Binuclear cobalt(II) complexes, [Co2(bpmp) (CH3COO)2]ClO4 and [Co2(bpmp) (CH3COO)] (ClO4)2 with 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-methylphenol (Hbpmp), were prepared. The complexes showed the reversible oxygenation in various solvents. Two to one (CO/O2) peroxo bridged complex, [Co2(bpmp)(CH3COO)O2](ClO4)2·2H2O, was isolated. The oxygen adduct was fairly stable towards further reactions.
Potentiometric equilibrium measurements of hydrogen ion concentrations have been employed for the determination of protonation constants and Cu(I1) stability constants of the macrobicyclic ligand C-BISTREN (1,4,10,13,16,22,27,33-octaazabicyclo-[11.11.1 llpentatriacontane) at 25.0 OC in solutions maintained at 0.10 M ionic strength by the addition of sodium perchlorate with and without a 0.010 M concentration of sodium fluoride. The results are compared with the corresponding equilibrium constants previously reported for 0-BISTREN (7,19,30-trioxa-1,4,10,13,16,22,27,33-octaazabicyclo[ 11.1 1.1 llpentatriacontane). The measurements made in the absence of fluoride provide six protonation constants of the ligands, the stability constants of mononuclear and binuclear Cu(I1) complexes, the protonation constants of the mononuclear copper(I1) cryptates, and the hydroxide-bridging constants of the binuclear copper(I1) cryptates. Potentiometric measurements of the ligands in the NaCIO4-NaF medium provide equilibrium constants for bridging of the bifluoride anion, HF2-, by both hexaprotonated ligands and pentaprotonated 0-BISTREN, and fluoride ion bridging in the tetra-, penta-and hexaprotonated 0-BISTREN. Potentiometric measurements of 1:l and 1:2 molar ratios of the ligands to Cu(I1) in the NaC104-NaF medium provide equilibrium constants for fluoride ion bridging between the two copper(I1) centers in the binuclear cryptate, as well as equilibrium constants for fluoride bridging between copper(I1) and protonated nitrogens in the mononuclear copper(I1) cryptate. New data for fluoride anion bridging of the protonated species of 0-BISTREN and its mononuclear and binuclear copper complexes are reported for 0.10 M ionic strength. The comparison between 0-BISTREN and C-BISTREN reveals the high specificity of the binuclear Cu(I1)-0-BIS-TREN cryptate for hydroxide ion bridging.
IntroductionThe protonation constants and metal ion stability constants of
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