The synthesis and structure of the tautomeric Cd(II) isoindoline zwitterion coordination compound [Cd(4'-MeLH)(NO3)(2)].CH3OH (4'-MeLH = 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 H-1 NMR spectroscopy and demonstrate that methanol of solvation and adventitious water facilitate rapid proton transfer.