NMR Spectra and Magnetic Exchange Interactions in Nickel(II) Complexes with a Chelated Nitronyl Nitroxide Radical.
1H or (2)H NMR contact shifts of the beta-diketonate methine in the radical complexes [Ni(beta-diketonato)(2)(NIT2-py)] and [Ni(beta-diketonato)(tmen)(NIT2-py)](+) (NIT2-py = 2-(2'-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-3-oxide-1-oxyl and tmen = N,N,N',N'-tetramethylethylenediamine) were found to correlate to a product of the respective (1)H or (2)H NMR contact shifts of the methine in the nonradical complexes [Ni(beta-diketonato)(2)(tmen)] and the fractional contribution to the Ni(II) moiety arising from the magnetic interaction between nickel(II) ion and NIT2-py radical, proposing a new method to estimate the exchange coupling constant J value from the NMR contact shifts. Variable temperature (2)H NMR measurements of the C-D signals in [Ni(acac-d)(2)(NIT2-py)], [Ni(acac-d)(tmen)(NIT2-py)](+), and [Ni(acac-d)(2)(tmen)] suggested the topological discrimination of the acetylacetonates.
Yoshida
Takafumi
T
Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560 Japan.
Kaizaki
Sumio
S