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Application of Bulky NHC-Rhodium Complexes in Efficient S-Si and S-S Bond Forming Reactions.

ABSTRACT: The efficient and straightforward syntheses of silylthioethers and disulfides are presented. The synthetic methodologies are based on new rhodium complexes containing bulky N-heterocyclic carbene (NHC) ligands that turned out to be efficient catalysts in thiol and thiol-silane coupling reactions. These green protocols, which use easily accessible reagents, allow obtaining compounds containing S-Si and S-S bonds in solvent-free conditions. Additionally, preliminary tests on coupling of mono- and octahydro-substituted spherosilicates with selected thiols have proved to be very promising and showed that these catalytic systems can be used for the synthesis of a novel class of functionalized silsesquioxane derivatives.

SUBMITTER: Bolt M

PROVIDER: S-EPMC8653157 | biostudies-literature |

REPOSITORIES: biostudies-literature

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N-Methylphthalimide-substituted benzimidazolium salts and PEPPSI Pd-NHC complexes: synthesis, characterization and catalytic activity in carbon-carbon bond-forming reactions.

Project description:A series of novel benzimidazolium salts (1-4) and their pyridine enhanced precatalyst preparation stabilization and initiation (PEPPSI) themed palladium N-heterocyclic carbene complexes [PdCl2(NHC)(Py)] (5-8), where NHC = 1-(N-methylphthalimide)-3-alkylbenzimidazolin-2-ylidene and Py = 3-chloropyridine, were synthesized and characterized by means of (1)H and (13)C{(1)H} NMR, UV-vis (for 5-8), ESI-FTICR-MS (for 2, 4, 6-8) and FTIR spectroscopic methods and elemental analysis. The synthesized compounds were tested in Suzuki-Miyaura cross-coupling (for 1-8) and arylation (for 5-8) reactions. As catalysts, they demonstrated a highly efficient route for the formation of asymmetric biaryl compounds even though they were used in very low loading. For example, all compounds displayed good catalytic activity for the C-C bond formation of 4-tert-butylphenylboronic acid with 4-chlorotoluene.

| S-EPMC4734419 | biostudies-other

Highly Efficient Deep Blue Luminescence of 2-Coordinate Coinage Metal Complexes Bearing Bulky NHC Benzimidazolyl Carbene.

Project description:The structural, photophysical and electrochemical properties of three luminescent 2-coordinate coinage metal (i.e., M = Cu, Ag, Au) complexes bearing a sterically bulky benzimidazolyl carbene, 1,3-bis(2,6-diisopropylphenyl)-1-H-benzo[d]imidazol-2-ylidene (BZI), and carbazolide (Cz) as the anionic ligand were investigated. All the complexes emit in the deep blue region (~430 nm) with relatively narrow spectra (full width at half maximum = 44 nm, 2,300 cm-1) characterized by vibronic fine structure in nonpolar media (methylcyclohexane at room temperature), and with high photoluminescence quantum yields (?PL > 80%) and radiative rate constants (k r ~ 7.8 × 105 s-1). The luminescence is solvatochromic, undergoing a red-shift in a polar solvent (CH2Cl2) at room temperature that are accompanied by a decrease in quantum yields (?PL < 23%) and radiative rate constants (k r < 4.0 × 104 s-1), whereas the non-radiative rate constants remain nearly constant (k nr ~ 1.0 × 105 s-1). The radiative rate is controlled via thermally assisted delayed fluorescence (TADF) and temperature-dependent luminescence studies of the gold complex (Au BZI) in methylcyclohexane solution reveal an energy difference between the lowest singlet and triplet excited states of 920 cm-1. An organic light-emitting diode (OLED) fabricated using Au BZI as a luminescent dopant has an external quantum efficiency of 12% and narrow, deep-blue emission (CIE = 0.16, 0.06).

| S-EPMC7225363 | biostudies-literature

Tandem application of C-C bond-forming reactions with reductive ozonolysis.

Project description:Several variants of reductive ozonolysis, defined here as the in situ generation of aldehydes or ketones during ozonolytic cleavage of alkenes, are demonstrated to work effectively in tandem with a number of C-C bond-forming reactions. For reactions involving basic nucleophiles (1,2-addition of Grignard reagents, Wittig or Horner-Emmons olefinations, and directed aldol reactions of lithium enolates), the one-pot process offers a rapid and high-yielding alternative to traditional two-step protocols.

| S-EPMC3537893 | biostudies-literature

Cellulose-supported chiral rhodium nanoparticles as sustainable heterogeneous catalysts for asymmetric carbon-carbon bond-forming reactions.

Project description:Cellulose-supported chiral Rh nanoparticle (NP) catalysts have been developed. The Rh NPs, which were well dispersed on cellulose, catalyzed the asymmetric 1,4-addition of arylboronic acids to enones and enoates, one of the representative asymmetric carbon-carbon bond-forming reactions, in the presence of chiral diene ligands, providing the corresponding adducts in high yields with outstanding enantioselectivities without metal leaching. The solid-state NMR analysis of the chiral NP system directly suggested interactions between the Rh NPs and the chiral ligand on cellulose. This is the first example of using polysaccharide-supported chiral metal nanoparticles for asymmetric carbon-carbon bond-forming reactions.

| S-EPMC6054049 | biostudies-literature

Rhodium(III) and Iridium(III) Complexes of a NHC-Based Macrocycle: Persistent Weak Agostic Interactions and Reactions with Dihydrogen.

