Oxaphosphirane-Borane Complexes: Ring Strain and Migratory Insertion/Ring-Opening Reactions
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- 作者：Arturo Espinosa ; Edgar de las Heras ; Rainer Streubel
- 刊名：Inorganic Chemistry
- 出版年：2014
- 出版时间：June 16, 2014
- 年：2014
- 卷：53
- 期：12
- 页码：6132-6140
- 全文大小：305K
- 年卷期：v.53,no.12(June 16, 2014)
- ISSN：1520-510X
文摘
DFT-based HSAB-related parameters predict most favorable P- versus O-complexation of parent oxaphosphirane (1) with a variety of borane reagents BR3 (2). In general, strong P鈥揃 bonds are formed, especially for R: H (3a), Cl (3d), and C6F5 (3g), in agreement with large dissociation energies, whereas O鈥揃 bonds are usually weaker. A remarkable increase in ring strain is observed upon P-complexation of phosphirane or oxaphosphiranes, especially in the case of 3g and 3d, whereas a moderate decrease occurs in the case of O-complexation for both oxirane and oxaphosphiranes. Stronger P鈥揃 bonds also correlate with larger charge transfer from the oxaphosphirane to the borane units. This in turn increases electron density at the boron center and weakens all B鈥揜 bonds, thus enabling migratory insertion/ring-opening reactions in which a substituent from the borate center shifts to a ring atom; these reactions are additionally driven by release of the high ring strain of P-complexes 3.