Terpyridine Diphosphine Ruthenium Complexes as Efficient Photocatalysts for the Transfer Hydrogenation of Carbonyl Compounds

Over the past decade, visible-light photoredox catalysis or photocatalysis has grown to become a commonly employed powerful tool in organic synthesis leading to new unique and valuable molecular transformations, inaccessible from thermally activated processes.[1] Photocatalysis can be conducted in homogeneous conditions as well as employing heterogeneous transition metal or solid semiconductors.[2] The commonly employed homogeneous visible-light photocatalysts are homoleptic Ru and Ir polypyridyl complexes, like [Ru(bpy)3]2+ and [Ir(ppy)3] (bpy = 2,2’-bipyridine; ppy = 2-phenylpyridine). These compounds, when excited by visible light undergo a metal-to-ligand-charge transfer (MLCT) transitions from HOMO and LUMO orbitals of the ligand.[3] The 2,2’:6’,2”- terpyridine (tpy) is an NNN-type Pincer ligand, which can give tight chelation of various metal cations in a nearly planar geometry. The presence of the electron-deficient pyridine cycles make it a strong σ-donor and also as a very good π-receptor, moreover the presence of low energetic LUMO levels allows it to participate in the redox reactions as a non-innocent ligand.[4] Among the catalytical reactions, the transfer hydrogenation (TH) of carbonyl compounds promoted by Ru complexes is a core process for the synthesis of alcohols in an environmentally friendly and widely accepted method in industry.[5] We report herein a practical and innovative procedure for the synthesis of a new class of ruthenium cationic [RuX(PP)(tpy)]Y (PP = diphosphine; X = Cl, OAc; Y = Cl, OAc, PF6) complexes containing tpy and a suitable diphosphine (Figure 1). These cationic complexes are active visible-light photocatalysts for the TH of carbonyl compounds at 30 °C in 2- propanol

CO2 fixation and catalytic reduction by a neutral aluminum double bond

CO2 fixation and reduction to value‐added products is of utmost importance in the battle against rising CO2 levels in the Earth's atmosphere. An organoaluminum complex containing a formal aluminum double bond (dialumene), and thus an alkene equivalent, was used for the fixation and reduction of CO2. The CO2 fixation complex undergoes further reactivity in either the absence or presence of additional CO2, resulting in the first dialuminum carbonyl and carbonate complexes, respectively. Dialumene (1 ) can also be used in the catalytic reduction of CO2, providing selective formation of a formic acid equivalent via the dialuminum carbonate complex rather than a conventional aluminum–hydride‐based cycle. Not only are the CO2 reduction products of interest for C1 added value products, but the organoaluminum complexes isolated represent a significant step forward in the isolation of reactive intermediates proposed in many industrially relevant catalytic processes

Ru–Ag and Ru–Au dicarbene complexes from an abnormal carbene ruthenium system

The first complexes containing an anionic dicarbene connected to two different d-block elements are reported. The synthetic pathway entails metalation and transmetalation reactions, starting from a cationic abnormal Ru-NHC complex

Exploring the C^N^C theme: Synthesis and biological properties of tridentate cyclometalated gold(III) complexes

A family of cyclometalated Au(III) complexes featuring a tridentate CNC scaffold has been synthesized and characterized. Microwave assisted synthesis of the ligands has also been exploited and optimized. The biological properties of the thus formed compounds have been studied in cancer cells and demonstrate generally moderate antiproliferative effects. Initial mechanistic insights have also been gained on the gold complex [Au(CNC)(GluS)] (3), and support the idea that the thioredoxin system may be a target for this family of compounds together with other relevant intracellular thiol-containing molecules. (C) 2017 Elsevier Ltd. All rights reserved

N-heterocyclic carbene-stabilized germa-acylium ion : reactivity and utility in catalytic CO2 functionalizations

The first acceptor-free heavier germanium analogue of an acylium ion, [RGe(O)(NHC)2]X (R = MesTer = 2,6-(2,4,6-Me3C6H2)2C6H3; NHC = IMe4 = 1,3,4,5-tetramethylimidazol-2-ylidene; X = (Cl or BArF = {(3,5-(CF3)2C6H5)4B}), was isolated by reacting [RGe(NHC)2]X with N2O. Conversion of the germa-acylium ion to the first solely donor-stabilized germanium ester [(NHC)RGe(O)(OSiPh3)] and corresponding heavier analogues ([RGe(S)(NHC)2]X and [RGe(Se)(NHC)2]X) demonstrated its classical acylium-like behavior. The polarized terminal GeO bond in the germa-acylium ion was utilized to activate CO2 and silane, with the former found to be an example of reversible activation of CO2, thus mimicking the behavior of transition metal oxides. Furthermore, its transition-metal-like nature is demonstrated as it was found to be an active catalyst in both CO2 hydrosilylation and reductive N-functionalization of amines using CO2 as the C1 source. Mechanistic studies were undertaken both experimentally and computationally, which revealed that the reaction proceeds via an N-heterocyclic carbene (NHC) siloxygermylene [(NHC)RGe(OSiHPh2)]

Photochemically Induced Ring Opening of Spirocyclopropyl Oxindoles: Evidence for a Triplet 1,3‐Diradical Intermediate and Deracemization by a Chiral Sensitizer

The photochemical deracemization of spiro[cyclopropane-1,3 '-indolin]-2 '-ones (spirocyclopropyl oxindoles) was studied. The corresponding 2,2-dichloro compound is configurationally labile upon direct irradiation at lambda=350 nm and upon irradiation at lambda=405 nm in the presence of achiral thioxanthen-9-one as the sensitizer. The triplet 1,3-diradical intermediate generated in the latter reaction was detected by transient absorption spectroscopy and its lifetime determined (tau=22 mu s). Using a chiral thioxanthone or xanthone, with a lactam hydrogen bonding site as a photosensitizer, allowed the deracemization of differently substituted chiral spirocyclopropyl oxindoles with yields of 65-98 % and in 50-85 %ee(17 examples). Three mechanistic contributions were identified to co-act favorably for high enantioselectivity: the difference in binding constants to the chiral thioxanthone, the smaller molecular distance in the complex of the minor enantiomer, and the lifetime of the intermediate 1,3-diradical

Reasons and Strategies for Privacy Features in Tracking and Tracing Systems—A Systematic Literature Review

In the course of the digitization of production facilities, tracking and tracing of assets in the supply chain is becoming increasingly relevant for the manufacturing industry. The collection and use of real-time position data of logistics, tools and load carriers are already standard procedure in entire branches of the industry today. In addition to asset tracking, the technologies used also offer new possibilities for collecting and evaluating position and biometric data of employees. Thus, these technologies can be used for monitoring performance or for tracking worker behaviour, which can lead to additional burdens and stress for employees. In this context, the collection and evaluation of employee data can influence the workplace of the affected employee in the company to his or her disadvantage. The approach of Privacy by Design can help to benefit from all the advantages of these systems, while ensuring that the impact on employee privacy is kept to a minimum. Currently, there is no survey available that reviews tracking and tracing systems supporting this important and emerging field. This work provides a systematic overview from the perspective of the impact on employee privacy. Additionally, this paper identifies and evaluates the techniques used with regard to employee privacy in industrial tracking and tracing systems. This helps to reveal new privacy preserving techniques that are currently underrepresented, therefore enabling new research opportunities in the industrial community