Aryl Organometallic Compounds of Ruthenium and Osmium

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dc.contributor.advisor Roper, Warren en
dc.contributor.advisor Wright, James en Clark, Alex M. en 2007-06-29T02:58:35Z en 2007-06-29T02:58:35Z en 1999 en
dc.identifier THESIS 00-146 en
dc.identifier.citation Thesis (PhD--Chemistry)--University of Auckland, 1999 en
dc.identifier.uri en
dc.description Full text is available to authenticated members of The University of Auckland only. en
dc.description.abstract A variety of aryl organometallic species of the form M(Ar)Cl(CO)(PPh3)2 where Ar is a σ-bound aryl ligand and M is Ru or Os, have been prepared by transmetallation. The metal hydrides MHCl(CO)(PPh3)3 were reacted with the appropriate mercury reagents of the form Ar2Hg. Aryl groups transferred by this method include simple hydrocarbons (I-naphthyl [Nap]) and multiaromatic ligands with chelating functional (8-quinolyl [Qn], 2-(2’-pyridyl)phenyl [Phpy], 2-(1:2’-pyridyl)naphthyl [Nppy], 2-(2’-quinolyl)phenyl [Phqn] and 2-(2’-(3’-phenyl)quinoxalyl)phenyl [Dpqx]). Although all complexes possess the same general composition M(Ar)Cl(CO)(PPh3)2, a stark contrast in properties and reactivity was observed between those aryl groups with and those without an internal chelating functional group. Complexes with the ligands Qn, Phpy, Nppy, Phqn and Dpqx were found to be robust 6-coordinate, 18 electron species. By contrast, complexes with the ligand Nap were 5-coordinate, 16 electron species which were prone to loss of the organic ligand unless derivatised. Many derivatives of the species M(Ar)Cl(CO)(PPh3)2 were prepared by changing the ligands at the metal centre. For the coordinatively unsaturated compounds M(Nap)Cl(CO)(PPh3)2 metal-centred derivatisation reactions were facile. Carbonylation of the ruthenium compound caused migratory insertion to form the dihapto acyl species. Ru(η2-C[O]-Nap)Cl(CO)(PPh3)2, whereas for the osmium analogue the dicarbonyl species, Os(Nap)Cl(CO)(PPh3)2, was formed. For the complexes of chelating ligands, it was necessary to first form a cation by removing the chloro ligand with a suitable silver salt, after which derivatisations could be achieved, including carbonylation, halide interchange and addition of potentially bidentate ligands. When dimethyldithiocarbamate was introduced, strong competition for chelating space resulted. Complexes of the Qn ligand gave rise to species whereby the 4-membered organometallic chelate ring was detached in order to make room in the coordination sphere. Complexes of Phpy, Nppy, Phqn and Dpqx all preferentially lost a phosphine in order that two ligands could form bidentate chelate rings. Carbonylation of coordinatively saturated species was only possible in the case of Ru(η2-Qn)Cl(CO)(PPh3)2, whereby migratory insertion occurred to expand the 4-membered ring to 5-membered, featuring an acyl unit. While complexes M(Nap)Cl(CO)(PPh3)2 were poor substrates for electrophilic aromatic substitution due to the easily severed metal-carbon bond, all complexes of Phpy, Nppy, Phqn and Dpqx were sufficiently robust for quite severe reaction conditions. Of the Qn ligand, only the osmium compound was found to be sufficiently robust to be useful. A variety of these substrates were brominated, iodinated, nitrated, sulfonated, formylated and chloromethylated, under unusually mild conditions. Not only did the aromatic rings of the ligands behave as if significantly activated, but the functionalisation reactions were found to be totally specific in their regiochemistry. For the ligands Qn, Phpy, Phqn and Dpqx, the first site of substitution occurred invariably in the ring position directly para to the metal-carbon bond. Only rarely did conditions permit a second substitution, which occurred in the ortho position on the same ring, undoubtedly less favourable due to the large steric bulk of the metal moiety. The ring systems not directly attached to the metal were not electronically activated, and no substitution was observed at these positions, except in the unusual case of sulfonation of Os(η2-Phqn)Cl(CO)(PPh3)2 where the 8'- position was also substituted. An unusual substitution pattern was observed when Os(η2-Nppy)Cl(CO)(PPh3)2 was nitrated, for no position para to the metal-carbon bond is available, and instead the activating effect was found to be spread throughout the naphthyl moiety. Most of the newly functionalised compounds were highly suitable for further reactions. Reaction of the brominated substrates with BuLi allowed subsequent introduction of –CHO, -C[O]Me, -Bu, -SnBu3,-Hg and –CO2H functional groups. Reduction of the mononitrated compound Os(η2-Qn-5-NO2)Cl(CO)(PPh3)2 gave the corresponding amine. Palladium catalysed cross-coupling of an iodinated substrate was carried out, imparting a-C≡C-Ph functional group were good substrates for further reactions, and reacted predictably with sodium borohydride, and with a Wittig reagent, to produce a primary alcohol, and an alkene, repectively. Os(η2-Qn-5-CHO)Cl(CO)(PPh3)2 was successfully tethered to a buckminsterfullerene, with the former-aldehyde functional group becoming part of a 5-membered pyrrolidine ring, via a condensation/decarboxylation reaction with sarcosine and C60 Os(η2-Phpy-4-CHO)Cl(CO)(PPh3)2 was reacted with di(4-methyl-3-propyl-2-pyrrolyl)methane to form novel organometallic porphyrin. Demetallation of Ru(η2-Phpy-4-Br)Cl(CO)(PPh3)2 was carried out in order to examine the possibility of using the functionalisation reactions as synthons for organic synthesis. The chemistry of complexes M(Th)Cl(CO)(PPh3)2(M = Ru, Os; Th = 2-thienyl)was reinvestigated, and a variant with a chelated ligand, M(η2-Thf)Cl(CO)(PPh3)2(M = Ru, Os; Th = 2-formyl-3-thienyl), was prepared. No functionalisation reactions of these complexes were successful, however. The chemistry of complexes of the form M(η2-Php)Cl(CO)(PPh3)2(M = Ru, Os; Php = o-C6H4PPh2)was also reinvestigated, and several new derivatives were prepared. Some work was done toward attempting to introduce the N,N-dimethylimidazol-2-ylidene carbene ligand to ruthenium and osmium via a mercury reagent. Only the mercury compound was successfully characterised. en
dc.language.iso en en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof PhD Thesis - University of Auckland en
dc.relation.isreferencedby UoA9990211414002091 en
dc.rights Restricted Item. Available to authenticated members of The University of Auckland. en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. en
dc.rights.uri en
dc.title Aryl Organometallic Compounds of Ruthenium and Osmium en
dc.type Thesis en Chemistry en The University of Auckland en Doctoral en PhD en
dc.rights.holder Copyright: The author en

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