Synthesis and Reactivity of (η5-Hydroxyalkylcyclohexadienyl)Mn(CO)3 Complexes

Abstract

(η5-1-Hydroxyalkylcyclohexadienyl)tricarbonylmanganese complexes 3a and 3b have been prepared, and their rearomatization delivered compounds 5 and 6, the first benzylic alcohol derivatives coordinated to the cationic Mn(CO)3 tripod. The structure of 5 has been determined by X-ray crystallography. 1-Hydroxyalkyl 3a, 7, 8, 2-hydroxyalkyl 19, 20, and 3-hydroxyalkyl 25, 26 (η5-cyclohexadienyl)tricarbonylmanganese complexes have been synthesized and studied toward trifluoroacetylation of the hydroxy group when submitted to the action of NEt3 and (CF3CO)2O. Only the 2-hydroxyalkyl-substituted complexes eclipsed by a Mn−CO bond of the Mn(CO)3 tripod gave the expected trifluoroacetate derivatives 21 and 22. For the 1-hydroxyalkyl-substituted complexes, elimination of the trifluoroacetoxy group took place followed by decoordination of the Mn(CO)3 moiety and trifluoroacetylation, giving rise to trifluoromethyltrienones 10, 11, and 12, whose stuctures were established by X-ray analysis. For 3-hydroxyalkyl-substituted complexes, elimination of the trifluoroacetoxy group also occurred, yielding free arenes 27 and 28 by decoordination of the Mn(CO)3 entity.