Reductive cleavage of N,N′-di-tert-butyl­carbodi­imide generates tert-butyl­cyanamide ligands, (Me3CNCN)−, that bind potassium both end-on and side-on in the same single crystal

N,N′-Di-tert-butyl­carbodi­imide, Me3CN=C=NCMe3, undergoes reductive cleavage in the presence of the GdII complex, [K(18-crown-6)2][GdII(NR2)3] (R = SiMe3), to form a new type of ligand, the tert-butyl­cyanamide anion, (Me3CNCN)−. This new ligand can bind metals with one or two donor atoms as demonstrated by the isolation of a single crystal containing potassium salts of both end-on and side-on bound tert-butyl­cyanamide anions, (Me3CNCN)−. The crystal contains [K(18-crown-6)(H2O)][NCNCMe3-kN], in which one (tBuNCN)− anion is coordinated end-on to potassium ligated by 18-crown-6 and water, as well as [K(18-crown-6)][η2-NCNCMe3], in which an 18-crown-6 potassium is coordinated side-on to the terminal N—C linkage. This single crystal also contains one equivalent of 1,3-di-tert-butyl urea, (C9H20N2O), which is involved in hydrogen bonding that may stabilize the whole assembly, namely, aqua­(tert-butyl­cyanamidato)(1,4,7,10,13,16-hexa­oxa­cyclo­octa­deca­ne)potas­sium(I)–(tert-butyl­cyanamidato)(1,4,7,10,13,16-hexa­oxa­cyclo­octa­deca­ne)potas­sium(I)–N,N′-di-tert-butyl­carbodi­imide (1/1/1) [K(C5H9N2)(C12H24O6)]·[K(C5H9N2)(C12H24O6)(H2O)]·C9H20N2.