Synthesis, structure and physical properties of transition metal bis 4-cyanobenzene-1,2-dithiolate complexes [M(cbdt)2]z - (M = Zn, Co, Cu, Au, Ni, Pd, z = 0, 1, 2)

Article abstract of DOI:10.1016/j.poly.2012.07.010

A series of new [M(cbdt)₂]^z- complexes of the 4-cyanobenzene-1,2-dithiolate (cbdt) ligand with a range of transition metals M (M = Zn, Co, Cu, Au, Ni, Pd) were prepared in different oxidation states (z = 0, 1, 2) as salts with several cations and characterised by X-ray diffraction, cyclic voltammetry, EPR and static magnetic susceptibility. Their properties are discussed in comparison either with the Fe analogue or corresponding complexes based on the dicyano substituted ligand (dcbdt) previously described by us. These complexes can be prepared either from the ligand dithiol as previously described for the Fe analogue, or in a more convenient way to obtain the more reduced forms, from the 4-cyanobenzene-1,3- dithiole-2-thione (1) which is described here for the first time. The structure of these complexes presents square planar coordination geometry, and belong to four distinct groups: (i) the Au monoanionic compound 4a is monoclinic, C ₂/c, where the complex presents a cis-trans disorder; (ii) the compounds 10b, 7b of the dianionic Pd and Ni complexes, are isostructural, monoclinic, P2₁/c, with the metal in an inversion centre, a perfect square-planar coordination geometry and a ligand trans configuration; (iii) the compounds (8a and 9a) of the Co and Cu dianionic complexes, which are monoclinic P2₁, with the metal located in a general position with square planar coordination and ligand trans configuration; and (iv) the monoanionic Cu compound 12 is triclinic, P1?, with the metal in a general position with almost ideal square-planar coordination and ligand trans configuration. These complexes present redox properties intermediate between those based on dcdbt and unsubstituted benzenedithiolate ligand (bdt), and the gold complex can be obtained in the neutral state. The EPR and static magnetic susceptibility measurements show that the dianionic cobalt and copper complexes (8a and 9a) the monoanionic nickel (3), and the neutral gold (11) complexes are paramagnetic corresponding to an S = state. The powder EPR spectrum of the dianionic Co complex 8a presents a hyperfine structure typical of I = 7/2 ⁵⁹Co with a component a_0x = 8.6 mT.

Full text of DOI:10.1016/j.poly.2012.07.010

Polyhedron 44 (2012) 228–237
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, structure and physical properties of transition metal bis 4-cyanobenzene-
1,2-dithiolate complexes [M(cbdt)2]zÀ (M = Zn, Co, Cu, Au, Ni, Pd, z = 0, 1, 2)
Ana C. Cerdeira a, Mónica L. Afonso a, Isabel C. Santos a, Laura C.J. Pereira a, Joana T. Coutinho a,
Sandra Rabaça a, Dulce Simão b, Rui T. Henriques b,c, Manuel Almeida a,
⇑
a Dep. Química, Instituto Superior Técnico/Instituto Tecnológico e Nuclear/CFMCUL, EN 10, P-2686-953 Sacavém, Portugal
b Departamento de Engenharia Química, Instituto Superior Técnico, Av. Rovisco Pais, P-1049-001 Lisboa, Portugal
c Instituto de Telecomunicações, Pólo de Lisboa, Instituto Superior Técnico, Av. Rovisco Pais, P-1049-001 Lisboa, Portugal
a r t i c l e i n f o
a b s t r a c t
A series of new [M(cbdt)2]zÀ complexes of the 4-cyanobenzene-1,2-dithiolate (cbdt) ligand with a range
of transition metals M (M = Zn, Co, Cu, Au, Ni, Pd) were prepared in different oxidation states (z = 0, 1, 2)
as salts with several cations and characterised by X-ray diffraction, cyclic voltammetry, EPR and static
magnetic susceptibility. Their properties are discussed in comparison either with the Fe analogue or cor-
responding complexes based on the dicyano substituted ligand (dcbdt) previously described by us. These
complexes can be prepared either from the ligand dithiol as previously described for the Fe analogue, or
in a more convenient way to obtain the more reduced forms, from the 4-cyanobenzene-1,3-dithiole-2-
thione (1) which is described here for the first time. The structure of these complexes presents square
planar coordination geometry, and belong to four distinct groups: (i) the Au monoanionic compound
4a is monoclinic, C2/c, where the complex presents a cis–trans disorder; (ii) the compounds 10b, 7b of
the dianionic Pd and Ni complexes, are isostructural, monoclinic, P21/c, with the metal in an inversion
centre, a perfect square-planar coordination geometry and a ligand trans configuration; (iii) the com-
pounds (8a and 9a) of the Co and Cu dianionic complexes, which are monoclinic P21, with the metal
located in a general position with square planar coordination and ligand trans configuration; and (iv)
Article history:
Received 18 April 2012
Accepted 8 July 2012
Available online 17 July 2012
Keywords:
Bisdithiolene complexes
4-Cyanobenzene-1,2-dithiolates
X-ray crystal structure
Cyclic voltammetry
Magnetic susceptibility
Electron paramagnetic resonance
ꢀ
the monoanionic Cu compound 12 is triclinic, P1, with the metal in a general position with almost ideal
square-planar coordination and ligand trans configuration. These complexes present redox properties
intermediate between those based on dcdbt and unsubstituted benzenedithiolate ligand (bdt), and the
gold complex can be obtained in the neutral state. The EPR and static magnetic susceptibility measure-
ments show that the dianionic cobalt and copper complexes (8a and 9a) the monoanionic nickel (3), and
the neutral gold (11) complexes are paramagnetic corresponding to an S = ½ state. The powder EPR spec-
trum of the dianionic Co complex 8a presents a hyperfine structure typical of I = 7/2 59Co with a compo-
nent a0x = 8.6 mT.
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
moments these complexes have been choice building blocks
for preparing conducting and magnetic molecular materials
Transition metal bisdithiolene complexes have, for almost
40 years, attracted considerable interest and became increas-
ingly important in many fields including materials science,
analytical chemistry, catalysis and biological systems [1]. The
[1c]. In this respect bisdithiolene complexes are quite promis-
ing when in a square planar coordination geometry, and based
on extended and delocalised
p-ligands because these features
are expected simultaneously to stabilize
a
wider range of
bisdithiolene complexes are known to exist in
a
variety of
accessible oxidation states and allow larger solid state inter-
molecular interactions.
oxidation states largely determined by the nature of the ligand
and its variable contribution to the redox processes. Depend-
ing on the oxidation state and on the transition metal, these
complexes can bear different magnetic moments. As a conse-
quence of their rich variety of oxidation states and magnetic
We have focused our research interests in exploring new com-
plexes with different ligands with variable degrees of extension
and capable of stabilizing higher and partial oxidation states since
the redox processes in these complexes are largely ligand centred.
Among many others we have studied complexes based on the li-
gand 4,5-dicyanobenzene-1,2-dithiolate, (dcbdt), and reported
the series [M(dcbdt)2]zÀ with different transition metals M = Ni,
⇑
Corresponding author.
E-mail address: malmeida@itn.pt (M. Almeida).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.07.010

A.C. Cerdeira et al. / Polyhedron 44 (2012) 228–237
229
Cu, Au Pd, Pt, Fe and Co, which were found to exist in a variety of
easily accessible oxidation states (z = 0.4, 1, 2) [2]. None of these
complexes could be obtained in the neutral state, which recently
became very attractive since it was found to provide examples of
compounds with high electrical metallic conductivity [3], but some
of them can exist in an unusual partially oxidised state with z = 0.4
and salts such as (n-Bu4N)2 [M(dcbdt)2]5 with M = Au, Ni and Cu
were found to be associated with relatively high electrical conduc-
tivity in the solid state [4].
