MOLECULAR STRUCTURES AND SINGLE CRYSTAL ESR SPECTRA OF IMIDAZO-LATE-BRIDGED Co(III)-Cu(II)-Co(III)AND Co(III)-Zn(III)-Co(III) COMPLEXES

The structures of the heterotrinuclear complexes, [(NH 3 ) 5 ColmCu(dien)ImCo(NH 3 ) 5 ]- (C10 4 ) 6 ·4H 2 0 and [(NH 3 ) 5 CoImZn(dien)ImCo(NH 3 ) 5 ]-(ClO 4 ) 6 ·4H_2O, are reported. Co--Cu--Co crystallizes in the monoclinic space group C2/c with a =32.414(4), b= 9.421(1), c= 15.167(5)?,β= 90.91(2)°, Z=4 and Co--Zn--Co in the same space group with a = 32.578 (2), b = 9.419(1), c = 15.125(3)?, β=91.10(1)°Z=4. The Cu(Ⅱ) and Zn(Ⅱ) geometries are intermediate between a trigonal bipyramid and a square pyramid,the Co(Ⅲ) is a- hexagonal coordination and the dien ligand shows a disordered contribution in the respective structure.The magnetic properties of Co--Cu--Co are investigated. From the single crystal ESR spectra studies, the anisotropic g and A tensors and electronic spin-density of Co--Cu --Co are obtained and the nature of the bonding for Cu 2+ is discussed.