Dinitrogen Labile Coordination versus Four-Electron Reduction, THF Cleavage, and Fragmentation Promoted by a (calix-tetrapyrrole)Sm(II) Complex

Guan, Jingwen; Dubé, Tiffany; Gambarotta, and Sandro; Yap, Glenn P. A.

doi:10.1021/om000698p

Cited by 74 publications

(50 citation statements)

References 24 publications

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“…The diamond motif is asymmetric with U1 À O2' 2.345(4) and acute and obtuse angles of 72.2(2)8 for O2-U1-O2' and 107.8(2)8 for U1-O2-U1', and a U1···U1' separation of 3.4706 (4) . These data compare favorably to those reported for the pentavalent diamond-shaped [UO 2 -(dbm) 2 {K [18]crown-6}] 2 [21] (type A) and reflect the propensity of pentavalent uranyl to form cation-cation interactions due to the increased Lewis basicity of the U V oxo groups. The Sm1 center also has two approximately axial pyridine nitrogen donors to complete the coordination sphere.…”

supporting

confidence: 82%

“…Focusing on one molecule of 2, both the uranium and samarium centers are sevencoordinate with approximate pentagonal bipyramidal geometry, but a greater distortion at Sm. This primarily results from the bond between the uranyl endo-oxo and the Sm cation, which at 2.238(5) is indicative of a single bond, [18,19] and represents the first example of a 4f-element to uranyl oxo bonding interaction. The Sm1-O1-U1 angle is effectively …”

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confidence: 99%

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Single‐Electron Uranyl Reduction by a Rare‐Earth Cation

et al. 2010

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Unlike their transition-metal analogues, the oxo groups of the uranyl dication, [UO 2 ] 2+ , which has a linear geometry and short, strong UÀO bonds are commonly considered inert. [1] Very little Lewis base character has been demonstrated for the uranyl oxo groups, [2,3] which makes them poor models for the heavier, highly radioactive transuranic actinyl cations such as neptunyl [NpO 2 ] n+ (n = 1, 2). [4,5] The heavier actinyls are important components in nuclear waste and demonstrate oxo basicity that can give rise to poorly understood cluster formation and problems in nuclear waste PUREX separation processes.[6] However, it has been shown recently that the more Lewis basic, pentavalent uranyl cation, [UO 2 ] + , can be stabilized indefinitely using suitable equatorial-binding ligands and anaerobic conditions. [7,8] Usually the [UO 2 ] + cation decomposes by disproportionation, which is also a poorly understood process, but is important in the precipitation of uranium salts out of aqueous environments. [9,10] The disproportionation is suggested, by analogy with the transuranic metal oxo Lewis base behavior, to involve the formation of cation-cation interactions (CCIs) [11,12] in which the oxo groups ligate to adjacent actinyl centers forming diamond (A) or T-shaped (B) dimers or clusters which can then allow the transfer of protons and electrons between metals, such as in C. [13] We reported that the use of rigid, Pacman-shaped macrocycles can allow the isolation of heterobimetallic uranyltransition metal complexes that form an oxo interaction with the transition metal in the solid state and solution, [14] and how the inclusion of more than one metal cation alongside the uranyl cation led to isolable, stable pentavalent uranyl complexes with a covalently functionalized oxo group. [15] More recently, pentavalent uranyl complexes with Group 1 cation oxo-coordination, [16] and a doubly silylated complex [17] have been isolated. Here, we report the first uranyl-4f metal interaction, prepared by either standard, or sterically induced reduction procedures, and demonstrate strong magnetic coupling between the 4f and 5f electrons.The reaction between the divalent samarium silylamide [Sm(THF) 2 {N(SiMe 3 ) 2 } 2 ] and the uranyl Pacman complex [UO 2 (py)(H 2 L)] (1) in pyridine resulted in the deposition of the new uranyl-samarium complex [UO 2 Sm(py) 2 (L)] 2 (2) as a very poorly soluble, thermally stable, red crystalline powder in good yield (Scheme 1), and containing crystals suitable for single-crystal X-ray diffraction studies (Figure 1).The 1 H NMR spectrum of 2 in [D 5 ]pyridine reveals the presence of paramagnetically shifted resonances between d = 12.4 and À21.5 ppm, the number and integrals of which are consistent with the retention of a wedged, Pacman structure in solution of C s symmetry. In the solid state, the molecular structure shows that 2 is dimeric (Figure 1) and the unit cell contains two similar molecules. Focusing on one molecule of 2, both the uranium and samarium centers are sevencoordinate w...

