Symbiosis and Preparative Chemistry

It would be closing the eyes to half of the content of Pearson s classification to consider only systems where complex formation constants have (or can) been measured. If one wants to stabilize unusually low oxidation numbers, it is well-known that the best chances are to select the ligands among the class H-, 1 , 

It is worthwhile to analyze why co-existing soft ligands assist low oxidation numbers. If we want to make a copper(I) compound, it is very difficult to try the aqua ion, the fluoride or the anhydrous sulphate because they disproportionate to the metallic element and a higher oxidation state, here Cu(II). However, as seen in Eq. (7) it is easier to make the ammonia complex Cu(NH3)2 under anaerobic conditions, and even easier to make copper(I) complexes of pyridine and of conjugated bidentate ligands such as 2,2 -dipyridyl and 1.10-phenanthroline. The experimental problems are reversed in the case of iodides and cyanides, where it is easy to precipitate Cul or CuCN or to prepare solutions in an excess of the ligand containing Cul J, 

Cu(CN)2 or Cu(CN)4 3 but a difficult kinetic problem to detect the intermediate Cu(II) complexes. 

Br04 and a rich folklore of xenon compounds. However, it is almost certain that Mn(CO)sF would disproportionate  

The four complexes Co(NH3)5X+2 are kinetically robust, but the AG values are in favour of X = F and the subsequent X = Cl, Br and I are monotonically weaker bound. This hard behaviour, one may argue, is superposed an unusually high affinity for ammonia making the chemistry of Co(III) quite different585 from Sc(III), Fe(III) and Ga(III) though in neutral solution, Eq. (6) is followed by other reactions finally precipitating dark brown Co(OH)3. The ligand field stabilization - 2.4 (Ac -Aa) = 

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