Reike Magnesium (Mg*)

In order to get my Grignard reactions to work even a little bit, I've been heating them considerably. This was fine when I was working in THF, as I would usually heat them to 70 C or so. The bomb flasks I'm using can handle the extra pressure (THF boils at 65 C). Now I'm using diethyl ether as a solvent to prevent activation of the alpha hydrogen in THF; unfortunately this means I'm restricted to lower temperatures. I tried to calculate the pressure I would build up in the flask while heating the ether to 70 C. I didn't get the number exactly, but suffice to say it's more than I'm comfortable with having in my hood. So the next great idea is to lower the required temperature by using "highly activated magnesium powder" also known as Reike Magnesium. (The abbreviation commonly used is Mg*.) This is made simply by reducing Mg-dihalide to elemental magnesium using a strong reductant, usually an alkali metal. The easiest way I can see to make this is to stir up the MgCl2 with potassium metal in THF while refluxing. Potassium melts at a slightly lower temperature than THF boils, so the molten potassium reacts quite easily with the MgCl2.

Rieke Magnesium is called such because Ruben D. Rieke has championed this form of magnesium as a route to generally inaccessable Grignard reactions. He has also commercialized this process, you can see his outfit here if you like. I browsed the website myself, and noticed a little grammatical mistake that I'll now make light of.

Often times my students, and occasionally even my well learned labmates, will do what is called "verbification". (This word actually shows up in several on line dictionaries now, very depressing) That is, they take a noun and use it as a verb to imply action of the noun on a subject in an obvious manner. One of the most common nouns which is subjected to verbification in the lab is "cannula", a long metal tube used to transfer liquids between reactions vessels while excluding the outside atmosphere. Often the transfer process is reffered to by the slur "cannulate". This appears in Rieke's website...

No need for a drybox or a solvent still. Simply cannulate Rieke® Metals in THF into a reaction flask under an atmosphere of argon or nitrogen.

I have been telling my students (and labmates) that "cannulate" is not a word, although you can in fact transfer something using a cannula. I was amused to see this grammatical miscue on a commercial website. Upon further investigation it turns out "cannulate" is actually a word, but it refers to the act of puncturing with a cannula, not transfering a vessel's contents. A near-miss for the author's of Ruben's website, but a miss for sure. As I tell my students quite often while they struggle to pronounce words like meridional, molybdenum, mesitylene; part of being educated is sounding educated.