title: Isopolyoxometalates derived from arylstibonic acids with "reverse-Keggin ion" structures based on [M(RSb) ₁₂O ₂₈] cores, M = Co(ii) or Zn(ii).

authors: Nicholson, Brian K.

subjects: Keggin ions

abstract: The preparations and structures are described of four new polyoxostibonates, [Co(p-MeC ₆H ₄Sb) ₁₂O ₂₈{Co(H ₂O) ₃} ₄]Cl ₂₋ 6H ₂O, [Co(p-ClC ₆H ₄Sb)₁₂O ₂₈{Co(H ₂O) ₃} ₄]Cl₂₋ 22H ₂O, (PhCH ₂NMe ₃) ₂[Zn(p-ClC ₆H ₄Sb) ₁₂O ₂₈Zn ₄Cl₂•₅₄ Br ₁•₄₆]•8MeCN•H ₂O and [BaCoH ₄(p-MeC ₆H ₄Sb)O ₂₈] •5H₂O. Each of these has a framework of 12 (RSb) groups linked by 28 O atoms, with one transition metal ion in a tetrahedral site in the centre. Other metal ions are coordinated to the polyhedral faces. Three of the complexes have the ε Keggin ion geometry, while the fourth is a δ isomer.

text: Isopolyoxometalates derived from arylstibonic acids with "reverse-Keggin ion" structures based on [M(RSb) ₁₂O ₂₈] cores, M = Co(ii) or Zn(ii). The preparations and structures are described of four new polyoxostibonates, [Co(p-MeC ₆H ₄Sb) ₁₂O ₂₈{Co(H ₂O) ₃} ₄]Cl ₂₋ 6H ₂O, [Co(p-ClC ₆H ₄Sb)₁₂O ₂₈{Co(H ₂O) ₃} ₄]Cl₂₋ 22H ₂O, (PhCH ₂NMe ₃) ₂[Zn(p-ClC ₆H ₄Sb) ₁₂O ₂₈Zn ₄Cl₂•₅₄ Br ₁•₄₆]•8MeCN•H ₂O and [BaCoH ₄(p-MeC ₆H ₄Sb)O ₂₈] •5H₂O. Each of these has a framework of 12 (RSb) groups linked by 28 O atoms, with one transition metal ion in a tetrahedral site in the centre. Other metal ions are coordinated to the polyhedral faces. Three of the complexes have the ε Keggin ion geometry, while the fourth is a δ isomer.

year: 2012

title: Cycloaurated triphenylphosphine-sulfide and –selenide

authors: Kilpin, Kelly Joan

subjects: gold complexes

abstract: The first examples of cycloaurated phosphine sulfides and triphenylphosphine selenide have been synthesised; these complexes are fairly rare examples of gold(III) complexes with potentially reducing sulfur- and selenium-donor ligands. The cycloaurated complex (AuCl₂ (2-C₆H₄P(S)Ph₂) was synthesised in good yield by transmetallation of the organomercury precursor Hg(2-C₆H₄P(S)Ph₂)₂ with Me₄N[AuCl₄]. A route to the chloro-mercury analogue ClHg(2-C₆H₄P(S)Ph₂) was developed by reaction of the cyclomanganated triphenylphosphine sulfide (CO)₄Mn(2-C₆H₄P(S)Ph₂) with HgCl₂; this mercury substrate was also used in the synthesis of AuCl₂(2-C₆H₄P(S)Ph₂). The cycloaurated triphenylphosphine selenide complex AuCl₂(2-C₆H₄P(Se)Ph₂) was synthesised by an analogous methodology using the new phosphine selenide Hg(2-C₆H₄P(Se)Ph₂)₂ [prepared from Hg(2-C₆H₄PPh₂)₂ and elemental Se under sonication]. The phosphonamidic analogue AuCl₂(2-C₆H₄P(S)(Net₂)₂) has also been synthesised from PhP(S)(Net₂)₂via lithiation and mercuration. X-Ray crystal structures of several compounds are reported, and show the presence of puckered ring systems.

text: Cycloaurated triphenylphosphine-sulfide and –selenide The first examples of cycloaurated phosphine sulfides and triphenylphosphine selenide have been synthesised; these complexes are fairly rare examples of gold(III) complexes with potentially reducing sulfur- and selenium-donor ligands. The cycloaurated complex (AuCl₂ (2-C₆H₄P(S)Ph₂) was synthesised in good yield by transmetallation of the organomercury precursor Hg(2-C₆H₄P(S)Ph₂)₂ with Me₄N[AuCl₄]. A route to the chloro-mercury analogue ClHg(2-C₆H₄P(S)Ph₂) was developed by reaction of the cyclomanganated triphenylphosphine sulfide (CO)₄Mn(2-C₆H₄P(S)Ph₂) with HgCl₂; this mercury substrate was also used in the synthesis of AuCl₂(2-C₆H₄P(S)Ph₂). The cycloaurated triphenylphosphine selenide complex AuCl₂(2-C₆H₄P(Se)Ph₂) was synthesised by an analogous methodology using the new phosphine selenide Hg(2-C₆H₄P(Se)Ph₂)₂ [prepared from Hg(2-C₆H₄PPh₂)₂ and elemental Se under sonication]. The phosphonamidic analogue AuCl₂(2-C₆H₄P(S)(Net₂)₂) has also been synthesised from PhP(S)(Net₂)₂via lithiation and mercuration. X-Ray crystal structures of several compounds are reported, and show the presence of puckered ring systems.

