The stability of mercaptobenzothiazole based soft scorpionate complexes.

The chemistry of the hydrotris(mercaptobenzothiazolyl)borate anion (Tbz) with metal salts (HgI2, SbI3, BiI3, CoCl2) is reported in an attempt to probe the stability of the of Tbz ligand once coordinated to hard and soft metals. Complexes of Tbz with bismuth, containing the [Bi(Tbz)I3](-) anion, are stable, but with the other metals this is not the case. Although simple complexes such as [Hg(Tbz)I] and [E(Tbz)I3](-) (E = Sb, Bi) can be isolated from the reaction mixtures, subsequent reactions lead to ligand modification or decomposition. In the presence of mercury and antimony we observe the formation of a hitherto unseen cationic pentacyclic heterocycle. With cobalt we observe a small quantity of a product which suggests a more complete decomposition. A simple benzothiazole (bz) adduct [Co(bz)2Cl2] has been identified, in which the Tbz ligand has disintegrated and the parent heterocycle, mercaptobenzothiazole, has been desulfurized. A rationale for these observations is given.

Soft scorpionate anions as platforms for novel heterocycles.

Soft scorpionates have thus far been seen mainly as a family of ligands. Their chemistry is extended here to the production of novel cationic macrocycles using dihaloalkanes. By replacing the dihaloalkanes with mild oxidising agents (NO(+), I2) we obtain two unique polycyclic heterocycles. The mechanism which leads to the formation of these polycyclic heterocycles is investigated using ab initio DFT calculations.

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 κ(3)-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.