Thiosemicarbazones are ligands with interesting ONS donor and chelating properties. Some of their metal complexes have been found to be cancerostatic [1]. Mononuclear dioxomolybdenum(VI) [MoO2L1L2] complexes with thiosemicarbazonato ligands have been prepared by the reaction of [MoO2(acac)2] with L1 = o-vanilin 4-phenylthiosemicarbazone (I and II) and salicylaldehyde 4-phenylthiosemicarbazone (III and IV) with addition of appropriate amine (L2 = bipyridine (I and III), pyridine (II) and g-picoline (IV)) [2, 3, 4]. Complex I crystallises in the monoclinic space group P21/c with cell parameters: a=10.692(2), b=14.764(2), c=14.009(2)A ; , betha= 108.844(2)o ; , R1=0.0497 for 4629 Fo>4s(Fo). Complex II crystallises in the monoclinic space group P21/n with cell parameters: a=10.7877(9), b=15.3255(11), c=12.926(1) A ; , betha=107.933(8)o ; , R=0.055 for 8013 Fo>4s(Fo). Complex III crystallises in the triclinic space group P-1 with cell parameters: a=10.780(2), b=10.936(1), c=11.808(1) A ; , alpha=84.952(8), betha=82.580(9), gamma=64.987(13) )o ; , R=0.059 for 7363 Fo>4s(Fo). Complex IV crystallises in the orthorhombic space group Pbca with cell parameters: a=10.7877(9), b=15.3255(11), c=12.926(1) A ; , R=0.0603 for 5512 Fo>4s(Fo). In all structures molybdenum is coordinated by a tridentate ONS chelating ligand, two oxo groups and N-donor ligands in a disturbed octahedral coordinations. The Mo=O bond length in these cis-dioxomolybdenum complexes is in range 1.6896(22) to 1.7101(25) A ; . [1] U. Abram, K. Ortner, R. Gust, K. Sommer, J.Chem . Soc Dalton, (2000)735. [2] D. Chattopadhyay & S. K. Mazumdar, Acta Cryst. C44 (1988) 1025-1028. [3] S. Purohit, A. P. Kaley, L. S. Prasad, P. T. Monoharan & S. Ghosh, Inorg Chem 28 (1989) 3735. [4] J. U. Mondal, J. G. Zamora, M. D. Kinon & F. A. Schultz, Inorg. Chim. Acta 309 (2000) 147.
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