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Metal Hydrides: Benchtop vs. BoxHydride = :H-
Hydrides are powerful Lewis bases and reducing agent◦ Exothermically form H2 (this should scare you)◦ Heating leads to faster reactivity◦ H2 evolution leads to rapid increase in
pressure◦ Uncontrolled reactions easily cause runaway
exotherm, class D fire, explosion, and death/unemployment
LiAlH4 is the #1 chemical cause of fatality in chemical industry
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Metal Hydrides: “I want to commit the murder I was imprisoned for†.”
LiAlH4◦ Insanely irritating (serious safety hazard)◦ Extremely moisture sensitive (don’t leave out for >2 minutes)◦ Ethereal mixtures are pyrophoric!
DiBuAl-H◦ Pyrophoric – it will explode upon exposure to oxygen
NaEt3BH◦ Pyrophoric in solution
LiH and NaH◦ Can be handled on the benchtop (not >2 minutes)◦ Parrafin oil dispersions much safer
KH◦ Pyrophoric if not in a dispersion◦ Handle with extreme care!
4† Sirius Black, Harry Potter and the Prisoner of Azkaban
Metal Hydrides: “I want to commit the murder I was imprisoned for†.”
CaH2◦ Very safe to handle on the benchtop
Pt-H, Pd-H, Ni-H◦ All very pyrophoric
NaBH4◦ Very safe in general
Other hydrides◦ Treat as pyrophoric◦ Transition metal hydrides vary in hydridic strength◦ General rule of thumb: if it does hydrogenations, it is probably
pyrophoric◦ If they’re in organics of any kind, they are probably pyrophoric
5† Sirius Black, Harry Potter and the Prisoner of Azkaban
Organometallic ChemistryBASIC PRINCIPLES, APPLICATIONS, AND A FEW CASE STUDIES
KENDALL, A . J . ; TYLER, D . R . LAB GROUP MEETING; 2015 /10 /14
Existential Motivation
History of organometallics
Fundamental principles of:◦ 18 e- rule◦ Crystal field theory◦ Molecular orbital theory◦ Metal-carbon bonding
Applications to catalysis◦ Fundamental mechanisms◦ Case studies
7
In Chemiae Veritas: Outline
What’s the big deal?
Principles of organic chemistry
Principles of inorganic chemistry
8
Oh, East is East and West is West, and never the twain shall meet,
Till Earth and Sky stand presently at God's great Judgment Seat;
But there is neither East nor West, Border, nor Breed, nor Birth,
When two strong men stand face to face, though they come from the ends
of the earth!
-Excerpt from: The Ballad of East and West by Rudyard Kipling, 1889
I. History of Organometallic ChemistryThe first complexes (1760-1827):
◦ Cadet (1760)◦ First O/M
◦ Zeise (1827)◦ First π-complex
9Seyferth, D. Organometallics 2001, 20, 1488–1498.
Zeise, W. C. Annalen der Physik und Chemie 1831, 97, 497.
I. History of Organometallic ChemistryThe first complexes (1849-1864)
◦ Frankland (1849-1860)◦ Air-sensitive O/M
10
“When (Et2Zn is) dropped into oxygen, however, it bursts into
brilliant white flame, attended with slight explosion.”- E. Frankland, 1864
E. Frankland, Prof. and B. F. Duppa, Esq. J. Chem. Soc., 1864, 17, 29-36.
I. History of Organometallic Chemistry Main group advances
◦ Friedel and Crafts (1863)◦ Organosilanes
◦ Schützenberger (1868)◦ First metal-carbonyls
◦ Mond (1890)◦ First binary metal-carbonyls
11
Organosilicon Chemistry S. Pawlenko Walter de Gruyter, New York, 1986.
Wisniak, J. Educación Química 2015, 26, 57-65.
Liptrot, G. F. (1983). Modern Inorganic Chemistry (4th ed.). Unwin Hyman. p. 386.
I. History of Organometallic Chemistry Main group advances
◦ Friedel and Crafts (1863)◦ Organosilanes
◦ Schützenberger (1868)◦ First metal-carbonyls
◦ Mond (1890)◦ First binary metal-carbonyls
12
Organosilicon Chemistry S. Pawlenko Walter de Gruyter, New York, 1986.
Wisniak, J. Educación Química 2015, 26, 57-65.
Liptrot, G. F. (1983). Modern Inorganic Chemistry (4th ed.). Unwin Hyman. p. 386.
