Reactivity of Amido-Digermynes, LGeGeL (L = Bulky Amide), toward Olefins and Related Molecules: Facile Reduction, C鈥揌 Activation, and Reversible Cycloaddition of Unsaturated Substrates

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• 作者：Terrance J. Hadlington ; Jiaye Li ; Markus Hermann ; Amelia Davey ; Gernot Frenking ; Cameron Jones
• 刊名：Organometallics
• 出版年：2015
• 出版时间：July 13, 2015
• 年：2015
• 卷：34
• 期：13
• 页码：3175-3185
• 全文大小：604K
• ISSN：1520-6041

文摘

Reactions of two sterically hindered amido-digermynes, L*GeGeL* (1; L* = 鈭扤(Ar*)(SiMe₃); Ar* = C₆H₂Me{C(H)Ph₂}₂-4,2,6) and L^{鈥?/sup>GeGeL鈥?/sup> (2; L鈥?/sup> = 鈭扤(Ar鈥?/sup>)(SiPri₃); Ar鈥?/sup> = C₆H₂Pri{C(H)Ph₂}₂-4,2,6), with a variety of olefins and related molecules are investigated. These lead to the facile reduction, C鈥揌 activation, dehydrogenation, and/or cycloaddition of the unsaturated substrate. Specifically, reaction of L鈥?/sup>GeGeL鈥?/sup> with ethylene proceeds via a formal [2 + 2 + 2] cycloaddition to give the digermabicyclo[2.2.0]hexane L鈥?/sup>Ge(渭-C₂H₄)₂GeL鈥?/sup> (3). In contrast, treating L鈥?/sup>GeGeL鈥?/sup> with norbornadiene proceeds via reductive insertion of one olefin moiety of the organic substrate into the Ge鈥揋e bond of 1, yielding the norbornenediyl-bridged bis(germylene) L鈥?/sup>Ge(渭-C₇H₈)GeL鈥?/sup> (4). Similarly, L*GeGeL* doubly reduces cyclooctatetraene (COT) to give the planar cyclooctateraenediyl inverse sandwich complex L*Ge(渭-畏2,畏2-COT)GeL* (5). An indication that this reaction occurs via an initial formal [2 + 2] cycloaddition intermediate comes from the reaction of L鈥?/sup>GeGeL鈥?/sup> with 1,5-cyclooctadiene (COD). This affords the [2 + 2] cycloaddition product L鈥?/sup>Ge(COD)GeL鈥?/sup> (6), which exists in solution in equilibrium with 2 and free COD. A computational study indicates that 6 readily dissociates, as the reaction that gave it is close to thermoneutral. Reaction of 1,3-cyclohexadiene (1,3-CHD) with L鈥?/sup>GeGeL鈥?/sup> yields the 1,4-bis(germylene) substituted cyclohex-2-enediyl L鈥?/sup>Ge(渭-C₆H₈)GeL鈥?/sup> (7), which is an isolated intermediate in the transfer hydrogenation, or C鈥揌 activation, reaction between L鈥?/sup>GeGeL鈥?/sup> and 1,3-CHD. Heating 7 gives benzene and the known digermene L鈥?/sup>(H)GeGe(H)L鈥?/sup>. Reactions of 1 or 2 with propyne, bis(trimethylsilyl)butadiyne, and azobenzene all lead to reductive insertion of the unsaturated substrate into the Ge鈥揋e bond of the digermyne and formation of L鈥?/sup>Ge{渭-HC鈺怌(Me)}GeL鈥?/sup> (8), L*Ge{渭-(Me₃Si)C鈺怌(CCSiMe₃)}GeL* (9), and L*Ge{渭-(Ph)NN(Ph)}GeL* (10), respectively. The reaction of 4-dimethylaminopyridine (DMAP) with L*GeGeL* gives the adduct complex L*(DMAP)GeGe(DMAP)L* (11). Taken as a whole, this study highlights both similarities and significant differences between the reactivities of the amido-digermynes 1 and 2 and those of their previously described terphenyl-substituted counterparts.}