S-alkylation of soft scorpionates

The alkylation reactions of soft scorpionates are reported. The hydrotris(S-alkyl-methimazolyl)borate dications (alkyl=methyl, allyl, benzyl), which were prepared by the reaction of Tm^Me anion and primary alkyl halides, have been isolated and structurally characterised. The reaction is, however, not universally successful. DFT analysis of these alkylation reactions (C-S versus B-H alkylation) indicates that the observed outcome is driven by kinetic factors. Extending the study to incorporate alternative imine thiones (mercaptobenzothiazole, bz; thiazoline, tz) led to the structural characterisation of di[aquo-μ-aquohydrotris(mercaptobenzothiazolyl) boratosodium], which contains sodium atoms in the κ³-S,S,S coordination mode. Alkylation of Na[Tbz] and Na[tzTtz] leads to decomposition resulting in the formation of the simple S-alkylated heterocycles. The analysis of the species involved in these reactions shows an inherent weakness in the B-N bond in soft scorpionates, which has implications for their use in more advanced chemistry. Alkylation reactions of soft scorpionates (see figure) are not universally successful. DFT analysis of these reactions indicates that the outcome is driven by kinetic factors. Di[aquo-μ- aquohydrotris(mercaptobenzothiazolyl)boratosodium] has been structurally characterized. The analysis of the species involved in these reactions shows that the B-N bond of soft scorpionates is weak.