An investigation of gold(I) and silver(I) thiosulfate complexes using ESI mass spectrometry; facile generation of gas-phase auride (Au−) and argentide (Ag−) ions

Abstract

• ESI mass spectrometric investigation of the gold(I) and silver(I) complexes [M(S 2 O 3 ) 2 ] 3- . • Observation of the bare metal anions auride (Au − ) and argentide (Ag − ) through fragmentation. • Other gold complexes [AuCl 4 ] − and [Au(SCN) 2 ] − do not give Au − . The gold(I) thiosulfate complex Na 3 [Au(S 2 O 3 ) 2 ]·2H 2 O has been studied in the gas phase by ESI MS, which showed the aggregate ion [Na 2 Au(S 2 O 3 ) 2 ] − ( m / z 466.78) at moderate capillary exit voltages, while at high capillary exit voltage (240 V) the major ion is the auride anion, Au − , ( m / z 196.96), together with [AuS] − ( m / z 228.93) at low relative intensity. The observation of Au − is surprising, and is related to the importance of relativistic effects in gold chemistry. No auride ions were produced when either [Me 4 N][AuCl 4 ] or K[Au(SCN) 2 ] were subjected to high capillary exit voltages. The ESI MS study of the corresponding silver thiosulfate complex Na 3 [Ag(S 2 O 3 ) 2 ]·2H 2 O showed a very low relative intensity argentide (Ag − ) anion, due to the much lesser impact of relativistic effects in silver chemistry.