Synthesis and characterization of bis(dithiolene) tungsten(VI), -(V), and -(IV) complexes and their reactivities in coupled electron-proton transfer: A new series of active site models of tungstoenzymes

Article abstract of DOI:10.1002/ejic.200700602

New tungsten(VI), -(V), and -(IV) complexes containing 3,6-dichloro-1,2- benzenedithiolate (bdtCl₂), (Et₄N)₂[W ^VIO₂(bdtCl₂)₂] {(Et ₄N)₂[1]}, (Et₄N)[W^VO(bdtCl ₂)₂] {(Et₄N)[2]}, and (Et₄N) ₂[W^IVO(bdtCl₂)₂] {(Et ₄N)₂[3]} were synthesized and characterized as active site models of tungstoenzymes. (Et₄N)₂[1] was prepared in high yield by the reaction of WO₂Cl₂ with 2bdtCl₂ at low temperature, and its crystal structure was determined. Isomerization between octahedral structures (Δ and Λ forms) of the tungsten center of (Bu₄N)₂[1] was characterized by variable-temperature ¹H NMR (VT ¹H NMR) spectral analysis, which offers the first example of six-coordinate bis(dithiolene) tungsten(VI) complexes. The isomerization of the molybdenum center of (Bu₄N) ₂[Mo^VIO₂(bdtCl₂)₂] {(Bu₄N)₂[4]} was similarly characterized. A comparison of their activation energies indicated that the tungsten center underwent slower isomerization than that of the molybdenum one. (Et₄N)₂[1] underwent an irreversible reduction at -2.1 V vs. SCE in CH₃CN by a coupled electron-proton transfer (CEPT) process to yield (Et₄N) ₂[3], while (Et₄N)₂[3] underwent an irreversible oxidation by a CEPT process at -0.27 V in the presence of 2 equiv. of Et₄NOH in CH₃CN to yield (Et₄N) ₂[1]. (Et₄N)[2] disproportionated into 0.5 equiv. of (Et₄N)₂[1] and 0.5 equiv. of (Et₄N) ₂[3] when treated with 1 equiv. of Et₄NOH in CH ₃CN. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Full text of DOI:10.1002/ejic.200700602

FULL PAPER
DOI: 10.1002/ejic.200700602
Synthesis and Characterization of Bis(dithiolene) Tungsten(VI), -(V), and -(IV)
Complexes and Their Reactivities in Coupled Electron–Proton Transfer: A New
Series of Active Site Models of Tungstoenzymes
Hideki Sugimoto,*[a] Makoto Tarumizu,[a] Hiroyuki Miyake,[a] and Hiroshi Tsukube[a]
Keywords: Bioinorganic chemistry / Enzyme models / Molybdenum / S ligands / Tungsten
New tungsten(VI), -(V), and -(IV) complexes containing 3,6-
dichloro-1,2-benzenedithiolate (bdtCl2), (Et4N)2[WVIO2-
(bdtCl2)2] {(Et4N)2[1]}, (Et4N)[WVO(bdtCl2)2] {(Et4N)[2]}, and
(Et4N)2[WIVO(bdtCl2)2] {(Et4N)2[3]} were synthesized and
characterized as active site models of tungstoenzymes.
(Et4N)2[1] was prepared in high yield by the reaction of
WO2Cl2 with 2bdtCl2 at low temperature, and its crystal
structure was determined. Isomerization between octahedral
terized. A comparison of their activation energies indicated
that the tungsten center underwent slower isomerization
than that of the molybdenum one. (Et4N)2[1] underwent an
irreversible reduction at –2.1 V vs. SCE in CH3CN by a cou-
pled electron–proton transfer (CEPT) process to yield
(Et4N)2[3], while (Et4N)2[3] underwent an irreversible oxi-
dation by a CEPT process at –0.27 V in the presence of
2 equiv. of Et4NOH in CH3CN to yield (Et4N)2[1]. (Et4N)[2]
disproportionated into 0.5 equiv. of (Et4N)2[1] and 0.5 equiv.
