Steric and electronic factors that control two-electron processes between metal carbonyl cations and anions

Reactions of metal carbonyl cations (Mn(CO){sub 6}{sup +}, Re(CO){sub 6}{sup +}, Mn(CO){sub 5}PPh{sub 3}{sup +}, Mn(CO){sub 4}(PPh{sub 3}){sub 2}{sup +}, Mn(CO){sub 5}PEt{sub 3}{sup +}, Mn(CO){sub 5}PPh{sub 2}Me{sup +}, Re(CO){sub 5}PPh{sub 3}{sup +}, and CpFe(CO){sub 3}{sup +}) with metal carbonyl anions (Co(CO){sub 3}PPh{sub 3}{sup {minus}}, Co(CO){sub 4}{sup {minus}}, Mn(CO){sub 5}{sup {minus}}, Mn(CO){sub 4}PPh{sub 3}{sup {minus}}, Mn(CO){sub 4}PEt{sub 3}{sup {minus}}, Mn(CO){sub 4}PPh{sub 2}Me{sup {minus}}, Mn(CO){sub 3}(PPh{sub 3}){sub 2}{sup {minus}}, CpFe(CO){sub 2}{sup {minus}}, Re(CO){sub 5}{sup {minus}}, and Re(CO){sub 4}PPh{sub 3}{sup {minus}}) are reported. Peak potentials are reported for all ions, and nucleophilicities (as measured by reaction with MeI) are reported for the anions. In over half of the reactions between metal carbonyl cations and anions, a two-electron change results in a new metal carbonyl cation and anion. The kinetic and thermodynamic driving forces and the suggested mechanism are examined.