C-13 NMR studies on carboranes and derivatives: Experimental/calculational correlations

The measured C-13 chemical shifts of over forty carborane compounds correlate very well with ab-initio/IGLO/NMR calculated values at both the DZ//3-21G and DZ//6-31G* (IGLO-NMR//Gaussian-geometry-optimized) levels of theory as well as with the ab-initio/GIAO/NMR values at the 6-31G*//6-31G* level of theory. For the carboranes in this study, the linear relationships delta(C-13-IGLO-D//N6-31G*) = 0.941 delta(C-13-exp) - 1.897 (r(2) = 0.990) and delta(C-13-GIAO-6-31G*//6-31G*) = 0.893 delta(C-13-exp) - 2.554 (r(2) = 0.991) are derived. Combined together with recently reported B-11 NMR correlations between experiment and theory, a significant means is added to the arsenal of carborane NMR structure proof methods available to the experimentalist having access to only modest computational resources. And this procedure, of course, also has the additional feature of yielding reasonably good structural information (bond distances, angles, etc.).