Ni(II)-mediated synthesis of the novel tripodal aminopyridyl ligand tamepyr: Coordination geometry and rigidity of complexes with the divalent 3d metals Fe-Zn and with In(III)

The synthesis of the novel tripodal chelator 'tamepyr' (N,N′,N″-tris(2-pyridylmethyl)-1,1,1-tris(aminomethyl)ethane) and complexation of the ligand with Fe(II) and Zn(II) has been studied. The Ni(II) complex of tamepyr was prepared cleanly by a template reaction of the 1,1,1-tris(aminomethyl)ethane framework with 2-pyridinecarboxaldehyde and Ni(ClO4)2 · 6H2O followed by a sodium borohydride reduction to afford the desired material (>40% yield). Treating the Ni(II) complex with excess sodium cyanide liberated the free ligand. A Zn(II) and low-spin Fe(II) complex form readily from free tamepyr.