Synthesis, Structure, and Magnetism of Binuclear Cu(II)Cu(II), Cu(II)Ni(II), and Ni(II)Ni(II) Complexes Doubly Bridged by Oxymate Groups

Binuclear complexes, [Cu(L)Cu(L′)(H2O)2]X2 (H2L=3,3′-trimethylenedinitrilobis(2-butanoneoxime) (H2dopn) or 3,3′-ethylenedinitrilobis(2-butanoneoxime) (H2doen); L′=2,2′-bipyridyl (bpy) or 1,10-phenanthroline (phen); X=ClO4 or NO3), [Ni(dopn)Cu(bpy)(H2O)](ClO4)2, and [Ni(dopn)Ni(bpy)2](ClO4)2, have been prepared and characterized. The structure of [Cu(dopn)Cu(phen)(CH3OH)2](ClO4)2 (di-methanol adduct) has been determined by single crystal X-ray method. The Cu(dopn) molecule coordinates to the second copper(II) ion through the deprotonated oximate oxygens to afford a binuclear structure doubly bridged by the oximate groups in the cis arrangement. The binuclear cation is bent at the oxymate oxygens with a dihedral angle of 26.7(2)°. The binuclear copper(II) complexes show a characteristic visible band of significant intensity (ε 2700–2900 dm3 mol−1cm−1) near 22000 cm−1 and a strong intramolecular antiferromagnetic spin-exchange interaction. The exchange integrals (J) are evaluated to be −413.3–−433.0 cm−1. The magnetic moment (per molecule) of the nickel(II)–copper(II) complex is 1.80 μB at room temperature and the moment of the binuclear nickel(II) complex is 2.94 μB, demonstrating that the Ni(dopn) entity of these complexes is diamagnetic.