氢化酶仿生化学是当前有机金属化学领域研究的前沿课题,其主要内容为针对氢化酶的活性中心结构和功能进行化学模拟研究.自然界中已经发现的氢化酶有三种,其中[NiFe]氢化酶、[FeFe]氢化酶研究较多.单铁氢化酶发现于1990年,是产甲烷杆菌在厌氧和镍缺乏的条件下合成的.区别于其他两种氢化酶,其活性中心不含Fe-S簇,且仅含有一个Fe原子,并且仅能在底物存在的情况下,催化异裂氢分子并选择性还原特定底物,为产甲烷杆菌代谢提供能量.研究单铁氢化酶的结构和功能,模拟其活化氢、利用氢的过程,对于探索清洁能源的利用和开发新的非贵金属催化剂具有重要意义.本文以单铁氢化酶(Hmd)结构和功能模拟为导向,针对单铁氢化酶一级配位结构,设计合成了两个新模型化合物.通过IR,NMR,X射线单晶衍射等手段表征分析了模型化合物的性质并确认其结构.探索了其质子化反应特性、电催化还原质子制氢的特性.为了进一步模拟Hmd催化裂解氢气、完成氢转移的功能,以所合成模型物为催化剂实现了在常温常压下,以乙醇作为质子源的催化转移氢化过程.新单铁模型配合物Fe(CO)2PR3(NN)(R=Cy(3),Ph(4),NN,邻苯二胺二价阴离子配体)由NN二齿配体与前体化合物Fe(CO)3I2PR3进行配体取代反应合成.模型化合物活性中心为一个二价铁原子,拥有两个处于cis-位置的羰基配体,一个邻苯二胺双齿配体(两个氮原子进行配位)以及一个有机膦配体.通过红外光谱表征所合成的具有不饱和五配位结构化合物的光谱性质,可以得到配合物Fe(CO)2PCy3(NN)的羰基红外特征谱峰为1974,1919 cm–1,配合物Fe(CO)2PPh3(NN)的红外特征谱峰在1985和1929cm–1处.通过单晶X射线衍射表征确认了两个化合物结构,并获取晶体学数据.经研究发现,Fe(CO)2PR3(NN)能够发生酸碱调控下可逆的质子化/?
Two mono iron complexes Fe(CO)2PR3(NN) (R = Cy (3), Ph (4), NN = o-phenylenediamine dianion ligand, N2H2Ph2-) derived from the ligand substitution of Fe(CO)3hPR3 by the NN ligand were isolated and structurally characterized by single crystal X-ray diffraction. They have a similar first coordination sphere and oxidation state of the iron center as the [Fe]-hydrogenase active site, and can be a model of it IR demonstrated that the effect of the NN ligand on the coordinated CO stretch- ing frequencies was due to its excellent electron donating ability. The reversible protonation/deprotonation of the NN ligand was identified by infrared spectroscopy and density functional theory computation. The NN ligand is an effective proton acceptor as the internal base of the cysteine thiolate ligand in [Fe]-hydrogenase. The electrochemical properties of complexes 3, 4 were investigated by cyclic voltammograms. Complex 3 catalyzed the transfer hydrogenation of benzoquinone to hydroquinone effectively under mild conditions.