Heavy atom analogues of 1,2,3-dithiazolylium salts: Preparation, structures and redox chemistry

Article abstract of DOI:10.1021/ic8013738

Synthetic routes to salts of the benzo[1,2,3]thiatellurazolylium cation [2c]⁺ and its selenium analogue [2b]⁺ are described. Access to the cation frameworks involves the intermediacy of N,N,S-trisilylated 2-aminobenzenethiol. The latter reacts smoothly with selenium and tellurium halides ECl₄ (E = Se, Te) to afford the desired heterocyclic benzo cations [2b]⁺ and [2c]⁺ as their chloride salts. Anion exchange provides the corresponding GaCl₄^-, OTf ^- and TeCl₅^- salts of [2c]⁺, all of which have been characterized by X-ray crystallography. While the gallate salts of the sulfur and selenium cations [2a]⁺ and [2b]⁺ crystallize as ion-paired cations and anions, salts of [2c]⁺ adopt solid-state structures that display strong association of the cations via short intermolecular Te-N′ bonds. However, crystallization of [2c]⁺ salts in dichloroethane in the presence of GaCl₃ leads to cleavage of the dimers and the formation of a Lewis acid adduct at nitrogen. Reduction of the benzo cations [2a,b]⁺ affords the respective radicals 2a,b, both of which have been characterized by electron paramagnetic resonance (EPR) spectroscopy. Attempts to generate the corresponding radical 2c have been unsuccessful, although a material of nominally correct elemental composition can be generated by chemical reduction. The energetics of association of [2a,b,c]⁺ in solution has been probed by means of density functional theory calculations using the polarized continuum model. The results suggest that the dimeric nature of the Te-centered cation is retained in solution. The strength of the interaction is, however, less than in N-alkylated tellurodiazolylium salts.

Full text of DOI:10.1021/ic8013738

Inorg. Chem. 2008, 47, 10100-10109
Heavy Atom Analogues of 1,2,3-Dithiazolylium Salts: Preparation,
Structures and Redox Chemistry
Maarit Risto,†,‡ Abdeljalil Assoud,† Stephen M. Winter,† Raija Oilunkaniemi,‡ Risto S. Laitinen,‡
and Richard T. Oakley*,†
Department of Chemistry, UniVersity of Waterloo, Waterloo, Ontario N2L 3G1 Canada, and
Department of Chemistry, UniVersity of Oulu, P.O. Box 3000, FI-90014 Finland
Received July 22, 2008
Synthetic routes to salts of the benzo[1,2,3]thiatellurazolylium cation [2c]+ and its selenium analogue [2b]+ are
described. Access to the cation frameworks involves the intermediacy of N,N,S-trisilylated 2-aminobenzenethiol.
The latter reacts smoothly with selenium and tellurium halides ECl4 (E ) Se, Te) to afford the desired heterocyclic
benzo cations [2b]+ and [2c]+ as their chloride salts. Anion exchange provides the corresponding GaCl4-, OTf-
and TeCl5- salts of [2c]+, all of which have been characterized by X-ray crystallography. While the gallate salts
of the sulfur and selenium cations [2a]+ and [2b]+ crystallize as ion-paired cations and anions, salts of [2c]+ adopt
solid-state structures that display strong association of the cations via short intermolecular Te-N′ bonds. However,
crystallization of [2c]+ salts in dichloroethane in the presence of GaCl3 leads to cleavage of the dimers and the
formation of a Lewis acid adduct at nitrogen. Reduction of the benzo cations [2a,b]+ affords the respective radicals
2a,b, both of which have been characterized by electron paramagnetic resonance (EPR) spectroscopy. Attempts
to generate the corresponding radical 2c have been unsuccessful, although a material of nominally correct elemental
composition can be generated by chemical reduction. The energetics of association of [2a,b,c]+ in solution has
been probed by means of density functional theory calculations using the polarized continuum model. The results
suggest that the dimeric nature of the Te-centered cation is retained in solution. The strength of the interaction is,
however, less than in N-alkylated tellurodiazolylium salts.
Introduction
as to whether the incorporation of tellurium into chalcazyl
radicals will further enhance transport properties. However,
while there is extensive literature on the chemistry and
structures of unsaturated organic5,6 and inorganic7 hetero-
cycles containing tellurium-nitrogen linkages, there are no
reports of the isolation or even observation of a neutral
radical akin to those seen for heterocycles containing SN
and SeN linkages.
There is increasing interest in the use of heavy atom
heterocyclic radicals as building blocks for the design of
molecular materials exhibiting conductive and magnetic
properties.1 Within this context we have recently demon-
strated that replacement of sulfur in resonance stabilized bis-
dithiazolyls by its heavier congener selenium can lead not
only to enhanced conductivity2 but also to dramatic magnetic
effects, including spin-canted antiferromagnetism3 and even
bulk ferromagnetism.4 These findings prompt the question
(3) Leitch, A. A.; Brusso, J. L.; Cvrkalj, K.; Reed, R. W.; Robertson,
C. M.; Dube, P. A.; Oakley, R. T. Chem. Commun. 2007, 3368.
(4) (a) Robertson, C. M.; Myles, D. J. T.; Leitch, A. A.; Reed, R. W.;
Dooley, B. M.; Frank, N. L.; Dube, P. A.; Thompson, L. K.; Oakley,
R. T. J. Am. Chem. Soc. 2007, 129, 12688. (b) Robertson, C. M.;
Leitch, A. A.; Cvrkalj, K.; Reed, R. W.; Myles, D. J. T.; Dube, P. A.;
Oakley, R. T. J. Am. Chem. Soc. 2008, 130, 8414.
* To whom correspondence should be addressed. E-mail: oakley@
uwaterloo.ca.
†
University of Waterloo.
University of Oulu.
‡
(1) (a) Rawson, J. M.; Alberola, A.; Whalley, A. J. Mater. Chem. 2006,
16, 2560. (b) Hicks, R. G. Org. Biomol. Chem. 2007, 5, 1321. (c)
Preuss, K. E. Dalton Trans. 2007, 2357. (d) Cordes, A. W.; Haddon,
R. C.; Oakley, R. T. Phosphorus, Sulfur, Silicon Relat. Elem. 2004,
179, 673.
(2) Brusso, J. L.; Cvrkalj, K.; Leitch, A. A.; Oakley, R. T.; Reed, R. W.;
Robertson, C. M. J. Am. Chem. Soc. 2006, 128, 15080.
(5) (a) Reeske, G.; Cowley, A. H. Chem. Commun. 2006, 4856. (b)
Srivastava, S.; Singh, D. Asian J. Chem. 1999, 11, 1559. (c) Lau, C.;
Neumu¨ller, B.; Krautscheid, H.; Dehnicke, K. Z. Anorg. Allg. Chem.
1997, 623, 1375. (d) Konu, J.; Chivers, T.; Schatte, G.; Parvez, M.;
Laitinen, R. S. Inorg. Chem. 2005, 44, 2973. (e) Chivers, T.; Enright,
G. D.; Sandblom, N.; Schatte, G.; Parvez, M. Inorg. Chem. 1999, 38,
5431.
10100 Inorganic Chemistry, Vol. 47, No. 21, 2008
10.1021/ic8013738 CCC: $40.75  2008 American Chemical Society
Published on Web 10/08/2008

HeaWy Atom Analogues of 1,2,3-Dithiazolylium Salts
Chart 1
tion and structural characterization of the three cations
[2a,b,c]+. In the case of [2c]+, the structures of several salts
are described. While dimerization of [2c]+ is observed in
all cases, the length of the interdimer Te-N′ interactions
suggests that the strength of the association is less than that
found in [1c]+. The effect has been modeled by means of
density functional theory (DFT) methods. The sulfur and
selenium cations [2a,b]+ undergo one-electron reduction to
the corresponding radicals 2a,b, which have been character-
ized by EPR spectroscopy. Attempts to generate the neutral
radical 2c are also described.
