COMPOUNDS OF NICKEL(II) WITH TRANS-6,13-DINITRO-6,13-DIMETHYL-1,4,8,11-TETRAAZACYCLOTETRADECANE AND TRANS-6,13-DIAMINO-6,13-DIMETHYL-1,4,8,11-TETRAAZACYCLOTETRADECANE, WITH STRUCTURAL STUDIES OF 5 (TRANS-6,13-DIAMINO-6,13-DIMETHYL-1,4,8,11-TETRAAZACYCLOTETRADECANE)NICKEL(II) COMPOUNDS

Compounds of Ni(II) with the macrocyclic ligand trans-6,13-dimethyl-6,13-dinitro-1,4,8,11-tetraazacyclotetradecane (dino), which is formed by condensation of bis(ethane-1,2-diamine)nickel(ii) salts, nitroethane and formaldehyde, are described, together with homologues formed by substituting propane-1,2-diamine and/or 1-nitropropane. The nitro functions of [Ni(dino)]2+ were reduced by catalytic hydrogenation to form (trans-6,13-diamino-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane)nickel(II), [Ni(diam)]2+, isolated as approximately equal amounts of two isomeric forms; designated alpha (with the R,S,R,S configuration of the chiral nitrogen centres, overall configuration 1alpha,4alpha,6beta,8alpha,11alpha,13alpha), and beta (with the R,R,S,S, 1alpha,4beta,6alpha,8beta,11alpha,13beta configuration). The alpha-isomer is metastable, and in solution isomerizes to the beta-isomer, with rate constant of 5.0(5) X 10(-5) s-1 in 2 mol l.-1. NaCl solution at 50-degrees-C, the rate of this reaction increasing in both acid and base. Protonation constants (pK at 25-degrees-C in 0.1 mol l.-l NaClO4) for diam are 11.2(l), 9.7(l), 6.2(l), 5.3(l), and for the isomeric nickel(ii) cations are alpha 4-94(2), 2.4(5); and beta 4.5(l), 4.0(1). Compounds of diam with the beta-configuration were prepared with triplet ground state Ni(II) with diam in hexadentate coordination (e.g. beta-[Ni(diam-N6)] Cl2) and in tetradentate coordination with the neutral (e.g. trans-beta-[Ni(diam-N4)(NCS)2]) or diprotonated ligand (e.g. trans-beta-[Ni(diamH2-N4)(NCS)2] (CNS)2). Compounds prepared with the alpha-configuration with triplet ground-state Ni(II) had pentadentate diam with the neutral (e.g. trans-alpha-[Ni(diam-N5)(H2O)] Cl2) or monoprotonated ligand (e.g. trans-alpha-[Ni(diaMH-N5)Cl] (ClO4)2). Singlet ground-state Ni(II) compounds with the square planar diprotonated ligand were prepared for both configurations. Structures are reported for beta-[Ni(diam-N6)](ClO4)2(H2O), R 0.062 for 5708 reflections; beta-[Ni(diam-N6)] [ZnCl4].1.5H2O, R 0.064 for 4332 reflections; beta-[Ni(diam-N6)] Cl2.6H2O, R 0-044 for 2001 reflections; trans-beta-[Ni(diam-N4)(NCS)2] R 0.056 for 1521 reflections; and trans-alpha-[Ni(diamH-N5)Cl](ClO4)2(H2O), R 0.047 for 2667 reflections.