Synthesis of Three-Dimensional Ring Fused Heterocycles by a Selective [4 + 2] Cycloaddition Between Bicyclic Thiazolo 2-Pyridones and Arynes.

A selective [4 + 2] cycloaddition reaction of thiazolo-2-pyridones with arynes has been demonstrated. The developed protocol allows rapid access to highly functionalized, structurally complex thiazolo-fused bridged isoquinolones in high yields, which are susceptible to further late-stage functionalization.

Unravelling strong temperature-dependence of in transition metal hydrides: solvation and non-covalent interactions temperature-elastic H-H bonds.

A number of transition metal hydrides reveal intriguing temperature-dependent in their deuterated derivatives and possibly the temperature dependent hydrogen-hydrogen distance ((H-H)) as well. Previously, theoretical studies rationalized and (H-H) changes in such compounds through a "temperature-elastic" structure model with a significant population of vibrational states in an anharmonic potential. Based on the first variable temperature neutron diffraction study of a relevant complex, (-H-POCOP)IrH, observation of its elusive counterpart with longer (H-H), crystallized as an adduct with CFI, and thorough spectroscopic and computational study, we argue that the model involving isomeric species in solution at least in some cases is more relevant.

Nonheme Fe═O Complexes Supported by Four Pentadentate Ligands: Reactivity toward H- and O- Atom Transfer Processes.

Four new pentadentate N5-donor ligands, [-(1-methyl-2-imidazolyl)methyl--(2-pyridyl)-methyl--(bis-2-pyridylmethyl)-amine] (), [-bis(1-methyl-2-imidazolyl)methyl--(bis-2-pyridylmethyl)amine] (), (-(isoquinolin-3-ylmethyl)-1,1-di(pyridin-2-yl)--(pyridin-2-ylmethyl)methanamine (), and ,-bis(isoquinolin-3-ylmethyl)-1,1-di(pyridin-2-yl)methanamine (), have been synthesized based on the N4Py ligand framework, where one or two pyridyl arms of the N4Py parent are replaced by (-methyl)imidazolyl or -(isoquinolin-3-ylmethyl) moieties. Using these four pentadentate ligands, the mononuclear complexes [Fe(CHCN)()] (), [Fe(CHCN)()] (), [Fe(CHCN)()] (), and [Fe(CHCN)()] () have been synthesized and characterized. The half-wave potentials () of the complexes become more positive in the order: < < ≤ ≤ [Fe(N4Py)(CHCN)].

Selective Valorization of Bio-derived Levulinic Acid and Its Derivatives into Hydrocarbons and Biochemicals by Using Hydrosilylation.

Herein we report an efficient hydrosilylation strategy to selectively defunctionalize biomass-derived levulinic acid into value-added chemicals such as pentane-1,4-diol, pentan-2-ol, 2-MTHF and C hydrocarbons by using cost-effective silanes and the commercially available catalyst B(C F ) at room temperature. All reactions work well in chlorinated solvents but, as a greener alternative, most reactions can be run in toluene or solvent-less.

Desulfurization of Morupule Coal with Subcritical Aqueous Ethanol Extraction.

Coal combustion greatly contributes to global emissions of toxic gases into the atmosphere, with sulfur emissions as one of the prominent pollutants in addition to carbon dioxide. Nevertheless, Botswana utilizes Morupule's sub-bituminous coal with average sulfur and ash contents, as determined in this study being 1.9 and 24.

Iridium-Catalyzed Dehydrogenation in a Continuous Flow Reactor for Practical On-Board Hydrogen Generation From Liquid Organic Hydrogen Carriers.

To enable the large-scale use of hydrogen fuel cells for mobility applications, convenient methods for on-board hydrogen storage and release are required. A promising approach is liquid organic hydrogen carriers (LOHCs), since these are safe, available on a large scale, and compatible with existing refueling infrastructure. Usually, LOHC dehydrogenation is carried out in batch-type reactors by transition metals and their complexes and suffers from slow H release kinetics and/or inability to reach high energy density by weight, owing to low conversion or the need to dilute the reaction mixture.

A mononuclear iron(III) complex with unusual changes of color and magneto-structural properties with temperature: synthesis, structure, magnetization, multi-frequency ESR and DFT study.

From the reaction of 2-hydroxy-6-methylpyridine (L) with iron(II) tetrafluoroborate, a new mononuclear iron(III) octahedral complex [FeL](BF) has been isolated. The color of the complex reversibly changed from red at room temperature to yellow-orange at the liquid nitrogen temperature. Magnetization measurements indicate that iron(III) in [FeL](BF) is in a high-spin state = 5/2, from room temperature to 1.

Hydrogen-atom and oxygen-atom transfer reactivities of iron(IV)-oxo complexes of quinoline-substituted pentadentate ligands.

A series of iron(II) complexes with the general formula [Fe()(L)] ( = 1, L = F, Cl; = 2, L = NCMe, HO) have been isolated and characterized. The X-ray crystallographic data reveals that metal-ligand bond distances vary with varying ligand field strengths of the sixth ligand. While the complexes with fluoride, chloride and water as axial ligand are high spin, the acetonitrile-coordinated complex is in a mixed spin state.

