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.