Interest in small ruthenium coordination complexes is at an all-time high. They can find use as catalysts, in optoelectronics, and as precursor compounds for chemical vapor deposition (CVD) techniques. In this study, we introduce ten new Ru complexes synthesized from the versatile (p-cymene)ruthenium(II) chloride dimer, featuring 1,3-N-coordinating amidinate-type ligands and either methyl or acetate coligands. All compounds were characterized by nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR), liquid injection field desorption ionization mass spectrometry (LIFDI-MS), and single-crystal X-ray diffraction (SC-XRD), which confirmed the structures of the chloride and acetate derivatives, allowing for assessment of their intermolecular interactions. Thermogravimetry (TG) revealed that the methyl-substituted complexes exhibit favorable one-step evaporation, rendering them promising candidates for vapor-phase deposition. Finally, the ease of synthesis, combined with good volatility, prompted us to select Ru p-cymene diacetate for proof-of-principle metal-organic CVD of Ru metal in a single-source route, as well as using either oxygen or ammonia as a coreactant. This work highlights the synthetic versatility of the Ru(II) p-cymene motif and its potential for CVD applications.

Magnesium(II) oxide (MgO) is a versatile material that is appealing for a wide range of applications including electronics and biocompatible coatings, as pharmaceutics, and gas barrier layers (GBLs). The growth of MgO films at low temperatures is required for these applications which can be enabled by atomic layer deposition (ALD). However, the chemistry of ALD precursors reported to date for MgO is limited and there are no suitable chemistries for low temperature deposition on sensitive substrates. In this work, we describe the ALD of MgO thin films close to room temperature which was triggered by the use of a new nonpyrophoric Mg precursor that possesses all the prerequisites needed for low temperature ALD. The highly volatile bis-3-(N,N-dimethylamino)propyl magnesium(II) [Mg(DMP)2] precursor is reactive toward water. The unique chemistry of the DMP ligand facilitates the ALD process in a broad temperature range (30-260 °C) with high growth per cycle (GPC) values (2.40 Å at 40 °C and 1.91 Å at 120 °C) on Si substrates and is supported by computational studies. The as deposited films were characterized using complementary tools to investigate the composition, structure and surface topology. Furthermore, we demonstrate the growth of MgO on poly(ethylene terephthalate) (PET) foils that can be exploited for implementation in temperature sensitive flexible devices by low temperature ALD. This work highlights the key role of the DMP ligand in developing a new Mg precursor promoting low temperature ALD of MgO thin films, opening the field of flexible electronics and new applications beyond semiconductor devices.

The synthesis of two stable monoylide-substituted stannylenes of type YCNSnR [R=Cl (1) or N(SiMe3)2 (2), and YCN=Ph3P(CN)C] starting from the cyanido-substituted alpha-metallated ylide YCN-K and SnCl2 or (SiMe3)2NSnCl is reported. Coordination of the cyano group to the tin center results in the dimerization of both stannylenes 1 and 2 in the solid state as well as in solution, where syn- and anti-isomers are present. X-ray diffraction analyses in combination with DFT calculations revealed that the pi-electron density of the ylide ligand is predominantly shifted into the cyano moiety rather than towards the tin center. This results in a strong preference of the dimers over the monomers, which is further emphasized by the reaction with 2,5-di-tert-butylhydroquinone, which undergoes a [1+4] addition to the tin center to yield a spiro compound while preserving the cyclic core of the dimer. In contrast, phenyl isocyanate and dicyclohexylcarbodiimide insert into the Sn-Cylide bond, ultimately leading to the cleavage of the dimer and the formation of monomeric stannylenes with an ylide-substituted thioamidato and amidinato ligand, respectively. image

Owing to the strong electron-donating ability of ylide substituents, diylidyltetrylenes are usually highly nucleophilic species with strong donor capacities. Here, we demonstrate that their electronic properties are in fact highly flexible and can be effectively tuned through variation of the substituent in the ylide backbone. Initial density functional theory studies showed that cyano groups are particularly capable in lowering the LUMO energy of diylidyl germylenes thus turning these usually highly nucleophilic species into electrophilic compounds. This was confirmed by experimental studies. Attempts to synthesize the germylene (YCN )2 Ge [with YCN =Ph3 P-(C)-CN] from the corresponding metalated ylide YCN K selectively led to germanide [(YCN )3 Ge)K]2 thus reflecting the electrophilic nature of the intermediate formed germylene. XRD analysis of single crystals of (YCN )2 Ge - serendipitously obtained through protonative cleavage of one ylide from the germanide - revealed a monomeric structure with rather long Ge-ylide linkages, which corroborates well with a pure single bond and no stabilization of the empty pπ orbital at germanium through π bonding. The germanide exhibits methanide-like reactivity towards chalcogens but a likewise weak Ge-C bond as demonstrated by the insertion of carbon dioxide.

