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

Abstract

This paper collects the results obtained in different studies on the interaction of the CO 2 molecule with transition metal atoms, using matrix isolation FTIR spectroscopy and density functional theory (DFT). Late-transition metal atoms (Fe, Co, Ni and Cu) form one-to-one M(CO 2) complexes, while those from the left-hand side in the periodic table (Ti, V, and Cr) insert spontaneously into a CO bond yielding oxocarbonyl species. Owing to isotopic experiments with 13CO 2 and C 18O 2, these results allow spectroscopic identification of carbon dioxide bonding modes in organometallic species containing CO 2 moiety. Special attention is paid to the interaction of CO 2 molecule with Ni and Ti atoms. In neat CO 2 matrices, it is shown that CO 2 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 after annealing. Interestingly, the coordination of CO 2 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 NiN 2 moiety with CO 2. The binding energy is then 32 kcal mol −1. DFT calculations 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 possible Ti(CO 2) complexes and reactive towards CO 2. An intrinsic reaction path for the insertion process is investigated.