Reactivity of CO2 Activated on Transition Metals and Sulfur Ligands
Reactivity of CO2 Activated on Transition Metals and Sulfur Ligands
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CO2 在过渡金属和硫配体上活化的反应性
DOI：
10.1021/ic502745u
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发表时间：
2015
影响因子：
4.6
通讯作者：
Koji Tanaka
中科院分区：
文献类型：
--
作者：
Katsuaki Kobayashi;Koji Tanaka
二羰基二阳离子[Ru（bpy）2（CO）2]2+（bpy = 2，2 ′-bipyridine）与[Ru（bpy）2（CO）（COOH）]+和[Ru（bpy）2（CO）（CO2）] 0的平衡混合物取决于水溶液的pH。这三种配合物分别作为CO、HCOOH生产和CO2载体的前体，在水溶液中进行电和光化学CO2还原。然而，[Ru（bpy）2（CO）2]2+在非质子条件下失去了对CO2还原的催化活性，因为在没有质子源的情况下[Ru（bpy）2（CO）2]2+不能从[Ru（bpy）2（CO）（CO2）] 0中再生.类似的单羰基钌配合物如[Ru（tpy）（bpy）（CO）]2+和[Ru（bpy）2（qu）（CO）]2+在不存在和存在质子源的情况下催化CO2还原。两种配合物在CO2还原反应中均通过氧化物从Ru-CO2向CO2的转移而再生，并在不存在质子供体的情况下产生相同量的CO和CO 32-.在质子源的存在下，由多吡啶基钌络合物催化的CO2的还原通过与钌络合物的情况基本上类似的机理发生。另一方面，在非质子条件下CO2还原中的CO释放归因于CO从二聚Re-C（O）OC（O）O-Re骨架上的解离。以[Ru（bpy）2（CO）2]2+/[Ru（bpy）3]2+/Me 2NH 2 +/Me 2NH为催化剂、光敏剂、质子给体和亲核试剂和电子给体组成的催化体系，在可见光照射下，在CO2饱和的CH 3CN中选择性地生成N，N-二甲基甲酰胺，而不伴随CO和HCOOH的生成.结构稳定的还原金属硫簇合物μ3-S为CO2的还原活化提供了合适的位点，同时保留了骨架。事实上，在[Fe 6 Mo 2S 8（SEt）3]5-的μ3-S上活化的CO2被固定在被捕获在簇合物的相邻铁上的硫酯的羰基碳上，并且催化产生α-酮酸。此外，[（CpMen）3 M3 S3]2+（n= 1，M = Co;n= 5，M = Rh，Ir）的双电子还原通过两个可能在μ3-S上活化的CO2分子与金属离子偶联产生草酸盐的催化能力。
Dicationic dicarbonyl [Ru(bpy)2(CO)2]2+(bpy = 2,2′- bipyridyl) exists as equilibrium mixtures with [Ru(bpy)2(CO)(COOH)]+and [Ru(bpy)2(CO)(CO2)]0depending on the pH in H2O. Those three complexes work as the precursors to CO, HCOOH production, and CO2carrier, respectively, in electro- and photochemical CO2reduction in aqueous solutions. However, [Ru(bpy)2(CO)2]2+loses the catalytic activity toward CO2reduction under aprotic conditions because [Ru(bpy)2(CO)2]2+is not regenerated from [Ru(bpy)2(CO)(CO2)]0in the absence of proton sources. Analogous monocarbonylruthenium complexes such as [Ru(tpy)(bpy)(CO)]2+and [Ru(bpy)2(qu)(CO)]2+catalyze CO2reduction in the absence and presence of proton sources. Both complexes are reproduced through oxide transfer from the corresponding Ru–CO2to CO2in CO2reduction and produce the same amount of CO and CO32–in the absence of proton donors. The reduction of CO2catalyzed by polypyridylrhenium complexes in the presence of proton sources takes place via essentially the similar mechanism as that in the case of ruthenium complexes. On the other hand, CO evolution in CO2reduction under aprotic conditions is ascribed to the dissociation of CO from a dimeric Re–C(O)OC(O)O–Re scaffold. Visible-light irradiation to a catalytic system composed of [Ru(bpy)2(CO)2]2+/[Ru(bpy)3]2+/Me2NH2+/Me2NH as the catalyst, photosensitizer, proton donor, and nucleophile in addition to the electron donor, respectively, in CO2-saturated CH3CN selectively producesN,N-dimethylformamide without concomitant CO and HCOOH formation. Structurally robust μ3-S of reduced metal–sulfur clusters provides a suitable site for reductive activation of CO2with retention of the framework. Indeed, CO2activated on μ3-S of [Fe6Mo2S8(SEt)3]5–is fixed at the carbonyl carbon of thioesters trapped on a neighboring iron of the cluster, and α-keto acids are produced catalytically. Furthermore, two-electron reduction of [(CpMen)3M3S3]2+(n= 1, M = Co;n= 5, M = Rh, Ir) creates the catalytic ability to produce oxalate through the coupling of two CO2molecules possibly activated on μ3-S and a metal ion.