Dinitrogen Reduction to Ammonium at Rhenium Utilizing Light and Proton-Coupled Electron Transfer
Dinitrogen Reduction to Ammonium at Rhenium Utilizing Light and Proton-Coupled Electron Transfer
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DOI：
10.1021/jacs.9b10031
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发表时间：
2019-12-25
影响因子：
15
通讯作者：
Miller, Alexander J. M.
中科院分区：
文献类型：
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作者：
Bruch, Quinton J.;Connor, Gannon P.;Miller, Alexander J. M.
金属配合物直接切断二氮（N-2）的三键是分子催化中N-2转化为氨（NH3）的一个诱人的切入点。本文报道了一种钳结铼体系，该体系通过一系列明确的反应将N-2还原为NH3，包括桥接N-2络合物的还原形成、N-2光解分裂和金属氮键的质子耦合电子转移（PCET）还原。新的配合物（PONOP）ReCl3 （PONOP = 2,6-二（二异丙基膦）吡啶）在N-2下还原得到双金属配合物RPONOP)ReCl2 [2]（u-N-2）的反式、反式异构体，作为可分离的动力学产物，加热后依次异构为反式、顺式和顺式、顺式异构体。所有的同分异构体对N-2的热裂解都是惰性的，反式、反式同分异构体对N-2的光解裂解也是惰性的。与此形成鲜明对比的是，蓝光（405 nm）照射反式、顺式和顺式、顺式异构体时，八面体氮化物配合物顺式-(PONOP)Re(N)Cl-2的光谱产率为47%，量子产率为11%。光子能量驱动N-2分裂反应，这在标准条件下热力学上是不利的，产生氮化物配合物，与SmI2/H2O反应生成四氢化铼配合物（产率38%），并以74%的产率提供氨。
The direct scission of the triple bond of dinitrogen (N-2) by a metal complex is an alluring entry point into the transformation of N-2 to ammonia (NH3) in molecular catalysis. Reported herein is a pincer-ligated rhenium system that reduces N-2 to NH3 via a well-defined reaction sequence involving reductive formation of a bridging N-2 complex, photolytic N-2 splitting, and proton-coupled electron transfer (PCET) reduction of the metal nitride bond. The new complex (PONOP)ReCl3 (PONOP = 2,6-bis(diisopropylphosphinito)pyridine) is reduced under N-2 to afford the trans,trans-isomer of the bimetallic complex RPONOP)ReCl2](2)(mu-N-2) as an isolable kinetic product that isomerizes sequentially upon heating into the trans,cis and cis,cis isomers. All isomers are inert to thermal N-2 scission, and the trans,trans-isomer is also inert to photolytic N-2 cleavage. In striking contrast, illumination of the trans,cis and cis,cis-isomers with blue light (405 nm) affords the octahedral nitride complex cis-(PONOP)Re(N)Cl-2 in 47% spectroscopic yield and 11% quantum yield. The photon energy drives an N-2 splitting reaction that is thermodynamically unfavorable under standard conditions, producing a nitrido complex that reacts with SmI2/H2O to produce a rhenium tetrahydride complex (38% yield) and furnish ammonia in 74% yield.