Results and Discussion
In order to explore the potential of tellurazyl radicals, we
are pursuing the synthesis and characterization of new
families of cationic heterocycles which might, upon reduc-
tion, afford radical species. To this end, we recently carried
out a comparative study of the structures and redox chemistry
of the family of N-methylated benzochalcodiazolylium
cations [1a,b,c]+ (Chart 1).8 While the triflate salt [1a][OTf]
(OTf- ) triflate) crystallized as discrete [1a]+ cations and
OTf- anions, the corresponding triflates of [1b]+ and [1c]+
consisted of centrosymmetric dimers [1b]22+ and [1c]22+. The
closeness of the intermolecular E-N′ contacts suggested
strong association, especially for E ) Te. The sulfur and
selenium cations [1a,b]+ could be reduced, both chemically
and electrochemically, to the corresponding radicals 1a,b,
which were characterized by electron paramagnetic resonance
(EPR) spectroscopy. However, the electrochemical behavior
of the tellurium cation [1c]+ was very different, both in terms
of half-wave potentials and reversibility, and no EPR signal
corresponding to 1c could be generated. Collectively, the
results led us to suggest that the association of [1c]+ observed
in the solid state was maintained in acetonitrile solution, in
Synthesis. Aromatic 1,2,3-dithiazolylium salts are easily
prepared by the Herz reaction, that is, the cyclization of an
aromatic amine with sulfur monochloride.11 This reaction
is, however, often accompanied by chlorination of the
aromatic ring.12
The latter complication can be avoided in the condensation
of an o-aminothiol with thionyl chloride.13 Thus, the reaction
of benzene-aminothiol 3 with thionyl chloride affords
[2a][Cl] in high yield (Scheme 1). This crude chloride salt
can be converted into the more soluble gallate [2a][GaCl4]
by treatment with gallium trichloride. The same approach
cannot be applied to the preparation of salts of the selenium
cation [2b]+, as complete elimination of 3 equiv of HCl
cannot be effected. The condensation route can, however,
be achieved if the amine and/or thiol groups are first
acetylated.14 Alternatively salts of [2b]+ can be generated
in a single step by heating salts of [2a]+ with SeO2 in acetic
acid.10a Unfortunately, the latter route cannot be adapted for
the preparation of [2c]+, as TeO2 does not react with
dithiazolylium salts.
In order to generate the Te-containing ring [2c]+ we sought
a soft organometallic condensation reagent that would react
cleanly with TeCl4 and circumvent the HCl elimination
problem noted above. To this end we prepared the N,S-
disilylated derivative 4 by treatment of 3 with hexamethyl-
disilazane (HMDS) at reflux. Deprotonation of 4 and
treatment of the intermediate amide with chlorotrimethylsi-
lane afforded the N,N,S-trisilylated compound 5, which
2+
which case one-electron reduction of [1c]2 would afford
+
not the neutral radical 1c but a dimer radical cation [1c]2 .
In order to explore the generality of these findings, in
particular the degree of association of heterocyclic tellurium-
nitrogen cations in both the solid state and in solution, we
have turned our attention to the family of benzochalcazoly-
lium cations [2a,b,c]+ and the corresponding radicals 2a,b,c.
While the all-sulfur cation [2a]+ and radical9 have been
known for many years, the selenium centered cation [2b]+
has received only passing attention,10 and radical 2b has
never been observed. Most importantly there is no mention
in the literature of the tellurium based cation [2c]+, let alone
the corresponding radical 2c. Herein we report the prepara-
(9) (a) Mayer, R.; Domschke, G.; Bleisch, S.; Bartl, A. Tetrahedron Lett.
1978, 4003. (b) Mayer, R.; Domschke, G.; Bleisch, S.; Bartl, A.;
Sta˜sko, A. Z. Chem. 1981, 21, 146; Z. Chem. 1981, 21, 264. (c) Mayer,
R.; Domschke, G.; Bleisch, S.; Fabian, J.; Bartl, A.; Sta˜sko, A. Collect.
Czech. Chem. Commun. 1984, 49, 684. (d) Mayer, R.; Bleisch, S.;
Domschke, G.; Tka´e`, A.; Sta˜sko, A.; Bartl, A. Org. Magn. Reson.
1979, 12, 532. (e) Tsveniashvili, V. Sh. Collect. Czech. Chem.
Commun. 1982, 47, 203. (f) Harrison, S. R.; Pilkington, R. S.; Sutcliffe,
L. H. J. Chem. Soc., Faraday Trans. 1 1984, 80, 669. (g) Preston,
K. F.; Sutcliffe, L. H. Magn. Reson. Chem. 1990, 28, 189. (h)
Bagryansky, V. A.; Vlasyuk, I. V.; Gatilov, Y. V.; Makarov, A. Y.;
Molin, Y. N.; Shcherbukhin, V. V.; Zibarev, A. V. MendeleeV
Commun. 2000, 10, 5.
(10) (a) Akulin, Y. I.; Gel’mont, M. M.; Strelets, B. Kh.; Efros, L. S. Khim.
Geterotsikl. Soedin. 1978, 912. (b) Efros, L. S.; Strelets, B. Kh.; Akulin,
Y. I. Khim. Geterotsikl. Soedin. 1976, 1361.
(11) Warburton, W. K. Chem. ReV. 1957, 57, 1011.
(12) Koutentis, P. A.; Rees, C. W. J. Chem. Soc., Perkin Trans. 1 1999,
111.
(6) (a) Cozzolino, A. F.; Vargas-Baca, I. J. Organomet. Chem. 2007, 692,
2654. (b) Cozzolino, A. F.; Britten, J. F.; Vargas-Baca, I. Cryst. Growth
Des. 2006, 6, 181. (c) Neidlein, R.; Knecht, D.; Gieren, A.; Ruiz-
Pe´rez, C. Z. Naturforsch. 1987, 42B, 84. (d) Gieren, A.; Betz, H.;
Hubner, T.; Lamm, V.; Neidlein, R.; Droste, D. Z. Naturforsch. 1984,
39B, 485. (e) Kovtonyuk, V. N.; Makarov, A. Yu.; Shakirov, M. M.;
Zibarev, A. V. Chem. Commun. 1996, 16, 1991. (f) Chivers, T.; Gao,
X.; Parvez, M. Inorg. Chem. 1996, 35, 9.
(7) (a) Haas, A. J. Organomet. Chem. 2002, 646, 80. (b) Haas, A.;
Hoppmann, E.; Merz, K. J. Fluorine Chem. 2001, 112, 197. (c)
Dworak, J.; Haas, A.; Hoppmann, E.; Olteanu, A.; Merz, K.; Schaefers,
M. Z. Anorg. Allg. Chem. 2001, 627, 2639. (d) Haas, A.; Pryka, M.;
Schaefers, M. Chem. Ber. 1994, 127, 1865.
(13) Huestis, L. D.; Walsh, M. L.; Hahn, N. J. Org. Chem. 1965, 30, 2763.
(14) Oakley, R. T.; Reed, R. W.; Robertson, C. M.; Richardson, J. F. Inorg.
Chem. 2005, 44, 1837.
(8) Risto, M.; Reed, R. W.; Robertson, C. M.; Oilunkaniemi, R.; Laitinen,
R. S.; Oakley, R. T. Chem. Commun. 2008, 3278.
Inorganic Chemistry, Vol. 47, No. 21, 2008 10101

Risto et al.
Scheme 1
of association of the tellurium based cation, we also
characterized the two salts [2c][OTf] and [2c][TeCl5] and
the Lewis acid adduct salt [2c][GaCl3][GaCl4]. Crystal-
lographic data are compiled in Table 1 and a summary of
pertinent intra- and intermolecular distances is provided in
Table 2. Representative views of the cation-anion pairs for
all six structures are presented in Figures 1-4.
Yellow crystals of the parent benzodithiazolylium salt
[2a][GaCl4] belong to the orthorhombic space group P212121,
with four cations and four anions per unit cell. As in other
simple 1,2,3-dithiazolylium salts,16 the cations are well
separated, and there is only one short cation-anion con-
tact, that is, S1-Cl4′ (3.4077(13) Å) shown in Figure 1.
