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

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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.