Formation of a dithiophosphinate ligand Ph2PS2 by sulfur insertion into the metal-phosphido bond on heterobimetallic phosphido-bridged complex Cp(CO)2W(μ-PPh2)Mo(CO) 5: A Rare Example of a Neutral Six-Electron Mixed-Metal Cluster with a Mo2WS4 Core

Article abstract of DOI:10.1021/om0608509

Reflux of a dichloromethane solution of elemental sulfur and phosphido-bridged heterodinuclear complex Cp(CO)₂W(μ-PPh ₂)Mo(CO)₅ (1) afforded Cp(S)W(μ-S)₂Mo(S) (S₂PPh₂) (2) and a neutral six-electron mixed-metal incomplete cubane-like cluster, CpW(μ₃-S)(μ-S) ₂Mo₂(μ-S)(μ-S₂PPh₂)(S ₂PPh₂)₂ (3), together with known compounds Cp(CO)₃W(μ-PPh₂)Mo(CO)₅ and (CpW(S)(μ-S))₂. T e electron-deficient 28e heterodinuclear complex 2 is stabilized via S(p_π) → Mo(d) ligand-to-metal dative π-bonding interactions. Room-temperature stirring of a THF solution of 2 and DMAD (dimethyl acetylenedicarboxalate) yielded compounds Cp(S₂C ₂(COOMe₂))₂)W(μ-S)₂Mo(O)(S ₂PPh₂) (4) and Cp(S₂C₂(COOMe ₂)₂)W(μ-S)₂W(O)Cp (5). Compounds 2-5 were characterized by single-crystal X-ray diffraction analysis. Molecular structures of 2 and 3 reveal sulfur insertion into the metal-phosphide bond on 1, resulting in a dithiophosphinate ligand Ph₂PS₂. Formation of the C-S bonds in 4 and 5 has resulted through the reaction of sulfide ligands on 2 and DMAD.

Full text of DOI:10.1021/om0608509

Organometallics 2007, 26, 685-691
685
Formation of a Dithiophosphinate Ligand Ph2PS2 by Sulfur
Insertion into the Metal-Phosphido Bond on Heterobimetallic
Phosphido-Bridged Complex Cp(CO)2W(µ-PPh2)Mo(CO)5: A Rare
Example of a Neutral Six-Electron Mixed-Metal Cluster with a
Mo2WS4 Core
Md. Munkir Hossain,† Hsiu-Mei Lin,§ and Shin-Guang Shyu*,†, ‡
Institute of Chemistry, Academia Sinica, Taipei, Taiwan, Republic of China, Department of Chemistry,
National Chung Hsing UniVersity, Taichung, Taiwan, Republic of China, and Institute of Bioscience and
Biotechnology, National Taiwan Ocean UniVersity, Keelung, Taiwan, Republic of China
ReceiVed September 17, 2006
Reflux of a dichloromethane solution of elemental sulfur and phosphido-bridged heterodinuclear complex
Cp(CO)2W(µ-PPh2)Mo(CO)5 (1) afforded Cp(S)W(µ-S)2Mo(S)(S2PPh2) (2) and a neutral six-electron
mixed-metal incomplete cubane-like cluster, CpW(µ3-S)(µ-S)2Mo2(µ-S)(µ-S2PPh2)(S2PPh2)2 (3), together
with known compounds Cp(CO)3W(µ-PPh2)Mo(CO)5 and (CpW(S)(µ-S))2. The electron-deficient 28e
heterodinuclear complex 2 is stabilized via S(pπ) f Mo(d) ligand-to-metal dative π-bonding interactions.
Room-temperature stirring of a THF solution of 2 and DMAD (dimethyl acetylenedicarboxalate) yielded
compounds Cp(S2C2(COOMe2))2W(µ-S)2Mo(O)(S2PPh2) (4) and Cp(S2C2(COOMe2)2)W(µ-S)2W(O)Cp
(5). Compounds 2-5 were characterized by single-crystal X-ray diffraction analysis. Molecular structures
of 2 and 3 reveal sulfur insertion into the metal-phosphido bond on 1, resulting in a dithiophosphinate
ligand Ph2PS2. Formation of the C-S bonds in 4 and 5 has resulted through the reaction of sulfide
ligands on 2 and DMAD.
metal-metal bond and labile carbonyl ligands for further
reaction,9 is a suitable precursor for oxidative addition of both
organic disulfides RSSR (R ) alkyl or aryl group)10 and
inorganic disulfide (Fe2(µ-S2)(CO)6)11 via the S-S bond cleav-
age. Formation of a hybrid ligand Ph2PSR by interaction
between phosphido-bridged PPh2 on 1 and SR during RSSR
activation and the S(pπ) f Mo(d) ligand-to-metal dative
π-bonding interactions in the complexes where SR is a terminal
ligand have also been reported.10
Introduction
Multimetallic sulfide clusters have attracted much attention
in relevance to the active sites of metalloenzymes,1 industrial
hydrotreating catalysis,2 and superconductive materials.3 In
particular, trinuclear triangular molybdenum clusters with the
incomplete cubane-like cluster core Mo3S4 have attracted many
chemists because these are used as the starting materials to form
cubane-like cluster analogues of Fe4S4(SR)2
2-4
and to form
Mo6S8 clusters.3 Although the homonuclear and heteronuclear
incomplete cubane-like cluster cores Mo3S4,5,6 W3S4,7 MoW2S4,8
and Mo2MS4 (M ) W, Pd, Rh),8 respectively, are known, the
heteronuclear incomplete cubane-like ionic cluster cores with
six cluster electrons such as Mo2WS4 or MoW2S4 are still limited
Elemental sulfur containing S-S bonding is reducing in
nature. It acts as a source of the sulfide ligands. Among the
(6) (a) Saito, T.; Yamamoto, N.; Yamagata, T.; Imoto, H. Chem. Lett.
1987, 2025. (b) Martinez, .; Ooi, B.-L.; Sykes, A. G. J. Am. Chem. Soc.
