Polarised Covalent Thorium(IV)- and Uranium(IV)-Silicon Bonds

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

doi:10.26434/chemrxiv.12732137.v1

“…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; 31 we have observed this phenomenon consistently for early metal silanide complexes of the ligands used here. 21 , 32 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: Resultsmentioning

confidence: 99%

Synthesis and Characterization of Yttrium Methanediide Silanide Complexes

Réant

¹

,

Wooles

²

,

Liddle

³

et al. 2022

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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.

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“…We decided to adapt our previous strategy where we prepared An(IV) silanide complexes with three Cp′ and one hypersilanide ligand, {Si(SiMe3)3}; 28 we were encouraged to continue using hypersilanide as this has provided the largest number of f-block silanide complexes to date, 6 and to increase the size of the Cp′ ring to Cp′′ ({C5H3(SiMe3)2-1,3}) in an effort to maintain kinetic stabilization of the M-Si bonds when the number of coordinated ligands is reduced.…”

Section: Introductionmentioning

confidence: 99%

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

Gransbury

¹

,

Réant

²

,

Wooles

³

et al. 2023

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“…Given that molecular f-block-silicon chemistry is developing, 17 and that elegant benchmarking studies have been performed for 29 Si NMR spectroscopy in main group and d transition metal arenas, 18 it is an opportune time to introduce 29 Si NMR studies of covalency to the f-block. We recently reported actinide (An) -silanide complexes, 19 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 17, 20 and group 2 21 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

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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.

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Polarised Covalent Thorium(IV)- and Uranium(IV)-Silicon Bonds

Cited by 3 publications

References 46 publications

Synthesis and Characterization of Yttrium Methanediide Silanide Complexes

Synthesis and Characterization of Yttrium Methanediide Silanide Complexes

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

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

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Polarised Covalent Thorium(IV)- and Uranium(IV)-Silicon Bonds

Cited by 3 publications

References 46 publications

Synthesis and Characterization of Yttrium Methanediide Silanide Complexes

Synthesis and Characterization of Yttrium Methanediide Silanide Complexes

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

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

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