NMR spectroscopy of paramagnetic complexes. Part 39—natural abundance2H NMR of paramagnetic sandwich compounds
作者:
Janet Blümel,
Peter Hofmann,
Frank H. Köhler,
期刊:
Magnetic Resonance in Chemistry
(WILEY Available online 1993)
卷期:
Volume 31,
issue 1
页码: 2-6
ISSN:0749-1581
年代: 1993
DOI:10.1002/mrc.1260310103
出版商: John Wiley&Sons, Ltd.
关键词: Paramagnetic NMR;Natural abundance2H NMR;2H signal narrowing;2H isotope effect;EHMO calculation
数据来源: WILEY
摘要:
AbstractThe methylated metallocenes (MeCp)2M with M = V, Cr, Mn, Co, Ni (1–5) were investigated by1H and2H NMR spectroscopy at natural abundance. The2H NMR signals are narrower by a factor of up to 30 compared with the corresponding1H 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 the1H 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 from13C 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 cr
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