Synthesis and characterization of a series of new thiocarboxylate complexes of molybdenum(V)

Article abstract of DOI:10.1016/S0020-1693(98)00292-8

The novel tetranuclear complexes of the type [Mo₄O₆S₂(R′COCHCOCH₃) ₂(OSCR″)₂], where R′ = -CH₃ or -C₆H₅ and R″ = -C₆H₅, -CH₃, -C(CH₃)₃ or -CH₂CH(CH₃)₂, have been prepared by the reactions of dinuclear oxomolybdenum(V) complexes [Mo₂O₃(acac)₄] (acac = 2,4-pentanedionato) or [Mo₂O₃(ba)₄] (ba = 1-phenyl-1,3-butanedionato) with thiobenzoic (1 and 5), thioacetic (2 and 6), thiotrimethylacetic (3 and 7) and thio-3-methylbutyric (4 and 8) acid, respectively. The molecular structures of the complexes 1, 3 and 6 have been determined by a single crystal X-ray crystallography. The centrosymmetrical tetranuclear complexes contain Mo₄O₆S₂ cores bridged through β-diketonato and thiocarboxylato ligands. Four coordination octahedra are fused by sharing common edges thus allowing the formation of localized metal-metal bonds between two pairs of molybdenum atoms. The insertion of sulfur atoms into the MoSMo bridges originates from H₂S produced in situ from the molybdenum catalysed hydrolysis of thioacids.

Full text of DOI:10.1016/S0020-1693(98)00292-8

Inorganica Chimica Acta 284 (1999) 223±228
Synthesis and characterization of a series of new
thiocarboxylate complexes of molybdenum(V)
*
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Marina Cindric, Dubravka Matkovic-Calogovic, Visnja Vrdoljak, Boris Kamenar
Laboratory of General and Inorganic Chemistry, Chemistry Department, Faculty of Science, University of Zagreb, Ulica kralja Zvonimira 8,
10000 Zagreb, Croatia
Received 19 March 1998; accepted 8 July 1998
Abstract
The novel tetranuclear complexes of the type [Mo4O6S2(R0COCHCOCH3)2(OSCR00)2], where R0 ˆ ±CH3 or ±C6H5 and R00 ˆ ±C6H5,
±CH3, ±C(CH3)3 or ±CH2CH(CH3)2, have been prepared by the reactions of dinuclear oxomolybdenum(V) complexes [Mo2O3(acac)4]
(acac ˆ 2,4-pentanedionato) or [Mo2O3(ba)4] (ba ˆ 1-phenyl-1,3-butanedionato) with thiobenzoic (1 and 5), thioacetic (2 and 6),
thiotrimethylacetic (3 and 7) and thio-3-methylbutyric (4 and 8) acid, respectively. The molecular structures of the complexes 1, 3 and 6
have been determined by a single crystal X-ray crystallography. The centrosymmetrical tetranuclear complexes contain Mo4O6S2 cores
bridged through b-diketonato and thiocarboxylato ligands. Four coordination octahedra are fused by sharing common edges thus allowing
the formation of localized metal±metal bonds between two pairs of molybdenum atoms. The insertion of sulfur atoms into the MoSMo
bridges originates from H2S produced in situ from the molybdenum catalysed hydrolysis of thioacids. # 1999 Elsevier Science S.A. All
rights reserved.
Keywords: Crystal structures; Oxomolybdenum complexes; Thiocarboxylate complexes; Tetranuclear molybdenum complexes; Polynuclear complexes
1. Introduction
the reactions of dinuclear acetylacetonato or benzoylaceto-
nato oxomolybdenum(V) complexes with thiobenzoic,
thioacetic, thiotrimethylacetic and thio-3-methylbutyric
acid. It appeared that all of them are of tetrameric nature
that had been proved by the X-ray diffraction analysis of
[Mo4O6S2(acac)2(OSCC6H5)2]Á2CH2Cl2, [Mo4O6S2(acac)2-
{OSCC(CH3)3}2]ÁCH2Cl2 and [Mo4O6S2(ba)2(OSCCH3)2]Á
2CH2Cl2 (Scheme 1).
