Polarised covalent thorium(<scp>iv</scp>)– and uranium(<scp>iv</scp>)–silicon bonds

Réant, Benjamin L. L.; Berryman, Victoria E. J.; Seed, John A.; Basford, Annabel R.; Formanuik, Alasdair; Wooles, Ashley J.; Kaltsoyannis, Nikolas; Liddle, Stephen T.; Mills, David P.

doi:10.1039/d0cc06044e

“…The multinuclear NMR spectra of 1–3 showed few impurities; thus, we are confident of the solid-state structures (see below) being representative of their bulk formulations. Carbon values obtained for 1 and 2 in elemental microanalyses were lower than expected values on multiple occasions, which we attribute to the formation of silicon carbides that do not fully combust; we have observed this phenomenon consistently for early metal silanide complexes of the ligands used here. , ATR-IR spectroscopy was also performed on 1–3 , with a number of overlapping absorptions observed showing that some similar vibrational modes are present in all three complexes (see Supporting Information Figures S1–S25 for spectroscopic data of 1–3 ).…”

Section: Resultssupporting

confidence: 51%

Synthesis and Characterization of Yttrium Methanediide Silanide Complexes

Réant

¹

,

Wooles

²

,

Liddle

³

et al. 2022

Self Cite

View full text Add to dashboard Cite

The salt metathesis reactions of the yttrium methanediide iodide complex [Y(BIPM)(I)(THF) 2 ] (BIPM = {C(PPh 2 NSiMe 3 ) 2 }) with the group 1 silanide ligand-transfer reagents MSiR 3 (M = Na, R 3 = t Bu 2 Me or t Bu 3 ; M = K, R 3 = (SiMe 3 ) 3 ) gave the yttrium methanediide silanide complexes [Y(BIPM)(Si t Bu 2 Me)(THF)] ( 1 ), [Y(BIPM)(Si t Bu 3 )(THF)] ( 2 ), and [Y(BIPM){Si(SiMe 3 ) 3 }(THF)] ( 3 ). Complexes 1–3 provide rare examples of structurally authenticated rare earth metal–silicon bonds and were characterized by single-crystal X-ray diffraction, multinuclear NMR and ATR-IR spectroscopies, and elemental analysis. Density functional theory calculations were performed on 1–3 to probe their electronic structures further, revealing predominantly ionic Y–Si bonding. The computed Y–Si bonds show lower covalency than Y=C bonds, which are in turn best represented by Y + –C – dipolar forms due to the strong σ-donor properties of the silanide ligands investigated; these observations are in accord with experimentally obtained 13 C{ 1 H} and 29 Si{ 1 H} NMR data for 1–3 and related Y(III) BIPM alkyl complexes in the literature. Preliminary reactivity studies were performed, with complex 1 treated separately with benzophenone, azobenzene, and N , N ′-dicyclohexyl-carbodiimide. 29 Si{ 1 H} and 31 P{ 1 H} NMR spectra of these reaction mixtures indicated that 1,2-migratory insertion of the unsaturated substrate into the Y–Si bond is favored, while for the latter substrate, a [2 + 2]-cycloaddition reaction also occurs at the Y=C bond to afford [Y{C(PPh 2 NSiMe 3 ) 2 [C(NCy) 2 ]-κ 4 C , N , N ′, N ′}{C(NCy) 2 (Si t Bu 2 Me)-κ 2 N , N ′}] ( 4 ); these reactivity profiles complement and contrast with those of Y(III) BIPM alkyl complexes.

show abstract

“…Given that molecular f-block silicon chemistry is developing and that elegant benchmarking studies have been performed for 29 Si NMR spectroscopy in the main-group and d transition-metal arenas, it is an opportune time to introduce 29 Si NMR studies of covalency to the f block. We recently reported actinide (An)–silanide complexes and sought to extend this work to lanthanide (Ln) derivatives, recognizing that diamagnetic 4f 14 Yb(II) constitutes an ideal test bed to delineate covalency in f-block M(II)–Si bonds by 29 Si NMR spectroscopy, and a range of Ln , and group 2 silanide complexes already exist to enable rigorous and meaningful comparisons to be made.…”

Section: Introductionmentioning

confidence: 99%

²⁹Si NMR Spectroscopy as a Probe of s- and f-Block Metal(II)–Silanide Bond Covalency

