Chapter 8,Carbene and Carbyne Complexes,Outline,Introduction to M-C multiple bonds Common synthetic routes to carbene complexes Reactivity of carbene complexes Common synthetic routes to carbyne complexes Reactivity of carbyne complexes,General introduction to metal-carbon multiple bonds.,Carbene or alkylidene complexes Vinylidene or alkylidene complexes Allenylidene complexes Carbyne or alkylidyne complexes,1. Carbene or alkylidene complexes:,There are many organometallic compounds containing metal carbon multiple bonds. e.g.,2. Vinylidene or alkylidene complexes:,3. Allenylidene complexes:,4. Carbyne or alkylidyne complexes:,Both carbene complexes are existent. A is Schrock carbenes and B is Fischer carbenes.,A,B,Schrock carbenes:,The carbene carbon will be attacked by Nu- or E+ ?,Fisher carbenes :,The carbene carbon will be attacked by Nu- or E+ ?,Answer: The carbyne carbon is usually negatively charged.,Question 3. Which one is thermodynamically more stable?,B. Common synthetic routes to carbene complexes,(1). From metal carbonyls, e.g.,(2). From isonitrile complexes.,(3). From LnM-CR=CRR“.,(4). From LnM=C=CRR,(5). From LnM-CXR2,thallium,(6). By a-elimination.,(7) How to prepare M=C=CR2 and M=C=C=CR2 ?,C. Reactivity of carbene complexes,(1) Reactions of Fischer carbene with nucleophiles,(3) Reactions with acetylenes Both Fischer and Schrock carbene can react with acetylenes.,(4) Reactions with olefins,There are at least there possible products for the reactions, depending on metal complexes and olefins used.,e.g.,(5) Other reactions,D. Common synthetic routes to carbyne complexes,(1) Lewis-acid-assisted abstraction of OR.,(2) Electrophilic addition to M-CNR and M-CS,(3) Transformation of M-C CR and M=C=CRR,(4). By a-H elimination. e.g.,E. Reactivity of MCR,(1) Reactions with electrophiles,e.g.,(2) Reactions with acetylenes,There are several possible products for the reactions, depending on metal complexes, and reaction conditions.,e.g.,Schrock carbynes undergo metathesis reactions,(3) Reactions of M CR with X=Y or other X Y bonds,