Silver(I) Pyrazolates. Synthesis and X-ray and 31P-NMR Characterization of Triphenylphosphine Complexes and Their Reactivity toward Heterocumulenes

Silver(I) pyrazolate was reacted with triphenylphosphine, leading to the dinuclear [Ag2(pz)2(PPh3)2] and [Ag2(pz)2 (PPh3)3] complexes (Hpz = pyrazole), which were extensively characterized by 31P-NMR methods and single-crystal X-ray analyses. Crystals of [Ag2(pz)2(PPh3)2] are triclinic, space group P1̄, with a = 9.567(2) Å, b = 11.440(2) Å, c = 10.073(2) Å, α = 93.59(2)°, β= 64.01(2)°, γ = 107.24(2)°, Z = 1, and Dcalc = 1.539 g·cm-3; final R = 0.028 for 2532 independent reflections having F > 4σ(F). They contain centrosymmetric dimers with trigonally coordinated silver atoms, which are 3.870(1) Å apart. Crystals of [Ag2(pz)2 (PPh3)3] are triclinic, space group P1̄, with a = 9.752(2) Å, b = 14.163(2) Å, c = 20.450(2) Å, α = 101.84(1)°, β= 99.83(2)°, γ = 100.68(2)°, Z = 2, and DCalc = 1.424 g·cm-3; final R = 0.025 for 7075 independent reflections having F > 4σ(F). Each molecule contains two inequivalent silver ions, bearing one and two phosphines, respectively, and a Ag(μ-pz)2Ag ring with a rare twisted conformation. Both complexes readily react with heterocumulenes such as CS2, COS, CO2, and RNCO, affording new derivatives, the nature of which is dependent on the experimental conditions. Single-crystal X-ray analysis of [Ag(pz-CS2)(PPh3)2] has shown the unexpected S,S coordination of the pyrazolecarbodithioate fragment. Its crystals are triclinic, space group P1̄, with a = 10.329(4) Å, b = 13.082(2) Å, c = 14.284(3) Å, α = 86.71(2)°, β= 75.14(2)°, γ = 74.79(2)°, Z = 2, and Dcalc = 1.431 g·cm-3; final R = 0.028 for 5179 independent reflections having F > 4σ(F).