Stability of metal–metal interactions in transmetallation intermediates based on electronics of bridging arene ligands determined through pyridine titrations

Abstract

In this contribution, we prepare the dinuclear complex [(CNC^F)(PPh₃)Pt–Au(PPh₃)]⁺ (2-F) supported by an electron deficient derivative of 2,6-diphenylpyridine (CNC), 2,6-di(4-fluorophenyl)pyridine (CNC^F). Solution state spectroscopic data and solid-state structural data reveals formation of the desired dinuclear complex occurs and that it remains intact in solution. The solid state structure of 2-F, compared to [(CNC)(PPh₃)Pt–Au(PPh₃)]⁺ (2), reveals a substantial change in the C–Au–P bond angle. We postulated that this change in bond angle arises due to a weaker interaction between [(PPh₃)Au]⁺ and (CNC^F)Pt(PPh₃) (1-F) vs. (CNC)Pt(PPh₃) (1). Through pyridine titration experiments, we demonstrate that the interaction is indeed weaker between [(PPh₃)Au]⁺ and 1-Fvs. 1. Cyclic voltammetry (CV) experiments confirm that 1-F is less electron rich than 1. DFT calculations demonstrate that the HOMO of 1 and 1-F is not d_z², helping explain the differences in electrochemical behavior of 1 and 1-F and bonding between 1 and 1-F with [(PPh₃)Au]⁺.