New plastic crystals of NEt3PrBBu4 and NEt2Pr2BBu4 were formed in a new region of ionic plastic crystal. In this area, globular cations and anions are assembled by weak interactions. Differential scanning calorimeter (DSC) measurements of these salts showed a low entropy change of 19.6 and 14.0 J K-1 mol(-1) at each melting point, respectively. On the basis of solid-state H-1 and C-13 nuclear magnetic resonance (NMR) spectra and electrical conductivity measurements, isotropic reorientation and ion transfer of globular cations and anions were detected in these crystals. The other compounds of NEtxMe(4-x)BBu4 (x = 1-3) showed tumbling motions and low activation energies of self-diffusion in crystals.