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1. Crystal structure of the [(THF)Cs(μ-η ⁵ :η ⁵ -Cp′) ₃ Yb] _n oligomer

   https://doi.org/10.1107/S2056989020008051  

   Huh, Daniel N. ; Ziller, Joseph W. ; Evans, William J. ( July 2020 , Acta Crystallographica Section E Crystallographic Communications)

   The green compound poly[(tetrahydrofuran)tris[μ-η 5 :η 5 -1-(trimethylsilyl)cyclopentadienyl]caesium(I)ytterbium(II)], [CsYb(C 8 H 13 Si) 3 (C 4 H 8 O)] n or [(THF)Cs(μ-η 5 :η 5 -Cp′) 3 Yb II ] n was synthesized by reduction of a red THF solution of (C 5 H 4 SiMe 3 ) 3 Yb III with excess Cs metal and identified by X-ray diffraction. The compound crystallizes as a two-dimensional array of hexagons with alternating Cs I and Yb II ions at the vertices and cyclopentadienyl groups bridging each edge. This, based off the six-electron cyclopentadienyl rings occupying three coordination positions, gives a formally nine-coordinate tris(cyclopentadienyl) coordination environment to Yb and the Cs is ten-coordinate due to the three cyclopentadienyl rings and a coordinated molecule of THF. The complex comprises layers of Cs 3 Yb 3 hexagons with THF ligands and Me 3 Si groups in between the layers. The Yb—C metrical parameters are consistent with a 4 f 14 Yb II electron configuration.
2. Crystal structures of trans -acetyldicarbonyl(η ⁵ -cyclopentadienyl)(1,3,5-triaza-7-phosphaadamantane)molybdenum(II) and trans -acetyldicarbonyl(η ⁵ -cyclopentadienyl)(3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane)molybdenum(II)

   https://doi.org/10.1107/S2056989020003679  

   Anstey, Mitchell R. ; Bost, John L. ; Grumman, Anna S. ; Kennedy, Nicholas D. ; Whited, Matthew T. ( April 2020 , Acta Crystallographica Section E Crystallographic Communications)

   The title compounds, [Mo(C 5 H 5 )(COCH 3 )(C 6 H 12 N 3 P)(CO) 2 ], (1), and [Mo(C 5 H 5 )(COCH 3 )(C 9 H 16 N 3 O 2 P)(C 6 H 5 ) 2 ))(CO) 2 ], (2), have been prepared by phosphine-induced migratory insertion from [Mo(C 5 H 5 )(CO) 3 (CH 3 )]. The molecular structures of these complexes are quite similar, exhibiting a four-legged piano-stool geometry with trans -disposed carbonyl ligands. The extended structures of complexes (1) and (2) differ substantially. For complex (1), the molybdenum acetyl unit plays a dominant role in the organization of the extended structure, joining the molecules into centrosymmetrical dimers through C—H...O interactions with a cyclopentadienyl ligand of a neighboring molecule, and these dimers are linked into layers parallel to (100) by C—H...O interactions between the molybdenum acetyl and the cyclopentadienyl ligand of another neighbor. The extended structure of (2) is dominated by C—H...O interactions involving the carbonyl groups of the acetamide groups of the DAPTA ligand, which join the molecules into centrosymmetrical dimers and link them into chains along [010]. Additional C—H...O interactions between the molybdenum acetyl oxygen atom and an acetamide methyl group joinmore »the chains into layers parallel to (101).« less
3. Structural diversity in copper(I) iodide complexes with 6-thioxopiperidin-2-one, piperidine-2,6-dithione and isoindoline-1,3-dithione ligands

   https://doi.org/10.1107/S2056989020009676  

   Wheaton, Amelia M. ; Guzei, Ilia A. ; Berry, John F. ( August 2020 , Acta Crystallographica Section E Crystallographic Communications)

   Copper(I) iodide complexes are well known for displaying a diverse array of structural features even when only small changes in ligand design are made. This structural diversity is well displayed by five copper(I) iodide compounds reported here with closely related piperidine-2,6-dithione (SNS), isoindoline-1,3-dithione (SNS6), and 6-thioxopiperidin-2-one (SNO) ligands: di-μ-iodido-bis[(acetonitrile-κ N )(6-sulfanylidenepiperidin-2-one-κ S )copper(I)], [Cu 2 I 2 (CH 3 CN) 2 (C 5 H 7 NOS) 2 ] ( I ), bis(acetonitrile-κ N )tetra-μ 3 -iodido-bis(6-sulfanylidenepiperidin-2-one-κ S )- tetrahedro -tetracopper(I), [Cu 4 I 4 (CH 3 CN) 4 (C 5 H 7 NOS) 4 ] ( II ), catena -poly[[(μ-6-sulfanylidenepiperidin-2-one-κ 2 O : S )copper(I)]-μ 3 -iodido], [CuI(C 5 H 7 NOS)] n ( III ), poly[[(piperidine-2,6-dithione-κ S )copper(I)]-μ 3 -iodido], [CuI(C 5 H 7 NS 2 )] n ( IV ), and poly[[(μ-isoindoline-1,3-dithione-κ 2 S : S )copper(I)]-μ 3 -iodido], [CuI(C 8 H 5 NS 2 )] n ( V ). Compounds I and II crystallize as discrete dimeric and tetrameric complexes, whereas III , IV , and V crystallize as polymeric two-dimensional sheets. To the best of our knowledge, compound III is the first instance of an extended hexagonal [Cu 3 I 3 ] structure that is notmore »supported by bridging ligands. Structures I , II , and IV display weak to moderately strong Cu...Cu cuprophilic interactions [Cu...Cu internuclear distances range between 2.5803 (10) and 2.8485 (14) Å]. All structures except III display weak hydrogen-bonding interactions between the N—H of the ligand and the μ 2 and μ 3 -I − atoms. Structure III contains classical N–H...O interactions between the SNO ligands that connect the molecules in a three-dimensional framework. Complex V features π–π stacking interactions between the aryl rings of the SNS6 ligands within the same polymeric sheet. In structure IV , there were three partially occupied solvent molecules of dichloromethane and one partially occupied molecule of acetonitrile present in the asymmetric unit. The SQUEEZE routine [Spek (2015). Acta Cryst . C 71 , 9–18] was used to correct the diffraction data for diffuse scattering effects and to identify the solvent molecules. The given chemical formula and other crystal data do not take into account the solvent molecules.« less
4. Laboratory and Astronomical Detection of the SiP Radical (X ² Π _i ): More Circumstellar Phosphorus

