trans-Disubstituted diamido/diamine cyclam zirconium complexes

The reaction of H2[1,8-dibenzyl-1,4,8,11-tetraazacyclotetradecane] (H2Bn2Cyclam) with 2 equiv of LiBu gives Li2Bn2Cyclam(L)2 (L = Et2O or THF) that reacts with ZrCl4(THF)2 to afford (Bn2Cyclam)ZrCl2 in 40% yield. Alternatively (Bn2Cyclam)ZrCl2 may be obtained via ZrCl2(CH2SiMe3)2(Et2O)2 in a significantly higher yield (87%), avoiding the lithiation of H2Bn2Cyclam. The syntheses of other H2∗Bn2Cyclam ligand precursors (∗Bn = 3,5-dimethylbenzyl and 3,5-di(tert-butyl)benzyl) and the corresponding Zr derivatives ({3,5-Me2Bn}2-Cyclam)ZrCl2 and ({3,5-tBu2Bn}2-Cyclam)ZrCl2 are also reported. Results on preliminary tests of ε-caprolactone and ethylene polymerisation reactions are presented.