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NMR spectroscopy of paramagnetic complexes. Part 39 —natural abundance 2 H NMR of paramagnetic sandwich compounds
Author(s) -
Blümel Janet,
Hofmann Peter,
Köhler Frank H.
Publication year - 1993
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260310103
Subject(s) - chemistry , paramagnetism , carbon 13 nmr satellite , natural abundance , deuterium nmr , nuclear magnetic resonance spectroscopy , nmr spectra database , transverse relaxation optimized spectroscopy , deuterium , spectroscopy , spectral line , isotope , analytical chemistry (journal) , chemical shift , fluorine 19 nmr , carbon 13 nmr , nuclear magnetic resonance , crystallography , mass spectrometry , stereochemistry , atomic physics , organic chemistry , physics , condensed matter physics , chromatography , astronomy , quantum mechanics
The methylated metallocenes (MeCp) 2 M with M = V, Cr, Mn, Co, Ni (1–5) were investigated by 1 H and 2 H NMR spectroscopy at natural abundance. The 2 H NMR signals are narrower by a factor of up to 30 compared with the corresponding 1 H NMR signals, thus establishing an inexpensive method and a general improvement of the NMR spectra of paramagnetic π‐complexes. This has allowed the resolution of the signal splitting of Cp deuterons of 1 and 5 which could not be observed earlier in the 1 H NMR spectra. The origin of the small (1 and 5) and large (2–4) signal splittings is discussed and related to an extended Hückel calculation. The relative magnitude of the signal splitting is reproduced, but the signal assignment had to be deduced from 13 C NMR results. Primary isotope shifts of up to 4.0 ppm were found for 1, 2, 4 and 5. The much higher values for 3 (up to 16.6 ppm) reflect the combined influence of the intrinsic isotope shift and the isotope effect on the spin crossover.