Geometries of transition metal complexes containing simple alkenes

The results of precise X-ray studies of the fumaronitrile complex of hydridocarbonylbis(triphenylphosphine)iridium and of the tetracyanoethylene complex of bromocarbonylbis(triphenylphosphine) iridium are presented and detailed comparisons are made with the results on other simple olefin-metal structures available in the literature.