Imagine that a new polyatomic anion called "platoate" is invented.

Well, since the name seems to be based off of Plato, the philosopher, though it would sound better as "platonate".

Explanation: Probably platonic acid, taking off the "ate" and adding "nic acid". That would emulate carbonate vs. carbonic acid, but avoid the awkwardness of saying "platoic acid" without a consonant in between two vowels.