Metal-induced ring contraction in a macrocyclic ligand; X-ray crystal structure of a cobalt complex

Abstract

Replacement of alkaline earth metal ions from a conjugated hexadentate nitrogen analogue of [18]-annulene by some first row transition metal ions significantly smaller than the macrocycle cavity is accompanied by an intramolecular ring contraction yielding a 15-membered quinquedentate macrocycle of improved fit; the X-ray crystal structure of the cobalt complex has been determined.