Unprecedented isolation of alk-1-en-3-yn-1-yl intermediates in the catalytic oligomerisation of alk-1-ynes by cationic Lewis base-free zirconocene complexes

Abstract

[Zr(C₅Me₅)₂Me{(4-C₆H₄F)₄}]1 catalyses the rapid regioselective oligomerisation of RCCH to 2,4-disubstituted-but-1-en-3-ynes (R = Bu^t, Prⁿ, Me, Ph, 4-C₆H₄Me) and 1,4,6-trisubstituted-hexa-1,3-dien-5-ynes (R = Prⁿ, Me); isolation of the unprecedented crystalline complexes, [Zr(C₅Me₆)₂{CHC(R)CCR}]⁺(R = Bu^t2a, Prⁿ2b) and [Zr(C₅Me₅)₂{C(SiMe₃)CHCHC(SiMe₃)CCSiMe₃}]⁺3f, provides firm evidence for the catalytic cycle.