An unexpected influence of the nature of the amine on the crystal structure of some Co(III)–Bi(III) heterobimetallic complexes

Abstract

Two novel cobalt(III)–bismuth(III) heterometallic compounds [Co(NxH) 2(An) 2] 2[Bi(EDTA)(H 2O)] 2 · 7H 2O ( 1) and [Co(NxH) 2( p-Tol) 2][Bi(EDTA)] · 4H 2O ( 2) [An-aniline, p-Tol- para-toluidine, NxH-1,2-cyclohexanedionedioximate-ion, EDTA-ethylenediaminetetraacetate-ion] have been synthesized and characterized by NMR, thermogravimetry and single X-ray crystallography. Substitution of the aniline by para-toluidine molecules leads to radical changes in the anionic sub-lattice: from monomeric form to polymeric one. The coordination number of bismuth is 7+1 in 1, and 8 in 2; Bi coordination polyhedron in 1 can be described as a two-capped trigonal prism, while in 2 as a dodecahedron. The Co atoms in 1 and 2 have an octahedral coordination. NMR spectroscopy in DMSO solution confirms the trans-configuration of the complex cations in 1 and 2 by observation of a broad singlet of two symmetric hydrogen bonds. The NCH 2CH 2N component of EDTA ligand is in the domain of the fast exchange and the signal from this group is a singlet, while four acetate methylene protons give rise to an AB quartet system. It was shown that thermolysis of 1 and 2 occurs in three successive stages, via the dehydration, pyrolysis of the ligands and, finally, the formation of a sillenite-type phase Bi 26− x Co x O 40−δ and small quantities of Co 3O 4.