Ferrocene substituted nitronyl nitroxide and imino nitroxide radicals. Synthesis, X-ray structure and magnetic properties

• Published in: Journal of organometallic chemistry 2001-12, Vol.637, p.507-513
• Main Authors: Sporer, Christian, Ruiz-Molina, Daniel, Wurst, Klaus, Kopacka, Holger, Veciana, Jaume, Jaitner, Peter
• Format: Article
• Language: English
• Subjects: Crystal structures; Ferrocene; Magnetochemistry; Organic radical
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/S0022-328X(01)00954-8

The synthesis, X-ray structure and magnetic properties of two new ferrocene substituted nitroxide monoradicals are described. The magnetic susceptibility data was nicely fitted in both cases to the Curie–Weiss law yielding the Weiss constants of θ=−1.8 and −1.1 K for radicals 1 and 2, respectively. This result evidenced the presence of very weak antiferromagnetic intermolecular interactions between neighbor molecules. Moreover, the X-ray structure of the key precursor 2,3-bis(hydroxyamino-)-2,3-dimethylbutane ( 3) is also included. The synthesis of the key precursor of Ullmann's radicals 2,3 bis(hydroxyamino-)-2,3-dimethylbutane is re-examined and a procedure for obtaining increasing yields and characterization by NMR methods including an X-ray crystal structure is presented. Single crystals of the free base 2,3 bis(hydroxyamino-)-2,3-dimethylbutane were obtained by sublimation. The reaction of ferrocene-diladehyde with 2,3 bis(hydroxyamino-)-2,3-dimethylbutane gives a mixture of formyl–ferrocene imino nitroxide and formyl–ferrocene nitronyl nitroxide. The X-ray crystal structure and magnetic characterization of both ferrocene radicals are reported.