Metallophilicity-assisted assembly of phosphine-based cage molecules

Abstract

A family of supramolecular cage molecules has been obtained via self-assembly of the phosphine–gold coordination complexes following an aurophilicity-driven aggregation approach. Use of the di- (PP) or tridentate (PPP) phosphine ligands P_n (n = 2, 3) with rigid polyaromatic backbones leads to clean formation of the coordination P_n(Au(tht))_nⁿ⁺ species, sequential treatment of which with H₂O/NEt₃ and excess of H₂NBu^t gives the finite 3D structures of two major types. The cylindrical-like hexametallic cages [(PPAu₂)₃(μ₃-NBu^t)₂]²⁺ are based on the diphosphines PP = 1,4-bis(diphenylphosphino)benzene (1), 4,4′-bis(diphenylphosphino)biphenyl (2), 4,4′′-bis(diphenylphosphino)terphenyl (3), while the triphosphine PPP (1,3,5-tris(diphenylphosphinophenyl)benzene) produces a tetrahedral dodecagold complex [(PPPAu₃)₄(μ₃-NBu^t)₄]⁴⁺ (4). The cages 1–4 have been studied using the ESI-MS and ¹H, ³¹P NMR spectroscopy, and the crystal structures of 1 and 4 were determined by an X-ray diffraction study. The NMR spectroscopic investigations showed that cylindrical complexes 1–3 undergo twisting-like interconversion of the helical P↔M isomers in solution, while 4 is a stereochemically rigid compound retaining its axially chiral architecture. The difference in dynamic behavior was rationalized using computational studies with density functional methods.