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Organometallic Chemistry
A structured introduc5on to a complex but fascina5ng field!
• Late discovery 1956…
• A zillion concepts at once
• Why study it…?
1. List of Nobel Prizes in recent years. 2. Check with important journals . 3. See what research is funded.
4. How much of the economy is driven by this topic ?
Checking the importance of a topic..
Nobel Prizes Heck, Negishi and Suzuki, 2010
Schrock, R. H. Grubbs, and Chauvin, 2005 Sharpless, Knowles and Noyori, 2001
Fukui and R. Hoffman 1981 Herbert Brown, G. WiZg 1979
W. Lipscomb 1976 Wilkinson and E. O. Fischer 1973
Zeigler and Na^a 1963
Nobel Prizes Heck, Negishi and Suzuki, 2010
Schrock, R. H. Grubbs, and Chauvin, 2005 Sharpless, Knowles and Noyori, 2001
Fukui and R. Hoffman 1981 Herbert Brown, G. WiZg 1979
W. Lipscomb 1976 Wilkinson and E. O. Fischer 1973
Zeigler and Na^a 1963
Nobel Prizes
Heck, Negishi and Suzuki, 2010 Schrock, R. H. Grubbs, and Chauvin, 2005 Sharpless, Knowles and Noyori, 2001
Fukui and R. Hoffman 1981 Herbert Brown, G. WiZg 1979
W. Lipscomb 1976 Wilkinson and E. O. Fischer 1973
Zeigler and Na^a 1963
Nobel Prizes
Heck, Negishi and Suzuki, 2010 Schrock, R. H. Grubbs, and Chauvin, 2005 Sharpless, Knowles and Noyori, 2001
Fukui and R. Hoffman 1981 Herbert Brown, G. WiZg 1979
W. Lipscomb 1976 Wilkinson and E. O. Fischer 1973
Zeigler and Na^a 1963
Nobel Prizes
Heck, Negishi and Suzuki, 2010 Schrock, R. H. Grubbs, and Chauvin, 2005 Sharpless, Knowles and Noyori, 2001
Fukui and R. Hoffman 1981 Herbert Brown, G. WiZg 1979
W. Lipscomb 1976 Wilkinson and E. O. Fischer 1973
Zeigler and Na^a 1963
Nobel Prizes
Heck, Negishi and Suzuki, 2010 Schrock, R. H. Grubbs, and Chauvin, 2005 Sharpless, Knowles and Noyori, 2001
Fukui and R. Hoffman 1981 Herbert Brown, G. WiZg 1979
W. Lipscomb 1976 Wilkinson and E. O. Fischer 1973
Zeigler and Na^a 1963
Nobel Prizes
Heck, Negishi and Suzuki, 2010 Schrock, R. H. Grubbs, and Chauvin, 2005 Sharpless, Knowles and Noyori, 2001
Fukui and R. Hoffman 1981 Herbert Brown, G. WiZg 1979
W. Lipscomb 1976 Wilkinson and E. O. Fischer 1973
Zeigler and Na^a 1963
Assessing Importance of a subject ?
1. List of Nobel Prizes in recent years ? OK!
2. Check with important journals ? 3. See what research is funded ?
4. How much of the economy is driven by it?
.
