A new family of sulfur-rich ligands based on the dmit system: Synthesis and metal complexation of 4-4′-covalently bridged bis(2-thioxo-1,3-dithiol-5-thiolato) units

Article abstract of DOI:10.1039/b201615j

The synthesis of a new series of sulfur-rich ligands is reported. These compounds, which are related to the dmit^2- (2-thioxo-1,3-dithiol-4,5-dithiolato) structure, comprise two 2-thioxo-1,3-dithiol-5-thiolato units linked by a bridging unit at the 4-position of the heterocycle via a dithioether spacer unit. Complexation reactions have been carried out on a variety of metal centres; dialkyl tin and gold(I) derivatives have been isolated and fully characterised. The X-ray crystal structure of an octahedral Ni(II) complex, involving two coordinating pyridine molecules, is presented.

Full text of DOI:10.1039/b201615j

View Article Online / Journal Homepage / Table of Contents for this issue
A new family of sulfur-rich ligands based on the dmit system:
synthesis and metal complexation of 4–4Ј-covalently bridged
bis(2-thioxo-1,3-dithiol-5-thiolato) units
David W. Allen,a Rory Berridge,a Neil Bricklebank,a Elena Cerrada,b Mark E. Light,c
Michael B. Hursthouse,c Mariano Laguna,b Ana Morenob and Peter J. Skabara*d
a Materials Research Institute, Sheffield Hallam University, City Campus, Howard Street,
Sheffield, UK S1 1WB
b Departamento de Química Inorgánica, Instituto de Ciencia de Materiales de Aragón,
Universidad de Zaragoza-C.S.I.C., 50009 Zaragoza, España
c Department of Chemistry, University of Southampton, Highfield, Southampton,
UK SO17 1BJ
d Department of Chemistry, University of Manchester, Oxford Road, Manchester,
UK M13 9PL. E-mail: peter.skabara@man.ac.uk
Received 13th February 2002, Accepted 1st May 2002
First published as an Advance Article on the web 27th May 2002
The synthesis of a new series of sulfur-rich ligands is reported. These compounds, which are related to the dmit2Ϫ
(2-thioxo-1,3-dithiol-4,5-dithiolato) structure, comprise two 2-thioxo-1,3-dithiol-5-thiolato units linked by a bridging
unit at the 4-position of the heterocycle via a dithioether spacer unit. Complexation reactions have been carried out
on a variety of metal centres; dialkyl tin and gold() derivatives have been isolated and fully characterised. The X-ray
crystal structure of an octahedral Ni() complex, involving two coordinating pyridine molecules, is presented.
electrocrystallisation to afford complexes with non-integral
Introduction
oxidation states (Rn[M(dmit)2], where n = non-integer) or by
The conducting and magnetic properties of molecular based
metathesis with a suitable electron donor molecule, such as
materials are normally sustained by a high level of order in the
bulk solid, orchestrated by a network of close intermolecular
TTF (e.g. in [TTF][Pd(dmit)2]2).3 The function of the metal in
the conducting mechanism is difficult to judge, but it is acknow-
contacts. Highly chalcogenated species are particularly good at
ledged that square planar complexes provide the best geometry
invoking such interactions through non-covalent X ؒ ؒ ؒ Y
for close intermolecular interactions. For this reason, Ni(),
bonds (X/Y = Group 16 atom). The most prevalent members of
Pd() and Pt() salts are a priori species for highly ordered
materials containing stacks of planar complexes. The conduct-
ing behaviour of metal(dmit)2 systems is dependent upon the
solid-state structure: nickel salts form molecular stacks, in
this family of materials are tetrathiafulvalene (TTF) 11 and its
derivatives, such as BEDT-TTF 2, together with the metal
dmit complexes [M(dmit)2]nϪ 3 (dmit2Ϫ = 2-thioxo-1,3-dithiol-
4,5-dithiolato),2 which form the basis of most of the known
which the Ni ؒ ؒ ؒ Ni separation is too great to foster a conduct-
organometallic molecular conductors and superconductors.
ing channel through the metal sites,4 whereas platinum gives rise
to dimeric species.5 The Group 10 metals also afford dmit com-
plexes with different stoichiometries and crystal phases within
the same complex, giving rise to materials with a range of con-
ductivity values. Closed-shell counter-cations affect the packing
motif of the heterocycles; for example, larger organic species
(such as Bu4Nϩ) restrict close packing of the metal(dmit)2
species. Open shell cations, such as TTF ϩ, offer greater dimen-
ؒ
sionality to the conducting medium, since conductivity can also
be manifested through the network of TTF units as well as the
metal(dmit)2 species. It is not surprising, therefore, that these
hybrid systems exhibit high levels of conductivity. Indeed,
[TTF][Ni(dmit)2]2,6 αЈ-[TTF][Pd(dmit)2]2,7 α-[TTF][Pd(dmit)2]2,8
and α-[EDT-TTF][Ni(dmit)2]9 comprise four of the nine
reported dmit-based superconductors.
Herein, we report on the synthesis and characterisation of a
new family of dmit-related ligands 6–1010 together with studies
In the case of the dmit2Ϫ complexes 3, previous work has
been constrained to the variation of the transition metal and/or
the counter-cation. The most common metal complexes con-
tain Ni, Pd, Pt, Fe, Cu, Au or Rh, whereas the counterion (R in
Rn[M(dmit)2]) is typically H4Nϩ, R4Nϩ, R4Pϩ, R4Asϩ, or
Me3SOϩ.3 Conducting materials can be prepared either by
of their complexation behaviour towards different metal
centres. In contrast to the dmit2Ϫ ligand, our target derivatives
incorporate two thioether and two thiolate environments as the
overall chelating species. The thioether functionalities are
linked via suitable spacer groups and this feature should present
a major advantage over traditional dmit2Ϫ complexes, by adding
2654
J. Chem. Soc., Dalton Trans., 2002, 2654–2659
This journal is © The Royal Society of Chemistry 2002
DOI: 10.1039/b201615j

View Article Online
solubility and structural and synthetic versatility to the overall
nature of the complex. The X-ray crystal structure of an
octahedral dithiolato nickel complex is also presented.
