Organometallics, Catalysis and Polymer Chemistry
Alexander von Humboldt Fellow, Technical University, Munich, 1975 (with Prof. E. O. Fischer, Nobel Laureate).
of the Chemical Institute of
Chemistry Department Excellence in Teaching Award, 1982, 1989, 2002, 2003, 2009.
Alcan Lecture Award of the Chemical Institute of Canada, 1986.
Inducted into the McMaster University Sports Hall of Fame, 1997.
Prize for Excellence in Research, Queen's University, 1998.
Award of the Chemical Institute of
Inaugural Inductee, Queen's University Athletic Coaches Hall of Fame, 2003.
Fellow of the Royal Society of
of the Canadian
Chemical Institute of
Many branches of chemistry and materials science now interface with organometallic chemistry, defined as the study of compounds containing carbon-metal bonds. Thus organometallic chemistry research in our lab is interdisciplinary in nature and involves research on aspects of inorganic, organic, polymer, and catalysis chemistry. As outlined below and on the linked pages, we are currently working on a wide variety of research projects which offer opportunities for students and PDFs to gain both useful scientific knowledge and also experience with a number of important spectroscopic and analytical tools.
Projects to be initiated over the next year or so will give new graduate students opportunities to synthesize interesting organometallic compounds which have never been prepared before, to explore the use of organometallic compounds as catalysts for "green" chemistry and for making plastics biodegradable, to develop new initiators for polymer synthesis and to develop new catalytic applications of organometallic compounds to both industrial processes and organic synthesis.
We have in the past few years initiated a new program of research into the synthesis and properties of phosphonium cyclopentadienylides and 1-indenylides such as methyldiphenylphosphonium 1-indenylide (I), a type of aromatic ylide ligand which shows great promise but which has been little investigated. Such ligands are interesting because they are intermediate in donor properties between anionic cyclopentadienide and neutral arene ligands, and because the 1-indenylide ligands form planar chiral complexes on coordination, as in II. Thus they may have very interesting properties as enantioselective catalysts since the chirality exists very close to the metal.
We have earlier prepared and studied I, and more recently we have also prepared the corresponding analogues Me2PhP-1-C9H6 and Ph3P-1-C9H6. We are now involved in the synthesis of series of complexes of the types [(h5-ylide)TiCl3]PF6, [(h5-ylide)2TiCl2][PF6]2 and [Cp(h5-ylide)TiCl2]PF6, with intentions of extending this chemistry to zirconium and hafnium. Of potentially great significance, we shall investigate the use of the new compounds as catalysts for polymerization of propylene and 1-alkenes since the chirality of the complexes should result in significant degrees of tacticity in the polymers formed. In addition, the new titanium complexes are structurally very similar to titanocene derivatives which we have previously studied as anticancer drugs and, in collaboration with colleagues in the Cancer Research Labs at Queen’s, we shall also investigate their cytotoxic properties.
Moving to the platinum metals, we have synthesized complexes of the types [CpRu(h5-ylide)]PF6 (III) and (h5-ylide)RuCl2, and will in the very near future assess these for potential catalytic properties and as anti-cancer drugs. On another tack, recognizing the enhanced stabilities of complexes of chelating ligands, we are preparing the chelating ligands 1-C9H6PPh2(CH2)nPPh2 (IV). These should coordinate to metals via both the five-membered ring and the pendant phosphine and, depending on n, the bonded C5 ring will be more or less skewed relative to the metal-C5 ring centroid. This will in turn induce subtle changes to the chemistry of the compounds and hence to catalytic properties. New chemistry involving rhodium is also in the works, with again the potential to make new compounds with potentially interesting catalytic properties.
These studies provide opportunities for new graduate students to both develop their synthetic skills and become adept at the use of NMR and IR spectroscopy, gas chromatography, mass spectrometry and X-ray crystallography. Compounds which have never before seen the light of day will be prepared, and potentially very interesting catalytic properties will be investigated.
Catalytic (“Green”) Organometallic Chemistry for Organic Synthesis
A wide variety of palladium-catalyzed C-C, C-N and C-O bond forming methodologies are available through the 2010 Nobel Prize winning chemistry pioneered by e.g. Heck, Suzuki and Negishi, etc. Unfortunately procedures for synthesizing the necessary catalysts, which are palladium complexes of the type PdL2 (L = tertiary phosphine), are not always readily available because of uncertainties in the modes of preparation of the catalyst systems. However, as we have recently reported (Norton et al. J. Org. Chem. 2009, 74, 6674), Pd(h3-1-PhC3H4)(h5-C5H5) (V) reacts readily with two equivalents of L as shown to form compounds of the type PdL2 in a much more atom efficient manner than is normally the custom. Compound V is air-, water- and thermally stable, and is thus very user friendly. It is, in fact, quite likely the best route to the catalytic species PdL2.
We are currently demonstrating that solutions of PdL2, generated from V, exhibit enhanced catalytic activities for a variety of C-C, C-N and C-O cross-coupling processes, a result which we attribute to our procedure being able to convert essentially all of the metal to PdL2 and thus to our achieving higher concentrations of active PdL2 species than is the case using conventional precursors. Current research is extending the scope of our investigation to other cross-coupling reactions and other ligands L which have not previously been properly assessed. Future research will also investigate the use of analogous nickel based catalyst systems, as there is reason to believe that they will catalyze types of cross-coupling reactions not induced by palladium. Success in these ventures will greatly increase the breadth and usefulness of catalytic cross-coupling methodologies.
This topic provides opportunities for new graduate students to carry out a wide range of catalyst studies. It will be of special interest to candidates with interests in organic chemistry and who wish to become adept at the use of NMR and IR spectroscopy, gas chromatography and mass spectrometry.