of (Et4N)2[3] when treated with 1 equiv. of Et4NOH in
CH3CN.
structures (∆ and
Λ forms) of the tungsten center of
(Bu4N)2[1] was characterized by variable-temperature 1H
NMR (VT 1H NMR) spectral analysis, which offers the first
example of six-coordinate bis(dithiolene) tungsten(VI) com-
plexes. The isomerization of the molybdenum center of
(Bu4N)2[MoVIO2(bdtCl2)2] {(Bu4N)2[4]} was similarly charac-
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
containing a square-pyramidal tungsten(IV) center have
been reported.[2]
Introduction
Since the characterization of tungstoenzymes by crystal-
lographic and EXAFS studies,[1] many coordination chem-
ists have paid much attention to intriguing coordination
structures of their catalytic centers.[2] Mononuclear tung-
sten complexes containing two pyranopterin dithiolenes oc-
cur as the catalytic centers of the aldehyde ferredoxin oxido-
reductase (AOR) family and the formate dehydrogenase
(FDH) family, varying the oxidation number between +6,
+5, and +4 and the coordination structure between that
of a trigonal prism and a square pyramid (Scheme 1).[1,3]
Therefore, synthetic tungsten(VI), -(V), and -(IV) complexes
with identical dithiolenes are of special interest as active
site models of these families.[2] However, such a series of
tungsten complexes is still limited.[2] A number of six-coor-
dinate bis(dithiolene) tungsten(VI) complexes have been
prepared and structurally characterized.[2] The tungsten(VI)
centers of the previously reported six-coordinate complexes
were best described as octahedrons, rather than trigonal
prisms, in the solid state, while their solution structures have
rarely been reported. In contrast, a large number of
[WX(dithiolene)2]2–/– (X = monodentate ligand) complexes
Scheme 1. Active site structures of DMSOR, AOR, and FDH fam-
ilies and their CEPT processes (X = O, OR, SR, SeR, etc.).
From the viewpoint of the functions of the AOR and the
FDH families, a coupled electron–proton transfer (CEPT)
process is essentially involved in the catalytic reactions,
where the five-coordinate tungsten(IV) center changes to
the six-coordinate tungsten(VI) center and a water molecule
is utilized as the source of an oxygen atom, protons, and
electrons.[1,3] A similar structural change of a tungsten cen-
ter by the CEPT process is involved in tungsten-substituted
DMSO reductase, where the six-coordinate tungsten(VI)
center changes to the five-coordinate tungsten(IV) center,
converting a net oxygen atom of DMSO to water.[3] The
CEPT process is further involved in the catalytic reaction
mediated by molybdenum containing arsenite oxidase.[1]
Until now, no involvement of the bis(dithiolene) tungsten
[a] Department of Chemistry, Graduate School of Science, Osaka
City University,
Sumiyoshi-ku 3-3-138, Osaka 558-8585, Japan
Fax: +81-6-6605-2522
E-Mail: sugimoto@sci.osaka-cu.ac.jp
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© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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H. Sugimoto, M. Tarumizu, H. Miyake, H. Tsukube
FULL PAPER
complex in a CEPT process has been reported. We recently {[Ni(dithiolene)2] Ǟ [W(CO)2(dithiolene)2] Ǟ [WO(di-
demonstrated that the CEPT process enabled the conver- thiolene)2]2– Ǟ [WO2(dithiolene)2]2–}.[10] Here, we directly
sion from (Et4N)2[MoO2(bdtCl2)2] {(Et4N)2[4]} to (Et4N)2- synthesized the bis(dithiolene) WVIO2 complex of bdtCl2
[MoO(bdtCl2)2] {(Et4N)2[5]} and its back reaction from from commercially available reagents. When WO2Cl2 was
(Et4N)2[5] to (Et4N)2[4].[5,6] Our crystallographic study on treated with 2 equiv. of H2bdtCl2 and 2 equiv. of Et4NI or
a series of (X)2[M(bdtCl2)3] (X = Et3NH, Et4N, Ph4P; M = Bu4NBr in the presence of 4 equiv. of Et3N at –40 °C, a red
Mo, W) complexes revealed that the metal centers can microcrystalline powder of (Et4N)2[1] or (Bu4N)2[1] precipi-
adopt both trigonal-prismatic and octahedral structures de- tated in 65% yield. (Et4N)[2] and (Et4N)2[3] were prepared
pending on the size of the counter cations.[7] A similar con- according to literature procedures by Nakamura et al. and
version between a trigonal prism and an octahedron was Holm et al.[8,11]
not observed in other (X)2[M(dithiolene)3] (M = Mo and
W) complexes.
