Assessing the stereoelectronic properties of pyrrolyl phosphines and related ligands. The quantitative analysis of ligand effects (QALE)
Abstract
By application of the QALE model (quantitative analysis of ° values) and the standard enthalpies of
°) of the η-Cp(CO)(PZ3)Fe(COMe)+/0 couple (PZ3 = a phosphorus(III)
p-XC6H4)3, P(OR)3, and P(O-p-XC6H4)3. The parameters for P(Pyr)3 are χd = 31.9 ± 0.7, θ = 145 ± 3, Ear = 3.3 ± 0.2 and πp = 1.9 ± 0.2; and for P(NC4H8)3 the parameters are χd = −1.2 ± 1.4, θ = 145 ± 5, Ear = −0.6 ± 0.4 and πp = 0.9 ± 0.3. P(Pyr)3 is a poor σ donor that possesses an Ear parameter comparable to P(
p-XC6H4)3 and a π acidity that is about two thirds that of P(OR)3 and half that of P(O-p-XC6H4)3. On the other hand, P(NC4H8)3, which is one of the strongest σ donor phosphorus(III)
p-XC6H4)3.