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S.; Sandor, R. B. W. Inorg. Chem. 1989, 28, 2623. (d) Cotton, F. A.; LIusar,
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Kawaguchi, H.; Tatsumi, K. Inorg. Chem. 1996, 35, 1743.
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A.; Khoda, K.; Kuroya, H. Inorg. Chim. Acta 1987, 127, L45. (c) Cotton,
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F.; Wu, X. T.; Lu, J. X. J. Mol. Struct. 1989, 196, 241.
8a,b
and that of a neutral one is still unknown.
We have reported that the phosphido-bridged heterodinuclear
complex Cp(CO)2W(µ-PPh2)Mo(CO)5 (1), which has a reactive
* Corresponding author. E-mail: sgshyu@chem.sinica.edu.tw.
† Institute of Chemistry, Academia Sinica.
‡ National Chung Hsing University.
§ National Taiwan Ocean University.
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10.1021/om0608509 CCC: $37.00 © 2007 American Chemical Society
Publication on Web 12/14/2006

686 Organometallics, Vol. 26, No. 3, 2007
Hossain et al.
Scheme 1
several means for the synthesis of sulfido complexes, oxidative
addition of elemental sulfur to a coordinatively unsaturated
electron-rich metal is a convenient one.12 Activation of the S-S
bond in S8 through its interaction with the phosphido bridge
PPh2 in 1 is promising to have different ligand combinations in
a cluster with high nuclearity. It can also determine the ligating
diversity through the π-donor ability of S when it is not bonded
with organic moieties. Herein, we report the synthesis and
single-crystal X-ray structures of a heterodinuclear electron-
compounds Cp(CO)3W(µ-PPh2)Mo(CO)5 and (CpW(S)(µ-S))2
reported earlier9,13 (Scheme 1). Typical reaction of 1 with 1.5
equiv of S8 produced compounds with comparatively low yields
similar to those of the reaction products using 3 equiv of S8. In
addition, there was a new band in trace amounts which could
not be characterized. Both 2 and 3 are air-stable, orange solids.
Compound 2 is a thio-Mo-W mixed-metal complex with a Ph2-
PS2 ligand, as shown by its molecular structure (Figure 1).
deficient 28e complex, Cp(S)W(µ-S)2Mo(S)(S2PPh2) (2), and
a neutral mixed-metal trinuclear triangular incomplete cubane-
like cluster, CpW(µ3-S)(µ-S)2Mo2(µ-S)(µ-S2PPh2)(S2PPh2)2 (3),
with a 6e Mo2WS4 core. The formation of the C-S bonds in
Cp(S2C2(COOMe2)2)W(µ-S)2Mo(O)(S2PPh2) (4) and Cp(S2C2-
(COOMe2)2)W(µ-S)2W(O)Cp (5) when 2 is reacted with DMAD
(dimethyl acetylenedicarboxalate) in THF solution is also
reported.
Results and Discussion
Figure 1. ORTEP drawing of 2, with 30% thermal ellipsoids.
Hydrogen atoms are omitted.
Reaction of 1 with S8. Reaction of 1 with 3 equiv of S8 in
refluxing dichloromethane gave compounds 2 and 3 and known
Molybdenum and tungsten complexes with oxo and/or thio
ligands have been widely used as model compounds to mimic
metalloenzymes whose active sites feature the said metals and
ligands such as xanthine oxidase (LMoOS-possessing enzymes),
sulfite oxidase (LMoO2-possessing enzymes), and DMSO
reductase (L2MoX-possessing enzymes).14 Moreover, when
dithiophosphinate R2PS2 is a co-ligand in these complexes, its
ambidentate nature facilitates reactions such as conversion of
Me2SO to Me2S.15 It is also realized that the generated
[MoOS]2+ center in the oxo-thio-M complex is stabilized via a
weak S‚‚‚S interaction15 between the S of ModS and the
noncoordinated S of the R2PS2 ligand. Thus, the oxo and/or
thio compounds of molybdenum and tungsten with R2PS2 as a
co-ligand are particularly relevant to mimic biological reac-
tions.15,16
(12) (a) Chatt, J.; Mingos, D. M. P. J. Chem. Soc. A 1970, 1243. (b)
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5368. (d) Hill, J. P.; Laughlin, L. J.; Gable, R. W.; Young, C. G. Inorg.
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Young, C. G. J. Am. Chem. Soc. 1992, 114, 9195. (g) Xiao, Z.; Bruck, M.
A.; Enemark, J. H.; Young, C. G.; Enemark, J. H.; Wedd. A. G. Inorg.
Chem. 1996, 35, 7508. (h) Doonan, C. J.; Slizys, D. A.; Young, C. G. J.
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G. N.; Young, C. G. Inorg. Chem. 2003, 42, 5909.
In compound 2, sulfur is coordinated to Mo and W as a
terminal as well as a bridging atom. Coordination of the
ambidentate Ph2PS2 in 2 indicates sulfur insertion into the

Neutral Six-Electron Mixed-Metal Cluster with a Mo2WS4 Core
Organometallics, Vol. 26, No. 3, 2007 687
Figure 2. ORTEP drawing of 3, with 30% thermal ellipsoids. Hydrogen atoms are omitted.
Table 1. List of a Few M2M′S4 Clusters with Six and Seven
phosphido-bridging PPh2 ligand in 1. The usual sources of Ph2-
PS2 ligand are the dithiophosphinic acid and its salts or
disulfanes R2P(S)S2(S)PR2.17 The participation of bridging
phosphido groups, with the insertion of small molecules into
the M-P bonds, causes its transformation into unique bridging
ligands such as µ-R2PdX (X ) O18, S18, CH2,19 or CRR20) and
alkenyl- and butadienylphosphines21 and -diphosphines.22 The
coupling of bridging phosphido ligands with CO and alkynes
has also been reported.23 Although insertion of sulfur into one
of the Rh-P bonds of the Rh(µ-PPh2)Rh system and formation
of a bridging Rh(µ-Ph2PdS)Rh is known,18 insertion of sulfur
into both the Mo-P and W-P bonds of the Mo(µ-PPh2)W in
1 and formation of a dithiophosphinate Ph2PS2 on Mo in 2 is
reported for the first time.
