Atomically Precise Rhodium‐Gold Carbonyl Nanoclusters: In‐Depth Synthesis and Multivalence Investigation of [Rh16Au6(CO)36]6−, and its Correlation with [Rh10Au(CO)26]3−

The synthesis of the previously-reported atomically-precise [Rh16Au6(CO)36]6− (1) nanocluster has been optimized by screening different reaction variables like solvent, stoichiometric ratio, counterion and atmosphere. Its multivalence properties have also been studied by means of electrochemical and spectroelectrochemical techniques; the results pointed out a remarkable electron-sponge behaviour, as under such experimental conditions 1 is capable to release one electron and accept up to four more, while retaining its molecular structure. This scarce structural variation has been confirmed through DFT calculations on those species whose redox processes showed the maximum reversibility, namely [Rh16Au6(CO)36]7− and [Rh16Au6(CO)36]5−. Moreover, we report herein the isolation and characterization of the new [Rh10Au(CO)26]3− (2) nanocluster, which represents one of the major fallouts of the synthetic pathway investigation of 1. Finally, we disclosed the existence of further species that, from preliminary results, appear to be new large atomically-precise Rh−Au nanoclusters, which will be the subject of future investigations. Cluster 2 has been identified via single-crystal X-ray diffraction analysis, and the characterization of both clusters 1 and 2 completed by infrared (IR) spectroscopy and Electrospray Ionization Mass Spectrometry (ESI-MS).