Neutral and dianionic organoantimony(III) dithiolene complexes: Syntheses, x-ray crystal structures, and unexpected reactivity

Article abstract of DOI:10.1021/om030056c

The new neutral PhSb(dmid) (dmid^2- = 4,5-dithiolato-1,3-dithiol-2-one) complexes has been synthesized upon reaction of deprotected 1,3,4,6-tetrathiapentalene-2,5-dione with dichlorophenylstibine. Single-crystal X-ray structure determination shows an original three-dimensional network in the solid state, via Sb- - -O and Sb- - -S secondary interactions, based on an octagonal Sb₄S₄ motif. Not only PhSb(dmid) but also PhSb(dmit) (dmit^2- = 4,5-dithiolato-1,3-dithiole-2-thione) reacts with a second 1 equiv of dithiolate to give a series of highly reactive dianionic complexes, unknown so far. One of these complexes, [Me₄N]₂[PhSb(dmid)₂], was structurally characterized by single-crystal X-ray measurements. Both dithiolene ligands, lying in the equatorial plane of a distorted octahedron, are unsymmetrically coordinated, with two Sb-s distances much longer than the other two. These dianionic species reacted with 1 equiv of PhSbCl₂ to give unexpectedly, a series of Sb(V) [Ph₂Sb(dithiolene)₂]^- complexes. The same compounds were obtained directly upon slow addition of 1 equiv of PhSbCl₂ on the corresponding dithiolate suspensions. This demonstrates that dianionic [PhSb^III(dithiolene)₂]^2- species are key intermediates in the synthesis of [Ph₂Sb^V(dithiolene)₂]^- salts. The single-crystal X-ray structure determination of the tetraethylammonium salts of [Ph₂Sb(dmid)₂]^-, [Ph₂Sb(dmit)₂]^-, and [Ph₂Sb(dmid)(dmit)]^- show a distorted-octahedral coordination geometry for the Sb center with a cis configuration of the phenyl groups. This is preserved also in solution, as established by ¹³ NMR. Using the same technique, combined with ¹H NMR, in a scrambling experiment, a fast dithiolene exchange has been emphasized. In the case of the [Ph₂Sb(dmid)₂]^- salt, two polymorphs, with different folding angles along the S - S hinge, were crystallized.

Full text of DOI:10.1021/om030056c

2042
Organometallics 2003, 22, 2042-2049
Neu tr a l a n d Dia n ion ic Or ga n oa n tim on y(III) Dith iolen e
Com p lexes: Syn th eses, X-r a y Cr ysta l Str u ctu r es, a n d
Un exp ected Rea ctivity
Narcis Avarvari and Marc Fourmigue´*
“Chimie Inorganique, Mate´riaux et Interfaces” (CIMI), FRE 2447 CNRS-Universite´ d’Angers,
UFR Sciences, Baˆt. K, 2 bd Lavoisier, 49045 Angers, France
Received J anuary 23, 2003
The new neutral PhSb(dmid) (dmid2- ) 4,5-dithiolato-1,3-dithiol-2-one) complex has been
synthesized upon reaction of deprotected 1,3,4,6-tetrathiapentalene-2,5-dione with dichlo-
rophenylstibine. Single-crystal X-ray structure determination shows an original three-
dimensional network in the solid state, via Sb- - -O and Sb- - -S secondary interactions, based
on an octagonal “Sb4S4” motif. Not only PhSb(dmid) but also PhSb(dmit) (dmit2- ) 4,5-
dithiolato-1,3-dithiole-2-thione) reacts with a second 1 equiv of dithiolate to give a series of
highly reactive dianionic complexes, unknown so far. One of these complexes, [Me4N]2[PhSb-
(dmid)2], was structurally characterized by single-crystal X-ray measurements. Both
dithiolene ligands, lying in the equatorial plane of a distorted octahedron, are unsymmetri-
cally coordinated, with two Sb-S distances much longer than the other two. These dianionic
species reacted with 1 equiv of PhSbCl2 to give, unexpectedly, a series of Sb(V)
[Ph2Sb(dithiolene)2]- complexes. The same compounds were obtained directly upon slow
addition of 1 equiv of PhSbCl2 on the corresponding dithiolate suspensions. This demonstrates
that dianionic [PhSbIII(dithiolene)2]2- species are key intermediates in the synthesis of
[Ph2SbV(dithiolene)2]- salts. The single-crystal X-ray structure determination of the tetra-
ethylammonium salts of [Ph2Sb(dmid)2]-, [Ph2Sb(dmit)2]-, and [Ph2Sb(dmid)(dmit)]- show
a distorted-octahedral coordination geometry for the Sb center with a cis configuration of
the phenyl groups. This is preserved also in solution, as established by 13C NMR. Using the
same technique, combined with 1H NMR, in a scrambling experiment, a fast dithiolene
exchange has been emphasized. In the case of the [Ph2Sb(dmid)2]- salt, two polymorphs,
with different folding angles along the S- - -S hinge, were crystallized.
In tr od u ction
behavior has found recently a nice application in solu-
tion, in the catalytic separation and purification of
olefins.2 In the solid state, besides the intrinsic elec-
tronic properties of the molecular entities, all the
intermolecular interactions occurring in the crystal
ultimately determine the collective properties such as
conductivity and magnetism. For example, in the crystal
structure of the mixed-valence superconducting salt
[Me4N][Ni(dmit)2]2 (dmit2- ) 4,5-dithiolato-1,3-dithiole-
2-thione), short intermolecular S- - -S contacts (3.49 Å)
ensure the 2D character of the conductor,3 or, more
recently, a single-component molecular metal, Ni(tmdt)2
(tmdt ) trimethylenetetrathiafulvalenedithiolate), syn-
thesized by Kobayashi et al. shows a 3D solid-state
organization of the molecules due to short S- - -S
intermolecular interactions.4
The coordination chemistry of dithiolene ligands has
been extensively and increasingly studied over the past
decade.1 The interest in using this class of ligands
relates on their “noninnocence” on one hand, since in
dithiolene-based transition-metal complexes the HOMO
has mainly a ligand character, and their capacity to
establish short intermolecular S- - -S interactions in the
solid state on the other hand. Both features are very
important for the synthesis of crystalline molecular
materials with conducting and magnetic properties.
Indeed, the redox behavior of dithiolene complexes,
determined by the nature and relative position of the
frontier orbitals, can be finely tuned by changing either
the substituents on the dithiolene or the coordinated
metallic center, leading to the stabilization of complexes
in several oxidation states. This specific electrochemical
If another heavy atom (X) of groups 14-17 is present
in the structure of sulfur-rich molecules such as dithi-
olenes, one can expect additional intermolecular inter-
* To whom correspondence should be addressed. Fax: 00-33-2-41
73 54 05. E-mail: marc.fourmigue@univ-angers.fr.
(2) Wang, K.; Stiefel, E. I. Science 2001, 291, 106.
