Structural and Electrochemical Investigations of the High Fluoride Affinity of Sterically Hindered 1,8-Bis(boryl)naphthalenes
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- 作者：Mohand Melaï ; mi ; Sté ; phane Solé ; Ching-Wen Chiu ; Huadong Wang ; Franç ; ois P. Gabbaï
- 刊名：Inorganic Chemistry
- 出版年：2006
- 出版时间：October 2, 2006
- 年：2006
- 卷：45
- 期：20
- 页码：8136 - 8143
- 全文大小：212K
- 年卷期：v.45,no.20(October 2, 2006)
- ISSN：1520-510X
文摘
The reaction of 10-bromo-9-oxa-10-boraanthracene with the tetrakis(tetrahydrofuran)lithium salt of dimesityl-1,8-naphthalenediylborate in diethyl ether affords 1-(dimesitylboryl)-8-(10'-bora-9'-oxaanthryl)naphthalene (2). This diboranereacts with [Me3SiF2][S(NMe2)3)] to afford the anionic complex [2-
2-F]-, which has been isolated as a [S(NMe2)3]+salt. The cyclic voltammograms of diborane 2 as well as 1-(dimesitylboryl)-8-(10'-bora-9'-thiaanthryl)naphthalene(1) exhibit two reversible reductions at E1/2 = -2.200 and -2.566 V (vs FcH/FcH+) for 1 and E1/2 = -2.248 and-2.620 V (vs FcH/FcH+) for 2 corresponding to the sequential reduction of the two boron centers. These twowaves simultaneously disappear upon fluoride addition, thus indicating the formation of fluoride chelate complexes[1-2-F]- and [2-2-F]-. To identify the origin of the high fluoride affinity displayed by these diboranes, the structuresof 2 and [2-2-F]- have been studied experimentally and computationally. The crystallographic studies show thatthe structure of 2 is distorted, thus indicating the presence of important steric repulsions between the neighboringboryl moieties. By contrast, the structure of the anionic complex [2-2-F]- is much more sterically relaxed than thatof 2, as indicated by a reduction of the B-B distance from 3.279(4) Å in 2 to 2.922(7) Å in [2-2-F]-. The structuralresults suggest that the high fluoride affinity displayed by 2 results, at least in part, from the relief of steric repulsionsinduced by fluoride binding. Finally, the nature of the bonding as well as the strength of the interactions involvedin the B-F-B bridge of [2-2-F]- has been studied using density functional theory calculations and Atoms-In-Molecules analyses. These calculations indicate that the enthalpic gain associated with the formation of two B-Fbonds in [2-2-F]- only amounts to a fraction of the energy of a terminal B-F bond. These calculations alsosuggest that the relief of steric repulsions induced by fluoride binding in 2 may contribute to the high fluorideaffinity of these types of molecules.
2-F]-, which has been isolated as a [S(NMe2)3]+salt. The cyclic voltammograms of diborane 2 as well as 1-(dimesitylboryl)-8-(10'-bora-9'-thiaanthryl)naphthalene(1) exhibit two reversible reductions at E1/2 = -2.200 and -2.566 V (vs FcH/FcH+) for 1 and E1/2 = -2.248 and-2.620 V (vs FcH/FcH+) for 2 corresponding to the sequential reduction of the two boron centers. These twowaves simultaneously disappear upon fluoride addition, thus indicating the formation of fluoride chelate complexes[1-2-F]- and [2-2-F]-. To identify the origin of the high fluoride affinity displayed by these diboranes, the structuresof 2 and [2-2-F]- have been studied experimentally and computationally. The crystallographic studies show thatthe structure of 2 is distorted, thus indicating the presence of important steric repulsions between the neighboringboryl moieties. By contrast, the structure of the anionic complex [2-2-F]- is much more sterically relaxed than thatof 2, as indicated by a reduction of the B-B distance from 3.279(4) Å in 2 to 2.922(7) Å in [2-2-F]-. The structuralresults suggest that the high fluoride affinity displayed by 2 results, at least in part, from the relief of steric repulsionsinduced by fluoride binding. Finally, the nature of the bonding as well as the strength of the interactions involvedin the B-F-B bridge of [2-2-F]- has been studied using density functional theory calculations and Atoms-In-Molecules analyses. These calculations indicate that the enthalpic gain associated with the formation of two B-Fbonds in [2-2-F]- only amounts to a fraction of the energy of a terminal B-F bond. These calculations alsosuggest that the relief of steric repulsions induced by fluoride binding in 2 may contribute to the high fluorideaffinity of these types of molecules.