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

Abstract

Phosphaamidine metal complexes Rh₂Cl₂[Ph₂PC(Ph)NPh]₂μ-CO (1), RuCl₂[Ph₂PC(Ph)N(Ph)]₂ (2), [Rh{ⁱPr₂PC(Ph)NⁱPr}(COD)]BF₄ (3), and RuCl₂[ⁱPr₂PC(Ph)NⁱPr](DMSO)₂ (4) are prepared by combining phosphaamidines Ph₂P-C(Ph)NPh and ⁱPr₂P-C(Ph)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)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.