Unexpected conformational dynamics associated with racemization in the [Cp′′′2NdI] complex in solution {where Cp′′′ = 1,3,4-tris(tert-butyl)cyclopentadienide}

Abstract

¹H NMR measurements are reported for the C₆D₆ solution of the complex bis(tris(tert-butyl)cyclopentadienyl)neodymium(III) iodide [Cp′′′₂NdI] {where Cp′′′ = 1,3,4-tris(tert-butyl)cyclopentadienide}. Temperature dependences of the ¹H NMR spectra of the complex have been analyzed using the bandshape analysis, taking into account the temperature variation of the paramagnetic chemical shifts, within the frame of the dynamic NMR method. The conformational dynamics of the complex are conditioned by the process of racemization (with the value of the Gibbs activation energy ΔG^‡₂₉₈ = 58 ± 3 kJ mol⁻¹). Due to the substantial temperature dependence of the paramagnetic shifts, the complex is essentially an NMR thermosensor reagent for local temperature monitoring. Good agreement between the calculated and experimental lanthanide-induced paramagnetic shifts in the ¹H NMR spectra indicates the similarity of the structure of the complex in a solution of C₆D₆ and the structure in the crystalline phase, found from the data of the X-ray structural study of the similar complex.