Whereas the strength of metal-ligand (M–L) bonding interactions is primarily dependent on the strength of the M–L σ-bonding, π contributions are of no less importance. In general, both σ and π interactions are necessary to correctly describe the electronic and geometric structures of most molecular systems. In actinide organometallic compounds, δ bonds can play as much a role as π bonds, however, the participation of the 5f and 6d orbitals in the formation of δ bonds has not yet been fully addressed in the literature. In my talk, I will describe the chemistry of actinide metallacycles with various ring sizes that leads to unusually complicated chemical bonding motifs. By means of electron localization techniques, I will show the importance of δ bonding interactions in An<sup>IV</sup> metallacycles and will demonstrate a unique type of δ-bonding, which is crucial for the understanding the M–L bonding in the actinide series from Th to Pu. These fundamental findings underline the significance of δ back-donation in actinide complexes in general, with a particular emphasis on the 5f unpaired electrons of Pa and U complexes.

Importance of the unprecedented δ back-donation in An<sup>IV</sup> metallacycles

256th National Meeting (2018)

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Importance of the unprecedented δ back-donation in AnIV metallacycles

Importance of the unprecedented δ back-donation in An^IV metallacycles