Download II. Main types of organometallic compounds

Chapter 4 Organometallic chemistry
Key points of Chapter 4
 The basic concept of organometallic compounds
 Ligand types and bonding method of organometallic
compounds
Effective atomic number rules(18 electronic rules) and
applications
Structure , properties and applications of the typical
organometallic compounds
Introduction
 Organometallic chemistry includes a large number of kinds
of compounds, such as organic chemistry, inorganic
chemistry, coordination catalysis and quantum chemistry ,
which is the edge field of mutual penetration of chemical
branch disciplines .
 It is the one of the extremely active emerging field of
inorganic chemistry.
Coordination
compounds
Atomic cluster
compounds
Metallorganic
compounds
Introduction

Metallorganic chemistry and organometallic chemistry
is same for chinese, usually for preferred for the later.
Introduction
Organometallic
compound novel • Ferrocene、 diphenyl
chromium layer structure
structure
• σ -π bonding ,
The unique
chemical bonding • π-acid bonding
Homogeneous
catalyst
• Ziegler–Natta catalyst：
ethylene/propylene
homogeneous polymerization
High economic
benefit
• [RhI2(CO)2] catalyst
Methanol carbonylation
• production rate 99%
Academic
significance
Practical
application
value
Content
Ⅰ. Introduction of organometallic chemistry
Ⅱ. Main types of organometallic compounds
Ⅲ Application of organometallic compounds
Ⅰ. Introduction of organometallic chemistry
1.1 Definition of organometallic chemistry/ compounds
1.2 Organometallic chemistry and Nobel chemistry prize
1.3 Classification of organometallic compounds
1.4 Difference of organometallic compounds with main
group and transitional metals
1.5 Ligand types of organometallic compounds and
bonding way with transition metals
Ⅰ. Introduction of organometallic chemistry
1.1 Definition of organometallic chemistry/compounds
Organometallic chemistry --Study on a class of compounds
that metals directly bonded with organic group.
Organometallic compounds --metal directly bonding with one or
more carbon atoms, that is ,M-C bonding.
Metallorganic compounds-- metal bonding with organic groups
( not carbon, but other non-metal atoms )
M-C
metalloid
B、P、Si
Non-M-C
non-metallic
Ⅰ. Introduction of organometallic chemistry
 Some compounds, even if they exist metal- carbon bond,
belong to inorganics, such as metallic carbide (CaC2,
Mg2C3, Al4C3) and cyanide (KCN).
metal compounds with carbonyl group (CO)
Organometallic
compounds
metal hydride
B - C and Si - C compounds
As、Sb、Bi compouds
Ⅰ. Introduction of organometallic
chemistry
1.2 Organometallic chemistry and Nobel chemistry prize
One of the earliest metallorganic was
synthesized with ethanol and chloroplatinate
salt in 1827 by the Danish pharmacist Zeise,
40 years earlier than the publishing of
Mendeleev’s periodic table of elements in
1968, and almost the same period (1828) of
the father of organic synthesis Weiler.
The earliest organic
metal compound
Grignard reagent, 1912 Nobel Prize in chemistry
In 1900, French scientists F. A.Grignard discovered
Grignard reagent (RMgX)，which is important
method for lengthening carbon chain in organic
synthesis.
Viccor Grignard
Karl Ziegler
Giulio Natta
Ziegler –Natta catalyst,1963 Nobel Prize in chemistry
Initially, olefin polymerization is free radical
polymerization, which required a high pressure
reaction, there are many kinds of moving chain
transfer reaction and the reaction lead to branched
product, the Ziegler-Natta catalyst(TiCl4/AlEt3) solved
the problem, can synthesize the regularity of the
branched polyolefin.
Organometallics,1973 Noble Prize in chemistry
Structural chemistry and
organometallic chemistry
research, found homogeneous
hydrogenation catalyst (formerly
Wilkinson catalyst)
Sir Geoffrey Wilkinson
Organometallic chemistry, including
aromatics metal π complex ,olefine metal π
complex, ferrocene intercalation compounds,
metal carbonyl compounds
Emst Otto Fischer
Conductive polymers, 2000 Nobel Prize in chemistry
In 1976, American scientists Alan j. Heeger, Alan g. MacDiarmid,
Japanese scientists Hideki Shirakawa developed polyacetylene
film with the conductivity of 3000 S/m.
