Reacting BF3 + NH3

A file containing both of these molecules is in the library. To load this file select Load a Molecule from Library on the Build Options dialog and OK.

open the inorganics directory

select the bf3_nh3 file and Open

You should now have

Run Mopac to optimize the structure.  Rotate the result it should be clear that the boron is no longer planar. You can examine the geometry in build mode.

Click to start the geometry calculation function. Click the N and B atoms and the information N   B 1.785 Cov.Sum 1.57 should be on the status line. The N-B distance indicates a long bond since it is 0.2 Angst longer than the sum of the covalent radii (this is normal for dative or coordinate bonds). The F-B-F angles are just over 113
which is a lot less than the 120 of a planar structure. If you would like to have a bond between the N and B atoms then use the Mk.CONN command in build mode to add a temporary bond or connection. These may be removed using the Rm.CONN command.

In build mode use the Rm.CONN command first and then Del.MOL to delete the ammonia molecule and optimize the BF3 again when it should return to planar geometry.