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 acetone, reacts with nickel(II) in alcohols to form a mixture of the meso- and the previously unreported rac-isomeric complex cations. The meso perchlorate salt crystallises as sparingly soluble adducts, bis acetonitrile from acetonitrile and bis ammine from ammonia/methanol, enabling facile separation of the isomers. Preparations of a selection of nickel(II) compounds of the rac-isomer are described, and their properties compared with those of the previously 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.