(1) (a) Mu¨ller-Westerhof, U. T.; Vance, B. In Comprehensive Coor-
dination Chemistry; Wilkinson, G., Gillard, R. D., McCleverty, J . A.,
Eds.; Pergamon Press: Oxford, U.K., 1987; Vol. 2, p 596. (b) Cassoux,
P.; Valade, L.; Kobayashi, H.; Kobayashi, A.; Clark, R. A.; Underhill,
A. E. Coord. Chem. Rev. 1991, 110, 115. (c) Fourmigue´, M. Coord.
Chem. Rev. 1998, 178-180, 823. (d) Pullen, A. E.; Olk, R.-M. Coord.
Chem. Rev. 1999, 188, 211. (e) Robertson, N.; Cronin, L. Coord. Chem.
Rev. 2002, 227, 93.
(3) (a) Kobayashi, A.; Kim, H.; Sasaki, Y.; Kato, R.; Kobayashi, H.;
Moriyama, S.; Nishio, Y.; Kajita, K.; Sasaki, W. Chem. Lett. 1987, 1819.
(b) Kobayashi, A.; Kim, H.; Sasaki, Y.; Moriyama, S.; Nishio, Y.; Kajita,
K.; Sasaki, W.; Kato, R.; Kobayashi, H. Synth. Met. 1988, 27, B339.
(c) Kajita, K.; Nishio, Y.; Moriyama, S.; Kato, R.; Kobayashi, H.; Sasaki,
W. Solid State Commun. 1988, 65, 361.
(4) Tanaka, H.; Okano, Y.; Kobayashi, H.; Suzuki, W.; Kobayashi,
A. Science 2001, 291, 285.
10.1021/om030056c CCC: $25.00 © 2003 American Chemical Society
Publication on Web 04/18/2003

Organoantimony(III) Dithiolene Complexes
Organometallics, Vol. 22, No. 10, 2003 2043
Syn th esis of P h en yl(1,3-d ith iol-2-on e-4,5-d ith iola to)-
a n tim on y(III) (2). In a Schlenk tube containing 1,3,4,6-
tetrathiapentalene-2,5-dione (1; 2 g, 9.6 mmol) in 70 mL of
THF, a solution of Me4NOH (7 g, 25 wt % in MeOH, 19.2 mmol)
in 10 mL of THF was added under magnetic stirring. A yellow
precipitate suddenly appeared, corresponding to the formation
of (Me4N)2(dmid). After 30 min of stirring at room temperature,
dichlorophenylstibine (2.6 g, 9.6 mmol) in 10 mL of THF was
rapidly added. The solution became orange, and a cream-
colored precipitate of tetramethylammonium chloride was
formed. The suspension was stirred for 1 h and then filtered
through Celite. After evaporation of solvent, the resulting oil
was dissolved in a minimum amount of toluene and then
rapidly chromatographed with toluene through a short silica
gel column. After removal of solvent under vacuum, addition
of a small volume of THF, precipitation with pentane, filtra-
tion, and drying on a vacuum line, complex 2 was recovered
as a yellow solid. Yield: 1.7 g (47%). Single crystals for X-ray
analysis were grown by slow diffusion of hexane into a solution
of 2 in toluene.
actions of X- - -S or X- - -X type, which could eventually
overcome the S- - -S interactions and thus drive the
solid-state organization of these compounds. This is
particularly well illustrated in the case of open antimony
sulfide frameworks,5 in which intermolecular Sb- - -S
and Sb- - -Sb contacts lead to a huge variety of struc-
tures. Therefore, the introduction of antimony in dithio-
lenes such as dmit and dmid (dmid2- ) 4,5-dithiolato-
1,3-dithiol-2-one), which can be also seen as “half-
tetrathiafulvalenes” (TTF), seemed to us particularly
interesting from structural, coordination, and materials
science points of view. In this respect, our recent results6
concerning the first organoantimony(III) dithiolene
complex, PhSb(dmit), confirmed our expectations, since
the cooperativity between S- - -S and Sb- - -S intermo-
lecular contacts led to the formation of an original three-
dimensional network in the solid state. Moreover, we
could clearly emphasize the existence of two reversible
single-crystal phase transitions involving the coordina-
tion sphere of antimony, thus showing its flexibility. We
describe here the synthesis and structural characteriza-
tion of PhSb(dmid) and investigate its reactivity to-
gether with that of PhSb(dmit). The interest in synthe-
sizing the former complex directly follows from the
crystal structure of PhSb(dmit), in which we observed
that all the secondary short Sb- - -S contacts involved
the CdS sulfur atoms: hence, the idea of replacing Cd
S by CdO in the ligand structure. One can notice that
the same interactions were present in the structure of
previously described monoanionic salts [Sb(dmit)2]-.7
1H NMR (δ, THF-d8): 7.31-7.41 (m, 3H, H para and meta),
3
4
7.79 (dd, 2H, J ) 8.0 Hz, J ) 0.7 Hz, H ortho). 13C NMR (δ,
THF-d8): 116.6 (s, CdC), 127.1 (s, CH meta), 128.1 (s, CH
para), 132.0 (s, CH ortho), 146.6 (s, C ipso), 192.0 (s, CdO).
IR (KBr, cm-1): 1661 (s, CdO), 1586 (s, CdO), 1480 (m, Cd
C), 894 (m, C-S), 727 (m, C6H5), 690 (m, C6H5), 464 (m, C6H5).
MS (EI) (m/z (ion, relative intensity)): 379, 377 (M+, 80), 351,
349 ((M - CdO)+, 12), 200, 198 (PhSb+, 100). Anal. Calcd for
C9H5OS4Sb: C, 28.51; H, 1.33. Found: C, 29.17; H, 1.33.
Syn th esis of P h en yl(1,3-d ith iole-2-th ion e-4,5-d ith iola -
to)a n tim on y(III) (4). A solution of 4,5-bis((2-cyanoethyl)thio)-
1,3-dithiole-2-thione (3′; 2 g, 6.58 mmol) in 40 mL of THF was
treated with a solution of Me4NOH (4.8 g, 25 wt % in MeOH,
13.2 mmol) in 10 mL of THF. A blue precipitate of (Me4N)2-
(dmit) was formed within a few minutes and after 30 min of
stirring dichlorophenylstibine (1.8 g, 6.6 mmol) in 10 mL THF
was rapidly added. The resulting deep orange solution was
stirred for 2 h and then filtered through Celite in order to
remove the precipitated Me4NCl and eluted through a short
silica gel column with THF. After evaporation of almost all
the solvent, precipitation upon addition of pentane, filtration
on a glass frit, washing of the resulting powder with methanol
and then with pentane and finally drying under vacuum, 4
was recovered as a deep red solid. Yield: 1.9 g (73%). All the
characterizations were in agreement with the published data.6
Syn t h esis of t h e Bis(t et r a m et h yla m m on iu m ) Sa lt
of P h en ylbis(1,3-d ith iol-2-on e-4,5-d ith iola to)a n tim on y-
(III) (5). Tetramethylammonium hydroxide (0.2 g, 25 wt %
in MeOH, 0.54 mmol) in 5 mL of THF was added, with
magnetic stirring, in a Schlenk tube containing a solution of
1 (0.055 g, 0.27 mmol) in 5 mL of THF. A yellow precipitate of
(Me4N)2(dmid) rapidly appeared, and after 30 min of stirring
a solution of PhSb(dmid) (2; 0.1 g, 0.27 mmol) in 5 mL of THF
was added. An orange solid started to precipitate, and then
the resulting suspension was stirred for a further 30 min.
