Although extensively exploited, the true nature of the in situ formed catalyst still remains unclear. Dialkylzinc (alkyl = Me, Et) forms a stable adduct L with N,N′-ethylenebis(1-phenylethylamine ) and metalates N,N′-ethylenebis(benzylamine) to give the dimeric amide M (see Scheme 2).(18, 19) When operating in aprotic solvents, the precurser complexes L and M are believed to convert into a monomeric nitrogen donor-stabilized alkyl zinc hydride species.
