TRANSITION-METAL METHYLENE COMPLEXES .5. PREPARATION AND UNUSUAL REARRANGEMENT OF TRIPLY BRIDGED MU-HETEROMETHYLENECOBALT COMPLEXES - MOLECULAR-STRUCTURE OF MU-ETHOXYCARBONYLMETHYLENEBIS[CARBONYL-(ETA-5-CYCLOPENTADIENYL)COBALT](CO-CO)

the μ-heteromethylenecobalt complexes, which have been synthesized by photolysis of (η5-C5H5)Co(CO)2 in the presence of the corresponding diazoacetates at < -90°C in tetrahydrofuran, undergo a novel type of intramolecular irreversible rearrangement yielding two isomers. The structure of one of the isomers has been established by X-ray analysis. A comparison of the structural parameters of all known μ-methylene-transition metal complexes shows that the internal angles α of the cyclopropane-like systems are far less sensitive to the compositions and structures of the molecules than the external angles β. The internal angles cannot be readily correlated with other features of the molecule. © 1979.