Filtration over a glass frit under an inert atmosphere, followed
by washing with THF and drying under vacuum, yielded 5 as
an orange solid highly sensitive to oxygen. Yield: 0.165 g
(88%). Suitable crystals for X-ray analysis have been grown
from a saturated solution of dianion 5 in acetonitrile at
-20 °C.
Exp er im en ta l Section
Gen er a l Com m en ts. The reactions were carried out under
an inert atmosphere of nitrogen by using Schlenk techniques.
Dry toluene and hexane were obtained by distillation over Na
and dry CH2Cl2 and MeCN by distillation over P2O5, and THF
was distilled over sodium and benzophenone. Nuclear mag-
netic resonance spectra were recorded for compounds 2, 4, and
8-10 on a Bruker ARX 400 spectrometer operating at 400.13
MHz for 1H and 100.62 MHz for 13C and for compounds 5-7
on a Bruker Avance DRX 500 spectrometer operating at 500.04
MHz for 1H and 125.75 MHz for 13C. Chemical shifts are
expressed in parts per million (ppm) downfield from external
TMS. The following abbreviations are used: s, singlet; d,
doublet; t, triplet; q, quartet; m, multiplet; b, broad. Mass
spectrometry was performed on an HP 5989A spectrometer
in the EI mode, with an ionization energy of 70 eV. Infrared
spectroscopy was measured on a Nicolet FTIR 20 SXC spec-
trometer. The following abbreviations are used: s, strong; m,
medium. Elemental analyses were performed by the “Service
d’Analyse du CNRS” at Gif/Yvette, France. 1,3,4,6-Tetrathia-
pentalene-2,5-dione8 (1), 4,5-bis((2-cyanoethyl)thio)-1,3-dithi-
ole-2-thione9 (3), and phenyldichlorostibine10 were prepared
according to published procedures.
(5) (a) Tan, K.; Ko, Y.; Parise, J . B.; Park, J .-H.; Darovsky, A. Chem.
Mater. 1996, 8, 2510. (b) Powell, A. V.; Boissie`re, S.; Chippindale, A.
M. Chem. Mater. 2000, 12, 182.
(6) Avarvari, N.; Faulques, E.; Fourmigue´, M. Inorg. Chem. 2001,
40, 2570.
(7) Doidge-Harrison, S. M. S. V.; Irvine, J . T. S.; Spencer, G. M.;
Wardell, J . L.; Wei, M.; Ganis, P.; Valle, G. Inorg. Chem. 1995, 34,
4581.
1H NMR (δ, CD3CN): 3.06 (s, 24H, CH3), 7.18-7.21 (m, 1H,
3
3
H para), 7.26 (t, 2H, J ) 7.1 Hz, H meta), 8.11 (d, 2H, J )
7.1 Hz, H ortho). 13C NMR (δ, CD3CN): 56.8 (t, J ) 3.9 Hz,
1
CH3), 122.6 (s, CdC), 128.7 (s, CH para), 128.9 (s, CH meta),
137.1 (s, CH ortho), 155.0 (s, C ipso), 196.5 (s, CdO).
(8) Schumaker, R. R.; Engler, E. M. J . Am. Chem. Soc. 1977, 99,
5521.
(9) Svenstrup, N.; Rasmussen, K. M.; Hansen, T. K.; Becher, J .
Synthesis 1994, 809.
(10) Nunn, M.; Sowerby, D. B.; Wesolek, D. M. J . Organomet. Chem.
1983, 251, C45.
Syn th esis of th e Bis(tetr a m eth yla m m on iu m ) Sa lt of
P h en ylbis(1,3-d ith iole-2-th ion e-4,5-d ith iola to)a n tim on y-
(III) (6). To a solution of 3 (0.25 g, 0.82 mmol) in 15 mL of
THF was added tetramethylammonium hydroxide (0.6 g, 25
wt % in MeOH, 1.64 mmol) in 5 mL of THF. After 30 min of

2044 Organometallics, Vol. 22, No. 10, 2003
Avarvari and Fourmigue´
stirring a solution of PhSb(dmit) (4; 0.32 g, 0.82 mmol) in 10
mL of THF was syringed in, and the blue precipitate of
(Me4N)2(dmit) rapidly dissolved. A deep red color appeared,
and the solution was stirred for a further 2 h. Then, precipita-
tion with hexane, filtration on a glass frit under an inert
atmosphere, and drying on a vacuum line allowed the isolation
of 6 as a red-purple solid highly sensitive to oxygen. Yield:
0.56 g (91%).
Syn th esis of th e Tetr a eth yla m m on iu m Sa lt of Dip h en -
ylbis(1,3-dith iole-2-th ion e-4,5-dith iolato)an tim on y(V) (9).
NEt4OH (1.94 g, 25 wt % in MeOH, 3.3 mmol) in 5 mL of THF
was added in a Schlenk tube containing a solution of 3 (0.5 g,
1.65 mmol) in 15 mL of THF. A violet suspension rapidly
formed, and after 30 min of stirring PhSbCl2 (0.23 g, 0.83
mmol) in 5 mL of THF was added in one portion. The resulting
red solution was stirred for 2 h, and after this period a second
1 equiv of PhSbCl2 (0.23 g, 0.83 mmol) in 10 mL of THF was
added dropwise. The mixture thus formed was stirred for 3 h,
and then it was filtered first through Celite and second
through a neutral alumina column with AcOEt as solvent.
After evaporation, precipitation with pentane, filtration, and
drying 9 was recovered as a red solid. Yield: 0.25 g (38%).
Deep red crystals were obtained by slow diffusion of hexane
into a solution of 9 in THF. 1H NMR and IR spectra are in
good agreement with already published data.11 The 13C NMR
spectrum was not reported in ref 11; therefore, it is presented
here.
1H NMR (δ, CD3CN): 3.06 (s, 24H, CH3), 7.21-7.25 (m, 1H,
3
3
H para), 7.30 (t, 2H, J ) 7.2 Hz, H meta), 8.05 (d, 2H, J )
7.2 Hz, H ortho). 13C NMR (δ, CD3CN): 56.8 (t, J ) 3.9 Hz,
1
CH3), 129.2 (s, CH para), 129.3 (s, CH-meta), 136.8 (s, CH
ortho), 137.1 (s, CdC), 154.0 (s, C ipso), 213.9 (s, CdS).
Syn th esis of th e Bis(tetr a m eth yla m m on iu m ) Sa lt of
P h en yl(1,3-d ith iole-2-th ion e-4,5-d ith iola to)(1,3-d ith iol-2-
on e-4,5-d ith iola to)a n tim on y(III) (7). In a Schlenk tube
containing 1 (0.105 g, 0.51 mmol) in 10 mL of THF, Me4NOH
(0.37 g, 25 wt % in MeOH, 1.02 mmol) in 5 mL of THF was
added. Rapid formation of (Me4N)2(dmid) occurred, and after
30 min of stirring, a solution of PhSb(dmit) (4; 0.2 g, 0.51
mmol) in 20 mL THF was syringed in. The red suspension thus
obtained was stirred for 2 h, and then hexane was added in
order to precipitate all the dianionic salt. The mixed bis-
(dithiolene) complex 7 was recovered as a red solid, sensitive
to oxygen, after filtration, washing with hexane, and drying
under vacuum. Yield: 0.33 g (90%).
