The reactions of tellurium tetrahalides with triphenylphosphine under ambient conditions

Article abstract of DOI:10.1021/ic049789v

The reactions of tellurium tetrahalides and triphenylphosphine in tetrahydrofuran have been carried out under ambient conditions and afford {(Ph₃PO)₂H}₂[Te₂X₁₀] [X = Cl (1), Br (2)] and {(Ph₃PO)₃(OH₃}) ₂[TeI₆] (4). The X-ray structures of 1 and 2 show that they are isostructural and contain discrete [Te₂X₁₀] ^2- anions exhibiting octahedral coordination around both tellurium atoms with one shared edge and {Ph₃POH...OPPh₃} ⁺ cations that show strong hydrogen bonds (the O...O distances are 2.399 and 2.404 A for 1 and 2, respectively). The compound 4 is built up with discrete octahedral hexaiodotellurate anions and {(Ph ₃PO)₃(OH₃)}⁺ cations. The reaction of TeBr₄ and PPh₃ also results in the formation of formally zwitterionic Ph₃PO(CH₂)₄TeBr ₄ (3). This reaction involves an unprecedented THF ring opening in which the oxygen atom becomes bonded to the phosphorus atom of triphenylphosphine and the carbon atom at the other end of the five-atomic chain becomes bonded to the tellurium atom of TeBr₄. The ring opening of the solvent THF is also taking place in the reaction involving tellurium tetraiodide, as indicated by the formation of C₄H ₈TeI₂ (5). The reaction may initially lead to Ph ₃Pl₂ that reacts with THF yielding Ph₃PO and ICH₂(CH₂)₂-CH₂I. The latter species reacts with elemental tellurium producing 5. Depending on the conditions upon crystallization, two polymorphs of C₄H₈TeI₂ (5a and 5b) are observed. While the molecular structures of the two forms are virtually identical, their packing and intermolecular contacts are different. Two further minor products (6a and 6b) were isolated in the reaction of TeI ₄ and PPh₃: Both are formally 1:1 adducts of 5 and TeI₄, but they differ considerably in their structures. 6a can be formulated as {C₄H₈TeI⁺}₂[Te ₂I₁₀^2-] and 6b as {C₄H ₈TeI⁺}₂(TeI₃⁺) ₂(I^-)₄. The latter compound exhibits framework similar to that of the tetramers in γ- and δ-TeI₄.

Full text of DOI:10.1021/ic049789v

Inorg. Chem. 2004, 43, 3742−3750
The Reactions of Tellurium Tetrahalides with Triphenylphosphine under
Ambient Conditions
,†
,†
Sari M. Na1rhi,† Raija Oilunkaniemi,* Risto S. Laitinen,* and Markku Ahlgre´n‡
Departments of Chemistry, P.O. Box 3000, FIN-90014 UniVersity of Oulu, Finland, and
UniVersity of Joensuu, P.O. Box 111, FIN-80101 Joensuu, Finland
Received February 17, 2004
The reactions of tellurium tetrahalides and triphenylphosphine in tetrahydrofuran have been carried out under ambient
conditions and afford {(Ph3PO)2H}2[Te2X ][X) Cl (1), Br (2)] and {(Ph3PO)3(OH })2[TeI ](4). The X-ray structures
10
3
6
of 1 and 2 show that they are isostructural and contain discrete [Te2X ]2- anions exhibiting octahedral coordination
10
around both tellurium atoms with one shared edge and {Ph3POH‚‚‚OPPh3}+ cations that show strong hydrogen
bonds (the O‚‚‚O distances are 2.399 and 2.404 Å for 1 and 2, respectively). The compound 4 is built up with
discrete octahedral hexaiodotellurate anions and {(Ph3PO)3(OH )}+ cations. The reaction of TeBr4 and PPh3 also
3
results in the formation of formally zwitterionic Ph3PO(CH ) TeBr4 (3). This reaction involves an unprecedented
2 4
THF ring opening in which the oxygen atom becomes bonded to the phosphorus atom of triphenylphosphine and
the carbon atom at the other end of the five-atomic chain becomes bonded to the tellurium atom of TeBr4. The ring
opening of the solvent THF is also taking place in the reaction involving tellurium tetraiodide, as indicated by the
formation of C4H TeI (5). The reaction may initially lead to Ph3PI that reacts with THF yielding Ph3PO and ICH (CH ) -
8
2
2
2
2 2
CH I. The latter species reacts with elemental tellurium producing 5. Depending on the conditions upon crystallization,
2
two polymorphs of C4H TeI (5a and 5b) are observed. While the molecular structures of the two forms are virtually
8
2
identical, their packing and intermolecular contacts are different. Two further minor products (6a and 6b) were
isolated in the reaction of TeI and PPh3: Both are formally 1:1 adducts of 5 and TeI , but they differ considerably
4
4
in their structures. 6a can be formulated as {C4H TeI+}2[Te2I102-] and 6b as {C4H TeI+}2(TeI +)2(I-)4. The latter
8
8
3
compound exhibits framework similar to that of the tetramers in γ- and δ-TeI .
4
3,4
5
Introduction
group C2V.2 In the solid state TeCl4 and TeBr4 display a
tetrameric cubane-like structure I in which the terminal
Te-X bonds are shorter than those involving the triply
bridging halogen atoms. The structure can be understood
either as covalently bound (Te4X16) molecules or in terms
Tellurium forms tetrahalides with all four halogen ele-
ments. Especially TeCl4, TeBr4, and TeI4 have seen consider-
able research activity because of their structural versatility
and potential utility as synthons in many chemical reactions.
The bonding in these compounds eludes simple description,
and concepts like hypervalence, multicenter bonding, charge-
transfer interactions, and secondary bonding have been
evoked in the understanding of their structural and chemical
properties (for a recent review of chalcogen halides, see ref
1).
of the ionic formulation [(TeX3 X-)4].3,6 The tellurium lone
pairs show stereochemical activity directed toward the center
of the cubane structure.
+
The early electron diffraction studies suggested that TeCl4-
(g) is a monomer displaying a Ψ-tbp structure with point
* Authors to whom correspondence should be addressed. R.O.: e-mail,
raija.oilunkaniemi@oulu.fi; tel, (3588) 553-1686; fax, (3588) 553-1608.
R.S.L.: e-mail, risto.laitinen@oulu.fi; tel, (3588) 553-1611; fax, (3588) 553-
1608.
† University of Oulu.
‡ University of Joensuu.
(1) Krebs, B.; Ahlers, F.-P. AdV. Inorg. Chem. 1990, 35, 235.
3742 Inorganic Chemistry, Vol. 43, No. 12, 2004
10.1021/ic049789v CCC: $27.50 © 2004 American Chemical Society
Published on Web 05/20/2004

Reactions of Tellurium Tetrahalides with Triphenylphosphine
Scheme 1
TeI4 differs from TeCl4 and TeBr4 by having five different
polymorphs (R-ꢀ) that can simultaneously be crystallized
from the methanol solution of TeI4 containing HI.6 The
orthorhombic δ-TeI4 is the thermodynamically stable poly-
morph at normal conditions.7 It shows another tetrameric
to afford Ph3PCl2 and Te(0),8 or TeCl2, Te(0), and Ph3PO.9
The last product was assumed to be formed upon hydrolysis
of Ph3PCl2 during the workup of the product mixture. In this
work we explored the reactions in air. We found that under
these conditions the reaction of TeCl4 with Ph3P in tetra-
hydrofuran affords {(Ph3PO)2H}2[Te2Cl10] (1) and that of
TeBr4 yields {(Ph3PO)2H}2[Te2Br10] (2) and Ph3PO(CH2)4-
TeBr4 (3).10 The reaction of TeI4 produces mainly {(Ph3-
PO)3H3O}2[TeI6] (4), but small amounts of C4H8TeI2 (5) and
C4H8Te2I6 (6) were also obtained. The products have been
characterized by 125Te and 31P NMR spectroscopy, as well
as by X-ray crystallography.
