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 Pn (n = 2, 3) with rigid polyaromatic backbones leads to clean formation of the coordination Pn(Au(tht))n(n+) 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 (1)H, (31)P 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.