The metal alkoxides are very important in the following two respects: (ⅰ) In contrary with the ordinary pi-acceptor ligands which can stabilize metal ions in low oxidation states, the alkoxide ligands can stabilize d...The metal alkoxides are very important in the following two respects: (ⅰ) In contrary with the ordinary pi-acceptor ligands which can stabilize metal ions in low oxidation states, the alkoxide ligands can stabilize d-electron poor metals in high oxidation state. Steric control of coordination number of the central metal ion and the binding sites with展开更多
The valence electronic structures of tantalum carbide (TaC) and tantalum nitride (TaN) are studied by using the empirical electronic theory (EET). The results reveal that the bonds of these compounds have covalent,met...The valence electronic structures of tantalum carbide (TaC) and tantalum nitride (TaN) are studied by using the empirical electronic theory (EET). The results reveal that the bonds of these compounds have covalent,metallic and ionic characters. For a quantitative analysis of the relative strength of these components,their ionicities have been calculated by implanting the results of EET to the PVL model. It has been found that the ionicity of tantalum carbide is smaller than that of tantalum nitride. The EET results also reveal that the covalent electronic number of the strongest bond in the former is larger than that of the latter. All these suggest that the covalent bond of TaC is stronger than that of TaN,which coincides to that de-duced from the first-principles method.展开更多
基金Project supported by the National Natural Science Foundation of China
文摘The metal alkoxides are very important in the following two respects: (ⅰ) In contrary with the ordinary pi-acceptor ligands which can stabilize metal ions in low oxidation states, the alkoxide ligands can stabilize d-electron poor metals in high oxidation state. Steric control of coordination number of the central metal ion and the binding sites with
基金Supported by the National Natural Science Foundation of China (Grant No. 10702060)the Ministry of Science and Technology of China (2005CB724400 and 2005CB724404)
文摘The valence electronic structures of tantalum carbide (TaC) and tantalum nitride (TaN) are studied by using the empirical electronic theory (EET). The results reveal that the bonds of these compounds have covalent,metallic and ionic characters. For a quantitative analysis of the relative strength of these components,their ionicities have been calculated by implanting the results of EET to the PVL model. It has been found that the ionicity of tantalum carbide is smaller than that of tantalum nitride. The EET results also reveal that the covalent electronic number of the strongest bond in the former is larger than that of the latter. All these suggest that the covalent bond of TaC is stronger than that of TaN,which coincides to that de-duced from the first-principles method.
