13703-97-4

Solid state 11B (and in one case 10B) NMR spectra of four cyclic boron-chalcogen compounds have been measured at various frequencies and analysed in terms of nuclear quadrupole and chemical shift interactions.Application of the Townes-Dailey theory to the quadrupole results, corrected for ionic contributions to the electric field gradient and to the bonding, yields detailed information about the importance of ?-bonding in the respective materials.The occupation number of the 2pz orbitals of the sp2-hybridized boron atoms appear to be particularly large for systems containing chalcogen-chalcogen bridges.From both the chemical point of view and the spectroscopic result, among the six- and five-membered rings, diiodotriselenadiborolane is distinguished by an exceptional position.

The preparation of solid H2B2S5 and its decomposition product H2S·xBS2, x = 4.84 ± 1.75, and observations of their properties by visual and chemical means and by x-ray, infrared, Raman, and mass spectrometry are reported. Metathioboric acid, (HBS2)3, was prepared by two methods and heated with sulfur in evacuated, sealed Vycor tubes to yield H2S·xBS2. Diiodotrithiadiborolane, I2B2S3, was prepared and treated with H2S to obtain H2B2S5 in benzene solution. Solid H2B2S5 decomposed and polymerized spontaneously to yield H2S·xBS2. X-ray, infrared, and Raman spectrometry revealed polymerization and extensive S-S bonding in the solid. Mass spectrometry of the vapor from the solid products gave predominantly H2B2S5+, H2S+, and their fragments at temperatures below 80°C and then high molecular weight ions up to B8S16+ at higher temperatures. Fragmentation of H2B2S5+ was shown to yield HBS3+ by identification of the corresponding metastable ion. A relationship of H2B2S5 to (BS2)n through polymerization and condensation is proposed.