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Current Drivers New Tools and Techniques Single-Site Polymerization. Catalysis  Materials

OPPORTUNITIES IN HOMOGENEOUS AND SINGLE-SITE HETEROGENEOUS CATALYSIS Tobin Marks, DOE Catalysis Workshop May 2002. Current Drivers New Tools and Techniques Single-Site Polymerization. Catalysis  Materials Multi-Site Catalysts and Cocatalysts Carbon-Heteroatom Bond Formation

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Current Drivers New Tools and Techniques Single-Site Polymerization. Catalysis  Materials

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  1. OPPORTUNITIES IN HOMOGENEOUS AND SINGLE-SITE HETEROGENEOUS CATALYSISTobin Marks, DOE Catalysis Workshop May 2002 • Current Drivers • New Tools and Techniques • Single-Site Polymerization. Catalysis  Materials • Multi-Site Catalysts and Cocatalysts • Carbon-Heteroatom Bond Formation • Homogeneous-Heterogeneous Interface • Biomimetic/Supramolecular, Enantioselective Catalysis • Opportunities and Needed Resources

  2. CURRENT DRIVERS FOR RESEARCH IN HOMOGENEOUS (HETEROGENEOUS) CATALYSISENORMOUS ECONOMIC IMPORTANCE!! • Environmental (Green Chemistry, Atom Efficiency, Waste Remediation, Recycling) • Polymeric Materials (New Polymers and Polymer Architectures, New Monomers, New Processes) • Pharmaceuticals and Fine Chemicals (Demand for Greater Chemo-, Regio-, Stereo-, and Enantioselectivity) • Feedstocks (Practical Alternatives to Petroleum and Natural Gas) • Cost of Energy (More Efficient, Selective Processes) • Completely New Materials (e.g., Carbon Nanotubes) • Cost Squeeze in Chemical Industry • Declining Corporate Investment in Basic Research

  3. NEW TOOLS FOR HOMOGENEOUS (HETEROGENEOUS) CATALYSIS RESEARCHSIMPLE TO EXPENSIVE • New and In Situ Spectroscopies (NMR, EPR, IR/Raman, SPM, EM, X-Ray, EXAFS/XANES) • Synthetic Techniques (Exotic Ligands, New Elements, Solid State, Sol-Gel, Nanoscale) • Reaction Techniques (Combinatorial, High-Pressure, Polymerization) • Computational (DFT, ab initio, MD, combinations) • New Characterization Techniques (Calorimetry, Polymer, Isotopic, Stop-Flow, Chiral GC/HPLC)

  4. A NEW GENERATION OF POLYOLEFINS

  5. Creating Highly Electrophilic d0 “Cations” On Surfaces In Solution • Important Questions • What are the Thermodynamic Constraints on Metallocenium Formation? • What is the Structural and Dynamic Nature of the M+ - - - - X- Interaction? • How Does the M+ - - - - X- Interaction Modulate Catalytic Properties? • What is the Ultimate X-?

  6. Organo-Lewis Acid Abstraction Chemistry Metallocene “Constrained Geometry” • M+. . . H3CB(C6F5)3- Interaction Largely Electrostatic • Extremely Active Polymerization Catalysts

  7. Alkyl Group Effects on Ion Pair Formation and Structural Reorganization EnergeticsCalorimetry and Dynamic NMR Data ‡ -D H D H reorganization formation + B(C6F5)3 CH3B(C6F5)3- M = Zr R = CH3 27 D H (kcal/mol) 24 24 Reaction Coordinate Bulkier R = Alkyl Groups Hformation More Negative (More Exothermic); H‡reorganizationSmaller Polar Solvents H‡reorganization Smaller; Bulkier R Less Sensitive Cyclopentadienyl Alkyl Substitution Hformation More Negative (More Exothermic)

  8. 1.32 1.36 2.37 2.05 2.05 6.49 4.72 AB INITIO COMPUTED REACTION COORDINATE FOR OLEFIN INSERTION 2.80 Å 2.37 Å Transition State Kinetic Product 1.55 E (kcal/mol) 1.41 2.09 1.53 2.16 2.14 2.93 6.62 5.48 8 3.5 3.0 2.5 2.0 1.5 Reaction Coordinate in Benzene [Ethylene]—[CH3Ti] Distance (Å)

