Editing Hydroxide (section)

===Transition and post-transition metals===
The hydroxides of the [[transition metal]]s and [[post-transition metal]]s usually have the metal in the +2 (M = Mn, Fe, Co, Ni, Cu, Zn) or +3 (M = Fe, Ru, Rh, Ir) oxidation state. None are soluble in water, and many are poorly defined. One complicating feature of the hydroxides is their tendency to undergo further condensation to the oxides, a process called [[olation]]. Hydroxides of metals in the +1 oxidation state are also poorly defined or unstable. For example, [[silver hydroxide]] Ag(OH) decomposes spontaneously to the oxide (Ag<sub>2</sub>O). Copper(I) and gold(I) hydroxides are also unstable, although stable adducts of CuOH and AuOH are known.<ref>{{cite journal|last=Fortman|first=George C. |author2=Slawin, Alexandra M. Z. |author3=Nolan, Steven P. |year=2010|title=A Versatile Cuprous Synthon: [Cu(IPr)(OH)] (IPr = 1,3 bis(diisopropylphenyl)imidazol-2-ylidene)|journal=Organometallics|volume=29|issue=17|pages=3966–3972|doi=10.1021/om100733n}}</ref> The polymeric compounds M(OH)<sub>2</sub> and M(OH)<sub>3</sub> are in general prepared by increasing the pH of an aqueous solution of the corresponding metal cation until the hydroxide [[precipitate]]s out of solution. On the converse, the hydroxides dissolve in acidic solution. [[Zinc hydroxide]] Zn(OH)<sub>2</sub> is amphoteric, forming the tetrahydroxido[[zincate]] ion {{chem|Zn(OH)|4|2−}} in strongly alkaline solution.<ref name=amph/>

Numerous mixed ligand complexes of these metals with the hydroxide ion exist. In fact, these are in general better defined than the simpler derivatives. Many can be made by deprotonation of the corresponding [[metal aquo complex]].
:L<sub>''n''</sub>M(OH<sub>2</sub>) + B {{eqm}} L<sub>''n''</sub>M(OH)<sup>–</sup> + BH<sup>+</sup> (L = ligand, B = base)

[[Vanadic acid]] H<sub>3</sub>VO<sub>4</sub> [[acid dissociation constant#Polyprotic acids|shows similarities]] with phosphoric acid H<sub>3</sub>PO<sub>4</sub> though it has a much more complex [[vanadate]] oxoanion chemistry. [[Chromic acid]] H<sub>2</sub>CrO<sub>4</sub>, has similarities with sulfuric acid H<sub>2</sub>SO<sub>4</sub>; for example, both form [[acid salt]]s A<sup>+</sup>[HMO<sub>4</sub>]<sup>−</sup>. Some metals, e.g. V, Cr, Nb, Ta, Mo, W, tend to exist in high oxidation states. Rather than forming hydroxides in aqueous solution, they convert to oxo clusters by the process of [[olation]], forming [[polyoxometalate]]s.<ref>Juan J. Borrás-Almenar, Eugenio Coronado, Achim Müller [https://books.google.com/books?id=RJwQO1Ip0SQC&pg=PA4 Polyoxometalate Molecular Science], Springer, 2003, {{ISBN|1-4020-1242-X}}, p.&nbsp;4</ref>