Synthesis and characterization of the bimetallic series [S 2WS2Fe(NCS)(X)]2- (X = Cl-, NCS -, N3-)

Article abstract of DOI:10.1016/j.ica.2004.07.017

The family of molecular dianions [S2WS2Fe(NCS)(X)]2-(X=Cl-,NCS-,N3-orN3-) has been synthesized and characterized by X-ray diffraction, IR, electronic and electrospray mass spectroscopies. This series of compounds was obtained using the lability of the terminal chloro ligands in [S₂WS ₂FeCl₂]^2-. A series of thioheterobimetallic anions have been synthesized: [S₂WS₂Fe(NCS)X]^2- (X = Cl^- (1); X = NCS^- (2); X=N3- (3)). The molecular dianions were isolated by substitution in [S₂WS₂FeCl ₂]^2- of the labile terminal chloro ligands by NCS ^- and/or N3-. Anions (1) and (3) are the first iron tris-heteroleptic complexes of the well-known [S₂WS₂FeX₂] ^2- (M = Mo, W) family. The structures of the three molecular anions, isolated as tetraphenylphosphonium salts, are reported, as well as characterization by IR, electronic and electrospray mass spectroscopies.

Full text of DOI:10.1016/j.ica.2004.07.017

Inorganica Chimica Acta 358 (2005) 70–76
www.elsevier.com/locate/ica
Synthesis and characterization of the bimetallic
ꢁ
2ꢁ
ꢁ
ꢁ
series ½S2WS2FeðNCSÞðXÞꢀ ðX ¼ Cl ; NCS ; N3 Þ
´ ˆ ´
Eddy Dumas , Jerome Marrot, Josseline Jullien, Francis Secheresse
*
´
Institut Lavoisier, IREM, UMR 8637, Universite de Versailles, Saint-Quentin, 45 Avenue des Etats-Unis, 78035 Versailles, France
Received 24 May 2004; accepted 10 July 2004
Available online 6 August 2004
Abstract
A series of thioheterobimetallic anions have been synthesized: [S2WS2Fe(NCS)X]2ꢁ (X = Clꢁ (1); X = NCSꢁ (2); X ¼ N3 (3)).
ꢁ
The molecular dianions were isolated by substitution in [S2WS2FeCl2]2ꢁ of the labile terminal chloro ligands by NCSꢁ and/or N3
.
ꢁ
Anions (1) and (3) are the first iron tris-heteroleptic complexes of the well-known [S2WS2FeX2]2ꢁ (M = Mo, W) family. The struc-
tures of the three molecular anions, isolated as tetraphenylphosphonium salts, are reported, as well as characterization by IR, elec-
tronic and electrospray mass spectroscopies.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Thiometalate; Tungsten complexes; Thiocyanate; Azide; Electrospray mass spectrometry
1. Introduction
due to (i) the possible addition reactions at the termi-
nal sulfur atoms, (ii) the presence of coordinatively
non-saturated metal atoms and (iii) the substitution
reactions which could be carried out at the chloro lig-
ands. The lability of the terminal chloro ligands in
[S2WS2FeCl2]2ꢁ was used to synthesize the three com-
pounds described herein: (PPh4)2[S2WS2Fe(Cl)(NC-
S)] Æ (CH3C(O)CH3)2 (1), (PPh4)2[S2WS2Fe(NCS)2] (2)
and (PPh4)2[S2WS2Fe(NCS)(N3)] (3). Compounds 1
and 3 are the first iron tris-heteroleptic complexes of
the family. This work was initiated in order to isolate
new polythiometallic systems, which could be associat-
ed with gold nanoparticles. Our group recently report-
ed the synthesis of a new nanocomposite system
formed by the interaction of gold nanoparticles with
The chemistry of heterobimetallic Fe–M–S
(M = Mo, W) complexes has been extensively devel-
oped since the late 1970s, mainly due to their rele-
vance to biological systems involving nitrogenase [1].