+ -
structure (II) that can be formulated as [(TeI3 I )2(TeI4)2].
The TeX6 octahedra in II are less distorted than in the cubane
structure (I). It has been suggested,1 that the formation of
the structure type II is a consequence of a smaller electro-
negativity difference between tellurium and iodine compared
to that between tellurium and chlorine or tellurium and
bromine, since the cubane structure (I) favors larger charge
separation with the formation of more polar bonds. Indeed,
orthorhombic â-TeI4 and monoclinic γ-TeI4 also exhibit the
structure II.6 Trigonal R-TeI4 shows a continuous 2H-CdI2
structure that can also be understood in terms of a repeating
structural unit similar to II.6 Interestingly, only the thermo-
dynamically least-stable tetragonal ꢀ-TeI4 shows the cubane
structure I.6
Experimental Section
General Procedures. All reactions were carried out in air. Ph3P
(Fluka), TeCl4 (Alfa), TeBr4 (Aldrich), and TeI4 (Aldrich) were
used without further purification.
Spectroscopic Methods. The 31P{1H} and 125Te spectra were
recorded on a Bruker DPX400 spectrometer operating at 161.98
and 126.24 MHz, respectively. The spectra were recorded unlocked.
The 31P chemical shifts are reported relative to 85% H3PO4. For
125Te a saturated solution of H6TeO6(aq) was used as an external
reference. The chemical shifts are reported relative to neat Me2Te
[δ(Me2Te) ) δ(H6TeO6) + 712]. All spectra were recorded in THF.
Reaction of TeCl4 with Ph3P. Ph3P (313 mg, 1.19 mmol) was
added into a stirred solution of 308 mg (1.14 mmol) of TeCl4 in
6.0 mL of THF. The reaction mixture was further mixed for 1 h.
During this time a black precipitate was obtained. It was removed
by filtration, and the solvent was evaporated from the green filtrate.
The remaining mixture of pale green crystals and dark oil was
washed with diethyl ether. Yield: 322 mg (63%, based on
triphenylphosphine.) Anal. Calcd for C72H62O4P4Te2Cl10 (1): C
50.13, H 3.62. Found: C 49.82, H 3.45.
The tetrameric tellurium tetrachlorides, -bromides, and
-iodides undergo a systematic stepwise degradation in the
presence of stoichiometric amounts of halides in nonpolar
solvents and form oligonuclear halogenotellurates(IV) (see
Scheme 1). There are numerous examples of the formation
and equilibria between the different anions (for a detailed
discussion, see ref 1).
Tellurium tetrahalides can react with both Lewis bases and
Lewis acids. There are several examples of adducts where
tellurium tetrahalides have acted both as acceptors and as
donors (see ref 1 and references therein). This amphoteric
behavior can be understood in terms of the partially ionic
Te-X bonding. We are interested in the reactivity trends of
tellurium tetrahalides TeX4 (X ) Cl, Br, I) and revisited their
reactions with Ph3P in tetrahydrofuran. In an inert atmo-
sphere, the reaction of TeCl4 with Ph3P has been reported
Reaction of TeBr4 with Ph3P. TeBr4 (499 mg; 1.12 mmol) was
dissolved in 10.0 mL of THF, and 295 mg (1.13 mmol) of Ph3P
was added to the resulting solution. The mixture turned yellow,
and a black precipitate was formed. After 1 h the reaction mixture
was filtered, the solvent was evaporated from the reddish filtrate,
and some hexane was added. The addition of hexane resulted in
the formation of orange crystals and reddish brown oil. The crystals
(2) Stevenson, D. J.; Schomaker, V. J. Am. Chem. Soc. 1940, 62, 1267.
(3) Buss, B.; Krebs, B. Inorg. Chem. 1971, 10, 2795.
(4) Alemi, A.; Soleimani, E.; Starikova, Z. A. Acta Chim. SloV. 2000,
47, 89.
(5) Krebs, B. NoVa Acta Leopold. 1985, 59, 131.
(6) (a) Beister, H. J.; Kniep. R.; Schaefer, A. Z. Kristallogr. 1986, 174,
12. (b) Kniep, R.; Beister, H. J.; Wald, D. Z. Naturforsch. 1988, 43,
966.
(7) (a) Krebs, B.; Paulat, V. Acta Crystallogr. 1976, B32, 1470. (b) Paulat,
V.; Krebs, B. Angew. Chem. 1976, 88, 28.
(8) Berry, F. J.; Gunduz, N.; Roshani, M.; Smith, B. C. Commun. Fac.
Sci. UniV. Ankara, Ser. B 1975, 22B, 21.
(9) Albeck, M.; Shaik, S. J. Chem. Soc., Perkin Trans. 1 1975, 1223.
(10) Kunnari, S. M.; Oilunkaniemi, R.; Laitinen, R. S.; Ahlgre´n, M. J.
Chem. Soc., Dalton Trans. 2001, 3417.
Inorganic Chemistry, Vol. 43, No. 12, 2004 3743

Na1rhi et al.
Table 1. Details of the Structure Determination of {(Ph3PO)2H}2[Te2Cl10] (1), {(Ph3PO)2H}2[Te2Br10] (2), {(Ph3PO)3H3O}2[TeI6] (4), (CH2)4TeI2 (5b),
and (CH2)4Te2I6 (6a and 6b)a
1
2
4
5b
6a
C4H8Te2I6
1072.70
monoclinic
P21/c
6b
C4H8Te2I6
1072.70
monoclinic
P21/c
formula
fw
C36H31O2P2Cl5Te
862.40
C36H31O2P2Br5Te
1084.70
triclinic
P1h
C108H96O8P6TeI6
2596.67
orthorhombic
Pba2
C8H16Te2I4
875.01
monoclinic
P21/c
crystal system
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V
triclinic
P1h
11.637(2)
12.429(3)
14.026(3)
72.11(3)
72.12(3)
84.09(3)
1837.2(6)
2
11.837(2)
12.509(3)
14.069(3)
71.90(3)
72.50(3)
83.07(3)
1887.5(7)
2
18.445(4)
32.344(7)
17.452(4)
9.860(5)
18.785(5)
9.639(5)
9.387(2)
9.593(2)
19.369(4)
9.589(2)
19.365(4)
9.616(2)
93.972(5)
94.46(3)
98.64(3)
10412(4)
4
1.657
2.211
5072
1781(1)
4
3.263
10.183
1520
1738.7(6)
4
4.098
13.976
1816
1765.2(6)
4
4.036
13.767
1816
Z
F
calcd, g cm-3
1.559
1.292
860
1.909
6.196
1040
µ(Mo KR), mm-1
F(000)
crystal size (mm3) 0.30 × 0.30 × 0.15 0.40 × 0.20 × 0.20 0.10 × 0.10 × 0.10 0.20 × 0.20 × 0.10 0.20 × 0.15 × 0.12 0.25 × 0.15 × 0.08
θ range (deg)
reflns collected
unique reflns
Rint
1.72-26.00
13227
6859
0.0596
0.0452
0.1254
1.013
2.31-26.00
23344
6942
0.0406
0.0277
0.0753
0.985
2.48-25.00
42516
15266
0.0689
0.0473
0.0892
0.979
2.07-25.99
23526
3492
0.0837
0.0290
0.0705
1.065
2.18-25.99
27050
3416
0.0513
0.0286
0.0708
1.163
2.99-24.99
19133
3085
0.0630
0.0544
0.1437
1.239
b
R1
c
wR2
GOF on F2
a T ) 150(2) K. b R1 ) [∑||Fo| - |Fc||]/[∑|Fo|] [I g 2σ(I)]. c wR2 ) {[∑w(Fo - Fc )2]/[∑w(Fo )2]}1/2 [all data].
