Water-trimer clusters as nucleophilic reagents in hydrolyses of substratesfor metal-alkoxides - a computational study

Density-functional-theory calculations were performed to simulate hydrolysi s paths of eight metal-methoxides, M(OMe)(n) M = Al and Ga for n = 3, M = S i, Ge, Ti, and Zr for n = 4 and M = V and Nb for n = 5. Those paths are ini tial steps of the sol-gel process and were found to consist of substrates M (OMe), and water-trimer clusters, strain-free hydrogen-bond networks are co nstructed at transition states (TSs) and may cause ready bond interchanges, i.e., M-O bond cleavage and formation and switch of O-H covalent and O . . .H hydrogen bonds. TSs have zwitterionic characters and are stabilized sub stantially by the solvent effect, The calculated activation energies correl ate well with energies of the lowest unoccupied molecular orbitals accordin g to the frontier-orbital theory. (C) 2001 Elsevier Science B.V. All rights reserved.