The ligand effect on the selective C–H versus C–C bond activation of propane by NiBr+: a theoretical study
The ligand effect on the selective C–H versus C–C bond activation of propane by NiBr+: a theoretical study
复制标题
DOI：
10.1007/s00214-015-1628-4
复制
发表时间：
2015-02
影响因子：
1.7
通讯作者：
Lianming Zhao;Qiuyue Ding;Wenbin Xu;Pengpeng Sang;Xiaoli He;Zemin Shi;YuHua Chi;Xiaoqing Lu;Wenyue Guo
中科院分区：
文献类型：
--
作者：
Lianming Zhao;Qiuyue Ding;Wenbin Xu;Pengpeng Sang;Xiaoli He;Zemin Shi;YuHua Chi;Xiaoqing Lu;Wenyue Guo
用密度泛函理论研究了配位的NiBr+与丙烷反应中的配体效应。根据势能面的拓扑结构分析了HBr、H2和CH 4损失的初始C-H和C-C键活化机制。HBr和H2的损失涉及三种C-H激活机制，即α，β-H、α，γ-H和β，α-H提取，其中最后的β，α-H提取是最有利的机制。CH 4的丢失涉及初始C-C活化，但它被高能势垒阻止。当丙烷与开壳层配位的NiBr+反应时，初始C-H活化的Br配体可以通过四中心过渡态直接从丙烷底物上夺取一个H原子，而不形成Ni+的多σ型键，而初始C-C活化的金属中心需要经历不利的三σ型键（与Br，CH 3，CH 2CH 3），这解释了BrNi+/C3 H8与CH 4 not反应生成HBr和H2的原因.
Density functional theory has been employed to investigate the ligand effect in the reaction of ligated NiBr+with propane. Both initial C–H and C–C bond activation mechanisms for losses of HBr, H2, and CH4are analyzed in terms of the topology of the potential energy surface. Losses of HBr and H2involve three C–H activation mechanisms, that is,α,β-H,α,γ-H, andβ,α-H abstractions, where the lastβ,α-H abstraction is the most favorable mechanism. Loss of CH4involves initial C–C activation, but it is prevented by the high-energy barrier. When propane reacts with the open-shell ligated NiBr+, the ligand of Br in the initial C–H activation could direct abstract a H atom from propane substrate via a four-center transition state, without forming multi-σ-type bonding of Ni+, whereas the metal center in the initial C–C activation needs to experience an unfavorable threeσ-type bonding (with Br, CH3, and CH2CH3), which explains why HBr and H2are formed in the reaction of BrNi+/C3H8and CH4not.