Unexpected formation of a fused double cycle trinuclear gold(i) complex supported by ortho-phenyl metallated aryl-diphosphine ligands and strong aurophilic interactions

Abstract

The first homoleptic trinuclear arylgold(I) complex, [Au₃(L′)₂](NO₃) (3), based on an ortho-phenyl metallated aryl-diphosphine ligand (L′ = o-C₆H₄PPh(C₁₅H₁₀O)PPh₂), has been obtained through a new thermolytic reaction of the corresponding diauracycle, [Au₂(L)₂](NO₃)₂ (L = xantphos). The formation of 3 involves activation of the ortho-phenyl C–H bond of the xantphos ligands. The presence of Au–C bonds in this new gold-diphosphine cluster is not its only remarkable feature, since it also displays two 12-membered rings fused together and a linear {Au₃} chain with aurophilic interactions. Complex 3 exhibits strong sky-blue luminescence that can be assigned to a triplet metal–metal (³MM) transition partially mixed with a ligand-to-metal–metal charge transfer (³LMMCT) transition related to the aurophilic bonding. This [Au₃(L′)₂]⁺ triauracycle also shows AIEE-activity, and is a selective luminescent chemosensor for metal ions.