Electrocatalytic Reduction of CO and HO with Zn(II) Complexes Through Metal-Ligand Cooperation.

Air and water-stable zinc (II) complexes of neutral pincer bis(diphenylphosphino)-2,6-di(amino)pyridine ("PNP") ligands are reported. These compounds, [Zn(κ-2,6-{PhPNR}(NCH))Br] (R=Me, 1; R=H, 2), were shown to be capable of electrocatalytic reduction of CO at -2.3 V vs.

Nickel-Catalyzed Homologation of Vinylidene Difluoride (CH═CF): Selective β-F β-H Elimination.

Hydrofluoroolefins (HFOs) constitute the newest generation of fluorocarbon refrigerants and foam-blowing agents due to their reduced global warming potential their saturated analogues. To identify new synthetic routes to HFOs, we show that reactions of bulky Ni(0) phosphine and -NHC complexes with vinylidene difluoride (VF2) afford μ-fluoro-1,1,3-trifluorobut-3-enyl Ni complexes. Moreover, addition of triisopropylsilane allows for reductive elimination of the reduced product─2,4,4-trifluoro-1-butene─demonstrating the Ni-catalyzed hydrodefluorodimerization of VF2.

Electrocatalytic reduction of CO to CO and HCO with Zn(II) complexes displaying cooperative ligand reduction.

Air-stable zinc(II) pyridyl phosphine complexes, [Zn(κ-2,6-{PhPNMe}(NCH))Br] (1) and [Zn(κ-2-{PhPNMe}(NCH))Br] (2) are reported and 1 was capable of electrocatalytic reduction of CO at -2.3 V Fc to yield CO/HCOH in mixed water/acetonitrile solutions. DFT computations support a proposed mechanism involving electron transfer reactions from a species with the anionic PNP ligand ("L/Zn(II)").

Electrocatalytic H Generation from Water Relying on Cooperative Ligand Electron Transfer in "PN P" Pincer-Supported Ni Complexes.

Water is the most sustainable source for H production, and the efficient electrocatalytic production of H from mixed water/acetonitrile solutions by using two new air-stable nickel(II) pincer complexes, [Ni(κ -2,6-{Ph PNR} (NC H )Br ] (R=H I, Me II) is reported. Hydrogen generation from H O/CH CN solutions is initiated at -2 V against Fc , and bulk electrocatalysis studies showed that the catalyst functions with an excellent Faradaic efficiency and a turnover frequency of 160 s . A DFT computational investigation of the reduction behavior of I and II revealed a correlation of H formation with charge donation from electrons originating in a reduced ligand-localized orbital.

Asymmetric Ring Opening in a Tetrazine-Based Ligand Affords a Tetranuclear Opto-Magnetic Ytterbium Complex.

We report the formation of a tetranuclear lanthanide cluster, [Yb (bpzch) (fod) ] (1), which occurs from a serendipitous ring opening of the functionalised tetrazine bridging ligand, bpztz (3,6-dipyrazin-2-yl-1,2,4,5-tetrazine) upon reacting with Yb(fod) (fod =6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octandionate). Compound 1 was structurally elucidated via single-crystal X-ray crystallography and subsequently magnetically and spectroscopically characterised to analyse its magnetisation dynamics and its luminescence behaviour. Computational studies validate the observed M energy levels attained by spectroscopy and provides a clearer picture of the slow relaxation of the magnetisation dynamics and relaxation pathways.

Shedding Light on the Diverse Reactivity of NacNacAl with N-Heterocycles.

The aluminum(I) compound NacNacAl (NacNac=[ArNC(Me)CHC(Me)NAr] , Ar=2,6-iPr C H , 1) shows diverse and substrate-controlled reactivity in reactions with N-heterocycles. 4-Dimethylaminopyridine (DMAP), a basic substrate in which the 4-position is blocked, induces rearrangement of NacNacAl by shifting a hydrogen atom from the methyl group of the NacNac backbone to the aluminum center. In contrast, C-H activation of the methyl group of 4-picoline takes place to produce a species with a reactive terminal methylene.

Two heads are better than one: improving magnetic relaxation in the dysprosium metallocene upon dimerization by use of an exceptionally weakly-coordinating anion.

Partial metathesis between two weakly-coordinating anions in the archetypical dysprosium metallocene results in the first example of [BPh4]- as a bridging ligand in 4f metals, with a unique η2,η2:η2,η2-bridge. Magnetic susceptibility and relaxation dynamics studies along with ab initio calculations reveal improved slow relaxation of the magnetization in over its mononuclear congener, resulting in an energy barrier of 490 K/340 cm-1 and waist-restricted hysteresis up to 6.5 K.

