What is the coordination number of the metal in the complex [CrCl2(H2O)4]Cl-H2O?

The coordination number of a metal in a coordination complex is determined by the number of ligand donor atoms that are bonded to the metal ion. In the case of the complex [CrCl2(H2O)4]Cl-H2O, we need to analyze the ligands surrounding the chromium (Cr) ion.

In this complex, there are two chloride (Cl) ions and four water (H2O) molecules acting as ligands. Each chloride ion and each water molecule contributes one donor atom to the coordination sphere of the chromium ion. Thus, the contribution from the ligands can be counted as follows:

• 2 from the two Cl ions

• 4 from the four H2O molecules

Adding these contributions together gives a total of 2 + 4 = 6 donor atoms. Therefore, the coordination number of chromium in this complex is 6, indicating that it is surrounded by six ligands.

This is consistent with the typical coordination geometries for chromium in such complexes, as it commonly exhibits a coordination number of 6, leading to an octahedral geometry. Understanding the concept of coordination number and how it relates to the structural composition of coordination complexes is vital in inorganic chemistry.