Synthesis of novel molybdenum(V) complexes: Structural characterization of two thiosemicarbazonato complexes [MoOCl 2{C 6H 4(O)CH:NNHC:SNHC 6H 5}] and [MoOCl 2{C 10H 6(O)CH:NNHC:SNHC 6H 5}] · CH 3CN, and two oxohalomolybdates NH 4[MoOCl 4(CH 3CN)] and [C 5H 5NH] 2[MoOCl 5] · CH 2Cl 2

Abstract

Mononuclear oxomolybdenum(V) complexes with thiosemicarbazonato ligands as condensation products of aldehydes (salicylaldehyde, 2-hydroxynaphthaldehyde) with thiosemicarbazides (H 2NNHC:SNHR; R = H, CH 3, C 6H 5) were prepared. The [MoOCl 2HL] complexes (HL = thiosemicarbazonato ligand) were characterized by chemical analysis, IR spectroscopy, thermogravimetry and two of them, [MoOCl 2{C 6H 4(O)CH:NNHC:SNHC 6H 5}] and [MoOCl 2{C 10H 6(O)CH:NNHC:SNHC 6H 5}] · CH 3CN, by single-crystal X-ray structural analysis. In both complexes the MoO 3+ core is coordinated by a monobasic tridentate ONS thiosemicarbazonato ligand and two chloro ligands. The coordination around the molybdenum atom is a distorted octahedron. NH 4[MoOCl 4(CH 3CN)] and unstable (C 5H 5NH) 2[MoOCl 5] · CH 2Cl 2 were isolated from the acetonitrile solution of (NH 4) 2[MoOCl 5] and from the acetonitrile and dichloromethane (1:1) solution of (C 5H 5NH) 2[MoOCl 5], respectively. Isolation and structural characterization of NH 4[MoOCl 4(CH 3CN)] from the acetonitrile solution suggests the [MoOCl 4(CH 3CN)] − anion to be the reaction intermediate in the synthesis of molybdenum(V) thiosemicarbazonato complexes. (C 5H 5NH) 2[MoOCl 5] · CH 2Cl 2 is a rare example of a structurally characterized simple oxohalomolybdate(V) with a six-coordinate octahedral [MoOCl 5] 2− anion.