3d Electrons
oxidation
state
no. of 3d X-ray
electrons structure
cluster
ref
[MoW2(µ3-S)(µ-S)3(H2O)9]-
(Pts)4)‚9H2Oa
4 (3d2)
6
6
6
6
yes
yes
yes
yes
8a
8a
8b
8b
[Mo2W(µ3-S)(µ-S)3(H2O)9]
4 (3d2)
(Pts)4)‚9H2O
Na2[MoW2(µ3-S)(µ-S)3(Hnta)3]‚ 4 (3d2)
5H2Ob
Na2[Mo2W(µ3-S)(µ-S)3(Hnta)3] 4 (3d2)
‚5H2O
CpMo2W(µ3-S)(µ-S)3(S2PPh2)3 4 (3d2)
6
7
7
yes
no
no
this work
40
40
Cp*3Mo2W(µ3-S)(µ-S)3
Cp*3Mo2Cr(µ3-S)(µ-S)3
3 (3d3), 4 (3d2)
3 (3d3), 4 (3d2)
a Pts ) para-toluenesulfonic acid. b Hnta ) nitrilotriacetic.
capped by the µ3-S atom, and the rest of the three sulfur atoms
bridged each edge of the triangle. Moreover, each of the Mo
sites is chelated by one Ph2PS2 ligand, and these Mo sites are
also linked to each other by a third bridging Ph2PS2 ligand.
Hence in 3, sulfur shows four different bonding modes as µ-S,
µ3-S, η2-S2PPh2, and µ-S2PPh2. It becomes a member of the
class of classic clusters with a M3S4 core. These clusters are
also classified on the basis of the total number of 3d electrons
of the metals that they have (Table 1). In the case of a seven-
electron Mo3S4-core cluster, the oxidation of the metal can be
MoIII and MoIV, while for a six-electron core it is MoIV.
Compound 3 is a six-electron cluster since both the molybdenum
and tungsten have +4 oxidation states. There are a few reports
on six-electron and seven-electron clusters having a M2M′S4
central unit, which have been synthesized as ionic or neutral
complexes (Table 1). A few mixed-metal complexes with
MoW2S4 and Mo2WS4 cores have been reported that are also
six-electron ionic complexes (Table 1). Compound 3 reported
here is a neutral six-electron cluster heterobimetallic complex.
To our knowledge, there are no other mixed-metal clusters with
MoW2S4 or Mo2WS4 cores that are reported to be neutral (Table
1).
The molecular structure of 3 (Figure 2) reveals a heterobi-
metallic trinuclear cluster containing the central Mo2WS4 unit
that forms a trigonal pyramid with a Mo-Mo-W triangle
(17) (a) Goh, L. Y.; Leong, W. K.; Leung, P.-H.; Weng, Z. Haiduc, I. J.
Orgnomet. Chem. 1990, 391, 397. (b) Keck, H.; Kuchen, K.; Mathow, J.;
Wunderlich, H. Angew. Chem., Int. Ed. Engl. 1982, 21, 929. (c) Kuchen,
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K.; Mathow, J.; Meyer B.; Mtooz, D. J.; Wunderlich, H. Angew. Chem.,
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G.; Balducc, G. J. Am. Chem. Soc 1984, 106, 3704. (b) Yu, Y.-F.; Chau,
C.-N.; Gallucci, J.; Wojcicki, A. J. Chem. Soc., Chem. Commun. 1984,
653. (c) Rosenberg, S.; Whittle, R. R.; Geoffroy, G. L. J. Am. Chem. Soc.
1984, 106, 5934. (d) Rosenberg, S.; Geoffroy, G. L.; Rheingold, A. L.
Organometallics 1985, 4, 1184. (e) Geoffroy, G. L. Rosenberg, S.; Shulman,
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H.; Zolk, R. Chem. Ber. 1987, 120, 1003.
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Commun. 1985, 247. (b) Henrick K.; Iggo J. A.; Mays, M. J.; Raithby, P.
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1986, 5, 47.
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Organometallics 1984, 3, 814. (b) Regragui, R.; Dixneuf, P. H.; Taylor, N.
J.; Carty, A. J. Organometallics 1990, 9, 2234.
Reaction of 2 with DMAD. Room-temperature stirring of a
THF solution of 2 and DMAD produced compounds 4 and 5
along with a few uncharacterized trace compounds. Compound
5 was also synthesized by the reaction of DMAD and the known
compound (CpW(S)(µ-S))2 (Scheme 1). The molecular struc-

688 Organometallics, Vol. 26, No. 3, 2007
Hossain et al.
terminal thio ligand of 2 with CH3OC(O)CC(O)COCH3 and
formation of 4 and 5 is noteworthy. In both 4 and 5, the Mo
and W retained their same oxidation states as in the parent
compound 2 by coordination of the oxo ligand on the Mo and
W site.
1
NMR Spectra of 2-5. The H NMR peaks at 6.43, 5.81,
5.50, and 6.12 ppm of the cyclopentadienyl group (Cp) for 2-5,
respectively, are shifted downfield compared to that of 1 (5.17
ppm) since the oxidation states of tungsten and molybdenum
in 2-5 are increased compared to that of parent compound 1.
The 31P{1H} NMR spectrum of 3 exhibits two resonances at
92.09 and 68.83 ppm in the intensity ratio 2:1, respectively.
This indicates that, out of the three phosphorus atoms, two are
equivalent, and this corresponds to the downfield peak at 92.09
ppm. The upfield peak at 68.83 ppm corresponds to the third
phosphorus atom. This is in agreement with the molecular
structure of 3, where the two terminal PPh2S2 ligands are
equivalent and the third is in bridging mode. The signals for
the phenyl proton of the PPh2S2 ligand in 2-4 and methyl
protons of DMAD in 4 and 5 appear at normal positions.
