Dinuclear gold(I) pseudohalogen complexes bridged by a ferrocenyl bisphosphine ligand: synthesis, structure, and reactivity toward isothiocyanate

Abstract

Ferrocenyl bisphosphine-bridged dinuclear gold(I) complexes containing CF₃COO as a pseudohalogen ligand were synthesized from the corresponding halides using CF₃COOAg. The sequential treatment of gold(I) trifluoroacetates with aqueous NaN₃ afforded the corresponding ferrocenyl bisphosphine-bridged dinuclear gold(I) azides. Isolated gold(I) pseudohalogen complexes were characterized through IR, NMR and X-ray crystallography. The characteristic IR absorption bands of ν(CO), ν(CF), and ν(N₃) were at 1690, 1190, and 2040 cm⁻¹, respectively, corresponding to the gold(I) trifluoroacetates and azides, verifying gold(I) pseudohalogen formation. The molecular structure of [Au₂(η¹-CF₃CO₂)₂(µ-dippf)] (dippf = 1,1’-bis(diisopropylphosphino)ferrocene) through X-ray diffraction showed intermolecular Au⋅⋅⋅Au interactions with close contacts between molecules. The crystallographic images illustrate the polymeric chain of bis(phosphino)ferrocenyl gold(I) formed via intermolecular Au⋅⋅⋅Au bonds and layered packing arrays. In contrast, the molecular structures of [Au₂(η¹-CF₃CO₂)₂(µ-dtbpf)] (dtbpf = 1,1’-bis(di-tert-butylphosphino)ferrocene) and Au₂(N₃)₂(µ-dippf) showed intramolecular Au⋅⋅⋅Au aurophilic interactions, but the structures of [Au₂(η¹-CF₃CO₂)₂(µ-dcpf)] (dcpf = 1,1′-bis(dicyclohexylphosphino)ferrocene) and Au₂(N₃)₂(µ-dppf) revealed no direct interaction within the dinuclear gold(I) system. Gold(I) azides gradually react with isothiocyanates (allyl, (S)-(+)-1-phenylethyl, and benzyl) to afford the corresponding gold(I) tetrazole-thiolates [Au₂X₂(µ-dippf)] or [Au₂X₂(µ-dtbpf)] (X = S[CN₄(Y)]) (Y = allyl, (S)-(+)-1-phenylethyl, and benzyl) via dipolar cycloaddition of the isothiocyanates into the Au-N₃ bond.

Keywords:

• Gold
• pseudohalogen
• azide
• intermolecular bond
• ferrocenyl bisphosphine

Disclosure Statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (Grant No. NRF-2020R1F1A1067303). This study was also supported by 2021 Academic Research Support Program in Gangneung-Wonju National University.