Formation of heterobinuclear Pt–Au complexes by chelate ring-opening of cis-[Pt(κ2-C6R4PPh2)2] (R = H, F)

Abstract

Mixed metal complexes of the type [Pt(κ2-2-C6R4PPh2) (PPh3) (μ-2-C6R4PPh2)AuCl] (R = H, F) can be prepared by treatment of cis-[Pt(κ2-C6R4PPh2)2] with [AuCl(PPh3)]. Under similar reaction conditions, the trans isomer of [Pt(κ2-C6F4PPh2)2] is unreactive. Computational studies have been performed to provide insights into the reasons for this difference in reactivity. Density Functional Theory (DFT) calculations show that formation of an AuCl adduct of [Pt(κ2-2-C6R4PPh2)2] is favoured over nucleophilic addition of PPh3 to Pt as the initial step of the reaction, and reveal the required energy of the cis and trans isomers of the bis-chelate [Pt(κ2-2-C6R4PPh2)2] in forming the mixed metal Pt–Au compounds. NBO analysis sheds more light on the bonding orbitals of the cis and trans isomers, suggesting that the Pt–P bonds in the cis isomer are more labile.