The versatile behaviour of a novel Janus scorpionate ligand towards sodium, potassium and bismuth(iii) ions

Abstract

Alkali metal salts of a novel Janus scorpionate ligand [(Tr^Me)]⁻ with hard and soft donor sites (N, S) were synthesized by the reaction of 3-mercapto-4-methyl-1,2,4-triazole (L) with NaBH₄ and KBH₄, respectively, via Trofimenko's protocol. The resulting compounds were the sodium and potassium complexes [Na(Tr^Me)] (1), [K(Tr^Me)] (2) and the mixed ion compound [KNa(Tr^Me)] (3). [K(Tr^Me)] (2) was reacted with bismuth(III) chloride to afford the complexes [Bi(Tr^Me)(Cl)(μ-Cl)₂]₂ (5) and [Bi(Tr^Me)(Cl)₂(μ-Cl)]_n (6). Compound 5 was formed when 2 was applied to BiCl₃ in a molar ratio 2 : 1, while 6 was achieved when a ratio of 1 : 1 was used. The reaction of 3-mercapto-4-methyl-1,2,4-triazole (L) with BiCl₃ led to the formation of the complex [Bi(L)₄(Cl)₂]Cl (7). The products were characterized by NMR and IR spectroscopy, elemental analyses and mass spectrometry. Solid state structures were determined by X-ray diffraction of single crystals of 1, 3, 3a, 5, 6 and 7. The alkali metal scorpionates 1–3 are coordination polymers with alternating orientation of the ligands. They dissociate in solution as observed in NMR measurements. Negative mode ESI-MS data also indicate the presence of monomers. The bismuth complex 5 is dimeric and 6 is polymeric, and both are bridged via chloro ligands. The three bismuth complexes 5, 6 and 7 have highly distorted octahedral coordination geometries. The influence of the stereochemically active lone pair was found to be most pronounced in the dimeric complex 5. The ligand Tr^Me and all bismuth complexes were also screened for their photo-luminescence activity. Whereas solutions of Tr^Me exhibit no luminescence, 7 is only emissive at 77 K, and 5 is emissive both at r.t. and 77 K.