Ⅰ. Introduction of organometallic chemistry
1.3 Classification of organometallic compounds
organic main group metal compounds
 metal elements
organic transition metal compound
σ-ligand
 ligand
alkyl, phenyl
π acid ligand neutral molecules, such as CO
alkenes, alkynes
π ligand
delocalized π-bonds ring system,
cyclopentadiene, benzene.
Ⅰ. Introduction of organometallic chemistry
1.3 Classification of organometallic compounds
alkyl, carbonyl, nitroso, cyano , isocyano
Organic group
cyclopolyene (cyclopentadiene , benzene)
unsaturated hydrocarbons (alkenes, alkynes)
carbene, carbyne
Ⅰ. Introduction of organometallic chemistry
1.4 Difference of organometallic compounds with main group
and transitional metals
Difference
Bond types of M-C
Valence electron
main group metals
ionic
octet rule
transitional metals
covalent
EAN rule
Ⅰ. Introduction of organometallic chemistry
1.4 Difference of organometallic compounds with main group
metals and transitional metals
octet rule:
The octet rule is a chemical rule of thumb that states that atoms of main-group
elements tend to combine in such a way that each atom has eight electrons in
its valence shell, the same electronic configuration as a noble gas. The rule is
especially applicable to carbon, nitrogen, oxygen, and the halogens, but also to
metals such as sodium or magnesium
For IA, IIA, IIIA metals, the valence electrons of metal and ligand valence
shell electron are less than 8, so their organometallic compounds were the
electron-deficient, which are often associated with solvent, polymerization
itself or multiple center bonding.
Ⅰ. Introduction of organometallic chemistry
1.4 Difference of organometallic compounds with main group
and transitional metals
Electron-deficient organometallic compound
Ex. Be(CH3)2 polymer
bridged bond of 3c-2e
Ⅰ. Introduction of organometallic chemistry
1.4 Difference of organometallic compounds with main group
and transitional metals
 Effective Atomic Number rule
For transition metal organometallics, the sum of the electron
of a metal and the σ electron of all the n ligand is equal to the
atomic number of the rare gas in that period of this metal. If
only considering the valence shell electron, the molecule is
stable if the sum of metal valence electron and σ electron of
ligand is 18, so the effective atomic number is also called 18
electrons rule.
This rule determined maximal bonding number of the
transition metal atoms is 9 valence orbits, including its 5 nd
orbits, 1 (n + 1) s orbit and and 3 p (n + 1) orbits.
Ⅰ. Introduction of organometallic chemistry
1.4 Difference of organometallic compounds with main group
and transitional metals
The number of electrons that ligand provided :








CO, R3P, R3As contribute 2 e each;
Free radicals ·CH2R, · CH3, · Cl, · Br contribute 1 e each;
NO contribute 3 e;
η2 - olefin H2C = CH2 contribute 2 e ;
η4 - butadiene C4H6 contribute 4 e ;
η5 - cyclopentadiene base by C5H5 contribute 5 e;
η6 - benzene C6H6 contribute 6 e.
ηn represent the atomic number of ligand that π bonding with
the metal atom
Ⅰ. Introduction of organometallic chemistry
1.5 Ligand types of organometallic compounds and bonding way
with transition metals
According to the bond nature of ligands and metals, ligands can
be divided into three categories: σ ligand , π acid ligand and π
ligand.
(1) σ ligands
Some carbonaceous organic group such as alkyl, alkenyl, alkynyl,
aromatic, acyl in the formation of the M – C bonding, there is only one
carbon atom directly bonding with metal atom, which is σ ligands, they
typically provide a pair of σ electron as anion (formal charge - 1), and
its coordination way is the terminal type
Ⅰ. Introduction of organometallic chemistry
(2) π acid ligand
 CO is a typical π acid ligand, the effects of bonding with
metal are in the following:
•There existed not only the filled σ orbital (5 MO) but
also empty π* orbital (2π* MO) available in the CO, so it
has two effects when bonding with transition metal atom:
σ bonding effect and feedback π bonding effect.
