Solvate-Assisted Grinding: Metal Solvates as Solvent Sources in Mechanochemically Driven Organometallic Reactions
Solvate-Assisted Grinding: Metal Solvates as Solvent Sources in Mechanochemically Driven Organometallic Reactions
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DOI：
10.1021/acs.organomet.1c00316
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发表时间：
2021-10-21
期刊：
影响因子：
2.8
通讯作者：
Hanusa, Timothy P.
中科院分区：
文献类型：
--
作者：
DeGroot, Henry P.;Hanusa, Timothy P.
合成化学中的溶剂效应可以通过多种方式进行分析，但一种可能违反直觉的方法是将溶剂完全从反应环境中去除。机械化学引发（固体试剂的研磨或碾磨）可以用来代替溶剂提供的混合和能量。然而，完全去除溶剂的效果可能是不可预测的，即使是部分去除，如在液体辅助研磨（LAG）领域中发现的，也可以深刻地改变反应结果。减少量的溶剂也可以以溶剂化物的形式存在，并且尽管它们的使用已被分类在“净”或“干”研磨的类别下，但“溶剂化物辅助研磨”（SAG）可能是更描述性的术语，因为此类反应的结果可以不同于LAG和净研磨的结果，后者更适当地限于仅使用无水或非溶剂化试剂。本文研究了机械力化学驱动下卤化物复分解合成双烯丙基金属配合物[MA（2 ′）]（M = Cr，Fe，Co，Ni; A ′ = 1，3-（SiMe 3）（2）C3 H3）。特别强调的是镍为基础的系统，其合成卤化镍的溶剂化物进行了比较，与相同的反应，使用无水金属卤化物和大量或LAG量的溶剂（几微升的溶剂每毫克的试剂）。采用溶剂化物辅助研磨的反应，或者单独（例如，用[Ni（py）（4）Cl-2]）或用LAG量的不同溶剂（例如，用[Ni（dme）Br-2]和THF作为LAG溶剂）最有效地产生镍烯丙基络合物，这表明配位溶剂与金属中心的密切相互作用是确定复分解反应结果的重要变量。虽然它们是在机械化学驱动反应的背景下开发的，但这些结果也对基于溶液的合成具有影响，其中溶剂化试剂的使用会强烈影响结果。
Solvent effects in synthetic chemistry can be analyzed in various ways, but a possibly counterintuitive approach is to remove the solvent entirely from the reaction environment. Mechanochemical initiation (grinding or milling of solid reagents) can then be used to replace the mixing and energy that would be supplied by a solvent. The effect of complete solvent elimination can be unpredictable, however, and even partial removal, as found in the realm of liquid-assisted grinding (LAG), can alter reaction outcomes profoundly. Reduced quantities of solvents can also be present in the form of solvates, and although their use has been classified under the category of "neat" or "dry" grinding, "solvate-assisted grinding" (SAG) might be a more descriptive term, as the outcome of such reactions can differ from those of both LAG and neat grinding, with the latter term more properly restricted to the use of anhydrous or unsolvated reagents only. This study examines the mechanochemically driven synthesis of the bis(allyl)metal complexes [MA(2)'] (M = Cr, Fe, Co, Ni; A' = 1,3-(SiMe3)(2)C3H3) via halide metathesis. Particular emphasis is given to the nickel-based system, whose synthesis from nickel halide solvates is compared with the same reaction using the anhydrous metal halide and either large or LAG quantities of solvent (a few microliters of solvent per milligram of reagents). The reactions employing solvate-assisted grinding, either alone (e.g., with [Ni(py)(4)Cl-2]) or with LAG amounts of a different solvent (e.g., with [Ni(dme)Br-2] and THF as the LAG solvent) yield the nickel allyl complex the most efficiently, suggesting that the intimate interaction of coordinated solvents with the metal centers is an important variable in determining the outcome of the metathesis reactions. Although they were developed in the context of mechanochemically driven reactions, these results have implications for solution-based synthesis as well, where the use of solvated reagents can strongly affect outcomes.