Diels-Alder reactions of phosphaalkene and phosphadiene complexes

Electron-rich dienes are well suited to cycloaddition reactions with unstable phosphaalkene-Mo(CO) 5 complexes. The chemical properties of the resulting adducts have been examined briefly. (l-Phospha-1,3-diene)Mo(CO) 5 complexes are generated transiently from the corresponding 1,2-dihydrophosphetes and reacted with various dienophiles in Diels-Alder-like reactions. The above cycloadditions offer a general approach to dihydro- or tetrahydrophosphinines which are intermediates in the synthesis of new phosphinine derivatives.