More recently we reported the synthesis of the related asym-
metrically monosubstituted cyano ligand cbdt = 4-cyanobenzene-
1,2-dithiolate and described its Fe complex [5]. Asymmetrically
substituted bisdithiolene complexes have been a lot less explored
despite their interest [6], namely due to potential applications in
optoelectronics [7] or as building blocks for materials with inter-
esting magnetic properties [8]. Trans cyano substituted dithiolene
complexes have recently been particularly suitable for preparing
heterometallic chains by CN coordination to other metallic centres
[8b,9]. In this paper we describe the synthesis and characterisation
of other transition metal complexes with this ligand [M(cbdt)2]
(M = Cu, Ni, Au, Pd, Co, Zn), which are prepared by an entirely
new route and their properties are compared with the analogues
with the unsubstituted benzenedithiolate (bdt) and dcbdt ligands.
was stirred at room temperature for 3 h. To the resulting red
suspension of potassium trithiocarbonate, 3,4-dichlorobenzoni-
trile (1.72 g, 10 mmol) was added, and the mixture was further
stirred for 24 h at 50 °C. The mixture was then poured into
water (100 mL), filtered, dried in vacuum, and isolated as a
yellow solid after separation by silica gel column chromatogra-
phy using CH2Cl2/hexane (v:v = 8:2) as eluent. (0.83 g, 3.96
mmol,
g
= 40%, Rf = 0.53). M.p. 204–205 °C. 1H NMR (300 MHz,
CDCl3, 25 °C, TMS) d = 7.43 (s, 1H), 7.65–7.56 (s, 1H; t, 1H),
13C (75.3373 MHz), CDCl3: d = 111.500, 117.330, 122.179,
124.706, 130.294, 141.939, 146.048, 209.407; IR (KBr pellet)
~
t
= 3075 (w, Ar–H), 2228 (m, C„N), 1577 (m, C@C), 1081 (s,
C@S), 698 (m, C–S) cmÀ1
; C8H3NS3 (209.31): Anal. Calc. C
45.91, H 1.44, N 6.69, S 45.96. Found: C 45.69, H 1.29, N
6.53, S 45.78%.
2.3. Synthesis of (Ph4P)2 [Zn(cbdt)2] (2a)
4-Cyanobenzene-1,2-dithiol (0.1 g, 0.6 mmol) was dissolved in
aqueous NaOH (40 mL, 5%). A solution of Ph4PBr (0.25 g, 0.6 mmol)
in EtOH/H2O (1:1) (25 ml) was added, followed by a solution of
ZnCl2 (0.04 g, 0.3 mmol) in the same solvent (10 mL). The mixture
was cooled and filtered and the precipitate was recrystallised from
The properties of these complexes are dominated by cis–trans dis-
order effects and they present redox properties intermediate be-
tween those based on dcdbt and bdt ligands. The partially
oxidised states obtained in complexes with the dcbdt ligand are
not observed in complexes with the cbdt ligand, however a com-
plex in the neutral state can be obtained with gold.
CH3CN/i-buOH to give 2a as yellow crystals (0.05 g, 0.047 mmol,
~
g
= 16%). M.p. 241–243 °C; IR (KBr pellet)
t
= 3050 (w, Ar–H),
2210 (s, C„N), 1580–1551 (w, C@C) cmÀ1
.
1H NMR (300 MHz
[D6] DMSO, 25 °C, TMS) d = 8.00 (m, 16 H), 7.87 (m, 24 H), 7.48
(s, 1H), 7.35 (d, 1 H), 6.63 (d, 1H). C62H46N2ZnS4P2 (1074.66): Anal.
Calc. C 69.29, H 4.31, N 2.61, S 11.93. Found: C 69.13, H 4.23, N
2.64, S 11.74%.
2. Experimental
2.4. Synthesis of (Ph4P) [Ni(cbdt)2] (3a)
2.1. Materials and methods
4-Cyanobenzene-1,2-dithiol (0.1 g, 0.6 mmol) was dissolved
in aqueous NaOH (15 mL, 5%). A solution of Ph4PBr (0.25 g,
0.6 mmol) in EtOH/H2O (1:1) (15 ml) was added, followed by
a solution of NiCl2Á6H2O (0.07 g, 0.3 mmol) in the same solvent
(10 mL). The mixture was cooled and filtered and the precipi-
tate was recrystallised from CH3CN/i-buOH to give 3a as dark
The ligand precursor 4-cyanobenzene-1,2-dithiol was prepared
as previously described [5]. All solvents were purified and dried
following standard procedures. Other chemicals were obtained
commercially and were used as received. Elemental analyses were
performed by the analytical services of Instituto Tecnológico e
Nuclear. 1H and 13C NMR: Varian (300 MHz), [D6] DMSO or acetone
as solvent, TMS as internal standard. IR: PERKIN-ELMER 1330
spectrophotometer. Cyclic voltammetry data were obtained using
a CV-50W BAS Voltammetric Analyser. The measurements were
performed at room temperature in freshly distilled acetonitrile
solutions containing (n-Bu4N)[PF6] 0.1 M as supporting electrolyte.
A 0.12 cm2 – area Platinum working electrode was used, which was
green crystals (0.03 g, 0.041 mmol,
g = 13.6%). M.p. 213–
~
215 °C. IR (KBr pellet)
t
= 3049 (w, Ar–H), 2217 (s, C„N),
1560 (w, C@C) cmÀ1
.
C38H26N2NiS4P (728.56): Anal. Calc. C
62.65, H 3.59, N 3.84, S 17.60. Found: C 62.25, H 2.30, N
3.95, S 17.16%.
polished with
(BuehlerÓ) and
a
0.05 micron alumina polishing suspension
polishing cloth (BuehlerÓ) between each
2.5. Synthesis of (n-Bu4N) [Ni(cbdt)2] (3b)
a
sweep. The voltammograms were recorded against an Ag/AgNO3
pseudo-reference electrode and a Platinum wire counter electrode
completed the 3-electrode cell.
Following a similar procedure as used to 3a but with a solu-
tion of n-Bu4NI instead of Ph4PBr. After recrystallisation from
CH3CN/i-buOH, 3b was obtained as dark green crystals. (0.04 g,
~
0.063 mmol,
g = 21%). M.p. 213–214 °C. IR (KBr pellet) t = 3060
2.2. Synthesis of 4-cyanobenzene-1,3-dithiole-2-thione (1)
(w, Ar–H), 2960–2870 (m, C–H), 2220 (s, C„N), 1550–1432 (s-
m, C@C), 430 (w, S–Ni) cmÀ1; C30H42N3NiS4 (631.68): Anal. Calc.
C 57.03, H 6.72, N 6.65, S 20.30. Found: C 56.50, H 6.84, N 6.37,
S 20.29%.
A mixture of potassium sulphide (43%, 3 g, 11.7 mmol), car-
bon disulphide (2 mL, 33 mmol) and dimethylformamide (8 mL)

230
A.C. Cerdeira et al. / Polyhedron 44 (2012) 228–237
2.6. Synthesis of (Ph4P) [Au(cbdt)2]Á0.5(H8C4O) (4a)
red solution was filtered and a solution of Ph4PBr (0.2 g,
0.48 mmol) in 4 mL of methanol was added. No precipitate forma-
tion was observed. The mixture was allowed to stand overnight at
room temperature, and a red polycrystalline precipitate appeared,
which was collected and recrystallised from CH2Cl2/hexane to be
recovered as dark red platelet crystals (0.14 g, 0.131 mmol,
~
4-Cyanobenzene-1,2-dithiol (0.1 g, 0.6 mmol) was dissolved in
aqueous NaOH (15 mL, 5%). A solution of Ph4PBr (0.13 g, 0.3 mmol)
in EtOH/H2O (1:1) (15 ml) was added, followed by a solution of
KAuCl4 (0.12 g, 0.3 mmol) in the same solvent (10 mL). The mixture
was cooled and filtered and the precipitate was recrystallised from
THF/i-buOH to give 4a as light green needles (0.1 g, 0.12 mmol,
~
g
= 54.6%). IR (KBr pellet) t = 3050 (w, Ar–H), 2220 (s, C„N),
1565 (m, C@C), 418 (w, S–Co) cmÀ1; C62H46CoN2P2S4 (1068.18):
Anal. Calc. C 69.71, H 4.34, N 2.26, S 12.01. Found: C 69.43, H
4.19, N 2.18, S 12.31%.
g
= 38%). M.p. 218–219 °C. IR (KBr pellet) t = 3055 (vw, Ar–H),
2217 (m, C„N), 1563 (m, C@C), 425 (w, S–Au) cmÀ1
.
