Brown, Sarah Ellen; (2012) Chemistry of the Lanthanides with Pyrazolylmethane Ligands. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The work presented in this thesis demonstrates the utility of the tris(3,5- dimethylpyrazolyl)methane ligand (TPm*) as an ancillary ligand for the lanthanides. Compounds of the formula [Ln(TPm*)Cb] have been synthesised. These new complexes [YTPm’Ch] and [SmTPm'Ch] have been crystallographically characterised, showing an interesting variation of coordination geometry with differing metal centre. The triflate aducts have also been prepared. New compounds [YTPm'fOTQj] and [HoTPm*(OTf)3] have been crystallographically characterised and are isomorphous, seven coordinate structures. Substituting the chloride ligands for OPhMe2 groups afforded new complexes [Ln Tpm’(OPhMe2)3], They have been crystallographically characterised and are highly symmetrical six coordinate complexes with a trigonal, anti-prismatic structure. Further attempts at substituting the chloride groups with ligands X (X=Cp,BH4,Tp‘,N(SiMe3)2) have not led to any further definitive characterisation. Further the fluoro-substituted alkoxide ligands (OPhFn) were prepared. This has afforded a new series of complexes of the type MOPhFn (M=K,Na, n=l,2,5). They exhibit solvent dependent speciation, being essentially dimeric in THF and tetrameric in diethylether. The structural characterisation of a number of these complexes reveals interaction between the metal ions and the ortho fluorines. In NaOPhF5,crystallised from ether, an extended cubic lattice structure was observed due to M-F interactions between metal centres and para-fluorines on neighbouring cubes. Using these alkoxide ligands new lanthanide complexes of the type Ln(OPhFn)3 were produced. ‘H NMR studies show encouraging results, however no crystals could be obtained. The NMR reveals that complexes Ln(OPhFn)3 are dimeric in solution with a combination of terminal and bridging OPhFn ligands. Synthesis of complexes of the type LnTPm‘(OPhFn).i were attempted. The reaction between the divalent lanthanide complex YbTPm’h and NaNPH? has given spectroscopic results suggestive of deprotonated TPm* ligands. Extreme air and moisture sensitivity of the product has precluded its full characterisation.

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