TeX4 (X = F, Cl, Br) as Lewis acids - Complexes with soft thio- and seleno-ether ligands

Article abstract of DOI:10.1039/c2dt30968h

TeF₄ reacts with OPR₃ (R = Me or Ph) in anhydrous CH₂Cl₂ to give the colourless, square based pyramidal 1:1 complexes [TeF₄(OPR₃)] only, in which the OPR₃ is coordinated basally in the solid state, (R = Me: d(Te-O) = 2.122(2) A; R = Ph: d(Te-O) = 2.1849(14) A). Variable temperature ¹⁹F{ ¹H}, ³¹P{¹H} and ¹²⁵Te{ ¹H} NMR spectroscopic studies strongly suggest this is the low temperature structure in solution, although the systems are dynamic. The much softer donor ligands SMe₂ and SeMe₂ show a lower affinity for TeF₄, although unstable, yellow products with spectroscopic features consistent with [TeF₄(EMe₂)] are obtained by the reaction of TeF₄ in neat SMe₂ or via reaction in CH ₂Cl₂ with SeMe₂. TeX₄ (X = F, Cl or Br) causes oxidation and halogenation of TeMe₂ to form X ₂TeMe₂. The Br₂TeMe₂ hydrolyses in trace moisture to form [BrMe₂Te-O-TeMe₂Br], the crystal structure of which has been determined. TeX₄ (X = Cl or Br) react with the selenoethers SeMe₂, MeSe(CH₂)₃SeMe or o-C₆H₄(SeMe)₂ (X = Cl) in anhydrous CH ₂Cl₂ to give the distorted octahedral monomers trans-[TeX₄(SeMe₂)₂], cis-[TeX ₄{MeSe(CH₂)₃SeMe}] and cis-[TeCl ₄{o-C₆H₄(SeMe)₂}], which have been characterised by IR, Raman and multinuclear NMR (¹H, ⁷⁷Se{¹H} and ¹²⁵Te{¹H}) spectroscopy, and via X-ray structure determinations of representative examples. Tetrahydrothiophene (tht) can form both 1:1 and 1:2 Te:L complexes. For X = Br, the former has been shown to be a Br-bridged dimer, [Br₃(tht) Te(μ-Br)₂TeBr₃(tht)], by crystallography with the tht ligands anti, whereas the latter are trans-octahedral monomers. Like its selenoether analogue, MeS(CH₂)₃SMe forms distorted octahedral cis-chelates, [TeX₄{MeS(CH₂)₃SMe}], whereas the more rigid o-C₆H₄(SMe)₂ unexpectedly forms a zig-zag chain polymer in the solid state, [TeCl ₄{o-C₆H₄(SMe)₂}]_n, in which the dithioether adopts an extremely unusual bridging mode. This is in contrast to the chelating monomer, cis-[TeCl₄{o-C₆H ₄(SeMe)₂}], formed with the analogous selenoether and may be attributed to small differences in the ligand chelate bite angles. The wider bite angle xylyl-linked bidentates, o-C₆H₄(CH ₂EMe₂)₂ behave differently; the thioether forms cis-chelated [TeX₄{o-C₆H₄(CH ₂SMe)₂}] confirmed crystallographically, whereas the selenoether undergoes C-Se cleavage and rearrangement on treatment with TeX ₄, forming the cyclic selenonium salts, [C₉H ₁₁Se]₂[TeX₆]. The tetrathiamacrocycle, [14]aneS₄ (1,4,8,11-tetrathiacyclotetradecane), does not react cleanly with TeCl₄, but forms the very poorly soluble [TeCl ₄([14]aneS₄)]_n, shown by crystallography to be a zig-zag polymer with exo-coordinated [14]aneS₄ units linked via alternate S atoms to a cis-TeCl₄ unit. Trends in the ¹²⁵Te{¹H} NMR shifts for this series of Te(iv) halides chalcogenoether complexes are discussed.

Full text of DOI:10.1039/c2dt30968h

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PAPER
TeX4 (X = F, Cl, Br) as Lewis acids – complexes with soft thio- and
seleno-ether ligands†‡
Andrew L. Hector, Andrew Jolleys, William Levason and Gillian Reid*
Received 3rd May 2012, Accepted 25th June 2012
DOI: 10.1039/c2dt30968h
TeF4 reacts with OPR3 (R = Me or Ph) in anhydrous CH2Cl2 to give the colourless, square based
pyramidal 1 : 1 complexes [TeF4(OPR3)] only, in which the OPR3 is coordinated basally in the solid state,
(R = Me: d(Te–O) = 2.122(2) Å; R = Ph: d(Te–O) = 2.1849(14) Å). Variable temperature 19F{1H},
31P{1H} and 125Te{1H} NMR spectroscopic studies strongly suggest this is the low temperature structure
in solution, although the systems are dynamic. The much softer donor ligands SMe2 and SeMe2 show a
lower affinity for TeF4, although unstable, yellow products with spectroscopic features consistent with
[TeF4(EMe2)] are obtained by the reaction of TeF4 in neat SMe2 or via reaction in CH2Cl2 with SeMe2.
TeX4 (X = F, Cl or Br) causes oxidation and halogenation of TeMe2 to form X2TeMe2. The Br2TeMe2
hydrolyses in trace moisture to form [BrMe2Te–O–TeMe2Br], the crystal structure of which has been
determined. TeX4 (X = Cl or Br) react with the selenoethers SeMe2, MeSe(CH2)3SeMe or
o-C6H4(SeMe)2 (X = Cl) in anhydrous CH2Cl2 to give the distorted octahedral monomers
trans-[TeX4(SeMe2)2], cis-[TeX4{MeSe(CH2)3SeMe}] and cis-[TeCl4{o-C6H4(SeMe)2}], which have
been characterised by IR, Raman and multinuclear NMR (1H, 77Se{1H} and 125Te{1H}) spectroscopy,
and via X-ray structure determinations of representative examples. Tetrahydrothiophene (tht) can form
both 1 : 1 and 1 : 2 Te : L complexes. For X = Br, the former has been shown to be a Br-bridged dimer,
[Br3(tht)Te(μ-Br)2TeBr3(tht)], by crystallography with the tht ligands anti, whereas the latter are trans-
octahedral monomers. Like its selenoether analogue, MeS(CH2)3SMe forms distorted octahedral cis-
chelates, [TeX4{MeS(CH2)3SMe}], whereas the more rigid o-C6H4(SMe)2 unexpectedly forms a zig-zag
chain polymer in the solid state, [TeCl4{o-C6H4(SMe)2}]n, in which the dithioether adopts an extremely
unusual bridging mode. This is in contrast to the chelating monomer, cis-[TeCl4{o-C6H4(SeMe)2}],
formed with the analogous selenoether and may be attributed to small differences in the ligand
chelate bite angles. The wider bite angle xylyl-linked bidentates, o-C6H4(CH2EMe2)2 behave differently;
the thioether forms cis-chelated [TeX4{o-C6H4(CH2SMe)2}] confirmed crystallographically, whereas
the selenoether undergoes C–Se cleavage and rearrangement on treatment with TeX4, forming the
cyclic selenonium salts, [C9H11Se]2[TeX6]. The tetrathiamacrocycle, [14]aneS4 (1,4,8,11-
tetrathiacyclotetradecane), does not react cleanly with TeCl4, but forms the very poorly soluble
[TeCl4([14]aneS4)]n, shown by crystallography to be a zig-zag polymer with exo-coordinated [14]-
aneS4 units linked via alternate S atoms to a cis-TeCl4 unit. Trends in the 125Te{1H} NMR shifts for this
series of Te(IV) halides chalcogenoether complexes are discussed.
metallic elements (Ga, In, Ge etc.) in electronics,2,3 and from the
Introduction
need to develop organ-specific carriers for medicinal radio-
isotopes (e.g. 68Ga, 111In, 113mIn, 117mSn).4,5 Similar chemistry
of the more non-metallic elements has received less attention,
particularly with neutral donor ligands.6,7 Tellurium(IV) halides,
TeX4 (X = F, Cl, Br, I) are Lewis acids, but whilst there are a
modest number of complexes of TeCl4 or TeBr4, TeI4 seems to
have little affinity for neutral donors,8 whilst TeF4 has been very
little studied.9,10 We recently reported11 the first examples of
thioether adducts of TeCl4 and TeBr4, including [X3(SMe2)Te-
(μ-X)2TeX3(SMe2)] and [TeX4{RS(CH2)2SR}] (X = Cl or Br,
Recent years have seen greatly increased interest in the coordi-
nation chemistry of the heavier p-block elements.1 Much of the
drive has stemmed from the importance particularly of the
School of Chemistry, University of Southampton, Southampton SO17
1BJ, UK. E-mail: G.Reid@soton.ac.uk
†Dedicated to Professor David Cole-Hamilton on the occasion of his
retirement and for his outstanding contribution to transition metal
catalysis.
‡Electronic supplementary information (ESI) available. CCDC
881025–881039. For ESI and crystallographic data in CIF or other elec-
tronic format see DOI: 10.1039/c2dt30968h
i
R = Me, Et or Pr), which have distorted octahedral coordination
at Te, composed of short (primary) Te–X bonds and longer
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Dalton Trans.

