Yang Wenbang, White Andrew J P, Crimmin Mark R
Molecular Sciences Research Hub, Imperial College London, London, UK.
Nat Synth. 2025;4(8):995-1000. doi: 10.1038/s44160-025-00790-y. Epub 2025 Apr 29.
Oxidative addition most commonly involves the addition of a substrate to a metal centre. This reaction is fundamental across synthetic chemistry and underpins numerous catalytic methods. In the textbook description of oxidative addition reactions, a net increase in the formal oxidation state of the metal occurs with simultaneous bond breaking at the substrate. The majority of known oxidative addition reactions, however, involve substrates bearing relatively electronegative elements (for example, hydrogen, carbon, nitrogen, oxygen and halogens) and there has been little discussion of how addition processes may fundamentally change if substrates were constructed from more electropositive elements. Here we show that the zinc-zinc bonded complex, CpZnZnCp (Cp* = pentamethylcyclopentadienyl), which is isoelectronic with dihydrogen, undergoes facile addition to the metal (or semi-metal) centres of a series of main group carbene analogues based on silicon, aluminium, gallium or indium. Reactions proceed with complete breaking of the zinc-zinc bond and an increase in the coordination number of the central metal from two to four. Our analysis suggests that these addition processes are not oxidative, but rather there is likely a continuum of redox outcomes spanning oxidative, redox neutral and reductive. The addition of CpZnZnCp to silicon(II) provides the most compelling case for a prototypical reductive addition process.
氧化加成最常见的是底物加到金属中心上。该反应在合成化学中是基础反应，支撑着众多催化方法。在氧化加成反应的教科书描述中，金属的形式氧化态净增加，同时底物发生键断裂。然而，大多数已知的氧化加成反应涉及带有相对电负性元素（例如氢、碳、氮、氧和卤素）的底物，对于如果底物由更正电性元素构成，加成过程可能会如何从根本上改变，几乎没有相关讨论。在此我们表明，与氢气等电子的锌-锌键合配合物CpZnZnCp（Cp* = 五甲基环戊二烯基）能轻易加成到一系列基于硅、铝、镓或铟的主族卡宾类似物的金属（或半金属）中心上。反应进行时锌-锌键完全断裂，中心金属的配位数从二增加到四。我们的分析表明，这些加成过程不是氧化过程，而是可能存在一系列从氧化到氧化还原中性再到还原的氧化还原结果。CpZnZnCp加到硅（II）上为典型的还原加成过程提供了最有说服力的例子。
