Unexpected chelation interaction for 2-hydroxy-2-(1-oxy-pyridin-2-yl)-N,N-diphenyl acetamide with La(III)

The lanthanide coordination chemistry of the new ligand 2-hydroxy-2-(1-oxy-pyridin-2-yl)-N,N-diphenyl acetamide (5) has been examined. X-ray crystal structure determinations for the free ligand 5 and for one complex, [La(5)6] (NO3)3·7H2O, have been completed and the latter reveals an unexpected bidentate chelation mode for 5 that involves the amide carbonyl oxygen atom and the 2-hydroxy oxygen atom of each ligand. The six bidentate ligands generate an icosohedral inner coordination sphere. The N-oxide oxygen atom of each ligand also hydrogen bonds with a 2-hydroxyl hydrogen atom in a neighboring ligand molecule in the same molecular unit.

The lanthanide coordination chemistry for 2-hydroxy-2-(1-oxy-pyridin-2yl)-N,N-diphenyl acetamide (5) has been examined and a novel homoleptic complex [La(5)63+](NO3)3·7H2O has been isolated and structurally characterized by single crystal X-ray diffraction methods. The La(III) accommodates six bidentate, neutral molecules of 5 that generate a twelve-membered distorted icosohedral inner coordination sphere with each ligand binding via the amide carbonyl and the 2-hydroxy oxygen atoms. This results in unexpected five-membered chelate rings. The pyridine N-oxide hydrogen bonds with a 2-hydroxy H-atom in a neighboring ligand.Figure optionsDownload as PowerPoint slide