Approximate force constants for tetrahedral metal carbonyls and nitrosyls

Article abstract of DOI:10.1021/ic50045a028

Approximate carbonyl and nitrosyl force constants have been calculated for the molecules in the tetrahedral isoelectronic series Mn(NO)₃(CO), Fe(NO)₂(CO)₂, Co(NO)(CO)₃, Ni(CO)₄, and their substituted derivatives. The required secular equations are given for species having two different oscillators. These force constants provide a quantitative means for comparing relative π-acceptor strengths of the substituent ligands. Explicit inclusion of the CN oscillator of isonitriles is shown to be important in derivatives of ligands of this type. Empirical relationships have been determined which allow the prediction of force constants and frequencies in substituted derivatives provided information on a related molecule is available.