Extension of the electrostatic-covalent model to 2:1 adducts

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• 作者：Joerg ; Steven ; Webster ; Charles Edwin ; Drago ; Russell S. ; et. al.
• 关键词：ECW model ; Phosphines ; Correlations ; Enthalpies of reaction
• 刊名：Polyhedron
• 出版年：1999
• 出版时间：March 12, 1999
• 年：1999
• 卷：18
• 期：8-9
• 页码：1097-1106
• 全文大小：99.9 K

文摘

An extension to the Electrostatic-Covalent model is proposed for the prediction of physicochemical properties and enthalpies of interaction for two donor molecules reacting with a single acceptor molecule. The coordination of the first base modifies the acceptor tendencies for binding a second base. Each different base forms a different acceptor for coordinating the second base, so in any model different acceptor parameters are required for the second step for each base. An E and C based model is derived to reflect this behavior and is applied to several 2:1 adducts providing a new interpretation of their reactivity. Literature correlations of 2:1 adducts which use a single average acceptor parameter for the sum of the two steps do not reflect this behavior so the meaning of the fit and the resulting parameters are not clear. Furthermore, since an average does not reflect a different acceptor parameter in the second step for each base the cause of deviations in such a fit is not clear. The model is extended to encompass reactivity of bidentate phosphines. Donor parameters are reported for the first coordination step of bidentate phosphines. The second step of bidentate donor binding is affected by the strength of the acceptor interaction in the first step. Equations are derived to correlate the total enthalpies of reaction of bidentate phosphines. Some generalizations concerning reactivity can be made but limited data precludes a thorough evaluation of the model.