Sn3I8 x 2 (18-crown-6): a mixed-valent tin-crown-ether complex

Area of Science:

• Inorganic Chemistry
• Solid-State Chemistry
• Materials Science

Background:

• Crown ethers are versatile ligands capable of coordinating metal ions.
• Ionic liquids offer unique reaction media for synthesizing novel inorganic compounds.
• Mixed-valence compounds exhibit interesting electronic and structural properties.

Purpose of the Study:

• To synthesize and characterize a new mixed-valence tin-iodine compound.
• To investigate the coordination behavior of 18-crown-6 with tin ions.
• To elucidate the crystal structure and bonding in the novel compound.

Main Methods:

• Single-crystal X-ray diffraction for crystal structure determination.
• (119)Sn-Mössbauer spectroscopy for confirming the mixed-valence state of tin.
• Synthesis in an ionic liquid medium ([NMe(n-Bu)(3)][N(Tf)(2)]) using SnI(2) and SnI(4).

Main Results:

• Successful synthesis of black, plate-shaped crystals of Sn(3)I(8) x 2 (18-crown-6).
• The compound crystallizes in a monoclinic lattice, featuring trigonal-bipyramidal [SnI(5)](-) anions and [Sn(2)I(3)(18-crown-6)(2)](+) cations.
• The cation shows endocyclic Sn(2+) coordination by the 18-crown-6 ether, forming an infinite network via I-I contacts.
• (119)Sn-Mössbauer spectroscopy confirmed the presence of mixed-valence tin species.

Conclusions:

• A novel mixed-valence tin-iodine compound with crown ether inclusion has been synthesized and structurally characterized.
• The crystal structure reveals complex ionic constituents and an extended network structure.
• The study highlights the utility of ionic liquids and crown ethers in designing novel inorganic materials.