Aryl-Aryl Interactions in (aryl-perhalogenated) 1,2-Diaryldisilanes.

Mitzel NW, Linnemannstöns M, Schwabedissen J, Neumann B, Stammler H-G, Berger R. Aryl-Aryl Interactions in (aryl-perhalogenated) 1,2-Diaryldisilanes. Chemistry. 2020;26(10):2169-2173.Three 1,2-diaryltetramethyldisilanes X5C6-(SiMe2)2-C6X5 with two C6H5, C6F5 or C6Cl5 groups were studied concerning the im-por-tan-ce of London dispersion driven interactions between their aryl groups. They were prepared from 1,2-di-chlo-rotetra-methyl-disi-la-ne by salt elimination. Their structures were determi-ned in the solid state by X-ray diffraction and for free molecules by gas elec-tron-diffraction. The solid-state struc-tures of the fluori-nated and chlo-rinated derivatives are domi-na-ted by aryl-aryl inter-actions. Unex-pectedly, Cl5C6-(SiMe2)2-C6Cl5 exists exclusive-ly as eclipsed syn-conformer in the gas phase with strongly distor-ted Si-C6Cl5 units due to strong intramo-le-cular interactions. In contrast, F5C6-(SiMe2)2-C6F5 reveals wea-ker inter-actions. The contributions to the total interaction energy was analyzed by SAPT calculations. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Spectroscopic Properties, Conformation and Structure of Difluorothiophosphoryl Isocyanate in the Gaseous and Solid Phase

Schwabedissen J, Trapp PC, Stammler H-G, et al. Spectroscopic Properties, Conformation and Structure of Difluorothiophosphoryl Isocyanate in the Gaseous and Solid Phase. ChemistryOpen. 2020;9(9):913-920.Difluorothiophosphoryl isocyanate, F2P(S)NCO was characterized with UV/vis, NMR, IR (gas and Ar‐matrix), and Raman (liquid) spectroscopy. Its molecular structure was also established by means of gas electron diffraction (GED) and single crystal X‐ray diffraction (XRD) in the gas phase and solid state, respectively. The analysis of the spectroscopic data and molecular structures is complemented by extensive quantum‐chemical calculations. Theoretically, the Cs symmetric syn‐conformer is predicted to be the most stable conformation. Rotation about the P−N bond requires about 9 kJ mol−1 and the predicted existence of an anti‐conformer is dependent on the quantum‐chemical method used. This syn‐orientation of the isocyanate group is the only one found in the gas phase and contained likewise in the crystal. The overall molecular structure is very similar in gas and solid, despite in the solid state the molecules arrange through intramolecular O⋅⋅⋅F contacts into layers, which are further interconnected by S⋅⋅⋅N, S⋅⋅⋅C and C⋅⋅⋅F contacts. Additionally, the photodecomposition of F2P(S)NCO to form CO, F2P(S)N, and F2PNCO is observed in the solid Ar‐matrix

Regiochemical Control in Triptycene Formation-An Exercise in Subtle Balancing Multiple Factors

