Homoleptic Organometallic Anions of Ti, Zr, Hf, and Nb

El‐Kurdi, Said; Seppelt, Konrad

doi:10.1002/chem.201003323

Cited by 20 publications

(13 citation statements)

References 27 publications

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“…As imilar distortion with lithium atom interaction has previously been reported for ahexaphenyl hafnium complex, [Li(THF) 4 ][(THF)LiHf(Ph) 6 ]. [18] With asuccessful method identified for the synthesis and isolation of 1,t he para-substituents of the aryl ring were varied in order to evaluate the effect of the electronic contribution of the ligands on the nature of the U À Cbond. As as tarting point, p-tolyllithium was selected in order to incorporate am ore electron-rich aryl ligand.…”

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Homoleptic Aryl Complexes of Uranium (IV)

et al. 2019

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The synthesis and characterization of sterically unencumbered homoleptic organouranium aryl complexes containing U À C s-bonds has been of interest to the chemical community for over 70 years.R eported herein are the first structurally characterized,s terically unencumbered homoleptic uranium (IV) aryl-ate species of the form [U(Ar) 6 ] 2À (Ar = Ph, p-tolyl, p-Cl-Ph). Magnetic circular dichroism (MCD) spectroscopya nd computational studies provide insight into electronic structure and bonding interactions in the U À C sbond across this series of complexes.O verall, these studies solve adecades-long challenge in synthetic uranium chemistry, enabling new insight into electronic structure and bonding in organouranium complexes.

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Homoleptic Aryl Complexes of Uranium (IV)

et al. 2019

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“…[1][2][3][4][5] In particular, the observation of a trigonal prismatic structure for these complexes, as opposed to the more common octahedral geometry, is considered strong evidence for the involvement of the d orbitals in the metal-carbon bonds. 2, 3 A number of trigonal prismatic [MR 6 ] qtype complexes have been structurally characterized, including [Li(TMEDA)] 2 [Zr(CH 3 ) 6 ], 6 [M(CH 3 ) 6 ] q (M = W, Re, Nb, Ta; q = 0,À1), 4 [Ta(CRCSitBu 3 ) 6 ] À , 7 [M(C 6 H 5 ) 6 ] 2À (M = Zr, Nb), 8 and [Ta(C 6 H 5 ) 6 ] À . 9 Notably absent from this list, however, are their heavier actinide analogues.…”

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confidence: 99%

“…It is insoluble in hexane, aromatic solvents, and diethyl ether, but very soluble in THF and DME. Its 1 H NMR spectrum in THF-d 8 at RT reveals resonances at 7.61 ppm, 7.00 ppm and 6.79 ppm in the ratio of 2 : 2 : 1, corresponding to the ortho, meta, and para protons of the phenyl ring, respectively. In addition, there is a single resonance in its 7 Li{ 1 H} NMR spectrum at 2.60 ppm.…”

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“…Nonetheless, the solution spectroscopic properties of 1 were examined with greater scrutiny (see Fig. S4 in the ESI † for variable temperature NMR spectra of 1 in THF-d 8 ) in an attempt to observe this structural perturbation in solution. Interestingly, upon cooling to À90 1C, the phenyl resonances decoalesce into five separate peaks, with d( 1 H) at 7.84, 7.16, View Article Online 7.01, 6.78, and 6.60 ppm, which we have tentatively assigned to the five proton environments anticipated for a C 3 symmetric structure with restricted Th-C bond rotation.…”

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Synthesis, structure and bonding of hexaphenyl thorium(iv): observation of a non-octahedral structure

et al. 2016

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We report herein the synthesis of the first structurally characterized homoleptic actinide aryl complexes, [Li(DME) 3 ] 2 [Th(C 6 H 5 ) 6 ] (1) and [Li(THF)(12-crown-4)] 2 [Th(C 6 H 5 ) 6 ] (2), which feature an anion possessing a regular octahedral (1) or a severely distorted octahedral (2) geometry.The solid-state structure of 2 suggests the presence of pseudo-agostic ortho C-HÁ Á ÁTh interactions, which arise from r(C-H) -Th(5f) donation. The non-octahedral structure is also favoured in solution at low temperatures.High-valent homoleptic transition metal complexes of the type [MR 6 ] q (R = alkyl, aryl; q = 0, À1, À2) have proven to be incredibly useful for exploring the nature of the M-C bond. [1][2][3][4][5] In particular, the observation of a trigonal prismatic structure for these complexes, as opposed to the more common octahedral geometry, is considered strong evidence for the involvement of the d orbitals in the metal-carbon bonds. 6 ]. 12,13 The latter was oxidized in situ to U(CH 2 SiMe 3 ) 6 , which was characterized using 13 C and 1 H NMR spectroscopies, accompanied by relativistic DFT calculations of NMR chemical shifts. 16 In each uranium example, an octahedral geometry was observed, which is perhaps not surprising, as significant f-orbital participation in bonding tends to favor an octahedral geometry. 17 In contrast, d orbital involvement in Th-C bonding is expected to be more significant than f orbital participation, 18,19 and therefore the observation of a trigonal prismatic structure should be more likely for this element relative to the other actinides. 10 Given this consideration, we endeavored to synthesize and structurally characterize the homoleptic actinide-aryl complex, [Th(C 6 H 5 ) 6 ] 2À , by reacting ThCl 4 with an excess of phenyl lithium.Addition of 8 equiv. of PhLi to a THF solution of ThCl 4 (DME) 2 results in the formation of a white solid and a dark amber solution. Isolation of this amber material, followed by recrystallization from concentrated DME, afforded [Li(DME) 3 ] 2 [Th(C 6 H 5 ) 6 ] (1) as a pale yellow crystalline material in 56% yield (Scheme 1). Complex 1 is thermally unstable at room temperature (RT), both as a solid and in solution, but is stable for up to 2 weeks as a solid at À25 1C. It is insoluble in hexane, aromatic solvents, and diethyl ether, but very soluble in THF and DME. Its 1 H NMR spectrum in THF-d 8 at RT reveals resonances at 7.61 ppm, 7.00 ppm and 6.79 ppm in the ratio of 2 : 2 : 1, corresponding to the ortho, meta, and para protons of the phenyl ring, respectively. In addition, there is a single resonance in its 7 Li{ 1 H} NMR spectrum at 2.60 ppm. The 13 C{ 1 H} NMR spectrum in THF-d 8 exhibits a key fingerprint resonance at 220.5 ppm, which corresponds to the ipso-carbon, as also confirmed by our relativistic DFT calculations of the NMR chemical shifts (cf. Table S2 in the ESI †). This resonance is shifted notably downfield from the corresponding 13 C-ipso shifts in related Ti, Zr, and Hf aryl complexes (which typically appear between 183 an...

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“…The three C‐U‐C angles for the lithium‐coordinating phenyl ligands range from 76.77(2)° to 79.33(2)°, whereas those for the three independent phenyl rings range from 92.74(19)° to 101.76(2)° (Table ). A similar distortion with lithium atom interaction has previously been reported for a hexaphenyl hafnium complex, [Li(THF) 4 ][(THF)LiHf(Ph) 6 ] …”

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confidence: 94%