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(secondary) Te–S bonds. The formal lone pair on the Te(IV)
centre was not apparently stereochemically active, although there
is no simple explanation for the (small) distortions from regular
six-coordinate geometries (similar effects are seen in Te(IV) com-
plexes of charged sulfur ligands, including dithiocarbamates,
and dithiolates).12 TeX4 adducts of the diphosphine disulfide
Ph2P(S)CH2P(S)Ph2 are also known,13,14 but with other phos-
phine sulfides and with phosphine selenides reduction to Te(II)
occurs.13 We also note that TeX4 cause halogenation of tertiary
phosphines,15,16 and that no adducts are known.
Here we report the preparation, spectroscopic and structural
properties of the first series of complexes of TeX4 (X = Cl or Br)
with selenoether coordination and the reactions of TeX4 with
TeMe2. Thioether complexes, which reveal new structure types,
are described, together with the first examples with TeF4.
Selected OPR3 complexes with TeF4 are included for
comparison.
Fig. 1 Crystal structure of [TeF4(OPMe3)] showing the atom number-
ing scheme. Ellipsoids are drawn at the 50% probability level and H
atoms are omitted for clarity. Selected bond lengths (Å) and angles (°):
Te1–F1 = 1.897(2), Te1–F2 = 1.971(2), Te1–F3 = 1.923(2), Te1–F4 =
1.962(2), Te1–O1 = 2.122(2), P1–O1 = 1.556(2), F1–Te1–F2 =
79.23(8), F1–Te1–F3 = 82.04(7), F1–Te1–F4 = 81.43(9), F2–Te1–F3 =
88.23(8), F2–Te1–F4 = 160.56(8), F3–Te1–F4 = 87.06(8), F1–Te1–
O1 = 80.83(7), F2–Te1–O1 = 89.52(8), F3–Te1–O1 = 162.84(7),
F4–Te1–O1 = 89.44(8).
Results and discussion
TeF4 complexes
Crystalline TeF4 contains square pyramidal TeF5 units linked via
two (cis) basal fluorines into zig-zag chains,17,18 whilst in the
gas phase it has a monomeric pseudo-trigonal bipyramidal
(“saw-horse”) geometry.9 The anion [TeF5]− is also square pyra-
midal,19,20 but despite claims in the older literature, [TeF6]2− has
never been certainly identified.20,21 The common structural fea-
tures in the solid compounds are that the Te is situated somewhat
below the TeF4 plane and Te–Fax < Te–Feq,9 consistent with the
vacant vertex being occupied by the lone pair. The only structu-
rally authenticated Group 16 donor ligand complexes of TeF4 are
with ether ligands, including [TeF4(thf)2],10 [TeF4{MeO(CH)2-
OMe}2], [TeF4(dioxane)] and [TeF4(OEt2)].9 The last has a struc-
ture close to that of solid TeF4 with a weakly associated ether
molecule (Te–O = 2.44(1), 2.42(1) Å), but the others contain
discrete TeF4 molecules similar to the gas phase, with very long
contacts to the oxygens (∼2.45–2.98 Å). For comparison, the
covalent radii sum for Te–O is ∼2.15 Å and the Van der Waals
radii sum is ∼3.5 Å.22 We suspected that since ether ligands
form only weak adducts with other p-block fluorides including
SnF4,23 GeF4,24 and SiF4,25 and do not complex with AsF3 or
SbF3,26 these complexes might not be representative of other
neutral oxygen donors. In contrast, phosphine oxides form stable
adducts with all five of these fluorides,26–29 and hence we syn-
thesised examples with TeF4 as model oxygen donor complexes.
The reaction of finely powdered TeF4 with a solution of OPR3
(R = Me or Ph) in a 1 : 1 molar ratio, in anhydrous dichloro-
methane, resulted in the formation of colourless solutions from
which colourless crystals of [TeF4(OPR3)] were isolated in good
yield. The same complexes were formed using a two-fold excess
of phosphine oxide, and in situ NMR studies showed no evi-
dence for other complexes. Crystals of both complexes were
obtained by refrigerating CH2Cl2/hexane solutions, and their
structures (Fig. 1 and 2) reveal discrete square pyramidal mo-
lecules with apical fluorine. The pattern of Te–F bond lengths is
much as expected from the structure of solid TeF4 discussed above,
with Te–Fax < Te–FtransO < Te–FtransF and with Fax–Te–Fbasal < 90°.
Fig. 2 Crystal structure of [TeF4(OPPh3)] showing the atom numbering
scheme. Ellipsoids are drawn at the 50% probability level and H atoms
are omitted for clarity. The phenyl groups are numbered cyclically start-
ing at the ipso C atom, and an adjacent C atom is labelled to indicate the
sequence order. Selected bond lengths (Å) and angles (°): Te1–F1 =
1.8575(12), Te1–F2 = 1.9488(14), Te1–F3 = 1.9005(13), Te1–F4 =
1.9464(16), Te1–O1 = 2.1849(14), P1–O1 = 1.5275(14), F1–Te1–F2 =
80.71(6), F1–Te1–F3 = 82.95(6), F1–Te1–F4 = 80.64(6), F2–Te1–F3 =
89.92(6), F2–Te1–F4 = 161.31(5), F3–Te1–F4 = 88.98(6), F1–Te1–
O1 = 80.04(6), F2–Te1–O1 = 89.85(6), F3–Te1–O1 = 62.80(5),
F4–Te1–O1 = 85.76(6).
However, significantly, the Te–O bonds are much shorter than
in the ether adducts (2.122(2) Å (R = Me) and 2.185(1) Å
(R = Ph)). The d(P–O) are lengthened by ∼0.05 Å compared
to the parent phosphine oxides,27 similarly suggesting a strong
Te–O bond. In contrast, TeX4 (X = Cl or Br) give cis octahedral
[TeX4(OPR3)2] adducts, with slightly longer d(Te–O) bonds,13,14
although this may mostly reflect the higher coordination number
at Te and screening by the stereochemically inactive lone pair in
the 5s orbital. In [TeF4(OPMe3)] long intermolecular Te⋯F
contacts (2.965(2) Å) weakly associate the molecular units into
zig-zag chains.
Dalton Trans.
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The IR and Raman spectra of [TeF4(OPR3)] show single
strong ν(PO) vibrations (R = Me 1032 cm−1, R = Ph,
1048 cm−1), markedly lowered from those in the parent OPR3
(1166 and 1196 cm−1 respectively),28 and several strong bands
480–650 cm−1 assigned as terminal Te–F modes (theory Cs =
3A′ + A′′), consistent with the crystal structures. In solution in
anhydrous CD2Cl2 at 295 K, the 19F{1H} NMR spectra show
very broad single resonances indicative of dynamic systems, but
on cooling the solution of [TeF4(OPMe3)] to 178 K, three broad
singlets with 125Te satellites were resolved δ = −23.8 (s, [1F],
dynamic down to very low temperatures. The IR spectra for each
complex shows strong features in the region expected for Te–F
stretching vibrations, and comparable with those for the structu-
rally authenticated [TeF4(OPR3)], suggesting a similar 1 : 1
TeF4 : EMe2 formulation. The instability of the complexes at
ambient temperatures precluded outsourced microanalytical
measurements. Upon cooling (−18 °C) a yellow-orange CH2Cl2
solution of the selenoether product for several days, a few small,
colourless crystals formed. X-Ray structural analysis on one of
these showed it to be [Me2SeSeMe][TeF5] (ESI‡), formed as a
minor decomposition product. The [Me2SeSeMe]+ cation has
been reported previously as its [BF4]− salt,31 however, in the
[TeF5]− salt reported here there are four intermolecular F⋯Se
contacts.
1
1JFTe = 2325 Hz), −40.3 (s, [2F], JFTe = 1313 Hz), −58.6
(s, [1F], 1JFTe = 1721 Hz), which from the integrals and by com-
parison with the spectrum of [TeF5]− 20 are assigned to TeFax,
TeFtransF and TeFtransO respectively. The 178 K spectrum of
[TeF4(OPPh3)] (Experimental section) is similar. Notably, for
both complexes the resonances are still quite broad and no
2JFF couplings were resolved. The 31P{1H} NMR spectra of both
complexes at 178 K were singlets with substantial high fre-
TeX4 (X = Cl or Br) selenoether complexes
quency coordination shifts. Neither complex exhibited
a
The addition of SeMe2 to a suspension of TeX4 in anhydrous
CH2Cl2 or thf at 0 °C, produced intensely coloured solutions,
which deposited almost black crystals of the 2 : 1 adducts
[TeX4(SeMe2)2]. This contrasts with the SMe2 reactions,11 which
gave only the 1 : 1 complexes, [X3(SMe2)Te(μ-X)2TeX3(SMe2)],
even with excess SMe2. The [TeX4(SeMe2)2] are isomorphous
and the structures reveal (Fig. 3a and ESI‡) they are centrosym-
metric trans isomers. The d(Te–Se) are very similar, indicating
little difference in Lewis acidity between the two tellurium
centres. There are two long intermolecular contacts, Se1⋯Cl1′ =
3.592(1) and Se1⋯Cl2′′ = 3.485(1) Å, which complete an
approximate square pyramid around Se1 (C1 axial), and links
the molecules into a 3-D network (Fig. 3b). Similar intermolecu-
lar contacts are present in the bromide.
The IR spectrum of the chloro-complex shows the Eu Te–Cl
stretch at 246 cm−1 and the Raman spectrum has strong bands at
256 and 280 cm−1 (A1g + B2g), consistent with the D4h geome-
try, but the corresponding bands in the bromo complex are
expected to lie near the lower limits (∼200 cm−1) of the spec-
trometers and were not reliably identified. Neither complex exhi-
bits a 77Se{1H} or 125Te{1H} NMR resonance in solution at
room temperature due to fast ligand exchange, but at 183 K sing-
lets are observed, consistent with the presence of a single
isomer, presumably the trans form found in the crystals
(Table 1). The complexes decompose quite rapidly in solution at
ambient temperatures with fragmentation of the selenoether (see
ESI‡).
