Bis( N , N -diethyl-4-methyl-4-piperazine-1-carboxamide) tetra-kis-(iso-thio-cyanato-κ N )-cobalt(II), a model compound for the blue color developed in the Scott test.

The complex, bis-( N , N -diethyl-4-methyl-4-piperazine-1-carboxamide) tetra-kis(iso-thio-cyanato-κ N )cobalt(II) ( N , N -diethyl-4-methyl-4-piperazine-1-carboxamide = di-ethyl-carbamazine), (C 10 H 22 N 3 O) 2 [Co(NCS) 4 ], is presented. This com-plex is a blue precipitate, insoluble in water but soluble in organic solvents, that is formed from the reaction of diethylcarbamazine citrate, a protonated tertiary amine, with cobalt(II) and thio-cyanate. This reaction, in the form of the Scott test, is a common presumptive test for cocaine hydro-chloride. The known cobalt compound, [K 2 Co(NCS) 4 ]·3H 2 O, has a deep-blue coloration due to the tetra-hedral [Co(NCS) 4 ] 2- that is also present in the ion pair with bulky amines, and is similar to the color of other tetra-hedral cobalt(II) complex ions, such as [CoCl 4 ] 2- . The structure is consistent with a previous proposal that a hydro-phobic ion pair formed between [Co(NCS) 4 ] 2- and two protonated mol-ecules of cocaine is responsible for the blue hydro-phobic products formed by cocaine in the Scott test.