Gold(I) η²-Arene Complexes

The reaction of 9-{[<i>N</i>-<i>n</i>-propyl-<i>N-</i>(diphenylphosphino)amino]methyl}anthracene (<b>1</b>) with Au(SMe₂)Cl yields complex <b>2</b> with an arm-opening configuration. The latter is treated with AgClO₄ to form complex <b>4</b> and then respectively reacted with acetonitrile, pyridine, and triphenylphosphine sulfide to afford novel gold(I) η²-arene complexes <b>3a</b>−<b>c</b>, which have arm-closing configurations and feeble or weak fluorescence emissions. The observation can be attributed to charge transfer from the anthracene unit to the Au⁺ ion. When the solution of <b>3a</b> or <b>4</b> in CH₂Cl₂ was added with 1 equiv of Ph₃P, complex <b>5</b> with the arm-opening configuration was formed and strong emission was restored.