Formation, Detection, and Reactions of Phosphinidenes (Phosphanediyls)

Formation and detection of phosphinidenes (RP̈:) in the decomposition of cyclophosphanes and in the reaction of dichlorophosphanes with metals are considered critically. Only in the thermolysis of pentaphenylcyclopentaphosphane can phenylphosphinidene be detected with certainty by pyrolysis‐mass spectroscopy. “Trapping reactions” such as “insertion” into SS or AsAs bonds, and addition reactions with 1,2‐diketones, 1,3‐dienes, or alkynes can also be interpreted without the assumption of free phosphinidenes. The pyrolysis products of cyclophosphanes add to 1,3‐dienes and alkynes, yielding five‐ and six‐membered heterocycles that contain one to three phosphorus atoms.