I. History of Organometallic Chemistry Where is organic chemistry during all of this?
◦ Sir. William H. Perkin discovers mauveine by accident◦ Attempting to make Quinine
13Hubner, K. Chemie in unserer Zeit. 2006, 40, 274–275.
I. History of Organometallic Chemistry Where is organic chemistry during all of this?
◦ Sir. William H. Perkin discovers mauveine by accident◦ Attempting to make Quinine
◦ Considered the first chemical industry
“Mauveine”
14Hubner, K. Chemie in unserer Zeit. 2006, 40, 274–275.
I. History of Organometallic Chemistry Where is organic chemistry during all of this?
◦ Sir. William H. Perkin discovers mauveine by accident◦ Attempting to make Quinine
◦ Considered the first chemical industry
“Mauveine”
15Hubner, K. Chemie in unserer Zeit. 2006, 40, 274–275.
I. History of Organometallic Chemistry Alfred Werner
◦ The father of coordination chemistry
Nobel Prize for Chemistry (1913)◦ First Nobel Prize for inorganic chemistry◦ ‘‘in recognition of his work on the linkage of atoms in molecules by
which he has thrown new light on earlier investigations and opened up new fields of research especially in inorganic chemistry’’
16
Kauffman, G. B. Bull. Hist. Chem. 1997, 20, 50-59.
Constable, E. C. and Housecroft , C. E. Chem. Soc. Rev., 2013, 42, 1429-1439
Alfred Werner c.a. 1900
I. History of Organometallic Chemistry Alfred Werner
◦ The father of coordination chemistry
Nobel Prize for Chemistry (1913)◦ First Nobel Prize for inorganic chemistry◦ ‘‘in recognition of his work on the linkage of atoms in molecules by
which he has thrown new light on earlier investigations and opened up new fields of research especially in inorganic chemistry’’
17
Kauffman, G. B. Bull. Hist. Chem. 1997, 20, 50-59.
Constable, E. C. and Housecroft , C. E. Chem. Soc. Rev., 2013, 42, 1429-1439
Alfred Werner c.a. 1900
Listen, old man; take my advice.
Give me the cobalt in a thrice.
Though Hell and Devil say me nay,
I shall resolve cobalt today-Student Christmas Play “Rotating and Resolving,” 1911
I. History of Organometallic Chemistry Early 20th century seminal developments
◦ Barbier (1899)◦ First “coupling” reaction
◦ Grignard (1900)◦ Nobel Prize 1912
◦ Pope (1909)◦ First metal-alkyl complex
◦ Hein (1919)◦ First “sandwich” complex
◦ Reilhen (1930)◦ First diene-complex
◦ Hieber (1931)◦ First hydride complex
18
Barbier, P. Compt. Rend. 1899, 128, 110.
Grignard, V. Compt. Rend. 1900, 130, 1322–1325.
Pope, W. J.; Peachey, S. J. J. Chem. Soc, Trans. 1909, 95, 571.
Hein, F. Berichte Deut. Chem. Gesellschaft, 1919, 52, 195 – 196.
Organometallic Chemistry and Catalysis Didier Astruc, Heidelberg, 2007.
I. History of Organometallic Chemistry Early 20th century catalysis
◦ Sabatier and Senderens (19011)◦ Heterogenous Ni catalysis◦ Nobel Prize 1912
◦ Fischer and Tropsch (1922)◦ Heterogenous Co catalysis
◦ Roelen (1938)◦ Homogenous hydroformylation
◦ Reppe (1948)◦ Homogenous cyclo-oligomerization
◦ Ziegler-Natta (1955)◦ Homogenous stereo-regular polymerization◦ Nobel Prize 1963
19
H. Schulz, Advance Catalysis, Volume 186, 3-12.
Cornils, B.; Herrmann, W. A.; Rasch, M. Angew. Chem. Int. Ed. 1994, 33, 2144–2163.
Neue Entwicklungen auf dem Gebiet der Chemie des Acetylen und Kohlenoxyds. Springer Berlin, Göttingen, Heidelberg. 1949.
I. History of Organometallic Chemistry Ferrocene
◦ Kealy and Pauson (1951)◦ bis σ-Fe complex
◦ “10 electron”
◦ E. O. Fischer, G. Wilkinson, and R. B. Woodward◦ Properly I.D. sandwich complex
◦ No net dipole and single C-H stretch by IR
◦ Aromatic characteristics
◦ Nobel Prize 1973 (E. O. Fischer and G. Wilkinson)
20
T. J. Kealy, P. L. Pauson Nature 1951, 168, 1039.
Zydowsky, T. The Chemical Intelligencer, Springer-Verlag, New York, 2000.
