title: Some metallacyclic complexes of the late transition metals

authors: Oliver, Allen G.

abstract: The principal aim of this thesis is the synthesis and characterisation of four-membered metallacyclic complexes. Reactions of square-planar palladium(II), platinum(II) and gold(III) dihalide complexes with a variety of amides, some in the presence of silver(I) oxide are discussed.

Chapter one reviews the literature of small-ring metallacyclic chemistry, in particular the synthesis of four-membered metallacycles, as they are, in the main, the complexes that are further reported throughout the remainder of the thesis.

Chapter two reports the synthesis of four-membered metallalactam complexes [M{N(Ph)C(O)CHC(O)Ph}L₂] (2.11 - 2.15) formed from the reactions of square-planar L₂MCl₂ complexes [M = Pt, Pd, L = PPh₃, L₂ = 1,5-cyclooctadiene (COD), 1,2-bis(diphenylphosphino)ethane (dppe), 2,2’-bipyridine (bipy)] with 2-benzoylacetanilide [PhC(O)CH₂C(O)NHPh] in the presence of silver(I) oxide. The X-ray crystal structure of [Pd{N(Ph)C(O)CHC(O)Ph}(bipy)].CH₂Cl₂ (2.14.CH₂Cl₂) was determined to confirm the geometry of the compounds. The reactions of acetoacetamide [NH₂C(O)CH₂C(O)CH₃] with cis-[PtCl₂ (PPh₃)₂], [PtCl₂(dppe)] and [PdCl₂(bipy)] (2.16 - 2.18) in the presence of silver(I) oxide are also discussed.

Chapter three describes the isolation and characterisation of a platinum(II)-amidate complex, believed to be the first characterised intermediate in silver(I) oxide mediated reactions. For short reaction times the complex cis-[Pt{N(C(O)CH₂CN)(CO₂Et)}Cl(PPh₃)₂] (3.4) can be isolated from the reaction mixture of cis-[PtCl₂(PPh₃)₂] with N-cyanoacetylurethane [NCCH₂C(O)NHCO₂Et] in the presence of silver(I) oxide. For long reaction times this synthesis is known to afford the four-membered metallalactam [Pt{N(CO₂Et)C(O)CHCN}(PPh₃)₂].

Chapter four details the synthesis and characterisation of four-membered gold(III) lactam complexes. A series of metallalactam complexes were characterised from the reaction of [LAuCl₂] [L = {C₆H₃(CH₂NMe₂)-2-OMe-5} or {C₆H₄(CH₂NMe₂)-2}] with N-cyanoacetylurethane, 2-benzoylacetanilide, acetoacetanilide or acetoacetamide in the presence of silver(I) oxide. A representative of these gold(III) metallacycles, [{C₆H₄-CH₂NMe₂-2}Au{N(Ph)C(O)CHC(O)CH₃}] (4.13), was structurally characterised. A novel and unprecedented dimerisation occurred with [{C₆H₃-CH₂NMe₂-2-OMe5}Au{N(CO₂Et)C(O)CHCN}], that formed an eight-membered metallacycle (4.15) which was characterised by an X-ray diffraction study.

The reactions of cis-[PtCl₂(PPh₃)₂] with either cyanoacetic acid or phenoxyacetic acid in the presence of silver(I) oxide are reported in chapter five. The reaction of phenoxyacetic acid with cis-[PtCl₂(PPh₃)₂] was found to form the simple platinum(II) bis(carboxylate) complex, cis-[Pt(O₂CCH₂OPh)₂(PPh₃)₂] (5.9). Conversely, cyanoacetic acid undergoes a novel decarboxylation reaction which results in the formation of the platinum(II) bis(alkyl) complex cis-[Pt(CH₂CN)₂PPh₃)₂] (5.7). The X-ray crystal structures of these two complexes are described.

