SYNTHESIS, SPECTROSCOPIC CHARACTERIZATION AND ELECTROCHEMICAL-BEHAVIOR OF NICKEL(II) COMPLEXES WITH C-MESO-5,5,7,12,12,14-HEXAMETHYLCYCLOTETRADECANE (ME6[14]ANEN4) - CRYSTAL-STRUCTURE OF (NI(ME6[14]ANEN4))I2

A series of complexes of formula {Ni(Me6[14]aneN4)X2} (Me6[14]aneN4 = 12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane and X = N3 (1), NCO (2), NCS (3), AcO (4) or I (5) has been synthesized. The crystal stru cture of (5) has been determined by X-ray diffraction methods. The nic kel atom is surrounded by a square-planar array of nitrogen atoms, giv ing a low-spin complex. The macrocyclic ligand shows the most stable c onformation, the six-membered rings exhibiting the chair form while th e gauche conformation is adopted by the five-membered rings. Spectrosc opic and magnetic data for (1)-(4) are consistent with octahedral coor dination around the nickel atom, which is achieved by four N atoms of the macrocyclic ligand in a single plane and by two azido-N (1), cyana to-N (2), thiocyanato-N (3) and carboxylato-O (4) groups occupying the axial positions. An electrochemical study of the oxidation of (1)-(5) has been carried out in nonaqueous solvents and the prospects of synt hesis of the corresponding nickel(III) species are discussed in the li ght of the electrochemical data.