Further studies of the metal–carbonyl bending vibrations of (π-ring)M(CO)2X derivatives of the first-row transition metals

The i.r. spectra of various (π-ring)M(CO)2X complexes of chromium, manganese, and iron have been investigated in the regions 225–700 and 1850–2100 cm–1. Absorption bands due to vibrations of the (π-ring)M(CO)2 moieties are reported and assigned. Trends in frequencies and relative intensities of those bands which are due largely to the δ(MCO) vibrations are discussed, and shown to depend on the ligand X.