In this report, different models of bonding and structure such as Lewis, VSEPR, Ligand close packing (LCP), VB, qualitative MO and QTAIM have been applied to analyze the Bonds and structures of two equilibrium geometries (planar D 2h and perpendicular D 2d ) of . The geometries were optimized at near RHF and MP2 limit using cc-pVTZ basis set. While the above bonding models are successfully applied for predicting the low energy isomers of molecules, prior to solving the Schrödinger equation, it

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... s shown that the cited models fail in predicting the existence of perpendicular, D 2d form of . In this regard the interpretations of significant energetic stabilization of D 2d form over planar isomer has also been revisited. This is attributed to the hidden effect of the Pauli Exclusion principle. 2 2 4 C H  2 2 4 C H 