CRYSTAL-STRUCTURES AND FERROMAGNETIC PROPERTIES OF 2 NEW DINUCLEAR COMPLEXES WITH THIOCYANATO BRIDGING LIGANDS - [(NI-2(1,2-DIAMINO-2-METHYLPROPANE)(3)(NCS)(2))(MU-NCS)(2)](2)[NI(1,2-DIAMINO-2-METHYLPROPANE)(2)(NCS)(2)].H2(O) AND [(NI-2(1,2-DIAMINO-2-METHYLPROPANE)(4)) (MU-NCS)(2)](PF6)(2) - MAGNETOSTRUCTURAL CORRELATIONS

Two complexes of formulas [{Ni-2(1,2-diamino-2-methylpropane)(3)(NCS)(2)}(mu-NCS)(2)](2)[Ni(1,2-diamino-2-methylpropane)(2)(NCS)(2)].H2O (1) and [{Ni-2(1,2-diamino-2-methylpropane)(4)}(mu-NCS)(2)](PF6)(2) (2) have been synthesized, and their crystal structures have been determined by single-crystal X-ray diffraction methods at room temperature. Complex 1 crystallizes in the triclinic system, space group P1 $($) over bar$$, Z = 1, with a = 11.400(3) Angstrom, b = 13.068(3) Angstrom, c = 14.381(3) Angstrom, alpha = 77.37(2)degrees, beta = 67.89(3)degrees, gamma = 73.21(3)degrees, and V = 1886(1) Angstrom(3). Complex 2 crystallizes in the monoclinic system, space group P2(1)/n, Z = 2, with a = 7.5937(8) Angstrom, b = 14.3627(9) Angstrom, c = 17.0895(12) Angstrom, beta = 91.03(2)0, and V = 1863.4(4) Angstrom(3). The crystal structures of 1 and 2 were determined from Patterson synthesis and refined by full-matrix least-squares techniques. The final values of the reliability factors R (R(W)) were 0.050 (0.055) for 1 and 0.065 (0.076) for 2, with 8558 and 3517 observed reflections, respectively. Their structures consist essentially of dinuclear Ni-2 entities in which the two Ni(II) atoms are linked by two NCS- bridges. In 1 this dinuclear entity is highly asymmetric: one Ni(II) atom has two bidentate 1,2-diamino-2-methylpropane molecules as blocking ligands whereas the second Ni(II) has only one amine and two terminal thiocyanate-AT ions as blocking ligands. On the other hand, in crystal structure of 1 there are two of these dinuclear entities together with one mononuclear [Ni(amine)(2)(NCS)(2)] entity. The two entities are neutral, and all Ni(II) ions are octahedrally coordinated. In 2 there is only one dinuclear entity in which each Ni(II) is octahedrally coordinated by two thiocyanato bridging ligands and two amines as blocking ligands, giving a dicationic complex. Two PF6- anions are present in the crystal lattice for each dinuclear entity. Magnetic susceptibility data, measured from 300 to 4 K, were fitted to the Ginsberg equation, giving the parameters J = 4.3 cm(-1), g = 2.13, D = -20 cm(-1), and z'J' = 0.20 cm(-1) for 1 and J = 6.3 cm(-1), g = 2.14, D = -2.0 cm(-1), and z'J' = -0.14 cm(-1) for 2. The magnetic behavior of these and related complexes is discussed, and some magneto-structural trends are given.