非血红素叠氮化铁 (III) 和异硫氰酸铁 (III) 络合物：自由基反弹反应性、选择性和催化作用,Journal of the American Chemical Society

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非血红素叠氮化铁 (III) 和异硫氰酸铁 (III) 络合物：自由基反弹反应性、选择性和催化作用
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2022-11-03 , DOI: 10.1021/jacs.2c07224
Vishal Yadav ₁ , Lyupeng Wen ₁ , Rodolfo J Rodriguez ₁ , Maxime A Siegler ₁ , David P Goldberg ₁

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新的非血红素铁络合物 Fe ^II (BNPA ^Ph2 O)(N ₃ ) ( 1 )、Fe ^III (BNPA ^Ph2 O)(OH)(N ₃ ) ( 2 )、Fe ^II (BNPA ^Ph2 O)(OH) ( 3 )、Fe ^III (BNPA ^Ph2 O)(OH)(NCS) ( 4 )、Fe ^II (BNPA ^Ph2 O)(NCS) ( 5 )、Fe ^III (BNPA ^Ph2 O)(NCS) ₂ ( 6 ) 和 Fe合成了^III (BNPA ^Ph2 O)(N ₃ ) ₂ ( 7 ) (BNPA ^Ph2 O = 2-(双((6-(新戊基氨基)吡啶-2-基)甲基)氨基)-1,1-二苯基乙醇酯)并通过单晶 X 射线衍射 (XRD) 以及¹ H NMR、⁵⁷ Fe 穆斯堡尔和 ATR-IR 光谱进行表征。配合物2与一系列碳自由基Ar ^X₃ C· (Ar ^X = p -XC ₆ H ₄ ) 反应，类似于针对非血红素铁羟化酶和卤化酶提出的自由基反弹步骤。结果表明，对于Ar ^X₃ C· (X = Cl、H、^t Bu)，仅发生OH·转移，得到Ar ^X₃ COH。然而，当X＝OMe时，得到醇(Ar ^X₃ COH)(30％)和叠氮化物(Ar ^X₃ CN _{3 )(40％)产物的混合物。}这些数据表明回弹选择性受到叠氮络合物碳自由基的富电子性质的影响。^{在Sc 3+}或H ⁺存在下，2与Ph ₃ C·的反应逆转了选择性，仅产生叠氮化物产物。与2的混合选择性相反，顺式-Fe ^III (OH)(NCS) 与 X = OMe 自由基衍生物的反应性仅导致羟基化。以1为催化剂，λ ³ -叠氮碘为氧化剂和叠氮化物源，Ph ₃ CH为测试底物，实现催化叠氮化，得到Ph ₃ CN ₃84% (TON = 8)。这些研究表明，对于非血红素铁 (III) 络合物，羟基化比叠氮化更有利，但碳自由基的性质可以改变这种选择性。如果可以避免 OH· 转移途径，则 Fe ^III (N ₃ ) 配合物能够介导化学计量和催化叠氮化。

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Nonheme Iron(III) Azide and Iron(III) Isothiocyanate Complexes: Radical Rebound Reactivity, Selectivity, and Catalysis

The new nonheme iron complexes Fe^II(BNPA^Ph2O)(N₃) (1), Fe^III(BNPA^Ph2O)(OH)(N₃) (2), Fe^II(BNPA^Ph2O)(OH) (3), Fe^III(BNPA^Ph2O)(OH)(NCS) (4), Fe^II(BNPA^Ph2O)(NCS) (5), Fe^III(BNPA^Ph2O)(NCS)₂ (6), and Fe^III(BNPA^Ph2O)(N₃)₂ (7) (BNPA^Ph2O = 2-(bis((6-(neopentylamino)pyridin-2-yl) methyl)amino)-1,1-diphenylethanolate) were synthesized and characterized by single crystal X-ray diffraction (XRD), as well as by ¹H NMR, ⁵⁷Fe Mössbauer, and ATR-IR spectroscopies. Complex 2 was reacted with a series of carbon radicals, Ar^X₃C· (Ar^X = p-X-C₆H₄), analogous to the proposed radical rebound step for nonheme iron hydroxylases and halogenases. The results show that for Ar^X₃C· (X = Cl, H, ^tBu), only OH· transfer occurs to give Ar^X₃COH. However, when X = OMe, a mixture of alcohol (Ar^X₃COH) (30%) and azide (Ar^X₃CN₃) (40%) products was obtained. These data indicate that the rebound selectivity is influenced by the electron-rich nature of the carbon radicals for the azide complex. Reaction of 2 with Ph₃C· in the presence of Sc³⁺ or H⁺ reverses the selectivity, giving only the azide product. In contrast to the mixed selectivity seen for 2, the reactivity of cis-Fe^III(OH)(NCS) with the X = OMe radical derivative leads only to hydroxylation. Catalytic azidation was achieved with 1 as catalyst, λ³-azidoiodane as oxidant and azide source, and Ph₃CH as test substrate, giving Ph₃CN₃ in 84% (TON = 8). These studies show that hydroxylation is favored over azidation for nonheme iron(III) complexes, but the nature of the carbon radical can alter this selectivity. If an OH· transfer pathway can be avoided, the Fe^III(N₃) complexes are capable of mediating both stoichiometric and catalytic azidation.

更新日期：2022-11-03

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