Reaction of a Rhodium(III) α-Chlorotolyl Complex with Water and Oxygen: Stable Rhodium Peroxo Compounds

Abstract

The reaction of the rhodium(III) α-chlorotolylcomplex [RhCl2(CHClPh)(2,6-(C(Me)N−i-Pr)2C5H3N)] (1) with H2O and O2 afforded the rhodium(III) chloride [RhCl3(2,6-(C(Me)N−i-Pr)2C5H3N)] (11), benzaldehyde, and H2O2 in 80−90% yield. This reaction proceeds via two reaction sequences. First, when O2 is absent the hydride complex [Rh(H)Cl2(2,6-(C(Me)N−i-Pr)2C5H3N)] (2), benzaldehyde, and HCl are formed. Hydrolysis of the metal-bonded CHClPh fragment gives a short-lived CH(OH)Ph moiety, which then by β-H elimination of the hydroxyl group affords the products. Alternatively, a rhodium carbene type of intermediate might be involved. The subsequent reaction sequence probably proceeds via two separate pathways. In the first one the hydride 2 may insert O2 to give a rhodium hydroperoxo species which converts with HCl to the Rh(III) complex 11 and H2O2. The second pathway appears to involve first the formation of the Rh(I) complex [RhCl(2,6-(C(Me)N−i-Pr)2C5H3N)] (8) from the hydride 2 in H2O, which subsequently reacts ...