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Modular O- vs. N-coordination of pyridylidene amide ligands to iron determines activity in alcohol oxidation catalysis
Dalton Transactions ( IF 3.5 ) Pub Date : 2020-11-02 , DOI: 10.1039/d0dt02818e Dide G. A. Verhoeven 1, 2, 3, 4 , Martin Albrecht 1, 2, 3, 4
Dalton Transactions ( IF 3.5 ) Pub Date : 2020-11-02 , DOI: 10.1039/d0dt02818e Dide G. A. Verhoeven 1, 2, 3, 4 , Martin Albrecht 1, 2, 3, 4
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A family of polydentate pyridine-substituted pyridylidene amide (PYA) complexes bound to iron(II) was developed. The variation of the coordination set from NN-bidentate PYA to tridentate pincer-type pyPYA2 systems (pyPYA2 = 2,6-bis(PYA)pyridine) had a large influence on the binding mode to iron(II), including a change from the N- to rare O-coordination of the PYA site and a concomitant shift of the predominant ligand resonance structure. These binding mode variations invoke changes in the reactivity of the complexes, which were probed in the peroxide-mediated oxidation of 1-phenylethanol to acetophenone. A comparison with uncomplexed FeCl2 indicated that bidentate NN coordination is unstable and presumably leads to the dissociation of FeCl2. In contrast, the tridentate ligand binding is robust. Remarkably, the tridentate PYA pincer coordination inhibits catalytic activity in the NNN binding mode, while the ONO coordination greatly enhances catalytic performance. Under optimized conditions, the bis-ligated ONO pincer iron complex [Fe(pyPYA2)2][2PF6] reaches full conversion within one hour (0.5 mol% catalyst loading) and under dilute conditions turnover numbers over 20 000 (0.005 mol% catalyst loading).
中文翻译：
亚吡啶酰胺配体与铁的模块化O-N配位决定了醇氧化催化的活性
开发了与铁（II）结合的多齿吡啶取代的亚吡啶基酰胺（PYA）配合物。从NN双齿PYA到三齿钳型pyPYA 2系统（pyPYA 2 = 2,6-bis（PYA）吡啶）的配位集变化对与铁（II）的结合方式有很大影响，包括变化从PYA位点的N-到罕见的O-配位，以及主要的配体共振结构的伴随位移。这些结合方式的变化引起复合物反应性的变化，这是在过氧化物介导的1-苯基乙醇氧化为苯乙酮中进行的。与未络合的FeCl 2的比较指出双齿NN配位不稳定，可能导致FeCl 2的离解。相反，三齿配体结合牢固。值得注意的是，三齿PYA钳形配位会抑制NNN结合模式下的催化活性，而ONO配位会大大增强催化性能。在优化条件下，双连接的ONO夹铁配合物[Fe（pyPYA 2）2 ] [2PF 6 ]在1小时内（催化剂负载量为0.5 mol％）达到完全转化，在稀薄条件下，周转量超过20000（0.005 mol％）催化剂负载量）。
更新日期：2020-11-25
中文翻译：
亚吡啶酰胺配体与铁的模块化O-N配位决定了醇氧化催化的活性
开发了与铁（II）结合的多齿吡啶取代的亚吡啶基酰胺（PYA）配合物。从NN双齿PYA到三齿钳型pyPYA 2系统（pyPYA 2 = 2,6-bis（PYA）吡啶）的配位集变化对与铁（II）的结合方式有很大影响，包括变化从PYA位点的N-到罕见的O-配位，以及主要的配体共振结构的伴随位移。这些结合方式的变化引起复合物反应性的变化，这是在过氧化物介导的1-苯基乙醇氧化为苯乙酮中进行的。与未络合的FeCl 2的比较指出双齿NN配位不稳定，可能导致FeCl 2的离解。相反，三齿配体结合牢固。值得注意的是，三齿PYA钳形配位会抑制NNN结合模式下的催化活性，而ONO配位会大大增强催化性能。在优化条件下，双连接的ONO夹铁配合物[Fe（pyPYA 2）2 ] [2PF 6 ]在1小时内（催化剂负载量为0.5 mol％）达到完全转化，在稀薄条件下，周转量超过20000（0.005 mol％）催化剂负载量）。
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