2
2
2
were washed with acetone. Yield: 217 mg (35%). Anal. Calcd for
C72H62O4P4Te2Br10 (2): C 39.86, H 2.88. Found: C 39.58, H 2.55.
Reaction of TeI4 with Ph3P. The reaction of TeI4 (705 mg; 1.11
mmol) and Ph3P (291 mg; 1.11 mmol) was carried out similarly to
those of other tellurium tetrahalides. A mixture of three compounds
was obtained. {(Ph3PO)3H3O}2[TeI6] (4) is the most abundant
product, and (CH2)4TeI2 (5) and (CH2)4Te2I6 (6) are formed in small
amounts. 5 and 6 crystallize as two different crystal modifications
(5a, 5b and 6a, 6b). The separation and isolation of the three
products was attempted by extraction with different solvents.
Crystals for X-ray structure determination were obtained in these
experiments, but the complete isolation of the products was not
successful. 4, 5b, and 6b were obtained from toluene and THF, 5a
was obtained from hexane and diethyl ether, and 6a was obtained
from toluene.
X-ray Crystallography. Diffraction data for 1-6 were collected
on a Nonius Kappa CCD diffractometer using graphite monochro-
mated Mo KR radiation (λ ) 0.71073 Å). Crystal data and the
details of the structure determinations are given in Table 1. All
structures were solved by direct methods using SHELXS-9711 and
refined using SHELXL-97.12 After the full-matrix least-squares
refinement of the non-hydrogen atoms with anisotropic thermal
parameters, the hydrogen atoms were placed in calculated positions
in the aromatic rings of 1, 2, and 4 (C-H ) 0.95 Å), and in the
methylene groups of 5 and 6 (C-H ) 0.98 Å). In the final
refinement the calculated hydrogen atoms were riding with the
carbon atom they were bonded to. The isotropic thermal parameters
of the hydrogen atoms were fixed at 1.2 times that of the
corresponding carbon atom.
difference Fourier synthesis. The scattering factors for the neutral
atoms were those incorporated with the programs.
Results and Discussion
General. The reaction of PPh3 and TeCl4 in air affords
{(Ph3PO)2H}2[Te2Cl10] (1) in good yield. The precipitation
of elemental tellurium was also observed in the course of
the reaction. The 125Te NMR spectrum of {(Ph3PO)2H}2[Te2-
Cl10] (1) shows one resonance at 1540 ppm. It is in agreement
with the previously reported value of [Te2Cl10]2- at 1570
ppm that was recorded in acetonitrile for [Ni(NCMe)6][Te2-
Cl10].13 The 31P{1H} spectrum of 1 displayed one resonance
in the region 37-47 ppm due to {(Ph3PO)2H}+. This
chemical shift is strongly dependent on the concentration.
Analogously, the reaction of PPh3 and TeBr4 yields {(Ph3-
PO)2H}2[Te2Br10] (2). In addition, Ph3PO(CH2)4TeBr4 (3) is
also formed in this reaction, as we have recently reported.10
It is interesting to note that the yields of 2 and 3 seem to be
dependent on each other. With increasing amount of 3, the
yield of 2 becomes smaller.14 A typical isolated yield of 2
was 35%, and that of 3 was 13-50% depending on the
reaction time.10
[(Ph3PO)2H]2[Te2Br10] (2) exhibits a 125Te NMR resonance
due to [Te2Br10]2- at 1200 ppm. The resonance of Ph3PO-
(CH2)4TeBr4 was observed at 1210 in THF (1225 ppm in
acetonitrile10). The assignment was carried out by recording
the spectra from solutions obtained by redissolving the pure
crystalline products. In the 31P{1H} spectrum of 2, a
concentration dependent resonance due to {(Ph3PO)2H}+ was
observed in the region 36-47 ppm. The resonance at 62.6
ppm is due to 3.
The bridging hydrogen atoms in the dimeric cations {(Ph3-
PO)2H}+ of 1 and 2 could be located and refined in the conventional
way by using a fixed isotropic thermal parameter of 0.04. The
hydrogen atoms of the oxonium ion in the trimeric cation {(Ph3-
PO)3(OH3)}+ of 4, however, could not be observed in the final
(11) Sheldrick, G. M. SHELXS-97. Program for Crystal Structure Deter-
mination; University of Go¨ttingen: Go¨ttingen, 1997.
(12) Sheldrick, G. M. SHELXL-97. Program for Crystal Structure Refine-
ment; University of Go¨ttingen: Go¨ttingen, 1997.
(13) Pietika¨inen, J.; Maaninen, A.; Laitinen, R. S.; Oilunkaniemi, R.;
Valkonen, J. Polyhedron 2002, 21, 1089.
(14) The relative concentrations of 2 and 3 in the reaction solution were
monitored by 31P NMR spectroscopy.
3744 Inorganic Chemistry, Vol. 43, No. 12, 2004

Reactions of Tellurium Tetrahalides with Triphenylphosphine
Table 2. Selected Bond Lengths (Å) and Angles (deg) in {(Ph3PO)2H}2[Te2Cl10] (1) and {(Ph3PO)2H}2[Te2Br10] (2)
1
2
1
2
Te(1)-X(1)
Te(1)-X(2)
Te(1)-X(3)
Te(1)-X(4)
Te(1)-X(5)
Te(1)-X(5)a
2.457(1)
2.332(1)
2.472(1)
2.504(1)
2.609(1)
3.071(1)
2.6467(11)
2.5541(7)
2.6067(8)
2.6744(11)
2.8606(9)
2.9683(8)
P(1)-O(1)
P(2)-O(2)
O(1)-H(1)
O(2)-H(2)
1.530(3)
1.523(3)
1.092(2)
0.886(3)
1.523(2)
1.520(2)
1.024(2)
0.966(2)
X(1)-Te(1)-X(2)
X(1)-Te(1)-X(3)
X(1)-Te(1)-X(4)
X(1)-Te(1)-X(5)
X(1)-Te(1)-X(5)a
X(2)-Te(1)-X(3)
X(2)-Te(1)-X(4)
X(2)-Te(1)-X(5)
X(2)-Te(1)-X(5)a
X(3)-Te(1)-X(4)
87.95(5)
90.05(5)
176.20(4)
89.67(5)
88.62(5)
89.18(5)
88.49(5)
90.12(5)
174.43(3)
91.22(5)
89.90(3)
90.47(3)
177.17(1)
88.76(3)
87.74(3)
91.64(3)
90.28(3)
92.90(3)
177.60(1)
92.34(3)
X(3)-Te(1)-X(5)
X(3)-Te(1)-X(5)a
X(4)-Te(1)-X(5)
X(4)-Te(1)-X(5)a
X(5)-Te(1)-X(5)a
Te(1)-X(5)-Te(1)a
O(1)-H(1)-O(2)
O(2)-H(2)-O(1)
H(1)-O(2)-P(2)
H(2)-O(1)-P(1)
179.25(4)
95.22(5)
89.02(5)
94.83(5)
85.47(4)
94.53(4)
167.7(2)
170.0(2)
128.3(2)
129.8(2)
175.39(1)
88.85(3)
88.42(3)
92.05(3)
86.58(3)
93.42(3)
163.7(2)
166.9(2)
125.2(2)
127.2(2)
a Symmetry operation: -x + 1, -y, -z + 1.
