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)
A, b = 10.012(1) A, c = 17.476(1) A, b =92.129(6) °, V = 1962.5(2) A3 and Z = 2; [Mo4O6S2(acac)2{OSCC(CH3)3}2]×CH2Cl2
(2), monoclinic space group P21/n, a = 10.265(1) A,
b = 15.823(2) A, c = 12.033(1) A, b = 113.001(9) °, V = 1799.0(4) A3 and Z = 2; [Mo4O6S2(ba)2(OSCCH3)2]×2CH2Cl2
(3), monoclinic, space group P21/n, a = 11.843(1)
A, b = 14.505(1) A, c = 13.681(1) A, b = 109.280(8) °, V = 2218.4(3) A3 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.