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

The lithium salt of stanna-closo-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 P2(1)/c (alpha = 15.0608(10) angstrom, b = 14.0778(8) angstrom, c = 18.3890(12) angstrom and beta = 110.324(5)degrees) 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 B-5-belt display the largest negative partial charges. Raman and IR spectra of the cesium salt of [SnB11H11](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 degrees C as determined with TG/DTA measurements.