The butyne, HC≡CCF(CF₃)₂, can be prepared via the dehydro-halogenation of ICH=CHCF(CF₃)₂, the olefin is produced by the ultraviolet irradiation of mixtures of (CF₃)₂CFI and acetylene. Group IV perfluoroalkynyl derivatives (CH₃)[subscript n]M(C≡CR[subscript f])[subscript 4-n] (n = 0 ↦ 3; M = Si, Ge, Sn; R[subscript f] = CF₃> C₂F₅, CF(CF₃)₂) can be prepared by the reaction of XMg C≡CR[subscript f] (X = Br, I) with the appropriate group IV organohalide. Some, but not all, of the combinations of n, M, and R[subscript f] are described. The reaction of CH₃Si[symbol omitted]₃ with IMgC≡CCF₃ produces (CH₃)₂Si(C≡CCF₃)₂. Difluorocarbene from (CH₃)₃SnCF₃ at 150° adds to the C≡C bond of HC≡CR[subscript f] (R[subscript f] = CF₃, C₂F₅, CF(CF₃)₂) and some of the (CH₃)[subscript n]M(C≡CR[subscript f])[subscript 4-n] derivatives to give the corresponding cyclopropenes, [formula omitted] and [formula omitted] respectively. The spectral properties of the group IV perfluoroalkynyl and cyclopropenyl derivatives exhibit several novel trends. The difluorocarbene species from (CH₃)₃SnCF₃ is electrophilic and is in a singlet state in gas phase addition reactions to unsaturated bonds. The carbene adds stereospecifically to both cis- and to trans-butene-2 to give the corresponding isomeric cyclopropanes. The carbene also inserts into the Sn-H bond of (CH₃)₃SnH. The ultraviolet irradiation of mixtures of (CF₃)₂CFI and (CH₃)₃SnSn(CH₃) produces (CH₃) ₃SnCF(CF₃) ₂. A similar reaction involving (CH₃)₃SnSn(CH₃)₃ and CF₂=CFI produces (CH₃)₃SnCF=CF₂. None of the derivatives, (CH₃)₃SnR[subscript f] (R[subscript f] = C₂F₅, CF(CF₃)₂, CF=CF₂) , produces a carbene upon pyrolysis. Bis(trifluoromethyl)diazomethane reacts with HC≡CCF₃ and with CF₃C≡CCF₃ at ca. 150° to give a mixture of the corresponding isopyrazole, [formula omitted], and cyclopropene, [formula omitted]. Similar reactions of the diazo compound with (CH₃)₃MC≡CCF₃ (M = Ge, Sn) produce [formula omitted] derivatives. The reaction of bis(trifluoromethyl)diazirine and (CH₃)₃GeC=CCF₃ also produces the cyclopropene. The diazo compound inserts C(CF₃)₂ into the M-H bonds of (CH₃)₃SnH and (CH₃)₂AsH and produces (CH₃ )₂AsCF(CF₃) ₂H and (CH₃)₂AsCF=CF₂ upon reaction with (CH₃)₂AsAs(CH₃)₂. The diazo compound fails to react however, with either (CH₃)₃MH (M = Si, Ge), (CH₃)₃GeBr, or (CH₃)₃ GeGe(CH₃ )₃. The Mössbauer spectra of the compounds (CH₃)₃SnR[subscript f] reveal that the quadrupole splitting in the Sn nucleus increases in the order R[subscript f] = CFH₂ < CF₂H < CF₃ ≲ CH(CF₃)₂ < C₂F₅ < CF(CF₃)₂ which indicates the order of increasing electronegativity of the R[subscript f] groups. The order of electronegativity, CF₃ < C₂F₃ < CF(CF₃)₂, is also supported by n.m.r. studies of the compounds HC≡CR[subscript f] and [formula omitted]. As an Appendix the stereochemistry of the olefins produced by the ultraviolet irradiation of mixtures of R[subscript f]I (R[subscript f] = CF₃, C₂F₅, CF(CF₃)₂) and acetylene is described. Predominantly trans addition takes place. / Science, Faculty of / Chemistry, Department of / Graduate

The chemoselective hydrozirconation reaction of a series of 1-ene-3-yne molecules 51a-d, using the commercially available hydride reagent, Cp₂ZrCl(H) 1, provides an efficient route to the syntheses of 1,3-dienes 55a-d, substituted at the 1-position by the Cp₂ZrCl moiety. Similar chemoselectivity was observed in the hydrozirconation reaction of α, β-unsaturated nitriles, to generate the corresponding 1-azadienyl complexes 68-71. The complexes 55a-d were found to be useful general precursors in the preparation of other heterosubstituted 1,3-dienes. Thus, corresponding tin-, phosphorus-, boron-, selenium-and sulfur-heterosubstituted 1,3-dienes 77a-d, 79a-d, 87a-d, 88a-d and 89a-d were readily prepared in good to excellent yields by a stereoselective transfer reaction from zirconium. The 1-azadienyl complexes also served as useful starting materials in the preparation of selenium-and phosphorus-substituted 1-azadienes. The selenium-substituted 1,3-dienes 88a-d underwent a facile isomerization reaction when exposed to fluorescent light, and when thermolysed in the dark at 80°C in unsealed reactors. Mechanistic studies of this isomerization process suggested that an intermolecular pathway involving free radical intermediates was operable. A comparable photochemical isomerization reaction of the sulfur-substituted 1,3-dienes was also observed. When the cycloaddition reactions of 88a-b and 88d with maleic anhydride were performed in the absence of light at reson able temperatures, good yields of the expected endo-cycloadducts were obtained. However, when the same reactions were repeated in room light or at temperatures in excess of those required for formation of the endo-cycloadducts an, interesting, apparent [l,3]-shift of the phenylselenenyl moiety resulted. The results of a crossover experiment indicated that this rearrangment was intermolecular in nature. The preparation of the trialkylstannyl and phenylselenenyl 2-substituted 1,3-dienes (128 and 129) was achieved via a transmetalation reaction of the Grignard reagent 24. The Diels-Alder reactivity of 1,3-dienes 128 and 129, with a series of electron-deficient dienophiles, was successfully investigated. [Formula Omitted] / Science, Faculty of / Chemistry, Department of / Graduate

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published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

This dissertation describes a study of the electronic structure of some selected cyclopentadienyl metal olefin, (mu)-alkylidene, and carbonyl complexes. While most studies of this type are largely theoretical in nature, this work relies on the experimental observations which result from the application of photoelectron spectroscopy to the measurements of the important molecular energies of these compounds. The first part of the discussion is a study of metal-olefin bonding in the CpM(CO)₂L (L = C₂H₄, C₃H₆) compounds. Of particular interest are the observed changes in ionization energies of the olefin (pi) orbital upon coordination. These results also allow a comparison of the coordination of CO and C₂H₄. The valence ionizations of μ-CH₂-[(C₅H₄CH₃)Mn(CO)₂]₂ are also presented. This example of the increasingly important μ-alkylidene complexes provides evidence of a 3C-6e configuration with a net Mn-Mn single bond. The final chapter describes a study of the valence electronic structure of the CpM(CO)₂ (M = Co, Rh; Cp = η⁵-C₅H₅⁻) and η⁵-C₅(CH₃)₅⁻ ) system. This group of four closely related molecules demonstrates how photoelectron spectroscopy can be used to monitor the electronic effects of specific chemical modifications. The intent throughout is to not only present a detailed analysis of the specific compounds chosen for this study, but to also further demonstrate the applicability of photoelectron spectroscopy to a broad spectrum of problems concerning the structural and electronic make-up of organometallic molecules.