Effect of fluorine and trifluoromethyl substitution on the donor properties and stereodynamical behaviour of triarylphosphines

A series of 2-, 3- or 4-trifluoromethyl substituted triarylphosphines and their oxide, chalcogenide and Fe(CO)4 derivatives have been prepared and characterised spectroscopically and crystallographically. Electronic effects of CF3 substitution are cumulative and felt equally in the 2, 3 or 4 position. Substitution in the 2 position substantially hinders the complexing ability for steric reasons. Correlated P–C rotation in the 2-substituted derivatives has been analysed by variable temperature NMR and molecular mechanics calculations.