X-ray Structure of 2-5. Compounds 2-5 were character-
ized by single-crystal X-ray diffraction analysis. Molecular
structures of these compounds are shown in Figures 1-4,
respectively. The experimental data are summarized in Table
2. Selected bond lengths and bond angles are listed in Tables 3
and 4, respectively. The Mo1-W1 bond distance in 2 is 2.8521-
(10) Å with average Mo-S-W acute angles of 76.31°. The
Mo-W bond is a single bond and compares well with the
reported Mo-W bond length of 34e dimers, such as Cp(CO)-
Figure 3. ORTEP drawing of 4, with 30% thermal ellipsoids.
Hydrogen atoms are omitted.
Figure 4. ORTEP drawing of 5, with 30% thermal ellipsoids.
Hydrogen atoms are omitted.
W(µ-SPh)2(µ-PPh2)Mo(CO)3 (2.8427(14) Å) and Cp(CO)W-
(µ-SPh)2(µ-PPh2)Mo(CO)2(PPh3) (2.8382(13) Å).10 This is quite
unusual, as the heterobimetallic 2 is a 28e system (making it
electron deficient according to the 18e rule). The average bond
distances Mo1-Sbr (2.3233 Å), W1-Sbr (2.2929 Å), and W1d
Ster (2.1505 Å) are within the range of reported bond distance
values in the molybdenum and tungsten dimers tabulated in ref
31 (2.29-2.357 Å), ref 32 (2.29-2.39 Å), and ref 33 (2.09-
2.144 Å), respectively. The bond length of ModSter in molyb-
denum dimers has been reported as 2.10-2.12 Å.33 In compound
2, the ModSter bond length is 2.0859(18) Å, which is even less
than that in molybdenum dimers.33 This suggests that the formal
bond order between molybdenum and sulfur is greater than 2.
The strong S(pπ)fMo(d) ligand-to-metal dative π-bonding
interaction involves the stabilization of the electron deficiency
in 2.33 Furthermore, the average Mo1-S bond distance (2.489
Å) of the terminal Ph2PS2 in 2 is shorter than the reported
average Mo-S bond distances for dimers such as [Mo(NC6H4-
CH3)(S2P(OC2H5)]2(µ-S)(µ-SH)(µ-O2CCF3) (2.5242 Å),34 [Mo-
(NC6H4CH3)(S2P(OC2H5)]2(µ-S)(µ-SCH3)(µ-O2CCF3) (2.5212
tures of 4 and 5 (Figures 3 and 4) reveal the formation of
dithiolene ligands in these complexes. The thio ligand of 2
involved in the C-S bond formation with DMAD has resulted
in the dithiolene linkages. There are two types of reactions of
alkynes with S-ligand complexes. In one way they coordinate
directly to the metal and produce either π-coordinated24 or
σ-cooridinated25 complexes, which is classical type. In other
way they react with sulfide, disulfide, or polysulfide ligands to
form a 1,2-dithiolene ligand.26 The latter one is interesting for
the case of Mo and W complexes to mimic Mo-(W)-containing
oxotransferase enzymes, which is featured by coordination of
pterine-1,2-enedithiolate.27 The activated alkynes such as CH3-
OC(O)CC(O)COCH3 and CF3CCCF3 are more reactive than
nonactivated alkynes such as PhCCH and PhCCPh to form
dithiolene ligands with S-ligand complexes.28 On the other hand,
reaction of alkynes with polysufides is occasionally observed,28
and that with the bridging monothio ligands is rare29 and even
more rare with terminal thio ones.30 Thus, the reaction of the
(24) (a) Tanaka, K.; Miyaka, S.; Tanaka, T. Chem. Lett. 1981, 189. (b)
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E.; McDonald, J. W.; Corbin J. L.; Richard., L.; Weiss, R. Inorg. Chem.
1980, 19, 1997.
(28) (a) Coucouvanis, D.; Hadjikyriacou, A.; Toupadakis, A.; Koo, S.-
M.; Iieperuma, O.; Draganjac, M.; Salifoglou, A. Inorg. Chem. 1991, 30,
754. (b) Coucouvanis, D.; Toupadakis, A.; Koo, S.-M.; Hadjikyriacou, A.
Polyhedron 1989, 8, 1705.
(25) Halbert, T. R.; Pan, W.-H.; Stiefel, E. I. J. Am. Chem. Soc 1983,
105, 5476.
(29) (a) Rakowski DuBois, M.; VanDerreer, M. C.; DuBois, D. L.;
Haltiwanger, R. C.; Miller, W. K. J. Am. Chem. Soc. 1980, 102, 7456. (b)
Boliger, C. M.; Rauchfuss, T. B.; Rheingold, A. L. J. Am. Chem. Soc 1983,
105, 6321. (c) Shibihara, T.; Sakane, G.; Mochida, S. J. Am. Chem. Soc.
1993, 115, 10408. (d) Rakowski, DuBois, M.; Jagiradar, B. R.; Diez, S.;
Noll, B. C. Organometallics 1997, 16, 294. (e) Rauchfuss, T. B.; Rodgers,
D. P. S.; Wilson, S. R. J. Am. Chem. Soc. 1986, 108, 3114.
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Chem. Soc. 1997, 119, 10346. (b) Eagle, A. A.; Harden, S. M.; Tiekink, E.
R. T.; Young, C. G. J. Am. Chem. Soc. 1994, 116, 9749.
(26) (a) Seyferth, D.; Henderson, R. S. J. Organomet. Chem. 1979, 182,
C39. (b) Bolinger, C. M.; Rauchfuss, T. B.; Wilson, S. R. J. Am. Chem.
Soc. 1981, 103, 5620. (c) Rakowski, DuBois, M.; Haltiwanger, R. C.; Miller,
D. J.; Galtzmaier, G. L. J. Am. Chem. Soc. 1979, 101, 5245. (d) Miller, D.
J.; Rakowski DuBois, M. J. Am. Chem. Soc. 1980, 102, 4925. (e) DuBois,
D. L.; Miller, W. K.; Rakowski DuBois, M. J. Am. Chem. Soc. 1981, 103,
3429.
