Allylphosphines and vinylphosphines are prepared by reaction of a phosphine with an allylhalide or a vinylhalide, respectively. Preferably the phosphine is a secondary phosphine, so that there is formed an allyldialkylphosphine or a dialkylvinylphosphine. The allyldialkylphosphine can be reacted further with dialkylphosphine under free radical conditions to yield a 1,3-bis-(dialkylphosphino)propane. The dialkylvinylphosphine can be reacted further with dialkylphosphine under free radical conditions to yield a 1,2 bis-(dialkylphosphino)ethane. These compounds are useful as bidentate ligands.