Syntheses and structures of hypervalent pentacoordinate carbon and boron compounds bearing an anthracene skeleton--elucidation of hypervalent interaction based on X-ray analysis and DFT calculation.
Syntheses and structures of hypervalent pentacoordinate carbon and boron compounds bearing an anthracene skeleton--elucidation of hypervalent interaction based on X-ray analysis and DFT calculation.
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DOI：
10.1021/ja0438011
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发表时间：
2005-03
影响因子：
15
通讯作者：
M. Yamashita;Yohsuke Yamamoto;K. Akiba;D. Hashizume;F. Iwasaki;Nozomi Takagi;S. Nagase
中科院分区：
文献类型：
--
作者：
M. Yamashita;Yohsuke Yamamoto;K. Akiba;D. Hashizume;F. Iwasaki;Nozomi Takagi;S. Nagase
以四个新合成的三齿配体为原料，合成了五配位和四配位碳、硼化合物(27，38，50-52，56-61)，它们的1，8-位都带有两个氧或氮原子。对几种碳、硼化合物进行了X-射线晶体结构分析，结果表明，具有给氧骨架的化合物27、56-59具有较长的顶距(约2.38-2.46A)的三方双锥(TBP)五配位结构。尽管顶端距离相对较长，但对碳物种27和硼物种56的密度泛函计算以及对56物种的实验准确的X射线电子密度分布分析支持顶端超价键的存在，尽管中心碳(或硼)与供体氧原子之间的超价相互作用的性质相对较弱和离子。另一方面，含给氮菲骨架的化合物50-52的X射线分析表明，不对称的四配位碳或硼原子只由两个给氮基团中的一个配位。有趣的是，具有供氧骨架的中心硼原子上有两个氯原子的化合物61表现为四配位结构，而相应的具有两个氟原子的化合物60表现为五配位结构。与中心硼原子上有两个甲氧基的59个样品相比，60个样品的B-O距离(av 2.29A)相对较短，表明由于氟原子的吸电子性质，B-O相互作用变强。
Pentacoordinate and tetracoordinate carbon and boron compounds (27, 38, 50-52, 56-61) bearing an anthracene skeleton with two oxygen or nitrogen atoms at the 1,8-positions were synthesized by the use of four newly synthesized tridentate ligand precursors. Several carbon and boron compounds were characterized by X-ray crystallographic analysis, showing that compounds 27, 56-59 bearing an oxygen-donating anthracene skeleton had a trigonal bipyramidal (TBP) pentacoordinate structure with relatively long apical distances (ca. 2.38-2.46 A). Despite the relatively long apical distances, DFT calculation of carbon species 27 and boron species 56 and experimental accurate X-ray electron density distribution analysis of 56 supported the existence of the apical hypervalent bond even though the nature of the hypervalent interaction between the central carbon (or boron) and the donating oxygen atom was relatively weak and ionic. On the other hand, X-ray analysis of compounds 50-52 bearing a nitrogen-donating anthracene skeleton showed unsymmetrical tetracoordinate carbon or boron atom with coordination by only one of the two nitrogen-donating groups. It is interesting to note that, with an oxygen-donating skeleton, the compound 61 having two chlorine atoms on the central boron atom showed a tetracoordinate structure, although the corresponding compound 60 with two fluorine atoms showed a pentacoordinate structure. The B-O distances (av 2.29 A) in 60 were relatively short in comparison with those (av 2.44 A) in 59 having two methoxy groups on the central boron atom, indicating that the B-O interaction became stronger due to the electron-withdrawing nature of the fluorine atoms.