Unsymmetric Mononuclear and Bridged Dinuclear CoIII(cyclam) Acetylides

Reported herein are the preparation and characterization of a new trans-bis­(acetylide) complex of CoIII(cyclam) (cyclam = 1,4,8,11-tetraazacyclotetradecane) bearing two different acetylide ligands (1) and the first example of an all-carbon (C4) bridged dinuclear Co species (2). Structural features of monomeric 1 and dimeric 2 are similar to those of the previously reported CoIII(cyclam) bis­(acetylides), and the CC and C–C bond lengths of the butadiynediyl bridge in 2 conform to the acetylenic resonance form. The Co centers in the bridged complex 2 do not exhibit a measurable electronic coupling, as revealed by voltammetric measurements, and this behavior is rationalized through the DFT analysis of complexes 1 and 2.