Protecting groups for stabilization of inter-element linkages

Various kinds of protective groups for stabilization of low-coordinated organophosphorus compounds are reviewed, in terms of steric effect and electronic effect, with some typical examples involving diphosphenes, phosphaalkenes, phosphaallenes, phosphabenzoquinones, diphosphinidenecyclobutenes, thioxophosphines, selenoxophosphines, dithioxophosphoranes, diselenoxophosphoranes, and phosphaalkynes.