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.