C38H26N2AuS4P (866.83): Anal. Calc. C 52.65, H 3.02, N 3.23, S
14.79. Found: C 52.96, H 2.93, N 3.23, S 15.01%.
2.11. Synthesis of (Ph4P)2 [Cu(cbdt)2] (9a)
2.7. Synthesis of (n-Bu4N) [Au(cbdt)2] (4b)
Under anaerobic conditions, 1 (0.1 g, 0.48 mmol) was added to a
sodium methoxide solution (0.113 g, 1.9 mmol), in methanol
(8 mL). After 4 h of stirring, a solution of CuCl2Á2H2O (0.041 g,
0.24 mmol) in methanol (4 mL) was added. One hour later, the
Following a similar procedure as used to 4a but with a solution
of n-Bu4NI instead of Ph4PBr. After recrystallisation from CH3CN/i-
buOH, 4b was obtained as green needles (0.07 g, 0.091 mmol,
red solution was filtered and
a solution of Ph4PBr (0.2 g,
g
= 30%). M.p. 186–188 °C. 1H NMR (300 MHz, [D6] acetone,
0.48 mmol) in 4 mL methanol was added. No precipitate formation
was observed. The mixture was layered with isopropanol and al-
lowed to stand overnight at room temperature. A red polycrystal-
line precipitate appeared, which was collected and recrystallised
from CH2Cl2/hexane to be recovered as red crystalline needles
25 °C, TMS): d = (A) 7.40 (d, 1H), (B) 7.26 (d, 1H), (C) 7.17 (dd,
1H) (J(A, B) = 0.9 Hz, J(B, C) = 8.1 Hz, J(A, C) = 1.5 Hz), 3.40 (t, 8H),
1.82 (m, 8H), 1.42 (m, 8H), 0.87 (t, 12 H); IR (KBr pellet)
(m, C–H), 2220 (s, C„N), 1550–1500 (s, C@C), 423 (w, S–Au)
cmÀ1; C30H42N3AuS4 (769.96): Anal. Calc. C 46.79, H 5.51, N 5.46,
S 16.66. Found: C 46.93, H 5.44, N 5.40, S 16.59%.
~
t
= 2960
(0.14 g, 0.13 mmol,
g = 54.4%). M.p. 209–210 °C. IR (KBr pellet)
~
t
= 3042 (w, Ar–H), 2213 (m, C„N), 1583–1482 (s-m, C@C), 421
(w, S–Cu) cmÀ1; C62H46CuN2P2S4 (1072.79): Anal. Calc. C 69.41, H
2.8. Synthesis of (Ph4P) [Co(cbdt)2] (5a)
4.32, N 2.61, S 11.96. Found: C 69.24, H 4.59, N 2.33, S 12.06%.
4-Cyanobenzene-1,2-dithiol (0.1 g, 0.6 mmol) was dissolved in
aqueous NaOH (15 mL, 5%). A solution of Ph4PBr (0.25 g, 0.6 mmol)
in EtOH/H2O (1:1) (15 ml) was added, followed by a solution of
CoCl2Á6H2O (0.07 g, 0.3 mmol) in the same solvent (10 mL). The
mixture was cooled and filtered and the precipitate was recrystal-
lised from CH3CN/i-buOH to give 5a as a dark blue powder (0.1 g,
~
g = 46.6%). M.p. 139–141 °C. IR (KBr pellet) t = 3057
2.12. Synthesis of (Ph4P)2[Pd(cbdt)2] (10a)
4-Cyanobenzene-1,2-dithiol (0.1 g, 0.6 mmol) was dissolved in
aqueous NaOH (15 mL, 5%). A solution of Ph4PBr (0.25 g, 0.6 mmol)
in EtOH/H2O (1:1) (15 ml) was added, followed by a solution of
PdCl2 (0.05 g, 0.3 mmol) in the same solvent (10 mL). The mixture
was cooled and filtered and the precipitate was recrystallised from
CH3CN/i-buOH to give 10a as dark orange crystals (0.1 g,
~
0.14 mmol,
(w, Ar–H), 2210 (s, C„N), 1560 (m, C@C), 415 (w, S–Co) cmÀ1
38H26N2CoS4P (728.79): Anal. Calc. C 62.63, H 3.59, N 3.84, S
.
C
0.089 mmol, g = 30%). M.p. 253–255 °C. IR (KBr pellet) t = 3050
17.59. Found: C 62.38, H 4.24, N 3.62, S 16.18%. As an alternative
procedure, 8a was oxidised by air exposure in a dichloromethane
solution, evidenced by the colour change from red to dark blue.
This solution was layered with i-buOH and allowed to slowly evap-
orate, until a dark blue precipitate (5a) appeared. The powder was
collected by vacuum filtration and dried.
(w, Ar–H), 2200 (m, C„N), 1565 (m, C@C) cmÀ1. C62H46N2PdS4P2
(1115.67): Anal. Calc. C 66.75, H 4.16, N 2.51, S 11.49. Found: C
66.86, H 4.36, N 2.59, S 11.61%.
2.13. Synthesis of (n-Bu4N)2[Pd(cbdt)2] (10b)
Following a similar procedure as used to 10a but with a solution
of n-Bu4NI instead of Ph4PBr. After recrystallisation from CH3CN/i-
buOH, 10b was obtained as dark red crystals (0.02 g, 0.022 mmol,
~
2.9. Synthesis of (n-Bu4N) [Cu(cbdt)2] (6b)
4-Cyanobenzene-1,2-dithiol (0.1 g, 0.6 mmol) was dissolved in
aqueous NaOH (15 mL, 5%). A solution of Ph4PBr (0.25 g, 0.6 mmol)
in EtOH/H2O (1:1) (15 ml) was added, followed by a solution of
CuCl2Á2H2O (0.05 g, 0.3 mmol) in the same solvent (10 mL). The
mixture was cooled and filtered, and the precipitate was recrystal-
lised from CH3CN/i-buOH, to give 6b as dark green polycrystals
g = 7%). M.p. 181–183 °C. IR (KBr pellet) t = 3060 (w, Ar–H),
2960–2870 (s-m, C–H), 2220 (s, C„N), 1550–1440 (s-m, C–C),
325 (w, S–Pd) cmÀ1. C46H78N4PdS4 (921.94): Anal. Calc. C 59.92,
H 8.55, N 6.08, S 13.91. Found: C 59.86, H 8.57, N 6.05, S 14.63%.
