Homo- and hetero-metallic rhenium oxomethoxide complexes with a M4(µ-O)2(µ-OMe)4 planar core—a new family of metal alkoxides displaying a peculiar structural disorder. Preparation and X-ray single crystal study

Abstract

The reaction of Re2O7 with MeOH at room temperature leads to a fine black powder. A product with the same crystal structure, according to X-ray powder data, was obtained in the form of single crystals on storage of solutions of Re2O3(OMe)6, obtained by anodic oxidation of Re metal. It was identified as Re4O6(OMe)12 (1) by an X-ray single crystal study. A mixed-valence complex of analogous composition and structure, Re4O6 − y(OMe)12 + y (2), earlier erroneously described as Re4O2(OMe)16, can be obtained via anodic dissolution of Re in MeOH using high current densities. The heterometallic members of this family, Re4 − xMxO6 − y(OMe)12 + y [M = Mo (3), W (4); x ≤ 0.55, y < 1.0], were obtained by interaction of Re2O7 with MO(OMe)4 or M(OMe)6 in toluene at reflux. Mo-poor samples of 3 (x ≤ 0.25) could also be obtained on storage of solutions prepared by anodic oxidation of Re in the presence of MoO(OMe)4. The reaction of Re2O7 with Nb(OMe)5 or Ta(OMe)5 in refluxing toluene gave M4(μ-O)2(μ-OMe)4(OMe)14(ReO4)2 [M = Nb (5), Ta (6)] as the only crystalline products. The compounds 1–6 are insoluble in organic solvents and display a remarkable resistance to ambient atmosphere, making them attractive precursors for soft chemical preparation of rhenium metal and alloy powders.