Structure, bonding and formation of molecular germanium oxides, hydroxidesand oxyhydroxides

Molecular germanium oxides, hydroxides and oxyhydroxides were studied by me ans of density functional theory. The polymerization reactions of GeO and G eO2 were found exothermic up to the tetramer, and possible product structur es were characterized. Important features are the instability of larger rin g structures, and how Ge2O2 rings become important building blocks, indepen dently on whether the long-range order resembles clusters or chains. This u nit is proposed to provide a clue to the unknown bulk structure of GeO(s). Water additions to both (GeO)(n), and (GeO2)(n) polymers are investigated. The reactions with Ge=O bonds are found exothermic by 230-250 kJ/mol, while similar water additions to Ge-O-Ge bridges are exothermic only when reacti ng with one of the bridges in the strained Ge2O2 ring. Reactions with large r clusters as well as further fragmentation are found slightly endothermic. The most stable product of water addition to Ge2O4 is (HO)(3)GeOGe(OH)(3), which has one Ge-O-Ge bridge and two intramolecular hydrogen bonds. In add ition, structures and stabilities of the 'odd' oxides Ge2O, Ge2O3, Ge3O4 an d GeO3 are investigated. (C) 1999 Elsevier Science B.V. All rights reserved .