Oxazolidine Nitroxide Transformation in a Coordination Sphere of the Ln(3+) Ions

Upon the interaction of the hydrated lanthanide(III) salts found in acetonitrile solution with a tripodal paramagnetic compound, 4,4-dimethyl-2,2-bis(pyridin-2-yl)-1,3-oxazolidine-3-oxyl (Rad), functionalized by two pyridyl groups, three neutral, structurally characterized complexes with diamagnetic polydentate ligands—[Dy(RadH)(hbpm)Cl(2)], [Yb(2)(ipapm)(2)(NO(3))(4)], and [Ce(2)(ipapm)(2)(NO(3))(4)(EtOAc)(2)]—were obtained. These coordination compounds are minor uncolored crystalline products, which were formed in a reaction mixture due to the Rad transformation in a lanthanide coordination sphere, wherein the processes of its simultaneous disproportionation, hydrolysis, and condensation proceed differently than in the absence of Ln ions. The latter fact was confirmed by the formation of the structurally characterized product of the oxazolidine nitroxide transformation during its crystallization in toluene solution. Such a conversion in the presence of 4f elements ions is unique since no similar phenomenon was observed during the synthesis of the 3d-metal complexes with Rad.