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New data are obtained on the thermal behavior and sublimation and melting of (pivaloyltrifluoroacetonato)(cyclooctadiene-1,5)iridium {[Ir(cod)(ptac)]}. The condensed phase is studied via differential scanning calorimetry, and the complex's temperature of melting is determined along with its enthalpy and entropy of fusion: Tmelt = 405.9 ± 0.5 K; (Tmelt) = 20.4 ± 0.3 kJ mol−1; ; (Tmelt) = 50.3 ± 0.7 J mol−1 K−1. The temperature dependence of the saturated vapor pressure of [Ir(cod)(ptac)] in the 363–397 K range of temperatures is obtained from the flow. The thermodynamic characteristics of sublimation are calculated at the average temperature of the experimental range and 298.15 K: (Tav) = 102.0 ± 1.8 kJ mol−1; (Tav) = 188.5 ± 3.3 J mol−1 K−1; (298.15 K) = 107.3 ± 2.9 kJ mol−1; and (298.15 K) = 204.1 ± 5.7 J mol−1 K−1. The resulting values are compared to those of similar compounds of iridium(I) and other β-diketones, [Ir(cod)(β-dik)]. The results form the basis for developing a way of assessing the thermodynamic properties of complexes [M(cod)(β-dik)], which is needed when compounds (e.g., [Ag(cod)(β-dik)]) are hypersensitive to heating and it is impossible to determine reliable thermodynamic characteristics experimentally in order to establish the optimum conditions for the gas-phase deposition of etal-containing coatings. [ABSTRACT FROM AUTHOR]

New data are obtained on the thermal behavior and processes of vaporization and melting of (hexafluoroacetylacetonato)(cyclooctadiene-1,5)silver, [Ag(cod)(hfac)]n (n = 1, 2). The dimeric form of the complex is synthesized and characterized. The condensed phase is studied via differential scanning calorimetry plus thermogravimetric and differential thermal analysis. The thermal stability and qualitative volatility are assessed, and the temperature, enthalpy, and entropy of melting are determined for the complex. It is shown that the compound is highly sensitive to heating, preventing the experimental determination of reliable thermodynamic characteristics. Thermodynamic characteristics of the evaporation of these chelates are calculated using standardized values of enthalpies and entropies of the sublimation and melting of similar heteroligand complexes of copper(I) and iridium(I). The data are used to construct structure–volatility correlations that allow estimates of the required phase transitions of the target silver complex. An approach to evaluating the thermodynamic properties of complexes of the composition [M(cod)(β-dik)]n is proposed to determine the optimum conditions for depositing coatings that contain metal. [ABSTRACT FROM AUTHOR]

New data on the thermal behavior, sublimation, and melting of (hexafluoroacetylacetonato)(cyclooctadiene-1,5)copper, [Cu(cod)(hfac)], have been obtained. The condensed phase was studied by thermal and differential thermal analysis and differential scanning calorimetry. The temperature, enthalpy, and entropy of melting of the complex were determined. The temperature dependence of the saturated vapor pressure of [Cu(cod)(hfac)] in the temperature range 293–337 K was obtained by the Knudsen effusion method with mass spectrometric recording of the gas phase composition. The thermodynamic characteristics of sublimation were calculated at the average temperature over the experimental range and at 298.15 K: (Tav) = 94.8 ± 1.5 kJ mol–1; (Tav) = 200.9 ± 3.2 J mol–1 K–1; (298.15 K) = 95.8 ± 3.1 kJ mol–1; (298.15 K) = 203.5 ± 6.6 J mol–1 K–1. The obtained values are compared with data for a similar iridium(I) compound, [Ir(cod)(hfac)]. The results were used formulate approaches to evaluation of the thermodynamic properties of [M(cod)(hfac)] complexes to determine the optimum conditions for the deposition of metal-containing coatings. These approaches are necessary in those cases when compounds of this type (e.g., [Ag(cod)(hfac)]) are hypersensitive to heating and it is impossible to determine reliable thermodynamic characteristics experimentally. [ABSTRACT FROM AUTHOR]

