Pariahs of chemistry

They always give this advice to aspiring chemists: spread your wings, use the whole palette of the Periodic Table and improvise, because there is likely a lot of unexplored reactivity at the fringes. While this might be true, I sometimes wish we could all take it easy and allow ourselves to appreciate the chemistry of super toxic elements such as thallium, lead, and mercury… While relatively inexpensive, they are all outcasts that are truly offensive from today’s green perspective. Look at the delightful molecule featured below. I was going through a folder of old papers on the ride home and came across this mercurial (no pun intended) aldehyde. My interest in structures of this kind stems from our lab’s quest to expand the scope of metal- and metalloid-containing aldehydes. The crystallographic characterization of the mercury derivative reveals some interesting stereoelectronic features, which result in unusual bond angles. The synthesis of these Hg(II) derivatives comes from the seminal work by Nesmeyanov in the 1960’s. I am positive that there is a ton of interesting chemistry awaiting compounds of this type, yet we will never find out.

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http://scripts.iucr.org/cgi-bin/paper?S056774087900604X

13 thoughts on “Pariahs of chemistry

  1. another no-no is beryllium. Grignard-like reagents containing beryllium allow preparation of naked acyl anions RCOBeX. Unfortunately there is little chance of Be-catalytic reactions, and no one is going to use stoechiometric Be reaction since the Be hygiene and waste disposal is so onerous

  2. Hg(II) is famously catalytic for addition of alcohols (or water) to alkynes, but nowadays Ag(I)-phosphine complexes are even more active for the reaction and since a very low catalyst load is needed, cost of gold is not an issue.

    But there is one organomercury reaction I would consider doing even with stoechiometric Hg(OAc)2: it is aminomercuration of C=C followed by removal of HgX in situ with borohydride, since there is no other satisfactory general method how to do it in intermolecular cases

    • Yes this is true. Of course Lewis acid catalysis is well known for Hg. I was referring to more “elaborate” catalytic properties, such as those that involve oxidation state change. This is what brings tremendous versatility to, say, palladium.

      As far as aminomercuration – this is interesting. But isn’t this hydroamination? I thought this has been addressed with catalysis numerous times.

      • I think the problem with intermolecular hydroamination is that thermodynamics is shifted generally to the starting materials, unless one uses O-subst hydroxylamines as partner, or closes as ring. I think there is still no general hydroamination intermolecular method that could rival aminomercuration efficiency and functional group tolerance .

  3. Well, they could always be studied computationally! Someone could calculate the bond angles of various XMCH2COH compounds and look at the bonding and energetics of reactions.

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