Question

Will all central metal atom in coordination complex be cation in coordination complex?!? if so Why should it have that charge???

Answer 1

Central metal atom not always cation in coordination complex
Metal complexes can be neutral, such as Co(NH3)3Cl3; positively charged, such as [Nd(H2O)9]3+; or negatively charged, such as [UF8]4−. Electrically charged metal complexes are sometimes called complex ions. A coordination compound contains one or more metal complexes.