Design and Synthesis of Novel Multidentate Ligands-Application to Main Group Elements and Transition Metal Chemistry-

双分子亲核取代反应（SN2）是有机化学中最重要和最常用的反应之一。引发中心碳构型反转的反应机理是有机反应的基本思想之一，并且在本科生的教科书中通常描述。SN2的过渡态（TS）结构应该是围绕中心碳的三角双锥（TBP）。因此，围绕碳的键合至少在形式上涉及价层的膨胀，称为超价。由于SN2的根本重要性，已经有各种努力来稳定TS，甚至制备TS的模型化合物。然而，五配位碳化合物的X射线结构从未报道过。本研究成功地合成了1，8-二甲氧基-9-二甲氧基甲基蒽一价阳离子，并对其晶体结构进行了表征 ...更多信息 首次通过使用新制备的蒽配体完全表征了高价10-C-5化合物。在1，8-位具有给体原子（O、N和P）的蒽三齿配体的制备。2第一个超价五配位碳化合物的合成和结构。新制备的配体用于在CO气体中通过Pd（0）介导的9位碳原子的引入。所得酯与三甲基氧鎓四氟硼酸盐（Me3O + BF 4-）反应得到1，8-二甲氧基-9-二甲氧基甲基蒽一价阳离子。七氟二硼酸盐形式的阳离子的晶体结构显示出该化合物的对称性质，具有几乎相同的两个O-C距离（2.43（1）和2.45（1）π）。围绕中心碳原子的几何构型为三角双锥（TBP）。通过与几种新合成的蒽化合物的晶体结构比较，证明了中心碳原子与1位和8位的两个甲氧基之间存在吸引作用。对阳离子的密度泛函计算表明，对称的Cs结构是能量最低的。应该注意的是，键路径是在中心碳原子和两个氧原子之间发现的，清楚地表明这些原子是键合的，即使键是弱的和离子的。因此，对于SN2过渡态模型，一价阳离子应视为高价碳化合物.超价五配位硼化合物的合成与结构。1，8-二甲氧基-9-锂基蒽与B-氯邻苯二酚硼烷反应生成1，8-二甲氧基-9-B-邻苯二酚硼基蒽，晶体结构表明该化合物具有对称性质，两个O-B距离几乎相同。可以制备多种衍生物，并且氟取代的硼化合物显示出紧密的5-配位结构。少

Bimolecular nucleophilic substitution (SN2) reaction at saturated carbon such as hydrolysis of methyl halides is one of the most important and the most popular reactions in organic chemistry. The mechanism of the reaction invoking inversion of configuration of the central carbon is one of the fundamental ideas of organic reactions and is described commonly in textbooks for undergraduate students. The structure of the transition state (TS) of SN2 should be trigonal bipyramid (TBP) around the central carbon. Hence the bonding about the carbon involves, at least formally, expansion of the valence shell and is called hypervalent. Due to the fundamental importance of SN2, there have been a variety of efforts to stabilize the TS and even to prepare model compounds of TS. However, X-ray structures of pentacoordinated carbon compounds have never been reported. In this research, we succeeded in synthesis and the crystal structure of 1,8-dimethoxy-9-dimethoxymethylanthracene monocation as the fi … More rst fully characterized hypervalent 10-C-5 compound by use of newly prepared anthracene ligands.1. Preparation of anthracence tridentate ligands having donor atoms (O, N, and P) at 1,8-positions.2 Synthesis and structure of first hypervalent pentacoordinate carbon compounds. The newly prepared ligand was used for introduction of a carbon atom at 9 position mediated by Pd(0) with CO gas. The obtained ester was treated with trimethyloxonium tetrafluoroborate (Me3O+BF4-) to give 1,8-dimethoxy-9-dimethoxymethylanthracene monocation. The crystal structure of the cation, in the form of heptafluorodiborate salt, shows the symmetrical nature of the compound with the almost identical two O--C distances (2.43(1) and 2.45(1) Å). The geometry around the central carbon atom is trigonal bipyramid (TBP). Comparison of the crystal structure of the cation with those of several newly prepared anthracene compounds provides evidence for the attractive interaction between the central carbon atom and the two methoxy oxygens at 1 and 8 positions. The density functional calculation on the cation indicates that the symmetrical Cs structure is the energy minimum. It should be noted that the bond paths are found between the central carbon atom and the two oxygen atoms, clearly showing that these atoms are bonded even if the bond is weak and ionic. In conclusion, the monocation should be regarded as a hypervalent carbon compound for a model of SN2 transition state.3. Synthesis and structure of hypervalent pentacoordinate boron compounds. The reaction of 1,8-dimethoxy-9-lithioanthracene with B-chlorocatecholateborane gave 1,8-dimethoxy-9-B-catecholateborylanthracene and the crystal structure shows the symmetrical nature of the compound with the almost identical two O--B distances. Several derivatives could be prepared and the fluorine substituted boron compounds showed a tight 5-coordinate structure. Less