CRYSTAL-STRUCTURE, SPECTROSCOPIC AND MAGNETIC-PROPERTIES OF 2 UNUSUALCOMPOUNDS - [CU(TERPY)(N-3)CL] AND [(CU(0.75)NI(0.25)(TERPY)(N-3)2)(2)].2H-2O (TERPY = 2,2' 6',2''-TERPYRIDINE)/

The crystal structures of two unusual complexes [Cu(terpy)(N3)Cl] 1 an d [{Cu0.75Ni0.25(terpy)-(N3)2}2].2H2O 2 (terpy = 2,2':6',2''-terpyridi ne) have been determined at room temperature: 1, space group P2(1)/c, a = 10.586(5), b = 8.572(1), c = 16.396(3) angstrom, beta = 100.69(3)- degrees, Z = 4, R = R' = 0.036, for 2818 reflections with I greater-th an-or-equal-to 3sigma(I); 2, space group P2(1)/c, a = 10.195(5), b = 9 .996(3), c = 15.866(8) angstrom, beta = 91.10(5)-degrees, Z = 4, R = R ' = 0.055 for 3134 reflections with I greater-than-or-equal-to 3sigma( I). Complex 1 possesses the first known co-ordination polyhedron inclu ding both halide (Cl) and pseudohalide (N3) ligands. It shows a square -pyramidal topology for the copper(II), with the three nitrogen atoms of the terpy ligand and one terminal nitrogen atom of the azide group in the basal positions while the chloride atom is in the apical one. C ompound 2 contains 25% of [{Ni(terpy)(N3)2}2].2H2O and 75% of [{Cu-(te rpy)(N3)2}2].2H2O enclosed in the global lattice. It possesses (end-on ) azide bridges and terminal azide ligands. The co-ordination polyhedr on of the metal ion is a slightly distorted octahedron with the nitrog en atoms of the terpy ligand and a nitrogen atom of one of the azide b ridging groups in the equatorial positions, while the nitrogen atoms o f both the bridge and terminal azide groups occupy the axial positions . The pure copper phase related to compound 2 exhibits a discrete mole cular topology; however, the pure nickel phase shows the same dimeric structure, which is useful for comparison. The magnetic properties of compound 2 can be explained by contributions from the isolated Cu2 and Ni2 entities, giving rise to global ferromagnetic interactions charac terised by the parameters J = 20.1 cm-1, D = - 1 2.5 cm-1, g(Ni) = 2.2 6 and rho = 0.76 corresponding to the copper proportion. The EPR measu rements for both compounds reveal rhombic symmetries for the g tensors . Single-crystal EPR measurements on 2 show the presence of two magnet ically different copper entities, with an antiferrodistortive ordering , in the lattice.