ABSTRACT Quantum chemical calculations using density functional theory BP86 and M06-2X functionals in conjunction with def2-TZVPP basis sets have been carried out on the title molecules. The calculation results reveal… Click to show full abstract
ABSTRACT Quantum chemical calculations using density functional theory BP86 and M06-2X functionals in conjunction with def2-TZVPP basis sets have been carried out on the title molecules. The calculation results reveal that the N-imides R3NNX are always clearly higher in energy than the imine isomers R2NN(X)R. In the case of phosphane imides R3PNX and the isomers R2PN(X)R, the substituent R plays a critical role in determining their relative stabilities. When R is hydrogen or phenyl group, R3PNX are always higher in energy than R2PN(X)R but the former are more stable than the latter when R = Cl. Interestingly, the Me3PNX and Me2PN(X)Me are quite close in energy. The energy decomposition analysis suggests that the P–N bond in the phosphane imides R3PNX (R = H, Cl, Me, Ph; X = H, F, Cl) should be described in terms of an electron-sharing single bond between two charged fragments R3P+-NX− that is supported by (R3P)+←(NX)− π-backdonation. The π-bond contributes 14–21% of the total orbital interactions while the σ-bond provides 60–68% of ΔEorb. GRAPHICAL ABSTRACT
               
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