trans-[Fe(DMeOPrPE)2(H2)H]+ and trans-[Fe(DMeOPrPE)2(N2)H]+ (DMeOPrPE = 1,2-bis(dimethoxypropylphosphino)ethane) were synthesized and their structures determined by X-ray crystallography. These complexes are important species in a dinitrogen reduction scheme involving protonation of an iron(0) dinitrogen complex to produce ammonia. The rates of substitution of the coordinated H2 and N2 molecules with acetonitrile were monitored in a variety of organic solvents. The coordinated N2 substituted â¼6 times faster than H2, but surprisingly the solvent had little effect on the observed rates. The results suggest that the H2 molecule in trans-[Fe(DMeOPrPE)2(H2)H]+ does not participate in hydrogen bonding to the bulk solvent, as was previously observed in the analogous Ru complex. The deprotonation of trans-[Fe(DMeOPrPE)2(N2)H]+ to yield Fe(DMeOPrPE)2N2 was investigated in the presence of a variety of anions, and it was found that the anion facilitates the reaction through an ion-pairing interaction in which the anion removes electron density from the hydride ligand.
合成了转- [Fe(
DMeOPrPE)2(H2)H]+ 和转- [Fe(
DMeOPrPE)2(N2)H]+(
DMeOPrPE = 1,2-双(亚甲氧基丙基膦)
乙烯),并通过X射线晶体学确定了其结构。这些配合物在氮气还原反应中具有重要作用,该反应涉及对
铁(0)氮气配合物的质子化以生成
氨。在多种有机溶剂中监测了配位的H2和N2分子与
乙腈的取代速率。结果显示,配位的N2的取代速率约为H2的6倍,但令人惊讶的是,溶剂对观察到的速率几乎没有影响。这些结果表明,转- [Fe(
DMeOPrPE)2(H2)H]+中的H2分子并未与增量溶剂形成氢键,正如在类似的Ru配合物中观察到的那样。研究了转- [Fe(
DMeOPrPE)2(N2)H]+的去质子化反应,生成Fe(
DMeOPrPE)2N2,该反应在多种阴离子存在下进行,结果发现,阴离子通过离子配对相互作用促进反应,其中阴离子从氢化
配体移除电子密度。