   https://doi.org/10.3847/2041-8213/ac9d9b  

   Koelemay, L. A. ; Burton, M. A. ; Singh, A. P. ; Sheridan, P. M. ; Bernal, J. J. ; Ziurys, L. M. ( November 2022 , The Astrophysical Journal Letters)

   The millimeter-wave spectrum of the SiP radical (X²Π_i) has been measured in the laboratory for the first time using direct-absorption methods. SiP was created by the reaction of phosphorus vapor and SiH₄in argon in an AC discharge. Fifteen rotational transitions (J+ 1 ←J) were measured for SiP in the Ω = 3/2 ladder in the frequency range 151–533 GHz, and rotational, lambda doubling, and phosphorus hyperfine constants determined. Based on the laboratory measurements, SiP was detected in the circumstellar shell of IRC+10216, using the Submillimeter Telescope and the 12 m antenna of the Arizona Radio Observatory at 1 mm and 2 mm, respectively. Eight transitions of SiP were searched: four were completely obscured by stronger features, two were uncontaminated (J= 13.5 → 12.5 and 16.5 → 15.5), and two were partially blended with other lines (J= 8.5 → 7.5 and 17.5 → 16.5). The SiP line profiles were broader than expected for IRC+10216, consistent with the hyperfine splitting. From non-LTE radiative transfer modeling, SiP was found to have a shell distribution with a radius ∼300R_*, and an abundance, relative to H₂, off∼ 2 × 10⁻⁹. From additional modeling, abundances of 7 × 10⁻⁹and 9 × 10⁻¹⁰were determined for CPmore »and PN, respectively, both located in shells at 550–650R_*. SiP may be formed from grain destruction, which liberates both phosphorus and silicon into the gas phase, and then is channeled into other P-bearing molecules such as PN and CP.

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5. Contrasting the Mechanism of H ₂ Activation by Monomeric and Potassium‐Stabilized Dimeric Al ^I Complexes: Do Potassium Atoms Exert any Cooperative Effect?

   https://doi.org/10.1002/chem.202103082  

   Villegas‐Escobar, Nery ; Toro‐Labbé, Alejandro ; Schaefer, III., Henry F. ( October 2021 , Chemistry – A European Journal)

   Aluminyl anions are low‐valent, anionic, and carbenoid aluminum species commonly found stabilized with potassium cations from the reaction of Al‐halogen precursors and alkali compounds. These systems are very reactive toward the activation ofσ‐bonds and in reactions with electrophiles. Various research groups have detected that the potassium atoms play a stabilization role via electrostatic and cationinteractions with nearby (aromatic)‐carbocyclic rings from both the ligand and from the reaction with unsaturated substrates. Since stabilizing K⋯H bonds are witnessed in the activation of this class of molecules, we aim to unveil the role of these metals in the activation of the smaller and less polarizable H₂molecule, together with a comprehensive characterization of the reaction mechanism. In this work, the activation of H₂utilizing a NON‐xanthene‐Al dimer, [K{Al(NON)}]₂(D) and monomeric, [Al(NON)]⁻(M) complexes are studied using density functional theory and high‐level coupled‐cluster theory to reveal the potential role of K⁺atoms during the activation of this gas. Furthermore, we aim to reveal whetherDis more reactive thanM(or vice versa), or if complicity between the two monomer units exits within theDcomplex toward the activation of H₂. The results suggest that activation energies using the dimeric and monomeric complexes were found to be very close (around 33 kcal mol⁻¹).more »However, a partition of activation energies unveiled that the nature of the energy barriers for the monomeric and dimeric complexes are inherently different. The former is dominated by a more substantial distortion of the reactants (and increased interaction energies between them). Interestingly, during the oxidative addition, the distortion of the Al complex is minimal, while H₂distorts the most, usually over 0.77. Overall, it is found here that electrostatic and induction energies between the complexes and H₂are the main stabilizing components up to the respective transition states. The results suggest that the K⁺atoms act as stabilizers of the dimeric structure, and their cooperative role on the reaction mechanism may be negligible, acting as mere spectators in the activation of H₂. Cooperation between the two monomers inDis lacking, and therefore the subsequent activation of H₂is wholly disengaged.

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