Chapter six discusses the triethylamine-mediated syntheses of four-membered metallalactam complexes. The reactions of cyanoacetylurea [NH₂C(O)NHC(O)CH₂CN] with cis-[PtCl₂(PPh₃)₂], [PtCl₂(COD)], [PtCl₂(dppe)] and [PdCl₂(dppe)] in the presence of triethylamine and details of their characterisation are described. One complex, cis-[Pt{N(C(O)NH₂)C(O)CHCN}(PPh₃)₂] (6.5), was structurally characterised and was found to crystallise as an H-bonded dimer. The reactions of N-cyanoacetylurethane, 2-benzoylacetanilide and acetoacetanilide with cis-[PtCl₂(PPh₃)₂] in the presence of silver(I) oxide are known to give well-characterised four-membered metallalactam complexes. The results of the reactions of these compounds when reacted under similar conditions, but with triethylamine as the base and halide abstractor, are also discussed.

Chapter seven describes a selection of four crystal structures. The X-ray structure of the first coordinatively saturated iridaureylene complex, [Ir{N(Me)C(O)NAc}(Cp*)(PPh₃)] (7.4), which is isoelectronic with four-membered metallalactam complexes, is described. The complex was found to adopt a “bar-stool” geometry. The structures of the complexes, [Rh{O₂CC₆H₄-S-2}Cp*]₂ (7.8) and [Ru{O₂CC₆H₄-S-2}(p-cymene)]₂ (7.9) were studied and found to be dimeric compounds. The complexes were found to adopt a pseudo-octahedral geometry, with a three-coordinate, bridging thiolate sulfur. The fourth structural analysis was that of the novel chelation product of cis-[Pt{NCH₂CH₂C(O)}₂(PPh₃)₂] with uranyl nitrate [UO₂(NO₃)₂]. The complex was found to form an eight-membered heterocycle (7.15), with the platinum bis(lactam) complex coordinating to the uranium via the lactam oxygen atoms.

text: Some metallacyclic complexes of the late transition metals The principal aim of this thesis is the synthesis and characterisation of four-membered metallacyclic complexes. Reactions of square-planar palladium(II), platinum(II) and gold(III) dihalide complexes with a variety of amides, some in the presence of silver(I) oxide are discussed.

Chapter one reviews the literature of small-ring metallacyclic chemistry, in particular the synthesis of four-membered metallacycles, as they are, in the main, the complexes that are further reported throughout the remainder of the thesis.

Chapter two reports the synthesis of four-membered metallalactam complexes [M{N(Ph)C(O)CHC(O)Ph}L₂] (2.11 - 2.15) formed from the reactions of square-planar L₂MCl₂ complexes [M = Pt, Pd, L = PPh₃, L₂ = 1,5-cyclooctadiene (COD), 1,2-bis(diphenylphosphino)ethane (dppe), 2,2’-bipyridine (bipy)] with 2-benzoylacetanilide [PhC(O)CH₂C(O)NHPh] in the presence of silver(I) oxide. The X-ray crystal structure of [Pd{N(Ph)C(O)CHC(O)Ph}(bipy)].CH₂Cl₂ (2.14.CH₂Cl₂) was determined to confirm the geometry of the compounds. The reactions of acetoacetamide [NH₂C(O)CH₂C(O)CH₃] with cis-[PtCl₂ (PPh₃)₂], [PtCl₂(dppe)] and [PdCl₂(bipy)] (2.16 - 2.18) in the presence of silver(I) oxide are also discussed.

Chapter three describes the isolation and characterisation of a platinum(II)-amidate complex, believed to be the first characterised intermediate in silver(I) oxide mediated reactions. For short reaction times the complex cis-[Pt{N(C(O)CH₂CN)(CO₂Et)}Cl(PPh₃)₂] (3.4) can be isolated from the reaction mixture of cis-[PtCl₂(PPh₃)₂] with N-cyanoacetylurethane [NCCH₂C(O)NHCO₂Et] in the presence of silver(I) oxide. For long reaction times this synthesis is known to afford the four-membered metallalactam [Pt{N(CO₂Et)C(O)CHCN}(PPh₃)₂].

