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Some metal hydroxides like $\ce{Ag(OH)}$ and $\ce{Cu(OH)2}$ dissolve in excess $\ce{NH4OH}$ to form metal ammonia complexes.

I want to know which other common metal hydroxides dissolve in excess $\ce{NH4OH}$. Also, can it be somehow predicted ? I couldn't find much relevant information on the Internet.

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  • $\begingroup$ There are a number of unknowns and a number of equations but this is a matter of the various equilibriums. Remember that you could also add NaOH so the solution could be more basic than you could get with NH4OH alone. $\endgroup$ – MaxW Feb 10 '17 at 22:35
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The Wikipedia article for "Metal amine complex" gives many examples. According to the article:

Almost all metal ions bind ammonia as a ligand, but the most prevalent examples of ammine complexes are for Cr(III), Co(III), Ni(II), Cu(II) as well as several platinum group metals.

Specific examples include:

$\ce{[Pt(NH3)4][PtCl4]}$
$\ce{[RhCl(NH3)5]Cl2}$
$\ce{[Cr(NH3)4Cl2]Cl}$
$\ce{[Co(NH3)6]Cl3}$
$\ce{NH4[Cr(NCS)4(NH3)2]}$
$\ce{[Zn(NH3)4]^2+}$
$\ce{[Ag(NH3)2]+}$
$\ce{[Ni(NH3)6]^2+}$
$\ce{[Cu(NH3)4(H2O)2]^2+}$

Several others are listed just in that one Wikipedia article, along with a fair list of references.

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