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N -Heterocyclic Carbene Conformational Change: A New Method to Tune the

N -Heterocyclic Carbene Conformational Change: A New Method to Tune the Reactivity of Transition Metal Complexes. Mark K. Rong - VU University Amsterdam. EWPC 10. March 2013. Vrije Universiteit Amsterdam. EWPC 10. March 2013. Vrije Universiteit Amsterdam. Introduction. E ( diss ) =

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N -Heterocyclic Carbene Conformational Change: A New Method to Tune the

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  1. N-Heterocyclic Carbene Conformational Change: • A New Method to Tune the • Reactivity of Transition Metal Complexes • Mark K. Rong - VU University Amsterdam EWPC 10 March 2013

  2. VrijeUniversiteitAmsterdam EWPC 10 March 2013

  3. VrijeUniversiteitAmsterdam Introduction E(diss) = 23.6 kcal/mol (exp.) E(diss) = 27.0 kcal/mol (exp.) • Classical tuning of complex • Expected: PR3  NHC increases σ-donation • Increased rate, but slower PCy3 dissociation (!) • How do NHCs affect TM complexes? • NHC: σ-donor or π-acceptor? R.H. Grubbs et al., J. Am. Chem. Soc., 2001, 123, 749

  4. VrijeUniversiteitAmsterdam Introduction • 42-fold faster! K.Lammertsmaet al., J. Am. Chem. Soc., 2009, 131, 6666

  5. VrijeUniversiteitAmsterdam Introduction • φ = 90 • φ = 0 Orthogonal favoured by 12.5 kcal/mol Coplanar favouredby 2.5 kcal/mol Pronounced σ-donating character Higher charge density on phosphorus Higher nucleophilicity of phosphinidene • Significant π-acceptor character • Lower charge density on phosphorus • Lower nucleophilicity of phosphinidene BP86/TZP K.Lammertsmaet al., J. Am. Chem. Soc., 2009, 131, 6666 I.E. Markóet al., Angew. Chem. Int. Ed., 2009, 48, 3161

  6. VrijeUniversiteitAmsterdam Concept • φ = 90 • φ = 0 • Conformational-drivenmodificationof activity? • - Synthesise and isolate both NHC-characters -

  7. VrijeUniversiteitAmsterdam Calculations E(Me,Me)= 0kcal/mol E (Me,Me) =+27.8kcal/mol E (H,H) = 0 kcal/mol E (H,H) =-3.8 kcal/mol BP86/TZP

  8. VrijeUniversiteitAmsterdam Complex 1: NHC(Me,Me) • φ = 90 EWPC 10 March 2013

  9. VrijeUniversiteitAmsterdam NHC(Me,Me) A. Kotschyet al., Org. Lett.,2007, 9, 3437 M.F. Lappertet al., J. Organomet. Chem., 1994, 481, 89

  10. VrijeUniversiteitAmsterdam NHC(Me,Me) • Nucleophillicphosphinidenes:31P-NMR:δ= 500-700 • Pronounced σ-donating effect 31P-NMR: δ= 687 31P-NMR: δ= 580.7 K.Lammertsmaet al., Organometallics, 2002, 21, 3196

  11. VrijeUniversiteitAmsterdam Complex 2: NHC(H,H) • φ = 0 EWPC 10 March 2013

  12. VrijeUniversiteitAmsterdam NHC(H,H) F.E. Hahn et al., Angew. Chem. Int. Ed., 2008, 47, 3122 F.E. Hahn et al., Organometallics, 2009, 28, 896 A. Kamalet al., Tetrahedron Lett., 2002, 43, 6861

  13. VrijeUniversiteitAmsterdam NHC(H,H) • Deprotonation of NH • Product • Significant π-accepting NHC 31P-NMR: δ= 687 31P-NMR: δ= 580.7 31P-NMR: δ= 670.0

  14. VrijeUniversiteitAmsterdam NHC(H,H): Protection approach

  15. VrijeUniversiteitAmsterdam NHC(H,H): Protection approach Work in progress: R.H. Crabtree et al., Organometallics, 2010, 29, 5728 W.J. Middleton, Org. Synth., 1986, 64, 221 R.G. Bergman et al., J. Am. Chem. Soc., 1995, 117, 12478