Ⅰ. Introduction of organometallic chemistry
(2) π acid ligand
(sp - sp antibonding)
(double degenerate)
sp(C)
(double degenerate)
(sp - sp bonding)
sp(O)
Molecular orbital energy level, shape and electron configuration of CO
Ⅰ. Introduction of organometallic chemistry
(2) π acid ligand
σ bonding
feedback π bonding
CO and transition metal bonding effect
Ⅰ. Introduction of organometallic chemistry
1.5 Ligand types of organometallic compounds and bonding modes
with transition metals
(3) π ligands
π ligands are mostly carbonaceous unsaturated organic
molecules, and coordinating to metal with more than one
carbon atom, by providing π electrons to the metal. Usually,
these unsaturated organic molecules have a chain structure
(alkenes, alkynes, π propyl, butadiene, etc.) and cyclic
structure (cyclopentadiene, benzene, cycloctatetraene, etc.).
Ⅰ. Introduction of organometallic
chemistry
1.5 Ligand types of organometallic compounds and bonding
mode with transition metals
Difference between π acid ligand and π ligand:
Difference
π ligand
π acid ligand
Electron acception
π orbit
π orbit
Electron donation
π orbit
σ orbit
Metal atom
Not necessarily in the
ligand plane.
e.g. Fe in FeCp2 is not
in Cp plane.
In the axis of the ligand
(carbonyl compounds,
metal atoms are on M-CO
axis) or in the plane of
planar ligand
II. Main types of organometallic compounds
2.1 Metal alkyl compounds
2.2 Metal carbonyl compounds
2.3 Carbonyl organometallic compounds
2.4 Unsaturated chain hydrocarbon complex
2.5 Sandwich-type complex
II. Summary of organometallic compounds
2.1 Metal alkyl compounds
The organometallic compounds, which are formed by the
main group metal of s and p region in the periodic table of
elements and alkyl groups, are metal alkyl compounds.
II. Main types of organometallic compounds
2.1 Metal alkyl compounds
Synthesis of metal alkyl compounds
(1) Directly reaction of metal and organic halide
(2) Metal substitution reaction
II. Main types of organometallic compounds
2.1 metal alkyl compounds
(3) Double decomposition reaction
(4) Addition reaction
II. Main types of organometallic compounds
2.1 metal alkyl compounds
Property and structure of the metal alkyl compounds
II. Main types of organometallic compounds
2.2 Metal carbonyl compounds
Features:
① The chemical bond between M and CO is strong
② Central metal atom is always presented a lower oxidation state
③ Most complexes are subject to effective atomic number rule
II. Main types of organometallic compounds
2.2 Metal carbonyl compounds
Preparation method:
(1) direct chemical combination
(2) reductive carbonylation method
(3) thermal (or photo) decomposition method
(4) metal carbonyl compound interactions
II. Main types of organometallic compounds
2.2 Metal carbonyl compounds
Reaction
(1)With alkali
(2) With acid
(3) Substitution reaction with X2 or NO
(4) REDOX reaction
II. Main types of organometallic compounds
2.2 Metal carbonyl compounds
Coordination mode between CO and metal
1. Terminal group coordination
2. Side group coordination
II. Main types of organometallic compounds
2.2 Metal carbonyl compounds
3. Edge bridge group coordination
Use symbols “μ2 - CO", μ 2 represent two atoms bridging
II. Main types of organometallic compounds
2.2 Metal carbonyl compounds
4. Surface bridge group coordination
In multiple core carbonyl compounds, a CO can be combined with three
metal atoms formed the bridge mode. “μ3 – CO”
II. Main types of organometallic compounds
2.2 Metal carbonyl compounds
5. Semi-bridge group coordination
A kind of highly asymmetric edge bridge
coordination，which reflect in asymmetric
dinuclear or multiple-nuclear carbonyl complexes.
