New Heterometallic Cubane-Like Clusters [{(η5-Cp)Mo}3S4M'(CO)3](pts) (M' = Cr, Mo, W; pts = p-Toluenesulfonate) Obtained by Ligand Substitution Reactions and Insertion of {M'(CO)3 Fragments

Article abstract of DOI:10.1021/om990029f

A series of group 6 heterometallic sulfide clusters have been prepared to establish a route to potential models of hydrodesulfurization catalysts suitable for application in nonaqueous media. The cluster compound [{(H₂O)Mo}₃S₄](pts)₄.9H₂O (pts = p-toluenesulfonate) was treated with triethyl orthoformate in the presence of a catalytic amount of Hpts to yield an ethanol complex of the [Mo₃S₄]⁴⁺ cluster core. The complex was subsequently converted in situ to acetonitrile and tetrahydrofuran complexes before treatment with thallium cyclopentadienide to yield the new cluster compound [{(η⁵5-Cp)Mo}₃S₄](pts) (1). Insertion of {M'-(C0)₃ fragments into 1 afforded the series of cubane-like, heterometallic clusters [{(η⁵- Cp)Mo}₃S₄M'(CO)₃](pts) (M' = Cr (2a), Mo (2b), W (2c)). Single-crystal X-ray analysis established the heterometallic S₄capped tetrahedral cluster core in the structure of 2c.1/2- CH₃OH.

Full text of DOI:10.1021/om990029f

Organometallics 1999, 18, 2309-2313
2309
New Heter om eta llic Cu ba n e-Lik e Clu ster s
[{(η5-Cp )Mo}3S4{M′(CO)3}](p ts) (M′ ) Cr , Mo, W; p ts )
p-Tolu en esu lfon a te) Obta in ed by Liga n d Su bstitu tion
Rea ction s a n d In ser tion of {M′(CO)3} F r a gm en ts
Barbara Rink and Michael Brorson*,†
Haldor Topsøe Research Laboratories, Nymøllevej 55, DK-2800 Lyngby, Denmark
Ian J . Scowen‡
University of Bradford, Bradford, West Yorkshire BD7 1DP, U.K.
Received J anuary 19, 1999
A series of group 6 heterometallic sulfide clusters have been prepared to establish a route
to potential models of hydrodesulfurization catalysts suitable for application in nonaqueous
media. The cluster compound [{(H2O)3Mo}3S4](pts)4‚9H2O (pts ) p-toluenesulfonate) was
treated with triethyl orthoformate in the presence of a catalytic amount of Hpts to yield an
ethanol complex of the [Mo3S4]4+ cluster core. The complex was subsequently converted in
situ to acetonitrile and tetrahydrofuran complexes before treatment with thallium cyclo-
pentadienide to yield the new cluster compound [{(η5-Cp)Mo}3S4](pts) (1). Insertion of {M′-
(CO)3} fragments into 1 afforded the series of cubane-like, heterometallic clusters [{(η5-
Cp)Mo}3S4{M′(CO)3}](pts) (M′ ) Cr (2a ), Mo (2b), W (2c)). Single-crystal X-ray analysis
established the heterometallic S4-capped tetrahedral cluster core in the structure of 2c‚1/2-
CH3OH.
In tr od u ction
[{(η5-Cp′)Mo}2S4{Co(CO)}2].5 Reaction of acidic, aqueous
solutions of [{(H2O)3Mo}3S4]4+ with either metal powder
alone or metal ions combined with a reducing agent
have provided an extensive series of compounds
[{{(H2O)3Mo}3S4}nM′mLp]q+ (M′ ) Cr, Mo, Fe, Co, Ni,
Pd, Cu, Hg, Ga, In, Tl, Sn, Pb, As, Sb, Bi; e.g. L ) H2O)6
Hydrodesulfurization (HDS) is an important refinery
process for removing sulfur from crude oil fractions.1
At elevated temperatures and in the presence of hydro-
gen at high pressure, the oil is placed into contact with
a heterogeneous catalyst, whereby organosulfur com-
pounds in the oil (e.g. thiols, sulfides, disulfides,
thiophenes, benzo- and dibenzothiophenes) are con-
verted into hydrocarbons and H2S. The industrially used
catalysts consist of MoS2 crystallites that are promoted
by Co or Ni and supported on a high-suface-area carrier
such as, for example, alumina. Careful studies of the
catalyst in its active state have shown that the promoter
atoms are bonded to the sulfide atoms that constitute
the MoS2 crystallite edges.1b,2,3
On the basis of the expectation that molecular metal
sulfide clusters may provide insight into the mechanism
for catalytic HDS, such clusters have attracted consid-
erable attention recently.4 In this context, heterometallic
CoMo and NiMo clusters are particularly relevant,
and Curtis and co-workers have found that [{(η5-Cp′)-
Mo}2S3{Co(CO)2}2] (Cp′ ) CH3Cp) reacts with thiophene
to yield a mixture of desulfurized hydrocarbons and
(4) E.g.: (a) Matsubara, K.; Okamura, R.; Tanaka, M.; Suzuki, H.
