Actinides

Löffler, Sascha T.; Meyer, Karsten

doi:10.1016/b978-0-12-409547-2.14754-7

Cited by 14 publications

(12 citation statements)

References 551 publications

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“…While uranium complexes with hard-donor ligands such as alkoxides, aryloxides, and amides have experienced a development boom in the past few decades, , with numerous examples of small molecule activations − and few catalytic applications, − the coordination chemistry of uranium with the softer chalcogenide sulfur trailed behind with only a fraction of publications, relatively. , Examples of low-valent U(III) thiolate complexes are still exceedingly rare, − and even more than half of the reported U(IV)–U(VI) compounds with thiophenolate ligands are the result of reactivity studies with relatively simple thiophenols, their salts, or their diphenyl disulfide precursors. ,− Sulfur-based ligand design efforts still focus mainly on aspects of lanthanide–actinide separation in nuclear fuel reprocessing, − by exploiting the different degrees of covalency for 4f and 5f metal–ligand bonds. − …”

Section: Introductionmentioning

confidence: 99%

Uranium Going the Soft Way: Low-Valent Uranium(III) Coordinated to an Arene-Anchored Tris-Thiophenolate Ligand

et al. 2021

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The synthesis of a tripodal, S-based ligand, namely the mesitylene-anchored, tris-thiophenolate-functionalized (mes-( Me,Ad ArS) 3 ) 3− (1) 3− , and its coordination chemistry with lowvalent uranium to form [U III ((SAr Ad,Me ) 3 mes)] (1-U) are reported. Single-crystal X-ray diffraction analysis reveals a C 3 -symmetric molecular structure. Full characterization of 1-U was performed using nuclear magnetic resonance, UV−vis−NIR electronic absorption, and electron paramagnetic resonance spectroscopies as well as SQUID magnetometry, thus confirming the U(III) oxidation state. Alternating current magnetic studies show that 1-U exhibits single-molecule magnet behavior at low temperatures in a non-zero external field. Comparison of these results to those of the previously reported mesitylene-anchored complexes, [U III ((OAr Ad,Me ) 3 mes)] and [U III ((OAr tBu,tBu ) 3 mes)], indicates a drastic change in the electronic structure when moving from phenolate-based ligands to thiophenolate-based 1, which is further discussed by means of computational analysis (NBO, DFT, and QTAIM). Despite the U−O bonds being stronger, a much higher covalency was found for the U−S analogue. Article pubs.acs.org/IC

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Section: Introductionmentioning

confidence: 99%

Uranium Going the Soft Way: Low-Valent Uranium(III) Coordinated to an Arene-Anchored Tris-Thiophenolate Ligand

et al. 2021

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“…For the past century, uranium has been one of the most studied actinides. Despite the increasing interest in fundamental organo-actinide chemistry of the last 20 years, 1 catalysis derived from uranium species remains relatively sparse. This is in part due to a number of challenges associated with organo-uranium chemistry, which diminish their catalytic utility.…”

Section: Introductionmentioning

confidence: 99%

From Chemical Curiosities and Trophy Molecules to Uranium-Based Catalysis: Developments for Uranium Catalysis as a New Facet in Molecular Uranium Chemistry

Hartline

Meyer

2021

JACS Au

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Catalysis remains one of the final frontiers in molecular uranium chemistry. Depleted uranium is mildly radioactive, continuously generated in large quantities from the production and consumption of nuclear fuels and accessible through the regeneration of “uranium waste”. Organometallic complexes of uranium possess a number of properties that are appealing for applications in homogeneous catalysis. Uranium exists in a wide range of oxidation states, and its large ionic radii support chelating ligands with high coordination numbers resulting in increased complex stability. Its position within the actinide series allows it to involve its f -orbitals in partial covalent bonding; yet, the U–L bonds remain highly polarized. This causes these bonds to be reactive and, with few exceptions, relatively weak, allowing for high substrate on/off rates. Thus, it is reasonable that uranium could be considered as a source of metal catalysts. Accordingly, uranium complexes in oxidation states +4, +5, and +6 have been studied extensively as catalysts in sigma-bond metathesis reactions, with a body of literature spanning the past 40 years. High-valent species have been documented to perform a wide variety of reactions, including oligomerization, hydrogenation, and hydrosilylation. Concurrently, electron-rich uranium complexes in oxidation states +2 and +3 have been proven capable of performing reductive small molecule activation of N 2 , CO 2 , CO, and H 2 O. Hence, uranium’s ability to activate small molecules of biological and industrial relevance is particularly pertinent when looking toward a sustainable future, especially due to its promising ability to generate ammonia, molecular hydrogen, and liquid hydrocarbons, though the advance of catalysis in these areas is in the early stages of development. In this Perspective, we will look at the challenges associated with the advance of new uranium catalysts, the tools produced to combat these challenges, the triumphs in achieving uranium catalysis, and our future outlook on the topic.

