Ligand-Centered Borenium Reactivity in Triaminoborane-Bridged Diphosphine Complexes.
Ligand-Centered Borenium Reactivity in Triaminoborane-Bridged Diphosphine Complexes.
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三氨基硼烷桥联二膦配合物中以配体为中心的硼反应性。
DOI：
10.1021/acs.inorgchem.8b01601
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发表时间：
2018
影响因子：
4.6
通讯作者：
Scott R. Daly
中科院分区：
文献类型：
--
作者：
Kyounghoon Lee;Clara Kirkvold;Bess Vlaisavljevich;Scott R. Daly
Borenium离子（即，三配位硼阳离子）由于其高的刘易斯酸性而已知可促进多种化学计量和催化反应。正如越来越多的化学反应性硼烷配体所证明的那样，人们对开发具有高度亲电硼位点的配体有相当大的兴趣，所述高度亲电硼位点促进金属络合物中的多位点反应性。然而，目前很少有配体为中心的硼离子的例子，特别是与各种金属形成配位络合物的配体。在这里，我们报告了一个高度通用的双膦配体的类硼反应性。（PhTBDPhos）NiCl_2（1）与强Bronsted酸（如HBF_4·Et_2O、HOTf或HNTf_2）反应，分别从BF_4-或NiCl_2中夺取氟或氯，在配体骨架上形成反式N-H和B-X键。HCl对桥头N-B键的加成是可逆的，反应性取决于支持抗衡阴离子的身份，如用HCl处理[（PhTBDPhos）NiCl]2X2（其中X = NTf 2-（3）、OTf-（4）或BArF 4-（5））时所观察到的。4与HNTf 2而不是HCl的反应产生了溶液中潜在的Borenium阳离子的NMR证据，并显示了弱亲核试剂如三氟甲磺酸酯如何与固态的Borenium离子结合。值得注意的是，用螯合和不太稳定的硫醇盐或儿茶酚盐取代1中的氯配体，或改变磷取代基（苯基至异丙基），减弱了配体骨架上的反应性。采用密度泛函理论对反应自由能进行了定量计算，理论结果与实验结果相吻合。鉴于双膦在均相催化中的广泛用途和强刘易斯酸促进剂在许多催化反应中的已知益处，我们预计结果将为涉及硼配体和金属的双位点反应性提供新的机会。
Borenium ions (i.e., three-coordinate boron cations) are known to promote a wide variety of stoichiometric and catalytic reactions because of their high Lewis acidity. As demonstrated by the growing number of chemically reactive borane ligands, there is considerable interest in developing ligands with highly electrophilic boron sites that promote multisite reactivity in metal complexes. However, there are currently few examples of ligand-centered borenium ions, especially with ligands that form coordination complexes with a wide range of metals. Here we report borenium-like reactivity on a highly versatile diphosphine ligand. Treating (PhTBDPhos)NiCl2 (1) with strong Bronsted acids such as HBF4·Et2O, HOTf, or HNTf2 resulted in fluoride or chloride abstraction from BF4- or NiCl2, respectively, to form trans N-H and B-X bonds on the ligand backbone. HCl addition to the bridgehead N-B bond is reversible, and the reactivity depends on the identity of the supporting counteranions, as observed when treating [(PhTBDPhos)NiCl]2X2, where X = NTf2- (3), OTf- (4), or BArF4- (5), with HCl. The reaction of 4 with HNTf2 instead of HCl yielded NMR evidence of the latent borenium cation in solution and showed how poor nucleophiles such as triflate bind to the borenium ion in the solid state. Remarkably, replacing the chloride ligands in 1 with chelating and less-labile thiolates or catecholates, or changing the phosphorus substituents (phenyl to isopropyl), attenuates the reactivity on the ligand backbone. Density functional theory was used to quantify the reaction free energies, and the theoretical results corroborate the experimental observations. Given the broad utility of diphosphines in homogeneous catalysis and the known benefits of strong Lewis acid promotors in many catalytic reactions, we anticipate that the results will provide new opportunities for dual-site reactivity involving boron ligands and metals.
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影响因子：
4.6
作者：
Solntsev, Pavlo V.;Spurgin, Katelynn L.;Nemykin, Victor N.
通讯作者：
Nemykin, Victor N.
影响因子：
62.1
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Karunananda, Malkanthi K.;Mankad, Neal P.
通讯作者：
Mankad, Neal P.
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15
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Kiernicki JJ;Zeller M;Szymczak NK
通讯作者：
Szymczak NK