Synthesis and characterization of diphenylglyoximato cobalt(III) complexes. The molecular structures of trans-bis(diphenylglyoximato)(alkyl)(pyridine)cobalt(III), with alkyl = CH2SiMe3, CH2CMe3 and CF3

Abstract A series of Co(III) diphenylglyoximato (dpgh) complexes, pyCo(dpgh) 2 R, with R=Cl ( 2a ), CH 3 ( 3a ), CH 2 Me ( 4a ), (CH 2 ) 2 Me ( 5a ), (CH 2 ) 3 Me ( 6a ), CHMe 2 ( 7a ), CH 2 SiMe 3 ( 8a ), CH 2 CMe 3 ( 9a ), CH 2 CHCH 2 ( 10a ), CH 2 Ph ( 11a ), and CF 3 ( 12a ) were prepared, using Co(dpgh)(dpgh 2 )Cl 2 ( 1a ) as an entry to this system. The compounds were thoroughly characterized by 1 H and 13 C NMR spectroscopy, the spectra of which were compared to the corresponding Co(III) dimethylglyoximato (DH) complexes, pyCo(DH) 2 R ( 2b – 12b ). The NMR results suggest that the dpgh ligand is less electron-donating than DH. X-ray diffraction studies of complexes 8a , 9a and 12a demonstrate that subtle, but detectable structural changes occur upon substitution of dpgh for DH, due to increased interactions of the axial alkyl ligand with the equatorial ligand set.