Li Ping, Wang Mei, Chen Lin, Liu Jihong, Zhao Zhenbo, Sun Licheng
State Key Laboratory of Fine Chemicals, DUT-KTH Joint Education and Research Centre on Molecular Devices, Dalian University of Technology (DUT), Dalian 116012, China.
Dalton Trans. 2009 Mar 21(11):1919-26. doi: 10.1039/b814336f. Epub 2009 Jan 28.
Diiron complexes containing pyridyl-phosphine ligands, that is, (mu-pdt)[Fe(2)(CO)(5)L] (pdt = S(CH(2))(3)S, L = Ph(2)PCH(2)Py, Ph(2)PPy, ) and (micro-pdt)[Fe(CO)(2)(PMe(3))][Fe(CO)(2)L] (L = Ph(2)PCH(2)Py, Ph(2)PPy, ) were prepared as model complexes of the [FeFe]-hydrogenase active site. Protonation of and by HOTf afforded the pyridyl-nitrogen protonated products [H(N)][OTf] and [H(N)][OTf], respectively. The molecular structures of, as well as [H(N)][OTf] and [H(N)][OTf] were confirmed by X-ray diffraction studies, which show that the Ph(2)PCH(2)Py ligand occupies the basal position both in and its protonated species [H(N)][OTf], while the Ph(2)PPy ligand prefers the apical position in and [H(N)][OTf]. The double protonation process of complex was monitored by in situ IR, (1)H and (31)P NMR spectroscopy at low temperature. The spectroscopic evidence indicates that the protonation of occurs first at the Fe-Fe bond and then at the pyridyl-nitrogen atom. Cyclic voltammograms reveal that protonation of and results in a considerable decrease in the overpotential for electrocatalytic proton reduction in the presence of HOTf, while the efficiency is not influenced by protonation. The electrocatalytic efficiency of for proton reduction in the presence of HOAc in CH(3)CN-H(2)O (50 : 1, v/v) is 5 times higher than that in pure CH(3)CN.
含有吡啶基膦配体的二铁配合物，即(μ-pdt)[Fe₂(CO)₅L]（pdt = S(CH₂)₃S，L = Ph₂PCH₂Py、Ph₂PPy等）和(μ-pdt)[Fe(CO)₂(PMe₃)][Fe(CO)₂L]（L = Ph₂PCH₂Py、Ph₂PPy等）被制备为[FeFe]-氢化酶活性位点的模型配合物。用HOTf对它们进行质子化分别得到吡啶基氮质子化产物[H(N)][OTf]和[H(N)][OTf]。通过X射线衍射研究确定了它们以及[H(N)][OTf]和[H(N)][OTf]的分子结构，结果表明Ph₂PCH₂Py配体在其本身及其质子化物种[H(N)][OTf]中均占据基部位置，而Ph₂PPy配体在其本身和[H(N)][OTf]中更倾向于占据顶端位置。在低温下通过原位红外光谱、¹H和³¹P NMR光谱监测配合物的双质子化过程。光谱证据表明其质子化首先发生在Fe-Fe键上，然后发生在吡啶基氮原子上。循环伏安图表明，在存在HOTf的情况下，它们的质子化导致电催化质子还原的过电位显著降低，而效率不受质子化的影响。在CH₃CN-H₂O（50 : 1，v/v）中存在HOAc的情况下，其对质子还原的电催化效率比在纯CH₃CN中高5倍。
