Crystal structure and bonding in octamethylphosphonitrilium salts

In the cyclic cations in [{NPMe2}4H+]2CoCl42–(I) and in the compound (NPMe2)4H·CuCl3(II) the bonds to the protonated nitrogen atom (N+) are long; the subsequent alternation of the P–N bond lengths, which is independent of the conformation of the ring, is interpreted in terms of the approximate equality of the components of a dual π-system.