J . Am. Chem. Soc. 1998, 120, 1108. (b) Gabay, J .; Dietz, S.; Bernatis,
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D. S.; Dietz, S.; Parker, K. G.; Carperos, V.; Gabay, J .; Noll, B.;
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R.; McGauley, K.; Pan, W.-H.; Czernuszewicz, R. S.; Stiefel, E. I. J .
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B.; Rheingold, A. L.; Wilson, S. R. J . Am. Chem. Soc. 1989, 111, 8828.
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S. R. J . Chem. Soc., Chem. Commun. 1994, 1283. (h) Skaugset, A. E.;
Rauchfuss, T. B.; Wilson, S. R. Organometallics 1990, 9, 2875.
(5) Riaz, U.; Curnow, O.; Curtis, M. D. J . Am. Chem. Soc. 1991,
113, 1416.
(6) (a) Routledge, C. A.; Humanes, M.; Li, Y.-J .; Sykes, A. G. J .
Chem. Soc., Dalton Trans. 1994, 1275. (b) Ooi, B.-L.; Sykes, A. G. Inorg.
Chem. 1989, 28, 3799. (c) Shibahara, T.; Akashi, H.; Kuroya, H. J .
Am. Chem. Soc. 1986, 108, 1342. (d) Shibahara, T.; Akashi, H.;
Yamasaki, M.; Hashimoto, K. Chem. Lett. 1991, 689. (e) Shibahara,
T.; Kuroya, H. J . Coord. Chem. 1988, 18, 233. (f) Shibahara, T.;
Yamasaki, M.; Akashi, H.; Katayama, T. Inorg. Chem. 1991, 30, 2693.
(g) Murata, T.; Gao, H.; Mizobe, Y.; Nakano, F.; Motomura, S.; Tanase,
T.; Yano, S.; Hidai, M. J . Am. Chem. Soc. 1992, 114, 8287. (h)
Shibahara, T.; Akashi, H.; Kuroya, H. J . Am. Chem. Soc. 1988, 110,
3313. (i) Shibahara, T.; Kobayashi, S.; Tsuji, N.; Sakane, G.; Fukuhara,
M. Inorg. Chem. 1997, 36, 1702. (j) Sakane, G.; Shibahara, T. Inorg.
Chem. 1993, 32, 777. (k) Varey, J . E.; Sykes, A. G. Polyhedron 1996,
15, 1887. (l) Akashi, H.; Shibahara, T. Inorg. Chem. 1989, 28, 2906.
(m) Brorson, M.; J acobsen, C. J . H.; Helgesen, H. K. M.; Schmidt, I.
Inorg. Chem. 1996, 35, 4808; 1997, 36, 264 (correction). (n) Saysell,
D. M.; Huang, Z.-X.; Sykes, A. G. J . Chem. Soc., Dalton Trans. 1996,
2623. (o) Hernandez-Molina, R.; Edwards, A. J .; Clegg, W.; Sykes, A.
G. Inorg. Chem. 1998, 37, 2989. (p) Shibahara, T.; Hashimoto, K.;
Sakane, G. J . Inorg. Biochem. 1991, 43, 280. (q) Saysell, D. M.; Sykes,
A. G. Inorg. Chem. 1996, 35, 5536.
† E-mail: mib@topsoe.dk.
‡ E-mail: i.scowen@bradford.ac.uk.
(1) (a) Gary, J . H.; Handwerk, G. E. Petroleum Refining-Technology
and Economics, 3rd. ed.; Marcel Dekker: New York, 1994. (b) Topsøe,
H.; Clausen, B. S.; Massoth, F. E. Hydrotreating Catalysis; Springer-
Verlag: Berlin, Heidelberg, Germany, 1996.
(2) Chianelli, R. R.; Daage, M.; Ledoux, M. J . Adv. Catal. 1994, 40,
177.
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Eng. 1998, 31, 1. (b) Alstrup, I.; Chorkendorff, I.; Candia, R.; Clausen,
B. S.; Topsøe, H. J . Catal. 1982, 77, 397.
10.1021/om990029f CCC: $18.00 © 1999 American Chemical Society
Publication on Web 05/20/1999

2310 Organometallics, Vol. 18, No. 12, 1999
Rink et al.
brownish green suspension. Filtration (P4) gave a green
solution, which was evaporated to dryness, forming 1 as a
brownish green solid. Yield: 196.4 mg (85%). Recrystallization
from a saturated CH2Cl2 solution at -20 °C gave small black
crystals. IR (KBr, ν in cm-1): 3086 (m, CHarom), 1425 (w,
all containing the cubane-like Mo3S4M′ motif. These
synthetic procedures are generally limited to application
in aqueous solution, and the aim of this work is to
establish the chemistry necessary to extend the study
of such species into nonaqueous media.
