Synthesis, characterization and reactivity of oxomolybdenum(V) complexes with ONS and NNS donors

The monomeric oxomolybdenum(V) complexes, MoOLCl₂]1a-1d HL = S-benzyl/methyl 3-(2-pyridyl)methylenedithiocarbazate (1a and1b), or N-methyl-S-benzyl/methyl 3-(2-hydroxy phenyl)methylenedithiocarbazate (1c and1d) are synthesized by the reaction of MoOCl ₅ ²⁻ with HL ligands. All these complexes show magnetic moment of about 1.7 B.M. The complexes,1a and1b, exhibit rhombicg-tensor anisotropy (like xanthine oxidase) whilst1c and1d show axial spectrum. The above complexes undergo irreversible electrochemical reduction furnishing Mo(IV) species and the potentials are dependent on the S-substituents. Reactions of MoOX ₅ ⁻ (X = Cl or Br) with H₂L¹ H₂L¹ = S-methyl 3-(5-R-2-hydroxyphenyl)methylenedithiocarbazate] (R = H, CH₃, Cl, Br) produce complexes of thiolatobridged dimers, Mo₂O₂L ₂ ¹ X₂], which show sub-normal magnetic moments at room temperature. The metal-centred irreversible oxidation and reduction of these complexes show expected dependence on the R-substituents of the salicyl phenyl ring of the ligands.