THE SYNTHESIS, CHARACTERIZATION, AND CHEMISTRY OF DITUNGSTEN ALKOXIDES OF THE TYPES TUNGSTEN(2)CHLORIDE(4)(MU-OR)(2)(OR)(2)(ROH)(2) AND TUNGSTEN(2)CHLORIDE(4)(MU-OR)(2)(OR)(4)
Abstract
Reaction of the dinuclear molybdenum(II) complex Mo(,2) (mhp)(,4) (where mhp represents the anion of 2-hydroxy-6-methylpyridine) with a cesium halide and a hydrogen halide gas in refluxing methanol produces the quadruply bonded octahalodimolybdate(II) Cs(,4)Mo(,2)X(,8) (X = Cl, Br). If the cesium halide is replaced by tertiary phosphines in the reaction mixture, oxidation occurs and trialkylphosphonium salts of Mo(,2)Cl(,8)H('3-) result. These results are contrasted to reactions of the related dinuclear complex W(,2)(mhp)(,4) with gaseous hydrogen halides in alcoholic solvents; if a cesium halide is present, the triply bonded complexes Cs(,3)W(,2)X(,9) (X = Cl, Br) result; if the cesium halide is replaced by trialkyl phosphines, the doubly bonded ditungsten(IV) alkoxide complexes W(,2)Cl(,4)((mu)-OR)(,2)(OR)(,2)(ROH)(,2) result. These molecules are diamagnetic and have been shown to contain tungsten-tungsten double bonds. They also contain novel hydrogen bonding interactions between syn-axial alcohol-alkoxide ligands in which the nature of the interaction is dependent upon the alkyl group of the alcohol-alkoxide ligands. The ditungsten(IV) alkoxides W(,2)Cl(,4)((mu)-OR)(,2)(OR)(,2)(ROH)(,2) have been oxidized by a variety of oxidants including molecular oxygen to the structurally similar ditungsten(V) alkoxides W(,2)Cl(,4)((mu)-OR)(,2)(OR)(,4). The ditungsten(IV) alkoxides have also been found to promote carbon-carbon bond formation in the reductive coupling of ketones to give complexes of the type W(,2)Cl(,4)((mu)-OR)(,2){R'R''C(O)C(O)R'R''}(,2).
Degree
Ph.D.
Subject Area
Chemistry
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