2.14. Synthesis of [Au(cbdt)2] (11)
(0.14 g, 0.22 mmol,
g
= 74%). M.p. 197–198 °C. 1H NMR (300 MHz,
[D6] acetone, 25 °C, TMS) d = 7.31 (d, 1 H), 7.23 (s, 1H), 7.09 (d,
1H), J = 8.9 Hz, 3.44 (t, 8 H), 1.83 (m, 8 H), 1.43 (m, 8 H), 0.98 (t,
A solution of 4a (0.026 g, 0.03 mmol) in freshly distilled CH2Cl2
(30 mL) was placed in a two-compartment electrocrystallisation
cell, separated by a glass frit, with platinum electrodes. Employing
~
12 H); IR (KBr pellet)
t
= 3060 (w, Ar–H), 2960–2870 (m, C–H),
2220 (s, C„N), 1560–1445 (s-m, C@C), 430 (w, S–Cu) cmÀ1
;
galvanostatic conditions (ca. 1 l
A/cm2) for 10 days, black polycrys-
C
30H42N3CuS4 (636.54): Anal. Calc. C 56.60, H 6.66, N 6.60, S
talline deposits grew on the anode surface. The product was col-
lected and washed with dichloromethane. C14H6AuN2S4 (527.44):
Anal. Calc. C 31.88, H 1.15, N 5.31, S 24.32. Found: C 32.05, H
1.28, N 5.23, S 24.47%.
20.15. Found: C 56.70, H 6.69, N 6.46, S 20.21%.
2.10. Synthesis of (Ph4P)2 [Co(cbdt)2] (8a)
Under anaerobic conditions, 1 (0.1 g, 0.48 mmol) was added to a
sodium methoxide solution (0.113 g, 1.9 mmol), in methanol
(8 mL). After 4 h of stirring, a solution of CoCl2Á6H2O (0.06 g,
0.24 mmol) in methanol (4 mL) was added. One hour later, the
2.15. Synthesis of [Ni(cyclam)] [Cu(cbdt)2]2.(CH3CN)2 (12)
To a test tube containing solid 6b (0.015 g, 0.024 mmol), a solu-
tion of [Ni(cyclam)] (BPh4)2 (0.014 g, 0.012 mmol) in acetonitrile

A.C. Cerdeira et al. / Polyhedron 44 (2012) 228–237
231
Table 1
(ꢀ10 mg) was placed inside a previously calibrated thin-walled
Teflon bucket. The force was measured with a microbalance (Sarto-
rius S3D-V). The SQUID system was used for magnetisation mea-
surements, under fields of 0.5–1 T, of similar polycrystalline
samples, typically 3 mg, placed in gelatine capsules. The paramag-
netic contributions were obtained from experimental data after
corrections for the core diamagnetism, estimated from tabulated
Pascal constants.
Redox potentials obtained by cyclic voltammetry for compounds 4a, 5a, 3b, 6b and
10b in acetonitrile (V vs. Ag/AgNO3).
M
[M(cbdt)2]2À
[M(cbdt)2]À
/
[M(cbdt)2]À/
[M(cbdt)2]0
[M(cbdt)2]0/
[M(cbdt)2]+
Au (4a)
Co (5a)
Ni (3b)
Cu (6b)
Pd (10b)
À1.52
À0.83
À0.51
À0.64
À0.24
+0.49
+1.41
+0.10
+0.015
+0.23
+1.28
+0.69
+1.16
3. Results and discussion
Table 2
Redox potentials for [M(L)2]2À/[M(L)2]À, L = bdt, cbdt, dcbdt (V vs. Ag/AgNO3).
3.1. Synthesis
M
bdt
cbdt
dcbdt
The synthesis of the [M(cbdt)2] complexes with different transi-
tion metals, M = Zn, Cu, Au, Pd, Ni, and Co, can be made either start-
ing from the corresponding ligand dithiol following the same
procedure already used to prepare the iron complex [5] or instead
from the 4-cyanobenzene-1,3-dithiole-2-thione (1) that is de-
scribed here for the first time. The thione 1 was obtained in fair
yield (40%) in a one-step reaction of commercial 3,4-dichloroben-
zonitrile with potassium trithiocarbonate generated in situ from
a mixture of potassium sulphide with carbon disulphide.
Under the first route, the 4-cyanobenzene-1,2-dithiol was al-
lowed to react in a basic hydro-alcoholic solvent mixture with
the appropriated metal chloride salts, and the complexes were pre-
cipitated by addition of cation salts (Scheme 1). Either tetrabutyl-
ammonium (n-Bu4N) or tetraphenylphosphonium cations (Ph4P)
were used without significant differences in their solubility or in
the ability to crystallise, yet slightly better yields were achieved
when tetraphenylphosphonium was used as cation. As an alterna-
tive route for the preparation of the complexes, the thione (1) is
cleaved with sodium methoxide under anaerobic conditions to
generate the dithiolate, which reacts with the metal salts. This
route makes the preparation of the complexes easier in more re-
duced forms due to the use of anaerobic conditions. It is worth
mention that despite several attempts, the preparation of the cor-
responding complexes with Pt could not be achieved using any of
these routes.
The oxidation states of the resulting complexes depend on their
redox stability and the reaction conditions. The gold complex was
obtained directly in the monoanionic state as a green salt. The Zn
and Pd complexes can be easily isolated in their dianionic state
as light yellow and dark red crystals respectively. With Cu, Ni
and Co, the brown-orange (Cu) orange (Ni) and blue (Co) dianionic
complexes initially obtained by the synthesis, upon recrystallisa-
tion under air are easily oxidised to monoanions and turn into dark
green. The dianionic Cu and Co complexes were isolated using the
second synthetic route from thione 1 under anaerobic conditions.
On the other hand, the Pd complex could not be isolated in its
monoanionic state although it could be detected in trace amounts
in solution with a characteristic EPR signal.
A salt of the copper complex with the Ni(cyclam) cation and
containing two acetonitrile solvent molecules incorporated in the
structure (12), was prepared by a metathesis reaction, in which a
solution of [Ni(cyclam)](BPh4)2 in acetonitrile was added to solid
(Ph4P) [Cu(cbdt)2] and allowed to stand for several days. A few
crystals could be obtained, suitable for the X-ray structural
analysis, which are presented below, as well as a fine precipitated
material which however, as judged from both elemental analysis
and X-ray powder diffraction, do not correspond to this composi-
tion and possibly it is a structure without the solvent. Salts of
these complexes with cyclam cations will be reported in detail in
a subsequent publication.
Au
Ni
Co
Cu
Fe
À1.52
À1.33 [2b]
À0.08 [2a]
À0.21 [2b]
À0.07 [2b]
À0.44 [2c]
À0.36 [2b]
À1.05 [17]
À1.38 [17]
À1.14 [17]
À1.53 [18]
À0.51
À0.83a
À0.64
À0.72 [5]
À0.24
Pd
(3 mL) was carefully added. The test tube was then tightly closed
and allowed to stand undisturbed in the dark for 15 days. A green
amorphous powder was collected and washed with dichlorometh-
ane. The mother liquor was allowed to slowly evaporate and after
2 days a few dark thin needle crystals suitable for X-ray diffraction
were collected.
2.16. X-ray crystallography
The X-ray diffraction analysis of compounds 4a, 7b, 8a, 9a, 10b
and 12 were performed on a Bruker AXS APEX CCD area detector
diffractometer, equipped with an Oxford Cryosystem low-temper-
ature device at 150(2) K in the
monochromated Mo K radiation (0.71073 Å). Empirical absorp-
tion correction was carried out using SADABS programme [10]. Data
collection and data reduction were done with the SMART and SAINT
programmes [11]. The structures were solved by direct methods
with SIR97 [12] and refined by full-matrix least-squares analysis
with SHELXL-97 [13] using the WINGX [14] suite of programs. All non-
hydrogen atoms were refined anisotropically. The remaining
hydrogen atoms were placed in idealised positions and allowed
to refine riding on the parent C atom. Molecular graphics were pre-
pared using ORTEP3 [15] and Mercury [16]. A summary of the crys-
tal data, structure solution and refinement parameters are given in
Table 2.
x and u scans mode using graphite
a
2.17. EPR spectroscopy
EPR spectra at 77 and 300 K were obtained with an X-band Bru-
ker ESP 300E spectrometer equipped with an ER041XK microwave
bridge, a rectangular cavity operating in T102 mode and an ER
032M field controller system. The modulation amplitude was kept
well below the line width and the microwave power well below
saturation.
