Terminal aminophosphinidene complexes of iron, ruthenium, and osmium

The chloroaminophosphido complexes [CP*M(CO)(2){P(Cl)(NPr2)-Pr-i}] (1, M = Fe; 2, M = Ru; 3, M = Os), formed by the reaction Of [CP*M(CO)(2)](-) with (Pr2NPCl2)-Pr-i, undergo abstraction of chloride by aluminum trichloride, affording isolable, thermally stable, cationic terminal aminophosphinidene complexes [Cp*M(CO)(2){(PNPr2)-Pr-i}] [AlCl4] (4, M = Fe; 5, M = Ru; 6, M = Os). The structures of all three complexes have been determined by single-crystal X-ray diffraction. The iron complex 4 has historical significance, having been spectroscopically detected at low temperature in 1984, prior to the description of the first stable eta(1)-phosphinidene complex, but not isolated or structurally characterized.