What properities of a molecule or ion will make a good ligand for forming complexes with transition metal ions

Answer 1

It needs to have lone pairs on it. The electronegativity of the centre on which the lone pair originates also has an effect. Softer nucleophiles like N or S will coordinate better or worse than harder nucleophiles like O, but this depends on the individual transition metal. Generally those to the left of the D-block will complex better to the softer nucleophiles than those to the right.

Answer 2

I. NH3 molecule contains a lone pair of electrons which could be used to type co-ordinate bonds by using being shared (covalently) with empty d orbitals (or d^2sp^3 hybrid orbitals) of the transition metallic ion eg [Cu(NH3)4(H2O)2]^2+; [Ag(NH3)2]^2+; [Co(NH3)6]^3+ {those are complicated cations, not compounds, yet they'll type compounds with anions at the same time with SO4^2- or Cl^- II. Cl^- ion has 4 pairs of electrons in outer point every physique of that can do what the lone pair above did eg [CuCl4]^2-; [AgCl2]^2-; [SnCl6]^2- III. CH4 molecule has no available pairs of electrons with which to type bonds with the metallic ion.