Ge(0) Compound Stabilized by a Diimino-Carbene Ligand: Synthesis and Ambiphilic Reactivity.

The germylone dimNHCGe (, dimNHC = diimino N-heterocyclic carbene) was successfully prepared via the reduction of the germanium cation [dimNHCGeCl] with KC. The molecular structure of was unambiguously established by both NMR spectroscopy and single-crystal X-ray diffraction. The reactivity of was investigated, revealing that it undergoes oxidative addition of HCl, CHI, and PhI, accompanied by an unusual migration of the H, Me, and Ph groups from germanium to the carbene ligand.

Mechanochemical Preparations of Anion Coordinated Architectures Based on 3-Iodoethynylpyridine and 3-Iodoethynylbenzoic Acid.

10.1002/open.201900194.

Sequential Oxidation and C-H Bond Activation at a Gallium(I) Center.

In situ oxidation of the Ga compound NacNacGa by either N O or pyridine oxide results in the generation of a labile monomeric oxide, NacNacGa(O), which can easily cleave the C-H bonds of aliphatic and aromatic substrates featuring good donor sites. The products of this reaction are gallium organyl hydroxides. DFT calculations show that these reactions start with the formation of NacNac-Ga(O)(L) adducts, the oxo ligand of which can easily abstract protons from nearby C-H bonds, even for sp -hybridized carbon centers.

Tetrazine-Based Ligand Transformation Driving Metal-Metal Bond and Mixed-Valence Hg/Hg.

Understanding the self-assembly of cluster aggregates remains an important challenge in coordination chemistry. A chelating tetrazine-based ligand was employed to isolate an unprecedented tetranuclear Hg complex exhibiting Hg/Hg mixed valence, which also contains metal-metal bonds. Single-crystal X-ray diffraction, X-ray photoelectron spectroscopy, solid-state nuclear magnetic resonance, and theoretical approaches (density functional theory) were employed to shed some light on the structure and self-assembly of this discrete molecule.

An integrated Re(i) photocatalyst/sensitizer that activates the formation of formic acid from reduction of CO.

The complex cis-[Re(bpy)(CO)]OTf (1OTf) is an integrated photosensitizer/catalyst for the selective visible light promoted photocatalytic reduction of CO. The formation of formic acid is unique among this class of Re catalysts, which yield CO as the selective product. A supplemental photosensitizer, Ru(bpy), considerably enhanced the performance of this catalyst.

A Luminescent Thermometer Exhibiting Slow Relaxation of the Magnetization: Toward Self-Monitored Building Blocks for Next-Generation Optomagnetic Devices.

The development and integration of Single-Molecule Magnets (SMMs) into molecular electronic devices continue to be an exciting challenge. In such potential devices, heat generation due to the electric current is a critical issue that has to be considered upon device fabrication. To read out accurately the temperature at the submicrometer spatial range, new multifunctional SMMs need to be developed.

Linear End-On Coordination Modes of CO.

The second case of linear end-on and evidence for an unprecedented bridging end-on coordination mode of CO have been discovered for vanadium aryloxide complexes of the tetradentate ligand system (ONNO) (ONNO=2,4-Me -2-(OH) C H CH ] N(CH ) NMe ). The reaction of divalent (ONNO)V (TMEDA) with CO and under the appropriate reaction conditions affords the trivalent (ONNO)V (OH)(η -CO ) resulting from an intermediate CO deoxygenation pathway followed by H-atom abstraction from the aromatic solvent, and CO fixation. In contrast, the reduction of trivalent (ONNO)V Cl(THF) with K, followed by exposure to CO in ethereal solvent, afforded the dinuclear [(ONNO)V ] (μ η -CO ).

Selective Copper Complex-Catalyzed Hydrodefluorination of Fluoroalkenes and Allyl Fluorides: A Tale of Two Mechanisms.

The transition to more economically friendly small-chain fluorinated groups is leading to a resurgence in the synthesis and reactivity of fluoroalkenes. One versatile method to obtain a variety of commercially relevant hydrofluoroalkenes involves the catalytic hydrodefluorination (HDF) of fluoroalkenes using silanes. In this work it is shown that copper hydride complexes of tertiary phosphorus ligands (L) can be tuned to achieve selective multiple HDF of fluoroalkenes.

Single-Crystal NMR Characterization of Halogen Bonds.

Oxygen-17-enriched triphenylphosphine oxide and three of its halogen-bonded cocrystals featuring 1,4-diiodotetrafluorobenzene and 1,3,5-trifluoro-2,4,6-triiodobenzene as halogen bond donors have been characterized by P and O single-crystal NMR spectroscopy. Single-crystal NMR allows for the measurement of not only the magnitudes of various NMR interaction tensors, but also their orientations relative to the crystal lattice and therefore relative to the halogen bonds themselves. P chemical shift tensors, O chemical shift tensors, O quadrupolar coupling tensors, and P-O indirect nuclear spin-spin () coupling tensors are reported here for P═O···I halogen bonds.

