title: Platinum(II) phosphonate complexes derived from endo-8-camphanylphosphonic acid

authors: Leach, Meto T.

subjects: platinum

abstract: The reactions of cis-[PtCl₂L₂] [L = PPh₃, PMe₂Ph or L₂ = Ph₂P(CH₂)₂PPh₂ (dppe)] with endo-8-camphanylphosphonic acid (CamPO₃H₂) and Ag₂O in refluxing dichloromethane gave platinum(II) phosphonate complexes [Pt(O₃PCam)L₂]. The X-ray crystal structure of [Pt(O₃PCam)(PPh₃)₂]•₂CHCl₃ shows that the bulky camphanyl group, rather than being directed away from the platinum, is instead directed into a pocket formed by the Pt and the two PPh₃ ligands. This allows the O₃P–CH₂ group to have a preferred staggered conformation. The complexes were studied in detail by NMR spectroscopy, which demonstrates non-fluxional behaviour for the sterically bulky PPh₃ and dppe derivatives, which contain inequivalent phosphine ligands in their ³¹P NMR spectra. These findings are backed up by theoretical calculations on the PPh₃ and PPhMe₂ derivatives, which show, respectively, high and low energy barriers to rotation of the camphanyl group in the PPh₃ and PPhMe₂ complexes. The X-ray crystal structure of CamPO₃H₂ is also reported, and consists of hydrogen-bonded hexameric aggregates, which assemble to form a columnar structure containing hydrophilic phosphonic acid channels surrounded by a sheath of bulky, hydrophobic camphanyl groups.

text: Platinum(II) phosphonate complexes derived from endo-8-camphanylphosphonic acid The reactions of cis-[PtCl₂L₂] [L = PPh₃, PMe₂Ph or L₂ = Ph₂P(CH₂)₂PPh₂ (dppe)] with endo-8-camphanylphosphonic acid (CamPO₃H₂) and Ag₂O in refluxing dichloromethane gave platinum(II) phosphonate complexes [Pt(O₃PCam)L₂]. The X-ray crystal structure of [Pt(O₃PCam)(PPh₃)₂]•₂CHCl₃ shows that the bulky camphanyl group, rather than being directed away from the platinum, is instead directed into a pocket formed by the Pt and the two PPh₃ ligands. This allows the O₃P–CH₂ group to have a preferred staggered conformation. The complexes were studied in detail by NMR spectroscopy, which demonstrates non-fluxional behaviour for the sterically bulky PPh₃ and dppe derivatives, which contain inequivalent phosphine ligands in their ³¹P NMR spectra. These findings are backed up by theoretical calculations on the PPh₃ and PPhMe₂ derivatives, which show, respectively, high and low energy barriers to rotation of the camphanyl group in the PPh₃ and PPhMe₂ complexes. The X-ray crystal structure of CamPO₃H₂ is also reported, and consists of hydrogen-bonded hexameric aggregates, which assemble to form a columnar structure containing hydrophilic phosphonic acid channels surrounded by a sheath of bulky, hydrophobic camphanyl groups.

year: 2011

title: Rheology and Flow Emplacement Processes of the 1954 Lavas, Mount Ngauruhoe

authors: Sanders, Fiona

subjects: Ngauruhoe

abstract: The rheology and emplacement dynamics of basaltic and rhyolitic lava flows have been studied extensively, leading to the development of numerous rheological and flow behaviour models; however, the flow dynamics of more intermediate composition lavas, particularly those emplaced on relatively steep slopes, is less well-constrained. The 1954-55 eruption of Mount Ngauruhoe, a young, composite cone of the Tongariro Volcanic Centre, generated at least 11, well-preserved, spatter-fed, basaltic andesite a'a lavas on the steep, north-west flanks of the cone. The rheological properties and flow dynamics of these lavas are quantified by incorporating morphological, petrographic and geochemical data collected from these flow deposits into a range of existing numerical models, and the results compared with documented eye-witness accounts. 

The lava flow deposits are typically long, narrow, discrete units characterised by comparable morphological traits on the steep slopes of the cone and varying in dimension, morphology and flow surface features on the shallower slopes. Flow surfaces are typically autobrecciated and display a large-scale, lateral trend in clast size and morphology across flow widths. The 1954 lavas are petrographically and geochemically homogenous with no apparent trends associated with successively emplaced lava flows. The rheological properties of the lavas at the time of initial flow advance are therefore assumed to be comparable for each flow. Lava viscosity was estimated at 102 to 104 Pa s for the temperature range 1150 to 950 C. Yield strength was difficult to quantify but is assumed in this study to be relatively low (~ 25 Pa). Calculated flow velocity, effusion rate and emplacement duration are not well-constrained against documented eye-witness accounts. Mean flow velocity (0.03 to 0.04 m/s) was estimated from eye-witness reports, and used to determine flow emplacement durations between ~ 2 to 48 hours, comparable with documented duration times. Effusion rates could not be definitively quantified but flow deposit morphology and documented accounts indicate that intermittent episodes of high effusion rates over a short duration were associated with the emplacement of the 1954 lavas. 