The structures of 1 and 2 consist of discrete [Te2X10]2-
(X ) Cl, Br) anions and {(Ph3PO)2H}+ cations. The anions
are composed of two slightly distorted TeX6 octahedra
sharing an edge. The terminal Te-X bonds lengths are in
the ranges 2.332(1)-2.504(1) Å and 2.5541(7)-2.6744(11)
Å for 1 and 2, respectively. The bridging bonds lengths in 1
are 2.609(9) and 3.071(1) Å. Those in 2 are 2.8606(9) and
2.9683(8) Å. The bond parameter data are expectedly in
accord with those reported previously for various salts
containing [Te2X10]2- anions.13,17 Krebs et al.17a have noted
the decreasing stereochemical influence of the tellurium lone
pair, as the halogen becomes heavier. As a consequence, the
bonding arrangement involving the bridging halido ligands
is more symmetric, and the relative lengths of the bridging
Te-X bonds compared to those of the terminal bonds are
smaller in 2 than in 1 (see Table 2).
The {(Ph3PO)2H}+ cation consists of a Ph3POH+ cation
and a Ph3PO molecule that are linked together by a strong
hydrogen bond [the O(1)‚‚‚O(2) distances are 2.399 Å and
2.404 Å in 1 and 2, respectively].18 The disordered hydrogen
atom lies in two alternative locations with the site occupation
factors being 50% in both cases. One of the positions is at
the single bond distance from O(1), and the other position
is at that from O(2) (see Table 2). Only one of the two
alternative positions has been shown in Figure 1. The P-O
bond lengths are 1.530(3) and 1.523(3) Å in 1 and 1.523(2)
and 1.520(2) Å in 2. They are somewhat longer than the
P-O bonds in Ph3PO‚H2O [1.483(10)-1.485(2) Å] that does
not show as strong hydrogen bonding.20
Figure 1. The crystal structure of {(Ph3PO)2H}2[Te2Cl10] (1) indicating
the numbering of the atoms. The thermal ellipsoids have been drawn at the
50% probability level. {(Ph3PO)2H}2[Te2Br10] (2) is isostructural with 1.
The reaction of TeI4 and PPh3 seems to be somewhat more
complicated. After the precipitation of elemental tellurium,
{(Ph3PO)3H3O}2[TeI6] (4) was obtained together with small
amounts of (CH2)4TeI2 (5) and (CH2)4Te2I6 (6). Only one
resonance at 870 ppm was observed in the 125Te NMR
spectrum of the reaction mixture. It was assigned to [TeI6]2-.
The concentrations of 5 and 6 were probably too low for
the detection of the 125Te resonances.15 Like in the case of
other tetrahalides, the 31P{1H} NMR spectrum of the reaction
mixture of TeI4 and PPh3 displayed a concentration depend-
ent resonance at 29-39 ppm that was assigned to the {(Ph3-
PO)2H3O}+ cation on the basis of the X-ray structure.
{(Ph3PO)2H}2[Te2X10] (X ) Cl, Br). {(Ph3PO)2H}2[Te2-
Cl10] (1) and {(Ph3PO)2H}2[Te2Br10] (2) are isomorphic. The
crystal structure of 1 with the atomic numbering scheme is
shown in Figure 1. That of 2 is identical. The selected bond
lengths and angles are shown in Table 2.
{(Ph3PO)3OH3}2[TeI6] (4). The crystal structure of {(Ph3-
PO)3OH3}2[TeI6] (4) with the atomic numbering scheme is
(16) (a) Al-Rubaei, A.; Alshirayda, H. A. Y.; Granger, P.; Chapelle, S. J.
Organomet. Chem. 1985, 287, 321. (b) Garc´ıa-Montalvo, V.; Marcelo-
Polo, A.; Montoya, R.; Toscano, R. A.; Herna´ndez-Ortega, S.; Cea-
Olivares, R. J. Organomet. Chem. 2001, 623, 74.
(17) (a) Krebs, B.; Bu¨schner, K. Z. Anorg. Allg. Chem. 1980, 463, 56. (b)
Hauge, S.; Marøy, K. Acta Chem. Scand. 1998, 52, 445. (c) Hauge,
S.; Marøy, K. Acta Chem. Scand. 1999, 53, 992. (d) James, M. A.;
Knop, O.; Cameron, T. S. Can. J. Chem. 1992, 70, 1795. (e) Hauge,
S.; Marøy, K. Acta Chem. Scand. 1996, 50, 1095. (f) Krebs, B.; Paulat,
V. Z. Natursforsch. 1979, 34B, 900. (g) Beck, J.; Hormel, A.; Koch,
M. Eur. J. Inorg. Chem. 2002, 2271.
(15) The 125Te chemical shift of (CH2)4TeI2 (5) has been reported at 929.2
(18) The {(Ph3PO)2H}+ cation has been characterized on few occasions
and has been shown to involve a strong hydrogen bond.19
16a
ppm in DMSO-d6 and 782 ppm in CDCl3.16b
Inorganic Chemistry, Vol. 43, No. 12, 2004 3745

Na1rhi et al.
Table 3. Selected Bond Lengths (Å) and Angles (deg) in
{(Ph3PO)3H3O}2[TeI6] (4)
Te(1)-I(11)
Te(1)-I(12)
Te(1)-I(13)
Te(1)-I(14)
Te(2)-I(21)
Te(2)-I(22)
Te(2)-I(23)
Te(2)-I(24)
Te(2)-I(25)
P(1)-O(1)
2.9136(6)
2.9002(12)
2.9485(11)
2.9368(5)
2.9427(5)
2.9400(16)
2.8558(17)
2.8787(17)
2.937318)
1.503(6)
P(3)-O(3)
P(4)-O(4)
P(5)-O(5)
P(6)-O(6)
O(7)‚‚‚O(1)
O(7)‚‚‚O(2)
O(7)‚‚‚O(3)
O(8)‚‚‚O(4)
O(8)‚‚‚O(5)
O(8)‚‚‚O(6)
1.510(5)
1.503(6)
1.493(6)
1.491(5)
2.464(7)
2.469(7)
2.458(7)
2.452(8)
2.463(7)
2.484(7)
P(2)-O(2)
1.499(5)
I(11)-Te(1)-I(11)a
I(11)-Te(1)-I(12)
I(11)-Te(1)-I(13)
I(11)-Te(1)-I(14)
I(11)-Te(1)-I(14)a
I(12)-Te(1)-I(11)a
I(12)-Te(1)-I(13)
I(12)-Te(1)-I(14)
I(12)-Te(1)-I(14)a
I(13)-Te(1)-I(14)
I(13)-Te(1)-I(14)a
I(13)-Te(1)-I(11)a
I(14)-Te(1)-I(14)a
I(11)a-Te(1)-I(14)a
I(21)-Te(2)-I(21)b
179.70(5) I(21)-Te(2)-I(22)
90.15(2) I(21)-Te(2)-I(23)
89.85(2) I(21)-Te(2)-I(24)
90.08(2) I(21)-Te(2)-I(25)
89.92(2) I(22)-Te(2)-I(23)
90.15(2) I(22)-Te(2)-I(24)
180.00(5) I(22)-Te(2)-I(25)
90.16(2) I(22)-Te(2)-I(21)b
90.15(2) I(23)-Te(2)-I(24)
89.84(2) I(23)-Te(2)-I(25)
89.84(2) I(23)-Te(2)-I(21)b
89.85(2) I(24)-Te(2)-I(25)
179.68(5) I(24)-Te(2)-I(21)b
90.08(2) I(25)-Te(2)-I(21)b
179.58(4)
88.64(4)
89.59(4)
92.27(4)
94.98(4)
90.02(10)
176.74(10)
87.42(8)
91.00(4)
93.12(9)
174.71(7)
90.19(4)
89.38(12)
88.10(4)
85.23(4)
a Symmetry operation: -x + 2, -y + 1, z. b Symmetry operation: -x
+ 1, -y + 1, z.
I(21)b axis. The site occupation factors of iodine atoms
I(22)-I(25) and their symmetry-related counterparts are 50%.
