| 1. |
- Stokes, F.A., et al.
(författare)
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Structure and Bonding of the Manganese(II) Phosphide Complex (t-BuPH(2))(eta(5)-Cp)Mn{mu-(t-BuPH)}(2)Mn(Cp)(t-BuPH(2))
- 2012
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Ingår i: Organometallics. - : American Chemical Society (ACS). - 0276-7333 .- 1520-6041. ; 31:1, s. 23-26
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Tidskriftsartikel (refereegranskat)abstract
- Rather than achieving bis-deprotonation of the phosphine, reaction of Cp2Mn (Cp = cyclopentadienyl) with t-BuPH2 at room temperature yields monodeprotonation of half of the available phosphine in the product (t-BuPH2)(η5-Cp)Mn{μ-(t-BuPH)}2Mn(Cp)(t-BuPH2) (1). This complex comprises a Mn(II) phosphide and is a dimer in the solid state, containing a Mn2P2 diamond core. Consistent with the observation of a relatively short intermetal distance of 2.8717(4) Å in 1, DFT analysis of the full structure points to a singlet ground state stabilized by a direct Mn–Mn single bond. This is in line with the diamagnetic character of 1 and an 18-electron count at Mn.
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| 2. |
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| 3. |
- Bengtsson, Gösta, et al.
(författare)
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The kinetics and mechanism of oxidation of hydroxylamine by iron(III)
- 2002
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Ingår i: Journal of the Chemical Society. Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1472-7773 .- 1364-5447. ; :12, s. 2548-2552
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Tidskriftsartikel (refereegranskat)abstract
- The kinetics of oxidation of hydroxylamine by iron() have been studied spectrophotometrically. The effects of pH, reactant and product concentrations led to two experimental rate expressions. The results obtained are consistent with a mechanism dependent on the relative iron(III)-to-hydroxylamine concentrations; an excess of iron() gives a stoichiometry of 2 : 1 for the total reaction and N2O as the oxidation product, whereas at equal amounts or excess of hydroxylamine the stoichiometry reduces to 1 : 1 with N-2 as the main product. In the latter case the rate expression d[ Fe(III)]/dt = k[Fe(III)](2) [NH2OH](2) /[Fe(III)](2) [H+](4) is obtained. The consistent mechanism identifies two pre-equilibria and the reaction of two different nitrogen-containing intermediates as the rate-determining step depending on the reactant ratios. The proposed mechanism does also involve the metal hydroxide complex Fe(OH)(2+), in agreement with previous results.
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| 4. |
- Guo, Y., et al.
(författare)
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Reversible Structural Isomerization of Nature's Water Oxidation Catalyst Prior to O-O Bond Formation
- 2022
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 144:26, s. 11736-11747
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Tidskriftsartikel (refereegranskat)abstract
- Photosynthetic water oxidation is catalyzed by a manganese-calcium oxide cluster, which experiences five "S-states" during a light-driven reaction cycle. The unique "distorted chair"-like geometry of the Mn4CaO5(6)cluster shows structural flexibility that has been frequently proposed to involve "open" and "closed"-cubane forms from the S1 to S3states. The isomers are interconvertible in the S1 and S2states, while in the S3state, the open-cubane structure is observed to dominate inThermosynechococcus elongatus (cyanobacteria) samples. In this work, using density functional theory calculations, we go beyond the S3+Yzstate to the S3nYz•→ S4+Yzstep, and report for the first time that the reversible isomerism, which is suppressed in the S3+Yzstate, is fully recovered in the ensuing S3nYz•state due to the proton release from a manganese-bound water ligand. The altered coordination strength of the manganese-ligand facilitates formation of the closed-cubane form, in a dynamic equilibrium with the open-cubane form. This tautomerism immediately preceding dioxygen formation may constitute the rate limiting step for O2formation, and exert a significant influence on the water oxidation mechanism in photosystem II.
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| 5. |
- Kloo, Mattias, et al.
(författare)
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Longitudinal links of authoritative teaching and bullying victimization in upper elementary school
- 2024
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Ingår i: Educational Psychology. - : ROUTLEDGE JOURNALS, TAYLOR & FRANCIS LTD. - 0144-3410 .- 1469-5820.
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to investigate whether authoritative teaching at the classroom-level was associated with bullying victimisation, and how this association evolved over the course of upper elementary school (i.e. in grades 4 through 6) by estimating whether the association declined with time. Data came from the first three waves of an ongoing longitudinal project examining social and moral correlates of school bullying. Survey data were analysed from 1,830 students. Multilevel analyses showed that teachers who displayed high levels of warmth, caring, and supportiveness together with high levels of structure, control, and demandingness tended to have students who reported less bullying victimisation. This association between authoritative teaching at the classroom-level and bullying victimisation, while still significant, decreased over the course of the two-year study.
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| 6. |
- Kloo, Y., et al.
(författare)
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Reaching net-zero in the chemical industry—A study of roadmaps for industrial decarbonisation
- 2024
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Ingår i: Renewable and Sustainable Energy Transition. - 2667-095X. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Striving to mitigate climate change, the European Union has adopted net-zero greenhouse gas emissions as a target for 2050. In this paper, European chemical industry roadmaps from the past six years are assessed and compared to uncover how the industry envisions its role in the transition to net-zero emissions. The roadmaps are assessed in terms of ambition level, technology and feedstock strategies, investment needs and costs, agency and dependency on other actors, as well as timeline and concretion. Although net-zero pathways are often drawn out in the roadmaps, some also choose to emphasize and argue for less ambitious pathways with emission reductions of only 40–60 %. The roadmaps vary widely in terms of the importance they assign to mechanical and chemical recycling, switching to biogenic carbon and carbon dioxide as feedstock, electrification and hydrogen, and carbon capture and storage. A commonality though, is that low-tech or near-term mitigation pathways such as demand reduction, reuse or material efficiency are seldom included. High investment needs are generally highlighted, as well as the need for policy to create enabling conditions, whereas the agency and responsibility of the chemical industry itself is downplayed. Our analysis highlights that the chemical industry does not yet have a strong and shared vision for pathways to net-zero emissions. We conclude that such a future vision would benefit from taking a whole value chain approach including demand-side options and consideration of scope 3 emissions.
