NEW MACROCYCLIC COMPLEXES DERIVED FROM COBALT(III) CAGE COMPLEXES

The synthesis and partial characterization of several green complexes, derived from the products of the reactions between [CO(Cl2-sar)]3+ (C l2-sar = loro-3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane) and zinc p owder in water, are described. Most of the complexes appear to have [C oCl2(N4)] chromophores, where N4 denotes the tetraaza maocrocyclic lig and, dimethylene-1,4,8,11-tetraazacyclotetradecane(Ll). For trans-[CoC l2(Ll)]+, three isomers due to different configurations about the asym metric nitrogen donor centres were obtained and characterized by the e lectronic absorption and C-13 n.m.r. spectra. Their stereochemistry is discussed and compared with that of 1,4,8,11-tetraazacyclotetradecane on the basis of strain energy minimized calculations. A trans-[CoC12( H2L2)]3+ complex containing a related macrocycle with a pendant ethane -1,2-diamine arm [H2L2+, l)-13-methylene-1,4,8,11-tetraazacyclotetrade cane] was also isolated and characterized by X-ray crystallographic an alysis. All these molecules are derived from the decomposition of zinc alkyl complexes formed by oxidative addition of zinc to the parent [C o(II)(Cl2-sar)]2+ ion in aqueous solution.