REACTIONS OF Cp2M(CO)2 AND Cp2M(CO)(PPh3) (M=Zr, Hf) WITH ACETYLENES: FORMATION OF SOME METALLACYCLOPENTADIENE COMPLEXES OF ZIRCONOCENE AND HAFNOCENE

Article abstract of DOI:10.1016/0022-328X(84)80601-4

The photolysis of Cp2Zr(CO)2 with diphenylacetylene or 3-hexyne yields, the respective zirconacyclopentadiene complexes Cp2Zr(C4R4) (R=Ph, Et).The thermolysis of Cp2Zr(CO)2 with 3-hexyne or bis(pentafluorophenyl)acetylene also leads to the formation of Cp2Zr(C4R4) (R=Et, C6H5).HCl degradation of Cp2Zr yields 1,2,3,4-tetrakis(pentafluorophenyl)-1,3-butadiene and Cp2ZrCl2.When Cp2Zr(CO)2 is heated with diphenylacetylene in a closed vessel, tetraphenylcyclopentadienone is formed along with Cp2Zr(C4Ph4).The hafnacyclopentadiene complexes Cp2Hf(C4R4) (R=Ph, C6G5, Et) are obtained when Cp2Hf(CO)2 is thermolyzed with the respective acetylene in refluxing octane.Complexes Cp2Hf(C4R4) (R=Ph, Et) are also formed when Cp2Hf(CO)2 is photolyzed with diphenylacetylene or 3-hexyne, respectively.The monocarbonyl-triphenylphosphine complexes Cp2M(CO)(PPh3) (M=Zr, Hf) can be prepared via the irradiation of hydrocarbon solutions of Cp2M(CO)2 and triphenylphosphine.These complexes react readily with diphenylacetylene and 3-hexyne at 55-60 deg C to afford the corresponding metallacyclopentadiene complexes Cp2M(C4R4) (M=Zr, Hf; R=Ph, Et).The metallocene dicarbonyls Cp2M(CO)2 (M=Zr, Hf) are readily prepared via the reduction of Cp2MCl2 (M=Zr, Hf) with amalgamated magnesium metal in THF solution under one atmosphere of carbon monoxide.