NMR-STUDIES OF (AMIDO)CUPRATES

A series of MeLi/Et2NCu ratios in THF and Et2O were examined by Li-7 and H-1 NMR spectroscopy. MeLi/CuNEt2 ratios between 0.5 and 1.0 appear to afford a series of species with composition [MeCu2(NEt2)2]Li (5), [Me2Cu3(NEt2)3]Li2 (6), and (MeCuNEt2)Li (8) analogous to Me3Cu2Li (2), Clive's reagent Me5Cu3Li2 (1), and Me2CuLi observed in the homocuprate series. Addition of 0.5 equiv of LiNEt2 to MeCu appears to form Me2CuLi and (Me2CU2NEt2)Li (7). Addition of 2.0 equiv of MeLi to Et2NCu affords a solution that may contain Me2CuLi, [Me4Cu2NEt]Li3 (13), or a mixture of the two species depending upon the mode of preparation. No new species are formed for 1.0-2.0 MeLi:Et2NCu ratios. Possible structures for 5-7 are suggested by analogy with reported X-ray structures for organocopper compounds with varying Li:Cu ratios in the metal cluster.