1. Para-Substituted diphenylborylated organocobaloximes: Effects of substituents on conformation and redox properties
- Author
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Renata Dreos, Giorgio Nardin, Claudio Tavagnacco, Giovanni Tauzher, Lucio Randaccio, Silvia Peressini, Giorgio Pellizer, Fioretta Asaro, Patrizia Siega, Asaro, Fioretta, Dreos, Renata, Nardin, G., Pellizer, Giorgio, Peressini, Silvia, Randaccio, Lucio, Siega, Patrizia, Tauzher, G., and Tavagnacco, Claudio
- Subjects
chemistry.chemical_classification ,Stereochemistry ,Chemistry ,Ligand ,Aryl ,Organic Chemistry ,conformation and redox properties ,Electrochemistry ,Biochemistry ,Medicinal chemistry ,Redox ,para-diphenylboryl organocobaloxime ,Dissociation (chemistry) ,Spectral line ,Homolysis ,Inorganic Chemistry ,chemistry.chemical_compound ,Materials Chemistry ,para-diphenylboryl organocobaloximes ,Physical and Theoretical Chemistry ,Alkyl - Abstract
Some new derivatives of organocobaloximes containing para -substituted diphenylboryl groups, RCo(DH) 2− n (DB( p- XPh) 2 ) n L (R=alkyl or aryl group, L= N -MeIm, Py or H 2 O, X=OCH 3 , CH 3 or Cl, n =1 or 2) have been synthesized. The X-ray structures and the 1 H-NMR spectra are compared with those of the corresponding RCo(DH) 2− n (DBPh 2 ) n L and RCo(DBF 2 ) 2 L complexes. The insertion of X groups in the phenyl rings does not significantly affect the equatorial CoN distances, whereas the CoPy distances increase slightly in the order (DB( p- OCH 3 Ph) 2 ) 2 p- ClPh) 2 ) 2 2 ) 2 . 1 H-NMR spectra suggest that the conformational distribution in solution is similar to that observed in the corresponding BPh 2 derivatives. Electrochemical studies on the corresponding MeCo(DB( p- XPh) 2 ) 2 H 2 O compounds show a mono-electron Co(III)/Co(II) transfer reaction followed by two parallel reactions: (a) mono-electron Co(II)/Co(I) transfer; (b) homolytic dissociation of the CoC bond with the formation of Co(I) species, the relative rates of the two processes being dependent on X. As the electron-withdrawing power of the equatorial ligand increases, the reduction potentials associated with both Co(III)/Co(II) and Co(II)/Co(I) processes shift towards more positive values, indicating a decrease of electron density on the Co atom. The effects are comparable with those observed by changing the axial ligands.