Catalytic oxidation of primary aromatic alcohols using half sandwich Ir(III), Rh(III) and Ru(II) complexes: A practical and theoretical study

Cationic N,S-chelate half-sandwich iridium complexes: synthesis, characterization, anticancer and antiplasmodial activity

A series of pyrazole-based ligands and their corresponding cationic N,S-chelate half-sandwich iridium complexes were successfully synthesized. All iridium complexes exhibited good anticancer activity against the MCF-7 and MDA-MB-231 human breast cancer cells. The cytotoxic activity of unsubstituted iridium complex 1 is greater than that of cisplatin against MCF-7 cells. In addition, the cationic half-sandwich iridium complexes are also efficient in antiplasmodial study and complex 1 displayed the best activity as its IC50 was observed to be approximately 0.11 μM against the CQS-NF54 strain. These iridium complexes generally exhibited enhanced activity against the CQS-NF54 strain in comparison with that against the CQR-K1 strain. An "IC50 speed assay" investigation against the CQS-NF54 strain indicated complexes 1-3 to be fast-acting complexes that reach their lowest IC50 values within 16 hours. All complexes were fully characterized by IR spectroscopy, NMR spectroscopy, and elemental analysis, and the structure of the iridium complex was confirmed by single-crystal X-ray diffraction.

Formation of Iridium(III) and Rhodium(III) Amine, Imine, and Amido Complexes Based on Pyridine-Amine Ligands: Structural Diversity Arising from Reaction Conditions, Substituent Variation, and Metal Centers

Herein, we present the different coordination modes of half-sandwich iridium(III) and rhodium(III) complexes based on pyridine-amine ligands. The pyridyl-amine iridium(III) and rhodium(III) complexes, the corresponding oxidation pyridyl-imine products, and 16-electron pyridyl-amido complexes can be obtained through the change in reaction conditions (nitrogen/adventitious oxygen atmosphere, reaction time, and solvents) and structural variations in the metal and ligand. Overall, the reaction of pyridine-amine ligands with [(η⁵-C₅(CH₃)₅)MCl₂]₂ (M = Ir or Rh) in the presence of adventitious oxygen afforded the oxidized pyridyl-imine complexes. The possible mechanism for the oxidation of iridium(III) and rhodium(III) amine complexes was confirmed by the detection of the byproduct hydrogen peroxide. Moreover, the formation of pyridyl-amine complexes was favored when nonpolar solvent CH₂Cl₂ was used instead of CH₃OH. The rarely reported complex with [(η⁵-Cp*)IrCl₃] anions can also be obtained without the addition of NH₄PF₆. The introduction of the sterically bulky i-Bu group on the bridge carbon of the ligand led to the formation of stable 16-electron pyridyl-amido complexes. The pyridyl-amine iridium(III) and rhodium(III) complexes were also synthesized under a N₂ atmosphere, and no H₂O₂ was detected in the whole process. In particular, the aqueous solution stability and in vitro cytotoxicity toward A549 and HeLa human cancer cells of these complexes were also evaluated. No obvious selectivity was observed for cancer cells versus normal cells with these complexes. Notably, the represented complex 5a can promote an increase in the reactive oxygen species level and induce cell death via apoptosis.

Crystal structure of chlorido-(η 5-pentamethylcyclopentadienyl)-(4-chloro-4-pyridyl-2,2′:6′,2′′-terpyridine-κ2N,N′) rhodium(III) hexaflourophosphate, C31H29Cl2F6N3PRh

C31H29Cl2F6N3PRh, monoclinic, P21/c (no. 14), a = 7.4069(7) Å, b = 13.245(1) Å, c = 32.141(3) Å, β = 93.924(2)°, V = 3145.8(5) Å3, Z = 4, R gt(F) = 0.0386, wR ref(F 2) = 0.0962, T = 123.15 K.

Tandem transfer hydrogenation–epoxidation of ketone substrates catalysed by alkene-tethered Ru(ii)–NHC complexes

Eight novel alkene-tethered Ru(ii)–NHC complexes were employed as catalysts in tandem transfer hydrogenation–epoxidation reactions using phenacyl bromide derivatives as substrates.

Friedel-Crafts Reaction of N,N-Dimethylaniline with Alkenes Catalyzed by Cyclic Diaminocarbene-Gold(I) Complex

In general, Friedel-Crafts reaction is incompatible with amines due to the Lewis acidity of the catalysts. Recently, we reported that cyclic diaminocarbene-Gold(I) can be used as catalyst for the Friedel-Crafts alkylation between aromatic amines and alkenes. Herein, a systematically theoretical research was performed on this rare Friedel-Crafts reaction. The adopted calculation method is accurate enough to reproduce the crystal structure of the catalyst. It was found that the reactions followed the electrophilic aromatic substitution mechanism. The gold cation can activate the C=C double bond and generate the electrophilic group which can be attacked by the aromatic ring. The para-product is more energy favorable which agrees well with the experimental results. The reaction of α-methylstyrene follows the Markovnikov rule, and the activation energy to generate the branched product of methylstyrene is lower than that producing the linear product. However, the reaction of butanone follows the anti-Markovnikov rule, and the activation energy to generate the branched product of butanone is higher than that producing the linear product. These calculation results reveal the mechanism of this new Friedel-Crafts reaction. It can well explain the high para-selectivity and the substrate-dependent of the product structures in the experiment.

Natural hydroxyapatite supported cobalt tetrasulfophthalocyanine: a green, renewable and biomaterial-based heterogeneous catalyst for selective aerobic oxidation of alkyl arenes and alcohols

Natural hydroxyapatite supported cobalt tetrasulfophthalocyanine (CoTSPc-NHAp) as a green, renewable and biomaterial-based heterogeneous catalyst promotes aerobic oxidation of alkyl arenes and alcohols.