2.18. Magnetic susceptibility
Magnetic measurements were performed using either a longitu-
dinal Faraday system (Oxford Instruments) with a 7 T supercon-
ducting magnet for static susceptibility measurements in the
range 2–300 K, or a 7 Tesla S700X SQUID magnetometer (Cryo-
genic Ltd.) in the temperature range 1.6–300 K. The Faraday sys-
tem was used with a magnetic field of 2 T and forward and
All complexes were characterised by elemental analysis (C, H, N,
reverse field gradients of 5 T/m.
A polycrystalline sample
S) and by IR spectroscopy. 1H spectra were also recorded for dia-

232
A.C. Cerdeira et al. / Polyhedron 44 (2012) 228–237
Scheme 1. Synthesis of the complexes [M(cbdt)2].
magnetic complexes 2a, 4b and 6b, giving rise to the expected
peak-intensities ratios, according to molecular structure and
stoichiometry.
tion also leads to a dark powder on the electrode. However the
elemental analysis of this oxidation product is not consistent with
the neutral complex and at this stage it could not be further
characterised.
3.2. Cyclic voltammetry
3.3. X-ray diffraction studies
The redox behaviour of the complexes was studied by cyclic
voltammetry in acetonitrile solutions containing (n-Bu4N)[PF6]
0.1 M as supporting electrolyte and potentials, with reference to
Ag/AgNO3, are listed in Table 1. Those obtained previously for the
Fe analogue as well as for the corresponding complexes with dcbdt
and bdt ligands are listed on Table 2.
The crystals obtained for compounds 4a, 7b, 8a, 9a, 10b and 12
enabled the structure determination by X-ray diffraction. Com-
pound 3b, upon recrystallisation, yielded dark green polycrystals
and a few orange monocrystals which were suitable for X-ray
diffraction, pertaining however to (n-Bu4N)2 [Ni(cbdt)2] (7b), the
dianionic Ni salt. Crystallographic data are listed in Table 3.
The crystals obtained for the Zn compound 2a enabled only
the determination of the unit cell parameters, (triclinic, space
Cyclic voltammetry of the studied complexes reveals three re-
dox processes, except for 5a which exhibits only one (see Supple-
mentary material, Fig. S1a–e). The processes observed at more
negative potentials are ascribed to the couple [M(cbdt)2]2À
/
group P1, a = 11.7740(13) Å, b = 11.8075(12) Å, c = 20.667(2) Å,
ꢀ
[M(cbdt)2]À, at intermediate potentials to [M(cbdt)2]À/[M(cbdt)2]0
and at more positive potentials to [M(cbdt)2]0/[M(cbdt)2]+. Studies
a = 91.209(7)°, b = 91.248(7)°, c = 113.021(6)°, cell volume 2642.4(5)
Å3 and Z = 2) and its structural refinement was not possible due
to severe ligand disorder.
in acetonitrile at several sweep rates (from 5 mVsÀ1 up to 5 VsÀ1
)
revealed that, the first process between dianion and monoanion is
quasi-reversible, occurring at À1.52, À0.51, À0.64 and À0.24 V
(versus Ag/AgNO3) for M = Au, Ni, Cu and Pd, respectively. In
the case of Co, only one process, ascribed to the pair
[Co(cbdt)2]2À/[Co(cbdt)2]À is observed at À0.830 V. However this
process (see Fig. S1b) presents features of a catalytic mechanism.
The second process, corresponding to the oxidation of the
monoanion to the neutral species, is dependent on the metal,
and different mechanisms are suggested by the cyclic voltammo-
grams for the different metal complexes. In the case of Au and
Ni, a current cross-over, typical of an electrodeposition process,
is observed at 0.49 and 0.10 V, respectively, which can be assigned
to the formation of the insoluble neutral species. However for
M = Cu and Pd no such crossover is observed, and these processes,
which start at 0.015 and 0.230 V respectively, are irreversible with
indication of possible adsorption and decomposition. At higher
potentials, at 1.41, 1.28, 0.69 and 1.16 V for M = Au, Ni, Cu and
Pd respectively, a further irreversible oxidation process is ob-
served, possibly with generation of unstable cationic species. For
Co, a sequence of oxidation waves starts to be observed at À0.83 V.
The crystal structures observed for [M(cbdt)2]zÀ, (z = 1, 2) salts,
in which the complexes present a square planar coordination
geometry, can be classified into four groups: (i) the compound
(4a) with monoanionic Au complex is monoclinic, C2/c, where the
complex presents a cis–trans disorder; (ii) compounds (7b and
10b) where dianionic Pd and Ni complexes are isostructural,
monoclinic, P21/c, with the metal in a inversion centre with a per-
fect square-planar coordination geometry and a ligand trans con-
figuration; (iii) the Co (8a) and Cu (9a) dianionic compounds
which are monoclinic, P21, with the metal located in a general po-
sition with coordination geometry almost square planar and ligand
trans configuration; and (iv) the monoanionic Cu compound 12 is
ꢀ
triclinic, P1, with the Cu atom in a general position, with almost
ideal square-planar coordination and ligand trans configuration.
Fig. 1 presents the ORTEP diagrams of the complex anions in
compounds 4a, 7b, 8a, 9a, 10b and 12, showing the atomic label-
ling scheme; selected bond lengths are presented in Table S1
(see Supplementary data). M–S bond lengths are consistent with
the values published in literature for bisdithiolene complexes of
the same transition metal and corresponding oxidation state
[1,19], and similar to those of their analogous [M(bdt)2]zÀ and
[M(dcbdt)2]zÀ (z = 1, 2) complexes [2a,b,4,20]. The ligand bond
lengths, namely S–C and C–C values are also identical within
experimental error, and therefore from these data no conclusion
can be taken about a different degree of ligand contribution to
the HOMOs.
The observed potentials for the processes [M(cbdt)2]2À
/
[M(cbdt)2]À are listed in Table 1 and, as expected, are intermediate
between those of the unsubstituted (bdt) and disubstituted (dcbdt)
ligands. In this respect it is also important to refer that while the
oxidation of the monoanionic complexes based in the dcbdt ligand
2À
leads to the formation of partially oxidised species [M(dcbdt)2]5
(M = Au, Ni, Cu, . . .), [4] with the monosubstituted ligand cbdt the
electrochemical oxidation of the M = Au monoanion leads directly
to the neutral complex, 11, which was isolated as a dark microcrys-
talline powder covering the electrode. The Ni complex upon oxida-
Compound 4a exists in a cis–trans equilibrium of ligand confor-
mation (60–40%), and the crystal structure (Fig. 2, top) shows the
anion units stacked in groups of two, separated by a layer of cation
units and incorporated THF solvent molecules. There are no short

A.C. Cerdeira et al. / Polyhedron 44 (2012) 228–237
233
Table 3
Crystallographic data for compounds 4a, 7b, 8a, 9a, 10b and 12.