Orange plates of the corresponding selenium salt [2b][GaCl4]
are not isomorphous; instead they belong to the monoclinic
space group P21/n. However, as in the case of [2a][GaCl4],
the cations in [2b][GaCl4] remain well separated, although
-
they are linked to a GaCl4 anion by a number of short
contacts, including Se1-Cl2′ (3.2155(10) Å) and S1-Cl2′
(3.3861(14) Å) shown in Figure 1. The absence of cation
association is notable, as in N-alkylated selenodiazolium salts
such as [6][GaCl4]17 and [1b][OTf]8 close centrosymmetric
cation pairing is observed (Chart 2).18 Also, while cation
association is absent for the benzo-cation [2b]+, addition of
another aromatic ring, as in the naphthothiaselenazolylium
salt [7][GaCl4],14 leads to association of the cations, although
the Se-N′ contacts (2.874(4) Å) are lengthened. The
energetics of these processes are explored below.
reacted very cleanly with SeCl4 in refluxing MeCN, and with
TeCl4 in refluxing dichloroethane (DCE), to produce the
corresponding selenazolylium chloride [2b][Cl] and tellu-
razolylium chloride [2c][Cl]. As above, treatment of the crude
chloride salts with GaCl3 in MeCN afforded the gallates
[2b,c][GaCl4], which could be crystallized from chloroben-
zene or DCE. A triflate salt [2c][OTf] was also prepared by
metathesis of the chloride salt [2c][Cl] with silver triflate.
In addition to [2c][GaCl4] and [2c][OTf], two other salts of
the tellurium cation were isolated. During early attempts to
perform the reaction of 5 with TeCl4 in MeCN at room
temperature, a crystalline material was isolated that displayed
a slightly different IR spectrum from that of [2c][Cl]. When
treated with GaCl3 in MeCN this material dissolved to afford
a deep red solution, evaporation of which afforded crystals
of the pentachlorotellurate salt [2c][TeCl5]. In a second and
somewhat surprising variation, when [2c][Cl] was treated
with gallium trichloride in a noncoordinating solvent (DCE
or liquid SO2), evaporation of the solvent afforded extremely
moisture-sensitive red plates of the N-coordinated Lewis acid
adduct [2c][GaCl3][GaCl4] (δ 125Te (DCE) ) 1337 ppm).
When redissolved in donor solvents, this complex appears
to dissociate. A solution of [2c][GaCl3][GaCl4] in MeCN,
for example, affords a 125Te NMR signal with a chemical
shift of 1429 ppm, which is virtually identical with that of
pure [2c][GaCl4] (δ 125Te ) 1427 ppm).15
The crystal structures of the tellurium centered salts
[2c][X] (X- ) GaCl4 , OTf-, TeCl5 ) all show the same
basic structural features (Figures 2 and 3), that is, centrosym-
metric pairing of cations [2c]+ to form almost coplanar19
-
-
2+
dimer dications [2c]2 bridged by short intermolecular
Te-N′ contacts of 2.5324(17) Å (X- ) GaCl4 ), 2.538(2)
-
Å (X- ) TeCl5 ) to 2.553(4) Å (X- ) OTf-). These are
-
remarkably short, well within the normal van der Waals
separation,20 although slightly longer than those seen in the
dimer [1c]2[OTf]2 (2.417(3) Å),8 and significantly longer than
in [(Cl2Te)2N]2[AsF6]2, where the intra- and intermolecular
Te-N bonds (1.98(4) Å and 2.04(4) Å respectively) are
almost equivalent.21 In addition, all the structures possess
short cation-anion pairing contacts spanning the Te-S unit
-
-
of the cation and a Cl atom (in GaCl4 and TeCl5 ) or an
oxygen atom (in OTf-). Collectively, the intramolecular
bonds and intermolecular contacts to tellurium afford what
can be described, in VSEPR parlance, as a pseudo square-
(16) Beer, L.; Cordes, A. W.; Haddon, R. C.; Itkis, M. E.; Oakley, R. T.;
Reed, R. W.; Robertson, C. M. Chem. Commun. 2002, 1872.
(17) Dutton, J. L.; Tindale, J. J.; Jennings, M. C.; Ragogna, P. J. Chem.
Commun. 2006, 2474.
(18) In the presence of the doubly charged anion SeCl62-, dimerization of
the cation [6]+ is suppressed, and replaced by strong cation/anion
pairing interactions. See Dutton, J. L.; Sutrisno, A.; Schurko, R. W.;
Ragogna, P. J Dalton Trans. 2008, 3470.
Crystal Structures. In order to establish the solid-state
structural preferences for the family of cations [2a,b,c]+,
we determined the crystal structures of their tetrachlorogallate
salts [2a,b,c][GaCl4]. In addition, and in order to explore
the possible effects of different counterions on the degree
(19) In [2c][GaCl4], [2c][OTf] and [2c][TeCl5] the two rings of the dimer
dication straddle an inversion centre, so they must be parallel. The
very slight departure from rigorous coplanarity of the two halves, most
notable in the TeCl5- derivative, is simply a result of crystal packing
forces.
(20) Bondi, A. J. Phys. Chem. 1964, 68, 441.
(21) Passmore, J.; Schatte, G.; Cameron, T. S. J. Chem. Soc., Chem.
Commun. 1995, 2311.
(15) Attempts to observe a possible dimer-monomer equilibrium, that is,
between [2c]+ and [2c]22+, by 125Te NMR (in MeCN and DCE) have
shown no evidence of a second species. Only one signal, which we
ascribe to the dimer, is observed.
10102 Inorganic Chemistry, Vol. 47, No. 21, 2008

HeaWy Atom Analogues of 1,2,3-Dithiazolylium Salts
Table 1. Crystal Data
compound
[2a][GaCl4]
[2b][GaCl4]
[2c][GaCl4]
[2c][OTf]
[2c][TeCl5]
[2c][GaCl3][GaCl4]
formula
M
C6H4Cl4GaNS2
365.74
C6H4Cl4GaNSSe
412.64
C6H4Cl4GaNSTe
461.29
C7H4F3NO3S2Te
398.85
C6H4Cl5NSTe2
554.61
C6H4Cl7Ga2NSTe
637.35
a (Å)
b (Å)
c (Å)
8.6904(4)
9.6874(5)
14.6214(7)
7.4587(3)
10.2322(4)
17.0845(7)
7.7297(9)
9.7183(5)
9.8185(5)
116.0530(10)
99.3900(10)
95.5220(10)
641.90(9)
2.387
12.0892(5)
12.0493(5)
7.9429(3)
8.2184(5)
8.2820(5)
11.0240(7)
82.7070(11)
72.9321(12)
74.4782(12)
690.18(7)
2.669
9.7208(3)
18.2525(5)
9.9986(3)
R (°)
ꢀ (°)
94.4450(10)
90.7930(10)
99.0130(10)
γ (°)
V (Å3)
Fcalcd (g cm-1
space group
Z
1230.94(10)
1.974
P212121
1299.95(9)
2.108
P21/n
1156.90(8)
2.290
P21/c
1752.14(9)
2.416
P21/n
)
j
j
P1
2
P1
2
4
4
4
4
temp (K)
296(2)
3.401
0.71073
3597/0/129
direct methods
0.0270, 0.0600
296(2)
5.860
0.71073
3755/0/128
direct methods
0.0401, 0.0653
290(2)
5.326
0.71073
3849/0/128
direct methods
0.0201, 0.0473
290(2)
2.966
0.71073
3287/0/154
direct methods
0.0284, 0.0738
296(2)
5.313
0.71073
4067/0/136
direct methods
0.0221, 0.0539
200(2)
5.874
0.71073
5093/0/164
direct methods
0.0307, 0.0591
µ (mm-1
λ (Å)
)
data/restr/parameters
solution method
R, Rw (on F2)
Table 2. Selected Distancesa (Å)
E-S
E-N
S-C
N-C
E-N′
δb
[2a][GaCl4]
[2b][GaCl4]
[2c][GaCl4]
[2c][OTf]
2.0243(14)
2.1744(11)
2.3818(6)
2.3757(12)
2.3881(8)
2.3407(9)
1.561(3)
1.740(3)
1.9543(16)
1.949(4)
1.954(2)
1.982(2)
1.693(3)
1.711(4)
1.702(2)
1.697(5)
1.698(3)
1.703(3)
1.345(4)
1.324(4)
1.327(3)
1.330(5)
1.328(3)
1.341(4)
0.0080
0.0235
0.0145
0.0084
0.0258
0.0186
2.5324(17)
2.553(4)
2.538(2)
[2c][TeCl5]
[2c][GaCl3][GaCl4]c
a Short intermolecular contacts: [2a][GaCl4]: S1-Cl4′ 3.4077(13) Å (no other short contacts); [2b][GaCl4]: Se1-Cl2′ 3.2155(10) Å, S1-Cl2′ 3.3861(14)
Å; [2c][GaCl4]: Te1-Cl2′ 3.2963(6), S1-Cl2′ 3.4709(8) Å; [2c][OTf]: Te1-O1′ 2.880(4), S1-O1′ 3.008(4) Å; [2c][TeCl5]: Te1-Cl5′ 3.3749(9), S1-Cl4′
3.4565(14) Å; [2c][GaCl3][GaCl4]: Te1-Cl2′ 3.1633(8), S1-Cl2′ 3.3019(13) Å. b Mean deviation from plane (Å) for cation. c Ga1-N1 2.011(3) Å.
