A Single-Strand Helical Motif Induced by Self-Assembly of [Ag(TFP)]+ Moieties with Nitrate Anions −31P NMR Spectroscopic and X-ray Crystal Structure Characterization of the Complexes Involved in Equilibrium Reactions of Silver Salts and TFP Ligand

Abstract

The ability of the ligand tris(2-furyl)phosphane (TFP) to coordinate AgI ions has been investigated. The molar ratio and the nature of the counterions used (NO3−; BF4−) affected the reaction. Moreover, equilibrium reactions were observed and the [Ag(TFP)n]+ (n = 1−4) species involved were identified by variable-temperature 31P NMR spectroscopy. The [Ag(TFP)3]BF4 complex turned out to be the more labile species in solution and it disproportionates by means of an SN2 mechanism to yield the complexes [Ag(TFP)2(H2O)]BF4 (3) and [Ag(TFP)4]BF4 (4). Most of the compounds detected in solution were isolated and characterized in the solid state. The molecular structures of the complexes [Ag(TFP)NO3] (1), [Ag(TFP)3NO3] (2), and [Ag(TFP)2(H2O)]BF4 (3) were determined by X-ray crystal structure diffraction confirming the solution characterization data. In these structures the TFP ligand was always only bonded to the metal centre by the phosphorous atom. It is noteworthy to underline that the molecular structure of complex 1 consists of an infinite single-strand helix arising from the ability of the bridging nitrate anions to connect the [Ag(TFP)]+ units. In the structure the nitrate anions are coordinated to the metal centres in unusual modes acting simultaneously as chelating and bridging ligands. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)