Hey, When looking in-game can you see more than just yourself? if so this is due to members that never migrated from Battle.net to Steam, it puts them in sort of a limbo where that are and aren't in the clan. You will need to have a dummy account join the clan then you can make it leader then you can leave, dissolving the clan is also impossible due to those members still being in the clan. Unfortunately those account will be stuck in the clan forever.