Theoretical study on the reaction mechanism of Sc atoms with carbon dioxide

B3LYP and CCSD(T) calculations with various basis sets show that the Sc + CO2 --> ScO + CO reaction can proceed by two distinct pathways, Se + CO2 --> (eta'-O)ScOCO --> (eta(2)-O, O)cyc-ScCO2 --> ScO + CO --> end-/side-OScCO with the largest barrier of 3.2 kcal/mol and barrier-less Sc + CO2 --> (eta(2)-C, O)(ScOC)O --> end-OScCO ScO --> + CO. The 'end-on* OSeCO complex bound by 7.2 kcal/mol relative to ScO + CO is predicted to be the dominant reaction product. The reaction is more than 30 kcal/mol exothermic and the Sc atom is expected to be efficient in reforming CO2 to carbon monoxide. (C) 2002 Published by Elsevier Science B.V.