ERROR opening https://cactus.nci.nih.gov/chemical/structure/InChI%3DInChI%3D1S/4P.3Sn/q4%2A-3%3B3%2A%2B4/file?format=sdf&get3d=True  -- InChI%3DInChI%3D1S/4P.3Sn/q4%2A-3%3B3%2A%2B4 could not be loaded.