Issue 37, 2020

Gauging aromatic conjugation and charge delocalization in the aryl silanes PhnSiH4−n (n = 0–4), with silicon K-edge XAS and TDDFT

Abstract

Si K-edge X-ray absorption spectra (XAS) have been measured experimentally and calculated using time-dependent density functional theory (TDDFT) to investigate electronic structure in aryl silanes, PhnSiH4−n (n = 0–4). Adding aryl groups to SiH4 splits the Si–H σ-antibonding orbitals into new orbitals with Si–Ph π-bonding (πb) and π-antibonding (π*) character. Greater aryl substitution is reflected by increasingly intense Si 1s → πb and Si 1s → π* transitions, and weaker transitions into the Si–H and Si–C σ* orbitals. These observations are consistent with known trends in the hydride donor ability of aryl silanes, which is driven in part by the composition of the LUMOs and the accessibility of pathways for electron delocalization through aromatic conjugation. Methodology developed for liquid-phase Si K-edge XAS measurements on PhSiH3 and Ph2SiH2 will enable dynamic studies of chemical transformations involving silicon-containing catalysts, intermediates, and substrates.

Graphical abstract: Gauging aromatic conjugation and charge delocalization in the aryl silanes PhnSiH4−n (n = 0–4), with silicon K-edge XAS and TDDFT

Supplementary files

Article information

Article type
Paper
Submitted
08 Sep 2020
Accepted
09 Sep 2020
First published
16 Sep 2020

Dalton Trans., 2020,49, 13176-13184

Author version available

Gauging aromatic conjugation and charge delocalization in the aryl silanes PhnSiH4−n (n = 0–4), with silicon K-edge XAS and TDDFT

N. A. Phillips, P. W. Smith, T. D. Tilley and S. G. Minasian, Dalton Trans., 2020, 49, 13176 DOI: 10.1039/D0DT03153D

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