  9. MODULATING CATION-ANION INTERACTION WITH PBA- L2M(CH3)2 + Ph3C+PBA- + Ph3CCH3 CGCZr(CH3)+PBA- rac-Me2Si(Ind)2Zr(CH3)+PBA- • Cation-Anion Interaction Very Sensitive to L2M (19F NMR, Crystal Structure) • Olefin Polymerization Activity Very Sensitive to L2M

  10. Are There Anion Effects on Me2C(Cp)(Flu)ZrMe2-Mediated Propylene Polymerization ? Syndiospecific Enchainment Mechanism : Does chain swinging require ion pair reorganization ? An ideal system to evaluate ion pairing effects !

  11. Polypropylene 13C NMR Spectra Me2C(Cp)(Flu)ZrMe2 + Cocatalysts rrrr Results Concentration Independent Over 32- Fold Range [mm] [m] [m] [mm] rrmr rrrm(r) rmmr rrmm rrrm(m) rrrr % B(C6F5)3(Borane)69 PBB84 B(C6F5)4-(Borate)84 PBA91 15.0 15.5 15.0 14.5 14.0 ppm

  12. LONG CHAIN BRANCH FORMATION IN ETHYLENE POLYMERIZATION Macromonomer Branch Formation How to make reinsertion more probable ?

  13. CATALYST NUCLEARITY MATRIX

  14. Grand Challenges in Catalytic Single-Site Polymerization 1. Nonpolar + Polar Monomer Copolymerization =acrylate, vinyl acetate, vinyl chloride, acrylonitrile 2. Control of Polymer Architecture Controlled Comonomer Incorporation Telechelic long chain branching Controlled Branching hard + soft Block Structures Controlled Tacticity Stars, Dendrimers

  15. Palladium-Catalyzed Hydroamination of 1,3-Dienes Mechanism in the presence of acid Mechanism in the absence of acid Löber, O; Kawatsura, M.; Hartwig, J. F. J. Am. Chem. Soc. 2001, 123, 4366-4367

  16. S O A r 2 N M e N 2 5 m o l % T i N N M e 2 A r N C H S O A r 3 2 N H 2 · A r 7 5 C C H 7 9 - 9 5 % 6 6 A r N A r P h 2 5 C H Z r N H P h C H C C H P h H + + Z r C C C T H F - T H F P h R a c e m i c P h P h H 1 . 8 e q u i v 1 e q u i v ( R ) 0 . 8 e q u i v ( S , S ) 9 8 % e e A l O 1 e q u i v 2 3 H H C C C P h P h ( S ) 9 0 % e e Use of Imido Complexes in Catalytic Hydroamination and Enantioselective Reactions of Allenes Ackermann, L.; Bergman, R.G. “A Highly Reactive and Selective Precatalyst for Intramolecular Hydroamination Reactions” Org. Let.2002; 4, 1475. Sweeney, Z. K.; Salsman, J. L.; Andersen, R. A.; Bergman, R. G. “Synthesis of Chiral, Enantiopure Zirconocene Imido Complexes: Highly Selective Kinetic Resolution and Stereoinversion of Allenes, and Evidence for a Non-Concerted [2+2] Cycloaddition/Retrocyclization Reaction Mechanism,” Angew. Chem. Int. Ed. Engl.2000, 39, 2339.

