Alcoholate and Mixed Alcoholate/Iodide Supported Hexanuclear Niobium Cluster Compounds with a Mixed Face-Bridged/Edge-Bridged Cluster Pair Example

Abstract

Chemical reactions of ball-mill activated [Nb6I11] with alcohol solutions of Mg alcoholates result in the formation of the three new hexanuclear Nb cluster compounds [Nb6I8(HOCH3)6][Nb6(OCH3)18]·2CH3OH (1), (PPh4)2[Nb6(OC2H5)12I6]·C2H5OH (2) and (PPN)2[Nb6(OC2H5)12I6] (3). They contain cluster anions, which have the edges of the Nb6 octahedra, i.e. the inner coordination sites, μ2-bridged by the O atoms of methanolato or ethanolato ligands. Thereby, they represent further characterized members of the so far very small group of hexanuclear cluster alcoholates. The terminal metal sites are bonded to further methanolato (1) or iodido ligands (2 and 3). Sterically demanding organic cations (PPh4+, PPN+, 2 and 3) or a cationic Nb6 cluster complex with terminal methanol ligands [Nb6I8(HOCH3)6]2+ in 1 compensate the negative charges of the cluster anions. Compound 1 is the first example of a M6 cluster ion pair of both the text-book known edge-bridged [M6X12] and face-bridged [M6X8] cluster units. The structures of the three title compounds were determined by means of single-crystal X-ray structure analysis.