The variable coordination geometries, multiple spin states, and high density of states of first row transition metals offer a new frontier in the catalytic chemistry. A DFT study has been performed in order to unveil these characteristic features of iron metallaboratrane complex in alkene hydrogenation. A detailed spin-state analysis reveals there exist two minimum energy crossing points in the formation of (TPB)(μ-H)Fe(H) 3^triplet from (TPB)Fe(N₂) 1^triplet. In the catalytic cycle, 3^triplet at triplet state plays a role of active species, and the hydrogenation at triplet state is more favorable than that at singlet state. The dissociation of phosphine arm of TPB ligand from Fe center occurs easily in the triplet state, because the antibonding dσ is singly occupied in 3^triplet. However, a nondissociative pathway without any phosphine ligand dissociation is not likely to occur. The product is formed via the σ-bond metathesis between a dihydrogen molecule and a Fe-styryl moiety. The usual direct reductive elimination involving bridging hydride (μ-H) is very difficult because the μ-H is strongly bonded with Fe and B atoms.

中文翻译：

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铁金属六硼烷烯烃加氢催化的DFT机理研究：铁物种的特征

第一排过渡金属的可变配位几何形状，多个自旋态和高密度态在催化化学中提供了新的领域。为了揭示烯烃加氢中金属金属硼烷络合物的这些特征，已进行了DFT研究。详细的自旋态分析表明，从（TPB）Fe（N ₂）1^三重态形成（TPB）（μ-H）Fe（H）3^三重态时，存在两个最小能量交叉点。在催化循环中，有3个^三重态三重态的氢化起活性物质的作用，三重态的氢化比单重态的氢化更有利。TPB配体的磷化氢臂从Fe中心容易在三重态中解离，这是因为抗键dσ仅占据了3个^三重态。然而，没有任何膦配体解离的非解离途径是不可能发生的。产物是通过二氢分子和Fe-苯乙烯基部分之间的σ键易位形成的。通常，涉及桥接氢化物（μ-H）的直接还原消除非常困难，因为μ-H与Fe和B原子牢固结合。