Quantitative comparison of the effect of methylD-glycopyranosides as cosolutes on the rates of base hydrolysis and aquation of some iron(II)-diimine Complexes

Abstract

Quantitative comparison of the effect of methyl D-glycopyranosides as cosolutes on the rates of base hydrolysis and aquation of some iron(II)-diimine complexes Milde, Siobhan P.; Blandamer, Michael J.; Burgess, John; Engberts, Jan B.F.N.; Galema, Saskia A.; Hubbard, Colin D. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. ABSTRACT: The kinetics of base hydrolysis and of aquation of some iron(II)-diimine complexes in the presence of stereoisomeric carbohydrates were monitored spectrophotometrically at 25.0°C. In basic aqueous solution dissociation of both Fe(1,10-phenanthroline) 3 2 and Fe(2,2'-bipyridine) 3 2 is accelerated when methyl Dglycopyranosides are present. The aquation reaction of Fe(1,10-phenanthroline) 3 2 in an aqueous EDTA medium is also accelerated in the presence of carbohydrates, but that of Fe(5-nitro-1,10-phenanthroline) 3 2 is retarded. An equation obtained from a modification of the Savage-Wood additivity of groups principle applied to kinetics is used to quantify the kinetic medium effects observed. The magnitudes of these effects can be explained in terms of the hydration characteristics of the carbohydrates, which depend on their stereochemistry, and the change in the hydration environment of the iron(II)-diimine complexes during activation. Results and their interpretation for the aquation in acidic medium of the Fe(5-bromo-1,10-phenanthroline) 3 2 and Fe(4,7-dimethyl-1,10-phenanthroline) 3 2 complexes in highly aqueous methanol and ethanol solutions are also presented. The kinetic medium effects of the carbohydrates are consistent with those of simple alcohols.

Salt effects on the reactivity of the base‐catalyzed hydrolysis of some novel low‐spin hydrophobic Fe(II)–amino acid azomethine chelates

“…The observed large values of Gibbs energies of interaction of the salt and reactant substrates (Table IV) indicate greater interaction between the added salts and reactants. These values of Gibbs energy were evaluated by means of a least‐mean‐squares of the slopes of ln( k/k 0 ) versus molal concentration of the salt ( m ) 22. The more hydrophobic complexes, viz.…”

26 Mechanisms of reactions in solution

“…Hay and McLaren have established 515 that base hydrolysis of [Co(tetren)(NCR)] 3 (R Me, Ph or C 6 H 4 OMe-4) involves an S N 1 CB displacement of the nitrile without carboxamide formation. Changes in the hydration environment of the complex during activation are believed 516 to be respon-sible for the acceleration of base hydrolysis of [Fe(bipy) 3 ] 2 in the presence of methyl D-glycopyranosides. Solvent effects have been reported on the base hydrolysis of [Co(O 2 CR)(tetren)] 2 (R amino-containing group).…”