Synthesis of organometallic tantalum indenyl and thorium guanidinate complexes

A great societal goal is the increase in efficiency of chemical processes that contribute to human well-being, but also in a serious way to climate change, usually through the generation of the energy required to perform difficult chemical reactions. One such example is the Haber-Bosch process, a means of producing ammonia for fertilizers from dinitrogen and hydrogen that consumes ~2% of the energy used annually. The reason for the great consumption in the Haber-Bosch and other processes is the energy cost incurred in breaking very strong chemical bonds, e.g. the nitrogen-nitrogen triple bond. In previous work, the Messerle research group has been able to synthesize small molecules containing unique coordination environments, particularly a ditantalum core with two bonds between the tantalum atoms. These molecules react cleanly with small molecules of energy importance, like dinitrogen, at room temperature and at pressures not exceeding 100 psi. Indeed, many examples of organometallic complexes have shown varied and remarkable reactivity towards small molecules, easily cleaving apart otherwise difficult chemical bonds.

The work to follow describes three projects aimed at the discovery of new organometallic complexes with potentially promising reactivity, particularly from a member of the fourth group of transition metals and thorium, and the synthesis of a new tantalum-tantalum dinuclear molecule for comparison with those already known. Two new tantalum molecules, four new thorium molecules, and a variety of new organic molecules were synthesized, and subjected to spectroscopic and X-ray crystallographic investigations in order to determine their structures and chemical properties, and some initial studies of reactivity are reported.