Figure 1. Single ion pairs of [2a][GaCl4] and [2b][GaCl4], with atom
numbering.
planar 12-electron AX4E2 coordination environment. In the
-
case of the TeCl5 salt, the anions are also associated by
bridging chlorines, to form edge-sharing octahedral [Te2-
Cl10]2-dianions, and the crystal structure consists of ribbons
of alternating [2c]2 dications and [Te2Cl10]2- anions, as
2+
Figure 2. The dimeric ion pair structures of [2c][GaCl4] and [2c][OTf],
shown in Figure 3. The terminal and bridging Te-Cl bonds
with atom numbering. Carbon atom numbering follows Figure 1.
within the [Te2Cl10]2- anions are expectedly in accord with
-
those reported previously for various other salts containing
S1-Cl2′ (3.3019(13) Å) with neighboring GaCl4 anions.
this species.22,23
The [2c][GaCl3]+ cation represents a rare example of a
In contrast to the dimeric nature of the simple [2c][X] salts,
the structure of the GaCl3 complex [2c][GaCl3][GaCl4]
consists of monomeric cations [2c][GaCl3]+ (Figure 4),
weakly ion paired via contacts Te1-Cl2′ (3.1633(8) Å) and
positively charged heterocycle serving as a donor to a Lewis
(23) (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.; Janickis, V.; 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. Naturforsch. 1979, 34B, 900. (g) Beck, J.;
Hormel, A.; Koch, M. Eur. J. Inorg. Chem. 2002, 2271.
(22) (a) Na¨rhi, S. M.; Oilunkaniemi, R.; Laitinen, R. S.; Ahlgre´n, M. Inorg.
Chem. 2004, 43, 3742. (b) Pietika¨inen, J.; Maaninen, A.; Laitinen,
R. S.; Oilunkaniemi, R.; Valkonen, J. Polyhedron 2002, 21, 1089.
Inorganic Chemistry, Vol. 47, No. 21, 2008 10103

Risto et al.
Chart 2
acid.24 In spite of the overall positive charge on the cation,
the nitrogen atom in the cation prefers to coordinate to GaCl3
rather than to develop a 4-center dimer with another cation.
Comparison of the C-N and N-Te bond lengths in the
dimerized and GaCl3-complexed cations (Table 2) reveal only
small differences in the C-N and N-Te distances, suggest-
ing little change in the electronic structure of the ring.
As illustrated in Figure 5, all three cations [2a,b,c]+ show
similar trends in the C-C bonds within the benzene ring.
The variations, which are well replicated by DFT calculations
using the B3LYP hybrid functional, with 6-31G(d,p) basis
sets for C, H, N and S, and SDB-cc-pVTZ effective core
potential basis sets for Se and Te, suggest the importance of
the quinoid valence bond contributor shown in Chart 3.
Redox Chemistry. Our main objective in preparing the
heavier members of the series of benzothiachalcazolylium
Figure 5. Calculated and experimental C-C distances in [2a,b,c]+ cations.
Chart 3
cations [2a,b,c]+ was to probe the possibility of generating
radical species by one-electron reduction. As a starting point
we carried out DFT calculations to model the spin distribu-
tions and ion energetics of the putative radicals. The results
are summarized in Figure 6, which shows the calculated
B3LYP/6-31G(d,p)/SDB-cc-pVTZ spin densities for the
Figure 3. The extended ion pair structure of [2c][TeCl5], with atom
numbering. Carbon atom numbering follows Figure 1.
Figure 4. Structure of the monomeric Lewis acid adduct [2c]-
[GaCl3][GaCl4], with atom numbering. Carbon atom numbering follows
Figure 1.
Figure 6. Computed spin distributions for 2a,b,c and CV scans for
[2a,b,c][GaCl4] in MeCN.
10104 Inorganic Chemistry, Vol. 47, No. 21, 2008

HeaWy Atom Analogues of 1,2,3-Dithiazolylium Salts
putative radicals 2a,b,c. As may be seen the transition from
S to Se to Te induces very little change in spin distribution
within the heterocycle and, consistently, the computed
adiabatic ionization energies for the three radicals are
virtually identical.25
Also shown in Figure 6 are the results of cyclic voltam-
metric (CV) analysis of solutions of [2a,b,c][GaCl4] in
MeCN. As expected, the S- and Se-based rings show a clear,
reversible +1/0 reduction wave at approximately the same
E1/2 values. In addition both compounds display a second,
but irreversible 0/-1 wave with Epc value of -0.96 V (E )
S) and -0.90 V (E ) Se) versus SCE. The CV behavior of
[2c][GaCl4] is less straightforward, indeed a reversible wave
cannot be obtained for the +1/0 couple, even with fast
cycling times and narrow sweep ranges.26 At best a profile
of the type illustrated in Figure 6 is obtained, with a barely
discernible cathodic peak with Epc near 0.47 V. Clearly this
potential is well removed (more anodic) from the range
observed for the reduction of [2a,b]+, although the difference
0/+1
is not as great as that seen between E1/2
[1a,b]+ and [1c]+.
couples for
In accord with the electrochemical results, chemical
reduction of the chloride salts of [2a,b][Cl] with tripheny-
lantimony in CH2Cl2 affords solutions that show a strong
and persistent EPR signal which can be assigned to the
respective radicals 2a,b.27 As illustrated in Figure 7, the
X-band EPR spectra of the two radicals are similar, although
that of 2b is broadened by spin-orbit coupling effects from
selenium and a consequent anisotropy in the g-value.28 The
observed fine structure is dominated by a triplet created by
a large hyperfine coupling to the 14N nucleus; this is split
into a more complex pattern by virtue of smaller coupling
to the four 1H nuclei on the benzene periphery. The relevant
coupling constants aN and aH have been extracted by spectral
simulation and assignments confirmed by comparison with
computed values obtained from DFT calculations (Figure 7).
Attempts to observe an EPR signal for the tellurium based
radical 2c using the same in situ reduction methods described
Figure 7. EPR spectra of 2a,b; SW ) 40 G. Experimentally derived (by
simulation) and calculated (in parentheses) coupling constants (in G) are
shown below.
were unsuccessful. However, preparative scale reduction of
salts of [2c]+ was, however, a relatively clean and reproduc-
ible process.29 For example, reaction of a solution of
[2c][OTf] in MeCN with dimethylferrocene afforded a
metallic gray, microcrystalline powder with an elemental (C,
H, N) composition near that expected for the formulation
2c. The material was not, however, EPR active and, despite
repeated attempts, crystals of sufficient size and quality for
single crystal X-ray analysis could not be obtained.30
Energetics of Cation Association. The results of structural
characterization of several salts of the Te-based cation [2c]+
confirm the apparently inevitable tendency of this material
to self-associate in the solid state to form centrosymmetic
dimers linked via short intermolecular Te-N linkages.8 This
mode of association has often been observed in cyclic and
acyclic Te-N compounds6 and, to a lesser extent, in Se-N
compounds.8,14,17 In the case of chalcodiazoles, where two
Te-N linkages are potentially available for intermolecular
association, polymeric structures can be generated. Vargas-
Baca and co-workers have examined the energetics of
association of these heterocycles, and have provided an
elegant evaluation of the electronic reasons for the increasing
strength of association along the series E ) S, Se, Te.31
The three cations [2a,b,c]+ reported here constitute the
second fully characterized family of heterocyclic chalcogen-
(24) (a) Sava, X.; Melaimi, M.; Me´zailles, N.; Ricard, L.; Mathey, F.; Le
Floch, P. New J. Chem. 2002, 26, 1378. (b) Burford, N.; Losier, P.;
Sereda, S. V.; Cameron, T. S.; Wu, G. J. Am. Chem. Soc. 1994, 117,
6474. (c) Burford, N.; Cameron, T. S.; LeBlanc, D. J.; Losier, P.;
Sereda, S.; Wu, G. Organometallics 1997, 16, 4712. (d) Ritter, S.;
Hu¨bener, R.; Abram, U. J. Chem. Soc., Chem. Commun. 1995, 2047.
