MAGNETIC INTERACTION IN DINUCLEAR TRIPHOS-COBALT COMPLEXES WITH CO-COSEPARATIONS OF 8-ANGSTROM AND 10-ANGSTROM

Weak antiferromagnetic exchange interactions are observed in two Co-II dimers of the general formula [{(triphos)Co}(2)(mu-dicarboxylato)](BF 4)(2) where the dicarboxylate is the dianion of fumaric acid [3.(BF4)( 2)] or terephthalic acid [4.(BF4)(2)] and triphos is the tridentate ph osphorus ligand 1,1,1-tris(diphenylphosphanomethyl)ethane. In these co mplexes the metal ions are separated by 8 and 10 Angstrom, as determin ed by X-ray crystallography. Insight into the interaction pathway is g ained through molecular orbital calculations performed on model compou nds. The influence of bridging-ligand distortions and the stereochemis try around the two cobalt centres is discussed.