Owing to the large amount of investigative synthetic work
carried out by many research groups, the applications of TTF
derivatives are no longer confined to the preparation and study
of conducting materials, but are extended towards other areas
of materials science, such as sensors, liquid crystals, nonlinear
optics, supramolecular switches and redox polymers.11 Our
route towards dmit-σ-dmit bridged ligands opens up an almost
infinite number of synthetic variations. Furthermore, the spacer
group can be designed to incorporate other features into the
ligand, such as chirality, rigidity, additional chelating atoms
and even other redox-active groups. With this type of design
strategy, the role of metal dmits in materials science could also
deviate from the traditional focus on the conducting and mag-
netic behaviour of these materials.
Results and discussion
Ligand synthesis
In general, our strategy involves the preparation of bis-
(2-thioxo-1,3-dithiol-5-cyanoethylthio) derivatives 6–10 that
are linked at the 4(4Ј)-positions of the sulfur heterocycles via a
spacer group. These new ligands can be prepared from the reac-
tion of compound 412 with one equivalent of base, followed by
the addition of a suitable difunctional bridging unit (Scheme 1).
Mono-deprotected intermediate 5 is stable in solution (under
N2) for several days, but is typically treated with a half molar
equivalent of dibromo compound immediately, affording the
corresponding bridged systems 6–10. Thus, compounds 6–9
were obtained from the reaction of 5 with 1,2-dibromoethane
(70%), 1,2-bis(bromomethyl)benzene (75%), 1,3-bis(bromo-
methyl)benzene (65%) and 1,4-bis(bromomethyl)benzene (60%)
respectively. The pyridine derivative 10, obtained as a crude
oil from the reaction of 5 and 2,6-bis(bromomethyl)pyridine
(50%), was converted into the analytically pure salt 10ؒHCl by
treatment with acetyl chloride/ethanol at 0 ЊC in ethyl acetate
(80% from 10). Under mildly basic conditions compounds 6–10
can be easily deprotected producing dithiolate salts 6a–10a
(Scheme 1), affording strong ligands for complexation to tran-
sition metal species. The bis(tetramethyl ammonium) salt of
thiolate 6a was isolated and found to be stable under ambient
conditions for several weeks,13 but in general dithiolates 6a–10a
were treated in situ with metal salts (vide infra). Using this
methodology, we are presented with a vast range of possible
derivatives due to the abundance of available difunctional sys-
tems that are capable of undergoing nucleophilic substitution
reactions with a thiolate functionality.
Scheme 1 Reagents and conditions: (i) R4NOH, THF (ii) 1/2 equiv.
Br–bridge–Br; (iii) R4NOH or NaOEt, THF or DMF; (iv) metal halide.
Direct metallation of thiolate ligands
Treatment of thiolate ligands 6a–10a with metal chlorides or
bromides MX2 (M = Fe, Co, Ni, Cu, Zn), gave impure coloured
solids, most of which were sparingly soluble in common
organic solvents or water. We were not able to purify the com-
plexes to give satisfactory elemental analyses and some of the
compounds showed signs of decomposition by a series of
colour changes on standing. Only in one case, the reaction of
o-xylene bridge ligand 7a with nickel bromide (Scheme 2), were
we able to characterise the product (11). The room temperature
magnetic moment of 11 (3.33 µB) is typical of a tetrahedrally-
distorted nickel() species.14 Complex 11 is soluble in DMSO,
and sparingly soluble in DMF or pyridine. Recrystallisation of
11 from pyridine afforded small black crystals of the complex
11ؒ(py)2, in which two molecules of pyridine have coordinated
to the nickel centre producing an octahedral species. The X-ray
structure of [Ni(dmit–o-CH2C6H4CH2–dmit)(py)2] (Fig. 1,
Table 1) displays a distorted octahedral coordination geometry
around the metallic centre with one of the pyridine ligands and
Scheme 2
one of the thioether groups in the apical positions. The main
distortion arises from the pinching of the S–Ni–S angles of the
coordinating dmit as commonly seen when in a non-square
planar geometry. The Ni–S distances range from 2.3842(17) to
2.5827(18) Å, with the Ni–S(thioether) distances greater than
the respective Ni–S(thiolate) bond lengths. The distances within
J. Chem. Soc., Dalton Trans., 2002, 2654–2659
2655

View Article Online
Table 1 Selected bond lengths [Å] and angles [Њ] for 11ؒ(py)2
In order to improve the solubility of the complexes, we
carried out the reaction of the dithiolate derivatives 6a–9a with
the nickel() complex [NiCl2dppe] (dppe = bis(diphenylphos-
phino)ethane). This reaction gave a mixture of products
(Scheme 3) which were purified by column chromatography and
Ni(1)–N(1)
Ni(1)–N(2)
Ni(1)–S(10)
Ni(1)–S(1)
Ni(1)–S(2)
Ni(1)–S(6)
S(1)–C(1)
2.095(5)
2.109(5)
2.3842(17)
2.4105(17)
2.5585(17)
2.5827(18)
1.717(6)
1.749(5)
1.841(6)
1.714(6)
1.743(6)
1.835(7)
S(5)–C(2)
S(5)–C(3)
S(3)–C(2)
S(3)–C(1)
S(9)–C(13)
S(9)–C(14)
S(7)–C(13)
S(7)–C(12)
S(4)–C(2)
S(8)–C(13)
C(3)–C(1)
1.712(6)
1.741(5)
1.734(6)
1.757(5)
1.737(7)
1.752(5)
1.711(7)
1.757(6)
1.644(6)
1.659(6)
1.351(8)
S(2)–C(3)
S(2)–C(4)
S(10)–C(14)
S(6)–C(12)
S(6)–C(11)
N(1)–Ni(1)–N(2)
N(1)–Ni(1)–S(10)
N(2)–Ni(1)–S(10)
N(1)–Ni(1)–S(1)
N(2)–Ni(1)–S(1)
S(10)–Ni(1)–S(1)
N(1)–Ni(1)–S(2)
N(2)–Ni(1)–S(2)
S(10)–Ni(1)–S(2)
S(1)–Ni(1)–S(2)
N(1)–Ni(1)–S(6)
N(2)–Ni(1)–S(6)
96.17(19)
94.61(13)
87.79(13)
87.01(13)
94.88(13)
176.71(7)
171.09(13)
83.39(14)
94.26(6)
S(10)–Ni(1)–S(6)
S(1)–Ni(1)–S(6)
S(2)–Ni(1)–S(6)
C(1)–S(1)–Ni(1)
C(3)–S(2)–Ni(1)
C(4)–S(2)–Ni(1)
C(14)–S(10)–Ni(1)
C(12)–S(6)–Ni(1)
C(11)–S(6)–Ni(1)
C(19)–N(1)–Ni(1)
C(15)–N(1)–Ni(1)
C(24)–N(2)–Ni(1)
85.05(6)
92.31(6)
98.32(6)
98.20(19)
96.9(2)
109.7(2)
100.5(2)
97.7(2)
121.5(2)
120.6(4)
122.7(4)
120.5(4)
84.16(5)
83.23(15)
172.75(13)
Scheme 3 Reagents and conditions: (i) NaOEt, [NiCl2(dppe)].
