Reactions of CH bonds in organica oxygenates with octaethylporphyrinato rhodium(II) and iridium(II) dimers

Abstract

Metalloporphyrin dimers, [(OEP)M] 2 ( 1a , M = Rh; rm1b, M = Ir; OEP = Octaethylporphrin dianion ), are observed to react with CH bond units in aldehyes, kenotes and benzyl alohols. Aldehydes, R 2CHCHO, preferentially react at the alkyl group adjacent to the carbonyl position to yield β-formyl complexes, (OEP)M-CR 2CHO, even when reaction of the aldehydic CH unit is thermodynamically favored. Reaction at the carbon-hydrogen bond adjacent to the carbonyl group is proposed to occur by addition of the metalloporphyrin to the enol isomer to produce an intermediate alkyl bridged complex, (OEP)M-CR'(OH)-M(OEP), which subsequently reacts by an effective β-OH migration to form (OEP)M-CR 2C(O)R' and (OEP)M-H complexes. [(OEP)Rh] 2 also reacts with benzyl alcohols C 6H 5CH(OH)R (R = H, CH 3, C(O)C 6H 5), to produce intermediate α-hydroalkyl derivatives, (OEP)Rh-CR(OH)C 6H 5, which subsequently dissociate to give organic carbonyl species, C 6H[in5]C(O)R, and (OEP)Rh-H.