1. Organometallic Chemistry Introduction to Organometallic Compounds

2. Organometallic Chemistry 2 Course Road map

3. Organometallic Chemistry 3 Course Objectives By the end of this course, you should be able to: Make an educated guess about stability and reactivity of a given compound, based on (a.o.) electron counting rules Propose reasonable mechanisms, based on "standard" organometallic reaction steps, for many metal-catalyzed reactions Use steric and electronic arguments to predict how changes in reactants, metal or ligands affect the outcome of reactions Read a current research literature paper, understand and explain its content and significance

4. Organometallic Chemistry 4 Useful Background Knowledge Organometallic chemistry (CHEM 4140) is a 8 th -level course because it builds on: Organic chemistry: reaction mechanisms, primarily nucleophilic and electrophilic attack Inorganic Chemistry: electronegativity; electron counting and stability; properties of (transition) metals Physical chemistry: orbitals and MO theory; free energy, enthalpy and entropy You will (now and then) need this background to understand the material or make assignments etc

5. Organometallics play a vital role in the economy, with about 10 of the world’s top 30 chemicals being produced using organometallic catalysts. Organometallic Chemistry 5

6. the history of organic chemistry was the accidental discovery that an inorganic compound could be converted into an organic compound. It was the German chemist Friedrich Wohler who, in 1828, synthesized the inorganic compound ammonium cyanate, (NH4)(NCO), and found that it spontaneously isomerized to urea, (NH2)2CO. Likewise, the synthesis was performed in 1760. It was in that year the French chemist Louis Claude Cadet de Gassicourt mixed potassium acetate with diarsenic trioxide and obtained “Cadet’s fuming liquid.” This poisonous, oily red liquid with a garlic odor we now know to be cacodyl oxide, As 2 (CH 3 ) 4 O: 4CH 3 COOK + As 2 O 3 As 2 (CH3) 4 O + 2 K 2 CO 3 + 2 CO 2 Organometallic Chemistry 6

7. lists the key early discoveries in the history of organometallic chemistry together with the location of where each compound is first mentioned in this chapter. Organometallic Chemistry 7

8. Introduction to Organometallic Compounds Organometallic compounds straddle both inorganic and organic chemistry. To be a member of this class, the compound must contain at least one direct metal-to-carbon covalent bond. The metal can be a transition, main group, or f-group metal, and the term “metal” is often stretched to include boron, silicon, germanium, arsenic, antimony, selenium, and tellurium. The carbon-containing group(s) may be carbonyl, alkyl, alkene, alkyne, aromatic, cyclic, or heterocyclic. Unlike inorganic compounds, many organometallic compounds are pyrophoric (spontaneously flammable) and thermodynamically unstable. Organometallic Chemistry 8

9. 9 Elements of interest Organic elements Main group metals Transition metals

10. However, it is the transition metal organometallic compounds that provide us with richness and variety in their structures and bonding types since transition metals can utilize s, p, and d orbitals in bonding. - Each orbital type can either donate or accept electron density, and the d orbitals on the metal are particularly well suited to interact with s and p orbitals on the organic species. - Unlike conventional transition metal complexes, the central metal atom in an organometallic compound is often in a very low oxidation state. organometallic compounds are of industrial importance as catalysts.. Organometallic Chemistry 10

11. Organometallic Chemistry 11 Example: Acetic Acid synthesis Acetic acid is an important industrial chemical. The traditional synthesis uses bio-oxidation of ethanol obtained via fermentation: C 6 H 12 O 6  2 C 2 H 5 OH + 2 CO 2 C 2 H 5 OH + O 2  CH 3 COOH + H 2 O This is not a clean and efficient process! Industrial acetic acid synthesis: CH 3 OH + CO  CH 3 COOH Catalyzed by a rhodium complex.

12. Organometallic Chemistry 12 Acetic Acid synthesis Moderately complex catalytic cycle:

13. Organometallic Chemistry 13 Acetic Acid synthesis This cycle is known in considerable detail: To understand it, you need to be familiar with electron counting and common reaction types Rh I 16 e Rh III 18 e Rh III 16 e Rh III 18 e oxidative addition insertion reductive elimination ligand binding

14. Organometallic Chemistry 14 What is organometallic chemistry ? Strictly speaking, the chemistry of compounds containing at least one metal-carbon bond. Metal hydrides are often included, H being considered as the "smallest organic group" (as in propyl, ethyl, methyl, hydride). Metal-carbon bonds are often formed temporarily or potentially, so in practice many compounds are included that do not actually contain metal-carbon bonds.

15. Organometallic Chemistry 15 Why should you care ? Organometallic chemistry is the basis of homogeneous catalysis, which is the method of choice for clean and efficient synthesis of fine chemicals, pharmaceuticals and many larger-scale chemicals. Many plastics (polythene, polypropene, butadiene rubber,...) and detergents are made via organometallic catalysis. Organometallic chemistry is also the basis for understanding important steps in heterogeneous catalysis reactions such as olefin hydrogenation and CO oxidation. Organometallic compounds are used on a large scale as precursors for generation of semiconductors (AlN, GaAs, etc). Silicone rubbers are one of the few classes of organometallic compounds used as "final products".

16. Naming Organometallic Compounds In addition to the general rules that we use to name simple inorganic compounds or transition metal complexes, a few supplementary rules are used to give additional information about the nature of the bonding within the organometallic molecule. First, we need to introduce a selection of the many organic species that act as ligands in organometallic chemistry. Organometallic Chemistry 16

17. The number of carbon atoms within an organic species that are directly interacting with the metal is specified by the prefix η (eta). This is called hapticity, : most ligands bond through one atom are described as monohapto. Organometallic Chemistry 17

18. The benzene molecule bonded to a metal via (a) two carbon atoms, (b) four carbon atoms, and (c) all six carbon atoms. Carbonyl ligands bridging (a) two metal centers and (b) three metal centers. Species that can bridge two metal centers, such as carbonyl, halide, or carbine ligands, are indicated by the prefix µ (mu) Organometallic Chemistry 18

19.  Decide whether each of the following compounds should be described as organometallic: (a) B(CH 3 ) 3 (e) CH 3 COONa (b) B(OCH 3 ) 3 (f) Si(CH 3 ) 4 (c) Na 4 (CH 3 ) 4 (g) SiH(C 2 H 5 ) 3 (d) N(CH 3 ) 3  Write the formula for each of the following species. (a) methylbismuth (b) tetraphenylsilicon (c) potassium tetraphenylboron (d) methyllithium (e) ethylmagnesium chloride Organometallic Chemistry 19

20. Name each of the compounds. Sketch the structures of the following compounds: (a) Li 4 (CH 3 ) 4 (d) (CH 3 ) 3 SnF (b) Be(CH 3 ) 2 (e) (CH 3 ) 3 PbCl (c) B(C 2 H 5 ) 3 Organometallic Chemistry 20