Normally, iodine just makes one bond, as you'd expect from a halogen. Some compounds, though, force it into lively higher oxidation states (hopefully without the tendency to explode, as some highly oxidized iodine reagents worryingly exhibit). There is a whole field of "hypervalent iodine" chemistry. A major use is to get something that is a good oxidizing agent, soluble in organic solvent, and milder than the time-honored usual suspects: things like permanganate or dichromate, which work a treat, but often too well, chewing your stuff up a bit more than you'd like. I (V) reagents tend to be milder. One popular hypervalent iodine reagent is the Dess-Martin reagent, named for the authors of a seminal paper on it about 20 years ago:
Pretty much the only people who use these are synthetic chemists. I tried a hypervalent iodine reagent only once and had no luck (although the oxidation I was after never really worked with anything, including the aforementioned transition metal sledgehammers). Still, it holds a special place in my heart - iodine (V) is really a singular beast. Plus they tend to smell weird, presumably due to liberated iodine and volatile compounds thereof. Sometimes a bonus, as long as they're not too noxious - at least you're not just mixing anonymous white powders with anonymous tan powders in anonymous clear liquids, which is all too often the case in synthesis.
Post your stories about iodine in an exciting oxidation state below!
In my old research group we used to use large amounts of IBX. I think the general procedure produced 50-100 grams of the stuff. I vaguely remember something about it being shock sensitive. I only ever had to make it once, and I avoided hitting it with a hammer.
Tiny bit of iodine in a melting point capillary, then flame sealed. Warm it in your hand and put into an argon laser green line. The resonant fluorescence is quite a thing to see. Compare ambient pressure to evacuated caps.
For that matter, tiny bit of iodine into a quartz UV/vis cuvette (no teflon!) and take the spectrum. Kewl! A 10 cm cell is better. Ambient pressure vs. evacuated at the same temp is again interesting.
Squeezing all the fun out of it
I have fond memories of attempting to fit LIF data and playing around with evacuated cells. It's easy enough that you can do it yourself (and since you care more about linespacing than intensity, you can use whatever piece of glass you can evacuate and flame seal).
You can probably get a good chunk of the spectrum hitting it with Nd/2 light@532nm (which many labs can get in the form of a $50 laser pointer) and watching with anything with a PMT in it (I'm sure a fluorimeter will work fine, not sure about the various types of UV-vis).
I think this lab should be in every single undergraduate pchem cirriculum (and the first electronic spectra you see should be stick spectra-type things like this or benzene vapor - that way the things make some quantum sense and aren't just blobs).
i go through a fair bit of IBX too, and i have tried hitting material prepared by both the KBrO3 and Oxone methods with a hammer (literally). nothing untoward happened at all, and words cannot express my disappointment ;-) so i take the "shock sensitive" stories with a bit of grain of salt, perhaps residual KBrO3 is to blame?
Kiwi: That's what wikipedia posits. I want to say our method involved Ag2O, but that's not definite. I'd have to whip out the old notebook.
I was a grad student at Vanderbilt during the last few years of J.C. Martin's career. Any student that joined the Martin group had to make Dess-Martin periodane as their first synthesis. It was the right of passage for entering the group. Of course, the material that was made was sold to Aldrich for a handsome sum I suspect. Nevertheless, the prep is a bit annoying and there were always endless number of explosions and small fires coming from the Martin lab. You could always tell when someone was working on the synthesis of Dess-Martin.
As a postscript, J.C. Martin unfortunately developed a form of dementia that was very similar to Alzheimer's. It was strongly "suggested" to him that he retire and so it was. It had gotten to the point that any time any of his students saw him coming, they would all sneak out the other door in the lab so they didn't have to interact with him. It was a sad way to go out like he did.