Rh(i) and Ru(ii) phosphaamidine and phosphaguanidine (1,3-P,N) complexes and their activity for CO2 hydrogenation.

Phosphaamidine metal complexes Rh2Cl2[Ph2PC(Ph)[double bond, length as m-dash]NPh]2μ-CO (1), RuCl2[Ph2PC(Ph)[double bond, length as m-dash]N(Ph)]2 (2), [Rh{iPr2PC(Ph)[double bond, length as m-dash]NiPr}(COD)]BF4 (3), and RuCl2[iPr2PC(Ph)[double bond, length as m-dash]NiPr](DMSO)2 (4) are prepared by combining phosphaamidines Ph2P-C(Ph)[double bond, length as m-dash]NPh and iPr2P-C(Ph)[double bond, length as m-dash]NiPr (1,3-P,N) with their corresponding metal ions. Complexes 1 and 2 are stable in air while 3 and 4 are stable under inert conditions. For further comparison of structure and stability, a Ru(ii) phosphaguanidine complex, RuCl2[Me2NC(PPh2)[double bond, length as m-dash]NiPr](DMSO)2 (6) was prepared. Complex 6 is stable in air and in the presence of water. The structures of the phosphaamidine and phosphaguanidine complexes, determined using single crystal X-ray diffraction, revealed P,N bidentate coordination. While all five complexes have some activity as precatalysts, complex 6 was the most active.