Mononuclear and polynuclear molybdenumw(VI) complexes with the interchangeable coordination site

Mononuclear and polynuclear dioxomolybdenum(VI) complexes with the tridentate Schiff base ligand have been prepared by the reaction of [MoO2(acac)(2)] with N-4-methoxysalicylidene-2-amino-3-hydroxyPYridine (H2L, 1) in methanol, ethanol or acetonitrile. All the prepared complexes of the general formulae [MoO2L(ROH)], [MoO2LD], ([MoO2L](2)D'}center dot D' and [MoO2L](n) consist of the cis-MoO22+ core coordinated by dianionic form of the Schiff-base ligand, L2-, in the tridentate manner through two deprotonated hydroxyl groups and one imino nitrogen atom. The octahedral coordination around the molybdenum atom is completed by neutral monodentate 0- or N-donor ligands (ROH: R = CH3 or C2H5; D: PY = Pyridine; gamma-pic = gamma-picoline; imid = imidazole; bipy = 4,4'-bipyridine). The combination of molybdenum coordination preferences and the ligand donor capabilities have led to the complexes with the labile sixth coordination site, which could be readily exchanged with the competitive ligand by tuning reaction conditions (solvent, atmosphere). All the complexes have been studied by means of elemental analysis, IR spectroscopy and thermogravimetric analysis. The crystal structures of ligand 1, four mononuclear [MoO2LD] or [MoO2L(ROH)] and one dinuclear {[MoO2L](2)D'}center dot D' complex [ROH = methanol (2), D = pyridine (5), gamma-picoline (6), imidazole (7), D' = 4, 4-bipyridine (8)] have been determined by the single crystal X-ray structure analysis. (C) 2012 Elsevier Ltd. All rights reserved.