A convenient and efficient approach for the construction of aryl trifluoromethyl selenoethers from aryl iodides under mild conditions is reported. Electrochemical activation of stable and inexpensive NiBr2bipy (bipy – bipyridine) complex instead of labile Ni(COD)2 (COD – cyclooctadiene) catalyst. [NMe4][SeCF3] is employed as shelf‐stable source of SeCF3 fragment. The reaction tolerates a wide range of substrates, including modification of drug‐like molecules. Cyclic voltammetry studies allow insight into the reaction mechanism. [ABSTRACT FROM AUTHOR]

The synthesis of some novel functionalized azaheterocyclic β‐amino esters with multiple chiral centers via a stereocontrolled synthetic route has been carried out using some cyclooctene β‐amino acids as starting model compounds. The strategy of the method was planned to create some novel unsaturated N‐protected cyclic β‐amino esters that were subjected to ring‐opening metathesis (ROM) followed by selective ring‐closing metathesis (RCM). A number of experimental conditions were accomplished to investigate the activity of catalysts, yields, conversions, and substrate effect on ring‐rearrangement metathesis (RRM) transformation. Importantly, the procedure used in this synthetic process does not affect the configuration of the chiral centers; therefore, the stereochemistry of the starting cyclooctadiene β‐amino acids predetermined the structure of the new azaheterocyclic derivatives. [ABSTRACT FROM AUTHOR]

Rhodium siloxide complexes have been used as homogeneous catalysts and model compounds for silica-supported metal catalysts. However, rhodium complexes with multidentate siloxide ligands have rarely been prepared. In this study, a dinuclear rhodium complex supported by a bidentate tetra-tert-butoxy disiloxide ligand, {Rh(COD)}2{μ-(OSi(OtBu)2)2O} (3) (COD = cyclooctadiene), was synthesized and its basic reactivity was elucidated. When 3 reacted with carbon monoxide, a dinuclear rhodium carbonyl complex, {Rh(CO)2}2{μ-(OSi(OtBu)2)2O} (A), formed as an intermediate, which produced a bis-dinuclear rhodium carbonyl complex, [{Rh(CO)2}2{μ-(OSi(OtBu)2)2O}]2 (4), by spontaneous dimerization. The dimerization of A could be attributed to the relatively weak electron-donating ability of the tetra-tert-butoxy disiloxide ligand, suggesting that substituents on siloxide ligands exert a significantly large effect on the formation of rhodium siloxide complexes. In addition, the reaction of 3 with trimethylphosphine (PMe3) afforded different dinuclear rhodium complexes, {(PMe3)Rh(COD)}2{(OSi(OtBu)2)2O} (5), {(PMe3)2Rh}{Rh(COD)}{μ-(OSi(OtBu)2)2O} (6), and {Rh(PMe3)2}2{μ-(OSi(OtBu)2)2O} (7), depending on the reaction temperature and the equivalent of PMe3 used, indicating that the substitution reaction of COD by PMe3 proceeds in a stepwise manner. Understanding the basic reactivity of these rhodium siloxide complexes may contribute to the development of silica-supported metal catalysts. [ABSTRACT FROM AUTHOR]

The facile synthesis of a range of eleven cyclooctadiene Ru(II) complexes of the type [RuCl2(cod)(NCR)2] featuring different nitrile ligands using two synthetic routes is reported. The solid‐state characterization (SCXRD) of twelve complexes is also described. Complex instability in solution led to spontaneous dimerization to yield a dimeric complex. Using these complexes, varied catalytic activity was observed in six different transformation reactions, of which the transfer hydrogenation of ketones was the highest (yields of 99 % after 30 minutes, TOF=156 h−1). The electrochemical (CV), DFT, and catalytic properties of the complexes evaluated showed that while the majority of the characteristics of the complexes are comparable, three complexes stood out with the lowest catalytic activity (16 % and lower), the highest (most positive) formal redox potentials for RuII/RuIII (E0′ of up to +1.4 V), as well as exhibiting some of the smallest energy gaps (as small as 1.21 eV) in the series. [ABSTRACT FROM AUTHOR]

