The reaction chemistry of both silanes and hydrogen at para-terphenyl diphosphine-supported molybdenum complexes was explored within the context of carbon dioxide (CO₂) reduction. CO₂ hydrosilylation commonly affords reduction products via silyl acetals. However, while silyl hydride complexes were characterized in the present system, synthetic, spectroscopic, and kinetic studies suggest C–O cleavage of CO₂ occurs independently of silanes. In their presence, a putative molybdenum oxo intermediate is hypothesized to undergo O-atom transfer, yielding silanol. In contrast, hydrogenation chemistry does occur through an intermediate molybdenum dihydride capable of inserting CO₂ to yield a formate hydride complex. This process is reversible; slow deinsertion under dinitrogen affords a mixture of molybdenum dihydride, η²-CO₂, and N₂ complexes. The molybdenum hydride formate species is a competent precatalyst for both CO₂ hydrogenation to formate (in the presence of lithium cations and base) and formic acid dehydrogenation to CO₂ and hydrogen (in the presence of base). Mechanistic studies of both catalytic processes are presented.

中文翻译：

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在低价钼三联苯二膦配合物中用二氢和硅烷还原二氧化碳：还原剂特性决定机制

在二氧化碳 (CO ₂ ) 还原的背景下探索了硅烷和氢在对三联苯二膦负载的钼配合物中的反应化学。CO ₂氢化硅烷化通常通过甲硅烷基缩醛提供还原产物。然而，虽然在本系统中表征了甲硅烷基氢化物复合物，但合成、光谱和动力学研究表明 CO _{2 的}C-O 裂解独立于硅烷发生。在它们存在的情况下，假设假定的钼氧代中间体进行 O 原子转移，产生硅烷醇。相比之下，氢化化学确实通过能够插入 CO ₂的中间体二氢化钼发生生成甲酸氢化物络合物。这个过程是可逆的；在二氮下缓慢脱嵌得到二氢化钼、η ² -CO ₂和N ₂配合物的混合物。氢化钼甲酸盐物质是CO ₂氢化成甲酸盐（在锂阳离子和碱存在下）和甲酸脱氢成CO ₂和氢（在碱存在下）的有效预催化剂。介绍了两种催化过程的机理研究。