Low-Spin Pseudotetrahedral Iron(I) Sites in Fe_2(μ-S) Complexes

摘要

Fe^I centers in iron–sulfide complexes have little precedent in synthetic chemistry despite a growing interest in the possible role of unusually low valent iron in metalloenzymes that feature iron–sulfur clusters. A series of three diiron [(L_3Fe)_2(μ-S)] complexes that were isolated and characterized in the low-valent oxidation states Fe^(II) S Fe^(II), Fe^(II) S Fe^I, and Fe^I S Fe^I is described. This family of iron sulfides constitutes a unique redox series comprising three nearly isostructural but electronically distinct Fe_2(μ-S) species. Combined structural, magnetic, and spectroscopic studies provided strong evidence that the pseudotetrahedral iron centers undergo a transition to low-spin S=1/2 states upon reduction from Fe^(II) to Fe^I. The possibility of accessing low-spin, pseudotetrahedral Fe^I sites compatible with S^(2−) as a ligand was previously unknown.