A sterically-hindered tricyclic biimidazoline ligand which is also a precursor to a novel tetramethyl-cyclen

The synthesis of a tricyclic biimidazoline L featuring gem-dimethyl-substituted carbons α to the imino-nitrogens is described. A tris-chelate cadmium complex [CdL3](ClO4)2 has been prepared and fully characterized. Unlike the parent ligandʹs cadmium(II) tris-chelate complex, this [CdL3]2+ does not undergo facile exchange with free ligand in solution at ambient temperature. Ligand L is a convenient precursor to a novel bis(gem-dimethyl) derivative of cyclen: 2,2,9,9-tetramethyl-1,4,7,10-tetraazacyclododecane (2,2,9,9-Me4-Cyclen). Crystal structures of the L2·dithiooxamide adduct, the [CdL3](ClO4)2 complex, as well as 2,2,9,9-Me4-Cyclen have been determined.