[Ni8(CNtBu)12][Cl]: A nickel isocyanide nanocluster with a folded nanosheet structure

The reaction of 1.75 equiv of tBuNC with Ni(1,5-COD)2, followed by crystallization from benzene/pentane, resulted in the isolation of [Ni8(CNtBu)12][Cl] (2) in low yields. Similarly, the reaction of Ni(1,5-COD)2 with 0.6 equiv of [Ni(CNtBu)4], followed by addition of 0.08 equiv of I2, resulted in the formation of [Ni8(CNtBu)12][I] (3), which could be isolated in 52% yield after work-up. Both 2 and 3 adopt folded nanosheet structures in the solid state, characterized by two symmetry-related planar Ni4 arrays, six terminally bound tBuNC ligands, and six tBuNC ligands that adopt bridging coordination modes. The metrical parameters of the six bridging tBuNC ligands suggest that they have been reduced to their [tBuNC]2− form. In contrast to the nanosheet structures observed for 2 and 3, gas phase Ni8 is predicted to feature a compact bisdisphenoid ground state structure. The strikingly different structural outcomes reveal the profound structural changes that can occur upon addition of ligands to bare metal clusters. Ultimately, the characterization of 2 and 3 will enable more accurate structural predictions of ligand-protected nanoclusters in the future.