title: Protonation, electrochemical properties and molecular structures of halogen-functionalized diiron azadithiolate complexes related to the active site of iron-only hydrogenases.
abstract: Diiron complexes [{(micro-SCH2)2NCH2C6H4X}{Fe(CO)2L}2] (L = CO, X = 2-Br, 1; 2-F, 2; 3-Br, 3; L = PMe(3), X = 2-Br, 4) were prepared as biomimetic models of the iron-only hydrogenase active site. The N-protonated species [(NH)]+ClO(4)(-), [(NH)](+)ClO(4)(-) and the micro-hydride diiron complex [4(FeHFe)]+PF(6)(-) were obtained in the presence of proton acids and well characterized. The protonation process of 4 was studied by in-situ IR and NMR spectroscopy, which suggests the formation of the diprotonated species [4(NH)(FeHFe)](2+) in the presence of an excess of proton acid. The molecular structures of 1, [(NH)]+ClO(4)(-), 4 and [4(FeHFe)]+PF(6)(-) were determined by X-ray crystallography. The single-crystal X-ray analysis reveals that an intramolecular H...Br contact (2.82 A) in the crystalline state of [1(NH)]+ClO(4)(-). In the presence of 1-6 equiv of the stronger acid HOTf, complex 1 is readily protonated on the bridged-N atom and can electrochemically catalyze the proton reduction at a relatively mild potential (ca.-1.0 V). Complex 4 is also electrocatalytic active at -1.4 V in the presence of HOTf with formation of the micro-hydride diiron species.
authors: State Key Laboratory of Fine Chemicals, DUT-KTH Joint Education and Research Center on Molecular Devices, Dalian University of Technology (DUT), Dalian 116012, China. symbueno@dlut.edu.cn
authors: Fujun
authors: F
authors: Wang
authors: Mei
authors: M
authors: Wang
authors: Xiaoyang
authors: X
authors: Liu
authors: Kun
authors: K
authors: Jin
authors: Weibing
authors: W
authors: Dong
authors: Licheng
authors: L
authors: Sun
mesh_terms: D018360:Crystallography, X-Ray; D004563:Electrochemistry; D006219:Halogens / Q000737:chemistry*; D006864:Hydrogenase / Q000378:metabolism*; D007202:Indicators and Reagents; D058085:Iron Compounds / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000378:metabolism*; D008958:Models, Molecular; D011522:Protons; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D006219:Halogens; D007202:Indicators and Reagents; D058085:Iron Compounds; D007506:Iron-Sulfur Proteins; D011522:Protons; D013438:Sulfhydryl Compounds; C118830:iron hydrogenase; D006864:Hydrogenase