Nitrogenous chelate complexes of transition metals. VI. Complexes of copper(II) with 2,2',2'-terpyridine

A series of compounds of the general type Cu(terpy)X2 (terpy = 2,2',2"- terpyridine; X = Cl, Br, I, NCS) have been prepared. The above complexes are sparingly soluble in non-aqueous media in which they show some ionization to yield species of the kind [Cu(terpy)X]+ which are isolable as their perchlorate salts. Reaction of terpyridine with excess copper(11) perchlorate yields [Cu(terpy)-(HzO)](ClO4)2. The water molecule can be replaced by both mono- and bi-dentate amine ligands giving the complexes Cu(terpy)L](ClO4)2 (L = NH3, py, bipy). Conductimetric titrations in non-aqueous solvents show that Cu(terpy)(H2O)]2+ reacts with halide ion to give, in turn, [Cu(terpy)X]+ and Cu(terpy)X2. The bis-terpyridine complexes [Cu(terpy)2]X2,nH2O (X = ClO4, n = 1; X = NCS, n = 2; X = I, n = 1) have also been prepared. [Cu(terpy)2]2+ is stable in the presence of halide ion in aqueous solution but in non-aqueous solution rearrangement to the corresponding mono-complex Cu(terpy)X2 is instantaneous. This was confirmed by conductimetric titrations. Reaction of terpyridine with excess copper(11) chloride affords a complex Cuz(terpy)Cl4, which is shown to be Cu(terpy)Cl][CuCl3].