New options in directed cupration: Studies in heteroleptic bis(amido)cuprate formation

AbstractThe 2:1 combination of MPLi (MP = 2-methylpiperidide) with CuBr gives the novel complex [(MP)2CuLi(THF)2]2LiBr 12 and introduces the chiral ligand MP to the evolving field of Directed ortho Cupration reagents. Subsequent syntheses have focused on developing heteroleptic bis(amido) arrangements at Cu, with 1:1 mixtures of two out of MPLi, DMPLi and TMPLi (DMP = 2,6-cis-dimethylpiperidide; TMP = 2,2,6,6-tetramethylpiperidide) being reacted with CuI salts in the presence of THF. Resulting lithiocuprates reveal solid state dimers based on the heteroleptic bis(amido) formulations R2N(TMP)Cu(Br)Li2(THF)2 (R2N = MP 13; R2N = DMP 14). The heteroleptic Gilman lithiocuprate PIP(TMP)CuLi (PIP = piperidide) 15 has also been prepared. In each of 12–15, significant variations in the orientations of the amide ligands can be rationalized in terms of steric effects and, in the case of 15, stabilization of the alkali metal by Me…Li interaction is evidenced