Carbonylmetallated Palladium Nanoclusters for Visible-Light-Driven Carbonylation under 1 atm of CO

Palladium nanoclusters (Pd NCs) hold great promise in organic synthesis; however their controlled synthesis via direct reduction remains challenging due to kinetically favored formation of nanoparticles. In this study, we employ carbonylmetallate ligands to regulate the reduction reaction kinetics and successfully achieve three [Co(CO)₄]^- terminated Pd₁₄ NCs. Magnetic studies, in conjunction with quantum chemical calculations, suggest that the Pd₁₄ cluster exhibits a quartet ground state and open-shell superatomic character with 1S¹ jellium configuration, representing the first open-shell palladium superatom containing one free electron. The high stability of the clusters is largely attributed to significant electron transfer from the [Co(CO)₄]^- ligand to the Pd₁₄ core, facilitated by polarized Pd(δ^-)-Co(δ⁺) bonds, along with pronounced Co→Pd σ-, π-, and δ-donor, as well as δ-acceptor, interactions between the [Co(CO)₄]^- ligands and the Pd₁₄ core. Remarkably, the Pd₁₄ NC exhibits exceptional catalytic activity in carbonylative cross-couplings under mild conditions (1 atm CO and 30 W of 450 nm LEDs), owing to enhanced nucleophile activation by the [Co(CO)₄] moieties. This protocol tolerates a broad range of challenging aryl and alkyl halides and is applicable to complex derivatization and the targeted synthesis of bioactive pharmaceuticals. Our findings demonstrate the potential of carbonylmetallate ligands in Pd cluster synthesis and enable further exploration of metal NCs with unique polar heterometallic components for synergistic catalytic applications.