Dr. Errington's interests lie at the interface between coordination/organometallic and solid state chemistry, where effects arising from the transition from small molecules to extended solid systems provide opportunities for advances in catalysis and materials science. Fundamental studies of solution reactivity, dynamics and aggregation processes underpin a "bottom-up" approach to the design and synthesis of metal-oxide based functional molecules and materials, where a key challenge is the control of aggregation so that the composition, size and morphology of large, polynuclear species and extended lattices can be engineered to give well defined reactive sites, surfaces and bulk properties. Metal alkoxides and polyoxometalates are used extensively as versatile procatalysts and/or molecular building blocks and their chemistry is under extensive investigation.
General design principles for co-operative dinuclear catalysis were established in studies of aluminium complexes of N-alkoxy-β-ketoimines, whereby treatment of inactive chloro complexes with one equivalent of epoxide produced efficient initiators for living lactide polymerisation. Insertion of the epoxide into one Al—Cl bond generates a nucleophilic alkoxide ligand on one metal adjacent to the electrophilic binding site for the lactide substrate, creating the optimum arrangement for ring-opening. The remaining chloride can shuttle between metals on the opposite face of the complex as the roles of the metals at each insertion cycle are reversed.
A major challenge in metal alkoxide chemistry is the controlled assembly of
We have been able to promote metal alkoxide aggregation by the strategic
introduction of bridging methoxide ligands, as demonstrated by the
preparation of the serpentine
Polyoxometalates possess an unrivalled range of properties and interest in these molecular metal-oxide semiconductors is growing rapidly due to potential applications in catalysis, materials, bioscience and medicine. Through the development of synthetic methodology involving the controlled hydrolysis of metal alkoxides in the presence of oxoanions we have been able systematically to manipulate surface ligands and heterometal for the first time in a range of molecular oxides [(X)M'M5O18]n- (M = Mo, W; M' = Ti, Zr, Hf, V, Nb). 17O enrichment is routine with this methodology and changes to the oxide framework are readily monitored by 17O NMR.
Protonolysis studies of
Analogies between polyoxometalates and solid oxides suggest that
heterogeneous catalytic processes may be modelled using polyoxometalates.
The structural characterisation of protonated ZrW5 derivatives
The incorporation of functional molecular oxides into materials to exploit their electronic, photoactive, magnetic or chemical properties requires the development of strategies for immobilisation and organisation. We have demonstrated the covalent linkage of TiW5O18 units to single-crystal and porous silicon by protonolysis of the metal-alkoxide bond in [(MeO)TiW5O18]3-.
Isolated clusters of oxometalates were formed rather than monolayer coverage, and competitive hydrolysis of Ti—O linkages occurred over time. We have extended our studies to other structural units and linkages that are more resistant to hydrolysis.