Date of Award
2011
Publication Type
Dissertation
Degree Name
Ph.D.
Department
Chemistry and Biochemistry
Supervisor
Samuel Johnson
Rights
info:eu-repo/semantics/openAccess
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Abstract
The reaction of the anthracene adduct ,(PiPr3)2Ni(172 -C14H10) with l ,2,4,5-C6F 4H2 affords the first isolable nickel C-H bond activation product, trans-(PiPr3) 2NiH(2,3,5,6- C6F 4H). Previously, only equilibrium amounts of C-H activation products could be observed using a Ni(PEt3)2 synthon. Increasing the steric bulk of the phosphine ligands offers a thermodynamic driving force that better promotes trans oxidative addition of the fluorinated substrate. We were also successful in activating 1,2,3,5-C6F4H2, 1,2,4- and 1,3,5-trifluorobenzene, and pentafluorobenzene, although there is spectroscopic evidence of C-F bond activation products in the crude reaction mixtures. Attempts to utilize commercially available Ni(COD)2 in the activation of tetrafluorobenzenes resulted in the unexpected insertion products, (1/-C8H13)Ni(PiPr3)(C6F4H), even in the case of 1,2,3,4- C6F4H2 where C-H bond activation was previously not observed.
This system readily participates in catalytic C-H bond functionalization en route toward the synthesis of new organofluorines (C6F0H5_0-CEt=CHEt) via catalytic alkenylation of the aforementioned fluorinated aromatics with 3-hexyne. As well, the reaction of Bu3Sn(vinyl) and fluoroarenes or fluoropyridines with catalytic amounts of Ni(COD)2 and P;Pr3 failed to produce the expected vinylated product via C-F functionalization, but rather produced the stannylated products Bu3SnC6FnHs-n and Bu3SnC5F0H4_0 N, respectively. The scope of fluoroarenes, as well as tetra- and trifluoropyridines has been covered.
The reaction of the anthracene adduct, (PiPr3)2Ni(172-C14H10) with C6F6 produced the expected C-F bond activation product, trans-(P;Pr3) 2NiF(C6F 5), as well as the paramagnetic complex (PiPr3)2Ni(C6F5) and the aryne (PiPr3)2Ni(l-3,4,5,6-C6F4), Analogous reactions with penta-, tetra-, and trifluorobenzenes simply produced their expected C-F bond activation products. Alternatively, these thermodynamic products could be synthesized by heating the isolated C-H activation compounds.
The low-temperature reaction of the phenanthrene adduct, (PEt3)2Ni(l-C14H10) with 2,3,5,6-tetrafluoropyridine affords the C-H activation product, trans-(PEt3)2NiH(2,3,5,6-C5F 4N), along with the mononuclear adduct, (PEt3)2Ni(,,,2-2,3,5,6- C5F4HN). Upon warming, we see spectroscopic evidence for the cis C-F activation product, cis-(PEt3)2NiF(3,5,6-C5F3HN), which undergoes a cis/trans isomerization to the thermodynamic product, trans-(PEt3)2NiF(3,5,6-C5F3HN). A theoretical investigation was conducted probing the mechanism for this reaction, as well as for pentafluoropyridine, 2,3,4,6-tetrafluoropyridine, 2,3,5-, 2,3,6-, and 2,4,6- trifluoropyridine, and 2,4,6-trifluoropyridimidine to support experimental findings for the scope of these substrates. Reactions with the anthracene adduct, (PiPr3)2Ni(172 -C14H1o) have also been carried out.
Recommended Citation
Hatnean, Jillian Anne, "C-H and C-F Bond Activation by Nickel Bis(Phosphine) Complexes" (2011). Electronic Theses and Dissertations. 9633.
https://scholar.uwindsor.ca/etd/9633