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 paramagnetic chemical shifts, within the frame of the dynamic NMR method. Conformational dynamics of the complex is conditioned by the process of racemization (with the value of the Gibbs activation energy ΔG≠298 = 58±3 kJ/mol). Due to substantial temperature dependence of paramagnetic shifts, the complex is essentially a 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 solution of C6D6 and the structure in the crystalline phase, found from the data of the X-ray structural study of the similar complex.