NITRONES AS LIGANDS IN COMPLEXES OF CU(II), MN(II), CO(II), NI(II), FE(II), AND FE(III) WITH N-TERT-BUTYL-ALPHA-(2-PYRIDYL)NITRONE AND 2,5,5-TRIMETHYL-1-PYRROLINE-N-OXIDE

The use of nitrones as ligands was explored by preparing and character izing complexes of N-tert-butyl-alpha-(2-pyridyl)nitrone (2-PyBN) and 2,5,5-trimethyl-1-pyrroline-N-oxide (M3PO) with Cu(II), Mn(II), Co(II) , Ni(II), Fe(II), and Fe(III) hexafluoroacetylacetonates (hfac). Neutr al Cu(2-PyBN)(hfac)(2), 1, was formed when equimolar amounts of Cu(hfa c)(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 struc tures. Geometry changes in 2-PyBN on complexation indicate a more loca lized nitrone C=N bond In 1-5. Crystalline dimers with formulas [M(M3P O)(hfac)(2)](2) for M(II) = Mn (6), Co (7), and Ni (8) were obtained f rom equimolar solutions of M(hfac)2 and the monodentate M3PO. The two M(II) ions are bridged by two M3PO coordinated in a bis, mu-1,1 fashio n. With Fe(hfac)(2) and M3PO, however, an apparent air oxidation led t o a (mu-oxo)diiron(III) complex [Fe(M3PO)(hfac)(2)](2)(mu-O) (9), whil e with Zn(hfac)(2) and N-tert-butyl-alpha-(phenyl-2-pyridyl)nitrone (2 PyPhBN) the neutral Zn(2-PyPhBN) (hfac)(2) (10) was obtained. Results are compared to reported nitronyl nitroxide complexes.