Complexing properties of α-nitroketones. Part III. A stereochemical investigation of some new copper(II)α-nitroketonate complexes and their base adducts with O- and N-donors
Complexes [CuL2], [CuL2B2], and [CuL2B′](L = an α-nitroketonato-anion obtained from nitroacetone, 3,3-dimethyl-1-nitrobutan-2-one, and 3-nitrocamphor; B = water or acetone; B′= 2,2′-bipyridine or 1,10-phenanthroline) have been prepared and investigated by electronic and e.s.r. spectroscopy, and magnetic and X-ray measurements. An elongated tetragonal symmetry is assigned to all the solid complexes studied, essentially square planar for the [CuL2] species (CuO4 chromophore), six-co-ordinate and pseudo-octahedral for [CuL2B2](CuO4O2 chromophore). For the [CuL2B′] species (CuO4N2 chromophore), which are also six-co-ordinate and pseudo-octahedral, with restricted tetragonal distortion, e.s.r. spectra indicate that both nitrogen atoms of the N-base are equatorially bound to CuII, with consequent in-plane co-ordination of only two of the oxygen atoms of the α-nitroketonic groups, while the other two oxygen atoms are displaced to the axial positions.