Isolated Neutral Organic Radical Unveiled Solvent-Radical Interaction in Highly Reducing Photocatalysis.

Diffusion-limited kinetics is a key mechanistic debate when consecutive photoelectron transfer (conPET) is discussed in photoredox catalysis. In-situ generated organic photoactive radicals can access catalytic systems as reducing as alkaline metals that can activate remarkably stable bonds. However, in many cases, the extremely short-lived transient nature of these doublet state open-shell species has led to debatable mechanistic studies, hindering adoption and development.

Structure and bonding patterns in heterometallic organometallics with linear Ln-Pd-Ln motifs.

Complexes with short intermetallic distances between transition metal fragments and lanthanide (Ln) fragments are fascinating objects of study, owing to the ambiguity of the nature of the interaction. The addition of the divalent lanthanide fragments Cp*Ln(OEt) (Ln = Sm or Yb) to a Pd(ii) complex bearing the deprotonated form of the redox-active, non-symmetrical ligand, 2-pyrimidin-2-yl-1-benzimidazole (Hbimpm), leads to two isostructural complexes, of the general formula (Cp*Ln)[μ-Pd(pyridyl)] (Ln = Sm (4) and Yb (5)). These adducts have interesting features, such as unique linear Ln-Pd-Ln arrangements and short Ln-Pd distances, which deviate from the expected lanthanide contraction.

Synthesis of CF-Containing Spirocyclic Indolines via a Red-Light-Mediated Trifluoromethylation/Dearomatization Cascade.

A red-light-mediated Pr-DMQA-catalyzed cascade intramolecular trifluoromethylation and dearomatization of indole derivatives with Umemoto's reagent has been developed. This protocol provides a facile and efficient approach for the construction of functionalized and potentially biologically important CF-containing 3,3-spirocyclic indolines with moderate to high yields and excellent diastereoselectivities under mild conditions. The success of multiple gram-scale (1 and 10 g) experiments further highlights the robustness and practicality of this protocol and the merit of the employment of red light.

Size-Controlled Hapticity Switching in [Ln(C H )(C H )] Sandwiches.

Sandwich complexes of lanthanides have recently attracted a considerable amount of interest due to their applications as Single Molecule Magnet (SMM). Herein, a comprehensive series of heteroleptic lanthanide sandwich complexes ligated by the cyclononatetraenyl (Cnt) and the cyclooctatetraenyl (Cot) ligand [Ln(Cot)(Cnt)] (Ln=Tb, Dy, Er, Ho, Yb, and Lu) is reported. The coordination behavior of the Cnt ligand has been investigated along the series and shows different coordination patterns in the solid-state depending on the size of the corresponding lanthanide ion without altering its overall anisotropy.

Trioxatriangulenium (TOTA) as a robust carbon-based Lewis acid in frustrated Lewis pair chemistry.

We report the reactivity between the water stable Lewis acidic trioxatriangulenium ion (TOTA) and a series of Lewis bases such as phosphines and N-heterocyclic carbene (NHC). The nature of the Lewis acid-base interaction was analyzed variable temperature (VT) NMR spectroscopy, single-crystal X-ray diffraction, UV-visible spectroscopy, and DFT calculations. While small and strongly nucleophilic phosphines, such as PMe, led to the formation of a Lewis acid-base adduct, frustrated Lewis pairs (FLPs) were observed for sterically hindered bases such as P( Bu).

Persistent, highly localized, and tunable [4]helicene radicals.

Persistent organic radicals have gained considerable attention in the fields of catalysis and materials science. In particular, helical molecules are of great interest for the development and application of novel organic radicals in optoelectronic and spintronic materials. Here we report the syntheses of easily tunable and stable neutral quinolinoacridine radicals under anaerobic conditions by chemical reduction of their quinolinoacridinium cation analogs.

Bis-cyclooctatetraenyl Thulium(II): Highly Reducing Lanthanide Sandwich Single Molecule Magnets.

Divalent lanthanide organometallics are well-known highly reducing compounds usually used for single electron transfer reactivity and small molecule activation. Thus, their very reactive nature prevented for many years the study of their physical properties, such as magnetic studies on a reliable basis. In this article, the access to rare organometallic sandwich compounds of Tm with the cyclooctatetraenyl (Cot) ligand impacts on the use of divalent organolanthanide compounds as an additional strategy for the design of performing Single Molecule Magnets (SMM).

Redox activity of a dissymmetric ligand bridging divalent ytter-bium and reactive nickel fragments.

