THE 1ST OBSERVATION OF GAMMA-OCTAMOLYBDATE - SYNTHESIS, CRYSTAL AND MOLECULAR-STRUCTURE OF [ME3N(CH2)6NME3]2[MO8O26].2H2O

The compound [Me3N(CH2)6NMe3]2[Mo8O26].2H2O crystallizes from an aqueous solution of sodium molybdate and [Me3N(CH2)6NMe3]Cl2, slightly acidified with hydrochloric acid. The crystals are monoclinic, space group P2(1)/n with a = 12.42(1), b = 12.897(3), c = 15.74(1) angstrom, beta = 106.41(5)-degrees and Z = 2. The structure was determined by direct methods and refined by least squares to R = 0.030 for 3153 observed reflections and 315 parameters. The [Mo8O26]4- anion is composed of six MoO6 octahedra interlinked along edges and two MoO5 trigonal bipyramids each sharing two edges with the octahedra. This is different from the previously observed alpha and beta-isomers of [Mo8O26]4- and lends credance to one of the proposed mechanisms for their interconversion.