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Title: Synthesis, characterisation and reactivity study of rare earth metal complexes
Author: Wang, Kai
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2018
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The chapter one introduces the reported examples of rare earth metal (RE) complexes with different oxidation states. It also reviews the synthesis and reactivity study of N-heterocyclic carbene (NHC) supported transition metal and RE metal complexes. Chapter two focusses on the synthesis and characterisation of a series of tetraaryloxide Ce and Pr complexes. With the reaction of bulky tetraphenol proligand H4LR(R = P, PT, M) with four equivalents of KN"(N" = N(SiMe3)2), a dimerised complex of [K4LP]2(thf)11 was synthesised and characterised. The salt metathesis reactions of this complex with RECl3(thf)2 afford bimetallic aryloxide complexes of K2L2RE2(thf)11 (RE = Ce, Pr), which display divergent structures under different conditions. Reactions of the CeIII complex of K2L2Ce2(thf)11 with a variety of oxidants(I2, CuCl2 and O2, etc.) lead to the oxidation of CeIII to CeIV, affording purple ceric dimer of L2Ce2. The reaction of the PrIII complexes with I2 under 60 °C affords a mixture from which PrIII iodide (LPr2I2) has been isolated and characterised. This chapter also discusses the reactivity of the bimetallic aryloxide complexes towards different substrates, such as MeLi, KC8 and KBn (Bn = benzyl). Bimetallic complexes of L(REX)2(py)8 (RE = Ce, Pr; X = Cl, BH4) are synthesised and characterised. The preliminary study on the copolymerization of cyclohexene oxide (CHO) and CO2 is conducted for CeIII and PrIII complexes. Chapter three details the work on two different types of NHC ligand. The first ligand is the β-ketoimidazolinium salts H2LBr {L = RC(O)CH2{CH[NCH2CH2NMes], R = tBu, naphth} which reacts with MHBEt3 (M = Na, K) to form carbene-borane adducts RC(O)CH2{C(BEt3[NCH2CH2NMes]}. This type of reactivity differs from the previous work on imidazole derivatives. The possible mechanism of these reactions is provided and discussed. The other ligand is p-aryloxy-tethered imidazolinium salt H2LX (L = N-3,5-di-tert-butyl-4-hydrooxyphenyl-N’-mesityl-imidazolinium, X = Cl, Br, PF6 ), which have been synthesised and characterised. The reactions of these salts with MN"(M = Na, K) enabled the characterisation of polymerised complexes of [NaL]n and [KL(thf)2]n. The yttrium complex YL3 is synthesised and its reactivity towards small molecules such as boranes, CO2 and CS2 is discussed. Chapter four presents the primary results on the study of macrocyclic NHC based cyclophane ligand H6LPF6 (L = calix[4]imidazolylidene[2]pyrazolato). Investigations on the reactivity of the ligand towards different bases (NaN", KN", KBn etc.) are examined and subsequent metathesis reactions with RE complexes are explored. Chapter five concludes the work presented in this thesis. Chapter six contains all experimental and characterisation details.
Supervisor: Arnold, Polly ; Shaver, Michael Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: rare earths ; N-heterocyclic carbene ; RE metal complexes ; tetraaryloxide Ce ; NHC ligands