Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK.
Chemistry. 2009 Oct 26;15(42):11346-60. doi: 10.1002/chem.200901382.
A range of N-donor ligands based on the 1H-pyridin-(2E)-ylidene (PYE) motif have been prepared, including achiral and chiral examples. The ligands incorporate one to three PYE groups that coordinate to a metal through the exocyclic nitrogen atom of each PYE moiety, and the resulting metal complexes have been characterised by methods including single-crystal X-ray diffraction and NMR spectroscopy to examine metal-ligand bonding and ligand dynamics. Upon coordination of a PYE ligand to a proton or metal-complex fragment, the solid-state structures, NMR spectroscopy and DFT studies indicate that charge redistribution occurs within the PYE heterocyclic ring to give a contribution from a pyridinium-amido-type resonance structure. Additional IR spectroscopy and computational studies suggest that PYE ligands are strong donor ligands. NMR spectroscopy shows that for metal complexes there is restricted motion about the exocyclic C-N bond, which projects the heterocyclic N-substituent in the vicinity of the metal atom causing restricted motion in chelating-ligand derivatives. Solid-state structures and DFT calculations also show significant steric congestion and secondary metal-ligand interactions between the metal and ligand C-H bonds.
已经制备了一系列基于 1H-吡啶-（2E）-亚基（PYE）基的 N-供体配体，包括非手性和手性配体。这些配体包含一个到三个 PYE 基团，通过每个 PYE 部分的环外氮原子与金属配位，所得金属配合物通过单晶 X 射线衍射和 NMR 光谱等方法进行了表征，以检查金属-配体键合和配体动力学。当 PYE 配体与质子或金属配合物片段配位时，固态结构、NMR 光谱和 DFT 研究表明，在 PYE 杂环中发生电荷重新分布，从而产生来自吡啶鎓-酰胺型共振结构的贡献。额外的红外光谱和计算研究表明，PYE 配体是强供体配体。NMR 光谱表明，对于金属配合物，环外 C-N 键的运动受到限制，这导致杂环 N-取代基在金属原子附近移动，从而导致螯合配体衍生物的运动受限。固态结构和 DFT 计算还表明，金属和配体 C-H 键之间存在显著的空间位阻和次要的金属-配体相互作用。