At that time, absence of structural characterization
of the MoFe protein of nitrogenase led to the synthe-
sis of numerous Fe–M–S clusters presented as poten-
tial models consistent with the data available (mainly
EXAFS analyses) [2]. Among them, a family of bime-
tallic molecular anions with the general formula
[S2MS2FeXn]2ꢁ (M = W and/or Mo; n = 1: X = S5
[3,4]; n = 2: X = Cl [5–7], SPh [4,7,8], OPh [9], NO
[10]) was structurally characterized. Muller et al. [5]
¨
pointed out that the [S2MS2FeCl2]2ꢁ (M = Mo, W)
molecular anion was a possible interesting building
unit to generate large multinuclear Fe–M complexes
tetra(oxo)thiotungstates WS4 or WO2S2 [11]. Due
to the presence of thiocyanato and/or azido ligands,
the title dianions should act as effective vibrational
spectroscopy probe to follow the reactivity of more
sophisticated thiometalate fragments with gold nano-
particles.
2ꢁ
2ꢁ
*
Corresponding author. Tel.: +33139254383; fax: +33139254381.
E-mail address: dumas@chimie.uvsq.fr (E. Dumas).
0020-1693/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.07.017

E. Dumas et al. / Inorganica Chimica Acta 358 (2005) 70–76
71
2. Experimental
1026(w), 996(m), 751(m), 722(s), 687(s), 527(vs); ace-
tone: 1359(m), 1221(m), m(CO) 1079(s); m(CN)
2050(vs); m(CS) 852(vw); m(WS)term 494(w), 485(m);
m(MS)br 438(w), 435(sh) 326(w).
2.1. General procedures
All syntheses were performed under an atmosphere of
nitrogen using standard Schlenk-line techniques. Aceto-
nitrile, acetone and methanol were previously distilled
from CaH2 before use. Pentane was degassed prior to
use. (PPh4)2[WS4] was synthesized according to previ-
ously published procedures [12]. All solid products are
air stable.
2.3. (PPh4)2[S2WS2Fe(NCS)2] (2)
Compound 2 was synthesized using the procedure de-
scribed above with an excess of KSCN (389 mg,
4 mmol). Yield: 880 mg (76%). Anal. Calc. for
C50H40N2P2S6FeW (1162.84): W, 15.81; Fe, 4.80; S,
16.54; P, 5.33; N, 2.41; C, 51.64. Found: W, 15.19; Fe,
4.69; S, 16.47; P, 3.79; N, 2.46; C, 51.86%. IR
Elemental analyses of solids were performed by the
Service Central dꢀAnalyse du CNRS, Vernaison
(France). IR spectra were recorded on a FTIR Nicolet
Magna-550 spectrophotometer. UV–Vis spectra were re-
corded on a Perkin–Elmer lambda 19 spectrophotome-
ter. Thermogravimetric analyses were carried out
under nitrogen flow (60 mL/min) with a Perkin–Elmer
electrobalance TGA-7 at a heating rate of 5 ꢁC/min.
Electrospray mass spectroscopy (ESMS) spectra
were obtained using a HP 5989B single quadrupole
mass spectrometer equipped with an electrospray
source from analytica of Brandford. The instrument
was operated in the negative ion mode. Source param-
eters were Vneedle = 0 V, Vcyl = 3500 V, Vend = 3000 V
and Vcap = 3500 V. The nebulizing gas (purified air)
was heated to approximately 150 ꢁC. The capillary ex-
it voltage was either ꢁ80 or ꢁ150 V. The mass axis
was calibrated using the cluster ions observed from
a 50 ng/lL solution of sodium dodecyl sulfate in
acetonitrile. Mass spectra were obtained from m/z
100 to 1200 by electrospraying 10ꢁ4 M sample solu-
(KBr pellet, cmꢁ1): PPh4 cations: 1583(m), 1482(m),
þ
1435(s), 1336(m), 1313(m), 1187(m), 1162(m), 1107(vs),
1026(w), 996(m), 753(m), 722(s), 687(s), 616(w),
530(vs); m(CN) 2042(vs), 2023(vs); m(CS) 850(vw);
m(WS)term 499(sh), 493(m); m(MS)br 434(w), 428(sh)
317(w).
