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

Bidentate [S-2]-donor bis(mercaptoimidazolyl) ligands, [Bm(Me)](-) and [Bm(Mes)](-), 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 [Bm(R)]ZnX complexes, namely [Bm(Me)]ZnMe, [Bm(Me)]ZnI and [Bm(Mes)]Zn(NO3), each of which possesses 3-center-2-electron [Zn ... H-B] interactions. The homoleptic complex, [Bm(Me)](2)Zn, may be obtained by a redistribution reaction of [Bm(Me)]ZnMe in CHCl3, and possesses a tetrahedral zinc center which is devoid of a 3-center-2-electron [Zn ... H-B] interaction.