A Highly Reactive Ruthenium Phosphido Complex Exhibiting Ru−P π-Bonding

Multiple bonding in the terminal phosphido complex [Ru(PCy2)(η5-indenyl)(PPh3)] (2a) is clearly
demonstrated by solution, solid-state, and computational studies. Reactions of this dark blue, half-sandwich
complex with CO, MeI, HNEt3Cl, HCl, NH4PF6, H2, and Et3SiH demonstrate an unusual range of behavior
resulting from combined coordinative unsaturation at Ru, high nucleophilicity/basicity of the phosphido
P, and π-character of the Ru−P interaction. The terminal, π-bound phosphido structure is general for a
range of PR2 species (R = Pri (2b), Ph (2c), Tolp (2d)). The very reactive diarylphosphido analogues
2c,d have been observed spectroscopically at low temperatures and can be trapped quantitatively as their
CO adducts, [Ru(PAr2)(η5-indenyl)(CO)(PPh3)] (3c,d), in which the Ru−P bond order is reduced to 1.
Complex 2a and its analogue [Ru(PPri2)(η5-indenyl)(PPh3)] (2b) are consistently isolated with ∼15% of
their structural isomers, the ruthenium hydrido phosphaalkenes 9a,b, resulting from an apparent 1,2-H
shift.