Au−Tl Linear Chains as Lewis Acids toward [Au(C6X5)2]- Metalloligands:  The First Anionic Heteropolymetallic Chains

The heteropolynuclear complexes [AuTlR2]n (R = 3,5-C6Cl2F3, C6Cl5) can react with [AuR2]- metalloligands leading to products of stoichiometry {NBu4[Tl2{Au(C6Cl5)2}{μ-Au(C6Cl5)2}2]}n (2), {NBu4[Tl{Au(3,5-C6Cl2F3)2}2]}n (3), or {NBu4[Tl{Au(C6Cl5)2}{Au(3,5-C6Cl2F3)2}]}n (4), which have incorporated a half (2) or one (3, 4) additional gold center per thallium atom. These complexes are the first anionic heteropolymeric chains built via unsupported metal−metal interactions, which are considered to be responsible for the luminescent behavior. These compounds display a strong visible luminescence at room temperature and at 77 K in the solid state under UV excitation, which is sensitive to the structural arrangement of metals as well as to the perhalophenyl group bonded to gold(I). The crystal structures of three of these complexes have been determined by X-ray diffraction crystallography, showing bridging (2) or terminal (3, 4) [AuR2]- fragments bonded to the thallium centers of the principal Au/Tl chain and an almost planar environment for the thallium atoms.