Alkyne-Functionalized Zirconocene Complexes: Synthesis, Structures, and Reactivities

Reactions of (phenylethynyl)lithium with substituted cyclopentenones gave the corresponding phenylethynyl-substituted cyclopentadienes 1,2-R2-4-(PhCC)C5H2 (R = Me (1a), Ph (1b)), which underwent subsequent deprotonation and transmetalation with ZrCl4 to yield the corresponding alkyne-functionalized zirconocene complexes {η5-[1,2-R2-4-(PhCC)C5H2]}2ZrCl2 (R = Me (2a), Ph (2b)). Thermal treatment of 2a,b with Ru3(CO)12 in refluxing benzene afforded the trinuclear complexes (3,4-R2C5H2)2(μ3-C4Ph2)Ru3(CO)6(μ-CO)2 (R = Me (3a), Ph (3b)) and the dinuclear complex (3,4-Ph2C5H2)2(μ-C4Ph2)Ru2(CO)5(μ-CO) (3c), via the unexpected cleavage of the two Cp′−Zr bonds. The crystal structures of 2b and 3a,c were determined by X-ray diffraction.