Fink Cornel, Laurenczy Gábor
École Polytechnique Fédérale de Lausanne, EPFL, ISIC, LCOM Lausanne, Switzerland.
Dalton Trans. 2017 Jan 31;46(5):1670-1676. doi: 10.1039/c6dt04638j.
The homogeneous catalytic dehydrogenation of formic acid in aqueous solution provides an efficient in situ method for hydrogen production, under mild conditions, and at an adjustable rate. We synthesized a series of catalysts with the chemical formula [(Cp*)M(N-N')Cl] (M = Ir, Rh; Cp* = pentamethylcyclopentadienyl; N-N = bidentate chelating nitrogen donor ligands), which have been proven to be active in selective formic acid decomposition in aqueous media. The scope of the study was to examine the relationship between stability and activity of catalysts for formic acid dehydrogenation versus electronic and steric properties of selected ligands, following a bottom-up approach by increasing the complexity of the N,N'-ligands progressively. The highest turnover frequency, TOF = 3300 h was observed with a Cp*Ir(iii) complex bearing 1,2-diaminocyclohexane as the N,N'-donor ligand. From the variable temperature studies, the activation energy of formic acid dehydrogenation has been determined, E = 77.94 ± 3.2 kJ mol. It was observed that the different steric and electronic properties of the bidentate nitrogen donor ligands alter the catalytic activity and stability of the Ir and Rh compounds profoundly.
甲酸在水溶液中的均相催化脱氢反应提供了一种在温和条件下以可调节速率高效原位制氢的方法。我们合成了一系列化学式为[(Cp*)M(N-N')Cl]的催化剂（M = Ir、Rh；Cp* = 五甲基环戊二烯基；N-N = 双齿螯合氮供体配体），这些催化剂已被证明在水性介质中对甲酸分解具有活性。该研究的范围是通过逐步增加N,N'-配体的复杂性，采用自下而上的方法，研究甲酸脱氢催化剂的稳定性和活性与所选配体的电子和空间性质之间的关系。以1,2-二氨基环己烷作为N,N'-供体配体的Cp*Ir(iii)配合物观察到最高的周转频率，TOF = 3300 h⁻¹。通过变温研究，确定了甲酸脱氢的活化能，E = 77.94 ± 3.2 kJ mol⁻¹。观察到双齿氮供体配体的不同空间和电子性质深刻地改变了Ir和Rh化合物的催化活性和稳定性。