Crystal Structure of (Et4N)2[WO2(bdtCl2)2]
We herein report the synthesis and characterization of
the novel (Et4N)2[WO2(bdtCl2)2] {(Et4N)2[1]}, (Et4N)[WO-
(bdtCl2)2] {(Et4N)[2]}, and (Et4N)2[WO(bdtCl2)2] {(Et4N)2-
Figure 2 shows the crystal structure of the anionic part
of (Et4N)2[1]. Selected bond lengths and angles are shown
[3]} complexes. The structural isomerization of the tungsten
center of (Bu4N)2[1] in [D8]THF is characterized using the
variable-temperature 1H NMR (VT 1H NMR) spectro-
scopic technique. Conversions between (Et4N)2[1] and
(Et4N)2[3] by a CEPT process are described. The UV/Vis,
IR, and EPR spectroscopic studies of the reaction of
(Et4N)[2] with Et4NOH indicate that (Et4N)[2] dispropor-
tionated into 0.5 eqiv. (Et4N)2[1] and 0.5 equiv. (Et4N)2[3]
and that the disproportionation is involved in the conver-
sion of (Et4N)2[3] to (Et4N)2[1]. Since (Et4N)2[1] and
(Et4N)2[3] are isostructural complexes of (Et4N)2[4] and
(Et4N)2[5], the present study is useful for understanding
Figure 2. Crystal structure of [1]2– shown with 50% ellipsoids.
roles of the tungsten centers of the AOR and the FDH fam-
ilies (Figure 1).
Table 1. Selected bond lengths [Å] and angles [°] for (Et4N)2-
[WO2(bdtCl2)2] {(Et4N)2[1]} and (Et4N)2[MoO2(bdtCl2)2] {(Et4N)2-
[4]}.
(Et4N)2[1]
1.741(6)
1.749(7)
2.563(2)
2.443(2)
2.426(2)
2.592(2)
1.72(1)
(Et4N)2[4][a]
1.726(3)
M–O1
M–O2
M–S1
M–S2
M–S3
M–S4
C1–S1
C2–S2
1.739(3)
2.596(1)
2.4462(9)
2.4486(9)
2.561(1)
1.741(3)
1.755(4)
1.750(4)
1.728(4)
1.762(9)
1.766(8)
1.707(9)
C7–S3
C8–S4
Figure 1. Structures of tungsten and molybdenum complexes.
