cis-Oxoruthenium complexes supported by chiral tetradentate amine (N4) ligands for hydrocarbon oxidations

Syntheses and crystal structures of (R,R)- and (S,S)-bis-(aceto-nitrile-κN)[N,N'-dimethyl-N,N'-bis(pyridin-2-ylmeth-yl)cyclo-hexane-1,2-di-amine-κ4 N]iron(II) bis-(hexa-fluoro-anti-monate)

Two enanti-omeric non-heme iron complexes [Fe(R,R-BPMCN)(CH3CN)2](SbF6)2 and [Fe(S,S-BPMCN)(CH3CN)2](SbF6)2 (BPMCM = N,N'-dimethyl-N,N'-bis-(pyridin-2-ylmeth-yl)-cyclo-hexane-1,2-di-amine, C22H28N4) were obtained in parallel syntheses starting from the enanti-omerically pure R,R and S,S BPMCN ligands. The FeII cations have a distorted octa-hedral FeN6 geometry formed by a chelating N,N,N,N-tetra-dentate BPMCN ligand and two mol-ecules of aceto-nitrile. The ligand adopts a cis-α topology with the two pyridine groups coordinated trans to each other. In the crystals, a system of C-H⋯F hydrogen bonds links the cations to the hexa-fluoro-anti-monate anions, resulting in a three-dimensional architecture.

Ru(IV)-Ru(IV) complexes having the doubly oxido-bridged core with a bridging carbonato or hydrogencarbonato ligand

Ru(IV)-Ru(IV) complexes having the doubly oxido-bridged diamond core with a bridging carbonato or hydrogencarbonato ligand, [{Ru^IV(ebpma)}₂(μ-O)₂(μ-O₂CO(H)_m)]X_n (ebpma; ethylbis(2-pyridylmethyl)amine, m = 0; [IV,IV]X₂ (X = PF₆, ClO₄), m = 1; [IV,IV_1H](ClO₄)₃), were isolated via the oxidation of the corresponding carbonato-bridged Ru(III)-Ru(IV) complex ([III,IV]⁺), and "[IV,IV](ClO₄)₂ and [IV,IV_1H](ClO₄)₃" were structurally characterized. The electrochemical and spectroscopic properties of [IV,IV]²⁺ and [IV,IV_1H]³⁺ were investigated both in organic solvents and aqueous solutions. The reactivity toward organic solvents having (a) methyl group(s) and reactions with organic substrates were studied as well. This should be the first time when systematic comparisons of the Ru(IV)-Ru(IV) species and corresponding Ru(III)-Ru(IV) complexes in the same tridentate ligand system were made.

Switching the Photoreactions of Ir(III) Diamine Complexes between C-N Coupling and Dehydrogenation under Visible Light Irradiation

The selective photoreactions under mild conditions play an important role in synthetic chemistry. Herein, efficient and mild protocols for switching the photoreactions of Ir(III)-diamine complexes between the interligand C-N coupling and dehydrogenation are developed in the presence of O₂ in EtOH solution. The photoreactions of achiral diamine complexes rac-[Ir(L)₂(dm)](PF₆) (L is 2-phenylquinoline or 2-(2,4-difluorophenyl)quinoline, dm is 1,2-ethylenediamine, 1,2-diaminopropane, 2-methyl-1,2-diamino-propane, or N,N'-dimethyl-1,2-ethylenediamine) are competitive in the oxidative C-N coupling and dehydrogenation at room temperature, which can be switched into the interligand C-N coupling reaction at 60 °C, affording hexadentate complexes in good to excellent yields, or the dehydrogenative reaction in the presence of a catalytic amount of TEMPO as an additive, affording imine complexes. Mechanism studies reveal that ¹O₂ is the major reactive oxygen species, and metal aminyl is the key intermediate in the formation of the oxidative C-N coupling and imine products in the photoreaction processes. These will provide a new and practical protocol for the synthesis of multidentate and imine ligands in situ via the postcoordinated strategy under mild conditions.

