Crystal structure of cobalt(II) complexes with imidazoline nitroxide

Abstract

The crystal structures of Co(II) coordination compounds CoL 2-α modification (I), CoL2(CH3OH)2 (II), and CoL2Py2(III) — where L is a stable nitroxide 4-(3′,3′,3′-trifluoro-2′-oxypropylene)-2,2,5,5-tetramethyl-3-imidazoline-l-oxyl (L), were determined. It was found that the tetrahedral surroundings of cobalt in I consist of the O and N donor atoms of the deprotonated enaminoketone groups of L. In II and III, the same atoms form the equatorial plane of the centrosymmetric octahedral environment of the central atom in which the axial positions are occupied by the methanol O atoms or the pyridine N donor atoms. In the octahedral coordination centers of II and III, the Co-O and Co-N distances exceed analogous distances in the tetrahedral coordination center of I, substantially increasing the chelate angle in I compared to II and III. In I, the Co-O and Co-N bond lengths and the OCoN chelate angles are, respectively, 1.921(4), 2.006(4) A, 93.6(2)° in II, 2.014(4), 2.177(4), Co-OOH 2.146(4) A, 86.9(2)° in the two crystallographically independent molecules of III, 2.031(2) and 2.022(2), 2.170(2) and 2.193(2), Co-NPy 2.213(2) and 2.219(2)A, 87.04(7) and 87.20(7)°. Compounds I and III are molecular. Compound II in the solid state has a layered polymer structure due to hydrogen bonding between the O atoms of the nitroxyl groups of L and the O atoms of the coordinated alcohol molecules.