2.4. (PPh4)2[S2WS2Fe(NCS)(N3)] (3)
A solution of NaN3 (11 mg, 0.175 mmol) in MeOH
was added to a solution of compound (1) (200 mg,
0.175 mmol) in CH3CN (20 mL) and the mixture stirred
overnight. The resulting red–brown solution was then
concentrated to 5 mL and diluted with 50 mL of Et2O.
The brown precipitate was filtered, washed with Et2O
and recrystallized in 1 day from a mixture of acetone
and pentane maintained at 4 ꢁC. Yield: 130 mg (65%).
Anal. Calc. for C49H40N4P2S5FeW (1146.79): W,
16.03; Fe, 4.87; S, 13.98; P, 5.40; N, 4.89; C, 51.31.
Found: W, 15.59; Fe, 4.81; S, 14.22; P, 5.01; N, 5.02;
tions in acetonitrile at a flow rate of 5 lL minꢁ1
.
C, 51.42%. IR (KBr pellet, cmꢁ1): PPh4 cations:
þ
2.2. (PPh4)2[S2WS2Fe(NCS)(Cl)] Æ (CH3C(O)CH3)2
(1)
1583(m), 1483(m), 1434(s), 1334(m), 1313(m), 1188(m),
1163(m), 1108(vs), 1026(w), 996(m), 753(m), 722(s),
687(s), 623(w) 527(vs); m(N3) 2062(vs); m(CN) 2020(vs);
m(CS) 847(vw); d(N3) 621(w); m(WS)term 502(w),
490(m); m(MS)br 437(w), 429(w), 319(w); m(FeN) 391(w).
A solution of FeCl2 Æ 4H2O (199 mg, 1 mmol) in
MeCN (25 mL) was added to a solution of (PPh4)2[WS4]
(990 mg, 1 mmol) in MeCN (100 mL). At this stage in
the synthesis, (PPh4)2[S2WS2FeCl2] can be isolated from
the resulting red solution with appropriate treatment or
used directly to react with KSCN. KSCN (97 mg,
1 mmol) was added to the red solution. After 1 h, a
white precipitate of KCl was removed by filtration.
The filtrate was concentrated to ca. 20 mL and diluted
with 50 mL of Et2O to precipitate the crude product.
The solid was washed with Et2O and dried in vacuo.
Red crystals of (1) were obtained from a mixture of ac-
etone and pentane maintained at 4 ꢁC overnight. Yield:
930 mg (74%). Anal. Calc. for C55H52NO2P2S5ClFeW
(1256.37): W, 14.63; Fe, 4.44; Cl, 2.82; S, 12.76; P,
4.93; N, 1.11; C, 52.58. Found: W, 14.99; Fe, 4.46; Cl,
2.22; S, 11.54; P,þ4.53; N, 1.53; C, 52.10%. IR (KBr pel-
let, cmꢁ1): PPh4 cations: 1585(m), 1482(m), 1435(s),
1337(m), 1312(m), 1186(m), 1162(m), 1107(vs),
2.5. X-ray crystallography
X-ray diffraction data sets were collected at room
temperature from single crystals of 1 (0.10 · 0.06 ·
0.04 mm), 2 (0.68 · 0.24 · 0.02 mm) and 3 (0.16 ·
0.08 · 0.06 mm) with a Siemens SMART three-circle
diffractometer equipped with a CCD bidimensional de-
tector using monochromated Mo Ka radiation
˚
(k = 0.71073 A). The absorption correction was based
on multiple and symmetry-equivalent reflections in the
data set using the SADABS program [13] based on the
method of Blessing [14]. The structures were solved by
direct methods and refined by full-matrix least-squares
using the SHELX-TL package [15]. Hydrogen atoms
were placed at fixed positions using the program
HFIX. A summary of crystal data and details of the

72
E. Dumas et al. / Inorganica Chimica Acta 358 (2005) 70–76
collection is presented in Table 1. Significant bond dis-
tances for 1–3 are given in Table 2.
