SF6, also known as sulfur hexafluoride, has a bond angle of 90 degrees. This molecule has six fluorines arranged evenly around the sulfur atom, so it has octahedral geometry.
Sulfur hexafluoride is very inert, as the fluorines bond strongly to the sulfur molecule, and they prevent large molecules from interacting with the sulfur. However, the chemical does react with lithium, a relatively small molecule, but sodium is too big to interact with the sulfur at all. This compound is inert enough to use in highly reactive settings, such as during the casting of magnesium. In this case, sulfur hexafluoride excludes the oxygen in the air that could react with the molten magnesium violently.