First Row Transition Metal Perfluoro-Alkyls and -Carbenes: Synthesis, Metathesis and More
Creators: name: Daniels, Alexander
Publisher: name: Université d'Ottawa / University of Ottawa
Year: 2019
Subjects: Metathesis
Fluoro-carbene
Fluoro-olefin
non-Chauvin
Nickel metathesis
First-row metal

description: Organofluorine compounds are highly sought-after products owing to the unique physical and chemical properties imparted by fluorine. However, the use of hazardous HF, reactive F2 and environmentally persistent long chain fluorosurfactants, all staples of the industrial processes used to prepare refrigerants, pharma-/agrochemicals and fluoropolymers, make the preparation of organofluorine compounds difficult. Therefore, new routes to some or all of these value-added products are desirable. Efficient transition metal-mediated or -catalyzed processes within the arena of fluoro-organic chemistry, however, are significantly less well developed than similar processes for both non-fluorinated and even halogenated compounds. For example, analogs of Group 4 metallocene catalysts for controlled polyolefin formation, or Ru and Group 6 catalysts for alkene metathesis are not generally useful with fluoroalkene substrates. Recent progress has focused on first row metal fluoroalkyl (M-RF) and fluorocarbene (M=CFRF) complexes that tend to have weaker M-C bonds than their second and third row counterparts. The synthesis, electronic structure and chemistry of such complexes is summarized in Chapter 1 along with an assessment of their potential for catalyzed C-C bond formation with fluoroalkenes via insertion or cycloaddition reactions. In Chapter 2 the synthesis and reactivity of new d8 [Co]-CF3 carbonyl complexes and their corresponding electrophilic {[Co]=CF2}+ complexes is described. In Chapter 3 we introduce the first examples of d10 metal fluorocarbenes, P3Ni=CF2 [P = P(OiPr)3; P3 = dppe, P(OiPr)3] along with their facile cycloaddition reactions with tetrafluoroethylene and some reactivity of the resulting stable perfluoronickelacyclobutanes (dppe = 1,2-bis(diphenylphos-phino)ethane). In Chapter 4 exploration of the more reactive Ni fluorocarbenes, Ni=CF(CF3)- [P(OR)3]3, (R = Me, iPr) leads, in reactions with fluoroalkenes, to formation of both metalla-cycles and metathesis products via separate pathways, in the first example of metathesis of fluoro-alkenes with a perfluoro-carbene. Detailed analysis of the latter by Texas A&amp;M collaborators Guan and Hall using density functional theory showed that the nature of the reaction products depends on the geometry of the four-coordinate C-C bond forming transition state. In Chapter 5 this novel fluoroalkene metathesis process is probed further by extending the substrate scope to additional fluoroalkenes and several non-fluorinated variants. In Chapter 6 a series of new Mn-CF3 carbonyl complexes are prepared with a view to enabling fluoroalkene insertion reactions. Although this goal has not yet been achieved, fluoride abstraction using Lewis acids afforded the first examples of [Mn]=CF2 complexes. Finally, in Chapter 7 the findings of this thesis are placed in the context of the current state of the art and logical next steps for further understanding and catalytic process development are proposed.