Synthesis of the three compounds clearly illustrates the
ability to substitute successively the terminal chloro lig-
ands of the [S2WS2FeCl2]2ꢁ fragment to generate asym-
metrically coordinated iron centers. A fourth member of
the series, containing the [S2WS2Fe(N3)2]2ꢁ molecular
anion, was identified in solution by electrospray mass
spectroscopy. This compound can be isolated by direct
substitution of the terminal chloro ligands in
[S2WS2FeCl2]2ꢁ or by addition of an excess of sodium
azide to 3 (Scheme 1). To date, all crystallization at-
tempts of this new compound remained unsuccessful.
3. Results and discussion
3.1. Synthesis
Reaction of appropriate amounts of isothiocyanato
and/or azido ligand with [S2WS2FeCl2]2ꢁ (presynthe-
sized [6] or generated in situ) in acetonitrile results in
an exchange of isothiocyanato and/or azido ligand for
terminal chloro ligand(s) to produce the new series of
thioheterobimetallic compounds (PPh4)2[S2WS2Fe(NC-
S)(Cl)] Æ (CH3C(O)CH3)2 (1), (PPh4)2[S2WS2Fe(NCS)2]
(2) and (PPh4)2[S2WS2Fe(NCS)(N3)] (3) (Scheme 1).
3.2. IR spectra
As already pointed out several years ago, IR vibra-
tional spectra remain a very useful method to character-
Table 1
Crystal data and structure refinement for (PPh4)2[S2WS2Fe(NCS)(Cl)] Æ (CH3C(O)CH3)2 (1), (PPh4)2[S2WS2Fe(NCS)2] (2) and
(PPh4)2[S2WS2Fe(NCS)(N3)] (3)
1
2
3
Empirical formula
Molecular weight
Crystal system
C
55ClFeH52NO2P2S5W
C50FeH40N2P2S6W
1162.84
C49FeH40N4P2S5W
1146.79
1256.37
triclinic
monoclinic
P21/c
monoclinic
P21/c
ꢀ
Space group
Unit cell dimensions
P1
˚
a (A)
11.6797(4)
12.1878(3)
10.5597(1)
42.6165(3)
10.6304(1)
41.9013(1)
˚
b (A)
˚
c (A)
12.3975(4)
113.834(1)
11.4785(1)
90
11.1371(2)
90
a (ꢁ)
b (ꢁ)
c (ꢁ)
106.683(2)
103.415(1)
1419.14(8)
104.727(1)
90
4995.83(7)
104.110(1)
90
4811.10(10)
3
˚
V (A )
Z
1
1.470
4
1.546
4
1.583
qcalc (g cmꢁ3
)
l (mmꢁ1
)
2.607
6634/5167 (0.0359)
5167/3/599
2.942
34725/13033 (0.0563)
13033/0/556
3.013
33638/12676 (0.0535)
12676/0/556
Reflections collected/unique (Rint
Data/restraints/parameters
Final R indices [I > 2r(I)]a
R indices (all data)a
)
R1 = 0.0664, wR2 = 0.1476
R1 = 0.0857, wR2 = 0.1614
1.074
R1 = 0.0542, wR2 = 0.0898
R1 = 0.0979, wR2 = 0.1033
1.069
R1 = 0.0653, wR2 = 0.0980
R1 = 0.1199, wR2 = 0.1133
1.118
Goodness-of-fit on F2
ꢁ3
˚
Largest difference peak and hole (e A
)
0.881 and ꢁ0.547
0.766 and ꢁ1.098
1.030 and ꢁ0.639
qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
a
P
P
P
P
2
2
2
R1 ¼ ðjF oj ꢁ jF cjÞ= jF cj;
wðF 2o ꢁ F 2cÞ = wðF o2Þ with 1=w ¼ r2F 2o þ ðaPÞ þ bP and a = 0.0916, b = 0 for 1; a = 0.0265, b = 2.3818
for 2; a = 0.0260, b = 5.1501 for 3.