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Rees, D. C. Science 1996, 272, 1615.
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(33) Cohen, S. A.; Stiefel, E. I. Inorg. Chem. 1985, 24, 4657.

Neutral Six-Electron Mixed-Metal Cluster with a Mo2WS4 Core
Table 2. Summary of Crystal Data for 2-5
Organometallics, Vol. 26, No. 3, 2007 689
2
3
4
5
formula
fw
C20H18PS6MoW
761.46
C41H35S10P3Mo2W
1316.93
C23H21O5S6PMoW
880.52
C16H16O5S4W2
784.23
space group
a [Å]
b [Å]
P1h
P1h
C2
Pcab
6.1840(15)
11.014(4)
18.399(2)
73.172(19)
81.516(17)
87.50(3)
1186.4(5)
2.132
11.4373(2)
11.4761(2)
20.4699(4)
81.8180(10)
82.9540(10)
75.1590(10)
2560.27(8)
1.708
28.204(6)
6.7865(14)
18.204(4)
6.7919(14)
23.052(5)
25.445(5)
c [Å]
R [deg]
â [deg]
γ [deg]
V [Å3]
120.183(3)
3012.0(11)
1.942
4
3983(14)
2.615
8
F(calcd) [Mg m-3
Z
]
2
2
cryst dimens [mm]
temp [K]
0.23 × 0.20 × 0.11
0.08 × 0.06 × 0.02
0.27 × 0.25 × 0.20
0.25 × 0.20 × 0.18
298(2)
298(2)
298(2)
298(2)
λ(Mo Ka) [Å]
2θ range [deg]
scan type
no. of reflns
no. of obsd reflns
no. of params refined
R
0.71073
50.0
ω
4206
4206 (>2.0σ(I))
262
0.0275
0.71073
50.0
ω
41 385
8948 (>2.0σ(I))
514
0.0356
0.71073
50.0
ω
3013
2918 (>2.0σ(I))
284
0.0558
0.71073
50.0
ω
3479
3479 (>2.0σ(I))
209
0.0503
Rw
0.0577
0.1035
0.1320
0.0976
GoF
D
1.014
-0.951, 0.752
1.102
-2.414, 1.846
1.010
-2.166, 2.066
1.020
-3.106, 2.621
map min., max. [e/Å3]
Table 3. Selected Bond Lengths (Å) for 2-5
density into the vacant metal dπ orbitals, leading to stabilization
of electron-deficient 2.
2
W1-Mo1
W1-S1
W1-S2
W1-S3
W1-C1
W1-C2
W1-C3
W1-C4
W1-C5
2.8521(10)
2.1505(17)
2.2925(16)
2.2933(18)
2.381(6)
Mo1-S2
Mo1-S3
Mo1-S4
Mo1-S5
Mo1-S6
P1-S5
2.3291(18)
2.3176(16)
2.0859(18)
2.4825(17)
2.4955(19)
2.026(2)
The trinuclear cluster 3 has 42 electrons assuming that the
µ3-S sulfur serves as a four-electron donor. It is electron-
deficient because a trinuclear cluster is expected to have an
electron count of 48. Formally, one can consider the metal-
metal bond order is 2 according to the 18-electron rule.
However, the number of metal d electrons is 6. The metal-
metal bond order should be 1. Therefore, it is expected that the
π electrons of the µ2-bridging sulfido ligands participate in the
bonding of the WMo2S4 core. In other words, π-bonding must
exist between the three metal atoms and the three µ2-bridging
sulfido ligands, making the Mo-W and Mo-Mo bond distances
shorter than expected. The Mo1-W1, Mo2-W1, and Mo1-
Mo2 bond distances are 2.7757(7), 2.7716(8), and 2.7403(10)
Å, respectively, and these are longer than the reported ModW
(2.702-2.718 Å)37 and ModMo (2.705(2) Å)32 bond distances.
However, they are shorter than the Mo1-W1 single bond
distance in 2 (2.8521(10) Å). This indicates the bond order
between the metals in cluster 3 is between 1 and 2 and is smaller
than expected. The average Mo-Sbr (2.3270 Å) and W-Sbr
(2.2857 Å) bond distances match well with the reported
values.31,32 The average Mo-S bond distance (2.590 Å) of the
terminal Ph2PS2 is normal.34-36
2.369(7)
2.404(6)
P1-S6
2.018(2)
2.396(6)
P1-C11
P1-C21
1.824(6)
1.807(6)
2.378(6)
3
W1-Mo1
W1-Mo2
W1-S1
W1-S2
W1-S4
W1-C1
W1-C2
W1-C3
W1-C4
W1-C5
Mo1-Mo2
Mo1-S2
2.7757(7)
2.7716(8)
2.267(2)
2.263(2)
2.327(2)
2.384(9)
2.386(9)
2.362(9)
2.341(9)
2.349(9)
2.7403(10)
2.332(2)
Mo1-S3
Mo1-S4
Mo2-S1
Mo2-S3
Mo2-S4
Mo1-S6
Mo1-S7
Mo1-S8
Mo2-S5
Mo2-S9
Mo2-S10
2.296(2)
2.351(2)
2.337(2)
2.299(2)
2.347(2)
2.576(2)
2.606(2)
2.578(2)
2.566(2)
2.587(2)
2.589(2)
4
W1-Mo1
W1-S1
W1-S2
W1-S3
W1-S4
W1-C1
W1-C2
W1-C3
W1-C4
W1-C5
Mo1-O1
2.893(2)
2.371(7)
2.355(7)
2.397(8)
2.434(7)
2.34(3)
Mo1-S1
Mo1-S2
Mo1-S5
Mo1-S6
P1-S5
2.296(8)
2.303(8)
2.491(8)
2.495(9)
2.031(12)
1.992(12)
1.85(3)
Compound 4 is a 28e dimer like 2. The Mo1-W1 bond
distance (2.893(2) Å) is a little longer than in 2 but quite similar
to the doubly bridged molybdenum and tungsten dimers.10 It is
also quite unusual like 2 (according to the 18e rule). The
shortening of the Mo1-S (2.493 Å (av)) bond distance of the
P1-S6
2.41(3)
P1-C11
P1-C21
C32-S3
C33-S4
2.41(3)
1.87(3)
2.27(2)
1.82(3)
2.28(3)
1.72(3)
1.684(19)
terminal S2PPh2 ligand from the reported molybdenum dimers
5
34-36
with S2PR2
and also from that of 3 again suggest that
W1-W2
W1-S1
W1-S2
W1-S3
W1-S4
W1-C1
W1-C2
W1-C3
W1-C4
W1-C5
2.9323(11)
2.378(5)
2.421(5)
2.402(5)
2.377(5)
2.374(19)
2.30(2)
2.286(19)
2.37(2)
2.37(2)
W2-O1
W2-S3
W2-S4
W2-C11
W2-C12
W2-C13
W2-C14
W2-C15
S1-C22
S2-C23
1.688(13)
2.280(5)
2.282(5)
2.40(3)
(34) Noble, M. E.; Huffman, J. C.; Wentworth, R. A. D. Inorg. Chem.
