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dc.contributor.advisorKilian, Petr
dc.contributor.authorFleming, Conor Gareth Edward
dc.coverage.spatialxvi, 202 p.en_US
dc.description.abstractThis thesis describes the effect of placing a phosphorus atom in a sterically strained environment with particular emphasis on the geminal disubstitution of two 2,4,6-tri-tert-butylphenyl (Mes*) groups on a single phosphorus centre and intramolecular sub-van der Waals interactions between peri-substituted atoms on naphthalene and acenaphthene. Chapter 2 outlines the reactive chemistry of a sterically encumbered phosphinic chloride (Mes*)₂P(=O)Cl, which was shown to have extremely low reactivity at the phosphorus centre. It has however, been demonstrated that synthetically significant transformations are possible. The phosphine oxide (Mes*)₂P(=O)H and a secondary phosphine Mes*(2,4-tBu₂C₆H₃)PH were obtained from the reduction of (Mes*)₂P(=O)Cl with hydridic reagents under forcing conditions. The corresponding phosphinite was acquired from the deprotonation of (Mes*)₂P(=O)H, which furnished very crowded tertiary phosphine oxides (Mes*)₂P(=O)R (R = Me and Et) on reactions with electrophiles. We have been unable to chlorinate or deprotonate Mes*(2,4-tBu₂C₆H₃)PH, however the reaction with elemental sulfur afforded the affiliated phosphine sulfide Mes*(2,4-[supercript(t)]Bu₂C₆H₃)P(=S)H, albeit under forcing conditions. Our computations (B3LYP and M06-2X level) show that strain energies of geminally substituted compounds are extremely high (180 to 250 kJ mol⁻¹), the majority of the strain is stored as boat distortions to the phenyl rings in Mes* substituents. Chapter 3 describes the strain inherent with non-bonding atomic distances shorter than the sum of their van der Waals radii, specifically heteroatom substitution of the peri-positions of naphthalene and acenaphthene. It also documents the importance of amine protecting groups in chlorophosphine chemistry. The preparation of Ace[P(Ph)N(ⁱPr)₂]Br (Ace = acenaphthene-5,6-diyl) and Ace[P(Ph)N(ⁱPr)₂]₂, plus the elucidation of the molecular structures of Mes*P[N(CH₃)₂]₂, Ace[P(Mes)N(ⁱPr)₂]Br (Mes = 2,4,6-tri-methylphenyl) and Ace[P([supercript(t)]Bu)N(Et)₂]Br sufficiently demonstrate the ring distorting characteristics of structurally encumbered molecules. The reaction of Ace[P(Ph)N(ⁱPr)₂]Br and Ace[P(Ph)N(ⁱPr)₂]₂ with a methylating agent was also investigated.en_US
dc.publisherUniversity of St Andrews
dc.subjectSteric hindranceen_US
dc.subjectRing distortionen_US
dc.subject.lcshPhosphorus compounds--Structureen_US
dc.subject.lcshPhosphorus compounds--Spectraen_US
dc.subject.lcshPhosphorus compounds--Synthesisen_US
dc.subject.lcshPolycyclic aromatic hydrocarbons--Synthesisen_US
dc.subject.lcshSubstitution reactionsen_US
dc.subject.lcshSteric hindranceen_US
dc.titleGeminally bis(supermesityl) substituted phosphorus compounds and a study of 5,6-substituted-acenaphthenesen_US
dc.type.qualificationnamePhD Doctor of Philosophyen_US
dc.publisher.institutionThe University of St Andrewsen_US

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