PNNL

Abstract

The decomposition of NdCl3L (L = N,N-dimethylformamide [DMF] or N,N-dimethyacetamide [DMA]) compounds has been investigated by thermogravimetric and differential thermal analysis (TGA and DTA) coupled with Fourier transform infrared (FTIR) spectroscopy. When heated in air, the NdCl3L compounds decompose by a mechanism involving oxidation of the amide ligand to CO2 and HCl. Some free amide is also released in the thermal decomposition in air. However, when heated under nitrogen, clean release of DMA or DMF is observed. In both cases, the amide is released in two steps. From 30 to 40% of the amide is initially released with little or no associated enthalpy as measured by DTA. As the temperature is increased, the remaining 60 to 70% of the amide is released via an endothermic process. The enthalpy for this release is 53.1 ± 3.8 kJ/mole for DMF and 40.9 ± 1.1 kJ/mole for DMA, suggesting that DMF binds more strongly to Nd(III) than does DMA. This is a surprising result given that DMA is more basic than DMF. Steric effects caused by the additional methyl group in DMA might be responsible for the weaker binding of this amide compared to DMF.