The reaction of a reactive nickel dimethyl bearing a redox-active, dissymmetric ligand, which is obtained by deprotonation of 2-pyrimidin-2-yl-1H-benzimidazole (Hbimpm) with a divalent lanthanide complex, Cp*Yb(OEt), affords an unprecedented, trimeric with C(sp)-C(sp) bond formation between two ligands in an exo position. Meanwhile, the transient, dimeric species can be isolated with the same ligand coupling fashion, however, with a drastic distorsion angle of the bimpm ligand and reactive NiMe fragment, revealing the possible mechanism of this rearrangement. A much more stable dimeric congener, , with an exo ligand coupling, is synthesized in the presence of 18-crown-6, which captures the potassium counter ion.

Influence of a Lanthanide Ion on the Ni Site of a Heterobimetallic 3d-4f Mabiq Complex.

This work presents the synthesis and characterization of a 3d-4f bimetallic complex based on the redox-active macrocyclic biquinazoline ligand, Mabiq. The mixed Yb-Ni complex, [(Cp*)Yb(Mabiq)Ni]BArF (), was synthesized upon reaction of [Ni(Mabiq)]BArF () with (Cp*)Yb(OEt). The molecular structures of and its sister complex, [(Cp*)Yb(Mabiq)Ni][(Cp*)Yb(OTf)] (), confirmed the presence of a Yb(III) center and a reduced Ni-Mabiq unit.

Fe and Fe Phosphasalen Complexes: Synthesis, Characterization, and Catalytic Application for 2-Naphthol Oxidative Coupling.

We report on the synthesis and characterization of three iron(III) phosphasalen complexes, [Fe (Psalen)(X)] differing in the nature of the counter-anion/exogenous ligand (X =Cl , NO , OTf ), as well as the neutral iron(II) analogue, [Fe (Psalen)]. Phosphasalen (Psalen) differs from salen by the presence of iminophosphorane (P=N) functions in place of the imines. All the complexes were characterized by single-crystal X-ray diffraction, UV/Vis, EPR, and cyclic voltammetry.

Reversible electron transfer in organolanthanide chemistry.

This article relates the synthesis and characterization of novel heterobimetallic complexes containing a low-valent lanthanide, a tetradentate redox non-innocent ligand, the 4,5,9,10-tetraazaphenanthrene, taphen ligand and transition metal fragments of PdMe and PtMe. The experimental results are supported by a theoretical study. Investigation of their reduction properties allowed the formation of isostructural original heterotrimetallic complexes containing two Cp*Yb fragments and the (taphen)MMe (M = Pd and Pt) motifs.

Reactive Heterobimetallic Complex Combining Divalent Ytterbium and Dimethyl Nickel Fragments.

This article presented the synthesis and characterization of original heterobimetallic species combining a divalent lanthanide fragment and a divalent nickel center bridged by the bipyrimidine ligand, a redox-active ligand. X-ray crystal structures were obtained for the Ni monomer (bipym)NiMe, , as well as the heterobimetallic dimer compounds, Cp*Yb(bipym)NiMe, , along with H solution NMR, solid-state magnetic data, and DFT calculations only for . The reactivity with CO was investigated on both compounds and the stoichiometric acetone formation is discussed based on kinetic and mechanistic studies.

Electronic Structure and Reactivity of One-Electron-Oxidized Copper(II) Bis(phenolate)-Dipyrrin Complexes.

The sterically hindered bis(phenol)-dipyrrin ligands LH and LH were reacted with 1 equiv of copper(II) under ambient conditions to produce the copper radical complexes [Cu(L)] and [Cu(L)]. Their X-ray crystal structures show relatively short C-O bond distances (mean bond distances of 1.287 and 1.

Ni(II) Complexes of the Redox-Active Bis(2-aminophenyl)dipyrrin: Structural, Spectroscopic, and Theoretical Characterization of Three Members of an Electron Transfer Series.

The sterically hindered bis(2-aminophenyl)dipyrrin ligand HL was prepared. X-ray diffraction discloses a bifurcated hydrogen bonding network involving the dipyrrin and one aniline ring. The reaction of HL with one equivalent of nickel(II) in the air produces a paramagnetic neutral complex, which absorbs intensively in the Vis-NIR region.

Mn(iv) and Mn(v)-radical species supported by the redox non-innocent bis(2-amino-3,5-di-tert-butylphenyl)amine pincer ligand.

The electron-rich pincer ligand 1 has been synthesized and chelated to manganese. The octahedral Mn(iv) bis(diiminosemiquinonate) and Mn(v) (diiminobenzoquinone) (diiminosemiquinonate) radicals were structurally characterized.

The structure of a one-electron oxidized Mn(iii)-bis(phenolate)dipyrrin radical complex and oxidation catalysis control via ligand-centered redox activity.

The tetradentate ligand dppH3, which features a half-porphyrin and two electron-rich phenol moieties, was prepared and chelated to manganese. The mononuclear Mn(iii)-dipyrrophenolate complex 1 was structurally characterized. The metal ion lies in a square pyramidal environment, the apical position being occupied by a methanol molecule.