The mononuclear tungsten(V) complexes: The preparation and the X-ray structures of a series of [WOX4(H2O)]− (X = Cl, Br) salts

A new synthetic entry into tungsten(V) chemistry is presented: a dinuclear tungsten(III) compound, K3W2Cl9, is oxidized in conc. HX (X = Cl, Br) with a mild oxidizing agent, hydrazinium or hydroxylammonium chloride, to [WVOX4(H2O)]– species. To identify the products formed, all compounds were authenticated using X-ray crystallography. The solid state structures of {(C4H9)4N}[WOCl4(H2O)] (1a), (Py2CH2)2[WOCl4(H2O)]3Cl (2a), (PicH)2[WOCl4(H2O)]Cl (3a), (Pic2CH2)2[WOCl4(H2O)]2[SnCl6] (4a), {(C4H9)4N}[WOBr4(H2O)] (1b) and (Py2CH2)2[WOBr4(H2O)]3Br (2b) (where PicH+ stands for protonated 4-methylpyridine, Py2CH22+ for N,N′-methylenedipyridinium cation, and Pic2CH22+ for N,N′-methylenedipicolinium cation) consist of the octahedrally-shaped [WOX4(H2O)]– complex ions. The anions are distorted with the equatorial halido ligands bent down and away from the oxide. Due to the trans influence of the latter, the aqua ligands bind at longer bond distances. Coordinated halides, aqua ligands and counterions are engaged in hydrogen bonds which result in interesting intermolecular connectivities.