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| 7. |
- Kopylovich, M. N., et al.
(författare)
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Facile Ni(II)/ketoxime-mediated conversion of organonitriles into imidoylamidine ligands. Synthesis of imidoylamidines and acetyl amides
- 2003
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 42:22, s. 7239-7248
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Tidskriftsartikel (refereegranskat)abstract
- Treatment of alkyl nitriles with NiX2.6H(2)O (X = Cl, NO3) and 2-propanone oxime, followed by (X = Cl) addition of [i-Pr4N](NO3) for precipitation of the product, resulted in the formation of amidinium nitrates [RC(=NH2)NH2](NO3) (R = Me, Et, n-Pr), The reaction went to another direction with NiX2.2H(2)O, i.e., the reaction between neat RCN (R = Me, Et, n-Pr, i-Pr, n-Bu, CH2Cl, CH2C6H4OMe-p) and NiCl2.2H(2)O/2-propanone oxime (other ketoximes can also be used) gave the (imidoylamidine)Ni(II) complexes [Ni{(N) under bar (H)=C(R)NHC(R)=(N) under barH}(2)](2+) (1(2+)-7(2+)). The latter were isolated in good yields (65-91%) as the bis-chloride salts 1.Cl-2-6.Cl-2 and the mixed salt 7.(Cl)(p-MeOC6H4CH2CO2). Remarkably, the latter transformation does not proceed at all if NiCl2.2H(2)O or the ketoxime are taken alone. Liberation of imidoylamidines was performed for one alkyl-containing complex [2.Cl-2] and one benzyl-containing complex [7.(Cl)(p-MeOC6H4CH2CO2)], by (i) addition of HBF4.Et2O to the acetonitrile solution of the complexes to yield [N(H)=C(R)NHC(R)=NH].2HBF(4) (R = Et 8 and R = CH2C6H4OMe-p 9) or (ii) substitution for ethanediamine (en) with following precipitation of the complex [Ni(en)(3)]Cl-2 with formation of free N(H) C(R)NHC(R)=NH (R = Et 10 and R = CH2C6H4OMe-p 11). In contrast to the liberation in nonaqueous media, treatment of 2.Cl-2 and 7.(CI)(P-MeOC6H4CH2CO2) with Na(2)EDTA.2H(2)O in water-methanol solutions led to substitution and hydrolysis to furnish the acyl amides {EtC(=O)} 2NH (12) and {p-MeOC6H4CH2C(=0)}(2)NH (13). Alternatively, 12 and 13 were obtained by hydrolysis of 10 and 11 in water at pH ca. 8.5. It was shown that the oxime complexes trans-[NiCl2(C4H8C=NOH)(4)] (14) or cis-[Ni(O,O-NO3)(2)(C4H8C=NOH)(2)] (15) can be intermediates in the formation of amidines and imidoylamidines. The sequence of the Ni(II)/oxime mediated formation of (imidoylamidine)Ni complexes and liberation (or hydrolytic liberation) of the ligands opens up a novel, facile and environmentally benign route to imidoylamidines and acyl amides.
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| 8. |
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| 9. |
- Lyubimtsev, A. L., et al.
(författare)
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The structure and bonding of Ni3Sn
- 2002
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Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 340:02-jan, s. 167-172
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of Ni3Sn was calculated at ab initio levels for the crystal structure of the low-temperature modification of Ni3Sn refined upon data of single-crystal X-ray diffractometry (P6(3)/mmc, a=5.2950(7), c=4.247(1) Angstrom R=0.0288). The calculations were made with the use of fixed Gaussian (CRYSTAL98 software) and energy-dependent (Stuttgart TB-LMTO-ASA software) basis sets. Difference electron charge density maps were analysed and compared with that of a hypothetical hcp Ni in order to understand bonding in Ni3Sn. It was found that bonding in Ni3Sn has multicentre character with Ni-Sn interaction stronger than Ni-Ni one.
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| 10. |
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| 11. |
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| 12. |
- Sabounchei, J. S., et al.
(författare)
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Rhodium complexes containing O-bonded NHxMe2-xCHO (x=0, 1, 2) : X-ray structure of Rh(PPh3)(3)(OCHNHMe) CIO4
- 2001
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Ingår i: Helvetica Chimica Acta. - 0018-019X .- 1522-2675. ; 84:10, s. 3075-3083
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Tidskriftsartikel (refereegranskat)abstract
- Displacement of norbornadiene (nbd; bicyclo[2.2.1]hepta-2,5-diene) from [Rh(PPh3)(2)(nbd)]ClO4 by hydrogenation in the presence of PPh3 and formamide or Me-substituted derivatives, results in the formation of O-bonded formamide complexes [Rh(PPh3)(3)(OCHNHxMe2-x)]ClO4 (x=0, 1, 2) rather than N-bonded derivatives. These have been characterised by spectroscopic measurements and, in the case of [Rh(PPh3)(3)(OCHNHMe)]ClO4, by X-ray crystallography. All undergo oxidative addition with H-2, and the rates of ligand exchange in the Rh-I and Rh-III complexes have been determined by magnetisation-transfer measurements.
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| 13. |
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