Reversible PCET and Ambient Catalytic Oxidative Alcohol Dehydrogenation by {V=O} Perfluoropinacolate Complexes
Reversible PCET and Ambient Catalytic Oxidative Alcohol Dehydrogenation by {V=O} Perfluoropinacolate Complexes
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DOI：
10.1021/acs.inorgchem.0c02367
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发表时间：
2020-11-16
影响因子：
4.6
通讯作者：
Doerrer, Linda H.
中科院分区：
文献类型：
--
作者：
Elinburg, Jessica K.;Carter, Samantha L.;Doerrer, Linda H.
研制了一种新型空气稳定型苄醇氧化脱氢催化剂。本文报道了该化合物以及相关的单体和二聚体V（IV）-和V（V）-pinF（pinF =全氟频哪醇盐）络合物的合成和表征。在环境条件下，在水中制备单体V（IV）络合物（Me 4 N）（2）[V（O）（pinF）（2）]（1）和二聚（mu-O）（2）-桥接的V（V）络合物（Me 4 N）（2）[V-2（O）（2）（mu-O）（2）（pinF）（2）]（3a）。单体V（V）络合物（Me 4 N）[V（O）（pinF）（2）]（2）可以通过1在惰性气氛下的化学氧化产生，但在暴露于空气时二聚为3a。配合物1和2在20 mV（vsAg/AgNO 3）处表现出完全可逆的VIV/V电对，而3a在-865 mV处表现出准可逆的VIV/V电对。3a与芴醇和TEMPOH的化学计量反应导致形成（Me 4 N）（2）[V-2（O）（2）（mu-OH）（2）（pinF）（2）]（4a），其包含两个显示反铁磁耦合的V（IV）中心。为了表征4a的双核阴离子的结构，使用了{K（18 C6）}（+）抗衡阳离子，其在抗衡阳离子与每个末端氧代部分之间形成稳定的K中心点O相互作用以及冠醚的氧原子与二聚体的μ-OH桥之间形成H-键，得到{K（18 C6）}（2）[V-2（O）（2）（μ OH）（2）（pinF）（2）]（4 b）。H-2在4a中的形式存储是可逆的，并且在暴露于空气中几天后，来自4a的晶体的质子耦合电子转移（PCET）使3a再生。此外，在环境条件下，3a（2%）与过量的芴醇、肉桂醇或苯甲醇反应，导致选择性地形成芴酮（82%转化率）、肉桂醛（40%）或苯甲醛（7%），再现了VOx表面已知的氧化醇脱氢（OAD）化学，并证明，在空气中，具有挑战性的选择性氧化醇为醛/酮。
A new air-stable catalyst for the oxidative dehydrogenation of benzylic alcohols under ambient conditions has been developed. The synthesis and characterization of this compound and the related monomeric and dimeric V(IV)-and V(V)-pinF (pinF = perfluoropinacolate) complexes are reported herein. Monomeric V(IV) complex (Me4N)(2)[V(O)(pinF)(2)] (1) and dimeric (mu-O)(2)-bridged V(V) complex (Me4N)(2)[V-2(O)(2)(mu-O)(2)(pinF)(2)] (3a) are prepared in water under ambient conditions. Monomeric V(V) complex (Me4N)[V(O)(pinF)(2)] (2) may be generated via chemical oxidation of 1 under an inert atmosphere, but dimerizes to 3a upon exposure to air. Complexes 1 and 2 display a perfectly reversible VIV/V couple at 20 mV (vs Ag/AgNO3), whereas a quasi-reversible VIV/V couple at-865 mV is found for 3a. Stoichiometric reactions of 3a with both fluorenol and TEMPOH result in the formation of (Me4N)(2)[V-2(O)(2)(mu-OH)(2)(pinF)(2)] (4a), which contains two V(IV) centers that display antiferromagnetic coupling. In order to structurally characterize the dinuclear anion of 4a, {K(18C6)}(+) countercations were employed, which formed stabilizing K center dot center dot center dot O interactions between the counterion and each terminal oxo moiety and H-bonding between the oxygen atoms of the crown ether and mu-OH bridges of the dimer, resulting in {K(18C6)}(2)[V-2(O)(2)(mu OH)(2)(pinF)(2)] (4b). The formal storage of H-2 in 4a is reversible and proton-coupled electron transfer (PCET) from crystals of 4a regenerates 3a upon exposure to air over the course of several days. Furthermore, the reaction of 3a (2%) under ambient conditions with excess fluorenol, cinnamyl alcohol, or benzyl alcohol resulted in the selective formation of fluorenone (82% conversion), cinnamaldehyde (40%), or benzaldehyde (7%), respectively, reproducing oxidative alcohol dehydrogenation (OAD) chemistry known for VOx surfaces and demonstrating, in air, the thermodynamically challenging selective oxidation of alcohols to aldehydes/ketones.