New organic phosphorus compounds, comprised of hetero-phosphacycloalkanes whose phosphorus atom forms a complex with a borane. They can be prepared by the action of a borane on a hetero-phosphacycloalkane, within a solvent, at temperatures ranging from -20.degree. to +60.degree. C. Their transformation into other derivatives, phosphinites or phosphines in particular, can be carried out without any modification in the chirality of the initial complex. An especially useful application is their conversion into highly optically active phosphines, used in particular as catalysts in various reactions.