Snapshots of Cooperative Trimetallic Alkene Hydrogenation.

Bimetallic cooperativity and synergistic effects have emerged as powerful tools that can enhance the reactivity and selectivity of catalytic systems, offering a pathway toward the development of catalysts based on Earth-abundant elements. Although not uncommon in nature, discrete molecular systems featuring more than two cooperative metal sites are virtually unknown. Herein we report the design of a well-defined molecular heterotrimetallic [Ga2Ni] system, which is effective in alkene hydrogenation catalysis. Species representing 'snapshots' of the catalytic cycle are isolated through consecutive addition of ethylene and dihydrogen, allowing for in-depth experimental mechanistic elucidation of two sequential 2-electron oxidative processes. Alongside combined computational, kinetic, and isotopic labeling studies, these findings reveal a fully mapped hydrogenation mechanism in which all three metal sites partake in the alkene hydrogenation process. This system thus provides unique insights into cooperative molecular multimetallic catalysis and establishes a blueprint for rationally designed multicentered cooperativity beyond established diatomic concepts.