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Chemical recycling, in particular hydrogenative depolymerization, offers a promising way to utilize plastic waste. This report covers the manganese‐catalyzed hydrogenation of polyurethane materials to the corresponding monomeric units. The key to success is a Mn pincer complex as a potent hydrogenation catalyst in combination with elevated temperatures (up to 200 °C) and appropriate solvents to ensure sufficient solubility of the polymers. A wide range of polyurethane samples of varying polyol and isocyanate compositions, some of which feature significant amounts of urea functionalities, are depolymerized, releasing polyetherols and diaminotoluene (TDA) in yields of up to 89 % and 76 %, respectively. [ABSTRACT FROM AUTHOR]

The hydrogenation of (+)‐Sclareolide to (−)‐ambradiol catalyzed by a manganese pincer complex is reported. The hydrogenation reaction is performed with an air‐ and moisture‐stable manganese catalyst and proceeds under relatively mild reaction conditions at low manganese and base loadings. A range of other esters could be successfully hydrogenated leading to the corresponding alcohols in good to quantitative yields using this easy‐to‐make catalyst. A scale‐up experiment was performed leading to 99.3 % of the isolated yield of (−)‐Ambradiol. [ABSTRACT FROM AUTHOR]

Early in John Updike's novel Rabbit Redux (1971), Harry Angstrom watches the Carol Burnett show with his son Nelson. Burnett and Gomer Pyle are doing a Lone Ranger skit in [...]

Early in John Updike's novel Rabbit Redux (1971), Harry Angstrom watches the Carol Burnett show with his son Nelson. Burnett and Gomer Pyle are doing a Lone Ranger skit in [...]

Early in John Updike's novel Rabbit Redux (1971), Harry Angstrom watches the Carol Burnett show with his son Nelson. Burnett and Gomer Pyle are doing a Lone Ranger skit in [...]

Chemical recycling provides a promising solution to utilize plastic waste. Here, a catalytic hydrogenative depolymerization of polyamide 66 (PA 66) and polyurethane (PU) was developed. The system employed Ru pincer complexes at high temperature (200 °C) in THF solution, and even technical‐grade polymers could be hydrogenated with satisfactory yields under these conditions. A comparison of the system with some known heterogeneous catalysts as well as catalyst poisoning tests supported the homogeneity of the system. These results demonstrate the potential of chemical recycling to regain building blocks for polymers and will be interesting for the further development of polymer hydrogenation. [ABSTRACT FROM AUTHOR]

A binary modulation and demodulation technique is presented which is particularly suited for channels with non white interferers and/or for channels with different attenuations at the two signalling frequencies. Because Spread Frequency Shift Keying is mainly based on classical FSK modem technology it can be easily implemented and it is well suited for low cost applications. The improvement in performance compared to FSK can be up to 15 dB depending on the characteristics of the channel. Finally, the use of a convolutional code leads to an additional gain of up to 4 dBs.

We report a N-heterocyclic carbene copper(I) complex-catalysed formal cycloaddition between readily available propargylic alcohols and carbon dioxide at room temperature. By using the combination of a sterically demanding BPDPrCuCl complex (BPDPr = 1,3-bis(2,6-diisopropylphenyl)-1,3-diazonine-2-ylidene) and CsF, as catalytic system, primary propargylic alcohols are efficiently converted to the corresponding α-alkylidene cyclic carbonates. Gram scale (up to 89% yield) and reusability experiments (74% global yield, turnover number value = 103) showcase the robustness of the catalytic system. This practically simple protocol also tolerates secondary and tertiary propargylic alcohols under CO2 at atmospheric pressure, enabling the direct synthesis of substituted and unsubstituted α-alkylidene cyclic carbonates at room temperature. [ABSTRACT FROM AUTHOR]

A straight‐forward approach to separate catalyst from the exo‐vinylene carbonate (EVC) products of the carboxylative cyclisation of primary propargylic alcohols has been developed. The liquid‐liquid phase synthesis utilises lipophilic silver(I) carboxylate salts and N,N‐dioctyl modified phosphine (FatPhos) ligands to enhance catalyst solubility in non‐polar solvents. Following simple liquid‐liquid phase separation, EVCs relevant as monomers for poly(urethane) and poly(carbonate) synthesis were isolated in the non‐miscible polar phase in good yields. In situ reaction monitoring by ReactIR gave insights into the reaction kinetics and informed the conditions used to afford good EVC selectivity. Under optimised conditions, silver leaching into the product phase was very minor as confirmed by ICP‐MS. Furthermore, a protocol for catalyst recycling by liquid‐liquid separation was demonstrated, with modest loss of catalytic activity over 3 runs. [ABSTRACT FROM AUTHOR]