The Te-I bond lengths span a narrow range of
2.867(1)-2.949(1) Å, and the bond angles depict only
slightly distorted octahedra (see Table 3 and Figure 2). These
values are quite typical for [TeI6]2-, as exemplified by
(Et4N)2[TeI6] [2.945(10)-2.948(6) Å]21 and H2TeI6‚8H2O
[2.938(1)-2.942(2) Å].22 It has been suggested that in the
case of electronegative monatomic ligands the almost ideal
octahedral coordination geometry of the 14-electron AX6E
species can be explained by interligand repulsions and that
the lone electron pair of tellurium resides in the stereochemi-
cally inactive 6s orbital (for a more detailed discussion, see
ref 1).
The three Ph3PO molecules in the cation are linked
together by the H3O+ ion. While the three hydrogen atoms
involving the oxonium ion could not be located, the three
short O‚‚‚O distances involving both O(7) and O(8) of
2.452(8)-2.484(7) Å imply strong hydrogen bonds (see
Table 3) like in the case of the {(Ph3PO)2H}+ cation in 1
and 2 or in the analogous cation {(Ph3PO)2(OH3)}+ found
in {(Ph3PO)2(OH3)}2[AuCl4].23 The existence of {(Ph3PO)3-
(OH3)}+ has also been reported previously.24
Figure 2. The crystal structure of {(Ph3PO)3H3O}2[TeI6] (4) indicating
the numbering of the atoms. The thermal ellipsoids have been drawn at the
50% probability level. The disorder of the other anion is displayed.
shown in Figure 2. The bond lengths and angles are presented
in Table 3.
The lattice is composed of discrete [TeI6]2- anions and
{(Ph3PO)3OH3}2}+ cations. The tellurium atoms in both of
the two crystallographically independent anions lie in the
special positions. The [TeI6]2- octahedron around Te(1) is
composed of four independent iodine atoms [I(11)-I(14)],
the octahedral coordination being completed by symmetry
(see Figure 2). The octahedron involving Te(2) analogously
contains independent iodine atoms I(21)-I(25), the octahe-
dron being completed by symmetry-equivalent atom I(21)b
(the symmetry operation b is -x + 1, -y + 1, z). The
[TeI6]2- octahedron involving Te(2) is disordered. The
symmetry operation -x + 1, -y + 1, z for the atoms I(22)-
I(25) creates another square-planar TeI4 fragment that is
rotated approximately 30° about the common I(21)-Te(2)-
C4H8TeI2 (5). It turned out that the small amounts of 5
that are formed in the reaction of TeI4 and PPh3 in THF can
be crystallized as two polymorphs, 5a and 5b, depending
(19) (a) Jones, P. G.; Sheldrick, G. M. Acta Crystallogr., Sect. B 1978, 34,
1353. (b) Antipin, M. Yu.; Kalinin, A. E.; Struchkov, Yu. T.; Matrosov,
E. J.; Kabachnik, M. I. Kristallografiya 1980, 25, 514. (c) Arens, G.;
Sundermeyer, W.; Pritzkow, H. Chem. Ber. 1986, 119, 3631. (d)
Carmalt, C. J.; Norman, N. C.; Farrugia, L. J. Polyhedron 1993, 12,
2081. (e) Lane, H. P.; Godfrey, S. M.; McAuliffe, C. A; Pritchard, R.
G. J. Chem. Soc., Dalton Trans. 1994, 3249. (f) De Aurajo, M. P.;
Queiroz, S. L.; Alzir, A.; Panepuzzi, E. H.; Oliva, G.; Castellano, E.
E. Transition Met. Chem. 2002, 27, 110.
(21) Srivastava, P. C.; Schmidt, H.-G.; Roesky, H. W. Z. Naturforsch. 1995,
50, 695.
(22) Katryniok, D.; Kniep, R.; Mootz, D. Z. Anorg. Allg. Chem. 1980, 461,
96.
(23) Jiang, D.-H.; Yang, Y.-H.; Gao, Z.-L.; Sun, S.-X.; Shen, J.-L. Acta
Chim. Sin. 1982, 50, 1091.
(20) (a) Baures, P. W.; Silverton, J. V. Acta Crystallogr., Sect. C 1990,
46, 715. (b) Baures, P. W. Acta Crystallogr., Sect. C 1991, 47, 2715.
(24) Auerswald, T. H.; Engelhardt, C.; Zentralinst, G. J. Prakt. Chem. 1979,
321, 835.
3746 Inorganic Chemistry, Vol. 43, No. 12, 2004

Reactions of Tellurium Tetrahalides with Triphenylphosphine
Figure 3. The molecular structures of C4H8TeI2 (5b) displaying the two
molecules in the asymmetric unit. The thermal ellipsoids have been drawn
at the 50% probability level.
Table 4. Selected Bond Lengths (Å) and Angles (deg) in (CH2)4TeI2
(5b)
Te(1)-I(11)
Te(1)-I(12)
Te(1)-C(11)
Te(1)-C(14)
2.866 (2)
3.003(2)
2.153(6)
2.163(6)
Te(2)-I(21)
Te(2)-I(22)
Te(2)-C(21)
Te(2)-C(24)
2.8442(9)
3.0140(9)
2.162(6)
2.160(6)
Figure 4. The packing of the molecules in (a) 5a and (b) 5b.
I(11)-Te(1)-I(12)
I(11)-Te(1)-C(11)
I(11)-Te(1)-C(14)
I(12)-Te(1)-C(11)
I(12)-Te(1)-C(14)
C(11)-Te(1)-C(14)
177.72(2)
89.0(2)
91.3(2)
90.0(2)
86.6(2)
84.7(2)
I(21)-Te(2)-I(22)
I(21)-Te(2)-C(21)
I(21)-Te(2)-C(24)
I(22)-Te(2)-C(21)
I(22)-Te(2)-C(24)
C(21)-Te(2)-C(24)
177.21(2)
90.6(2)
89.9(2)
86.8(2)
88.8(2)
84.9(2)
The C4H8TeI2 molecules in both 5a and 5b are linked
together by Te‚‚‚I and I‚‚‚I secondary bonding interactions.
The short Te‚‚‚I intermolecular contacts in 5a span a range
of 3.6483(8)-3.948(1) Å and those in 5b the range
3.626(2)-3.937(1) Å. These secondary bonds expand the
coordination polyhedra of tellurium in both cases to an
AX4Y2E (X ) primary bond, Y ) secondary bond, E )
lone pair) octahedron and are shown in Figure 4. The
differences in the packing of the C4H8TeI2 molecules in the
two lattices are also apparent in Figure 4. The short I‚‚‚I
contacts are 3.916(1) and 3.982(1) Å for 5a, and 3.821(2)
and 3.975(1) Å for 5b. The complete network of Te‚‚‚I and
I‚‚‚I intermolecular interactions in both 5a and 5b is also
shown in Figure 4.
There is a qualitative correlation between the lengths of
the Te-I bonds in R2TeI2 and the strength of the secondary
bonding interactions (see Supporting Information),28 though
the bond lengths are also affected by the organic group.
McCullough et al.28l have correlated the secondary bonds
with the color of the crystalline material. In absence of I‚‚‚I
close contacts the crystals appear orange. With increasing
influence of the I‚‚‚I interactions the color becomes deeper
red and tends toward purple and black. The slight change of
color from orange-red in 5a to deeper red in 5b is consistent
on the crystallizing conditions. Orange-red crystals of 5a
were obtained from hexane and diethyl ether, and those of
5b exhibiting deeper red color were obtained from toluene
and THF. It has been reported already in the 1930s that C4H8-
TeI2 (5) can exist as two different polymorphs,25 but the
crystal structure of only 5a has previously been known.26
The molecular structure of 5b together with the atomic
numbering scheme is shown in Figure 3, and the bond lengths
and angles are presented in Table 4. Like in 5a,16b,27 the
asymmetric unit in 5b also consists of two crystallographi-
cally independent C4H8TeI2 molecules. In both cases the
geometries of individual molecules are quite similar. The
coordination polyhedron of tellurium is based on a trigonal
bipyramid with two iodine atoms occupying the axial
positions and the two carbon atoms lying in two equatorial
positions. The tellurium lone pair occupies the third equato-
rial position. As a consequence, the I-Te-I fragment has
slightly deviated from linearity, the iodine atoms leaning
away from the lone pair [the I-Te-I bond angles in the
two independent molecules are 177.72(2)° and 177.21(2)°].