We report herein that insertion reactions analogous
to those established in the preparation of heterometallic
cubane-like sulfide clusters in aqueous solution6 can be
made in organic media using the new compound [{(η5-
Cp)Mo}3S4](pts) (1; pts ) p-toluenesulfonate) as a source
of the [Mo3S4]4+ cluster core. The cation of 1 has
previously been isolated in 50% yield in [{(η5-Cp)-
Mo}3S4][Sn(CH3)3Cl2].7 However, the synthesis from
[(η5-Cp)Mo(CO)3Cl] and [Sn(CH3)2]2S is less well-
established and the resulting complex counterion is
likely to interfere in the development of further chem-
istry for these systems.
CHarom). 1H NMR (CDCl3, δ in ppm): 7.79 (d, 2H, CHarom
,
3J (H,H) ) 8.1 Hz), 7.11 (d, 2H, CHarom, 3J (H,H) ) 8.1 Hz), 6.22
(15 H, Cp), 2.31 (s, 3H, CH3). FAB+ mass spectrum (m/z (%
abundance)): 609 (M+ - pts, 14), 547 (M+ - pts - Cp, 6). Anal.
Calcd for C22H22Mo3O3S5‚CH2Cl2: C, 31.84; H, 2.79; S, 18.48.
Found: C, 32.19; H, 2.93; S, 18.65.
Syn th esis of [{(η5-Cp )Mo}3S4{Cr (CO)3}](p ts) (2a ). A
338.2 mg (0.432 mmol) amount of [{(η5-Cp)Mo}3S4](pts) (1)
dissolved in 45 mL of CH2Cl2 was added to freshly isolated
[(CH3CN)3Cr(CO)3] (prepared from 938.9 mg (4.267 mmol) of
freshly sublimed [Cr(CO)6] by refluxing in 30 mL of MeCN for
16 h and evaporating to dryness9). The dark brownish green
solution was stirred at RT for 3 h. The dark solution obtained
was filtered (P3), and from the dark brownish green filtrate
the solvent was completely evaporated; 40 mL of n-hexane was
added to the dark residue, this mixture was stirred for 10 min,
and the supernatant light green solution was removed; the
procedure was repeated using 20 mL of n-hexane. The residue
was dried in vacuo, giving 2a as a brownish green solid.
Yield: 277.0 mg (64%). IR (KBr, ν in cm-1): 2012 (vs, CdO),
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All experiments were carried out
under dry nitrogen atmosphere using standard Schlenk tech-
niques. Solvents were dried and distilled before use (dichlo-
romethane, acetonitrile, and chloroform-d from P2O5; methanol
from magnesium; n-hexane, tetrahydrofuran (THF), and di-
ethyl ether from sodium/benzophenone) and stored under
nitrogen; triethyl orthoformate (Aldrich) was degassed and
stored under nitrogen. [{(H2O)3Mo}3S4](pts)4‚9H2O8 and [(CH3-
CN)3M′(CO)3] (M′ ) Cr, Mo, W)9 were isolated by the methods
described in the literature. Thallium cyclopentadienide (Ald-
rich) was sublimed prior to use and stored under nitrogen.
Silica gel (70-230 mesh, 60 Å; Aldrich) was dried in vacuo at
180 °C for 14 h, deactivated with 5% distilled and degassed
water, and stored under nitrogen. Products were purified by
low-pressure liquid column chromatography under nitrogen;
solvents for chromatography (dichloromethane and metha-
nol: SPS quality, purchased from Romil) were degassed before
use and stored under nitrogen. Elemental analysis were
performed at DB-Lab, Dansk Bioprotein A/S, Odense, Den-
mark.
Sp ectr a . Infrared spectra were recorded on a Bio-Rad FTS-
60 spectrometer as solids in KBr disks. 1H NMR spectra were
recorded at room temperature on a Varian UNITY 300 MHz
spectrometer and were referenced to the chemical shift of the
nondeuterated part in the deuterated solvents relative to TMS.
Mass spectra were obtained on a J EOL SX-102 spectrometer.