125Te{1H} NMR spectrum at 220 K, but on further cooling a
broad resonance appeared and then split, and at 178 K both
spectra approximated to twelve line multiplets centred ∼δ +
1150 (expect d,d,t). However, even at this temperature the lines
were still quite broad and somewhat distorted, showing that the
low temperature limiting spectrum had not been reached at
the freezing point of CD2Cl2. Addition of a small excess of the
appropriate OPR3 to solutions of [TeF4(OPR3)] showed only a
singlet in the 31P{1H} NMR spectrum of each even at 178 K,
consistent with fast exchange of the OPR3. Excess OPR3 caused
some sharpening of the 19F{1H} resonances, suggesting suppres-
sion of ligand dissociation, although no new complexes formed.
The solution data show that the complexes are dynamic down to
very low temperatures, both dissociative exchange of the OPR3
and fluxionality of the TeF4 unit being present.
The reaction of TeF4 with OAsPh3 in anhydrous CH2Cl2 solu-
tion gave a good yield of colourless crystals identified by their
unit cell30 and 19F{1H} NMR spectrum (δ = −89.5)26 as
Ph3AsF2, showing fluorination of the arsine oxide instead of
coordination. Tertiary arsine oxide complexes are known for
29
SnF4 and GeF4,28 but AsF3 causes only fluorination,26 whilst
with SbF3, the square pyramidal [SbF3(OAsR3)2] are the major
products, although some R3AsF2 also form.26
The reaction of TeF4 with neat SMe2 led to dissolution of the
TeF4 to give a colourless solution, and following removal of the
excess SMe2, a sticky yellow solid formed, which could be
stored for some days in the freezer, but darkened over ca. 24 h at
room temperature. TeF4 and SeMe2 react similarly in CH2Cl2 to
Similar reaction of MeSe(CH2)3SeMe with TeX4 produced
dark orange (Cl) or red (Br) complexes [TeX4{MeSe(CH2)3-
SeMe}], while o-C6H4(SeMe)2 gives [TeCl4{o-C6H4(SeMe)2}]
as dark-red crystals. The [TeCl4{MeSe(CH2)3SeMe}] decom-
posed quite rapidly at room temperature and was very poorly
soluble in non-coordinating solvents, precluding NMR studies.
1
form a yellow, unstable product. H NMR spectroscopy shows a
single resonance for each complex substantially to high fre-
quency of the ‘free’ ligand resonance, which is little changed
over the temperature range 295 to 193 K. Room temperature
19F{1H} NMR spectra on each showed a relatively sharp singlet
which broadened on cooling the solution to 193 K, but remained
a single resonance. Together with the absence of any 77Se{1H}
or 125Te{1H} NMR resonances over this temperature range, these
data are consistent with the complexes being dynamic in solu-
tion. These observations are consistent with expectations for a
soft chalcogenoether complex of the hard Lewis acidic TeF4. As
discussed above, even the hard OPR3 donor complexes are
However, the more soluble bromo-analogue exhibited
a
77Se{1H} and a 125Te{1H} NMR resonance in CH2Cl2 solution
at 183 K, with reasonable chemical shifts (Table 1). Spectro-
scopic data on [TeCl4{o-C6H4(SeMe)2}] complex also support
cis-chelation, although in solution the complex is dynamic at
room temperature. This assignment is supported by a crystal
structure determination (Fig. 4) which shows the molecule has
mirror symmetry with cis-chelate coordination, Te–Se = 2.969(1) Å.
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NMR spectroscopy (1H, 125Te{1H} and for X = F, 19F{1H})
which unequivocally identified TeMe2X2 as the only significant
new product in each system. The comparisons with literature
NMR data34,35 are detailed in the Experimental section. The
reactions of related p-block element halides and alkyls show a
range of behaviour. Arsenic(III) halides form crystallographically
authenticated complexes with tertiary arsines, including [As2X6-
{o-C6H4(AsMe2)2}2] (X = Cl, Br or I)36 and [{AsCl3(AsEt3)}2].37
In contrast, with the sole exception of the very unstable
[Sb2I6(thf)2(SbMe3)2]38 the reactions of EX3 with ER3 (E = Sb
or Bi, R = Me, Ph, etc.) result in substituent scrambling to form
EX3−nRn.39 The reactions of TeX4 and TeMe2 described here
differ in that they involve redox chemistry as well as substituent
scrambling – the dimethyltellurium(II) is converted to dimethyl-
dihalotellurium(IV) and Te(0). The solution from the reaction of
TeBr4 with TeMe2 deposited colourless crystals on standing for a
few days, which proved to be the oxo-bridged Me2BrTe(μ-O)-
TeMe2Br (Fig. 5), which presumably formed by hydrolysis of
TeMe2Br2. The molecule has two-fold symmetry and a non-
linear bridge Te1–O1–Te1a = 121.3(3)°. Several structures of
related molecules, including nBu2BrTeOTenBu2Br40 and Me2I-
TeOTeMe2I,41 are known and the core dimensions of the current
compound are unexceptional. Longer secondary Br⋯Te inter-
actions (3.4–3.6 Å) link the molecules.
TeX4 (X = Cl or Br) thioether complexes
In our initial study of TeX4/thioether systems we observed two
types of complex, six-coordinate dinuclear [X3(SMe2)Te(μ-X)2-
TeX3(SMe2)] and mononuclear [TeX4{RS(CH2)2SR}] with five-
membered chelate rings. P-block complexes are often strongly
influenced by ligand architecture and hence we explored a wider
range of thioethers seeking other structural motifs. The reaction
of the cyclic thioether, tetrahydrothiophene (tht) with TeX4 (X =
Cl or Br) in a 2 : 1 mol. ratio, gave almost black crystals of
[TeX4(tht)2]. The crystal structures show very similar trans octa-
hedral geometries (Fig. 6 and ESI‡), although the crystals are
not isomorphous, with Te–S very slightly longer in the bromide
(2.7502(8) Å (X = Cl), 2.7598(7) Å (X = Br)), and both are
markedly shorter than the Te–S observed in [X3(SMe2)Te-
(μ-X)2TeX3(SMe2)] (2.813(2), 2.822(2) Å).11 The differences are
readily explained by the nature of the trans ligands in each case.
In the tht complexes, symmetrical 3c–4e bonds are present,
whereas in the SMe2 there are asymmetric 3c–4e bonds with a
strong Te–X interaction and a correspondingly weaker Te–S.
The 125Te{1H} NMR spectrum of [TeCl4(tht)2] was a sharp
singlet at 295 K (δ = 1500) and showed a considerable low fre-
quency shift on cooling, reaching δ = 1475 at 183 K. However,
the 125Te{1H} NMR spectrum of [TeBr4(tht)2] showed no reson-
ances at room temperature, but at 183 K two resonances with
integrals ∼5 : 1 were present at δ = 1655 and 1508. The initial
possibility that these were cis and trans isomers was ruled
out when red crystals deposited over a few days in the solution
used for NMR studies. The structure (Fig. 7) showed these to
be the centrosymmetric dimer [Br3(tht)Te(μ-Br)2TeBr3(tht)] with
similar bond lengths and angles to the [Br3(SMe2)Te(μ-Br)2-
TeBr3(SMe2)] reported previously.11 The 1 : 1 dimer complex
accounts for the 125Te{1H} NMR resonance at 1655 ppm.
Fig. 3 (a) Crystal structure of the centrosymmetric [TeCl4(SeMe2)2]
molecule showing the atom numbering scheme. Ellipsoids are drawn at
the 50% probability level and H atoms are omitted for clarity. Symmetry
operation: a = − x, −y, −z. Selected bond lengths (Å) and angles (°):
Te1–Cl1 = 2.5133(8), Te1–Cl2 = 2.5086(8), Te1–Se1 = 2.8727(6),
Cl1–Te1–Cl2 = 89.48(3), Cl1–Te1–Se1 = 89.85(2), Cl2–Te1–Se1 =
89.04(3), C1–Se1–C2 = 97.38(10), C1–Se1–Te1 = 98.10(7), C2–Se1–
Te1 = 97.73(7). (b) View of [TeCl4(SeMe2)2] showing the intermolecular
Se⋯Cl contacts (red dotted lines).
The Se–Te–Se of 68.61(4)° is extremely acute. Long intermole-
cular Se⋯Cl contacts of 3.626(2) Å are also evident from the
crystal structure.
The o-xylyl selenoether, o-C6H4(CH2SeMe)2 fragmented on
reaction with TeX4 to form high yields of the cyclic selenonium
hexahalotellurates(IV), [o-C6H4CH2Se(CH3)CH2]2[TeX6]. The
selenonium cation has been observed as a fragmentation product
32
of this ligand on reaction with GaCl3 and also forms on reac-
tion with MeI.33 Further details are given in ESI.‡
Reaction of TeX4 (X = F, Cl or Br) with telluroethers
The addition of TeMe2 to a suspension of the TeX4 (X = F, Cl or
Br) in anhydrous CH2Cl2 resulted in immediate black precipi-
tates, which were identified by powder XRD as elemental tellur-
ium. The supernatant solutions were examined by multinuclear
Dalton Trans.