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Sugar alcohols are of great importance for the food industry and are promising building blocks for bio‐based polymers. Industrially, they are produced by heterogeneous hydrogenation of sugars with H2, usually with none to low stereoselectivities. Now, we present a homogeneous system based on commercially available components, which not only increases the overall yield, but also allows a wide range of unprotected ketoses to be diastereoselectively hydrogenated. Furthermore, the system is reliable on a multi‐gram scale allowing sugar alcohols to be isolated in large quantities at high atom economy. [ABSTRACT FROM AUTHOR]

The direct access to dimethoxymethane (DMM) from CO2/H2 in MeOH is an attractive approach, but more active, selective, and robust catalyst systems are still desirable for an application of this system. Herein, we present the performance enhancing effect of additives on ruthenium-triphos catalyst systems for CO2 hydrogenation to DMM. In the presence of PPh3, functioning as both additional ligand and precursor for Lewis-acidic phosphonium salts, increased turnover numbers for DMM are achieved. Moreover, PPh3 significantly diminishes catalyst degradation via carbonylation to cationic [RuH(CO)2(triphos)]OTf, which remains an active species in the synthesis of DMM. Catalyst recycling over up to five runs with minimal loss in catalyst performance underlines the robustness of the system. Both, the recyclability of the system and the suppression of catalyst deactivation pathways encourage for application in sustainable continuous processes. [ABSTRACT FROM AUTHOR]

Investigations concerning the reactivity of Ni(0) complexes [Ni(NHC)2] of NHCs (N‐heterocyclic carbene) of different steric demand, Mes2Im (= 1,3‐dimesitylimidazoline‐2‐ylidene) and iPr2Im (= 1,3‐diisopropyl‐imidazoline‐2‐ylidene), with olefins, ketones and aldehydes are reported. The reaction of [Ni(Mes2Im)2] 1 with ethylene or methyl acrylate afforded the complexes [Ni(Mes2Im)2(η2‐C2H4)] 3 and [Ni(Mes2Im)2(η2‐(C,C)‐H2C=CHCOOMe)] 4, as it was previously reported for [Ni2(iPr2Im)4(µ‐(η2:η2)‐COD)] 2 as a source for [Ni(iPr2Im)2]. In contrast to 2, complex 1 does not react with sterically more demanding olefins such as tetramethylethylene, 1,1‐diphenylethylene and cyclohexene. The reaction of [Ni(NHC)2] with more π‐acidic ketones or aldehydes led to formation of complexes with side‐on η2‐(C,O)‐coordinating ligands: [Ni(iPr2Im)2(η2‐O=CHtBu)] 5, [Ni(iPr2Im)2(η2‐O=CHPh)] 6, [Ni(iPr2Im)2(η2‐O=CMePh)] 7, [Ni(iPr2Im)2(η2‐O=CPh2)] 8, [Ni(iPr2Im)2(η2‐O=C(4‐F‐C6H4)2)] 9, [Ni(iPr2Im)2(η2‐O=C(OMe)(CF3))] 10 and [Ni(Mes2Im)2(η2‐O=CHPh)] 11, [Ni(Mes2Im)2(η2‐O=CH(CH(CH3)2))] 12, [Ni(Mes2Im)2(η2‐O=CH(4‐NMe2‐C6H4))] 13, [Ni(Mes2Im)2(η2‐O=CH(4‐OMe‐C6H4))] 14, [Ni(Mes2Im)2(η2‐O=CPh2)] 15 and [Ni(Mes2Im)2(η2‐O=C(4‐F‐C6H4)2)] 16. The reaction of 1 and 2 with these simple aldehydes and ketones does not lead to a significantly different outcome, but NHC ligand rotation is hindered for the Mes2Im complexes 3, 4 and 11–16 according to NMR spectroscopy. The solid‐state structures of 3, 4, 11 and 12 reveal significantly larger CNHC‐Ni‐CNHC angles in the Mes2Im complexes compared to the iPr2Im complexes. As electron transfer in d8‐ (or d10‐) ML2 complexes to π‐acidic ligands depends on the L–M–L bite angle, the different NHCs lead thus to a different degree of electron transfer and activation of the olefin, aldehyde or ketone ligand, i.e., [Ni(iPr2Im)2] is the better donor to these π‐acidic ligands. Furthermore, we identified two different side products from the reaction of 1 with benzaldehyde, trans‐[Ni(Mes2Im)2H(OOCPh)] 17 and [Ni2(Mes2Im)2(µ2‐CO)(µ2‐η2‐C,O‐PhCOCOPh)] 18, which indicate that radical intermediates and electron transfer processes might be of importance in the reaction of 1 with aldehydes and ketones. [ABSTRACT FROM AUTHOR]

