BINUCLEAR LEAD(II) AND COPPER(II) COMPLEXES OF 1,4-DIHYDRAZINOPHTHALAZINE (DHPH) - STABILIZATION OF COPPER(II) IN THE PRESENCE OF A HYDRAZINE MOIETY AND X-RAY CRYSTAL-STRUCTURE AND MAGNETIC-PROPERTIES OF [CU2(DHPH)2(H2O)2(CLO4)2](CLO4)2

The tetradentate, binucleating ligand, 1,4-dihydrazinophthalazine (DHPH) does not form stable copper(II) complexes on direct reaction with copper(II) salts, because of its strongly reducing nature. However, binuclear copper(II) complexes of DHPH can be produced as relatively stable solid-state species by transmetalation of [Pb2(DHPH)2(MeOH)2(ClO4)2](ClO4)2 (I) with copper(II) salts. The single-crystal X-ray structure of [Cu2(DHPH)2(H2O)2(ClO4)2](ClO4)2 (II) has been determined. Cu2C16H24N12Cl4O18 (II) crystallized in the triclinic system, space group P1BAR with a = 8.0732 (22) angstrom, b = 10.0881 (19) angstrom, c = 10.2377 (24) angstrom, alpha = 97.357 (18)-degrees, beta = 99.960 (22)-degrees, gamma = 106.677 (18)-degrees, and one formula unit per unit cell. Refinement by full-matrix least squares gave final residuals R = 0.068 and R(w) = 0.051. Each copper centre is bonded by four short planar contacts to ligand nitrogen atoms (Cu-N 1.96-2.02 angstrom) with longer axial contacts to water (2.351 angstrom) and a perchlorate oxygen (2.615 angstrom). II exhibits fairly strong intradimer antiferromagnetic coupling with -2J = 489 (1) cm-1. A comparison of this complex with a structurally related binuclear copper pyridazine complex indicates a capacitor-like effect associated with the phthalazine-benzene ring, which leads to reduced spin-coupling for the phthalazine bridge.