Aquation

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

A Radiochromatograpic Study Of The Reaction Of 51cro3 With Hydrochloric Acid

Abstract: The objective of the present work is to verify the reduction of CrO 3 in concentrated hydrochloric acid, using 5 1 Cr as a tracer. For the study, 5 1 CrO 3 was added to 37% HCI and maintained under agitation at 20°C for specified time periods. Aliquots were diluted to approximately pH 2 and analyzed by open column cation and anion chromatography, either immediately or after storage for specified time periods. The separations, which were made by stepwise elution using HClO 4 and Ca(ClO 4 ) 2 solutions as eluents with fraction collection, followed by counting with a NaI(Tl) detector and a single channel analyzer, permitted construction of elution profiles whose peaks were identified by comparison with authentic samples. The results show that CrO 3 is reduced to Cr(III) in 37% HCl and that the initial identifiable product is [CrCl 3 (H 2 O) 3 ], a product which undergoes slow aquation at pH 2 to [Cr(H 2 O) 4 Cl 2 ] + , [Cr(H 2 O) 5 Cl] 2 + and [Cr(H 2 O) 6 ] 3 + .

Catalysis by reversed micelles in non-polar solvents, aquation and electron-transfer reactions of chromium(iii) and cobalt(iii) complexes in benzene

Abstract: Rate constants for aquation of the ion [Cr(C2O4)3]3– by octylammonium tetradecanoate-solubilized water in benzene and for aquations of [Cr(C2O4)3]3–, [CO(C2O4)3]3–, and cis-[Co(en)2(N3)2]+(en = ethylenediamine) by dodecylammonium propionate-solubilized water in benzene are factors of up to 5 × 106, 1 × 106, ca. 1 500, and 11, respectively, greater than those for the same reactions in water. At constant surfactant concentration there is a linear dependence of the aquation rate on the concentration of solubilized water, while at constant water concentration increasing surfactant concentration results in an exponential rate decrease. These results are discussed in terms of favourable substrate orientation in polar cavities of alkylammonium carboxylate aggregates, formed from these surfactants in benzene, where hydrogen bonding facilitates proton transfer and enhanced water activity accelerates synchronous M–O bond-breaking and nucleophilic attack by water. An implication of these results is that, in the hydrophilic environment of the reversed micelle, aquations of CoIII and CrIII complexes follow rate-determining bimolecular mechanisms subsequent to formation of ‘one-ended dissociated’ species. No micellar effects have been observed for the electron-transfer process in the aquation of the ion [Co(C2O4)2(H2O)2]–. Rate enhancement by surfactant-solubilized water in non-aqueous solutions and the utility of these systems in elucidating the mechanistic roles of water are discussed.

Synthesis, crystal structure and properties of three different derivatives of bis[di(2-pyridyl)methanediol]copper(II), [Cu(bpmd)2]2+ ¶

Abstract: In an attempt to obtain ternary copper(II) [Cu(II)] complexes where bis(2-pyridyl) ketone (bpk) could induce the fac-O2 + N(apical) conformation in the HL2− form of two different nitrilotriacetates (HNTA2− and HDNTA2−), we obtained [Cu(bpmd)2][Cu(HNTA)2] · 2H2O (1) and [Cu(bpmd)2](H2DNTA)2 · 4H2O (2) where bpmd is di(2-pyridyl)methanediol. On this basis, the salt [Cu(bpmd)2][Cu(IDA)2] · 6H2O (3) [iminodiacetate (IDA) ligand] was also obtained. The crystallographic studies of these compounds revealed that the common cation of these salts results from aquation of bpk in the aqueous media. The aquation of bpk is unexpectedly fast in the case of 1 because crystals appeared on the same day of the synthesis. ¶This article is dedicated to Professor Alfredo Mederos for his contribution to the coordination chemistry.

Dialkyl sulphoxides as starting materials for the preparation of alkyl-transition-metal complexes. Formation of penta-aquamethylchromium(III) and pentacyanomethylcobaltate(III) salts, and the reduction of methyl radicals by vanadium(II)

Abstract: The penta-aquamethylchromium(III) ion is formed in high yield from the chromium(II)–hydrogen peroxide–dimethyl sulphoxide system in aqueous solution. The methyl-deuteriated analogue has been prepared by the corresponding reaction with [2H6]dimethyl sulphoxide. The secondary kinetic deuterium isotope effect for the acid-catalysed aquation has been measured. The analogous ‘Fenton reagents’ with pentacyanocobaltate(II) and with vanadium(II) yield the pentacyanomethylcobaltate(III) ion and methane, respectively.

Structural and mechanistic studies of co-ordination compounds. Part VI. Preparation, aquation, and base hydrolysis of some octahedral trans-chlorocyanocobalt(III) amine complexes

Abstract: The preparation of the complex trans-[Co(NH3)4(CN)Cl]+ is described. The kinetics of aquation and base hydrolysis of this complex and the base hydrolysis of the complex trans-[Co (cyclam)(CN)Cl]+(cyclam = 1,4,8,11-tetra-azacyclotetradecane) have been studied over a range of temperature, and the following parameters have been obtained: trans-[Co(NH3)4(CN)Cl]+, kOH2(at 25 °C)= 9·8 × 10–4 s–1, ΔHOH2‡= 20·7 kcal mol–1, ΔSOH2‡=–3 cal K–1 mol–1, and kOH(at 0 °C)= 3·5 × 10–2 l mol–1 s–1, ΔHOH‡= 23·8 kcal mol–1, ΔSOH‡= 22 cal K–1mol–1; trans-[Co(cyclam)(CN)Cl]+,KOH(at 0 °C)= 8·1 × 10–1 l mol–1 s–1, ΔHOH‡= 22·6 kcal mol–1, ΔSOH‡= 24 cal K–1 mol–1. Thermodynamically, it was found that the extent of aquation of complexes of the type trans-[Co(amine)4(CN)Cl]+ increases in the order cyclam < (en)2 < (NH3)4(en = ethylenediamine). Kinetically, the aquation rate constants of these complexes increase, but the base-hydrolysis rate constants decrease in the above order. The results support the proposed nephelauxetic effects which these amine ligands exert on the central cobalt(III) ion. Spectroscopic evidence is produced to support the above conclusion.