Chapter four details the synthesis and characterisation of four-membered gold(III) lactam complexes. A series of metallalactam complexes were characterised from the reaction of [LAuCl₂] [L = {C₆H₃(CH₂NMe₂)-2-OMe-5} or {C₆H₄(CH₂NMe₂)-2}] with N-cyanoacetylurethane, 2-benzoylacetanilide, acetoacetanilide or acetoacetamide in the presence of silver(I) oxide. A representative of these gold(III) metallacycles, [{C₆H₄-CH₂NMe₂-2}Au{N(Ph)C(O)CHC(O)CH₃}] (4.13), was structurally characterised. A novel and unprecedented dimerisation occurred with [{C₆H₃-CH₂NMe₂-2-OMe5}Au{N(CO₂Et)C(O)CHCN}], that formed an eight-membered metallacycle (4.15) which was characterised by an X-ray diffraction study.

The reactions of cis-[PtCl₂(PPh₃)₂] with either cyanoacetic acid or phenoxyacetic acid in the presence of silver(I) oxide are reported in chapter five. The reaction of phenoxyacetic acid with cis-[PtCl₂(PPh₃)₂] was found to form the simple platinum(II) bis(carboxylate) complex, cis-[Pt(O₂CCH₂OPh)₂(PPh₃)₂] (5.9). Conversely, cyanoacetic acid undergoes a novel decarboxylation reaction which results in the formation of the platinum(II) bis(alkyl) complex cis-[Pt(CH₂CN)₂PPh₃)₂] (5.7). The X-ray crystal structures of these two complexes are described.

Chapter six discusses the triethylamine-mediated syntheses of four-membered metallalactam complexes. The reactions of cyanoacetylurea [NH₂C(O)NHC(O)CH₂CN] with cis-[PtCl₂(PPh₃)₂], [PtCl₂(COD)], [PtCl₂(dppe)] and [PdCl₂(dppe)] in the presence of triethylamine and details of their characterisation are described. One complex, cis-[Pt{N(C(O)NH₂)C(O)CHCN}(PPh₃)₂] (6.5), was structurally characterised and was found to crystallise as an H-bonded dimer. The reactions of N-cyanoacetylurethane, 2-benzoylacetanilide and acetoacetanilide with cis-[PtCl₂(PPh₃)₂] in the presence of silver(I) oxide are known to give well-characterised four-membered metallalactam complexes. The results of the reactions of these compounds when reacted under similar conditions, but with triethylamine as the base and halide abstractor, are also discussed.

Chapter seven describes a selection of four crystal structures. The X-ray structure of the first coordinatively saturated iridaureylene complex, [Ir{N(Me)C(O)NAc}(Cp*)(PPh₃)] (7.4), which is isoelectronic with four-membered metallalactam complexes, is described. The complex was found to adopt a “bar-stool” geometry. The structures of the complexes, [Rh{O₂CC₆H₄-S-2}Cp*]₂ (7.8) and [Ru{O₂CC₆H₄-S-2}(p-cymene)]₂ (7.9) were studied and found to be dimeric compounds. The complexes were found to adopt a pseudo-octahedral geometry, with a three-coordinate, bridging thiolate sulfur. The fourth structural analysis was that of the novel chelation product of cis-[Pt{NCH₂CH₂C(O)}₂(PPh₃)₂] with uranyl nitrate [UO₂(NO₃)₂]. The complex was found to form an eight-membered heterocycle (7.15), with the platinum bis(lactam) complex coordinating to the uranium via the lactam oxygen atoms.

year: 1999

title: Tree encroachment may lead to functionally-significant changes in peatland testate amoeba communities

authors: Payne, Richard J.

