Noble gases are often thought of as non-reactive, inert elements; however, Neil Bartlett made a breakthrough over 60 years ago by successfully bonding xenon for the first time. He produced an orange-yellow solid known as XePtF6. Growing large enough crystals containing noble gases has proven to be difficult, which has left many of their structures—and functions—unexplored. Recently, researchers have been able to study tiny crystallites of noble gas compounds, revealing the structures of several xenon compounds in an article published in ACS Central Science.
Noble gases have a reputation for being unreactive, inert elements, but more than 60 years ago Neil Bartlett demonstrated the first way to bond xenon. He created XePtF6,an orange-yellow solid. Because it’s difficult to grow sufficiently large crystals that contain noble gases, some of their structures — and therefore functions — remain elusive. Now, researchers have successfully examined tiny crystallites of noble gas compounds. They report structures of multiple xenon compounds in ACS Central Science.
Since Bartlett’s discovery, which has earned recognition as an International Historic Chemical Landmark, many noble gas compounds have been created, and some have had their crystal structures analyzed through single-crystal X-ray diffraction. However, these noble gas crystals are often sensitive to moisture in the air, making them highly reactive and complicating their handling. This sensitivity necessitates specialized techniques and equipment to grow large enough crystals for X-ray analysis. Consequently, detailed structures of the initial xenon compound and other noble gas compounds have remained elusive. Recently, a new approach—3D electron diffraction—has allowed scientists to examine small nanoscale crystals. While these smaller crystals can be stable in the air, the technique has not been widely used on compounds that are sensitive to air. Hence, Lukáš Palatinus, Matic LozinÅ¡ek, and their colleagues sought to apply 3D electron diffraction to xenon-containing crystallites.
The researchers produced three compounds consisting of xenon difluoride and manganese tetrafluoride, yielding distinct red crystals and pink crystalline powders. To maintain stability, they first cooled a holder with liquid nitrogen, added the sample, and then protected the holder with several layers during its transfer to a transmission electron microscope. The team measured the bond lengths and angles of xenon-fluoride (Xe-F) and manganese-fluoride (Mn-F) within the nanometer-sized crystallites from the pink crystalline powder using 3D electron diffraction. They then compared these structures with those obtained from larger, micrometer-sized wine-red crystals analyzed via single-crystal X-ray diffraction. The two methods yielded comparable results, with only minor differences noted by the researchers. This study revealed the following structures:
- Infinite zigzag chains for 3XeF2·2MnF4.
- Rings for XeF2·MnF4.
- Staircase-like double chains for XeF2·2MnF4.
Given the success of applying 3D electron diffraction to xenon compounds, the researchers believe this technique could also unlock the structures of XePtF6 and other challenging noble gas compounds that have avoided characterization for many years, along with other air-sensitive materials.
