Accordingly, the charges at the C1 (q(C1) = -0.38) and nitrogen atom (q(N) = -0.27) in 3d are more negative than the corresponding values (q(C1) = -0.31; q(N) = -0.20) in 3b. The comparison of the structure parameters of 3 with the ketenyl (L2 = CO (4)) and diazomethanide anion (L2 = N2 (5) confirms the trends in the bending angles observed in experiment (see the Supporting Information). However, the bending potential at C1 toward a linear coordination is shallow, requiring only between 0.4 kcal (for 4) and 5.5 kcal/mol (for 5). Despite this, the significant deviation from linear geometry at C1, which minimizes steric repulsion between ligands, supports the structural interpretation of these species as anionic carbones [(POPh2)→C←L2] -. The calculated partial charges for the ligands P(O)Ph2 and L2 and for the C1 atom show that the negative charge of the anions is distributed across the three moieties (Table ). The CNAr ligand of 3b has a significantly higher negative partial charge than the other L2 ligands in 3d, 4 and 5. It is surprising that N2 in 4 has nearly the same negative charge (-0.22 e) as CO in 5 (-0.23 e), despite CO being much more strongly bonded than N₂. Further information about the chemical bonds is obtained from the energy decomposition analysis-natural orbital for chemical valence (EDA-NOCV) analysis of the anions. The intrinsic interaction energies ΔEint between the frozen fragments [(POPh2)C] -+ L2 follow the order 3b > 3d > 4 >> 5 (Table ), which is slightly different than the BDE values where 4 has a slightly higher De value than 3d. It indicates that the :CNCy ligand of 3d has a larger relaxation energy than CO in compound 4, which appears reasonable in view of the different size of the ligands. The relevance of the relaxation energy of the fragments for the BDE values has been stressed by Bickelhaupt, who coined the term "activation stress" for the fragment relaxation. The breakdown of ΔEint into the attractive components (∆Eorb, ∆Eelstat, ∆Edisp) and the Pauli repulsion ∆EPauli reveals the surprising result that the sum of the attractive forces in 5 between [(POPh2)C] -and N2 are higher than in 3b (L2 = CNAr) and 4 (L2 = CO). The significantly lower total attraction, however, results from the much higher Pauli repulsion in 5 than in the other molecules. It has been shown before that the Pauli repulsion between electrons with the same spin is a very important but often neglected energy term in chemical bonding. The bond lengths of chemical bonds are not determined by the maximum overlap of the bonding orbitals, which occurs at much shorter distances than the equilibrium length. Instead, they result from the strong influence of the Pauli repulsion on the electronic structure. The primary contribution to the bonding interactions between [(POPh2)C] -and L2 arises from the covalent (orbital) term ∆Eorb, which accounts for 65 -70 % of the total attraction. There are three orbital pair interactions ∆Eorb1-3, which account for over 90 % of ∆Eorb. The orbitals involved in these pairwise interactions can be identified through the shape of the deformation densities Δρ1-3 and the corresponding fragment orbitals associated with the orbital interactions ∆Eorb1-3. These interactions in 3b are depicted in Figure (see the Supporting Information for the other anions). The orbital interactions are dominated by the [(POPh2)C] -←L2 σ donation and the in-plane and out-of-plane [(POPh2)C] -→L2 π backdonation, in accordance with the classical Dewar-Chatt-Duncanson concept. Note that the division of the orbital interactions into σ and π orbitals comes from the symmetry of the fragments, which is lost in the final molecules. This leads to a mixture of [(POPh2