Studies of the spectra of copper dimethyl-glyoxime, nickel dimethylglyoxime and nickel ethylmethylglyoxime in various solvents

Abstract

The ultraviolet and visible spectra of copper dimethyl-glyoxime exhibit significant shifts as the solvent medium is varied; no such changes were observed for nickel dimethylglyoxime and nickel ethylmethylglyoxime. The observed variations in the metal-to-ligand charge transfer bands for copper dimethylglyoxime are attributed to slight changes in the nature of the Cu-N bonds; the absence of such changes in the corresponding band in nickel dimethylglyoxime is taken to indicate an insignificant variation in the Ni-N bonds of the two chelates of nickel in different solvents. The presence of small amounts of n-butylamine changed the spectra of copper dimethylglyoxime very significantly while 100-fold excesses of n-butylamine did not alter the spectra of the chelates of nickel. These changes in the spectra of copper dimethylglyoxime were used to establish the assignment of the metal-to-ligand charge transfer band. Finally, in agreement with other investigators, it is concluded that the difference in solubility between copper dimethylglyoxime and nickel dimethylglyoxime in polar solvents is due to the greater tendency of copper dimethylglyoxime to complex with solvent molecules. The higher solubility of nickel ethylmethyl-glyoxime in organic solvents is attributed to stronger crystal forces in both nickel dimethylglyoxime and copper dimethylglyoxime. The stronger forces in copper dimethylglyoxime are due to the well-established Cu-O bonds, and the stronger forces in nickel dimethylglyoxime are attributed to Ni-Ni interactions.