The syntheses and structures of mono- and di-bromovinylidenes

Reactions of metal acetylide complexes M(Ctriple bond; length of mdashCAr)(PP)Cp′ (M = Fe, Ru; Ar = C6H5, C6H4Me-4; PP = (PPh3)2, dppe; Cp′ = Cp, Cp*; not all combinations), or the analogous vinylidene, with cyanogen bromide yield monobromovinylidene complexes [M{Cdouble bond; length as m-dashC(Br)Ar}(PP)Cp′]+, isolated as PF6− salts. The trimethylsilyl-capped acetylides M(Ctriple bond; length of mdashCSiMe3)(PP)Cp′ react with cyanogen bromide to give [M(Cdouble bond; length as m-dashCBr2)(PP)Cp′]+, the first examples of metal complexes containing a terminal dihalovinylidene ligand, which can be isolated as the BF4− salts. Molecular structures of representative mono- and di-bromovinylidene complexes are reported, together with those of Ru(Ctriple bond; length of mdashCSiMe3)(PPh3)2Cp and Ru(Ctriple bond; length of mdashCSiMe3)(dppe)Cp*.