Similarly, the C-Te-C bond angles are rather small
[84.7(2)° and 84.9(2)°]. The Te-I bond lengths in 5b are in
the range 2.8442(9)-3.0140(9) Å, and the Te-C bond
lengths are in the range 2.153(6)-2.163(6) Å. The corre-
sponding values in 5a are 2.875(1)-2.942(1) Å and
2.155(7)-2.163(6) Å, respectively (see Supporting Informa-
tion). There are a number of related R2TeI2 species28 for
which the geometry of the tellurium environment is similar.
In all species the Te-I bonds are somewhat longer than the
single bond, as expected for the axial bonds in trigonal-
bipyramidal geometry.29
(28) (a) Chao, G. Y.; McCullough, J. D. Acta Crystallogr. 1962, 15, 887.
(b) Knobler, C.; McCullough, J. D.; Hope, H. Inorg. Chem 1970, 9,
797. (c) Chan, L. Y. Y.; Einstein, F. W. B. J. Chem. Soc., Dalton
Trans. 1972, 316. (d) Hope, H.; Knobler, C.; McCullough, J. D. Inorg.
Chem. 1973, 12, 2665. (e) McCullough, J. D. Inorg. Chem. 1973, 12,
2669. (f) McCullough; J. D. Inorg. Chem. 1975, 14, 1142. (g) Ziolo,
R. F.; Gunther, W. H. H. J. Organomet. Chem. 1978, 146, 245. (h)
Knobler, C.; Ziolo, R. F. J. Organomet. Chem. 1979, 178, 423. (i)
Pritzkow, H. Inorg. Chem. 1979, 18, 311. (j) Singh, H. B.; McWhinnie,
W. R.; Hamor, T. A. Jones, R. H. J. Chem. Soc., Dalton Trans. 1984,
23. (k) Alcock, N. W.; Harrison, W. D. J. Chem. Soc., Dalton Trans.
1984, 869. (l) McCullough, J. D.; Knobler, C.; Ziolo, R. F. Inorg.
Chem. 1985, 24, 1814. (m) Hu, N.-H.; Jin, Z.-S.; Li, Z.-S. Acta
Crystallogr., Sect. C. 1991, 47, 1858. (n) Al-Rubaie, A. Z.; Uemura,
S.; Masuda, H. J. Organomet. Chem. 1991, 410, 309. (o) Morkved,
E. H.; Faccin, G.; Manfrotto, D.; Kjosen, H.; Becker, J. Y.; Shapiro,
L.; Ellern, L.; Bernstein, J.; Khodorkovsky, V. J. Mater. Chem. 1997,
7, 1697. (p) Farran, J.; Alvarez-Larena, A.; Capparelli, M. V.; Piniella,
J. F.; Germain, G.; Torres-Castellanos, L. Acta Crystallogr., Sect. C
1998, 54, 995. (q) Schulz Lang, E.; Fernandes, R. M., Jr.; Silveira, E.
T.; Abram, U.; Vazquez-Lopez, E. M. Z. Anorg. Allg. Chem. 1999,
625, 1401. (r) Asahara, M.; Tanaka, M. Erabi, T. Wada, M. J. Chem.
Soc., Dalton Trans. 2000, 3493.
(25) Morgan, G. T.; Burstall, F. H. J. Chem. Soc. 1931, 180.
(26) Both previous crystal structure determinations of 5a have been carried
out at room temperature.16b,
Since the X-ray data of 5b were
27
collected at 150 K, we have also redetermined the crystal structure of
5a at low temperature in order to facilitate the direct comparison of
bond parameters between the two forms (see Supporting Information).
(27) Srivastava, P. C.; Bajpai, S.; Lath, R.; Butcher, R. J. J. Organomet.
Chem. 2000, 608, 96.
(29) The sum of the covalent radii of tellurium and iodine is 2.70 Å.30
(30) Emsley, J. The Elements, 3rd ed.; Clarendon Press: Oxford, 1998.
Inorganic Chemistry, Vol. 43, No. 12, 2004 3747

Na1rhi et al.
Table 5. Selected Bond Lengths (Å) and Angles (deg) in (CH2)4Te2I6 (6a and 6b)
6a
6b
6a
6b
Te(1)-I(11)
Te(1)-C(11)
Te(1)-C(14)
Te(1)-I(21)
Te(2)-I(21)
2.7338(8)
2.141(8)
2.152(9)
3.3270(9)
3.0270(8)
2.755(2)
2.171(14)
2.154(18)
3.261(2)
3.328(1)
Te(2)-I(22)
Te(2)-I(23)
Te(2)-I(24)
Te(2)-I(25)
Te(2)-I(25)a
2.7982(8)
2.7982(8)
2.8743(8)
3.1514(9)
3.1579(9)
2.767(1)
2.777(1)
2.783(1)
3.197(1)
3.249(1)
I(11)-Te(1)-C(11)
I(11)-Te(1)-C(14)
C(11)-Te(1)-C(14)
I(11)-Te(1)-I(21)
I(21)-Te(1)-C(11)
I(21)-Te(1)-C(14)
Te(1)-I(21)-Te(2)
I(21)-Te(2)-I(22)
I(21)-Te(2)-I(23)
I(21)-Te(2)-I(24)
I(21)-Te(2)-I(25)
96.8(2)
93.3(2)
83.7(4)
173.83(2)
88.3(2)
95.0(5)
93.2(5)
84.1(6)
169.65(5)
94.7(5)
I(21)-Te(2)-I(25)a
I(22)-Te(2)-I(23)
I(22)-Te(2)-I(24)
I(22)-Te(2)-I(25)
I(22)-Te(2)-I(25)a
I(23)-Te(2)-I(24)
I(23)-Te(2)-I(25)
I(23)-Te(2)-I(25)a
I(24)-Te(2)-I(25)
I(24)-Te(2)-I(25)a
I(25)-Te(2)-I(25)a
87.10(3)
95.35(2)
92.56(3)
86.55(2)
172.78(2)
91.36(2)
177.10(2)
91.86(2)
86.36(2)
87.62(3)
86.25(2)
92.67(3)
96.17(4)
92.78(4)
89.46(4)
177.74(4)
93.15(5)
174.09(4)
85.87(3)
84.76(5)
88.08(3)
88.53(3)
83.8(2)
84.1(5)
124.61(2)
92.86(4)
87.41(2)
174.53(2)
94.70(2)
95.22(4)
86.30(4)
91.78(5)
175.06(4)
90.37(4)
a Symmetry operations: 6a -x + 1, -y + 2, -z + 1; 6b -x + 1, -y + 1, -z + 2.
