6533b86dfe1ef96bd12caa6b

RESEARCH PRODUCT

Chlorodicyclopentadienyloxoniobium(V) complexes revisited: The origin of the asymmetry in the 1H- and 13C-NMR spectra, X-ray crystal structures and ab initio/HF and DFT/B3LYP calculations

Bernard GautheronAlexander PerjéssyJuha LinnantoErkki KolehmainenKatri LaihiaMaija NissinenR. Broussier

subject

ChemistryChemical shiftOrganic ChemistryAb initioSpace groupCrystal structureTriclinic crystal systemBiochemistryInorganic ChemistryCrystallographyCyclopentadienyl complexMaterials ChemistryPhysical and Theoretical ChemistryConformational isomerismMonoclinic crystal system

description

Abstract 1H- and 13C-NMR spectra of chlorodicyclopentadienyloxoniobium(V) complex I and its four 1,1′-dialkyl substituted derivatives II–V have been recorded and assigned based on DQF 1H,1H-COSY and PFG 1H,13C-HMQC and HMBC experiments. Non-equivalences of all cyclopentadienyl protons and carbons in II–V (as reflected by their different 1H- and 13C-NMR chemical shifts) are explained by synchronous and out-of-phase rotations of the substituted cyclopentadienyl rings. A non-equivalence of the methyls in III (1,1′-di-isopropyl) is explained by a detailed inspection of the rotamers of the isopropyl groups. The X-ray structural data show that III and IV (1-methyl-1′-tert-butyl) crystallize in the monoclinic P21/m no. 14 (with crystallographic mirror plane) and in the triclinic P1 no. 2 space groups, respectively. Ab initio/HF and DFT/B3LYP calculations gave energetically optimized structures close to those obtained by X-ray structural analyses. Further, calculated and experimental 13C-NMR chemical shifts are comparable for a majority of carbons.

http://www.scopus.com/inward/record.url?eid=2-s2.0-0037944142&partnerID=MN8TOARS