Chapter 10: Organometallic Chemistry
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- 440869
Organometallic chemistry is a subfield of inorganic chemistry involving the study of compounds containing, and reactions involving, metal-carbon bonds. The metal-carbon bond may be transient or temporary, but if one exists during a reaction or in a compound of interest, we’re squarely in the domain of organometallic chemistry. In addition to M-C bond, bonds between metals and the other common elements of organic chemistry also appear in organometallic chemistry: metal-nitrogen, metal-oxygen, metal-halogen, and even metal-hydrogen bonds all play a role. Metals cover a vast swath of the periodic table and include the alkali metals, alkali earth metals, transition metals, the main group metals, and the lanthanides and actinides. We will focus most prominently on the transition metals in this chapter.
Why is the subject worth studying? Organometallic complexes are catalysts for a wide range of industrially important chemical reactions from polymers to pharmaceuticals. There’s a reason the “organo” comes first in “organometallic chemistry”—These catalysts usually the aid in the creation of new bonds in organic compounds, building up complex products from simple starting materials. The fact is that you can do things with organometallic chemistry that you cannot do using straight-up organic chemistry. Case in point:
The venerable Suzuki reaction...unthinkable without palladium!
The establishment of a bond between two phenyl rings seems unthinkable to the pure organic chemist, but with a palladium catalyst it si a commonplace reaction. Bromobenzene looks like a potential electrophile at the bromine-bearing carbon, and if you’re familiar with hydroboration you might see phenylboronic acid as a potential nucleophile at the boron-bearing carbon. Catalytic palladium makes it all happen. Organometallic chemistry is full of these mind-bending transformations, and can expand the synthetic toolbox of the organic chemist considerably.
Contributors and Attributions
- Illustrate the orbital overlap involved in metal-ligand bonding for different classes of organometallic ligands
- Determine the metal electron count and use that to predict reactivity of the metal complex
- Recognize the different classes of reactions important to organometallic catalysis
Thumbnail image shows Wilkinson's catalyst (CC0; Benjah-bmm27 via Wikimedia Commons)
- Section 10.1: The 18 Electron Rule
- Electron counting is important because the number of electrons in a complex can tell us a lot about the stability and reactivity in a coordination compound. In addition, it allows us to predict and understand structures to a certain extent. Electron counting sounds trivial, but it is not as trivial as it seems, actually there are even two different methods for electron counting. Each method leads to the same result, whichever method you prefer is your choice.
- Section 10.2: Organometallic Ligands
- There are some classes of ligands and modes of bonding that are important and in some cases unique to organometallic complexes and reactions. Before discussing reactions of organometallic complexes we will start with an overview of ligands common to organometallic complexes. In organometallic reactions, ligands can be either spectators, not chemically involved or changed during the reaction, or actors, chemically changed during the reaction.