REACTIVITY OF THE METALLOPHOSPHINES [CPM(CO)3PPH2] (CP = ETA-C5H5, M = MO, W) TOWARDS ALKYNES - X-RAY CRYSTAL-STRUCTURE OF [CPMO(CO)2(PH2PCH=C(PH)CO)]

The mononuclear phosphido complexes [CpM(CO)3PPh2] (Cp = eta-C5H5; M = Mo, W) react with the electron deficient alkynes methyl propiolate (HC = CCO2Me) and dimethyl acetylenedicarboxylate (DMAD, MeO2CC = CCO2Me) to give the metallacyclic complexes [CpM(CO)2{Ph2PCR1 = C(R2)CO}] (R1 = H, CO2Me; R2 = CO2Me), which contain a five-membered chelate ring formed by the linking of the phosphido group, the alkyne, and one CO ligand. The molybdenum phosphido complex, though not the tungsten, also reacts with phenylacetylene to give the corresponding metallacycle [CpMo(CO)2-{Ph2PCH = C(Ph)CO}], which has been characterised by a single crystal X-ray structure determination. This complex can also be produced by the action of PPh2Cl on the dinuclear mu-acetylide Li[Cp2Mo2(mu-C = CPh)(CO)4].