Interaction of Co(CO)(x) with surface sites of SiO2: theoretical study

The interaction of Co(CO)(4) and Co(CO)(3) species with silica surface was modeled by a non-local density functional method. The geometries of the cob alt carbonyl complexes interacting with the silica surface via Si-Co, Si-O- C-Co and Si-O-Co bonds were optimised, and the interaction energies were ca lculated. The results of the adsorbate models and the surface complexes bon ded via Si-Co bonds were found to be in agreement with previously published theoretical data and with available experimental findings. According to ou r results, cobalt carbonyl species form strong bonds with silica sites and are plausible surface complexes. Bonding via carbonyl ligand was the weakes t type of interaction, while bonding via surface oxygen was the strongest. The interaction energies of charged species were higher than those of the r adical species. The bond distances between cobalt and its nearest neighbour s decreased when there were fewer carbonyl ligands in the complex. The inte raction energies and the bond distances between cobalt and its nearest neig hbours correlated with the charge of the central cobalt atom. (C) 2000 Else vier Science B.V. All rights reserved.