Solid state 119Sn NMR and Mossbauer spectroscopy of "distannynes":: Evidence for large structural differences in the crystalline phase

The "distannynes" Ar'SnSnAr' (Ar' = C6H3-2,6(C6H3-2,6-Pr-2(i))(2)) and Ar*SnSnAr* (Ar*) C6H3-2,6(C6H2-2,4,6-Pr-3(i))(2)) were examined by solid-state Sn-119 NMR and Mossbauer spectroscopy. The two compounds display substantially different spectroscopic parameters, while differing only in the absence (Ar'SnSnAr') or presence (Ar*SnSnAr*) of a para-Pr-i group in the flanking aryl rings of their terphenyl substituents. The spectroscopic differences can be interpreted in terms of a more trans-bent geometry and a longer Sn-Sn bond for Ar*SnSnAr* in comparison to the wider Sn-Sn-C angle (125.24(7)) and shorter Sn-Sn bond length (2.6675(4)angstrom) determined from the crystal structure of Ar'SnSnAr'. The differences are consistent with previously published calculations by Nagase and Takagi for Ar*SnSnAr*.