可溶性铁-氧-钾组装体与 N 2 的反应有助于深入了解多金属 N 2配位的机制。我们报告了一系列非常富电子的三配位、β-二酮亚胺负载的苯酚铁 ( I ) 络合物,它们是亚稳态的,但已通过晶体学和溶液方法在 Ar 下表征。单体和二聚体 Fe-OPh-K 化合物都已被表征,它们的铁环境在固体和溶液状态下非常相似。在二聚体中,钾离子将两半的苯氧基氧和芳环结合在一起,形成灵活的二铁核。单体和二聚铁( I )化合物与N 2 的反应惊人的不同:单核铁(I)配合物不与 N 2反应,但二聚体 Fe 2 K 2 配合物迅速反应生成二铁-N 2产物。计算研究表明,二聚体快速N 2反应的关键是两个铁原子的预组织。因此,Fe(削弱N-N 键)和K(使Fe 原子定向)之间的合作可用于为N 2反应创建低能量途径。
Ligand Dependence of Binding to Three-Coordinate Fe(II) Complexes
摘要:
A series of three- and four-coordinate iron(II) complexes with nitrogen, chlorine, oxygen, and sulfur ligands is presented. The electronic variation is explored by measuring the association constant of the neutral ligands and the reduction potential of the iron(II) complexes. Varying the neutral ligand gives large changes in K-eq, which decrease in the order (CNBu)-Bu-t > pyridine > 2-picoline > DMF > MeCN > THF > PPh3. These differences can be attributed to a mixture of steric effects and electronic effects (both sigma-donation and pi-backbonding). The binding constants and the reduction potentials are surprisingly insensitive to changes in an anionic spectator ligand. This suggests that three-coordinate iron(II) complexes may have similar binding trends as proposed three-coordinate iron(II) intermediates in the FeMoco of nitrogenase, even though the anionic spectator ligands in the synthetic complexes differ from the sulfides in the FeMoco.