The facile synthesis of a range of eleven cyclooctadiene Ru(II) complexes of the type [RuCl2(cod)(NCR)2] featuring different nitrile ligands using two synthetic routes is reported. The solid‐state characterization (SCXRD) of twelve complexes is also described. Complex instability in solution led to spontaneous dimerization to yield a dimeric complex. Using these complexes, varied catalytic activity was observed in six different transformation reactions, of which the transfer hydrogenation of ketones was the highest (yields of 99 % after 30 minutes, TOF=156 h−1). The electrochemical (CV), DFT, and catalytic properties of the complexes evaluated showed that while the majority of the characteristics of the complexes are comparable, three complexes stood out with the lowest catalytic activity (16 % and lower), the highest (most positive) formal redox potentials for RuII/RuIII (E0′ of up to +1.4 V), as well as exhibiting some of the smallest energy gaps (as small as 1.21 eV) in the series. [ABSTRACT FROM AUTHOR]

Diene rhodium complexes are important catalysts in modern organic synthesis. Herein, we report a new approach to such complexes with the uncommon planar chirality. The synthesis is achieved by face‐selective coordination of the prochiral 2,5‐disubstituted‐1,4‐benzoquinones (R2‐Q) with rhodium precursors containing the chiral auxiliary ligand S‐salicyl‐oxazoline (S‐Salox). Such coordination leads to the formation of (R,R‐R2‐Q)Rh(S‐Salox) complexes in high yields and with exceptional diastereoselectivity (d. r.>20 : 1). Subsequent replacement of the auxiliary ligand provides various benzoquinone rhodium complexes with retention of the planar chirality. Combined theoretical and experimental studies show that due to their electron‐withdrawing nature benzoquinones bind metals stronger than the related 1,4‐cyclohexadiene, but weaker than other common diene ligands, such as cyclooctadiene. [ABSTRACT FROM AUTHOR]

Addition polymerization of cycloalkenes (cyclopentene, cyclopentadiene, cyclooctene, cyclooctadiene) in the presence of a new type of catalytic systems—Pd(0) complexes activated with arendiazonium salts—was studied. It was shown that cyclopentene, cyclooctene, and cyclooctadiene are not active in polymerization with these catalytic systems, while cyclopentadiene is actively involved in polymerization. The polycyclopentadiene structure was confirmed by 1H NMR spectroscopy. The molecular weight parameters and microstructure of the polymer were determined. [ABSTRACT FROM AUTHOR]

The title compounds, [Ir(C51H64N2)Cl(C8H12)]·CH2Cl2, (I), and [Ir(C51H64N2)Cl(C8H12)], (II), represent the first two examples of hexahydrobenzoimidazole-based N-heterocyclic carbene (NHC) iridium complexes. The diastereomeric complexes differing only in their axial chirality, which could be separated via column chromatography, show noticeable differences in their 1H NMR spectra. Compound (I) crystallizes in the monoclinic system (P21) with two independent complexes and two half-occupied dichloromethane molecules in the asymmetric unit, while compound (II) crystallizes in the orthorhombic system (P212121) with one complex in the asymmetric unit. The fused five-membered N-heterocycles of NHCs show unusually high backbone torsion angles of −34.1 (5) and −30.9 (5)° for (I) and −31.5 (7)° for (II), but the Ir—Ccarbene bond lengths of 2.046 (6) and 2.021 (6) Å for (I) and 2.045 (8) Å for (II) present typical NHC—Ir bond lengths. The solvent molecule in the crystal of (I) was found to be highly disordered and its contribution to the scattering was masked using the solvent-masking routine smtbx.mask in OLEX2 [Dolomanov et al. (2009). J. Appl. Cryst. 42, 339–341]. The solvent contribution is not included in the reported chemical formula and other crystal data.

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N‐fused porphyrin (NFP) is a unique class of photostable near‐infrared dyes with an 18π aromatic tetrapyrrole macrocyclic skeleton containing a tri‐fused pentacyclic moiety. Here, the synthesis of an iridium complex of N‐fused bilatrienone is reported as the degradation product of Ir‐cyclooctadiene (cod)‐induced oxidative cleavage of NFP under aerobic conditions. Similar to the native bilin chromophores, the ring‐opened complex featured a broken π‐conjugation circuit and exhibited a broad visible absorption band. In contrast, metalation of NFP using an iridium(I)(cod) complex under an inert atmosphere resulted in the formation of a cod‐isomerized (κ1,η3‐C8H12)‐Ir complex. [ABSTRACT FROM AUTHOR]