History of Organometallic Chemistry Ferrocene
◦ Kealy and Pauson (1951)◦ bis σ-Fe complex
◦ “10 electron”
◦ E. O. Fischer, G. Wilkinson, and R. B. Woodward◦ Properly I.D. sandwich complex
◦ No net dipole and single C-H stretch by IR
◦ Nobel Prize 1973 (E. O. Fischer and G. Wilkinson)
21
T. J. Kealy, P. L. Pauson Nature 1951, 168, 1039.
Zydowsky, T. The Chemical Intelligencer, Springer-Verlag, New York, 2000.
“The notice in the Times of the award of this year’s
Nobel Prize in Chemistry leaves me no choice but to
let you know, most respectfully, that you have –
inadvertently, I am sure – committed a grave
injustice… Indeed, when I, as a gesture to a friend and
junior colleague interested in organometallic chemistry,
invited Professor Wilkinson to join me and my
colleagues in the simple experiments which verified my
structural proposal, his reaction to my views was close
to derision… But in the event, he had second thoughts
about his initial scoffing view to my structural
proposal and its consequences, and altogether we
published the initial seminal communication that was
written by me.”-R. B. Woodward to the Nobel Committee, 1973
I. History of Organometallic Chemistry Where is organic chemistry these days?
◦ Mechanistic understanding◦ Ingold discovered SN2 and SN1 mechanisms (1934)
◦ Natural products◦ Robinson
◦ Tropinone (1917)
◦ R. B. Woodward◦ Quinine (1944)◦ Cholesterol (1952)◦ Cortisone (1951)◦ Strychnine (1954)◦ Lysergic acid (1956)◦ Reserpine (1958)◦ Chlorophyll (1960)◦ Vitamin B12 (1972)◦ Nobel Prize (1965)
22Ingold, Christopher K. Chem. Rev. 1934, 15, 238–274.
Organometallic Chemistry and Catalysis Didier Astruc, Heidelberg, 2007
Vitamin B12
Existential Motivation
History of organometallics
Fundamental principles of:◦ 18 e- rule◦ Crystal field theory◦ Ligand field theory◦ Metal-carbon bonding
Applications to catalysis◦ Fundamental mechanisms◦ Case studies
23
In Chemiae Veritas: Outline
II. Fundamental Principles of Organometallics
Coordination modes ◦ μ – metal centers coordinated to the same atom
◦ η – hapticity, ligand atoms coordinated to metal
◦ κ – polydentate ligands, denotes ligating atoms
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II. Fundamental Principles of Organometallics 18 e- rule
◦ Metals go up to 6-coordinate◦ Valence orbitals on the metal
◦ 9 orbitals (5d, 3p, 1s)
◦ Empirically derived
◦ Valid: ◦ Oh with large field splitting (Δo)
◦ Ligands are strong σ-donors or π-acceptors
◦ Not as valid:◦ Weak field ligands (> 18e-)
◦ π-donor ligands (< 18e-)
◦ Square planar (16e- rule)
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II. Fundamental Principles of Organometallics
Ligand field theory◦ Ligand spectrochemical
series◦ Small Δ to large Δ
◦ Stems from a mix of σ- and π-interactions
◦ Metal spectrochemical series◦ Δ increases with oxidation state
◦ Δ increases from 1st to 3rd row
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Mn2+ < Ni2+ < Co2+ < Fe2+ < V2+ <
Fe3+ < Cr3+ < V3+ < Co3+
Existential Motivation
History of organometallics
Fundamental principles of:◦ 18 e- rule◦ Crystal field theory◦ Ligand field theory◦ Metal-carbon bonding
Applications to catalysis◦ Fundamental mechanisms◦ Case studies
34
In Chemiae Veritas: Outline
III. Applications to Catalysis: Mechanisms Ligand
substitution◦ Associative
◦ < 18e-
◦ Dissociative◦ 18e-
◦ Interchange
35http://chemwiki.ucdavis.edu/Inorganic_Chemistry/
III. Applications to Catalysis: Mechanisms Oxidative addition
◦ Non-polar◦ Concerted
◦ Polar◦ Either concerted or step
◦ Can be radical
◦ More e- on metal promotes O/A
◦ e- poor R◦ Less steric hindrance
promotes O/A
36Hartwig, J. Organotransition Metal Chemistry; University Science Books: Sausalito, CA, 2010.
