Homo- and heterometallic complexes designed on group 11 metals and tris(6-methyl-2-pyridyl)phosphine: Synthesis, metallophilic interactions and room-temperature phosphorescence

Tris(6-methyl-2-pyridyl)phosphine (L) has been highlighted as a promising multidentate ligand for design of original clusters based on group 11 metals. The interaction of this ligand with Au(tht)Cl and Au(tht)Cl-KPF6 system affords complexes [Au(L)Cl] and [AuL2]PF6, in which a linear P–Au–P coordination is realized. Complex [AuL2]PF6, upon treatment with AgPF6 or CuPF6, unexpectedly forms penta-nuclear clusters [Au@Ag4L4](PF6)5 and [Au@Cu4L4](PF6)5, respectively, showing Au-centered tetrahedral Ag4/Cu4 kernel supported by four L ligands in P,N,N′,N″-bridging manner. The structurally similar all-silver cluster [Ag@Ag4L4](BF4)5 has been assembled by the direct reaction of L with AgBF4. According to X-ray crystallography data and QTAIM study, the synthesized clusters {Au@Ag4}, {Au@Cu4} and {Ag@Ag4} feature the pronounced attractive metallophilic d10-d10 interactions between the central (Au/Ag) and peripherical (Cu, Ag) metal atoms. At ambient temperature, the title complexes exhibit room-temperature phosphorescence at λmax = 501–572 nm with emission lifetimes of microsecond order (τ = 0.86–20 µs) and the quantum yields of up to 23 %.