Kinetic Study of the Insertion and Deinsertion of Carbon Dioxide into <i>f</i><i>ac</i>-(CO)₃(dppe)MnOR Derivatives

The insertion of carbon dioxide into the Mn−O bond of fac-(CO)3(dppe)MnOCH3 (1) was observed to occur instantaneously at −78 °C by in situ infrared spectroscopy. The product of carboxylation of 1, fac-(CO)3(dppe)MnOC(O)OCH3 (2), underwent decarboxylation with a first-order rate constant of 1.49 × 10-4 s-1 at 23 °C. The kinetic parameters for this process were determined by trapping the intermediate produced upon CO2 extrusion, complex 1, with COS to provide the very stable fac-(CO)3(dppe)MnSC(O)OCH3 (3) derivative. The structure of 3 was determined by single-crystal X-ray diffraction analysis, establishing the presence of the Mn−S bond.