14-4 Heterogeneous Catalysts

14-3 Organometallic Catalysts

14-2 Reactions Involving Modification of Ligands

14-1 Reactions Involving Gain or Loss of Ligands

Organometallic Reaction and Catalysis

“Inorganic Chemistry” Third Ed. Gary L. Miessler, Donald A. Tarr, 2004, Pearson Prentice Hallhttp://en.wikipedia.org/wiki/Expedia

Chapter 14 Organometallic Reaction and Catalysis

Organometallic reactions

• Loss or gain of ligands• Molecular rearrangement• Formation or breaking of metal-metal bonds• Reactions at the ligands themselves

14-1 Reactions Involving Gain or Loss of Ligands

Addition or dissociation vs oxidative addition or reductive elimination

14-1 Reactions Involving Gain or Loss of Ligands; ligand dissociation and substitution

CO dissociation

Independent of the concentration of L → ???

14-1 Reactions Involving Gain or Loss of Ligands; ligand dissociation and substitution

CO dissociation

Two pathways

14-1 Reactions Involving Gain or Loss of Ligands; ligand dissociation and substitution

Dissociation of phosphine

Dissociation• The strength of M-L bonding• The degree of crowding of ligand

around metal

14-1 Reactions Involving Gain or Loss of Ligands; ligand dissociation and substitution

14-1 Reactions Involving Gain or Loss of Ligands; oxidative addition

An increase in both the formal oxidation state and the coordination #

14-1 Reactions Involving Gain or Loss of Ligands; oxidative addition

orthometallation

OA

cyclometallations

14-1 Reactions Involving Gain or Loss of Ligands; reductive elimination

A decrease in both the formal oxidation state and the coordination #

The rates of RE reactions are also affected by ligand bulk

Useful organic compounds

14-1 Reactions Involving Gain or Loss of Ligands; nucleophilic displacement

Nucleophilic anionic organometallic complexes

Acyl complex ester

Collman’s reagent

14-2 Reactions Involving Modification of Ligands; insertion

1,1 insertion

1,2 insertion

14-2 Reactions Involving Modification of Ligands; carbonyl insertion (alkyl migration)

3 plausible mechanisms

14-2 Reactions Involving Modification of Ligands; carbonyl insertion (alkyl migration)

3 plausible mechanisms

14-2 Reactions Involving Modification of Ligands; carbonyl insertion (alkyl migration)

14-2 Reactions Involving Modification of Ligands; carbonyl insertion (alkyl migration)

14-2 Reactions Involving Modification of Ligands; 1,2 insertions

Alkenes into M-R bondspolymerization

14-2 Reactions Involving Modification of Ligands; hydride elimination

The transfer of a hydrogen atom from a ligand to a metalConsidered an oxidative additionThe reverse of 1,2-insertionLack of β hydrogens → ???Coordinatively saturated complexes → ???

14-2 Reactions Involving Modification of Ligands; abstraction

Elimination reactions in which the coordination # of the metal does not change (by the action of an external reagent)α and βCarbene

14-3 Organometallic Catalysts; catalytic deuteration

14-3 Organometallic Catalysts; hydroformylation

14-3 Organometallic Catalysts; hydroformylation

Reactivity and selectivityLinear and branched productHCo(CO)3(PBu3), HRh(CO)2(PPh3)2

14-3 Organometallic Catalysts; monsanto acetic acid process

The synthesis of acetic acid from methanol and CO

14-3 Organometallic Catalysts; wacker (smidt) process

The synthesis of acetaldehyde from ethylene

Palladium modified the chemical behavior of ethylene to enable reactions to occur

14-3 Organometallic Catalysts; hydrogenation by wilkinson’s catalyst

Bulky phosphine ligands play an important role in making the complex selective

14-3 Organometallic Catalysts; hydrogenation by wilkinson’s catalyst

Selective hydrogenation by Wilkinson’s catalyst

14-3 Organometallic Catalysts; olefin methathesis

Chauvin mechanism

14-3 Organometallic Catalysts; olefin methathesis

More active but more sensitive to oxygen and water

Less expensive and less sensitive

14-3 Organometallic Catalysts; olefin methathesis

More active and less sensitive to oxygen and water

14-3 Organometallic Catalysts; olefin methathesis

More active and less sensitive to oxygen and water

Alkyne metathesis

Ring-opening polymerization of norbornene

14-4 Heterogeneous Catalysts

The reactions occurring on the surface of the catalyst may be extremely difficult to ascertainPractically important

14-4 Heterogeneous Catalysts; ziegler-natta polymerizations

14-4 Heterogeneous Catalysts; water gas reaction

This reaction occurs at elevated T and P between water and natural sources of carbon

Synthesis gas or syn gas

Fischer-Tropsch process produce hydrocarbons, alcohols, alkenes, and other products from syn gas

Steam reforming natural gas + steam to CO + hydrogen

Water gas shift reaction recycling the CO to react further with steam

14-4 Heterogeneous Catalysts; water gas reaction

Homogeneous catalysis of water gas shift reaction

Homework

Exercise 14-1~14-6

Problem 1, 2, 3, 6, 8, 11, 21.

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