Ruthenium alkylidene mediated ring‐opening metathesis polymerizations (Ru‐ROMP) are evaluated in green chemical solvents to increase their green metrics. The Ru‐ROMP of representative monomers of norbornene, oxa‐norbornene, and cyclooctadiene were compared in reference solvents (tetrahydrofuran and chloroform) and green solvents (2‐methyl tetrahydrofuran, ethyl acetate, dimethyl carbonate, and acetone). The results showed that the use of a green solvent is promising. All green solvents exhibited excellent Ru‐ROMP efficiency while their chain length controls were sensitive to solvents and monomers. Among the candidates, dimethyl carbonate expressed the general applicability of various combinations of monomers and solvents. [ABSTRACT FROM AUTHOR]

Compound [Ir(C8H12)(C51H45P4)]Cl2 or [Ir(cod)(CH(dppm)2-κ3P,C,P)]Cl2 (1a), was obtained from [IrCl(cod)]2 and the carbodiphosphorane (CDP) salt [CH(dppm)2]Cl [where cod = cycloocta-1,5-diene and dppm = bis(diphenylphosphino)methane]. Treatment of 1a with thallium(I) trifluoromethanesulfonate [Tl(OTf)] and subsequent crystallization gave complex [Ir(C8H12)(C51H45P4)](OTf)2·CH3CO2C2H5·CH2Cl2 or [Ir(cod)(CH(dppm)2-κ3P,C,P)](OTf)2·CH3CO2C2H5·CH2Cl2 (1b) [systematic name: (cycloocta-1,5-diene)(1,1,3,3,5,5,7,7-octaphenyl-1,7-diphospha-3,5-diphosphoniaheptan-4-yl)iridium(I) bis(trifluoromethanesulfonate)–ethyl acetate–dichloromethane (1/1/1)]. This five-coordinate iridium(I) complex cation adopts a trigonal–bipyramidal geometry with the CDP carbon and one cod double bond in axial sites. Compound 1b represents the first example of a non-meridional coordination of the PCP pincer ligand [CH(dppm)2]+ with a P—Ir—P angle of 98.08 (2)°. Compound 2, [IrCl2H(C51H44P4)]·(CH3)2CO or [IrCl2H(C(dppm)2-κ3P,C,P)]·(CH3)2CO [systematic name: dichloridohydrido(1,1,3,3,5,5,7,7-octaphenyl-1,5λ5,7-triphospha-3-phosphoniahept-4-en-4-yl)iridium(III) acetone monosolvate], crystallizes as an acetone monosolvate. It is a six-coordinate IrIII coordination compound. Here, the PCP pincer ligand is coordinated in a meridional manner; one chlorido ligand is positioned trans to the carbon donor, the remaining two coordination sites being occupied by the second chlorido and a hydrido ligand trans to each other. Complex 3, [IrCl2H(C51H45P4)]Cl·5H2O or [IrCl2H(CH(dppm)2-κ3P,C,P)]Cl·5H2O [systematic name: dichloridohydrido(1,1,3,3,5,5,7,7-octaphenyl-1,7-diphospha-3,5-diphosphoniaheptan-4-yl)iridium(III) chloride pentahydrate], represents the conjugate CH acid of 2. The ligand [CH(dppm)2]+ is coordinated in a meridional manner. In the cationic six-coordinate IrIII complex 4, [IrClH(CO)(C51H44P4)]Cl·2CH3OH·H2O or [IrClH(CO)(C(dppm)2-κ3P,C,P)]Cl·2CH3OH·H2O [systematic name: carbonylchloridohydrido(1,1,3,3,5,5,7,7-octaphenyl-1,5λ5,7-triphospha-3-phosphoniahept-4-en-4-yl)iridium(III) chloride–methanol–water (1/2/1)], the chlorido ligand is found in the plane defined by the Ir center and the meridional PCP ligand; the H and CO ligands are positioned axially to this plane and trans to each other.

