Nickel(II) compounds of a tri-amine mono-imine macrocycle: Preparations and structures of (5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradec-4-ene)nickel(II) compounds

Reduction of one imine function of (5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene)nickel(II) with 1 molar proportion of NaBH4 produces as the major product the tri-amine-monoimine macrocyclic cation (5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradec-4-ene)nickel(II), Ni(tm)](2+). Pairs of isomeric singlet ground state perchlorate and tetrachlorozincate salts of [Ni(tm)](2+) were prepared and the structures determined for the 1RS,8SR,11SR,12RS (labeled as beta) and 1RS,8RS,11RS,12SR (labeled as alpha) tetrachlorozincate salts. Triplet ground state trans-beta-[Ni(tm)(NCS)(2)] and catena-trans-{beta-Ni(tm)-NC-Ni(CN)(2)-CN-}(n)center dot 2nH(2)O have the macrocycle in planar coordination and alpha-[{Ni(tm)}(2)(C2O4)](ClO4)(2) has the macrocycle folded. With pentane-2,4-dione the compounds [beta-Ni(tm)]center dot[alpha-Ni(tm)(acac)](ClO4)(3) and [Ni(teta)]center dot[alpha-Ni(tm)(acac)](ClO4)(3) (teta = C-meso-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) with both square-planar and octahedral Ni(II) cations were prepared and the latter was structurally characterized. Isomerisation in solution of metastable alpha-[Ni(tm)](2+) to stable beta-[Ni(tm)](2+) is extremely slow, even in base. (C) 2011 Elsevier Ltd. All rights reserved.