The mixtures of chlorinated cobalt dicarbollide (CCD) and bidentate organophosphorous compounds were used for high-level radioactive waste reprocessing. In the organic phase carbamoylphosphine oxides (CMPO) interacted both with nitric acid and the protonated form of CCD. It was confirmed by the signal displacement to lower fields in the ³¹P NMR spectra. The signals of the phenyl protons and methylene groups in ¹H NMR spectra were also shifted. The results show that the most pronounced chemical shift occurred in the ³¹P NMR spectra, attributed to a strong interaction at the phosphoryl oxygen and indicating that the most useful spectra for studying other BNOPC was the ³¹P NMR spectra.