Macrocyclic Cu-2(II), Cu-4(II), Ni-3(II), and Ni-4(II) complexes: Magnetic properties of tetranuclear systems

A binuclear tetraprotonated macrocyclic complex [Mg-2(L-2-H-4)(NO3)(2) . 6H(2)O (1) has been obtained by template condensation of 4-methyl-2,6-diformylphenol and 1,2-diaminoethane in the presence of magnesium acetate and nitrate. Complex 1 On reduction with NaBH4, followed by the removal of magnesium, yields the 36-membered octaaminotetraphenol macrocyclic ligand H4L1. The replacement Of magnesium in 1 with copper(II) leads to the formation Of the binuclear complex [CU2L3(ClO4)(2)] (2) derived from the [2+2] cyclization product of 4-methyl-2,6-diformylphenol and 1,2-diaminoethane. From H4L1 a series of tetranuclear nickel(II) complexes 5-8 with the core cation [Ni4L1(mu(2)-X)(2)(mu(2)-H2O)(2)](2+) (X = NCS, N-3, OAc, or Cl) have been synthesized and characterized. The trinuclear complex [Ni3L1(acac)(2)(H2O)(2) . 2H(2)O (9), obtained by reacting nickel(II) acetylacetonate with H4L1, on treatment with nickel(II) perchlorate produces the tetranuclear compound [Ni4Li(acac)(2)(H2O)(4)](ClO4)(2) (10). Variable-temperature (4-300 K) magnetic susceptibility measurements have been carried out for the tetracopper(II) complex [Cu1L1(H2O)(4)](ClO4)(4) (3) and the tetranickel(II) complexes [Ni4L1(mu(3)-OH)(mu(2)-H2O)(2)(ClO4](ClO4)(2) . 2CH(3) COCH3 . H2O (4), [Ni4L1(mu(2)-NCS)(2)(mu(2)-H2O)(2)](ClO4)(2) . 2CH(3)CN (5), [Ni4L1(mu(2)-N-3)(2)(mu(2)-H2O)(2)](ClO4)(2) . 2CH(3)OH (6), [Ni4L1(mu(2)-OAc)(2)(mu(2)-H2O)(2)](ClO4)(2) . 2H(2)O (7), and [Ni4L1(mu(2)-Cl)(2)(mu(2)-H2O)(2)](Cl-2 . 4H(2)O (8). The X-ray structure of 5 has been determined. The complex (C50H70N12O14Cl2S2Ni4) crystallizes in the triclinic: Space group P1 with a = 11,794(6) Angstrom, b = 12.523(4) Angstrom, c = 12.794(5) Angstrom, alpha = 117.28(5)degrees, beta = 96.38(4)degrees, gamma = 109.65(3)degrees, and Z = 1. In the asymmetric unit each Of the nickel(II) centers with distorted octahedral geometry is triply-bridged by a phenoxide group, a water molecule, and a N-bonded thiocyanate and these metal centres are further bridged to their symmetry-related counterparts bg another phenoxide group. The experimental susceptibility data have been analyzed using appropriate Heisenberg Spin coupling models (H = -2 Sigma(j>i=1)(4)J(ij)S(i) . S-j) and the best spin exchange parameters obtained are as follows: J = -288(3) cm(-1) (3); J(1) = -8.1(2) cm(-1), J(2) = -10.2(2) cm(-1) (4); J(1) = -34.5(1.0) cm(-1), J(2) = -9.5(2.0) cm(-1) (5); J(1) = -34(1) cm(-1), J(2) = 11(2) cm(-1) (6); J(1) = -30(1) cm(-1),J(2) = -7.0(1. 5) cm(-1) (7); J(1) = -32(1) cm(-1), J(2) = -4(1) cm(-1) (8).