| Abstract
| - Theab initio/IGLO/NMR method has been successfully applied to establishthe structures of the three known isomers ofnido-C4B7H11. Themethod determines the structures to benido-7,8,9,10-C4B7H11,1a,nido-1,7,8,10-C4B7H11,2b, andnido-2,7,9,10-C4B7H11,3b. The relative order of stability is 1a>2b >3b. A comparison of the relativeenergies of the nine cage structures considered in this study showsthat, in complete agreement with previous empirically determinedpatterns, the most stable structures are those in which the carbonsoccupy low coordinate sites. This preference is more importantthan avoiding carbon−carbonconnections.
- The ab initio/IGLO/NMR method has been successfully applied toestablish the structures of the three knownisomers of nido-C4B7H11.The method confirms the previously proposed structure,nido-7,8,9,10-C4B7H11,1a, asone of the three known isomers. Of four candidates considered forthe second isomer, one of the previouslyproposed structures,nido-1,7,8,10-C4B7H11,2b, is selected. Of four candidates considered for thethird isomer,structurenido-2,7,9,10-C4B7H11,3b, which had not been previously proposed, is established.The relative orderof stability is 1a> 2b> 3b. Acomparison of the relative energies of the nine cage structuresconsidered in thisstudy shows that, in complete agreement with previous empiricallydetermined patterns, the most stable structuresare those in which the carbons occupy low coordinate sites. Thispreference is more important than avoidingcarbon−carbon connections.
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