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Table 1 Selected NMR spectroscopic dataa
Complex
δ
125Te{1H} (ppm)
δ
77Se{1H} (ppm)
Temperature
Reference
[TeF4(OPPh3)]
[TeF4(OPMe3)]
[TeCl4(SeMe2)2]
1148b
1151b
1280
1437
n.o.
1484
1475
1504
1531
1517
n.o.
1433
1317
1455
1650
1507
1655
1760
1702
1705
—
—
233
291
n.o.
—
—
—
—
—
—
—
226
169
—
—
—
—
—
183 K
183 K
183 K
193 K
(poor solubility)
200 K
183 K
200 K
200 K
This work
This work
This work
This work
This work
11
This work
11
11
This work
This work
This work
This work
This work
11
This work
This work
11
[TeCl4{o-C6H4(SeMe)2}]
[TeCl4{MeSe(CH2)3SeMe}]
[{Cl3(Me2S)Te}2(μ-Cl)2]
[TeCl4(tht)2]
[TeCl4{MeS(CH2)2SMe}]
[TeCl4{iPrS(CH2)2SiPr}]
[TeCl4{MeS(CH2)3SMe}]
[TeCl4{o-C6H4(SMe)2}]n
[TeCl4{o-C6H4(CH2SMe)2}]
[TeBr4(SeMe2)2]
[TeBr4{MeSe(CH2)3SeMe}]
[{Br3(Me2S)Te}2(μ-Br)2]
[TeBr4(tht)2]
[{Br3(tht)Te}2(μ-Br)2]
[TeBr4{MeS(CH2)2SMe}]
[TeBr4{iPrS(CH2)2SiPr}]
[TeBr4{MeS(CH2)3SMe}]
203 K
193 K
183 K
183 K
200 K
183 K
183 K
200 K
200 K
223 K
11
—
This work
a Spectra recorded in CH2Cl2 solution. b See text.
Fig. 5 Crystal structure of (BrMe2Te)2O·nCH2Cl2 (n = 0.6) showing
the atom numbering scheme. The molecule has 2-fold symmetry. Ellip-
soids are drawn at the 50% probability level and H atoms and the
solvate are omitted for clarity. Symmetry operation: a = 3/4 − z, 3/4 − y,
3/4 − x. Selected bond lengths (Å) and angles (°): Te1–O1 = 1.985(3),
Te1–C2 = 2.099(5), Te1–C1 = 2.115(5), Te1–Br1 = 2.8858(7), O1–Te1–
C2 = 88.6(2), O1–Te1–C1 = 89.4(2), C2–Te1–C1 = 96.6(2), O1–Te1–
Br1 = 171.1(1), C2–Te1–Br1 = 86.4(2), C1–Te1–Br1 = 83.9(1), Te1–
O1–Te1a = 121.3(3).
Fig. 4 Crystal structure of [TeCl4{o-C6H4(SeMe)2}] showing the atom
numbering scheme. The molecule has mirror symmetry. Ellipsoids are
drawn at the 50% probability level and H atoms are omitted for clarity.
Symmetry operation: a = x, 1/2 − y, z. Selected bond lengths (Å) and
angles (°): Te1–Cl1 = 2.445(2), Te1–Cl3 = 2.463(1), Te1–Cl2 = 2.579(2),
Te1–Se1 = 2.969(1), Cl1–Te1–Cl3 = 91.93(5), Cl3–Te1–Cl3a = 94.62(7),
Cl1–Te1–Cl2 = 174.21(6), Cl3–Te1–Cl2 = 91.99(5), Cl3–Te1–Se1a =
166.52(3), Cl1–Te1–Se1 = 83.74(5), Cl3–Te1–Se1 = 98.28(5), Cl2–
Te1–Se1 = 91.49(4), Se1–Te1–Se1a = 68.61(4).
We also explored the effects of changing the linking backbone
within the dithioether ligands. The RS(CH2)2SR ligands gave
cis chelate complexes [TeX4{RS(CH2)2SR}],11 and replacing the
–(CH2)2– links by –(CH2)3– led only to [TeX4{RS(CH2)3SR}]
which are also cis chelates (ESI‡). However, replacing the
–(CH2)2– links by o-C6H4–, as in o-C6H4(SMe)2, led to
[TeCl4{o-C6H4(SMe)2}]n in which the dithioether does not
chelate, but instead bridges to an adjacent Te centre, forming a
chain polymer (Fig. 8), with the two S atoms coordinated to
Te mutually cis. The Te–S bond distances in this complex are
3.0375(8) and 3.0580(9) Å, significantly longer than in the
chelate complexes. The S–Te–S angle is also very much more
Fig. 6 Crystal structure of the centrosymmetric trans-[TeBr4(tht)2]
showing the atom numbering scheme. Ellipsoids are drawn at the 50%
probability level and H atoms are omitted for clarity. Symmetry oper-
ation: a = −x, 1 − y, −z. Selected bond lengths (Å) and angles (°): Te1–
Br1 = 2.6830(7)), Te1–Br2 = 2.26814(5), Te1–S1 = 2.7598(7), Br1–
Te1–Br2 = 90.775(11), Br1–Te1–S1 86.01(2), Br2–Te1–S1 = 84.59(2).
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Fig. 7 Crystal structure of the centrosymmetric [Br3(tht)Te-
(μ-Br)2TeBr3(tht)] showing the atom numbering scheme. Ellipsoids are
drawn at the 50% probability level and H atoms are omitted for clarity.
Symmetry operation: a = 2 − x, 1 − y, −z. Selected bond lengths (Å)
and angles (°): Te1–Br1 = 2.5367(7), Te1–Br2 = 2.5757(7), Te1–Br3 =
2.5364(9), Te1–Br4 = 2.921(1), Te1–Br4a = 2.9350(8), Te1–S1 =
2.876(1), Br1–Te1–Br2 = 94.08(2), Br1–Te1–Br3 = 92.32(1), Br1–Te1–
Br4 = 89.32(1), Br1–Te1–Br4a = 174.81(1), Br1–Te1–S1 = 84.92(3),
Br2–Te1–Br3 = 93.92(1), Br2–Te1–Br4 = 91.94(1), Br2–Te1–Br4a =
90.64(2), Br2–Te1–S1 = 175.33(2), Br3–Te1–Br4 = 173.79(1), Br3–
Te1–Br4a = 89.49(1), Br3–Te1–S1 = 90.69(2), S1–Te1–Br4 = 83.49(2),
S1–Te1–Br4a = 90.21(3), Br4–Te1–Br4a = 88.37(1), Te1–Br4–Te1a =
91.63(1).
obtuse at 105.11(2)°. It seems likely that the small bite angle of
the o-C6H4(SMe)2 ligand is insufficient to favour chelation to
the large Te(IV) atom, and hence leads to the observed bridging
coordination mode, which is very unusual for the orthopheny-
lene dichalcogenoether ligand family, the only precedent being
the polymeric [Agn{μ-o-C6H4(SeMe)2}n{o-C6H4(SeMe)2}n]n+.42
Attempts to isolate a TeBr4 complex with this ligand were unsuc-
cessful. Replacing the rigid small bite o-C6H4– linkage with the
more flexible, wider bite angle o-C6H4(CH2)2– linkage resulted
in a return to chelation in the complexes [TeX4{o-C6H4-
(CH2SMe)2}] as shown crystallographically for [TeCl4{o-C6H4-
(CH2SMe)2}]. This complex is a molecular monomer with crys-
tallographic mirror symmetry and with the thioether bidentate,
forming a seven-membered chelate ring (Fig. 9). The bond
angles at Te are severely distorted from a regular octahedron,
with <S–Te–S = 108.78(2)°, and in this case the Te–S =
2.8675(6) Å, in line with the Te–S distances in the other chelate
monomers.
Attempts to prepare TeX4 complexes with the macrocyclic
thioether [14]aneS4, gave yellow insoluble powders which were
not single species. However, from one preparation some small
yellow crystals grew amongst colourless crystals (of the macro-
cycle itself) by cooling the CH2Cl2 filtrate. The former proved to
be [TeCl4([14]aneS4)]n, the structure showing a zig-zag polymer
with exo-coordinated [14]aneS4 units linked via alternate
S atoms to a cis-TeCl4 unit (Fig. 10). The macrocyclic rings are
centrosymmetric. The Te–S distances in this complex are in a
similar range to those in the thioether examples described above.
While exocyclic coordination in tetrathia-crown complexes is
very rare in transition metal chemistry43 a notable structurally
authenticated exception being [(NbCl5)2([14]aneS4)],44 it has
been observed more frequently in p-block coordination
Fig. 8 (a) Crystal structure of [TeCl4{o-C6H4(SMe)2}]n showing the
atom numbering scheme. Ellipsoids are drawn at the 50% probability
level and H atoms are omitted for clarity. The structure forms a chain of
which part is shown. The long bonds from Te1 to S atoms are shown
with open bonds. Symmetry operation: a = 2 − x, 1 − y, 1/2 + z. Selected
bond lengths (Å) and angles (°): Te1–Cl1 = 2.4389(7), Te1–Cl2 =
2.3521(9), Te1–Cl3 = 2.5212(8), Te1–Cl4 = 2.3435(9), Te1–S1 =
3.0580(9), Te1–S2a = 3.0375(8), Cl1–Te1–Cl2 = 91.10(3), Cl1–Te1–
Cl3 = 177.32(4), Cl1–Te1–Cl4 = 89.64(3), Cl2–Te1–Cl3 = 90.16(3),
Cl2–Te1–Cl4 = 90.57(3), Cl3–Te1–Cl4 = 87.99(3), Cl1–Te1–S1 =
93.56(3), Cl2–Te1–S1 = 81.98(3), Cl3–Te1–S1 = 88.96(2), Cl4–Te1–
S1 = 171.93(3), Cl1–Te1–S2a = 87.20(3), Cl2–Te1–S2a = 172.79(3),
Cl3–Te1–S2a = 91.25(3), Cl4–Te1–S2a = 82.42(3), S1–Te1–S2a =
105.11(2). (b) View of part of the polymeric structure of [TeCl4{o-C6H4-
(SMe)2}]n.
complexes, possibly a result of the relatively low affinity of the
soft, modest σ-donor thioether functions for the harder p-block
Lewis acids, and their tendency not to displace halide co-
ligands.6,45
Multinuclear NMR trends
Table 1 lists selected 125Te{1H} and 77Se{1H} NMR parameters
for the TeX4 chalcogenoether complexes. The complexes are
extensively dissociated at ambient temperatures and even at the
Dalton Trans.
