Synthesis and Reactivity of Reduced α-Diimine Nickel Complexes Relevant to Acrylic Acid Synthesis
Synthesis and Reactivity of Reduced α-Diimine Nickel Complexes Relevant to Acrylic Acid Synthesis
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DOI：
10.1021/acs.organomet.8b00350
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发表时间：
2018-10-22
期刊：
影响因子：
2.8
通讯作者：
Chirik, Paul J.
中科院分区：
文献类型：
--
作者：
Joannou, Matthew, V;Bezdek, Mate J.;Chirik, Paul J.
合成了芳基取代的α-二亚胺（DI）镍乙烯基配合物（（DI）-D-iPr）Ni（CH= CH 2）（（DI）-D-iPr = [2，6-（Pr-i）（2）C6 H3 N =C（CH 3）]（2）），并对其结构进行了表征。该配合物在固态下是二聚的，并且在镍处具有扭曲的正方形平面几何形状。单晶X-射线衍射，EPR，磁化率和NMR分析的组合被用来阐明该化合物的电子结构，它是最好的描述为低自旋镍（II）衍生物与单一减少的α-二亚胺螯合物。向镍乙烯基络合物中加入CO2导致插入镍-碳键，得到相应的丙烯酸镍（（DI）-D-iPr）Ni（kappa（2）-O2 CCH = CH 2）。EPR光谱结合DFT计算确定S = 1/2产物保持镍（II）氧化态，具有α-二亚胺中心自由基。将丙烯酸加入到（（DI）-D-iPr）Ni（CH= CH 2）中，诱导快速的净还原消除以释放丁二烯，并产生亚稳态烯烃结合的丙烯酸络合物（（DI）-D-iPr）Ni（eta（2）-CH 2 = CHCO 2 H）。在23 ° C下2小时的过程中，该络合物经历净氧化以产生（（DI）-D-iPr）Ni（kappa（2）-O2 CCH = CH 2），伴随着H-2的损失。
The aryl-substituted alpha-diimine (DI) nickel vinyl complex ((DI)-D-iPr)Ni(CH=CH2) ((DI)-D-iPr = [2,6-(Pr-i)(2)C6H3N=C(CH3)](2)) was synthesized and structurally characterized. The complex is dimeric in the solid state and has a distorted-square-planar geometry at nickel. A combination of single-crystal X-ray diffraction, EPR, magnetic susceptibility, and NMR analyses was used to elucidate the electronic structure of the compound, and it is best described as a low-spin Ni(II) derivative with a singly reduced alpha-diimine chelate. Addition of CO2 to the nickel vinyl complex resulted in insertion into the nickel-carbon bond to yield the corresponding nickel acrylate ((DI)-D-iPr)Ni(kappa(2)-O2CCH=CH2). EPR spectroscopy coupled with DFT calculations established that the S = 1/2 product maintains the nickel(II) oxidation state with an alpha-diimine-centered radical. Addition of acrylic acid to ((DI)-D-iPr)Ni(CH=CH2) induced rapid, net bimetallic reductive elimination to release butadiene and produced the metastable olefin-bound acrylic acid complex ((DI)-D-iPr)Ni(eta(2)-CH2=CHCO2H). Over the course of 2 h at 23 degrees C, this complex underwent a net oxidation to produce ((DI)-D-iPr)Ni(kappa(2)-O2CCH=CH2), with concomitant loss of H-2.