Department of Chemistry, North Carolina State University, Raleigh, 27695-8204, USA.
Dalton Trans. 2011 Nov 28;40(44):11815-21. doi: 10.1039/c1dt11143d. Epub 2011 Oct 4.
The detailed syntheses of complexes 1-4, Re(O)(X)(DAP) (X = Me, 1; Cl, 2; I, 3; OTf (triflate), 4) incorporating the diamido pyridine (DAP) ancillary ligand (2,6-bis((mesitylamino)methyl)pyridine) are described and shown to be effective catalysts for oxygen atom transfer (OAT) reactions of PyO to PPh(3). The catalytic activities are as follows: 4≈3 > 2 > 1. The observed electronic trend is consistent with the turnover limiting reduction of the proposed Re(VII) dioxo intermediate, Re(O)(2)(X)(DAP), during the catalytic cycle. The catalytic activity of complexes 1-3 was compared to previously published diamido amine (DAAm) oxorhenium complexes of the type Re(O)(X)(DAAm) (X = Me, 5; Cl, 6; I, 7 and DAAm = N,N-bis(2-arylaminoethyl)methylamine) which exhibit hydrolytic degradation during the catalytic reaction. Complexes 1-3 displayed higher turnover frequencies compared to 5-7. This higher catalytic activity was attributed to the more rigid DAP ligand backbone, which makes the complexes less susceptible to decomposition. However, another decomposition pathway was proposed for this catalytic system due to the observation of Re(O)(3)((MesNCH(2))(MesNCH)NC(5)H(3)) 8 in which one arm of the DAP ligand is oxidized.
描述了配合物 1-4 的详细合成，其中 Re(O)(X)(DAP)（X = Me，1；Cl，2；I，3；OTf（三氟甲磺酸根），4）包含二酰胺吡啶（DAP）辅助配体（2,6-双（（mesitylamino）甲基）吡啶），并证明它们是 PyO 到 PPh（3）的氧原子转移（OAT）反应的有效催化剂。催化活性如下：4≈3 > 2 > 1。观察到的电子趋势与催化循环中所提出的 Re(VII)二氧中间物 Re(O)(2)(X)(DAP)的周转限制还原一致。配合物 1-3 的催化活性与之前报道的类型为 Re(O)(X)(DAAm)（X = Me，5；Cl，6；I，7 和 DAAm = N，N-双（2-芳基氨基乙基）甲胺）的二酰胺胺（DAAm）氧化铼配合物进行了比较，这些配合物在催化反应中会发生水解降解。与 5-7 相比，配合物 1-3 显示出更高的周转频率。这种更高的催化活性归因于更刚性的 DAP 配体骨架，这使得配合物不易分解。然而，由于观察到 Re(O)(3)((MesNCH(2))(MesNCH)NC(5)H(3))8，因此提出了另一种用于该催化体系的分解途径，其中 DAP 配体的一个臂被氧化。
