Versatile Synthesis of Sila-and Germa-(Dewa-benzene) and Their Valence Isomerization

1，4-二硅杂苯（Dewar-benzvalene）是一种高产率、通用的合成方法，采用Jung等人的方法，由四氯环己二烯经硅烷基化制得的1，4-二氯环己二烯经还原偶联，再经光解得到二硅杂苯（disilabenzvalene）。基质（3-MP）中的低温光解揭示了1，4-二硅杂苯作为一种瞬态中间体。1，4-二硅（Dewar-benzene）的还原产生二价阴离子。为了生成1，4-二硅苯，用BrCH_2CH_2Br氧化二价阴离子物种失败，为了分离稳定的金属配合物1，4-二硅苯，研究了1，4-二硅（Dewar-benzene）与金属羰基化合物的光化学反应。结果表明，CO插入到1，4-二硅醛（Dewar-benzene）的Si-Si键中。在没有金属羰基的情况下，在CO气氛下的光化学反应也得到了同样的产物.另一种合成尝试是在Si原子上引入更多的小取代基，如甲基和甲苯基，但没有成功.对1，4-二硅杂（Dewar-benzene）及其价态异构化进行了理论计算.几种过渡结构揭示了1，4-二硅杂苯价态异构化的独特反应途径。

As versatile and high-yield synthetic method of 1,4-disila(Dewar-benzene), it has been found that reductive coupling of 1,4-dichlorocyclohexadiene, which was prepared by silylation of teterachlorocyclohexadiene following Jung's report.The photolysis of 1,4-disila(Dewar-benzene) afforded to give disilabenzvalene. Low-temperature photolysis in matrix (3-MP) disclosed 1,4-disilabenzene as a transient, intermediate. The reduction of 1,4-disila(Dewar-benzene) yielded dianion species. In order to gernerate 1,4-disilabenzene, oxidation of dianion species with BrCH2CH2Br met with failure.Toward the isolation of 1,4-disilabenzene as a stable metal complex, photochemical reaction of 1,4-disila(Dewar-benzene) with metal carbonyls were cried out. As a result, CO insertion into Si-Si bond of 1,4-disial(Dewar-benzene) was occurred. Without metal carbolyls, photochemical reaction under CO gas also gave the same product.Another synthetic attempts, more smaller substituents such as methyl and tolyl groups on Si atoms were tried to introduce without success.Theoretical calculations on the 1,4-disila(Dewar-benzene) and its's valence isomerization have been done. Several transition structures disclosed a unique reaction pathways on 1,4-disilabenzene valence isomerization.