Synthesis of novel molybdenum(V) complexes:: Structural characterization of two thiosemicarbazonato complexes [MoOCl2{C6H4(O)CH:NNHC:SNHC6H5}] and [MoOCl2{C10H6(O)CH:NNHC:SNHC6H5}].CH3CN, and two oxohalomolybdates NH4[MoOCl4(CH3CN)] and [C5H5NH]2[MoOCl5]-CH2Cl2

Mononuclear oxomolybdenum(V) complexes with thiosemicarbazonato ligands as condensation products of aldehydes (salicylaldehyde, 2-hydroxynaphthaldehyde) with thiosernicarbazides (H,NNHC:SNHR; R = H, CH3, C6H5) were prepared. The [MoOCl2HL] complexes (HL = thiosemicarbazonato ligand) were characterized by chemical analysis, IR spectroscopy, thermogravimetry and two of them, [MoOCl2{C6H4(O)CH:NNHC:SNHC6H5}] and [MoOCl2{C10H6(O)CH:NNHC:SNHC6H5}]center dot CH3CN, by single-crystal X-ray structural analysis. In both complexes the MoO3+ core is coordinated by a monobasic tridentate ONS thiosernicarbazonato ligand and two chloro ligands. The coordination around the molybdenum atom is a distorted octahedron. NH4[MoOCl4(CH3CN)] and unstable (C5H5NH)(2)[MoOCl5]center dot CH,Cl, were isolated from the acetonitrile solution of (NH4)2[MoOCl5] and from the acetonitrile and dichloromethane (1: 1) solution Of (C5H5NH)(2)[MoOCl5], respectively. Isolation and structural characterization of NH4[MoOCl4(CH3CN)] from the acetonitrile solution suggests the [MoOCl4(CH3CN)]anion to be the reaction intermediate in the synthesis of molybdenum(V) thiosemicarbazonato complexes. (C5H5NH)(2)(MoOCl5]center dot CH2Cl2, is a rare example of a structurally characterized simple oxohalomolybdate(V) with a six-coordinate octahedral [MoOCl5](2-) anion. (c) 2007 Elsevier Ltd. All rights reserved.