On the Concept of Hemilability: Insights into a Donor-Functionalized Iridium(I) NHC Motif and Its Impact on Reactivity

Novel
iridium­(I) complexes bearing N-donor-functionalized N-heterocyclic
carbene ligands were synthesized. Although hemilabile coordination
of the attached donor is considered beneficial in catalysis, no detailed
study of this phenomenon in these systems is available to date. The
present report provides insight into the hemilabile bonding properties
of a N,N′-bis­(pyridin-2-yl)-imidazolylidene
(NCN) ligand motif on iridium­(I). In most cases, the presented compounds
exhibit rare fluxional hemilabile coordination of the N donor, and
remarkable performance in catalytic transfer hydrogenation is observed.
Further, extensive reactivity studies often led to unexpected products.