Group aquated ions

Neither gold(i) nor gold(lll) forms a stable aquated ion ([Au(OH2)2 4 ] or [Au(OH2)4 ], respectively) analogous to those found for many transition metal and main group cations. Both are thermodynamically unstable with respect to elemental gold and can be readily reduced ... 

The importance of knowing the stoichiometry of a reaction can be simply illustrated by considering the aquation of c -Cr(en)2(NCS)Cl+ ion.Is Cl or NCS replaced in the initial step and is the product cis or trans or both Does the product of this first step aquate further, and if so what groups are then replaced Chemical and spectral analysis answers these questions. The results reveal the surprising fact that the bidentate ligand en is lost at one stage, a behavior that appears more common with ammines of Cr(III) than with Co(III), where its occurrence is only occasionally noted. 

The process by which one or more water molecules are incorporated into another molecular entity until no other atoms, ions, and groups or moieties are further displaced. In the case of metal ions, aquation reflects the ability of nonbonded electrons on water oxygens to form coordinate covalent bonds with the metal ion. See also Hydration Water... 

Substitution reactions taking place in water solution can often be accelerated by the presence of an acid or base. If the coordinated leaving group (X) has lone pairs whicb can interact with H+ or metal ions such as Ag+ or Hg2, the M—X bond may be weakened and loss of X facilitated.25 This effect is seen in the aquation of [Cr(H2OUF]2+ ... 

In their first publication on this subject,59 Werner and Miolati showed that the molecular conductances (fx) of coordination compounds decreased as successive molecules of ammonia were replaced by acid residues (negative groups or anions). For cobalt(III) salts, they found that fi for luteo salts (hexaammines) > fi for purpureo salts (acidopentaammines) > /t for praseo salts (di-acidotetraammines). The conductance fell almost to zero for the triacidotriammine Co(N02)3-(NH3)3 and then rose again for tetracidodiammines, in which the complex behaved as an anion. By such measurements, Werner and Miolati determined the number of ions in complexes of cobalt(III), platinum(II) and platinum(IV). They not only found support for the coordination theory, but they also elucidated the process of dissociation of salts in aqueous solution and followed the progress of aquations. 

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