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lowest temperatures it is likely that some dynamic processes are
still significant. For example, resonances for individual inverto-
mers are not observed in the cis-chelates. However, some trends
are very clear from the low temperature data reported. Firstly, the
77Se{1H} NMR shifts in the selenoether complexes are substan-
tially to high frequency of the parent selenoether.
For a common chalcogenoether, from the 125Te{1H} NMR
spectra we observe that the bromo complexes all have resonances
to high frequency of those of the chlorides, although the geo-
metric isomer has a significant effect, i.e. where X is trans to
X the differences in δ(125Te) for X = Cl vs. X = Br is much less
than for the cis chelates, where X is trans to chalcogen. Finally,
we note that the 125Te NMR resonances for the selenoether com-
plexes are typically at a frequency than their thioether analogues.
Therefore, the 125Te NMR shifts provide a useful guide to the
coordination geometry and donor set present in these complexes.
Fig. 9 Crystal structure of [TeCl4{o-C6H4(CH2SMe)2}] showing the
atom numbering scheme. Ellipsoids are drawn at the 50% probability
level and H atoms are omitted for clarity. Symmetry operation: a = x,
1/2 − y, z. Selected bond lengths (Å) and angles (°): Te1–Cl1 =
2.5052(8), Te1–Cl2 = 2.5049(8), Te1–Cl3 = 2.4213(6), Te1–S1 =
Conclusions
2.8675(6), Cl1–Te1–Cl2
= 168.57(3), Cl1–Te1–Cl3 = 93.83(2),
Cl2–Te1–Cl3 = 94.41(2), Cl3–Te1–Cl3a = 87.62(3), Cl3–Te1–S1a =
169.29(2), Cl1–Te1–S1a = 85.44(2), Cl2–Te1–S1 = 87.92(2), Cl3–Te1–
S1 = 81.78(2), S1–Te1–S1a = 108.78(2).
We have prepared and fully characterised the first examples of
selenoether complexes of TeX4 Lewis acids, as well as demon-
strating that Se–C bond cleavage occurs in some cases. In con-
trast, there are no telluroether complexes formed with TeX4;
dimethyltelluride is halogenated to X2TeMe2 (X = F, Cl or Br).
Fig. 10 (a) Crystal structure of a portion of the [TeCl4([14]aneS4)]n polymer showing the atom numbering scheme. Ellipsoids are drawn at the 50%
probability level and H atoms are omitted for clarity. Symmetry operations: a = −x + 1, −y − 1, –z; b = −x + 1, −y, −z. Selected bond lengths (Å) and
angles (°): Te1–Cl1 = 2.3799(9), Te1–Cl2 = 2.3859(9), Te1–Cl4 = 2.492(1), Te1–Cl3 = 2.499(1), Te1–S1 = 2.885(1), Te1–S3 = 3.014(1), Cl1–Te1–
Cl2 = 90.58(4), Cl1–Te1–Cl4 = 89.19(3), Cl2–Te1–Cl4 = 92.93(3), Cl1–Te1–Cl3 = 92.76(3), Cl2–Te1–Cl3 = 91.28(3), Cl4–Te1–Cl3 = 175.34(3),
Cl1–Te1–S1 = 81.77(3), Cl2–Te1–S1 = 170.40(3), Cl4–Te1–S1 = 92.75(3), Cl3–Te1–S1 = 83.35(3), Cl1–Te1–S3 = 179.03(3), Cl2–Te1–S3 =
90.33(3), Cl4–Te1–S3 = 90.43(3), Cl3–Te1–S3 = 87.55(3), S1–Te1–S3 = 97.36(3). (b) View of the polymeric structure of [TeCl4([14]aneS4)]n.
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1
A range of new structure types has been identified for thioether
complexes of Te(IV) halides, which are subtly dependent on the
ligand architecture, and include a rare example of bridging by an
o-phenylene dithioether in [TeCl4{o-C6H4(SMe)2}]n.
1JFTe = 2850 Hz), −36.5 (s, [2F], JFTe = 1290 Hz), −59.8 (s,
[1F], JFTe = 1830 Hz). 31P{1H} NMR (CD2Cl2/CH2Cl2,
1
178 K): 44.8 (s). 125Te{1H} NMR (CD2Cl2/CH2Cl2, 178 K): see
text. IR (Nujol/cm−1): 501s, 576s, 647s Te–F, 1048s PvO.
Raman (cm−1): 571, 620, 647 Te–F.
TeF4 forms stable five-coordinate complexes with hard
O-donor phosphine oxides, but much less stable adducts form with
thio- or selenoethers. It appears that the TeF4 is a considerably
harder Lewis acid than the heavier halides, and while there is
little evidence for a stereochemically active Te-based lone pair in
the chloro or bromo complexes, there is a vacant vertex obvious
in the [TeF4(L)] species, which is assumed to be occupied by the
lone pair. Systematic shifts in the 125Te NMR spectra of the com-
plexes with halide, chalcogen and geometric isomer are
observed, and are consistent with the Te–X bonding dominating
the electronic environment at Te(IV).
[TeF4(OPMe3)]
Analogous procedure, using TeF4 (0.100 g, 4.91 × 10−4 mol)
and OPMe3 (0.048 g, 5.21 × 10−4 mol). Colourless crystals.
Yield: 0.088 g, 61%. Required for C3H9F4OPTe: C, 12.2; H, 3.1.
Found: C, 12.2; H, 3.1. 1H NMR (CDCl3, 298 K): 1.78 (d, [9H],
2JHP = 13 Hz). 19F{1H} NMR (CD2Cl2, 295 K): −39.8 (s, [4F]);
1
(183 K): −23.8 (s, [1F], JFTe = 2325 Hz), −40.3 (s, [2F],
1
1JFTe = 1313 Hz), −58.6 (s, [1F], JFTe = 1721 Hz). 31P{1H}
NMR (CD2Cl2/CH2Cl2, 293 K): 64.5 (s); (243 K): 66.1 (s);
(183 K): 68.3 (s). 125Te{1H} NMR (CD2Cl2/CH2Cl2, 183 K):
∼1151 see text. IR (Nujol/cm−1): 480s, 514s, 543s, 624s Te–F,
1032s, PvO. Raman (cm−1): 482, 518, 535, 620 Te–F, 1032
PvO.
Experimental
Infrared spectra were recorded as Nujol mulls between CsI plates
using a Perkin-Elmer Spectrum 100 spectrometer over the range
4000–200 cm−1. Raman spectra were obtained using a Perkin-
1
Elmer FT2000R with a Nd:YAG laser. H NMR spectra were
[TeF4(SMe2)]
recorded in CDCl3 or CD2Cl2 unless otherwise stated, using a
Bruker AV300 spectrometer. 19F{1H}, 31P{1H}, 77Se{1H} and
125Te{1H} NMR spectra were recorded using a Bruker DPX400
spectrometer and are referenced to CFCl3, 85% H3PO4, external,
neat SeMe2 and TeMe2 respectively. Electrospray (ES) MS data
were obtained from solutions in MeCN using a VG Biotech Plat-
form. Microanalyses were undertaken by Medac Ltd. Solvents
were dried by distillation prior to use, CH2Cl2 from CaH2,
hexane from sodium benzophenone ketyl. TeF4 was prepared by
heating TeO2 with SF4 in a Monel autoclave (120 °C) according
to the method of Seppelt and co-workers.46 Tht, SMe2,
[14]aneS4, TeCl4 and TeBr4 (Aldrich) were used as received.
Ligands OPPh3 and OAsPh3 (Aldrich) were dried in vacuo and
OPMe3 was freshly sublimed prior to use. SeMe2, TeMe2, MeSe-
(CH2)3SeMe, o-C6H4(SMe)2, o-C6H4(SeMe)2, o-C6H4(CH2SMe)2
and o-C6H4(CH2SeMe)2 were prepared via the literature
methods.47,48 All preparations were performed under an atmos-
phere of dry N2 using Schlenk techniques, with samples stored
and spectroscopic samples prepared in a dry N2-purged
glove box.
SMe2 (ca. 2 mL) was condensed directly onto solid TeF4
(0.05 g, 2.46 × 10−4 mol). Upon warming to room temperature,
a colourless solution was obtained. This was stirred for 15 min,
and then the excess SMe2 was removed in vacuo. The sticky
yellow solid that remained darkened considerably over 24 h at
room temperature in the glove box. A freshly prepared sample
1
was dissolved in CD2Cl2 for NMR studies. H NMR (CD2Cl2,
295 K): 2.38 (s); 188 K: 2.38(s). 19F{1H} NMR (CD2Cl2,
295 K): −45.9 (br, s); 188 K: −46.6 (br, s, w1/2 = 1500 Hz).
No 125Te{1H} NMR resonance observed at any temperature
down to 185 K. IR (Nujol/cm−1): 450 sh, 468 br s, 622 m Te–F.