Interaction of Multiple Bonds with NacNacGa: Oxidative Cleavage vs Coupling and Cyclization.

The reactivity of the gallium(I) compound NacNacGa (4) to a variety of unsaturated compounds has been studied. Whereas 4 proved surprisingly unreactive toward olefins, ketones, guanidines, and thioureas, it reacts with isocyanates and carbodiimides to furnish the products of coupling of two heterocumulenes. With isothiocyanate, the C═S cleavage occurs, leading to the dimer (NacNacGa)(μ-S)(μ-CNPh) and the cyclization product NacNacGa(SC═NPh).

Visible-Light Photocatalytic Reduction of CO to Formic Acid with a Ru Catalyst Supported by N,N'-Bis(diphenylphosphino)-2,6-diaminopyridine Ligands.

Visible-light photocatalytic CO reduction is carried out by using a Ru complex supported by N,N'-bis(diphenylphosphino)-2,6-diaminopyridine ("PNP") ligands, an unprecedented molecular architecture for this reaction that breaks the longstanding domination of α-diimine ligands. These competent catalysts transform CO into formic acid with high selectivity and turnover number. A proposed mechanism, with combined electron transfer and catalytic cycles, models the experimental rate of formic acid production.

7-Metalla-1,4-diphosphanorbornadienes: cycloaddition of monovalent group 13 NacNac complexes to a stable 1,4-diphosphinine.

This work presents the first example of a dienophilic property of the monovalent group-13 NacNac complexes, which are well-known for their carbene-like reactivity, e.g., addition to multiple bonds, insertion into single bonds, and oxidative cleavage of some multiple bonds.

Imino-stabilised phosphinidene (or azaphosphole?) and some of its derivatives.

Diiminophenyl (dimph) proved to be an excellent ligand platform to stabilise a low-valent phosphorus centre. The resultant compound dimphP (3), which can be rationalized as an imino-stabilised phosphinidene or benzoazaphosphole, shows remarkable chemical stability: it withstands treatment with water and oxidizers (O2 and pyridine oxide) and only reacts with excess strong acid (e.g.

Synthesis and Investigation of 2,3,5,6-Tetra-(1H-tetrazol-5-yl)pyrazine Based Energetic Materials.

The structures and properties of several energetic compounds based on a high-nitrogen-content anion, namely 2,3,5,6-tetra(1H-tetrazol-5-yl)pyrazine (H TTP) are reported here for the first time. These energetic salts were synthesized by reacting H TTP with various alkali metal hydroxides (sodium, potassium, rubidium, caesium) and N-based (ammonia, hydrazine, hydroxylamine, guanidine carbonate, aminoguanidine bicarbonate). The resulting materials were comprehensively characterized by multinuclear ( H, C) NMR spectroscopy, infrared spectroscopy, elemental analysis, DSC, as well as low-temperature single-crystal X-ray diffraction.

Photocatalytic CO Reduction with Manganese Complexes Bearing a κ-PN Ligand: Breaking the α-Diimine Hold on Group 7 Catalysts and Switching Selectivity.

The fundamental challenge of reducing CO into more valuable energy-containing compounds depends on revealing new catalysts for this process. By removal of the long-standing limitation of α-diimine ligation, which is dominant in photocatalytic complexes in this area, new visible-light, CO-reducing photocatalysts based on Mn and Re supported by κ-PN phosphinoaminopyridine ligands were identified. These catalysts, [M{κ-(PhP)NH(NCH)}(CO)Br], displayed excellent product selectivity and, by a change of only the metal center, gave a dramatic product switch from CO with M = Mn to HCOH with M = Re.

A rare example of a phosphine as a halogen bond acceptor.

We report the preparation and characterisation of a cocrystal of triphenylphosphine with 1,3,5-trifluoro-2,4,6-triiodobenzene. The structure features a rare example of phosphorus acting as a halogen bond acceptor.

[Ln] complexes (Ln = Gd, Dy): molecular analogues of natural minerals such as hydrotalcite.

Two new hexadecanuclear lanthanide complexes employing the 1,5-bis(salicylidene)carbohydrazide (Hbsc) ligand are reported herein. These polynuclear aggregates crystallize in the R3[combining macron] space group, which is unprecedented in a family of lanthanide complexes with such high nuclearity. Magnetic susceptibility measurements reveal weak intramolecular interactions between the magnetic centres, and in the case of compound 2 (Dy), single-molecule magnet properties are observed.