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Ammonia Stronger Ligand Than Water
The strength of ammonia as a ligand
stronger than water is related to its ability to bind to the central ion. Compared with water, ammonia is a stronger ligand. The reason for this can be analyzed from the number of ends.
First, the electron giving ability. In ammonia molecules, nitrogen atoms have a lone pair of electrons. The electronegativity of nitrogen is larger than that of hydrogen, and the electron cloud is biased towards the nitrogen atom, so that the electron density around the nitrogen atom is relatively high. Moreover, the radius of the nitrogen atom is small, and the force binding the lone pair electrons is relatively concentrated. In contrast to water molecules, although oxygen atoms also have lone pair electrons, the electronegativity of oxygen is greater than that of nitrogen. After bonding with hydrogen, the electron cloud is more biased towards the oxygen atom, resulting in a greater degree of dispersion of the electron cloud around the oxygen atom. The ability of lone pair electrons to give central ions is weaker than that of nitrogen atoms in ammonia. Therefore, ammonia, with its lone pair electrons that are easy to give away on the nitrogen atom, exhibits stronger coordination ability when bound to the central ion.
Second, the influence of spatial structure. Ammonia molecules are triangular cones, with nitrogen atoms located at the top of the cone and three hydrogen atoms at the bottom of the cone. This structure makes the lone pair electrons of nitrogen atoms more exposed, and it is easy to approach and coordinate with the central ion. The water molecule has a V-shaped structure, and the solitary pair electron of the oxygen atom is affected by the spatial position of the hydrogen atom, and the spatial hindrance when it approaches the central ion is relatively large. The difference in spatial structure makes ammonia more favorable when coordinating with the central ion, thereby enhancing its strength as a ligand.
Furthermore, from the perspective of complex stability. Complexes formed by ammonia and the central ion are often more stable than those formed by water and the central ion. This difference in stability is due to the strength of the coordination bond between ammonia and the central ion. Due to the strong electron giving ability of ammonia and the favorable spatial structure, the formed coordination bond is more firm and the stability of the complex is higher. Taking the common complexes formed by metal ions with ammonia and water as an example, the metal-ammonia complexes are more difficult to dissociate in solution, which further proves that ammonia is stronger as a ligand than water.
In summary, ammonia becomes a stronger ligand than water due to factors such as strong electron delivery ability, favorable spatial structure and stability of complex formation.
stronger than water is related to its ability to bind to the central ion. Compared with water, ammonia is a stronger ligand. The reason for this can be analyzed from the number of ends.
First, the electron giving ability. In ammonia molecules, nitrogen atoms have a lone pair of electrons. The electronegativity of nitrogen is larger than that of hydrogen, and the electron cloud is biased towards the nitrogen atom, so that the electron density around the nitrogen atom is relatively high. Moreover, the radius of the nitrogen atom is small, and the force binding the lone pair electrons is relatively concentrated. In contrast to water molecules, although oxygen atoms also have lone pair electrons, the electronegativity of oxygen is greater than that of nitrogen. After bonding with hydrogen, the electron cloud is more biased towards the oxygen atom, resulting in a greater degree of dispersion of the electron cloud around the oxygen atom. The ability of lone pair electrons to give central ions is weaker than that of nitrogen atoms in ammonia. Therefore, ammonia, with its lone pair electrons that are easy to give away on the nitrogen atom, exhibits stronger coordination ability when bound to the central ion.
Second, the influence of spatial structure. Ammonia molecules are triangular cones, with nitrogen atoms located at the top of the cone and three hydrogen atoms at the bottom of the cone. This structure makes the lone pair electrons of nitrogen atoms more exposed, and it is easy to approach and coordinate with the central ion. The water molecule has a V-shaped structure, and the solitary pair electron of the oxygen atom is affected by the spatial position of the hydrogen atom, and the spatial hindrance when it approaches the central ion is relatively large. The difference in spatial structure makes ammonia more favorable when coordinating with the central ion, thereby enhancing its strength as a ligand.
Furthermore, from the perspective of complex stability. Complexes formed by ammonia and the central ion are often more stable than those formed by water and the central ion. This difference in stability is due to the strength of the coordination bond between ammonia and the central ion. Due to the strong electron giving ability of ammonia and the favorable spatial structure, the formed coordination bond is more firm and the stability of the complex is higher. Taking the common complexes formed by metal ions with ammonia and water as an example, the metal-ammonia complexes are more difficult to dissociate in solution, which further proves that ammonia is stronger as a ligand than water.
In summary, ammonia becomes a stronger ligand than water due to factors such as strong electron delivery ability, favorable spatial structure and stability of complex formation.
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