Gold-acetylide chemistry: the structure of the complex [Au2(μ-dppm) (C≡C—CMe3)2]

The complex [Au2(μ-dppm)(C≡Ct-Bu)2], 1, dppm=Ph2PCH2PPh2, is formed by reaction of [AuC≡Ct-Bu] with dppm. Compound 1, as an acetone solvate, crystallizes in the monoclinic space group P21/c with cell dimensions a = 14.047(1), b = 16.124(1), c = 17.140(3) Å, β = 103.17(2)° and four formula units per cell. The crystal and molecular structures of this salt were solved by X-ray diffraction techniques using 2634 counter data with I > 2σ(I). Refinement of 278 variables by full-matrix least squares converged at an agreement factor R = 0.023. Thermolysis of complex 1 in refluxing toluene led to intermolecular elimination of t-BuC≡CH, by combination of a t-BuC≡C ligand of one molecule of 1 with a proton from the CH2P2 group of a second, and formation of the stable tetragold(I) complex [Au4(μ3-Ph2PCHPPh2)(μ-dppm)(C≡Ct-Bu)3], 2, which was characterized by its spectroscopic properties. Keywords: acetylide complexes, gold complexes, X-ray crystallography, nmr spectroscopy, bis(diphenylphosphino)methane.