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首页> 外文期刊>Chemistry: A European journal >Synthetic, Mechanistic, and Theoretical Studies on the Generation of Iridium Hydride Alkylidene and Iridium Hydride Alkene Isomers
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Synthetic, Mechanistic, and Theoretical Studies on the Generation of Iridium Hydride Alkylidene and Iridium Hydride Alkene Isomers

机译：氢化铱亚炔基和氢化铱烯异构体的合成，机理和理论研究

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摘要

Experimental and theoretical studies on equilibria between iridium hydride alkylidene structures, [(TpMe2)Ir(H){=CACHTUNGTRENUNG(CH2R)ArO}] (TpMe2=hydrotris(3,5-dimethylpyrazolyl) borate; R=H, Me; Ar=substituted C6H4 group), and their corresponding hydride olefin isomers, [(TpMe2)Ir(H){R(H)C=C(H)OAr}], have been carried out. Compounds of these types are obtained either by reaction of the unsaturated fragment [(TpMe2)IrACHTUNGTRENUNG(C6H5)2] with o- C6H4(OH)CH2R, or with the substituted anisoles 2,6-Me2C6H3OMe, 2,4,6- Me3C6H2OMe, and 4-Br-2,6- Me2C6H2OMe. The reactions with the substituted anisoles require not only multiple C-H bond activation but also cleavage of the Me-OAr bond and the reversible formation of a C-C bond (as revealed by 13C labeling studies). Equilibria between the two tautomeric structures of these complexes were achieved by prolonged heating at temperatures between 100 and 140 8C, with interconversion of isomeric complexes requiring inversion of the metal configuration, as well as the expected migratory insertion and hydrogen-elimination reactions. This proposal is supported by a detailed computational xploration of the mechanism at the quantum mechanics (QM) level in the real system. For all compounds investigated, the equilibria favor the alkylidene structure over the olefinic isomer by a factor of between approximately 1 and 25. Calculations demonstrate that the main reason for this preference is the strong Ir–carbene interactions in the carbene isomers, rather than steric destabilization of the olefinic tautomers.
机译：关于氢化铱亚烷基结构[[TpMe2）Ir（H）{= CACHTUNGTRENUNG（CH2R）ArO}]之间平衡的实验和理论研究（TpMe2 =氢三（3,5-二甲基吡唑基）硼酸盐; R = H，Me; Ar =取代的C 6 H 4基团）和它们相应的氢化烯烃异构体，[（TpMe2）Ir（H）{R（H）C = C（H）OAr}]已经进行。这些类型的化合物可通过不饱和片段[（TpMe2）IrACHTUNGTRENUNG（C6H5）2]与o- C6H4（OH）CH2R或与取代的异构体2,6-Me2C6H3OMe，2,4,6-Me3C6H2OMe反应获得和4-Br-2,6- Me2C6H2OMe。与取代的茴香醚的反应不仅需要多次C-H键活化，而且还需要Me-OAr键的裂解和C-C键的可逆形成（如13C标记研究所揭示）。这些配合物的两个互变异构结构之间的平衡是通过在100至140 8℃之间的温度下长时间加热来实现的，异构体配合物的相互转化需要金属构型的反转，以及预期的迁移插入和氢消除反应。这项建议得到了真实系统中量子力学（QM）级别的详细计算机制的支持。对于所有研究的化合物，平衡度比烯烃异构体更偏爱亚烷基结构，约为1到25。计算表明，这种偏爱的主要原因是卡宾异构体中强烈的Ir-卡宾相互作用，而不是空间不稳定的烯烃互变异构体。

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