Low-Valent Cobalt(I) CNC Pincer Complexes as Catalysts for Light-Driven Carbon Dioxide Reduction
Low-Valent Cobalt(I) CNC Pincer Complexes as Catalysts for Light-Driven Carbon Dioxide Reduction
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低价钴 (I) CNC Pincer 配合物作为光驱动二氧化碳还原的催化剂
DOI：
10.1021/acscatal.2c01281
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发表时间：
2022
期刊：
影响因子：
12.9
通讯作者：
Delcamp, Jared H.
中科院分区：
文献类型：
--
作者：
Boudreaux, Chance M.;Nugegoda, Dinesh;Yao, Wenzhi;Le, Nghia;Frey, Nathan C.;Li, Qing;Qu, Fengrui;Zeller, Matthias;Webster, Charles Edwin;Delcamp, Jared H.
光催化CO2还原反应（PCO 2 RR）需要基于丰富金属的耐用催化剂。因此，我们合成了一系列低价钴（I）配合物，[（CNC）Co（CO）2]+[Co（CO）4]-，其中H（1Co-）或OMe（2Co-）位于吡啶基N供体基团的4-位（其中CNC = L1和L2来自[CNC]2+前配体的双去质子化L1（HOTf）2= 1，1 ′-L2（HOTf）2= 1，1 ′-（4-甲氧基吡啶-2，6-二基）双（3-甲基-1H-咪唑-3-鎓）二三氟甲磺酸盐）。[BArF 24]−（四（3，5-三氟甲基）苯基）硼酸盐）的阴离子交换生成1和2，膦取代生成结构为[（CNC）Co（CO）（PR′3）]+[BArF 24]−的1 PMe 3、1 PPh 3和2 PPh 3配合物。在1DPPP中，DPPP配体桥接两个Co（I）中心（DPPP = 1，3-双（二苯基膦基）丙烷）。所有的配合物进行了充分的特点，和电化学测量表明，对于大多数的膦配合物，CO2结合的复杂发生之前，由于一个空的协调位点的减少。有趣的是，膦配体的引入导致了从三角双锥到四方锥的几何形状的变化，这与CO2与络合物的预缔合和PCO 2 RR中更高的反应性相关。配合物1，1 PMe 3，1 PPh 3，1DPPP，2，2 PPh 3和Na[Co（CO）4]是具有甲氧基取代基失活和膦配体活化的PCO 2 RR催化剂。在单齿膦催化剂1 PPh 3（1 μM）中，转化频率（TOFM= 3.9 h-1）和转化数（TON = 199）最高。双核1DPPP配合物是最具活性和稳定性的催化剂，在1 μM负载量下，TON = 278，TOF = 21.1 h-1。在稀释条件下（1 nM），1 PPh 3在6天内产生高达36，000 TON，TOF = 10800 h-1，这表明这是一种持久的分子催化剂，在PCO 2 RR中以快速速率起作用。因此，稳定低价钴可以为高活性PCO 2 RR催化剂提供独特的切入点。虽然钴（I）已被提出作为催化物质，但以前没有制备过从Co（I）开始的催化剂，并且膦共配体的使用使得这些催化剂实现高活性。
Durable catalysts based on abundant metals are needed for the photocatalytic CO2reduction reaction (PCO2RR). Thus, we synthesized a series of low-valent cobalt(I) complexes, [(CNC)Co(CO)2]+[Co(CO)4]−, with H (1Co-) or OMe (2Co-) in the 4-position of the pyridyl N donor group (where CNC =L1andL2from double deprotonation of the [CNC]2+preligandsL1(HOTf)2= 1,1′-(pyridine-2,6-diyl)bis(3-methyl-1H-imidazol-3-ium) ditriflate andL2(HOTf)2= 1,1′-(4-methoxypyridine-2,6-diyl)bis(3-methyl-1H-imidazol-3-ium) ditriflate). Anion exchange for [BArF24]−(tetrakis(3,5-trifluoromethyl)phenyl)borate) produced1and2and phosphine substitution produced1PMe3,1PPh3, and2PPh3complexes with the structure [(CNC)Co(CO)(PR′3)]+[BArF24]−. In1DPPP, the DPPP ligand bridges two Co(I) centers (DPPP = 1,3-bis(diphenylphosphino)propane). All complexes were fully characterized, and electrochemical measurements suggest that for most of the phosphine complexes, CO2binding by the complex occurs prior to reduction due to a vacant coordination site. Intriguingly, the introduction of a phosphine ligand resulted in a geometry change from trigonal bipyramidal to square pyramidal which correlates to preassociation of CO2to the complex and higher reactivity in the PCO2RR. Complexes1,1PMe3,1PPh3,1DPPP,2,2PPh3, and Na[Co(CO)4] are PCO2RR catalysts with a methoxy substituent deactivating and a phosphine ligand activating. With monodentate phosphines, catalyst1PPh3(1 μM) had the highest turnover frequency (TOFM= 3.9 h–1) and turnover number (TON = 199). The dinuclear1DPPPcomplex was the most active and robust catalyst with TON = 278 and TOF = 21.1 h–1at 1 μM loading. Under dilute conditions (1 nM),1PPh3produced up to 36,000 TON with TOF = ∼800 h–1over 6 days, which shows that this is a durable molecular catalyst acting with fast rates in the PCO2RR. Thus, stabilizing low-valent cobalt can offer a unique entry point to highly active PCO2RR catalysts. While cobalt(I) has been proposed as a catalytic species, catalysts that start from Co(I) have not been made previously and the use of phosphine co-ligands has allowed these catalysts to achieve high activity.