A new carbyne ligand; synthesis of novel MIV(M = Mo, W) complexes containing terminal halogenomethylidyne ligands: X-ray crystallographic characterisation of η1-chloromethylidyne(dicarbonyl)[tetrakis(1-pyrazolyl)borato]molybdenum(IV)

Oxidation of the poly(1-pyrazolyl)borato complexes [M(CO)3{HB(3,5-Me2-C3HN2)3}]–(M = Mo, W) with either [ArN2]+(Ar = aryl) or [Ph2l]+ in the presence of a source of dihalogenoalkyl radicals leads to the formation of the η1-halogenomethylidyne complexes [Mo(η1-CX)(CO)2{HB(3,5-Me2-C3HN2)3}](X = Cl, Br, and I) and [W(η1-CCl)(CO)2{HB(3,5-Me2-C3HN2)3}]; a closely related complex, {Mo(η1-CCl)(CO)2{B(C3H3N2)4}] has been characterised by X-ray crystallographic methods.