Table 2
Selected bond distances (A) in [S2WS2Fe(NCS)(Cl)] (1), [S2WS2Fe(NCS)2]2ꢁ (2) and [S2WS2Fe(NCS)(N3)]2ꢁ (3)
2ꢁ
˚
1
2
3
W–Fe
W–Ster
2.8012(15)
2.7537(8)
2.7459(9)
2.151(4)–2.155(4)
2.245(3)–2.255(4)
2.295(3)–2.310(4)
2.258(5)
2.1461(16)–2.1476(15)
2.2496(13)–2.2511(13)
2.2950(17)–2.2963(16)
2.1033(19)–2.1462(18)
2.2416(15)–2.2473(16)
2.2863(19)–2.291(2)
W–Sbr
Fe–Sbr
Fe–Cl
Fe–N(CS)
Fe–N(NN)
N–C
1.967(12)
1.949(5)–1.961(5)
1.950(6)
1.946(7)
1.146(8)
1.589(8)
1.196(8)
1.241(9)
1.026(18)
1.655(17)
1.153(7)–1.155(7)
1.599(7)–1.592(7)
C–S
(Fe)N–N(N)
(FeN)N–N

E. Dumas et al. / Inorganica Chimica Acta 358 (2005) 70–76
73
[WS4Fe(NCS)(N3)]2-
-
-
1 eq N3
excess N3
1 eq NCS-
2 eq N3
-
[WS4Fe(NCS)(Cl)]2-
[WS4FeCl2]2-
2 eq NCS-
[WS4Fe(N3)2]2-
1 eq NCS-
[WS4Fe(NCS)2]2-
Scheme 1. Summary of the dianions isolated in this work by replacement of the terminal chloro ligands in the [S2WS2FeCl2]2ꢁ fragment.
ize thiometalate complexes [1]. The two band split of the
stretching vibration m(WS)ter (510–480 cmꢁ1 region), ob-
served in the IR spectra of the three title compounds, is
peak being unambiguously attributed to the
p(t1) ! d(2e) LMCT transition [1]. Electronic spectra
of (PPh4)2[S2WS2FeCl2], (1)–(3) show a set of three to
five peaks in the 280–420 nm region. This group of
bands is therefore assigned to the splitting of the LMCT
2ꢁ
characteristic of the bidentate coordination of WS4 to
the iron center. Presence of strong bands in the 2100–
2000 cmꢁ1 is characteristic of thiocyanato and/or azido
ligands. The IR spectrum of 1 shows a single strong
band at 2050 cmꢁ1 attributed to the m(CN) stretching vi-
bration of the thiocyanato ligand. Two bands, at 2042
and 2023 cmꢁ1, are observed in the IR spectrum of 2, as-
signed to the same vibration mode. By analogy, the
strong bands observed at 2062 and 2020 cmꢁ1 in the
spectrum of 3 are attributed to masðN3ꢁÞ and mðCNÞ,
respectively.
2ꢁ
absorption bands in the WS4 fragment perturbed by
coordination of a FeX2 ðX ¼ Clꢁ; NCSꢁ; N ꢁÞ unit
3
[1,16]. In this region, substitution of the terminal chloro
ligands induces the appearance of one (compounds 2
and 3) or two (compound 1) bands compared to the
spectrum of (PPh4)2[S2WS2FeCl2].
