Organo nickel and platinum chemistry at the edge of corannulene
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Corannulene (C[subscript 20]H[subscript 10]), a polycyclic aromatic hydrocarbon (PAH) is a bowl shaped fullerene fragment. This work involves investigations into the chemistry of corannulene with transition metals, which can be used to expand the carbon bond at the edge of corannulene as a synthetic model for corannulene based carbon nanotubes and fullerene fragments. Initial efforts to synthesize novel transition metal complexes and explore the feasibility and application of corannulene based nanotube synthesis via the previously established reactivity of PAHs are imposed on this dissertation. The first complexes with transition metals directly [lower-case sigma]- bonded to the edge of corannulene, nickel and platinum corannulene complexes and derivatives are reported. Potential metal mediated functionalization method of PAHs via directing halogenation of C-H bond is established by photoinduced selective bromination. Therefore, this research is of interest not only for the synthesis of novel complexes, but also as the investigation of a potential chemical method for the functionalization of PAHs. Zero valent electron rich nickel and platinum metal was oxidatively added to carbon- halogen bond to give the first transition metal complexes directly bonded to the edge of corannulene derivatives. The reaction of corannulene bromide with �NiL[subscript 2]� or �PtL[subscript 2]� (L = Pet[subscript 3] or PMe[subscript 3]) gives corannulenyl complexes of [lower-case sigma]- bonded nickel and platinum, cis- and trans-MBrL2R (M = Ni, Pt, R = C[subscript 20]H[subscript 9], C[subscript 20]H[subscript 6]Br[subscript 3]). Mono and dinuclear platinum complexes were also established via single and double oxidative addition of �ML[subscript 2]� (M = Ni, Pt) with tetrabromocorannulene (C[subscript 20]H[subscript 6]Br[subscript 4]) and well- isolated by the column chromatography. The corresponding bowl-to-bowl inversion barriers are evaluated by NMR experiments in the range of 10-12 kcal/mol. The reaction of platinum (II) derivatives of poly aromatic hydrocarbons (PAHs) with bromine followed by irradiation with light gives selectively aromatic ring brominated products via preceding platinum (IV) intermediates. The reaction of bromocorannulene, 9-bromophenanthrene and 1-bromonaphthalene with PtL[subscript 4] affords trans-PtBrL[subscript 2]R. (L=Pet[subscript 3], R = corannulenyl, phenanthrenyl and naphthalenyl) Addition of bromine to the corresponding platinum (II) complexes generates hexa coordinated platinum (IV) complexes, trans-PtBr[subscript 3]L[subscript 2]R. In the presence of light, the neighboring C-H bond to platinum metal center on the aromatic ring is regioselectively brominated with conversion to platinum (II) complexes, trans-PtBrL[subscript 2]R? along with HBr. (R? = bromocorannulenyl, bromophenanthrenyl and bromonaphthalenyl). A series of decreasing bromination yields in presence of hydrogen atom donors demonstrates that this photoreaction involves a bromine radical mechanism.
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