A Gold(I) Mononuclear Complex and Its Association into Binuclear and Cluster Compounds by Hydrogen Bonding or Metal Ion Coordination

The mononuclear Au(I) complex, Au(Spy)(PPh2py) (1), has been synthesized and characterized structurally. The complex possesses the expected linear coordination geometry with a S−Au−P bond angle of 176.03(6)° and no evidence of aurophilic interactions between nearest neighbor Au(I) ions in the solid state. Protonation of the pendant pyridyl groups of 1 leads to the formation of the H-bonded dimer [{Au(SpyH)(PPh2py)}2](PF6)2 (2), which has also been structurally characterized. A linear coordination geometry at the Au(I) ions in 2 with a S−Au−P bond angle of 173.7(2)° is augmented by evidence of a strong aurophilic interaction with a Au···Au distance of 2.979(1) Å. The pendant pyridyl groups of 1 have also been used to bind Cu(I) by reactions with [Cu(NCMe)4](PF6) and Cu(P(p-tolyl)3)2(NO3) leading to the formation of the heterobimetallic complexes [{AuCu(μ-Spy)(μ-PPh2py)}2](PF6)2 (3) and [AuCu(P(p-tolyl)3)2(μ-Spy)(μ-PPh2py)](NO3) (4), respectively. A structure determination of 3 reveals a tetranuclear complex composed of two AuCu(μ-Spy)(μ-PPh2py)+ units held together by bridging thiolate ligands. A strong metal−metal interaction is noted between the two different d10 ions with nearest Au−Cu distances averaging 2.6395 Å. The S−Au−P bond angles in 3 deviate slightly from linearity due to the Au···Cu interactions, while the coordination geometries at Cu(I) are distorted tetrahedral consisting of the two pyridyl nitrogen atoms, a bridging thiolate sulfur, and the interacting Au(I) ion. While mononuclear complex 1 is only weakly emissive in the solid state and in fluid solution, complexes 24 show stronger photoluminescence in the solid state and rigid media at 77 K, and in fluid solution. The emission maxima for 24 in ambient temperature fluid solution are 470, 635, and 510 nm, respectively. A tentative assignment of the emitting state as a S(pπ) → Au LMCT transition is made on the basis of previous studies of Au(I) thiolate phosphine complexes. Shifts of λem result from the influence of H bonding or Cu(I) coordination on the filled thiolate orbital energy, or on the effect of metal−metal interaction on the Au(I) acceptor orbital energy. Crystal data for Au(Spy)(PPh2py) (1):  triclinic, space group P1̄ (No. 2), with a = 8.3975(4) Å, b = 11.0237(5) Å, c = 12.4105(6) Å, α = 98.6740(10)°, β = 105.3540(10)°, γ = 110.9620(10)°, V = 995.33(8) Å3, Z = 2, R1 = 3.66% (I > 2σ(I)), wR2 = 9.04% (I > 2σ(I)) for 2617 unique reflections. Crystal data for [{Au(SpyH)(PPh2py)}2](PF6)2 (2):  triclinic, space group P1̄ (No. 2), with a = 14.0284(3) Å, b = 14.1093(3) Å, c = 15.7027(2) Å, α = 97.1870(10)°, β = 96.5310(10)°, γ = 117.1420(10)°, V = 2692.21(9) Å3, Z = 2, R1 = 7.72% (I > 2σ(I)), wR2 = 15.34% (I > 2σ(I)) for 5596 unique reflections. Crystal data for [{AuCu(μ-Spy)(μ-PPh2py)}2](PF6)2 (3):  monoclinic, space group P21/c (No. 14), with a = 19.6388(6) Å, b = 16.3788(4) Å, c = 17.2294(5) Å, β = 91.48°, V = 5540.2(3) Å3, Z = 4, R1 = 3.99% (I > 2σ(I)), wR2 = 8.38% (I > 2σ(I)) for 10597 unique reflections.