A new, easily recyclable arylating agent based on a diphosphino-digold(i) complex

Abstract

The synthesis of two organogold(I) complexes, [(Au(NCN))₂(dppbp)] (6) and [(Au(Phebox))₂(dppbp)] (9), and their application in subsequent transmetalating reactions are described. A trinuclear organogold(I) complex, [(AuCl)₃(tdpppb)] (4) is also reported, which exhibits a surprisingly high solubility in dichloromethane. It was found that 6 and 9 can cleanly transfer the anionic NCN-([C₆H₃(CH₂NMe₂)₂-2,6]⁻) or Phebox-([2,6-bis(oxazolinyl)phenyl]⁻) moiety to Ti^IV and Pd^II centers, respectively. The coproduct [(AuCl)₂(dppbp)] (3, dppbp is [4-Ph₂PC₆H₄]₂ (1)) formed during this transmetalation reaction, precipitates almost quantitatively from the reaction mixture (toluene) and can thus be separated by simple filtration. In comparison, [AuCl(PPh₃)], formed as the coproduct in the transmetalation reaction of [Au(NCN)(PPh₃)] with metal salts, has a higher solubility in apolar solvents and thus is more difficult to separate from the resultant organometallic complex. Digold complex 6 has been characterized by NMR spectroscopy and crystallographic analyses. These analyses show that the two gold units are essentially independent. The formation of a dimetallic transmetalating agent based on gold(I) had no effect on its transmetalating properties.