Reaction of a transiently formed terminal phosphinidene complex with triethylamine resulted in the formation of an sp3 C-H insertion product, as revealed by 31P NMR spectroscopy, which was isolated as semi-solid compound. However, if the reaction was continued for 24 h, a primary phosphane complex was obtained eventually. The compounds were characterised by NMR spectroscopy and mass spectrometry. Formation of the final products is explained by a mechanistic proposal based on DFT calculations.