Aqua-ions

Richens D T 1997 The Chemistry of Aqua-ions (Chichester Wiley)... 

Aqueous Chemistry. Molybdenum has weU-characterized aqueous chemistry in the five oxidation states, VI, V, IV, III, and II. A listing of aqua ions is given in Table 2. Except for the Mo(VI) species all of the aqua ions are only soluble or stable in acidic media (17). The range of aqueous ions known for molybdenum is far broader than that of other elements. 

Oxidation States. The common oxidation state of silver is +1, ie,, as found in AgCl, which is used with Mg in sea- or freshwater-activated batteries (qv) AgNO, the initial material for photographic materials, medical compounds, catalysts, etc and silver oxide, Ag20, an electrode in batteries (see Silver compounds). Few compounds are known. The aqua ion [Ag(H2 O), which has one unpaired electron, is obtained... 

The ruthenium(II) aqua ion reacts with nitrogen at room temperature under high pressure (200 bar) forming yellow-brown [Ru(H20)5N2]2+, isolated as a tosylate salt, showing i/(N=N) at 2141cm-1 in its IR spectrum [59]. 

No simple osmium aqua ion has been definitely isolated and characterized, though in alkaline solution (and the solid state) the osmium(VIII) species 0s04(0H)2 is well characterized (sections 1.4.1 and 1.12.1). 

The pentammine aqua ion [Ru(NH3)j(H20)]2+, best made by zinc amalgam reduction and aquation of [Ru(NH3)5C1]2+, undergoes extensively studied substitution reactions first order in both the ruthenium complex and the incoming ligand (e.g. NH3, py) and is a convenient source of other... 

Rhodium(III) hydroxide is an ill-defined compound Rh(0H)3.nH20 (n 3) obtained as a yellow precipitate by careful addition of alkali to Na3RhCl6-Addition of imidazole solution to suitable aqua ions leads to the precipitation of active rhodium(III) hydroxides formulated as Rh(0H)3(H20)3, Rh2(/x-0H)2(0H)4(H20)4 and Rh3(/z-0H)4(0H)5(H20)5 [31]. Hydrated iridium(III) hydroxide is obtained as a yellow precipitate from Ir3+ (aq.) at pH 8. 

In addition to the aqua ion, a range of mixed aquo-halo complexes are known [38], including all 10 isomers of Rh(H20)6 VC1(X3 x)+. Synthetic entry into the series is possible from either end, the determining factor being the labilizing effect of chloride ... 

The lantern structure is quite stable, unlike certain other Rh2 dimers. Protonation was formerly claimed to give Rh2+ aqua ions, but they are believed now to be [Rh2(OCOMe)3]+ (aq.) and [Rh2(OCOMe)2]2+ (aq.) [73],... 

The aqua ion Ir(H20) + and halide complexes IrX - have already been mentioned above. The kinetic inertness of the low spin d6 complexes means that hydrolysis of IrClg- is slow complexes up to IrCl2(H20)4 have been produced and separated from mixtures by high-voltage electrophoresis. 

Syntheses of palladium and platinum aqua ions [42] include... 

Complexes of O-donors are relatively rare, explicable by the soft nature of the divalent ions. A telling indication is that sulphoxide ligands will only bind through O if steric effects make S-bonding impractical. The most important complexes are diketonates and carboxylates (for the aqua ions see section 3.5). 

The aqua ion as a ligand is discussed in section 4.5. Silver forms a range of light-sensitive, insoluble carboxylates that find application in the synthesis of, for example, alkyl halides and esters. The benzoate, trifluoroacetate and perfluorobutyrate have dimeric structures others are polymers (Figure 4.6). 

Alkene complexes Ammine complexes Aqueous chemistry Arsine complexes Binary compounds Bipyridyl complexes Bond lengths acetylacetonate alkene complexes alkyl and aryl complexes ammine complexes aqua ion... 

Ruthenium aqua ions — their comparison to ruthenium ammines. P. Bernhard, H. Lehmann and A. Ludi, Comments Inorg. Chem., 1983, 2, 145-156 (22),... 

This supramolecular approach has been used as a way to facilitate the crystallization of cuboidal aqua ions and to capture single intermediates present in complex solution mixtures. For example, [M3Q4Clx(H20)9.x] (Q = S, Se) supramolecular adducts have been isolated for x =1-5 from aqueous HCl solutions by varying the acid concentrations where the aggregates contain in each case only one of all possible isomers [46]. In addition to the hydrogen bonds, other kinds of interactions, namely C1---H20, C1---C1 and Q---Q contacts, are also involved in the network propagation. This supramolecular approach has also been efficiently employed for the crystallization of a large number of aqua complexes within the [M3M Q4] cubane-type family, where M is a transition or post-transition metal [47]. 

Skipper, N. (1987). Diffraction and study of aqua ions. Journal of Physical Chemistry, 91, 5851-8. 

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