A Benchmark Ab Initio and DFT Study of the Structure and Binding of Methane in the σ-Alkane Complex CpRe(CO)2(CH4)
A Benchmark Ab Initio and DFT Study of the Structure and Binding of Methane in the σ-Alkane Complex CpRe(CO)2(CH4)
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DOI：
10.1021/ct400013p
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发表时间：
2013-05-01
影响因子：
5.5
通讯作者：
Ball, Graham E.
中科院分区：
文献类型：
--
作者：
Chan, Bun;Ball, Graham E.
本文采用从头算分子轨道理论和密度泛函理论（DFT）方法研究了CpRe（CO）（2）（CH 4）中甲烷的结合.我们发现最佳Re中心点C、Re中心点H和C中心点H距离分别为2.60、1.92和1.15埃，在二阶Moller-Plesset微扰理论水平上对复合CCSD（T）/def 2-QZVPP（CCSD（T）/def 2-TZVP，并对def 2-QZVPP基组进行了补充）在这个理论水平上已经绘制出来的势能面。在复合物-CCSD（T）/CBS//B3-PW 91/aug-cc-pVTZ-PP水平上，测定了298 K时的结合焓为62.0 kJ mol（-1）。各种DFT程序的基准表明，一些泛函给出了良好的几何结构，但低估了结合能，而另一些泛函给出了较差的几何结构，但与复合物-CCSD（T）结合能更接近。另一方面，omega B 97 X-D泛函给出了与复合物-CCSD（T）在几何优化以及结合能方面的公平协议。因此，它似乎是一个可靠的，易于实施，并具有成本效益的手段，用于研究Realkane复合物。良好的结合能也得到了几个常见的泛函时，D3色散修正。选定的色散校正DFT方法（B3 PW 91-D3，TPSSh-D3，和B 98-D3）被认为是相当准确的计算结合能的其他几个模型金属-CH 4络合物含有一系列的金属中心（Rh，Pd，W，Ir，Pt）。我们还注意到，对于Re-CH 4结合的单点能量计算，PWP-B 95-D3双杂化DFT程序提供了一个很好的协议与基准能量仅略高的计算要求。
Ab initio molecular orbital theory and density functional theory (DFT) procedures have been used to study the binding of methane in CpRe(CO)(2)(CH4), the simplest sigma-alkane complex in the experimentally widely studied CpRe(CO)(2)(alkane) family. We find the optimal Re center dot center dot center dot C, Re center dot center dot center dot H and C center dot center dot center dot H distances to be 2.60, 1.92, and 1.15 angstrom, respectively, on the composite-CCSD(T)/def2-QZVPP (CCSD(T)/def2-TZVP with supplement for the larger def2-QZVPP basis set at the second-order Moller-Plesset perturbation theory level) potential energy surface which has been mapped out at this level of theory. The enthalpy of binding at 298 K was determined to be 62.0 kJ mol(-1) at the composite-CCSD(T)/CBS//B3-PW91/aug-cc-pVTZ-PP level. Benchmarks on the various DFT procedures show that some functionals give good geometries but underestimate binding energies, while others yield poor geometries but give closer agreements with the composite-CCSD(T) binding energy. On the other hand, the omega B97X-D functional gives fair agreements with composite-CCSD(T) for both geometry optimization as well as binding energy. Thus, it appears to be a reliable, easily implemented, and cost-effective means for studying Realkane complexes. Good binding energies are also obtained with several common functionals when D3 dispersion corrections are applied. Selected dispersion-corrected DFT methods (B3PW91-D3, TPSSh-D3, and B98-D3) were found to be quite accurate for the calculation of binding energies of several other model metal-CH4 complexes containing a range of metal centers (Rh, Pd, W, Ir, Pt). We also note that, for single-point energy calculation of the Re-CH4 binding, the PWP-B95-D3 double-hybrid DFT procedure provides an excellent agreement with the benchmark energy at only a slightly higher computational requirement.