Photoreactions of Phenylborylene with Dinitrogen and Carbon Monoxide
Photoreactions of Phenylborylene with Dinitrogen and Carbon Monoxide
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DOI：
10.1021/jacs.7b08497
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发表时间：
2017-10-25
影响因子：
15
通讯作者：
Bettinger, Holger F.
中科院分区：
文献类型：
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作者：
Edel, Klara;Krieg, Matthias;Bettinger, Holger F.
从硼烷BR 3中正式去除两个键合伙伴，产生亚硼基RB，其已被推断为许多反应中的活性中间体。苯基亚硼基（R = C6 H5; 1）可通过在基质隔离条件下光化学挤出二氮从苯基二叠氮基硼烷中获得。同时，氮宾PhNBN通过苯基重排形成。在这里，我们使用了一个组合的UV/维斯，IR和ESR光谱在低温基质隔离条件下，研究苯硼烯的性能和反应性。我们在375 nm处检测到苯硼烯的吸收带（S-0 -> S-2），并初步将S-0 -> S-1跃迁归属于518 nm处的一个非常弱的带。我们还表明，第一次，亲电子的硼，如1可以与N-2可逆反应和CO不可逆的光化学条件下。相应的光产物PhBNN和PhBCO具有三重电子基态。它们的小E值与密度泛函理论计算得到的Ph-B-N-N和Ph-B-C-O的线性排列一致。D值按PhNBN > PhBNN > PhBCO的顺序减小，并接近苯基卡宾（PhCH）的值。事实上，PhBCO中的硼中心与PhCH中的卡宾中心是等电子的。这些化合物是重氮烷（R2 CNN）和烯酮（R2 CCO）的硼类似物的第一个例子，它们的形成可以作为苯基硼烯的高反应性的证明。
Formal removal of two bonding partners from boranes, BR3, yields borylenes, RB, which have been inferred as reactive intermediates in a number of reactions. Phenylborylene (R = C6H5; 1) is accessible from phenyldiazidoborane by photochemical extrusion of dinitrogen under matrix isolation conditions. Concomitantly, the nitrene PhNBN is formed via phenyl rearrangement. Here we used a combination of UV/vis, IR, and ESR spectroscopy under cryogenic matrix isolation conditions to investigate the properties and reactivity of phenylborylene. We detected an absorption band of phenylborylene at 375 nm (S-0 -> S-2) and tentatively assigned the S-0 -> S-1 transition to a very weak band at 518 nm. We also show for the first time that an electrophilic borylene such as 1 can react with N-2 reversibly and with CO irreversibly under photochemical conditions. The corresponding photoproducts PhBNN and PhBCO have triplet electronic ground states. Their small E values are in agreement with the linear arrangements Ph-B-N-N and Ph-B-C-O obtained by density functional theory computations. The D values decrease in the series PhNBN > PhBNN > PhBCO and approach the value for phenylcarbene (PhCH). Indeed, the boron center in PhBCO is isoelectronic with the carbene center in PhCH. The compounds are the first examples of boron analogues of diazoalkanes (R2CNN) and ketenes (R2CCO), and their formation may serve as a demonstration of the high reactivity of phenylborylene.