Explain with two examples each of the following: coordination entity, ligand, coordination number, coordination polyhedron, homoleptic and heteroleptic.
Coordination entity: A central metal atom/ion bonded to fixed number of oppositely charged ions or neutral molecules. Examples include [Ni(CO)4],[CoCl3(NH3)3]. Ligand: An atom or molecule or ion capable of donating a pair of electrons to the central metal or ion and forms a coordinate bond with it. Examples include chloride ions, water and ammonia. Coordination number: The total number of ligands in a coordination compound attached to the central metal atom or ion. For example, in [Ni(CO)4], the coordination number of Ni is . In CoCl3(NH3)3, the coordination number of Co3+ is 6. Coordination polyhedron: The spatial arrangement of ligand atoms which are directly attached to the central atom. For example, [Co(NH3)6]3+ has octahedral geometry and Ni(CO)4 has tetrahedral geometry. homoleptic : Metal is bound to only one kind of donor groups. For example [Ni(NH3)6]2+,[Co(NH3)6]3+. heteroleptic : Metal is bound to more than one kind of donor groups. For example [CoCl3(NH3)3],[NiCl2(H2O)4].