O1–M–O2
M–S1–C1
S1–M–S2
S1–M–S3
S1–M–S4
S1–M–O1
S1–M–O2
S2–M–S3
S2–M–S4
S2–M–O1
S2–M–O2
S3–M–S4
S3–M–O1
S3–M–O2
S4–M–O1
S4–M–O2
M–S2–C2
M–S3–C7
M–S4–C8
102.6(3)
103.2(1)
108.5(3)
79.71(7)
85.72(7)
85.55(7)
88.6(2)
160.3(2)
159.21(7)
84.64(7)
111.0(3)
81.2(2)
79.49(7)
83.2(3)
111.4(2)
162.0(3)
88.2(2)
108.2(1)
78.90(4)
86.07(4)
85.85(5)
87.9(1)
160.5(1)
158.97(5)
85.01(4)
111.1(1)
82.0(1)
79.30(4)
81.5(1)
112.5(1)
160.2(1)
89.0(1)
Results and Discussion
Preparation of WVIO2 and WIVO/WVO Complexes of bdtCl2
Three synthetic methods have been established for bis(di-
thiolene) WVIO2 complexes. In the synthesis of (Bu4N)2-
[WO2(mnt)2], Na2WO4, starting compound, was treated
with Na2mnt and NaHSO3 at pH 5.5 (yield 59%).[2a] Sev-
eral bis(dithiolene) WVIO2 complexes of bdt and its deriva-
tives were obtained in modest yields (1–15%) by several
steps {WCl6 Ǟ [WOCl3(THF)2] Ǟ [WO(SC6H5)4]–
Ǟ
[WO(SC6H5)4]2– Ǟ [WO(benzendithiolates)2]2– Ǟ [WO2-
(benzendithiolates)2]2–}.[8,9] The yields of bis(dithiolene)
WVIO2 complexes of aliphatic dithiolenes were also modest
111.1(3)
111.3(3)
108.0(3)
111.6(6)
110.8(1)
108.4(2)
(20–30%) because the following reactions were required [a] Ref.[5]
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Bis(dithiolene) Tungsten(VI), -(V), and -(IV) Complexes
in Table 1. The tungsten center was coordinated by two oxo dissociation of the M–S bonds in solution. The trigonal-
groups in a cis position and four sulfur atoms from the two prismatic structures probably occur in the transition states
bdtCl2 ligands in a similar fashion to that observed for where the structural isomerization of the metal center of
(Et4N)2[4].[5] The geometry around the metal centers of (Bu4N)2[1] and (Bu4N)2[4] is faster than the NMR timescale
(Et4N)2[1] and (Et4N)2[4] is described as a distorted-octahe- at high temperatures.
dral structure on the basis of the torsion angles[4a] made by
the four sulfur atoms {S2–S1–S3–S4, 101.1° for (Et4N)2[1]
and 100.4° for (Et4N)2[4]}. The W=O bond lengths
[1.749(7) Å and 1.741(6) Å] of (Et4N)2[1] are not signifi-
cantly different from those of (Et4N)2[4]. The W–S2 and
W–S3 distances [2.563(2) Å and 2.592(2) Å, respectively] of
(Et4N)2[1] are longer than the W–S1 and W–S4 distances
[2.443(2) Å and 2.426(2) Å, respectively] due to the trans
influence of the two W=O bonds. The long W–S (2 and 3)
Scheme 2. Structural isomerization of anions of (Bu4N)2[1] and
bond lengths and the short W–S (1 and 4) bond lengths
affect the S–C bond lengths of (Et4N)2[1]. The S1–C1 and
S4–C8 bonds [1.762(9) Å and 1.766(8) Å, respectively] are
longer than the S2–C2 and S3–C7 bonds [1.72(1) Å and
1.707(9) Å, respectively].
(Bu4N)2[4].
∆G values for the isomerizations of (Bu4N)2[1] and
(Bu4N)2[4] were calculated to be 43.2 and 36.4 kJmol–1,
respectively, which are similar to the energy difference
(37.2 kJmol–1) between the octahedron and the trigonal
prism of [MoVI(OCH3)(OSMe2)(S2C2Me2)2]–.[4a] The fact
that the value of ∆G calculated for (Bu4N)2[1] is larger than
that for (Bu4N)2[4] means that the tungsten center is kinet-
ically more stable than the molybdenum one. This is consis-
tent with the fact that the AOR family of tungsten enzymes
belongs to the hyperthermophilic archaea.