13C NMR (δ, CD3CN): 7.1 (s, CH3), 52.5 (s, CH2), 128.5 (s,
CH meta), 129.9 (s, CH para), 132.9 (s, CH ortho), 135.1 (s,
CdC), 141.7 (s, CdC), 152.2 (s, C ipso), 212.0 (s, CdS). Anal.
Calcd for C26H30NS10Sb: C, 39.09; H, 3.78. Found: C, 38.27;
H, 3.74.
Syn th esis of th e Tetr a eth yla m m on iu m Sa lt of Dip h en -
yl(1,3-d ith iole-2-th ion e-4,5-d ith iola to)(1,3-d ith iol-2-on e-
4,5-d ith iola to)a n tim on y(V) (10). To a solution of 1 (0.11 g,
0.5 mmol) in 10 mL of THF was added Et4NOH (0.6 g 25 wt
% in MeOH, 1 mmol) in 5 mL of THF. The orange suspension
thus obtained was stirred for 30 min, and then a solution of
PhSb(dmit) (4; 0.2 g, 0.5 mmol) in 10 mL of THF was added.
The resulting solution, which became rose red upon addition,
was stirred for a further 2 h. After this period PhSbCl2 (0.14
g, 0.5 mmol) in 5 mL of THF was added dropwise and a color
change to deep red was observed. Formation of 10 was
assumed to be complete after 3 h of stirring, and then the
mixture was filtered through Celite and chromatographed
through neutral alumina with acetone as solvent. Removal of
solvent, precipitation with pentane, and filtration on a glass
frit allowed the isolation of 10 as a red solid. Yield: 0.15 g
(38%). Single crystals were grown by diffusion of hexane into
a THF solution of 10.
1H NMR (δ, CD3CN): 3.06 (s, 24H, CH3), 7.22-7.23 (m, 1H,
3
3
H para), 7.28 (t, 2H, J ) 7.2 Hz, H meta), 8.07 (d, 2H, J )
7.2 Hz, H ortho). 13C NMR (δ, CD3CN): 56.8 (t, J ) 3.9 Hz,
1
CH3), 122.1 (s, CdC), 128.9 (s, CH para), 129.1 (s, CH meta),
136.9 (s, CH ortho), 138.2 (s, CdC), 154.4 (s, C ipso), 196.2 (s,
CdO), 213.7 (s, CdS).
Syn th esis of th e Tetr a eth yla m m on iu m Sa lt of Di-
ph en ylbis(1,3-dith iol-2-on e-4,5-dith iolato)an tim on y(V) (8).
Meth od A. To a solution of 1 (0.5 g, 2.4 mmol) in 30 mL of
THF was added Et4NOH (2.83 g, 25 wt % in MeOH, 4.8 mmol)
in 10 mL of THF with magnetic stirring. An orange suspension
was rapidly formed, and after 30 min of stirring, PhSbCl2 (0.33
g, 1.2 mmol) in 5 mL of THF was added in one portion.
Formation of the bis(dithiolate) was considered to be complete
after 2 h of stirring, and then the second 1 equiv of PhSbCl2
(0.33 g, 1.2 mmol) in 5 mL of THF was slowly added. The red
suspension thus formed was stirred for a further 3 h and then
filtered through Celite. Fast elution through neutral alumina
with ethyl acetate (AcOEt), evaporation of almost all the
solvent, precipitation with pentane, filtration, and drying
under vacuum yielded 8 as a red air-stable solid. Yield: 0.3 g
(33%).
3
1H NMR (δ, THF-d8): 1.23 (t, 12H, J ) 7.2 Hz, CH3), 3.20
(q, 8H, 3J ) 7.2 Hz, CH2), 7.19-7.24 (m, 6H, H para and meta),
7.69-7.73 (m, 4H, H ortho). 13C NMR (δ, THF-d8): 7.9 (s, CH3),
53.3 (s, CH2), 124.2 (s, CdC), 125.0 (s, CdC), 128.6 (s, CH
meta), 128.7 (s, CH meta), 128.7 (s, CH meta), 128.8 (s, CH
meta), 129.7 (s, CH para), 129.8 (s, CH para), 129.9 (s, CH
para), 130.0 (s, CH para), 130.9 (s, CdC), 131.0 (s, CdC), 134.0
(s, CH ortho), 134.1 (s, CH ortho), 134.2 (s, CH ortho), 134.8
(s, CdC), 135.4 (s, CdC), 142.0 (s, CdC), 153.6 (s, C ipso), 154.0
(s, C ipso), 154.1 (s, C ipso), 154.5 (s, C ipso), 191.9 (s, CdO),
192.0 (s, CdO), 211.4 (s, CdS), 211.6 (s, CdS). IR (KBr, cm-1):
1662 (s, CdO), 1610 (s, CdO), 1474 (m, CdC), 1425 (m, Cd
C), 1058 (s, CdS), 898 (m, C-S), 733 (m, C6H5), 690 (m, C6H5),
461 (m, C6H5). Anal. Calcd for C26H30NOS9Sb: C, 39.89; H,
3.86. Found: C, 39.39; H, 3.91.
Meth od B. The same conditions were employed as in
method A to generate the dithiolate. Then a solution of PhSb-
(dmid) (2; 0.91 g, 2.4 mmol) in 10 mL of THF was syringed in
and the resulting orange-red suspension was stirred for a
further 2 h. After this period PhSbCl2 (0.65 g, 2.4 mmol) in 10
mL of THF was added dropwise and the color rapidly changed
to red upon addition. After 3 h of stirring the resulting mixture
was worked up as in method A. Yield: 0.75 g (41%).
Suitable single crystals for X-ray analysis were grown by
slow diffusion of hexane into a THF solution of 8 (monoclinic
phase 8a ) or by cooling to -18 °C a THF-toluene solution of
8 (orthorhombic phase 8b).
X-r a y Cr ysta llogr a p h y. Details about data collection and
solution refinement are given in Table 1. Data were collected
on a Stoe-IPDS imaging plate system for all the compounds.
The structure for 5 was solved by Patterson methods, and the
other structures were solved by direct methods (SHELXS); all
were refined (SHELXL-97)12 by full-matrix least-squares
methods. Absorption corrections were made for every struc-
ture. Hydrogen atoms were introduced at calculated positions
3
1H NMR (δ, THF-d8): 1.17 (t, 12H, J ) 7.2 Hz, CH3), 3.16
(q, 8H, 3J ) 7.2 Hz, CH2), 7.16-7.26 (m, 6H, H para and meta),
7.70 (dd, 4H, 3J ) 7.4 Hz, 4J ) 1.47 Hz, H ortho). 13C NMR (δ,
THF-d8): 5.2 (s, CH3), 50.6 (s, CH2), 121.5 (s, CdC), 125.9 (s,
CH meta), 127.0 (s, CH para), 128.1 (s, CdC), 131.3 (s, CH
ortho), 151.4 (s, C ipso), 189.1 (s, CdO). IR (KBr, cm-1): 1657
(s, CdO), 1607 (s, CdO), 1474 (m, CdC), 890 (m, C-S), 729
(11) Howie, R. A.; Low, J . N.; Spencer, G. M.; Wardell, J . L.
