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<p>Atomic partial charges are local, model-dependent descriptors that often fail to capture the global electrostatic environment governing chemical reactivity. This study demonstrates that the molecular electrostatic potential (ESP) at the Si–H hydrogen in trisubstituted silanes reliably predicts electrophilic versus nucleophilic behavior, whereas local charges alone can mislead. Electron-donating substituents generate hydridic hydrogens with negative ESP near hydrogen, favoring nucleophilicity. Electron-withdrawing substituents typically leave hydrogen with a negative local charge but generate a positive ESP region along the Si–H axis, promoting electrophilic character. Increasing solvent polarity amplifies these contrasts, driving minima more negative for electron-donating substituents and maxima more positive for electron-withdrawing substituents. The resulting positive region near hydrogen in electron-withdrawing silanes is directionally σ-hole-like, yet unlike classical σ-holes from lone-pair depletion, it reflects a collective molecular electrostatic effect. These findings highlight the importance of global electrostatics for understanding structure–reactivity relationships and predicting substituent-controlled behavior in silicon hydrides.</p><p></p>

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Ambiphilic behavior of hydrogen in trisubstituted silanes induced by substituent controlled polarity inversion

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年3月20日

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  • Vítězslav Hrubý,
  • Debashree Manna,
  • Rabindranath Lo,
  • Pavel Hobza

摘要

Atomic partial charges are local, model-dependent descriptors that often fail to capture the global electrostatic environment governing chemical reactivity. This study demonstrates that the molecular electrostatic potential (ESP) at the Si–H hydrogen in trisubstituted silanes reliably predicts electrophilic versus nucleophilic behavior, whereas local charges alone can mislead. Electron-donating substituents generate hydridic hydrogens with negative ESP near hydrogen, favoring nucleophilicity. Electron-withdrawing substituents typically leave hydrogen with a negative local charge but generate a positive ESP region along the Si–H axis, promoting electrophilic character. Increasing solvent polarity amplifies these contrasts, driving minima more negative for electron-donating substituents and maxima more positive for electron-withdrawing substituents. The resulting positive region near hydrogen in electron-withdrawing silanes is directionally σ-hole-like, yet unlike classical σ-holes from lone-pair depletion, it reflects a collective molecular electrostatic effect. These findings highlight the importance of global electrostatics for understanding structure–reactivity relationships and predicting substituent-controlled behavior in silicon hydrides.