Carboxylates chelating

Transplutonium(VI) complexes aqua,3,1220 carbonates, 3, 1220 carboxylates chelating, 3, 1220 halogens, 3,1220 monocarboxylates, 3,1220 nitrato, 3,1220 oxides, 3,1220 oxoanions, 3, 1220 Transport cations... 

In addition to phosphate and halide anion binding, carboxylate chelation by sapphyrin macrocycles has been the subject of recent investigation. To date, two crystal structures have been solved. A 2 1 complex formed between diprotonated sapphyrin 3 and trifluoroacetic acid shows that the oxyanions are chelated above and below the sapphyrin plane (Figure 10). ° Greater complexity of organi-... 

Stability constants for Cu11 complexation of Gly—X and X—Gly dipeptides show that even relatively small alkyl side chains can influence coordination. 3 At low pH, for example, the bidentate chelates N(amino),0(peptide) of L-Leu-Gly and L-Ile-Gly are the thermodynamically less stable, presumably due to steric hindrance from the branched side chains. Similar coordination by Gly—X is virtually independent of the nature of X. This latter result is not unexpected since only the Gly moiety is coordinating. However, on raising the solution pH (> 4) the peptide deprotonation that occurs to give tridentate N(amino),N(peptide),0(carboxyl) chelation is slightly inhibited by the Leu and lie residues (by 0.7-0.8 log units). 

Carboxylate, chelating carboxylate, CO, COj, RCOf and oxalate ligands 1141... 

The chelated phosphoramidate (22) is formed as an intermediate in the reaction of [Co(NH3)5(DNPP)]+ in alkaline solution, through intramolecular nucleophihc attack of a deprotonated m-ammine (Scheme 1). Similar reactivity is observed in the monodentate pyruvate complex [Co(NH3)50C(0)C(0)CH3] +, where the imino carboxylate chelate (23) is formed at pH > 12. ... 

The use of bipy or terp as the auxiliary ligand can also lead to the formation of the monomeric or dimeric structures. In [PrL3(bipy)2] (HE = trichloroacetic acid) [42], the three carboxylates chelate (ti ) to Pr(III), whereas the two bipy coordinate to the metal center with their two nitrogen atoms. [TbE3(terp)(H20)]2 (E = 4-aminobenzonic acid) is a dimer, where the... 

Transplutonium(VI) complexes aqua,1220 carbonates, 1220 carboxylates chelating, 1220 halogens, 1220 monocarboxyiates, 1220 nitrato, 1220 oxides, 1220 oxoanions, 1220 Triethanolamine alkali metal complexes, 23 Triethylamine, 2,2, 2"-trimethoxy-alkali metal complexes, 24 Trimolybdates, 1032 Trithioarsenates, 249 1,3,6,2-Trithioarsocane, 2-chloro-, 249 Trithioraolybdates, 1378 Trivanadates, 1027... 

Carboxylate, chelating carboxylate CO, C(, RCO2 and oxalate ligands... 

S-substituted organoCoM or thioglycolate derivatives.Control experiments pointed to the requirement of the heteroatom group (sulfonate or carboxylate) chelating zinc, although the transmetalation appeared to proceed via an external organozinc species. 

On the other hand data reported in Fig. 8 Indicate that the higher charge-density of Xanthan compared to PS-10 shows up in a higher heat of Cu ion binding and in a lower activity coefficient of Na counterions. From the initial slope of the Qg against [Cu2tl /N plots of Fig. 6 one estimates for Xanthan in water a differential enthalpy of Cu2+ binding of about 1 Kcal per mole of copper bound. In conclusion, as found with the sulfated polysaccharides (Fig. 4) as well as with different synthetic poly-carboxylates ( ), chelation of Cu2+ ions by polyanions is a process systematically driven by the entropy. 

Various Ca(II) complexes with carboxylates have been synthesized and crys-tallographically characterized [75]. Three modes are most commonly observed for these complexes the unidentate mode, the bidentate mode, and the anti-mode. In the unidentate mode, the Ca ion interacts with only one of the two 0 atoms of the carboxylate group. The coordinating atom is a carboxylate oxyanion rather than the carbonyl 0 atom. In the bidentate mode, the two 0 atoms of the carboxylate chelates to one Ca ion. In the anti-mode, the Ca complex is chelated between one of the carboxylate 0 atoms and a neighboring atom. Furthermore, the anti-mode is involved in a polynuclear mode with the 0 atom of the carboxylate forming a bridge between two Ca ions. 

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