The fact that many molybdoenzymes contain one or more
sulfur atoms coordinated to molybdenum increased the
interest in the coordination chemistry of molybdenum com-
plexes with sulfur-containing ligands [1±4]. However, the
existing data for molybdenum(V) complexes with thioacids
are still relatively scarce. One of the rare publications
dealing with the synthesis of such complexes was published
by Rakowski DuBois almost twenty years ago. It describes
the preparation and characterization of the dimeric di-m-oxo
and m-oxo-m-sul®do complexes of the formulae
[Mo2O3XL2(py)2] and Na2[Mo2O3XL4] with X ˆ O or S,
and L ˆ thiobenzoate [5]. The prepared complexes were
characterized only by analytical and physico-chemical
methods, but no X-ray structures have been done so far.
In the continuation of our research on molybdenum(V)
chemistry with thio-ligands [6±8] we have synthesized two
series of novel complexes containing different thiocarboxy-
lato ligands: (i) [Mo4O6S2(acac)2(OSCR)2], and (ii)
This ®nding has enhanced our knowledge concerning
such tetranuclear molybdenum complexes. They are formed
[Mo4O6S2(ba)2(OSCR)2]
±C(CH3)3 and ±CH2CH(CH3)2. They were prepared by
with
R ˆ ±C6H5,
±CH3,
*Corresponding author. Tel.: +38-51-4611-207; fax: +38-51-4554-960.
Scheme 1.
0020-1693/99/$ ± see front matter # 1999 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(98)00292-8

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M. Cindric et al. / Inorganica Chimica Acta 284 (1999) 223±228
224
either by a simple linkage of two dinuclear species, such as
in K6[{Mo2O4(mal)2}2(mal)]Á4H2O [9], or in [Mo4O4S2X2-
(C2O4)4(C2O4)]6 (X ˆ O or S) [8,10] in which one mal-
onato or oxalato ligand acts as a quadridentate ligand, or by
building Mo4XaYbZc (where X, Y, Z are different ligands)
cluster complexes as found for such class of metal alkox-
ides. However, while in the alkoxides a ‡ b ‡ c ˆ 16 as
found in the propoxo complexes [Mo4Cl4O6(OnPr)4-
(HOnPr)2] [11,12] and [Mo4O8(OiPr)4(py)4] [13] and in
the ethoxo complexes [Mo4Cl4O8(OC2H5)2(HOC2H5)2]2
[12,14], [Mo4Cl4O6(OC2H5)4(HOC2H5)2] [15], in the car-
boxylates, a ‡ b ‡ c ˆ 14 as in the acetate [Mo4Cl2O6-
(OCOCH3)6] [16] benzoate [Mo4Cl2O6(OCOC6H5)6 [17]
and propionate [Mo4X2O6(OCOC2H5)6] (X ˆ Cl or Br)
[18]. Consequently, while in the alkoxides four Mo-
octahedra are fused, allowing formation of localized
metal±metal bonds between two pairs of molybdenum
atoms, in the carboxylates only two of four molybdenum
atoms participate in the Mo±Mo bonding. (a) In the former
complexes all four octahedra share common edges; (b) in
the latter only two octahedra share a common edge while the
other two are attached to them by sharing common corners
(Fig. 1).
2. Experimental
2.1. General procedures
All reagents and solvents were of reagent grade and used
as purchased. The starting complexes [Mo2O3(C5H7O2)4]
[21] and [Mo2O3(C10H9O2)4] [22] were prepared as
described in the literature. Thio-3-methylbutyric acid was
prepared according to the procedure described for the
preparation of thioacetic acid [23].
Infrared spectra were recorded in KBr with an FTIR 1600
1
Fourier transform spectrophotometer in the 4500±450 cm
region. Magnetic measurements were carried out at room
temperature by the Gouy method.
2.2. Synthesis of the complexes
2.2.1. Bis(ꢀ-2,4-pentanedionato)di-ꢀ3-oxo-di-ꢀ-sulfido-
bis(ꢀ-thiobenzoato)tetraoxotetramolybdenum(V)
dichloromethane(1/2), (Mo4O6S2(C5H7O2)2-
(C7H5OS)2]Á2CH2Cl2 (1)
A mixture of [Mo2O3(C5H7O2)4] (0.25 g, 0.39 mmol) and
thiobenzoic acid (0.3 g, 2.17 mmol) was heated for 45 min
in dichloromethane (15 ml). The resulting substance was
®ltered off and rinsed with cold dichloromethane and ether.