Au (4a)
Ni (7b)
Co (8a)
Cu (9a)
Pd (10b)
Cu (12)
Crystal size (mm)
Crystal colour and shape
Empirical formula
0.18 Â 0.16 Â 0.02
0.20 Â 0.04 Â 0.02
orange needle
C46H78N4NiS4
0.16 Â 0.14 Â 0.03
brown plate
C62H46CoN2P2S4
0.14 Â 0.10 Â 0.03
brown plate
C62H46CuN2P2S4
0.24 Â 0.22 Â 0.12
orange prism
C46H78N4PdS4
0.12 Â 0.06 Â 0.02
green needle
C42H38Cu2N10NiS8
green plate
C
80H58N4Au2
S8P2O
Molecular mass
Crystal system
Space group
a (Å)
b (Å)
c (Å)
1803.66
monoclinic
C2/c
44.2641(13)
7.4861(7)
27.6091(12)
90
124.052(7)
90
7580.0(10)
4, 1.581
4.176
874.07
monoclinic
P21/c
9.7022(8)
13.2635(11)
19.1382(15)
90
91.534(3)
90
1068.12
monoclinic
P21
10.8463(17)
16.275(3)
14.734(3)
90
95.823(6)
90
2587.6(8)
2, 1.371
0.598
1072.73
monoclinic
P21
10.7959(8)
16.2702(12)
14.8043(11)
90
95.644(2)
90
921.76
monoclinic
P21/c
9.6915(3)
13.2060(4)
19.2181(6)
90
91.727(2)
90
1125.09
triclinic
ꢀ
P1
9.571(4)
10.402(3)
12.460(4)
72.272(15)
84.196(9)
87.745(9)
1175.5(7)
1, 1.589
a
(°)
b (°)
c
(°)
V (Å3)
2461.9(3)
2, 1.179
0.597
2587.8(3)
2, 1.377
0.689
2458.53(13)
2, 1.245
0.581
Z, Dcalc (Mg/m3)
l
(mmÀ1
)
1.692
F(000)
3560
948
1106
1110
984
574
h Range (°)
Index range (h,k,l)
2.78–25.03
À52/52, À8/8,
À30/32
3.03–21.97
À10/8, À13/13,
À20/20
3.20–23.23
À11/12, À18/18,
À15/15
2.86–25.30
À12/10, À19/19,
À17/17
2.79–25.83
À11/11, À16/16,
À23/23
2.98–25.02
À11/11, À9/12,
À11/14
Reflection collected
Unique reflections/Rint
T (maximum/minimum)
Number of reflection
parameters
21835
12852
12121
17328
23904
6902
6445/Rint = 0.1185
0.9211/0.5202
479
2990/Rint = 0.0936
0.9882/0.8899
254
6690/Rint = 0.0948
0.9823/0.9104
641
9044/Rint = 0.0633
0.9796/0.9098
640
4691/Rint = 0.0809
0.9335/0.8731
254
4033/Rint = 0.1138
0.9669/0.8227
287
Goodness-of-fit on F2
1.021
1.062
0.909
0.964
0.960
0.850
Final R1, [I > 2
r(I)], wR2
0.0637/0.1066
0.0849/0.2055
0.0652/0.1014
0.0579/0.1134
0.0486/0.1044
0.0760/0.1194
contacts between these two anion units, but each of them is con-
nected in chains through short S(2)ÁÁÁS(3)⁄ contacts at 3.526(3) Å
with the adjacent anion (⁄x,y À 1,z) (Fig. 2, bottom).
EPR signal as shown in Fig. 6 for 3b with g1 = 2.177, g2 = 2.074 and
g3 = 2.018, values comparable to other monoanionic Ni bisdithio-
lene complexes [2]. Static magnetic measurements confirm the
paramagnetic nature of the complex and susceptibility data, after
a correction of diamagnetism estimated from tabulated Pascal con-
stants as À3.92 Â 10À4 emu/mol, indicates an effective magnetic
Compounds 7b and 10b are isostructural and the complexes
present a perfectly square planar geometry, with the transition
metal atom located at an inversion centre and a ligand trans config-
uration. The crystal structure of these compounds is made up of
dianionic [M(cbdt)2]2À layers parallel to the a,c plane, separated
by cation layers alternating along b, preventing any short anion–
anion contacts, as shown in Fig. 3.
moment
10–300 K (see Fig. S2). This temperature independent behaviour
is indicative of fairly isolated S = ½ spins in the anions. The eff va-
leff = 2.0 lB/f.u. temperature independent in the range
l
lue corresponds to g = 2.2, a value slightly above the average of the
values observed in EPR, probably a consequence of some preferred
alignment of the needle shaped crystals.
The Cu (9a) and Co (8a) dianionic compounds, which are iso-
structural, crystallise in monoclinic space group P21, with the me-
tal located in
a
general position presenting
a
coordination
The monoanionic gold complex is diamagnetic, but the neutral
gold-bisdithiolene complex 11 is paramagnetic, as expected for a
formally AuIV d7 ion, and it presents an EPR signal shown in
Fig. 7. However, the paramagnetic susceptibility derived from
raw data assuming a diamagnetic contribution estimated from tab-
ulated Pascal constants as À2.06 Â 10À4 emu/mol is rather weak
and follows a Curie law corresponding to only circa 10% of S = ½
spins. The EPR signal is typical of a rhombic anisotropic species
with g1 = 1.863, g2 = 2.037 and g3 = 2.067. This EPR signal and the
paramagnetic susceptibility are ascribed to defects corresponding
to uncoupled species which are most probably dimerised as in
geometry almost perfectly square planar with a ligand trans config-
uration. The crystal structure (Fig. 4) is such that the anions are
completely surrounded by cations and there are no short anion-an-
ion contacts.
The Ni(cyclam) cations in 12 presents the Ni atom being coordi-
nated, in addition to the cyclam nitrogen atoms, by two acetoni-
trile solvent molecules incorporated in the structure. Apparently,
the acetonitrile solvent molecules are more efficient in coordinat-
ing nickel ions than the nitrile groups of the cbdt ligands and there-
fore alternated cation-anion coordination structures as described
in other dithiolenes with peripheral CN groups are not obtained
[9b,21]. The crystal structure for compound 12 (Fig. 5), shows
two anion units in the centre of the unit cell, while the cation units
are located with the Ni atom in an inversion centre at the edges of
the cell. The two anion units connect through short contacts
0
[Au(bdt)2]2 [22] and other neutral Au bisdithiolene complexes
[23]. The electrical conductivity of 11 measured in a polycrystalline
powder compacted sample was found to be 10À4 S/cm at room
temperature decreasing upon cooling, so this neutral complex is
a semiconductor with rather modest electrical conductivity. These
results contrast with some highly conducting Au or Ni neutral
complexes which may behave as metals and where the susceptibil-
ity is also temperature independent but of much smaller magni-
tude (ꢀ2 Â 10À4 emu/mol) and of Pauli type [3].
S(2)ÁÁÁS(3)⁄ at 3.546(4)
Å
and S(3)⁄ÁÁÁS(3) at 3.453(4) Å,
(⁄Àx + 1,Ày + 1,Àz + 1). These anion pairs are interconnected in
chains along a + b through hydrogen bonds C(10)–H(10)ÁÁÁN(1)
and C(4)–H(4)ÁÁÁN(2).
The dianionic Pd complex in 10b is diamagnetic, however its
frozen solutions in acetone were found to present a weak rhombic
EPR signal, with g1 = 2.077, g2 = 2.047 and g3 = 1.942, (Fig. S3) sug-
gesting that at least small amounts of the complex were oxidised in
solution to the paramagnetic monoanionic species. Similar values
3.4. Magnetic properties
The monoanionic Ni complexes in 3a and 3b are paramagnetic,
as expected, and as polycrystalline samples they present a rhombic

234
A.C. Cerdeira et al. / Polyhedron 44 (2012) 228–237
Fig. 2. Crystal structure of (Ph4P) [Au(cbdt)2] 0.5(H8C4O) (4a); on top, view along
the b axis; bottom, partial view evidencing short contacts.
