IONIC ORGANOBORANES .6. THE OUSENES REVISITED - B-11 NMR-SPECTRA OF 2POLYHEDRAL BORANE ANIONS, A NIDO-CARBORANE ANION, AND A CLOSO-CARBORANE WITH CARBOCYCLIC CATIONIC TROPENYLIUMYL SUBSTITUENTS

The ousenes are a class of ionic or zwitterionic organoboranes in whic h polyhedral borane anions or carboranes have carbocyclic cationic tro penyliumyl (cyclo-C7H6+) substituents. B-11 Fourier transform NMR stud ies have been used to probe ground state electronic interaction betwee n cage and ring. Tropenyliumyl substitution on B12H122- C2B10H12 resul ts in relatively minor electron withdrawal from the cage by a -I effec t, while such substitution on B10H102- or a nido-C2B9H122- results in significant -I withdrawal of electron density at the point of attachme nt and, in addition, strong +T electron donation from cage to ring by borons other than at the point of attachment. Coupled with previous st udies these observations confirm that modification of ousene structure can vary cage to ring electronic interaction from negligible, through excited state charge transfer, to significant electron delocalization from ground state electron density donation from cage to ring, and su ggests that the electrical properties of these materials may well be w orth further study.