Investigating the synthesis of fluoroalkenyl phosphines and their use in catalytic systems

UoM administered thesis: Phd

  • Authors:
  • Amina Ejgandi

Abstract

The synthesis of a number of perfluoroalkyl and perfluoroalkenyl phosphines isreported based on HFC-134a and HFC-236ea or R2PLi and RfI. These include the newair-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 thechemistry 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 firstexample of a mixed fluorovinyl phosphite system. The direct reaction of P(V) startingmaterials 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 withBrCH2CH2(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 effectivelyinsulates the phosphorus centre from the electron withdrawing effects of the fluorovinylgroup. The phosphines do not appear to act as hemi-labile ligands.The synthesis of a fluoroalkenyl PCP ligand was investigated via a sequence ofreactions starting with triethyl phosphite and alpha,alpha- dibromo-m-xylol. This was convertedstepwise 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 ofbis[(diethoxyphosphoryl)methyl]benzene and PCl 5 which, according to NMR evidencesuggests 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 containingphosphines 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 ofthese complexes a triflate ion was found to be coordinated to the palladium centre, andthis is assumed to arise due to the poor donor ability of P(C6F5)3. These complexes wereused as catalysts for the allylation of aniline with allyl alcohol. It was found that thecomplexes of more electron donating phosphines (PPh2 Me and PPh3 ) rather than offluorinated ligands, gave the highest yields. The Suzuki coupling of naphthaleneboronic acid and allyl alcohol to generate allylnaphthalene under metal catalysedconditions 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-Villigeroxidation of a four member ring with urea.H2 O2 the most successful ligand system wasfound to be Ph2P(CF=CF2). This is interpreted as reflecting the stability of such ligandsunder the oxidative conditions of the reaction.

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Original languageEnglish
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Award date1 Aug 2016