Evaluation of the Stereoelectronic Parameters of Fluorinated Phosphorus(III) Ligands. The Quantitative Analysis of Ligand Effects (QALE)

Using the QALE model, we determined the QALE stereoelectronic parameters for the following ligands: P(CF 3 ) 3 (χ d = 33 ± 2, θ = 137 ± 13°, E ar = 0, π p = 11.1 ± 0.6), P(CH 2 CH 2 C 6 F 13 ) 3 (χ d = 9 ± 3, θ = 137 ± 2°, E ar = 0, π p = 2.5 ± 0.4), P[ p -(F 13 C 6 )C 6 H 4 ] 3 (χ d = 23 ± 1, θ = 145°, E ar = 2.7, π p = 0), and P(C 6 F 5 ) 3 (χ d = 34 ± 2, θ = 191 ± 13°, E ar = 4.3 ± 0.5, π p = 0). In addition, we evaluated the parameters for P[Pyr-3,4-(CO 2 Et) 2 ] 3 (Pyr = pyrrolyl; χ d = 43 ± 2, θ = 145°, E ar = 3.3, π p = 2 ± 1). Revised parameters for PF 3 are also presented: χ d = 33 ± 2, θ = 110 ± 24 °, E ar = 0, π p = 13.2 ± 0.5. The absence of an indicated error means that these values were assigned initially to the particular parameters in the analyses or that the parameters are statistically indistinguishable from zero. Where a comparison can be made, we find that our calculated values of θ are indistinguishable from those of Tolman; therefore, we suggest the continued use of Tolman's values. It is observed that the perfluoroalkyl groups are highly π acidifying and that this effect is transmitted through intervening CH 2 groups.