1
VT H NMR Spectroscopic Study of [MO2(bdtCl2)2]2–
(M = W and Mo)
As described in the crystal structural study, the tungsten
center of [WO2(bdtCl2)2]2– ([1]2–) offers two distinguishable
S atoms in one bdtCl2 ligand, consequently, two protons on
one bdtCl2 ligand, Ha and Hb, are not equivalent in the
crystal structure. Unexpectedly, the 1H NMR spectra of
(Bu4N)2[1] at 25 °C in [D6]acetone, [D3]acetonitrile, and
[D8]THF show one singlet at δ = 6.61 ppm in the aromatic
region, revealing that the Ha and Hb protons are appar-
ently equivalent in solution.[12] This singlet broadens as the
[D8]THF solution temperature decreases from +40 °C to
–60 °C. Two separate peaks are observed at –70 °C and each
peak is further divided into two peaks at –90 °C (Figure 3).
The singlet from bdtCl2 of (Bu4N)2[4] similarly broadens at
low temperature and is divided into two peaks at –110 °C
(Figure 3). When the temperature of the [D8]THF solutions
of (Bu4N)2[1] and (Bu4N)2[4] was again increased to +40 °C
their original 1H NMR spectra at +40 °C were regenerated.
Redox Properties of [WVIO2(bdtCl2)2]2– and
[WO(bdtCl2)2]–/2–
Figure 4 shows a cyclic voltammogram of (Et4N)2[1] in
CH3CN. (Et4N)2[1] undergoes one irreversible reduction at
Epc = –2.1 V vs. SCE, indicating that the octahedral struc-
ture of the tungsten center is unstable below –2.1 V. The
coulometric measurement during the electrolysis at –2.2 V
indicated that 2.3 electrons were consumed for the comple-
tion of the electrolysis. The electrolysis at –2.2 V caused the
color to change from orange to pale yellow. Since the re-
sulting pale yellow species exhibited an identical absorption
spectrum and CV to those of (Et4N)2[3], (Et4N)2-
[1] was suggested to change to (Et4N)2[3] by a two-electron-
reduction coupled process accompanied by H2O pro-
duction, with contaminant protons arising from the
CH3CN solution (Scheme 3).
1
Since these VT H NMR spectral changes are independent
of the complex concentrations, (Bu4N)2[1] and (Bu4N)2[4]
exhibit structural isomerisation between the octahedral
structures (50% ∆ and 50% Λ forms, Scheme 2) without
Figure 3. VT 1H NMR spectra of (Bu4N)2[1] (4.1 m, left) and
(Bu4N)2[4] (4.1 m, right) in [D8]THF.
Figure 4. Cyclic voltammogram of (Et4N)2[1] (0.1 m, 100 mVs–1)
in 0.1  TBAPF6 containing CH3CN.
Eur. J. Inorg. Chem. 2007, 4663–4668
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H. Sugimoto, M. Tarumizu, H. Miyake, H. Tsukube
FULL PAPER
Whereas (Et4N)[2] reacted with Et4NOH. When Et4NOH
was added to the CH3CN solution of (Et4N)[2] the absorp-
tion band at 600 nm decreased while the bands at 470 nm
and 421 nm increased (Figure 6). The plots of absorbance
at 600 nm and 421 nm against the equivalence of the added
Et4NOH per (Et4N)[2] indicated that (Et4N)[2] reacted with
1 equiv. of OH– (Figure 6, inset). The anisotropic EPR sig-
nal at gav = 1.96 for (Et4N)[2] completely disappeared when
1 equiv. of Et4NOH was added. In the IR spectrum of
(Et4N)[2] the ν(W5+=O) stretching band at 953 cm–1 also
disappears with the appearance of three new bands at 911,
892, and 848 cm–1 when 1 equiv. of Et4NOH is added. The
band at 911 cm–1 is identical to the ν(W4+=O) stretching
band of (Et4N)2[3] and the other two bands are identical
to the ν(W6+=O)sym and ν(W6+=O)asym stretching bands of
(Et4N)2[1] (Figure 7). Thus, it is concluded that the dispro-
portionation of (Et4N)[2], when treated with 1 equiv. of Et4-
NOH in CH3CN, yields 0.5 equiv. of (Et4N)2[1] and
0.5 equiv. of (Et4N)2[3] [Equation (1)], where (Et4N)2-
[WVO(OH)(bdtCl2)2] was proposed as an intermediate in-
volved in the conversion process from (Et4N)2[3] to (Et4N)2-
[1].