Syn th esis of [{(η5-Cp )Mo}3S4](p ts) (1). A 423 mg (0.297
mmol) amount of [{(H2O)3Mo}3S4](pts)4‚9H2O8 was dissolved
at room temperature (RT) in 12 mL of (C2H5O)3CH, and in
the presence of a catalytic amount (a few crystals) of Hpts the
mixture was stirred. After 15 h a green solid had precipitated,
the supernatant solution was removed, and the suspended
solid was washed twice with 15 mL of diethyl ether and dried
in vacuo. The solid was dissolved in CH3CN (10 mL) with
stirring to give a green solution to which, after 15 min of
stirring and vacuum evaporation of solvent, THF (25 mL) was
added; this mixture was stirred for 10 min. The greenish brown
solution obtained was added to 286 mg (1.061 mmol) of TlCp,
and the color changed spontaneously to intense dark green.
The mixture was stirred for 15 h, forming a brown suspension.
All solvent was removed by evaporation, 100 mL of CH2Cl2
was added, and the mixture was stirred for 1 h, yielding a
1
1984 (vs, CdO), 1960 (sh, CdO). H NMR (CDCl3, δ in ppm):
7.82 (d, 2H, CHarom, ,
3J (H,H) ) 7.7 Hz), 7.11 (d, 2H, CHarom
3J (H,H) ) 7.7 Hz), 5.84 (s, 15 H, Cp), 2.31 (s, 3H, CH3). FAB+
mass spectrum (m/z (% abundance)): 661 (M+ - pts - 3CO,
30). Anal. Calcd for C25H22CrMo3O6S5‚2CH2Cl2: C, 29.80; H,
2.41; S, 14.73. Found: C, 29.39; H, 2.98; S, 15.50.
Syn th esis of [{(η5-Cp )Mo}3S4{Mo(CO)3}](p ts) (2b). To a
mixture of 228.4 mg (0.292 mmol) of [{(η5-Cp)Mo}3S4](pts) (1)
and 98.9 mg (0.326 mmol) of [(CH3CN)3Mo(CO)3]9 was added
20 mL of CH2Cl2, and the mixture was stirred for 15 h at RT.
The solution was adsorbed on SiO2 (5% H2O) and separated
by column chromatography (column 2.5 × 23 cm). With a
mixture of CH2Cl2 and CH3OH (10:1) a purple fraction was
obtained, which after evaporation to dryness gave 2b as a dark
solid. Yield: 120.8 mg (43%). Recrystallization at -20 °C from
a saturated CH3OH solution gave dark needles. IR (KBr, ν in
cm-1): 2019 (vs, CdO), 1989 (s, CdO), 1972 (vs, CdO). 1H
NMR (CDCl3, δ in ppm): 7.84 (d, 2H, CHarom,
3J (H,H) ) 8.4
Hz), 7.12 (d, 2H, CHarom, 3J (H,H) ) 8.4 Hz), 5.84 (s, 15 H, Cp),
2.31 (s, 3H, CH3). FAB+ mass spectrum (m/z (% abundance)):
790 (M+ - pts, 14), 708 (M+ - pts - 3CO, 50). Anal. Calcd for
C
25H22Mo4O6S5: C, 31.20; H, 2.30; S, 16.66. Found: C, 31.55;
H, 2.43; S, 16.75.
Syn th esis of [{(η5-Cp )Mo}3S4{W(CO)3}](p ts) (2c). Com-
pound 2c was prepared in the same manner as for 2b: 579.6
mg (1.482 mmol) of [(CH3CN)3W(CO)3]9 and 201.8 mg (0.258
mmol) of 1 in 20 mL of CH2Cl2, 18 h at RT. Yield: 138.1 mg
(56%). IR (KBr, ν in cm-1): 2013 (vs, CdO), 1981 (s, CdO),
1960 (vs, CdO). 1H NMR (CDCl3, δ in ppm): 7.84 (d, 2H,
3
3
CHarom, J (H,H) ) 8.1 Hz), 7.11 (d, 2H, CHarom, J (H,H) ) 8.1
Hz), 5.83 (s, 15 H, Cp), 2.31 (s, 3H, CH3). FAB+ mass spectrum
(m/z (% abundance)): 878 (M+ - pts, 6%), 796 (M+ - pts -
3CO, 20%). Anal. Calcd for C25H22Mo3O6S5W‚CH3OH: C,
28.85; H, 2.42; S, 14.81. Found: C, 29.36; H, 2.49; S, 14.81.
X-r a y Cr ysta llogr a p h y. Single crystals of [{(η5-Cp)Mo}3S4-
{W(CO)3}](pts)‚1/2CH3OH (2c‚1/2CH3OH) were grown from a
saturated methanol solution at -20 °C, and a selected speci-
men was mounted in a Lindemann tube under N2. X-ray data
were collected using a Stoe IPDS diffractometer (æ, 0-180°;
sample-to-plate distance, 70 mm; 2 min exposure per 1.5°
increment) with graphite-monochromated Mo KR radiation.
The structure was solved by direct methods and refined10 to
convergence with all non-H atoms anisotropic (except the
(7) Vergamini, P. J .; Vahrenkamp, H.; Dahl, L. F. J . Am. Chem. Soc.
