In addition, keteniminyl anion 3d and 3e with the alkyl substituent at nitrogen exhibit more acute P-C-C angles (3d: 139. Hydrogen atoms (except H40 in 3e) and disordered parts in the molecules are omitted for clarity. Thermal ellipsoids are shown at the 50% probability level. Important bond lengths and angles are given in Table , and crystallographic details are given in the supporting information. The comparison of the keteniminyl anions 3 with the ketenyl anion 4 and diazomethanide 5 reveals distinct differences in their P-C-C angles. The angle in ketenyl anion 4 is smaller than those of the aryl-substituted keteniminyl anions 3a-c but larger than those in the alkylsubstituted systems 3d and 3e (Table ). In contrast, the corresponding angle in the diazomethanide 5 amounts to 125.9(2), making it the most acute angle within the isoelectronic series 3-5. In case of neutral "carbones", the degree of bending has been attributed to the acceptor properties of the ligands, with stronger accepting capabilities resulting in larger angles. For instance, the dicarbonyl complex C(CO)2 (carbon suboxide C3O2) has a larger bending angle of 156 o than the dinitrogen complex C(N2)2 (122 o ), because CO is a better π-acceptor than N2. The same trend is observed for the anions [C(CN)(CO)] -(166 o ) and [C(CN)(N2)] -(134 o ) and for compounds 4 and 5. Hence, the structures 3-5 reflect the decreasing accepting property of the ligands in the series: :CNAr > CO > :CNAlk > N2. This aligns with the viability of the exchange reactions, which follows the relative stability order: