Copper(II) complexes with a tridentate chelating ligand within the general 2N, X (X = O or S) donor class, containing a bis(benzimidazolyl) donor set, were prepared and characterized. X-band e.p.r, spectra of the complexes indicate 911 > 9β’ and the large 911 and low All have been interpreted in terms of a distorted basal plane. Superimposed on the 9β’ component are five SHF lines with A N = 16 + 2 G, supporting the interaction of two nitrogen atoms with the copper nucleus. Thus, the basal plane of the complex comprises 2N atoms, with the ligand hetero atom being axially coordinated. 180mmol) and then heated for ca. 3 h at ca. 150 ~ C on an oil bath, until all effervescence ceased. The resulting red-blue glass-like solid, after cooling, was powdered and added to 4M HCI (250cm 3) in small amounts. Upon scratching of the sides of the flask a grey white precipitate formed which was removed by filtration and washed by stirring several times in Me2CO. The hydrochloride was dissolved in distilled H20 (200cm 3) and the resulting filtrate was neutralized with 1:1 ammonia until a white precipitate formed. This precipitate was collected, washed with Et20 and recrystallized from Me20 (yield 75~o, m.p. 280 295 ~ C).