Ligand-Oriented Catalyst Design . . . studying the fundamentals

The Group has a long-standing interest in understanding the relationships between ligand systems and the way in which their electronic and steric properties can be exploited to stabilise unusual metal coordination environments and new catalyst systems.

The isolobal relationship between cyclopentadienyl and imido metal complexes

For example, we've studied the isolobal relationship between bis(imido) complexes of the Group 6 metals, half-sandwich imido complexes of the Group 5 metals and Group 4 metallocenes. The molecular orbital basis for the relationship was established through extensive synthesis and structural investigations on half-sandwich imido and bis(imido) metal derivatives, supported by computational studies. A variety of novel complexes have been described including benzyne and benzylidene derivatives of niobium and a high valent alkylidene derivative of chromium.

We have also carried out a more detailed analysis of structure and bonding patterns in compounds containing metal-ligand bonds. It was recognised how these strong pi-donating ligands can affect the coordination of other pi-bonding ligands, allowing a set of rules to be developed for predicting the orientation preferences of pi-bonded ligands when in competition for metal d-pi orbitals. These principles are being actively exploited in the design of new catalyst systems for the polymerisation reactions outlined in the following sections.

Examples of complexes synthesised to illustrate the isolobal relationship between cyclopentadienyl and imido metal fragments.

Representative publications:

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