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Noninnocent Ligand in Rhodium(III)-Complex-Catalyzed C–H Bond Amination with Tosyl Azide
Inorganic Chemistry ( IF 4.6 ) Pub Date : 2018-05-17 00:00:00 , DOI: 10.1021/acs.inorgchem.8b00289
Daiki Fujita 1 , Hideki Sugimoto 1 , Yuma Morimoto 1 , Shinobu Itoh 1
Affiliation  

Six-coordinate rhodium(III) complexes coordinated by a planar trianionic ligand (L3–) are synthesized. One of the axial positions is occupied by chloride (Cl), bromide (Br), or iodide (I), and another axial position is coordinated by a solvent molecule such as acetonitrile (AN), water (H2O), tetrahydrofuran (THF), or pyridine (PY) to complete an octahedral rhodium(III) center; [RhIII(L3–)(X)(Y)] (1X/Y; X = Cl, Br, or I, Y = AN, H2O, THF, or PY). Coordination of the AN, H2O, and THF ligands to the metal center is rather weak, so that these solvent molecules are easily replaced by PY to give [RhIII(L3–)(Cl)(PY)]. In the electrochemical measurements, all complexes have two reversible redox couples based on the ligand-centered oxidation L3– to L•2– and to L, as reflected by the very similar redox potentials regardless of the different axial ligands. The rhodium(III) complexes catalyze C–H bond amination of xanthene with tosyl azide (TsN3). Because the yields of the aminated product are nearly the same among the complexes, replacement of the axial solvent ligands with TsN3 readily occurs to give a nitrene-radical-bound rhodium(III) complex, [RhIII(L•2–)(NTs)(X)], as an active oxidant, which is generated by one-electron transfer from the trianionic L3– to the nitrene nitrogen atom. Generation of such a diradical intermediate was substantiated by the direct reaction of 1Cl/AN with TsN3 in the absence of the substrate (xanthene). In this case, a rhodium(III) iminosemiquinone complex, 2, was generated by the intramolecular reaction between the nitrene-radical moiety and the radical moiety of the ligand L•2–.

中文翻译:

铑(III)络合物催化的甲苯磺酰基叠氮化物的非纯配体

合成了由平面三阴离子配体(L 3–)配位的六配位铑(III)配合物。一轴向位置的是通过酰氯(CL占用- ),溴(溴- ),或碘化物(I - ),和另一轴向位置由一个溶剂分子配位,如乙腈(AN),水(H 2 O) ,四氢呋喃(THF)或吡啶(PY)来完成八面体铑(III)中心; 的[Rh III(L 3- )(X)(Y)] - 1 X / Y ; X =氯- ,溴- ,或I -,Y = AN,H 2 O,THF,或PY)。AN,H 2的配位O和金属中心的THF配体很弱,因此这些溶剂分子很容易被PY取代,得到[Rh III(L 3–)(Cl)(PY)] -。在电化学测量中,所有络合物都有两个基于配体中心氧化L 3–到L •2–和L –的可逆氧化还原对,这反映了非常相似的氧化还原电位,而与轴向配体不同。铑(III)配合物催化x吨与叠氮化甲苯磺酰基(TsN 3)的C–H键胺化。由于络合物之间胺化产物的产率几乎相同,因此用TsN 3代替轴向溶剂配体容易发生与氮原子自由基键合的铑(III)络合物[Rh III(L •2–)(N Ts)(X)] -的活性氧化剂,它是通过从三阴离子L 3–到亚硝基氮原子。在不存在底物(x吨)的情况下,1 Cl / AN与TsN 3的直接反应证实了这种双自由基中间体的产生。在这种情况下,铑(III)亚氨基半醌络合物2是通过配体L •2-的氮原子-自由基部分与自由基部分之间的分子内反应生成的。
更新日期:2018-05-17
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