Fluxional Behavior of a Cadmium Zwitterion Complex: Proton Transport and Tautomerism in Methylene Chloride Solution

The synthesis and structure of the tautomeric Cd(II) isoindoline zwitterion coordination compound [Cd(4ʹ-MeLH)(NO3)2]·CH3OH (4ʹMeLH = 1,3-bis{2-(4-methylpyridyl)imino}isoindoline) are reported. In methylene chloride solution, tautomer interconversion occurs as the N-H proton moves between the identical imine nitrogen atoms. We report the kinetics of proton transfer as followed by variable temperature 1H NMR spectroscopy and demonstrate that methanol of solvation and adventitious water facilitate rapid proton transfer.