II. Main types of organometallic compounds
2.2 Metal carbonyl compounds
The different ways of coordination of CO could be identified
through infrared spectrum, the following is the change of C-O
stretching vibration frequency after the CO coordination.
Free CO：
νCO＝2143 cm－1，
Terminal group CO：
νCO＝2000 ± 100 cm－1;
Bridge group CO:
νCO(μ2－CO)＝1800 ± 75 cm－1;
Surface bridge group CO:
νCO(μ3－CO)＝1625 cm－1
The CO coordinating to M resulted in the weakening of C-O bonding,
which is prototype for heterogeneous catalysis for CO transformation
on noble metal surface.
II. Main types of organometallic compounds
2.2 Metal carbonyl compounds
Cr(CO)6: the Cr (3d54s1), with d2sp3 hybridization, pointing to the six
vertices of octahedron, each hybrid orbital accept a pair of 5σ orbital
electron of CO, which form the σ bond.
The dxy of Cr and the 2π* of CO match symmetrically, they then
compose π MO. And a pair of electrons on the original dxy occupy π
orbital, equivalent to electron from Cr to empty 2π* MO of CO, so it
called feedback π bond.
II. Main types of organometallic compounds
2.2 Metal carbonyl compounds
The σ bond combined with the feedback π bond is called σ-π bond.
II. Main types of organometallic compounds
2.3 Carbonyl organic metal compounds
(1) CN－ coordination compound
When CN - coordinate with metal ions, C atoms provide
the lone pair electrons to form the σ bond with metal ions,
and utilize the empty π* bond orbital to the accept d electron
of the metal ions to form the feedback π bond, constitute a
similar complex to metal carbonyl compound.
σ-π bond system.
Isoelectronic species: molecules with same number of atom
and same number of valence electron.
e.g: CO, CN-, N2 , NO+.
II. Main types of organometallic compounds
2.3 Carbonyl organic metal compounds
(2) N2 coordination compound
The lone pair electrons on the nitrogen atoms enter into the empty
orbits of the metal ions (atomic) then form σ bond, and N2
molecule use its empty π* bond orbital accept d electron of the
metal ions, form the feedbackπ bond, constitute σ -π double
bond structure.
Important for N2 fixation and activation
II. Main types of organometallic compounds
2.3 Carbonyl organic metal compounds
(2) N2 coordination compound
(a) N2 molecules form a linear
coordination compound using end group
(b) N2 via donating π electron form T coordination
compound in side group;
(c) N2 molecules with metal ions form
the dinuclear coordination compound
II. Main types of organometallic compounds
2.4 Unsaturated chain hydrocarbon complex
Metal and olefins or alkyne complex is a kind of important
organometallic compound.
(1) Zeise salt:
chemical formula: K[PtCl3(C2H4)]·H2O
The chemical bond between Pt (II) and ethylene
II. Main types of organometallic compounds
2.4 Unsaturated chain hydrocarbon complex
(2) Diene and polyene coordination complex
When the ligand contained more than one
double bonds, it can provide more than a pair
of π electron to form multiple σ bonds, this
ligand is multidentated or chelated.
II. Main types of organometallic compounds
2.4 Unsaturated chain hydrocarbon complex
(3) Alkyne coordination complex
Complexes formed by alkynes and metal
Due to the two mutually perpendicular π and π bonds in the alkynes, so the
alkyne ligand and metal form polynuclear complexes with the triple bonds
as the bridge group.
II. Main types of organometallic compounds
2.5 Sandwich structure complex
The sandwich structure complex is
composed of transition metal ions and
contains delocalization π cyclic ligand. It
shaped like a sandwich.
Including metallocene, Bischromium,
cyclooctatetraene sandwich compound, etc
Ⅲ. Application of organometallic compounds
3.1 Alkylating reagents in organic synthesis
3.2 Homogeneous catalysts
3.3 Application in the biomedicine field
Ⅲ. Application of organometallic compounds
3.1 alkylating reagents in organic synthesis
Metal alkyl compounds is one of the important reagents in
organic synthesis, including alkyl lithium, alkyl aluminium and
Grignard reagent are of the most commonly used carbanion
reagents.