III. Applications to Catalysis: Mechanisms Reductive Eliminations
◦ Non-polar bonds◦ Tend to be easier
◦ Polar bonds◦ More difficult for very
electronegative groups (F, CN, etc.)
◦ Microscopic reverse of O/A◦ Less e- on metal promotes R/E
◦ e- rich R and X
◦ More steric hindrance promotes R/E
37Hartwig, J. Organotransition Metal Chemistry; University Science Books: Sausalito, CA, 2010.
III. Applications to Catalysis: Mechanisms Migratory Insertion
◦ No redox chemistry at the metal
38http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Hartwig, J. Organotransition Metal Chemistry; University Science Books: Sausalito, CA, 2010.
III. Applications to Catalysis: Mechanisms Migratory Insertion
◦ No redox chemistry at the metal
◦ Stereochemical control
39http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Hartwig, J. Organotransition Metal Chemistry; University Science Books: Sausalito, CA, 2010.
III. Applications to Catalysis: Mechanisms Elimination Reaction
◦ Often in equilibrium with insertion
◦ Driving force is M-X bond or Le Châtelier
40
E1
E2
http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Hartwig, J. Organotransition Metal Chemistry; University Science Books: Sausalito, CA, 2010.
III. Applications to Catalysis: Mechanisms Alkene/Alkyne Metathesis
◦ Nobel Prize 2005◦ Cross-metathesis
◦ Ring opening
◦ Ring closing
◦ Equilibrium reaction◦ Driving force is
thermodynamics
41http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Hartwig, J. Organotransition Metal Chemistry; University Science Books: Sausalito, CA, 2010.
III. Applications to Catalysis: Mechanisms Alkene/Alkyne Metathesis
◦ Nobel Prize 2005◦ Cross-metathesis
◦ Ring opening
◦ Ring closing
◦ Equilibrium reaction◦ Driving force is
thermodynamics
42http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Hartwig, J. Organotransition Metal Chemistry; University Science Books: Sausalito, CA, 2010.
III. Applications to Catalysis: Catalysis Principles of catalysis
◦ A substance which increases the rate of a reaction without being consumed (Otswald, 1894)
◦ Stabilize the transition state
O/M has “extra mechanisms”◦ Stereochemical control◦ Isomerization equilibria
Thermodynamically downhill◦ At a given T and P
Transition metal mediated◦ Open coordination (16 or 14e-)
43
Crabtree, R. H. Chem. Rev. 2015, 115, 127-150.
Astruc, D. Organometallic Chemistry and Catalysis; Springer: Berlin, Germany, 2007.Hartwig, J. Organotransition Metal Chemistry; University Science Books: Sausalito, CA, 2010.
III. Applications to Catalysis: Case StudyHydrogenation
of alkenes ◦ Wilkinson-
Osborn catalyst (1964)
44Astruc, D. Organometallic Chemistry and Catalysis; Springer: Berlin, Germany, 2007.
III. Applications to Catalysis: Case Study Olefin isomerization
(migration)
45
Astruc, D. Organometallic Chemistry and
Catalysis; Springer: Berlin, Germany, 2007.
III. Applications to Catalysis: Case Study Monsanto
acetic acid process
46Astruc, D. Organometallic Chemistry and
Catalysis; Springer: Berlin, Germany, 2007.
III. Applications to Catalysis: Case Study Wacker
Process (1953)
47Astruc, D. Organometallic Chemistry and
Catalysis; Springer: Berlin, Germany, 2007.
III. Applications to Catalysis: Outlook Examples of heterogenous catalysis
48
Crabtree, R. H. Chem. Rev. 2015, 115, 127-150.
Astruc, D. Organometallic Chemistry and Catalysis; Springer: Berlin, Germany, 2007.Hartwig, J. Organotransition Metal Chemistry; University Science Books: Sausalito, CA, 2010.
SummaryOrganometallics marries organic principles and
inorganic principles to a “hybrid” field
Inorganic mechanisms are unique and therefore can catalytically control an organic reaction very precisely
Most reactivity can be rationalized by first principles
Designing better catalysts can be done from first principles
You need open coordination sites to do catalysis
Good catalysts change the world
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