Iodination of stanna-closo-dodecaborate

The dianionic stannaborate [SnB₁₁H₁₁]^2- oxidatively adds iodine at the tin vertex to give the iodinated cluster [I ₂SnB₁₁H₁₁]^2- which maintains a closo structure, albeit having a nido electron count. The iodo-stannaborate [I ₂SnB₁₁H₁₁]^2- is unstable at room temperature, but its structure was elucidated via single-crystal X-ray diffraction at low temperatures. The low-temperature ¹¹B NMR spectrum exhibits a 5:1:5 signal pattern, and the ¹¹⁹Sn NMR shows a resonance at -1039 ppm. Iodination of the zwitterionic stannaborate iron complex Fe(SnB₁₁H₁₁)(triphos) leads to the formation of the corresponding iodo-stannaborate iron complex Fe(I₂SnB ₁₁H₁₁)(triphos) which features an iodinated stannaborate moiety that has a structure analogous to that of [I₂SnB ₁₁H₁₁]^2-. The zwitterionic iodostannaborate complex is stable at room temperature, and the crystal structure and the ¹H, ¹¹B, ³¹P, and ¹¹⁹Sn NMR parameters were determined. ¹¹⁹Sn Mössbauer spectroscopy supports the assignment of a tin oxidation state of +II for Fe(SnB ₁₁H₁₁)(triphos) (δ = 2.71 mm s^-1) and +IV for Fe(I₂SnB₁₁H₁₁)(triphos) (δ = 1.22 mm s^-1). Additional ⁵⁷Fe Mössbauer spectra confirm the iron oxidation state +II for both compounds.