PREPARATION OF DIMOLYBDENUM CARBONYL AND DITUNGSTEN CARBONYL-COMPLEXES CONTAINING TRIPLE FLUORO BRIDGES

The reaction of [WH6(PMe2Ph)3] with HBF4.OEt2, under an atmosphere of carbon monoxide, in tetrahydrofuran gives [{W(CO)2(PMe2Ph)2}2(mu-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) angstrom, with the remaining 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) angstrom, as are the two phosphines, (W-P)av 2.457(1) angstrom. The spectroscopic characteristics of [{W(CO)2(PMe2Ph)2}2(mu-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.