Copper(I1) complexes with a tridentate chelating ligand within the general 2 N, 0 donor class, containing a bis(benzimidazo1e) ether donor set, have been synthesized and characterized. Complexes of 1:l stoichiometry form on mixing C~( C 1 0~)~. 6 H~0 with the ligand in acetonitrile. X-band EPR spectra of the above complexes examined as a frozen acetonitrile solution indicate gll > g,. The gll and A,, values are consistent with the binding of less than three nitrogen atoms to the complex and border on Peisach and Blumberg plots of All vs gll for two nitrogen and two oxygen atoms in the equatorial plane. Copper complexes of 1:2 stoichiometry form in the presesnce of an added exogenous ligand, viz. azide, acetate, and benzimidazole. X-Band EPR spectra of the above complexes indicate a severe distortion of the tetragonal symmetry. All of these show less than four g,, components and a broadening of the g, component. Superimposed on the broad g, component are eleven lines due to super hyperfine interaction (shf), with an average coupling constant of BN 14 f 1 G. Only in one case does the m, = -3/2 component in the gll region show well-resolved shf, with nine lines and AN = 11 1 G, and the intensity pattern of the shf lines is in fair agreement with that observed for splitting due to four nitrogen atoms, Le.

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 > 9• and the large 911 and low All have been interpreted in terms of a distorted basal plane. Superimposed on the 9• 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).

Manganese(II) complexes of bis(2-benzimidazolylmethyl) ether (DGB), bis(2-benzimidazolylmethyl) sulphide (TGB) and the n-butyl derivative ofDGB (BDGB) were prepared and characterised. The solution e.p.r, spectrum of [Mn(TGB)C12] in DMF at 143 K is commensurate with an axially distorted monomeric manganese(II) complex, room temperature magnetic moment (6.04B.M.) per manganese(II) atom being in the range found for other d s monomeric manganese(II) complexes. The solution e.p.r. spectrum of [Mn(BDGB)Clz].ZHzO in DMF at 143 K indicates the presence of two equivalent manganese(II) ions coupled by an exchange interaction, fostered by bridging chlorides. Evidence for this is provided by a nearly isotropic 11 line hyperfine structure of 5SMn, with a coupling constant 45_ 5G. Contact-shifted 1H n.m.r. data also supports an exchange coupled dimeric manganese complex. The room temperature magnetic moment, 5.64 B.M., per manganese(II) indicates quenching of the magnetic moment below that of monomeric manganese(II) ion. The [Mn(DGB)Clz].HzO complex exhibits a magnetic moment of 6.02 B.M. per manganese, indicating a monomeric manganese complex. E.p.r. data of the complex diluted in an analogous Zn-DGB complex (1:20) correlates well for D = 0.22 cm-1 and 2-~ 0.267. The [Mn(DGB)-(ClOg)z ] and [-Mn(BDGB)(C1Og)2] complexes, diluted in analogous Zn-DGB and Zn-BDGB complexes (1:20), show a strong single e.p.r, line at gerf ~ 2. The complexes have low magnetic moments; 4.44 B.M./Mn and 4.39 B.M./ Mn, at room temperature.

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