Apical Isomer

Lithiums:

This is the apical lithium.

These make up a rectangle.

This is opposite the apical lithium

Methyl groups from two of the occupied faces (blue, pink, pink) have moved towards the unoccupied faces (red, pink, pink) to become almost coplanar with the four equivalent red lithiums. These methyl groups are located nearly over the edge separating the occupied and unoccupied edge. In order to pass from the occupied face (blue,pink, pink) to the unoccupied (red, pink, pink) a rotation of the methyl group hydrogens by 60 degrees is expected as the hydrogens are usually found (in calculations)to be eclipsing the lithium atoms of the face over which they reside. See the view which includes the hydrogens.