3. Make simple 2-level models for forward and back-donation between BFs (electro

Question

3. Make simple 2-level models for forward and back-donation between BFs (electron acceptor) and NH3 (electron donor) based on the following data: BF3 NH3 ionization energy +10 eV ionization energy = +15 eV, electron affinity = + 2.5 eV electron affinity 2.0 eV (a) Make an estimate for the relevant HOMO and LUMO energies from the data above (explain the basis for your estimate) (b) Make a guess for what the matrix element coupling HOMO(NH) with LUMO(BF3) (c) Then construct and diagonalize the 2 by 2 matrix describing electron donation from NH3 (d) Repeat steps (b) and (c) for HOMO(BF) coupled to LUMO(NH3). Justify in particular should be (sign, magnitude), explaining your reasoning carefully (energy or spatial considerations). The geometry of the complex is F3B...NH3 to BF3 and report your predicted energy lowering in kcal/mol (1 eV 100 kJ/mol), and show the new eigenvector you obtain and discuss it. why your value for the coupling (W) is the same, or larger, or smaller and compare your energy lowering and eigenvectors.

Explanation / Answer

Lewis base is a species with an available (reactive) pair of electrons

Lewis acid is an electron pair acceptor

Lewis acid's LUMO – its Lowest Unoccupied Molecular Orbital (MO)- NH3
interacts with the
Lewis base's HOMO – its Highest Occupied Molecular Orbital –   BF3
  to give a bonding molecular orbital

LUMO + HOMO Bonding MO

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