Redox-Noninnocence of the S,S'-Coordinated Ligands in Bis(benzene-1,2-dithiolato)iron Complexes

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• 作者：Kallol Ray ; Eckhard Bill ; Thomas Weyhermü ; ller ; and Karl Wieghardt
• 刊名：Journal of the American Chemical Society
• 出版年：2005
• 出版时间：April 20, 2005
• 年：2005
• 卷：127
• 期：15
• 页码：5641 - 5654
• 全文大小：382K
• 年卷期：v.127,no.15(April 20, 2005)
• ISSN：1520-5126

文摘

The electronic structures of complexes of iron containing two S,S'-coordinated benzene-1,2-dithiolate, (L)^2-, or 3,5-di-tert-butyl-1,2-benzenedithiolate, (L^Bu)^2-, ligands have been elucidated in depthby electronic absorption, infrared, X-band EPR, and Mössbauer spectroscopies. It is conclusively shownthat, in contrast to earlier reports, high-valent iron(IV) (d⁴, S = 1) is not accessible in this chemistry. Instead,the S,S'-coordinated radical monoanions (L)^1- and/or (L^Bu)^1- prevail. Thus, five-coordinate [Fe(L)₂(PMe₃)]has an electronic structure which is best described as [Fe^III(L)(L)(PMe₃)] where the observed triplet groundstate of the molecule is attained via intramolecular, strong antiferromagnetic spin coupling between anintermediate spin ferric ion (S_Fe = ³/₂) and a ligand radical (L)^1- (S_rad = ¹/₂). The following complexescontaining only benzene-1,2-dithiolate(2-) ligands have been synthesized, and their electronic structureshave been studied in detail: [NH(C₂H₅)₃]₂[Fe^II(L)₂] (1), [N(n-Bu)₄]₂[Fe^III₂(L)₄] (2), [N(n-Bu)₄]₂[Fe^III₂(L^Bu)₄] (3);[P(CH₃)Ph₃][Fe^III(L)₂(t-Bu-py)] (4) where t-Bu-py is 4-tert-butylpyridine. Complexes containing an Fe^III(L)(L)- or Fe^III(L^Bu)(L^Bu)- moiety are [N(n-Bu)₄][Fe^III₂(L^Bu)₃(L^Bu)] (3^ox), [Fe^III(L)(L)(t-Bu-py)] (4^ox), [Fe^III(L^Bu)(L^Bu)(PMe₃)] (7), [Fe^III(L^Bu)(L^Bu)(PMe₃)₂] (8), and [Fe^III(L^Bu)(L^Bu)(PPr₃)] (9), where Pr represents the n-propylsubstituent. Complexes 2, 3^ox, 4, [Fe^III(L)(L)(PMe₃)₂] (6), and 9 have been structurally characterized byX-ray crystallography.