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“…Uranium nitride molecules and materials have been the subject of intense study in recent years due to the diverse reactivity profile of actinide-ligand multiple bonds − and the utility of these compounds as model systems for next-generation nuclear fuels. − Molecular uranium nitride complexes have been shown to facilitate a wide range of chemical transformations, such as C–H activation, − C–N bond formation, − and activation of small molecules such as N 2 , H 2 , CO, and CO 2 . − Haber first discovered that bulk uranium nitrides could be used as effective catalysts for the conversion of N 2 to NH 3 in 1909, and molecular models containing uranium nitride linkages have more recently been shown to undergo nitrogen fixation and conversion to NH 3 . In addition to their versatile reactivity, uranium nitride complexes and clusters have also gathered interest as single-molecule magnets, and the degree of magnetic communication between metal centers has been found to vary substantially based on the ligand environment in these species. − …”

Section: Introductionmentioning

confidence: 99%

Amidinate Supporting Ligands Influence Molecularity in Formation of Uranium Nitrides

et al. 2021

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Uranium nitride complexes are attractive targets for chemists as molecular models for the bonding, reactivity, and magnetic properties of next-generation nuclear fuels, but these molecules are uncommon and can be difficult to isolate due to their high reactivity.Here, we describe the synthesis of three new multinuclear uranium nitride complexes, 9) (BCMA = N,N-bis(cyclohexyl)methylamidinate, BIMA = N,N-bis(iso-propyl)methylamidinate), from U(III) and U(IV) amidinate precursors. By varying the amidinate ligand substituents and azide source, we were able to influence the composition and size of these nitride complexes. 15 N isotopic labeling experiments confirmed the bridging nitride moieties in 7−9 were formed via two-electron reduction of azide. The tetra-uranium cluster 8 was isolated in 99% yield via reductive cleavage of the amidinate ligands; this unusual molecule contains nitrogen-based ligands with formal 1−, 2−, and 3− charges. Additionally, chemical oxidation of the U(IV) precursor U(N 3 )(BCMA) 3 yielded the cationic U(V) species [U(N 3 )(BCMA) 3 ][OTf]. Magnetic susceptibility measurements confirmed a U(IV) oxidation state for the uranium centers in the three nitride-bridged complexes and provided a comparison of magnetic behavior in the structurally related U(III)-U(IV)-U(V) series U(BCMA) 3 , U(N 3 )(BCMA) 3 , and [U(N 3 )(BCMA) 3 ][OTf]. At 240 K, the magnetic moments in this series decreased with increasing oxidation state, i.e., U(III) > U(IV) > U(V); this trend follows the decreasing number of 5f valence electrons along this series.

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Actinides

Cited by 14 publications

References 551 publications

Uranium Going the Soft Way: Low-Valent Uranium(III) Coordinated to an Arene-Anchored Tris-Thiophenolate Ligand

Uranium Going the Soft Way: Low-Valent Uranium(III) Coordinated to an Arene-Anchored Tris-Thiophenolate Ligand

From Chemical Curiosities and Trophy Molecules to Uranium-Based Catalysis: Developments for Uranium Catalysis as a New Facet in Molecular Uranium Chemistry

Amidinate Supporting Ligands Influence Molecularity in Formation of Uranium Nitrides

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