Low- and Mid-Valent Uranium Species Supported by Phenyltris(oxazolinyl)borate Ligands

Abstract

The synthesis and characterization of a family of uranium derivatives featuring the phenyltris­(4,4-dimethyl-2-oxazolinyl)­borate (ToM) ligand framework was achieved. Uranium­(IV) halide compounds, specifically ToMUCl3(THF) and ToMUI3, were generated by adding 1 equiv of Tl­[ToM] to either UCl4 or UI3(THF)4, respectively. The tetravalent derivatives ToMUCl2(NPh2) and ToMUI­(N-Ad)­(THF) were also synthesized, showing that ToM supports uranium amido and imido species. Attempts to make bis­(phenyltris­(oxazolinyl)­borate) compounds were unsuccessful. However, when the smaller hydrotris­(pyrazolyl)­borate (Tp) ligand was used, a mixed bis­(ligand) derivative, TpToMUI, was isolated. All of the compounds were characterized by 1H NMR, infrared, and electronic absorption spectroscopies. Where possible, X-ray crystallography was used to assess structural parameters.

Rare Earth Metal Complexes Supported by a Tripodal Tris(amido) Ligand System Featuring an Arene Anchor

“…The coordination chemistry of f-block metals supported by tripodal ligands has attracted considerable attention and resulted in new coordination modes and selective small molecule activation. − Most notably, Meyer and co-workers developed an arene-anchored tris­(aryloxide) tripodal ligand system and showed that it can stabilize multiple oxidation states of f-block elements, including lanthanides and uranium, − as well as empowering redox catalysis. , In particular, the arene anchor of Meyer’s ligand played an important role in tuning the electronic structures at the metal centers. , Inspired by this work, we aimed to develop a tripodal tris­(amido) ligand system with an arene anchor to combine the strong donating ability of amido ligands and the ambiphilic nature of the arene anchor. Despite the ubiquity of amido ligands in coordination chemistry, to the best of our knowledge, no example of tripodal-type tris­(amido) ligands with an arene anchor has been reported.…”

Unconventional Pathways to Carbide Phase Synthesis via Thermal Decomposition of UI4(1,4-dioxane)2

“…The compound UI 4 (1,4-dioxane) 2 easily offered access to new uranium (+IV) organometallic compounds. The presence of the weak donor group dioxane allows for simple ligand exchanges. − Its synthesis is relatively simple (obtained from U metal or from UCl 4 ), high yielding, and can be produced in gram-scale quantity. The synthesis and characterization of uranium organometallic compounds (i.e., properties, structure, and reactivity) are performed under mild conditions since these compounds are highly sensitive to air, moisture, and heat.…”

Insights into the Electronic Structure of a U(IV) Amido and U(V) Imido Complex

“…[12] The main factors influencing the stability of a certain oxidation state and thus reactivity arise from differences of the actinides' electronic structure, which is strongly affected by for example organic ligands as complexation partners but also by the reaction conditions. In recent years, N donor ligands gained centre stage for stabilizing uranium over a wide range of oxidation states due to the quite flexible number of bonds they can form: They can thus be utilized as amide [12][13][14][15] or imine [16][17][18][19] functionalities, and even triple bonds as nitrides [12,[20][21][22][23] are possible. Interestingly, bonds from imino ligands to U(VI) are more covalent compared to their dioxo analogues and capable of inducing further electronic effects like the inverse trans influence (ITI), opening an opportunity to shed light on 5forbital involvement.…”