Carbanion (R-) refers to the organic groups covalent bonding
with the electropositivite metal atoms, making it a strong
nucleophilic reagent or Lewis base, as a nucleophilicR group
source in organic synthesis.
Ⅲ. Application of organometallic compounds
3.1 Alkylating reagents in organic synthesis
The R group of metal alkyl compounds
attack the carbonyl carbon atom of ketone, and hydrolyze to tertiary
alcohol;
react with formaldehyde, hydrolyze to secondary alcohol;
react with SO2Cl2 or SOCl2 reaction to sulfone or sulfoxide, etc.
Ⅲ. Application of organometallic compounds
3.2 Homogeneous catalyst
Many transition metal organometallics have significant catalysis
activity, becoming one important catalyst in organic synthesis.
Organometallic compounds have catalytic activity, which is
realted to the weak bonding between L and M, making the
formation and rupture of M-C bonds more easily, and transition
metal ions have various available valence orbit in the reaction, a
high coordination number.
Ⅲ. Application of organometallic compounds
3.2 Homegeneous catalyst
The basic types of catalytic reaction of organometallic compounds:
(1) Adduction and dissociation reactions
Many center metal atoms of transition metal compounds have
ligand unsaturated structure, and their valence electronic is only 16
or even 14 ( less than 18).
L4M + :X
L4MX
X is CO, olefin or halide ion
Ⅲ. Application of organometallic compounds
3.2 Homegeneous catalyst
The basic types of catalytic reaction of organometallic compounds:
(2) Oxidation addition and reduction elimination reactions
Oxidative addition generally refers to the neutral molecules XY
adding to coordination space of transition metal compounds
Reduction elimination reaction is the reverse reaction of oxidative addition
Ⅲ. Application of organometallic compounds
3.2 Homegeneous catalyst
The basic types of catalytic reaction of organometallic compounds:
(3) Insertion reactions
Most of the catalytic reaction include insertion reaction.
ligand insert the bond between M and R
Ⅲ. Application of organometallic compounds
3.2 Homegeneous catalyst
The basic types of catalytic reaction of organometallic compounds:
(4) β-hydrogen transfer
The metal hydride and alkenes formed by β- hydrogen transfer.
Ⅲ. Application of organometallic compounds
3.2 Homegeneous catalyst
Example: The reaction of olefin polymerization generates polyolefin
Ziegler – Natta Catalyst
Ⅲ. Application of organometallic compounds
3.2 Homegeneous catalyst
Olefin polymerization catalyst has experienced three stages:
1. Ziegler – Natta Catalyst
2. Metallocene (Kaminsky) Catalyst
3. Late transition metal catalyst
Ⅲ. Application of organometallic compounds
3.2 Homegeneous catalyst
Example: asymmetric drugs catalyst synthesized, such as chiral copper, tin, and
nickel.
Chiral copper catalyst: a certain mole fraction of chiral copper can catalytic
asymmetric cyclopropane olefin, synthetic dipeptide inhibition Cilastatin.
Ⅲ. Application of organometallic compounds
3.3 Application of in the biomedicine field
Application in pesticides.
Many metallorganic compounds have been widely used in pesticide
because of its biological toxicity.
(1) Zineb , widely used in the prevention and control of all kinds of wheat
rust, the potato late blight, cucumber downy disease and vegetable diseases
Ⅲ. Application of organometallic compounds
3.3 Application of in the biomedicine field
Application in pesticides.
(2) West force and tag, they are organomercury compounds, used in the
prevention and control of the seed disinfection of various bacteria
Ⅲ. Application of organometallic compounds
3.3 Application of in the biomedicine field
Application in medicine
(1) Organomercury drugs such as
mercury phenylacetic acid. Mercury
phenylacetic acid is used as the
preservative.
Ⅲ. Application of organometallic compounds
3.3 Application of in the biomedicine field
Application in medicine
(2) Organic antimony drugs such as antimony potassium tartrate
also called tartar emetic which can use for schistosomiasis.
Antimony sodium gluconate used for kala-azar. Antimony
nitrilotriacetic acid can use for fibrosarcoma, stomach tumor,
colon cancer treatment, etc