The molecular structure of the 2, 4, 6-Tri-Phenyl- λ 3 -Phosphinine dianion was investigated. The geometric parameters are calculated by B3LYP density functional model using the 6-31G**, 6-31+G**, 6-311G** and 6311+G** basis set, resulting in a stable structure with minimal energy. The molecular structure of titled compound admits C2 symmetry, which coincides with the bisector of the heterocycle ring. The NBO analysis was calculated using both variation principle (B3LYP) and perturbation theory (MP2). The results from natural bond orbital (NBO) analysis describe the type of hybridization for each NBO and indicate different transfers of intra-molecular charge (ICT), which stabilizes this system.

Also, the NBO calculations show that σ (P-C) bonds are formed from an sp2,26, sp2.22 and sp2.09 hybrid on carbon, respectively, at B3LYP/6-31G (d, p), B3LYP/6-31+G (d, p) and MP2/6-31G levels of theory. These calculations determined that strongest electron donation occurs from a lone pair orbital on the carbon atom LP (C34) to the anti-bonding acceptors π *(C32-C33) and π *(C35-C36); the corresponding E2 measures 67.42 k.cal/mol and 115.42 k.cal/mol, respectively, at B3LYP and MP2 theoretical levels. The MP2 method overestimates the energy E2 compared to B3LYP calculation.

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DFT calculation and NBO population analysis of the 2,4,6-Tri-Phenyl- λ 3 - Phosphinine dianion