Trapping reactions of an intermediate containing a tungsten-phosphorus triple bond with alkynes

The thermolysis of the phosphinidene complex Cp*PW(CO)5]2] (1) in toluene in the presence of tBuC(triple bond)CMe leads to the four-membered ring complexes eta2-C(Me)C(tBu)]Cp*(CO)W(mu3-P)W(CO)3]]eta4:eta1:eta1-PW(CO)5]WCp*(CO)C(Me)C(tBu)]] (4) as the major product and WCp*(CO)2]W(CO)2WCp*(CO)eta1:eta1-C(Me)C(tBu)]](mu,eta3:eta2:eta1-P2W(CO)5]] (5). The reaction of 1 with PhC(triple bond)CPh leads to W(Co)2eta2-C(Ph)C(Ph)]](eta4:eta1-P(W(CO)5]WCp*(CO)2)C(Ph)C(Ph)]] (6). The products 4 and 6 can be regarded as the formal cycloaddition products of the phosphido complex intermediate Cp*(CO)2W(triple bond)P --> W(CO)5] (B), formed by Cp* migration within the phosphinidene complex 1. Furthermore, the reaction of 1 with PhC(triple bond)CPh gives the minor product eta2:eta1-C(Ph)C(Ph)]2W(CO)4]2]mu,eta1:eta1-PC(Me)C(Me)]3C(Me)]C(Ph)](C(Ph)]] (7) as a result of a 1,3-dipolaric cycloaddition of the alkyne into a phosphaallylic subunit of the Cp*P moiety of 1. Compounds 4-7 have been characterized by means of their spectroscopic data as well as by single-crystal X-ray structure analysis.