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首页> 外文期刊>Chemistry: A European journal >Can [M(H)(2)(H-2)(PXP)] pincer complexes (M = Fe, Ru, Os; X = N, O, S) serve as catalyst lead structures for NH3 synthesis from N-2 and H-2?
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Can [M(H)(2)(H-2)(PXP)] pincer complexes (M = Fe, Ru, Os; X = N, O, S) serve as catalyst lead structures for NH3 synthesis from N-2 and H-2?

机译：[M（H）（2）（H-2）（PXP）]钳形配合物（M = Fe，Ru，Os; X = N，O，S）是否可以用作由N-2和H-2？

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The potential of pincer complexes [M(H)(2)(H-2)(PXP)] (M=Fe, Ru, Os; X=N, O, S) to coordinate, activate, and thus catalyze the reaction of N-2 with classical or nonclassical hydrogen centers present at the metal center, with the aim of forming NH3 with H-2 as the only other reagent, was explored by means of DF (density functional) calculations. Screening of various complexes for their ability to perform initial hydrogen transfer to coordinated N-2 showed ruthenium pincer complexes to be more promising than the corresponding iron and osmium analogues. The ligand backbone influences the reaction dramatically: the presence of pyridine and thioether groups as backbones in the ligand result in inactive and result in unprecedented low activation barriers (23.7 and 22.1 kcal mol(-1), respectively), low enough to be interesting for practical application. Catalytic cycles were calculated for [Ru(H)(2)(H-2)(POP)] catalysts (POP= 2,5-bis(dimethylphosphanylmethyl)furan and 2,6-bis(dimethylphosphanylmethyl)-gamma-pyran). The height of activation barriers for the furan system is somewhat more advantageous. Formation of inactive metal nitrides has not been observed. SCRF calculations were used to introduce solvent (toluene) effects. The Gibbs free energies of activation of the numerous single reaction steps do not change significantly when solvent is included. The reaction steps associated with the formation of the active catalyst from precursors [M(H)(2)(H-2)(PXP)] were also calculated. The otherwise inactive pyridine ligand system allows for the generation of the active catalyst species, whereas the ether ligand systems show activation barriers that could prohibit practical application. Consequently the generation of the active catalyst species needs to be addressed in further studies.
机译：钳形复合物[M（H）（2）（H-2）（PXP）]（M = Fe，Ru，Os; X = N，O，S）协调，激活并催化C反应的潜力通过DF（密度泛函）计算，探索了在金属中心存在经典氢原子或非经典氢原子的N-2，目的是用H-2作为唯一的其他试剂形成NH3。筛选各种复合物以完成将氢初始转移至配位的N-2的能力，显示钌钳形复合物比相应的铁和类似物更有希望。配体主链极大地影响了反应：吡啶和硫醚基团作为主链在配体中的存在导致无活性并导致空前的低活化势垒（分别为23.7和22.1 kcal mol（-1）），其低到足以引起人们的兴趣实际应用。计算了[Ru（H）（2）（H-2）（POP）]催化剂（POP = 2,5-双（二甲基膦基甲基）呋喃和2,6-双（二甲基膦基甲基）-γ-吡喃）的催化循环。呋喃系统的活化屏障的高度在某种程度上更有利。尚未观察到形成惰性金属氮化物。 SCRF计算用于引入溶剂（甲苯）效应。当包括溶剂时，许多单个反应步骤的活化的吉布斯自由能没有明显改变。还计算了与由前体[M（H）（2）（H-2）（PXP）]形成活性催化剂相关的反应步骤。否则为非活性的吡啶配体系统可生成活性催化剂，而醚配体系统则显示出可能阻碍实际应用的活化障碍。因此，需要在进一步的研究中解决活性催化剂种类的产生。

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