.2, 35.0 (CH2 coordinated
diselenoether), 24.3 (CH2 ‘free’ diselenoether), 14.8, 14.6 (CH3
coordinated diselenoether), 4.0 (CH3 free diselenoether). IR
(Ph), 35.9, 33.0 (CH2). IR (νTiCl)/cmϪ1: 413, 400, 386, 378. Elec-
Ϫ3
tronic spectrum (10
ν
/cmϪ1): 20.5 (br), 28.5 (sh).
max
(νTBr)/cmϪ1: 317, 312, 300, 294. Electronic spectrum (10Ϫ3 νmax
/
[TiCl4{o-C6H4(SMe)2}]. Orange solid. Yield 55%. Required
for C8H10Cl4S2Ti: C, 26.7; H, 2.8. Found: C, 26.5; H, 3.0%. 1H
NMR: δ 7.14–7.25 (m, o-C6H4, 4H), 2.47 (s, CH3, 6H). 13C{1H}
NMR (300 K): δ 129–134 (o-C6H4), 26.8 (CH3); (200 K): 128–
134 (o-C6H4), 28.0, 27.0 (CH3). IR (νTiCl)/cmϪ1: 405, 396, 387,
382.
cmϪ1): 20.5, 26.0, 39.2.
[TiBr4{MeSe(CH2)3SeMe}]. Dark red solid. Yield 52%.
Required for C5H12Br4Se2Ti: C, 10.5; H, 2.0. Found: C, 10.3; H,
2.2%. 1H NMR: δ 2.68 (s, SeCH2, 4H), 2.05 (s, CH3, 6H), 2.00
(s, CH2, 2H). 13C{1H} NMR (300 K): no spectrum. IR (νTiBr)/
Ϫ3
cmϪ1: 327, 317, 308, 300. Electronic spectrum (10
21.8 (br).
ν
/cmϪ1):
max
[TiCl4{MeSe(CH2)2SeMe}]. Orange solid. Yield 90%.
Required for C4H10Cl4Se2Ti: C, 11.8; H, 2.5. Found: C, 11.5; H,
1
2.0%. H NMR: δ 3.30 (br s, CH2, 4H), 2.60 (br s, CH3, 6H).
13C{1H} NMR (300 K): δ 34.2 (CH2), 14.5 (CH3); (200 K): 34.4,
34.2 (CH2), 14.9, 14.6 (CH3). 77Se{1H} NMR (200 K): δ 313,
[TiBr4{o-C6H4(SeMe)2}]. Orange brown solid. Yield 57%.
Required for C8H10Br4Se2Ti: C, 15.2; H, 1.6. Found: C, 15.8; H,
1.8%. 1H NMR: δ 7.20–7.42 (m, o-C6H4, 4H), 2.47 (s, CH3, 6H).
13C{1H} NMR (300 K): no spectrum; (200 K): δ 127–134 (o-
C6H4 from both ‘free’ and coordinated ligand), 25.9, 25.5 (CH3,
307. IR (νTiCl)/cmϪ1: 414, 402, 393, 380. Electronic spectrum
Ϫ3
(10
ν
/cmϪ1): 23.0, 24.0, 29.5 (sh), 34.0.
max
coordinated ligand), 8.1 (CH3, ‘free’ ligand). IR (νTiBr)/cmϪ1
:
[TiCl4{MeSe(CH2)3SeMe}]. Bright red solid. Yield 84%.
Required for C5H12Cl4Se2Ti: C, 14.3; H, 2.9. Found: C, 14.2; H,
3.0%. 1H NMR: δ 2.90 (s, SeCH2, 4H), 2.28 (s, CH3, 6H), 2.22
(s, CH2, 2H). 13C{1H} NMR (300 K): no spectrum; (200 K):
δ 34.3, 32.1 (SeCH2), 30.8 (CH2), 17.0, 15.8 (CH3). 77Se{1H}
326, 321, 305, 299. Electronic spectrum (10Ϫ3 νmax/cmϪ1): 20.5
(br), 29.0 (sh).
[TiI4{MeSe(CH2)2SeMe}]. TiI4 (0.20 g, 0.36 mmol) was
dissolved in refluxing anhydrous CH2Cl2 (80 cm3) under N2.
After cooling to room temperature, the solution was allowed
to settle and the remaining solid was removed by filtration.
To this purple solution was added MeSe(CH2)2SeMe (0.09 g,
0.36 mmol), resulting in an immediate change to an orange–
red solution. This solution was stirred at room temperature for
ca. 30 min and then concentrated in vacuo to ca. 5 cm3. Dry
hexane (20 cm3) was then added and this mixture was then
concentrated to ca. 5 cm3 in vacuo to afford a dark red–purple
solid which was collected by filtration. Yield 0.05 g, 19%.
Required for C4H10I4Se2Ti: C, 6.2; H, 1.3. Found: C, 6.5; H,
1.5%. 1H NMR: δ 3.0 (s, SeCH2, 4H), 2.3 (s, CH3, 6H).
NMR (200 K): δ 183, 180. IR (νTiCl)/cmϪ1: 396, 384, 378, 373.
