Impact of Swapping Ethyl for Phenyl Groups on Diphosphine-Protected Undecagold

Abstract

1,3-Bis(diethylphosphino)propane (depp) protected gold clusters are synthesized and studied via electrospray ionization mass spectrometry. An undecagold cluster, [Au11(depp)4Cl2]+, is observed under soft ionization conditions and is found to persist in solution for at least 1 month. The importance of the Cl ligands is discussed in terms of the electron-donating nature of the depp ligands, and we contrast the core−ligand interactions observed here with those found in the previously reported [Au11(dppp)5]3+ (where dppp = 1,3-bis(diphenylphosphino)propane). The experimental observations are supported by density functional theory calculations, which suggest that the dppp ligand is a better electron acceptor than depp. Further calculations illustrate some of the subtleties that emerge when attempting to model core−ligand interactions on small clusters. The results demonstrate that a degree of caution is merited when making ligand approximations for modeling of monolayer-protected nanoparticles.