Digold(I) Thianthrenyl Complexes. Effect of Diphosphine Ligands on Molecular Structures in the Solid State and in Solution.

A series of digold complexes possessing two thianthrenyl ligands, Au 2 (Thi) 2 (Ph 2 P(CH 2 ) n PPh 2 ) (Thi: 1-thianthrenyl; 1 : n = 1, 2 : n = 2, 3 : n = 3, 4 : n = 4), were prepared and characterized by crystallographic and spectroscopic measurements. X-ray crystallography of complexes 1 and 3 revealed U-shaped structures with short Au-Au distances [3.2171(3) Å and 3.0735(2) Å]. Complex 2 and three of the four structure-determined molecules of complex 4 showed structures without Au-Au contacts. UV-vis spectroscopic measurements of 1 - 4 and TD-DFT calculations of the two conformers of 1 revealed that complexes 1 and 3 in the solution phase contained conformers with Au(I)-Au(I) interactions in a much higher proportion than complexes 2 and 4 . As a result, complexes with diphosphine ligands containing an odd number of methylene groups preferred structures with Au-Au interactions in the solid state and in solution. Oxidation of 1 with 2 equiv of PhICl 2 yielded a mixture of monomeric and dimeric thianthrenes and its dimer via ligand elimination and C-C coupling, respectively.