COPPER COORDINATION CHEMISTRY OF NOVEL OCTADENTATE, TETRANUCLEATING, BIS(DIAZINE) LIGANDS - STRUCTURAL AND MAGNETIC-PROPERTIES OF TETRANUCLEAR COMPLEXES INVOLVING A RECTANGULAR ARRAY OF COPPER(II) CENTERS

The potentially octadentate, tetranucleating ligands 1,4,6,9-tetrakis((R-2-pyridyl)amino)benzodipyridazine (TNLR: TNL (R = H), TNL4 (R = 4 Me), TNL5 (R = 5Me), TNL4E (R = 4Et) bond four copper(II) centers in a rectangular structure involving two distant copper pairs in one molecular entity in the derivatives [Cu4(L)(mu(2)-OH)2(H2O)8](CF3SO3)6 (L = TNL4 (I), TNL5 (IV)), [Cu4(TNL)(mu(2)-OH)2(H2O)6(EtOH)2](CF3SO3)6 (II), [Cu4(TNL)(mu(-2)-OH)2(NO3)4](NO3)2.2H2O (III), [Cu4-(TNL4)(mu(-2)-OH)2(H2O)2Br6] (V), and [Cu4(TNL4E)(mu(-2)-Cl)4Cl4] (VI). Variable-temperature magnetic studies indicate strong local, intrapair antiferromagnetic coupling in the hydroxide-bridged compounds but also the presence of significant, distant, interpair antiferromagnetic coupling across the benzodipyridazine ring system. Exchange in the chloro-bridged complex (VI) is dominated by weak ferromagnetic coupling. The crystal and molecular structures are reported for [Cu4(TNL4)(mu(-2)-OH)2(H2O)8]-(CF3SO3)6.6H2O (I) and [Cu4(TNL)(mu(-2)-OH)2(H2O)6(EtOH)2](CF3SO3)6 (II). I crystallizes in the monoclinic system, space group I2/m, with a = 10.813 (9) angstrom, b = 26.204 (15) angstrom, c = 13.489 (15) angstrom, beta = 98.73 (8)-degrees, and two formula units per unit cell. II crystallizes in the monoclinic system, space group I2/m, with a = 11.907 (3) angstrom, b = 19.858 (3) angstrom, c = 15.965 (4) angstrom, beta = 105.31 (2)-degrees, and two formula units per unit cell. In both structures pairs of square-pyramidal copper centers are bridged by a hydroxide and diazine unit with Cu-OH-Cu angles of 116.3-degrees (I) and 116.0-degrees (II) and Cu-Cu separations of 3.202 angstrom (I) and 3.190 (2) angstrom (II).