Yield: 0.1 g, 50%. Anal. Calc. for C24H24Mo4O12S4
(Mr ˆ 1016.44): C, 28.34; H, 2.38; Mo, 37.75; S, 12.62.
Found (for the crystals left in a desiccator up to constant
weight): C, 28.61; H, 2.65; Mo, 37.84; S, 12.29%. Selected
IR data (cm 1): 1563(s), 1528(s), 1478(s), 1353(s), 1309(s),
974(s), 947(s).
Owing to the bidentately bonded b-diketonato and thio-
carboxylato ligands, the complexes described here follow
the alkoxide pattern. Their structures support Bradley's
structural theory based on the desire of metal atoms to
achieve the preferred coordination (in our case octahedral)
by the minimum degree of oligomerization [19]. All com-
plexes of such type are centrosymmetric, while the carb-
oxylate complex molecules possess or are very close to two-
fold symmetry.
Moreover, such complexes are interesting also from
another point of view. They all contain Mo4X16, or more
general Mo4XaYbZc (where a ‡ b ‡ c ˆ 16) cluster units,
analogously as some catalytically active ternary tungsten
and molybdenum oxides contain M4O16 units [13,20]. In
such a way, they can be potential models for a better
understanding of the reactions between organic molecules
and catalytic oxide surfaces.
2.2.2. Bis(ꢀ-2,4-pentanedionato)di-ꢀ3-oxo-di-ꢀ-sulfido-
bis(ꢀ-thioacetato)tetraoxotetramolybdenum(V),
[Mo4O6S2(C5H7O2)2(C2H3OS)2] (2)
The procedure described above for the preparation of 1
was applied also for synthesis of 2. The reaction mixture of
[Mo2O3(C5H7O2)4] (0.5 g, 0.79 mmol) and thioacetic acid
(0.35 g, 4.6 mmol) in dichloromethane (20 ml) was heated
only for 30 min and the warm solution was ®ltered off. After
Fig. 1. Polyhedral plots of the tetranuclear molybdenum(V) species found in (a) alkoxides and (b) in carboxylates. The complexes described here follow the
pattern (a).

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225
2 days an orange microcrystalline substance was obtained,
2.2.6. Bis(ꢀ-1-phenyl-1,3-butanedionato)-di-ꢀ3-oxo-di-ꢀ-
®ltered, and the precipitate rinsed with cold dichloro-
methane and ether. Yield: 0.15 g, 42.8%. Anal. Calc. for
C14H20Mo4O12S4 (Mr ˆ 892.30): C, 18.84; H, 2.26; Mo,
43.01; S, 14.37. Found: C, 19.09; H, 2.56; Mo, 42.57; S,
14.05%. Selected IR data (cm 1): 2996(w), 1573(s),
1530(s), 1417(m), 1356(s), 1273(s), 970(s), 929(m),
689(m), 473(m).
sulfido-bis(ꢀ-thioacetato)tetraoxotetramolyb-
denum(V) dichloromethane(1/2), [Mo4O6S2-
(C10H9O2)2(C2H3OS)2]Á2CH2Cl2 (6)
This complex was prepared in a similar way from a
mixture of [Mo2O3(C10H9O2)4] (0.5 g, 0.56 mmol) and
thioacetic acid (0.2 g, 2.6 mmol) in dichloromethane
(20 ml). Yield: 0.1 g, 34.81%. Anal. Calc. for
C24H24Mo4O12S4 (Mr ˆ 1016.44): C, 28.36; H, 2.38; Mo,
37.76; S, 12.62. Found (for the crystals left in the desiccator
up to the constant weight): C, 28.37; H, 2.44; Mo, 37.86; S,
12.42%. Selected IR data (cm 1): 2920(w), 1585(m),
1530(s), 1486(s), 1453(s), 1418(s), 1309(s), 1289(s),
969(s), 959(s), 688(s), 455(m).