[TeF4(SeMe2)]
TeF4 (0.05 g, 2.46 × 10−4 mol) was suspended in CH2Cl2
(10 mL) and stirred at room temperature with SeMe2 (0.02 mL,
0.028 g, 2.58 × 10−4 mol), forming a cloudy yellow solution.
After 15 min the volatiles were removed in vacuo to leave a
sticky yellow solid which darkened over a few hours at room
temperature. A freshly prepared sample was used for spectro-
scopic studies. 1H NMR (CD2Cl2, 295 K): 2.43 (s); 188 K: 2.45 (s).
19F{1H} NMR (CD2Cl2, 295 K): −43.4 (br, s); 188 K: −41.7
(br, s, w1/2 = 1600 Hz). No 77Se{1H} or 125Te{1H} NMR reson-
ance observed at any temperature down to 185 K. IR (Nujol/
cm−1): 447 s, 470 br s, 623 m Te–F.
Preparations
[TeF4(OPPh3)]
A Schlenk tube was loaded with TeF4 (0.101 g, 4.96 × 10−4 mol)
and OPPh3 (0.140 g, 5.03 × 10−4 mol). CH2Cl2 (20 mL) was
added at room temperature, giving a colourless solution with
some undissolved TeF4. After stirring for approximately 30 min,
the mixture had become almost clear. It was then filtered, con-
centrated in vacuo to ca. 5 mL, layered with hexane (15 mL) and
refrigerated. Colourless crystals suitable for X-ray diffraction
formed rapidly. These were collected by filtration, washed with a
small amount of hexane and dried in vacuo. Yield: 0.132 g,
55%. Required for C18H15F4OPTe: C, 44.9; H, 3.1. Found: C,
trans-[TeCl4(SeMe2)2]
TeCl4 (0.268 g, 9.95 × 10−4 mol) was suspended in THF
(20 mL) and cooled to 0 °C with the aid of an external ice-bath.
With stirring, SeMe2 (0.09 mL, 0.127 g, 1.16 × 10−3 mol) was
added, causing a rapid colour change to very dark orange-black.
After stirring for 30 min, the mixture was concentrated in vacuo
to ca. 5 mL, filtered to remove any solids and the filtrate
was placed in the freezer. Small almost black crystals suitable for
1
45.3; H, 3.3%. H NMR (CDCl3, 295 K): 7.4–7.7(m). 19F{1H}
NMR (CD2Cl2, 295 K): −38.4 (s, [4F]); (178 K): −25.9 (s, [1F],
Dalton Trans.
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1
X-ray diffraction appeared over a few days. Yield: 0.262 g, 54%.
Required for C4H12Cl4Se2Te: C, 9.9; H, 2.5. Found: C, 9.9;
17.3; H, 2.3%. H NMR (CD2Cl2, 298 K): 2.74 (s, [6H], Me),
7.39 (m, [2H], aromatic H), 7.49 (m, [2H], aromatic H).
77Se{1H} NMR (CH2Cl2/CD2Cl2, 298 K): 272; (193 K): 291.
IR (Nujol/cm−1): 235, 287 Te–Cl. Raman (cm−1): 226, 244, 272,
296 Te–Cl.
1
H, 2.3%. H NMR (CDCl3, 298 K): 2.59 (s). 125Te{1H} NMR
(CD2Cl2/CH2Cl2, 183 K): 1280 (s). 77Se{1H} NMR (CD2Cl2/
CH2Cl2, 183 K): 233 (s). IR (Nujol/cm−1): 246 br Te–Cl. Raman
(cm−1): 280 s, 254 m Te–Cl.
Reaction of TeX4 (X = F, Cl or Br) with TeMe2
trans-[TeBr4(SeMe2)2]
1H/19F NMR experiments
Analogous procedure, using TeBr4 (0.440 g, 9.84 × 10−4 mol)
and SeMe2 (0.08 mL, 0.113 g, 1.04 × 10−3 mol). Small, almost
black crystals of X-ray quality formed over a few days in the
freezer. Yield: 0.181 g, 54%. Required for C4H12Br4Se2Te: C,
A 5 mm diameter NMR tube was loaded with ca. 0.01 g of the
appropriate tellurium halide. Against a flow of N2, CD2Cl2 was
added followed by ca. 0.01 mL of TeMe2.
1
7.2; H, 1.8. Found: C, 7.1; H, 1.9%. H NMR (CDCl3, 298 K):
2.66 (s). 125Te{1H} NMR (CD2Cl2/CH2Cl2, 183 K): 1317 (s).
77Se{1H} NMR (CD2Cl2/CH2Cl2, 183 K): 226 (s).
125Te{1H} NMR experiments
A 10 mm diameter NMR tube was loaded ca. 0.03 g of the
appropriate tellurium halide. Against a flow of N2, a mixture of
CD2Cl2 and CH2Cl2 was added, followed by ca. 0.02 mL of
TeMe2.
[TeCl4{MeSe(CH2)3SeMe}]
TeCl4 (0.271 g, 1.01 × 10−3 mol) was suspended in CH2Cl2
(20 mL), and the mixture was cooled to 0 °C with the aid of an
external ice-bath. With stirring, MeSe(CH2)3SeMe (0.269 g,
1.17 × 10−3 mol) was added, which caused a rapid colour
change to orange-brown, concomitant with the formation of an
orange precipitate. After stirring for approximately 1 h, the
amount of solid had increased, and this was collected by filtra-
tion and dried in vacuo. Yield: 0.373 g, 75%. This compound
has very low solubility in all common non- or weakly-coordinating
solvents, and darkens rapidly at room temperature. Required for
C5H12Cl4Se2Te: C, 12.0; H, 2.4. Found: C, 12.0; H, 2.4%.
In all cases an immediate black precipitate formed, identified
as elemental Te by powder XRD. The supernatants were exam-
ined by multinuclear NMR spectroscopy at 295 K, each showing
only one significant new resonance in addition to residual TeMe2
1
[1H NMR (CD2Cl2): 1.91 (s, JTeH = 22 Hz); 125Te{1H} NMR
(CD2Cl2/CH2Cl2, 295 K): −16.9 (s); note the substantial solvent
shift for the 125Te resonance compared to neat TeMe2, δ = 049).
The small variations between the 125Te chemical shifts reported
in the present work and the literature data are due to similar
sensitivities to solvent and concentration, but set against the very
wide chemical shift range of tellurium are unequivocal con-
firmation of the products.]
[TeBr4{MeSe(CH2)3SeMe}]
1
1
X = F: H NMR (CD2Cl2 295 K): 2.57 (t, JTeH = 7 Hz).
19F{1H} (CD2Cl2 295K): −123.5(s, J125TeF = 860 Hz).
1
TeBr4 (0.225 g, 5.03 × 10−4 mol) was dissolved in THF
(20 mL), and the solution was cooled to 0 °C with the aid of an
external ice-bath. With stirring, MeSe(CH2)3SeMe (0.151 g,
6.56 × 10−4 mol) was added, giving an opaque red-black solu-
tion. After stirring for 15 min, the mixture was concentrated
in vacuo to ca. 10 mL, which caused the precipitation of a deep-
red solid. This was collected by filtration and dried in vacuo.
Yield: 0.160 g, 47%. Required for C5H12Br4Se2Te: C, 8.9;
H, 1.8. Found: C, 8.9; H, 1.8%. 1H NMR (CD2Cl2, 298 K): 2.10
(br m, [2H], CH2CH2CH2), 2.21 (br s, [6H], SeCH3), 2.83 (m,
[4H], CH2CH2CH2). 125Te{1H} NMR (CD2Cl2/CH2Cl2, 183 K):
1455 (s). 77Se{1H} NMR (CD2Cl2/CH2Cl2, 183 K): 169 (s).
125Te{1H} NMR (CD2Cl2/CH2Cl2, 295 K): +1207 (t, J125TeF
=
1
860 Hz). [Lit:35 1H NMR (CDCl3 298 K): 2.57 (t, 1JTeH = 7 Hz).
19F{1H} (CDCl3 298 K): −124.9 (s, J125TeF = 871 Hz). Proton
1
coupled 125Te NMR (CDCl3, 298 K): +1232 (t of sept)].
1
1
X = Cl: H NMR (CD2Cl2 295 K): 3.12 (s, JTeH = 25 Hz).
125Te{1H} NMR (CD2Cl2/CH2Cl2, 295 K): +739 (s). [Lit.34
(neat liquid): H NMR (295 K): 3.13 (s, JTeH = 26 Hz). 125Te
1
1
NMR (neat liquid by INDOR2, 295 K): +749 (s)].
1
1
X = Br: H NMR (CD2Cl2 295 K): 3.20 (s, JTeH = 25 Hz).
125Te{1H} NMR (CD2Cl2/CH2Cl2, 295 K): +653 (s). [Lit.34
(neat liquid): H NMR (295 K): 3.19 (s, JTeH = 26 Hz). 125Te
NMR (neat liquid by INDOR2, 295 K): +669 (s)].
The reaction mixture from the TeBr4 reaction deposited
colourless crystals over a few days which were identified as the
hydrolysis product Me2BrTe(μ-O)TeMe2Br by an X-ray crystal
structure.
