phosphoranes

The mononuclear hydridePH5 , systematically named λ 5-phosphane, and its hydrocarbyl derivatives. By extension, the literature also applies the term to phosphonium ylides.
See also: phosphanes
Source:
PAC, 1995, 67, 1307 (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1358