Hwang Seung Jun, Powers David C, Maher Andrew G, Nocera Daniel G
Department of Chemistry and Chemical Biology , 12 Oxford Street , Cambridge , MA 02138-2902 , USA . Email:
Department of Chemistry , Massachusetts Institute of Technology , 77 Massachusetts Avenue , Cambridge , MA 02139-4307 , USA.
Chem Sci. 2015 Feb 1;6(2):917-922. doi: 10.1039/c4sc02357a. Epub 2014 Oct 8.
Photoactivation of M-X bonds is a challenge for photochemical HX splitting, particularly with first-row transition metal complexes because of short intrinsic excited state lifetimes. Herein, we report a tandem H photocycle based on combination of a non-basic photoredox phosphine mediator and nickel metal catalyst. Synthetic studies and time-resolved photochemical studies have revealed that phosphines serve as photochemical H-atom donors to Ni(ii) trihalide complexes to deliver a Ni(i) centre. The H evolution catalytic cycle is closed by sequential disproportionation of Ni(i) to afford Ni(0) and Ni(ii) and protolytic H evolution from the Ni(0) intermediate. The results of these investigations suggest that H photogeneration proceeds by two sequential catalytic cycles: a photoredox cycle catalyzed by phosphines and an H-evolution cycle catalyzed by Ni complexes to circumvent challenges of photochemistry with first-row transition metal complexes.
对于光化学HX裂解而言，M-X键的光活化是一项挑战，特别是对于第一排过渡金属配合物，因为其固有激发态寿命较短。在此，我们报道了一种基于非碱性光氧化还原膦介导剂和镍金属催化剂组合的串联H光循环。合成研究和时间分辨光化学研究表明，膦作为光化学氢原子供体与三卤化镍（II）配合物反应，生成Ni（I）中心。通过Ni（I）的顺序歧化生成Ni（0）和Ni（II），以及从Ni（0）中间体进行质子解氢反应，从而完成析氢催化循环。这些研究结果表明，氢的光生成通过两个连续的催化循环进行：一个由膦催化的光氧化还原循环和一个由镍配合物催化的析氢循环，以规避第一排过渡金属配合物光化学的挑战。
