The Organometallic Reader

Dedicated to the teaching and learning of modern organometallic chemistry.

Posts Tagged ‘coordinative unsaturation

What is an Open Coordination Site?

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The concept of coordinative unsaturation can be confusing for the student of organometallic chemistry, but recognizing open coordination sites in OM complexes is a critical skill. Why? Let’s begin with a famous example of coordinative unsaturation from organic chemistry.

An analogy from organic chemistry. The reactivity of the carbene flows from its open coordination site.

An analogy from organic chemistry. The reactivity of the carbene flows from its open coordination site.

Carbenes are both nucleophilic and electrophilic, but the essence of their electrophilicity comes from the fact that they don’t have their fair share of electrons (8). They have not been saturated with electrons—carbenes want more! To achieve saturation, carbenes may inherit a pair of electrons from a σ bond (σ-bond insertion), π bond (cyclopropanation), or lone pair (ylide formation). Notice that, simply by spotting coordinative unsaturation, we’ve been able to fully describe the carbene’s reactivity! We can do the same with organometallic complexes—open coordination sites suggest specific reactivity patterns. That’s why understanding coordinative unsaturation and recognizing its telltale sign (the open coordination site) are essential skills for the organometallic chemist. Read the rest of this entry »

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