Kinetics and mechanism of substitution reaction of PPN+(η5-MeCp)Mn(CO)2Cl- with PR3 (R=Me, Et, OEt, C6H5)

초록

The transition metal carbonylate, PPN+(η5-MeCp)Mn(CO)<inf>2</inf>Cl- undergoes a novel ligand substitution reaction with PR<inf>3</inf> (R=Me, Et, OEt, C<inf>6</inf>H<inf>5</inf>) in THF at elevated temperatures (40 °C up to 60 °C) under the pseudo-first-order reaction conditions (usually 20-fold excess of PR<inf>3</inf> with respect to metal carbonylate concentrations) where chloride is displaced by PR<inf>3</inf>. The reaction follows overall first order dependence on [(η5-MeCp)Mn(CO)<inf>2</inf>Cl-]; however, the negative entropy changes of activation (ΔS≠ = -19.3 e.u. for P(OEt)<inf>3</inf>; ΔS≠ = -16.4 e.u. for PPh<inf>3</inf>) suggest the existence of the intermediate, (η3-MeCp)Mn(CO)<inf>2</inf>(THF)Cl-, which eventually transforms to the product (η5-MeCp)Mn(CO)<inf>2</inf>(PR<inf>3</inf>).