Sterically protected organophosphorus compounds in low co-ordination states

The chemistry of sterically protected low co-ordinate organophosphorus compounds is described; these compounds comprise diphosphenes, phosphaethenes, phosphaallenes, phosphabutatrienes, phosphinidenecyclobutenes, and so forth, and are discussed in terms of syntheses, 31P NMR analyses, X-ray crystallographic structure analyses, as well as physical and chemical properties.