2.2.3. Bis(ꢀ-2,4-pentanedionato)-di-(3-oxo-di-ꢀ-sulfido-
bis(ꢀ-thiotrimethylacetato)tetraoxotetramolyb-
denum(V) dichloromethane, [Mo4O6S2(C5H7O2)2-
(C5H9OS)2]ÁCH2Cl2 (3)
This complex was prepared in a similar way as 2 from a
mixture of [Mo2O3(C5H7O2)4] (0.5 g, 0.79 mmol) and thio-
trimethylacetic acid (0.45 g, 0.38 mmol) in dichloro-
methane (15 ml). Yield: 0.2 g, 52%. Anal. Calc. for
C20H32Mo4O12S4 (Mr ˆ 976.46): C, 24.60; H, 3.30; Mo,
39.30; S, 13.14. Found (for the crystals left in a desiccator
up to the constant weight): C, 24.52; H, 3.85; Mo, 38.83; S,
13.00%. Selected IR data (cm 1): 2971(m), 1568(s),
1531(s), 1503(s), 1420(m), 1353(s), 1273(s), 972(s),
955(m), 930(m), 692(m), 452(m).
2.2.7. Bis(ꢀ-1-phenyl-1,3-butanedionato)di-ꢀ3-oxo-di-ꢀ-
sulfido-bis(ꢀ-thiotrimethylacetato)tetraoxo-
tetramolybdenum(V), [Mo4O6S2(C10H9O2)2-
(C5H9OS)2] (7)
This complex was prepared analogously as 6 by heating
[Mo2O3(C10H9O2)4] (0.5 g, 0.56 mmol) and thiotrimethyl-
acetic acid (0.25 g, 2.1 mmol) in dichloromethane (20 ml).
After 2 days the orange substance was obtained. Yield:
0.08 g, 25.7%. Anal. Calc. for C30H36Mo4O12S4
(Mr ˆ 1100.60): C, 32.74; H, 3.30; Mo, 34.87; S, 11.65.
Found: C, 32.07; H, 3.94; Mo, 34.55; S, 11.28%. Selected IR
data (cm 1): 2967(w), 2927(w), 1586(m), 1527(s), 1488(s),
1418(s), 1310(s), 1290(s), 969(s), 959(s), 691(s), 453(m).
2.2.4. Bis(ꢀ-2,4-pentanedionato)-di-ꢀ3-oxo-ꢀ-sulfido-
bis(ꢀ-thio-3-methylbutyrato)tetraoxo-
tetramolybdenum(V), [Mo4O6S2(C5H7O2)2-
(C5H9OS)2] (4)
2.2.8. Bis(ꢀ-1-phenyl-1,3-butanedionato)-di-ꢀ3-oxo-ꢀ-
sulfido-bis-(ꢀ-thio-3-methylbutyrato)-
tetraoxotetramolybdenum(V),
Thio-3-methylbutyric acid (0.3 g, 2.54 mmol) was added
to a suspension of [Mo2O3(C5H7O2)4] (0.3 g, 0.47 mmol) in
dichloromethane. The red solution was heated for 45 min
and ®ltered off. After standing for 2 days the crystalline
substance was ®ltered off and rinsed with cold dichloro-
methane and ether. Yield: 0.09 g, 39.1%. Anal. Calc. for
C20H32Mo4O12S4 (Mr ˆ 976.46): C, 24.60; H, 3.30; Mo,
39.30; S, 13.14. Found: C, 24.36; H, 3.26; Mo, 38.72; S,
12.92%. Selected IR data (cm 1): 2954(m), 1564(s),
1529(s), 1417(m), 1350(s), 1272(s), 968(m), 690(m),
454(m).
[Mo4O6S2(C10H9O2)2(C5H9OS)2] (8)
This complex was prepared in a similar way as 7 from
[Mo2O3(C10H9O2)4] (0.5 g, 0.56 mmol) and thio-3-methyl-
butyric acid (0.3 g, 2.54 mmol) in dichloromethane (20 ml).
Yield: 0.05 g, 16.07%. Anal. Calc. for C30H36Mo4O12S4
(Mr ˆ 1100.60): C, 32.74; H, 3.30; Mo, 34.87; S, 11.65.
Found: C, 32.38; H, 3.58; Mo, 34.50, S, 11.32%. Selected IR
data (cm 1): 2954(w), 1585(m), 1530(s), 1487(s), 1455(s),
1415(s), 1309(s), 1290(s), 970(s), 958(s), 687(s), 452(m).