1
1
[TeCl4{o-C6H4(SeMe)2}]
TeCl4 (0.271 g, 1.01 × 10−3 mol) was suspended in CH2Cl2
(20 mL), and the mixture was cooled to 0 °C. With stirring,
o-C6H4(SeMe)2 (0.263 g, 9.97 × 10−4 mol) was added giving a
very deep red solution. After stirring for approximately 30 min,
the solution had become almost clear, and was then concentrated
in vacuo to ca. 10 mL. The resulting dark red precipitate, was
collected by filtration, washed with a small amount of CH2Cl2
and dried in vacuo. Storage of the filtrate at ca. −18 °C yielded
single crystals suitable for X-ray diffraction. Yield: 0.388 g,
73%. Required for C8H10Cl4Se2Te: C, 18.0; H, 1.9. Found: C,
trans-[TeCl4(tht)2]
TeCl4 (0.269 g, 9.98 × 10−4 mol) was suspended in CH2Cl2
(20 mL) at room temperature, and tht (0.175 mL, 0.175 g,
1.98 × 10−3 mol) was added, causing a rapid colour change to
orange-brown. After heating briefly, the mixture was stirred at
room temperature for approximately 1 h, and then filtered.
This journal is © The Royal Society of Chemistry 2012
Dalton Trans.

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The filtrate was concentrated in vacuo to ca. 7 mL, over-layered
with hexane (20 mL) and stored at ca. −18 °C. A large mass of
nearly black X-ray quality crystals appeared over a period of a
few days. These were collected by filtration, washed with hexane
and dried in vacuo. Yield: 0.180 g, 40%. Required for
C8H16Cl4S2Te: C, 21.5; H, 3.6. Found: C, 20.9; H, 3.3%.
1H NMR (CD2Cl2, 298 K): 2.10 (m, [8H], CH2), 3.25 (m, [8H],
CH2). 125Te{1H} NMR (CD2Cl2/CH2Cl2): 1500 (295 K); 1475
(183 K). IR (Nujol/cm−1): 248 br Te–Cl. Raman (cm−1): 255,
283 Te–Cl.
period of approximately 30 min and then filtered to remove any
unreacted TeCl4. The clear orange filtrate was concentrated
in vacuo to ca. 5 mL, layered with hexane (15 mL) and refrige-
rated. Large bright-red crystals formed over a few days, which
were collected by filtration, washed with hexane and dried
in vacuo. Yield: 0.254 g, 59%. Required for C8H10Cl4S2Te: C,
1
21.8; H, 2.3. Found: C, 21.3; H, 2.6%. H NMR (300 MHz,
CDCl3, 298 K): 2.69 (s, [6H], Me), 7.32 (m, [4H], aromatic H);
(400 MHz, CD2Cl2, 183 K): 2.72 (s, [6H], Me), 7.33 (br, [2H],
aromatic H), 7.37 (br, [2H], aromatic H). IR (Nujol/cm−1): 250,
282, 323, 337 Te–Cl.
trans-[TeBr4(tht)2]
[TeCl4{o-C6H4(CH2SMe)2}]
Analogous procedure, using TeBr4 (0.224 g, 5.01 × 10−4 mol)
and tht (0.09 mL, 0.09 g, 1.02 × 10−3 mol). Black crystals.
Yield: 0.182 g, 58%. Required for C8H16Br4S2Te: C, 15.4;
A Schlenk tube was loaded with TeCl4 (0.266 g, 9.87 × 10−4 mol)
and o-C6H4(CH2SMe)2 (0.201 g, 1.01 × 10−3 mol). CH2Cl2
(20 mL) was added at room temperature, causing the rapid
formation of an orange suspension. This was stirred for a further
2 h, then filtered. Owing to the low solubility of this compound,
it was washed several times with CH2Cl2 to separate it from any
unreacted TeCl4. The orange extracts were combined and con-
centrated in vacuo, causing the precipitation of an orange solid.
After addition of hexane (20 mL), the product was collected by
filtration, washed with hexane and dried in vacuo. Yield:
0.217 g, 47%. Crystals suitable for X-ray diffraction were
obtained by slow evaporation of a CH2Cl2 solution. Required for
C10H14Cl4S2Te: C, 25.7; H, 3.0. Found: C, 26.2; H, 3.4%.
1H NMR (CD3CN, 298 K): 2.40 (s, [6H], Me), 4.04 (s, [4H],
CH2), 7.32 (m, [2H], aromatic H), 7.39 (m, [2H], aromatic H);
(400 MHz, CD2Cl2, 183 K): 2.65 (br s, [6H], Me), 4.07 (br s,
[4H], CH2), 7.40 (br, [2H], aromatic H), 7.46 (br, [2H], aromatic
H). 125Te{1H} NMR (CD2Cl2/CH2Cl2, 193 K): 1433 (s). IR
(Nujol/cm−1): 256, 265, 284, 303 Te–Cl.
1
H, 2.6. Found: C, 15.5; H, 2.5%. H NMR (CD2Cl2, 298 K):
2.10 (m, [8H], CH2), 3.28 (m, [8H], CH2). 125Te{1H} NMR
(CD2Cl2/CH2Cl2, 193 K): 1507.
[TeCl4{MeS(CH2)3SMe}]
TeCl4 (0.265 g, 9.84 × 10−4 mol) was suspended in CH2Cl2
(20 mL) and stirred at room temperature. MeS(CH2)3SMe
(0.14 mL, 0.14 g, 1.04 × 10−3 mol) was added, causing a rapid
change from colourless to bright orange. After stirring for 1 h,
the mixture was filtered to remove excess TeCl4. The orange
filtrate was concentrated in vacuo to ca. 5 mL, which caused the
precipitation of an orange solid. Addition of hexane (20 mL)
caused further precipitation, and the product was collected by
filtration, washed with hexane and dried in vacuo. Yield:
0.235 g, 59%. Crystals suitable for X-ray diffraction were
obtained by slow evaporation of a CH2Cl2 solution. Required
for C5H12Cl4S2Te: C, 14.8; H, 3.0. Found: C, 14.1; H, 2.6%.
1H NMR (CDCl3, 298 K): 2.28 (quintet, [2H], CH2), 2.51 (s,
6H, Me), 3.06 (t, [4H], SCH2); (400 MHz, CD2Cl2, 183 K):
2.32 (br, [2H], CH2), 2.56 (br s, [6H], Me), 3.13 (br, [4H],
SCH2). 125Te{1H} NMR (CD2Cl2/CH2Cl2, 203 K): 1517 (s).
IR (Nujol/cm−1): 248, 261, 278, 290 Te–Cl.
[TeBr4{o-C6H4(CH2SMe)2}]
A Schlenk tube was loaded with TeBr4 (0.445 g, 9.95 × 10−4 mol)
and o-C6H4(CH2SMe)2 (0.203 g, 1.02 × 10−3 mol). THF
(20 mL) was added, and with stirring the mixture was heated to
reflux. The resulting clear red solution was filtered while hot.
Upon cooling, the filtrate began to deposit a deep-red solid. Con-
centration in vacuo to ca. 5 mL caused further precipitation,
leaving the supernatant almost colourless. The product was
collected by filtration, washed with hexane (10 mL) and dried
in vacuo. Yield: 0.400 g, 62%. Required for C10H14Br4S2Te:
[TeBr4{MeS(CH2)3SMe}]
Analogous procedure, using TeBr4 (0.446 g, 9.97 × 10−4 mol)
and MeS(CH2)3SMe (0.14 mL, 0.14 g, 1.04 × 10−3 mol). Bright
1
red solid. Yield: 0.171 g, 30%. H NMR (CDCl3, 298 K): 2.28
1
C, 18.6; H, 2.2. Found: C, 19.0; H, 2.1%. H NMR (CD3CN,
298 K): 2.07 (s, [6H], Me), 3.88 (s, [4H], CH2), 7.24 (m, [2H],
aromatic H), 7.28 (m, [2H], aromatic H).
(quintet, [2H], CH2), 2.58 (s, [6H], Me), 3.05 (t, [4H], SCH2);
(400 MHz, CD2Cl2, 183 K): 2.34 (br, [2H], CH2), 2.69 (br s,
[6H], Me), 3.12 (br s, [4H], SCH2). 125Te{1H} NMR (CD2Cl2/
CH2Cl2, 223 K): 1705 (s).
[TeCl4([14]aneS4)]n
[TeCl4{o-C6H4(SMe)2}]n
TeCl4 (0.077 g, 2.86 × 10−4 mol) and [14]aneS4 (0.078 g,
2.90 × 10−4 mol) were loaded into a Schlenk tube, and THF
(20 mL) was added forming a clear, colourless solution. After
stirring at room temperature for one hour, the THF was removed
in vacuo leaving a yellow solid residue. Addition of CH2Cl2
(20 mL) gave a yellow suspension, and the solid yellow product
was removed by filtration and washed with CH2Cl2.
TeCl4 (0.265 g, 9.84 × 10−4 mol) was suspended in CH2Cl2
(20 mL), and the mixture was cooled to 0 °C with the aid of an
external ice-bath. With stirring, o-C6H4(SMe)2 (0.15 mL, 0.17 g,
9.98 × 10−4 mol) was added, which caused a rapid change from
colourless to intense orange-yellow. The mixture was allowed to
stir at 0 °C for a further 2 h, warmed to room temperature for a
Dalton Trans.
