ERROR opening https://cactus.nci.nih.gov/chemical/structure/C%3DC%5BSn%5D%28C%3DC%29%28C%3DC%29C%3DC/file?format=sdf&get3d=True  -- C%3DC%5BSn%5D%28C%3DC%29%28C%3DC%29C%3DC could not be loaded.