1983, 22, 1756.
(35) Noble, M. E.; Floting, K.; Huffman, J. C.; Wentworth, R. A. D.
Inorg. Chem. 1984, 23, 631.
(36) Noble, M. E.; Williams, D. E. Inorg. Chem. 1988, 27, 749.
(37) (a) Acum, G. A.; Mays, M. J.; Raithby, P. R.; Solan, G. A. J. Chem.
Soc., Dalton Trans. 1995, 3049. (b) Brew, S. A.; Carr, N.; Mortimer, M.
D.; Stone, F. G. A. J. Chem. Soc., Dalton Trans. 1991, 811. (c) Brew, S.
A.; Dosset, S. J.; Jeffery, J. C.; Stone, F. G. A. J. Chem. Soc., Dalton Trans.
1990, 3709. (d) Carriedo, G. A.; Howard, J. A. K.; Jeffery, J. C.; Sneller,
K.; Stone, F. G. A.; Weerasuria, A. M. M. J. Chem. Soc., Dalton Trans.
1990, 953. (e) Cotton, F. A. Eglin, J. A.; James, C. A. Inorg. Chem. 1993,
32, 687.
2.42(2)
2.38(3)
2.35(3)
2.38(3)
1.755(19)
1.721(18)
Å),35 and [Mo2(NTo)2(S2P(OC2H5)2)2S(O2CMe)(SSC2H5)] (2.534
Å).36 This indicates delocalization of the Ph2PS2 π-electron

690 Organometallics, Vol. 26, No. 3, 2007
Hossain et al.
Table 4. Selected Bond Angles (deg) for 2-5
W1-S (2.4155 Å (av)) of dithiolene and ModO1 (1.684(19)
Å) bond distances are normal.33,38
2
W1-S2-Mo1
W1-S3-Mo1
S1-W1-S2
S1-W1-S3
S1-W1-Mo1
S2-W1-S3
S2-W1-Mo1
S3-W1-Mo1
S2-Mo1-S3
S2-Mo1-S4
S2-Mo1-S5
S2-Mo1-S6
76.21(5)
76.42(5)
106.54(6)
105.08(7)
102.26(5)
102.14(6)
52.48(4)
52.17(4)
100.30(6)
106.36(7)
80.95(6)
146.83(6)
S2-Mo1-W1
S3-Mo1-S4
S3-Mo1-S5
S3-Mo1-S6
S3-Mo1-W1
S4-Mo1-S5
S4-Mo1-S6
S4-Mo1-W1
S5-Mo1-S6
S5-Mo1-W1
S6-Mo1-W1
S6-P1-S5
51.32(4)
107.26(7)
142.25(6)
80.56(6)
Compound 5 contains 30 valence electrons, which is 6
electrons less to satisfy the 18e rule. Thus, it is an electronically
poor compound, and the expected formal W-W bond order
between tungsten atoms is 3. The disulfide-bridged W1-W2
bond distance is 2.9323(11) Å, which is comparable to the
reported doubly bridged single-bonded tungsten dimers.13 This
deficiency of electrons in 5 may be compensated by the π
electrons of oxo and thio donors around it. Although, the average
distance W1-Sbr (2.3895 Å) is within the range of the reported
values listed in ref 32, the average W2-Sbr (2.281 Å) distance
is less than that of the reported values,32 indicating that strong
S(pπ)fMo(d) ligand-to-metal dative π-bonding interactions
between bridged sulfur and tungsten may exist. The average
W1-S (2.3995 Å) of dithiolene and W2dO1 (1.688 Å) bond
distances are normal.38
51.41(4)
108.48(7)
104.92(7)
103.84(6)
78.94(6)
128.21(5)
129.44(4)
102.98(9)
3
W1-S1-Mo2
W1-S2-Mo1
W1-S4-Mo2
W1-S4-Mo1
Mo1-S3-Mo2
Mo1-S4-Mo2
S1-W1-S2
74.01(7)
74.31(7)
72.74(6)
72.79(6)
73.22(7)
71.38(6)
100.23(8)
106.44(8)
99.13(6)
54.16(6)
105.65(8)
53.97(6)
100.58(6)
53.99(5)
53.96(5)
59.21(2)
97.81(8)
102.74(8)
162.48(8)
88.79(8)
85.96(8)
51.72(6)
99.73(6)
106.94(8)
88.64(8)
163.25(8)
87.30(8)
97.38(6)
53.45(6)
90.80(8)
S4-Mo1-S7
S4-Mo1-S8
S4-Mo1-W1
S4-Mo1-Mo2
S6-Mo1-S7
S6-Mo1-S8
S7-Mo1-S8
W1-Mo1-Mo2
S1-Mo2-S3
S1-Mo2-S4
S1-Mo2-S5
S1-Mo2-S9
S1-Mo2-S10
S1-Mo2-Mo1
S1-Mo2-W1
S3-Mo2-S4
S3-Mo2-S5
S3-Mo2-S9
S3-Mo2-S10
S3-Mo2-W1
S3-Mo2-Mo1
S4-Mo2-S5
S4-Mo2-S9
S4-Mo2-S10
S4-Mo2-W1
S4-Mo2-Mo1
S5-Mo2-S9
S5-Mo2-S10
S9-Mo2-S10
W1-Mo2-Mo1
86.39(7)
161.84(8)
53.21(5)
54.25(5)
80.92(8)
78.05(8)
77.79(7)
60.32(2)
95.47(8)
103.55(8)
164.19(8)
88.70(8)
87.64(8)
98.38(6)
51.83(6)
106.94(8)
91.03(8)
87.46(6)
87.47 (8)
97.41(6)
53.33(6)
88.23(8)
86.73(8)
160.50(8)
53.30(5)
54.38(5)
81.38(8)
78.24(8)
77.49(8)
60.471(2)
Conclusion
S1-W1-S4
S1-W1-Mo1
S1-W1-Mo2
S2-W1-S4
Generation of the ligands S2- and Ph2PS2 and their participa-
tion in the formation of the electron-deficient 28e dimer 2 and
the neutral Mo2WS4 core cluster 3 in a single flask during the
reaction of elemental sulfur and 1 is really a unique observation.