Scheme 3. Reversible structural change between (Et4N)2[1] and
(Et4N)2[3] via CEPT processes.
(Et4N)2[3] shows one reversible oxidation wave at
–0.27 V [Figure 5 (solid line)] in CH3CN, which is assigned
to the [WO(bdtCl2)2]2–/– process. The redox potential is
more positive than those of [WO(bdt)2]2–/– (–0.63 V) and
[WO(naphthalenedithiolate)2]2–/– (–0.52 V),[8,9] suggesting
that the Cl atoms attached to the benzene ring decrease the
S Ǟ W electron donations. Because the isostructural
MoIVO complex, (Et4N)2[5], changes to the MoVIO2 com-
plex, (Et4N)2[4], in the presence of 2 equiv. of OH– under
oxidative conditions,[6] the CV change of (Et4N)2[3] was in-
vestigated. The reversible WV/IV couple at –0.27 V became
an irreversible wave upon addition of Et4NOH to the
CH3CN solution of (Et4N)2[3], increasing the current inten-
sity of the Epa while decreasing that of the Epc. The CV
change depended on the added amount of Et4NOH, and
was completed when 2 equiv. of Et4NOH and 1 equiv. of
[WO(bdtCl2)2]2– was added to the solution (dashed line in
Figure 5). The absorption spectrum of the orange solution
obtained after electrolysis of (Et4N)2[3] at –0.1 V in the
presence of 2 equiv. of Et4NOH was identical to that of
(Et4N)2[1]. The coulometric measurement taken during the
electrolysis indicated that 1.9 electrons were consumed for
the completion of the electrolysis. Thus, (Et4N)2[3] was re-
vealed to be converted to (Et4N)2[1] by the CEPT process
as in the case of the isostructural molybdenum complex,
(Et4N)2[5]. Since (Et4N)2[3] was also changed to (Et4N)2[1]
by the CEPT process, the tungsten center coordinated with
two bdtCl2 ligands was demonstrated to be convertible be-
tween the six-coordinate WVIO2 structure, (Et4N)2[1], and
the five-coordinate WIVO structure, (Et4N)2[3], by CEPT
processes (Scheme 3).
2[WVO(bdtCl2)2]– + 2OH– Ǟ [WVIO2(bdtCl2)2]2–
+
[WIVO(bdtCl2)2]2– + H2O (1)
Figure 6. Absorption spectral changes of (Et4N)[2] (1.7ϫ10–4 )
upon addition of n equiv. of Et4NOH in CH3CN (left). Titration
plots of the absorbance at 410 and 600 nm (right) against the n
values.
Figure 7. IR spectra of (Et4N)[2] (dashed line) and an equimolar
mixture (solid line) of (Et4N)[2] and Et4NOH.
Figure 5. Cyclic voltammograms of (Et4N)2[3] (0.1 m,
100 mVs–1): complex only (solid line) and complex + 2 equiv. of
Et4NOH (dashed line) in 0.1  TBAPF6 containing CH3CN.
Conclusion
The absorption spectrum of (Et4N)2[3] in CH3CN re-
Tungsten(VI), -(V), and -(IV) complexes with two bdtCl2
mained the same when 2 equiv. of Et4NOH was added, in- ligands were synthesized and characterized as a new series
dicating that the tungsten(IV) center does not bind OH–. of active site models of tungstoenzymes as well as tungsten-
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Eur. J. Inorg. Chem. 2007, 4663–4668

Bis(dithiolene) Tungsten(VI), -(V), and -(IV) Complexes
dm3 mol–1 cm–1) = 415 (1200), 330 (11100) nm. IR (KBr): ν
=
˜
substituted DMSO reductase. The tungsten center of
(Et4N)2[1] adopted an octahedral structure and underwent
isomerization between the ∆ and Λ forms. This is the first
observation involving six-coordinate bis(dithiolene) tung-
sten(VI) complexes. Its isomerization rate was slower than
that of the isostructural molybdenum(VI) complex, [4]2–.
