Synthese von isopropylsubstituierten cyclopentadienylliganden

Abstract

Abstract Starting from diisopropylcyclopentadiene, tri- and tetraisopropylcyclopentadienes can be synthesized by deprotonation with sodium amide and then by alkylation with 2-bromopropane. Pure tetraisopropylcyclopentadienylsodium and a 1:4 mixture of 1,2,3- and 1,2,4-triisopropylcyclopentadienylsodium are isolable. 200 MHz 1 H NMR spectra of octaisopropylferrocene were recorded at variable temperature. The activation barrier for tetraisopropylcyclopentadienyl ligand rotation was found to be 56.8 kJ/mol from the Eyring equation. The signal patterns observed in 1 H and 13 C NMR spectra of the ferrocenes [η 5 -C 5 H 5- n (i-Pr) n ] 2 Fe and the molybdenum complexes [η 5 -C 5 H 5- n (i-Pr) n ]Mo(CO) 3 CH 3 ( n = 1–4), are attributed to the presence of enantiotopic and diastereotopic methyl positions.