Spectroscopic studies on organometallic compounds. Part XII. Infrared spectra of tetracarbonylcobalt complexes in the carbonyl stretching region

Abstract

An analysis has been made of the carbonyl stretching frequencies of complexes of formula R₃MCo(CO)₄(M = Si, Ge, Sn, or Pb; R = Cl, Br, I, Me, Et, Ph, and MeO) and of some mixed derivatives R¹ ₂R²GeCo(CO)₄. Force constants have been calculated for these compounds, and for the complexes Fe(CO)₅, LFe(CO)₄(L = Et₃P and Ph₃P), using CO stretch–stretch interaction relationships derived from elementary bonding considerations. The force constants obtained show a linear dependence upon the Taft polarity constants of the groups attached to the particular ligand atom M.