Comparison of donor properties of N-heterocyclic carbenes and N-donors containing the 1H-pyridin-(2E)-ylidene motif

被引：43

作者：

Slattery, John ^{[1
]}

Thatcher, Robert J. ^{[1
]}

Shi, Qi ^{[1
]}

Douthwaite, Richard E. ^{[1
]}

机构：

[1] Univ York, Dept Chem, York YO10 5DD, N Yorkshire, England

来源：

PURE AND APPLIED CHEMISTRY | 2010年 / 82卷 / 08期

关键词：

density functional theory; N-heterocyclic carbenes; metal-ligand bonding; 1H-pyridin-(2E)-ylidenes; SUZUKI COUPLING REACTIONS; MIXED AQUEOUS-MEDIUM; CATALYTIC APPLICATION; STRUCTURAL VARIATION; PALLADIUM COMPLEXES; OXIDATIVE ADDITION; CRYSTAL-STRUCTURE; METAL-COMPLEXES; ARYL BROMIDES; SOFT ACIDS;

D O I：

10.1351/PAC-CON-09-11-10

中图分类号：

O6 [化学];

学科分类号：

0703 ;

摘要：

IR spectroscopic and X-ray structural data of rhodium and palladium complexes of N-heterocyclic carbene (NHC) and 1H-pyridin-(2E)-ylidene (PYE) ligands indicate that both ligand classes exhibit similar electron-donating properties. However, catalytic application of palladium PYE complexes appears to be limited by PYE ligand loss. Density functional theory (DFT) calculations show that the Pd-C-NHC sigma-bond is very low-lying in energy (HOMO-14 and 15, ca. -11 eV) and a pi-backbonding contribution is also present, whereas the N-PYE sigma-bond is comparatively high-lying (HOMO-9 and 10, ca. -8 eV) and the highest occupied molecular orbital (HOMO) lowest unoccupied molecular orbital (LUMO) gap is also significantly less (4.0 vs. 5.6 eV). Essentially, electronegativity differences between Pd, C, and N render the Pd-N bond much more polarized and susceptible to electrophilic and nucleophilic attack and hence ligand substitution.

引用

页码：1663 / 1671

页数：9

共 75 条

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