Organometallic Reaction and Catalysis · 2017-11-13 · 14-4 Heterogeneous Catalysts 14-3...
Transcript of Organometallic Reaction and Catalysis · 2017-11-13 · 14-4 Heterogeneous Catalysts 14-3...
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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