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  1. Abstract Understanding the chemistry of the inert actinide oxo bond in actinyl ions AnO22+is important for controlling actinide behavior in the environment, during separations, and in nuclear waste (An=U, Np, Pu). The thioether calixarene TC4A (4‐tert‐butyltetrathiacalix[4]arene) binds equatorially to the actinyl cation forming a conical pocket that differentiates the twotrans‐oxo groups. The ‘ate’ complexes, [A]2[UO2(TC4A)] (A=[Li(DME)2], HNEt3) and [HNEt3]2[AnO2(TC4A)] (An=U, Np, Pu), enable selective oxo chemistry. Silylation of the UVIoxo groups by bis(trimethylsilyl)pyrazine occurs first at only the unencapsulatedexooxo and only one silylation is needed to enable migration of theendooxo out of the cone, whereupon a second silylation affords the stable UIVcis‐bis(siloxide) [A]2[U(OSiMe3)2(TC4A)]. Calculations confirm that only one silylation event is needed to initiate oxo rearrangement, and that the putativecisdioxo isomer of [UO2(TC4A)]2−would be stable if it could be accessed synthetically, at only 23 kcal.mol−1in energy above the classicaltransdioxo. Calculations for the transuraniccis[AnO2(TC4A)]2−(An=Np, Pu) are at higher energies, 30–35 kcal.mol−1, retaining the U complexes as the more obvious target for acis‐dioxo actinyl ion. The aryloxide (OAr) groups of the macrocycle are essential in stabilizing this as‐yet unseen uranyl geometry as further bonding in the TC4A U‐OArgroups stabilizes the U=O ‘yl’ bonds, explaining the stability of the putativecis[UO2(TC4A)]2−in this ligand framework. 
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    Free, publicly-accessible full text available February 21, 2026
  2. Dinitrogen is a challenging molecule to reduce to useful products under ambient conditions. The range of d-block metal complexes that can catalyze dinitrogen reduction to ammonia or tris(silyl)amines under ambient conditions has increased recently but lacks electropositive metal complexes, such as those of the f-block, which lack filled d-orbitals that would support classical binding modes of N2. Here, metallacyclic phenolate structures with lanthanide or group 4 cations can bind dinitrogen and catalyze its conversion to bis(silyl)amines under ambient conditions. The formation of this unusual product is controlled by metallacycle sterics. The group 4 complexes featuring small cavities are most selective for bis(silyl)amine, while lanthanide complexes and the solvated uranium(IV) congener, with larger cavities, can also make a conventional tris(silyl)amine product. These results offer new catalytic applications for plentiful titanium and more earth-abundant members of the lanthanides that are also less toxic than many base metals used in catalysis. 
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  3. X-ray absorption spectroscopy and variable temperature magnetometry show evidence of 4f-orbital mixing in Cp′3Eu, which increases its magnetic susceptibility. 
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    Free, publicly-accessible full text available August 14, 2025
  4. null (Ed.)
    The new PtVO(SOCR) 4 lantern complexes, 1 (R = CH 3 ) and 2 (R = Ph) behave as neutral O-donor ligands to Ln(OR) 3 with Ln = Ce, Nd. Four heterotrimetallic complexes with linear {LnOVPt} units were prepared: [Ln(ODtbp) 3 {PtVO(SOCR) 4 }] (Ln = Ce, 3Ce (R = CH 3 ), 4Ce (R = Ph); Nd, 3Nd (R = CH 3 ), 4Nd (R = Ph); ODtbp = 2,6-ditertbutylphenolate). Magnetic characterization confirms slow magnetic relaxation behaviour and suggests antiferromagnetic coupling across {Ln–OV} in all four complexes, with variations tunable as a function of Ln and R. 
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