Hydroamination reactions catalyzed by [Au2(μ-Cl)(μ-bis(phosphino) ferrocene)][BArF24]

1,1'-bis(phosphino) ferrocene ligands are commonly employed in a variety of catalytic systems. These ligands are of particular interest as the steric and electronic properties of the phosphorus donor atoms can be altered by changing the substituents of the phosphines. In addition, the ferrocene backbone of the ligands provides unique electronic and conformational flexibility to these ligands. Previous investigations in this lab have examined catalytic ring closing reactions using a series of gold compounds with bis(phosphino)ferrocene ligands, [Au2Cl2(mu-PP)]. These gold compounds were shown to react with sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate, Na[BArF24], to generate a cationic species with the general formula [Au-2(mu-Cl)(mu-PP)][BArF24] that are much more efficient catalysts than the [Au2Cl2(mu-PP)] compounds. In this study, a series of [Au2Cl2(mu-PP)] (mu-PP = 1,1'-bis(diphenylphosphino)ferrocene (dppf), 1,1'-bis(diiso-propylphosphino)ferrocene (dippf), 1,1'-bis(dicyclohexylphosphino)ferrocene (dcpf), 1,1'-bis(ditert-butylphosphino)ferrocene (dtbpf), 1-diphenylphosphino-1'-ditert-butylphosphinoferrocene (dppdtbpf) or 1,1'-bis(5-methyl-2-furanylphosphino)ferrocene (dfurpf)) compounds were examined as catalysts for the intramolecular ring-closing hydroamination of 3-(vinyloxy)propan-1-amine and the intermolecular hydroamination of phenylacetylene with a variety of phenylamine reagents. The catalytic activity of the corresponding [Au-2(mu-Cl)(mu-PP)][BArF24] compounds that were generated in situ was also explored. Two new [Au2Cl2(mu-PP)] compounds with chiral bis(phosphino)ferrocene ligands (PP = 1,1'-bis(2R,5R-dimethylphospholanyl)ferrocene (R-d(Me)plf) or 1,1'-bis(2S,5S-dimethylphospholanyl)ferrocene (S-d(Me)plf)) were prepared, characterized spectroscopically and electrochemically, and evaluated as catalysts in the ring-closing hydroamination reaction. In addition, the X-ray structures of [Au2Cl2(mu-PP)] (PP = dppdtbpf, R-d(Me)plf and S-d(Me)plf) were determined. (C) 2019 Elsevier B.V. All rights reserved.