ERROR opening https://cactus.nci.nih.gov/chemical/structure/O%5BSn%5D%28c1ccccc1%29%28c2ccccc2%29c3ccccc3/file?format=sdf&get3d=True  -- O%5BSn%5D%28c1ccccc1%29%28c2ccccc2%29c3ccccc3 could not be loaded.