1971, 93, 6327.
(8) Shibahara, T.; Akashi, H. Inorg. Synth. 1992, 29, 268.
(9) (a) Tate, D. P.; Knipple, W. R.; Augl, J . M. Inorg. Chem. 1962,
1, 433. (b) Herrmann, W. A., Salzer, A., Eds. Synthetic Methods of
Organometallic and Inorganic Chemistry (Herrmann/ Brauer); Georg
Thieme Verlag: Stuttgart, Germany, 1997; Vol. 1, p 120.
(10) Sheldrick, G. SHELXTL 97-2, University of Go¨ttingen, Go¨ttin-
gen, Germany, 1997.

Heterometallic Cubane-Like Clusters
Organometallics, Vol. 18, No. 12, 1999 2311
Ta ble 1. Cr ysta l Da ta for
[{(η5-Cp )Mo}3S4{W(CO)3}](p ts)‚1/2CH3OH
(2c‚1/2CH3OH)
Sch em e 1
empirical formula
fw
C25.5H24Mo3O6.5S5W
1066.42
source
a, b, c (Å)
CH3OH, -20 °C
9.6470(19), 10.900(2),
16.267(3)
R, â, γ (deg)
107.96(3), 90.27(3), 99.53(3)
1601.9(6)
2, 2.211
5.091
1018
V (Å3)
Z, calcd density (Mg/m3)
abs coeff (mm-1
F(000)
)
λ (Å)
temp (K)
radiation
cryst syst, space group
cryst size (mm)
0.71073
293(2)
Mo KR
triclinic, P1h
0.39 × 0.31 × 0.08
θ range for data collecn (deg)
limiting indices
6.01-25.00
-10 e h e 10, -12 e k e 12,
-19 e l e 19
no. of rflns collected/unique
abs cor
10084/5210 (Rint ) 0.0402)
empirical
Sch em e 2
max and min transmissn
refinement method
no. of data/restraints/params
goodness-of-fit on F2
final R indices (I > 2σ(I))
0.7671 and 0.3463
full-matrix least squares on F2
5210/55/374
0.998
R1(F)a ) 0.0506,
wR2(F2)b ) 0.1816
R1(F)a ) 0.0570,
wR2(F2)b ) 0.1871
R indices (all data)
largest diff peak and hole (e/Å3) 2.414 (1.23 Å from W)
and -1.463
a
R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) [∑[w(Fo2 - Fc2)2/∑[w(Fo2)2]0.5
,
where w ) 1/[σ2(Fo2) + (aP)2 + bP] and P ) (Fo + 2Fc2)/3.
2
carbons of the two components of a disordered Cp ring) and H
atoms in idealized positions with Uiso(Hmethyl) ) 1.5Ueq(C) and
U
iso(Haromatic) ) 1.2Ueq(C). Crystallographic data are sum-
marized in Table 1.
brown suspension was formed, from which the new
cluster salt [{(η5-Cp)Mo}3S4](pts) (1) was isolated as a
brownish green solid in 85% yield (Scheme 1).
The compound 1 was stable under a nitrogen atmo-
sphere for at least several months and in the air for at
least 1 day. It was soluble in polar organic solvents.
Crystals could be obtained at -20 °C from a saturated
dichloromethane solution.
Resu lts a n d Discu ssion
The crystalline aqua cluster [{(H2O)3Mo}3S4](pts)4‚
9H2O8 was dissolved in triethyl orthoformate, forming
an ethanol-substituted,11 highly moisture-sensitive clus-
ter salt. The compound thus obtained was reacted in
situ with acetonitrile and, after the solvent was re-
moved, with tetrahydrofuran (THF), giving a brownish
green solution (Scheme 1). Treatment with acetonitrile
before the THF complex was formed assured that traces
of the triethyl orthoformate were removed and improved
the final yield.
1
The H NMR spectrum showed two doublets at 7.79
and 7.11 ppm for the aromatic protons and a singlet at
2.31 ppm for the methyl group of the p-toluenesulfonate
anion; additionally, a singlet at 6.22 ppm for the protons
of the three Cp ligands was observed. This last chemical
shift is consistent with the chemical shift of the Cp
ligands in [{(η5-Cp)Mo}3S4][Sn(CH3)3Cl2].7
Reactions of the THF solution with sodium cyclopen-
tadienide as the source of a carbocyclic ligand led to
mixtures, probably because of the reducing ability12 of
The FAB+ mass spectrum of 1 showed the peak of the
cluster cation [{(η5-Cp)Mo}3S4]+ at m/z 609 with a
relative intensity of 14%.
1
NaCp. H NMR spectra of the crude product indicated
that the desired product was present in the mixture,
but purification by chromatography and fractionated
crystallization failed.
