Abstract:

Ligand exchange reactions important in the formation of L³- and L⁵-protected gold clusters (L³ = 1,3-bis(diphenylphosphino)propane; L⁵ = 1,5-bis(diphenylphosphino)pentane) are investigated at the molecular level. We establish that molecular complexes, [Au(PPh₃)_xL_2-xⁿ]⁺, in which Au⁺ is bound to at least one triphenylphosphine ligand (PPh₃) act as precursors to cluster formation, while complexes in which Au⁺ is bound only to the diphosphine ligands do not. Ligand exchange reactions and ion equilibria were studied via electrospray ionization mass spectrometry, and a critical reaction was studied with ab initio molecular dynamics simulations. The displacement of one PPh₃ by L³ on [Au(PPh₃)₂]⁺ was studied with transition path sampling calculations with Car−Parrinello molecular dynamics simulations. The experiments and simulations are in excellent agreement, and we demonstrate the applicability of these tools to chemical reactions involving ligand exchange.