Metal鈥揕igand Synergistic Effects in the Complex Ni(畏2-TEMPO)2: Synthesis, Structures, and Reactivity

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• 作者：Derek Isrow ; Nathan J. DeYonker ; Anjaneyulu Koppaka ; Perry J. Pellechia ; Charles Edwin Webster ; Burjor Captain
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：December 16, 2013
• 年：2013
• 卷：52
• 期：24
• 页码：13882-13893
• 全文大小：585K
• 年卷期：v.52,no.24(December 16, 2013)
• ISSN：1520-510X

文摘

In the current investigation, reactions of the 鈥渂ow-tie鈥?Ni(畏²-TEMPO)₂ complex with an assortment of donor ligands have been characterized experimentally and computationally. While the Ni(畏²-TEMPO)₂ complex has trans-disposed TEMPO ligands, proton transfer from the C鈥揌 bond of alkyne substrates (phenylacetylene, acetylene, trimethylsilyl acetylene, and 1,4-diethynylbenzene) produce cis-disposed ligands of the form Ni(畏²-TEMPO)(魏¹-TEMPOH)(魏¹-R). In the case of 1,4-diethynylbenzene, a two-stage reaction occurs. The initial product Ni(畏²-TEMPO)(魏¹-TEMPOH)[魏¹-CC(C₆H₄)CCH] is formed first but can react further with another equivalent of Ni(畏²-TEMPO)₂ to form the bridged complex Ni(畏²-TEMPO)(魏¹-TEMPOH)[魏¹-魏¹-CC(C₆H₄)CC]Ni(畏²-TEMPO)(魏¹-TEMPOH). The corresponding reaction with acetylene, which could conceivably also yield a bridging complex, does not occur. Via density functional theory (DFT), addition mechanisms are proposed in order to rationalize thermodynamic and kinetic selectivity. Computations have also been used to probe the relative thermodynamic stabilities of the cis and trans addition products and are in accord with experimental results. Based upon the computational results and the geometry of the experimentally observed product, a trans鈥?i>cis isomerization must occur.