Controlled Synthesis of Diphosphine-Protected Gold Cluster Cations Using Magnetron Sputtering Method.

We demonstrated, for the first time, atomically precise synthesis of gold cluster cations by magnetron sputtering of a gold target onto a polyethylene glycol (PEG) solution of 1,3-bis(diphenylphosphino)propane (Ph 2 PCH 2 CH 2 CH 2 PPh 2 , dppp). UV-vis absorption spectroscopy and electrospray ionization mass spectrometry revealed the formation of cationic species, such as [Au(dppp) n ] + ( n = 1, 2), [Au 2 (dppp) n ] 2+ ( n = 3, 4), [Au 6 (dppp) n ] 2+ ( n = 3, 4), and [Au 11 (dppp) 5 ] 3+ . The formation of [Au(dppp) 2 ] + was ascribed to ionization of Au(dppp) 2 by the reaction with PEG, based on its low ionization energy, theoretically predicted, mass spectrometric detection of deprotonated anions of PEG. We proposed that [Au(dppp) 2 ] + cations thus formed are involved as key components in the formation of the cluster cations.