Learning objectives
Knowledge an understanding: educate students on the basic concepts of organometallic chemistry with particular emphasis to the synthesis, structure and reactivity of the main classes of organometallic compounds. The concept of donation/back-donation (from ligand to metal and from metal to ligand, respectively), will be particularly addressed. Applying knowledge and understanding: the course furnishes knowledge for the design of organometallic syntheses, for the understanding of the reactivity of organometallic compounds and a critical analysis on the choice of the characterization techniques needed to fully understand the structure and reactivity of a given compound. Making judgments: the student is invited to use all the chemical background acquired from the course and from other courses previously attended (Inorganic and Organic Chemistry) in order to understand the structural and reactivity properties of organometallic compounds, with particular emphasis to the structural and reactivity changes experienced by the coordinated ligand. Communication skills: the student learns the technical-scientific language associated with the organometallic chemistry, being able to give an accurate description of the structural and reactivity features associated with a particular compound. Learning ability: the student is able to understand advanced scientific literature, to analyse spectroscopic data and define the best experimental conditions for carrying out organometallic syntheses.
Prerequisites
Knowledge of the fundamental concepts of inorganic, organic and coordination chemistry
Course unit content
Review of some basic knowledge of coordination chemistry (metal-ligand bonding, coordination geometries, chelation).
Metal-carbon interaction based on the type of C-ligand (sigma-donor, sigma-donor/pi-acceptor, pi-donor/pi-acceptor), 18e rule.
Organometallic chemistry of some s and p-blocks metals: organolithium compounds, organomagnesium compounds, organoalluminium compounds, organisilicon compounds, organophosphorious compounds.
Systematic study of the main classes of C-based ligands for transition metals: alkyls and aryls, carbonyls, monoolefins, dienes, allens, alkynes, cyclopentadienyls, arenes, carbenes, isonitriles.
Agostic interactions, beta-elimination, alfa-elimination.
Substitution reaction is octahedral and square-planar complexes.
Nucleophilic and electrophilic addition reactions to coordinated ligands.
Oxidative addition, migratory insertion, reductive elimination.
Organometallic catalysis: main differences between homogeneous and heterogeneous catalysis, role played by an organometallic catalyst (ligand and metal effect), efficiency of a catalyst. Homogeneous hydrogenation, hydrogen transfer reaction, coupling reactions (Heck, Suzuki, Sonogashira, Negishi), nucleophilic addition to coordinated allenes.
Full programme
Review of some basic concepts of Coordination Chemistry, such as Lewis donor/acceptor, coordination geometries, crystal filed theory, ligands filed theory, magnetism of the coordination compounds, trans-influence and trans-effect, reactivity of the coordinated ligand.
Concept of ligand-to-metal electron donation and metal-to-ligand back-donation (sigma-donor ligands, sigma/pi donor ligands, sigma-donor/pi-acceptor, pi-donor/pi-acceptor ligands). 18 electron-rule, coordinatively saturated/unsaturated complexes.
Organometallic compounds of some elements of the s and p blocks (synthesis, solid and solution structure, reactivity): organolithium, organomagnesium, organoaluminum (Grignard and binary compounds), organosilicon.
Systematic study of the main classes of organometallic ligands: hydrides, phosphines, alkyls and aryls, carbonyls, mono-olefins, poly-olefins (dienes and allyls), cyclopentadienes, arenes, carbenes and isonitriles. For each class of ligands the structural features (solid state and solution), the main synthetic protocols and the main reactive behaviors will be addressed.
Alpha-aghostic interaction, beta-aghostic interaction, beta-elimination, their role in organometallic synthesis and (catalytic) reactivity.
Substitution reactions in octahedral and square-planar complexes: dissociative mechanism and associative mechanism, hybrid mechanisms.
Nucleophilic and electrophilic addition reactions onto coordinated ligands (CO, olefins, arenes, cyclopentadienes, dienes and allenes)
Oxidative addition (concerted mechanism, Sn2, ionic mechanism, radical and oxidative coupling), migratory insertion (1.1 and 1.2 mechanisms), reductive elimination (in octahedral and tetracoordinated complexes).
Metallorganic catalysis: comparison between homogeneous and heterogeneous catalysis (advantages and drawbacks). Role of the organometallic catalyst. Efficiency and selectivity of a catalyst (turnover number, turnover frequency, enantiomeric (diasteromeric) excess, chemoselectivity, regioslectivity). Homogeneous hydrogenation (Wilkinson catalyst and further generations), hydrogen transfer (internal and external sphere mechanism, Noyori mechanism), hydroformylation (Co and Rh-based catalysts), olefins metathesis, coupling reactions (Heck, Suzuki, Sonogashira, Negishi). Crytical discussion about the true homogeneous nature of some organometallic catalytic processes.
Bibliography
- The Organometallic Chemistry of the Transition Metals, Robert H. Crabtree Wiley
- Organometallics, A Coincise Introduction, Ch. Elschenbroich, A. Salzer Wiley-VCH
- Fundamentals of Organometallic Chemistry, Steinborn D., Wiley-VCH - Notes and educational materials made available by the teacher.
Teaching methods
Class lectures (48 hours) by which all the program will be covered. In particular, a critical discussion on how to choose the correct experimental conditions under which to conduct the syntheses and the characterizations of the classes of compounds listed in the program will be done. A critical discussion on how to choose the best instrumental tools for the monitoring of the chemical reactions will also be done.
Assessment methods and criteria
Oral exam, where the following points will be addressed: Learning of the basic concepts of organometallic chemistry, with particular emphasis to the ligand to metal electronic donation and metal to ligand back-donation, in order to understand the different reactivity shown by a free ligand (not coordinated organic molecule) and metal-bound organic molecule. Analysis of the effect played by all the actors involved in the reaction that's, type of organic ligand, substituents directly attached to the C-atoms bound to the metal, type of metal (its position in the Periodic Table and its electronegativity), type of ancillary (spectators) ligands. Definition of a possible synthetic strategy for the preparation of simple organometallic compounds, taking into consideration the type of ligand, metal and experimental conditions (temperature, solvent) required for getting the requested molecular structure and chemical reactivity. Ability to rationalize the most convenient spectroscopic and analytical techniques for the characterization of a given organometallic compounds. Ability to use the acquired concepts in order to understand some catalytic mechanisms governing some useful metal-catalyzed organic syntheses.
Other information
The slides of the lessons are available on the web. The teacher is available for tutoring (upon agreement).