The Te(1)-I(11) bond of 2.7338(8) Å found in the {C4H8-
TeI}+ cation is shorter than the Te-I bonds in 5a or 5b and
is close to the single bond length,29 as expected for the
8-electron AX3E cation. The I-Te-C bond angles of
93.3(2)° and 96.8(2)° and the C-Te-C bond angle of
83.7(4)° are also consistent with the three-coordinate tellu-
ronium cation. The structural differences in 5 and the cation
in 6a can be compared to those observed in Cl2TeSeN2S31
and (ClTeTeN2S+)(Cl-).32 The axial Te-Cl bond lengths in
the former are 2.403(2) and 2.782(2) Å, and the coordination
environment of tellurium is a trigonal bipyramid [Cl-Te-
Cl ) 173.6(1)°].31 In the cationic species, the Te-Cl bond
length of 2.336(4) Å is shorter and the coordination is based
on the tetrahedron [the bond angles around tellurium span
88.7(4)-101.1(1)°].32
The Te(1)-I(21) distance of 3.3270(9) Å in 6a is very
long for covalent interaction. It is comparable to the I3Te+‚
6,7
‚‚(µ-I-) distances of 3.187-3.343 Å found in γ- and δ-TeI4
and somewhat shorter than the R3Te+‚‚‚I- distances, for
instance, in Me3TeI33 and Et3TeI.34
The cations and anions in 6a are further linked together
by weaker Te(1)‚‚‚I(21) and Te(1)‚‚‚I(24) contacts of
3.937(1) and 3.887(1) Å, respectively (see Figure 5). There
are also several I‚‚‚I contacts between the [Te2I10]2- anions
in the range 3.609(1)-3.900(1) Å.
The formal presentation of 6b is somewhat more complex.
The crystal structure is shown in Figure 6 together with the
numbering of the atoms. The bond parameters are presented
in Table 5. The interatomic distances in the Te2I10 fragment
differ considerably from the corresponding distances in 6a
and from those in {(C7H7)(C2H5)3N+}2[Te2I102-]5 and do not
imply the presence of a discrete [Te2I10]2- anion. Comparing
all bond parameters in 6b with those found in γ- and
δ-TeI4,6,7 the following inferences can be made.
Figure 5. The crystal structure of 6a. The compound can be formulated
as {C4H8TeI+}2[Te2I102-]. The thermal ellipsoids have been drawn at the
50% probability level.
with this scheme, since the I‚‚‚I contacts are shorter in 5b
than in 5a. These colors are consistent with the initial report
of Morgan and Burstall.25
C4H8Te2I6 (6). There are two distinct forms of C4H8Te2I6
(6a and 6b) that are formed depending on the crystallizing
conditions. Though both compounds can formally be con-
sidered as 1:1 adducts of TeI4 and C4H8TeI2, their structures
differ considerably from that of a simple straightforward
adduct. Though superficially similar, the structures of 6a and
6b also differ from each other.
The crystal structure of 6a is presented in Figure 5 together
with the atomic numbering scheme. The most important bond
lengths and angles are presented in Table 5. The compound
can be formulated as {C4H8TeI+}2[Te2I102-]. The bond
lengths and angles in the [Te2I10]2- anion are virtually
identical to those found in {(C7H7)(C2H5)3N+}2[Te2I102-].5
(31) Haas, A.; Kasparowski, J.; Pryka, M. Chem. Ber. 1992, 125, 789.
(32) (a) Haas, A.; Kasparowski, J.; Pryka, M. J. Chem. Soc., Chem.
Commun. 1992, 1144. (b) Haas, A.; Pryka, M.; Scha¨fers, M. Chem.
Ber. 1994, 127, 1865.
(33) (a) Collins, M. J.; Ripmeester, J. A.; Sawyer, J. F. J. Am. Chem. Soc.
1988, 110, 8583. (b) Zhou, Z.-L.; Huang, Y.-Z.; Tang, Y.; Chen, Z.-
H.; Shi, L.-P-; Jin, X.-L.; Yang, Q.-C. Organometallics 1994, 13, 1575.
(34) Chadha, R. K.; Drake, J. E. J. Organomet. Chem. 1986, 299, 331.
3748 Inorganic Chemistry, Vol. 43, No. 12, 2004

Reactions of Tellurium Tetrahalides with Triphenylphosphine
in 6b two (TeI3)+ cations can be found in the locations where
γ- and δ-TeI4 contain two TeI4 molecules. This inference is
based on the differences in the corresponding interatomic
distances and angles. The three Te-I bonds in question
[Te(2)-I(22), Te(2)-I(23), and Te(2)-I(24)] span virtually
equal single bond29 lengths of 2.767(1)-2.783(1) Å and are
close to those of 2.753-2.789 Å and 2.738-2.773 Å reported
for the two (TeI3)+ fragments in γ- and δ-TeI4, respectively.6,7
It should be noted that the axial Te(2)-I(24) in γ- and
δ-TeI46,7 is significantly longer than that in 6b. Conversely,
the Te(2)-I(21) distance that represents the other axial bond
of the TeI4 molecule, and is therefore of comparable length
to the Te(2)-I(24) bond in γ- and δ-TeI4,6,7 is significantly
longer in 6b [3.261(2) Å] and can be inferred as the cation-
anion distance.
The two types of the cations in 6b are linked together by
two bridging µ2-I- anions and two µ3-I- anions that
together build up the framework of the structure type II. It
can be seen from Table 6 that the Te(2)-I(25) bonds in 6b
and in γ- and δ-TeI4 are of comparable length, in the range
3.197(1)-3.257 Å. Whereas the long Te(1)-I(25) distance
of 3.676(2) Å represents a secondary bonding interaction in
6b, the corresponding interatomic separation is shorter in
γ- and δ-TeI4 (3.187-3.214 Å).6,7 They represent typical
cation-anion distances.
Figure 6. (a) The crystal structure of 6b. The compound can be formulated
as {C4H8TeI+}2(TeI3+)2(I-)4. The thermal ellipsoids have been drawn at
the 50% probability level. (b) The crystal structure of δ-TeI4 (adapted from
the data taken from ref 7).
Table 6. The Comparison of Te-I Distances in (CH2)4Te2I6 (6b) and
a
in γ- and δ-TeI4
b
c
6b
3.261(2)
3.900(2)
3.676(2)
3.328(1)
2.767(1)
2.777(1)
2.783(1)
γ-TeI4
δ-TeI4
3.231
3.279
Te(1)-I(21)
Te(1)-I(24)
Te(1)-I(25)
Te(2)-I(21)
Te(2)-I(22)
Te(2)-I(23)
Te(2)-I(24)
Te(2)-I(25)
3.252, 3.337
3.265, 3.343
3.187, 3.207
2.921, 3.035
2.743, 2.751
2.753, 2.785
2.897, 3.002
3.228-3.257
3.200, 3.214
2.933
We note that the two polymorphs of Me2TeI2 also show
significantly differing structures. R-Me2TeI2 is composed of
discrete molecules,35 while â-Me2TeI2 is ionic and contains
(Me3Te)+ cations and [MeTeI4]- anions.36
2.766
2.770
2.989
3.197(1), 3.249(1)
3.241, 3.247
a The tellurium and iodine atoms in γ- and δ-TeI4 have been renumbered
to correspond to the numbering of 6b (see Figure 5). b Reference 6.
c Reference 7.
Reaction Pathways. The reactions between tellurium
tetrahalides and triphenylphosphine in tetrahydrofuran in air
are very versatile. Early reports under an inert atmosphere
have suggested that, in the case of TeCl4 and Ph3P, Ph3PCl2
and Te(0)8 or Ph3PO, TeCl2, and Te(0)9 are formed. In the
latter case, the formation of Ph3PO was explained by the
hydrolysis of Ph3PCl2. We have observed that under ambient
conditions the reactions of TeCl4 or TeBr4 and Ph3P afford
{(Ph3PO)2H}2[Te2X10] [X ) Cl (1), Br (2)] in good yields.
The main product in the reaction involving TeI4 is
{(Ph3PO)3(OH3)}2[TeI6] (4).37
It can be seen from Figure 6 that the structural framework
of 6b is very similar to that of the tetramers in γ- and δ-TeI4
implying the structure type II. Krebs and Ahlers1 have
6,7
formulated the (TeI4)4 tetramer as (TeI3 )2(I-)2(TeI4)2 based
+
on the interatomic distances. Using the same arguments, 6b
+
can be considered as {C4H8TeI+}2(TeI3 )2(I-)4 (the ionic and
molecular fragments of 6b and the TeI4 tetramer are indicated
in Figure 6). The relevant framework Te-I distances in 6b
and in the two polymorphs of TeI4 are compared in Table 6.
