Some hexadentate Ni(II)-edta-type complexes containing five-membered diamine rings. The molecular and crystal structure of the trans(O5) isomer of barium(ethylenediamine-N,N′-diacetato-N,N′-di-3-propionato) nickelate (II) hexahydrate, trans(O5)-Ba[Ni(eddadp)]·6H2O, and strain analysis of edta-type chelates in relation to their octahedral distortion

Two paramagnetic octahedral Ni(II)-edta-type complexes, Ba[Ni(eddadp)]·6H2O (1) (eddadp = ethylenediamine-N,N′-diacetate-N,N′-di-3-propionate ion) and Ba[Ni(edtp)]·3H2O (2) (edtp = ethylenediamine-tetra-3-propionate ion) have been prepared and characterized. The ligands used, forming β-alaninate rings, are likely to function as hexadentate ligands with a larger metal ions. Because of the strain in the equatorial plane, as expected, the trans(O5) configuration of complex 1 was found to dominate and this geometry was verified crystallographically. The crystal is monoclinic with the space group C2/c, a = 11.091 (3), b = 13.526(4), c = 28.064(6) Å, β = 93.56(2)° and Z = 8. The IR (carboxylate region) and electronic absorption spectra of these complexes are reported. There is no added multiplicity found in the electronic spectra of complexes that generally are seen for octahedral or pseudooctahedral Ni(II) complexes. Spectra of these complexes are discussed in comparison with those of the trans (O5)-[Ni(SS-edds)]2- complex (SS-edds = SS-ethylenediamine-N,N′-disuccinate ion) of known structure. The magnetic measurements are also reported for the complexes studied. Structural parameters and strain analysis data of M-edta-type complexes are discussed in relation to their octahedral distortion. © 1998 Elsevier Science S.A. All rights reserved.