Synthesis and characterization of phenanthren-o-iminoquinone complexes of rare earth metals

The complexes Ln(L)3 (L = N-(2,6-di-isopropylphenyl)-phenanthren-o-iminoquinone, Ln = Sc (1), Yb (2)) were synthesized by the reactions of phenanthren-o-iminoquinone L with scandium or ytterbium metals in benzene medium. The X-ray analysis revealed that the molecule of 2 consists of Yb3+ cation coordinated by three phenanthren-o-iminosemiquinone ligands in η2 fashion. Both complexes are paramagnetic. The magnetic moments of 1 (2.7 μB) are consistent with the formulation Sc(L−)3 (L− = radical anion), in which spins on the individual units are uncoupled. The magnetic moments of 2 (3.7 μB) indicate some antiferromagnetic coupling of paramagnetic centers in the molecules. The EPR spectrum of 1 in toluene exhibits a broad unresolved signal with g 2.0029 assigned to unpaired electrons of phenanthren-o-iminosemiquinone ligands. The reactions of phenanthren-o-iminoquinone L with NdI2 and DyI2 in benzene led to formation of iodide/phenanthren-o-iminoquinone complexes I2Ln(L)2 of Nd(III) (3) and Dy(III) (4). Besides, from the reaction with DyI2 the product of partial disproportionation of 4 was isolated and identified as homoleptic complexes Dy(L)3 (5), structure of which turned out identical to that of 2. The same reactions in ether or crystallization of 3 and 4 from ether yielded solvated complexes I2Ln(L)2(Et2O)2 (Ln = Nd (6), Dy (7)). The X-ray analysis of 6 and 7 has displayed unprecedented for iminoquinonates η1 mode of metal–ligand coordination. Magnetic moments of 3, 4, 6 and 7 (3.3, 10.4, 3.4 and 10.6 μβ respectively) corresponding to μeff of Nd(III) and Dy(III) suggest that in the compounds exists quick reversible intramolecular interligand electron transfer which results in diamagnetism of the total ligand system. Magnetic moment of 5 (12.8 μB) corresponds to formulation of Dy3+(L−)3 with uncoupled spins of metal atom and the ligands.

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