Parchomyk Tobias, Koszinowski Konrad
Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany.
Chemistry. 2016 Oct 24;22(44):15609-15613. doi: 10.1002/chem.201603574. Epub 2016 Sep 28.
Iron-catalyzed cross-coupling reactions have an outstanding potential for sustainable organic synthesis, but remain poorly understood mechanistically. Here, we use electrospray-ionization (ESI) mass spectrometry to identify the ionic species formed in these reactions and characterize their reactivity. Transmetalation of Fe(acac) (acac=acetylacetonato) with PhMgCl in THF (tetrahydrofuran) produces anionic iron ate complexes, whose nuclearity (1 to 4 Fe centers) and oxidation states (ranging from -I to +III) crucially depend on the presence of additives or ligands. Upon addition of iPrCl, formation of the heteroleptic Fe complex [Ph Fe(iPr)] is observed. Gas-phase fragmentation of this complex results in reductive elimination and release of the cross-coupling product with high selectivity.
铁催化的交叉偶联反应在可持续有机合成方面具有巨大潜力，但在反应机理方面仍了解甚少。在此，我们使用电喷雾电离（ESI）质谱来鉴定这些反应中形成的离子物种并表征其反应活性。在四氢呋喃（THF）中，Fe(acac)（acac = 乙酰丙酮基）与PhMgCl发生金属转移反应生成阴离子铁酸酯配合物，其核数（1至4个铁中心）和氧化态（范围从-I到+III）关键取决于添加剂或配体的存在。加入异丙基氯（iPrCl）后，观察到杂配铁配合物[Ph Fe(iPr)]的形成。该配合物在气相中的碎片化导致交叉偶联产物以高选择性进行还原消除并释放出来。
