Copper iminopyrrolidinates: a study of thermal and surface chemistry

Several copper(I) iminopyrrolidinates have been evaluated by thermogravimetric analysis (TGA) and solution based (1)H NMR studies to determine their thermal stability and decomposition mechanisms. Iminopyrrolidinates were used as a ligand for copper(I) to block previously identified decomposition routes of carbodiimide deinsertion and β-hydrogen abstraction. The compounds copper(I) isopropyl-iminopyrrolidinate (1) and copper(I) tert-butyl-iminopyrrolidinate (2) were synthesized for this study, and compared to the previously reported copper(I) tert-butyl-imino-2,2-dimethylpyrrolidinate (3) and the copper(I) guanidinate [Me(2)NC((i)PrN)(2)Cu](2) (4). Compounds 1 and 2 were found to be volatile yet susceptible to decomposition during TGA. At 165 °C in C(6)D(6), they had half-lives of 181.7 h and 23.7 h, respectively. The main thermolysis product of 1 and 2 was their respective protonated iminopyrrolidine ligand. β-Hydrogen abstraction was proposed for the mechanism of thermal decomposition. Since compound 3 showed no thermolysis at 165 °C, it was further studied by chemisorption on high surface area silica. It was found to eliminate an isobutene upon chemisoption at 275 °C. Annealing the sample at 350 °C showed further evidence of the decomposition of the surface species, likely eliminating ethene, and producing a surface bound methylene diamine.