Synthesis, structure and properties of mononuclear and dinuclear molybdenum(III) bromide compounds. Ligand-induced, reversible breakage of a metal-metal bond in Mo 2Br 6(dppe) 2

Abstract

MoBr 3(THF) 3 reacts with 1 equivalent of bis(diphenylphosphino)ethane (dppe) in THF to yield MoBr 3(dppe)(THF) ( 1). The THF ligand in the latter molecule can be easily replaced by MeCN to afford MoBr 3(dppe)(MeCN) ( 2). When treated in a non-donor solvent, 1 loses THF and dimerizes to one of two isomeric Mo 2Br 6(dppe) 2 molecules (green, 3, kinetic product; purple, 4, thermodynamic product) depending on experimental conditions. An X-ray analysis of 4 shows an edge-sharing bioctahedral structure and the presence of a MoMo bond. Both 3 and 4 can be reconverted to the parent compound 1 by warming in the presence of excess THF. Compound 2 can also be transformed into the dinuclear compound 4.