A much cleaner reaction with less reduction was
performed with thallium cyclopentadienide.13 The reac-
tion of the brownish green THF solution with a slight
stoichiometric excess of TlCp led to a spontaneous
change of color to dark green. After a few minutes a
Tris(acetonitrile)tricarbonyl complexes9 of Cr, Mo, and
W were used to insert14 {M′(CO)3} fragments into the
[{(η5-Cp)Mo}3S4]+ cluster cation, thereby forming three
new cubane-like clusters [{(η5-Cp)Mo}3S4{M′(CO)3}](pts)
(M′ ) Cr (2a ), Mo (2b), W (2c)), which are all soluble in
common polar organic solvents (Scheme 2).
The compound 2a was purified by washing with
n-hexane and recrystallizing from dichloromethane. The
compounds 2b,c were isolated as dark solids after
chromatography on silica gel. Dissolution of 2a in
(11) Driessen, W. L.; Reedijk, J . Inorg. Synth. 1992, 29, 115.
(12) Herrmann, W. A., Ed. Synthetic Methods of Organometallic and
Inorganic Chemistry (Herrmann/ Brauer); Georg Thieme Verlag: Stut-
tgart, Germany, 1997; Vol. 8, p 2.
(13) Edelmann, F. T., Ed. Synthetic Methods of Organometallic and
Inorganic Chemistry (Herrmann/ Brauer); Georg Thieme Verlag: Stut-
tgart, Germany, 1997; Vol. 6, p 178.
(14) Coucouvanis, D.; Al-Ahmad, S. A.; Salifoglou, A.; Papaefthy-
miou, V.; Kostikas, A.; Simopoulos, A. J . Am. Chem. Soc. 1992, 114,
2472.

2312 Organometallics, Vol. 18, No. 12, 1999
Rink et al.
dichloromethane or methanol gave a green solution,
whereas 2b,c gave purple solutions. All three com-
pounds were stable in the air for at least a few days.
In the solid state the infrared spectrum of 2a con-
tained two intense peaks at 2012 and 1984 cm-1 as well
as a shoulder at 1960 cm-1. The spectra of the homolo-
gous compounds 2b,c contained similar patterns con-
sisting of three intense and discrete peaks for the three
terminal fac-CO ligands15 at 2019, 1989, and 1972 cm-1
for 2b and at 2013, 1981, and 1960 cm-1 for 2c. The
relatively high wavenumbers are a reflection of the
positive charge of the complex16 and the predominant
σ character of the M-C bond.16,17 This means that the
inserted metal atoms M′ are relatively electron-poor.
1
The H NMR spectra showed the typical signals: two
doublets at lowest field for the aromatic protons of the
p-toluenesulfonate counterion, an intense singlet for the
15 protons of the three Cp ligands of the cluster cation,
and a singlet at higher field for the methyl group of the
p-toluenesulfonate anion. The chemical shifts were
nearly identical for 2a -c; the signals for the Cp ligands
of 2a -c were shifted to higher field relative to the peak
for the Cp ligands in 1. This indicates an increase in
electron density at the connected molybdenum atoms
in 2a -c compared with those of 1.
F igu r e 1. ORTEP plot of the Mo3W cluster cation in the
crystal structure of 2c‚1/2CH3OH showing the numbering
scheme adopted.
Both IR and 1H NMR spectroscopic data are in
accordance with the results17 from Fenske-Hall mo-
lecular orbital calculations on similar systems, namely
[{LxMo}3S4{M′(CO)}]n+ (M′ ) Co, Ni). The calculations
predict an increase in electron density on the Mo3S4
fragment when a heterometal atom is inserted and a
relatively electron-poor situation at the inserted metal
atom.
The FAB+ mass spectra of 2a -c showed the peaks of
the cluster cations [(C5H5)3Mo3S4M′(CO)3]+ with relative
intensities of 30, 14, and 6%, followed by intense signals
from the peaks [(C5H5)3Mo3S4M′]+ with intensities of 55,
50, and 20% for the Cr, Mo, and W derivative.
