Digold Phosphinine Complexes Are Stable with a Bis(Phosphinine) Ligand but Not with a 2-Phosphinophosphinine

The reaction of [bis{3-methyl-6-(trimethylsilyl)phosphinine-2-yl}dimethylsilane] (19) with one and two equivalents of [AuCl(tht)] was attempted in order to selectively form the mono and digold species, respectively. The digold species [(AuCl)(2)(19)] (21) was synthesized in 32% yield and comprehensibly characterized (multinuclear NMR spectroscopy, elemental analysis, mass spectrometry and single-crystal X-ray diffraction). The monogold species showed no P-31 nuclear magnetic resonance at 25 degrees C but two resonances at -70 degrees C due to rapid exchange of AuCl between the phosphinine donors at 25 degrees C and was also susceptible to redistribution reactions to form the digold species. Analogous reactions of [AuCl(tht)] with 2-diphenylphosphino-3-methyl-6-trimethylsilylphosphinine (22) revealed preferential coordination of the AuCl unit to the PPh2 donor first, with coordination to the phosphinine achieved upon reaction with the second equivalent of [AuCl(tht)]. Unexpectedly, the digold complex was not stable, undergoing decomposition to give an unidentified black precipitate. Structural information could only be obtained on the digold hydrolysis product [(AuCl)(2)(1-OH-2-PPh2-3-MePC5H4)], which showed an aurophilic interaction.

Automated summary

In this study, the selective formation of mono and digold species was attempted by reacting with one and two equivalents of [AuCl(tht)]. The synthesized digold species were comprehensively characterized, and the reaction conditions were found to have an important impact on the formation of the products. The instability of some reactions was also revealed.