This journal is © The Royal Society of Chemistry 2012

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Concentration of the filtrate and storage at ca. −18 °C furnished
a few small yellow crystals suitable for X-ray diffraction. IR
(Nujol/cm−1): 240 br, 265, 278, 314 Te–Cl. Raman (cm−1): 262,
280, 343 Te–Cl.
molybdenum rotating anode generator with VHF Varimax optics
(100 μm focus) with the crystal held at 100 K (N2 cryostream) or
a Bruker-Nonius FR591 rotating anode diffractometer fitted with
confocal mirrors and with the crystal held at 120 K (N2 cryo-
stream)([TeCl4{MeS(CH2)3SMe}], [TeCl4{o-C6H4(SMe)2}]n).
Structure solution and refinement were straightforward,50,51
except as detailed below, with H atoms being placed in calcu-
lated positions using the default C–H distance. For [TeCl4{MeS-
(CH2)3SMe}] the systematic absences suggested space group
I41/a (Laue group 4/m), but there was a query over the hhl reflec-
tions which suggested space group I41/amd (Laue group
4/mmm). In practice, attempts to refine the structure in I41/amd
X-ray crystallography
Summary details of the crystallographic data collection and
refinement are given in Table 2. Crystals were obtained as
described above. Data collection used a Rigaku AFC12 gonio-
meter equipped with an enhanced sensitivity (HG) Saturn724+
detector mounted at the window of an FR-E+ SuperBright
Table 2 Crystal data and structure refinement detailsa
[TeCl4{o-
(BrMe2Te)2O·
[TeCl4{o-
C6H4(SMe)2}]n
Compound
Formula
[TeF4(OPMe3)] [TeF4(OPPh3)] [TeCl4(SeMe2)2] [TeBr4(SeMe2)2] C6H4(SeMe)2}] 0.6CH2Cl2
C3H9F4OPTe
C18H15F4OPTe C4H12Cl4Se2Te
C4H12Br4Se2Te
C8H10Cl4Se2Te C4H12Br2OTe2· C8H10S2Cl4Te
0.6CH2Cl2
M
295.67
Orthorhombic
P212121 (19)
6.500(4)
10.790(5)
12.442(8)
90
90
90
872.6(9)
4
3.598
481.87
Monoclinic
P21/n (14)
9.933(3)
18.151(5)
10.604(7)
90
113.90(4)
90
1747.9(14)
4
1.836
936
7751
0.018
3965
226, 0
487.46
Monoclinic
P21/n (14)
6.487(2)
12.872(4)
8.215(3)
90
108.245(8)
90
651.4(4)
2
8.641
448
3103
0.019
1475
54, 0
665.30
Monoclinic
P21/n (14)
6.720(2)
13.138(4)
8.486(3)
90
107.967(5)
90
712.7(4)
2
18.361
592
2502
0.020
1387
533.48
Monoclinic
P21/m (11)
6.804(3)
10.725(5)
9.969(5)
90
99.156(7)
90
718.3(6)
2
7.850
492
3583
0.028
1717
74, 0
542.11
Cubic
Ia3d (230)
25.509(3)
25.509(3)
25.509(3)
90
439.68
Orthorhombic
Pna21 (33)
10.038(2)
14.622(2)
9.5760(10)
90
90
90
1405.5(4)
4
3.140
840
16 155
0.032
3181
138, 1
Crystal system
Space group (no.)
ˉ
a (Å)
b (Å)
c (Å)
α (°)
β (°)
γ (°)
U (Å3)
Z
90
90
16 599(4)
48
10.187
11 674
34 117
0.026
1585
μ(Mo-Kα) (mm−1
F(000)
)
552
Total number reflns 2336
Rint
0.019
1815
94, 0
Unique reflns
No. of params,
restraints
54, 0
54, 0
R1, wR2 [I > 2σ(I)]b 0.014, 0.033
0.018, 0.043
0.020, 0.044
0.016, 0.034
0.019, 0.034
0.020, 0.035
0.023, 0.036
0.034, 0.080
0.045, 0.084
0.029, 0.077
0.031, 0.078
0.020, 0.038
0.022, 0.039
R1, wR2 (all data)
0.014, 0.034
a Common items: temperature = 100 K; wavelength (Mo-Kα) = 0.71073 Å; θ(max) = 27.5°. b R1 = ΣkFo| − |Fck/Σ|Fo|; wR2 = [Σw(Fo − Fc ) /
2
2 2
4 1/2
ΣwFo ]
.
[TeCl4{MeS-
(CH2)3SMe}]
[TeCl4{o-C6H4-
(CH2SMe)2}]
[Br3(tht)Te(μ-Br)2-
TeBr3(tht)]
[TeCl4-
([14]aneS4)]n
Compound
[TeCl4(tht)2]
[TeBr4(tht)2]
Formula
M
Crystal system
Space group (no.)
C5H12Cl4S2Te
405.67
Tetragonal
I41/a (88)
9.881(3)
9.881(3)
26.388(8)
90
C10H14Cl4S2Te
467.73
Orthorhombic
Pnma (62)
19.451(3)
11.603(2)
7.1757(10)
90
90
90
1619.5(4)
4
2.732
C8H16Cl4S2Te
445.73
Monoclinic
P21/n (14)
7.882(3)
9.450(3)
10.280(5)
90
97.08(2)
90
759.8(5)
2
C8H16Br4S2Te
623.57
Monoclinic
P21/n (14)
8.624(2)
7.5542(12)
12.754(2)
90
109.630(5)
90
782.6(3)
2
C8H16Br8S2Te2
1070.81
C10H20Cl4S4Te
537.90
Monoclinic
P21/n (14)
9.080(2)
20.950(5)
9.990(4)
90
96.068(7)
90
1889.8(9)
4
Triclinic
ˉ
P1 (2)
a (Å)
b (Å)
c (Å)
α (°)
β (°)
γ (°)
U (Å3)
Z
8.502(3)
8.623(3)
8.734(3)
71.099(5)
87.043(6)
72.783(5)
577.9(3)
1
90
90
2576.4(14)
8
3.416
μ(Mo-Kα) (mm−1
F(000)
)
2.905
432
12.350
576
16.523
480
2.567
1056
1552
904
Total number reflns
Rint
12 362
0.054
1596
12 485
0.029
1937
4432
0.019
1721
70, 0
5336
0.024
1774
70, 0
5419
0.023
2630
91, 0
13 343
0.044
4293
Unique reflns
No. of params,
restraints
58, 0
83, 0
172, 0
R1, wR2 [I > 2σ(I)]b
R1, wR2 (all data)
0.041, 0.067
0.042, 0.067
0.020, 0.042
0.021, 0.043
0.013, 0.031
0.014, 0.032
0.018, 0.041
0.020, 0.042
0.019, 0.037
0.022, 0.038
0.032, 0.060
0.047, 0.065
This journal is © The Royal Society of Chemistry 2012
Dalton Trans.

View Online
23 M. F. Davis, M. Clarke, W. Levason, G. Reid and M. Webster,
Eur. J. Inorg. Chem., 2006, 2773.
24 N. W. Mitzel, U. Losehand and K. Vojinovic, Inorg. Chem., 2001, 40,
5302.
25 J. P. Guertin and M. Onyszchuk, Can. J. Chem., 1968, 46, 988.
26 W. Levason, M. E. Light, S. Maheshwari, G. Reid and W. Zhang, Dalton
Trans., 2011, 40, 5291.
27 K. George, A. L. Hector, W. Levason, G. Reid, G. Sanderson,
M. Webster and W. Zhang, Dalton Trans., 2011, 40, 1584.
28 F. Cheng, M. F. Davis, A. L. Hector, W. Levason, G. Reid, M. Webster
and W. Zhang, Eur. J. Inorg. Chem., 2007, 2488.
failed, while refinement in space group I41/a using a TWIN/
BASF command led to successful refinement. The structure of
(BrMe2Te)2O was found to contain a partially occupied (0.6) dis-
ordered CH2Cl2 solvent molecule which was evident as three
Q peaks close together which were modelled as fractional
Cl atoms. There were two recognisable CH2Cl2 residues
(from Cl⋯Cl distances). Cl1⋯Cl1′ (atom C3 was located) and
Cl2⋯Cl3 as overlapping solvate molecules (no C atom was
located for this).
29 M. F. Davis, W. Levason, G. Reid and M. Webster, Polyhedron, 2006, 25,
930.
30 A. Augustine, G. Ferguson and F. C. Marsh, Can. J. Chem., 1975, 53,
1647.
31 H. Poleschner and K. Seppelt, Angew. Chem., Int. Ed., 2008, 47, 6461.
32 C. Gurnani, W. Levason, R. Ratnani, G. Reid and M. Webster, Dalton
Trans., 2008, 6274.
Acknowledgements
We thank EPSRC for support (EP/I010890/1) and Dr M. Webster
for assistance with the X-ray crystallographic analyses.
33 W. Levason, L. P. Ollivere, G. Reid and M. Webster, J. Organomet.
Chem., 2010, 695, 1346.
34 H. C. E. McFarlane and W. McFarlane, J. Chem. Soc., Dalton Trans.,
1973, 2416.
35 T. Klapötke, B. Krumm, P. Mayer, H. Piotrowski, O. P. Ruscitti and
A. Schiller, Inorg. Chem., 2002, 41, 1184.
36 N. J. Hill, W. Levason and G. Reid, J. Chem. Soc., Dalton Trans., 2002,
1188.
37 G. Baum, A. Greiling, W. Massa, B. C. Hiu and J. Lorberth, Z. Natur-
forsch. B: Chem. Sci., 1989, 44, 560.
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