Synthesis and structural characterization of inverse-coordination clusters from a two-electron superatomic copper nanocluster

Abstract

We have synthesized and structurally characterized a series of centred cuboctahedral copper clusters, namely [Cu13{S2CNR2}6{C=CR′}4](PF6), 1a-d (where a: R = nBu, R′ = CO2Me; b: R = nBu, R′ = CO2Et; c: R = iPr, R′ = CO2Et; d: R = nPr, R′ = 3,5-(CF3)2C6H3); [Cu12(μ12-S){S2CNR2}6{C=CR′}4], 2a-c; [Cu12(μ12-Cl){S2CNR2}6{C=CR′}4](PF6), 3a-e (where e: R =nBu, R′ = Ph); [Cu12(μ12-Br){S2CNnBu2}6{C=CPh}4](PF6), 4e; and [Cu12(μ12-Cl)(μ3-Cl){S2CNnBu2}6{C=CCO2Me}3]+5a. Cluster 1a is the first structurally characterized copper cluster having a Cu13 centered cuboctahedral arrangement, a miniature of the bulk copper fcc structure. Furthermore, the partial Cu(0) character in the 2-electron superatoms 1 was confirmed by XANES. Inverse coordination clusters 2-5 are the first examples of copper clusters containing main group elements (Cl, Br, S) with a hyper-coordination number, twelve. A combined theoretical and experimental study was performed, which shows that the central copper (formally Cu1−) in nanoclusters 1 can be replaced by chalcogen/halogen atoms, resulting in the formation of clusters 2-5 which show enhanced luminescence properties and increase in the ionic component of the host-guest interaction as Br ≈ Cl > S > Cu, which is consistent with the Cu-X Wiberg indices. The new compounds have been characterized by ESI-MS,1H,13C NMR, IR, UV-visible, emission spectroscopy, and the structures 2a-b, 3d-e, 4e and 5a were established by X-ray diffraction analysis.