Ordination of lanthanide nitrates with N,N,N ' ,N '- tetramethylsuccinamide

Two compound classes have been identified from the reaction of trivalent la nthanide nitrates with tetramethyl-succinamide (TMSA). The nature of these Ln-TMSA compounds has been examined in the solid phase by thermogravimetric analysis (TGA) and single-crystal X-ray diffraction and in solution by inf rared spectroscopy. Isostructural, 10-coordinate compounds with a 2:1 TMSA: Ln stoichiometry were found for the lanthanides La and Ce. Single-crystal X -ray diffraction analysis of the Ln-TMSA nitrate compounds, Ln = La and Ce, reveals a polymeric structure with each metal center containing one chelat ing bidentate succinamide and two bridging bidentate succinamides. For the remaining lanthanides Pr, Nd, Gd, Yb, and Lu, a series of isostructural, 9- coordinate compounds containing a 3:2 TMSA:Ln ratio were formed. Single-cry stal X-ray diffraction analysis of the Ln-TMSA products, Ln = Ce, Pr, Nd, G d, and Yb, reveals these compounds to be dimeric, with each metal center co ntaining one chelating bidentate succinamide and two bridging bidentate suc cinamides. The solution stoichiometries were examined in acetonitrile-water mixtures and support the stoichiometries observed in the solid-state struc tures. Cerium nitrate appears to be a special (and transitional) lanthanide in its reaction with TMSA. Although infrared and TGA analyses indicate a 2 :1 ligand-to-metal product, crystals for both the 2:1 and 3:2 compounds wer e isolated. No evidence for such multiple forms was found with any of the o ther lanthanides.