Hillier, Anna Catherine; (1998) Chemistry of the lanthanides with pyrazolylborate ligands. Doctoral thesis (Ph.D.), University College London.

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Abstract

In this thesis we present continuing work on the synthesis of new tris(pyrazolylborate)lanthanide complexes. Chapter 1 introduces, and offers a limited review of, the chemistry of the lanthanides with particular emphasis on sandwich and half-sandwich complexes with cyclopentadienyl ligands. The poly(pyrazolyl)borate class of ligands is introduced and their use in lanthanide chemistry reviewed. Chapter 2 reviews the synthesis of lanthanide complexes with chalcogenolate ligands and describes the preparation of a series of compounds of formula Sm(TpMe,Me)2EAr (E = O, S, Se, Te). The compounds formed by reduction of anthraquinone and tetraethylthiuram disulfide are also described. These complexes have been shown to exhibit fluxionality in solution on the NMR timescale and have been characterised by X- ray crystallography. The work presented in Chapter 3 details the reactivity of half-sandwich and sandwich (pyrazolylborate)lanthanide (Sm, Yb) complexes with transition metal carbonyl species. The preparation of divalent lanthanide complexes with isocarbonyl bridges to molybdenum is described. The reaction of [Sm(TpMe,Me)2] with Mn2(CO),10 affords two products, [Sm(TpMe,Me)2[Mn(CO)5] and [Sm(TpMe,Me)2]2(O2CH); a mechanism of formation of the latter is proposed. The X-ray structure of [Re4H(CO)17]- is described and compared with similar spiked triangular clusters. Chapter 4 describes our attempts to prepare new sandwich and half-sandwich (pyrazolylborate)lanthanide complexes with halide, carboxylate, hydrocarbyl, amide, borohydride and aluminohydride ligands. Problems with ligand redistribution have been encountered in many of these syntheses, including the formation of LiTpMe,Me in reactions where lithium reagents were employed.

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