Tripodal tris(2-aminoethyl)amine (tren) based ligands were synthesized via a reaction of tren with three equivalents of benzaldehyde derivatives containing electron donating and withdrawing substituents, followed by the reduction with sodium borohydride.  The resulting ligands were evaluated in copper catalyzed atom transfer radical addition (ATRA) utilizing free-radical diazo initiator AIBN (2,2'-azobis(2-methylpropionitrile)).   Electron donating groups such as methyl in the starting benzaldehyde were found to increase the catalytic activity in the addition of carbon tetrachloride to 1-hexene.  The opposite was observed with electron withdrawing groups such as chlorine.  Cyclic voltammetry of the copper(II) complexes confirmed that higher active complexes  also have more negative reduction potential (E1/2).  Molecular structure of the benzaldehyde derivative in the solid state indicated that copper(II) center was distorted trigonal bipyramidal in geometry, which was mostly due not only to the steric hindrance imposed by the benzyl group, but also relatively large coordinated halogen anion.

Novel tripodal tris(2-aminoethyl)amine (tren)-based ligand for copper catalyzed atom transfer radical addition (ATRA)

243rd National Meeting (2012)

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