identified by NMR and mass spectroscopy. The corresponding
metallic bis-dithiolate compound, bridged by the spacer unit,
was not obtained from any of the experiments performed.
Instead, we identified [Ni(dmit)dppe]18 as the major product (as
a result of the cleavage of the spacer unit), together with cyclic
compounds 6b, 8b and 9b, presumably from the oxidation of
the thiolate functionalities followed by radical coupling. Similar
S–S bond formation was previously described by some of us in
the reaction of [Sn(dmit)Me2] with [Ni(Mes)Br(PPh2Me)2].19
Additionally, some derivatives of the diphosphine were
also detected: the dioxide and disulfide of bis(diphenyl-
phosphino)ethane (O2dppe and S2dppe), were identified by
comparison of their spectroscopic properties with pure
samples; on the basis of 31P NMR and mass spectra we identi-
fied diphenylphosphineoxide(diphenylphosphinesulfide)ethane
(SOdppe).
Fig. 1 X-Ray crystal structure of 11ؒ(py)2 (H atoms omitted for
clarity).
the dmit unit (S–C 1.736 Å on average and C᎐C 1.351(8),
᎐
1.340(8) Å) are similar to those found in the [Ni(C3S5)2] unit.4
The Ni–N bond lengths (2.095(5) and 2.109(5) Å) are similar to
those found in related nickel thioether complexes with pyridine
as additional ligands.15–17 The angle between the least squares
planes of the two pyridine rings is 53.89(26)Њ.
Interestingly, the molecules form chains running along the a
axis via weak S ؒ ؒ ؒ S interactions within the sum of the van der
Waals radii (S5–S7 = 3.418(3), S5–S6 = 3.521(4) Å) (Fig. 2).
Transmetallation reactions of thiolates
Since the synthesis of metal complexes starting directly from
the dithiolate species 6a–10a proved problematical, we decided
to investigate the use of tin derivatives as dithiolate transfer
reagents. We pursued this approach because similar dithiolate
tin complexes have shown that they can easily transfer the
dithiolate ligand to other metals.20 The dithiolate species
6a–10a were treated with [SnCl2Me2] according to Scheme 4.
The resulting tin compounds 12–16 can be isolated as yellow
air-stable solids which are insoluble in most organic solvents
(14–97% yield from 6a–10a).
The 1H NMR spectra of 12–16 in d6-DMSO show the
corresponding peaks due to the spacer units and the signals due
to the methyl groups co-ordinated to the metallic centre. These
occur as multiplets in 12, 15 and 16, two singlets in the case
of 13 and 15 and a unique signal flanked by tin satellites for
compound 14. In all cases the mass spectra (LSIMSϩ) do
not show the molecular ion peak; instead, fragmentation peaks
Fig. 2 Chains extending along the a axis of 11ؒ(py)2.
Despite the non-planar geometry of the complex (cf. typical
square planar metal-dmit2 systems), this feature indicates that
such materials can display long-range order through short
intermolecular S ؒ ؒ ؒ S contacts, which satisfies one criterion
for a material with conducting properties.
2656
J. Chem. Soc., Dalton Trans., 2002, 2654–2659

View Article Online
way as those using the dithiolates 6a–9a, though higher yields
were obtained for cyclic derivatives 6b, 8b and 9b.
Conclusion
We have presented the synthesis of a new series of sulfur-based
ligands as variants of the well-known dmit2Ϫ system. The
methodology used for the synthesis of the ligands opens up
a plethora of structural possibilities within the bridging
fragment. The incorporation of functional groups and more
complex species should be readily accessible. Attempts at
forming transition metal complexes directly from dithiolated
species mostly resulted in poorly soluble, unstable and impure
products. Nevertheless, dialkyl tin derivatives have been suc-
cessfully isolated, which have potential use in transmetallation
reactions. For example, gold() complexes have been prepared
by this route. The major challenge ahead is to design and syn-
thesise similar ligands with enhanced solubility, enforcing
stability and square planar geometry in the resulting transition
metal complexes.
Experimental
Infrared spectra were recorded on a Perkin-Elmer 883 and ATI
Mattson Instruments Genesis Series spectrophotometer, over
the range 4000–200 cmϪ1, by using Nujol mulls between poly-
ethylene sheets or as KBr discs. 1H and 31P NMR spectra on a
Varian UNITY 300 or Bruker AC 250 in CDCl3 or [D6]DMSO
solutions; chemical shifts are quoted relative to SiMe4 (1H) and
H3PO4 (external 31P). The C, H, N and S analyses were per-
formed with a Perkin-Elmer 2400 microanalyser and also by
MEDAC Ltd. Mass spectra were recorded on a VG Autospec,
by liquid secondary ion mass spectrometry (LSIMSϩ) using
nitrobenzylalcohol as matrix and a caesium gun or using a VG
7070E in EI or FAB mode. Absorption spectra were obtained
using a Unicam UV2 spectrophotometer. The melting points
were measured using Gallenkamp or Electrothermal apparatus.
