Cluster Expansion of Luminescent Digold(I) and Disilver(I) Phosphine-Phosphide Oxide Complexes

Deprotonation of a diphosphine-secondary phosphine oxide ligand (o-Ph₂PC₆H₄)₂P(O)H (HP³O) affords disilver(I) and digold(I) complexes [M₂(P³O)₂], M = Ag (1) and Au (2). These compounds readily add coordinatively unsaturated AuX fragments (X = C₆F₅, SPh) by means of metallophilic interactions supported by bridging ligands. The extension of the metal core produces a series of penta- to octanuclear clusters [{M₂(P³O)₂}(AuX)_n] 3-7 (n = 3-6), the structures of which depend on the X group, the nature of the constituting metals, and P = O···HR hydrogen bonding. The newly synthesized clusters demonstrate moderate to intense luminescence as microcrystalline powders, predominantly originating from the triplet excited state and covering a range of wavelengths from 517 to 585 nm. Complexes 3-5 containing perfluorophenyl ligands exhibit high photoemission quantum yields under ambient conditions of up to 0.76 in combination with a relatively short lifetime of 0.98 μs for the pentagold cluster [Au₂(P³O)₂(AuC₆F₅)₃] (4). The results illustrate a feasible approach for the preparation of nonionic d¹⁰ coinage metal bright luminophores, derived from a hybrid P{OP^-}P scaffold.