Synthesis of rare earth complexes involving pyrazolate ligands

Eslamirad, Nazli (2018) Synthesis of rare earth complexes involving pyrazolate ligands. PhD thesis, James Cook University.

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View at Publisher Website: https://doi.org/10.25903/5c884921af569
 
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Abstract

This thesis explores the synthesis and characterisation of rare earth complexes involving pyrazolate ligands. Redox transmetallation/protolysis and high temperature metal-based routes were employed to synthesis the complexes. Besides, some chemistry of Li, Zn and Al pyrazolate complexes is also discussed when metalation of the pyrazole using nBuli and metal alkyls produced a range of compounds. Below are the ligands that were used for each chapter

3,5- dimethylpyrazolate (Me₂pz) Chapters: 2,3,4

3,5- Di-tert-Butylpyrazolate (tBu₂pz) Chapters: 2,3,4

3,5-Diphenylpyrazolate (Ph₂pz) Chapters: 2,3,4

4-nitropyrazolate (Me₂pzNO₂) Chapters: 4

[4 illustrations] Ligands used throughout chapters two to four.

Chapter 2 describes a series of rare earth pyrazolate complexes which were prepared by redox transmetallation/protolysis (RTP) using the rare earth metals (Sc, Y, La, Ce, Sm, Tb, Er and Lu), bispentafluorophenyl mercury (Hg(C₆F₅)₂), a pyrazole and using different solvents such as THF, DME and Et₂O. A variety of trivalent rare earth pyrazolate complexes were synthesised and characterised in this chapter: dinuclear [Ln(Me₂pz)₃(thf)]₂, oxide cage complexes and complexes formed by C-F activation. Investigations into the high reactivity of 3,5-dimethylpyrazolate resulted in the isolation of several novel structures such as [Sc₃O(Me₂pz)₇(Me₂pzH)₂], [Sc(Me₂pz)₂(Me₂pz(SiMe₂O))]₂, [Y₃O(Me₂pz)₉Na₂(Et₂O)₂] and [Y₃O(Me₂pz)₉Na₂(Me₂PzH)₂]. This chapter also describes the synthesis of [La₄(Me₂pz)₉(μ₂-F)₂(μ₄-F)(thf)₄].3THF with a significant feature of having three different pyrazolate bonding modes: ƞ², μ- ƞ¹: ƞ¹ and μ- ƞ²: ƞ¹ in the one structure. The complexes were characterised using NMR spectroscopy, IR and microanalysis.

Chapter 3 investigates new metal-based solvent-free elevated temperature reactions involving rare earth metals (Y, La, Ce, Pr, Dy and Ho) and three pyrazole pro-ligands (Me₂pzH, tBu₂pzH and Ph₂pzH). This chapter suggests a simple route to isolate predominantly homoleptic but also some heteroleptic rare earth pyrazolate complexes. Another surprising ligation of lanthanoid pyrazolates is observed in homoleptic [La(Me₂pz)₃]ₙ. η⁵ Bonding in this compound gives the Me₂pz ligands a "cyclopentadienyl (Cp)" type coordination that has a few examples in rare earth pyrazolate chemistry.

Finally, chapter 4 presents small contribution to main group chemistry involving pyrazolates, while presenting the synthesis and structural characterisation of the newly synthesised complexes [(Li₄(Me₂pz)₄(Et₂)₄], [Li₆(Me₂pz)₆(tmeda)₂], [Li₂(C₂N₃H₆O₂)₂(thf)₂]ₙ, {[Zn(tBu₂pz)₂(tBu₂pzH)₂].1/2THF} and {AlMe₂(Ph₂pz)]₂.1/2THF}. The hexameric pyrazolate complex using nBuLi is being reported for the first time in this study. Also, polymeric complex [Li₂(C₅N₃H₆O₂)₂thf₂]ₙ is now being reported for the first time. These compounds should have utility as reagents in metathesis chemistry or in protolysis reactions where, for example the alkyl group, in the Al complex can be substituted.

Item ID: 57403
Item Type: Thesis (PhD)
Keywords: pyrazolate ligands, redox transmetallation/protolysis (RTP), rare earth metals, reactive ligands
Copyright Information: Copyright © 2018 Nazli Eslamirad
Date Deposited: 13 Mar 2019 00:20
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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Last 12 Months: 13
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