I would not do it. There's just to much that can go wrong. White's are tropical, leopards are temperate. There is a chance of cross contamination and cross infection. And its quite possible the White's may eat your leopard frog.
Rule of thumb is keep all enclosures species specific. One species per tank. There are exceptions, of course, but these should only be attempted by those with a lot of experience and then only with very closely related species, preferably from the same region.