Stabilizing Effect of Bulky β-Diketones on Homogeneous Mo Catalysts for Deoxydehydration
Stabilizing Effect of Bulky β-Diketones on Homogeneous Mo Catalysts for Deoxydehydration
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DOI：
10.1021/acssuschemeng.8b02532
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发表时间：
2018-07
影响因子：
8.4
通讯作者：
M. Stalpaert;D. D. De Vos-D.
中科院分区：
文献类型：
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作者：
M. Stalpaert;D. D. De Vos-D.
邻位二醇脱氧脱水生成烯烃是生物质脱氧的一个很有前途的反应。虽然迄今为止大多数报道涉及基于Re的催化剂，但近年来基于更丰富的Mo和V的催化剂获得了更多的兴趣。然而，这些催化剂的产率和活性相对较低，特别是对于Mo，关于配体对金属催化剂的影响知之甚少。在这里，我们研究了一系列具有不同空间和电子性质的β-二酮作为Mo催化剂的配体前体。我们表明，加入β-二酮2，2，6，6-四甲基庚二酮（TMHD）导致使用不同还原剂在一系列底物的DODH中所需产物的产率大幅增加。这种增加的产率的最可能的解释是空间上庞大的配体，即共轭的β-二酮化物，阻碍Mo催化剂的低聚，因此抑制沉淀。电喷雾质谱法证实了这一假设。
The deoxydehydration (DODH) of vicinal diols to alkenes is a promising reaction for the deoxygenation of biomass. While most reports so far concern Re-based catalysts, catalysts based on more abundant Mo and V have gained more interest in recent years. However, yields and activity are relatively low for these catalysts and, especially for Mo, little is known about the influence of ligands on the metal catalyst. Here, we study a series of β-diketones with different steric and electronic properties as ligand precursors for a Mo catalyst. We show that addition of the β-diketone 2,2,6,6-tetramethylheptanedione (TMHD) leads to a strong increase in yield for the desired product in DODH of a range of substrates using different reductants. The most likely explanation for this increased yield is that the sterically bulky ligand, that is, the conjugated β-diketonate, impedes oligomerization of the Mo catalyst and, hence, inhibits precipitation. This hypothesis was confirmed by electrospray mass spectrometry.