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,
Au2(Thi)2(Ph2P­(CH2)nPPh2) (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 PhICl2 yielded a mixture of monomeric
and dimeric thianthrenes and its dimer via ligand
elimination and C–C coupling, respectively.