Addition of [UI2(THF)3(μ-OMe)]2⸱THF (2⸱THF) to THF solutions containing 6 equiv. of K[C14H10] generates the heteroleptic dimeric complexes [K(18-crown-6)(THF)2]2[U(η6-C14H10)(η4-C14H10)(μ-OMe)]2⸱4THF (118C6⸱4THF) and {[K(THF)3][U(η6-C14H10)(η4-C14H10)(μ-OMe)]}2 (1THF) upon crystallization of the products in THF in...

In this Forum Article, we review the development of chelating borohydride ligands called aminodiboranates (H 3 BNR 2 BH 3 − ) and phosphinodiboranates (H 3 BPR 2 BH 3 − ) for the synthesis of trivalent f-element complexes. The advantages and history of using mechanochemistry to prepare molecular borohydride complexes are described along with new results demonstrating the mechanochemical synthesis of M 2 (H 3 BP t Bu 2 BH 3 ) 6 , where M = U, Nd, Tb, Er, and Lu (1−5). Multinuclear NMR, IR, and singlecrystal X-ray diffraction data are reported for 1−5 alongside complementary density functional theory calculations to reveal differences in their structure and reactivity with and without tetrahydrofuran. The results demonstrate how mechanochemistry can be used to access f-element complexes with chelating borohydrides in improved and reproducible yields, which is an important step toward investigating the properties of lanthanide and actinide phosphinodiboranate complexes with different phosphorus substituents. The relevance of these results is contextualized by a discussion of structural factors known to influence the volatility of f-element borohydrides and applications that require the development of volatile f-element complexes.

Reaction of [UI2(HMPA)4]I with potassium anthracenide gives the unprecedented arenide-sandwich complex U(η6-C14H10)(η4-C14H10)(HMPA)2. CASSCF calculations indicate the U–C bonding to solely consist of π-interactions.

Qualitative differences in the reactivity of trivalent lanthanide and actinide complexes have long been attributed to differences in covalent metal‐ligand bonding, but there are few examples where thermodynamic aspects of this relationship have been quantified, especially with U3+ and in the absence of competing variables. Here we report a series of dimeric phosphinodiboranate complexes with trivalent f‐metals that show how shorter‐than‐expected U−B distances indicative of increased covalency give rise to measurable differences in solution deoligomerization reactivity when compared to isostructural complexes with similarly sized lanthanides. These results, which are in excellent agreement with supporting DFT and QTAIM calculations, afford rare experimental evidence concerning the measured effect of variations in metal‐ligand covalency on the reactivity of trivalent uranium and lanthanide complexes.

Low-valent uranium(iii) primary phosphido complexes supported by hydrotris(3,5-dimethylpyrazolyl)borate (Tp*) were synthesized with phosphines of varying steric and electronic profiles.