Flash column chromatography was carried out using Fluka
Kiesselgel (70–230 mesh). Most of the reactions were per-
formed under a nitrogen atmosphere. (NEt2)2[Zn(dmit)2],22
[AuCl(PPh2Me)],23 [NiCl2(dppe)]24 were obtained according to
the literature procedures. All solvents were dried and distilled
prior to use, using standard literature procedures. All organic
reagents were used as supplied.
Scheme 4 Reagents and conditions: (i) [SnCl2Me2]; (ii) 2[AuCl-
(PPh2Me)].
are observed due to the cleavage of the spacer units to give
[Sn(dmit)Me2]ϩ species.
Tin dithiolates act as good transfer reagents with gold() and
gold()20 complexes under very mild conditions. The dialkyl
tin analogues of 12–16 are, therefore, suitable reagents for the
reaction with gold() species. Complexes 17–21 with the formula
[Au2(dmit–bridge–dmit)(PPh2Me)2] (Scheme 4) can be isolated
as air and moisture stable yellow solids which are soluble in
common organic solvents. The 31P{1H}NMR spectra display a
singlet at about 22 ppm assignable to only one type of phos-
Syntheses
General procedure for the synthesis of compounds 6–10. To
a stirred solution of 412 (2.0 g, 6.57 mmol) in THF (40 ml), at
Ϫ5 ЊC, was added tetrabutylammonium hydroxide (7.9 ml,
1 M solution in methanol, 7.90 mmol) over 20–30 min. To
the resulting purple mixture was added 1,2-dibromoethane,
αЈα-dibromo-o-xylene, αЈα-dibromo-m-xylene, αЈα-dibromo-p-
xylene or 2,6-bis(bromomethyl)pyridine (0.6 eq.). The reaction
was allowed to stir at room temperature for 16 h. The solvent
was evaporated under reduced pressure and the residue
chromatographed on silica gel using dichloromethane as the
eluent.
1
phorus. The H NMR spectra show multiplets in the phenyl
region due to the PPh2Me phosphine and the aromatic groups
in 18–21. For complex 17, a singlet centred at 2.99 ppm is
assignable to the SCH2CH2S fragment. In all cases, a doublet at
ca. 2 ppm is observed, corresponding to the methyl group of the
PPh2Me unit coupled with the phosphorus atom. In the IR
3-(5-{2-[5-(2-Cyanoethylsulfanyl)-2-thioxo-1,3-dithiol-4-yl-
sulfanyl]ethylsulfanyl}-2-thioxo-1,3-dithiol-4-ylsulfanyl)propio-
nitrile (6). Yellow powder, recrystallised from acetonitrile.
spectra of compounds 17–21, the ν(C᎐S) vibration appears at
᎐
about 1060 and 1020 cmϪ1, which is similar to those found in
other dmit-gold derivatives.21
Yield 70%. mp 125–126 ЊC. MS (EI, Mϩ): m/z: 528. H NMR
1
Complexes 17, 18 and 21 show the parent peak in LSIMSϩ
(nba as matrix) with low abundance. In addition [S(AuP-
Ph2Me)3]ϩ and [S(AuPPh2Me)2]ϩ are also present in all cases, as
a consequence of the decomposition of the dmit fragments.
On the basis that the tin derivatives are good transfer
reagents for the preparation of gold() complexes, we performed
the reaction of compounds 12–16 with the nickel complex
[NiCl2(dppe)] in order to transfer the dithiolate ligand to the
Ni() centre. Nevertheless, the reactions proceeded in the same
(250 MHz, [D6]DMSO, 25 ЊC) δ 3.31 (s, 4H), 3.26 (t, 4H, J =
6.5 Hz) and 2.95 (t, 4H, J = 6.5 Hz). 13C NMR (63 MHz,
[D6]DMSO, 25 ЊC) δ 210.8, 137.6, 135.5, 118.8, 35.7, 31.5 and
18.2. IR (cmϪ1) 2245 (C᎐N), 1050 (C᎐S). Elemental anal. Calc.
᎐
᎐
᎐
for C14H12N2S10 C, 31.8; H, 2.3; N, 5.3%. Found: C, 31.9; H, 2.2;
N, 5.4%.
3-(5-{2-[5-(2-Cyanoethylsulfanyl)-2-thioxo-1,3-dithiol-4-yl-
sulfanylmethyl]benzylsulfanyl}-2-thioxo-1,3-dithiol-4-ylsulfanyl)-
propionitrile (7). Orange/red oil. Yield 75%. MS (EI, Mϩ): m/z:
J. Chem. Soc., Dalton Trans., 2002, 2654–2659
2657

View Article Online
604. 1H NMR (250 MHz, CDCl3, 25 ЊC) δ 7.29 (m, 4H), 4.29 (s,
4H), 2.95 (t, 4H, J = 6.95 Hz) and 2.57 (t, 4H J = 6.95 Hz). 13
NMR (63 MHz, CDCl3, 25 ЊC) δ 210.5, 139.0, 136.2, 134.5,
131.6, 129.4, 117.8, 39.1, 32.4 and 19.1. Elemental anal. Calc.
for C20H16N2S10 C, 39.7; H, 2.7; N, 4.6%. Found: C, 39.9; H, 2.6;
N, 4.6%.
8b. Method (a). The reaction was performed in a similar
way as the previous one. Starting from 8 (0.10 g, 0.16 mmol) in
THF (10 ml) a solution of 0.1 M NaOEt (0.4 mmol; 4 ml) was
added and to the resulting red solution, [NiCl2(dppe)] (0.0845 g,
0.16 mmol) was added. After stirring for 12 hours, the red
solution became brown and the solvent was removed in vacuo.
