I did it with guppies into my reef tank a while back. As long as you acclimate them slowly, mines was over several weeks of 10% water changes with the "new water" being salt water you should be ok.
The guppies did fairly well however some of the older ones did not like it, and I think there life span decreased because of it. However the younger ones, fry included who are super sensitive, lived and are still alive today in my reef tank.
Honestly though, it looked cool at first, but I wouldn't do it, it just looks out of place to have them in there.
I know guppies aren't mollies, but they are very close.