Mono- and trinuclear metal complexes of a 12-membered tetraaza macrocycle: Synthesis and characterization

The macrocycle 1,4,7,10-tetraazacyclododecane-2,3-dione (tadd) was prepared and characterized by elemental analyses, and KR spectral data. A monometallic complex, [La(tadd)Cl-2(H2O)(2)]Cl, was prepared by the template reaction of diethyl oxalate (deo) and triethylenetetraamine (teta) in the presence of the lanthanide chloride. When the monometallic complex was reacted with transition metal chlorides, the trinuclear complexes of the type [{La(tadd)Cl-2(H2O)(2)}(2)MCl2]Cl-2 [M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) were prepared. The chemical compositions of the complexes have been established on the basis of analytical, molar conductance, and ES mass data. The coordination number eight around the encapsulated La3+ ion and six-coordinate octahedral geometry around the exo-oxygen bonded M2+ ions are reported.