Three major controls on the emplacement of the 1954 lava flows have been identified. Effusion rate and duration was the primary control on the development of single unit lava flows, flow channel drainage on steep slopes and in limiting run-out distances from the vent. Low initial viscosity and yield strength promoted high flow velocities on steep slopes and low surface cooling rates. Relatively short flow emplacement duration times precluded significant downflow viscosity and yield strength increases. Slope gradient and topographic obstacles were major controls on flow emplacement processes. Slope gradient was the dominant control on flow velocity, flow width and depth and surface autobrecciation, while morphology, flow path direction and surface folding were constrained by local slope gradient variations and/or topographic obstacles.

text: Rheology and Flow Emplacement Processes of the 1954 Lavas, Mount Ngauruhoe The rheology and emplacement dynamics of basaltic and rhyolitic lava flows have been studied extensively, leading to the development of numerous rheological and flow behaviour models; however, the flow dynamics of more intermediate composition lavas, particularly those emplaced on relatively steep slopes, is less well-constrained. The 1954-55 eruption of Mount Ngauruhoe, a young, composite cone of the Tongariro Volcanic Centre, generated at least 11, well-preserved, spatter-fed, basaltic andesite a'a lavas on the steep, north-west flanks of the cone. The rheological properties and flow dynamics of these lavas are quantified by incorporating morphological, petrographic and geochemical data collected from these flow deposits into a range of existing numerical models, and the results compared with documented eye-witness accounts. 

The lava flow deposits are typically long, narrow, discrete units characterised by comparable morphological traits on the steep slopes of the cone and varying in dimension, morphology and flow surface features on the shallower slopes. Flow surfaces are typically autobrecciated and display a large-scale, lateral trend in clast size and morphology across flow widths. The 1954 lavas are petrographically and geochemically homogenous with no apparent trends associated with successively emplaced lava flows. The rheological properties of the lavas at the time of initial flow advance are therefore assumed to be comparable for each flow. Lava viscosity was estimated at 102 to 104 Pa s for the temperature range 1150 to 950 C. Yield strength was difficult to quantify but is assumed in this study to be relatively low (~ 25 Pa). Calculated flow velocity, effusion rate and emplacement duration are not well-constrained against documented eye-witness accounts. Mean flow velocity (0.03 to 0.04 m/s) was estimated from eye-witness reports, and used to determine flow emplacement durations between ~ 2 to 48 hours, comparable with documented duration times. Effusion rates could not be definitively quantified but flow deposit morphology and documented accounts indicate that intermittent episodes of high effusion rates over a short duration were associated with the emplacement of the 1954 lavas. 

Three major controls on the emplacement of the 1954 lava flows have been identified. Effusion rate and duration was the primary control on the development of single unit lava flows, flow channel drainage on steep slopes and in limiting run-out distances from the vent. Low initial viscosity and yield strength promoted high flow velocities on steep slopes and low surface cooling rates. Relatively short flow emplacement duration times precluded significant downflow viscosity and yield strength increases. Slope gradient and topographic obstacles were major controls on flow emplacement processes. Slope gradient was the dominant control on flow velocity, flow width and depth and surface autobrecciation, while morphology, flow path direction and surface folding were constrained by local slope gradient variations and/or topographic obstacles.

year: 2010

title: Through the eyes of whānau: Destruction of cultural identity through education

authors: Ngaamo, Raewyn Brenda

subjects: Māori

abstract: This thesis examines how the schooling experiences of a dual cultural heritage whānau influenced the development of their identity, their language and culture across three generations. Koro, Tuakana, Teina and Moko share their experiences with us and through these stories reveal how they were forced through the colonising beliefs and practices of schooling to reshape themselves in a bid to belong. The compromise and abuse of cultural identity in wider society, replicated and validated in schooling, created a vicious and dehumanising experience for each of them. School was a major site of assimilation for this whānau. They experienced racism, rejection, low expectations and cultural disconnection across the three generations. They suffered particularly as dual heritage children who experienced rejection and racial micro aggressions from both Pākehā and Māori alike. Instead of education being a means to realise their potential and to achieve success it was actually the vehicle for the destruction of their cultural identity.

text: Through the eyes of whānau: Destruction of cultural identity through education This thesis examines how the schooling experiences of a dual cultural heritage whānau influenced the development of their identity, their language and culture across three generations. Koro, Tuakana, Teina and Moko share their experiences with us and through these stories reveal how they were forced through the colonising beliefs and practices of schooling to reshape themselves in a bid to belong. The compromise and abuse of cultural identity in wider society, replicated and validated in schooling, created a vicious and dehumanising experience for each of them. School was a major site of assimilation for this whānau. They experienced racism, rejection, low expectations and cultural disconnection across the three generations. They suffered particularly as dual heritage children who experienced rejection and racial micro aggressions from both Pākehā and Māori alike. Instead of education being a means to realise their potential and to achieve success it was actually the vehicle for the destruction of their cultural identity.

year: 2019