Reduction of alkyl halides by homonuclear bridging hydride, (μH)[(n5-MeCp)Mn(CO)2]2-PPN+ 1

초록

Alkyl halides were reduced to the corresponding alkanes by the homonuclear bridging hydride, (μ-H)[n5-MeCp)Mn (CO)<inf>2</inf>]<inf>2</inf>-PPN+ in THF at the elevated temperatures (40°-60 °C) under the pseudo first order reaction conditions where excess of alkyl halide was employed under nitrogen atmosphere. The reaction is of overall second order; first order with respect to [bridging hydride] and first order with respect to [alkyl halide] with the activation parameters, ΔH# = 28.93 kcal/mol and ΔS# = 17.95 e.u. The kinetic data, the ESR evidence and the reaction with cyclopropyl canbinyl bromide ensure that two possible reaction pathways are operable in this reaction: (1) concerted mechanism, and (2) single electron transfer pathway are in competition leading to the same product, the corresponding alkane.