Preparation of dimolybdenum carbonyl and ditungsten carbonyl complexes containing triple fluoro bridges

Abstract

The reaction of [WH₆(PMe₂Ph)₃] with HBF₄·OEt₂, under an atmosphere of carbon monoxide, in tetrahydrofuran gives [{W(CO)₂(PMe₂Ph)₂}₂(µ-F)₃]BF₄. The X-ray crystal structure of this compound reveals that the geometry about each tungsten atom is best considered as having a basal plane containing three fluorine atoms, (W–F)_av 2.12(1)Å, with the reamining four ligands (two carbon monoxide and two phosphines) forming a second, parallel plane, in which the two carbon monoxide ligands are mutually trans, (W–C)_av 1.949(6)Å, as are the two phosphines, (W–P)_av 2.457(1)Å. The spectroscopic characteristics of [{W(CO)₂(PMe₂Ph)₂}₂(µ-F)₃]⁺ are discussed and from this the nature of species formed in the reactions of [MoH₄(PR₃)₄](R₃= Et₃ or MePh₂) with HBF₄·OEt₂ under an atmosphere of carbon monoxide can be inferred.