3.4. Electrospray mass spectroscopy
ESMS spectra of (PPh4)2[S2WS2FeCl2], (1)–(3) and the
tetraphenylphosphonium salt of the [S2WS2 Fe(N3)2]2ꢁ
molecular dianion have been obtained from 10ꢁ4 mol Lꢁ1
solutions in acetonitrile, with capillary exit voltage values
of ꢁ80 and ꢁ150 V. Typical example of these spectra is
presented in Fig. 1 for compound 2. Assignments of the
major ESMS signals are given in Table 4. Assignments
were confirmed by the experimental values of m/z as well
as the isotopic distribution. With a cap exit voltage value
of ꢁ80 V, ESMS spectra show three sets of peaks (m/z re-
gions: 210–250, 400–430 and 770–830, with a low in-
tensity peak for the later) attributed, respectively, to
3.3. Electronic spectra
Exchange of NCSꢁ and/or N3 for the terminal chlo-
ꢁ
ro ligands in [S2WS2FeCl2]2ꢁ can be easily checked by
UV–Vis spectroscopy. Electronic spectra in acetonitrile
of (PPh4)2[S2WS2FeCl2], (1)–(3) are listed in Table 3.
The peak observed at 518 nm for [S2WS2FeCl2]2ꢁ is
red shifted by substitution of Clꢁ by NCSꢁ and/or
N3ꢁ. Comparison of the spectra of [S2WS2Fe(Cl)2 ꢁ n
(NCS)n]2ꢁ shows that the shift to lower energy increases
(together with a hyperchromic effect) in the order n = 0,
1, 2. Such low energy bands, not observed in the elec-
tronic spectrum of WS42ꢁ, were previously attributed
to the Fe–L chromophores in analogous iron–tungsten
compounds [16]. Two intense peaks, at 277 and 392
nm, are found in the electronic spectrum of WS42ꢁ. Both
peaks are attributed to S ! W transition, the second
(i) the molecular dianions of general formula
2ꢁ
½S2WS2FeðX1ÞðX2Þꢀ ðX1; X2 ¼ Clꢁ; NCSꢁ; N ꢁÞ, (ii)
3
the molecular anions of general formula [S2WS2Fe(X1)]ꢁ
and (iii) the ion-pairs of general formula (PPh4)[S2WS2-
Fe(X1)(X2)]ꢁ. ESMS allowed us to characterize the
Table 3
Electronic spectra of (PPh4)2[S2WS2FeCl2], (PPh4)2[S2WS2Fe(NCS)(Cl)] Æ (CH3C(O)CH3)2 (1), (PPh4)2[S2WS2Fe(NCS)2] (2) and
(PPh4)2[S2WS2Fe(NCS)(N3)] (3) in CH3CN
Complexes
k (nm) (e/L molꢁ1 cmꢁ1 a
)
(PPh4)2[S2WS2FeCl2]
518(500)
545(797)
554(1449)
533(790)
415(6240)
414(4745)
418(6070)
417(6880)
372(6390)
368(7345)
364(13970)
361(10440)
286(16100)
285(14260)
285(14370)
287(13250)
(1)
(2)
(3)
a
335(7760)
331(13480)
327(12030)b
316(8073)
A shoulder at about 450 nm is also observed in the four spectra.
Very broad band.
b

74
E. Dumas et al. / Inorganica Chimica Acta 358 (2005) 70–76
presence of acetone was confirmed by IR spectroscopy
(strong m(CO) band observed at 1079 cmꢁ1). The num-
ber of acetone molecules identified by single crystal X-
ray diffraction was confirmed by TGA analysis which
showed one weight-loss step of 8.91% (theoretical:
9.25%) between room temperature and 100 ꢁC, attrib-
uted to the release of the crystallization acetone.
