Synthesis and Characterization of and Cis−Trans Influence in Cobaloximes with Glyoxime as the Equatorial Ligand

Abstract

The synthesis and characterization of RCo(gH)2Py (R = methyl through decyl) and XCo(gH)2Py (X = Cl, Br, NO2, N3) is described. Most of these complexes are new and have been synthesized for the first time. The X-ray structure of N3Co(gH)2Py is reported. The cis−trans influence has been studied by 1H and 13C NMR, UV−vis, and X-ray diffraction. For a range of X ligands, a clear trend between the 1H and 13C chemical shifts of the axial and equatorial ligands as well as with the Co-dioxime CT band has been observed. More than 20 correlations have been found. δ(13C) values for CN, Pyα, Pyβ, and Pyγ in the alkylcobaloximes always occur upfield by 1−3 ppm compared to those in the inorganic cobaloximes, and δ(13C) for CN in gH complexes occur significantly upfield, by 12−13 ppm, compared to the values in the corresponding dmgH, chgH, and dpgH complexes.