year: 2010

title: Tephras and New Zealand archaeology

authors: Lowe, David J.

subjects: tephrochronology

abstract: Establishing an accurate date for earliest Polynesian settlement in New Zealand is essential for understanding patterns of settlement and associated environmental impacts, and the processes and rates of cultural change in Eastern Polynesia. Tephra deposits from five volcanic centres, together with exotic sea-rafted pumice, provide isochronous constraints on the timing of earliest settlement and human impacts in northern New Zealand. A local basaltic tephra from Rangitoto Island (Auckland) and locally distributed andesitic tephras from Egmont volcano directly date human occupation to c. AD 1400–1450. Distal andesitic tephras (Tufa Trig Formation) from Mt Ruapehu, Tongariro volcanic centre, help constrain the timing of earliest anthropogenic deforestation signals in Hawke's Bay. Sea-rafted Loisels Pumice(s), although of uncertain stratigraphic reliability in places, overlies cultural remains that can be no younger than c. AD 1350 along the east coast, North Island. The regionally extensive rhyolitic Kaharoa Tephra, which erupted from Okataina volcano between c. AD  1300–1390, is the critical “settlement layer” datum for dating prehistory in the North Island: no human artefacts are recorded beneath it and the earliest inferred environmental impacts by humans are dated to c. AD  1280, just prior to its deposition. This maximum date matches the earliest radiocarbon dates derived for both settlement and human impacts from archaeological and natural sites (c. AD 1250), and implies that the onset of deforestation was essentially contemporaneous with initial settlement.
The widespread rhyolitic Taupo Tephra, which erupted from Taupo volcano c. AD 200, provides an isochronous benchmark well before earliest settlement. The tephra may coincide approximately with a putative earlier transient contact in New Zealand based on Pacific rat-bone (Rattus exulans) dates. More precise calendrical dates on the tephras—via dendrochronology or ice-core records or other dating methods—would help refine assessment of the timing of earliest settlement, while extending the distributional range of critical tephra layers, through application of crypto-tephra analysis, could lead to a greater understanding of settlement patterns.

text: Tephras and New Zealand archaeology Establishing an accurate date for earliest Polynesian settlement in New Zealand is essential for understanding patterns of settlement and associated environmental impacts, and the processes and rates of cultural change in Eastern Polynesia. Tephra deposits from five volcanic centres, together with exotic sea-rafted pumice, provide isochronous constraints on the timing of earliest settlement and human impacts in northern New Zealand. A local basaltic tephra from Rangitoto Island (Auckland) and locally distributed andesitic tephras from Egmont volcano directly date human occupation to c. AD 1400–1450. Distal andesitic tephras (Tufa Trig Formation) from Mt Ruapehu, Tongariro volcanic centre, help constrain the timing of earliest anthropogenic deforestation signals in Hawke's Bay. Sea-rafted Loisels Pumice(s), although of uncertain stratigraphic reliability in places, overlies cultural remains that can be no younger than c. AD 1350 along the east coast, North Island. The regionally extensive rhyolitic Kaharoa Tephra, which erupted from Okataina volcano between c. AD  1300–1390, is the critical “settlement layer” datum for dating prehistory in the North Island: no human artefacts are recorded beneath it and the earliest inferred environmental impacts by humans are dated to c. AD  1280, just prior to its deposition. This maximum date matches the earliest radiocarbon dates derived for both settlement and human impacts from archaeological and natural sites (c. AD 1250), and implies that the onset of deforestation was essentially contemporaneous with initial settlement.
The widespread rhyolitic Taupo Tephra, which erupted from Taupo volcano c. AD 200, provides an isochronous benchmark well before earliest settlement. The tephra may coincide approximately with a putative earlier transient contact in New Zealand based on Pacific rat-bone (Rattus exulans) dates. More precise calendrical dates on the tephras—via dendrochronology or ice-core records or other dating methods—would help refine assessment of the timing of earliest settlement, while extending the distributional range of critical tephra layers, through application of crypto-tephra analysis, could lead to a greater understanding of settlement patterns.

year: 2000