The reactivity of an organic molecule is often discussed in relation to the bond length at the reaction site. The electronic structures of organic molecules containing sp2-carbons in organic solvents were studied by C K-edge XAS, named as ‘Soft-XAS-OS’. For investigating the mechanism of the Hiyama cross-coupling reaction, the C K-edge XAS spectra of arylsilanes and silicates in organic solvents were rationalized in terms of C‒Si bond elongation through the inner-shell calculations combined with molecular dynamics simulations. The reactive glycol-derived silicate Ph‒Si(OCH2CH2O)2 exhibited longer C‒Si bonds in solution than the less reactive Ph‒Si(OMe)3.
