Ligand properties of N-heterocyclic and Bertrand carbenes: A density functional study

Chun Liang Lai, Wen Hsin Guo, Ming Tsung Lee, Ching Han Hu

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Abstract

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 > no)(alkyl) carbenes 6a-6c.

Original languageEnglish
Pages (from-to)5867-5875
Number of pages9
JournalJournal of Organometallic Chemistry
Volume690
Issue number24-25
DOIs
Publication statusPublished - 2005 Dec 1

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All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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