STRUCTURAL RELATIONSHIPS AFFORDED BY THE COORDINATION OF 2,2'-BIPYRIDINE TO THE (IMINODIACETATO) COPPER (II) CHELATE: SYNTHESIS, STRUCTURE AND PROPERTIES OF (2,2'-BIPYRIDINE) (N-(2-HYDROXYETHYL)IMINODIACETATO) COPPER(II) TETRAHYDRATE

摘要

The stoichiometric reaction of copper(II) hydroxycarbonate, N-(2-hydroxyethyl)iminodiacetic acid (H_2 heida valence HOCH_2CH_2N(CH2CO_2H)_2)) and 2,2'-bipyridine (bipy) in water yields crystalline (2,2'-bipyridine)(N-(2-hydroxyethyl)iminodiacetato)copper (II) tetrahydrate, (Cu(heida)-(bipy)) centre dot 4H_2O (compound I). This was studied by TG analysis (with FT-IR study of evolved gases), IR, electronic and ESR spectra, magnetic susceptibility data and single crystal X-ray diffraction methods. The compound crystallises in the triclinic system, space group P1, a valence 7.011(2), b valence 12.586(3), c valence 13.052(3)A', #alpha# valence 62.14(1), #beta# valence 80.51(2), #gamma# valence 77.09(2)o, Z valence 2, final R_1 valence 0.051 for 3900 independent reflections. The Cu(II) atom exhibits an asymmetric, elon-gated, octahedral coordination (type 4 + 1 + 1), and bipy acts as an N,N-bidentate ligand sup-plying two among the four closest donor atoms of the metal (Cu-N bond lengths of 1.994(2) and 2.053(2) A); heida plays an N,O,O',O"-tetradentate chelating role (bond lengths Cu-N valence 2.075(2),, Cu O(carboxyl) valence 1.958(2). Cu-O'(carboxyl) valence 2.337(2) and Cu-O"(hydroxyl) valence 2.459(2) A). The effective bidentate chelation of bipy imposes fac-chelation to the iminodiace-tate moiety of heida in I, as previously reported in mixed-ligand complexes having a 1:1:2 Cu(II)/IDA/N(heterocyclic) or a 1/1/(1 + 1) Cu/IDA/(N-heterocyclic + N-aliphatic) donor ratio. The tetradentate role of heida in I reveals its noticeable conformational flexibility. The crystal features a hydrogen bond network forming supra-molecular chains extending along the a axis. These are linked by two symmetry-related hydrogen bonds of the type O(hydroxyl)H ... O~i(carboxyl) between two adjacent complex units (symmetry code i valence -x, -y + 1,-z + 1), related to each other by an inversion centre.