Electronic structure comparisons of isostructural early d- and f-block metal(<scp>iii</scp>) bis(cyclopentadienyl) silanide complexes

Gransbury, Gemma K.; Réant, Benjamin L. L.; Wooles, Ashley J.; Emerson-King, Jack; Chilton, Nicholas F.; Liddle, Stephen T.; Mills, David P.

doi:10.1039/d2sc04526e

Cited by 7 publications

(37 citation statements)

References 107 publications

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“…The observed uranium-alkoxide products, 2-THF and 2-DME, were likely formed by σ bond metathesis at the U−Si bond with the Lewis basic solvents, resulting from a combination of both the greater oxophilicity of uranium vs silicon, and the steric bulk of Tp* hindering a strong interaction of the (Me 3 Si) 3 Si− fragment with the uranium(III) ion. In the case of 2-DME, formation of (Me 3 Si) 3 SiMe is confirmed from 1 H and 29 45 studies suggest the chemistry of (Me 3 Si) 3 SiK and related silylpotassium species is dominated by two electron transformations. 30 As observed with ethereal solvents, (Me 3 Si) 3 SiK is also stable in pyridine with no reaction noted.…”

Section: ■ Introductionmentioning

confidence: 79%

“…Attempting to synthesize uranium(III)-silyl bonds using the bis(Tp*) framework ultimately generated the isolable products of Lewis basic solvent activation. The wide range of NMRactive nuclei in these compounds enabled characterization by paramagnetic 1 H, 2 H, 11 B, and 29 Si NMR spectroscopy. Infrared spectroscopy and electronic absorption spectroscopy were used to identify and characterize these new uranium(III) derivatives as well, with the latter helping to corroborate the U(III) oxidation state of these derivatives.…”

Section: ■ Conclusionmentioning

confidence: 99%

“…Missing in the repertoire of bis-Tp* uranium complexes is the U–Si bond. Although U–Si bonds, including U(IV)–Si(SiMe 3 ) 3 , exist in the literature, , only recently have silyl bonds been observed for a uranium(III) center . In attempts to expand the library of U(III)–Si bonds by treating Tp* 2 UI with (Me 3 Si) 3 SiK, it was discovered that the base-stabilized U–Si bond was not observed using the Tp* scaffold, but instead a variety of base-activated products are isolated.…”

Section: Introductionmentioning

confidence: 99%

“…Although U−Si bonds, including U(IV)− Si(SiMe 3 ) 3 , exist in the literature, 27,28 only recently have silyl bonds been observed for a uranium(III) center. 29 In attempts to expand the library of U(III)−Si bonds by treating Tp* 2 UI with (Me 3 Si) 3 SiK, 30 it was discovered that the base-stabilized U−Si bond was not observed using the Tp* scaffold, but instead a variety of base-activated products are isolated. These derivatives were fully characterized using multinuclear NMR, electronic absorption, and IR spectroscopies, as well as X-ray crystallography in cases where suitable single crystals were obtainable.…”

Section: ■ Introductionmentioning

confidence: 99%

“…-py CH) 11. B NMR (C 6 D 6 , 300 MHz, 25 °C) δ = −9.85 ppm (503, broad) 29. Si NMR (C 6 D 6 , 79.49 MHz, 25 °C) δ (ppm) = −6.8 (s, (Me 3 Si) 3 Si), −51.0 (s, (Me 3 Si) 3 Si).…”

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confidence: 99%

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Lewis Base Activation by Uranium(III) Complexes

et al. 2023

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The combination of a bulky hypersilyl potassium [(Me 3 Si) 3 SiK] reagent with Tp* 2 UI (Tp* = hydrotris(3,5-dimethylpyrazolyl)borate) in the presence of ethereal Lewis donors resulted in the formation of base-activated products Tp* 2 U[O(CH 2 ) 4 Si(SiMe 3 ) 3 ] (1-THF) and Tp* 2 U[O(CH 2 ) 2 OMe] (2-DME). The reactivity with another Lewis base, pyridine, was explored by treating Tp* 2 UI and hypersilyl potassium or benzyl potassium in the presence of pyridine, which resulted in formation of Tp* 2 U[NC 5 H 5 -4-Si(SiMe 3 ) 3 ] (3-py-Si) and Tp* 2 U(NC 5 H 5 -4-Bn) (4-py-Bn, Bn = benzyl), respectively. Multinuclear paramagnetic NMR spectroscopy ( 1 H, 11 B{ 1 H}, 29 Si{ 1 H}) supported the formation of the Lewis base activated uranium compounds as corroborated by electronic absorption spectroscopy and X-ray crystallography. To recognize the mechanistic possibilities, radical trap experiments were performed and [K(18-crown-6)][4-benzylpyridinide] (4-K), Tp*U(IV)[(�NC(Me)C(H)C(Me)N)-B(H)(3,5-dimethylpyrazole) 2 ] (6-Tp*UTp′), and [Tp* 2 U(NC 5 H 5 )] 2 (5-py-py) were observed.

