461054-08-0Relevant articles and documents
29Si NMR Spectroscopy as a Probe of s- And f-Block Metal(II)-Silanide Bond Covalency
Basford, Annabel R.,Berryman, Victoria E. J.,Kaltsoyannis, Nikolas,Liddle, Stephen T.,Mills, David P.,Nodaraki, Lydia E.,Réant, Benjamin L. L.,Tuna, Floriana,Wooles, Ashley J.
, p. 9813 - 9824 (2021/07/21)
We report the use of 29Si 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(SitBu3)2(THF)2(THF)x] (1-M: M = Mg, Ca, Yb, x = 0; M = Sm, Eu, x = 1) and [M(SitBu2Me)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 29Si 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(SiMe3)3}-, {Si(SiMe2H)3}-, and {SiPh3}-substituted analogues provide 20 representative examples spanning five silanide ligands and four divalent metals, revealing that the metal-bound 29Si NMR isotropic chemical shifts, ?Si, span a wide (?225 ppm) range when the metal is kept constant, and direct, linear correlations are found between ?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 ?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.