2.2.5. Bis(ꢀ-1-phenyl-1,3-butanedionato)-di-ꢀ3-oxo-di-ꢀ-
sulfido-bis(ꢀ-thiobenzoato)tetraoxotetra-
2.3. X-ray crystallography
molybdenum(V),[Mo4O6S2(C10H9O2)2(C7H5OS)2](5)
A mixture of [Mo2O3(C10H9O2)4] (0.5 g, 0.56 mmol)
and thiobenzoic acid (0.35 g, 2.53 mmol) was heated in
dichloromethane (20 ml) for 1 h. After standing for 1 h
the orange product was ®ltered off and rinsed with cold
dichloromethane. Yield: 0.08 g, 24.8%. Anal. Calc. for
C34H28Mo4O12S4 (Mrˆ1140.58): C, 35.80; H, 2.47;
Mo, 33.64; S, 11.25. Found: C, 35.45; H, 2.73;
Mo, 33.27; S, 11.46%. Selected IR data (cm 1):
1591(m), 1527(s), 1488(s), 1455(s), 1420(s), 1349(s),
1310(s), 1291(s), 974 (s), 956(s), 709(s), 677(s), 649(s),
453(m).
Well-formed crystals suitable for X-ray diffraction ana-
lysis were grown from the solutions left at room temperature
for a period of 2±3 days. Since the crystalline products 1 and
3 were losing the structural solvent if left in the air, they
were protected from decomposition by a thin layer of epoxy
resin. The crystals of 6 were even more sensitive and
decomposed within 1 min due to the loss of the solvent,
and were therefore mounted in a glass capillary with some
mother liquor. X-ray diffraction data were collected at
293 K on a STOE updated Philips PW1100 diffractometer
using graphite-monochromated Mo Ka radiation
Ê
(ꢁ ˆ 0.71073 A) and the ꢂ±2ꢂ scan-type. The unit cell

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M. Cindric et al. / Inorganica Chimica Acta 284 (1999) 223±228
226
Table 1
Crystal and structure refinement data for 1, 3 and 6
1
3
6
Molecular formula
Formula weight
Space group
C
1186.32
24H24Mo4O12S4Á2CH2Cl2
C20H32Mo4O12S4ÁCH2Cl2
1061.41
C24H24Mo4O12S4Á2CH2Cl2
1186.33
P21/c
P21/n
P21/n
Ê
a (A)
Ê
b (A)
Ê
c (A)
11.224(1)
10.012(1)
17.476(1)
92.129(6)
1962.5(2)
2
10.265(1)
11.843(1)
14.505(1)
13.681(1)
109.280(8)
2218.4(3)
2
15.823(2)
12.033(1)
ꢃ (8)
V (A )
113.001(9)
1799.0(4)
Ê 3
Z
2
3
)
Dcalc (g cm
2.008
1.956
1.776
1
)
Absorption coefficient (mm
F (000)
Crystal size (mm)
1.788
1.794
1.582
1160
1040
1160
0.24 Â 0.38 Â 0.30
2.33±30.02
15ꢁhꢁ15
1ꢁkꢁ14
0.06 Â 0.19 Â 0.30
2.57±30.01
14ꢁhꢁ13
0.24 Â 0.25 Â 0.47
2.30±30.07
16ꢁhꢁ15
0ꢁkꢁ20
ꢂ Range for data collection (8)
Index ranges
0ꢁkꢁ22
0ꢁlꢁ24
1ꢁlꢁ16
0ꢁlꢁ19
No. of independent reflections
No. of parameters refined
Final R (I>2ꢄ(I)
5687 (Rintˆ0.028)
227
5212 (Rintˆ0.042)
6438 (Rintˆ0.048)
186
210
R1a ˆ 0.043, wR2b ˆ 0.104
R1a ˆ 0.106, wR2b ˆ 0.122
0.0698
R1a ˆ 0.056, wR2b ˆ 0.131
R1a ˆ 0.120, wR2b ˆ0.156
0.0850
R1a ˆ 0.069, wR2b ˆ 0.195
R1a ˆ 0.127, wR2b ˆ 0.234
0.1504
R (all data)
Weighting parameter (g)
c
Goodness-of-fit on F2
0.958
1.256, 0.687
0.998
2.442, 1.283
1.018
3.049, 1.007
3
Ê
Largest peak, hole (eA
)
P
P
aR1 ˆ jjFoj jFcjj= jFoj
P
P
2 1=2
2
bwR2ˆ‰ wꢀFo
Fc †2= wꢀFo † Š ; w ˆ ꢄ2ꢀFo † ‡ ꢀgP† Š 1; P ˆ ꢀFo ‡ 2Fc †=3
2
2
2
2
2
2
P
2
2
1=2
cgoodness-of-fit ˆ ‰ ‰wꢀFo
Fc † Š=ꢀNobs Nparams†Š
2
Ê
Ê
Ê
dimensions were determined from the setting angles of 40,
