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(k² -2-C₆R₄PPh₂) (PPh₃) (m-2-C₆R₄PPh₂)AuCl] (R ¼ H, F) can be prepared by treatment of cis-[Pt(k² -C₆R₄PPh₂)₂] with [AuCl(PPh₃)]. Under similar reaction conditions, the trans isomer of [Pt(k² -C₆R₄PPh₂)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(k² -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(k² -2-C₆R₄PPh₂)₂] in forming the mixed metal PteAu compounds. NBO analysis sheds more light on the bonding orbitals of the cis and trans isomers, suggesting that the PteP bonds in the cis isomer are more labile.