Tri- and tetracoordinate copper(i) complexes bearing bidentate soft/hard SN and SeN ligands based on 2-aminopyridine

Can water act as a nucleophile in CO oxidation catalysed by Mo/Cu CO-dehydrogenase? Answers from theory

The aerobic CO dehydrogenase from Oligotropha carboxidovorans is an environmentally crucial bacterial enzyme for maintenance of subtoxic concentration of CO in the lower atmosphere, as it allows for the oxidation of CO to CO₂ which takes place at its Mo−Cu heterobimetallic active site. Despite extensive experimental and theoretical efforts, significant uncertainties still concern the reaction mechanism for the CO oxidation. In this work, we used the hybrid quantum mechanical/molecular mechanical approach to evaluate whether a water molecule present in the active site might act as a nucleophile upon formation of the new C−O bond, a hypothesis recently suggested in the literature. Our study shows that activation of H₂O can be favoured by the presence of the Mo=O_eq group. However, overall our results suggest that mechanisms other than the nucleophilic attack by Mo=O_eq to the activated carbon of the CO substrate are not likely to constitute reactive channels for the oxidation of CO by the enzyme.

Following Molecular Mobility during Chemical Reactions: No Evidence for Active Propulsion

The reported changes in self-diffusion of small molecules during reactions have been attributed to "boosted mobility". We demonstrate the critical role of changing concentrations of paramagnetic ions on nuclear magnetic resonance (NMR) signal intensities, which led to erroneous measurements of diffusion coefficients. We present simple methods to overcome this problem. The use of shuffled gradient amplitudes allows accurate diffusion NMR measurements, even with time-dependent relaxation rates caused by changing concentrations of paramagnetic ions. The addition of a paramagnetic relaxation agent allows accurate determination of both diffusion coefficients and reaction kinetics during a single experiment. We analyze a copper-catalyzed azide-alkyne cycloaddition "click" reaction, for which boosted mobility has been claimed. With our methods, we accurately measure the diffusive behavior of the solvent, starting materials, and product and find no global increase in diffusion coefficients during the reaction. We overcome NMR signal overlap using an alternative reducing agent to improve the accuracy of the diffusion measurements. The alkyne reactant diffuses slower as the reaction proceeds due to binding to the copper catalyst during the catalytic cycle. The formation of this intermediate was confirmed by complementary NMR techniques and density functional theory calculations. Our work calls into question recent claims that molecules actively propel or swim during reactions and establishes that time-resolved diffusion NMR measurements can provide valuable insight into reaction mechanisms.

Mononuclear Cu Complexes Based on Nitrogen Heterocyclic Carbene: A Comprehensive Review

During the last decade, organometallic, coordination, and catalytic chemistry of the three-dimensional metals such as copper (Cu) has been greatly affected by the emergence of nitrogen heterocyclic carbene (NHC) complexes. The NHCs, and in particular the mononuclear Cu^I-based ones, have been proven vastly useful in several applications such as in biosynthesis, catalysis, photochemistry, etc. This review tries to thoroughly describe a series of mononuclear Cu^I NHC complexes and their subcategories such as heteroleptics, and bidentate and tridentate heteroatom complexes, and give some detailed insights on their development, emergence, and applications. A brief outlook is also disclosed to enable other researchers to further develop a platform for future advances and studies in the field of Cu^I-based NHCs.

N-Heterocyclic Carbene Complexes of Copper, Nickel, and Cobalt

The emergence of N-heterocyclic carbenes as ligands across the Periodic Table had an impact on various aspects of the coordination, organometallic, and catalytic chemistry of the 3d metals, including Cu, Ni, and Co, both from the fundamental viewpoint but also in applications, including catalysis, photophysics, bioorganometallic chemistry, materials, etc. In this review, the emergence, development, and state of the art in these three areas are described in detail.

Syntheses, structures, and catalytic properties of two arene-ruthenium(II) complexes bearing N-(2-pyridinyl)aminodiphenylphosphine sulfide ligands

Treatment of [(arene)Ru(μ-Cl)Cl]2 with Ph2P(S)NH(2-py) in the presence or absence of base gave two arene-ruthenium(II) complexes [(η 6-p-cymene)Ru{κ 2-N,N-Ph2P(S)N(2-py)}Cl] (1) and [(η 6-benzene)Ru{κ 1-N-Ph2P(S)NH(2-py)}Cl2] (2), which have been characterized by infrared, nuclear magnetic resonance spectroscopies, and mass spectrometry along with microanalyses. Crystal structures of Ph2P(S)NH(2-py) · ¼C6H14, 1 and 2 · ½CH2Cl2 were determined by single-crystal X-ray diffraction. Two arene-ruthenium(II) complexes were tested as precatalysts for the transfer hydrogenation of acetophenone to give 1-phenyl ethanol.

Copper(i) 5-phenylpyrimidine-2-thiolate complexes showing unique optical properties and high visible light-directed catalytic performance

Copper(i) 5-phenylpyrimidine-2-thiolate complexes exhibit intriguing luminescence properties and excellent visible light-directed catalytic activity towards aerobic oxidative hydroxylation of arylboronic acids.

2-[(Diisopropyl-thio-phosphor-yl)amino]-pyridinium tetra-fluoro-borate

The title compound, C₁₁H₂₀N₂PS⁺·BF₄⁻, is a salt of 2-(diisopropyl­thio­phospho­ryl­amino)­pyridine, a chelating bidentate ligand that furnishes an S atom as a soft donor and a pyridine N atom as a hard atom for transition-metal complexation. The title salt crystallizes with two formula units in the asymmetric unit. The two independent cations are protonated at the pyridine N atoms and have the S atoms syn-oriented to them so as to form bent intra­molecular N—H⋯S hydrogen bonds, one of which one is bifurcated by involving also an N—H⋯F inter­action. The phospho­ryl­amino NH groups form near linear hydrogen bonds to proximal tetra­fluoro­borate anions. Five weak C—H⋯F and three weak C—H⋯S inter­actions link the constituents into a three-dimensional framework. As a result of the crystal packing, the two cations differ notably in conformation, as can be seen from the S—P—N—C torsion angles of −18.7 (1)° in the first and −35.1 (1)° in the second cation.