Monodentate ligands sulfate

EDTA, rather than increasing the yield of hydroxylation, as has been observed in several other model hydroxylases (7, 29), reduces it drastically. The role of EDTA is twofold first, it chelates preferentially with the ferric ions decreasing the amount of ferric-NBNH complex second, it reduces the oxidizing ability of ferric. The monodentate ligands —sulfate, chloride, and cyanide—do not act in the same way. 

The ammonia and amine complexes are the most numerous chromium derivatives and the most extensively studied. They include the pure ammine [CrAm6]3+, the mixed ammine-aqua types, that is, [CrAm4 (H20) ]3+ (n = 0-4, 6), the mixed ammine-acido types, that is, [CrAm6 X ](3" )+ (n = 1-4, 6), and mixed ammine-aqua-acido types, for example, [CrAm6 m(H20) Xm](3 m7+ (here Am represents the monodentate ligand NH3 or half of a polydentate amine such as ethylenediamine, and X an acido ligand such as halide, nitrite, or sulfate ion). These complexes provide examples of virtually all kinds of isomerism possible in octahedral complexes. 

There are old reports of tris sulfate complexes " and a number of chromium(lll) sulfate hydrates are known. In recent years monosulfatopentaaquachromium(III) complexes have been prepared and characterized by IR spectroscopy sulfate probably behaves as a monodentate ligand. The basic chromium(III) sulfate Cr(0H)S04 H20 crystallizes in the non-centrosymmetric, monoclinic, space group O. Each chromium atom is coordinated octahedrally by two hydroxo groups, three sulfate O atoms and a water molecule. The metal atoms are joined by single hydroxo bridges forming an infinite chain. 

The sulfate ion, well known as a monodentate and simple bidentate ligand, has been observed also as a bridging ligand, as exemplified in [(en)2Co(OS(O2)O)2Co(en)2]2+.10°3 The c/.v-bisf/x-sulfato) bridge undergoes hydrolysis to c -[Co(en)2(OS03)(OH2)]+ in acidic solution, hydrolyzing further with loss of coordinated sulfate in aqueous base to the dihydroxo complex. 

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