Diene self-exchange reactions of the 17-electron, formally cobalt(0) cyclooctadienyl precatalyst, (R,R)-(iPrDuPhos)Co(COD) (P2CoCOD, (R,R)-iPrDuPhos = 1,2-bis((2R,5R)-2,5-diisopropylphospholano)benzene, COD = 1,5-cyclooctadiene) were studied using natural abundance and deuterated 1,5-cyclooctadiene. Exchange of free and coordinated diene was observed at ambient temperature in benzene-d6 solution and kinetic studies support a dissociative process. Both neutral P2CoCOD and the 16-electron, cationic cobalt(I) complex, [(R,R)-(iPrDuPhos)Co(COD)][BArF4] (BArF4 = B[(3,5-(CF3)2)C6H3]4) underwent instantaneous displacement of the 1,5-cyclooctadiene ligand by carbon monoxide and generated the corresponding carbonyl derivatives. The solid-state parameters, DFT-computed Mulliken spin density and analysis of molecular orbitals suggest an alternative description of P2CoCOD as low-spin cobalt(II) with the 1,5-cyclooctadiene acting as a LX2-type ligand. This view of the electronic structure provides insight into the nature of the ligand substitution process and the remarkable stability of the neutral cobalt complexes toward protic solvents observed during catalytic alkene hydrogenation. [ABSTRACT FROM AUTHOR]

The reactions of 2-pyridinesulfenyl halides with cyclopentene, 1,4-cyclohexadiene, 1,5-cyclooctadiene, 1,3-cyclooctadiene, and norbornene, depending on the structure of the alkene, the nature of the halogen, and the duration of the process, lead to the formation of two types of adducts, electrophilic addition products or condensed compounds, [1,3]thiazolo[3,2-a]pyridinium derivatives, in high yields. [ABSTRACT FROM AUTHOR]

Summary of main observation and conclusion: Controlling the regio‐ and stereochemistry of the photoproducts in solution is far more challenging for polyenes than for monoalkenes. Herein, a supramolecularly‐controlled topochemical reaction of conjugated dienes in homogeneous system is developed, ultimately providing two cyclooctadiene‐cored tetraimidazolium molecular receptors exclusively. These cyclooctadiene derivatives exhibited highly sensitive and selective fluorescence sensing for thymine relative to other biologically relevant species in aqueous solution at physiological pH. Both the cyclooctadiene moieties and imidazolium units play important roles in the selective recognition observed. The presented supramolecularly‐controlled method allows the simple yet rare selective photoconversion of flexible cyclooctadiene derivatives in solution. This study offers a new synthetic strategy for the preparation of functional molecules with potential for use in biological applications. [ABSTRACT FROM AUTHOR]

The title compounds, [Ir(C51H64N2)Cl(C8H12)]CH2C2, (I), and [Ir(C51H64N2)- Cl(C8H12)], (II), represent the first two examples of hexahydrobenzoimidazolebased N-heterocyclic carbene (NHC) iridium complexes. The diastereomeric complexes differing only in their axial chirality, which could be separated via column chromatography, show noticeable differences in their 1H NMR spectra. Compound (I) crystallizes in the monoclinic system (P21) with two independent complexes and two half-occupied dichloromethane molecules in the asymmetric unit, while compound (II) crystallizes in the orthorhombic system (P212121) with one complex in the asymmetric unit. The fused five-membered N-heterocycles of NHCs show unusually high backbone torsion angles of 34.1 (5) and 30.9 (5) for (I) and 31.5 (7) for (II), but the Ir--Ccarbene bond lengths of 2.046 (6) and 2.021 (6) A ° for (I) and 2.045 (8) A ° for (II) present typical NHC-- Ir bond lengths. The solvent molecule in the crystal of (I) was found to be highly disordered and its contribution to the scattering was masked using the solventmasking routine smtbx.mask in OLEX2 [Dolomanov et al. (2009). J. Appl. Cryst. 42, 339--341]. The solvent contribution is not included in the reported chemical formula and other crystal data. [ABSTRACT FROM AUTHOR]

Summary of main observation and conclusion: Controlling the regio‐ and stereochemistry of the photoproducts in solution is far more challenging for polyenes than for monoalkenes. Herein, a supramolecularly‐controlled topochemical reaction of conjugated dienes in homogeneous system is developed, ultimately providing two cyclooctadiene‐cored tetraimidazolium molecular receptors exclusively. These cyclooctadiene derivatives exhibited highly sensitive and selective fluorescence sensing for thymine relative to other biologically relevant species in aqueous solution at physiological pH. Both the cyclooctadiene moieties and imidazolium units play important roles in the selective recognition observed. The presented supramolecularly‐controlled method allows the simple yet rare selective photoconversion of flexible cyclooctadiene derivatives in solution. This study offers a new synthetic strategy for the preparation of functional molecules with potential for use in biological applications. [ABSTRACT FROM AUTHOR]

