Enhanced reactivity of 2-rhodaoxetanes through a labile acetonitrile ligand

New cationic, square-planar, ethene complexes [(Rbpa)Rh-1(C2H4)](+) [2a](+) - [2c] (Rbpa = N-alkyl-N, N-di(2-pyridylmethyl)amine; [2a]-: alkyl = R = M e; [2b](+): R = Bu: [2c] R = Bz) have been selectively oxygenated in aceton itrile by aqueous hydrogen peroxide to 2-rhoda(III)oxetanes with a labile a cetonitrile ligand, [(Rbpa)Rh-III-(kappa (2)-C, O-CH2CH2O-)(MeCN)(+), [3a]( +)-[3c](+). The rate of elimination of acetal-dehyde from [(Rbpa)Rh-III(kap pa (2)-C, O-CH2-CH2O-)(MeCN)](+) increases in the order R = Me < R = Bu< R - Bz, Elimination of acetaldehyde from [(Bzbpa)Rh-III(kappa (2)-C,O-CH2CH2O )(MeCN)](+) [3c](+),in the presence of ethene results in regeneration of et hene complex [(Bzbpa)-Rh-I(C2H4,)](+) [2c](+), and closes a catalytic cycle . in the presence of Z,Z-1,5-cyclo-octadiene (cod) the corresponding cod co mplex [(Bzbpa)Rh-I(cod)](+) [6c]- is formed. Further oxidation of [3c](+) b y H2O2 results in the transient formyl-methyl-hydroxy complex [(Bzbpa)-Rh-I II(OH){kappa (1)-C-CH2C(O)H}](+) [5e](+).