Yield for [Ni(dmit)(dppe)]: 82% (based on [NiCl2(dppe)]). The
organic compound 8b was obtained in very small quantity, 3%
overall, as a yellow oil.
Method (b). To a solution of 14 (0.10 g, 0.15 mmol) in
distilled THF (10 ml) was added [NiCl2(dppe)] (0.0792 g,
0.15 mmol). After stirring for 12 hours, the orange solution
became brown and the solvent was removed in vacuo. The crude
product was purified by column chromatography using hexane–
acetone (1 : 1). Yield for [Ni(dmit)(dppe)]: 84% (based on
[NiCl2(dppe)]). The organic compound 8b was obtained in 10%
overall yield as a yellow oil. 1H NMR (300 MHz, CDCl3,
25 ЊC): δ 7.73–7.69 (m, 2 H, Ph), 7.57–7.52 (m, 2 H, Ph) and
4.28–4.16 (m, 4 H, SCH2).
9b. To a suspension of compound 9 (0.10 g, 0.15 mmol) in
10 ml of THF was added [NidppeCl2] (0.0792 g, 0.15 mmol).
After stirring for 12 hours, the suspension became a brown
solution and the solvent was removed in vacuo. The crude
product was purified by column chromatography using ether–
dichloromethane (1 : 1). Yield for [Ni(dmit)(dppe)]: 78% (based
on [NiCl2(dppe)]). The organic compound 9b was obtained in
21% overall yield as a yellow oil. 1H NMR (300 MHz, CDCl3,
25 ЊC): δ 7.73–7.69 (m, 2 H, Ph), 7.56–7.51 (m, 2 H, Ph) and
4.24–4.21 (m, 4 H, SCH2).
C
3-(5-{3-[5-(2-Cyanoethylsulfanyl)-2-thioxo-1,3-dithiol-4-yl-
sulfanylmethyl]benzylsulfanyl}-2-thioxo-1,3-dithiol-4-ylsulfanyl)-
propionitrile (8). Orange/red oil. Yield 65%. MS (FAB, Mϩ):
1
m/z: 605. H NMR (250 MHz, CDCl3, 25 ЊC) δ 7.33 (m, 4H),
4.10 (s, 4H), 2.99 (t, 4H, J = 7.01 Hz) and 2.61 (t, 4H J = 6.89
Hz). 13C NMR (63 MHz, CDCl3, 25 ЊC) δ 210.6, 140.1, 137.0,
134.1, 130.0, 129.3, 117.7, 41.1, 32.4 and 19.1.
3-(5-{4-[5-(2-Cyanoethylsulfanyl)-2-thioxo-1,3-dithiol-4-yl-
sulfanylmethyl]benzylsulfanyl}-2-thioxo-1,3-dithiol-4-ylsulfanyl)-
propionitrile (9). Yellow powder, recrystallised from
1
acetonitrile. Yield 60%. mp 120–121 ЊC. H NMR (250 MHz,
[D6]DMSO, 25 ЊC) δ 7.35 (s, 4H), 4.26 (s, 4H), 3.15 (t, 4H,
J = 6.70 Hz) and 2.83 (t, 4H J = 6.70 Hz). 13C NMR (63 MHz,
[D6]DMSO, 25 ЊC) δ 210.9, 138.8, 136.1, 135.2, 129.4, 118.8,
40.0, 31.5 and 18.1. IR (cmϪ1) 2250 (C᎐N), 1065 (C᎐S).
᎐
᎐
᎐
Elemental anal. Calc. for C20H16N2S10 C, 39.7; H, 2.7; N, 4.6%.
Found: C, 39.9; H, 2.8; N, 4.9%.
3-(5-{6-[5-(2-Cyanoethylsulfanyl)-2-thioxo-1,3-dithiol-4-yl-
sulfanylmethyl]pyridin-2-ylmethylsulfanyl}-2-thioxo-1,3-dithiol-
4-ylsulfanyl)propionitrile hydrochloride (10ؒHCl). Compound
10 was isolated as the hydrochloride salt as a yellow solid:
following the general procedure given above, compound 10 was
then dissolved in ethyl acetate. A solution of HCl in ethyl acet-
ate (prepared by mixing equimolar amounts of acetyl chloride
and ethanol at 0 ЊC) was added to precipitate the product.
Overall yield 40%. mp 154–155 ЊC. 1H NMR (250 MHz,
[D6]DMSO, 25 ЊC) δ 7.90 (t, 1H, J = 7.74 Hz), 7.46 (d, 2H, J =
7.72 Hz), 6.89 (br s, 1H), 4.34 (s, 4H), 3.17 (t, 4H J = 6.80 Hz)
and 2.86 (t, 4H J = 6.80 Hz). 13C NMR (63 MHz, [D6]DMSO,
25 ЊC) δ 219.0, 155.6, 139.2, 138.0, 136.0, 122.9, 118.7, 31.5 and
[Ni(dmit-o-CH2C6H4CH2-dmit)(py)2] (11ؒ(py)2). Under N2 to
a stirred solution of compound 7 (0.50 g, 0.80 mmol) in 10 ml
of THF was added NaOEt (0.124 g, 1.8 mmol) in 5 ml of dry
distilled ethanol to yield a dark red solution. After stirring for
20 minutes at room temperature, a solution of NiBr2 (0.175 g,
0.80 mmol) in 5 ml of dry ethanol was added to yield a dark
brown solution and brown precipitate. The precipitate was
filtered off, and washed sequentially with 20 ml ethanol, 20 ml
deionised water and 20 ml propan-2-ol to yield 0.260 g of
brown powder. The brown powder was dissolved in 15 ml
pyridine to give a brown/black solution and after 3 days several
small black crystals of 11ؒ(py)2 formed at the surface of the
pyridine.
18.2. IR (cmϪ1) 2246 (C᎐N), 1060 (C᎐S). Elemental anal. Calc.
᎐
᎐
᎐
for C19H16N3ClS10 C, 35.5; H, 2.5; N, 6.5%. Found: C, 35.9;
H, 2.5; N, 6.5%.
