Phosphinidene reactivity toward unsaturated phosphorus heterocycles

The transient electrophilic phosphinidene complex PhPW(CO)₅ reacts in the presence of CuCl at room temperature with phospholene 2 and phospholes 4a-c to give the corresponding W(CO)₅ complexed products 3 and 5a-c. The intermediate phosphoranylidene phosphine complexes, formed, from the addition of PhPW(CO)₅ to the phosphorus atom of the substrates, are characterized by NMR spectroscopy and by a single crystal X-ray structure determination for the one generated from phospholene 2. This intermediate 8 is a CuCl-complexed dimer, which speculatively results from dissociating the phosphole-CuCl tetramer on insertion of PhPW(CO)₅ into the P-Cu bonds. Reacting PhPW(CO)₅ with phospholene 2 at 110°C in the absence of CuCl gives besides the W(CO)₅-complexed phospholene 3 also a bisphospholene-W(CO)₄ complex 13. The formation of 13 is attributed to a ligand exchange reaction in the intermediate phosphinidene-phospholene adduct.