Synthesis and structural studies of transition metal complexes of cyclic amidines

Cyclic amidines PHZ and MPHZ (shown below) can be viewed as eight-membered cyclic diamines with two of the methylene carbons fused to the benzene rings. Although the axial positions in the bis-complexes of PHZ and MPHZ are open for fifth and sixth coordination, only four-coordinated complexes with copper(II), cobalt(II), nickel(II) and zinc(II) could be prepared. The molecular structures of these compounds and of some palladium(II), platinum(II) and platinum(IV) compounds are explained on the basis of their analytical, spectroscopic, magnetic and conductance data. Thermogravimetric analyses were carried out to explain mode of decomposition. The results show that complexation of cyclic amidines is not only sterically controlled, but factors such as unusual chelate bite angle, multiple chelate ring formation and crystal field stabilization play important role in affecting the stability and coordination number of the complexes.