Bis(tetramethylammonium) salt (6a). To a stirred solution
of 6 (0.5 g, 0.945 mmol) in dry THF (20 ml) was added tetra-
methylammonium hydroxide (0.72 ml of a 25% w/w solution
in methanol, 1.98 mmol), dropwise over 10 min to give a red
solution. After 30 min, the resulting precipitate was isolated by
filtration and washed with dry THF, followed by dry diethyl
ether, to give an orange powder. Yield: 0.52 g (96%), recrys-
tallised from methanol, mp 165 ЊC (decomp.). 1H NMR
(250 MHz, [D6]DMSO, 25 ЊC) δ 3.12 (s, 24H) and 3.01 (s, 4H).
13C NMR (63 MHz, [D6]DMSO, 25 ЊC) δ 210.9, 171.7, 110.4,
Crystal data for 11ؒ(py)2. Data were collected on a Bruker
Nonius Kappa CCD area detector diffractometer with a rotat-
ing molybdenum anode following standard procedures. Crystal
data: C24H18N2NiS10, Mr = 713.71, T = 298(2) K, triclinic, space
¯
group P1, a = 9.5662(6), b = 12.5254(8), c = 14.0131(8) Å,
α = 76.558(3), β = 86.314(3), γ = 67.969(3)Њ, V = 1513.32(16) Å3,
ρcalc = 1.566 g cm Ϫ3, µ = 1.350 mmϪ1, Z = 2, reflections collected:
18864, independent reflections: 4319 (Rint = 0.1189), final R
indices [I > 2σ(I )]: R1 = 0.0517, wR2 = 0.1149, R indices (all
data): R1 = 0.1009. wR2 = 0.1364.
54.5 and 34.2. IR (cmϪ1) 1058 (C᎐S).
᎐
2,3,5,7,9,12,14,16-Octathia-tricyclo[11.3.0.04,8]hexadeca-1-
(13),4(8)-diene-6,15-dithione (6b).
Method (a). To a suspension of compound 6 (0.10 g, 0.19
mmol) in THF (10 ml) was added a solution of 0.1 M NaOEt
(0.4 mmol; 4 ml) and to the resulting red solution, [Ni
Cl2(dppe)] (0.10 g, 0.19 mmol) was added. After stirring for
12 hours, the red solution became brown and the solvent was
removed in vacuo. The crude product was purified by column
chromatography using hexane/acetone (2 : 1). Yield for [Ni-
(dmit)(dppe)]: 76% (based on [NiCl2(dppe)]). The organic com-
pound 6b was obtained in very small quantity, 3% overall, as a
yellow oil.
CCDC reference number 181362.
See http://www.rsc.org/suppdata/dt/b2/b201615j/ for crystal-
lographic data in CIF or other electronic format.
General procedure for the synthesis of dimethyl tin derivatives
12–16. To a suspension or solution of the corresponding
protected dithiolate (6–10, 0.33 mmol) in THF (10 ml) was
added a solution of NaOEt (6.6 ml, 0.1 M, 0.66 mmol) and to
the resulting red solution, [SnCl2Me2] (0.0725 g, 0.33 mmol).
After stirring for 30 minutes, partial evaporation of the solvent
and addition of cold methanol or diethyl ether (10 ml) afforded
yellow solids, which were filtered off, washed with water and
dried in vacuo.
Method (b). To a suspension of 12 (0.10 g, 0.18 mmol)
in dried acetone (10 ml) was added [NiCl2(dppe)] (0.095 g,
0.18 mmol). After stirring for 12 hours, the suspension became
a brown solution and the solvent was removed in vacuo. The
crude product was purified as above. Yield for [Ni(dmit)(dppe)]:
93% (based on [NiCl2(dppe)]). The organic compound 6
12. Yield 97%. mp 184 ЊC. 1H NMR (300 MHz, [D6]DMSO,
25 ЊC) δ 3.00 (s, 4 H, SCH2CH2S) and 1.01–0.62 (m, 6 H, CH3).
1
was obtained in 11% overall yield as a yellow oil. H NMR
(300 MHz, CDCl3, 25 ЊC): δ 2.31 (s, 4 H, SCH2CH2S).
IR (cmϪ1) 1065, 1040 (C᎐S) and 515, 464 (Sn–Me). Elemental
᎐
2658
J. Chem. Soc., Dalton Trans., 2002, 2654–2659

View Article Online
anal. Calc. for C10H10SnS10: C, 21.1; H, 1.8; S, 56.3%. Found:
C, 20.7; H, 1.9; S, 55.4%.
21. Yield (a) 98%, (b) 55%. mp 80 ЊC. MS (LSIMSϩ):
1
m/z (%): 1223 (74, [S(AuPPh2Me)3]ϩ); 1292 (4, Mϩ). H NMR
13. Yield 14%. mp 200 ЊC. 1H NMR (300 MHz, [D6]DMSO,
25 ЊC) δ 7.29–7.27 (m, 4 H, Ph), 4.56–4.24 (m, 4 H, SCH2), 1.23
(300 MHz, CDCl3, 25 ЊC) δ 7.65–7.55 (m, 8 H, PPh2Me),
7.52–7.45 (m, 12 H, PPh2Me), 7.44 (t, 1 H, J (H–H) = 7 Hz),
7.02 (d, 2 H, J (H–H) = 7 Hz), 3.97 (s, 4 H, SCH2) and 2.12 (d,
6 H, J (P–H) = 10 Hz, CH3). 31P-{1H}NMR (300 MHz, CDCl3,
(s, 3 H, CH3) and 1.0 (s, 3 H, CH3). IR (cmϪ1) 1066, 1030 (C᎐S)
᎐
and 575, 455 (Sn–Me). Elemental anal. Calc. for C16H14S10Sn:
C, 37.2; H, 2.7; S, 24.8%. Found: C, 37.5; H, 2.9; S, 24.7%.
25 ЊC): δ 22.0 (s). IR (cmϪ1) 1059, 1023 (C᎐S). Elemental anal.
