Institute for Molecular Science, National Institutes of Natural Sciences, Myodaiji, Okazaki 444-8787, Japan.
Inorg Chem. 2013 Aug 19;52(16):9557-66. doi: 10.1021/ic401270j. Epub 2013 Aug 2.
This paper reports preparation, characterization, and reactivity of iodosylarene adducts of a manganese(IV) salen complex. In order to systematically investigate steric and electronic factors that control reactivity and selectivity, we prepared iodosylarene adducts from iodosylbenzene, iodosylmesitylene, 2,4,6-triethyliodosylbenzene, and pentafluoroiodosylbenzene. We also investigated the effect of anions on I(III) by using chloride, benzoate, and p-toluenesulfonate. Spectroscopic studies using (1)H NMR, electron paramagnetic resonance, infrared spectroscopy, and electrospray ionization mass spectrometry show that these iodosylarene adducts are manganese(IV) complexes bearing two iodosylarenes as external axial ligands. Reactions with thioanisole under the pseudo-first-order conditions show that the electron-withdrawing pentafluorophenyl group and the p-toluenesulfonate anion on I(III) significantly accelerate the oxygen-atom transfer. The high reactivity is correlated with a weakened I-OMn bond, as indicated by IR spectroscopy and mass spectrometry. Stoichiometric reactions with styrenes show that both enantioselectivity and diastereoselectivity are dependent on the arenes and anions on I(III) of the coordinate iodosylarenes. Notably, the pentafluorophenyl group and the p-toluenesulfonate anion suppress the cis-to-trans isomerization in the epoxidation of cis-β-methylstyrene. The present results show that iodosylarene adducts of manganese(IV) salen complexes are indeed active oxygen-atom-transfer reagents and that their reactivity and selectivity are regulated by steric and electronic properties of the arenes and anions on I(III) of the coordinated iodosylarenes.
本文报道了锰(IV)salen 配合物碘酰基芳烃加合物的制备、表征和反应性。为了系统地研究控制反应性和选择性的空间和电子因素，我们制备了碘苯、间碘甲苯、2,4,6-三乙基碘苯和五氟碘苯的碘酰基芳烃加合物。我们还研究了阴离子对 I(III)的影响，使用了氯离子、苯甲酸盐和对甲苯磺酸盐。使用 (1)H NMR、电子顺磁共振、红外光谱和电喷雾电离质谱等光谱研究表明，这些碘酰基芳烃加合物是带有两个碘酰基芳烃作为外部轴向配体的锰(IV)配合物。在准一级条件下与硫代苯甲醚的反应表明，吸电子的五氟苯基和对甲苯磺酸盐阴离子在 I(III)上显著加速了氧原子转移。高反应性与 IR 光谱和质谱表明的 I-OMn 键的减弱有关。与苯乙烯的计量反应表明，对映选择性和非对映选择性都取决于碘酰基芳烃上的芳烃和阴离子。值得注意的是，五氟苯基和对甲苯磺酸盐阴离子抑制了 cis-β-甲基苯乙烯环氧化反应中的顺式-反式异构化。目前的结果表明，锰(IV)salen 配合物的碘酰基芳烃加合物确实是活性的氧原子转移试剂，其反应性和选择性受配位碘酰基芳烃上的芳烃和阴离子的空间和电子性质的调节。
