6533b853fe1ef96bd12ad421

RESEARCH PRODUCT

Potentiometric study of the formation of hydroxo complexes of [Cu(terpy)]2+. Synthesis and crystal structure of [Cu(terpy) (H2O)](CF3SO3)2

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Two complexes of formula [Cu(terpy)(H2O)](CF3SO3)2 (1) and [Cu(terpy)(OH)]BPh4 (2) (terpy=2,2′∶6′,2″-terpyridine and BPh4=tetraphenylborate anion) have been synthesized and characterized by spectroscopic techniques. The x-ray crystal structure of (1) has been determined by x-ray diffraction. The structure is made up of [Cu(terpy)(H2O)]2+ mononuclear cations plus semi-coordinated CF3SO3 − anions. The coordination geometry around the copper atom is approximately elongated tetragonal octahedral. The oxygen atom of water and the three nitrogen atoms of terpy occupy the equatorial sites whereas the apical ones are filled by trifluoromethanesulphonate oxygen atoms. The formation of hydroxo complexes of [Cu(terpy)(H2O)]2+ has been investigated by potentiometry in aqueous solutions and the constants of the Equilibria (1) and (2) have been determined at 25°C and 0.1 mol dm−3 NaNO3: log K1=−8.106(1) and log K2=−6.96(2). The influence of tridentate N-donor ligands (Ln−) on the acidity of the coordinated water molecule of [Cu(L)(H2O)]2−n + complexes is analyzed and discussed in the light of reported thermodynamic and structural data.