Cation–Cation Interactions, Magnetic Communication, and Reactivity of the Pentavalent Uranium Ion [U(NtBu)2]+

Spencer, Liam; Schelter, Eric J.; Yang, Ping; Gdula, Robyn L.; Scott, Brian L.; Thompson, J. D.; Kiplinger, Jaqueline L.; Batista, Enrique R.; Boncella, James M.

doi:10.1002/anie.200806190

Cited by 137 publications

(120 citation statements)

References 28 publications

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“…Experimental and theoretical DFT investigations of their magnetic properties have shown that both isomers exhibit a rather weak ferromagnetic and antiferromagnetic character for meta-and para-DEB, respectively [78]. A new bis(imido) diuranium(V) complex [U(N t Bu) 2 (I) ( t Bu 2 bpy)] 2 exhibiting an moderate antiferromagnetic coupling between two metallic 5f 1 -5f 1 spin active centres has been synthesized and theoretically investigated [77]. For this system, B3LYP calculations predicted correctly that the BS state is lower in energy than the triplet HS state, providing an exchange coupling constant J (-12 cm -1 ) in agreement with the experimental fitting of susceptibility measurements.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, recent reports in synthetic efforts toward paramagnetic actinide-containing assemblies indicate that ketimide (1,4-phenylenediketimide) ligands could lead to diverse and interesting magnetic behaviours [74][75][76][77]. Consequently, simple bis(ketimide) [(C 5 Me 4 Et) 2 (Cl)An] 2 (l-{N=CMe-(C 6 H 4 )-MeC=N}) binuclear An IV /An IV (Th, U) complexes [75] were synthesized; in the uranium case, metal-metal electronic communication could occur between the two 5f 2 -5f 2 spin centres through the aromatic spacer ligand.…”

Section: Introductionmentioning

confidence: 99%

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A relativistic DFT study of magnetic exchange coupling in ketimide bimetallic uranium(IV) complexes

et al. 2012

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International audienceMagnetic exchange couplings in bis(ketimide) binuclear UIV/UIV complexes [Cp′2UCl]2(μ-ketimide) diuranium(IV) and [(C5H5)2(Cl)An]2(μ-ketimide) (Cp′ = C5Me4Et; ketimide = N=CMe-(C6H4)-MeC=N) have been investigated computationally using relativistic density functional theory (DFT) combined with the broken symmetry (BS) approach. Using the B3LYP hybrid functional, the BS ground state of these UIV/UIV 5f 2-5f 2 complexes has been found of lower energy than the high spin (HS) quintet state, indicating an antiferromagnetic character (estimated coupling constant |J| < 5 cm−1) which has not yet been evidenced unambiguously experimentally. On the contrary, the BP86 GGA functional overestimates greatly the antiferromagnetic character of the complexes (|J| > 100 cm−1). As recently reported for para-bis(imido) [(C5H5)3U]2(μ-imido) uranium(V) complex, spin polarization is mainly responsible for the antiferromagnetic coupling through the π-network orbital pathway within the bis(ketimide) bridge. Furthermore, spin polarization is exalted by the combined roles of the 5f metal orbitals and of the π-conjugated ketimide bridging ligand which permit electronic communication between the two uranium atoms albeit separated by a distance of the order of 10 Å. The MO analysis clarifies which MOs contribute to the antiferromagnetic coupling in the binuclear complexes under consideration and brings to light the 5f orbitals driving contribution

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A relativistic DFT study of magnetic exchange coupling in ketimide bimetallic uranium(IV) complexes

et al. 2012

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“…[5] Temperature-dependent magnetic data were collected in the temperature range 2-300 K. At 300 K, 4 displays an effective magnetic moment of 1.96 m B per uranium ion, which is lower that the theoretical value calculated for the free f 1 ion in the L-S coupling scheme (m eff = 2.54 m B ), but within the range of values reported for U V compounds. [32,33] The plot of c versus T (Figure 3) clearly indicates the presence of an unambiguous antiferromagnetic coupling [6] between the f 1 ions, with a maximum at 6 K. Unambiguous evidence of magnetic communication between uranium centers is limited to three examples of dimeric complexes, which include the [{UO 2 (dbm) 2 K(18C6)} 2 ] dimer. [6,8,34] This is the first example of tetranuclear complex that shows unambiguous magnetic coupling, although the presence of magnetic coupling at temperature lower than 2 K had been suspected for 1.…”

mentioning

confidence: 95%

“…[32,33] The plot of c versus T (Figure 3) clearly indicates the presence of an unambiguous antiferromagnetic coupling [6] between the f 1 ions, with a maximum at 6 K. Unambiguous evidence of magnetic communication between uranium centers is limited to three examples of dimeric complexes, which include the [{UO 2 (dbm) 2 K(18C6)} 2 ] dimer. [6,8,34] This is the first example of tetranuclear complex that shows unambiguous magnetic coupling, although the presence of magnetic coupling at temperature lower than 2 K had been suspected for 1. The observation of a stronger coupling in the salen tetramer 4 compared to 1 could be the result of small differences in the structural parameters associated with the presence of a stronger UO 2 + ···UO 2 + interaction and anticipates the possibility of establishing the first magnetostructural correlation in actinides.…”

