Safety Moment - cpb-us-e1.wpmucdn.com · Transition metal hydrides vary in hydridic strength General rule of thumb: if it does hydrogenations, it is probably pyrophoric If they’re

Safety MomentTYLER LAB GROUP MEETING

1

Safety MomentTYLER LAB GROUP MEETING

2

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

3

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.



◦ Considered the first chemical industry

“Mauveine”




◦ Considered the first chemical industry

“Mauveine”


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



Fundamental principles of:◦ 18 e- rule◦ Crystal field theory◦ Ligand field theory◦ Metal-carbon bonding


23


II. Fundamental Principles of Organometallics

Ligands ◦ L-type

◦ X-type

◦ Cationic

24


Interactions◦ σM→L or σL→M

◦ πM→L or πL→M

◦ δ

25


Coordination modes ◦ μ – metal centers coordinated to the same atom

◦ η – hapticity, ligand atoms coordinated to metal

◦ κ – polydentate ligands, denotes ligating atoms

26

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)

27


Crystal field theory

28


Ligand field theory

29


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

30

Mn2+ < Ni2+ < Co2+ < Fe2+ < V2+ <

Fe3+ < Cr3+ < V3+ < Co3+


Dewar-Chatt-Duncanson◦ Zeitse’s salt

31


Dewar-Chatt-Duncanson◦ HOMOPt(II)sp to LUMOC2H4

32


Dewar-Chatt-Duncanson◦ HOMOC2H4 to LUMOPt(II)sp

33



Fundamental principles of:◦ 18 e- rule◦ Crystal field theory◦ Ligand field theory◦ Metal-carbon bonding


34


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


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


III. Applications to Catalysis: Mechanisms Alkene/Alkyne Metathesis

◦ Nobel Prize 2005◦ Cross-metathesis

◦ Ring opening

◦ Ring closing

◦ Equilibrium reaction◦ Driving force is

thermodynamics


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


III. Applications to Catalysis: Case Study Wacker

Process (1953)

47Astruc, D. Organometallic Chemistry and


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

49

Questions

50

Documents

Safety Moment - cpb-us-e1.wpmucdn.com · Transition metal hydrides vary in hydridic strength General rule of thumb: if it does hydrogenations, it is probably pyrophoric If they’re