Theoretical study of electrophilic versus nucleophilic character of transition metal complexes of phosphinidene

A comparative theoretical study of the terminal phosphinidene complexes HPCr(CO)₅, HPTi(Cp₂) and HPTiCl₂, at the MP2 and DFT levels, has been carried out. The calculated results have then been used for determining the electron localization function (ELF) in these moieties. Both techniques show that in the singlet ground state of HPCr(CO)₅, one gets a weak double P-Cr bond, with an electrophilic character on P (i.e. electron-deficient center). Conversely, in the singlet ground state of Ti complexes, the P-Ti bond shows a greater double bond character than in the P-Cr linkage, associated with an overall nucleophilic character of P. These results are in good agreement with all available experimental data.