Structural studies of lanthanide complexes with new hydrophobic malonamidesolvent extraction agents

Two new hydrophobic malonamide ligands butyl-N,N'-dimethyl-N,N'-diphenyl ma lonamide and ethoxyethyl-N,N'-dimethyl-N,N'-diphenyl malonamide and corresp onding lanthanide complexes [Ln(NO3)(3)(L)(2)], Ln = Nd or Pr, have been pr epared and structurally characterised. The structural studies establish tha t the alkyl or alkyloxy groups attached to the central carbon atom of the m alonamides do not effect the bidentate co-ordination of adjacent carbonyl o xygen atoms. All the metal complexes presented show the lanthanide to be 10 -co-ordinate, being bonded to four oxygen atoms of two malonamides and six oxygen atoms of three nitrates. Malonamide ligands with alkyloxy groups hav e been shown previously to be better extractants for lanthanide(III) and ac tinide(III) ions than those with just alkyl groups. This solid state eviden ce seems to suggest that the enhanced extraction performance of ligands wit h an ether oxygen in the alkyloxy chain is not due to direct co-ordination between the metal ion and the ether oxygen.