Synthesis and Reactivity of Lanthanide(II) Hydrides

The overarching aim of this Thesis is to investigate the synthesis of new molecular lanthanide(II) hydrides in which the lanthanide centres are in the 2+ oxidation state. The synthesis of new ytterbium(II) hydrides will allow for direct comparisons with the current literature with respect to known lanthanide(II) hydrides, systems that are all based on Yb(II). In contrast, there are no reports of the synthesis of molecular europium(II) or samarium(II) hydrides; thus, isolating these compounds presents a unique opportunity to explore their reactivity for the first time. Chapter Two first discusses the synthesis of a new molecular ytterbium(II) hydride supported by the previously reported BDIDipep ancillary ligand. This Chapter then details the synthetic method for a new derivative of the β–diketiminate ligand framework, BDIDicyp, and the subsequent isolation of a new bulkier ytterbium(II) hydride. The chemistry of these two systems, as well as the previously reported [(BDIDipp)YbH]2, was explored with respect to the functionalisation of white phosphorus and the two-electron aromatisation of aromatic and polyaromatic hydrocarbons. Chapter Three demonstrates that synthesising a molecular Eu(II) hydride is not a simple extension of Group 2 chemistry, where utilisation of the BDIDipep ligand system afforded a plethora of Schlenk-type redistribution or ligand rearrangement products. However, utilisation of bulkier, symmetrical, and unsymmetrical derivatives of the β–diketiminate ligand, BDIDicyp, BDIDipp,dicyp and BDIDipp,TCHP, respectively, produced three of the first examples of divalent europium hydrides. All three systems were proven to affect the two-electron aromatisation of COT to give the respective inverted sandwich complexes, in which the 2+ oxidation state of the europium centre was retained. Chapter Four diverges from the chemistry presented in the previous two Chapters, focusing on the reduction of benzene and its derivatives by a monomeric samarium(II) alkyl complex. It was found that the respective inverted sandwich complexes contained two Sm(III) ions bridged by a tetraanionic arene, confirmed by magnetic susceptibility calculations in the solution- and solid-state and DFT calculations. This was further confirmed by the ability of the samarium(II) monoalkyl to effect the two-electron reduction of COT by a single samarium centre. Finally, this Chapter continues to explore the reduction chemistry of the Sm(II) alkyl as well as the benzene tetraanion complex.