Zinc-Zinc Bonded Zincocene Structures. Synthesis and Characterization of Zn2(5-C5Me5)

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• 作者：Abdessamad Grirrane ; Irene Resa ; Amor Rodriguez ; Ernesto Carmona ; Eleuterio Alvarez ; Enrique Gutierrez-Puebla ; Angeles Monge ; Agust&iacute ; n Galindo ; Diego del R&iacute ; o ; Richard A. Andersen
• 刊名：Journal of the American Chemical Society
• 出版年：2007
• 出版时间：January 24, 2007
• 年：2007
• 卷：129
• 期：3
• 页码：693 - 703
• 全文大小：356K
• 年卷期：v.129,no.3(January 24, 2007)
• ISSN：1520-5126

文摘

While, in general, decamethylzincocene, Zn(C₅Me₅)₂, and other zincocenes, Zn(C₅Me₄R)₂ (R =H, Bu^t, SiMe₃), react with dialkyl and diaryl derivatives, ZnR'₂, to give the half-sandwich compounds (mages/gifchars/eta.gif" BORDER=0 >⁵-C₅Me₄R)ZnR', under certain conditions the reactions of Zn(C₅Me₅)₂ with ZnEt₂ or ZnPh₂ produceunexpectedly the dizincocene Zn₂(mages/gifchars/eta.gif" BORDER=0 >⁵-C₅Me₅)₂ (1) in low yields, most likely as a result of the coupling of two(mages/gifchars/eta.gif" BORDER=0 >⁵-C₅Me₅)Zn^{mages/entities/bull.gif">} radicals. An improved, large scale (ca. 2 g) synthesis of 1 has been achieved by reductionof equimolar mixtures of Zn(C₅Me₅)₂ and ZnCl₂ with KH in tetrahydrofuran. The analogous reduction ofZn(C₅Me₄R)₂ (R = H, SiMe₃, Bu^t) yields only decomposition products, but the isotopically labeleddimetallocene ⁶⁸Zn₂(mages/gifchars/eta.gif" BORDER=0 >⁵-C₅Me₅)₂ and the related compound Zn₂(mages/gifchars/eta.gif" BORDER=0 >⁵-C₅Me₄Et)₂ (2) have been obtained bythis procedure. Compound 2 has lower thermal stability than 1, but it has been unequivocally characterizedby low-temperature X-ray diffraction studies. As for 1 a combination of structural characterization techniqueshas provided unambiguous evidence for its formulation as the Zn-Zn bonded dimer Zn₂(mages/gifchars/eta.gif" BORDER=0 >⁵-C₅Me₄Et)₂,with a short Zn-Zn bond of 2.295(3) Å indicative of a strong Zn-Zn bonding interaction. The electronicstructure and the bonding properties of 1 and those of related dizincocenes Zn₂(mages/gifchars/eta.gif" BORDER=0 >⁵-Cp')₂ have been studiedby DFT methods (B3LYP level), with computed bond distances and angles for dizincocene 1 very similarto the experimental values. The Zn-Zn bond is strong (ca. 62 kcal·mol^-1 for 1) and resides in the HOMO-4, that has a contribution of Zn orbitals close to 60%, consisting mostly of the Zn 4s orbitals (more than96%).