THE VIBRATIONAL-SPECTRA OF COBALT AND IRON CYCLIDENE DIOXYGEN COMPLEXES AND THEIR RELATION TO MOLECULAR-GEOMETRY

Infrared spectra were obtained for dioxygen adducts of a series of cob alt(II) and iron(II) cyclidene complexes with 1-methylimidazole as the axial base. The nu(O-O) bands were located in the range 1137-1163 cm- 1, and their identity was confirmed by O-18(2) isotopic substitution. The frequency was found to be insensitive of the metal ion but depende nt on both the sigma and pi electron donating properties of the cyclid ene ligands. There is no apparent correlation between nu(O-O) and the oxygen affinity; nu(O-O) alternates with the even or odd number of car bon atoms in the bridging polymethylene group because of a symmetry ef fect on the pi electron system of the ligand.