Complexes of the nitroxide ligand 2-(2-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-l/f-imidazolyl-1 -oxy 3-oxide (NIT2-Py) with NiCl2 (1, CmHjíCIíNíNíO*) and MnCl2 (2, C26H36Cl6MnN604) have been structurally and magnetically characterized. Both complexes are centrosymmetric three-spin systems in which the nitroxyl group is coordinated to the metal ion. Metal-nitroxide interactions of -110 cm-1 for 1 and -80 cm-1 for 2 (H = -2JS¡Sj) are observed. These coupling constants are weaker than usually observed in previously reported examples (<-200 cm-1 for Ni and -150, -200 cm-1 for Mn). This result was rationalized by considering a reduced overlap of the magnetic orbitals due to a peculiar geometric arrangement in the chelate. Comparison to literature reported species is obtained from the homologous hexafluoroacetylacetonates, 3 (C22H18F12N3Ni06) and 4 (C22Hi8F12MnN3C>6), which exhibit similar structural and magnetic properties. Coordination of the nitroxyl group in these derivatives illustrates the use of the chelate effect for designing exchange-coupled nitroxide derivatives of poor electrophilic metal centers. Relevant structural parameters are as follows: 1, monoclinic, P2\¡c, a = 8.890
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