(1) 0.4 g of analytically pure Co(ClO4)2-6H20, and 0.2 g of analytically pure ethoxysalicylaldehyde, and 0.3 mL of an aqueous solution of methylamine with a weight percent concentration of 40% were dissolved in 10 mL of a mixed solution of anhydrous methanol and analytically pure N,N'-dimethylformamide (DMF) in a volume ratio of 1:1;
(2) slowly add analytically pure potassium hydroxide to the solution prepared in step (1) with constant stirring, and adjust the pH at 9.5;
(3) transfer the solution prepared in step (2) into a reaction kettle of polytetrafluoroethylene, and react it at 140C for 100 hrs, cool it down to room temperature, open the kettle, filter it, and wash it with anhydrous methanol, to obtain a single-crystalline grade of N,N '-dimethylcarbamic acid complex, and then N,N'-dimethylcarbamic acid can be obtained by dissolving and recrystallizing the single crystal grade N,N'-dimethylcarbamic acid complex.
