Magnitudes of Electron-Withdrawing Effects of the Trifluoromethyl Ligand in Organometallic Complexes of Copper and Nickel
Magnitudes of Electron-Withdrawing Effects of the Trifluoromethyl Ligand in Organometallic Complexes of Copper and Nickel
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DOI：
10.1021/om901122z
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发表时间：
2010-03-22
期刊：
影响因子：
2.8
通讯作者：
Vicic, David A.
中科院分区：
文献类型：
--
作者：
Kieltsch, Iris;Dubinina, Galyna G.;Vicic, David A.
为了通过电化学方法量化相对于它们的氯和甲基对应物的氧化还原电位，已经制备了具有三氟甲基配体的各种镍和铜络合物。配位数和几何形状，以及金属的氧化态，对三氟甲基配合物可以被氧化的相对容易的影响已首次被确定。在d（10）体系[（NHC）Cu（X）]（NHC = N-杂环卡宾，X =甲基或三氟甲基）中，甲基对三氟甲基的单一取代使有机金属络合物的氧化电位相对于二茂铁/二茂铁（Fc/Fc（+））对提高约+0.6 V，这证明了三氟甲基配体的极端吸电子性质。d（8）镍络合物的Δ E-ox（甲基对三氟甲基）具有相似的量级;然而，绝对氧化电位显著依赖于配体（dippe = 1，2-双（二异丙基膦基）乙烷对BOXAM =双（4-异丙基-4，5-二氢恶唑-2-基）苯基）胺）。
A variety of nickel and copper complexes bearing the trifluoromethyl ligand have been prepared in order to quantify by electrochemical methods the redox potentials relative to their chloro and methyl counterparts. The effects of coordination number and geometry, as well as the oxidation state of the metal, on the relative ease with which trifluoromethyl complexes can be oxidized have for the first time been identified. In the d(10) system [(NHC)Cu(X)] (NHC = N-heterocyclic carbene, X = methyl or trifluoromethyl), a single substitution of methyl for trifluoromethyl raised the oxidation potential of the organometallic complex by approximately +0.6 V versus the ferrocene/ferrocenium (Fc/Fc(+)) couple, a testament to the extreme electron-withdrawing properties of the trifluoromethyl ligand. The Delta E-ox (methyl vs trifluoromethyl) for d(8) nickel complexes were of similar magnitude; however the absolute oxidation potentials were dramatically dependent on the ligand (dippe = 1,2-bis(diisopropylphosphino)ethane vs BOXAM = bis(4-isopropyl-4,5-dihydrooxazol-2-yl)phenyl)amine).