A series of new oxomolybdenum(IV) complexes involving some NSO donors as the main ligand frame; the first use of diacetyldihydrazones to stabilize the MoO +2 acceptor centre

Abstract

An array of neutral oxomolybdenum(IV) complexes with potentially pentadentate ONSNO donor Schiff bases in the form of thiocarbodihydrazone of salicylaldehyde and substituted salicylaldehydes actually acting as tridentate ONS donor ligands (H 3L) were synthesized through oxo abstraction of the corresponding cis-dioxomolybdenum(VI) complexes. Oxomolybdenum(IV) complexes with similar ONS main ligands but different N–N donor coligands were also obtained by one-pot synthesis from the corresponding cis-dioxomolybdenum(VI) precursors. The complexes are found to be of the form [MoO(LH)] n and [MoO(LH)(N–N)], where N–N=bipy (2,2 ′-bipyridine), ophen (1,10-phenanthroline) and diacetyldihydrazones. In this work diacetyldihydrazones were used as N–N coligands for the first time in molybdenum chemistry. The complexes were characterized by elemental analyses, UV–Vis and IR spectroscopy, magnetic susceptibility measurement at room temperature in the solid state, molar conductivity in solution and by cyclic voltammetry. One of the complexes, [MoO(LH)( o-phen)] is structurally characterized by X-ray crystallography. The structure reveals that the molybdenum acceptor centre is present in a distorted octahedral N 3O 2S donor environment. The N–N coligand was found to occupy a plane perpendicular to that taken up by the ONS ligand. It is to be noted that structurally characterized oxomolybdenum(IV) complexes are quite scarce.