Polymeric Complexes containing Bridging Oxygen Atoms

Polymeric Complexes containing Bridging Oxygen Atoms. The redetermined crystal structure of [(H3N)5Cr0Cr(NH3)5]Cl4,H20 is in agreement with the earlier report (Vol. 1, p. 58), the cation possessing ca. D4 symmetry with a linear 

The crystal and molecular structure of di- i-hydroxo-tetraglycinatodi-chromium(iii), [(gly)2Cr(OH)2Cr(gly)2] has been determined. The structure consists of well-separated dimeric pairs of octahedrally co-ordinated chromium atoms, each complexed to two glycinato NO-ligands and linked by two hydroxo-bridges. The whole mplex has a centre of symmetry and therefore the 

Cr02Cr unit is strictly planar with Cr-Cr and O-O separations of297.4(2) 

A spectroscopic study of [Cr30(0Ac)6(H20)3]Cl,6H20 at low temperatures has confirmed the presence of two sets of inequivalent trimeric clusters. 

The addition of alkali to solutions of [Cr(H20)6] initially causes simple deprotonation followed by precipitation of [Cr(0H)3(H20)3], which may be obtained in a crystalline form by precipitation at low temperatures. The structure of [Cr(0H)3(H20)3] is of the inverse bayerite-type with the metal atoms in one-third of the octahedral sites, and the structure consists of hydrogen-bonded layers of [Cr(OH)3(OH2)3]oo units in which the octahedral units are also linked by hydrogen bonds. Ehmination of water from [Cr(0H)3(H20)3] occurs readily to form a well-ordered structure in which the metal centres are connected by p-hydroxo-bridges.  

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Reaction of dialkyl H-phosphonates with ZrCl4 yields, depending on the ratio of the reagents, complexes with different coordination numbers at the metal center [421]. These complexes contain chlorine- and phosphonate-type bridges that form a polymeric network. In the course of this reaction, partial dealkylation of the dialkyl H-phosphonates takes place, and results in the formation of Zr-O-P links. On the other hand, the phosphoryl oxygen forms additional donor-acceptor bonds with the zirconium atom. 

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