Synthesis and Characterization of Chelating Alkyl-borohydride Complexes of Thorium and Uranium: Th(CH₂NMe₂BH₃)₄ and U(CH₂NMe₂BH₃)₄

Abstract

This paper describes the synthesis and characterization of two actinide alkyls: thorium and uranium compounds of stoichiometry M(CH 2 NMe 2 BH 3 ) 4 (M = Th, U) where CH 2 NMe 2 BH 3 − is the boronatodimethylaminomethyl group (abbreviated BDAM). The crystal structures of these compounds show that the coordination geometry of the metal center can be described in terms of a D 2d dodecahedron, whose eight vertices are defined by the four metal-bound carbon atoms and the four boron atoms of the BH 3 groups. Two of the BH 3 groups in each compound bind to the metal centers in a κ 2 fashion (i.e., by means of two B−H−M bridges) and two in a κ 1 fashion. Thus, both compounds can also be described as ten-coordinate in which four carbon atoms and six hydrogen atoms form the inner coordination sphere. The structures of both complexes and the nature of the BH 3 −M interactions were investigated computationally. The NMR spectra of the diamagnetic thorium(IV) compound and paramagnetic uranium(IV) compound are discussed; both compounds are fluxional in solution even at −124 °C. Variable temperature magnetization studies of the paramagnetic uranium(IV) compound in the solid state are consistent with its tetravalent oxidation state.

Photolysis-driven bond activation by thorium and uranium tetraosmate polyhydride complexes

“…In contrast, while actinide (An) borohydride and aluminohydride chemistry is well-established, 5,23–27 multimetallic hydride chemistry of the actinides is underdeveloped. Ephritikhine reported a series of U/Re complexes supported by three bridging hydrides, utilizing potassium rhenate salts to install the rhenium center on uranium pentamethylcyclopentadienyl (Cp*) halide complexes.…”