SYNTHESIS AND STRUCTURAL STUDIES OF COPPER(II), NICKEL(II) AND COBALT(II) COMPLEXES OF A 14-MEMBERED TRANS-N2S2 DIBENZO MACROCYCLE WITH 2 PENDANT PYRIDYLMETHYL GROUPS

The 8,17-bis(2-pyridylmethyl)-functionalised derivative (L2) of a 14-membered trans-N2S2 dibenzo macrocycle 6,7.8,9,15,16,17,18-octahydrodibenzo[fm][1,8,4,11]dithiadiazacyclotetradecine has been prepared and its crystal structure determined. The ligand L2 forms stable complexes with nickel(II) 1, copper(II) 2 and cobalt(II) 3. The complexes have been isolated in the solid state and characterised by standard methods and single-crystal X-ray diffraction. Crystal data for L2: space group P2(1)/c, a = 945.6(l), b = 1467.9(2), c = 1041.1(2) pm, beta = 115.67(1)-degrees, Z = 2, R(R') = 0.035(0.040) for 2183 observed reflections. Complex 1: space group P2(1)/n, a = 141 8.8(3), b = 1 288.8(3), c = 1867.0(4) pm, beta = 109.20(3)-degrees, Z = 4, R(R') = 0.067(0.068) for 4124 observed reflections. The nickel atom lies outside the macrocyclic cavity and is in a distorted octahedral cis-N4S2 environment. Complex 2: space group P1BAR, a = 787.8(2), b = 1137.5(2), c = 1800.5(4) pm, alpha = 98.84(3), beta = 99.43(3), gamma = 94.74(3)-degrees, Z = 2, R(R') = 0.082(0.075) for 2165 observed reflections. The copper atom exhibits a highly distorted trigonal-prismatic co-ordination geometry with the following distances: Cu-S, 242.7(4) and 269.8(4), Cu-N(amine) 225.8(11) and 255.2(10) and Cu-N(pyridine) 198.4(11) and 200.2(12) pm, respectively. Complex 3: space group P1BAR, a = 789.3(2), b = 1165.8(2), c = 1806.2(3) pm, alpha = 98.90(1), beta = 98.86(2), 7=94.24(2)-degrees, Z = 2, R(R') = 0.066(0.063) for 3039 observed reflections. The geometry about high-spin cobalt(II) is trigonal prismatic with average Co-S, Co-N(amine) and Co-N(pyridine) bond lengths of 252.5, 229.0 and 213.7 pm, respectively. The stereochemistry of the free and complexed ligand is discussed with respect to these structures.