NMR spectra and magnetic exchange interactions in nickel(II) complexes with a chelated nitronyl nitroxide radical

H-1 or H-2 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 H-1 or H-2 NMR conta ct 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, propos ing a new method to estimate the exchange coupling constant J value from th e NMR contact shifts. Variable temperature H-2 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 acetyl acetonates.