  17. Catalytic Pathways for d0,fn-Metal Mediated C-Heteroatom Bond Formation New Routes to Heteroatom-Substituted Molecules and Polymers

  18. THERMODYNAMICALLY BASED STRATEGIES FOR CATALYTIC HETEROATOM ADDITION EXAMPLE: Olefinic Substrates (X = Heteroatom Group) Intramolecular Intermolecular EXPECTATIONS • S, S‡ Favor Intramolecular Process • Hii < Hi• kii > ki • Hi (X): CH3  H < Pr2, NR2 < SR, OR

  19. Diastereoselectivity in Aminodiene Cyclization Good to excellent 2,5-trans (80% de), and 2,6-cis (99% de) diastereoselectivities Concise synthesis of (±)-pinidine with excellent stereocontrols (2,6-cis and trans-alkene)

  20. Is Hydrophosphination Analogous?

  21. Metallocene – Metal Oxide Chemisorption • Lewis Acid Surfaces (Dehydroxylated Al2O3, MgCl2) High Catalytic Activity Active Sites ~8% • Weak Brønsted Acid Surfaces • (SiO2, Partially Dehydroxylated Al2O3) Poorly Electrophilic Negligible Catalytic Activity

  22. Catalysis with Organozirconium Hydrocarbyls Supported on Sulfated Zirconia Solid BrØnsted Super Acid Polymerization activity varies with coordinative unsaturation: ZrR4 > CpZrR3 > Cp2ZrR2 Most active benzene hydrogenation catalyst known

  23. Scott’s Cr/SiO2 Ethylene Polymerization Catalyst S. Scott, J. Aijou J.Am.Chem.Soc. 2000, 122(37), 8968-76. S. Scott, J. Aijou Chem.Eng.Sci.2001, 56, 4155-68.

  24. Alkane Metathesis by Basset ethane metathesis propane metathesis isobutane metathesis Vidal, V., et.al. Science, 1997, 276, 99 – 102.

  25. Bifunctional Single-Site Supported Catalysts • Tailored Supports • Molecular Precursors (chemo-, regio-, stereoselectivity) Ziegler Site Oligomerization Site ROMP Site Chain Transfer Site Cationic Site Anionic Site Second Ziegler Site Hydrogenation Site Close Proximity  Multiple Coupled Transformations

  26. Structure of Carbonic Anhydrase A Metalloenzyme CO2 + H2O H2CO3 Nt ~ 107 – 109 sec-1 Now with Cd: T.W. Lane and F.M.M Morel Proc. Nat. Acad. Sci. USA2000, 97, 4627-4631

  27. Artificial Enzyme for Olefin Epoxidation º • Encapsulation of catalyst ==> 100-fold increase in lifetime. • Incorporation of ligands predictably modifies the internal cavity size to induce substrate selectivity Nguyen, Hupp and coworkers

  28. Cyclic Carbonates from CO2 + Epoxides Nguyen and coworkers

  29. High Activity Allows Polymerization of More Sterically Hindered Monomers • Kinetic resolutions of inexpensive monomers for production of chiral polymers and resolved olefin monomers C l M e S i Z r 2 M e S i 2 C l R , S (isotactic)poly( S -3,4-dimethylpentene-1) k S k R S R + + MAO s = > 12 John Bercaw, et al

  30. Thermal, Catalytic, Regiospecific Functionalization of Alkanes (RBpin) • terminal product only steric preference for a linear metal-alkyl complex Chen, H.; Schlecht, S.; Semple, T.C.; Hartwig, J. F. Science2000, 287(5460), 1995-1997

  31. Electrochemical Synthesis of Diamines Yudin and coworkers

  32. SUMMARY. FUTURE OPPORTUNITIES • MULTINUCLEAR / MULTIFUNCTIONAL CATALYSTS • Multisite Substrate Activation, Conversion • New Polymer Architectures, Modifications • NEW SURFACES • New Molecular Catalyst Activation Routes • Single-Site Ensembles • NEW OR IMPROVED TRANSFORMATIONS • Improved Selectivity (Chemo-, Regio-, Enantio-) • C-Heteroatom Formation (C-O, C-N, C-P, C-S, etc.) • Abundant Feedstocks (CO2, SiO2, Saturated Hydrocarbons, Biomass, Bioproducts, Waste) • Atom-Efficient, Heat-Efficient Transformations • NEW ELEMENTS, LIGANDS, COCATALYSTS • Early Transition Metals, Lanthanides, Actinides • Ligand Engineering • Cocatalyst Engineering

  33. Catalytic Cycle for Aryl Ether Synthesis

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