The coordination number for the complex [Co Cl NH3 5]2+ is 6. This is because there are 5 NH3 ligands and 1 Cl ligand surrounding the central Co ion, making a total of 6 ligands.The geometry for this complex is octahedral. In an octahedral geometry, the six ligands are arranged around the central metal ion at equal distances and angles of 90 between any two adjacent ligands.