Controlling Gold Nanoclusters by Diphospine Ligands

We report the synthesis and structure determination of a new Au-22 nanocluster coordinated by six bidentate diphosphine ligands: 1,8-bis(diphenylphosphino) octane (L-8 for short). Single crystal X-ray crystallography and electrospray ionization mass spectrometry show that the cluster assembly is neutral and can be formulated as Au-22(L-8)(6). The Au-22 core consists of two Au-11 units clipped together by four L-8 ligands, while the additional two ligands coordinate to each Au-11 unit in a bidentate fashion. Eight gold atoms at the interface of the two Au-11 units are not coordinated by any ligands. Four short gold-gold distances (2.64-2.65 angstrom) are observed at the interface of the two Au-11 clusters as a result of the clamping force of the four clipping ligands and strong electronic interactions. The eight uncoordinated surface gold atoms in the Au-22(L-8)(6) nanocluster are unprecedented in atom-precise gold nanoparticles and can be considered as potential in situ active sites for catalysis.