Reversible 1,2-Alkyl Migration to Carbene and Ammonia Activation in an N‑Heterocyclic Carbene–Zirconium Complex

Addition of trimethylphosphine
to a bis­(phenolate)­benzyl­imidazolyl­idene­(dibenzyl)­zirconium
complex induces migration of a benzyl ligand from the metal center
to the Ccarbene atom. This process may be reversed, resulting
in Csp3–Csp3 activation,
by abstraction of the phosphine, an example of regulated, reversible alkyl migration. Addition of ammonia to the dibenzyl
complex results in migration of one benzyl group and protonolysis
of the other to generate a bis­(NH2)-bridged dimer via an
NMR-observable intermediate NH3 adduct.