33 and 44 re¯ections in the range 15.6 < 2ꢂ < 19.08,
10 < 2ꢂ < 14.68 and 10.1 < 2ꢂ < 17.88 for 1, 3 and 6, respec-
tively. The details of the data collection and crystallographic
data are summarized in Table 1. The absorption corrections
based on scans were applied to the data for all three
structures. Four standard re¯ections monitored every
90 min showed decay of 7.2, 2.5 and 9.6% for 1, 3 and
6, respectively. Data were corrected for these decays. The
structures were solved from the Patterson map by the
standard heavy-atom method using SHELXS-86 [24]. Sub-
sequent cycles of least-squares re®nements and difference
Fourier maps were used to locate the remaining non-hydro-
gen atoms by full-matrix least-squares calculations with
SHELXL-96 [25]. For 3, the analysis of peak heights around
the inversion centre at 0.5, 0, 0 showed that the carbon atom
belonging to the dichloromethane solvent molecule is dis-
ordered over two symmetrically related positions, each with
the occupancy factor 0.35(2), since the whole molecule has
an occupancy of 0.71(3). A thorough examination of a
Fourier difference map for 6 revealed the existence of cavity
(methyl d(C±H) ˆ 0.96 A, methylene d(C±H) ˆ 0.97 A,
aromatic d(C±H) ˆ 0.93 A). The isotropic temperature fac-
tor was set at 1.2 times the Ueq of the parent C atom. The
potential solvent area was calculated by PLATON [26], and
the ORTEP [27,28] program was used to draw the repre-
sentations of 1, 3 and 6.
3. Results and discussion
3.1. Synthesis of the complexes
For the preparation of complexes 1 to 4, [Mo2O3(acac)4]
was used as a starting reagent in the reaction with thioben-
zoic (1), thioacetic (2), thiotrimethylacetic (3) and thio-3-
methylbutyric acid (4). Analogously, for complexes 5±8,
[Mo2O3(ba)4] was used in the reaction with thiobenzoic (5),
thioacetic (6), thiotrimethylacetic (7) and thio-3-methyl-
butyric acid (8). The reactions follow the Eq. (1):
2‰Mo2O3ꢀR0COCHCOCH3† Š ‡ 4R00COSH ‡ 2H2O
4
! ‰Mo4O6S2ꢀR0COCHCOCH3†2ꢀOSCR00† Š
2
Ê 3
of about 460 A with six maxima of electronic density
‡2R00COOH ‡ 6R0COCH2COCH3
R0 ˆ CH3 or C6H5
ranging from 0.72 to 4.29 eA 3. These residual peaks were
from the disordered dichloromethane molecules of crystal-
lization, one of them with an occupancy of 0.42(1) could be
modeled. Such occupancy factors clearly show a gradual
loss of solvent molecules. The hydrogen atoms bound to
carbon atoms were introduced in their calculated positions
R00 ˆ C6H5; CH3; CꢀCH3†3; CH2CHꢀCH3†
As shown in the above reaction, carboxylic acids and
(1)
2
b-diketones were generated as byproducts. However, due to

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M. Cindric et al. / Inorganica Chimica Acta 284 (1999) 223±228
227
Table 2
the relatively low yield of such reactions (less than 50 %)
Ê
Selected bond lengths (A) and angles (8) for 1, 3 and 6
other byproducts may also be generated; e.g. disul®des
formed by the oxidation of the corresponding thioacids.
