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Title: Optically active diphos ligands with inorganic backbones
Author: Smith , Katharine Florence
ISNI:       0000 0004 5915 3036
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2014
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Seconcary phosphine oxide, (S,S-2.5-diphenylphospholane-1 oxide (2.26) has been synthesied from (S,S)-2,5-diphenylphospholanic acid, and its rhodium complex, Rh(2.23)2( cod)] [SbF 6] (2.29) has been crystallographically characterised. Secondary phosphite oxides were synthesised by the reaction of PCh, BuOH and 3,3-R-1,1-bi-2-naphthol in which R = H (3.7a), Me (3.7b) and Ph (3.7c). [M(L) (cod)J[SbF6] (L = 2.26, 3.7a, 3.7c) were tested as catalysts for the asymmetric hydrogenation of methylacetamido cinnamate (MAC), methylacetamido acrylate C~lAA) and dimethyl itaconate (DMI). BINOL derived complexes were hydrolytically unstable and poor enantioselectivity was observed in the catalysis. With hydroxyphospholane complex (2.29) the absolute configuration of the major enantiomer formed depended on the solvent used for the reaction. Hydroxyphospholane complex (2.29) was used as a precursor for the synthesis of chiral diphosphine complexes possessing an OZO inorganic backbone. Deprotonation of (2.29) formed the POHOP pseudo-chelate complex and the O(BF2)O backbone fmmed as a result of the reaction of the [BF4r counterion of [Rh(2.26h(cod)][BF4]. The anionic O(SnCIR2)O backbones were synthesised by the reaction of the deprotonated hydroxyphospholane complex with a dichlorostannane (R = Me, Ph). The neutral backbones, O(SnPh2)O, O(ZrCp2)O and O(HfCp2)O, were formed as a result of the elimination of gaseous methane from the reaction of complex (2.29) with SnMe2Ph2, ZrCp2Me2 and HfCp2Me2 respectively. The phospho lane-derived PCH2CH2CH2P chelate was synthesised from the secondary phospholane and 1,3-dichloropropane. The resultant bis(phospholane) with the (CH2)3 backbone was coordinated to rhodium and applied as an asymmetric hydrogenation catalyst. The OZO-backbone complexes were also tested as catalysts for the asymmetric hydrogenation of MAC, MAA and DMI. The C3 backbone complex was a more selective catalyst for DMI but conversely the OZO backbone complexes gave higher enantioselectivity in the hydrogenation of MAC and MAA where enantiomeric excess of 85-99% were achieved. The analogous reactions to form OZO backbones from the BINOL derived oxide complexes were attempted, but were problematic. O(BPh2)O, O(ZrCp2)O and O(HfCp2)O backbones have been synthesised from [Rh(7.3a)2(cod)][SbF6J but resistance of the hydrolytically sensitive oxide complex towards deprotonation has hindered the formation of other inorganic backbones. The hydrolytic sensitivity of the complexes also impeded their function as hydrogenation catalysts, in which generally low enantioselectivity was observed. Secondary aniinophospholane ligands (5.4-5.6) were synthesised by a condensation reaction of (R,R)-2,5-diphenyl-l-chlorophospholane and primary amines RNH2 (R = iPr (5.4), tBu (5.5), Tol (5.6)). N_iPr substituted aminophospholane (5.4) was coordinated to rhodium and the resultant [Rh(5.4)2(nbd)][BF4J complex crystallographically characterised and tested as an asymmetric hydrogenation catalyst, although low enantioselectivity was observed. Preliminary investigation of a novel route to aminophospholane/Rh complexes for a potentially high-throughput approach, from the rhodium complex of 2,5-diphenyl-l-chlorophospholane, has been developed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available