Metal vapor synthesis, chemical oxidation, and electrochemistry of bis(bipyridyl)cobalt(0). Preparation of bromide, tetracyanoethylene, and tetracyanoquinodimethane salts

Article abstract of DOI:10.1021/ic50225a010

The first preparation of bis(2,2′-bipyridyl)cobalt [Co(bpy)₂] has been carried out by metal vapor methods. Three techniques have been employed: (a) solution, (b) cocondensation, and (c) the use of toluene-solvated Co atoms. Method c was preferred. Spectral analysis of Co(bpy)₂ suggests that substantial Co → bpy charge transfer has taken place. Chemical oxidations with Br₂, tetracyanoquinodimethane (TCNQ), and tetracyanoethylene (TCNE) have yielded (bpy)₂CoBr with the bpy ligands highly negative, (bpy)₂Co(TCNQ)₂ with the bpy ligands neutral and the TCNQ ligands highly negative, and (bpy)Co(TCNE) with one bpy displaced and the other neutral. It appears that the TCNE ligand bears high negative charge. Cyclic voltammetric behavior of Co(bpy)₂ suggests that in acetonitrile a disproportionation reaction to produce Co(bpy)₂^- and Co(bpy)₂⁺·sol takes place. The electrochemical redox behavior then shows similarities to that of Co(bpy)₃²⁺; that is, a series of facile, reversible electron-transfer processes are observed. Overall, (bpy)₂Co appears to be a useful new Co(0) intermediate.