Four-electron deoxygenative reductive coupling of carbon monoxide at a single metal site
Four-electron deoxygenative reductive coupling of carbon monoxide at a single metal site
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DOI：
10.1038/nature16154
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发表时间：
2016-01-07
期刊：
影响因子：
64.8
通讯作者：
Agapie, Theodor
中科院分区：
文献类型：
--
作者：
Buss, Joshua A.;Agapie, Theodor
二氧化碳是化石燃料的最终来源，化石燃料既是现代生活的核心，也存在问题：它们的使用会增加大气中温室气体的含量，而且它们的可用性受到地缘政治的限制(1)。原则上，使用二氧化碳作为原料生产合成燃料可能会缓解这些担忧。尽管许多均相和非均相催化剂将二氧化碳转化为一氧化碳(2)，但一氧化碳的进一步脱氧偶联以生成有用的多碳产物具有挑战性(3)。钼和钒固氮酶能够使用离散电子和质子源在温和条件下将一氧化碳转化为碳氢化合物(4)。铜催化剂上一氧化碳的电催化还原 (5) 也使用电子和质子的组合，而工业费托工艺使用氢气作为电子和亲电子试剂的组合源，在高温高压下进行一氧化碳偶联 (6)。然而，这些酶促和异质系统很难进行机械探测。人们已经对分子催化剂进行了广泛的研究(6-23)，以研究一氧化碳脱氧和偶联的基本步骤，但尚未记录到能够有效诱导所需的碳-氧键断裂并生成碳-碳键的单一金属位点。在这里，我们描述了一种由三联苯二膦配体支持的钼化合物，它激活并裂解一氧化碳的强碳-氧键，发生碳-碳偶联，并自发解离所得片段。这种复杂的四电子转化是由三联苯二膦配体 (24,25) 实现的，该配体充当电子库并表现出稳定整个反应序列中涉及的不同中间体所需的配位灵活性。我们预计这些设计元素可能有助于开发将一氧化碳转化为化学燃料的高效催化剂，并且应该在单个金属位点执行复杂的多电子转化的更广泛背景下证明有用。
Carbon dioxide is the ultimate source of the fossil fuels that are both central to modern life and problematic: their use increases atmospheric levels of greenhouse gases, and their availability is geopolitically constrained(1). Using carbon dioxide as a feedstock to produce synthetic fuels might, in principle, alleviate these concerns. Although many homogeneous and heterogeneous catalysts convert carbon dioxide to carbon monoxide(2), further deoxygenative coupling of carbon monoxide to generate useful multicarbon products is challenging(3). Molybdenum and vanadium nitrogenases are capable of converting carbon monoxide into hydrocarbons under mild conditions, using discrete electron and proton sources(4). Electrocatalytic reduction of carbon monoxide on copper catalysts(5) also uses a combination of electrons and protons, while the industrial Fischer-Tropsch process uses dihydrogen as a combined source of electrons and electrophiles for carbon monoxide coupling at high temperatures and pressures(6). However, these enzymatic and heterogeneous systems are difficult to probe mechanistically. Molecular catalysts have been studied extensively(6-23) to investigate the elementary steps by which carbon monoxide is deoxygenated and coupled, but a single metal site that can efficiently induce the required scission of carbon-oxygen bonds and generate carbon-carbon bonds has not yet been documented. Here we describe a molybdenum compound, supported by a terphenyl-diphosphine ligand, that activates and cleaves the strong carbon-oxygen bond of carbon monoxide, enacts carbon-carbon coupling, and spontaneously dissociates the resulting fragment. This complex four-electron transformation is enabled by the terphenyl-diphosphine ligand(24,25), which acts as an electron reservoir and exhibits the coordinative flexibility needed to stabilize the different intermediates involved in the overall reaction sequence. We anticipate that these design elements might help in the development of efficient catalysts for converting carbon monoxide to chemical fuels, and should prove useful in the broader context of performing complex multi-electron transformations at a single metal site.