Di/mono-nuclear iron(I)/(II) complexes as functional models for the 2Fe2S subunit and distal Fe moiety of the active site of [FeFe] hydrogenases: protonations, molecular structures and electrochemical properties.
Di/mono-nuclear iron(I)/(II) complexes containing conjugated and electron-withdrawing S-to-S linkers, [{(μ-S)(2)(C(4)N(2)H(2))}Fe(2)(CO)(6)] (1), [{(μ-S)(2)(C(4)N(2)H(2))}Fe(2)(CO)(5)(PMe(3))] (1P), and [{(μ-S)(2)(C(4)N(2)H(2))}Fe(CO)(2)(PMe(3))(2)] (2) were prepared as biomimetic models for the 2Fe2S subunit and distal Fe moiety of the active site of [FeFe] hydrogenases. The N atoms in the heterocyclic pyrazines of 1 and 2 were protonated in the presence of proton acid to generate one and two hydrides, [1(NH)](+) CF(3)SO(3)(-), [2(NH)](+) CF(3)SO(3)(-), and [2(NH)(2)](2+) (CF(3)SO(3)(-))(2), respectively. The protonation processes were evidenced by in situ IR and NMR spectroscopy. The molecular structures of the protonated species [1(NH)](+) CF(3)SO(3)(-) and [2(NH)(2)](2+) (CF(3)SO(3)(-))(2) together with their originating complexes and , and the mono-PMe(3) substituted diiron complex were identified by X-ray crystallography. The IR and single-crystal analysis data all suggested that the electron-withdrawing bridge, pyrazine, led to decreased electron density at the Fe centers of the model complexes, which was consistent with the electrochemical studies. The cyclic voltammograms indicated that complex exhibited a low primary reduction potential at -1.17 V vs. Fc-Fc(+) with a 270 mV positive shift compared with that of the benzene-1,2-dithiolate (bdt) bridged analogue [(μ-bdt)Fe(2)(CO)(6)]. Under the weak acid conditions, complexes 1 and 2 could electrochemically catalyze the proton reduction. More interestingly, the mononuclear ferrous complex 2 showed two catalytic peaks during the formation of hydrogen, confirming its potential as a catalyst for hydrogen production.
School of Materials Science and Engineering, Changchun University of Science and Technology, 7989 Weixing Road, Changchun 130022, PR China. cust_gaoshang@yahoo.cn
Shang
S
Gao
Jiangli
J
Fan
Shiguo
S
Sun
Fengling
F
Song
Xiaojun
X
Peng
Qian
Q
Duan
Dayong
D
Jiang
Qingcheng
Q
Liang
D056831:Coordination Complexes / Q000737:chemistry*; D003460:Crystallization; D004563:Electrochemistry; D006859:Hydrogen / Q000737:chemistry; D006864:Hydrogenase / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D011522:Protons; D013055:Spectrophotometry, Infrared; D013455:Sulfur / Q000737:chemistry*; D014961:X-Ray Diffraction
D056831:Coordination Complexes; D007506:Iron-Sulfur Proteins; D011522:Protons; D013455:Sulfur; D006859:Hydrogen; D007501:Iron; C118830:iron hydrogenase; D006864:Hydrogenase