New Complexes of Antimony(III) with Tridentate O,E,O-Ligands (E = O, S, Se, Te, NH, NMe) Derived from N-Methyldiethanolamine.

We synthesized a series of new antimony(III) compounds by reaction of Sb(OEt)3 with organic ligands of the type E(CH2-CH2-OH)2, with E = NH, NMe, O, S, Se, and Te. The synthesized compounds have the general composition [E(CH2-CH2-O)2]Sb(OEt). For comparison, the compound (O-CH2-CH2-S)Sb(OEt) was prepared. All compounds are characterized using NMR, IR, and Raman spectroscopy. The molecular structures of the products reveal the formation of chelate complexes, wherein the ligand molecules coordinate as tridentate O,E,O-ligands to the antimony atom. Dimer formation in the solid state allows the antimony atoms to reach pentacoordination. Quantum chemical calculations including topological analysis of electron density reveal that there are polar shared bonds between antimony and the oxygen atoms bound to antimony. The interactions between the donor atom E and the Sb atom and the interactions in the dimers can be characterized as Van der Waals interactions. The reactivity of [MeN(CH2-CH2-O)2]Sb(OEt) was investigated as an example. For this purpose, the compound reacted with a range of organic compounds such as carboxylic acids and carboxylic anhydrides and small molecules like CO2 and NH3. This study establishes a new and easy accessible class of antimony(III) compounds, provides new insights into the chemistry of antimony compounds and opens up new opportunities for further research in this field.

9-(Pyrrolidinium-1-yl)-9-boranuidabi-cyclo-[3.3.1]nona-ne.

The title compound, C12H24BN, is an adduct formed from 9-borabi-cyclo-[3.3.1]nonane (9-BBN) and pyrrolidine. It crystallizes in the triclinic space group P with three mol-ecules in the asymmetric unit, one of which has disorder of the pyrrolidine ring. The B-N bond lengths are between 1.631 (2) and 1.641 (2) Å. The boron and nitro-gen atoms are bound to one hydrogen atom each. These hydrogen atoms are in anti-periplanar orientation. Both six-membered rings of the 9-BBN unit are in a chair conformation in all three mol-ecules. Differences between the three crystallographic independent mol-ecules are found in the five-membered rings of the pyrrolidine unit. These adopt different twisted and envelope conformations.

Two polymorphs of N,N'-diphenyl-2-[1-(propyl-amino)-ethyl-idene]propanedi-amide.

Two polymorphs of the title compound, C20H23N3O2, have been isolated. Polymorph (I) crystallizes in the monoclinic space group P2 1/n and polymorph (II) in the tetra-gonal space group I4 1/a. The main difference between the two polymorphs on the mol-ecular level is the orientation of the n-propyl group. This group is anti-periplanar in (I) and synclinal in (II). The core of the mol-ecule consists of two carbamoyl units bound to an enamine unit. The most prominent features are intra-molecular N-H⋯O hydrogen bonds in both polymorphs. Both polymorphs form dimers with graph set R 2 2(12) via inter-molecular N-H⋯O hydrogen bonds. Adjacent dimers of (I) are connected via a weak C-H⋯O inter-action, resulting in a chain parallel to the crystallographic a-axis. The dimers of (II) are connected by weak C-H⋯π inter-actions, forming inter-molecular chains along the c-axis direction.

(E)-N-Phenyl-N-(phenyl-carbamo-yl)-3-[prop-yl(tri-methyl-sil-yl)amino]-acryl-amide chloro-form hemisolvate.

The title compound, C22H29N3O2Si·0.5CHCl3, crystallizes in the the triclinic space group P with two host mol-ecules and one chloro-form mol-ecule in the asymmetric unit. The core of the mol-ecule consists of a urea unit bound to a 3-amino-acryloyl group. These units are almost planar in both mol-ecules [average deviation from plane of 0.05 (6) Šin mol-ecule A and 0.04 (5) Šin mol-ecule B]. The main difference between mol-ecules A and B involves the dihedral angles of the phenyl groups. One phenyl ring makes dihedral angles of 71.14 (6)° (mol-ecule A) and 82.81 (7)° (mol-ecule B) with respect to the core (C4N3O2) of the mol-ecule [14.56 (9)° (mol-ecule A) and 5.7 (1)° (mol-ecule B) for the other phenyl ring]. Another prominent feature is the intra-molecular N-H⋯O hydrogen bond present in both crystallographically independent mol-ecules.

CO2 Capture with Silylated Ethanolamines and Piperazines.

Invited for this month's cover is the group of Marcus Herbig from the TU Bergakademie in Freiberg. The cover picture shows the reaction of CO2 with a silyl derivative of the biogenic amine ethanolamine. The role of CO2 as a contributor to climate change makes "carbon capture" a desirable goal. However, in addition to simply capture CO2, aminosilanes form silylcarbamates, which represent starting materials for a variety of crucial chemicals. Thus, the entrapped CO2 represents a useful C1 building block. The ESF-funded Junior Research Group CO2-Sil at the TU Bergakademie Freiberg (represented by their Logo and location) pursues that kind of goals. CO2-Sil studies these key reactions of CO2 insertion in depth by syntheses, quantum chemical calculations and calorimetric experiments. CO2 brought to the ground by our method shall be feedstock for various branches in chemistry. Read the full text of their Full Paper at 10.1002/open.201900269.

CO2 Capture with Silylated Ethanolamines and Piperazines.

Amine treatment is commonly used to capture CO2 from exhaust gases and from ambient air. The Si-N bond in aminosilanes is capable of reacting with CO2 more readily than amines. In the current study we have synthesized trimethylsilylated ethanolamines, diethanolamines and piperazines and investigated their reaction toward CO2. All products were characterized by 1H, 13C, and 29Si NMR, RAMAN spectroscopy as well as mass spectrometry. The product of a twofold CO2-insertion into bis-trimethylsilylated piperazine was analysed by single-crystal X-ray diffraction. Furthermore, quantum chemical calculations (DFT) were used to supplement the experimental results. Geometry optimizations and NBO calculations for each starting material were carried out at the B3LYP level with different basis sets. DFT calculations at the B3LYP, WB97XD and M062x level were conducted for geometry optimization and frequency calculations to examine the thermochemical data. The calculations were carried out both for the gas phase and in solvent environment. The calculated reaction enthalpies varied between -37 and -107 kJ mol-1, while experimental values around -100 kJ mol-1 were determined.