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(CF3)(3) (chi (d) = 33 +/- 2, theta = 137 +/- 13 degrees, E-ar = 0, pi (p) = 11.1 +/- 0.6), P(CH2CH2C6F13)(3) (chi (d) = 9 +/- 3, theta = 137 +/- 2 degrees, E-ar = 0, pi (p) = 2.5 +/- 0.4), P[p-(F13C6)C6H4](3) (chi (d) = 23 +/- 1, theta = 145 degrees, E-ar = 2.7, pi (p) = 0), and P(C6F5)(3) (chi (d) = 34 +/- 2, theta = 191 +/- 13 degrees, E-ar = 4.3 +/- 0.5, pi (p) = 0). In addition, we evaluated the parameters for P[Pyr-3,4-(CO2Et)(2)](3) (Pyr = pyrrolyl; chi (d) = 43 +/- 2, theta = 145 degrees, E-ar = 3.3, pi (p) = 2 +/- 1). Revised parameters for PF3 are also presented: chi (d) = 33 +/- 2, theta = 110 +/- 24 degrees, E-ar = 0, pi (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 theta 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 pi acidifying and that this effect is transmitted through intervening CH2 groups.