Synthesis and Structure of Raft-Type Molybdenum Chalcogenide Clusters

Abstract

Tetranuclear molybdenum cluster complexes [Mo4S6X2(PMe3)6] (X = SH, Cl, Br, I, NCS) and [Mo 4 S 6 (dtc)2(PMe3)4] have been synthesized. They have rhombic metal cores of molybdenum atoms in +3.5 oxidation state with 10 cluster valence electrons. Hexanuclear molybdenum cluster complexes [Mo6E8Cl6(PEt3)6] (E = S, Se) with 14 cluster valence electrons form by reduction of the trinuclear cluster complexes with six cluster valence electrons. An intermediate seven-electron cluster complex [Mo3S4Cl3(dppe)2(PEt3)] has been isolated. The X-ray structures of these cluster complexes are described.Chemistry of molybdenum chalcogenide cluster complexes has made a remarkable progress in the last decade with the discoveries of cluster compounds of various types (7-7). A number of compounds with triangular and cuboidal cluster cores are now known but relatively few cluster compounds with raft-type frameworks have been reported. Hie raft structures are built from triangular cores by fusion of the edges. The simplest one is a tetranuclear rhombus and a pentanuclear trapezoid and a hexanuclear parallelogram are also found. Although there have been several examples of such tetranuclear clusters of other metals, there are still a very limited number of molybdenum chalcogenide clusters. The present article is concerned with synthesis and structural characterization of a few tetranuclear and hexanuclear cluster complexes coordinated by trialkylphosphines. Apart of the results have been published previously (28, 29, 35). Tetranuclear Cluster ComplexesSynthesis. The reaction of (NH4)2Mo3Si3 (8) dissolved in butylamine and a THF 0097-6156/96/0653-0240$15. 00/0