Parchomyk Tobias, Demeshko Serhiy, Meyer Franc, Koszinowski Konrad
Institut für Organische und Biomolekulare Chemie , Universität Göttingen , Tammannstraße 2 , 37077 Göttingen , Germany.
Institut für Anorganische Chemie , Universität Göttingen , Tammannstraße 4 , 37077 Göttingen , Germany.
J Am Chem Soc. 2018 Aug 1;140(30):9709-9720. doi: 10.1021/jacs.8b06001. Epub 2018 Jul 24.
We have applied a combination of electrospray-ionization mass spectrometry, electrical conductivity measurements, and Mössbauer spectroscopy to identify and characterize the organoferrate species R Fe formed upon the transmetalation of iron precursors (Fe(acac), FeCl, FeCl, Fe(OAc)) with Grignard reagents RMgX (R = Me, Et, Bu, Hex, Oct, Dec, MeSiCH, Bn, Ph, Mes, 3,5-(CF)-CH; X = Cl, Br) in tetrahydrofuran. The observed organoferrates show a large variety in their aggregation (1 ≤ m ≤ 8) and oxidation states (I to IV), which are chiefly determined by the nature of their organyl groups R. In numerous cases, the addition of a bidentate amine or phosphine changes the distributions of organoferrates and affects their stability. Besides undergoing efficient intermolecular exchange processes, several of the probed organoferrates react with organyl (pseudo)halides R'X (R' = Et, Pr, Bu, Ph, p-Tol; X = Cl, Br, I, OTf) to afford heteroleptic complexes of the type RFeR'. Gas-phase fragmentation of most of these complexes results in reductive eliminations of the coupling products RR' (or, alternatively, of R). This finding indicates that iron-catalyzed cross-coupling reactions may proceed via such heteroleptic organoferrates RFeR' as intermediates. Gas-phase fragmentation of other organoferrate complexes leads to β-hydrogen eliminations, the loss of arenes, and the expulsion of organyl radicals. The operation of both one- and two-electron processes is consistent with previous observations and contributes to the formidable complexity of organoiron chemistry.
我们运用了电喷雾电离质谱、电导率测量和穆斯堡尔光谱相结合的方法，来鉴定和表征铁前体（Fe(acac)、FeCl、FeCl、Fe(OAc)）与格氏试剂RMgX（R = Me、Et、Bu、Hex、Oct、Dec、MeSiCH、Bn、Ph、Mes、3,5-(CF)-CH；X = Cl、Br）在四氢呋喃中进行金属转移反应时形成的有机铁酸盐物种R Fe。观察到的有机铁酸盐在聚集态（1 ≤ m ≤ 8）和氧化态（I至IV）方面表现出很大的多样性，这主要由其有机基团R的性质决定。在许多情况下，添加双齿胺或膦会改变有机铁酸盐的分布并影响其稳定性。除了经历高效的分子间交换过程外，一些被研究的有机铁酸盐还会与有机（拟）卤化物R'X（R' = Et、Pr、Bu、Ph、p-Tol；X = Cl、Br、I、OTf）反应，生成RFeR'类型的杂配配合物。这些配合物中的大多数在气相中的碎片化会导致偶联产物RR'（或者R）的还原消除。这一发现表明，铁催化的交叉偶联反应可能通过这种杂配有机铁酸盐RFeR'作为中间体进行。其他有机铁酸盐配合物的气相碎片化会导致β-氢消除、芳烃的损失以及有机自由基的排出。单电子和双电子过程的发生与先前的观察结果一致，并且导致了有机铁化学极其复杂的情况。
