The study of the ESR spectra parameters of Cu(Acac)2 in different solvents shows that the anisotropy of the nuclear hyperfine interaction tensor varies with changes in solvent. The effect is most clearly exhibited by the parameter A⊥. A correlation is obtained between the spectral data and the nature of the solvent ligand. The results are in agreement with the empirical parameters DII,I of Selbin and DN of Gutmann. Our empirical parameter is also a moderately sensitive one for ranking solvents.

Epr spectra of some cupric /3-ketoenolates, -dioximates, 0-dioximates, and Schiff bases in chloroform solution were recorded at room temperature and at -160°( frozen state). The bonding parameters were calculated from spectral data. The bonding properties of the odd electron were derived as a function of the nature of the ligand donor atoms, the size of the chelate ring, and substituent effects. The relationship between covalency of bonding and complex stability is discussed.This work was aimed at studying the electron spin resonance spectra of several copper(II) complexes and to draw some conclusions concerning the bonding properties of the odd electron, depending on the nature of the donor atoms in the ligands, the size of the chelate ring, and effects of substituents on the chelate ring. The epr spectra of copper(II)-acetylacetonate type complexes have been treated by several authors. [1][2][3][4][5][6] In all of the above complexes, it was assumed that the Cu11 ion is surrounded by the four donor atoms in a planar configuration (Dih symmetry) and that each donor atom has a 2s,2px,2py,2pz atomic orbital available for the formation of molecular orbitals with the atomic d orbitals of the central ion. From group theory, Gersmann and Swalen8 obtained the proper linear combinations of ligand orbitals with the copper d orbitals which form the antibonding wave functions of the planar cupric chelate compound. The expressions for the in-plane antibonding wave functions are Big = Qtdxy --[-(1) + (2> + ffxy(3) -VXy(4) ] Ag = /?dx2_y2 -y2(l -/32)1/2[-pxy(1) -pxy(2) + Pxy<3) + Pxy(4) ] The above wave functions are applicable also for tetradentate Schiff base chelates of C2" symmetry, where the corresponding symmetry designations are B2 and Ai, in the sense used by Swett and Dudek.6

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The reactions between Fe 3+ ions and acetylacetonedioxlme (AADO) have been studied by potentiometric, polarographic and spectrophotometric methods. Two Fel+ ions are reduced in aqueous solution by one AADOmolecule to give Fe 2+ ions and the oxidized form of AADO(NPO= AADO-2e = 2-nitrosopent-2-en-4-one oxime). NPO forms a water soluble, red coloured complex with FeOlI). The synthesiS of bis(2-nitrosopent-2-en-4-one oximato) Fe(III) complex is described. The elemental analysis of the solid complex is consistent with the composition FeO(NP0>Z<0H). The IR, EPR and Mossbauer spectra of the cOIDplex are presented and the bonding properties of the coordination environment of Fe(IIO is discussed. A mechanism for the oxydoreducnon and complexation reactions for the Fe 3+'AAOOsystem is proposed and its kinetic parameters are: k ox. red. =1.72 x 10 -I min -1, kcompl.= 5.13 10-2 min~l.