Polyhedron 1997, 16, 2563.
(12) Sheldrick, G. M. Programs for the Refinement of Crystal
Structures; University of Go¨ttingen, Go¨ttingen, Germany, 1997.
(m, C6H5), 688 (m, C6H5), 452 (m, C6H5). Anal. Calcd for C26H30
NO2S8Sb: C, 40.73; H, 3.94. Found: C, 40.12; H, 4.09.
-

Organoantimony(III) Dithiolene Complexes
Organometallics, Vol. 22, No. 10, 2003 2045
Ta ble 1. Cr ysta llogr a p h ic Da ta
8a 8b
C26H30NO2S8Sb C26H30NO2S8Sb C26H30NS10Sb
2
5
9
10
formula
fw
C9H5OS4Sb
379.12
C20H29N2O2S8Sb
707.68
C26H30NOS9Sb
782.80
766.74
766.74
798.86
temp (K)
cryst syst
space group
a (Å)
b (Å)
c (Å)
293
250
293
293
293
293
monoclinic
P21/ c (No. 14)
10.087(2)
16.123(3)
14.689(3)
99.06(3)
2359.1(8)
8
orthorhombic
P212121 (No. 19)
12.606(3)
14.742(3)
16.379(3)
90.00
3044.0(10)
4
1.544
monoclinic
P21/ c (No. 14)
16.1301(10)
12.5159(10)
17.0510(10)
112.161(10)
3188.0(4)
4
orthorhombic
Pbca (No. 61)
18.886(4)
12.885(3)
26.254(5)
90.00
6389(2)
8
1.594
monoclinic
P21/ c (No. 14)
16.800(3)
12.457(3)
17.418(4)
112.94(3)
3356.6(12)
4
monoclinic
P21/ c (No. 14)
16.503(3)
12.462(3)
17.325(4)
112.92(3)
3281.8(11)
4
â (deg)
V (Å3)
Z
dcalcd (g cm-3
)
2.135
3.014
0.71073
1.597
1.415
0.71073
1.581
1.463
0.71073
1.584
1.436
0.71073
µ (mm-1
)
1.475
0.71073
1.412
0.71073
λ(Mo KR) (Å)
cryst size (mm)
2θ range (deg)
0.25 × 0.08 × 0.03 0.25 × 0.25 × 0.2 0.52 × 0.3 × 0.1 0.3 × 0.2 × 0.13 0.7 × 0.32 × 0.1 0.66 × 0.1 × 0.08
3.8-51.7
4.1-52.1
5915
2.8-52.0
6243
3.8-51.8
6114
4.1-51.9
6408
4.1-51.8
6281
no. of unique rflns 4433
no. of obsd data
(I > 2σ(I))
3593
4659
4651
3816
4636
4097
no. of params
R1
271
306
343
343
343
361
0.026
0.053
0.98
0.031
0.056
0.98
0.032
0.095
1.10
0.032
0.057
0.86
0.025
0.045
0.85
0.029
0.054
0.82
wR2 (all data)
goodness of fit
Sch em e 1
F igu r e 1. ORTEP view and numbering scheme of one
independent molecule (Sb1) of PhSb(dmid), with 50%
probability displacement ellipsoids. Hydrogen atoms have
been omitted. Dashed bonds represent intermolecular short
contacts.
(riding model), included in structure factor calculations, and
not refined. All the heavy atoms were refined anisotropically.
Resu lts a n d Discu ssion
hereafter, on general positions in the unit cell, which
are not chemically significantly different (Figure 1).
The primary coordination pattern about Sb atom
consists, as expected, of two S (dithiolato) atoms and
one C (ipso) atom, with the phenyl group practically
perpendicular to the S-Sb-S plane, and values for bond
lengths and angles in the normal range (Table 2).
In both independent molecules, the antimony atom
completes its coordination sphere by two secondary
contacts of Sb- - -O and Sb- - -S type, shorter than the
sum of van der Waals radii (about 3.6 and 3.9 Å,
respectively),14 located in the least-squares equatorial
plane along with the two dithiolene sulfur atoms. The
deviation of Sb from this mean plane amounts to 0.1 Å
for Sb1 and 0.36 Å for Sb2. The Sb- - -O contacts, with
values of 2.891(3) Å for Sb1 and 3.422(3) Å for Sb2, are
established between the same type of molecules, whereas
a crossed situation is observed for the Sb- - -S (thiolato)
interactions, with values of 3.422(1) Å (Sb1- - -S5) and
3.315(1) Å (Sb2- - -S1). Altogether, the coordination
geometry around Sb is of distorted-octahedral type if
one takes into account the 5s2 lone pair, probably lying
trans to the phenyl group. An interesting geometrical
parameter, characteristic for a coordinated dithiolene
Syn th esis a n d Cr ysta l Str u ctu r e of P h Sb(d m id ).
The first attempts to synthesize the complex 2 consisted
of deprotection of 4,5-bis((2-cyanoethyl)thio)-1,3-dithiole-
2-one (3) with 2 equiv of base, followed by reaction with
phenyldichlorostibine, but for any deprotection condi-
tions we tried, such as different bases and solvents, no
desired compound was recovered. This preference for
the starting reagent 3 was motivated by the successful
synthesis of PhSb(dmit) (4) by the same route, using 3′
as the protected dmit and Me4NOH as base (Scheme
1).
This preparation method of 4 parallels that already
published,6 although a higher yield has been now
obtained. The failure of this method in the synthesis of
2 is very likely due to the competition between hydrogen
abstraction in the position R to the CN group and
nucleophilic attack on CdO, leading to a mixture of
thiolates. Reaction of compound 1, the masked dmid,
by deprotection with base and quenching with PhSbCl2
afforded 2 as a yellow solid. A fast addition of dichlo-
rophenylstibine in the dithiolate solution appears to be
crucial; otherwise, 2 is obtained in very low yield, as
discussed below. Assignment of 1H and 13C NMR signals
were made by comparison with published data for PhSb-
(dmit)6 and R2Sn(dmid)13 complexes. PhSb(dmid) crys-
tallizes in the monoclinic system, space group P21/c,
with two independent molecules, named as Sb1 and Sb2
(13) Chohan, Z. H.; Howie, R. A.; Wardell, J . L. J . Organomet. Chem.
1999, 577, 140.
