多核过渡金属氰化物的理论研究

Though transition metal cyanides, which are always with complicated structures, have been widely used, their toxicity brings much difficulty to the experiment. Based on the above characteristics of transition metal cyanides, in the present project, a series of multinuclear transition metal cyanides will be studied by quantum chemical methods to explore the structures, properties and their relationship, and then to investigate the structures of isomers for the transition metal cyanides that may exist. It will be very interesting to seek the three kinds of connections as following: the connection between the electronic structures, such as, metal-metal multiple bonds(double bond, triple bond, or even quadruple bond and quintuple bond) and the variety of CN- coordination number and coordination mode (two-electron or four-electron donor ligand); the connection between the high spin ground state of each compound and the variety of CN- coordination number and coordination mode; the connection between the applicability of 18-electron rule and the variety of CN- coordination number and coordination mode. At the same time, the potential application of multinuclear transition metal cyanides will also be investigated in this project. From the results of this project, it will not only help us to deepen the understanding of the nature of transition metal-metal multiple bonds, coordination modes of CN-, high-spin ground state and spin-crossover, but also provide the theoretical clues for the experimental synthesis and application of transition metal cyanides.

基于过渡金属氰化物结构复杂、应用广泛，同时又因其毒性导致实验困难等特点，本项目拟采用量子化学方法，研究多核过渡金属氰化物的结构、性质及其之间的关系，进而设计可能存在的多核过渡金属氰化物稳定异构体，并寻求其电子结构（例如：金属-金属多重键，包括双键、三键、甚至四重键和五重键,多重态基态及18价电子数规则适用性）随配位CN-的数目和配位方式(两电子和四电子配位)变化的规律，探索多核过渡金属氰化物可能具有的性质和在磁性材料、催化剂方面潜在的应用。以期加深对过渡金属-金属多重键，CN-的多种配位形式，以及高自旋基态和自旋交叉等问题的认识，为过渡金属氰化物实验合成和应用开发提供理论线索。

本课题采用密度泛函方法，研究了一系列双核过渡金属氰化物及其取代物，主要结果如下：.(1)探索了双核过渡金属氰化物的计算方案。对Cp2Pd2(CN)2和Cp2Rh2(CN)n (Cp = h5-C5H5；n = 2, 3, 4)，采用MPW1PW91和BP86方法，结合DZP和SDD基组；对Cp2Fe2(CN)n (n=6-1)采用B3LYP/DZP和MPW1PW91/ DZP计算方案，而对Cp2Co2(CN)4则采用B3LYP*/DZP计算方案。.(2)对Cp2Fe2(CN)n和Cp2Fe2Cln(n=6-1)的研究发现，其最稳定异构体都为高自旋态结构，表明其为潜在磁性材料；大部分该高自旋态低能异构体都具有端Cp环和桥连配体；Cp2Fe2(CN)n 和Cp2Fe2Cln (n=4、3、2)都具有较好的热力学稳定性。.(3)对Cp2Co2(CN)4和Cp2Co2F4的研究发现，Cp2Co2F4能量最低异构体是五重态，而Cp2Co2(CN)4则为三态； Cp2Co2(CN)4和Cp2Co2F4的大部分异构体中，Co•••Co间都没有化学键作用。.(4)对Cp2Pd2X2(X=F、Cl、CN、CO、CNCH3、CS)的研究发现，钯(ΙΙ)衍生物Cp2Pd2X2(X=F、Cl、CN)的能量最低异构体为垂直结构，而钯(I)衍生物Cp2Pd2L2(L=CO、CS)则为共轴结构；Cp2Pd2X2 (X = F, CN)的最低能量异构体均包含一个C5H5X；Cp2Pd2L2 (L = CO 和 CS)大部分异构体中Pd-Pd键都为单键，而Cp2Pd2X2(X=F、Cl、CN)大部分异构体中，则为双键或不成键。.(5)对Cp2Rh2Xn (X = Cl、F、CN；n = 2-4)的研究发现，其最低能量异构体均为连有两个端连Cp环和双桥连X配体的Cp2Rh2(µ-X)2Xn–2结构；预测的Cp2Rh2Cln(n=2, 4)最稳定构型与实验检测的 (Me5C5)2Rh2Cln (n = 2, 4)的结构相似; Cp2Rh2Cl2最稳定结构单态-三态之间能量差较小，与实验(Me5C5)2Rh2(µ-Cl)2中Rh–Rh活性较高相对应； Cp2Rh2X4在分解为单核片段CpRhX2的反应中，表现较好的热力学稳定性，而Cp2Rh2X3稳定性较差，易发生歧化反应。