DINUCLEAR AND TETRANUCLEAR COPPER(II) COMPLEXES OF THE TETRADENTATE LIGAND 1,4-BIS(2-PYRIDYLTHIO)PHTHALAZINE - STRUCTURAL, MAGNETIC, AND ELECTROCHEMICAL STUDIES

The tetradentate ligand 1,4-bis(2-pyridylthio)phthalazine (PTPH) forms dinuclear copper(II) complexes [Cu2(PTPH)Cl4].2CH3OH(1) and [Cu2(PTPH)Br4].1.5H2O(2), involving both diazine and double halogen bridges between the copper centers, an unusual tetranuclear complex [Cu2(PTPH)(mu3-OH)(NO3)3(H2O)]2(3), and a dinuclear nitrate complex [Cu2(PTPH)(mu2-OH)(NO3)2(H2O)2](NO3) (4). 1 crystallizes in the monoclinic system, space group C2/c, with a = 20.710(4) angstrom, b = 11.694(3) angstrom, c = 15.509(4) angstrom, beta = 133.85(l)-degrees, and Z = 8. 3 crystallizes in the triclinic system, space group P1BAR, with a = 12.075(2) angstrom, b = 12.344(1) angstrom, c = 8.728(2) angstrom, alpha = 97.78(l)-degrees, beta = 96.70(l)-degrees, gamma = 110.390(9)-degrees, and Z = 2. 4 crystallizes in the triclinic system, space group P1BAR, with a = 10.687(3) angstrom, b = 13.472(3) angstrom, c = 9.638(2) angstrom, a = 103.03(2)-degrees, beta = 90.75(2)-degrees, gamma = 110.44(2)-degrees, and Z = 2. Variable-temperature magnetic measurements for 1-4 show dominant antiferromagnetic coupling with -2J values in the range 124-313 cm-1. A significant pyramidal distortion at the mu3-OH in 3 suppresses the antiferromagnetic exchange below the anticipated value. Compounds 1 and 2 exhibit two-electron reduction at positive potentials (vs SCE), to produce rearranged dinuclear copper(I) species.