HOMO AND HETERONUCLEAR COMPLEXES OF DIOXIME LIGANDS

Abstract

The mononuclear fragments [Cu(HDopn)(OH)2]+ and [Cu(HPopn)(OH)2]+, [H2Dopn=3,3′-(trimethylene- dinitrilo)-dibutan-2–one dioximate and H2Popn, = 3, 3′-(phenylenedinitrilo)-dibutan-2–one dioximate] were used to prepare four binuclear complexes [(OH2)Cu (Dopn)Cu(ditn)]2+, [(OH2)Cu(Dopn)Ni(ditn)(H2O)]2+ (ditn=diethylenetriamine) and [(OH2)Cu(Popn)Cu(L) (H2O)]2+ (L=2,2′-bipyridine or 1,10–phenanthroline). Two trinuclear complexes, [{Cu(Popn)(OH2)}2M (H2O)n]2+ (when M=CuII, n=1; M=ZnII, n= 2), have been synthesised and characterised by elemental analyses, f.a.b. mass, i.r., electronic, e.s.r. spectroscopy and variable temperature (5–300K) magnetic susceptibility measurements. A strong antiferromagnetic interaction (J=−545cm−1 to −700cm−1) has been found for the binuclear copper(II) complexes. The X-band e.s.r. spectra of these complexes at 300K and for trinuclear complexes at 120K indicate square-pyramidal geometry for the copper centres with a (dx2−y2)1 ground state. The binuclear complex of copper(II)–nickel(II) centres with antiferromagnetic interaction (J=−107 cm−1) is described, and moderately strong zero-field splitting within the quartet state leads to Kramers doublet, as indicated by X-band e.s.r. spectra of this complex. The trinuclear copper(II) complex with an antiferromagnetic interaction (J= −350cm−1) is also described. The heterometallic trinuclear copper(II)–zinc(II)–copper(II) system shows a very weak interaction (J≤−1cm−1).