Saha Ranajit, Pan Sudip, Chattaraj Pratim K
Department of Chemistry and Centre for Theoretical Studies, Indian Institute of Technology Kharagpur, Kharagpur 721302, India.
Institute of Advanced Synthesis, School of Chemistry and Molecular Engineering, Jiangsu National Synergetic Innovation Center for Advanced Materials, Nanjing Tech University, Nanjing 210028, China.
ACS Omega. 2018 Oct 19;3(10):13720-13730. doi: 10.1021/acsomega.8b02305. eCollection 2018 Oct 31.
Density functional theory-based computations are carried out to analyze the electronic structure and stability of B(MIC) complexes, where MIC is a mesoionic carbene, viz., imidazolin-4-ylidenes, pyrazolin-4-ylidene, 1,2,3-triazol-5-ylidene, tetrazol-5-ylidene, and isoxazol-4-ylidene. The structure, stability, and the nature of bonding of these complexes are further compared to those of the previously reported B(NHC) and B(cAAC). A thorough bonding analysis via natural bond order, molecular orbital, and energy decomposition analyses (EDA) in combination with natural orbital for chemical valence (NOCV) reveals that MICs are suitable ligands to stabilize B species in its (3)∑ excited state, resulting in an effective B-B bond order of 3. Their high dissociation energy and endergonicity at 298 K for the dissociations L-BB-L → 2 B-L and L-BB-L → BB + 2 L (L = Ligand) indicate their viability at ambient condition. The donor property of MICs is comparable to that of NHC. The orbital interaction plays a greater role than the coulombic interaction in forming the B-L bonds. The EDA-NOCV results show that the sum of the orbital energies associated with the (+, +) and (+, -) L→[B]←L σ-donations is far larger than that of L←[B]→L π-back donation. It also reveals that cAAC possesses the largest σ-donation and π-back donation abilities among the studied ligands, and the σ-donation and π-back donation abilities of MICs are comparable to those of NHC. Therefore, the present study shows that MICs would also be an excellent choice as ligands to experimentally realize new compounds having a strong B-B triple bond.
进行了基于密度泛函理论的计算，以分析B(MIC)配合物的电子结构和稳定性，其中MIC是一种中氮茚卡宾，即咪唑啉-4-亚基、吡唑啉-4-亚基、1,2,3-三唑-5-亚基、四唑-5-亚基和异恶唑-4-亚基。将这些配合物的结构、稳定性和键合性质与先前报道的B(NHC)和B(cAAC)的进行了进一步比较。通过自然键序、分子轨道和能量分解分析(EDA)结合化学价自然轨道(NOCV)进行的全面键合分析表明，MIC是稳定处于(3)∑激发态的B物种的合适配体，导致有效的B-B键级为3。它们在298 K时对于L-BB-L → 2 B-L和L-BB-L → BB + 2 L(L =配体)解离具有高解离能和吸能性，表明它们在环境条件下的可行性。MIC的给体性质与NHC相当。在形成B-L键时，轨道相互作用比库仑相互作用起更大的作用。EDA-NOCV结果表明，与(+，+)和(+，-)L→[B]←L σ-给体相关的轨道能量之和远大于L←[B]→L π-反馈给体的轨道能量之和。还表明，在所研究的配体中，cAAC具有最大的σ-给体和π-反馈给体能力，并且MIC的σ-给体和π-反馈给体能力与NHC相当。因此，本研究表明，MIC作为配体也是一个很好的选择，可用于通过实验实现具有强B-B三键的新化合物。