(14) (a) Bondi, A. J . J . Phys. Chem. 1964, 68, 441. (b) Spackman,
M. A. J . Chem. Phys. 1986, 85, 6579.

2046 Organometallics, Vol. 22, No. 10, 2003
Avarvari and Fourmigue´
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 2 a n d 5
Compound 2
Bond Lengths
Sb1-S1
Sb1-S2
Sb1-C4
Sb1- - -O1
Sb1- - -S5
2.493(1)
2.466(1)
2.163(3)
2.891(3)
3.422(1)
Sb2-S5
2.497(1)
2.449(1)
2.139(4)
3.422(3)
3.315(1)
Sb2-S6
Sb2-C13
Sb2- - -O2
Sb2- - -S1
Bond Angles
S1-Sb1-S2
S1-Sb1-C4
S2-Sb1-C4
S1-Sb1-S5
S2-Sb1-O1
S5-Sb1-O1
86.68(3)
95.71(9)
100.35(9)
76.27(3)
65.31(6)
131.44(5)
S5-Sb2-S6
S5-Sb2-C13
S6-Sb2-C13
S6-Sb2-S1
S5-Sb2-O2
S1-Sb2-O2
85.95(4)
100.48(9)
97.30(10)
74.23(3)
72.12(7)
125.51(7)
Compound 5
Bond Lengths
Sb1-S1
Sb1-S2
Sb1-S5
2.935(1)
2.576(1)
2.871(1)
Sb1-S6
2.569(1)
2.171(4)
Sb1-C7
F igu r e 2. “Sb4S4” tetrameric motif in the structure of
PhSb(dmid). Dashed, filled bonds represent intermolecular
Sb- - -S or Sb- - -O contacts, whereas the dashed, open bond
evidences the intermolecular Sb2- - -Sb2 contact.
Bond Angles
S1-Sb1-S2
S5-Sb1-S6
S1-Sb1-S5
S2-Sb1-S6
78.89(4)
77.18(5)
118.14(4)
85.89(4)
C7-Sb1-S1
C7-Sb1-S2
C7-Sb1-S5
C7-Sb1-S6
86.78(12)
91.88(13)
83.48(12)
95.50(13)
Sch em e 2
ligand, is the dihedral angle about the S- - -S hinge
within the five-membered C2S2Sb metallacycle. We can
observe from Table 4 that the values for Sb1 and Sb2
are quite different, although the distortion is in the
same direction. Theoretical calculations in the case of
heteroleptic dithiolene complexes have shown that the
rotation barrier around the S- - -S axis is rather low:
hence, the role of packing forces in this type of distor-
tion.15 The alternate Sb1- - -S5 and Sb2- - -S1 short
secondary contacts run in such a manner that they lead
to the formation of a centrosymmetric cyclic octagonal
“Sb4S4” motif, represented in Figure 2, as a result of a
formal tetramerization of the PhSb(dmid) molecule.
This type of cyclic pattern can be also identified in
the structure of open-framework antimony sulfides.5b
The octagon is “compressed” along the Sb2- - -Sb2 axis,
the corresponding distance, which amounts to 3.963(1)
Å, being shorter by about 0.3 Å than the sum of van
der Waals radii of two Sb atoms.16 Furthermore, each
[Ph(Sb(dmid)]4 tetramer is not isolated but interacts
with eight other tetramers via Sb- - -O interactions, thus
leading to the formation of an original extended 3D
network. Unlike the structure of PhSb(dmit), of chain-
like type with transversal S- - -S interactions, no short
intermolecular S- - -S contacts occur this time. In con-
clusion, counting on the the coordinative unsaturation
of the Sb(III) center, we induced a huge modification of
the 3D network in the crystalline state when comparing
the structures of PhSb(dmit) and PhSb(dmid), only by
changing CdS with CdO in the structure of the dithio-
lene ligand.
to a low yield in PhSb(dmid) but afforded instead the
salt of the [Ph2Sb(dmid)2]- anion, with Sb in the +5
oxidation state coordinated to two dithiolene ligands
(vide infra). This Sb(V) species is likely to be formed by
oxidation of a dianionic [PhSbIII(dmid)2]2- intermediate.
The latter was indeed obtained from the reaction of 1
equiv of neutral PhSb(dmid) with (Me4N)2(dmid) or by
the fast addition of 0.5 equiv of PhSbCl2 in a (Me4N)2-
(dmid) suspension (Scheme 2). 5 was purified by recrys-
tallization in CH3CN to afford an orange crystalline
solid sensitive to oxygen and moisture.
The complex crystallized in the orthorhombic system,
space group P212121, with the two Me4N+ cations and
the dianion (Figure 3) in general positions in the unit
cell. Values for bond lengths and angles are listed in
Table 2.
Interestingly, both dithiolene ligands are coordinated
in an unsymmetrical manner on the antimony center,
with one “short” and one “long” antimony-sulfur bond
for each of them. The “short” bonds, Sb1-S2 (2.576(1)
Å) and Sb1-S6 (2.569(1) Å), are on average about 0.1
Å longer than Sb-S bonds in neutral complexes, whereas
the “long” bonds, Sb1-S1 (2.935(1) Å) and Sb1-S5
(2.871(1) Å), are significantly longer and approach the
characteristic values for secondary Sb- - -S contacts.5
This latter feature suggests that S1 and S5 bear an
important negative charge and, hence, a significant
Syn th esis a n d Ch a r a cter iza tion of [P h SbIII(d i-
th iolen e)2]2- Com p lexes. As mentioned earlier, a slow
addition of PhSbCl2 in the dithiolate suspension leads
(15) Domercq, B.; Coulon, C.; Fourmigue´, M. Inorg. Chem. 2001, 40,
371.
(16) Much shorter intermolecular Sb- - -Sb contacts, of about 3.6-
3.7 Å, have been observed in the solid-state structure of distibines
presenting a thermochromic activity: (a) Ashe, A. J ., III; Butler, W.;
Diephouse, T. R. J . Am. Chem. Soc. 1981, 103, 207. (b) Mundt, O.;
Riffel, H.; Becker, G.; Simon, A. Z. Naturforsch., B 1984, 39B, 317.

Organoantimony(III) Dithiolene Complexes
Organometallics, Vol. 22, No. 10, 2003 2047
Sch em e 3
F igu r e 3. ORTEP view and numbering scheme of
[PhSb(dmid)2]2- in 5, with 50% probability displacement
ellipsoids. Hydrogen atoms have been omitted.
nucleophilic character, which could explain the further
reactivity of the complex. The four coordinating sulfur
atoms are in the equatorial plane, with a relative cis
arrangement of the “short” and, respectively, “long”
Sb-S bonds, from which Sb deviates by about 0.06 Å.
The phenyl ring is practically perpendicular to this
plane, and the Sb lone pair is very likely located trans
to Cipso, which leads to a distorted-octahedral coordina-
tion geometry. Since the antimony is pentacoordinated,
this geometry should be fluxional in solution.17 Both
dithiolene ligands are highly folded (38.87 and 54.81°,
respectively) along the S- - -S hinge, with distortions in
the opposite direction when compared with the neutral
PhSb(dmid) (Table 4). No additional intermolecular
Sb- - -S or S- - -S short contacts are observed within this
structure, which represents the first example of a
dianionic antimony dithiolene complex.
F igu r e 4. ORTEP view and numbering scheme of
[Ph2Sb(dmid)2]- in 8a , with 50% probability displacement
ellipsoids. Hydrogen atoms have been omitted.
