Cadmium(II) complexes of fully condensed Schiff-base ligands derived from two different symmetrical and asymmetrical tripodal tetraamines and 2-acetylpyridine; the novel observations for heptadentate mono-capped trigonal antiprismatic Schiff-base complexes

In the presence of cadmium(II), 2-acetylpyridine condenses with tris(3-amin opropyl)amine, tpt, and bis(3-aminopropyl)(2-aminoethyl)amine, ppe, in abso lute methanol to produce two fully condensed potentially heptadentate Schif f-base complexes, [Cd(py(3)tpt)](ClO4)(2) and [Cd(py(3)ppe)](ClO4)(2). X-ra y structure analysis of the former complex shows mono-capped distorted trig onal antiprism geometry wherein the Cd-unique nitrogen distance is 2.486 An gstrom. In comparison with the weighted mean of other Cd-N distances, 2.425 Angstrom, this indicates a 'bonding' interaction. The mean of the bond ang les about the bridging amine atom (C-N1-C), 107.43 degrees, is quite close to sp(3) hybridization as expected for an unconstrained tertiary amine nitr ogen atom. The H-1 NMR, COSY and HMQC spectra shows six inequivalent proton s, two for each methylene group caused by the rigidity of resulting six-mem bered chelate rings. (C) 2000 Elsevier Science Ltd. All rights reserved.