Preparation and reactivity of new dioxygen adducts of rhodium containing phosphine ligands.

The rhodium(I) complexes [Rh(LL)(NBD)]BF4 and [Rh(LL)]BF4 (LL=diphosphines, bidentate phosphorus and sulfur or nitrogen ligands) react with dioxygen to give 1:1 adducts of various stabilities, the ligands being stable towards oxidation. The mononuclear [Rh(dppe)(H2O)O2]BF4, which has been isolated in the solid state, oxidizes inorganic oxides (SO2, N2O4) in stoichiometric reactions giving the corresponding sulfato and di-nitrato derivatives, respectively, as solid compounds. The [Rh(LL)O2]+ cations also catalyze the aldol-condensation of acetone. ESR studies on the essentially diamagnetic [Rh(dppe)H2O)O2]BF4 complex show the presence of significant amounts of a paramagnetic rhodium(II)-superoxide species