Development of novel ligands occupying the specified positions and their application to the synthesis of new hypervalent compounds

本研究的目的是开发新型配体，利用这些配体的空间和电子稳定效应占据高价主基化合物的特定位置，并利用这些配体合成具有新型框架的高价化合物。我们主要开发了几种五配位主基元化合物的配体，如占据两个顶点位置和一个赤道位置的平面三齿配体，占据三个赤道位置和一个顶点位置的四齿配体，占据赤道位置的大体积树状配体，以及连接两个高度配位主基元的二硫代羧基配体。结果，我们成功地利用四配位的1,2-碘二十烷作为热稳定的氧化剂，合成了碳磷酸酯和碳四烷，其中三个氧原子和一个碳原子分别占据赤道和顶端位置，并合成了五配位硅原子和七配位硅原子之间有键的二烷。此外，我们还成功地合成了它们的相关化合物，如含磷铝的丙磷烷，具有烯烃聚合活性的阳离子硅酮氧化锆配合物，以及迄今为止已知的相关碳烯中具有最高电子给体能力的氨基（酰）碳烯。如上所述，我们利用自己开发的配体并阐明其结构、键模式和反应性，构建了具有热力学不利构型的新型高价化合物。我们可以获得基于新结构的新知识，这将对主基团化学新范式的发展做出重大贡献。

The object of this study is to develop novel ligands, which occupy the specific positions of hypervalent main group compounds on the basis of the steric and electronic stabilization effects, and synthesize the hypervalent compounds with novel frameworks by use of these ligands. Mainly, we have developed several ligands for pentacoordinated main-group-element compounds, such as a planar tridentate ligand which occupies two apical positions and one equatorial position, tetradentate ligands which occupy three equatorial positions and one apical position, a bulky dendrimer-type ligand which occupies the equatorial position, and the dithiocarboxylato ligand which bridges two highly coordinate main-group elements. As a result, we succeeded in applying tetracoordinated 1,2-iodoxetane as a thermally stable oxidant, synthesizing carbaphosphatranes and a carbasilatrane where three oxygen atoms and one arbon atom occupy the equatorial and apical positions, respectively, and synthesizing disilanes with bonds between pentacoordinated silicon atoms and between heptacoordinated silicon atoms.In addition, we also succeeded in synthesizing their related compounds such as prophosphaalatrane containing phosphorus and aluminum, a cationic silanolatozirconium complex that has olefin polymerization activity, and an amino(ylide)carbene having the highest electron donating ability among the related carbenes known to date. As mentioned above, we achieved the construction of the novel hypervalent compounds bearing a thermodynamically unfavorable configuration by taking advantages of the ligands that we developed by ourselves and elucidation of their structures, bonding modes, and reactivities. We could obtain new knowledge based on new structures that would contribute significantly to the development of a new paradigm in main group chemistry.