Thus conversion of 1 into 2 and 3, in which sulfur is the key
element in both the ambidentate ligand Ph2PS2 and the thio
ligand S2-, illustrated the formation of ModS, WdS, Mo-S-
W, and Mo-S-P bonds in the same reaction. Formation of
the thiophosphinate ligand PPh2S2 ligand by sulfur insertion into
the M-P bond of the phosphido-bridged PPh2 ligand on 1 is
reported for the first time. The 28e dimer 2, where both metals
have a 3d1 configuration shortage of 3d electrons for further
bonding between them other than a single bond, is stabilized
via S(pπ)fMo(d) ligand-to-metal dative π-bonding interactions,
keeping almost a single Mo-W bond order.10 Participation of
π electrons of the µ2-bridging sulfido ligands in the electron-
deficient WMo2S4 core of 3 makes the metal-metal bond order
higher than 1, and thus Mo-W and Mo-Mo bond distances
shorter than expected are observed. The involvement of the
terminal thio ligand of 2 in the C-S bond formation to form 4
and 5 is also a rare occurrence.
S2-W1-Mo1
S2-W1-Mo2
S4-W1-Mo1
S4-W1-Mo2
Mo1-W1-Mo2
S2-Mo1-S3
S2-Mo1-S4
S2-Mo1-S6
S2-Mo1-S7
S2-Mo1-S8
S2-Mo1-W1
S2-Mo1-Mo2
S3-Mo1-S4
S3-Mo1-S6
S3-Mo1-S7
S3-Mo1-S8
S3-Mo1-W1
S3-MoI-Mo2
S4-Mo1-S6
4
W1-S1-Mo1
W1-S2-Mo1
S1-W1-S2
S1-W1-S3
S1-W1-S4
S1-W1-Mo1
S2-W1-S3
S2-W1-S4
S2-W1-Mo1
S3-W1-S4
S3-W1-Mo1
S4-W1-Mo1
O1-Mo1-S1
O1-Mo1-S2
76.6(3)
76.8(3)
97.3(3)
134.8(3)
75.9(3)
50.53(19)
74.8(3)
136.1(3)
50.79(18)
80.1(3)
121.1(2)
122.33(19)
106.6(8)
111.1(7)
O1-Mo1-S5
O1-Mo1-S6
O1-Mo1-W1
S1-Mo1-S2
S1-Mo1-S5
S1-Mo1-S6
S1-Mo1-W1
S2-Mo1-S5
S2-Mo1-S6
S2-Mo1-W1
S5-Mo1-S6
S5-Mo1-W1
S6-Mo1-W1
S5-P1-S6
105.7(7)
104.3(7)
103.1(6)
101.0(3)
81.3(3)
146.3(3)
52.85(18)
140.5(3)
79.9(3)
52.41(18)
77.7(3)
131.2(2)
131.0(2)
102.0(4)
Experimental Section
General Procedures. All reactions and other manipulations were
performed under an atmosphere of nitrogen using standard Schlenk
techniques unless otherwise stated. Commercially available chemi-
cals were purchased and used without further purification. All
solvents were dried with Na and benzophenone under N2 and
distilled immediately prior to use. Compound 1 was prepared
1
following the reported procedure.9 The H and 31P NMR spectra
were run using a Bruker Ac-300 spectrometer. The 31P shifts are
referenced to 85% H3PO4. Microanalyses were performed by use
of a Perkin-Elmer 2400 CHN analyzer
5
W1-S3-W2
W1-S4-W2
S1-W1-S2
S1-W1-S3
S1-W1-S4
S1-W1-W2
S2-W1-S3
S2-W1-S4
S2-W1-W2
77.49(15)
77.98(15)
79.85(18)
76.31(18)
130.8(2)
118.63(12)
139.9(2)
76.06(18)
122.06(12)
S3-W1-S4
S3-W1-W2
S4-W1-W2
O1-W2-S3
O1-W2-S4
O1-W2-W1
S3-W2-S4
S3-W2-W1
S4-W2W1
95.96(18)
49.40(13)
49.57(14)
107.3(5)
106.6(5)
102.1(4)
102.19(18)
53.11(14)
52.45(13)
Reaction of 1 with Sulfur (S8). To a solid mixture of 1 (500
mg, 0.68 mmol) and 3 equiv of sulfur (500 mg, 1.95 mmol) was
added dichloromethane (50 mL) and the mixture heated at reflux
for 40 h. The reaction mixture was filtered through Celite to remove
insoluble materials and evaporated to dryness. The residue was then
dissolved in dichloromethane (10 mL), and the solution was
subjected to silica gel chromatographic workup. Elution with CH2-
Cl2/hexane (1:1) afforded three fractions. Compounds Cp(CO)3W-
(µ-PPh2)Mo(CO)5 and (CpWS(µ-S))2 were separated as the first,
delocalization of S2PPh2 π-electron density into vacant metal
dπ orbitals occurred in order to stabilize electron-deficient 4.
