Stereochemistry of six-co-ordinate bis(tridentate ligand)metal complexes

Abstract

Repulsion-energy calculations show that the mer isomer of [M(tridentate ligand)₂] exists as a potential-energy minimum at all values of the normalised bite, b, of the chelate rings, whereas the two fat isomers exist only at high values of the normalised bite. The mer isomer is generally more stable than the fac isomers. The unsym-fac isomer formed with ligands of small normalised bite is not closely related to the octahedron, but approaches a skew rectangular bipyramid, or trigonal prism, the latter description being particularly appropriate for unsymmetrical tridentate ligands. These predictions are compared with known crystal structures.