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

Abstract

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)-(H_zO)](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 Cu_z(terpy)Cl₄, which is shown to be Cu(terpy)Cl][CuCl₃].