Syntheses, structures and reactivity of organolanthanoid complexes

Ali, Safaa Hussein (2017) Syntheses, structures and reactivity of organolanthanoid complexes. PhD thesis, James Cook University.

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Abstract

The focus of this thesis is divided into two directions. The first explores the pseudo- Grignard reaction involving the oxidative addition of aryl halide to lanthanoid metals (Yb, Eu) (Chapter two). The second aspect details the synthesis and reactivity of a series of lanthanoid biphenolate {2,2'-methylenebis(6-tert-butyl-4-methylphenolate)} complexes (Chapters three and four).

Chapter 1 gives an overall introduction to lanthanoid chemistry. This chapter details the general properties, extracting and separating techniques and applications of lanthanoid elements. In addition to highlighting the diverse range of the synthetic methods of lanthanoid formamidinate and lanthanoid phenolate complexes.

Chapter 2 explores the oxidative addition of aryl halide to lanthanoid metal (Yb, Eu) as a synthetic route to prepare different species of pseudo-Grignard reagents involving formamidinates such as [Yb(RForm)(thf)ₙX]₂ (Form = ArNCHNAr; R = 2,4,6-Me₃; 2,6-Me₂; 2,6-Et₂; 2,6-ⁱPr₂; X = Br, I) (see Figure below).

[Figure of complex structure, where X = Br, I; R = 2,4,6-Me;2,6-Me₂; 2,6-Et₂; 2,6-ⁱPr₂]

In addition, the reactivity of these pseudo-Grignard reagents [Yb(RForm)(thf)ₙX]₂ towards a range of ketones with different polar functionalities such as 9-fluorenone, 1,4-benzoquinone and benzil is discussed.

Chapter 3 discusses the synthesis and characterisation of a series of lanthanoid biphenolate {2,2'-methylenebis(6-tert-butyl-4-methylphenolate)} complexes. Redox transmetallation protolysis reactions between the lanthanoid metals and the biphenol in the presence of Hg(C₆F₅)₂ yielded mononuclear [Ln(BPO₂)(BP(OH)O)(thf)₃] (Ln = Y, Gd, Er) or dinuclear [Ln₂ (BPO₂)₂ (thf)ₙ] (Ln = Sm, Tb n = 3, Ho, Yb n = 2) complexes depending on the extent of phenol deprotonation. When the biphenolate ligand was partially deprotonated the mononuclear form was produced and yielded the dinuclear form when it was doubly deprotonated described below.

[Figure of complex structure]

Chapter 4 details the synthesis and characterisation of a series of heterobimetallic complexes. Lanthanoid biphenolate complexes [Ln(BPO₂)(BP(OH)O)(thf)₃] have been metallated with different metal alkyls/amides such as (ⁿBuLi, KN(SiMe₃)₂, AlMe₃, ZnEt₂) and led to ionic and non-ionic heterobimetallic complexes, for example, [Li(thf)₂Ln(BPO₂)₂(thf)₂] (Ln = La, Pr) described below, [Li(thf)ₙ][Ln(BPO₂)₂(thf)ₙ] (Ln = Y, Ho), [K(thf)₃Gd(BPO₂)₂(thf)₂], [ZnEtYb(BPO₂)₂(thf)], [La(BPO₂)(thf)₅][AlMe₂(BPO₂)], [AlMe₂Ln(BPO₂)₂(thf)ₙ] (Ln = Sm, Tb).

[Figure of complex structure]

Overall, this thesis presents a significant contribution to pseudo-Grignard reagents. Formamidinate ligands can form stable and structurally interesting pseudo-Grignard reagents with divalent lanthanoid metals (Sm, Eu, Yb) as they can be readily modulated sterically and electronically in addition to their anionic, chelating features. Additionally, this thesis demonstrates the ability of the biphenolate ligand to stabilise lanthanoid in all readily known oxidation states (+2, +3, +4) for these metals. Additionally, the biphenolate ligands are able to stabilise a range of heterobimtallic complexes.

Item ID: 52747
Item Type: Thesis (PhD)
Keywords: chemical complexes; chemical compounds; chemical structures; Grignard reagents; lanthanoids; organolanthanoids; organometallic chemistry; organometallics; rare earth elements (REEs); react syntheses; synthesis reactions
Date Deposited: 01 Mar 2018 03:48
FoR Codes: 03 CHEMICAL SCIENCES > 0302 Inorganic Chemistry > 030202 f-Block Chemistry @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970103 Expanding Knowledge in the Chemical Sciences @ 100%
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