SYNTHESIS AND CHARACTERIZATION OF A SERIES OF NEW TETRANUCLEAR THIOCARBOXYLATE COMPLEXES OF MOLYBDENUM(V)
Višnja Vrdoljak, Marina Cindric', Dubravka Matkovic'-Calogovic' and Boris Kamenar
Laboratory of General and Inorganic Chemistry, Chemistry Department, Faculty of Science, University of Zagreb, Ulica kralja Zvonimira 8, 10000 Zagreb, Croatia,
E-mail: visnja@zagreb.zoak.pmf.hr
Keywords: Crystal structures;
Oxomolybdenum(V) complexes; Thiocarboxylate complexes;
Tetranuclear molybdenum complexes; Thio-ligands
Molybdenum(V) complexes with sulphur donor
ligands are of interest due to their relevance in the redox
active molybdoenzymes [1]. The novel tetranuclear complexes have
been prepared by the reactions of binuclear oxomolybdenum(V)
complexes [Mo2O3(acac)4] (acac =
2,4-pentanedionato) with thiobenzoic (1) and
thiotrimethylacetic (2) as well as by reaction of
[Mo2O3(ba)4] (ba = 1-phenyl-1,3-butanedionato) with thioacetic
acid (3). The molecular structures of the complexes 1,
2 and 3 have been determined by single crystal
X-ray crystallography. Structural characteristics are as follows:
[Mo4O6S2(acac)2(OSCC6H5)2]×2CH2Cl2
(1), monoclinic, space group P21/c,
a = 11.224(1) Ä, b = 10.012(1) Ä, c =
17.476(1) Ä, b =92.129(6) °, V = 1962.5(2) Ä3
and Z = 2; [Mo4O6S2(acac)2OSCC(CH3)3}2]×CH2Cl2
(2), monoclinic space group P21/n,
a = 10.265(1) Ä, b = 15.823(2) Ä, c =
12.033(1) Ä, b = 113.001(9) °, V = 1799.0(4) Ä3
and Z = 2; [Mo4O6S2(ba)2(OSCCH3)2]×2CH2Cl2
(3), monoclinic, space group P21/n,
a = 11.843(1) Ä, b = 14.505(1) Ä, c =
13.681(1) Ä, b = 109.280(8) °, V = 2218.4(3) Ä3
and Z = 2. The centrosymmetrical tetranuclear complexes
contain Mo4O6S2 cores bridged
through b-diketonato and thiocarboxylato ligands. Four
coordination octahedra are fused together 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.
R' = -CH3 or -C6H5
R" = -C6H5,
-CH3, -C(CH3)3
References:
1. (a) M. Coughlan, Molybdenum and
Molybdenum-Containing Enzymes, Pergamon, New York, 1980; (b)
W.E. Newton and S. Otsuka, Molybdenum Chemistry of Biological
Significance, Plenum, New York, 1980; (c) E.I. Stiefel, Prog.
Inorg. Chem., 22 (1977) 1-223 and references therein;
(d) B. Spivack and Z. Dori, Coord. Chem. Rev., 17
(1975) 99.