The synthesis and structural characterization of bis(mercaptoimidazolyl)hydroborato complexes of lithium, thallium and zinc

Bidentate [S2]-donor bis(mercaptoimidazolyl) ligands, [BmMe]− and [BmMes]−, have been synthesized by reaction of [BH4]− with 2-mercapto-1-methylimidazole and 2-mercapto-1-mesitylimidazole, respectively. Subsequent treatment with ZnX2 (X = Me, I, NO3) yields a series of 1∶1 [BmR]ZnX complexes, namely [BmMe]ZnMe, [BmMe]ZnI and [BmMes]Zn(NO3), each of which possesses 3-center–2-electron [Zn⋯H–B] interactions. The homoleptic complex, [BmMe]2Zn, may be obtained by a redistribution reaction of [BmMe]ZnMe in CHCl3, and possesses a tetrahedral zinc center which is devoid of a 3-center–2-electron [Zn⋯H–B] interaction.