Mechanistic investigation of CO2 hydrogenation by Ru(II) and Ir(III) aqua complexes under acidic conditions:: two catalytic systems differing in the nature of the rate determining step
Mechanistic investigation of CO2 hydrogenation by Ru(II) and Ir(III) aqua complexes under acidic conditions:: two catalytic systems differing in the nature of the rate determining step
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DOI：
10.1039/b607993h
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发表时间：
2006-01-01
影响因子：
4
通讯作者：
Fukuzumi, Shunichi
中科院分区：
文献类型：
--
作者：
Ogo, Seiji;Kabe, Ryota;Fukuzumi, Shunichi
钌水络合物[（eta（6）-C6 Me 6）Ru-II（L）（OH 2）]（2+）{L = bpy（1）和4，4 ′-OMe-bpy（2），bpy = 2，2 ′-联吡啶，4，4 ′-OMe-bpy = 4，4 ′-二甲氧基-2，2 ′-联吡啶}和铱水络合物[Cp* Ir-III（L）（OH 2）]（2+）{Cp* = eta（5）-C5 Me 5，L = bpy（5）和4，4 ′-OMe-bpy（6）}在pH 3.0的水溶液中对CO2加氢生成HCOOH具有催化作用。在用钌配合物氢化CO_2的反应中没有观察到活性氢化物催化剂，而在用铱配合物氢化CO_2后，已成功地分离出活性氢化物催化剂[Cp* Ir-III（L）（H）]（+）{L = bpy（7）和4，4 ′-OMe-bpy（8）}。如动力学研究所示，成功分离活性氢化物催化剂的关键是在CO2的催化氢化中从活性氢化物催化剂[（eta（6）-C6 Me 6）Ru-II（L）（H）]（+）的形成到[Cp* Ir-III（L）（H）]（+）与CO2的反应的速率控制步骤的改变。
Ruthenium aqua complexes [(eta(6)-C6Me6) Ru-II(L)(OH2)](2+) {L = bpy ( 1) and 4,4'-OMe-bpy ( 2), bpy = 2,2'-bipyridine, 4,4'-OMe-bpy = 4,4'-dimethoxy-2,2'-bipyridine} and iridium aqua complexes [Cp* Ir-III(L)(OH2)](2+) {Cp* = eta(5)-C5Me5, L = bpy ( 5) and 4,4'-OMe-bpy (6)} act as catalysts for hydrogenation of CO2 into HCOOH at pH 3.0 in H2O. The active hydride catalysts cannot be observed in the hydrogenation of CO2 with the ruthenium complexes, whereas the active hydride catalysts, [Cp* Ir-III(L)(H)](+) {L = bpy ( 7) and 4,4'- OMe-bpy ( 8)}, have successfully been isolated after the hydrogenation of CO2 with the iridium complexes. The key to the success of the isolation of the active hydride catalysts is the change in the rate-determining step in the catalytic hydrogenation of CO2 from the formation of the active hydride catalysts, [(eta(6)-C6Me6) Ru-II(L)(H)](+), to the reactions of [Cp* Ir-III(L)(H)](+) with CO2, as indicated by the kinetic studies.