(25) The spin distributions and ionization energies of 1,2,3-dithiazolyls,
including 2a, have been studied in some detail. See, for example,(a)
Kaszynski, P J. Phys. Chem. A 2001, 105, 7626. (b) Kaszynski, P. J.
Phys. Chem. A 2001, 105, 7615. (c) Cordes, A. W.; Mingie, J. R.;
Oakley, R. T.; Reed, R. W.; Zhang, H. Can. J. Chem. 2001, 79, 1352.
(26) In spite of its low solubility, we have examined the electrochemical
behavior of [2c][GaCl4] in DCE, in which cation dimerization should
be less favorable. The results were very similar to those reported here
for MeCN.
(27) Despite many attempts, with different solvents and reducing agents,
we have not been able to isolate 2a or 2b. Similar difficulties with
other monofunctional 1,2,3-dithiazolyls, and their selenium analogues,
have been encountered before, although the naphthalene version of
2a has been structurally characterized (see ref 14).
(28) (a) Bagryanskaya, I. Y.; Gatilov, Y. V.; Gritsan, N. P.; Ikorskii, V. N.;
Irtegova, I. G.; Lonchakov, A. V.; Lork, E.; Mews, R.; Ovcharenko,
V. I.; Semenov, N. A.; Vasilieva, N. V.; Zibarev, A. V. Eur. J. Inorg.
Chem. 2007, 4751. (b) Bestari, K.; Ferguson, G.; Gallagher, J. F.;
Oakley, R. T. Inorg. Chem. 1992, 31, 442. (c) Bestari, K.; Cordes,
A. W.; Oakley, R. T.; Young, K. M. J. Am. Chem. Soc. 1990, 112,
2249.
(29) Electroreduction of [2c][GaCl4] affords a black microcrystalline deposit
on the electrode. This material is, we presume, the same as that
generated by chemical reduction.
(30) The product obtained from the reduction of [2c]+ is remarkably robust
(air stable). Its infrared spectrum is strong, reproducible and not that
of elemental tellurium; it also provided a good powder X-ray
diffraction pattern. While we were unable to index this pattern, it was
certainly not that of elemental tellurium.
(31) Cozzolino, A. F.; Vargas-Baca, I.; Mansour, S.; Mahmoudkhani, A. H.
J. Am. Chem. Soc. 2005, 127, 3184.
Inorganic Chemistry, Vol. 47, No. 21, 2008 10105

Risto et al.
families, regardless of the nature of the chalcogen. The same
effect, that is, endothermic heats of association of Group 16
cations, has been observed elsewhere, for example, in the
reaction 2 [SI2]+ f [S2I4]2+.32 In the present systems there
is a pronounced local minimum for the tellurium based rings
[1c]+ at 2.389 Å and for [2c]+ at 2.668 Å, the former being
substantially deeper. There is also a shallow local minimum
in [1b]+ at 2.811 Å which is completely washed out for
[2b]+. In neither case does the sulfur-based variant exhibit
a minimum. While correlation of the trends in the gas phase
local minima with the solid state structures can only be
considered as qualitative, it is satisfying to note that the
2+
intermolecular Te-N′ contacts in salts of [1c]22+ and [2c]2
are close to those predicted by the DFT calculations.
Similarly, the weaker association of the cation in [1b][OTf]
(with d(Se-N′) ) 2.711(4) Å) and the absence of dimer-
ization in [2b][GaCl4] are both consistent with the theoretical
predictions.
Of equal if not greater importance to the rationalization
of the solid state results is the potential for DFT methods to
aid in the assessment of the extent of cation association in
solution. The gallate and triflate salts of [1a,b,c]+ and
[2a,b,c]+, for example, are sparingly soluble in DCE and
liquid SO2, and as a result more polar solvents such as MeCN
(and DMSO) were preferred for physical measurements
(NMR spectroscopy) as well as electrochemical and bulk
chemical reductions. In order to probe the extent of associa-
tion of [1a,b,c]+ and [2a,b,c]+ in solution, we employed the
polarized continuum model (PCM)33 to assess the effects of
the solvent dielectric (ε) on the stability of the dimeric
dications relative to the separated monomeric cations. The
method, which assesses the interaction of the solvent,
represented by a dielectric continuum, has been applied to
the study of inorganic and organic ions, including sulfenium
cations,34 in a wide range of solvents.
In the present work we have examined the effects of two
solvents, DCE (ε ) 10.36) and MeCN (ε ) 36.64), and
carried out single point calculations of the total free energy
of the solvated cations and dications using geometries
obtained from the gas phase optimizations. The resulting
changes in free energy of dimerization ∆Gdim as a function
of internuclear separation are shown in Figure 8. As expected,
the incorporation of solvation stabilizes the dications by
mollifying the repulsive electrostatic interaction between the
two cations. As the dielectric constant increases, that is
between DCE and MeCN, so too does the stabilization of
the dication, to the extent that the free energy minima in
MeCN for the tellurium-based dication [2c]+ (-5.2 kcal
mol-1) and [1c]+ (-11.1 kcal mol-1) suggest that dimeric
Figure 8. Gas phase ∆Hdim and PCM ∆Gdim of [1a,b,c]+ (left) and [2a,b,c]+
(right) in MeCN and DCE, plotted as a function of d(E-N′).
nitrogen cations. Taken together with our earlier work on
[1a,b,c]+, the results provide an opportunity to probe the
strength of intermolecular interactions as a function of ring
system and heteroatom. In order to interpret the observed
trends, and to provide a quantitative estimate of the energies
involved, we have carried out a series of DFT calculations
at the B3LYP/6-31G(d,p)/SDB-cc-pVTZ level on both
families of cations and their respective dimers. The results
are illustrated in Figure 8, which shows plots of the gas phase
enthalpy change ∆Hdim for the association of the two cations
[1]+ and [2]+ as a function of the interdimer separation
d(E-N′) (eqs 1 and 2).
(32) (a) Brownridge, S.; Crawford, M.-J.; Du, H.; Harcourt, R. D.; Knapp,
C.; Laitinen, R. S.; Passmore, J.; Rautiainen, J. M.; Suontamo, R. J.;
Valkonen, J. Inorg. Chem. 2007, 46, 681. (b) Tuononen, H. M.;
Suontamo, R.; Valkonen, J.; Laitinen, R. S. J. Phys. Chem. A 2004,
108, 5670.
(33) (a) Tomasi, J.; Persico, M. Chem. ReV. 1994, 94, 2027. (b) Cossi, M.;
Barone, V.; Cammi, R.; Tomasi, J. Chem. Phys. Lett. 1996, 255, 327.
(c) Menucci, B.; Tomasi, J. J. Chem. Phys. 1997, 106, 5151. (d)
Barone, V.; Cossi, M.; Tomasi, J. J. Chem. Phys. 1997, 107, 3210.
(34) Brinck, T.; Carlqvist, P.; Holm, A. H.; Daasbjerg, K. J. Phys. Chem.
A 2002, 106, 8827.
