Metal aquo complex

The water molecules function as Lewis bases, donating a pair of electrons to the metal ion and forming a dative covalent bond with it.

[9] Aquo complexes of lanthanide(III) ions are eight- and nine-coordinate, reflecting the large size of the metal centres.

[8] Monomeric aquo complexes of Nb, Ta, Mo, W, Mn, Tc, Re, and Os in oxidation states +4 to +7 have not been reported.

[11] With the higher oxidation states the effective electrical charge on the cation is further reduced by the formation of oxo-complexes.

This reaction usually applies to the interconversion of di- and trivalent metal ions, which involves the exchange of only one electron.

[13] Using labels to keep track of the metals, the self-exchange process is written as: The rates of electron exchange vary widely, the variations being attributable to differing reorganization energies: when the 2+ and 3+ ions differ widely in structure, the rates tend to be slow.

Solutions of metal aquo complexes are acidic owing to the ionization of protons from the water ligands.

This effect is related to the stabilization of the pi-donor hydroxide ligand by the (t2g)5 Ru(III) centre.

[8] In concentrated solutions, some metal hydroxo complexes undergo condensation reactions, known as olation, to form polymeric species.