Review Ac)va)on of C−H Bonds by Metal Complexes
Abstract Full Text HTML
Hi-‐Res PDF[1214 KB] Ci5ng Ar5cles
Alexander E. Shilov and Georgiy B. Shul'pin* N. N. Semenov Ins5tute of Chemical Physics, Russian Academy of Sciences,
117977 Moscow, Russia Chem. Rev., 1997, 97 (8), pp 2879–2932
DOI: 10.1021/cr941186 Publica5on Date (Web): December 18, 1997 Copyright © 1997 American Chemical Society
TOP 20 ar5cles accessed from JACS As of 20th Sept. 2010
Palladium-‐Catalyzed Ligand-‐Directed C–H Func)onaliza)on Reac)ons
• Thomas W. Lyons and Melanie S. Sanford Chem. Rev., 2010, 110(2), pp 1147-‐1169. DOI: 10.1021/cr900184e
• Total Synthesis of (+)-‐Complanadine A Using an Iridium-‐Catalyzed Pyridine C–H Func)onaliza)on
• Daniel F. Fischer and Richmond Sarpong J. Am. Chem. Soc., 2010, 132(17), pp.5926-‐5927. DOI:10.1021/ja101893b
NATURE Vol 463, 28 January 2010. doi:10.1038/nature08730
Cleaving carbon–carbon bonds by inser5ng tungsten into unstrained aroma5c rings Aaron Sa^ler & Gerard Parkin
PNAS 2005, vol. 102 p 1853–1858 Characteriza)on of an organometallic xenon complex using NMR and IR
spectroscopy Graham E. Ball ,Tamim A. Darwish, Spili Gerakis Michael W. George , Douglas J. Lawes
Peter Por5us, Jonathan P. Rourke § ,
Ball G E et al. PNAS 2005;102:1853-1858 ©2005 by National Academy of Sciences
19F NMR spectra of Re(iPrCp)(CO)2(PF3) (1) in liquid Xe at 163 K obtained during prolonged photolysis and expansions of the highlighted region that corresponds to one of the resonances from 3. (1) NMR Using 129Xe as solvent. (2) Using unlabeled Xe. A small spliZng caused by 3JXeF can be seen. (a) No spliHng in the spectrum with unlabeled Xe.
Assessing Importance of a
subject ?
1. List of Nobel Prizes in recent years ?
2. Check with important journals ? 3. See what research is funded?
4. How much it is driving the industry..
• Papers with the concept organometallics • ~ 2300 in 2012 • 2213 papers in 2011 • 2703 papers in 2009-‐10 • 2303 papers in 1999-‐2000
– 1400 key papers every year on the topic “organometallics”
Is the subject important?
1. List of Nobel Prizes in recent years OK 2. Check with important journals OK 3. See what research is funded OK
4. See what research is pracKced in the industry
Industrial uses of organometallics • Metal complexes used as addi5ves in polymers and fuels. (Sn
and Mn compounds) • Many million tons of silicones, and organolithium compounds
are made. • Metal complexes used as catalysts for making polymers • Ace5c acid, acetaldehyde, and fine chemicals, …
Is the subject important?
1. List of Nobel Prizes in recent years OK 2. Check with important journals OK 3. See what research is funded OK 4. See what research is pracKced OK
Why is the subject important?
Are we dealing with ‘a’ special element?
C • What is special about carbon?
– Forms bonds with other carbons (C-‐C) readily and they are strong (catena5on)
– Forms strong mul5ple bonds (C=C) – Forms very strong bonds with another special element H !!
– Cyclic “C=C-‐C” fragments would be extra stable AROMATIC..
C and its Electronic configura5on! 1s2 2s2 2p2
`Why is this special ? To form a full shell, it would require 4 covalent bonds
Gap between the 2s and 2p is just right! 1s2 2s1 2px1 2py1 2pz1 When 4 equivalent covalent bonds are formed,
no extra electrons / no vacant orbitals
Tm • Transi5on metals are exactly the opposite!!
– Vacant orbitals – Or extra electrons.
• Rarely do they keep a noble gas configura5on
Consider [Co(H2O)6]2+ 19 e 7 electrons + 12 electrons
Ni2+ aquo complex has 20 e. V2+ complex has 15 e. Very few complexes would have exactly 18 electrons! Full shell / no extra electrons is rare.
What happens to “Tm” in “Tm-‐organometallics”
• The 18 electron rule prevails.. – Most complexes with Tm-‐C bonds have a full shell. C seems to have forced its preferences on the metal!
• When C combines with a transi5on metal – Both metal and carbon loose their iden5ty!
“So what about carbon?”
Why is the subject important?
1. List of Nobel Prizes in recent years 2. Check with important journals 3. See what research is funded
4. See what research is pracKced
We are dealing with ‘a’ special combina5on of elements!!
