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UBC Theses and Dissertations

Manganese, rhenium and rhodium complexes containing pyrazolylgallate ligands Louie, Brenda Maureen


Dimethylbis(1-pyrazolyl)gallate anions reacted with [Re(CO)₄Cl]₂ to form unstable rhenium tetracarbonyl complexes of the type [Me₂Ga(C₃HN₂R₂)₂]Re(CO)₄ (R=H or Me). These compounds reacted with PPh₃ or pzH, the nucleophile displacing the carbonyl group mutually cis to both donor sites of the chelating, bidentate ligand. Novel bidentate dimethylmonoCl-pyrazolyl)hydroxogallate ligands have been prepared and four rhenium complexes incorporating these ligands, [Me₂Ga(C₃HN₂R₂)(OH)]Re(CO)₃X (R=H or Me; X=CO or PPh₃) are discussed. The phosphino bridged rhenium molecule, [Me₂Ga(pz)(PPh₂) ] Re(CO)₅ has also been considered. The reactions between various tridentate unsymmetric mono-(1-pyrazolyl) gallate ligands and either [Re (CO) ₄Cl]₂or Mn (CO)₅ -Br resulted in a series of tricarbonyl products. The nitrosylations of selected pyrazolylgallate rhenium species are discussed. The exposure of these nitrosylated cations to a hydride source did not lead to the isolation, or spectroscopic identification, of any reduced coordinated carbonyl moieties. In addition, selected pyrazolylgallate rhenium tricarbonyl or nitrosyl cationic species could not be induced to undergo carbonyl metathesis with tertiary phosphines. The unique stereoisomers formed from the reactions between [Re(CO)₄Cl]₂and tridentate pyrazolylgallate anions containing a chiral carbon are also discussed. A series of rhodium(I) complexes containing the [Me₂Ga(pz)₂]⁻ bidentate ligand have been prepared. These molecules were found to be stereochemically nonrigid in solution. Although one compound containing the more sterically demanding [Me₂Ga(pz")₂ ]⁻ anion could be isolated, the majority of reactions with this ligand resulted in the formation of extremely stable 3,5 dimethylpyrazolyl bridged rhodium dimers, together with [Me₂Ga(μ-pz")]₂. The reaction of [MeGa(pz)₃] ⁻ with [Rh(CO)₂Cl]₂ resulted in the novel triply carbonyl bridged dimer [MeGa (pz)₃]₂Rh₂(μ-CO)₃. The first examples.of transition metal carbonyl species containing a meridionally coordinated unsymmetric mono(1-pyrazolyl) gallate tridentate ligand have been discussed, namely [Me₂Ga(pz) (OCH₂CH₂NMe₂) ]Rh(CO)[sub n] (n=l and 2). In addition the first example of a mixed transition metal pyrazolylgallate complex, [MeGa(pz)₃]MoRh(μ-CO)₂ (CO)(PPh₃)₂, is presented. None of the novel pyrazolylgallate rhodium species prepared exhibited measurable activity as catalysts for the hydrogenation of 1-hexene or cyclohexene.

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