65521-62-2Relevant academic research and scientific papers
Chemical reduction of bis[bis(diphenylphosphino)ethane]rhodium(1+), [Rh(dppe)2]+. Characterization of Rh(dppe)20 and Rh(dppe)2-
Kunin, Amanda J.,Nanni, Edward J.,Eisenberg, Richard
, p. 1852 - 1856 (2008/10/08)
The reduction of bis[bis(diphenylphosphino)ethane]rhodium(1+), [Rh(dppe)2]+, has been reexamined, employing a purely chemical approach. The reduction is found to proceed in two discrete single-electron steps, with initial formation of Rh(dppe)20, followed by reduction to Rh(dppe)2-. In dry benzene, Rh(dppe)2+ is reduced with 1 equiv of sodium naphthalenide (NaNp) to yield an extremely air-sensitive solution that shows a strong EPR signal with coupling to four equivalent phosphorus atoms, assigned to Rh(dppe)20. Further reduction with NaNp yields Rh(dppe)2-, characterized by NMR and by chemical quenching experiments. The fully reduced species Rh(dppe)2- reacts with proton sources by acid-base chemistry to produce RhH(dppe)2, while Rh(dppe)20 is inert to reaction with MeOH, CH3CN, cumene, and triphenylmethane. A kinetic barrier to H atom transfer exists as shown by the lack of reaction between Rh(dppe)20 and Ph3CH and between RhH(dppe)2 and Ph3C· radical. Through variation of solvent and temperature conditions, the intermediate d9 Rh(0) species is found to be in equilibrium with Rh(dppe)2+ and Rh(dppe)2-. In toluene, the Rh(dppe)20 species is found to be fluxional on the EPR time scale.