Project description:The synthesis and characterization of five-coordinate rhodium(III) and iridium(III) 2,2'-biphenyl complexes [M(CNC-12)(biph)][BArF 4] (M = Rh (1a), Ir (1b)), featuring the macrocyclic lutidine- and NHC-based pincer ligand CNC-12 are reported. In the solid state these complexes are notable for the adoption of weak ?-agostic interactions that are characterized by M···H-C contacts of ca. 3.0 Å by X-ray crystallography and ?(CH) bands of reduced wavenumber by ATR IR spectroscopy. Remarkably, these interactions persist on dissolution and were observed at room temperature using NMR spectroscopy (CD2Cl2) and solution-phase IR spectroscopy (CCl4). The associated metrics point toward a stronger M···H-C interaction in the iridium congener, and this conclusion is borne out on interrogation of 1 in silico using DFT-based NBO and QTAIM analyses. Reaction of 1 with dihydrogen resulted in hydrogenolysis of the biaryl and formation of fluxional hydride complexes, whose ground state formulations as [Rh(CNC-12)H2][BArF 4] (2a?) and [Ir(CNC-12)H2(H2)][BArF 4] (2b?) are proposed on the basis of inversion recovery and variable-temperature NMR experiments, alongside a computational analysis. Reactions of 1 and 2 with carbon monoxide help support their respective structural properties.

| S-EPMC6234485 | biostudies-literature

Versatile deprotonated NHC: C,N-bridged dinuclear iridium and rhodium complexes.

Project description:Bearing the versatility of N-heterocyclic carbene (NHC) ligands, here density functional theory (DFT) calculations unravel the capacity of coordination of a deprotonated NHC ligand (pNHC) to generate a doubly C2,N3-bridged dinuclear complex. Here, in particular the discussion is based on the combination of the deprotonated 1-arylimidazol (aryl = mesityl (Mes)) with [M(cod)(?-Cl)] (M = Ir, Rh) generated two geometrical isomers of complex [M(cod){µ-C3H2N2(Mes)-?C2,?N3}]2). The latter two isomers display conformations head-to-head (H-H) and head-to-tail (H-T) of C S and C 2 symmetry, respectively. The isomerization from the H-H to the H-T conformation is feasible, whereas next substitutions of the cod ligand by CO first, and PMe3 later confirm the H-T coordination as the thermodynamically preferred. It is envisaged the exchange of the metal, from iridium to rhodium, confirming here the innocence of the nature of the metal for such arrangements of the bridging ligands.

| S-EPMC4734348 | biostudies-literature

Synthesis of a Benzodiazepine-derived Rhodium NHC Complex by C-H Bond Activation.

Project description:The synthesis and characterization of a Rh(I)-NHC complex generated by C-H activation of 1,4-benzodiazepine heterocycle are reported. This complex constitutes a rare example of a carbene tautomer of a 1,4-benzodiazepine aldimine stabilized by transition metal coordination and demonstrates the ability of the catalytically relevant RhCl(PCy(3))(2) fragment to induce NHC-forming tautomerization of heterocycles possessing a single carbene-stabilizing heteroatom. Implications for the synthesis of benzodiazepines and related pharmacophores via C-H functionalization are discussed.

| S-EPMC3010370 | biostudies-literature

Novel Porous Rhodium Metal-Organic Aerogel for Efficient Removal of Organic Dyes and Catalysis of Si-H Insertion Reactions.

Project description:Metal-organic gels (MOGs) are attracting increasing attention for removal of organic dyes from aqueous solution and for catalysis of Si-H insertion reactions. Herein, we report that a reaction of porphyrin derivative 1 with Rh2(OAc)4 generates stable metal-organic gels and subsequent subcritical carbon dioxide drying affords metal-organic aerogels. Owing to their micro- and mesoporosity, the aerogels adsorbed dyes. Moreover, aerogel I catalyzed Si-H insertion reactions to give organosilicon compounds in high yields.

| S-EPMC8515819 | biostudies-literature

Biological and Bioinspired Inorganic N-N Bond-Forming Reactions.

Project description:The metallobiochemistry underlying the formation of the inorganic N-N-bond-containing molecules nitrous oxide (N2O), dinitrogen (N2), and hydrazine (N2H4) is essential to the lifestyles of diverse organisms. Similar reactions hold promise as means to use N-based fuels as alternative carbon-free energy sources. This review discusses research efforts to understand the mechanisms underlying biological N-N bond formation in primary metabolism and how the associated reactions are tied to energy transduction and organismal survival. These efforts comprise studies of both natural and engineered metalloenzymes as well as synthetic model complexes.

| S-EPMC7339862 | biostudies-literature

Stereoisomeric Tris-BINOL-Menthol Bulky Monophosphites: Synthesis, Characterisation and Application in Rhodium-Catalysed Hydroformylation.

Project description:Four stereoisomeric monoether derivatives, based on axially chiral (R)- or (S)-BINOL bearing a chiral (+)- or (-)-neomenthyloxy group were synthesised and fully characterised by NMR spectroscopy and X-ray crystallography. The respective tris-monophosphites were thereof prepared and fully characterised. The coordination ability of the new bulky phosphites with Rh(CO)2(acac), was attested by 31P NMR, which presented a doublet in the range of δ = 120 ppm, with a 1J(103Rh-31P) coupling constant of 290 Hz. The new tris-binaphthyl phosphite ligands were further characterised by DFT computational methods, which allowed us to calculate an electronic (CEP) parameter of 2083.2 cm-1 and an extremely large cone angle of 345°, decreasing to 265° upon coordination with a metal atom. Furthermore, the monophosphites were applied as ligands in rhodium-catalysed hydroformylation of styrene, leading to complete conversions in 4 h, 100% chemoselectivity for aldehydes and up to 98% iso-regioselectivity. The Rh(I)/phosphite catalytic system was also highly active and selective in the hydroformylation of disubstituted olefins, including (E)-prop-1-en-1-ylbenzene and prop-1-en-2-ylbenzene.

| S-EPMC8954005 | biostudies-literature

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