Dynamic 1H NMR spectroscopy of η2-ethylene transition metal complexes

The low-temperature ¹H NMR spectra of bis(ethylene)trimethylphosphinenickel (1), η⁵-cyclopentadienyl(ethylene)methylnickel (2a), bis(ethylene)-η⁵-cyclopentadienylcobalt (2b), [bis(1-ethyl-2,4,6-triphenylphosphorinyl)nickel]P,P′-nickel(ethylene) (3) and η⁵-cyclopentadienyl(ethylene)hydrido(triphenylphosphine)ruthenium (4) exhibit {AA′B′B} (1) {ABB′A} (2a and 2b), {ABA′B′} (3) or {ABCD} (4) spin patterns, respectively, for the complexed ethylene. A full line shape analysis including all the proton couplings was performed for the ethylene rotation in 1, 2a and 2b. In addition to olefin rotation, a reversible intramolecular β-H-elimination was confirmed for 4 by magnetization transfer experiments.