In addition to pioneering the cone angle concept, C. A. Tolman proposed a parameter (ch...

In addition to pioneering the cone angle concept, C. A. Tolman proposed a parameter (chi) as a measure of the electronic effect of phosphine and related ligands, based on infrared spectra of complexes containing these ligands (C. A. Tolman, J. Am. Chem. Soc. , 1970 , 92 , 2953).

a. What was the general formula of the complexes used by Tolman?

b. How was defined?

c. What types of ligands had high values of ?

d. To what extent does this approach distinguish between the sigma donor and pi acceptor nature of the ligands studied?