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confidence: 82%

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confidence: 99%

Single‐Electron Uranyl Reduction by a Rare‐Earth Cation

et al. 2010

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“…161 Yet, thorough drying and recrystallization from toluene yields the enolate (cypg)Sm(THF)(Li 2 {Li(THF)}(µ 3 -OCHdCH 2 ) (70cy), the cy analogue of 63cy. 164,165 Both enolates react with acetylene to form different compounds. In both cases H 2 is released and the Sm atoms are oxidized to the trivalent state.…”

Section: Complexes Derived From LI 4 (Pg)mentioning

confidence: 99%

“…In both complexes the enolate group obviously affects the redox potential of the metal centers to such an extent that no further reaction with N 2 takes place. 164 Finally, slow decomposition of the N 2 complexes 75cy and 76cy in THF, accelerated under reflux conditions, affords the O-bridged dimer [(cypg)Sm{Li(THF)} 3 (µ 3 -Cl)] 2 (µ-O) (79cy). 164 …”

Section: Complexes Derived From LI 4 (Pg)mentioning

confidence: 99%

Synthesis and Structural Chemistry of Non-Cyclopentadienyl Organolanthanide Complexes

2002

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Over the years one major challenge has remained in organolanthanide chemistry: the synthesis of homoleptic alkyl and aryl complexes. The simplest organometallic compounds of the rare earths are the species LnR 2 or LnR 3 with the rare earth metals in their common oxidation states Ln 2+ and Ln 3+ which imply the coordination of only two or three ligands to the metal center. This is usually insufficient to meet the lanthanides' demands of steric saturation through high coordination numbers.Hence for a long time, only indirect evidence could be found for the existence of simple homoleptic organolanthanide compounds; the isolation and characterization of compounds belonging to this class were first achieved recently using pentafluorophenyl for Ln 2+ derivatives 12 and very bulky alkyl ligands for Ln 3+ species. [13][14][15] Especially for alkyls, very little structural data are available for compounds without any trimethylsilyl-substituted ligands which generally ensure higher stability. But nevertheless, due to the difficulties of their synthesis and their high reactivity alkyls and aryls still represent an interesting class of compounds. 16 Homoleptic σ-Alkyl ComplexesShortly after the synthesis of the first divalent solvent-free Ln alkyl, [(Me 3 Si) 3 C] 2 Yb, 17 the Eu analogue was prepared similarly by the reaction of EuI 2 and KC(SiMe 3 ) 3 in benzene. 18 It also features the bent structure displayed by the Yb complex but with a slightly smaller C-Eu-C angle (C-Eu-C ) 136°, C-Yb-C ) 137°) and longer Eu-C bonds (Eu-C ) 261 pm, Yb-C ) 249/250 pm). Salt metathesis was then again applied successfully to synthesize the first divalent Sm alkyl, Sm[C(SiMe 3 ) 2 (SiMe 2 OMe)] 2 (THF) Frank T. Edelmann was born in Hamburg, Germany, in 1954. He studied chemistry from 1974 to 1979 at the University of Hamburg, where he obtained his Diplom in 1979 and doctoral degree in 1983. His Ph.D. thesis entitled "The chemistry of the tricarbonyl(fulvene) chromium complexes" was carried out under the supervision of Prof. Ulrich Behrens. This was followed by two years (1983−1985) of postdoctoral research as a Feodor Lynen Fellow of the Alexander-von-Humboldt Foundation in the groups of Professors Josef Takats (

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“…This is proposed on the basis of the N-N bond distance (1.371(16) Å; slightly shorter than that expected for an N-N single bond), magnetic moment (4.05 μB; lower than the analogous divalent complex 63) and short Sm-Sm contacts in the solid state which may promote magnetic couplings. [105]. It should be noted that the crystallographic data for 67 was only of a good enough quality to obtain structural connectivity.…”

Section: Amide Ancillary Ligandsmentioning

confidence: 99%