Isolation of cationic digold-frame with free carboxylic acid pendants

Abstract

Use of different diphosphines enables the isolation and crystallographic characterization of gold pyridylcarboxylate complexes with different structural motifs. Dppm [bis(diphenylphosphino)methane] supports side-by-side-like complexes [Au₂(dppm)(IsonicH)₂]²⁺ (isonicH = 4-NC₅H₄CO₂H) with aurophilic and π⋯π interactions of the pyridyl rings. Use of dppen [1,2-bis(diphenylphosphino)ethylene] removes the latter interaction but keeps the orthogonal closed-shell interaction of Au(I) in [Au₂(dppen)(IsonicH)₂]²⁺. The ligand dppe [1,2-bis(diphenylphosphino)ethane] helps to push the gold centers apart in [Au₂(dppe)(isonicH)₂]²⁺ and remove both interactions. These digold complexes are potential metalloligands that carry functional acids which can be conveniently activated by deprotonation.