The synthesis and structure analysis of a series of mono and diylide-substituted tetrylenes of type YEX and Y2E (E=Ge, Sn, Pb; X=Cl or Br) using a thiophosphinoyl-tethered metallated ylide (Y=Ph2P(S)-C-P(pip)Ph-2 with pip=piperidyl) is reported, amongst the first ylide-substituted plumbylenes. The tetrylenes feature distinct trends in the spectroscopic and structural properties of the ylide ligand with increasing atomic number of the tetrel element. For instance, an increasingly high-field shifted signal for the thiophosphinoyl group is observed in the P-31{H-1} NMR spectrum as a consequence of the increasing polarity of the element-carbon bond, which likewise results in a shortening of the ylidic C-P bond in the solid-state structure. The diylidyltetrylenes are unstable towards transylidation forming the mono(ylide)tetrylenes when treated with the tetrel dihalides according to the stability trend: Y2Pb<Y2Sn<Y2Ge<YPbBr<YSnCl<YGeCl. Starting from the monoylide-substituted chlorotertrylenes the first unsymmetrical diylidyltetrylenes of type YEY' can be accessed, whose solid-state structures revealed that not the C-E but the S-E bond to the thiophosphinoyl group is most affected by the second ylide substituent.

The intrinsic properties of semiconducting oxides having nanostructured morphology are highly appealing for gas sensing. In this study, the fabrication of nanostructured WO3 thin films with promising surface characteristics for hydrogen (H2 ) gas sensing applications is accomplished. This is enabled by developing a chemical vapor deposition (CVD) process employing a new and volatile tungsten precursor bis(diisopropylamido)-bis(tert-butylimido)-tungsten(VI), [W(Nt Bu)2 (Ni Pr2 )2 ]. The as-grown nanostructured WO3 layers are thoroughly analyzed. Particular attention is paid to stoichiometry, surface characteristics, and morphology, all of which strongly influence the gas-sensing potential of WO3 . Synchrotron-based ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), X-ray photoelectron emission microscopy (XPEEM), low-energy electron microscopy (LEEM) and 4-point van der Pauw (vdP) technique made it possible to analyze the surface chemistry and structural uniformity with a spatially resolved insight into the chemical, electronic and electrical properties. The WO3 layer is employed as a hydrogen (H2 ) sensor within interdigitated mini-mobile sensor architecture capable of working using a standard computer's 5 V 1-wirebus connection. The sensor shows remarkable sensitivity toward H2 . The high, robust, and repeatable sensor response (S) is attributed to the homogenous distribution of the W5+ oxidation state and associated oxygen vacancies, as shown by synchrotron-based UPS, XPS, and XPEEM analysis.

The Front Cover shows the structure of the newly reported, isolated metallated ylide. Due to the high negative charge at the ylidic carbon center this compound is „on fire“, but can be stabilized by smart molecular design. Structure analyses of the different alkali metal complexes combined with computational studies provide insights into the electronic structure of the compounds. More information can be found in the Communication by by Mike Jörges et al.

Invited for this month's cover is the group of Viktoria H. Gessner at the Ruhr-University in Bochum (Germany). The cover shows the structure of the newly reported, isolated metallated ylide. Due to the high negative charge at the ylidic carbon center this compound is "on fire", but can be stabilized by smart molecular design. Structure analyses of the different alkali metal complexes combined with computational studies provide insights into the electronic structure of the compounds Read the full text of their Communication at 10.1002/open.202100178.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Ionic liquids – ionic crystals – ionic liquid crystals? Structural order in imidazolium-based ILs, a series of asymmetrical 1-dodecyl-2-methyl-3-alkylimidazolium bromides, [C12C1Cnim][Br] with n = 0–12.

The use of iminophosphoryl-tethered ruthenium carbene complexes to activate secondary phosphine P-H bonds is reported. Complexes of type [(p-cymene)-RuC(SO2 Ph)(PPh2 NR)] (with R = SiMe3 or 4-C6 H4 -NO2 ) were found to exhibit different reactivities depending on the electronics of the applied phosphine and the substituent at the iminophosphoryl moiety. Hence, the electron-rich silyl-substituted complex undergoes cyclometallation or shift of the imine moiety after cooperative activation of the P-H bond across the M=C linkage, depending on the electronics of the applied phosphine. Deuteration experiments and computational studies proved that cyclometallation is initiated by the activation process at the M=C bond and triggered by the high electron density at the metal in the phosphido intermediates. Consistently, replacement of the trimethylsilyl (TMS) group by the electron-withdrawing 4-nitrophenyl substituent allowed the selective cooperative P-H activation to form stable activation products.

