Tetramic acids nitration

The tetramer exists in two-molal zirconium chloride and nitrate solutions, but it polymerizes into cross-linked chains on hydrolysis (190—191) in strong acid solutions, the hydroxyl bridges can be replaced by other anions to form trimers (192) and monomers (192—193). 

The bromide, [Cr(XH3)4(C204)]Br. H20, and the chloride, [Cr(NH3)4 (C204)]C1, are obtained from the nitrate by treating with concentrated hydrobromic and hydrochloric acid respectively. They crystallise in orange-coloured leaflets. If chloro-aquo-tetraminino-chromic chloride be treated with ammonium oxalate and hydrobromic acid successively, Cleve s triammino-chromium oxalate is formed and not oxalato-tetram-mino-salt.2... 

In a first approximation, the nitrate ion does not form complexes with zirconium, except under highly acidic conditions. Therefore, in moderately acidic media, zirconium should form the tetramer polycation as in the case of the perchlorate or die chloride [10]. However, after dissolution of zirconia in concentrated nitric acid, the basic salt Zr(0H>2(N03)2 4.7H2O crystallizes. Its structure consists of chains of [Zr(OH)2(OH2)2(N03) ] built with Zr in coordination 8 (dodecahedra), themselves linked by double OH bridges. Each atom of zirconium contains a bidentate nitrate... 

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