An Efficient Synthesis of Acetylide/Trimetal/Acetylide Molecular Wires

Efficient syntheses are reported for incorporating trimetal units of the type M3(dpa)42+ (M = Cr, Co, Ni, and dpa = 2,2‘-dipyridylamide) into polyalkynyl assemblies to give the prototypical bis-phenylacetylide complexes M3(dpa)4(CCPh)2. Reactions of M3(dpa)4Cl2 with LiCCPh have led only to mixtures of products which cocrystallize forming materials of the composition M3(dpa)4(CCPh)xCl2-x. Here we report that acetonitrile complexes [M3(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 [Co3(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.