Challenges for today • Synthesis and understanding of new compounds and their reac5vity
• Ac5va5on of inert molecules like CH4, CO2, R3C-‐F
• Cataly5c efficiencies far exceeding approaching that of enzymes!
• Asymmetric induc5on in catalysis
Organiza5on of the course..
• Modular, based on ligand systems • How does one classify the ligand?
– Hap5city of the ligand is the key: – η with superscript: – η3 number of carbons bonded to the metal is 3
Current approach
• Simple to complex: Avoid complex ligands un5l we discuss them towards the la^er part of the course.
• Integrate discussion on reac5ons with study of new structure types – Deal with inser5on reac5ons (purely C1 chemistry) – Only oxida5on state change at the metal! – Oxida5on state change and C-‐C coupling!
Text books? Title Authors Publisher ISBN no.
Organometallics: A Concise Introduc5on
Christoph Elschenbroich Wiley-‐VCH 3rd Edi5on 3-‐527-‐29390-‐6 2006
Organometallic Chemistry,
B. D. Gupta and Anil J. Elias
Universi5es Press
Fundamentals of Organometallic Catalysis
Dirk Steinborn
Wiley-‐VCH ISBN: 978-‐3-‐527-‐32717-‐1 2012
Electron coun5ng the organometallic way..
• Metal has all d electrons whatever be the oxdn. state
• Ligands can be ionic or neutral / adjust metals d-‐electron count
• Net charge is added (electrons are nega5ve and so the no. of electrons in the complex are reduced if the charge is +ve. If the charge is –ve then one has to add to the electron count)
Electron coun5ng in two ways
• Let us try a few.. – Cp2TiCl2 complex is neutral
– Handout with homework…
Stoichiometric reac5ons and Catalysis
• Reac5ons with increasing complexity.. • Without oxida5on state change..
– Subs5tu5on and inser5on reac5ons.. • With oxida5on state change
– Reac5ons with oxida5on state change at metal.. – Ox-‐ad and Red-‐el
• Catalysis and cataly5c cycles – A series of stoichiometric reac5ons regenera5ng the catalyst when the product is formed.
Ligands Ionic Method A Method B
H
Cl, Br, I
OH, OR
CN
CH3, CR3
NO (bent M-‐N-‐O)
CO, PR3
NH3, H2O
=CRR’
H2C=CH2 (ethylene)
CNR
=O, =S
2 (H-‐)
2 (X-‐)
2 (OH-‐,OR-‐)
2 (CN-‐)
2 (CH3-‐,CR3-‐)
2 (NO-‐)
2
2
2
2
2
4 (O2-‐,S2-‐)
1
1
1
1
1
1
2
2
2
2
2
2
Ligands Ionic Method A Method B
NO (Linear M-‐N-‐O)
η3-‐C3H5 (π-‐allyl)
CR (Carbyne)
N
Ethylenediamine (en)
Bipyridine (Bipy)
Butadiene
η5-‐C5H5 (cyclopentadienyl)
η6-‐C6H6 (benezene)
η7-‐C7H7 (cycloheptatrienyl)
2 (NO+)
2 (C3H5+)
3
6 (N3-‐)
4 (2 per nitrogen)
4 (2 per nitrogen)
4
6 (C5H5-‐)
6
6 (C7H7+)
3
3
3
3
4
4
4
5
6
7
Counting electrons
Method A
Determine formal oxidation state of metal Deduce number of d electrons
Add d electrons + ligand electrons (A)
Ignore formal oxidation state of metal Count number of d electrons for M(0)
Add d electrons + ligand electrons (B)
Method B
The end result will be the same
Nitrosyls are very complicated few +ve charged donors exist NO ⊕
Alternatively if it is ONNOM =⇒−⊕ )(&ONM −− Angle will be less than 180
Due to sp2 hybridization
NOMNOMNOMNOM−→
−→⊕− &
&)( Now NO+ is like CO
Remember the odd electron is on a π* orbital Having more contribution from N
:
