(η6-Bromoarene)Mn(CO)3+ Complexes: Synthesis and Applications to the Functionalization of (η5-Cyclohexadienyl)Mn(CO)3 Complexes by Halogen−Metal Exchange Reaction

(η6-Bromoarene)Mn(CO)3+ complexes substituted by methoxy or silyl groups were easily prepared in good to excellent yields, and the molecular structure of [(η6-1-bromo-4-methoxybenzene)Mn(CO)3]+BF4− has been determined by X-ray crystallography. Nucleophilic additions of LiAlH4 or PhMgCl delivered the corresponding neutral (η5-bromocyclohexadienyl)Mn(CO)3 complexes. Using ClCO2Et and DMF as electrophiles, bromide substitution was achieved by metal−halogen exchange reaction applied to the (η5-bromocyclohexadienyl)Mn(CO)3 complexes and allows the regioselective functionalization of the η5-cyclohexadienyl ligand when the two substituents of the starting complex are not adjacent. Furthermore the synthesis of the first (η5-cyclohexadienyl)Mn(CO)3 complexes substituted at one of the extremities of the π-system by a formyl group and the X-ray analysis of one of them emphasized the excellent agreement between the structural and energetic data obtained in the present work and the computed results already reported.