Department of Chemistry, University of Oregon , Eugene, Oregon 97403, United States.
Inorg Chem. 2013 Dec 16;52(24):14178-87. doi: 10.1021/ic402081q. Epub 2013 Nov 20.
The reactivity of Fe(DMeOPrPE)2N2 with water and acid was explored. (DMeOPrPE is the bidentate phosphine 1,2-[bis(dimethoxypropyl)phosphino]ethane.) The complex reacts with acid to form trans-Fe(DMeOPrPE)2(N2)H and small amounts of ammonia and hydrazine. When reacted with H2O, cis-Fe(DMeOPrPE)2(H)2 is formed. To increase the yields of ammonia and hydrazine, we investigated the effect of anion, solvent, and acid addition rate on the yields of ammonia. Of these parameters, only the properties of the anion (i.e., of the acid) had a significant impact on the yields of ammonia. The highest yields of NH3 occurred with the largest/least-coordinating anion (triflate). A short-lived purple intermediate (τ1/2 < 5 s at 23 °C) was observed in the reaction of Fe(DMeOPrPE)2N2 with triflic acid. Because the structure of this purple species could potentially provide valuable insights into the mechanism of ammonia formation, a method was developed for independently synthesizing and stabilizing the complex. Spectroscopic characterization of the purple species identified it as the paramagnetic ((DMeOPrPE)2Fe)2(μ-N2) complex (1). This purple dimer (1) exists in equilibrium with yellow, monomeric, paramagnetic Fe(DMeOPrPE)2N2 (2). The role of 1 in the formation of hydrazine and ammonia was probed by reacting 1 with acid.
探索了 Fe(DMeOPrPE)2N2 与水和酸的反应性。(DMeOPrPE 是双齿膦 1,2-[双(二甲氧基丙基)膦]乙烷。)该配合物与酸反应生成反式-Fe(DMeOPrPE)2(N2)H和少量氨和联氨。当与 H2O 反应时，形成顺式-Fe(DMeOPrPE)2(H)2。为了提高氨和联氨的产率，我们研究了阴离子、溶剂和酸添加速率对氨产率的影响。在这些参数中，只有阴离子（即酸）的性质对氨的产率有显著影响。用最大/最小配位阴离子（三氟甲磺酸根）时，NH3 的产率最高。在 Fe(DMeOPrPE)2N2 与三氟甲磺酸的反应中观察到一种短寿命的紫色中间体（23°C 时半衰期<5 s）。由于这种紫色物种的结构可能为氨形成的机理提供有价值的见解，因此开发了一种独立合成和稳定该配合物的方法。对紫色物种的光谱表征将其鉴定为顺磁性((DMeOPrPE)2Fe)2(μ-N2)配合物（1）。这种紫色二聚体（1）与黄色、单体、顺磁性Fe(DMeOPrPE)2N2（2）处于平衡状态。通过用酸与 1 反应，探究了 1 在肼和氨形成中的作用。
