Contrasting E-H Bond Activation Pathways of a Phosphanyl-Phosphagallene.
Contrasting E-H Bond Activation Pathways of a Phosphanyl-Phosphagallene.
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DOI：
10.1002/anie.202109334
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发表时间：
2021-09-27
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影响因子：
--
通讯作者：
Goicoechea JM
中科院分区：
文献类型：
--
作者：
Feld J;Wilson DWN;Goicoechea JM
膦基-磷杂联三烯[H2 C {N（Dipp）}] 2 PP =Ga（Nacnac）（Nacnac=HC[C（Me）N（Dipp）]2; Dipp= 2，6-iPr 2C 6 H3）对一系列具有E-H键的试剂（伯胺、氨、水、苯乙炔、苯基膦和苯基硅烷）的反应性被报道。观察到两种截然不同的反应途径，由底物的E-H键的极性决定。在质子试剂（δ−E−Hδ+）的情况下，受抑刘易斯对类型的机制在室温下起作用，其中镓金属中心充当刘易斯酸，侧基磷烷基部分使底物去质子化。有趣的是，在升高的温度下，NH 2 iPr和氨都可以通过第二种更高能量的途径反应，导致Ga=P键的氢胺化。相比之下，对于双金属试剂（δ+E−Hδ−），如苯基硅烷，只观察到Ga=P键的氢元素化，与Si−H和Ga=P键的极化一致。我们描述了一个膦基phosphagallene的合成和反应性对试剂与质子和质子的E-H键。这些研究表明，有两个竞争的反应途径可用于这样的键活化反应：一个受挫的刘易斯对类型的机制，和竞争的途径，导致在Ga=P双键的水解。
The reactivity of the phosphanyl‐phosphagallene, [H2C{N(Dipp)}]2PP=Ga(Nacnac) (Nacnac=HC[C(Me)N(Dipp)]2; Dipp=2,6‐ i Pr2C6H3) towards a series of reagents possessing E−H bonds (primary amines, ammonia, water, phenylacetylene, phenylphosphine, and phenylsilane) is reported. Two contrasting reaction pathways are observed, determined by the polarity of the E−H bonds of the substrates. In the case of protic reagents (δ−E−Hδ+), a frustrated Lewis pair type of mechanism is operational at room temperature, in which the gallium metal centre acts as a Lewis acid and the pendant phosphanyl moiety deprotonates the substrates. Interestingly, at elevated temperatures both NH2 i Pr and ammonia can react via a second, higher energy, pathway resulting in the hydroamination of the Ga=P bond. By contrast, with hydridic reagents (δ+E−Hδ−), such as phenylsilane, hydroelementation of the Ga=P bond is exclusively observed, in line with the polarisation of the Si−H and Ga=P bonds. We describe the synthesis and reactivity of a phosphanyl phosphagallene towards reagents with protic and hydridic E−H bonds. These studies reveal that there are two competing reactivity pathways available for such bond activation reactions: a frustrated Lewis pair type of mechanism, and a competing pathway which results in the hydroelementation of the Ga=P double bond.
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