Molecular Hydrogen‐Induced Carbon Chain Rearrangement in Cyclopentadienyl‐Tethered Titanium(III) Permethyltitanocene Complexes

Abstract

Dihydrogen added at atmospheric pressure and ambient temperature to cyclopentadienyl‐tethered titanium(III) permethyltitanocene complexes induced the rearrangement of their tether [–CH2–C(Me)=C(R)–Ti], moving the double bond to the lateral position [–CH2–C(=CHR)–CH2–Ti]. The methyl substituent on the β‐carbon from the cyclopentadienyl ring is converted to methylene group binding the rearranged tether to titanium. Subsequent hydrogenation of compounds with [–CH2–C(=CHR)–CH2–Ti] R = Ph or SiMe3 gave saturated rearranged products whereas compound with [–CH2–C(=CMeCMe=CHMe)–CH2–Ti] resisted. Computational studies elucidated the reaction mechanism and established the catalytical role of molecular hydrogen. This type of isomerization can be conceived as a σ‐bond metathetic rearrangement leading to the formation of tethered complexes with decreased steric strain.