Formation of Binuclear Zigzag Hexapentaene Titanium Complexes via a Titanacumulene [Ti=C=C=CH2] Intermediate

Abstract

AbstractThe reaction of bis(η5:η1‐pentafulvene)titanium complexes with an allylidenephosphorylide Ph3P=C(H)‐ C(H)=CH2 leads to binuclear zigzag hexapentaene titanium complexes (Ti2a, Ti2b). The formation of the central C6H4 unit can be described as a spontaneous double C−H bond activation process, leading to an R3P=C=C=CH2 intermediate, as a synthon for a titanabutatriene fragment [(CpR)2Ti=C=C=CH2] (R: 2‐adamantyl, CH(p‐tol)2). In a subsequent dimerization Ti2a and Ti2b are formed, proofed by single‐crystal X‐ray diffraction and NMR measurements. The reaction sequence is confirmed by DFT calculations.