Which complexes have zero oxidation state?

An example of a double salt is:

The coordination number of chromium in $K[Cr(H_2O)_2(C_2O_4)_2]$ is

What is the number of donor atoms in dimethylglyoximato ligand?

What is the number of moles of ionisable $Cl^{-}$ ions in a coordination complex if it forms $2 \ moles$ of $AgCl$ when treated with silver nitrate solution in excess?

The secondary valency of platinum in tetra-amminedichloroplatinum$(IV)$ chloride is