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