Molybdenum and tungsten methoxo clusters with differently bonded methoxo groups.: Crystal structure of [Na(CH3OH)5]2[Mo6(μ3-Br)8(OCH3)6]

New molybdenum and tungsten methoxo clusters of the composition [M-6(mu(3)-X)(8)X-2(mu-OCH3)(4/2)].2CH(3)OH (M = Mo, W; X = Cl, Br), [Mo-6(mu(3)-X)(8)(OCH3)(2)(mu-OCH3)(4/2)].CH3OH (X = Cl, Br) and [Na(CH3OH)(5)](2)[Mo-6(mu(3)-Br)(8)(OCH3)(6)] containing bridging (g), both bridging and terminal, or terminal methoxo groups, respectively, have been prepared. The preparation procedures, spectroscopic and physical properties, including X-ray photoelectron spectra (XPS) have been correlated. The crystal structure has been solved for [Na(CH3OH)(5)](2)[Mo-6(mu(3)-Br)(8)(OCH3)(6)]. The compound crystallizes in the triclinic crystal system. The structure is built of two [Na(CH3OH)(5)](+) cations and the [Mo-6(mu(3)-Br)(8)(OCH3)(6)](2-) anion. All six-oxygen atoms from coordinated methoxo groups are acceptors of hydrogen of coordinated methanol molecules from the six neighbouring cations making a three-dimensional packing network. (C) 2003 Elsevier Science Ltd. All rights reserved.