Ϫ3
Electronic spectrum (10
(sh).
ν
/cmϪ1): 20.1, 24.5, 29.0 (sh), 32.2
max
[TiCl4{PhSe(CH2)2SePh}]. Dark red solid. Yield 79%.
Required for C14H14Cl4Se2Ti: C, 31.7; H, 2.7. Found: C, 32.0; H,
1
2.8%. H NMR: δ 7.9–8.2 (m, Ph, 10H), 3.7 (br s, CH2, 4H).
13C{1H} NMR (300 K): δ 128.1–133.8 (Ph), 31.0 (CH2); (200
K): 129.2–133.6 (Ph), 32.6, 32.2 (CH2). 77Se{1H} NMR (200 K):
δ 441, 436. IR (νTiCl)/cmϪ1: 405, 385, 377, 373. Electronic
Ϫ3
spectrum (10
ν
/cmϪ1): 20.4, 31.6 (br).
max
[TiCl4{o-C6H4(SeMe)2}]. Orange red solid. Yield 76%.
Required for C8H10Cl4Se2Ti: C, 21.2; H, 2.2. Found: C, 21.0; H,
2.3%. 1H NMR: δ 7.28–7.46 (m, o-C6H4, 4H), 2.58 (s, CH3, 6H).
13C{1H} NMR (300 K): δ 131.0, 134.9 (o-C6H4), 21.7 (CH3);
(200 K): 134.8, 131.1 (o-C6H4), 23.5, 22.9 (CH3). 77Se{1H}
[TiI4{o-C6H4(SeMe)2}]. Red–brown solid. Yield 30%.
Required for C8H10I4Se2Ti: C, 11.7; H, 1.2. Found: C, 11.3; H,
1.1%. 1H NMR: δ 7.2–7.4 (m, o-C6H4, 4H), 2.90 (s, CH3, 6H).
X-Ray crystallographic studies
NMR (200 K): δ 399, 390. IR (νTiCl)/cmϪ1: 390, 386, 382, 379.
Ϫ3
Electronic spectrum (10
ν
/cmϪ1): 21.6, 28.5 (sh), 34.6 (sh).
Details of the crystallographic data collection and refinement
parameters are given in Table 6. Crystals were obtained from
slow evaporation from a solution of the appropriate complex in
CH2Cl2 (except [{TiCl3{MeS(CH2)2SMe}}2(µ-O)] which were
max
[TiBr4{MeS(CH2)2SMe}]. TiBr4 (0.31 g, 0.84 mmol) was dis-
solved in refluxing, dry CH2Cl2 (40 cm3) under N2. After cool-
J. Chem. Soc., Dalton Trans., 2000, 3001–3006
3005

View Article Online
Table 6 Crystallographic data
[TiCl4{MeS(CH2)2-
[TiCl4{MeS(CH2)3-
SMe}]
[TiCl4{MeSe(CH2)3-
SeMe}]
[TiCl4{o-C6H4-
(SeMe)2}]
[{MeS(CH2)2SMe}-
Cl3Ti]2(µ-O)
SMe}]
Formula
M
Crystal system
Space group
C4H10Cl4S2Ti
311.95
Monoclinic
P21/n
C5H12Cl4S2Ti
325.98
C5H12Cl4Se2Ti
449.77
Tetragonal
I41/a
C8H10Cl4Se2Ti
453.80
C8H20Cl6OS4Ti2
569.00
Monoclinic
P21/n
Tetragonal
Triclinic
¯
¯
I42d
P1
a/Å
b/Å
c/Å
α/Њ
6.922(2)
13.335(1)
12.678(1)
90
95.17(1)
90
1165.4(3)
4
19.51
10.071(1)
10.071(1)
24.542(3)
90
90
90
2489.1(7)
8
18.41
683
10.029(6)
10.029(6)
25.698(14)
90
90
90
2585(3)
8
70.74
8.2588(9)
11.091(2)
8.232(1)
90.74(1)
97.72(1)
108.93(1)
705.5(2)
2
8.963(1)
10.672(2)
11.196(1)
90
90.36(1)
90
1070.8(3)
2
18.77
β/Њ
γ/Њ
U/Å3
Z
µ(Mo-Kα)/cmϪ1
Unique obs. reflections
Obs. reflections
[Io > 2σ(Io)]
Ra
64.42
2478
2151
1145
2013
1755
0.023
0.029
525
0.041
0.041
792
1972
0.031
0.035
1412
0.049
0.060
0.054c
0.142d
b
Rw
¹
2

²
2
a R = Σ(|Fo|i Ϫ |Fc|i)/Σ|Fo|i. b Rw = [Σwi(|Fo|i Ϫ |Fc|i) /Σwi|Fo|i ] . c R1 [I > 2σ(I)]. d wR2 [I > 2σ(I)].
E. Turin, R. M. Nielson and A. E. Merbach, Inorg. Chim. Acta,
1987, 134, 67; E. Turin, R. M. Nielson and A. E. Merbach, Inorg.