The structures of the dianions [S2WS2Fe(NCS)(Cl)]2ꢁ
(1), [S2WS2Fe(NCS)2]2ꢁ (2) and [S2WS2Fe(NCS)(N3)]2ꢁ
(3) (Fig. 2) can be described as two tetrahedra, WS4 and
S2Fe(NCS)X (X = Cl, NCS or N3), sharing an edge;
2ꢁ
therefore, WS4 plays its common bidentate ligand role
Fig. 1. ESMS spectra of (PPh4)2[S2WS2Fe(NCS)2] (2) with capillary
exit voltage of ꢁ80 V.
for the iron center. The basic {S2WS2Fe} cores identified
in the three molecular anions show comparable struc-
tural parameters, among them, and with bimetallic
[S2WS2FeXn]2ꢁ complexes (n = 1, X = S5 [3,4]; n = 2,
X = Cl [5b,6], SPh [4], NO [10]) previously characterized.
The only noticeable structural difference between the
three title compounds deals with the Wꢂ ꢂ ꢂFe distances,
new [S2WS2Fe(N3)2]2ꢁ molecular dianion for which all
crystallization attempts have yet failed. Fragmentation
2ꢁ
of the parent dianions ½S2WS2FeðX1ÞðX2Þꢀ ðX1; X2 ¼
Clꢁ; NCSꢁ; N3ꢁÞ generates the [S2WS2Fe(X1)]ꢁ ions in
which one chloro or pseudo-halide ligand has been re-
moved. Increasing the cap exit voltage value strengthens
˚
nearly 0.05 A longer in 1 compared with 2 and 3. Atoms
of the {W-(l-S)2-Fe} fragment are nearly coplanar with
˚
a maximum deviation of 0.03, 0.08 and 0.08 A from the
the fragmentation process. Peaks attributed to the diani-
least-squares plane for 1–3, respectively. The S–W–S an-
2ꢁ
2ꢁ
ons ½S2WS2FeðX1ÞðX2Þꢀ ðX1; X2 ¼ Clꢁ; NCSꢁ; N ꢁÞ
3
gles in WS4 are close to the ideal Td symmetry (range:
are no longer present in the ESMS spectra measured with
a capillary exit voltage of ꢁ150 V.
105.75(13)–110.83(13)ꢁ for 1, 106.41(5)–111.27(6)ꢁ for 2
and 106.46(6)–110.79(7)ꢁ for 3). The Wꢂ ꢂ ꢂS distances
can be divided in two pairs of terminal and bridging
˚
bonds, the former nearly 0.1 A shorter than the later (Ta-
3.5. Structures
ble 2). The {S2FeX2} unit (X = Cl or N) is comparatively
more distorted from the ideal Td symmetry with the X–
Fe–Y angles (X, Y = Cl, N or S) ranging between
102.39(14)ꢁ and 112.54(17)ꢁ for 1, 103.44(5)ꢁ and
115.40(17)ꢁ for 2, 103.55(7)ꢁ and 114.0(2)ꢁ for 3. The
The structures of the three compounds consist of a
molecular dianion [S2WS2Fe(NCS)X]2ꢁ (X = Clꢁ (1);
X = NCSꢁ (2); X ¼ N3 (3)) and PPh4 cations. Com-
pounds 2 and 3 are isostructural and crystallize in the
P21/c monoclinic space group with close cell parameters,
ꢁ
þ
˚
Fe–Cl distance (2.258(5) A) found in 1 is consistent with
ꢀ
the average terminal metal–ligand distances measured in
[S2WS2FeCl2]2ꢁ anions (in which a crystal disorder of Fe
while compound 1 crystallizes in the P1 triclinic space
group with two additional molecules of acetone. The
Table 4
Assignments of the major ESMS signals of (PPh4)2[S2WS2FeCl2], (PPh4)2[S2WS2Fe(NCS)(Cl)] Æ (CH3C(O)CH3)2 (1), (PPh4)2[S2WS2Fe(NCS)2] (2),
(PPh4)2[S2WS2Fe(NCS)(N3)] (3) and (PPh4)2[S2WS2Fe(N3)2]a in CH3CN (capillary exit voltage: ꢁ80 V)
Compounds
m/z (Exp.)b
m/z (Theo.)c
Assignment
(PPh4)2[S2WS2FeCl2]
219.1
402.5
230.4
402.3
425.4
241.9
425.8
233.9
409.7
425.7
225.7
409.7
218.9
402.7
230.4
402.7
425.7
241.9
425.7
233.9
409.8
425.7
225.9
409.8
[S2WS2FeCl2]2ꢁ
[S2WS2FeCl]ꢁ
1
[S2WS2Fe(NCS)(Cl)]2ꢁ (1)
[S2WS2FeCl]ꢁ
[S2WS2Fe(NCS)]ꢁ
[S2WS2Fe(NCS)2]2ꢁ (2)
[S2WS2Fe(NCS)]ꢁ
[S2WS2Fe(NCS)(N3)]2ꢁ (3)
[S2WS2Fe(N3)]ꢁ
[S2WS2Fe(NCS)]ꢁ
[S2WS2Fe(N3)2]2ꢁ
[S2WS2Fe(N3)]ꢁ
2
3
(PPh4)2[S2WS2Fe(N3)2]a
a
Formula suggested by ESMS.
