Reductive cleavage of N,N′-di-tert-butyl­carbodi­imide generates tert-butyl­cyanamide ligands, (Me(3)CNCN)(−), that bind potassium both end-on and side-on in the same single crystal

N,N′-Di-tert-butyl­carbodi­imide, Me(3)CN=C=NCMe(3), undergoes reductive cleavage in the presence of the Gd(II) complex, [K(18-crown-6)(2)][Gd(II)(NR (2))(3)] (R = SiMe(3)), to form a new type of ligand, the tert-butyl­cyanamide anion, (Me(3)CNCN)(−). 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, (Me(3)CNCN)(−). The crystal contains [K(18-crown-6)(H(2)O)][NCNCMe(3)-kN], in which one ((t)BuNCN)(−) anion is coordinated end-on to potassium ligated by 18-crown-6 and water, as well as [K(18-crown-6)][η(2)-NCNCMe(3)], 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, (C(9)H(20)N(2)O), 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(C(5)H(9)N(2))(C(12)H(24)O(6))]·[K(C(5)H(9)N(2))(C(12)H(24)O(6))(H(2)O)]·C(9)H(20)N(2).