Str u ctu r a l Stu d y. Single-crystal X-ray analysis of
[{(η5-Cp)Mo}3S4{W(CO)3}](pts)‚1/2CH3OH (2c‚1/2CH3-
OH) established the cubane-like cluster cation derived
from three {(η5-Cp)Mo} units, one {W(CO)3} fragment,
and four sulfur atoms (Figure 1); selected bond lengths
and angles are presented in Table 2. This is the first
heterometallic M3M′ group 6 cluster to be established
unambiguously.18 Previous examples have shown dis-
order of metal positions in the cluster core.19
The Mo-Mo and W-Mo distances are consistent with
single bonds between the four metal atoms forming a
tetrahedral framework (Figure 2), whose triangular
faces are capped by four µ3-coordinating sulfur atoms,
leading to a cubane-like cluster frame. The Mo-S and
W-S bond lengths are within the usual range for single
bonds,19,20 where the average W-S bond with 2.475 Å
is ca. 6% longer then the average Mo-S bond with 2.336
Å. The bond angles between the metal atoms (57.75-
(4)-61.46(4)°) correspond quite closely to a regular
tetrahedron, although the smaller S-W-S angles are
consistent with the longer W-S and W-Mo bond
lengths and with a noticeable extrusion of the tungsten
atom from the cluster core. The displacement of the
tungsten can be further illustrated by comparing its
height above the respective face of the S4 tetrahedron
(1.200(3) Å above the S(2),S(3),S(4) plane) with those
observed for the Mo atoms (in the range 0.981(3) (for
Mo(1) above S(1),S(2),S(3)) to 0.986(3) Å (for Mo(3) above
S(1),S(3),S(4))). The extrusion of W cannot be attributed
simply to size, and the more efficient acceptor character
of its CO substituents in comparison to the Cp ligands
attached to Mo21 may play a role here. Further distor-
tion of the overall cubane-like framework derives from
considerably smaller dimensions of the metal tetrahe-
dron with respect to the S4 tetrahedron, and in this
context, M-M bonds of ca. 2.9 Å compare with S‚‚‚S
distances of over 3.6 Å. The average S-M-S angles are
relatively obtuse (98.46° at W and 103.49° at Mo), while
the average M-S-M angles (76.18°) are much smaller
than 90°; similar tendencies were observed for related
compounds.6,19,20,22 The distances from the Mo atoms to
the centers of their connected Cp rings (between 2.023
and 2.026 Å) are very similar to the distances found in
[{(η5-Cp)Mo}3S4][Sn(CH3)3Cl2].7
According to the Wade-Mingos rules for electron
counting for polyhedra,23 the cluster cation of 2c, as well
as its homologues in 2a ,b,18 are all electron-precise
tetrahedra.
(15) Sellmann, D.; Zapf, L. J . Organomet. Chem. 1985, 289, 57.
(16) (a) Braterman, P. S., Ed. Metal Carbonyl Spectra; Academic
Press: London, 1975; pp 172, 182, 214. (b) Elschenbroich, Ch.; Salzer,
A. Organometallics, A Concise Introduction, 1st ed.; VCH: Weinheim,
Germany, 1989; pp 220, 229.
(17) Bahn, C. S.; Tan, A.; Harris, S. Inorg. Chem. 1998, 37, 2770.
(18) A crystallographic analysis of a twinned crystal of the homo-
logue cluster [{CpMo}3S4{Cr(CO)3}](pts) (2a ; monoclinic, P21/c, a )
15.160(3) Å, b ) 9.619(2) Å, c ) 21.108(4) Å, â ) 108.33(3)°) showed
the same type of cluster framework.
(19) (a) Deeg, A.; Keck, H.; Kruse, A.; Kuchen, W.; Wunderlich, H.
Z. Naturforsch., B 1988, 43, 1541. (b) Huang, J .-Q.; Lu, S.-F.; Wu, Q-J .
Acta Chim. Sin. 1994, 52, 474.
(20) Bandy, J . A.; Davies, C. E.; Green, J . C.; Green, M. L.; Prout,
K.; Rodgers, D. P. S. J . Chem. Soc., Chem. Commun. 1983, 1395.
(21) Purcell, K. F.; Kotz, J . C. Inorganic Chemistry; W. B. Saun-
ders: Philadelphia, 1977; p 892.
