Rare Earth and Actinide Cyclopentadienyl Complexes

Abstract

Rare Earth and Actinide Cyclopentadienyl Complexes. A thesis submitted to The University of Manchester for the degree of Doctor of Philosophy in the Faculty of Science and Engineering. Cyclopentadienyl ligands (Cp) and their derivatives have been used throughout the Periodic Table since the 1950s. They have provided landmark complexes across the s-, p-, d- and f-block elements, including the first metallocenium f-element complexes and the first complete series of non-traditional Ln2+ complexes. Herein, this work utilises bulky substituted cyclopentadienyl ligands, including Cpttt {C5H2(tBu)3-1,2,4}, Cptt {C5H3(tBu)2-1,3}, Cp'' {C5H3(SiMe3)2-1,3}, to prepare novel f-block complexes in low oxidation states. Chapter 1 reviews the literature on cyclopentadienyl ligands as used on rare earth and actinide metals, which sets the context of the thesis. Additionally, chapter 1 also reviews bulky substituted Cp ligands that have stabilised low oxidation states for rare earth and actinide metals. In Chapter 2, the Cpttt ligand was employed to stabilise the early lanthanide metallocenium complexes [Ln(Cpttt)2{(C6F5-k1-F)B(C6F5)3}] (Ln = La, Ce, Pr, Nd) and [Sm(Cpttt)2][B(C6F5)4], which were synthesised by halide abstraction of the heteroleptic precursors [Ln(Cpttt)2(Cl)] using [H(SiEt3)2][B(C6F5)4]. In Chapters 3 and 4, the Cptt ligand was employed to prepare homoleptic early lanthanide complexes in both +2 and +3 oxidation states. Treatment of LnCl3 with KCptt gave a series of trivalent complexes [Ln(Cptt)3] (Ln = La, Ce, Pr, Nd, Sm), which were reduced by KC8 in the presence of 2.2.2-cryptand to yield a series of divalent complexes [K(2.2.2-cryptand)][Ln(Cptt)3] (Ln = La, Ce, Pr, Nd). In Chapter 5, a phospholyl ligand Htp (Htp = 2,5-di-tert-butylphosphoyl), which is similar to Cptt, was employed in the synthesis of the heteroleptic complexes [Ln(Htp)2(u-BH4)]2 (Ln = La, Ce, Nd, Sm) and [Ln(Htp)2(u-BH4)2K(S)2] (Ln = La, Ce, S = DME; Ln = Ce, S = Et2O and THF) to investigate differences between substituted phospholyl ligands and their corresponding CpR ligands. Chapter 6 (also known as appendix) contains results that did not form a coherent part of the overall story in this thesis. In this chapter, the Th4+ alkyl complex [Th(Cp'')3(Me)] was obtained by the reaction of [Th(Cp'')3] with the N-heterocyclic olefin H2C=C(NMeCH)2.

Date of Award	31 Dec 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	David Mills (Supervisor)