(Et4N)2[1] changed to (Et4N)2[3] by the CEPT process be-
low –2.1 V vs. SCE, whereas (Et4N)2[3] was similarly con-
verted to (Et4N)2[1] above –0.27 V in the presence of
2 equiv. of Et4NOH. (Et4N)2[WVO(OH)(bdtCl2)2] was sug-
gested to be an intermediate in the CEPT process from
(Et4N)2[3] to (Et4N)2[1].
max
911 [ν(W=O)] cm–1.
Other Measurements: 1H NMR spectra were measured with a
JEOL-Lambda 300. IR and Electronic spectra were recorded with
a Perkin–Elmer Spectrum One and a Shimazu-U2550 spectrometer
at room temperature. CV measurements and bulk electrolyses were
performed with a Hokuto HZ-3000, and the working and counter
electrodes were a glassy-carbon disk and a platinum wire, respec-
tively. The complex solutions of 1.0 m (complexes = 0.01 mmol)
were deoxygenated with a stream of nitrogen gas. The reference
electrode that was used was SCE. The coulometric measurements
performed during the electrolyses were recorded with a Hokuto
HF-201 coulomb/ampere meter.
Calculation of Activation Free Energies (∆G‡ Values): The values
were calculated according to the equation ∆G/RTc = 22.96 + ln(Tc/
δv), where Tc and δv are the coalescence point and the frequency
difference between sites in the exchange system, respectively.[13] Tc
= –65 and δv = 32.5 for (Bu4N)[1], and Tc = –95 and δv = 34.4 for
(Bu4N)[4] were employed.
Experimental Section
General: All reagents and solvents were used as received unless
otherwise noted. CH3CN was dried with CaH2 and then P2O5, and
distilled under nitrogen prior to use. All manipulations were carried
out under argon in Schlenk tubes. (Bu4N)2[MoO2(bdtCl2)2]
{(Bu4N)2[4]} was synthesized by a procedure that was reported in
the literature.[5,6]
X-ray Crystallographic Study: A single crystal of (Et4N)[1] was
recrystallized from acetonitrile/ether and mounted on top of a glass
fiber. X-ray data of the crystal were collected with graphite-mono-
chromated Mo-Kα radiation with a Rigaku/MSC Mercury CCD
diffractometer at –130 °C. The structure was solved by direct meth-
ods (SIR-97)[14] and expanded using the program DIRDIF 99.[15]
The structure was refined anisotropically by full-matrix least-
squares on F2. The non-hydrogen atoms in the structure were at-
tached at the idealized positions on carbon atoms and not refined.
The structure converted in the final stages of the refinement showed
no movement in the atom positions. All calculations were per-
formed using Single-Crystal Structure Analysis Software, Ver.
3.6.0.[16] Further crystal data and agreement factors are listed in
Table 2.
(Et4N)2[WO2(bdtCl2)2] {(Et4N)2[1]}: WO2Cl2 (87 mg, 0.3 mmol)
was added to an ethanol solution (15 mL) containing H2bdtCl2
(126 mg, 0.60 mmol), Et3N (169 µL, 1.2 µmol), and Et4NI (231 mg,
0.9 mmol) at –40 °C. After stirring for 10 h at 0 °C, the orange
solution that was obtained was concentrated to 3 mL. An orange
microcrystalline powder precipitated, which was collected and
dried in vacuo. Yield: 174 mg (65%). C28H44Cl4N2O2S4W (894.59):
calcd. C 37.59, H 4.96, N 3.13; found C 37.64, H 4.85, N 3.07.