The average Mo1-Sbr (2.2995 Å) and W1-Sbr (2.363 Å) bond
distances are within the ranges tabulated in refs 31 and 32. The
(38) Rau, M. S.; Kretz, C. M.; Geoffory, G. L. Organometallics 1993,
12, 3447.

Neutral Six-Electron Mixed-Metal Cluster with a Mo2WS4 Core
Organometallics, Vol. 26, No. 3, 2007 691
yellow and the second, dirty-green band, respectively. Compound
2 was obtained from the third, orange-red band. Elution with neat
dichloromethane afforded compound 3 as the fourth, brown band.
Cp(CO)3W(µ-PPh2)Mo(CO)5: Yield: 109 mg, 23%. (CpWS(µ-
S))2: Yield: 33 mg, 15%. 2: Yield: 105 mg, 21%. Anal. Calcd
for C17H15PS6MoW: C, 28.25; H, 2.08. Found: C, 28.48; H, 2.09.
1H NMR (CD3COCD3): δ 7.85-7.52 (m, 10H, C6H5), 6.43 (s, 5H,
C5H5). 31P{1H} NMR (CH2Cl2): δ 110.68 (s). 3: Yield: 60 mg,
13%. Anal. Calcd for C41H35P3S10Mo2W: C, 37.36; H, 2.66.
in air and then evaporated to dryness. The residue was then
dissolved in dichloromethane, and the solution was subjected to
preparative TLC workup using dichloromethane. Compound 5 was
collected as an orange-red band in 27% yield (33 mg).
Crystal Structure Determination of 2-5. The single crystals
of 2 for X-ray diffraction analyses were grown by slow evaporation
of dichloromethane solution layered by benzene, and those of 3-5
from the evaporation of their respective dichloromethane solution
layered by hexane at 0 °C. Crystals of 2-5 were mounted on a
glass fiber for data collection, and the data of 2, 4, and 5 were
collected by using Mo KR radiation on an Enraf Nonius CAD4
diffractometer, whereas those of 3 were collected on a Nonius
Kappa CCD diffractometer at room temperature. Detailed data
collection parameters are given in Table 2. Cell parameters were
refined from 25 reflections with the 2θ range 20-37°. Three
standard reflections were monitored every 1 h throughout the data
collection. The variation was within 6%. Lorentz and polarization
corrections were applied. A semiempirical absorption correction
was applied based on azimuthal scans of three reflections. The
structures were solved by the direct method. The atomic and
isotropic thermal parameters for all hydrogen atoms were fixed.
Structure refinement was performed using the NRCSDP39 program
on a VAX workstation machine.
1
Found: C, 37.51; H, 2.73. H NMR (CDCl3): δ 7.99-7.81 (m,
10H, C6H5), 7.58-7.31 (m, 20H, C6H5), 5.81 (s, 5H, C5H5). 31P-
{1H} NMR (CH2Cl2): δ 92.09 (s, 2P, η-S2PPh2), 68.83 (s, 1P, µ-S2-
PPh2). When 1.5 equiv of S8 (256 mg, 1 mmol) was used in this
reaction, compounds Cp(CO)3W(µ-PPh2)Mo(CO)5, (CpWS(µ-S))2,
2, and 3 were isolated in 10% (51 mg), 9% (22 mg), 14% (72 mg),
and 9% (42 mg) yield, respectively. An additional small orange
band was eluted as the fifth band, and the residue was not
characterized.
Reaction of 2 with DMAD. To a THF solution (50 mL) of 2
(100 mg, 0.14 mmol) was added DMAD (29 µL, 34 mg, 0.28
mmol), and the mixture was stirred for 0.5 h in air. The reaction
mixture was evaporated to dryness. The residue was then dissolved
in dichloromethane (10 mL), and the solution was subjected to
preparative TLC workup. Two bands were collected after elution
with dichloromethane. The first, orange-red band contained com-
pound 4. The second, orange-red band was compound 5. 4: Yield:
22 mg, 18%. Anal. Calcd for C23H21O5PS6MoW: C, 31.36; H, 2.38.
Acknowledgment. We acknowledge the National Science
Council of the Republic of China and Academia Sinica for
financial support of this work.
1
Found: C, 31.69; H, 2.53. H NMR (CDCl3): δ 7.71-7.39 (m,
10H, C6H5), 5.50 (s, 5H, C5H5), 3.89 (s, 6H, CH3). 31P{1H} NMR
(CH2Cl2): δ 105.83 (s). 5: Yield: 8 mg, 14%. Anal. Calcd for
C16H16O5P2S4W2: C, 24.49; H, 2.04. Found: C, 24.58; H, 2.06.
1H NMR (CDCl3): δ 6.12 (s, 10H, C5H5), 3.85 (s, 6H, CH3).
Typical reaction with the same molar ratio of 2 (100 mg, 0.14
mmol) and DAMD (29 µL, 34 mg, 0.28 mmol) under nitrogen
produced compounds 4 and 5 in 21% (26 mg) and 9% (5 mg) yields,
respectively.
Supporting Information Available: Tables of atomic coordi-
nates, isotropic and anisotropic displacement parameters, and all
bond distances and angles and experimental details of the X-ray
studies for 2-5. This material is available free of charge via the
Internet at http://pubs.acs.org.
OM0608509
Reaction of (CpWS(µ-S))2 with DMAD. To a dichloromethane
solution (50 mL) of (CpWS(µ-S))2 (100 mg, 0.16 mmol) was added
DMAD (45 mg, 0.32 mmol), and the mixture was stirred for 20 h
(39) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837.
(40) Brunner, H.; Kauermann, H.; Wachter, J. J. Organomet. Chem. 1984,
265, 189.