  16. VrijeUniversiteitAmsterdam Discussion • φ = 90 • φ = 0 31P-NMR: δ= 580.7 31P-NMR: δ= 670.0 Pronounced σ-donating character(Higher phosphinidenenucleophilicity) Successfully synthesised • Significant π-acceptor character (Lower phosphinidenenucleophilicity) • Significant advancements EWPC 10 March 2013

  17. VrijeUniversiteitAmsterdam Conclusion • NHC conformational-drivenmodificationof activity. EWPC 10 March 2013

  18. VrijeUniversiteitAmsterdam Acknowledgements • Dr. Carolin A. Dumke • Prof. Dr. F.Ekkehardt Hahn • Funding: • Dr. J. Chris Slootweg • Dr. Andreas W. Ehlers • Prof. Dr. Koop Lammertsma • Andrei ChirilaMSc • David FranciolusBASc Thank you for your attention! EWPC 10 March 2013 18

  19. VrijeUniversiteitAmsterdam Additional slides EWPC 10 March 2013

  20. VrijeUniversiteitAmsterdam Phosphinidenes First isolated phosphinidene complex (1987) Free phosphinidene 77K, solid Argon-matrix (1994) K.Lammertsma in Top. Curr. Chem., 2003, 229, 95 M. F. Lappertet al., Chem. Commun.1987, 1282-1283 P. Gaspar et al., J. Am. Chem. Soc. 1994, 116, 7899-7900

  21. VrijeUniversiteitAmsterdam Phosphinidenes • Isolobal with carbenes • ‘Carbene analogue with additional lone-pair’ • Terminal phosphinidenes complexes • Versatile: nucleophile or electrophile? D.W. Stephan et al., Organometallics, 1993, 12, 3158 K.Lammertsmaet al., Eur. J. Org. Chem, 2002, 1127 K.Lammertsmaet al., Angew. Chem. Int. Ed., 2010, 49, 2102 K.Lammertsma in Top. Curr. Chem., 2003, 229, 95

  22. VrijeUniversiteitAmsterdam Phosphinidenephilicity Carbenes Phosphinidenes Electrophilic Carbene (Fischer type) Nucleophilic Carbene (Schrock type) Electrophilic Phosphinidene Nucleophilic Phosphinidene S.P. Nolan et al., Coord. Chem. Rev., 2009, 253, 862 K.Lammertsmaet al., Eur. J. Org. Chem, 2002, 1127 K.Lammertsmaet al., Angew. Chem. Int. Ed., 2010, 49, 2102

  23. VrijeUniversiteitAmsterdam Phosphinidenes • Isolobal with carbenes • ‘Carbene analogue with additional lone-pair’ • Terminal phosphinidenes complexes • Nucleophile or electrophile? Electrophilic Phosphinidene Nucleophilic Phosphinidene K.Lammertsmaet al., Eur. J. Org. Chem, 2002, 1127 K.Lammertsmaet al., Angew. Chem. Int. Ed., 2010, 49, 2102

  24. VrijeUniversiteitAmsterdam Electrophilicphosphinidenes Electrophilic Phosphinidene K.Lammertsma in Top. Curr. Chem., 2003, 229, 95

  25. VrijeUniversiteitAmsterdam Nucleophilicphosphinidenes Nucleophilic Phosphinidene K.Lammertsma in Top. Curr. Chem., 2003, 229, 95

  26. VrijeUniversiteitAmsterdam Previous work Grubbs’ Catalyst (1st generation) Grubbs’ Catalyst (2nd generation) K.Lammertsmaet al Chem. Eur. J. 2003, 9, 3577-3582 K.Lammertsmaet al., J. Am. Chem. Soc., 2009, 131, 6666

  27. VrijeUniversiteitAmsterdam NHC(H,Me) Crabtree et al., Organometallics, 2010, 29, 5728

  28. VrijeUniversiteitAmsterdam NHC(H,H): Protection approach

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