Aminorhenium carbon dioxide complexes: formal oxidation of a carbon monoxide ligand with peroxy-acids or bromine/hydroxide

Abstract

The electron-rich aminorhenium complexes η 5:η 1-C 5H 4CH 2CH 2NR(CH 3)Re(CO) 2 ( 3a– d; R=methyl, benzyl, n-butyl, n-butyl-OH) are easily oxidized with peroxy-acids to give the corresponding η 2-CO 2 complexes η 5: η 1- C 5H 4CH 2CH 2NR(CH 3)Re(CO)(η 2-CO 2) ( 4a– d) in excellent yield. The resultant η 2-CO 2 complex is predominantly the anti-isomer. The structures of η 2-CO 2 complex η 5:η 1-C 5H 4CH 2CH 2N(CH 3)( n- C 4H 8OH)Re(CO)(η 2-CO 2) ( 4d-anti) and the corresponding CO complex 3d have been confirmed by X-ray crystallography. The η 2-CO 2 complexes 4a– 4d are stable at ambient temperature under air. In addition to peroxy-acid oxidation, bromination of the aminorhenium dicarbonyl complexes followed by base treatment also provided the corresponding η 2-CO 2 complexes. The reaction mechanism for the formation of CO 2 complex from the corresponding dicarbonyl is discussed briefly.