Oxidative decomplexation of the eta(4)-1,3-diphosphete ligands of aren
e iron (arene = 1,3-diphosphinine, toluene) or cyclopentadienyl-cobalt
complexes by C2Cl6 leads to 1,2-diphosphetene, (Fe) or 1,3-diphosphet
ane (Co) derivatives, respectively. Isolation of the pure P2C2-heteroc
ycles is rapid and simple.