Low-Nuclearity Alkynyl d10 Clusters Supported by Chelating Multidentate Phosphines

The coordination chemistry of the tri- and tetradentate chelating phosphines (2-PPh2C6H4)(2)P(O)Ph ((PO)-O-3) and (2-PPh2C6H4)(3)P (P-4) with respect to d(10) copper subgroup metal ions has been investigated. Depolymerization of (MC2R)(n) (M = Cu, Ag) with P-4 affords the series of mono and trinudear complexes (P-4)CuC2Ph (1), (P-4)Cu-3(C2Ph)(3) (2), (P-4)Ag-3(C2Ph) (Hal)(2) (Hal = Cl (3), Br (4), I (5)). Reactions of the M+ (M = Cu, Ag) ions with (M'C2R)(n) (M' = Cu, Ag, Au) acetylides in the presence of P-4 yield the family of dinuclear species [(P-4)MM'(C2R)](+) (6-12), which comprise the Cu-2/Ag-2 (6, 7; R = Ph), AuCu (8-10; R = Ph, C(OH)Me-2, C(OH)Ph-2), and AuAg (11, 12; R = Ph, C(OH)Ph-2) metal cores. A related triphosphine, (2-PPh2C6H4)(2)PPh (P-3), applied in a similar protocol undergoes partial oxidation and leads to the heterotrimetallic clusters [{((PO)-O-3)M}(2)Au(C2R)(2)](+) (M = Cu, R = C(OH)Ph-2, 13; M = Ag, R = C(OH)Ph-2, 14; M = Ag, R = Ph, 15), which can be prepared more efficiently starting from the oxidized ligand (PO)-O-3. The structures of the complexes 1-4 and 6-15 were established by single-crystal X-ray crystallography. According to the variable-temperature H-1 and P-31{H-1} NMR experiments, compounds 1-12 demonstrate fluxional behavior in solution. The title complexes do not show appreciable luminescence in solution at 298 K, and the photophysical properties of 1-15 were studied in the solid state. The observed phosphorescence (Phi(em) up to 0.46, lambda(em) from 440 to 635 nm) is assigned to cluster-centered transitions mixed with some MLCT d -> pi*(alkynyl) character.