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Pauling Electronegativity On/Off Effects Assessed by 13 C and 29 Si NMR Spectroscopic Analysis
Author(s) -
Benedetti Michele,
De Castro Federica,
Fanizzi Francesco P.
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201703934
Subject(s) - electronegativity , chemical shift , halogen , chemistry , halide , atom (system on chip) , carbon 13 nmr , ionic bonding , silicon , analytical chemistry (journal) , computational chemistry , crystallography , stereochemistry , inorganic chemistry , ion , organic chemistry , alkyl , computer science , embedded system
In carbon and silicon tetrahalide compounds, the experimental 13 C and 29 Si NMR chemical‐shift values are known to increase or decrease on increasing the overall sum of the ionic radii of the bonded halides Σ( r h ) (normal and inverse halogen dependence (NHD and IHD, respectively)). Herein, we extrapolate the main factors responsible for such NMR chemical shifts. Intriguingly, we found a characteristic value for the overall sum of the Pauling electronegativities of the bonded halides Σ( χ h ), which works as a triggering factor to determine the transition from the NHD to IHD. Below this Σ( χ h ) value, the chemical shift of the central atom was strictly related to only the Σ( r h ) value, thus producing a NHD trend. Conversely, above this value, the chemical shift of the central atom was dependent on both the Σ( r h ) and Σ( χ h ) values, thus producing a IHD trend. A simple model, in which the effect of the Σ( χ h ) value on 13 C and 29 Si NMR chemical shifts is related to an apparent increase in the Σ( r h ) value, is deduced.