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

• Published in: Inorganic chemistry 1998-04, Vol.37 (7), p.1446-1453
• Main Authors: Villamena, Frederick A, Dickman, Michael H, Crist, DeLanson R
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic9709741

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 (M3PO) 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)2hfac][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(M3PO)(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 M3PO. The two M(II) ions are bridged by two M3PO coordinated in a bis, μ-1,1 fashion. With Fe(hfac)2 and M3PO, however, an apparent air oxidation led to a (μ-oxo)diiron(III) complex [Fe(M3PO)(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.