γ-Phosphino-ketimines Ph 2 PC[C(Me)O][C(Me)NAr] (Ar = 2,6-diisopropylphenyl, L 1 H; Ar = 2,6-difluorophenyl, L 2 H) were synthesized by treating deprotonated ketimines with PPh 2 Cl. Their Mg complexes [(L 1 ) 2 (THF)Mg] (1) and [(L 2 ) 2 (THF) 2 Mg] (2) were obtained in excellent yields from a reaction between LH and di-nbutylmagnesium in THF. Addition of a slight excess of trimethylaluminum to LH in toluene yielded the Al complexes [L 1 AlMe 2 ] ( 3) and [L 2 AlMe 2 ] (4). Complexes 1 and 3 displayed high catalytic activity in the synthesis of cyclic carbonates from CO 2 and epoxides and also in the ring-opening polymerization (ROP) of ε-caprolactone. However, complexes 2 and 4, which contain fluoro substituents, showed poor activity in the synthesis of cyclic carbonates and could not initiate the ROP reaction. The pentacoordinated Mg complex 1 was found to be a better catalyst than the aluminum complex 3. It was also observed that the complexes 1 and 3 were more efficient than the unsubstituted ketiminate complexes reported in the literature.