Ab Initio Calculations of pKa Values of Transition-Metal Hydrides in Acetonitrile
Ab Initio Calculations of pKa Values of Transition-Metal Hydrides in Acetonitrile
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DOI：
10.1021/om0608859
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发表时间：
2006-11
期刊：
影响因子：
2.8
通讯作者：
Xiufang Qi;Lei Liu;Yao Fu;Q. Guo
中科院分区：
文献类型：
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作者：
Xiufang Qi;Lei Liu;Yao Fu;Q. Guo
建立了一种定义良好的从头算方法，可用于计算乙腈中各种过渡金属氢化物的pKa值，精度为1.5 pKa单位。气相能量的计算采用双层niom方法，其中核心层由CCSD(T)理论处理。此外，先前为小有机分子开发的C-PCM溶剂化模型被证实可以可靠地预测大块有机金属配合物的溶剂化能。利用该方案，我们研究了Fe-， Co-和ni -基团金属氢化物的酸的结构-性质关系。结果表明，这些氢化物的pKa值随金属中心的不同而有较大的变化。与第一排和第二排金属氢化物相比，第三排金属氢化物的酸性总是最小的。另一方面，第一排和第二排金属氢化物之间的相对酸度强烈依赖于金属氢化物的化学式。
A well-defined ab initio protocol was developed which could be used to calculate the pKa values of a variety of transition-metal hydrides in acetonitrile with a precision of 1.5 pKa units. The gas-phase energies were calculated using a two-layer ONIOM method where the core layer was handled by the CCSD(T) theory. In addition, the C-PCM solvation model previously developed for small organic molecules was confirmed to be reliable for predicting the solvation energies of bulky organometallic complexes. Using the protocol, we studied the structure−property relationships for the acidities of the Fe-, Co-, and Ni-group metal hydrides. It was found that the pKa values of these hydrides varied considerably with respect to the metal centers. The third-row metal hydrides always appeared to be the least acidic, as compared to the first- and second-row metal hydrides. On the other hand, the relative acidity between the first- and second-row metal hydrides was strongly dependent on the chemical formulas of the metal c...