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.