᎐
1
14. Yield 85%. mp 92 ЊC. H NMR (300 MHz, [D6]DMSO,
Calc. for C39H33NAu2P2S10 C, 36.3; H, 2.6; N, 1.1; S, 24.8%.
Found: C, 36.5; H, 2.7; N, 1.2; S, 24.5%.
25 ЊC) δ 7.29–7.16 (m, 4 H, Ph), 4.12 (s, 4 H, SCH2) and 0.9
(s, 6 H, J (Sn–H) = 114 Hz, CH3). IR (cmϪ1) 1128 (br) (C᎐S)
᎐
and 517, 441 (Sn–Me). Elemental anal. Calc. for C16H14SnS10:
C, 29.8; H, 2.2; S, 49.6 %. Found: C, 30.3; H, 2.5; S, 48.2%.
15. Yield 85%. mp 172 ЊC. 1H NMR (300 MHz, [D6]DMSO,
25 ЊC) δ 7.23 (s, 4 H, Ph), 4.10 (s, 4 H, SCH2), 0.67–1.0 (m, 6 H,
Acknowledgements
M. L., E. C. and A. M. would like to thank DGES (PB98–0542)
for financial support and Caja Inmaculada (Programa
EUROPA) for a travel grant to A. M. We thank Sheffield
Hallam University for financial support to R. B.
CH3). IR (cmϪ1) 1058, 1020 (C᎐S) and 516, 465 (Sn–Me).
᎐
Elemental anal. Calc. for C16H14SnS10: 29.8; H, 2.2; S, 49.6 %.
Found: C, 30.2; H, 2.3; S, 48.5%.
16. Yield 75%. mp 132 ЊC. 1H NMR (300 MHz, [D6]DMSO,
25 ЊC) δ 7.65 (t, 1 H, J (H,H) = 13 Hz), 7.20 (d, 2 H, J (H,H) =
13 Hz), 4.25 (s, 4 H, SCH2) and 1.30–0.60 (m, 6 H, CH3). IR
References
1 M. R. Bryce, Chem. Soc. Rev., 1991, 20, 355; Organic
Superconductors (including Fullerenes), J. M. Williams, J. R. Ferraro,
R. J. Thorn K. D. Carlson, U. Geiser, H. H. Wang, A. M. Kini and
M.-H. Whangbo, Prentice Hall, New Jersey, 1992; M. R. Bryce,
J. Mater. Chem., 1995, 5, 1481; T. Ishiguro, K. Yamaji and G. Saito,
Organic Superconductors, 2nd edn., Springer-Verlag, Berlin,
Heidelberg, 1998.
2 P. Cassoux, L. Valade, H. Kobayashi, A. Kobayashi, R. A. Clark
and A. E. Underhill, Coord. Chem. Rev., 1991, 110, 115.
3 P. Cassoux, Coord. Chem. Rev., 1999, 185–186, 213.
4 L. Valade, M. Bousseau, A. Gleizes and P. Cassoux, J. Chem. Soc.,
Chem. Commun., 1983, 110; L. Valade, J.-P. Legros, M. Bousseau,
P. Cassoux, M. Garbauskas and L. V. Interrante, J. Chem. Soc.,
Dalton Trans., 1985, 783; R. Kato, H. Kobayashi, A. Kobayashi and
Y. Sasaki, Chem. Lett., 1985, 131; H. Kim, A. Kobayashi, Y. Sasaki,
R. Kato and H. Kobayashi, Chem. Lett., 1987, 1799.
5 M. Bousseau, L. Valade, J.-P. Legros, P. Cassoux, M. Garbauskas
and L. V. Interrante, J. Am. Chem. Soc., 1986, 108, 1908.
6 L. Brossard, M. Ribault, M. Bousseau, L. Valade and P. Cassoux,
C. R. Acad. Sci., Ser. II, 1986, 302, 205.
7 L. Brossard, H. Hurdequint, M. Ribault, L. Valade, J.-P. Legros and
P. Cassoux, Synth. Met., 1988, 27, B157.
8 L. Brossard, M. Ribault, L. Valade and P. Cassoux, J. Phys. (Paris),
1989, 50, 1521.
9 H. Tajima, M. Inokuchi, A. Kobayashi, T. Ohta, R. Kato,
H. Kobayashi and H. Kuroda, Chem. Lett., 1993, 1235.
10 Preliminary communication: R. Berridge, N. Bricklebank, D. W.
Allen, P. J. Skabara, K. M. A. Malik, S. J. Coles and M. B.
Hursthouse, Synth. Met., 2001, 120, 1023.
(cmϪ1) 1060, 1020 (C᎐S) and 573, 465 (Sn–Me). Elemental anal.
᎐
Calc. for C15H13NSnS10 C, 27.4; H, 2.2; N, 1.8; S, 48.3%. Found:
C, 27.9; H, 2.1; N, 2.2; S, 49.6%.
General procedure for the synthesis of gold derivatives 17–21
[Au2(dmit–bridge–dmit)(PPh2Me)2]. Method (a). To a suspen-
sion of the corresponding protected dithiolate 6–10 (0.1 mmol)
in ethanol (10 ml) was added a solution of NaOEt (4 ml, 0.1 M,
0.4 mmol;) with stirring and cooling using an ice-bath, followed
by [AuCl(PPh2Me)] (0.0864 g, 0.2 mmol). After stirring for
6 hours, the yellow solids obtained were filtered off, washed
with ethanol and dried in vacuo.
Method (b). To a suspension of the corresponding tin
derivative 12–16 (0.1 mmol) in ethanol (10 ml), cooled by an
ice-bath, was added [AuCl(PPh2Me)] (0.0864 g, 0.2 mmol).
After stirring overnight, the yellow solids obtained were filtered
off, washed with ethanol and dried in vacuo.
