CO₂ Coordination to Nickel Atoms:  Matrix Isolation and Density Functional Studies

The interaction of the CO 2 molecule with nickel atoms was studied by using matrix isolation spectroscopy and density functional theory. In argon dilute matrices, no reaction occurs, even after annealing the deposit. In neat CO 2 matrices, it is shown that carbon dioxide forms a 1:1 complex with nickel which is characterized by its UV−visible and FTIR absorptions, including isotopically labeled species. Theory predicts the side-on coordination mode to be the most stable. The binding energy of the side-on Ni(CO 2 ) complex is estimated to be 18 kcal/mol. The calculated OCO angle is 145°, which is quite a large value compared to those encountered in other known CO 2 complexes. In dinitrogen matrices, the yield of CO 2 complexation is considerably enhanced relative to that in argon dilute and neat CO 2 matrices, which is attributed to the formation of unsaturated Ni(N 2 ) n complexes prior to CO 2 coordination. The CO 2 binding energies calculated for the Ni(CO 2 )(N 2 ) n ( n = 1, 2) complexes (respectively 32 and 4 kcal/mol) suggest that CO 2 probably coordinates to the Ni(N 2 ) complex. This is a very interesting result, owing to the fact that CO 2 does not react with nickel atoms in dilute argon matrices.