Such disul®des have been detected chemically as well as by
IR spectra.
1
3
6
Ê
Bond lengths (A)
Mo1±Mo2a
Mo1±S1
Mo1±S2
Mo1±O1
Mo1±O3a
Mo1±O3
Mo1±O5
Mo2±S1a
Mo2±O2
Mo2±O3
Mo2±O4
Mo2±O5
Mo2±O6
2.695(1)
2.313(1)
2.486(1)
1.673(3)
1.981(3)
2.248(3)
2.259(3)
2.322(1)
1.663(3)
1.952(3)
2.142(3)
2.302(3)
2.055(3)
2.6933(7)
2.315(2)
2.495(2)
1.673(5)
1.983(4)
2.246(4)
2.268(4)
2.330(2)
1.674(4)
1.942(4)
2.130(5)
2.310(4)
2.054(4)
2.6908(9)
2.317(2)
2.478(3)
1.690(6)
1.994(5)
2.232(5)
2.257(5)
2.320(2)
1.665(5)
1.948(4)
2.148(5)
2.282(5)
2.065(5)
In all reactions dichloromethane was chosen as the most
suitable solvent. The complexes obtained were insoluble in
all common solvents. The insertion of the sulfur atom into
the Mo±S±Mo bridge is explained by the appearance of H2S
produced in situ from molybdenum catalysed hydrolysis of
thioacids in the presence of moisture. We have already
observed such catalytic hydrolysis in the formation of
molybdenum(V) complexes with monothio-b-diketones
[6], and other molybdenum(V) complexes containing either
MoSMo or MoS2Mo bridging cores [29].
Angles (8)
3.2. Structures
O1±Mo1±O3a
O3a±Mo1±O3
O1±Mo1±O5
O3a±Mo1±O5
O3±Mo1±O5
O1±Mo1±S1
O3a±Mo1±S1
O3±Mo1±S1
O1±Mo1±S2
O3±Mo1±S2
O5±Mo1±S2
S1±Mo1±S2
O2±Mo2±O3
O2±Mo2±O6
O2±Mo2±O4
O3±Mo2±O4
O6±Mo2±O4
O3±Mo2±O5
O6±Mo2±O5
O4±Mo2±O5
O2±Mo2±S1a
O3±Mo2±S1a
O6±Mo2±S1a
O5±Mo2±S1a
Mo1±S1±Mo2a
Mo2±O3±Mo1a
Mo2±O3±Mo1
Mo1a±O3±Mo1
106.1(2)
73.4(1)
91.2(1)
85.6(1)
72.5(1)
103.0(1)
97.8(1)
93.1(1)
97.0(1)
82.2(1)
86.3(1)
84.2(1)
104.3(1)
95.1(1)
92.9(2)
85.6(1)
82.2(1)
77.1(1)
81.6(1)
74.9(1)
105.5(1)
98.3(1)
87.1(1)
86.3(1)
71.1(0)
86.5(1)
111.2(1)
106.6(1)
105.7(2)
74.4(2)
90.2(2)
85.0(2)
71.9(2)
102.8(2)
98.0(1)
94.8(1)
95.6(2)
82.7(1)
86.1(1)
85.7(1)
104.0(2)
95.9(2)
93.7(2)
85.4(2)
79.7(2)
76.6(2)
81.3(2)
75.4(2)
105.1(2)
98.7(1)
89.1(2)
85.5(1)
70.9(1)
86.7(2)
112.3(2)
105.7(2)
106.2(3)
74.5(2)
89.7(2)
84.1(2)
71.1(2)
103.8(2)
97.9(1)
95.1(1)
96.1(2)
81.5(1)
87.4(2)
84.9(1)
104.9(2)
97.1(2)
92.4(3)
84.6(2)
81.5(2)
75.8(2)
80.3(2)
77.3(2)
104.8(2)
99.2(1)
87.5(2)
85.2(1)
71.0(1)
86.1(2)
112.7(2)
105.5(2)
Table 2 lists selected bond lengths and angles. As proved
by X-ray structure analysis, complexes 1, 3 and 6 are
tetranuclear and contain Mo4O6S2 cores. These cores are
bridged by b-diketonato (acetylacetonato and benzoylace-
tonato) and by thiocarboxylato ligands (Fig. 2).
