Nitrones as Ligands in Complexes of Cu(II), Mn(II), Co(II), Ni(II), Fe(II), and Fe(III) with N-tert-Butyl-α-(2-pyridyl)nitrone and 2,5,5-Trimethyl-1-pyrroline-N-oxide

The use of nitrones as ligands was explored by preparing and characterizing complexes of N - tert -butyl-α-(2-pyridyl)nitrone (2-PyBN) and 2,5,5-trimethyl-1-pyrroline- N -oxide (M 3 PO) with Cu(II), Mn(II), Co(II), Ni(II), Fe(II), and Fe(III) hexafluoroacetylacetonates (hfac). Neutral Cu(2-PyBN)(hfac) 2, 1, was formed when equimolar amounts of Cu(hfac) 2 and the bidentate 2-PyBN were mixed in methylene chloride. Under the same preparation conditions, an unexpected ligand exchange led to crystalline salts of formula [M(2-PyBN) 2 hfac][M(hfac) 3 ] for M(II) = Mn ( 2 ), Co ( 3 ), Ni ( 4 ), and Fe ( 5 ) as determined by their X-ray structures. Geometry changes in 2-PyBN on complexation indicate a more localized nitrone C N bond In 1 − 5 . Crystalline dimers with formulas [M(M 3 PO)(hfac) 2 ] 2 for M(II) = Mn ( 6 ), Co ( 7 ), and Ni ( 8 ) were obtained from equimolar solutions of M(hfac) 2 and the monodentate M 3 PO. The two M(II) ions are bridged by two M 3 PO coordinated in a bis, μ-1,1 fashion. With Fe(hfac) 2 and M 3 PO, however, an apparent air oxidation led to a (μ-oxo)diiron(III) complex [Fe(M 3 PO)(hfac) 2 ] 2 (μ-O) ( 9 ), while with Zn(hfac) 2 and N - tert -butyl-α-(phenyl-2-pyridyl)nitrone (2PyPhBN) the neutral Zn(2-PyPhBN) (hfac) 2 ( 10 ) was obtained. Results are compared to reported nitronyl nitroxide complexes.