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1. Functionalized planar aromatic rings as precursors to energetic N , N ′-(4,6-dinitro-1,3-phenylene)dinitramide and its salts

   https://doi.org/10.1039/d2qm00092j  

   Singh, Jatinder; Lal, Sohan; Staples, Richard J.; Shreeve, Jean’ne M. (March 2022, Materials Chemistry Frontiers)

   Functionalization of planar aromatic rings is very straightforward, up scalable, and economical in comparison with many azole, caged, linear or cyclic structures. In our present work, a facile synthesis of N , N ′-(4,6-dinitro-1,3-phenylene)dinitramide (3) is obtained by a single-step nitration of 4,6-dinitrobenzene-1,3-diamine (2). Compound 3 exhibits a surprisingly high density of 1.90 g cm −3 at 100 K (1.87 g cm −3 at 298 K). Its reactions with bases result in the formation of a series of energetic salts (4–7) which exhibit relatively high densities (1.74 to 1.83 g cm −3 ), and acceptable thermal sensitivities (177 to 253 °C). Energetic salt formation increases intermolecular hydrogen bonding while the planarity of the aromatic ring maximizes weak non-covalent interactions (π-stacking, cation/π, anion-π, X-H/π, etc. ,). The synergetic effect of these stabilizing interactions plays a crucial role in increasing thermal stability and decreasing sensitivity toward the external stimuli. Overall, these easily accessible new energetic compounds exhibit high densities and good denotation properties with potential applications as new high-energy materials. 

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2. Engendering reactivity at group 5-heteroatom multiple bonds via π-loading

   https://doi.org/10.1039/D2SC02706B  

   Fostvedt, Jade I.; Mendoza, Jocelyne; Lopez-Flores, Sacy; Alcantar, Diego; Bergman, Robert G.; Arnold, John (July 2022, Chemical Science)

   In this Perspective, we discuss the strategy of π-loading, i.e. , coordination of two or more strongly π-donating ligands to a single metal center, as it applies to promoting reactivity at group 5 transition metal-imido groups. When multiple π-donor ligands compete to interact with the same symmetrically-available metal d π orbitals, the energy of the imido-based frontier molecular orbitals increases, leading to amplified imido-based reactivity. This strategy is of particular relevance to group 5 metals, as mono(imido) complexes of these metals tend to be inert at the imido group. Electronic structure studies of group 5 bis(imido) complexes are presented, and examples of catalytically and stoichiometrically active group 5 bis(imido) and chalcogenido–imido complexes are reviewed. These examples are intended to encourage future work exploring π-loaded bis(imido) systems of the group 5 triad. 

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3. Crystal structure of cis -[1,2-bis(diphenylphosphanyl)ethene-κ ² P , P ′]dichloridoplatinum(II) chloroform disolvate: a new polymorph

   https://doi.org/10.1107/S2056989018008836  

   Mugemana, Jimmy; Bender, John; Staples, Richard J.; Biros, Shannon M. (July 2018, Acta Crystallographica Section E Crystallographic Communications)

   The title compound, [PtCl 2 (C 26 H 22 P 2 )]·2CHCl 3 (I), is the third monoclinic polymorph of this platinum(II) complex involving the bidentate ligand cis -1,2-bis(diphenylphosphanyl)ethylene ( cis -dppe) [for the others, see: Oberhauser et al. (1998 a ). Inorg. Chim. Acta , 274 , 143–154, and Oberhauser et al. (1995). Inorg. Chim. Acta , 238 , 35–43]. The structure of compound (I) was solved in the space group P 2 1 / c , with one complex molecule in the asymmetric unit along with two solvate chloroform molecules. The Pt II atom is ligated by two P and two Cl atoms in the equatorial plane and has a perfect square-planar coordination sphere. In the crystal, the complex molecule is linked to the chloroform solvate molecules by C—H...Cl hydrogen bonds and face-on C—Cl...π interactions. There are also weak offset π–π interactions present [intercentroid distances are 3.770 (6) and 4.096 (6) Å], linking the molecules to form supramolecular sheets that lie in the bc plane. 

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4. N -[6-(Dimethylamino)-9-phenyl-3 H -telluroxanthen-3-ylidene]- N -methylmethanaminium hexafluorophosphate monoclinic polymorph

   https://doi.org/10.1107/S2414314621005459  

   Myers, Shea; Johnson, Patrick; Benedict, Jason B (June 2021, IUCrData)

   The title compound C₂₃H₂₃N₂Te⁺·PF₆⁻, is a monoclinic polymorph of the previously reported triclinic structure [Calitreeet al.(2007).Organometallics,26, 6248–6257]. In the crystal, parallel offset π–π stacking [shortest centroid–centroid separation = 3.9620 (9) Å] and ionic interactions help to establish the packing. 

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5. Study of through-space substituent–π interactions using N -phenylimide molecular balances

   https://doi.org/10.1039/C9QO00195F  

   Hwang, Jungwun; Li, Ping; Vik, Erik C.; Karki, Ishwor; Shimizu, Ken D. (April 2019, Organic Chemistry Frontiers)

   Substituent–π interactions associated with aromatic stacking interactions were experimentally measured using a small N -phenylimide molecular balance model system. The direct interaction of the substituent (NH 2 , CH 3 , OH, F, Br, CF 3 and NO 2 ) with an aromatic ring was measured in the absence of the aromatic stacking interactions in solution. The measured substituent–π energies were found to correlate well with the Hammett σ m parameter similar to the substituent effects observed in aromatic stacking systems. The persistent electrostatic trends in substituent effects can arise from the direct electrostatic interactions between substituents and opposing π-systems. 

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