Aquation

About: Aquation is a research topic. Over the lifetime, 1443 publications have been published within this topic receiving 17507 citations.

Mutarotation of D(+)-glucose. III. Evidence for cooperative and competitive nucleophilic catalysis by molybdenum(VI) and tungsten(VI) anions

Abstract: The rate of mutarotation of α-D(+)-glucose is subject to general base catalysis by a variety of oxo anions. The relative magnitudes of the second-order rate constants are B4O72->W7O246->Mo7O246- > HCO3->WO42->MoO42- Catalysis by W7O246- and Mo7O246- is competitive but that by WO42- and MoO42- is cooperative. A mechanism for catalysis by the polymeric anions is proposed which involves ion-pair formation between the anion and the conjugate acid of glucose. Specifically oriented aquation sheaths about the charged ions cause them to act as enhanced nucleophiles in the rate-determining step to form the aldehyde intermediate. Activation parameters support this model.

Catalytic cycle of NO x conversion based on pentacyanoferrate complexes

Abstract: Conversion of NO x + NH 3 to N2, catalysed by the [Fe I I (CN) 5 L] n - complexes (L= NO + , NH 3 , H 2 O) proceeds through addition, comproportionation and substitution processes within the complexes and the reaction rates are sensitive to the different parameters. In this study the role of added cations was investigated and the main impact found concerned acceleration of the [Fe(CN) 5 NO] 2 - production from [Fe(CN) 5 L] 3 - (L= H 2 O, NH 3 ) and NO - 2 in alkaline medium. This could be achieved by increasing the amount ratio of [Fe(CN) 5 H 2 O] 3 - to its parent ammonia complex at given pH taking advantage from the specific cation effect on the rate of the [Fe(CN) 5 NH 3 ] 3 - aquation. The rate was affected not only by concentration but also by the nature of the cation, i.e. by the hydrated radius of cation and its influence on the solution viscosity. The reaction of [Fe(CN) 5 NO] 2 - with ammonia was re-examined in aspects of the pH dependent production of molecular nitrogen. The results are summarised in the overall photocatalytic cycle for which the optimal working pH range is limited to 10-11. The trend is consistent with the nucleophilic attack of NH 3 on the N(NO) atom in [Fe(CN) 5 NO] 2 - , followed by comproportionation within the N(NO)NH + 3 ligand, which results in N2 generation.

Specific effects of nucleophiles on the mercury(II)-assisted chloride aquation of the penta-amminechlorocobalt(III) cation and of the chloro[ethylenediaminetetra-acetato(3–)]cobaltate(III) anion

Abstract: Simple anions (X–) such as CH3CO2–, Cl–, N3–, Br– SCN–, and CN– influence the Hg2+-assisted chloride aquation of [CoCl(NH3)5]2+ and [Co(edta)Cl]2–(H4edta = ethylenediamine-NNN′N′-tetra-acetic acid) through the formation of HgX+. Observed rate changes reflect both the electrostatic and the inductive effects; the former predominates for CH3CO2–, Cl–, and N3–, while the latter does for CN–. Aminopolycarboxylates, such as edta4– and cdta4–(H4cdta = cyclopentane-1,2-diamine-NNN′N′-tetra-acetic acid) were specifically effective. A feature of the reactions with [CoCl(NH3)5]2+ is the production of [CoY(NH3)5]–(Y = edta or cdta) alongside [Co(NH3)5(OH2)]3+.