17. Yield (a) 95%, (b) 72%. mp 87 ЊC. MS (LSIMSϩ):
1
m/z (%): 1215 (5, Mϩ), 1223 (20, [S(AuPPh2Me)3]ϩ). H NMR
(300 MHz, CDCl3, 25 ЊC) δ 7.65–7.59 (m, 8 H, Ph), 7.57–7.49
(m, 12 H, Ph), 2.99 (s, 4 H, SCH2CH2S) and 2.14 (d, 6 H,
J (P–H) = 10 Hz, CH3). 31P-{1H}NMR (300 MHz, CDCl3,
25 ЊC): δ 22.1 (s). IR (cmϪ1) 1058, 1020 (C᎐S). Elemental
᎐
anal. Calc. for C34H30Au2P2S10 C, 33.6; H, 2.5; S, 26.4%. Found:
C, 33.7; H, 2.5; S, 26.1%.
11 M. R. Bryce, J. Mater. Chem., 2000, 10, 589.
12 N. Svenstrup, K. M. Rasmussen, T. K. Hansen and J. Becher,
Synthesis, 1994, 809.
18. Yield 98%, method (a). mp 95 ЊC. MS (LSIMSϩ):
1
m/z (%): 1292 (3, Mϩ), 1223 (10, [S(AuPPh2Me)3]ϩ). H NMR
13 The X-ray crystal structure of 6a has already been reported in
(300 MHz, CDCl3, 25 ЊC) δ 7.63–7.56 (m, 8 H, PPh2Me), 7.46–
7.30 (m, 12 H, PPh2Me), 7.16–7.11 (m, 2H), 7.10–7.08 (m, 2 H),
4.20 (s, 4 H, SCH2) and 2.07 (d, 6 H, J (P–H) = 10 Hz, CH3).
ref. 10; CCDC reference number 147053.
14 F. A. Cotton, G. Wilkinson, C. A. Murillo and M. Bochmann,
Advanced Inorganic Chemistry, 6th edn., Wiley-Interscience,
Chichester, 1999.
15 A. J. Blake, J. Casabo, F. A. Devillanova, L. Escriche, A. Garau,
F. Isaia, V. Lippolis, R. Kivekas, V. Muns, M. Schröder, R. Sillanpaa
and G. Verani, J. Chem. Soc., Dalton Trans., 1999, 1085.
16 M. Cha, C. L. Gatlin, S. C. Critchlow and J. A. Kovacs, Inorg.
Chem., 1993, 32, 5868.
17 D. Sellman, H. Schillinger and F. Knock, Z. Naturforsch., Teil B,
1992, 47, 645.
18 R. Vicente, J. Ribas, X. Solans, M. Font, A. Mari, P. de Loth and
P. Cassoux, Inorg. Chim. Acta, 1987, 132, 229.
31P-{1H}NMR (300 MHz, CDCl3, 25 ЊC): δ 21.9 (s). IR (cmϪ1
)
1057, 1020 (C᎐S). Elemental anal. Calc. for C H Au P S
᎐
40 34
2
2
10
C, 37.2; H, 2.7; S, 24.8%. Found: C, 37.5; H, 2.8; S, 24.4%.
19. Yield 98%, method (a). mp 82 ЊC. MS (LSIMSϩ):
m/z (%): 1223 (32, [S(AuPPh2Me)3]ϩ). 1H NMR (300 MHz,
CDCl3, 25 ЊC) δ 7.68–7.61 (m, 8 H, PPh2Me), 7.53–7.42 (m,
12 H, PPh2Me), 7.26–7.22 (m, 2 H), 7.22–7.13 (m, 2 H),
4.13–3.9 (s, 4 H, SCH2) and 2.12 (d, 6 H, J (P–H) = 10 Hz,
CH3). 31P-{1H}NMR (300 MHz, CDCl3, 25 ЊC): δ 21.7 (s).
IR (cmϪ1) 1058, 1022 (C᎐S). Elemental anal. Calc. for C H -
19 E. Cerrada, S. Elipe, M. Laguna, F. Lahoz and A. Moreno, Synth.
Met., 1999, 102, 1759.
᎐
40 34
Au2P2S10 C, 37.2; H, 2.7; S, 24.8%. Found: C, 37.1; H, 2.7;
S, 25.1%.
20 E. Cerrada, E. J. Fernández, M. C. Gimeno, A. Laguna, M. Laguna,
R. Terroba and M. D. Villacampa, J. Organomet. Chem., 1995,
492, 105; E. Cerrada, E. J. Fernández, P. G. Jones, A. Laguna,
M. Laguna and R. Terroba, Organometallics, 1995, 14, 5537;
E. Cerrada, M. Laguna and P. A. Sorolla, Polyhedron, 1997, 17,
295.
21 E. Cerrada, P. G. Jones, A. Laguna and M. Laguna, Inorg. Chem.,
1996, 35, 2995.
22 G. Steimecke, R. Kirmse and E. Hoyer, Z. Chem., 1975, 15, 28.
23 R. Usón and A. Laguna, Organomet. Synth., 1985, 3, 325.
24 J. Chatt and G. Booth, J. Chem. Soc., 1965, 3238.
20. Yield (a) 98%, (b) 50%. mp 95 ЊC. MS (LSIMSϩ):
m/z (%): 1223 (44, [S(AuPPh2Me)3]ϩ). 1H NMR (300 MHz,
CDCl3, 25 ЊC) δ 7.64–7.57 (m, 8 H, PPh2Me), 7.49–7.48 (m,
12 H, PPh2Me), 7.25–7.12 (m, 2 H), 7.01 (s, 2 H), 3.90 (s, 4 H,
SCH2) and 2.08 (d, 6 H, J 10 Hz, CH3). 31P-{1H}NMR
(300 MHz, CDCl3, 25 ЊC): δ 22.1 (s). IR (cmϪ1) 1055, 1022
(C᎐S). Elemental anal. Calc. for C H Au P S10 C, 37.2; H, 2.7;
᎐
40 34
2
2
S, 24.8%. Found: C, 37.3; H, 2.8; S, 24.6%.
J. Chem. Soc., Dalton Trans., 2002, 2654–2659
2659