Solid-State Reactions of Eicosaborate [B₂₀ H₁₈ ]^2- Salts and Complexes

A series of salts and complexes containing trans- and iso-isomers of octadecahydro-eicosaborate [B₂₀ H₁₈ ]^2- dianion is synthesized and characterized using FTIR and ¹¹ B NMR spectroscopies and X-ray diffraction techniques. Both isomers are found to act as four-, bi-, or zero-dentate ligands in reactions with copper(II), silver(I), and lead(II) through apical and/or equatorial boron atoms. Solid-state photo- and thermoinitiated reactions of octadecahydro-eicosaborate isomerization and solvent cleavage occurring in these compounds in a single-crystal-to-single-crystal manner are studied in situ. In contrast with solutions, in solids the reaction of boron cluster transformation occurs rarely, thus, analysis of crystal packing allowed us to suggest some criteria of isomerization of macropolyhedral boranes in crystals. X-ray diffraction data are used to confirm reaction path of isomerization of the [B₂₀ H₁₈ ]^2- dianion.