Toward Rational Construction of Gold, Gold−Silver, and Gold−Mercury String Complexes: Syntheses, Structures, and Properties of [Au(Tab)₂]₂L₂ (L = I and PF₆), {[(Tab)₂M][Au(CN)₂]}₂ (M = Au and Ag), and {[Hg(Tab)₂][Au(CN)₂]₂} [Tab = 4-(Trimethylammonio)benzenethiolate]

The reaction of AuI with 2 equiv of TabHPF6 [TabH = 4-(trimethylammonio)benzenethiol] in the presence of excess
Et3N in dimethylformamide (DMF)/MeOH afforded a binuclear gold(I) complex [Au(Tab)2]2I2·2H2O (1). Anion exchange
of 1 with NH4PF6 in DMF gave rise to the more soluble complex [Au(Tab)2]2(PF6)2 (2). Treatment of 2 with K[Au(CN)2] produced a tetranuclear gold(I) complex {[(Tab)2Au][Au(CN)2]}2 (3). Analogous reactions of two known
mononuclear complexes [Ag(Tab)2](PF6) (4) and [Hg(Tab)2](PF6)2 (5) with 1 or 2 equiv of K[Au(CN)2] generated
one Ag2Au2 complex {[(Tab)2Ag][Au(CN)2]}2 (6) and one Au/Hg complex {[Hg(Tab)2][Au(CN)2]2} (7), respectively.
Compounds 1−3, 6, and 7 were fully characterized by elemental analysis, IR spectra, UV−vis spectra, 1H NMR,
and single-crystal X-ray crystallography. 1 and 2 have a similar [Au(Tab)2]22+ dimeric structure in which the two
[Au(Tab)2]+ cations are connected via one Au−Au aurophilic interaction. In the structure of 3 or 6, each of the two
pairs of [M(Tab)2]+ cation and [Au(CN)2]- anion is held together via ionic interactions to form a {[(Tab)2M][Au(CN)2]} species (M = Au, 3; Ag, 6). Two such species are further connected by one Au−Au aurophilic bonding
interaction to form an uncommon Au4 or Ag2Au2 linear string structure with three ligand-unsupported metal−metal
bonds. For 7, the [Hg(Tab)2]2+ dication and the [Au(CN)2]22- dianion are interconnected by the secondary Hg···N(CN) interactions to form a 1D chain structure. The thermal and luminescent properties of 1−3, 6, and 7 in solid
state were also investigated.