Synthesis and characterization of three novel molybdenum(VI) complexes: Mononuclear [MoO2(C6H4(O)CH=NCH(COO)CH2C=(O)NH2)], [MoO2(C19H19N2O5)(CH3OH)]Cl • CH3OH and dinuclear [Mo2O4(C6H4(O)CH=NCH(COO)CH2C=(O)NH2)2]

The molybdenum(VI) complexes [Mo2O4(C6H4(O)CH=NCH(COO)CH2C=ONH2)(2)] (1), [MoO2-(C6H4(O)CH=NCH(COO)CH2C=(O)NH2)](3) and [MoO2(C19H19N2O5)(CH3OH)]Cl center dot CH3OH (4), of salicylaldehyde amino acid derivatives (M-asparagine or L-ornithine hydrochloride) have been synthesized and characterized. The Schiff base containing a saturated heterocyclic ring (in complex 4) is the first example Of Such a molecule derived from salicylaldehyde and the amino acid, L-ornithine hydrochloride. We proposed that the formation of a molybdenum(VI) complex coordinated by a Schiff base containing a saturated heterocyclic ring depends upon the nature of the solvent and upon the presence of molybdenum(VI). In the absence of molybdenum(VI), the condensation product obtained from the reaction of L-ornithine hydrochloride and salicylaldehyde was the Schiff base N-salicylidene-L-ornithine (5). In the dinuclear complex I and the mononuclear complexes 3 and 4, the molybdenum atoms are octahedrally coordinated with two cis oxo-oxygen atoms (in 3 and 4), oxo-bridging atoms (in 1) and the Schiff base ligand. In 3 the N-salicylidene-DL-asparaginato ligand coordinates molybdenum tetradentately while in 1 and 4 the Schiff base ligand acts as a tridentate ligand. (C) 2008 Elsevier Ltd. All rights reserved.