New Isolable Dialkylsilylene and Its Isolable Dimer That Equilibrate in Solution

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• 作者：Takashi Abe ; Ryoji Tanaka ; Shintaro Ishida ; Mitsuo Kira ; Takeaki Iwamoto
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：December 12, 2012
• 年：2012
• 卷：134
• 期：49
• 页码：20029-20032
• 全文大小：324K
• 年卷期：v.134,no.49(December 12, 2012)
• ISSN：1520-5126

文摘

The new isolable dialkylsilylene 3 bearing a bidentate alkyl substituent was synthesized. Recrystallization of silylene 3 gave yellow crystals of 3 and orange-red crystals of tetraalkyldisilene 4, a dimer of 3. In the solid state, 3 exists as a monomer with a closest distance of 6.745 脜 between dicoordinate silicon atoms, while disilene 4 has a remarkably long Si鈺怱i double bond distance of 2.252 脜. An equilibrium between 3 and 4 in solution was observed by NMR and UV鈥搗is spectroscopies, and the thermodynamic parameters of the equilibrium were estimated to be 螖H = 鈭?6 卤 3 kJ mol^鈥? and 螖S = 鈭?70 卤 15 J mol^鈥? K^鈥?. Analysis of the percent buried volume, a measure of the steric demand around the divalent silicon, showed that the flexible steric bulkiness of the alkyl substituent of 3 and 4 allows the reversible dimerization of silylene 3 to disilene 4 and the isolation of both species.