Complexes with Atomic Gold Ions: Efficient Bis-Ligand Formation

Abstract

Complexes of atomic gold with a variety of ligands have been formed by passing helium nanodroplets (HNDs) through two pickup cells containing gold vapor and the vapor of another dopant, namely a rare gas, a diatomic molecule (H2, N2, O2, I2, P2), or various polyatomic molecules (H2O, CO2, SF6, C6H6, adamantane, imidazole, dicyclopentadiene, and fullerene). The doped HNDs were irradiated by electrons; ensuing cations were identified in a high-resolution mass spectrometer. Anions were detected for benzene, dicyclopentadiene, and fullerene. For most ligands L, the abundance distribution of AuLn+ versus size n displays a remarkable enhancement at n = 2. The propensity towards bis-ligand formation is attributed to the formation of covalent bonds in Au+L2 which adopt a dumbbell structure, L-Au+-L, as previously found for L = Xe and C60. Another interesting observation is the effect of gold on the degree of ionization-induced intramolecular fragmentation. For most systems gold enhances the fragmentation, i.e., intramolecular fragmentation in AuLn+ is larger than in pure Ln+. Hydrogen, on the other hand, behaves differently, as intramolecular fragmentation in Au(H2)n+ is weaker than in pure (H2)n+ by an order of magnitude.

Relativistic Effects in the Ligation of Atomic Coinage Metal Cations with O2 and C6H6: Anomalous Formation of Relativistic Mono- and Bis-adducts with Au+

“…They also note satisfactory agreement with the earlier computational predictions of Bauschlicher et al for Cu + (214 ± 21 kJ mol –1 ) and Ag + (153 ± 21 kJ mol –1 ) and the experimental CID results for Cu + / C 6 H 6 : 218 ± 10 kJ mol –1 reported by Armentrout et al and 209 ± 38 kJ mol –1 reported by Hetrich and Freiser . Also, in the case of gold, their computed value agrees with the estimate of 280 ± 29 kJ mol –1 reported by Schröder et al However, the computed value of 179 kJ mol –1 for the binding energy of the gold cation to benzene reported very recently by Duensing et al is much lower. These authors also reported a binding energy of 242 kJ mol –1 for the second benzene in the formation of the bis-adduct in which the gold cation forms covalent bonds over two adjacent carbon atoms in each ring.…”

“…Table provides a summary of our calculated ligation enthalpies at 298 K. We have included the recent computed value by Duensing et al for the bis-adduct of Au + and benzene for which our calculations did not converge.…”

“… a The product ions of the addition reactions are indicated in the table. Energies represent enthalpies of the reaction at room temperature in kJ mol –1 . b From ref . …”

“…Very recently, the formation of higher adducts of Au + has been surveyed in doped helium droplets with L = a rare gas, a diatomic molecule (H 2 , N 2 , O 2 , I 2 , P 2 ), or a polyatomic molecule (H 2 O, CO 2 , SF 6 , C 6 H 6 , adamantane, imidazole, dicyclopentadiene, and fullerene). Many of these ligands, including O 2 and benzene, exhibited multiple ligation and a “magic” ligation number of 2 in the formation of the bis adduct …”

Electronic spectroscopy of cationic adamantane clusters and dehydrogenated adamantane in helium droplets

“…The cluster formation of adamantane cations within helium droplets has been explored previously by our group, [49][50][51] employing time-of-flight mass spectrometry. Fig.…”