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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