(22) Curtis, M. D.; Riaz, U.; Curnow, O. J .; Kampf, J . W.; Rheingold,
A. L.; Haggerty, B. S. Organometallics 1995, 14, 5337.
(23) (a) Mingos, D. M. P. Acc. Chem. Res. 1984, 17, 311. (b) Wade,
K. Adv. Inorg. Radiochem. 1976, 18, 1.

Heterometallic Cubane-Like Clusters
Organometallics, Vol. 18, No. 12, 1999 2313
1
Ta ble 2. Selected Bon d Len gth s a n d An gles for [{(η5-Cp )Mo}3S4{W(CO)3}](p ts)‚ /2CH3OH (2c‚1/2CH3OH)
Bond Lengths (Å)
W(1)-Mo(1)
W(1)-Mo(2)
W(1)-Mo(3)
Mo(1)-Mo(2)
Mo(1)-Mo(3)
Mo(2)-Mo(3)
W(1)-C(10)
W(1)-C(20)
2.9645(16)
2.9753(13)
2.9838(16)
2.8770(17)
2.8724(17)
2.8811(15)
2.047(17)
2.038(16)
W(1)-S(2)
W(1)-S(3)
W(1)-S(4)
Mo(1)-S(1)
Mo(1)-S(2)
Mo(1)-S(3)
W(1)-C(30)
C(10)-O(10)
2.464(3)
2.478(3)
2.483(3)
2.337(3)
2.330(3)
2.337(3)
2.068(18)
1.118(19)
Mo(2)-S(1)
Mo(2)-S(2)
Mo(2)-S(4)
Mo(3)-S(1)
Mo(3)-S(3)
Mo(3)-S(4)
C(20)-O(20)
C(30)-O(30)
2.338(3)
2.333(3)
2.331(3)
2.332(3)
2.336(3)
2.346(3)
1.104(19)
1.11(2)
Bond Angles (deg)
Mo(1)-W(1)-Mo(2)
Mo(1)-W(1)-Mo(3)
Mo(2)-W(1)-Mo(3)
Mo(3)-Mo(1)-Mo(2)
Mo(2)-Mo(1)-W(1)
Mo(3)-Mo(1)-W(1)
Mo(1)-Mo(2)-Mo(3)
Mo(1)-Mo(2)-W(1)
Mo(3)-Mo(2)-W(1)
Mo(1)-Mo(3)-Mo(2)
Mo(1)-Mo(3)-W(1)
Mo(2)-Mo(3)-W(1)
57.94(4)
57.75(4)
57.83(3)
60.15(4)
61.22(4)
61.46(4)
59.85(4)
60.84(4)
61.24(4)
60.01(4)
60.79(4)
60.94(4)
Mo(1)-S(1)-Mo(2)
Mo(3)-S(1)-Mo(1)
Mo(3)-S(1)-Mo(2)
Mo(1)-S(2)-Mo(2)
Mo(1)-S(2)-W(1)
Mo(2)-S(2)-W(1)
S(2)-W(1)-S(3)
S(2)-W(1)-S(4)
S(3)-W(1)-S(4)
S(1)-Mo(1)-S(3)
S(2)-Mo(1)-S(1)
S(2)-Mo(1)-S(3)
75.96(10)
75.93(10)
76.19(10)
76.17(10)
76.32(9)
76.60(10)
98.74(11)
98.30(11)
98.35(11)
101.88(12)
101.87(12)
106.97(12)
S(2)-Mo(2)-S(1)
S(4)-Mo(2)-S(1)
S(4)-Mo(2)-S(2)
S(1)-Mo(3)-S(3)
S(1)-Mo(3)-S(4)
S(3)-Mo(3)-S(4)
Mo(3)-S(3)-Mo(1)
Mo(1)-S(3)-W(1)
Mo(3)-S(3)-W(1)
Mo(2)-S(4)-Mo(3)
Mo(2)-S(4)-W(1)
Mo(3)-S(4)-W(1)
101.74(12)
101.89(12)
106.70(12)
102.08(12)
101.63(11)
106.64(12)
75.86(10)
75.93(9)
76.54(10)
76.06(10)
76.28(10)
76.27(10)
into the organically soluble compound [{(η5-Cp)Mo}3S4]-
(pts). From a geometrical point of view the Mo3S4 cluster
core is incomplete, and the possibility of introducing a
heterometal atom to produce cubane-like M′Mo3S4 cores
is well-established in the aqueous chemistry of [Mo3S4]4+
.
We have now, in nonaqueous media, inserted {M′(CO)3}
(M′ ) Cr, Mo, W) fragments into [{(η5-Cp)Mo}3S4]+ and
thus been able to produce the new series of heterome-
tallic sulfide clusters [{(η5-Cp)Mo}3S4{M′(CO)3}](pts) (M′
) Cr, Mo, W). Work is in progress with the aim of
inserting other metallic elements, with particular focus
on the hydrodesulfurization promoters Ni and Co.
Ack n ow led gm en t. This work was supported by the
European Commission (TMR-Network “Metal Clusters
in Catalysis and Organic Synthesis”; Contract FMRX-
CT96-0091; postdoctoral grant to B.R.). We thank our
TMR partner at the University of Lund, Lund, Sweden,
for access to their Varian UNITY 300 MHz NMR
spectrometer.
F igu r e 2. The cubane-like sulfide-capped cluster core of
the cation of 2c‚1/2CH3OH.
Con clu sion
A new and convenient procedure for synthesis of a
tris-Cp derivative of the [Mo3S4]4+ cluster core has been
presented. Since no good and acceptable routes exist by
which the cluster core [Mo3S4]4+ can be synthesized in
nonpolar solvents, [{(H2O)3Mo}3S4](pts)4‚9H2O was syn-
thezised in aqueous solution by the established method
and then, by a series of ligand substitutions, converted
Su p p or tin g In for m a tion Ava ila ble: X-ray crystallo-
graphic files, in CIF format, are available. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM990029F