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OBJECTIVE: We report a case series of patients with prolonged but reversible unconsciousness after coronavirus disease 2019 (COVID-19)-related severe respiratory failure. METHODS: A case series of patients who were admitted to the intensive care unit due to COVID-19-related acute respiratory failure is described. RESULTS: After cessation of sedatives, the described cases all showed a prolonged comatose state. Diagnostic neurologic workup did not show signs of devastating brain injury. The clinical pattern of awakening started with early eye opening without obeying commands and persistent flaccid weakness in all cases. Time between cessation of sedatives to the first moment of being fully responsive with obeying commands ranged from 8 to 31 days. CONCLUSION: Prolonged unconsciousness in patients with severe respiratory failure due to COVID-19 can be fully reversible, warranting a cautious approach for prognostication based on a prolonged state of unconsciousness.

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The mechanism of the IndolPhos-Rh-catalyzed asymmetric hydrogenation of prochiral olefins has been investigated by means of X-ray crystal structure determination, kinetic measurements, high-pressure NMR spectroscopy, and DFT calculations. The mechanistic study indicates that the reaction follows an unsaturate/dihydride mechanism according to Michaelis-Menten kinetics. A large value of K(M) (K(M) = 5.01+/-0.16 M) is obtained, which indicates that the Rh-solvate complex is the catalyst resting state, which has been observed by high-pressure NMR spectroscopy. DFT calculations on the substrate-catalyst complexes, which are undetectable by experimental means, suggest that the major substrate-catalyst complex leads to the product. Such a mechanism is in accordance with previous studies on the mechanism of asymmetric hydrogenation reactions with C(1)-symmetric heteroditopic and monodentate ligands.

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A procedure is described for the automated screening and lead optimization of a supramolecular-ligand library for the rhodium-catalyzed asymmetric hydrogenation of five challenging substrates relevant to industry. Each catalyst is (self-) assembled from two urea-functionalized ligands and a transition-metal center through hydrogen-bonding interactions. The modular ligand structure consists of three distinctive fragments: the urea binding motif, the spacer, and the ligand backbone, which carries the phosphorus donor atom. The building blocks for the ligand synthesis are widely available on a commercial basis, thus enabling access to a large number of ligands of high structural diversity. The simple synthetic steps enabled the scale-up of the ligand synthesis to multigram quantities. For the catalyst screening, a library of twelve new chiral ligands was prepared that comprised substantial variation in electronic and steric properties. The automated procedures employed ensured the fast catalyst assembly, screening, and direct acquisition of samples for analysis. It appeared that the most selective catalyst was different for every substrate investigated and that small variations in the building blocks had a major impact on the catalyst performance. For two substrates, a catalyst was found that provided the product with outstanding enantioselectivity. The subsequent automated optimization of these two leads showed that an increase of catalyst loading, dihydrogen pressure, and temperature had a positive effect on the catalyst activity without affecting the catalyst selectivity.

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Sulfonamido-phosphoramidite ligands lead to the formation of Rh-Rh dinuclear complexes through the anionic P-N(-) bridging character. The resulting "boat-shaped" dinuclear catalysts activate molecular H(2) through a cooperative dinuclear endocyclic mechanism, resulting in one bridging and one classical hydride on the dinuclear complex. These new complexes are very active hydrogenation catalysts that operate via a new cooperative hydrogenation activation mechanism, as calculated with density functional theory, and they display unequaled high selectivities in the hydrogenation of hindered cyclic acetamidoalkenes.

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We report SUPRAphos-based rhodium catalysts that are unusually regioselective in the hydroformylation of styrene at low temperatures (40 degrees C) producing mainly the linear aldehyde (72%). This ligand-specific phenomenon is observed for two rhodium catalysts with heterobidentate phosphine-phosphoramidite ligands. We propose that the high selectivity for the linear product is caused by enhanced beta-hydride elimination, due to specific substrate-ligand interactions, most likely pi-pi interactions.

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We report the assembly of supramolecular boxes and coordination polymers based on a rigid bis-zinc(II)-salphen complex and various ditopic nitrogen ligands. The use of the bis-zinc(II)-salphen building block in combination with small ditopic nitrogen ligands gave organic coordination polymers both in solution as well as in the solid state. Molecular modeling shows that supramolecular boxes with small internal cavities can be formed. However, the inability to accommodate solvent molecules (such as toluene) in these cavities explains why coordination polymers are prevailing over well-defined boxes, as it would lead to an energetically unfavorable vacuum. In contrast, for relatively longer ditopic nitrogen ligands, we observed the selective formation of supramolecular box assemblies in all cases studied. The approach can be easily extended to chiral analogues by using chiral ditopic nitrogen ligands.

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A new type of supramolecular building block, Zn(II)-salpyr [salpyr = N,N'-3-pyridylenebis(salicylideneimine)], is described that contains both a pyridyl donor and a Lewis acidic Zn(II) acceptor site in the salen framework. As a consequence, this building block self-organizes into a stable tetrameric vase structure via cooperative intermolecular Zn-N(pyr) interactions.

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The template-induced formation of chelating bidentate ligands by the selective self-assembly of two monodentate pyridyl phosphorus ligands on a rigid bis-zinc(II) salphen template with two identical binding sites was studied. Using UV-vis, NMR-spectroscopy and X-ray analysis the formed structures were unambiguously proven. The application of these templated bidentate ligands in transition metal catalysis showed, in most cases, typical bidentate character. Compared to previous work based on a more flexible bis-zinc(II) porphyrin template, the current catalytic data suggest that the rigidity of the template is not an important factor for the improvement of the regio- and enantioselectivity under the applied reaction conditions.

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We report the template-induced formation of chelating heterobidentate ligands by the selective self-assembly of two different monodentate ligands on a rigid bis-zinc(II)-salphen template with two identical binding sites; these templated heterobidentate ligands induce much higher enantioselectivities (up to 72% ee) in the rhodium-catalyzed asymmetric hydroformylation of styrene than any of the corresponding homobidentate ligands or non-templated mixed ligand combinations (up to 13% ee).

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We report the formation of high-precision catalysts using encapsulated rhodium complexes. In the current example, the encapsulated rhodium catalyst shows unprecedented high selectivity in the rhodium-catalyzed hydroformylation of internal alkenes, forming predominantly one of the branched aldehydes. This catalyst system is the first example that is able to discriminate between carbon atoms C3 and C4 in trans-3-octene.

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The tris(para-pyridyl)phosphine template (1) has been used in conjunction with a series of meso-substituted Zn(II)-tetraphenylporphyrins complexes (2-10) to create supramolecular encapsulated ligand assemblies via Zn-N(pyr) interactions. The structural features of supramolecular ligand 1.[2](3) have been investigated in detail using X-ray crystallography, NMR specroscopy, and UV-vis spectroscopy. The pyridylphosphine-porphyrin stoichiometry determined in solution (1:3) differs markedly with that observed in the solid state (2:5, for assembly [1](2).[2](5)). The difference originates from an unusual coordination behavior of one of the Zn centers, which is octahedrally surrounded through double axial coordination by the pyridyl groups of the two different molecules of 1.

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Polycationic dendrimer 1 forms a well-defined, stoichiometric assembly with eight anionic metal complexes; this assembly is successfully applied as a Lewis acidic catalyst which performs comparably to the unsupported metal complex.