Stanna-closo-dodecaborate: The crystal structure of [Li(thf) ₃]₂[SnB₁₁H₁₁], vibrational spectroscopy, thermal analysis and DFT calculations

The lithium salt of stanna-c/oso-dodecaborate was prepared and single-crystalline material was obtained from tetrahydrofurane. The salt crystallizes as [Li(thf)₃]₂[SnB₁₁H ₁₁] in the monoclinic space group P2₁/c (a = 15.0608(10) Å, b = 14.0778(8) Å, c = 18.3890(12) Å and ß= 110.324(5)°) and both lithium ions are coordinated to triangular cluster faces via B - H - Li bonds. DFT calculations in combination with a natural population analysis reveal that the tin vertex exhibits a positive partial charge while all boron atoms of the stannaborate cluster carry a negative charge. The boron atoms of the first B₅-belt display the largest negative partial charges. Raman and IR spectra of the cesium salt of [SnB ₁₁H₁₁]^2- reveal that the cluster breathing modes which involve the tin vertex are found at around 250 cm^-1. Furthermore, the thermal stability of the group-14-heteroborate is remarkably large with a decomposition temperature of above 900 °C as determined with TG/DTA measurements.