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Section: ■ Introductionmentioning

confidence: 79%

Section: ■ Conclusionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

“…-py CH) 11. B NMR (C 6 D 6 , 300 MHz, 25 °C) δ = −9.85 ppm (503, broad) 29. Si NMR (C 6 D 6 , 79.49 MHz, 25 °C) δ (ppm) = −6.8 (s, (Me 3 Si) 3 Si), −51.0 (s, (Me 3 Si) 3 Si).…”

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Lewis Base Activation by Uranium(III) Complexes

et al. 2023

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Covalency-Driven Differences in the Hydrogenation Chemistry of Lanthanide- and Actinide-Based Frustrated Lewis Pairs

Brackbill,

Rajeshkumar,

Douair

et al. 2024

J. Am. Chem. Soc.

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The electronic organization of Frustrated Lewis Pairs (FLPs) allows them to activate strong bonds in mechanisms that are usually free of redox events at the Lewis acidic site. The unique 6d/ 5f manifold of uranium could serve as an interesting FLP acceptor site, but to date FLP-like catalysis with actinide ions is unknown. In this paper, the catalytic, FLP-like hydrogenation reactivity of trivalent uranium complexes is explored in the presence of basestabilized silylenes. Comparison to isoelectronic, isostructural lanthanide and thorium complexes lends insight into the electronic factors governing dihydrogen activation. Mechanistic studies of the uranium-and lanthanide-catalyzed hydrogenations are presented, including discussion of likely intermediates. Computational modeling of the f-element complexes, combined with experimental comparison to p-block Lewis acids, elucidates the relevance of steric hindrance to productive reactivity with dihydrogen. Consideration of the complete experimental and theoretical evidence provides a clear picture of the electronic and steric factors governing dihydrogen activation by these FLPs.

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Tris-Silanide f-Block Complexes: Insights into Paramagnetic Influence on NMR Chemical Shifts

Réant,

Mackintosh,

Gransbury

et al. 2024

JACS Au

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The paramagnetism of f-block ions has been exploited in chiral shift reagents and magnetic resonance imaging, but these applications tend to focus on 1 H NMR shifts as paramagnetic broadening makes less sensitive nuclei more difficult to study. Here we report a solution and solid-state (ss) 29 Si NMR study of an isostructural series of locally D 3h -symmetric early fblock metal(III) tris-hypersilanide complexes, [M{Si-(SiMe 3 ) 3 } 3 (THF) 2 ] (1-M; M = La, Ce, Pr, Nd, U); 1-M were also characterized by single crystal and powder X-ray diffraction, EPR, ATR-IR, and UV−vis−NIR spectroscopies, SQUID magnetometry, and elemental analysis. Only one SiMe 3 signal was observed in the 29 Si ssNMR spectra of 1-M, while two SiMe 3 signals were seen in solution 29 Si NMR spectra of 1-La and 1-Ce. This is attributed to dynamic averaging of the SiMe 3 groups in 1-M in the solid state due to free rotation of the M−Si bonds and dissociation of THF from 1-M in solution to give the locally C 3vsymmetric complexes [M{Si(SiMe 3 ) 3 } 3 (THF) n ] (n = 0 or 1), which show restricted rotation of M−Si bonds on the NMR time scale. Density functional theory and complete active space self-consistent field spin−orbit calculations were performed on 1-M and desolvated solution species to model paramagnetic NMR shifts. We find excellent agreement of experimental 29 Si NMR data for diamagnetic 1-La, suggesting n = 1 in solution and reasonable agreement of calculated paramagnetic shifts of SiMe 3 groups for 1-M (M = Pr and Nd); the NMR shifts for metal-bound 29 Si nuclei could only be reproduced for diamagnetic 1-La, showing the current limitations of pNMR calculations for larger nuclei.

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Electronic structure comparisons of isostructural early d- and f-block metal(iii) bis(cyclopentadienyl) silanide complexes

Abstract: We report the synthesis of the U(III) bis(cyclopentadienyl) hypersilanide complex [U(Cp′′)2{Si(SiMe¬3)3}] (Cp′′ = {C5H3(SiMe3)2-1,3}), together with isostructural lanthanide and group 4 M(III) homologues, in order to meaningfully compare metal-silicon bonding...

Cited by 7 publications

References 107 publications

Lewis Base Activation by Uranium(III) Complexes

Lewis Base Activation by Uranium(III) Complexes

Covalency-Driven Differences in the Hydrogenation Chemistry of Lanthanide- and Actinide-Based Frustrated Lewis Pairs

Tris-Silanide f-Block Complexes: Insights into Paramagnetic Influence on NMR Chemical Shifts

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