Fig. 3. View of the crystal structure of (n-Bu4N)2 [Ni(cbdt)2] (7b) along the a axis.
principal values g1, g2 and g3 indicated above, and an anisotropic
hyperfine tensor ao, of the interaction with the 59Co nuclear spin
I = 7/2 spin [2b,25], such that it assumes significant values, of about
8.6 mT, only close to the maximum g-value, in a situation compa-
Fig. 1. ORTEP diagrams: (Ph4P) [Au(cbdt)2] (4a), (n-Bu4N)2[Ni(cbdt)2] (7b), (Ph4P)2
[Co(cbdt)2] (8a), (Ph4P)2 [Cu(cbdt)2] (9a), (n-Bu4N)2 [Pd(cbdt)2] (10b), and
[Ni(cyclam)] [Cu(cbdt)2]2Á(CH3CN)2 (12). The diagrams are drawn with 50%
probability thermal ellipsoids.
rable to that previously observed in single crystals of
a
[Co(dcbdt)2]2À salts where a0 was found to be 9.2 mT [2b]. This is
a rare situation where such hyperfine structure can be observed
in the solid state and as a polycrystalline sample. A more detailed
analysis of the a0- and g-tensors, which are expected to have coin-
cident principal axis and maximum values when the magnetic field
is perpendicular to plane of the complex, will have to wait for sin-
gle crystals large enough for orientation dependent EPR studies.
The dianionic copper complex is paramagnetic and 9a, as a
polycrystalline sample, presents at 77 K an EPR signal (Fig. 9) indic-
ative of a rhombic S = ½ system with g1 = 2.273, g2 = 2.026 and
g3 = 1.937 (gav = 2.077). These g-values are comparable to those ob-
served in other monoanionic copper dithiolene complexes, which
however have shown only axial anisotropy [2b,26]. The static para-
magnetic susceptibility of 9a calculated from raw data magnetisa-
tion data, assuming a diamagnetic contribution estimated from
tabulated Pascal constants as À6.08 Â 10À4 emu/mol, correspond
to an effective magnetic moment of 1.75 lB almost constant in
the whole range of measurements (see Fig. S2). This value is very
close to the expected for a system of independent S = ½ spins
and an average gav = 2.077.
of g were reported in literature for related monoanionic Pd bisdi-
thiolene complexes e.g. [Pd(mnt)2]À (g1 = 2.071, g2 = 2.043,
g3 = 1.956) [24].
The dianionic cobalt complex is paramagnetic, as expected, and
the static paramagnetic susceptibility of 8a calculated from raw
data magnetisation data, assuming a diamagnetic contribution
estimated from tabulated Pascal constants as À5.98 Â 10À4 emu/
mol, correspond to an effective magnetic moment
leff = 2.05 lB
fairly constant in the range 20–300 K (see Fig. S2), indicative of
well isolated anions in agreement with the crystal structure. This
leff value is the expected value for a S = ½ system of independent
spins with g = 2.37, in fair agreement with average value observed
in EPR gav = 2.38 (see below). It was not possible to obtain single
crystals of any [Co(cbdt)2]2À salt large enough for EPR spectros-
copy. However 8a, as a polycrystalline sample, presents at 77 K a
complex EPR spectrum (Fig. 8) containing two main single compo-
nents at g1 = 1.920, g2 = 2.144 and a third component at g3 ꢀ 3.084,
which appears split as a multiplet of 8 individual lines. This spec-
trum is interpreted as corresponding to a rhombic g system with
The monoanionic [Co(cbdt)2]À complex in 5a was found to be
EPR silent. Magnetic susceptibility data of 5a show a paramagnetic

A.C. Cerdeira et al. / Polyhedron 44 (2012) 228–237
235
Fig. 4. View of the crystal structure of (Ph4P)2 [Cu(cbdt)2] (9a) along the a axis.
Fig. 5. View along a of the [Ni(cyclam)] [Cu(cbdt)2]2 (CH3CN)2 (12) structure.
behaviour however with a reduced magnetic moment of ꢀ1.2 lB
,
which is taken as in indication that the sample, which presents a
low degree of crystallinity, may exist as a mixture of high spin
(S = 1) and low spin (S = 0) states.
Fig. 6. EPR spectra of (n-Bu4N) [Ni(cbdt)2] (3b) as a polycrystalline sample at room
temperature.
Fig. 7. EPR spectra of [Au(cbdt)2]0 (11) as a polycrystalline sample at T = 77 K.

236
A.C. Cerdeira et al. / Polyhedron 44 (2012) 228–237
336-033; or e-mail: deposit@ccdc.cam.ac.uk. Supplementary data
associated with this article can be found, in the online version, at
http://dx.doi.org/10.1016/j.poly.2012.07.010.
References
[1] (a) H.B. Gray, Transition Met. Chem. 1 (1965) 239;
(b) G.N. Schrauzer, Transition Met. Chem. 4 (1968) 299;
(c) J.A. McCleverty, Prog. Inorg. Chem. 10 (1968) 49;
(d) D. Coucouvanis, Prog. Inorg. Chem. 11 (1970) 233;
(e) R. Eisenberg, Prog. Inorg. Chem. 12 (1970) 295;
(f) L. Alcácer, H. Novais, in: J.S. Miller (Ed.), Extended Linear Chain Compounds,
vol. 3, Plenum Press, New York, 1983, p. 319;
Fig. 8. EPR spectra of (Ph4P)2 [Co(cbdt)2] (8a) as
T = 77 K.
a polycrystalline sample at
(g) R.P. Burns, C.A. McAuliffe, Adv. Inorg. Chem. Radiochem. 22 (1986) 303;
(h) N. Robertson, L. Cronin, Coord. Chem. Rev. 227 (2002) 93;
(i) E.I. Stiefel (Ed.), Dithiolene Chemistry, Prog. Inorg. Chem., 2004, pp. 52.;
(j) R. Kato, Chem. Rev. 104 (2004) 5319.
[2] (a) D. Simão, H. Alves, D. Belo, S. Rabaça, E.B. Lopes, V. Gama, M.T. Duarte, R.T.
Henriques, H. Novais, M. Almeida, Eur. J. Inorg. Chem. 12 (2001) 3119;
(b) H. Alves, D. Simão, I.C. Santos, S. Rabaça, E.B. Lopes, V. Gama, M.T. Duarte,
R.T. Henriques, H. Novais, M. Almeida, Eur. J. Inorg. Chem. 6 (2004) 1318;
(c) H. Alves, D. Simão, H. Novais, I.C. Santos, C. Giménez-Saiz, V. Gama, J.C.
Waerenborgh, R.T. Henriques, M. Almeida, Polyhedron 22 (2003) 2481.
[3] (a) D. Belo, H. Alves, E.B. Lopes, M.T. Duarte, V. Gama, R.T. Henriques, M.
Almeida, A. Perez-Benitez, C. Rovira, J. Veciana, Chem. A Eur. J. 7 (2001) 511;
(b) H. Tanaka, Y. Okano, H. Kobayashi, W. Suzuki, A. Kobayashi, Science 291
(2001) 285;
(c) A. Kobayashi, E. Fujiwara, H. Kobayashi, Chem. Rev. 104 (2004) 5243;
(d) J.P.M. Nunes, M.J. Figueira, D. Belo, I.C. Santos, B. Ribeiro, E.B. Lopes, R.T.
Henriques, J. Vidal-Gancedo, J. Veciana, C. Rovira, M. Almeida, Chem. A Eur. J.
13 (2007) 9841;
(e) N. Tenn, N. Bellec, O. Jeannin, L. Piekara-Sady, P. Auban-Senzier, J. Iguez, E.
Canadell, D. Lorcy, J. Am. Chem. Soc. 131 (2009) 16961;
(f) D. Belo, M. Almeida, Coord. Chem. Rev. 254 (2010) 1479.
[4] (a) H. Alves, D. Simão, E.B. Lopes, D. Belo, V. Gama, M.T. Duarte, H. Novais, R.T.
Henriques, M. Almeida, Synth. Metals 120 (2001) 1011;
(b) H. Alves, I.C. Santos, E.B. Lopes, D. Belo, V. Gama, D. Simão, H. Novais, M.T.
