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Prof. Vernon C. Gibson’s Research presented by Gülşah Chisholm Group Monday Literature Meeting February 22, 2006.

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Presentation on theme: "Prof. Vernon C. Gibson’s Research presented by Gülşah Chisholm Group Monday Literature Meeting February 22, 2006."— Presentation transcript:

1 Prof. Vernon C. Gibson’s Research presented by Gülşah Chisholm Group Monday Literature Meeting February 22, 2006

2 Prof. Vernon C. Gibson PhD, under Professor Malcolm Green at the University of Oxford NATO postdoctoral fellow with Professor John Bercaw at Caltech Lecturer in Inorganic Chemistry at the University of Durham Professor in Inorganic Chemistry at the University of Durham 1995-present The first holder of the Sir Geoffrey Wilkinson Chair of Chemistry at Imperial College ; Head of the Catalysis and Materials research section at Imperial College The Sir Edward Frankland BP Professor of Inorganic Chemistry

3 Research Interests Ligand-Oriented Catalyst Design Olefin Polymerization Poly(methyl methacrylate) (Perspex®) Poly(lactic acid) (PLA) Atom Transfer Radical Polymerization (ATRP) Ring-Opening Metathesis Polymerization (ROMP)

4 Ligand-Oriented Catalyst Design … studying the fundamentals The isolobal relationship between cyclopentadienyl and imido metal complexes Examples of complexes synthesized to illustrate the isolobal relationship between cyclopentadienyl and imido metal fragments. J.K. Cockcroft, V.C. Gibson, J.A.K. Howard, A.D. Poole, U. Siemeling and C. Wilson, J. Chem. Soc. Chem. Commun., 1992,

5 Olefin Polymerization An iron-catalyzed Aufbau reaction on zinc and a nickel catalyzed displacement reaction to give linear alpha-olefins with a Poisson distribution. G.J.P. Britovsek, S.A. Cohen, V.C. Gibson, P.J. Maddox and M. van Meurs, Angew. Chem. Int. Ed. Engl., 2002, 41,

6 Developing high throughput screening (HTS) methodology to assist polymerization catalyst discovery. Olefin Polymerization (continued) D.J. Jones, V.C. Gibson, S. Green and P.J. Maddox, Chem. Commun., 2002,

7 Poly(methyl methacrylate) (Perspex®) A.P. Dove, V.C. Gibson, E.L. Marshall, A.J.P. White and D.J. Williams, Chem Commun, 2002,

8 Poly(lactic acid) (PLA) A.P. Dove, V.C. Gibson, E.L. Marshall, A.J. P. White, D.J. Williams, Chem. Commun., 2001, V.C. Gibson, E.L. Marshall, D. Navarro-Llobet, A.J.P. White and D.J. Williams, J. Chem. Soc. Dalton Trans., 2002,

9 V.C. Gibson, R.K. O'Reilly, W. Reed and D.F. Wass, Chem. Commun., 2002, Atom Transfer Radical Polymerization (ATRP) Efficient catalysts for the well-controlled atom transfer radical polymerization of styrene

10 Ring-Opening Metathesis Polymerization (ROMP) Bioactive materials via living ROMP S.C.G. Biagini, V.C. Gibson, M.R. Giles, E.L. Marshall and M. North, Chem. Commun., 1997,

11 Pyridine N-Alkylation by Lithium, Magnesium, and Zinc AlkylReagents: Synthetic, Structural, and Mechanistic Studies on the Bis(imino)pyridine System Ian J. Blackmore, Vernon C. Gibson,* Peter B. Hitchcock, Charles W. Rees, David J. Williams, and Andrew J. P. White Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AY, UK, and Department of Chemistry, Uni v ersity of Sussex, Falmer, Brighton BN1 9QJ, UK J. Am. Chem. Soc. 2005, 127,

12 Bis(imino)pyridines

13 Clentsmith, G. K. B.; Gibson, V. C.; Hitchcock, P. B.; Kimberley, B. S.; Rees, C. W. Chem. Commun. 2002, 1498.

14 Reardon, D.; Conan, F.; Gambarotta, S.; Yap, G.; Wang, Q. J. Am. Chem. Soc. 1999, 121, 9318.

15 J. Am. Chem. Soc. 2005, 127, Reactivity of Bis(imino)pyridines toward Methyllithium

16 J. Am. Chem. Soc. 2005, 127, Reactivity of Bis(imino)pyridines toward Methyllithium

17 J. Am. Chem. Soc. 2005, 127, Reactivity of Bis(imino)pyridines toward Dialkylmagnesium Reagents

18 J. Am. Chem. Soc. 2005, 127,

19 Reactivity of Bis(imino)pyridines toward Dialkylzinc Reagents

20 J. Am. Chem. Soc. 2005, 127, Selected Bond Lengths (Å) and Angles (deg) for 7, 8, 11, 12a, and 18 (for 7, Dimensions Are Given for the Ordered Molecule)

21 J. Am. Chem. Soc. 2005, 127, Tautomerization of N-Alkylated Products to C-Alkylated Species

22 J. Am. Chem. Soc. 2005, 127, Dissociation of MgR 2 ?

23 J. Am. Chem. Soc. 2005, 127, Reversibility of the N-Alkylation Reactions

24 J. Am. Chem. Soc. 2005, 127, ZnR 2 : N-Alkylation is Irreversible

25 J. Am. Chem. Soc. 2005, 127, Cationic Derivatives

26 J. Am. Chem. Soc. 2005, 127, Cationic Derivatives

27 J. Am. Chem. Soc. 2005, 127, Intermediate?

28 J. Am. Chem. Soc. 2005, 127, Mechanism of Alkylation

29 J. Am. Chem. Soc. 2005, 127, Conclusions The transformations in the nonelectrophilic pyridine N-alkylation reactions documented in this study are undoubtedly attributable to the special electronic and steric characteristics of 2,6-bis(imino)pyridines, which facilitate strong binding of the bis(imino)pyridine to the main group metal centers while disfavoring attack at the imino nitrogen or carbon centers due to the presence of bulky imino aryl substituents. Pyridine and imino functionalities have the capacity to engage in metal-to- ligand charge transfer and, under certain circumstances, even to formally accept one or more electrons. When combined with the extensive charge delocalization made possible through the two adjoining imino groups, the aromatic stabilization of the pyridine moiety is overcome. These results serve to highlight in a unique fashion the “noninnocent” behavior of the bis(imino)pyridine ligand system and may illuminate why the combination of pyridine and imino donors is so special in the metal- based chemistry and catalysis they support.


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