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

Multiple bonding in the terminal phosphido complex [Ru(PCy 2 )(η 5 -indenyl)(PPh 3 )] ( 2a ) is clearly demonstrated by solution, solid-state, and computational studies. Reactions of this dark blue, half-sandwich complex with CO, MeI, HNEt 3 Cl, HCl, NH 4 PF 6, H 2, and Et 3 SiH 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 PR 2 species (R = Pr i ( 2b ), Ph ( 2c ), Tol p ( 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(PAr 2 )(η 5 -indenyl)(CO)(PPh 3 )] ( 3c, d ), in which the Ru−P bond order is reduced to 1. Complex 2a and its analogue [Ru(PPr i 2 )(η 5 -indenyl)(PPh 3 )] ( 2b ) are consistently isolated with ∼15% of their structural isomers, the ruthenium hydrido phosphaalkenes 9a, b, resulting from an apparent 1,2-H shift.