An efficient synthesis of acetylide/trimetal/acetylide molecular wires

Efficient syntheses are reported for incorporating trimetal units of the type M-3(dpa)(4)(2+) (M = Cr, Co, Ni, and dpa = 2,2'-dipyridylamide) into polyalkynyl assemblies to give the prototypical bis-phenylacetylide complexes M-3(dpa)(4)(CCPh)(2). Reactions of M-3(dpa)(4)Cl-2 with LiCCPh have led only to mixtures of products which cocrystallize forming materials of the composition M-3(dpa)(4)(CCPh)(x)Cl2-x. Here we report that acetonitrile complexes [M-3(dpa)(4)(NCCH3)(2)]-(PF6)(2) react cleanly with LiCCPh in MeCN to afford the desired target molecules in 40-60% yield and in excellent purity. Isolation of the mixed ligand complex [Co-3(dpa)(4)(NCCH3)(CCPh)]PF6 has been accomplished, which suggests that these reactions are stepwise and that it will be possible to synthesize mixed acetylide complexes (i.e., M3- (dpa)(4)(CCR)(CCR')) via this method.