Duarte, R.T. Henriques, M. Almeida, Synth. Metals 133 (2003) 397;
(c) H. Alves, D. Simão, I.C. Santos, E.B. Lopes, H. Novais, R.T. Henriques, M.
Almeida, Synth. Metals 135 (2003) 543;
Fig. 9. EPR spectra of (Ph4P)2 [Cu(cbdt)2] (9a) as
T = 77 K.
a polycrystalline sample at
4. Conclusions
(d) E.B. Lopes, H. Alves, I.C. Santos, D. Graf, J.S. Brooks, E. Canadell, M. Almeida,
J. Mater. Chem. 18 (2008) 2825.
[5] A.C. Cerdeira, D. Simão, I.C. Santos, A. Machado, L.C.J. Pereira, J.C. Waerenborgh,
R.T. Henriques, M. Almeida, Inorg. Chim. Acta 361 (2008) 3836.
[6] V. Madhu, S.K. Das, Inorg. Chem. 47 (2008) 5055.
[7] S. Shi, in: D.M. Roundhill, J.P. Fackler Jr. (Eds.), Optoelectronic Properties of
Inorganic Compounds, Plenum Press, New York, 1999, p. 52.
[8] (a) M. Fourmigué, J.N. Bertran, Chem. Comm. (2000) 2111;
(b) L.N. Dawe, J. Miglioni, L. Turnbow, M.L. Taliaferro, W.W. Shum, J.D.
Bagnato, L.N. Zakharov, A.L. Reingold, A.M. Arif, M. Fourmigué, J.S. Miller, Inorg.
Chem. 44 (2005) 7530.
[9] (a) O. Jeannin, J. Delaunay, F. Barriere, M. Fourmigue, Inorg. Chem. 44 (2005)
9763;
(b) S. Rabaça, M. Almeida, Coord. Chem. Rev. 254 (2010) 1493.
[10] W. Sadabs, Area-Detector Absorption Correction, Bruker AXS Inc., Madison, WI,
2004.
[11] M. Sa, Area-Detector Integration Software, Bruker AXS Inc., Madison, WI,
2004.
[12] A. Altomare, M.C. Burla, M. Camalli, G.L. Cascarano, C. Giacovazzo, A.
Guagliardi, A. Grazia, G. Moliterni, G. Polidori, R.J. Spagna, Appl. Crystallogr.
32 (1999) 115.
In conclusion, we have prepared and characterised a large series
of new complexes [M(cbdt)2] with different transition metals,
enlarging the range of bisdithiolene complexes with interesting
potential applications in the preparation of new molecular materi-
als. These complexes can be prepared either starting from the pre-
viously described ligand precursor dithiol or, in a more convenient
way, from the corresponding thione that was described here for
the first time, and they present a vivid redox behaviour intermedi-
ate between those of analogous complexes based on dicyanoben-
zenedithiolate and benzenedithiolate ligands. However, at
variance with the complexes based on the other ligands, the
[Au(cbdt)2] complex could be obtained in the neutral state. The
use of these complexes to prepare new molecular materials with
interesting magnetic and electrical properties, namely acting as
bridging ligands in heterobimetallic coordination networks, is cur-
rently being explored.
[13] G.M. Sheldrick, SHELXL-97: Program for the Refinement of Crystal Structure,
University of Gottingen, Germany, 1997.
[14] L.J. Farrugia, J. Appl. Crystallogr. 32 (1999) 837.
[15] L.J. Farrugia, J. Appl. Crystallogr. 30 (1997) 565.
Acknowledgments
[16] C.F. Macrae, I.J. Bruno, J.A. Chisholm, P.R. Edgington, P. McCabe, E. Pidcock, L.
Rodriguez-Monge, R. Taylor, J. van de Streek, P.A. Wood, J. Appl. Crystallogr. 41
(2008) 466.
[17] M.J. Baker-Hawkes, E. Billig, H.B. Gray, J. Am. Chem. Soc. 88 (1966) 4870.
[18] D. Sellmann, M. Geck, M. Moll, J. Am. Chem. Soc. 113 (1991) 5259.
[19] C.L. Beswick, J.M. Schulman, E.I. Stiefel, in: E.I. Stiefel (Ed.), Dithiolene
Chemistry, Synthesis Properties and Applications, Prog. Inorg. Chem., vol. 52,
2004, pp. 55.
This work was partially supported by FCT (Portugal) through
contracts PTDC/QUI/64967/2006 and PTDC/QUI-QUI/101788/
2008. A.C.C. is grateful to FCT (Portugal) for support through grant
SFRH/BD/46543/2008.
[20] (a) D. Sellmann, S. Funfgelder, F. Knoch, M.Z. Moll, Naturforsch. Teil B 46
(1991) 1601;
Appendix A. Supplementary data
(b) K. Ray, T. Weyhermüller, F. Neese, K. Wieghardt, Inorg. Chem. 44 (2005)
5345;
(c) K. Ray, T. Weyhermüller, A. Goossens, M.W.J. Crajé, K. Wieghardt, Inorg.
Chem. 42 (2003) 4082;
CCDC-855601 (for 7b), -855602 (for 10b), -855603 (for 4a) -
855604 (for 12) -859672 (for 9a) and -863724 (for 8a), contain
the supplementary crystallographic data for this paper. These data
can be obtained free of charge via http://www.ccdc.cam.ac.uk/con-
ts/retrieving.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-
ˇ
ˇ
(d) K. Mrkvová, J. Kamenícek, Z. Šindelár, L. Kvítek, Trans. Metal Chem. 29
(2004) 238.
[21] O. Jeannin, R. Clerac, T. Cauchy, M. Fourmigué, Inorg. Chem. 47 (2008) 10656.
[22] (a) A.J. Schultz, H.H. Wang, L.C. Soderholm, T.L. Sifter, J.M. Williams, K.
Bechgaard, M.H. Whangbo, Inorg. Chem. 26 (1987) 3757;

A.C. Cerdeira et al. / Polyhedron 44 (2012) 228–237
237
(b) N.C. Schiodt, T. Bjornholm, K. Bechgaard, J.J. Neumeier, C. Allgeier, C.S.
Jacobsen, N. Thorup, Phys. Rev. B 53 (1996) 1773;
(c) O.J. Daute, M. Fourmigué, E. Canadell, P. Aubin-Senzier, Adv. Funct. Mater.
12 (2002) 693;
(d) R. Perochon, L. Piekara-Sady, W. Jurga, R. Clérac, M. Fourmigué, Dalton
Trans. (2009) 3052.
[25] (a) J.A. Weil, J.R. Bolton, J. Wertz, Electron Paramagnetic Resonance, Wiley-
Interscience Publication, New York, 1994;
(b) F.A. Walker, J. Bowen, J. Am. Chem. Soc. 107 (1985) 7632;
(c) B.M. Hoffman, D.L. Diemente, F. Basolo, J. Am. Chem. Soc. 92 (1970) 61.
[26] (a) A.H. Maki, N. Edelstein, A. Davison, R.H. Holm, J. Am. Chem. Soc. 86 (1964)
4580;
[23] R. Perochon, C. Poriel, O. Jeannin, L. Piekara-Sady, M. Fourmigué, Eur. J. Inorg.
Chem. (2009) 5413.
[24] R. Kirmse, W.J. Dietzsch, Inorg. Nucl. Chem. 38 (1976) 255.
(b) R. Kirmse, J. Stach, W. Dietzsch, E. Hoyer, Inorg. Chim. Acta 26 (1978) L53;
(c) D. Belo, M.J. Figueira, I.C. Santos, V. Gama, L.C. Pereira, R.T. Henriques, M.
Almeida, Polyhedron 24 (2005) 2035.