Question

Is water a ligand?

Answer 1

Hint:The atoms molecules and ions which have a tendency to donate electrons or lone pairs of electrons to a metal atom or an ion for the formation of a coordinate bond are termed as ligands.
And the metal ion or the atom, which is accepting these electrons from the ligands could also be termed as the central ion or atom.

Complete step-by-step answer:In order to answer this question, we should be clear about the definition of ligands. The species which has a tendency to donate electrons in a coordinate compound, to the metal atom in order to form a coordinate bond, is termed as a ligand. The ligands could be classified on the basis of the type or the number of donor atoms which a compound contains. If a compound has only one donor atom and can donate electrons from only one site, they are called monodentate ligands. Or in other words, the ligands which form only one coordinate bond directly to the central metal atom, are termed as the monodentate ligands. For instance, chloride ions, or ammonia, are monodentate ligands.
On the other hand, the ligands which have more than one atom to which it could form a coordinate bond with the metal atom, is termed a bidentate ligand. For example ethylene diamine.
Water is a type of monodentate ligand as it contains oxygen which has a lone pair of electrons. However it could look like water is bidentate because of the availability of two lone pairs of electrons but the bidentate ligand should have two different donor atoms.
So, the answer would be, yes water is a ligand.

Note:The ligands could be classified on the basis of the number of donor atoms it contains. Monodentate ligands contain only one donor atom in the ligand molecule and bidentate ligands have two.
Moreover there are polydentate ligands too, which have more than two donor atoms and hence can have more than two coordinate bonds with the central metal ion.