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The compounds RENi(BN) with RE ϭ Y, La, Ce, Pr, Tm and Yb were synthesized by solid state reactions from metal powders and α-BN at temperatures between 1000°and 1200°C. In addition, the mixed phases (Ca,Yb)Ni(BN) and (Ca,Tm)Ni(BN) were synthesized. All products were characterized by powder XRD measurements and indexed isotypic with the structure of Introduction Nitridoborates represent a group of compounds containing different types of (BN x ) anions, such as [BN] nϪ , [BN 2 ] 3Ϫ , [B 3 N 6 ] 9Ϫ , [B 2 N 4 ] 8Ϫ , and [BN 3 ] 6Ϫ [1]. Compounds with the [BN 2 ] 3Ϫ ion are well-known in combinations with alkaline and alkaline earth ions [2Ϫ14]. All the other nitridoborate ions are known from compounds containing rare-earth elements. These nitridoborates can occur as insulators (La 3 B 3 N 6 [15]), semiconductors (La 3 B 2 N 4 [16]), and as metals or superconductors (La 3 Ni 2 (BN) 2 N [17, 18]). Compounds with the [BN] nϪ anion are considered as being special, not only because the [BN] nϪ ion can be contained in superconducting compounds, but also because there is no clear charge assignment available in compounds owing the [BN] nϪ ion. In our present work we compare the electronic situation of [BN] nϪ with that of [C 2 ] nϪ where n can formally range between 2 and 6. In this context the BϪN or CϪC bond distances in compounds may serve as indicators for the respective ionic charge (n). The first single-crystal XRD structure determination of a compound containing a [BN] anion was established for CaNi(BN) [19], revealing a BϪN distance of 138 pm. For the superconducting compound La 3 Ni 2 (BN) 2 N, the BϪN 1799 CaNi(BN), consistent with the tetragonal space group P4/nmm. The bonding conditions of the (BN) anion are discussed in a perspective view on new nitridoborate compounds REM(BN) containing transition metal atoms (M) other than Ni.