Metal–Ligand Cooperation Facilitates Bond Activation and Catalytic Hydrogenation with Zinc Pincer Complexes

A series of PNP zinc pincer complexes
capable of bond activation
via aromatization/dearomatization metal–ligand cooperation
(MLC) were prepared and characterized. Reversible heterolytic N–H
and H–H bond activation by MLC is shown, in which hemilability
of the phosphorus linkers plays a key role. Utilizing this zinc pincer
system, base-free catalytic hydrogenation of imines and ketones is
demonstrated. A detailed mechanistic study supported by computation
implicates the key role of MLC in facilitating effective catalysis.
This approach offers a new strategy for (de)­hydrogenation and other
catalytic transformations mediated by zinc and other main group metals.