An ultrastable thiolate/diglyme ligated cluster: Au 20 (PET) 15 (DG) 2 .

The synthesis and characterization of an Au 20 (PET) 15 (DG) 2 (PET = phenylethane thiol; DG = diglyme) cluster is reported. Mass spectrometry reveals this as the first diglyme ligated cluster where diglyme ligands survive ionization into the gas phase. Thermal analysis shows the cluster degrades at 156 °C, whereas the similar Au 20 (PET) 16 cluster degrades at 125 °C, representing markedly increased thermal stability. A combination of NMR spectroscopy and computational modeling suggests that the diglyme molecules bind in a tridentate manner for this cluster, resulting in a binding energy of 35.2 kcal mol -1 for diglyme, which is comparable to the value of ∼40 kcal mol -1 for thiolates. IR and optical spectroscopies show no evidence of assembly of this cluster, in contrast to Au 20 (PET) 15 (DG), which readily assembles into dimeric species, which is consistent with a tridentate binding motif. Evidence for stacking among Au-bound and non-bound diglyme molecules is inferred from thermal and mass analysis.