Synthesis of cyclic carbonates from epoxides and carbon dioxide catalyzed by talc and other phyllosilicates.

Naturally occurring phyllosilicate minerals such as talc and vermiculite in conjunction with n-tetra butyl ammonium bromide (TBAB) co-catalyst were found to be efficient in the coupling of CO with epoxides to form cyclic carbonates. The reaction was carried out in a pressurized autoclave reactor at moderate pressures of 10-35 bars and temperatures of 100-150 °C. The optimized catalyst system exhibited > 90% conversion of the epoxides and > 90% selectivity for the desired cyclic carbonates, in the presence or absence of a solvent.

Directed C-H Halogenation Reactions Catalysed by Pd Supported on Polymers under Batch and Continuous Flow Conditions.

A new generation of N-heterocyclic carbene palladium(II) complexes containing vinyl groups in different positions in the backbone of the N-heterocycle have been developed. The fully characterised monomers were copolymerised with divinylbenzene to fabricate robust polymer supported NHC-Pd complexes and these polymers were applied as heterogeneous catalysts in directed C-H halogenation of arenes with a pyridine-type directing group. The catalysts demonstrated medium-high catalytic activity with up to 90 % conversion and 100 % selectivity in chlorination.

An Approach to Carbide-Centered Cluster Complexes.

We report the first examples of the carbide ligand in (CyP)ClRu≡C (RuC) developing into a μ ligand toward metal centers. Conventionally, sterics exclude this coordination mode, but Fe(CO) and Co(CO) expel bridging CO ligands upon reaction with RuC to form trimetallic (CyP)ClRu═CFe(CO) (RuCFe) and (CyP)ClRu═CCo(CO) (RuCCo) complexes. Thus, the proximity offered by metal-metal associations in bimetallic carbonyl complexes allows the formation of trinuclear carbide complexes as verified by NMR, Mössbauer, and X-ray spectroscopic techniques.

Ru-Catalyzed Cross-Dehydrogenative Coupling between Primary Alcohols to Guerbet Alcohol Derivatives: with Relevance for Fragrance Synthesis.

A simple method has been developed for the cross dehydrogenative coupling between two different primary alcohols using readily available RuCl(PPh) as a precatalyst through the borrowing-hydrogen approach. The present methodology is applicable to a large variety of alcohol derivatives including long chain aliphatic alcohols and heteroaryl alcohols. In addition, the methodology was applied in a straightforward protocol to synthesize commercially available fragrances such as Rosaphen and Cyclamenaldehyde in good yields.

Synthesis, characterisation and ion-binding properties of oxathiacrown ethers appended to [Ru(bpy)]. Selectivity towards Hg, Cd and Pb.

A series of complexes with oxathiacrown ethers appended to a [Ru(bpy)] moiety have been synthesized and characterised using H NMR, C NMR, IR, electronic absorption and emission spectroscopies, mass spectrometry and elemental analyses. The complexes exhibit strong MLCT luminescence bands in the range 608-611 nm and one reversible metal centred oxidation potential in the range 1.00-1.

Polymer-Supported Palladium(II) Carbene Complexes: Catalytic Activity, Recyclability, and Selectivity in C-H Acetoxylation of Arenes.

Heterogeneous catalysts for selective oxidation of C-H bonds were synthesized by co-polymerization of new N-heterocyclic carbene-palladium(II) (NHC-Pd ) monomers with divinylbenzene. The polymer-supported NHC-Pd -catalysed undirected C-H acetoxylation of simple and methylated arenes as well as polyarenes, with similar or superior efficiency compared to their homogeneous analogues. In particular, the regioselectivity has been improved in the acetoxylation of biphenyl and naphthalene compared to the best homogeneous catalysts.

Csp -H Activation without Chelation Assistance in an Iridium Pincer Complex Forming Cyclometallated Products.

Cyclometallation of 8-methylquinoline and 2-(dimethylamino)-pyridine in an iridium-based pincer complex is described. The C-H activation of 2-(dimethylamino)pyridine is not chelation assisted, which has not been described before for Csp -H bonds in cyclometallation reactions. The mechanism of the cyclometallation of 2-(dimethylamino)pyridine was studied by DFT calculations and kinetic measurements.

An electron poor iridium pincer complex for catalytic alkane dehydrogenation.

A novel electron deficient 4,6-bis(trifluoromethyl)-1,3-phenylene diphosphinite ligand 4 was developed and synthesized. Reaction of Ir precursors with ligand 4 gave chloro(hydride) pincer complex 5, which demonstrated a higher TON in alkane dehydrogenation reactions compared to similar phosphinite based pre-catalysts. The formation of cyclooctene (COE) and tert-butylethylene adducts of the 14e catalysts was also studied and the COE adduct is implicated as the resting state of the catalyst.