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confidence: 95%

Stable Pentavalent Uranyl Species and Selective Assembly of a Polymetallic Mixed‐Valent Uranyl Complex by Cation–Cation Interactions

et al. 2009

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Cation-cation interactions are a key feature of actinide chemistry. These interactions can be used in two areas that currently attract great interest, namely the expansion of felement supramolecular chemistry and the enhancement of magnetic interactions in actinide compounds. [1][2][3][4][5][6][7][8][9][10][11][12] Moreover, oligomeric cation-cation species that present mutually coordinated actinyl ions are likely to play a crucial role in nuclear waste reprocessing and in the migration of radioactive actinides in the environment. [1] Cation-cation interactions are known to be important in neptunyl(V) structural chemistry, [13] but are more rarely found in uranyl(VI) compounds because of the lower basicity of the UO 2 2+ oxygen atoms. Dimeric compounds formed through the mutual binding of pentavalent uranyl(V) ions have been proposed as intermediates in the disproportionation of pentavalent uranyl ions to UO 2 2+ and U IV species.[14]As a result, bulky ligands have been used in the past few years to disfavor cation-cation interactions and allow the synthesis of rare UO 2 + complexes, [15][16][17][18][19][20][21] which have been the subject of two recent reviews.[ [8] The presence of antiferromagnetic coupling between the oxo-bridged uranium centers was unambiguously demonstrated for the dimetallic complex but is less evident for the tetrametallic complex. [8] The decomposition of these polymetallic complexes of pentavalent uranyl ions to UO 2 2+ and U IV species starts rapidly after dissolution in organic solvents and is accelerated by traces of water. From these reactivity studies, it occurred to us that the stability of these polymeric systems could possibly be modulated by fine-tuning the electronic and steric properties of the ligand and coordinating cation. Herein, we report the first example of a UO 2 + ···UO 2 + complex that is highly stable in organic solvents and, significantly, is stable toward hydrolysis. We also describe the selective synthesis and the structure of the first mixed-valent UO 2 + ···UO 2 2+ molecular complex, which provides a rare example of functionalization of the U VI =O group. [20,22] By breaking away from the current trend of using steric bulk to prevent dimer formation and the associated disproportionation of UO 2 + complexes, we show that the non-bulky Schiff base ligand salen 2À (N,N'-bis(salicylidene)ethylenediamine) can stabilize pentavalent uranyl ions through the formation of a highly stable cation-cation complex. Moreover, we demonstrate that the resulting tetrameric uranyl(V) complex exhibits unambiguous antiferromagnetic coupling between the uranium centers.The reaction of the recently reported UO 2 + complex [(UO 2 Py 5 )(KI 2 Py 2 )] n (2; Py = pyridine) [23] with salenK 2 in pyridine led to the formation of the complex of pentavalent uranyl 3 as a violet powder that was insoluble in pyridine. The elemental analysis of 3 indicates the presence of a complex of general formula [(UO 2 )(salen)K(Py)]·1.4 KI, which most likely has a solid-state polymeric structure. Compound ...

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“…31 Recently, the same method has been applied to another pentavalent uranium complex consisting of a pair of uranium bis-imido moieties. 32 It should be noted that both systems involve U(V) multiply-bonded to imide ligands, which results in the strong crystal field required for this approach. While this approach is straightforward, the requirement for a well-isolated ground state limits the instances where it may be applied.…”

Section: Introductionmentioning

confidence: 99%

Quantifying Exchange Coupling in f-Ion Pairs Using the Diamagnetic Substitution Method

Lukens

Walter

2010

Inorg. Chem.

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One of the challenges in the chemistry of actinide and lanthanide (f-ion) is quantifying exchange coupling between f-ions. While qualitative information about exchange coupling may be readily obtained using the diamagnetic substitution approach, obtaining quantitative information is much more difficult. This article describes how exchange coupling may be quantified using the susceptibility of a magnetically isolated analog, as in the diamagnetic substitution approach, along with the anisotropy of the ground state as determined by EPR spectroscopy. Several examples are used to illustrate and test this approach.

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Cation–Cation Interactions, Magnetic Communication, and Reactivity of the Pentavalent Uranium Ion [U(NtBu)₂]⁺

Cited by 137 publications

References 28 publications

A relativistic DFT study of magnetic exchange coupling in ketimide bimetallic uranium(IV) complexes

A relativistic DFT study of magnetic exchange coupling in ketimide bimetallic uranium(IV) complexes

Stable Pentavalent Uranyl Species and Selective Assembly of a Polymetallic Mixed‐Valent Uranyl Complex by Cation–Cation Interactions

Quantifying Exchange Coupling in f-Ion Pairs Using the Diamagnetic Substitution Method

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