Réant

¹

,

Berryman

²

,

Basford

³

et al. 2021

Self Cite

View full text Add to dashboard Cite

We report the use of 29 Si NMR spectroscopy and DFT calculations combined to benchmark the covalency in the chemical bonding of s-and f-block metal−silicon bonds. The complexes [M(Si t Bu 3 ) 2 (THF) 2 (THF) x ] (1-M: M = Mg, Ca, Yb, x = 0; M = Sm, Eu, x = 1) and [M(Si t Bu 2 Me) 2 (THF) 2 (THF) x ] (2-M: M = Mg, x = 0; M = Ca, Sm, Eu, Yb, x = 1) have been synthesized and characterized. DFT calculations and 29 Si NMR spectroscopic analyses of 1-M and 2-M (M = Mg, Ca, Yb, No, the last in silico due to experimental unavailability) together with known {Si(SiMe 3 ) 3 } − -, {Si(SiMe 2 H) 3 } − -, and {SiPh 3 } − -substituted analogues provide 20 representative examples spanning five silanide ligands and four divalent metals, revealing that the metal-bound 29 Si NMR isotropic chemical shifts, δ Si , span a wide (∼225 ppm) range when the metal is kept constant, and direct, linear correlations are found between δ Si and computed delocalization indices and quantum chemical topology interatomic exchange-correlation energies that are measures of bond covalency. The calculations reveal dominant s-and d-orbital character in the bonding of these silanide complexes, with no significant f-orbital contributions. The δ Si is determined, relatively, by paramagnetic shielding for a given metal when the silanide is varied but by the spin−orbit shielding term when the metal is varied for a given ligand. The calculations suggest a covalency ordering of No(II) > Yb(II) > Ca(II) ≈ Mg(II), challenging the traditional view of late actinide chemical bonding being equivalent to that of the late lanthanides.

show abstract

“…The 11 B{ 1 H} NMR chemical shift for bis-Tp* 2 U(III) complexes typically lies within the range of −20 to 10 ppm, while bis-Tp* 2 U(IV) complexes typically resonate between −60 to −80 ppm. The 29 Si{ 1 H} NMR spectrum shows two clear resonances at −8.6 and −75.0 ppm, assigned as the (Me 3 Si) 3 Si and the (Me 3 Si) 3 Si atoms, respectively, with the latter much further shifted from a known uranium-bound silicon atom (−137 ppm) and not representative of free ligand [(Me 3 Si) 3 SiK = −4.55, −194.10 ppm] . These multinuclear NMR data suggested THF activation and formation of Tp* 2 U[O(CH 2 ) 4 Si(SiMe 3 ) 3 ] ( 1-THF ) (Scheme ).…”

Section: Resultsmentioning

confidence: 97%

“…25 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, 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.…”

Section: ■ Introductionmentioning

confidence: 99%

Lewis Base Activation by Uranium(III) Complexes

Lin

¹

,

Perales

²

,

Matson

³

et al. 2023

View full text Add to dashboard Cite

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.

show abstract

Polarised covalent thorium(iv)– and uranium(iv)–silicon bonds

Abstract: We report the synthesis and characterisation of isostructural thorium(IV)- and uranium(IV)-silanide actinide (An) complexes, providing an opportunity to directly compare Th-Si and U-Si chemical bonds. Quantum chemical calculations show significant...

Cited by 15 publications

References 45 publications

Synthesis and Characterization of Yttrium Methanediide Silanide Complexes

Synthesis and Characterization of Yttrium Methanediide Silanide Complexes

²⁹Si NMR Spectroscopy as a Probe of s- and f-Block Metal(II)–Silanide Bond Covalency

Lewis Base Activation by Uranium(III) Complexes

Contact Info

Product

Resources

About

Polarised covalent thorium(iv)– and uranium(iv)–silicon bonds

Abstract: We report the synthesis and characterisation of isostructural thorium(IV)- and uranium(IV)-silanide actinide (An) complexes, providing an opportunity to directly compare Th-Si and U-Si chemical bonds. Quantum chemical calculations show significant...

Cited by 15 publications

References 45 publications

Synthesis and Characterization of Yttrium Methanediide Silanide Complexes

Synthesis and Characterization of Yttrium Methanediide Silanide Complexes

29Si NMR Spectroscopy as a Probe of s- and f-Block Metal(II)–Silanide Bond Covalency

Lewis Base Activation by Uranium(III) Complexes

Contact Info

Product

Resources

About

²⁹Si NMR Spectroscopy as a Probe of s- and f-Block Metal(II)–Silanide Bond Covalency