As a result of the electrostatic repulsion between the
cations, ∆Hdim is predicted to be endothermic for both
10106 Inorganic Chemistry, Vol. 47, No. 21, 2008

HeaWy Atom Analogues of 1,2,3-Dithiazolylium Salts
structure [2c]22+ and, more particularly, [1c]22+represent the
most likely formulations for these species in polar
solvents.
Preparation of Trimethylsilanyl(2-trimethylsilanylsulfanylphe-
nyl)amine 4. A neat mixture of 3 (27.0 g, 216 mmol) and hexamethyl-
disilazane (56 mL, 265 mmol) was gently refluxed for 16 h. The
mixture was concentrated in vacuo to leave a yellow oil that was
distilled at 89-91 °C/10-2 Torr to yield 4 as a colorless oil (51.7
g, 192 mol, 89%). 1H NMR (CDCl3): δ 7.36 (d, 1H), 7.12 (tr, 1H),
6.81 (d, 1H), 6.64 (tr, 1H), 4.95 (s, 1H), 0.33 (s, 9H), 0.30 (s, 9H).
Preparation of 1,1,1,3,3,3-Hexamethyl-2-(2-trimethylsilanyl-
sulfanylphenyl)disilazane 5. n-Butyl lithium (100 mL, 160 mmol)
was added dropwise to a solution of 4 (38.2 g, 142 mmol) in diethyl
ether (100 mL) at 0 °C. The mixture was stirred at 0 °C for 30 min
and then at room temperature for 1 h to give a white suspension.
The suspension was cooled back to 0 °C, and chlorotrimethylsilane
(23 mL, 181 mmol) was slowly added via a dropping funnel. The
mixture was stirred at room temperature overnight. A white
precipitate of LiCl was filtered off, and the solvent was flash distilled
from the filtrate to leave a pale yellow oil. Vacuum distillation at
123-125 °C/10-2 Torr afforded 5 as a colorless oil, yield 42.5 g
(124 mmol, 87%). 1H NMR (CDCl3): δ 7.33 (d, 1H), 6.95 (m, 3H),
0.41 (s, 9H), 0.08 (s, 18 H). Anal. Calcd. for C15H31NSSi3: C, 52.72;
H, 9.14; N, 4.10%. Found: C, 52.88; H, 8.91; N, 4.20%.
Preparation of 3H-Benzo[1,2,3]dithiazolylium Chloride [2a]-
[Cl]. A solution of thionyl chloride (1.75 mL, 24.1 mmol) in 10
mL of MeCN was added dropwise to a solution of 3 (1.00 g, 7.99
mmol) in 25 mL of MeCN at 0 °C. The mixture was stirred for 15
min at room temperature, and then refluxed for 1 h. The resulting
golden brown precipitate of [2a][Cl] was filtered off, washed with
3 × 15 mL of benzene, and dried in vacuo. Yield 1.20 g (6.33
mmol, 79%). IR (cm-1): 3069 (w), 1583 (m), 1514 (m), 1428 (m),
1338 (m), 1306 (m), 1243 (vw), 1187 (vw), 1129 (m), 1010 (m),
989 (m), 955 (s), 947 (s), 870 (w), 817 (vs), 771 (vs), 739 (s, br),
693 (vs), 611 (m), 529 (vw), 493 (w), 487 (w), 454 (m), 441 (m).
Preparation of 3H-Benzo[1,2,3]dithiazolylium Tetrachloro-
gallate [2a][GaCl4]. Gallium trichloride (3.00 g, 17.0 mmol) was
added to a slurry of [2a][Cl] (3.00 g, 15.8 mmol) in 80 mL of
MeCN, and the resulting dark green solution was stirred for 1 h
and filtered. The solvent was flash distilled to leave a dark green
crystalline mass that was recrystallized from chlorobenzene as
yellow plates of [2a][GaCl4]. Yield 4.00 g (10.9 mmol, 69%); mp.
180-181 °C. Anal. Calcd. for C6H4Cl4GaNS2: C, 19.70; H, 1.10;
N, 3.83%. Found: C, 19.91; H, 1.34; N, 4.00%. IR (cm-1): 3083
(m), 1583 (vs), 1517 (s), 1438 (s), 1425 (vs), 1343 (vs), 1319 (vs),
1250 (w), 1239 (vw), 1178 (vw), 1131 (m), 1067 (vw), 1005 (w),
972 (vw), 953 (m), 944 (w), 813 (vs), 769 (vs), 696 (s), 612 (m),
510 (w), 454 (m), 450 (m). The X-ray quality crystals of [2a][GaCl4]
were obtained by recrystallization from DCE.
Summary and Conclusions
The condensation of persilylated 2-aminobenzenethiol with
ECl4 (E ) Se, Te) provides a simple and effective route to
heavy atom thiachalcazolylium cations [2]+. The tendency
for salts of the tellurium based cation [2c]+ to crystallize as
centrosymmetric dimers parallels that seen for the related
N-methyl chalcodiazolylium cation [1c]+. In support of
crystallographic data the results of DFT calculations on the
two series of cations [1a,b,c]+ and [2a,b,c]+ indicate that
association is generically stronger for the former, and that
within each series the strength of the intermolecular E-N′
interaction increases with E ) S < Se < Te. The weaker
association of [2c]+ (relative to [1c]+) has allowed the
isolation of a monomeric complex [2c][GaCl3][GaCl4], in
which the nitrogen atom of the heterocycle is coordinated
to GaCl3. In contrast to the behavior of the light atom cations
[1a,b]+and [2a,b]+, electrochemical reduction of salts of
[1c]+ and [2c]+ are strongly irreversible, and attempts to
observe the putative radical 2c have been unsuccessful.
Chemical reduction of [2c][OTf] has, however, afforded a
diamagnetic material of nominal composition 2c, although
no structural information could be obtained. Attempts to
characterize structurally a related derivative are ongoing.
Experimental Section
General Procedures and Starting Materials. All reactions were
carried out under an atmosphere of dry nitrogen. The reagents
2-aminobenzenethiol, hexamethyldisilazane, n-butyl lithium (1.6 M
in hexanes), chlorotrimethylsilane, thionyl chloride, gallium trichlo-
ride, silver triflate (trifluoromethanesulfonate) and dimethylferrocene
were obtained commercially. All were used as received, save for
dimethylferrocene, which was recrystallized from acetonitrile before
use. Selenium tetrachloride was prepared by direct chlorination of
selenium,35 and tellurium tetrachloride by the reaction of tellurium
dioxide and chlorotrimethylsilane.36 All solvents were at least the
reagent grade: acetonitrile (MeCN), dichloroethane (DCE), and
chlorobenzene were dried by distillation over P2O5 under a nitrogen
atmosphere prior to use. Melting points are uncorrected. Elemental
analyses were performed by MHW Laboratories, Phoenix, AZ.
Infrared spectra (Nujol mulls, KBr optics) were recorded on a
Nicolet Avatar FTIR spectrometer (at 2 cm-1 resolution). 1H,
77Se{1H}, and 125Te NMR spectra were recorded on a Bruker
Avance 300 spectrometer operating at 300.13, 57.318 and 94.918
MHz, respectively. The spectral widths were 4.34, 56.98, and 75.19
kHz, and the pulse widths were 12.0, 9.70 and 6.30 µs. The pulse
delay for proton, selenium, and tellurium was 1.0, 2.0 and 2.0 s,
Preparation of 3H-Benzo[1,2,3]thiaselenazolylium Chloride
[2b][Cl]. A solution of 5 (2.46 g, 7.20 mmol) in 20 mL of MeCN
was added slowly to a slurry of SeCl4 (1.50 g, 6.79 mmol) in 60
mL of MeCN at 0 °C. The mixture was stirred for 30 min at room
temperature, and then refluxed for 1 h. The resulting dark brown
precipitate of [2b][Cl] was filtered off, washed with 3 × 10 mL of
MeCN, and dried in vacuo. Yield 1.25 g (5.28 mmol, 78%). IR
(cm-1): 3057 (vw), 1605 (w), 1583 (s), 1505 (m), 1432 (m), 1420
(s), 1347 (s), 1340 (s), 1308 (s), 1230 (m), 1184 (w), 1167 (vw),
1131 (m), 1068 (vw), 993 (vw), 965 (vw), 879 (w), 771 (vs), 737
(m), 729 (m), 685 (s), 583 (m), 450 (w).
