Reactions of Cp 2M(CO) 2 and Cp 2M(CO)(PPh 3) (M = Zr, Hf) with acetylenes: Formation of some metallacyclopentadiene complexes of zirconocene and hafnocene

Abstract

The photolysis of Cp 2Zr(CO) 2 with diphenylacetylene or 3-hexyne yields the respective zirconacyclopentadiene complexes Cp 2Z(C 4R 4) (R = Ph, Et). The thermolysis of Cp 2Z(CO) 2 with 3-hexyne or bis(pentafluorophenyl)acetylene also leads to the formation of Cp 2Z(C 4R 4) (R = Et, C 6F 5). HCl degradation of Cp 2Zr[C 6(C 6F 5) 4] yields 1,2,3,4-tetrakis(pentafluorophenyl)-1,3-butadiene and Cp 2ZrCl 2. When Cp 2Zr(CO) 2 is heated with diphenylacetylene in a closed vessel, tetraphenylcyclopentadienone is formed along with Cp 2Zr(C 4Ph 4). The hafnacyclopentadiene complexes Cp 2Hf(C 4R 4) (R = Ph, C 6F 5, Et) are obtained when Cp 2Hf(CO) 2 is thermolyzed with the respective acetylene in refluxing octane. Complexes Cp 2Hf(C 4R 4) (R = Ph, Et) are also formed when Cp 2Hf(CO) 2 is photolyzed with diphenylacetylene or 3-hexyne, respectively. The monocarbonyl-triphenylphosphine complexes Cp 2M(CO)(PPh 3) (M = Zr, Hf) can be prepared via the irradiation of hydrocarbon solutions of Cp 2M(CO) 2 and triphenylphosphine. These complexes react readily with diphenylacetylene and 3-hexyne at 55–60 °C to afford the corresponding metallacyclopentadiene complexes Cp 2M(C 4R 4) (M = Zr, Hf; R = Ph, Et). The metallocene dicarbonyls Cp 2M(CO) 2 (M = Zr, Hf) are readily prepared via the reduction of Cp 2MCl 2 (M = Zr, Hf) with amalgamated magnesium metal in THF solution under one atmosphere of carbon monoxide.