Synthesis, Isolation, and Structures of Multiple Bonded Compounds Containing Heavier Main-Group Elements

包含较重的主族元素的多重键通常是不稳定的，因为两个元素之间的键长很长，而且由于轨道瓣宽，□-轨道无法有效重叠。此外，轨道杂化在高阶元素中不有效，导致这些元素的多键不稳定。然而，通过在系统中引入一个非常庞大的基团，我们已经能够分离出不寻常的含磷化合物，其中磷原子处于低配位状态。本课题利用2,4,6-三-叔丁基苯基等保护基团稳定配位数为1和2的低配位磷化合物。对保护的化合物进行了分离、表征，并用多核磁共振波谱和x射线晶体学对其结构进行了分析。1)在制备二膦烯、二膦烯、二膦烯环丁烯和磷酸炔的过程中，开发了新的保护基团，这些保护基团在空间和电子取代效应的研究中都很有用。2)制备了顺式二膦、磷烯、硫代膦和类磷醌化合物，并利用新型位位保护基团对其进行了表征。3)以磷酸代烷与烷基锂试剂反应，制备了二磷酸代环丁烯及其双自由基二磷酸代环丁二基。4)合成了受立体保护的磷酸乙烯基类碳化合物，研究了其形成磷酸烷、二磷酸丁烯、二磷酸丁烯、三磷酸黄烯和二磷酸黄烯的各种反应活性。其结构主要通过x射线晶体学分析。5)制备了多种二膦二烯环丁烯，形成了过渡金属配合物。研究了它们在偶联反应中的催化活性，证明了它们是有效的催化剂。

Multiple bonds involving heavier main-group elements are normally unstable, because bond lengths between the two elements are long and because effective overlap of □-orbitals cannot be expected due to the wide orbital lobes. Furthermore, hybridization of orbitals is not effective in higher elements causing multiple bonds of such elements to be unstable. By introducing a very bulky group into the systems, however, we have been able to isolate unusual phosphorus-containing compounds, where the phosphorus atoms are in low coordination states.In this research project, protection groups, such as the 2,4,6-tri-t-butylphenyl group, have been utilized in the stabilization of low coordinated phosphorus compounds of coordination number 1 and 2. Compounds thus protected were isolated, characterized, and the structures were analyzed by multinuclear NMR spectroscopy and X-ray crystallography.1)Novel protection groups, which are useful in studies of substitution effects, both steric and electronic, have been developed for preparation of diphosphenes, phosphaallenes, diphosphinidenecyclobutenes, and phosphaalkynes.2)Cis-diphosphenes, phosphaallenes, thioxophosphines, and phosphaquinoid compounds were prepared and characterized by use of novel steric protection groups.3)Diphosphacyclobutenes and biradical species, diphosphacyclobutanediyls, were prepared and isolated by the reaction of phosphaalkynes with alkyllithium reagents.4)Sterically protected phosphaethenylcarbenoids were generated and the various reactivities were studied involving the formation of phosphaalkynes, diphosphabutatrienes, diphosphabutadienes, triphosphafulvenes, and diphosphafulvenes. The structures were analyzed mostly by X-ray crystallography.5)Various kinds of diphosphinidenecyclobutenes were prepared and the transition metal complexes were formed. The catalytic activities in the coupling reactions were investigated to show that they are effective catalysts.