Coinage Metal Complexes Supported by the Tri- and Tetraphosphine Ligands

A series of tri-
and tetranuclear phosphine complexes of d10 metal ions
supported by the polydentate ligands, bis­(diphenylphosphinomethyl)­phenylphosphine
(PPP) and tris­(diphenylphosphinomethyl)­phosphine
(PPPP), were synthesized. All the compounds under
study, [AuM2(PPP)2]3+ (M = Au (1), Cu (2), Ag (3)), [M4(PPPP)2]4+ (M = Ag (4), Au (5)), [AuAg3(PPPP)2]4+ (6), and [Au2Cu2(PPPP)2(NCMe)4]4+ (7), were characterized
crystallographically. The trinuclear clusters 1–3 contain a linear metal core, while in the isostructural
tetranuclear complexes 4–6 the metal
framework has a plane star-shaped arrangement. Cluster 7 adopts a structural motif that involves a digold unit bridged by
two arms of the PPPP phosphines and decorated two
spatially separated CuI ions chelated by the remaining
P donors. The NMR spectroscopic investigation in DMSO solution revealed
the heterometallic clusters 2, 3, and 6 are stereochemically nonrigid and undergo reversible metal
ions redistribution between several species, accompanied by their
solvation–desolvation. The complexes 1–3 and 5–7 exhibit room temperature
luminescence in the solid state (Φem = 6–64%)
in the spectral region from 450 to 563 nm. The phosphorescence observed
originates from the triplet excited states, determined by the metal
cluster-centered dσ* → pσ transitions.