Anything marketed/designed to outright kill could/would be toxic to something as sensitive as amphibians.
Some newer repellants are based on natural ingredients like garlic, which would be fine as long as the non-active ingredients aren’t harmful (that’s a very loaded if), but likely won’t be toxic to adult mosquitoes.
Larval control based on BtI (Bacillus thuringiensis ‘israelensis’) would also not harm an amphibian, but again ineffective against adult skeeters.
What’s the issue? Trying to kill adults in the house (adult mosquitoes, of course )?