Highest intensity peak.
Most abundant isotopic mass.
b
c

E. Dumas et al. / Inorganica Chimica Acta 358 (2005) 70–76
75
at 169.0(5)ꢁ in 2, the bending is more important in the
remaining Fe–NCS group (158.1(5)ꢁ), a trend even more
pronounced for the Fe–N3 group in 3 (Fe–N–N angle:
134.7ꢁ).
S
Cl
S
S
(1)
W
Fe
4. Conclusion
N
S
C
The three compounds presented here further enhance
the reactivity perspectives of the [S2WS2FeCl2]2ꢁ dian-
ion. Stepwise substitution of the terminaꢁl chloro ligands
by pseudo-halide ions like NCSꢁ or N3 allowed us to
synthesize the first iron tris-heteroleptic complexes of
the [S2WS2FeX2]2ꢁ family. Both the synthesis of new
derivatives of the [S2WS2FeCl2]2ꢁ fragment (replace-
ment of the chloro, or more generally halide, terminal
ligand by various potentially bridging ligands) and the
study of the reactivity of the dianions presented here,
for example with various transition metals are currently
investigated in our group. The thiocyanato ligands are
well-known for their bonding versatility and have al-
ready proven to be effective ligands to generate poly-
meric thiometallic structures [17]. Azido ligands also
show versatile bridging coordination modes and mag-
netic coupler properties [18]. Hence, the title dianions
offer new perspectives for the synthesis of multimetallic
molecular or extended systems with potential interesting
magnetic properties and should allow the study of the
influence of thiometalate fragments on these properties.
S
(a)
S
C
S
N
(2)
S
S
W
Fe
N
C
S
S
(b)
N
N
S
N
S
(3)
5. Supplementary material
W
Fe
CCDC-239354 (1), CCDC-239355 (2) and CCDC-
239356 (3) contain the supplementary crystallographic
data for this paper. These data can be obtained free of
charge at www.ccdc.cam.ac.uk/conts/retrieving.html [or
from the Cambridge Crystallographic Data Centre, 12,
Union Road, Cambridge CB2 1EZ, UK; fax: (internat.)
+44-1223/336-033; e-mail: deposit@ccdc.ca;.ac.uk].
N
S
S
C
S
(c)
Fig. 2. Molecular dianions (a) [S2WS2Fe(NCS)(Cl)]2ꢁ (1), (b)
[S2WS2Fe(NCS)2]2ꢁ (2) and (c) [S2WS2Fe(NCS)(N3)]2ꢁ (3) (thermal
ellipsoids at 30% probability).
Acknowledgments
and W as well as terminal sulfurs and chlorides occurs)
[5b,6].
We gratefully thank Vincent Steinmetz for ESMS
measurements.
Fe–N(CS) and Fe–N(NN) distances are similar in the
three molecular dianions. The thiocyanato ligands in 2
and 3 display comparable classical N–C and C–S dis-
tances. In 1, the N–C distance is comparatively nearly
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