Compounds of nickel(II) with rac- and meso-5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene

The macrocycle 5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradeca- 4,11-diene, formed by reaction of ethane-1,2-diamine with benzylidene aceto ne, reacts with nickel(II) in alcohols to form a mixture of the meso- and t he previously unreported rac-isomeric complex cations. The meso perchlorate salt crystallises as sparingly soluble adducts, bis acetonitrile from acet onitrile and bis ammine from ammonia/methanol, enabling facile separation o f the isomers. Preparations of a selection of nickel(II) compounds of the r ac-isomer are described, and their properties compared with those of the pr eviously reported meso-analogues. The relative strain energies of the three possible configurations of each of the isomeric complex nickel(II) cations are calculated by molecular mechanics modelling. (C) 2001 Elsevier Science B.V. All rights reserved.