Strong evidence for the low-temperature formation of an axially positioned NR(3) (R = H, CH3) adduct of an "open" cage C2B7H9 structure is Obtained via comparison of the experimentally obtained C-13 and B-11 NMR data (R = CH3) with that obtained from ab initio/IGLO/NMR and ab initio/GIAO/NMR approaches (R = H, CH3). The amine is positioned at a boron surrounded by the two carborane carbon atoms along a chair arrangement of a six-atom CBCB3 open face belonging to a cluster that can be formally derived by removing a triangular set of three adjacent vertices from a 12-vertex icosahedral unit. Rapid equilibration of the adduct NR(3) . C2B7H9 With dissociated NR(3) and closo-C2B7H9 is proposed to explain the NMR chemical shift observations.