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The Field Group - Research

Directed by Professor Les Field

The Organometallic Chemistry of coordinated dinitrogen – nitrogen fixation

(with Assoc. Prof. Barbara Messerle).

Industrially, the chemical conversion of nitrogen to ammonia via the Haber-Bosch process requires both high temperatures and pressures. Nitrogen-fixing bacteria are able to efficiently carry out this conversion at atmospheric temperatures and pressures using transition metal based catalysts. We are interested in the development of reagents and catalysts (based on iron, molybdenum, tungsten and ruthenium) for converting molecular N₂ into NH₃ and nitrogen-containing organic compounds; particularly the synthesis of new organometallic compounds that bind and activate nitrogen, and the chemistry of metal nitrynes and metal nitrenes. Projects involve the synthesis of new organometallic compounds that bind and activate nitrogen, and then exploring the chemistry of the coordinated N₂ with the aim of sequentially breaking the nitrogen-nitrogen bond and liberating nitrogen as ammonia or another nitrogen containing compound.

Metal Complexes for the Activation of Organic Compounds – the chemistry of transition metal hydrides and metal alkyls.

Organometallic complexes (containing rhodium, iridium, iron, ruthenium, platinum, palladium, osmium and cobalt) can form highly electron-deficient reagents capable of reacting with C-H bonds in organic compounds. Projects involve the synthesis of new metal complexes that are efficient reagents for the activation and functionalisation of methane, ethane and other alkanes or alkyl fragments on larger organic molecules. Projects make extensive use of advanced spectroscopic methods including multinuclear NMR (³¹P, ¹H, ¹³C, ¹⁹F, ¹⁵N etc).

Specific targets include: (i) reaction of coordinatively unsaturated metal complexes with a C-H bonds to generate alkyl-, alkenyl- or aryl- metal hydrides, (ii) the development of catalysts for converting alkanes (arenes and alkenes) into alcohols, ethers and other functionalised hydrocarbons (iii) the development of catalysts (based on Ru and Ir) for the formation of alkene and alkyne bonds in organic molecules.

The Organometallic Chemistry of Carbon Dioxide

In many reactive organometallic compounds, CO₂ reacts with metal hydrides and metal alkyls typically to give metal formates or carboxylates where the CO₂ is incorporated into the metal complex. Our interest lies in developing new ways (and new metal complexes) to activate CO₂ then incorporate it into an organic compound leading to catalytic cycles that could utilise CO₂ and convert it to useful products. This may provide new ways to trap and capture CO₂ and new alternative uses for this wasted and potential environmentally dangerous compound.

The metal complexes are also being examined for their reactions with other hetero-allenes such as CS₂, COS and diimides to explore their organometallic chemistry.

Transition metal catalysis in Organic Synthesis

(with Assoc. Prof. Barbara Messerle).

Transition-metal-based catalysis has the potential to provide efficient routes into both fine chemicals and important pharmaceutical compounds. We are interested in the design of novel transition-metal-based reagents and catalysts for performing organic transformations, in particular the development of catalysts for the synthesis of heterocyclic compounds by cyclisation of appropriate amino, thiol or hydroxy substituted alkynes and alkenes to pyrroles, indoles, thiophenes, furans etc. This is effectively a one-step approach to a wide range of heterocyclic compounds.

Transition-metal Acetylides, Organometallic Polymers and New Materials.

Transition-metal centres bridged by a conjugated organic framework have many potential applications in materials science, in areas such as molecular electronics and liquid crystals development. Our interest is in the synthesis of dimeric, oligomeric and polymeric assemblies containing transition metal atoms covalently bonded within a conjugated an organic framework, and in studying the optical, electrochemical, electronic, spectroscopic properties of highly conjugated polymetal-acetylides.

New approaches to the synthesis of metal acetylides have been developed, for example via the photochemical metathesis of methyl-substituted metal complexes in the presence of terminal acetylenes.

Projects involve: (i) the development of new methods for forming the metal-to-acetylide bond; (ii) the variation of the secondary ligands "L" to modulate chemical and physical properties of the poly-metallic assemblies; (iii) the chemistry of metal acetylides including their rearrangement to other classes of compounds.

Development of New Multidentate Nitrogen-Based Ligands for Transition Metals

(with Dr. Guy Clentsmith)

The chemistry of complexes containing multidentate pyrazole-based ligands, for example tris(pyrazolyl)borate, is well developed across the periodic table and other nitrogen-based ligands (eg. tren, N(CH₂CH₂NSiMe₃)₃^3-) also feature extensively in transition-metal coordination chemistry. We are interested in the synthesis and development of new nitrogen-based ligands that incorporate either a pyrazolyl or imido functionality. The coordination chemistry of these new ligands is also of interest.

Multiple Quantum NMR Spectroscopy of Partially Aligned Molecules.

Projects include the development of pulse sequences and new NMR methods for extracting dipolar coupling constants from the spectra of molecules aligned in liquid crystalline solution and the computer analysis of 2-dimensional multiple quantum NMR spectra to give structural information on organic and organometallic species aligned in liquid crystalline solvents.

The Organometallic Chemistry of Silanes and Silylenes.

Suitably activated transition metal compounds react with organosilanes and other silanes to form silicon metal hydrides. These are reactive species in their own right, capable of silylating and hydrosilylating organic substrates but also serve as potential precursors for metal sylylenes (M=Si), which are developing into an important class of carbene-like organometallic catalysts for polymerisation and as reagents for organic synthesis.

Our interests are in strategies for catalytic formation metal-silicon, silicon-silicon and silicon-oxygen bonds and the design of transition metal catalysts for the formation of polysilanes and polysiloxanes and the control of the nature of the polymer (weight distribution, stereochemistry etc).

Metal Complexes of Molecular Hydrogen.

With Brönsted acids (even exceptionally weak protic acids such as alcohols and terminal acetylenes), iron and ruthenium hydrides are protonated to give metal complexes containing molecular hydrogen, ("H₂"), bound in a side-on η²-fashion. This is a rare bonding mode and only weakly links the H₂ ligand to the metal. General methods for synthesis and characterisation of η²-H₂ complexes of iron were developed as part of this program. H₂ is a good leaving group and synthetic approaches to metal thiolates, halides, azides, phosphines and acetylides etc. have been opened up.

This is a useful development in organometallic synthesis for many transition metal systems as coordinated molecular hydrogen ligand can be introduced under experimentally very mild conditions (effectively by dissolving a metal hydride in alcohol solution at room temperature) and the liberated H₂ is inert and, in most cases, simply bubbles from the reaction mixture as it is substituted.

Metallocene Chemistry.

We are interested in the synthesis of highly hindered metallocenes (particularly polyaryl metallocenes) incorporating metals, which are catalytic active particularly for olefin oligomerisation, rearrangement and polymerisation, steric control of the coordination sphere of the metal centre in metallocenes and the structure and properties of the highly hindered decaphenylmetallocenes.

Click here to download a pdf document detailing potential honours and Ph.D. projects.