PNNL

Abstract

Hydride transfer from Cp(CO)2(PPh3)MoH to Ph3C+ BAr'4 [Ar' = 3,5-bis(trifluoromethyl)phenyl] produces [Cp(CO)2(?3 PPh3)Mo]+[BAr'4] . Spectroscopic and crystallographic data indicate that one C=C of a Ph ring is weakly bound to the Mo, so that the PPh3 ligand is four-electron donor ligand. Computations (DFT/B3LYP and MP2 on [Cp(CO)2(?3 PPh3)Mo]+ and [Cp(CO)2(?3 PH2Ph)Mo]+, and DFT/B3LYP on [Cp(CO)2(?3 PHtBuPh)Mo]+ and [Cp(CO)2(?3 PH2Ph)Nb]) provide further information on the bonding, and on the preference for bonding of the metal to the C=C bond rather than an agostic C H interaction found in many related complexes. The hemilabile C=C bond is readily displaced by CH3I or H2O, and crystal structures are reported for [Cp(CO)2(PPh3)Mo(ICH3)]+ and [Cp(CO)2(PPh3)Mo(OH2)]+. The equilibrium constant for [Cp(CO)2(?3 PPh3)Mo]+ + ICH3 to give [Cp(CO)2(PPh3)Mo(ICH3)]+ is Keq = 5.2 ? 102 M 1 in CD2Cl2 at 22 °C.