Synthesis, characterisation and application of lanthanide cyclen complexes in organic synthesis

Hexadentate cyclen complexes of Sm(III), Eu(III) and Yb(III) have been prepared from 1,4- bis[(R)-alpha-methylbenzyl-aminocarbonylmethyl]- 1,4,7,10-tetraazacycldodecane and characterised. The crystal structures of the isomorphous complexes of Eu(III) and Sm (III) have been determined. These may be electrochemically reduced to the +II oxidation state and employed in organic synthesis. However, no asymmetric induction was observed and this can be attributed to the fluxional nature of these complexes in solution and the limited asymmetric influence imparted by the N-(alpha-methylbenzyl) acetamide chiral auxiliary.