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 8a a n d 8b
8a
8b
Bond Lengths
2.540(1)
Sb-S1
Sb-S2
Sb-S5
Sb-S6
Sb-C7
Sb-C13
2.557(1)
2.608(1)
2.529(1)
2.577(1)
2.165(3)
2.153(3)
2.628(1)
2.534(1)
2.640(1)
2.170(5)
The same strategy was applied to the synthesis of 6,
the dmit analogue of 5, by deprotection of 3 with
Me4N+OH-, followed by the reaction of the resulting
dithiolate with 1 equiv of PhSb(dmit). The mixed dmid/
dmit dianion 7 was also synthesized, by base deprotec-
tion of the dmid precursor 1 and trapping with 1 equiv
of PhSb(dmit). Very likely, this mixed bis(dithiolene)
complex is a statistical mixture of 5-7, with eventually
a preference for the unsymmetrical compound as ob-
served in mixed nickel bis(dithiolene) complexes.18 By
the successful preparation of this series of dianionic
complexes 5-7, we have in our hands the supposed key
intermediates in the synthesis of the [Ph2SbV(dithio-
lene)2]- type complexes.
2.158(5)
Bond Angles
80.11(5)
S1-Sb-S2
S5-Sb-S6
S1-Sb-S6
S2-Sb-S5
S2-Sb-S6
C7-Sb-S1
C7-Sb-S2
C7-Sb-S5
C7-Sb-C13
C13-Sb-S1
C13-Sb-S5
C13-Sb-S6
79.25(4)
80.55(4)
92.36(4)
94.70(3)
80.71(3)
91.55(9)
89.52(9)
94.54(9)
98.00(12)
92.46(10)
92.72(10)
92.52(10)
80.33(5)
89.69(5)
90.69(5)
86.30(5)
96.83(14)
89.74(14)
92.42(14)
94.18(19)
92.46(13)
96.14(13)
90.67(14)
Syn th esis a n d Ch a r a cter iza tion of [P h 2SbV(d i-
th iolen e)2]- Com p lexes. Mech a n istic Discu ssion s.
To study the reactivity of the [PhSbIII(dithiolene)2]2-
series with a second 1 equiv of PhSbCl2, the dianions
was established by a single-crystal X-ray measurement.
Single crystals of the first polymorph, named 8a , have
been grown by slow diffusion of hexane into a THF
solution of the complex. The compound crystallized in
the monoclinic system, space group P21/c, with one
anion and one tetrahedral ammonium cation in general
positions. An ORTEP representation of [Ph2Sb(dmid)2]-
is shown in Figure 4, and important bond lengths and
angles are listed in Table 3.
The antimony center, now in the +5 oxidation state,
is hexacoordinated, within a distorted-octahedral field.
In such an environment, Sb(V) is coordinatively satu-
rated: hence, the absence of any Sb- - -S or Sb- - -O
secondary short contact. One can note the cis arrange-
ment of the phenyl groups; therefore, each dithiolene
+
5′-7′ have been generated as NEt4 salts, since they
+
are more soluble than the corresponding NMe4 salts
5-7. Addition of PhSbCl2 to the suspension of 5′ and
purification workup afforded the complex 8 as the single
reaction product, in a moderate yield (Scheme 3).
Attempts to isolate or to identify other reaction
byproducts have been unsuccessful. The structure of 8
(17) Barucki, H.; Coles, S. J .; Costello, J . F.; Hursthouse, M. B. J .
Organomet. Chem. 2001, 622, 265.
(18) (a) Davison, A.; McCleverty, J . A.; Shawl, E. T.; Wharton, E. J .
J . Am. Chem. Soc. 1967, 89, 830. (b) Kato, R.; Kashimura, Y.; Sawa,
H.; Okano, Y. Chem. Lett. 1997, 921.

2048 Organometallics, Vol. 22, No. 10, 2003
Avarvari and Fourmigue´
Sch em e 4
Ta ble 4. Dih ed r a l An glesa (d eg)
S1-Sb-S2
S5-Sb-S6
2
5
8a
8b
-19.71(7)
38.87(16)
43.08(21)
-49.68(10)
-26.17(11)
54.81(10)
39.64(12)
-49.51(10)
a
Negative values correspond to a dithiolene deviation toward
the phenyl rings.
the reaction of intermediary dianions with a second 1
equiv of PhSbCl2 appears to be more complex, since it
implies the phenyl transfer accompanied by the oxida-
tion of Sb(III) in Sb(V). However, we can attempt to
explain this second stage (Scheme 4) and reasonably
imagine a nucleophilic attack of a coordinated sulfur
atom, still bearing an important negative charge (vide
supra), on PhSbCl2 leading to an intermediate adduct
with concomitant elimination of 1 equiv of NEt4Cl.
F igu r e 5. ORTEP view and numbering scheme of
[Ph2Sb(dmid)2]- in 8b, with 50% probability displacement
ellipsoids. Hydrogen atoms have been omitted.
ligand is unsymmetric, with distances slightly longer
for the Sb-S bonds trans to Sb-Cipso than for the pair
of Sb-S bonds trans to each other. Nevertheless, bond
lengths and angles are in the usual range.11,19 Both
dithiolene ligands are highly folded along the S- - -S
hinge, back toward the phenyl rings, in a face-to face
conformation, with calculated values for the dihedral
angles of 43.08° (S1- - -S2) and 39.64° (S5- - -S6)
(Table 4).
Interestingly, the dithiolene folding is in the opposite
direction, toward the phenyl rings, in the case of the
second polymorph 8b, represented in Figure 5, crystal-
lized this time by cooling a THF-toluene solution of 8.
The two dihedral angles have now values of -49.68°
(S1- - -S2) and -49.51° (S5- - -S6). This second poly-
morph crystallized in the orthorhombic system, space
group Pbca, with the anion and cation in general
positions.
Bond lengths and angles (Table 3) are in the normal
range, the only striking difference on comparison with
8a being the torsion angles previously discussed. At
room temperature the molecule is fluxional in solution
on the NMR time scale. Indeed, the phenyl groups are
equivalent by 1H and 13C NMR, as well as the dithiolene
ligands by 13C NMR. Furthermore, in 13C NMR spectra
we can observe two signals for the CdC dithiolene
carbon atoms, at 121.5 and 128.1 ppm, proving that we
have only the cis stereoisomer in solution, since the two
carbon atoms in each dithiolene are connected to non-
equivalent sulfur atoms.
Formation of [Ph2SbV(dithiolene)2]- complexes di-
rectly from dithiolates and PhSbCl2 represents an
original and elegant route to synthesize the former class
of compounds. The mechanism of this unprecedented
transformation in antimony series very likely involves,
in a first step, the generation of reactive [PhSbIII(dithio-
lene)2]2- dianions. Isolation and unambiguous charac-
terization of these latter compounds (vide supra) strongly
support our first mechanistic hypothesis. Subsequently,
In the adduct, the antimony atoms would be bridged
by two sulfur atoms, thus forming a “Sb2S2” motif, and
in such a conformation a secondary Sb- - -Ph contact
could be established, previous to the effective phenyl
transfer. This kind of weak Sb- - -Ph interaction occurs
in solid-state structures of Ar‚SbX3 (X ) Cl, Br) com-
pounds,20 also known as Menshutkin type complexes,21
or of [PPh4]2[Sb2X8] (X ) Br, I) salts.22 Then a phenyl
transfer would lead to the final [Ph2SbV(dithiolene)2]-
after oxidation. Unfortunately, we could not isolate
or identify any but [Ph2Sb(dithiolene)2]--antimony-
containing compounds in the resulting reaction mixture.
