π(Arene) versus donor ligand complexation in the formation of the heterobimetallic lithium–potassium dianion of (S)-N-(α-methylbenzyl)allylamine

Reaction of the chiral amine (S)-N-(α-methylbenzyl)allylamine with n-BuLi in hexane and the subsequent addition of the thus formed lithium amide to n-BuK followed by thf results in the formation and crystallisation of the cyclic heterobimetallic tetramer, {[(S)-α-(PhC(H)Me)(CH2CHdouble bond; length as m-dashCHK)N]Li · (thf)}4 (1), containing the C-metallated and N-metallated dianion of the chiral amine. The structure reveals a degree of asymmetry derived from competitive binding of K+ cations to available thf molecules, π(arene) electrons, and deprotonated allylamine moieties. Solution studies indicate very strong agostic interactions with C–H bonds in the allylamine group and retention of the terminal vinylic anion rather than delocalisation.