Investigations concerning the reactivity of Ni(0) complexes [Ni(NHC)2] of NHCs (N‐heterocyclic carbene) of different steric demand, Mes2Im (= 1,3‐dimesitylimidazoline‐2‐ylidene) and iPr2Im (= 1,3‐diisopropyl‐imidazoline‐2‐ylidene), with olefins, ketones and aldehydes are reported. The reaction of [Ni(Mes2Im)2] 1 with ethylene or methyl acrylate afforded the complexes [Ni(Mes2Im)2(η2‐C2H4)] 3 and [Ni(Mes2Im)2(η2‐(C,C)‐H2C=CHCOOMe)] 4, as it was previously reported for [Ni2(iPr2Im)4(µ‐(η2:η2)‐COD)] 2 as a source for [Ni(iPr2Im)2]. In contrast to 2, complex 1 does not react with sterically more demanding olefins such as tetramethylethylene, 1,1‐diphenylethylene and cyclohexene. The reaction of [Ni(NHC)2] with more π‐acidic ketones or aldehydes led to formation of complexes with side‐on η2‐(C,O)‐coordinating ligands: [Ni(iPr2Im)2(η2‐O=CHtBu)] 5, [Ni(iPr2Im)2(η2‐O=CHPh)] 6, [Ni(iPr2Im)2(η2‐O=CMePh)] 7, [Ni(iPr2Im)2(η2‐O=CPh2)] 8, [Ni(iPr2Im)2(η2‐O=C(4‐F‐C6H4)2)] 9, [Ni(iPr2Im)2(η2‐O=C(OMe)(CF3))] 10 and [Ni(Mes2Im)2(η2‐O=CHPh)] 11, [Ni(Mes2Im)2(η2‐O=CH(CH(CH3)2))] 12, [Ni(Mes2Im)2(η2‐O=CH(4‐NMe2‐C6H4))] 13, [Ni(Mes2Im)2(η2‐O=CH(4‐OMe‐C6H4))] 14, [Ni(Mes2Im)2(η2‐O=CPh2)] 15 and [Ni(Mes2Im)2(η2‐O=C(4‐F‐C6H4)2)] 16. The reaction of 1 and 2 with these simple aldehydes and ketones does not lead to a significantly different outcome, but NHC ligand rotation is hindered for the Mes2Im complexes 3, 4 and 11–16 according to NMR spectroscopy. The solid‐state structures of 3, 4, 11 and 12 reveal significantly larger CNHC‐Ni‐CNHC angles in the Mes2Im complexes compared to the iPr2Im complexes. As electron transfer in d8‐ (or d10‐) ML2 complexes to π‐acidic ligands depends on the L–M–L bite angle, the different NHCs lead thus to a different degree of electron transfer and activation of the olefin, aldehyde or ketone ligand, i.e., [Ni(iPr2Im)2] is the better donor to these π‐acidic ligands. Furthermore, we identified two different side products from the reaction of 1 with benzaldehyde, trans‐[Ni(Mes2Im)2H(OOCPh)] 17 and [Ni2(Mes2Im)2(µ2‐CO)(µ2‐η2‐C,O‐PhCOCOPh)] 18, which indicate that radical intermediates and electron transfer processes might be of importance in the reaction of 1 with aldehydes and ketones. [ABSTRACT FROM AUTHOR]