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) (<b>1</b>), 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 <b>1</b> leads to the formation of the H-bonded dimer [{Au(SpyH)(PPh₂py)}₂](PF₆)₂ (<b>2</b>), which has also been structurally characterized. A linear coordination geometry at the Au(I) ions in <b>2</b> 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 <b>1</b> have also been used to bind Cu(I) by reactions with [Cu(NCMe)₄](PF₆) and Cu(P(<i>p</i>-tolyl)₃)₂(NO₃) leading to the formation of the heterobimetallic complexes [{AuCu(μ-Spy)(μ-PPh₂py)}₂](PF₆)₂ (<b>3</b>) and [AuCu(P(<i>p</i>-tolyl)₃)₂(μ-Spy)(μ-PPh₂py)](NO₃) (<b>4</b>), respectively. A structure determination of <b>3</b> 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 <b>3</b> 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 <b>1</b> is only weakly emissive in the solid state and in fluid solution, complexes <b>2</b>−<b>4</b> show stronger photoluminescence in the solid state and rigid media at 77 K, and in fluid solution. The emission maxima for <b>2</b>−<b>4</b> 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 λ_em 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) (<b>1</b>):  triclinic, space group <i>P</i>1̄ (No. 2), with <i>a</i> = 8.3975(4) Å, <i>b</i> = 11.0237(5) Å, <i>c</i> = 12.4105(6) Å, <i>α</i> = 98.6740(10)°, <i>β</i> = 105.3540(10)°, <i>γ</i> = 110.9620(10)°, <i>V</i> = 995.33(8) ų, <i>Z</i> = 2, R1 = 3.66% (<i>I</i> > 2σ(<i>I</i>)), wR2 = 9.04% (<i>I</i> > 2σ(<i>I</i>)) for 2617 unique reflections. Crystal data for [{Au(SpyH)(PPh₂py)}₂](PF₆)₂ (<b>2</b>):  triclinic, space group <i>P</i>1̄ (No. 2), with <i>a</i> = 14.0284(3) Å, <i>b</i> = 14.1093(3) Å, <i>c</i> = 15.7027(2) Å, <i>α</i> = 97.1870(10)°, <i>β</i> = 96.5310(10)°, <i>γ</i> = 117.1420(10)°, <i>V</i> = 2692.21(9) ų, <i>Z</i> = 2, R1 = 7.72% (<i>I</i> > 2σ(<i>I</i>)), wR2 = 15.34% (<i>I</i> > 2σ(<i>I</i>)) for 5596 unique reflections. Crystal data for [{AuCu(μ-Spy)(μ-PPh₂py)}₂](PF₆)₂ (<b>3</b>):  monoclinic, space group <i>P</i>2₁/<i>c</i> (No. 14), with <i>a</i> = 19.6388(6) Å, <i>b</i> = 16.3788(4) Å, <i>c</i> = 17.2294(5) Å, <i>β</i> = 91.48°, <i>V</i> = 5540.2(3) ų, <i>Z</i> = 4, R1 = 3.99% (<i>I</i> > 2σ(<i>I</i>)), wR2 = 8.38% (<i>I</i> > 2σ(<i>I</i>)) for 10597 unique reflections.