Both molybdenum atoms in the asymmetric unit have
octahedral geometry although taking into account the Mo±
Ê
Mo bonds of 2.6949(6), 2.6933(7) and 2.6908(9) A in 1, 3
and 6, respectively, they are formally seven-coordinated
(here and elsewhere, the quoted metrical data relate to the
structures of 1, 3 and 6, respectively). Such bond length
values correspond to the value considered as Mo±Mo single
bond [30,31]. Mo(1) and Mo(2) have different surroundings:
Mo(1) is coordinated by two sulfurs, one bridging sul®do (at
Ê
2.313(1), 2.315(2), 2.317(2) A) and one thiocarboxylato-
Ê
sulfur atom (2.486(1), 2.495(2), 2.478(3) A), one diketo-
Ê
nato-oxygen (2.259(3), 2.268(4), 2.257(5) A), and three
oxo-oxygens, one terminal (1.673(3), 1.673(5), 1.690(6)
Ê
A) and two triply-bridging oxygens (at 2.248(3),
Ê
2.246(4), 2.232(5)
Ê
A
1.994(5) A). Mo(2) is coordinated by only one sulfur, the
and at 1.981(3), 1.983(4),
Ê
bridging one (at 2.322(1), 2.330(2), 2.320(2) A), two dike-
tonato-oxygens (2.055(3), 2.054(4), 2.065(5) and 2.302(3),
Ê
2.310(4), 2.282(5) A) and one thiocarboxylato-oxygen
aSymmetry transformation used to generate equivalent atoms: ±x, ±y, ±z.
Ê
(2.142(3), 2.130(5), 2.148(5) A), one terminal (1.663(3),
Ê
1.674(4), 1.665(5) A) and one triply-bridging oxygen (at
Ê
1.952(3), 1.942(4), 1.948(4) A). All given bond-length
considerably distorted as it is usual for such types of
structures. The mean values of the angles at the molybde-
num atoms range from 71.9(2) to 103.2(2)8. The Mo2OS
bridging cores are also not planar but folded at the angles of
166.56(4), 152.05(2) and 151.16(2)8 (for 1, 3 and 6) along
the lines connecting bridging oxygen and sulfur atoms. The
distances and angles in the diketonato and thiocarboxylato
ligands are within expected values.
values are expected for such a class of molybdenum com-
plexes. The Mo-to-oxygen bond lengths vary signi®cantly
according to their positions in the structure, i.e. cis or trans
to the oxo-oxygen atom. The trans in¯uence of the terminal
oxo-oxygen atoms is very obvious in all three structures.
The oxo-oxygens bridging the three molybdenum atoms
Ê
form one longer (mean value 2.242(4) A) and two signi®-
Ê
cantly shorter (mean values 1.986(4) and 1.947(4) A) Mo±O
The average oxidation state of molybdenum atoms in the
clusters is ‡5 with four Mo atoms yielding a total of four
electrons to form two localized Mo±Mo single bonds.
Consequently, all complexes described in this paper are
bonds. The m3±OMo3 system is nonplanar with the angles at
m3±O varying from 86.4(2) to 112.1(2)8 (all mean values for
1, 3 and 6). The octahedra around Mo(1) and Mo(2) are

Â
M. Cindric et al. / Inorganica Chimica Acta 284 (1999) 223±228
228
Ministry of Science and Technology of the Republic of
Croatia (Grant No. 119407).
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Fig. 2. Molecular structure and atom-labeling schemes for [Mo4O6S2-
(acac)2(OSCC6H5)2]Á2CH2Cl2(1), [Mo4O6S2(acac)2(OSCC(CH3)3)2]-
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structural ®ndings.
Ï
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Acknowledgements
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[29] M. Cindric, D. Matkovic-Calogovic, V. Vrdoljak, B. Kamenar, in
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[30] F.A. Cotton, Inorg. Chem. 4 (1965) 334.
[31] F.A. Cotton, J. Less-Common Met. 54 (1977) 3.
Â
We thank Miss I. Jelic, Miss T. Kajfez and Mr V. Roje
for technical assistance. This work was supported by the
Ï