Question

K₂PtCl₆ is a well known compound, whereas the corresponding Ni compound is not known. State a reason for it.

Answer 1

1. K₂PtCl₆ contains Pt in the +4 oxidation state, which is stable due to the low ionisation energy for Pt to reach the +4 state.
2. Ni prefers the +2 oxidation state because its higher ionisation energy makes the formation of the +4 state difficult.
3. Therefore, Pt forms stable K₂PtCl₆, but the corresponding Ni compound in the +4 state is not known.
4. Ni compounds mainly exist in the +2 state, so the analogous compound to K₂PtCl₆ with Ni is unstable and unknown.

This difference is due to the difference in ionisation energies and oxidation state stability of Pt and Ni.