Preparation of 3H-Benzo[1,2,3]thiaselenazolylium Tetrachlo-
rogallate [2b][GaCl4]. Gallium trichloride (1.00 g, 5.68 mmol) was
added to a slurry of [2b][Cl] (1.22 g, 5.16 mmol) in 50 mL of
MeCN, and the resulting dark red solution was filtered. The solvent
was then flash distilled from the filtrate to leave a dark brown
crystalline mass that was recrystallized from DCE as orange-brown
1
respectively. H NMR spectra are referenced to the solvent signal
and are reported relative to Me4Si. The 77Se and 125Te NMR spectra
are referenced externally to a D2O solution of SeO2 and H6TeO6,
and the chemical shifts are reported relative to neat Me2Se and
Me2Te, respectively [δ(Me2Se) ) δ(SeO2) + 1302.6; δ(Me2Te) )
δ(H6TeO6) + 712].
(35) Brauer, G. Handbook of PreparatiVe Inorganic Chemistry; Academic
Press: New York, 1963; Vol. 1, p 423.
(36) Fukuzawa, S.-I.; Irgolic, K. J.; O’Brien, D. H. Heteroatom Chem. 1990,
1, 43.
Inorganic Chemistry, Vol. 47, No. 21, 2008 10107

Risto et al.
plates of [2b][GaCl4]. Yield 1.51 g (3.66 mmol, 71%); mp.
168-170 °C. Anal. Calcd. for C6H4Cl4GaNSSe: C, 17.46; H, 0.98;
N, 3.39%. Found: C, 17.50; H, 1.16; N, 3.15%. IR (cm-1): 3083
(w), 1586 (s), 1507 (m), 1428 (s), 1424 (vs), 1344 (vs), 1317 (s),
1242 (w), 1232 (vw), 1179 (vw), 1132 (m), 1065 (vw), 1000 (vw),
773 (vs), 750 (m), 745 (m), 685 (m), 582 (m), 448 (w). 77Se{1H}
NMR (CD3CN): δ 1560. The X-ray quality crystals of [2b][GaCl4]
were obtained by recrystallization from chlorobenzene.
Preparation of 3H-Benzo[1,2,3]thiatellurazolylium Chloride
[2c][Cl]. A solution of 5 (4.25 g, 12.4 mmol) in 20 mL of DCE
was added slowly to a slurry of TeCl4 (3.04 g, 11.3 mmol) in 200
mL of DCE. The mixture was stirred for 10 min at room
temperature and then gently refluxed for 1.5 h. The resulting dark
black precipitate of [2c][Cl] was filtered off, washed with 3 × 15
mL of DCE, and dried in vacuo. Yield 2.64 g (9.26 mmol, 82%).
IR (cm-1): 3074 (vw), 3056 (vw), 3031 (vw), 1585 (m), 1568 (w),
1503 (m), 1449 (vs), 1429 (s), 1422 (vs), 1366 (m), 1354 (m), 1293
(s), 1276 (s), 1248 (s), 1240 (w), 1228 (m), 1159 (m), 1129 (s),
1061 (m), 1029 (s), 925 (vw), 894 (vw), 875 (s), 850 (vw), 829
(vw), 767 (s), 735 (m), 721 (s), 682 (vs), 608 (w), 586 (s), 455
(m), 429 (m).
[2c][TeCl5] matched that of the original precipitate from condensa-
tion reaction above. Anal. Calcd. for C6H4Cl5NSTe2: C, 12.99; H,
0.73; N, 2.53%. Found: C, 13.06; H, 0.83; N, 2.49%. IR (cm-1):
3068 (w), 1585 (m), 1501 (s), 1429 (m, sh), 1421 (s), 1366 (m),
1349 (m), 1238 (s), 1172 (m), 1139 (m), 1062 (m), 1021 (vw),
1004 (vw), 960 (vw), 871 (m), 848 (vw), 767 (vs), 741 (s), 716
(s), 681 (vs), 577 (s), 461 (w), 443 (w).
Preparation of the Gallium Trichloride Complex of 3H-
Benzo[1,2,3]thiatellurazolylium Tetrachlorogallate [2c][GaCl3]-
[GaCl4]. Gallium trichloride (0.434 g, 2.46 mmol) was added to a
slurry of [2c][Cl] (0.335 g, 1.17 mmol) in 15 mL of DCE. The
solution was stirred at room temperature for 15 min, and the red
microcrystalline solid of [2c][GaCl3][GaCl4] obtained by n-hexane
(30 mL) precipitation was filtered and dried in vacuo. Yield 0.570
g (0.894 mmol, 76%). Anal. Calcd. for C6H4Cl7Ga2NSTe: C, 11.31;
H, 0.63; N, 2.20%. Found: C, 11.26; H, 0.86; N, 2.09%. IR (cm-1):
1584 (w), 1511 (m), 1423 (m), 1353 (s), 1261 (vw), 1246 (w),
1178 (vw), 1151 (w), 1066 (w), 1018 (w), 879 (w), 770 (m), 762
(vs), 696 (m), 679 (vw), 593 (w), 449 (vw), 425 (m). 125Te NMR:
δ (CD3CN) 1429; δ (DCE) 1337. The X-ray quality crystals of
[2c][GaCl3][GaCl4] were obtained by recrystallization from liquid
SO2.
Preparation of 3H-Benzo[1,2,3]thiatellurazolylium Tetrachl-
orogallate [2c][GaCl4]. Gallium trichloride (0.322 g, 1.83 mmol)
was added to a slurry of [2c][Cl] (0.474 g, 1.66 mmol) in 10 mL
of MeCN, and the resulting red solution was filtered. The solvent
was then flash distilled to leave a dark red microcrystalline solid
of [2c][GaCl4] which was washed with 10 mL of DCE, filtered off
and dried in vacuo. Yield 0.616 g (1.34 mmol, 81%); dec >95 °C.
Anal. Calcd. for C6H4Cl4GaNSTe: C, 15.62; H, 0.87; N, 3.04%.
Found: C, 15.49; H, 1.03; N, 2.92%. IR (cm-1): 1583 (m), 1569
(vw), 1559 (w), 1539 (w), 1503 (m), 1428 (sh, m), 1421 (m), 1362
(w), 1346 (m), 1311 (w), 1261 (vw), 1237 (w), 1229 (vw), 1173
(vw), 1139 (w), 1060 (w), 1022 (vw), 994 (vw), 869 (vw), 800
(br, w), 767 (vs), 741 (s), 717 (s), 678 (vs), 577 (m), 458 (w), 445
(w). 125Te NMR (CD3CN): δ 1427. The X-ray quality crystals of
[2c][GaCl4] were obtained by recrystallization from DCE.
Preparation of 3H-Benzo[1,2,3]thiatellurazolylium Trifluo-
romethanesulfonate [2c][OTf]. Silver triflate (0.799 g, 3.11 mmol))
and [2c][Cl] (0.877 g, 3.08 mmol) were stirred at gentle reflux in
70 mL of MeCN for 1.5 h to afford a deep red solution and a white
AgCl precipitate. The solution was filtered and concentrated to the
volume of 10 mL. The red microcrystalline solid of [2c][OTf] was
filtered off and dried in vacuo. Yield 0.830 g (2.08 mmol, 68%);
dec >130 °C. Anal. Calcd. for C7H4F3NO3S2Te: C, 21.08; H, 1.01;
N, 3.51%. Found: C, 21.23; H, 0.83; N, 3.68%. IR (cm-1): 1511
(w), 1295 (s), 1286 (s), 1232 (s), 1219 (s), 1180 (vw), 1151 (m),
1029 (m), 954 (vw), 759 (m), 743 (vw), 684 (m), 637 (m), 575
(w), 519 (w), 514 (w), 451 (vw). 125Te NMR (CD3CN): δ 1431.
The X-ray quality crystals of [2c][OTf] were obtained by recrys-
tallization from MeCN.