By applying method A to the appropriate dmit pre-
cursor 3′, we synthesized the [Ph2Sb(dmit)2]- salt 9, the
sulfur counterpart of 8 (Scheme 3). Preparation of
complex 9 by a different route, involving the reaction
of preformed Sb(V) Ph2SbCl3 with [NEt4]2[Zn(dmit)2] in
the presence of KSCN, was previously reported by
Wardell et al.11 The authors described, along with IR
1
and H NMR data, the X-ray structure of the compound,
which was solved in the monoclinic system, space group
P21/n. In our case, 9 crystallized in the monoclinic
system, space group P21/c. One can observe that this
complex is isostructural with 8a ; therefore, no further
structural parameters will be discussed here but, rather,
in the Supporting Information. The distortion of dmit
ligands, in a face-to-face conformation and with corre-
sponding dihedral angles amounting to about 40°, is
exactly the same as in 8a . In the 13C NMR spectrum
two signals, at 135.1 and 141.7 ppm, are observed for
CdC carbon atoms. This feature, along with the singlets
observed for Cipso and CdS carbon atoms, unambigu-
ously indicates the cis stereochemistry of 9 also in
solution.
(20) (a) Mundt, O.; Becker, G.; Stadelmann, H.; Thurn, H. Z. Anorg.
Allg. Chem. 1992, 617, 59. (b) Schmidbaur, H.; Nowak, R.; Huber, B.;
Mu¨ller, G. Organometallics 1987, 6, 2266. (c) Hulme, R.; Mullen, D. J .
E. J . Chem. Soc., Dalton Trans. 1976, 802.
(21) Menshutkin, B. N. Zh. Russ. Fiz. Chim. Ova. 1911, 43, 1298.
(22) (a) Pohl, S.; Saak, W.; Haase, D. Angew. Chem. 1987, 99, 462.
(b) Pohl, S.; Saak, W.; Lotz, R.; Haase, D. Z. Naturforsch., B 1990,
45B, 1355.
(19) Spencer, G. M.; Wardell, J . L.; Aupers, J . H. Polyhedron 1996,
15, 2701.

Organoantimony(III) Dithiolene Complexes
Organometallics, Vol. 22, No. 10, 2003 2049
Sch em e 5
The mixed dmid/dmit Sb(V) dithiolene complex,
(BHET), in which antimony(III)-containing complexes,
such as antimony ethylene glycolate [Sb2(OCH2CH2O)3]n,
were utilized as catalysts.23 Conversely, both features
can lead in the solid state to a huge variety of structures,
as emphasized through the examples described so far.
[NEt4][Ph2SbV(dmit)(dmid)] (10), was also synthesized
by generating first the mixed dianion [NEt4]2[PhSbIII
-
(dmit)(dmid)] (7′), which was then quenched by 1 equiv
of PhSbCl2, as depicted in Scheme 3. Single crystals of
10, grown by slow diffusion of hexane into a THF
solution of the complex, crystallized in the monoclinic
system, group space P21/c, and the compound proved
to be isostructural with its congeners 8a and 9. An
occupational disorder was found for terminal CdX
(X ) O, S) and refined at 0.6 O and 0.4 S5′ occupational
factors for C6dX and 0.4 O′ and 0.6 S5 occupational
factor for C3dX. However, this X-ray measurement did
not allow us to determine whether we crystallized a pure
compound or cocrystallized a statistic mixture of 8a , 9,
and 10. 13C NMR spectra of THF-d8 solutions of 10, one
obtained from single crystals and the other from a
powder, were similar, with signals characterizing a
mixture of 8-10 in a roughly statistical (1/1/2) ratio.
The question arises whether this statistical mixture is
only the consequence of the obvious rearrangement,
previous to the reaction with PhSbCl2, of the intermedi-
ary dianion 7, in fact a mixture of 5-7, or if also 8-10,
Con clu sion s
New neutral and anionic organoantimony dithiolene
complexes have been synthesized and characterized.
The neutral complex PhSb(dmid) forms an original 3D
network in the solid state, based on interacting octago-
nal cyclic motifs of “Sb4S4” type. Short intermolecular
Sb- - -S and Sb- - -O contacts have been identified in this
structure. To rationalize the unexpected formation of
the anionic [Ph2SbV(dmid)2]- complex as a secondary
product in the synthesis of PhSb(dmid), we prepared a
series of highly reactive [PhSbIII(dithiolene)2]2- salts.
These were thought to be key intermediates in the new
and original synthesis of [Ph2SbV(dithiolene)2]- com-
plexes. By analyzing the single-crystal X-ray structure
of [Me4N]2[PhSbIII(dmid)2], in which Sb(III) center is
coordinated in a distorted octahedral field if we consider
the lone pair, we can conclude that two out of four
coordinated sulfur atoms bear an important negative
charge. This explains the reactivity of [PhSbIII(di-
thiolene)2]2- toward PhSbCl2 leading to the series of
[Ph2SbV(dithiolene)2]- species. These latter species are
octahedral complexes, as determined by single-crystal
X-ray measurements, and in the case of [Ph2Sb(dmid)2]-
two polymorphs, differing in the coordinated dithiolene
conformation, have been crystallized. The fluxionality
of these complexes in solution, expressed in a fast
dithiolene exchange, has been evidenced by NMR mea-
surements.
1
once formed, are in equilibrium in solution. The H and
13C NMR spectra of a solution of mixture of 8-10
obtained by the “normal” synthetic procedure and those
of a solution obtained from equimolar amounts of 8 and
9 and measured immediately after mixing are exactly
the same, demonstrating the formation of the mixed
[Ph2Sb(dmit)(dmid)]- salt from 8 and 9 and showing
that the coordination of dithiolene ligands on the Sb(V)
center is quite labile, even in an octahedral environ-
ment. A plausible redistribution mechanism (Scheme
5) would involve a partial decoordination of a dithiolene
to a five-coordinate antimony species followed by a
concerted fast ligand exchange between two such inter-
mediates. Otherwise, a complete decoordination of a
dithiolene seems quite unlikely. The question whether
there is also a phenyl scrambling within these Sb(V)
complexes still remains open.
Ackn owledgm en t. Financial support from the CNRS
(Centre National de la Recherche Scientifique) is grate-
fully acknowledged.
All these experimental results show that the currently
studied organoantimony dithiolene complexes are highly
fluxional in solution and sensitive to the presence of
other donor or acceptor groups, which express the
flexibility of the antimony coordination sphere on one
hand and that of the coordinated dithiolene on the other
hand. Interestingly, the former aspect was nicely ex-
plored in solution in catalytic processes, as for example
the polycondensation of bis(hydroxyethyl)terephthalate
Su p p or tin g In for m a tion Ava ila ble: Crystallographic
data, bond distances, bond angles, anisotropic displacement
parameters, and all atom coordinates and thermal parameters
in CIF format and figures giving NMR spectra for compounds
5-7. This material is available free of charge via the Internet
at http://pubs.acs.org.
OM030056C
(23) Aharoni, S. M. Polym. Eng. Sci. 1998, 38, 1039.