Ion Pairing in Cationic Au(I)(μ-H)2WCp2 Bimetallic Dihydrides

The interionic structure in solution of a series of [LAu(mu-H)(2)WCp2][BF4] ion pairs (L=N-heterocyclic carbene, phosphine or phosphite) has been elucidated by means of heteronuclear NOE and diffusion NMR. Selective ion pairing based on specific metallocene-anion interactions has been observed for all species. The ancillary ligand L plays only a minor role in dictating the availability of secondary ion pair structures, mainly owing to steric factors. DFT calculations have indicated that the tungstenocene fragment delocalizes most of the positive charge and acts as the preferential anion anchoring point. Even though the interaction is highly specific, ion association in CD2Cl2 is not enhanced and the typical aggregation behavior of linear Au(I) ion pairs is observed.

Automated summary

The interionic structure in solution of a series of [LAu(mu-H)(2)WCp2][BF4] ion pairs has been studied using heteronuclear NOE and diffusion NMR. Selective ion pairing based on specific metallocene-anion interactions has been observed for all species. The role of the ancillary ligand L in dictating the availability of secondary ion pair structures is minimal, mainly due to steric factors. DFT calculations have shown that the tungstenocene fragment acts as the preferential anion anchoring point. However, ion association in CD2Cl2 is not enhanced and the typical aggregation behavior of linear Au(I) ion pairs is observed.