Olation
At low pH, many metal ions exist in aqueous solution as aqua coordination complexes, often with the formula [M(HO)]. As the pH increases, one O-H bond ionizes to give the hydroxide complex, the conjugate base of the parent hexaaqua complex:
The hydroxo complex is poised to undergo olation, which is initiated by displacement of one water by a neighboring complex:
In this product, the hydroxide ligand bridges between the two metals, this bridge is denoted with the symbol μ.
In the resulting 5+ ion, the remaining water and hydroxo ligands are highly acidic and the ionization and condensation processes can continue at still higher pHs. The formation of the oxo-dimer is a process called "oxolation," although sometimes olation and oxolation are not distinguished:
Ultimately one observes the formation of the metal oxide:
Hydroxide
Few hydroxo complexes of germanium have been characterized. Tin(II) hydroxide Sn(OH) was prepared in anhydrous media. When tin(II) oxide is treated with alkali the pyramidal hydroxo complex is formed. When solutions containing this ion are acidified, the ion [Sn(OH)] is formed together with some basic hydroxo complexes. The structure of [Sn(OH)] has a triangle of tin atoms connected by bridging hydroxide groups. Tin(IV) hydroxide is unknown but can be regarded as the hypothetical acid from which stannates, with a formula [Sn(OH)], are derived by reaction with the (Lewis) basic hydroxide ion.