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.