Koordinaatiomäärä

Koordinaatiomäärä refers to the number of atoms, ions, or molecules that are directly bonded to a central atom in a coordination complex. This central atom is typically a metal ion. The surrounding atoms, ions, or molecules are called ligands. The coordination number is a fundamental property of coordination complexes and plays a crucial role in determining their geometry, chemical properties, and reactivity.

Coordination numbers can vary widely, but common values range from 2 to 9. For instance, simple complexes like [Ag(NH3)2]+ have a coordination number of 2, while octahedral complexes like [Co(NH3)6]3+ have a coordination number of 6. Some larger metal ions can accommodate even higher coordination numbers. The coordination number is not always equal to the charge of the complex or the number of ligands, especially when polydentate ligands (ligands that can bind to the central atom at multiple points) are involved.

The coordination number is determined by factors such as the size of the central metal ion, the size and electronic properties of the ligands, and steric hindrance. Understanding the coordination number is essential for predicting the structure and behavior of coordination compounds, which have applications in catalysis, medicine, and materials science. For example, the coordination number of platinum in cisplatin, a common chemotherapy drug, is 4.