The complex diberyllocene, CpBeBeCp (Cp, cyclopentadienyl anion), has been the subject of numerous chemical investigations over the past five decades yet has eluded experimental characterization. We report the preparation and isolation of the compound by the reduction of beryllocene (BeCp2) with a dimeric magnesium(I) complex and determination of its structure in the solid state by means of x-ray crystallography. Diberyllocene acts as a reductant in reactions that form beryllium-aluminum and beryllium-zinc bonds. Quantum chemical calculations indicate parallels between the electronic structure of diberyllocene and the simple homodiatomic species diberyllium (Be2). Description Editor’s summary Most people who have heard of beryllium know of it as a structural component of emeralds. Its molecular chemistry is more obscure but has provoked decades of controversy over whether the element can be coaxed into bonding with itself. Boronski et al. now report a long, elusive example of a molecule stable in solid state at room temperature that features a beryllium–beryllium bond (see the Perspective by Dutton). Each beryllium center is also bonded to a cyclopentadienyl ligand. The compound was characterized by x-ray crystallography and reacted reductively with metal iodides to form bonds with aluminum and zinc. —Jake Yeston A stable compound featuring a beryllium-beryllium bond has been synthesized and characterized in solution and solid state.

Diberyllocene, a stable compound of Be(I) with a Be–Be bond

The emerging field of 3D electron diffraction (3D ED) opens new opportunities for structure determination from sub-micrometre-sized crystals. Although the foundations of this technology emerged earlier, the past decade has seen developments in cryo-electron microscopy and (X-ray) crystallography that particularly enable the widespread use of 3D ED. This Perspective describes to chemists and chemical crystallographers just how similar electron and X-ray diffraction are and discusses their complementary aspects. We wish to establish 3D ED in the broader chemistry community, such that electron crystallography becomes a common part of the analytical chemistry toolkit. With a suitable instrument at their disposal, every skilled crystallographer can quickly learn to perform structure determinations using 3D ED. Although a stalwart in materials science, electron diffraction has only recently become popular for characterizing molecular structures. This Perspective describes practical aspects of the method, which affords complementary information to X-ray and neutron diffraction.

Establishing electron diffraction in chemical crystallography

Synthetic Doping of Diamondoids through Skeletal Editing.

The positions of hydrogen atoms in molecules are fundamental in many aspects of chemistry. Nevertheless, most molecular structures are obtained from refinements of X-ray data exploiting the independent atom model (IAM), which uses spherical atomic densities and provides bond lengths involving hydrogen atoms that are too short compared to the neutron reference values. To overcome the IAM shortcomings, the wave function-based Hirshfeld atom refinement (HAR) method has been recently proposed, emerging as a promising strategy able to give element-hydrogen bond distances in excellent agreement with the neutron ones in terms of accuracy and precision. In this Letter, we propose a significant improvement of HAR based on the idea of describing the crystal environment explicitly in the underlying wave function calculation through a quantum mechanical embedding strategy that exploits extremely localized molecular orbitals. Test-bed refinements on a crystal structure characterized by strong intermolecular interactions are also discussed.

/pdf/climbing-jacob-s-ladder-of-structural-refinement-l97keou5co.pdf

Climbing Jacob's Ladder of Structural Refinement: Introduction of a Localized Molecular Orbital-Based Embedding for Accurate X-ray Determinations of Hydrogen Atom Positions.

Abstract The cobalt (II) complexes have been synthesized from the reaction of the cationic entities (3,4-dimethylaniline ( 1 ) and histamine ( 2 )) with metallic salt CoCl 2 ⋅6H 2 O and thiocyanate ion (SCN − ) as a ligand in H 2 O/ethanolic solution and processing by the evaporation crystal growth method at room temperature to get crystals. The synthesized complex has been fully characterized by single-crystal X-ray diffraction. UV–Visible, FTIR spectroscopy, TGA analysis, and DFT circulations were also performed. The crystal structural analysis reveals that the solid ( 1 ) {[Co(SCN) 4 ] (C 8 H 12 N) 3 }·Cl crystallizes in the monoclinic system with the space group P2 1 /n and the solid (2) {[Co(SCN) 4 ](C 5 H 11 N 3 ) 2 }·2Cl crystallizes in the monoclinic space group P2 1 /m. Metal cations are joined into corrugated chains parallel to the b -axis direction in ( 1 ) and ( 2 ) by four thiocyanate anions. The crystal structures of ( 1 ) and ( 2 ) were calculated using XRPD data, indicating that they are closely connected to the DRX mono-crystal results. Different interactions pack the system into a ring formed by N–H⋯Cl and N–H⋯S hydrogen bonds. C–H⋯π and the π⋯π stacking of anilinuim ring for ( 1 ) and N–H⋯S intermolecular interactions for ( 1 ) and ( 2 ) increase the crystals' robustness. Hirshfeld surface analysis cum 2D fingerprint plots visualize the main intermolecular interactions with their contributions in the solid-state phase. The molecular geometries of both complexes obtained from the crystal structure were used for quantum chemical calculation. Here, frontier orbital analysis and electrostatic potential illustrate the chemical reactivities of metal–organic complexes. QTAIM and NCI analysis reveal the strength of interactions at the electronic level. 

/pdf/self-assembly-of-new-cobalt-complexes-based-on-co-scn-4-blscwnlj.pdf

Self-assembly of new cobalt complexes based on [Co (SCN)4], synthesis, empirical, antioxidant activity, and quantum theory investigations

The relationship between the structure and the properties of a drug or material is a key concept of chemistry. Knowledge of the three-dimensional structure is considered to be of such importance that almost every report of a new chemical compound is accompanied by an X-ray crystal structure – at least since the 1970s when diffraction equipment became widely available. Crystallographic software of that time was restricted to very limited computing power, and therefore drastic simplifications had to be made. It is these simplifications that make the determination of the correct structure, especially when it comes to hydrogen atoms, virtually impossible. We have devised a robust and fast system where modern chemical structure models replace the old assumptions, leading to correct structures from the model refinement against standard in-house diffraction data using no more than widely available software and desktop computing power. We call this system NoSpherA2 (Non-Spherical Atoms in Olex2). We explain the theoretical background of this technique and demonstrate the far-reaching effects that the improved structure quality that is now routinely available can have on the interpretation of chemical problems exemplified by five selected examples.

/pdf/accurate-crystal-structures-and-chemical-properties-from-4rpnpljxnl.pdf

Accurate crystal structures and chemical properties from NoSpherA2

In order to address the loss of crystallographic training opportunities resulting from the cancelation of conventional schools around the world due to the COVID-19 pandemic, we have started an online crystallography school with live lectures and live Q&A using Zoom Webinar. Since we were trying to reach a large audience in a relatively short period, we have limited the school to ten 1 h lectures covering practical aspects of small molecule crystallography including data collection, data processing, and structure solution. In the school, we also covered some advanced topics that students commonly see in their work: absolute structure determination, twinning, and disorder. To round out the education, we provided lectures on macromolecular crystallography and powder diffraction. For students to practice on their own, we used freely available data reduction and structure solution software, as well as datasets with which to practice. To give students credit for course completion, we provided an online exam and an electronic certificate of completion. In this editorial, we will provide some insight into the issues of holding lectures with up to 750 students of very diverse backgrounds and review the efficacy of the school in teaching crystallography for the two cohorts of students.

Teaching a large-scale crystallography school with Zoom Webinar

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Accurate crystal structures and chemical properties from NoSpherA2

Teaching a large-scale crystallography school with Zoom Webinar