Die Chemie wässeriger Metallsalzlösungen

Abstract

+ nachgewiesen worden, offenbar der erste einer langen Serie polynuclearer Komplexe, deren Zusammensetzung beim Übergang von p H 2 zu 5 immer komplizierter wird, bis wir schließlich das endlose Netzwerk der schwerlöslichen Fällung erreichen, die man in nicht gealtertem Zustand mit einem röntgenamor-phen organischen Hochpolymeren vergleichen kann.Formulierungen wie (1) und (2) sind also zum mindesten sehr ungenau, was stark dazu beigetragen hat, die Probleme wässeriger Metallsalzlösungen zu verkennen. Neben den einfachen, solvatisierten Metallionen kommen fast stets ganze Serien von Komplexen in den Lösungen vor. Weil es deren so viele gibt, ist es zweckmäßiger, diese als Assoziationsprodukte weniger einfacher Ionen zu beschreiben als umgekehrt die einfachen Ionen als Dissoziationsprodukte der Komplexe. Das ist auch der Grund, weshalb man bei der quantitativen Beschreibung der Verhältnisse heute allgemein Assoziationskonstanten an Stelle der früher üblichen Dissoziationskonstanten der Komplexe verwendet. Das Metallion als valenzchemischer BegriffWenn wir von Metallionen reden, so dürfen wir nie vergessen, daß es sich dabei niemals um nackte Ionen handelt, wie sie bei der Aufnahme von Spektren im elektrischen Funken oder Flammenbogen vorkommen. Die Metallionen ') B. O. A. Hedström, Ark. Kemi 6, 1 [1953].

Carbonic anhydrase activity of dinuclear CuIIcomplexes with patellamide model ligands

“…4) involves CO 2 coordination to one of the Cu II centers, nucleophilic attack of a hydroxido group, coordinated to the other Cu II center, at the CO 2 carbon atom, leading to a bridging HCO 3 − anion, and release of HCO 3 − to reform the catalytically active hydroxidodicopper(II)-patellamide complex [the important forms of the complexes (unbridged, hydroxido-bridged, carbonato-bridged) have been thoroughly characterized by electrospray massspectrometry (ESI-MS), UV-vis-NIR, CD, EPR spectroscopy, X-ray crystallography, 13 C and 18 O labeling studies and computational methods) ‡ and preliminary conformational analyses (Monte Carlo and molecular dynamics simulations) support the release of the bridging carbonate]. 13,14 The maximum rate with Tris as the base ( pK a = 8.07, 10 5 -fold acceleration) and relatively small rates at lower pH (3,5-lutidine pK a = 6.21, uncatalyzed; imidazole pK a = 7.14, 10 3 -fold acceleration) indicate that the pK a value of the a In addition to the usual fixed parameters for fitting kinetic data of CO 2 hydration, the pK a value of Cu II -coordinated water (see Schemes 2 and 3, K H ; pK a [Cu II (H 2 O) 6 ] 2+ = 7.50) 48 and the association constant of CO 2 with the catalyst (see Scheme 2, log K Cat = 4) 36,47,60 were estimated from published data (standard deviations given in brackets). Cu II -coordinated OH 2 molecule, responsible for a maximum concentration of the catalytically active hydroxido complex, is 7.1 < pK a < 8.1, and this is as expected for Cu II aqua ions 48 and the assumed pK a values of the two coordinated water molecules in our complexes in H 2 O-MeCN as solvent ( pK a = 6.8 and 7.5), based on the analysis of the phosphoester hydrolysis kinetics.…”

“…13,14 The maximum rate with Tris as the base ( pK a = 8.07, 10 5 -fold acceleration) and relatively small rates at lower pH (3,5-lutidine pK a = 6.21, uncatalyzed; imidazole pK a = 7.14, 10 3 -fold acceleration) indicate that the pK a value of the a In addition to the usual fixed parameters for fitting kinetic data of CO 2 hydration, the pK a value of Cu II -coordinated water (see Schemes 2 and 3, K H ; pK a [Cu II (H 2 O) 6 ] 2+ = 7.50) 48 and the association constant of CO 2 with the catalyst (see Scheme 2, log K Cat = 4) 36,47,60 were estimated from published data (standard deviations given in brackets). Cu II -coordinated OH 2 molecule, responsible for a maximum concentration of the catalytically active hydroxido complex, is 7.1 < pK a < 8.1, and this is as expected for Cu II aqua ions 48 and the assumed pK a values of the two coordinated water molecules in our complexes in H 2 O-MeCN as solvent ( pK a = 6.8 and 7.5), based on the analysis of the phosphoester hydrolysis kinetics. 15 We assume that coordination of CO 2 (see Fig.…”

“…Fixed general parameters for the hydration of CO 2 at 25°C (see Scheme 2; the hydration of CO 2 (eqn (1a), k 1 *) is treated as a pseudo-firstorder reaction, [H 2 O] = 55.6 M)43,57-59 a In addition to the usual fixed parameters for fitting kinetic data of CO 2 hydration, the pK a value of Cu II -coordinated water (see Schemes 2 and 3, K H ; pK a [Cu II (H 2 O) 6 ] 2+ = 7.50)48 and the association constant of CO 2 with the catalyst (see Scheme 2, log K Cat = 4)36,47,60 were estimated from published data (standard deviations given in brackets). Two-dimensional (absorbance vs. wavelength, recorded in the first 2 s, top) and three-dimensional (absorbance vs. wavelength vs.…”

Solutions of Electrolytes

“…Miscellany.-Reviews have appeared by Kraus (152) concerning the qualitative physical significance of a variety of properties of solutions of electrolytes, and by Schwarzenbach (153) concerning the chemical species present in aqueous solutions of metal salts. In extremely thorough fashion (33 (157) intramolecular exchange interaction within a binuclear complex.…”