Binding interactions of mono- and diatomic silver cations with small alkenes: experiment and theory

Abstract

Temperature-dependent equilibrium methods were used to measure sequential association energies and entropies for the attachment of C 2H 4 and C 3H 6 ligands to ground-state Ag +( 1S, 4d 10) and Ag 2 +( 2Σ g, 4d 20 σ(5s) 1). Experimental bond dissociation energies (BDEs) of Ag +(C 2H 4) n are 32.2, 30.1, 13.6, 6.5 and 4.4 kcal/mol for n = 1–5, respectively, with the BDE of the sixth ligand estimated to be 3.3 kcal/mol. The BDEs of Ag 2 +(C 2H 4) n are 24.7, 22.5, 12.5, 7.7 and 2.9 kcal/mol for n = 1–5, respectively. The BDEs of Ag +(C 3H 6) n are 39.2, 32.9, 13.3, 7.0 and 3.0 kcal/mol and the BDEs of Ag 2 +(C 3H 6) n are 28.1, 25.8, 12.4, 9.3 and 4.2 kcal/mol for n = 1–5, respectively. A first solvation shell of four is observed for the attachment of both C 2H 4 and C 3H 6 ligands to both the Ag + and Ag 2 + core ions with all subsequent ligand additions taking place in the second solvation shell. Electronic structure calculations at the DFT-B3LYP level were performed in order to determine the vibrational frequencies, rotational constants and geometries of all the observed Ag + and Ag 2 + clusters as well as the nature of the bonding of these clusters and its variation with core ion coordination.