[2.2]Paracyclophanediyldiphosphane Complexes of Gold

We have prepared digold(I) complexes with the rigid-backbone diphosphane ligands PhanePhos, xyl-PhanePhos, and Ph-2-GemPhos. All complexes were characterized by single-crystal X-ray diffraction, NMR, IR, Raman, and photoluminescence (PL) spectroscopy. [PhanePhos(AuCl)(2)] and [GemPhos(AuCl)(2)] show a very similar ligand scaffold, but different (aurophilic vs. nonaurophilic) intramolecular AuAu distances. Absorption and PL spectra of both compounds are quite similar. Theoretical investigations reveal that the excited states are of different character (i.e., influenced by the AuAu contacts). The respective transition energies, however, lie close to each other, thus resulting in similar experimental spectra. The gold atoms appear to produce a significant heavy-atom effect in the electronic relaxation dynamics. Thus, [PhanePhos(AuCl)(2)] and [GemPhos(AuCl)(2)] both show bright-green millisecond-long phosphorescence at low temperatures, although the latter is quenched at ambient temperature. [PhanePhos(AuCl)(2)] and [GemPhos(AuCl)(2)] were also used as catalysts in the intra- and intermolecular hydroamination of alkynes. Good to quantitative conversions on a reasonable time scale were observed. The overall performance of these catalysts in the studied reactions was similar, showing that AuAu contacts do not have a major influence on the catalytic performance.