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Title: Investigating the synthesis of fluoroalkenyl phosphines and their use in catalytic systems
Author: Ejgandi, Amina
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2016
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The synthesis of a number of perfluoroalkyl and perfluoroalkenyl phosphines is reported based on HFC-134a and HFC-236ea or R2PLi and RfI. These include the new air-stable compounds PhP(CF=CFCF3)2, Ph2P(CF=CFCF3), iPr2 P(CF=CFCF3),PhCH2P(CF=CFCF3)2, (CF2=CF)2PCH2CH2P(CF=CF2)2, (CF3CF=CF)BuPCH2-CH2PBu(CF=CFCF3) and (CF3CF=CF)2PCH2CH2P(CF=CFCF3 )2. Some of the chemistry of these ligands was investigated and the crystal structures of (CF 3CF=CF)2PCH2CH2P(CF=CFCF3)2 and Mo(CO)4{(CF3CF=CF)2PCH2-CH2P(CF=CFCF 3)2 } are reported. In an extension of this work the reaction of (EtO)2 PCl with perfluorovinyl lithium gave (CH 3CH2O) 2P(CF=CF2 ) as the first example of a mixed fluorovinyl phosphite system. The direct reaction of P(V) starting materials with perfluoroalkenyllithium reagents was shown to generate O=PR 3-n(CF=CFCF3 )n (R=Ph, n=1,2) in one step, but in low yields. The formation of phosphines of the type R2PCH2CH2 (CF=CF2) [R = Ph2, MePh, (2-CH3C6H4 )2] were investigated from the reaction of lithium phosphides with BrCH2CH2(CF=CF2). The resulting phosphines were found to be oxidatively sensitive. Oxidation with elemental selenium generated the corresponding phosphine selenides, from which 1J(PSe) coupling constants suggest that the -CH2CH2- spacer effectively insulates the phosphorus centre from the electron withdrawing effects of the fluorovinyl group. The phosphines do not appear to act as hemi-labile ligands. The synthesis of a fluoroalkenyl PCP ligand was investigated via a sequence of reactions starting with triethyl phosphite and alpha,alpha- dibromo-m-xylol. This was converted stepwise into 1,3-bis(diethoxyphosphonomethyl)benzene and 1,3-bis(phosphinomethyl)benzene as an extremely air sensitive, pungent smelling liquid. Attempts to by-pass this material were investigated based on the reaction of bis[(diethoxyphosphoryl)methyl]benzene and PCl 5 which, according to NMR evidence suggests that each P(O)(OEt)2 group is transformed into a P(O)Cl(OEt) fragment. Reaction of [Pd(allyl)Cl]2 with a wide range of fluorine and non-fluorine containing phosphines gave a series of [Pd(allyl)P2]OTf complexes. The X-ray crystal structure of [Pd(allyl)P(C6F5)3 OTf], and [Pd(allyl)(PhP(OEt)2) 2]OTf were obtained. In the first of these complexes a triflate ion was found to be coordinated to the palladium centre, and this is assumed to arise due to the poor donor ability of P(C6F5)3. These complexes were used as catalysts for the allylation of aniline with allyl alcohol. It was found that the complexes of more electron donating phosphines (PPh2 Me and PPh3 ) rather than of fluorinated ligands, gave the highest yields. The Suzuki coupling of naphthalene boronic acid and allyl alcohol to generate allylnaphthalene under metal catalysed conditions was investigated. In this case high yields were obtained when using P(p-FC6H4)3, P(m-CH 3OC6H4) and P(p-ClC6H4)3. In the palladium-catalysed Bayer-Villiger oxidation of a four member ring with urea. H2 O2 the most successful ligand system was found to be Ph2P(CF=CF2). This is interpreted as reflecting the stability of such ligands under the oxidative conditions of the reaction.
Supervisor: Brisdon, Alan Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available