subjects: Science & Technology

abstract: Climate change is likely to cause increased tree recruitment on open peatlands but we currently have little idea what consequences this vegetation change may have below-ground. Here we use transects across forested to open bog ecotones at three Russian peatland complexes to assess potential changes in the most abundant group of peatland protists – the testate amoebae. We show that the testate amoeba communities of forested and open bog are markedly different with a very abrupt boundary at, or near, the vegetation ecotone. Changes along our transects suggest that tree encroachment may reduce the trophic level of testate amoeba communities and reduce the contribution of mixotrophic testate amoebae to primary production. Our study strongly suggests that increased tree recruitment on open peatlands will have important consequences for both microbial biodiversity and microbially-mediated ecosystem processes.

text: Tree encroachment may lead to functionally-significant changes in peatland testate amoeba communities Climate change is likely to cause increased tree recruitment on open peatlands but we currently have little idea what consequences this vegetation change may have below-ground. Here we use transects across forested to open bog ecotones at three Russian peatland complexes to assess potential changes in the most abundant group of peatland protists – the testate amoebae. We show that the testate amoeba communities of forested and open bog are markedly different with a very abrupt boundary at, or near, the vegetation ecotone. Changes along our transects suggest that tree encroachment may reduce the trophic level of testate amoeba communities and reduce the contribution of mixotrophic testate amoebae to primary production. Our study strongly suggests that increased tree recruitment on open peatlands will have important consequences for both microbial biodiversity and microbially-mediated ecosystem processes.

year: 2016

title: The Mātauranga Māori in Mathematics Directive: Exploring the place of mātauranga Māori in Mathematics teaching and learning

authors: Williams, Jessica Elizabeth

subjects: mathematics education

abstract: This thesis explores issues concerning mātauranga Māori in mathematics teaching and learning here in Aotearoa. The Ministry of Education has directed that mana ōrite mō te mātauranga Māori be embedded in teaching, learning, and assessment. Thus, this research primarily aims to understand the development leading to the directive of including mātauranga Māori in education policies. For the English-medium secondary education settings, the second and third aims of this research are to explore what mātauranga Māori means to teachers of mathematics and to consider the connections between mātauranga Māori and mathematics teaching and learning. To investigate these aims, a semi-structured group discussion with four secondary mathematics teachers from an English-medium setting was conducted. The results of this thesis highlight the confusion and challenges secondary mathematics educators have toward defining, and subsequently, implementing mātauranga Māori in their classrooms. This thesis also found that there is enthusiasm and interest around learning how to ensure indigenous and marginalised learners reach their mathematics potential. Believing that indigenous worldviews have the potential to shift education outcomes for minority learners, this thesis adds to literature related to indigenous education, secondary mathematics education, and English-medium education of Māori learners.

text: The Mātauranga Māori in Mathematics Directive: Exploring the place of mātauranga Māori in Mathematics teaching and learning This thesis explores issues concerning mātauranga Māori in mathematics teaching and learning here in Aotearoa. The Ministry of Education has directed that mana ōrite mō te mātauranga Māori be embedded in teaching, learning, and assessment. Thus, this research primarily aims to understand the development leading to the directive of including mātauranga Māori in education policies. For the English-medium secondary education settings, the second and third aims of this research are to explore what mātauranga Māori means to teachers of mathematics and to consider the connections between mātauranga Māori and mathematics teaching and learning. To investigate these aims, a semi-structured group discussion with four secondary mathematics teachers from an English-medium setting was conducted. The results of this thesis highlight the confusion and challenges secondary mathematics educators have toward defining, and subsequently, implementing mātauranga Māori in their classrooms. This thesis also found that there is enthusiasm and interest around learning how to ensure indigenous and marginalised learners reach their mathematics potential. Believing that indigenous worldviews have the potential to shift education outcomes for minority learners, this thesis adds to literature related to indigenous education, secondary mathematics education, and English-medium education of Māori learners.

year: 2023