Preparation of 3H-Benzo[1,2,3]thiatellurazolyl 2c. Dimeth-
ylferrocene (0.161 g, 0.752 mmol) was added to a solution of
[2c][OTf] (0.300 g, 0.752 mmol) in 15 mL of degassed MeCN.
After stirring the reaction mixture for 15 min at room temperature
the resulting metallic gray powder of 2c was filtered off, washed
with 2 × 15 mL of MeCN and dried in vacuo. Yield 0.167 g (0.669
mmol, 89%). Anal. Calcd. for C6H4NSTe: C, 28.85; H, 1.61; N,
5.61%. Found: C, 27.79; H, 1.76; N, 4.32%. IR (cm-1): 1528 (w),
1434 (s), 1306 (w), 1262 (w), 1232 (m), 1155 (w), 1060 (m), 1023
(m), 737 (s), 709 (w), 636 (vw), 439 (w).
X-Ray Measurements. Diffraction data for compounds [2a]-
[GaCl4], [2b][GaCl4], [2c][GaCl4], [2c][OTf], [2c][TeCl5] and
[2c][GaCl3][GaCl4] were collected on a Bruker SMART APEX
CCD-based diffractometer at 296 K, 290 or 200 K using graphite
monochromated Mo KR radiation (λ ) 0.71073 Å). Crystals were
mounted onto glass fibers with silicone oil or epoxy. Crystal data
and details of the structure determinations are given in Table 1.
All structures were solved by direct methods using SHELXL-9737
and refined by least-squares methods on F2 using SHELXL-97
incorporated in the SHELXTL38 suite program. After the full-matrix
least-squares refinement of non-hydrogen atoms with anisotropic
thermal parameters, the hydrogen atoms were placed in calculated
positions in the aromatic ring (C-H ) 0.95 Å). In the final
refinement the hydrogen atoms were riding with the carbon atom
to which they were bonded. The isotropic thermal parameters of
the aromatic hydrogen atoms were fixed at 1.2 times to that of the
corresponding carbon atom. The scattering factors for the neutral
atoms were those incorporated with the programs.
EPR Spectroscopy. The X-band EPR spectra of 2a and 2b were
recorded at ambient temperature using a Bruker EMX-200 spec-
trometer. The radicals 2a and 2b were conveniently generated by
in situ reduction of a slurry of the appropriate chloride salt
[2a,b][Cl] with triphenylantimony in dichloromethane. Hyperfine
coupling constants were obtained by spectral simulation using PEST
WinSim39 and Bruker WinEPR Simfonia.40
Formation of 3H-Benzo[1,2,3]thiatellurazolylium Pentachlo-
rotellurate [2c][TeCl5]. A solution of 5 (3.04 g, 8.90 mmol) in
100 mL of MeCN was added slowly to a slurry of TeCl4 (2.00 g,
7.42 mmol) in 200 mL of MeCN at 0 °C. After stirring the reaction
mixture for 2 h at room temperature the resulting dark black powder
was filtered, washed with 3 × 10 mL of MeCN and dried in vacuo;
yield 1.21 g. Gallium trichloride (0.213 g, 1.21 mmol) was then
added to a slurry of this dark black powder (0.313 g) in 25 mL of
MeCN. The resulting red solution was filtered after 10 min. The
solvent was flash distilled to leave a dark red solid which was heated
back into 5 mL of MeCN. Cooling of the red solution in freezer
overnight afforded dark red X-ray quality crystals of [2c][TeCl5]
(0.071 g, 0.128 mmol); dec >125 °C. The IR spectrum of
(37) Sheldrick, G. M. SHELXL-97. Program for Crystal Structure Refine-
ment; University of Go¨ttingen: Go¨ttingen, Germany 1997.
(38) SHELXTL, version 6.12. Program Library for Structure Solution and
Molecular Graphics, Bruker Advanced X-Ray Solutions, Inc., Madison,
WI, 2001.
(39) Duling, D. R. J. Magn. Reson., Series B 1994, 104, 105.
10108 Inorganic Chemistry, Vol. 47, No. 21, 2008

HeaWy Atom Analogues of 1,2,3-Dithiazolylium Salts
Cyclic Voltammetry. Cyclic voltammetry was performed using
a PINE Bipotentiostat, model AFCClBP1, with scan rates of 100
mV s-1 on solutions (<10-3 M) of [2a,b,c][GaCl4] in oxygen free
MeCN (dried by distillation from P2O5) containing 0.1 M tetra-n-
butylammonium hexafluorophosphate. Potentials were scanned with
respect to the quasi-reference electrode in a single-compartment
cell fitted with Pt electrodes and referenced to the Fc/Fc+ couple
of ferrocene at 0.38 V vs SCE.41 The Epa - Epc separation of the
reversible couple of [2a,b]+ was within 10% of that of the Fc/Fc+
couple.
Theoretical Calculations. Density functional theory calculations
were performed with the Gaussian 03 suite of programs,42 using
the B3LYP hybrid density functional with the 6-31G(d,p) basis set
for light atoms (H, C, N, S). The relativistic effective core potential
basis set SDB-cc-pVTZ was used for selenium and tellurium.43
The gas phase dimerization enthalpy of the [2]+ cations was
evaluated in terms of the energetic difference between the cations
and their respective dications as a function of internuclear separa-
tion. Total electronic energies of the gas phase cations M+ were
derived from geometries fully optimized within Cs (planar) sym-
metry. That these geometries were stationary points was confirmed
by frequency calculations. Total electronic energies of the gas phase
2+
dications [2]2 were computed using structures optimized within
a C2h symmetry constraint, using the two equivalent intermolecular
E-N′ distances as the reaction coordinate. The effects of solvation
in dichloroethane and acetonitrile were investigated using the
polarization continuum solvation model (PCM),33,44 with atom radii
defined by the united simple atom topological (UA0) model.
Convergence over the d(E-N′) range of 1.8-6.0 Å required a
solvent-specific scaling parameter set at R ) 1.0 (for E ) S) and
R ) 1.2 (for E ) Se, Te). Given the size of the dications, no attempt
was made to probe structural relaxation in solution; instead, single
point calculations were performed using molecular parameters
obtained from the gas phase optimizations over a range of
intermolecular distances d(E-N′). Gas phase molecular ion ener-
getics, spin densities and hyperfine coupling constants were
evaluated using the same method and basis sets noted above.
Adiabatic ionization potentials (IP) and electron affinities (EA) were
calculated using ∆SCF methods on fully optimized anions, radicals
and cations.
(40) WinEPR Simfonia, version 1.25; Bruker Instruments, Inc.: Billerica,
MA, 1996.
(41) Boere´, R. T.; Moock, K. H.; Parvez, M. Z. Anorg. Allg. Chem. 1994,
620, 1589.
Acknowledgment. We thank the Natural Sciences and
Engineering Research Council of Canada (NSERCC) and
the Academy of Finland for financial support. We especially
acknowledge the Academy of Finland for a Graduate
Scholarship to M. R. and the Canada Council for a Killam
Research Fellowship to R. T. O.
(42) Gaussian 03, ReVision C.02; Frisch, M. J.; Trucks, G. W.; Schlegel,
H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Montgomery,
Jr., J. A.; Vreven, T.; Kudin, K. N.; Burant, J. C.; Millam, J. M.;
Iyengar, S. S.; Tomasi, J.; Barone, V.; Mennucci, B.; Cossi, M.;
Scalmani, G.; Rega, N.; Petersson, G. A.; Nakatsuji, H.; Hada, M.;
Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima,
T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li, X.; Knox, J. E.;
Hratchian, H. P.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.;
Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi,
R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.; Voth,
G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich,
S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck,
A. D.; Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul,
A. G.; Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko,
A.; Piskorz, P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.;
Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe, M.;
Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Gonzalez, C.;
Pople, J. A.; Gaussian, Inc.: Wallingford CT, 2004.
Supporting Information Available: Details of X-ray crystal-
lographic data collection and structure refinement at ambient
temperature, tables of atomic coordinates, bond distances and
angles, anisotropic thermal parameters, and hydrogen atom positions
in CIF format. This information is available free of charge via the
Internet at http://pubs.acs.org.
IC8013738
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Inorganic Chemistry, Vol. 47, No. 21, 2008 10109