It can be seen from Figure 6 that whereas the TeI4 exhibits
a (TeI3)+ cation both at the top and bottom of the molecule,
6b contains two {C4H8TeI}+ cations in the corresponding
locations. The Te(1)-I(11) bond length of 2.755(2) Å in the
cation is again close to that of the single bond,29 and the
I-Te-C bond angles of 93.2(5)° and 95.0(5)°, as well as
the C-Te-C angle of 84.1(6)° (see Table 5), indicate a
pyramidal telluronium ion.
In both γ- and δ-TeI4 the two (TeI3)+ cations show close
contacts of 3.231-3.279 Å to two TeI4 molecules.6,7 These
interatomic distances are in good agreement with the cation-
anion contacts in 6a. The two TeI4 fragments in γ- and δ-TeI4
show the expected trigonal-bipyramidal geometry, with the
axial Te(2)-I(21) and Te(2)-I(24) bonds [2.921-3.035 Å]
longer than the equatorial Te(2)-I(22) and Te(2)-I(23)
bonds [2.743-2.785 Å]. It can be seen from Figure 6 that
The cations in 1, 2, and 4 that consist of Ph3PO molecules
linked into dimeric or trimeric units by bridging H+ or H3O+
cations, respectively, are probably produced by hydrolysis
of Ph3PX2 due to atmospheric moisture, as suggested by
Arens et al.19c and Lane et al.19e The formation of various
(35) Chan, L. Y. Y.; Einstein, F. W. B. J. Chem. Soc., Dalton Trans. 1972,
316.
(36) Einstein, F.; Trotter, J.; Williston, C. S. J. Chem. Soc. A 1967, 2018.
(37) For comparison, we also tested the reaction of TeCl4 and PPh3 in an
argon atmosphere. After the dark precipitate was filtered off, two
resonances could be observed in the 31P NMR spectrum of the
remaining solution. The resonance at 66.5 ppm is probably due to
Ph3PCl2.38 The second resonance falls within the range assigned to 1
and indicates that even traces of adventitious water play a role in the
reaction.
(38) (a) Wiley, G. A.; Stine, W. R. Tetrahedron Lett. 1967, 2321. (b) Dillon,
K. B.; Lynch, R. J.; Reeve, Waddington, T. C. J. Chem. Soc., Dalton
Trans. 1976, 1243. (c) Godfrey, S. M.; McAuliffe, C. A.; Pritchard,
R. G.; Sheffield, M. Chem. Commun. 1996, 2521. (d) Godfrey, S.
M.; McAuliffe, C. A.; Pritchard, R. G.; Sheffield, M.; Thompson, G.
M. J. Chem. Soc., Dalton Trans. 1997, 4823.
Inorganic Chemistry, Vol. 43, No. 12, 2004 3749

Na1rhi et al.
anions from tellurium tetrahalides and the structural relation-
ships between them have been explained by Krebs and
Paulat,17f and are depicted in Scheme 1. It is not quite clear
what factors determine the product distribution and isolation
of the actual anions. The 125Te NMR spectra of different
reaction solutions only indicate the presence of one type of
anion in each case. This has also been recently observed for
the reaction of Te and SO2Cl2.13 Different chlorotellurate
anions are produced depending on the solvent, but only one
type of anion is observed in every case.
We have recently observed that in the case of TeBr4 the
reaction with PPh3 in THF results also in the opening of the
tetrahydrofuran ring with the formation of Ph3PO(CH2)4TeBr4
(3) that is formally zwitterionic.10 The ring opening is
probably initiated by the attack of PPh3 at the THF oxygen
in the same fashion as the reaction of PPh3 with elemental
sulfur.39 The open-chain intermediate reacts with TeBr4 to
afford 3.10
PCl2,8 or Te(0), TeCl2, and Ph3PO.9 In this contribution we
have shown that under ambient conditions the reactions
afford {(Ph3PO)2H}2[Te2X10] [X ) Cl (1), Br (2)] and
{(Ph3PO)3OH3}2[TeI6] (4). Compounds 1 and 2 are isos-
tructural and contain discrete [Te2X10]2- anions and dimeric
{Ph3POH‚‚‚OPPh3}+ cations. Compound 4 contains octa-
hedral hexaiodotellurate anions and trimeric {(Ph3PO)3-
(OH3)}+ cations.
In addition to the products mentioned above, TeBr4 and
PPh3 afford zwitterionic Ph3PO(CH2)4TeBr4 (3). This reaction
involves an unprecedented THF ring opening in which the
oxygen atom is bonded to phosphorus and the carbon atom
is bonded to tellurium. A THF ring opening is probably also
effected in the formation of the side product (CH2)4TeI2 (5)
during reaction of TeI4 and PPh3. This product can be
crystallized as two different polymorphs 5a and 5b that differ
only in the packing of the molecules. 5 can be explained to
be formed from elemental tellurium and ICH2(CH2)2CH2I.
Tellurium is produced in the initial reaction of TeI4 and PPh3.
The latter product is obtained as a consequence of the attack
of Ph3PI2 at the THF molecule resulting also in the formation
of Ph3PO. Most Ph3PO, however, is probably produced by
the influence of atmospheric moisture.
The reaction of TeI4 and PPh3 leads upon crystallization
to the formation of two different forms of (CH2)4Te2I6 (6a
and 6b) that can both formally be considered as 1:1 adducts
of TeI4 and (CH2)4TeI2. They are superficially similar, but
their structures differ from each other. 6a can be formulated
Anderson and Freenor40 have established that Ph3PBr2 also
effects a THF ring opening and produces Ph3PO and
BrCH2(CH2)2CH2Br in good yield. It is reasonable to assume
that TeI4 reacts with PPh3 and affords elemental tellurium
and Ph3PI2 in an analogous manner to TeCl4.8,9 Ph3PI2 then
reacts with THF and produces Ph3PO and ICH2(CH2)2CH2I.
The reaction between the elemental tellurium and ICH2(CH2)2-
CH2I leads to the formation of (CH2)4TeI2 (5), as reported
by Morgan and Burstall.25
+
as {(CH2)4TeI+}2[Te2I102-] and 6b as {(CH2)4TeI+}2(TeI3 )2-
(I-)4. Though the interatomic distances vary, the structural
framework of 6b is very similar to that of the tetramers in
γ- and δ-TeI4.
The formation of 6a and 6b can most conveniently be
viewed as a simple interaction between (CH2)4TeI2 (5) and
TeI4. It is possible that the structural and bonding differences
between the two forms originate only upon crystallization
of the two species.
Acknowledgment. Financial support from the Academy
of Finland and the Ministry of Education in Finland
(Graduate School of Inorganic Materials Chemistry) is
gratefully acknowledged.
Supporting Information Available: Seven X-ray crystal-
lographic files in CIF format, two tables containing crystal data
and selected bond lengths and angles of 5a, and a figure illustrating
the effect of intermolecular I‚‚‚I and I‚‚‚Te interactions on the
corresponding Te-I bond lengths in R2TeI2. This material is
available free of charge via the Internet at http://pubs.acs.org.
Conclusions
The reaction of tellurium tetrachloride and triphenylphos-
phine has been reported to form elemental tellurium and Ph3-
(39) Bartlett, P. D.; Meguerian, G. J. Am. Chem. Soc. 1956, 78, 3710.
(40) Anderson, A. G.; Freenor, F. J. J. Org. Chem. 1972, 37, 626.
IC049789V
3750 Inorganic Chemistry, Vol. 43, No. 12, 2004