Organometallic Clusters in Catalysis: From Designed Synthesis and Structural Evolution to Functional Applications

ConspectusMetal catalysis has profoundly shaped the landscape of organic synthesis, driving advancements in chemical manufacturing, pharmaceuticals, and material science. While traditional mechanistic understanding has been largely based on mononuclear organometallic complexes and their elementary reaction steps, recent studies increasingly reveal that single metal species often undergo structural evolution to generate organometallic clusters, nanoclusters, and larger aggregates during catalytic processes. These in situ formed polynuclear organometallic clusters with diverse nuclearities, charges, and configurations not only impact catalytic efficiency and selectivity but also reshape the viewpoint about active species in metal catalysis. A deep understanding of this structural evolution process is highly needed to optimize catalytic performance, minimize catalyst loading, and lower metal residues in final products. Moreover, systematic studies on the synthesis, structural evaluation, and application of these polynuclear organometallic clusters will expand frontiers of cluster chemistry into many interdisciplinary fields. Over the past decade, we have successfully developed a cyclization-based synthetic strategy to achieve a series of structurally diverse polynuclear organometallic compounds and clusters (OMCs) of Group 11 metals. A key focus has been paid to the unique carbon-polymetallic bonding in OMCs, including the carbon-polymetal interactions of varying nuclearities and the newly discovered hyperconjugative aromaticity formed in gem-diaurated aryl complexes. Furthermore, we have unraveled two major pathways, redox-driven aggregation and ligand abstraction-caused assembly, to propel structural evolution from low nuclear number compounds to polymetallic organometallic nanoclusters containing several carbanionic units. The role of these in situ formed OMCs in catalytic reactions has been comprehensively evaluated and classified as active and inactive ingredients. Based on the understanding of the structures and reactivity of OMCs, we have exploited the applications of OMCs spanning catalysis, luminescent materials, and bioinorganic chemistry, particularly including the cancer therapy of hypercoordinated gold clusters via synergistic C-Au bond cleavage. Overall, in this Account we try to highlight designed synthesis of polynuclear organometallic compounds and clusters via a cyclization-based synthetic strategy, mechanistic studies on the reactivity of carbon-polymetal bonding therein and the structural evolution process from low to high nuclearity cluster transformation, and functional applications enabled by their distinctive bonding motifs. We hope that this summary can provide a novel perspective to bridge organic synthesis and cluster chemistry and open new avenues for designing functional polynuclear organometallic compounds and clusters.