Polynuclear oxomolybdenum(VI) complexes of dihydroxybenzoic acids: Synthesis, spectroscopic and structure characterization of a tetranuclear catecholato-type coordinated 2,3-dihydroxybenzoate and a novel tridentate salicylato-type coordinated 2,5-dih

摘要

In order to Study the reaction of molybdenum(VI) with dihydroxybenzoic acids (DHBAs), compounds (PPh4)(2) (.) [Mo4O6(mu-O)(4)-(mu(3)-OCH3)(2)(2,3-DHBA)(2)] (1) and (PPh4)(2) (.) [Mo3O6(mu-O)(2)(2,5-DHBA)(2)] (.) CH3CN (2) were isolated and determined by X-ray crystallography. The structure of complex 1 consists of four distorted MoO6 octahedra with two cis-MoO22+ units and two molybdenum atoms having each ligand coordinated and one terminal oxygen atom, while two triple bridged methanol molecules are present. The ligand 2,3-dihydroxybenzoic acid (2,3-DHBA) prefers the catecholate-type coordination with strong hydrogen bonding between the carboxylic hydrogen and the ortho-phenolic oxygen. The structure of complex 2 consists of three distorted MoO6 octahedra. The 2,5-dihydroxybenzoic acid (2,5-DHBA) acts as a tridentate ligand using both carboxyl oxygen atoms, giving thus all unusual trinuclear molybdenum complex with a unique coordination mode of the ligand. The Compounds were further investigated using IR, UV-Vis, ESR and NMR spectroscopy, elemental and themiogravimetric analysis, as well as cyclic voltammetry. (c) 2005 Elsevier Ltd. All rights reserved.