1. Search the Cambridge Structural Database (CSD) and find the structure of FeCl(SANE)₂. Create a data file with the information on that structure.

   Hint:

   • The best way is to perform a Formula search to get all structures in one search.
   • The hit structures should be saved in FDAT format so that they can be read properly by Cerius² (version 3.5).
   • One of the two structures for FeCl(SANE)₂ (1974 paper) you will find in the database is incorrect. The positional parameters of some atoms are faulty. However, this doesn't affect the discussions in this problem set.

2. Now, enter the Cerius² program and display the unit cell of FeCl(SANE)₂, first as a stick figure, then with cylinder bonds, then in a space-filling representation. For each representation, rotate the unit cell and view it from many perspectives. 

3. Using the "evaluate" option and stick bonds, obtain the intramolecular Fe-Cl and Fe-O distances. As a check, compare these to those reported in the publications. Now calculate the two shortest intermolecular Fe/O contacts. Compare to those in the "loose dimer". In general what is it about the packing in the C2/c space group which makes the difference?

   Hint:

   • Hide all the hydrogen atoms for clarity.
   • More unit cells should be included in the display to measure distances between the atoms in the molecules in different cells.
   • The Geometry/Close Contacts feature can be utilized to implement multiple distance measurements simultaneously. To measure intermolecular Fe/O distances:
     • Set the Selection Target popup to Atom and the Selection Criterion popup to EI on the toolbar.
     • Click an O atom then <Shift>-click a Fe atom to select all O and Fe atoms.
     • Click Geometry/Close Contacts to open the Close Contacts control panel. On this panel, choose between SELECTED atoms; choose DISTANCE for Contact Criteria and set Cut-off to 7 (for PESALF01, or 4 for PESALF10); choose FRAGMENT for Contact Exclusions and ensure Annotate close-contacts is checked.
     • Hit the Monitor close-contacts button.

4. Now view, using the full screen area, the unit cell with stick bonds. Rotate the unit cell to all angles to fully appreciate the view of the packing. Do you see any signs of face-to-face P-stacking of arene rings in the C2/c structure?

   Hint:

   • Hit F2 key on the keyboard to turn the full screen display on or off.
   • More unit cells should be included in the display to check the interactions between molecules in different cells.
   • The stereo view feature can be utilized for this purpose (note: Splatter is the only computer in room A701 which is equipped with the stereo view accessory):
     • Wear the stereo eyewear (please be careful, it is fragile and expensive) and turn it on by pushing the button on it.
     • Hit F4 key on the keyboard to turn the stereo view on.
     • Move and view the structure in usual way.
     • When you are done, turn the eyewear off by pushing the button again -- be sure that you don't see the structure in 3D any more, then hit F4 key to turn the stereo view off.
     • Put the stereo eyewear back to the box !!

References

1. J. A. Bertrand, J. L. Breece, P. G. Eller, Inorg. Chem., 13, 125 (1974)
2. C. J. Magurany, C. E. Strouse, Inorg. Chem., 21, 2348 (1982)