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

摘要

The ousenes are a class of ionic or zwitterionic organoboranes in which polyhedral borane anions or carboranes have carbocyclic cationic tropenyliumyl (cyclo-C7H6+) substituents. B-11 Fourier transform NMR studies have been used to probe ground state electronic interaction between cage and ring. Tropenyliumyl substitution on B12H122- C2B10H12 results in relatively minor electron withdrawal from the cage by a -I effect, while such substitution on B10H102- or a nido-C2B9H122- results in significant -I withdrawal of electron density at the point of attachment and, in addition, strong +T electron donation from cage to ring by borons other than at the point of attachment. Coupled with previous studies 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 suggests that the electrical properties of these materials may well be worth further study. [References: 14]