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One thousand interactive organometallic and coordination complexes have been selected and prepared for practice and discovery in electron counting problems. The structures can be displayed and manipulated without requiring software installation using a web browser with JavaScript and JSmol. The user can drag to rotate, shift-drag vertical to zoom, and shift-drag horizontal to turn the structure. See the Web Resources linked below.
The problems are numbered alphabetically with four structures in each problem for small group work. Each member could present their electron count for one of the four. Sometimes a set designated by { } will contain more than one structure. In such cases the electron-count work is identical for all of them, for example {Co, Rh, Ir} or {Cl, Br, I} or {cis, trans} or {fac, mer}.
Selected display options are retained while on a given page. The user can switch a given view to another representation (e.g. space-filling or ball&stick) or label atoms. One display option is to display the metal-metal distance but double-clicking can also be used to measure observed distances and angles between atoms.
The displayed structures are derived from crystallographic results. If the hydrogen atom positions were not reported, then hydrogen atoms have been added and their positions energy-minimized. Any disorder is not shown. Counter ions may or may not be included; overall charge of the displayed portion is shown in the upper right of the JSmol window. Small deviations from ideal geometry may be due to crystal packing. See the link at the bottom of each page for the original references and cif files.
Later pages use ligands from earlier pages so examining the pages in order is helpful. The bottom of each page has links to all the other pages.
A thousand problems are probably more than you want to assign, but they have been useful for in-class or online groups of four working together. The goal is to do these problems as quickly as you do Lewis octet problems to begin to understand the bonding. This takes lots of practice.
| Attachment | Size |
|---|---|
| Descriptions of each page and course plans with links | 386.01 KB |
Students should be able to do electron counting by both the neutral ligand and closed shell methods. Remember that the names of these methods tell what you need to do to the ligand (use its neutral or closed shell form). For determining oxidation state, you have to use the closed shell method since oxidation states assume closed shell ligands.
For the closed shell method, remember to show the charges on each ligand!
For the neutral ligand method, remember to show the electron count from each ligand!
Lewis Dot Theory is an assumed prerequisite.
See the attachment, Descriptions of each page and course plans with links, for implementation notes.
This activity should be spread out over several days and it is not necessary to finish a page before starting the next one.
The pages are set up independently for instructor choice. For example you could use the Metal Nitrogen Complexes page to discuss cis, trans, fac, and mer notation.