Synthesis and crystal structure of trans-di-chlorido[3-methyl-1-(4-vinyl-benz-yl)-1H-imidazol-3-ium-2-yl-κC (2)](4-phenyl-pyridine-κN)palladium(II).

The title compound, [PdCl2(C11H9N)(C13H14N2)], represents a new class of palladium-based polymerizable monomer which could give a potentially catalytically active polymer. It was synthesized via transmetallation from the corresponding silver complex. The Pd(II) ion coordinates two Cl anions, one C atom from the N-heterocyclic carbene (NHC) ligand and one N atom from the 4-phenyl-pyridine ligand, displaying a slightly distorted square-planar geometry.

Solvent-Dependent Structure of Iridium Dihydride Complexes: Different Geometries at Low and High Dielectricity of the Medium.

The hydride iridium pincer complex [(PCyP)IrH2] (PCyP=cis-1,3-bis[(di-tert-butylphosphino)methyl]cyclohexane, 1) reveals remarkably solvent-dependent hydride chemical shifts, isotope chemical shifts, JHD and T1(min), with rHH increasing upon moving to more polar medium. The only known example of such behaviour (complex [(POCOP)IrH2], POCOP=2,6-(tBu2PO)2C6H3) was explained by the coordination of a polar solvent molecule to the iridium (J. Am.

Regioselectivity in C-H activation: reagent control in cyclometallation of 2-(1-naphthyl)-pyridine.

2-(1-Naphthyl)-pyridine () possesses sp(2) C-H bonds in both the γ- and δ-positions and is therefore a suitable substrate for studying the cyclometallation selectivity with different reagents and conditions. Such selectivity studies are reported. Based on deuterium-exchange experiments it is concluded that cycloruthenation with RuCl2(p-cymene) dimer is reversible with kinetic and thermodynamic preference for γ-substitution.

A Protocol for the exo-Mono and exo,exo-Bis Functionalization of the Diazocine Ring of Tröger's Base.

An efficient protocol has been developed for the exo-mono and exo,exo-bis functionalization of Tröger's base in the benzylic 6 and 12 positions of the diazocine ring. The lithiation of Tröger's base using s-BuLi/TMEDA followed by electrophilic quench affords exo-mono- and exo,exo-bis-substituted derivatives of Tröger's base in good to excellent yields. The variation of the number of equivalents of s-BuLi/TMEDA and the order of addition of the electrophile strongly govern the outcome of the reaction for each electrophile.

Synthesis, molecular structure, and chiroptical properties of dibenzylidene derivatives of bicyclo[3.3.1]nonane and brexane.

Synthesis of several enantiomerically pure unsaturated bicyclo[3.3.1]nonane and related brexane (tricyclo[4.

Crystal structure of (piperidine-1-carbo-di-thio-ato-κ(2) S,S)[2-(pyridin-2-yl)phenyl-κ(2) C (1),N]palladium(II).

The title compound, [Pd(C11H8N)(C6H10NS2)], crystallizes with three similar and discrete mol-ecules in the asymmetric unit. The CNS2 donor set defines a distorted square-planar geometry around the Pd(II) atom, with very small deviations from planarity. The bidentate nature of the ligands gives fairly large deviations from the ideal 90° angles; the C-Pd-N angles are all around 81° and the S-Pd-S angles are around 75°.

Reversible α-Hydrogen and α-Alkyl Elimination in PC(sp(3))P Pincer Complexes of Iridium.

Despite significant progress in recent years, the cleavage of unstrained C(sp(3))-C(sp(3)) bonds remains challenging. A C-C coupling and cleavage reaction in a PC(sp(3))P iridium pincer complex is mechanistically studied; the reaction proceeds via the formation of a carbene intermediate and can be described as a competition between α-hydrogen and α-alkyl elimination; the latter process was observed experimentally and is an unusual way of C(sp(3))-C(sp(3)) bond scission, which has previously not been studied in detail. Mechanistic details that are based upon kinetic studies, activation parameters, and DFT calculations are also discussed.

Formation of a C-C double bond from two aliphatic carbons. Multiple C-H activations in an iridium pincer complex.

The search for novel, atom-economic methods for the formation of C-C bonds is of crucial importance in synthetic chemistry. Especially attractive are reactions where C-C bonds are formed through C-H activation, but the coupling of unactivated, alkane-type C -H bonds remains an unsolved challenge. Here, we report iridium-mediated intramolecular coupling reactions involving up to four unactivated C -H bonds to give carbon-carbon double bonds under the extrusion of dihydrogen.

Cyclometallated gold(III) aryl-pyridine complexes as efficient catalysts for three-component synthesis of substituted oxazoles.

Cyclometallated aryl-pyridine gold(iii) complexes are shown to be efficient catalysts for the multicomponent reaction between N-benzyl imines, alkynes, and acyl chlorides to form trisubstituted oxazoles. The reaction typically proceeds in good yields (up to over 80%) and short reaction times (∼15 minutes). The high stability of the investigated cyclometallated catalysts enables a retained efficiency for this reaction in terms of rate and yield using as little as 0.