EXPLORATION OF THORIUM HYDROTRIS(PYRAZOLYL)BORATE COMPLEXES TO ACCESS RARE MULTIPLE BONDS

Actinide complexes have been targeted for their potential in group transfer applications. The study of these metals, such as thorium and uranium, is essential to better understand the reactions these metals are capable of facilitating.  Hydrotris(pyrazolyl)borates such as hydrotris(3,5-dimethylpyrazolyl)-borate (Tp*) and hydrotris(pyrazolyl)-borate (Tp) are superbulky, scorpionate ligands that have previously been used to synthesize novel uranium complexes and probe the reactivity of these materials. Similar thorium analogs have also been synthesized, but their reactivity has yet to be explored in great depth. Tp*ThCl3(THF) and Tp2ThCl2 have been reproduced and investigated as possible starting materials for such reactivity studies. While the former was found to be largely unreactive, the latter presents promising reactivity for the synthesis of thorium-element multiple bonds, and a novel thorium imido, Tp2Th(NDipp)(THF), has been synthesized and characterized using this scaffold. 

The reactivity of a uranium tetrakis(imido), [U(NDipp)4][K2], has also been investigated to probe the prospect of group transfer reactions for potential catalysis applications in the future. An isocyanate, PhNCO, was reacted with this compound; the observed product showed that group transfer was incomplete, and a four-membered metallocycle product is likely formed instead. The synthesis of a novel thorium tris(imido) has also been targeted, and preliminary results are outlined.