A tetranuclear nickel hydride cluster capable of reversible activation of aromatic and aliphatic C–H bonds

Metal cluster complexes supported by multiple hydrides are useful for activating inert bonds and molecules, while nickel-based variants capable of activating external substrates remain scarce. Here, we report a tetranuclear Ni-hydride-phosphine cluster, [Ni4H4(PtBu3)4] (1), which we synthesize by reacting [Li(THF)x][Ni{N(SiMe3)2}3] (x ≈ 4.5 − 5) with pinacolborane (HBpin) in the presence of tri-tert-butylphosphine (PtBu3). Its molecular structure features a tetrahedral Ni4 core, with four face-capping μ3-hydrides and four terminally bound PtBu3 ligands. Cluster 1 is capable of reversible C–H and C–D bond cleavage of benzene-d6, toluene-d8, n-octane-d18, and its own PtBu3 ligands at 50 °C, leading to H/D exchange between the deuterated solvents and the ligands in 1. This reactivity is further utilized in the catalytic hydrogen isotope exchange reaction between benzene-d6 and toluene. The reversible dissociation of one PtBu3 ligand in 1 is proposed as the key step to trigger the C–H and C–D bond activation. Quantum chemical computations propose the reversible displacement of one of the PtBu3 ligands in 1 as the key step in triggering C–H and C–D bond activation. Metal cluster complexes supported by multiple hydrides are useful for activating inert bonds and molecules, but nickel-based variants capable of activating external substrates remain scarce. Here, the authors report the synthesis and C—H(D) bond cleavage of a tetranuclear Ni-hydride-phosphine cluster.