Structural Consequences of the Use of Hard and Soft Tripodal Ligands during Metathesis Reactions: Synthesis of the [Bis(hydrotris(methimazolyl)borato]bismuth(III) [Bis(hydrotris(pyrazolyl)borato]sodiate

Tripodal ligands such as the hydrotris(pyrazolyl)borate anion (Tp) have found great favor in studies of structure and reactivity1 relevant to catalysis2 and inorganic biochemistry.3 Considering the accepted synthetic utility of Tp-based ligand systems, it is surprising that the range of analogous soft tripodal ligands is so limited.4 By replacing pyrazole with methimazole (2-mercapto-1-methylimidazole) in the synthetic method of Trofimenko5 (Scheme 1) we were recently successful6 in the direct synthesis of the simple tridentate, sulfur-based ligand, hydrotris(methimazolyl)borate (Tm).