A spectrophotometric method was used to determine the acidity constant of 4'-carboxybenzo-24-crown-8 in 52% (w/w) ethanol-water mixture. The acid dissociation constant, Ka, was found to increase in the presence of Na+, K+, Rb+, Cs+ and Tl+ ions. The formation constants of the resulting 1:1 complexes between the carboxycrown a...

aminocarboxylic acids, such as 2-aminobenzoic acid, react easily with [ir(cod)(pme3)3]cl, (cod=1,5-cyclooctadiene), in thf to produce hydridoaminocarboxylato iridium(iii) complexes in high yields. these octahedral complexes are formed via oxidative addition reaction of the o-h bond of the carboxylic group with the central metal. the starting iridium(i) complex losses the cod molecule, the chlor...

Reaction of [U(TrenTIPS )(PH2 )] (1, TrenTIPS =N(CH2 CH2 NSiPri3 )3 ) with C6 H5 CH2 K and [U(TrenTIPS )(THF)][BPh4 ] (2) afforded a rare diuranium parent phosphinidiide complex [{U(TrenTIPS )}2 (μ-PH)] (3). Treatment of 3 with C6 H5 CH2 K and two equivalents of benzo-15-crown-5 ether (B15C5) gave the diuranium μ-phosphido complex [{U(TrenTIPS )}2 (μ-P)][K(B15C5)2 ] (4). Alternatively, reaction...

First-row transition-metal complexes hold great potential as catalysts for hydrogenations and related reductive reactions. Homo- and heteroleptic arene/alkene metalates(1-) (M=Co, Fe) are a structurally distinct catalyst class with good activities in hydrogenations of alkenes and alkynes. The first syntheses of the heteroleptic cobaltates [K([18]crown-6)][Co(η4 -cod)(η2 -styrene)2 ] (5) and [K(...

The extraction-separation of alkali, alkaline earth, and rare earth metal ions could be improved by using macrocyclic ligands as ion size selective masking reagents. By adding a macrocyclic ligand to the aqueous phase of a conventional chelate extraction system, the extraction of metal ions with larger ionic radii was shifted to a higher pH region. Consequently, the separation among the metal i...

The elucidation of the structural requirements for molecular recognition by the crown ether (18-crown-6)-2,3,11,12-tetracarboxylic acid (18c6H(4)) and its cationic complexes constitutes a topic of current fundamental and practical interest in catalysis and analytical sciences. The flexibility of the central ether ring and its four carboxyl side arms poses important challenges to experimental an...

Dried varnish is rich in many ester moieties, which may be broken down into small, soluble compounds by esterase activity or alkaline hydrolysis. Two methods for varnish removal have been developed, including the treatment of either lipase or RbOH / PEG-400 crown ether which allow aged oil varnishes or paint coverings to be removed or thinned. These techniques are designed to proceed in a contr...