Tautomerism in dienedicarbonylcobalt dimer complexes, [{Co(π-diene)-(CO)2}2]

Abstract

The i.r. spectra of [{Co(π-diene)(CO)₂}₂] complexes indicate that these contain a planar rather than a puckered Co(CO)₂Co bridge. Consequently they are isostructural with [{Fe(π-C₅H₅)(CO)₂}₂] and exhibit a similar tautomerism. Some exist in solution solely as the trans- or cis-bridged isomers, and others as mixtures of the two. Although these equilibria are partly solvent dependent, methyl substituents on the 2- and 3-carbon atoms of butadiene ligands have a much greater effect. This is attributed to steric interactions between these substituents which destabilise the cis-species.