Lamm J-H, Vishnevskiy Y, Ziemann E, Neumann B, Stammler H-G, Mitzel NW. Regiochemical Control in Triptycene Formation-An Exercise in Subtle Balancing Multiple Factors. ChemistryOpen. 2018;7(1):111-114.Reactions between 1,8-dichloroanthracenes with substituents in position 10 and ortho-chloroaryne afford mixtures of 1,8,13- (syn) and 1,8,16-trichlorotriptycenes (anti). The syn/anti ratio is dependent on these substituents. Electropositive substituents like SiMe3 and GeMe3 lead to preferred formation of the syn-isomer, whereas CMe3 groups exclusively afford the anti-isomer. Different quantum chemical calculations including location of transition states give conflicting results, but indicate the importance of dispersion forces for an at least qualitative prediction of results. The syn-trichlorotriptycenes with SiMe3 and GeMe3 substituents were characterized by using NMR spectroscopy, mass spectrometry, and X-ray diffraction experiments. Triptycene represents one of a few rigid organic frameworks of D3h symmetry without any (Lewis-basic) heteroatoms. It was first synthesized by Bartlett et al. in 1942 using a multi-step procedure starting from anthracene and p-benzoquinone.[1] In 1956, Wittig and Ludwig reported a more efficient access to triptycene in one step from anthracene by reacting it with in situ-formed benzyne.[2] The symmetry and rigidity of triptycene have inspired a plethora of applications in fundamental and applied chemical research.[3-5] Substituted triptycenes are widely used, for example, as building blocks for fluorescent or non-fluorescent organic macromolecules, polymers, and liquid crystals,[3, 6] as rigid spacers in several Pd complexes used for cross coupling reactions,[7] as devices in molecular machines,[8] in crystal engineering processes,[9, 10] and as a basis for the design of highly porous organic materials with numerous applications.[11] Although the chemistry of triptycenes and their functionalization is generally in an advanced state, the 1,8,13-trisubstitution motif remains a challenge for synthesis. However, exactly this pattern is interesting to introduce three functionalities oriented in the same direction. We try to make use of such 1,8,13-trisubstituted triptycenes (also called syn-triptycenes) as rigid organic frameworks for constructing directed polydentate Lewis acids,[12, 13] but many other applications might be envisioned. syn-Triptycenes can be obtained through Diels–Alder reactions of 1,8-disubstituted anthracenes with ortho-functionalized arynes, a protocol introduced by Rogers and Averill in 1986.[14] The drawback of this method is that the corresponding anti-trisubstituted 1,8,16-isomer is always formed as the main product when, for example, Cl-functionalized anthracenes and arynes are used.[12, 14] In 2010, we reported attempts to increase the syn/anti ratio by making use of the steric interference of the (bulky) anthracene substituent at C-10 with the chlorine atom of the chloroaryne (Scheme 1). We expected this strategy to provide an increased formation of the syn-isomer. However, the steric influence of the C-10 substituent turned out to be minimal, whereas the electronic properties are dominant;[12] of all substituents tested, the biggest R=C(CH3)3 led to the formation of 100 % anti-isomer, despite the formation of an extremely deformed product by mutual repulsion of the Cl and R substituents, as indicated in Scheme 1 b

The anthropology of extraction: critical perspectives on the resource curse

Attempts to address the resource curse remain focussed on revenue management, seeking technical solutions to political problems over examinations of relations of power. In this paper, we provide a review of the contribution anthropological research has made over the past decade to understanding the dynamic interplay of social relations, economic interests and struggles over power at stake in the political economy of extraction. In doing so, we show how the constellation of subaltern and elite agency at work within processes of resource extraction is vital in order to confront the complexities, incompatibilities, and inequities in the exploitation of mineral resources

Unorthodoxy in legislation: The Hungarian experience

This paper deals with legal unorthodoxy. The main idea is to study the so-called unorthodox taxes Hungary has adopted in recent years. The study of unorthodox taxes will be preceded by a more general discussion of how law is made under unorthodoxy, and what are the special features of unorthodox legal policy. Unorthodoxy challenges equality before the law and is critical towards mass democracies. It also raises doubts on the operability of the rule of law, relying on personal skills, or loyalty, rather than on impersonal mechanisms arising from checks and balances as developed by the division of political power. Besides, for lack of legal suppositions, legislation suffers from casuistry and regulatory capture

Mutagenesis and Functional Studies with Succinate Dehydrogenase Inhibitors in the Wheat Pathogen Mycosphaerella graminicola

A range of novel carboxamide fungicides, inhibitors of the succinate dehydrogenase enzyme (SDH, EC 1.3.5.1) is currently being introduced to the crop protection market. The aim of this study was to explore the impact of structurally distinct carboxamides on target site resistance development and to assess possible impact on fitness

Connecting Planetary Composition with Formation

The rapid advances in observations of the different populations of exoplanets, the characterization of their host stars and the links to the properties of their planetary systems, the detailed studies of protoplanetary disks, and the experimental study of the interiors and composition of the massive planets in our solar system provide a firm basis for the next big question in planet formation theory. How do the elemental and chemical compositions of planets connect with their formation? The answer to this requires that the various pieces of planet formation theory be linked together in an end-to-end picture that is capable of addressing these large data sets. In this review, we discuss the critical elements of such a picture and how they affect the chemical and elemental make up of forming planets. Important issues here include the initial state of forming and evolving disks, chemical and dust processes within them, the migration of planets and the importance of planet traps, the nature of angular momentum transport processes involving turbulence and/or MHD disk winds, planet formation theory, and advanced treatments of disk astrochemistry. All of these issues affect, and are affected by the chemistry of disks which is driven by X-ray ionization of the host stars. We discuss how these processes lead to a coherent end-to-end model and how this may address the basic question.Comment: Invited review, accepted for publication in the 'Handbook of Exoplanets', eds. H.J. Deeg and J.A. Belmonte, Springer (2018). 46 pages, 10 figure