The Steric Requirements of N,N′-Bis(salicylidene)-2-aminobenzylamines on Metal Chelate Formation

Abstract

Abstract Copper(II), Ni(II), Co(II), Zn(II), and Be(II) chelates of N,N′-bis(salicylidene)-2-aminobenzylamine and its methyl and dimethyl salicylidene derivatives have been prepared and characterized. According to the molecular models, the ligands are favorable to tetrahedral arrangement on complex formation. The spectral and magnetic properties revealed that all the Co(II) and some of the Cu(II) chelates were pseudo-tetrahedral, while the Ni(II) and other Cu(II) chelates were square-planar, with a considerable angle strain. This ligand property is somewhat inconsistent with the conclusion derived from N,N′-bis (salicylidene) polymethylenediamine chelates, in which the trimethylene analogue could not take a pseudotetrahedral arrangement around a metal ion. The difference in stereochemistry between the two ligands with the same number of bridging carbon atoms will be discussed on the basis of the flexibility and the steric requirement of the central chelate ring.