Covalent Bonding of Molecular Catalysts to Metal Oxide Supports via Transesterification Leads to High Loading and Tunable Hybrid Nickel Catalysts

Here, we report the synthesis, characterization, and structure-function properties for a new class of hybrid catalysts covalently bound to metal oxide (MOx) supports via metal-ester bonds. This MOx-ester bonding motif exhibits several notable differences compared to traditional hybrid catalysts. One key advantage is the ability to achieve monolayer catalyst surface coverage, effectively creating single-atom catalysts at a density of two catalyst molecules per nm² of metal oxide support. This motif also introduces tunable electronic interactions between the metal oxide support and the molecular catalyst, enabling control over catalyst speciation and oxidation states. A series of MOx-ester nickel catalysts on varying metal oxide supports were synthesized and characterized by infrared and X-ray spectroscopies. The influence the support imparted on the molecular nickel catalyst was elucidated through reactivity trends. By exploiting the alternating redox step in the Suzuki-Miyaura cross-coupling reaction, we were able to correlate catalyst properties and reactivity to the point of zero charge (PZC) of the MOx supports. Observed reactivity differences are attributed to the ability of the MOx supports to influence the surface-bound molecular nickel catalyst through electronic induction. By modulating the electron density at the nickel center through just changing the metal oxide support, this class of hybrid catalysts allows for precise control of the accessible molecular catalyst oxidation states can coordination environment, thus enabling tailored catalytic mechanisms. These findings highlight the potential of MOx-ester hybrid catalysts as a platform for advancing small molecule activations and sustainable nickel-based catalysis.