Carbon dioxide interaction with metal atoms: matrix isolation spectroscopic study and DFT calculations

This paper collects the results obtained in different studies on the intera ction of the CO2 molecule with transition metal atoms, using matrix isolati on FTIR spectroscopy and density functional theory (DFT). Late-transition m etal atoms (Fe, Co, Ni and Cu) form one-to-one M(CO2) complexes, while thos e from the left-hand side in the periodic table (Ti, V, and Cr) insert spon taneously into a CO bond yielding oxocarbonyl species. Owing to isotopic ex periments with (CO2)-C-13 and (CO2)-O-18, these results allow spectroscopic identification of carbon dioxide bonding modes in organometallic species c ontaining CO2 moiety. Special attention is paid to the interaction of CO2 m olecule with Ni and Ti atoms. In neat CO2 matrices, it is shown that CO2 is side-on coordinated to nickel in a 1:1 complex. The binding energy is weak (18 kcal mol(-1)). In argon diluted matrices, no reaction occurs, even aft er annealing. Interestingly, the coordination of CO2 is promoted by adding N-2 in the rare gas matrix. This is rationalized by comparing the potential energy curves corresponding to the interaction of the Ni atom or the NiN2 moiety with CO2. The binding energy is then 32 kcal mol(-1). DFT calculatio ns show that Ti inserts with no energy barrier into a CO bond, resulting in an OTiCO insertion product, which is far more stable than any of the possi ble Ti(CO2) complexes and reactive towards CO2. An intrinsic reaction path for the insertion process is investigated. (C) 1999 Elsevier Science S.A. A ll rights reserved.