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

The thermolysis of the phosphinidene complex [Cp*P{W(CO)(5)}(2)] (1) in tol uene in the presence of tBuC=CMe leads to the four-membered ring complexes [[{eta (2)-C(Me)C(tBu)}Cp*-(CO)W(mu (3)-P) (W(CO)(3)}]{eta (4)eta (1):eta ( 1)-P{W-(CO)(5)}WCp* (CO5)(2)(Me)C(tBu)}] (4) as the major product and [[W{C p*(CO)(2)}-(mu,eta (3):eta (2):eta (1)-{W(CO)(5)}] (5). (mu,eta (3):eta (2) :eta (1)-P-2(W(CO)(5)}] (5) The reaction of 1 with Ph=CPh leads to [[W(CO)( 2)(eta (2)-C(Ph)C(Ph)}][(eta (4):eta (1)-P{W-(CO)(2)}W(Cp*(CO)(2)}C(Ph)C(Ph )]] (6) The products 4 and 6 can be regarded as the formal cycloaddition pr oducts of the phosphido complex intermediate [Cp*(CO)(2)W=P -->W(CO)(5)] (B ), formed by Cp* migration within the phosphinidene complex 1. Furthermore, the reaction of 1 with PhC=CPh gives the minor product [[{eta (2):eta (1)- C(Ph)C(Ph)}(2){W(CO)(4)}(2)] {mu,eta (1):eta (1)-P{C(Me){C(Me)}(3)C(Me)}(C( Ph)}-(C(Ph)}] (7) as a result of a 1,3-dipolaric cycloaddition of the alkyn e 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 sing le-crystal X-ray structure analysis.