《有机金属化学》课件Chapter 4

1、Chapter 4Complexes of p-bound Ligands1.Alkene complexes2.Butadiene complexes3.Alkyne complexes4.Enyl Complexes 5.Complexes of the cyclic p-perimeters CnHnMetal p-complexes of Unsaturated ligands with heteroatoms7.Characterization of organometallic compounds OutlineReferences and suggested readings:1

2、. The Organometallic Chemistry of the Transition Metals, Robert H. Crabtree, 3rd Edition, 2001, Chapters 5, 10.2. Organometallic Chemistry, G. O. Spessard, G. L. G. L. Miessler, Prentice-Hall: New Jersey, 1997, Chapter 5. 3. Organometallics, C. Elschenbrouch, A. Salzer, 1989, Chapter 15.4. Organotra

3、nsition Metal Chemistry, Akio Yamamoto, 1986. Chapters 3.4-3.9, 6.1d.B. Preparation of olefin complexes1. Alkene complexesA. Structure and bonding of monoolefin complexesC. Reactivity of olefin complexesA. Structure and bonding of monoolefin complexesExamples: Non-planarBonding:Q1. Which interaction

4、 is dominant? High valent metal (e- poor) systems:-Donation is dominant. Low valent metal (e- rich) systems:-Backdonation is dominant.Q2. What are the effects of complexation? d(C-C) u(C=C)e- density on C Q3. Consider the fragment Pt(PPh3)2. Which of the following olefins would you expect to form th

5、e most stable olefin adduct A? (a) CH2=CH2(b) CH3-CH=CH2 (c) CH2=CHCNAnswer: (c) more backdonationQ4. Which of the following olefin complexes is more stable?* Usual stability of olefin complexes: Answer: (A) small steric hindrance Q5. Which of the following olefin complexes is more stable?Answer: (b

6、) release ring strain Strong ring strainring strain releasedB. Preparation of olefin complexes1. From Substitution reactions:LnM-L + olefin - L + LnM-(olefin)Examples: precipitation2. Metal salt + olefin + reducing agents.e.g. Mechanism ?3. From alkyl and related species:1). Insertion reactionsExamp

7、les:C. Reactivity of olefin complexesExamples:monomer3). Nucleophilic attack on coordinated olefins. Examples: Summary: Reactions of olefin complexes.2. Butadiene complexesA. Most common structures of butadiene complexes B. Synthesis of butadiene complexesC. Reactions of butadiene complexes A. Most

8、common structures of butadiene complexes B. Synthesis of butadiene complexes1. by substitution reactions. e.g. 2. Reaction of coordinated ligands. e.g. Correct your notes !C. Reactions of butadiene complexes Examples:16e18e18e18e18e3. Alkyne complexesA. Structure and bonding of alkyne complexesB. Pr

9、eparation of alkyne complexesC. Reactivity of alkyne complexesA. Structure and bonding of alkyne complexesR-CC-R can be simple h2-ligand or bridging ligand. As simple h2-ligand, they can be 2e or 4e donors. e.g. 18e18eQ1. How can they be 2e or 4e donors? In terms of bonding: Correct your notes !As b

10、ridging ligands:Q2. For each pair of the following complexes, which one is more stable?B. Preparation of alkyne complexes1. By substitution reactions: e.g. 2. By other methods: e.g. C. Reactivity of alkyne complexesSimilar to olefins complexes, e.g. Q1. Give the product for the following reaction.4.

11、 Enyl Complexes A. Allyl complexesExamples of other enyl complexes and their preparationEnyl: Organic ligands with odd number of carbon chains.Examples:A. Allyl complexes1. Structure of allyl complexes2. Preparation of allyl complexesa. Metal salt + main group organometallic reagents.Examples: Corre

12、ct your notes !b). Low valent metal complexes + allylhalide.Correct your notes !c) Metal salts + olefin + base. A previously mentioned example:Examples 3. Reactivity of allyl complexesa). With Nucleophiles:b). With electrophile (for h1-allyls):c). Insertion reactions.B. Examples of other enyl comple

13、xes and their preparationThey can be prepared similar to allyl complexes.Examples:a). Metal salt + main group organometallic reagents.b). Transfer of H+ or H- h5h75. Complexes of the cyclic p-perimeters CnHnA. C3R3 as ligands B. C4R4 as ligandsC. C5R5 as ligands D. Arene complexesE. C7H7 and C8H8 as

14、 ligands Common complexes of cyclic p-perimeters CnHn:Common structural typesa). Sandwich complexes, e.g. Cr Mn Fe Co Nib) Half-sandwich complexes c) Multidecker sandwich d). Complexes with tilted sandwich structures.A. C3R3 as ligands Common starting materials for preparing h3-C3R3 complexes?Exampl

15、es and preparation.B. C4R4 as ligandsQ1. What are the common starting materials for preparing M(h4-C4R4) complexes? Example and preparation.Important chemical properties: a. Show aromatic properties. e.g. b). Can be used as a source of C4R4. C. C5R5 as ligands Common C5R5Binding mode of C5R5A).How t

16、o prepare CpM complexes?Common starting materials: Examples.1). From a source of Cp - : most common routeCp- reagents: NaCp, CpMgBr, TlCp, CpSnMe32). From C5H6 or related ligands. e.g. c). From a source of Cp+. e.g. B. What are the typical chemical properties of h5-Cp ligand? - h5-Cp ligand is usual

17、ly unreactive.- The following reactions may occur to h5-Cp. * Electrophilic substitution-like benzene * Metallation reactions * Nucleophilic attack on Cp Exercise. Provide the product for the following reactions.D. Arene complexes1). Common structures - As simple h6, h4, h2 ligands.h6 - most common1

18、8e16e18eAs bridging ligands 18e18e16e18e2). Common synthetic routesBy substitution reactions Benzene + metal salts + reducing agents Expected reactivity:Less reactive toward E+, more reactive toward Nu-. 3). Common Chemical reactionsExercise. Provide the product for the following reactions.E. C7H7 a

19、nd C8H8 as ligands * C7H7 can be a h1, h3, h5 and h7 ligand. e.g.18e18e18e18e* C8H8 can be h2, h4, h6 and h8 ligands. e.g. Exercise: Suggest the products or reagents for the following reactions.uraniumAcetonitrile (20e)6. Metal p-complexes of unsaturated ligands with heteroatoms.Many unsaturated lig

20、ands with heteroatoms can form complexes. Examples:18e18e18e5e donor:6e donor:4e donor:3e donor:6e6e6e5e4eDonor:Donor:6e6e6eSynthesis: similar to organic ones. e.g. Give the reagents or products for the following preparations.18e18e4e6e18e7. Characterization of Organometallic Compounds.1). Characteristic IR frequencies of some common organometallic groups.2). NMR (1H, 13C) in characterization of organometallics. This