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

Molecular germanium oxides, hydroxides and oxyhydroxides were studied by means of density functional theory. The polymerization reactions of GeO and GeO2 were found exothermic up to the tetramer, and possible product structures were characterized. Important features are the instability of larger ring structures, and how Ge2O2 rings become important building blocks, independently on whether the long-range order resembles clusters or chains. This unit 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 reacting with one of the bridges in the strained Ge2O2 ring. Reactions with larger 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 addition, structures and stabilities of the 'odd' oxides Ge2O, Ge2O3, Ge3O4 and GeO3 are investigated. (C) 1999 Elsevier Science B.V. All rights reserved.