SOME HEXADENTATE NI(II)-EDTA-TYPE COMPLEXES CONTAINING 5-MEMBERED DIAMINE RINGS - THE MOLECULAR AND CRYSTAL-STRUCTURE OF THE TRANS(O-5) ISOMER OF -N,N'-DIACETATO-N,N'-DI-3-PROPIONATO)NICKELATE(II) HEXAHYDRATE,TRANS(O-5-)BA[NI(EDDADP)]CENTER-DOT-6H(2)O, AND STRAIN ANALYSIS OF EDTA-TYPE CHELATES IN RELATION TO THEIR OCTAHEDRAL DISTORTION

Two paramagnetic octahedral Ni(II)-edta-type complexes, Ba[Ni(eddadp)] . 6H(2)O (1) (eddadp = thylenediamine-N,N'-diacetate-N,N'-di-3-propio nate ion) and Ba[Ni(edtp)] . 3H(2)O (2) (edtp = ethylenediamine-tetra- 3-propionate ion) have been prepared and characterized. The ligands us ed, forming beta-alaninate rings, are likely to function as hexadentat e ligands with a larger metal ions, Because of the strain in the equat orial plane, as expected, the trans (O-5) configuration of complex 1 w as found to dominate and this geometry was verified crystallographical ly. The crystal is monoclinic with the space group C2/c, a = 11.091(3) , b = 13.526(4), c = 28.064(6) Angstrom, beta = 93.56(2)degrees 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 octahe dral or pseudooctahedral Ni(II) complexes. Spectra of these complexes are discussed in comparison with those of the trans (O-5)-[Ni(SS-edds) ](2-) complex (SS-edds = SS-ethylenediamine-N,N'-disuccinate ion) of k nown structure. The magnetic measurements are also reported for the co mplexes studied. Structural parameters and strain analysis data of M-e dta-type complexes are discussed in relation to their octahedral disto rtion. (C) 1998 Elsevier Science S.A. All rights reserved.