Bonding implications of interatomic distances and ligand orientations in the iminolithium hexamers [LiNC(Ph)But]6 and [LiNC(Ph)NMe2]6: a stacked-ring approach to these and related oligomeric organolithium systems

The ligand orientations and Li–N distances in the title compounds show that their µ-3-imino units NC(Ph)R (R = But or NMe2) function as 3-electron ligands, forming one 2-centre LiN bond and one 3-centre Li2N bond to isosceles triangles of bridged metal atoms, prompting treatment of each hexamer [LiNC(Ph)R]6 as a pair of stacked cyclic trimers [LiNC(Ph)R]3; extension of this ring-stacking principle allows many other structures to be rationalised in lithium chemistry and facilitates structural predictions.