Structures of some hexacarbonyl-(π-dienyl)iron–cobalt complexes, [(π-ring)Fe(CO)2Co(CO)4], and the ruthenium compound [(π-C5H5)Ru(CO)2Co(CO)4]

The i.r. spectra of the [(π-ring)Fe(CO)2Co(CO)4] complexes [ring = C5H5, MeC5H4, and C9H7(indenyl)] have been investigated. In the solid state, the iron derivatives exist as carbonyl-bridged species which probably possess puckered di-µ-carbonyl bridging systems between the metal atoms. In solution, one non-bridged (nb) and two bridged (b) isomers are present. The proportions of the nb forms decrease with decreasing temperature, in polar solvents, and along the series C5H5 > MeC5H4 > C9H7. Only the nb form of the ruthenium compound has been observed.