Hydrocarbon Oxidation Depth: H2O2/Cu2Cl4·2DMG/CH3CN System

The oxidation of hydrocarbons of different structures under the same conditions is an important stage in the study of the chemical properties of both the hydrocarbons themselves and the oxidation catalysts. In a 50% H2O2/Cu2Cl4·2DMG/CH3CN system, where DMG is dimethylglyoxime (Butane-2,3-dione dioxime), at 50 °C under the same or similar conditions, we oxidized eleven RH hydrocarbons of different structures: mono-, bi- and tri-cyclic, framework and aromatic. To compare the composition of the oxidation products of these hydrocarbons, we introduced a new quantitative characteristic, “distributive oxidation depth D(O), %” and showed the effectiveness of its application. The adiabatic ionization potentials (AIP) and the vertical ionization potentials (VIP) of the molecules of eleven oxidized and related hydrocarbons were calculated using the DFT method in the B3LYP/TZVPP level of theory for comparison with experimental values and correlation with D(O). The same calculations of AIP were made for the molecules of the oxidant, solvent, DMG, related compounds and products. It is shown that component X, which determines the mechanism of oxidation of hydrocarbons RH with AIP(Exp) ≥ AIP(X) = 8.55 ± 0.03 eV, is a trans-DMG molecule. Firstly theoretically estimated experimental values of AIP(trans-DMG) = 8.53 eV and AIP(cis-DMG) = 8.27 eV.

Site and Enantioselective Aliphatic C-H Oxidation with Bioinspired Chiral Complexes

Selective oxidation of aliphatic C-H bonds stands as an unsolved problem in organic synthesis, with the potential to offer novel paths for preparing molecules of biological interest. The quest for reagents that can perform this class of reactions finds oxygenases and their mechanisms of action as inspiration motifs. Among the numerous families of synthetic catalysts that have been explored, complexes with linear tetraazadentate ligands combining two aliphatic amines and two aromatic amine heterocycles display a structural versatility proven instrumental in the design of C-H oxidation reactions showing site and enantioselectivities, not accessible by conventional oxidants. This manuscript makes a review of recent advances in the field.

Visible-Light-Induced Amination of Quinoline at the C8 Position via a Postcoordinated Interligand-Coupling Strategy under Mild Conditions

The postcoordinated interligand-coupling strategy provides a useful and complementary protocol for synthesizing polydentate ligands. Herein, diastereoselective photoreactions of Λ-[Ir(pq)₂(d-AA)] (Λ-d) and Λ-[Ir(pq)₂(l-AA)] (Λ-l, where pq is 2-phenylquinoline and AA is an amino acid) are reported in the presence of O₂ under mild conditions. Diastereomer Λ-d is dehydrogenatively oxidized into an imino acid complex, while diastereomer Λ-l mainly occurs via interligand C-N cross-dehydrogenative coupling between quinoline at the C8 position and AA ligands at room temperature, affording Λ-[Ir(pq)(l-pq-AA)]. Furthermore, the photoreaction of diastereomer Λ-l is temperature-dependent. Mechanistic experiments reveal the ligand-radical intermediates may be involved in the reaction. Density functional theory calculations were used to eluciate the origin of diastereoselectivity and temperature dependence. This will provide a new protocol for the amination of quinoline at the C8 position via the postcoordinated interligand C-N cross-coupling strategy under mild conditions.

Metal complex catalysis in the chemistry of lower diamondoids

The review presents the first survey of published data on the use of compounds, complexes and nanoparticles of transition metals (Fe, Co, Ni, Mn, V, Mo, Cu, Pd, Pt, Rh, Ru, Os, Au, Re and Th) in the catalytic transformations of lower diamondoids — adamantane, diamantane and their derivatives. Catalytic halogenation, oxidation, alkylation and cross-coupling reactions are considered, and the formation pathways of C–N, C–S and C–Se bonds in the series of adamantanoids are discussed. Reaction conditions, appropriate catalytic systems and the structures of products are presented.

The bibliography includes 242 references.