ESI-mass: m/z = 764 [(M + Et4N)–], 634 [(M)–]. UV/Vis spectrum
(CH3CN): λ (ε, dm3 mol–1 cm–1) = 470 (sh, 1320), 421 (2820), 344
(sh, 13300) nm. IR (KBr): ν
= 892 [ν(W=O)sym] and 848
˜
max
[ν(W=O)asym] cm–1. Raman (solid): ν
= 893 [ν(W=O)sym] and
˜
max
Table 2. Crystallographic data for (Et4N)2[WO2(bdtCl2)2] {(Et4N)2-
[1]}.
848 [ν(W=O)asym] cm–1.
(Bu4N)2[WO2(bdtCl2)2] {(Bu4N)2[1]}: The synthesis was carried out
in the same manner as that of (Et4N)2[1] using Bu4NBr instead of
Et4NI. The UV/Vis and IR spectral profiles based on the anion
were consistent with those of (Et4N)2[1].
(Et4N)2[1]
Formula
C28H44Cl4N2O2S4W
894.57
–130
orthorhombic
Fdd2
28.113(6)
21.888(4)
22.688(4)
13961(5)
16
1.702
18901
7323
0.0460
Molecular weight (gmol–1)
Temperature (°C)
Crystal system
Space group
a (Å)
(Et4N)[WO(bdtCl2)2] {(Et4N)[2]}: The synthesis was carried out by
a similar procedure to that of (Et4N)[WO(bdt)2] reported by Holm
et al.[11] A CH3CN solution (5 mL) of 3,6-dichloro-1,2-benzenedi-
thiol (55 mg, 0.26 mmol) and Et3N (73 µL, 0.52 mmol) was slowly
added to a CH3CN solution (5 mL) of (Et4N)[WO(benzenethiol)4]
(100 mg, 0.13 mmol) at –40 °C. The temperature of the solution
was increased to 25 °C and the resultant solution was stirred for
1 h. The deep blue solution that was obtained was reduced to a
volume of 1 mL. Diffusion of ether into the solution gave a black
powder, which was collected by filtration and dried in vacuo. Yield:
66 mg (68%). C20H24Cl4NOS4W (748.34): calcd. C 32.10, H 3.23,
N 1.87; found C 32.21, H 3.38, N 2.04. ESI-mass: m/z = 618
[(M)–]. UV/Vis spectrum (CH3CN): λ (ε, dm3 mol–1 cm–1) = 600
b (Å)
c (Å)
V (Å3)
Z
Dcalcd. (gcm–3)
Unique data
Observed data
R
wR
GOF
0.1200
1.001
= 953 [ν(W=O)] cm–1.
CCDC-616400 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
(2050), 468 (1070) nm. IR (KBr): ν
˜
max
(Et4N)2[WO(bdtCl2)2] {(Et4N)[3]}: A CH3CN solution (2 mL) of
Et4NBH4 (4 mg, 0.027 mmol) was added to a THF solution
(10 mL) of (Et4N)2[2] (20 mg, 0.027 mmol). After the solution was
stirred for 30 min a white yellow powder precipitated out of the
solution, which was collected by filtration and dried in vacuo.
Yield: 19 mg (82%). C28H44Cl4N2OS4W (878.60): calcd. C 38.28,
Acknowledgments
H 5.05, N 3.19; found C 38.50, H 4.95, N 3.20. ESI-mass: m/z This work was partly supported by the Japan Society for Pro-
= 748 [M + Et4N+]–, 618 [M]–. UV/Vis spectrum (CH3CN): λ (ε, motion of Science, Grant No. 18750052 to H. S.
Eur. J. Inorg. Chem. 2007, 4663–4668
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4667

H. Sugimoto, M. Tarumizu, H. Miyake, H. Tsukube
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Received: June 11, 2007
Published Online: August 28, 2007
4668
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© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 4663–4668