Prof. Vernon C. Gibson’s Research

presented by

Gülşah Yaman

@

Chisholm Group Monday Literature Meeting

February 22, 2006

Prof. Vernon C. Gibson

• PhD, under Professor Malcolm Green at the University of Oxford

• NATO postdoctoral fellow with Professor John Bercaw at Caltech

• 1986-1993 Lecturer in Inorganic Chemistry at the University of Durham

• 1993-1995 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

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)

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., 1992,1668-1670.

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, 489-491.

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, 1038-1039 .

Poly(methyl methacrylate) (Perspex®)

A.P. Dove, V.C. Gibson, E.L. Marshall, A.J.P. White and D.J. Williams, Chem Commun, 2002, 1208-1209.

Poly(lactic acid) (PLA)

A.P. Dove, V.C. Gibson, E.L. Marshall, A.J. P. White, D.J. Williams, Chem. Commun., 2001, 283-284.

V.C. Gibson, E.L. Marshall, D. Navarro-Llobet, A.J.P. White and D.J. Williams, J. Chem. Soc. Dalton Trans., 2002, 4321-4322.

V.C. Gibson, R.K. O'Reilly, W. Reed and D.F. Wass, Chem. Commun., 2002, 1850-1851.

Atom Transfer Radical Polymerization (ATRP)

Efficient catalysts for the well-controlled atom transfer radical polymerization of styrene

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, 1097-1098.

Pyridine N-Alkylation by Lithium, Magnesium, and Zinc AlkylReagents:

Synthetic, Structural, and Mechanistic Studies onthe 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, University of Sussex, Falmer,

Brighton BN1 9QJ, UK

J. Am. Chem. Soc. 2005, 127, 6012-6020.

Bis(imino)pyridines

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

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

J. Am. Chem. Soc. 2005, 127, 6012-6020.

Reactivity of Bis(imino)pyridines toward Methyllithium

J. Am. Chem. Soc. 2005, 127, 6012-6020.

Reactivity of Bis(imino)pyridines toward Methyllithium

J. Am. Chem. Soc. 2005, 127, 6012-6020.

Reactivity of Bis(imino)pyridines toward Dialkylmagnesium Reagents

J. Am. Chem. Soc. 2005, 127, 6012-6020.

J. Am. Chem. Soc. 2005, 127, 6012-6020.

Reactivity of Bis(imino)pyridines toward Dialkylzinc Reagents

J. Am. Chem. Soc. 2005, 127, 6012-6020.

Selected Bond Lengths (Å) and Angles (deg) for 7, 8, 11, 12a, and 18 (for 7, Dimensions Are Given for the Ordered Molecule)

J. Am. Chem. Soc. 2005, 127, 6012-6020.

Tautomerization of N-Alkylated Products to C-Alkylated Species

J. Am. Chem. Soc. 2005, 127, 6012-6020.

Dissociation of MgR2 ?

J. Am. Chem. Soc. 2005, 127, 6012-6020.

Reversibility of the N-Alkylation Reactions

J. Am. Chem. Soc. 2005, 127, 6012-6020.

ZnR2: N-Alkylation is Irreversible

J. Am. Chem. Soc. 2005, 127, 6012-6020.

Cationic Derivatives

J. Am. Chem. Soc. 2005, 127, 6012-6020.

Cationic Derivatives

J. Am. Chem. Soc. 2005, 127, 6012-6020.

Intermediate?

J. Am. Chem. Soc. 2005, 127, 6012-6020.

Mechanism of Alkylation

J. Am. Chem. Soc. 2005, 127, 6012-6020.

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.