Chim. Acta, 1987, 134, 79.
obtained by slow evaporation from a solution of [TiCl4-
{MeS(CH2)2SMe}] in CH2Cl2–hexane. The data were corrected
for absorption using ψ-scans. Structure solution and refinement
were routine,15–19 except for [TiCl4{MeSe(CH2)3SeMe}], for
which the diffraction data were apparently in the Laue group
4/mmm but with systematic absences not fitting any appropriate
space group. The structure was therefore solved in space group
I41/a (no. 88, Laue group 4/m) with twinning from two equal
components (TWIN 010 100 00-1 in SHELXL 9718). The mole-
cule has crystallographic two-fold symmetry with atoms Ti(1)
and C(1) occupying 8e sites. Selected bond lengths and angles
for the structures are presented in Tables 1–5.
5 P. J. McKarns, T. S. Lewkebandara, G. P. A. Yap, L. M. Liable-
Sands, A. L. Rheingold and C. H. Winter, Inorg. Chem., 1998, 37,
418; T. S. Lewkebandara, P. J. McKarns, B. S. Heggerty, G. P. A.
Yap, A. L. Rheingold and C. H. Winter, Polyhedron, 1998, 17, 1.
6 G. A. Barclay, I. K. Gregor, M. J. Lambert and S. B. Wild, Aust. J.
Chem., 1967, 20, 1571; M. F. Lappert, J. Chem. Soc., 1962, 542.
7 B. J. Brisdon, T. E. Lester and R. A. Walton, Spectrochim. Acta, Part
A, 1967, 23, 1969.
8 S. E. Dann, A. R. J. Genge, W. Levason and G. Reid, J. Chem. Soc.,
Dalton Trans., 1996, 4471; S. E. Dann, A. R. J. Genge, W. Levason
and G. Reid, J. Chem. Soc., Dalton Trans., 1997, 2207; A. R. J.
Genge, W. Levason and G. Reid, J. Chem. Soc., Dalton Trans., 1997,
4549.
CCDC reference number 186/2090.
See http://www.rsc.org/suppdata/dt/b0/b002792h/ for crystal-
lographic files in .cif format.
9 A. J. Blake, P. Mountford, M. Schröder and P. J. Wilson, Chem.
Commun.,1998, 1007.
10 V. V. Krug and U. Muller, Acta Crystallogr., Sect. C, 1990, 46, 547;
G. R. Willey, J. Palin and M. G. B. Drew, J. Chem. Soc., Dalton
Trans., 1994, 1799; U. Thewalt and D. Schomburg, J. Organomet.
Chem., 1977, 127, 169.
11 F. R. Hartley, W. Levason, C. A. McAuliffe, S. G. Murray and
H. E. Soutter, Inorg. Chim. Acta, 1979, 35, 265.
Acknowledgements
We thank the EPSRC for support.
12 T. Kemmitt and W. Levason, Organometallics, 1989, 8, 1303.
13 D. J. Gulliver, E. G. Hope, W. Levason, S. G. Murray, D. M. Potter
and G. L. Marshall, J. Chem. Soc., Perkin Trans. 2, 1984, 429.
14 E. G. Hope, T. Kemmitt and W. Levason, J. Chem. Soc., Perkin
Trans. 2, 1987, 487.
References
1 For examples see E. W. Abel, S. K. Bhargava and K. G. Orrell, Prog.
Inorg. Chem., 1984, 33, 1; A. J. Blake and M. Schröder, Adv. Inorg.
Chem., 1990, 35, 1; E. G. Hope and W. Levason, Coord. Chem. Rev.,
1993, 122, 109.
15 SHELXS-86, G. M. Sheldrick, Acta Crystallogr., Sect. A, 1990, 46,
467.
2 W. Levason, S. D. Orchard and G. Reid, Organometallics, 1999, 18,
1275; A. J. Barton, W. Levason and G. Reid, J. Organomet. Chem.,
1998, 579, 235.
3 For examples, see Lithium Batteries, ed. J. P. Gabane, Academic
Press, London, 1983; M. S. Whittingham, Prog. Solid State
Chem., 1978, 12, 41; B. Scrosati, Electrochim. Acta, 1981, 26, 1559;
R. H. Friend and A. D. Yoffe, Adv. Phys., 1987, 36, 1.
16 PATTY, The DIRDIF Program System, P. T. Beurskens,
G. Admiraal, G. Beurskens, W. P. Bosman, S. Garcia-Granda, R. O.
Gould, J. M. M. Smits and C. Smykalla, Technical Report of
the Crystallography Laboratory, University of Nijmegen, The
Netherlands, 1992.
17 TeXsan: Crystal Structure Analysis Package, Molecular Structure
Corporation, The Woodlands, TX, 1995.
4 A. D. Westland and L. Westland, Can. J. Chem., 1965, 43, 426;
R. J. H. Clark and W. Errington, Inorg. Chem., 1966, 5, 650;
M. Valloton and A. E. Merbach, Helv. Chim. Acta, 1975, 58, 272;
18 G. M. Sheldrick, SHELXL 97, Program for crystal structure
refinement, University of Göttingen, 1997.
19 H. D. Flack, Acta Crystallogr., Sect A, 1983, 39, 876.
3006
J. Chem. Soc., Dalton Trans., 2000, 3001–3006