A series of cobalt(II) (silyl)amides, pyrrolates and aminopyridinates were synthesized. Inspired by the dimeric bis(trimethylsilylamido)cobalt(II) complex ([Co(TMSA)2]2), facile salt metathesis employing the ligand 2,2,5,5-tetramethyl-1,2,5-azadisilolidinyl (TMADS) yielded its congener [Co(TMADS)2]2. Novel, heteroleptic Lewis adducts of the former resulted in unusual three- to four-fold coordination geometry around the metal center. Similarily, the salt [Co(TMADS)3Li(DAD)2] was isolated which demonstrates an ion separated Co(II) anion with silylamide ligation and Li+ counter cation. Transpyrrolylation using [Co(TMSA)2]2 was established for the synthesis of bis[N,N’-2-(dimethylaminomethyl)pyrrolyl]cobalt(II), and bis(N-2-(tert-butyliminomethyl)pyrrolyl)cobalt(II). Treatment of CoCl2 with two equivalents of lithiated N,N-dimethyl(N’-tert-butyl)ethane-1-amino-2-amide and N,N-dimethyl(N’-trimethylsilyl)ethane-1-amino-2-amide resulted in the respective Co(II) amido-amines. Reaction of CoCl2 with lithium 4-methyl-N-(trimethylsilyl)pyridine-2-amide yielded the first binuclear, homoleptic Co(II) aminopyridinate complex with a distorted trigonal bipyramidal coordination environment (τ5 = 0.533) for one central Co(II) ion and a weakly distorted tetrahedral coordination geometry (τ4 = 0.845) for the other. All of the new compounds were thoroughly characterized in terms of composition and structure. Finally, the key thermal characteristics of volatility and thermal stability were assessed using a combination of thermogravimetric analysis and complementary bulk sublimation experiments.

The combination of high efficiencies and long lifetime in a single light-emitting electrochemical cell (LEC) device remain a major problem in LEC technology, preventing its application in commercial lighting devices. Three green light-emitting cationic iridium-based complexes of the general composition [Ir((CN)-N-<^>)(2)((NN)-N-<^>)][PF6] with 4-Fppy (2-(4-fluorophenyl)pyridinato) as the cyclometalating (CN)-N-<^> ligand and 1,10-phenanthroline (1), 4,7-diphenyl-1,10-phenanthroline (bathophenanthroline, bphen, 2), and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (bathocuprione, dmbphen, 3) as ancillary (NN)-N-<^> ligands are synthesized and characterized. Computational studies are carried out in order to compare the electronic structure of the three ionic transition metal complexes (iTMCs) and provide insights into their potential as LEC emitter materials. LECs are then fabricated with complexes 1-3. Driven under a pulsed current, they display a high luminance and current and power efficiencies. As the LEC based on complex 2 displays the overall best device performance, including the longest lifetime of 474 h, it is selected for subsequent driving conditions optimization. An extraordinary power efficiency of 25 lm W-1 and current efficiency of 30 cd A(-1) are achieved under optimized operation conditions with reduced current density, resulting in a long device lifetime of 720 h. Altogether, ligand design in iTMCs and optimization of the device driving conditions leads to a significant improvement in LEC performance.

Light-emitting electrochemical cells (LECs) could represent the “green” lighting technology of the future as they are not only energy efficient, but can be manufactured in a simple and easy way minimizing the environmental footprint and contributing to a sustainable future while maintaining our standard of living. In article number 1909809, Jude E. Namanga, Anja-Verena Mudring, and co-workers report on the development of long-lived, efficient bright-green light emitting LECs.

The use of the bis(1-piperidinyl)-substituted carbodiphosphorane (Ph2(Pip)P)2C (1) as an NCN ligand for the stabilization of phosphorus cations was studied. A simple ligand for halide exchange allowed the synthesis and isolation of a series of phosphorus monocations of the type [1-PR2]+ (with R = Cl, Br, I, CyCl, Ph). These cations exhibit characteristic NMR and structural properties which nicely correlate with the charge at the central phosphorus atom and the interaction between the ligand and the PR2 moiety. Halide abstraction from the monocations does not result in isolable dicationic compounds but in an unexpected intramolecular Csp3–H activation in the piperidinyl group. DFT studies show that the selective activation of the CH2 group next to the nitrogen atom instead of a CH group at the phenyl substituents proceeds via an iminium intermediate formed by hydride transfer from the carbon atom to the cationic phosphorus center. This observation clearly demonstrates the pronounced π acidity of the dicationic phosphorus species in comparison to compounds with a further π-donor substituent.