Binding of a Coordinatively Unsaturated Mercury(II) Thiolate Compound by Carboxylate Anions

Reactions of [Hg(Tab)2](PF6)2 (TabH = 4-(trimethylammonio)benzenethiol) (1) with acetic acid (HAc), propanoic acid (HPro), salicylic acid (HSal), benzoic acid (HBez), malonic acid (H2Mal), oxalic acid (H2Oxa), adipic acid (H2Adi), or methylimindiacetic acid (H2Meida) in the presence of Et3N gave rise to a family of mercury(II)-thiolate-carboxylate compounds, [Hg(Tab)2(Ac)](PF6)·0.5H2O (2·0.5H2O), [Hg(Tab)2(Pro)](PF6) (3), [Hg(Tab)2(Sal)](PF6)·MeOH (4·MeOH), [Hg(Tab)2(Sal)](Sal)·MeOH (5·MeOH), [Hg(Tab)2(Bez)](PF6)·H2O (6·H2O), [Hg(Tab)2(HMal)](Mal)0.5 H2O (7·H2O), [{Hg(Tab)2}2(μ-Oxa)](PF6)2 H2O (8·2H2O), [{Hg(Tab)2}2(μ-Adi)](PF6)2 (9), [Hg(μ-Tab)(μ-Adi)]2n (10), and [Hg(Tab)2(Meida)]·2.5H2O (11·2.5H2O). These compounds were characterized by elemental analysis, IR spectra, UV−vis spectra, 1H NMR, and single-crystal X-ray crystallography. Each mercury(II) atom in [Hg(Tab)2]2+ dication of 2−7 is further coordinated by two oxygen atoms from one Ac−, Pro−, Sal−, Bez−, Mal2− or HMal− anion, forming a unique seesaw-shaped coordination geometry. In 8 or 9, two [Hg(Tab)2]2+ dications are connected by one bridging oxalate or adipate dianion to generate a dimeric structure with each mercury(II) center adopting a seesaw-shaped geometry. In 10, a pair of octahedrally coordinated mercury(II) atoms are bridged by two sulfur atoms of two Tab ligands to form a [Hg(μ-Tab)2Hg]4+ fragment, which is further connected to its equivalent ones via four adipate dianions, thereby forming a rare two-dimensional network. In 11, the mercury(II) atom in the [Hg(Tab)2]2+ dication is coordinated by one nitrogen and two oxygen atoms from one Meida2− dianion to have a rare square pyramidal geometry. The formation of 2−11 from 1 may be applicable to mimicking the interactions of the mercury(II) sites of Hg-MerR and Hg-MT with various amino acids encountered in nature.