邻苯二硫酚桥联双核双氮过渡金属配合物N—N键活化规律的理论研究

Theoretical Study on N-N Activation by Thiolate-bridged Dinuclear Dinitrogen Transition-metal Complexes

采用密度泛函理论方法研究了具有仿生固氮结构的两类化合物[Cp＊Fe（μ-η^2η^2bdt）（μ-η^1η^1Me N=NMe）Fe Cp＊]以及[Cp＊Fe（μ-SEt）2（μ-η^1η^1Me N=NMe）Fe Cp＊]的90种不同结构,调变过渡金属中心,研究不同自旋态下（单重态和三重态）具有side-on或end-on配位键型的双核双氮过渡金属配合物,基于计算结果分析了BDT（邻苯二硫酚）和乙基类型配体的不同过渡金属配合物活化双氮的程度.研究结果表明,N—N键活化程度与配合物过渡金属中心所在周期存在密切关系,更高周期对双氮的活化程度更高,同周期金属过渡金属配合物对N—N键的活化程度从第四副族至第八族呈现折线型下降,同时,过渡金属中心的外层价电子数的奇偶性对双氮的活化程度具有一定影响.此外,side-on键型对双氮的活化程度要高于end-on键型,具有不同基团的同种骨架配体对N—N键的活化能力没有明显区别。

90 kinds of dinitrogen binuclear transition-metal complexes at singlet and triplet states in Group 4-10 from Period 4 to 6 based on the biomimetic dinitrogen fixation species were studied using DFT method, [Cp＊Fe（μ-η^2η^2bdt）-（μ-η^1η^1Me N=NMe）Fe Cp＊] and [Cp＊Fe（μ-SEt）2（μ-η^1η^1Me N=NMe）Fe Cp＊], in order to investigate the transition-metal effect in N—N activation. The calculated results indicate that N—N bond activation is strongly related to the period of transition metal. N—N activation by transition metals in Period 6 is stronger than those in Period 5 and Period 4. For transition metals in the same period, N—N activation ability decreases from Group 4 to Group 10. The odd-even electron number of transition metal center also shows certain influence on the N—N activation. In addition, side-on coordination mode is more favorable than end-on mode for thiolate-bridged dinuclear transition-metal complexes on N—N bond activation. The type of ligands（BDT ligand or ethyl ligand） in this system has little impact on N—N activation.