ISSN:
0009-2940
Keywords:
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Description / Table of Contents:
MO-π-Bond Order-Bond Length Relations for Hetero-π-Systems, V. π-Systems with NO-BondsFor NO-π-bonds the following empirical resonance integral parameters have been derived by means of HMO-π-bond- bond polarizabilities in combination with the previously obtained HMO-π-bond order-bond lengths relation and experimentally determined bond lengths: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {k = \mathop {\rm N}\limits^ \oplus - \mathop {\rm O}\limits_ - ^ - - = 0.8;} & {k - \mathop {\rm N}\limits_{||}^ \oplus - \mathop {\rm O}\limits_ - ^{\mathop \ominus \limits_ - } = 1.9;} & {k - {\rm \bar N}} \\\end{array} = \mathop {\rm O}\limits_ - ^ - = 1.4 $$\end{document} The linear equation derived by the method of least squares which represents the relationship between HMO-π-bond orders calculated with these new parameters and experimental bond lengths is \documentclass{article}\pagestyle{empty}\begin{document}$$ R_{{\rm rs}}^{{\rm HMO,NO}} [{\rm \AA}] = 1.474 - 0.371p_{{\rm rs}} $$\end{document} with a standard deviation (σ) of 0.034 Å and a correlation coefficient (k) of 0.902 for 159 points. For CN-bonds in these NO-π-systems the following linear equation results \documentclass{article}\pagestyle{empty}\begin{document}$$ R_{{\rm rs}}^{{\rm HMO,NO\ in\ NO}} [{\rm \AA}] = 1.512 - 0.263\ p_{{\rm rs}} $$\end{document} with σ = 0.043 Å and k = 0.795 for 114 points.The values for the bond lengths in this equation are relatively high because -bonds, for instance in nitro compounds, are extremely long. The combination of all CN-bonds in π-systems treated in the previous communications gives the relation \documentclass{article}\pagestyle{empty}\begin{document}$$ R_{{\rm rs}}^{{\rm HMO,CN}} [{\rm \AA}] = 1.478 - 0.234\ p_{{\rm rs}} $$\end{document} with σ = 0.030 Å and k = 0.772 for 479 points.For NN-bonds in NO-π-systems the equation \documentclass{article}\pagestyle{empty}\begin{document}$$ R_{{\rm rs}}^{{\rm HMO,NN \ in \ NO}} [{\rm \AA}] = 1.497 - 0.271\ p_{{\rm rs}} $$\end{document} with σ = 0.028 Å and k = 0.914 for 11 points is obtained.Combination with the NN-bonds of the previous contribution 1) leads to \documentclass{article}\pagestyle{empty}\begin{document}$$ R_{{\rm rs}}^{{\rm HMO,NN}} [{\rm \AA}] = 1.443 - 0.190\ p_{{\rm rs}} $$\end{document} with σ = 0.027 Å and k = 0.900 for 48 Points.
Notes:
Für NO-π-Bindungen werden aus HMO-π-Bindungs-Bindungs-Polarisierbarkeiten mittels der zuvor ermittelten HMO-π-Bindungsordnung-Bindungslängen-Beziehungen und den entsprechenden experimentellen Bindungsabständen folgende empirische Resonanzintegralparameter abgeleitet: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {k = \mathop {\rm N}\limits^ \oplus - \mathop {\rm O}\limits_ - ^ - - = 0.8;} & {k - \mathop {\rm N}\limits_{||}^ \oplus - \mathop {\rm O}\limits_ - ^{\mathop \ominus \limits_ - } = 1.9;} & {k - {\rm \bar N}} \\\end{array} = \mathop {\rm O}\limits_ - ^ - = 1.4 $$\end{document} Die nach der Methode der kleinsten Fehlerquadrate aus den mit diesen Parametern berechneten HMO-π-Bindungsordnungen und den experimentellen Bindungslängen ermittelte Ausgleichsgerade beträgt \documentclass{article}\pagestyle{empty}\begin{document}$$ R_{{\rm rs}}^{{\rm HMO,NO}} [{\rm \AA}] = 1.474 - 0.371p_{{\rm rs}} $$\end{document} mit einer Standardabweichung (σ) von 0.034 Å und einem Korrelationskoeffizienten (k) von 0.902 für 159 Punkte.Für die CN-Bindungen dieser NO-π-Systeme ergibt sich die Ausgleichsgerade \documentclass{article}\pagestyle{empty}\begin{document}$$ R_{{\rm rs}}^{{\rm HMO,NO\ in\ NO}} [{\rm \AA}] = 1.512 - 0.263\ p_{{\rm rs}} $$\end{document} mit σ = 0.043 Å und k = 0.795 für 114 Werte, deren relativ hohe Lage daher kommt, daß die - Bindungen, z. B. in Nitroverbindungen, extrem lang sind.Die Zusammenfassung aller bisherigen CN-π-Bindungen liefert die Beziehung: \documentclass{article}\pagestyle{empty}\begin{document}$$ R_{{\rm rs}}^{{\rm HMO,CN}} [{\rm \AA}] = 1.478 - 0.234\ p_{{\rm rs}} $$\end{document} mit Å = 0.030 σ und k = 0.772 für 479 Punkte. Für NN-Bindungen in NO-Systemen ergibt sich \documentclass{article}\pagestyle{empty}\begin{document}$$ R_{{\rm rs}}^{{\rm HMO,NN \ in \ NO}} [{\rm \AA}] = 1.497 - 0.271\ p_{{\rm rs}} $$\end{document} mit σ = 0.028 Å und k = 0.914 für 11 Werte.Für die Gesamtheit der NN-Bindungen gilt: \documentclass{article}\pagestyle{empty}\begin{document}$$ R_{{\rm rs}}^{{\rm HMO,NN}} [{\rm \AA}] = 1.443 - 0.190\ p_{{\rm rs}} $$\end{document} mit σ = 0.027 Å und k = 0.900 für 48 Punkte.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19701031103
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