SOLID-STATE STRUCTURAL-ANALYSIS OF THE NAKED ISODICYCLOPENTADIENIDE ANION

The crystallographically determined structural features of Na(isodiCp) (15-crown-5) and [K-cryptand(2.2.2)](+)(isodiCp)(-) are compared to th ose of the corresponding Li(TMEDA) complex and the sandwich dimer invo lving Li+ (cocrystallized with Li(12-crown-4)(2)). features of the pot assium salt are distinctively different from those of its congeners. c onsequence of the encapsulation of the K+ ion by the cryptand, no inte raction occurs with the isodiCp anion, which is ''naked''. Notwithstan ding the complete dissociation that exists, the stand-alone isodiCp an ion exhibits appreciable folding about the bond that it shares with th e norbornyl framework. The dihedral angle is 8.3(1)degrees in a downwa rd direction away from the exo surface. This unrivaled opportunity to observe the free isodicyclopentadienide anion is shown to be in agreem ent with the results of HF-SCF calculations.