Reactions of in situ generated (η2-phenyltrimethylsilylacetylene)zirconocene

Article abstract of DOI:10.1016/0022-328X(91)86143-E

The five-membered metallacycle (1, R¹ = SiMe3, R² = Ph) is a suitable starting material for the in situ generation of the reactive (η²-phenyltrimethylsilylethyne)zirconocene (3).Thus, thermolysis of 1 (70 deg C) with trimethylphosphane gives Cp2Zr(Me3SiC<*>CPh)(PMe3) (8) and free Me3SiC<*>CPh (4).Subsequent reaction of 8 with acetophenone produces (9, R¹ = SiMe3, R² = Ph).Thermolysis of 1 in the presence of CpW(CO)3H also results in the liberation of one equivalent of 4.The reactive intermediate 3 is protonated to giveCp2Zr(CR¹=CHR²)(μ-OC)W(CO)2Cp (12, R¹ = SiMe3, R² = Ph).Treatment of 1 with in acetonitrile gives the cationic (13a: R¹ = SiMe3, R² = Ph) and its regioisomer 13b (R¹ and R² exchanged).There is evidence that the complexes 13 are formed by acetonitrile addition to thermally-generated 3 to give , which is then subsequently protonated at the basic ring nitrogen.These reactions show that a readily available metallacyclopentadiene system can be used as a convenient synthetic equivalent of a very reactive (η²-alkyne)metallocene complex by thermally induced equilibration in the presence of suitable trapping reagents.