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題名: Ligand Properties of N-Heterocyclic and Bertrand Carbenes: A Density Functional Study
作者: Lai, C. L.;Guo, W. H.;Lee, M. T.;Hu, Ching-Han
貢獻者: 化學系
關鍵詞: N-heterocyclic carbene;Nucleophilicity;Electrophilicity;Hardness;Electronegativity
日期: 2005-12
上傳時間: 2012-05-03T06:17:55Z
出版者: Elsevier
摘要: In order to probe the ligand properties we have examined a series of Cr(CO)5L and Ni(CO)3L complexes using density functional theory (DFT). The ligands included in our study are N-heterocyclic carbenes (NHCs) and Bertrand-type carbenes. Our study shows that the carbene–metal bonds of imidazol-2-ylidenes (1), imidazolin-2-ylidenes (2), thiazo-2-ylidenes (3), and triazo-5-ylidenes (4) are significantly stronger than those of Bertrand-type carbenes (5–7). The force constants of C–O in complexes are related to the property of isolated carbenes such as proton affinity (PA), electronegativity (χ), and charge transfer (ΔN). NHCs and Bertrand-type carbenes are identified as nucleophilic, soft ligands. Carbene stabilization energy (CSE) computations indicate that carbenes 1 and 4 are the most stable species, while 2 and 3 are less stable. In contrast to NHCs, CSE of carbenes 5–7 are much smaller, and their relative stabilities are in the order (amino)(aryl) carbenes 7e–7g > (amino)(alkyl) carbenes 7a–7d > (phosphino)(aryl) 6d–6e, and (phosphino)(silyl) carbenes 5a–5c > (phosphino)(alkyl) carbenes 6a–6c.
關聯: J. Organometallic Chem., 690(24-25): 5867-5875
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