Rare examples of (high spin) Co(II) complexes with geometrically constrained tetrathioether ligands exhibit a very unusual structural isomerism, switching reversibly between tetrahedral monomers in solution and octahedral chain polymers in the solid; the crystal structures of one polymeric species and a tetrahedral monomer model compound are described.
Beginning from the first reports of COVID-19 out of China, this article provides a commentary on the actions taken by the Government of New Zealand in terms of nine themes—a national response with an elimination goal, speed, and comprehensiveness of the initial response; an evidence-based, science-led approach, prioritised on protecting lives; effective communication; leadership style which appealed to collective responsibility and attempted to de-politicise the Government’s response to the virus; flexibility of response characterised by ‘learning as you go’; oversight of coercive state powers, including a pragmatic response which attempted to defuse conflict and reserved use of ‘hard power’ to a last resort; deployment of public health interventions, and health system adaptations; the impact on Māori and marginalised communities; and economic protection and stimulus—to identify factors that might help explain why New Zealand’s pandemic response was successful and those which could have been managed better. The partially successful legal challenge brought to the four-and-a half week lockdown, the most stringent in the world, in Borrowdale v Director-General of Health, is also considered.
Contents EntryEfficient preparative routes to the new small-ring Se 3 macrocycles L 1 and L 3 and the mixed Se 2 Ndonor macrocycles L 4 and L 5 are described, together with crystal structures of L 1 and L 4 . The
IntroductionThe chemistry of thioether macrocyclic ligands has advanced significantly over the last twenty or
Treatment of O(CH2CH2SeCN)2 with Na in NH3(l), followed by dropwise addition of a thf solution of o-C6H4(CH2Br)2 at -40 degrees C leads to formation of three mixed Se/O-donor macrocycles which are separable by column chromatography, the [1 + 1] species L1, the [2 + 2] ring L2 and the [3 + 3] ring L3, of which L2 is by far the major species. Using the same starting materials, but in a high dilution cyclisation at room temperature with NaBH4 in thf/EtOH gives exclusively the [1 + 1] ring, L1. The saturated ring Se/O-donor macrocycles, L4 and L5 are obtained by simultaneous dropwise addition of solutions of O(CH2CH2SeCN)2 and Br(CH2)3Br to NaBH4 suspended in thf/EtOH. The small tridentate Se2O-donor ring, L4, is again the dominant product under these conditions (71%), although the more flexible precursors in this reaction also give rise to the larger Se4O2-donor ring, L5, as a by-product in 8% yield. These compounds are readily separated and purified by column chromatography (ethyl acetate:hexane, 1:19). The new macrocycles have been characterised by 1H, (13)C{1H} and (77)Se{1H} NMR spectroscopy and mass spectrometry, together with crystal structures of L1 and L2. Complexes of L1 and L2 with late transition metals (Pd(II), Pt(II), Cu(I) and Ag(I)) are also described.
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