| Abstract |
The isolation of stable low-coordination number and low oxidation state derivatives of the group 14 elements (i.e. formal analogues of carbenes, alkenes, alkynes and related species) remains one of the most exciting and challenging areas of contemporary main group chemistry. Of these compounds the diorganotetrylenes R2E [E = tetrel element: Si, Ge, Sn, Pb] are perhaps the most intriguing since, in addition to fundamental questions regarding their electronic structures and stabilities, these compounds are also potential ligands for transition metal centres. This project aims to build on a remarkable preliminary result from the applicant's laboratory which suggests that dialkyltetrylenes R2E (R = alkyl) may be significantly stabilised by weak E'-H...E interactions [E' = B, Si; E = Si, Ge, Sn, Pb]. The project will exploit this new agostic stabilisation paradigm for the synthesis of a wide range of dialkyltetrylenes. It will explore how the stability of the dialkyltetrylene is related to the nature of the tetrel centre, the type of agostic donor , and the steric and electronic properties of the organic substituents. Detailed structural and spectroscopic studies combined with theoretical calculations will be used to gain insight into the nature of the agostic-type interactions and to provide quantitative information on their contribution to the stability of the tetrylenes. The application of these compounds as ligands for transition metal centres will be explored, with the aim of elucidating their sigma-donor/pi-acceptor properties. We confidently expect that this project will yield numerous examples of previously inaccessible types of dialkyltetrylene and that these will have unique and novel properties as ligands. |