This review presents an update on the emerging field of enantioselective multicatalyzed tandem reactions published since the beginning of 2015. It illustrates how much the combination of different types of catalyst allows unprecedented enantioselective one‐pot reactions of many types to be achieved, allowing a direct access to a variety of very complex chiral molecules. Abbreviations: acac: acetylacetonate; Ar: aryl; Bn: benzyl; Boc: tert‐butoxycarbonyl; BPE: 1,2‐bis(2‐pyridyl)ethane; Bz: benzoyl; CAPT: chiral anion phase‐transfer; Cbz: benzyloxycarbonyl; cod: cyclooctadiene; Cy: cyclohexyl; dba: (E,E)‐dibenzylideneacetone; DBU: 1,8‐diazabicyclo[5.4.0]undec‐7‐ene; DCE: dichloroethane; de: diastereomeric excess; DIPEA: diisopropylethylamine; dme: 1,2‐dimethoxyethane; DPG: 1,3‐diphenylguanidine; dppe: 1,2‐bis(diphenylphosphino)ethane; ee: enantiomeric excess; EWG: electron‐withdrawing group; Hept: heptyl; Hex: hexyl; L: ligand; MTBE: methyl tert‐butyl ether; MOM: methoxymethyl; MS: molecular sieves; Naph: naphthyl; NHC: N‐heterocyclic carbene; Pent: pentyl; Phth: phthaloyl; pin: pinacolato; Pybox: 2,6‐bis(2‐oxazolyl)pyridine; r.t.: room temperature; TEMPO: 2,2,6,6‐tetramethylpiperidine 1‐oxyl; Tf: trifluoromethanesulfonyl; THF: tetrahydrofuran; TMP: 2,2,6,6‐tetramethylpiperidine; TMS: trimethylsilyl; Tol: tolyl; triphos: bis(diphenylphosphinoethyl)phenylphosphine; Ts: 4‐toluenesulfonyl (tosyl). [ABSTRACT FROM AUTHOR]

The switching of single cyclooctadiene molecules chemisorbed on a Si(100) surface between two stable conformations, can be achieved with a scanning tunneling microscope [Nacci et al., Phys. Rev. B 77, 121405(R) (2008)]. Recently, it was shown by quantum chemical and quantum dynamical simulations that major experimental facts can be explained by a single-mode model with switching enforced by inelastic electron tunneling (IET) excitations and perturbed by vibrational relaxation [Nacci et al., Nano Lett. 9, 2997 (2009)]. In the present paper, we extend the previous theoretical work in several respects: (1) The model is generalized to a two-mode description in which two C2H4 units of COD can move independently; (2) contributions of dipole and, in addition, (cation and anion) resonance-IET rates are considered; (3) the harmonic-linear vibrational relaxation model used previously is generalized to anharmonic vibrations. While the present models highlight generic aspects of IET-switching between two potential minima, they also rationalize specific experimental findings for COD/Si(100): (1) A single-electron excitation mechanism with a linear dependence of the switching rate on tunneling current I, (2) the capability to switch both at negative and positive sample biases, and (3) a crossover temperature around ∼60 K from an IET-driven, T-independent atom tunneling regime, to classical over-the-barrier isomerization with exponential T-dependence at higher temperatures for a bias voltage of +1.5 V and an average tunneling current of 0.73 nA. [ABSTRACT FROM AUTHOR]

Chloride abstraction from [(R,R)‐(iPrDuPhos)Co(μ‐Cl)]2 with NaBArF4 (BArF4=B[(3,5‐(CF3)2)C6H3]4) in the presence of dienes, such as 1,5‐cyclooctadiene (COD) or norbornadiene (NBD), yielded long sought‐after cationic bis(phosphine) cobalt complexes, [(R,R)‐(iPrDuPhos)Co(η2,η2‐diene)][BArF4]. The COD complex proved substitutionally labile undergoing diene substitution with tetrahydrofuran, NBD, or arenes. The resulting 18‐electron, cationic cobalt(I) arene complexes, as well as the [(R,R)‐(iPrDuPhos)Co(diene)][BArF4] derivatives, proved to be highly active and enantioselective precatalysts for asymmetric alkene hydrogenation. A cobalt–substrate complex, [(R,R)‐(iPrDuPhos)Co(MAA)][BArF4] (MAA=methyl 2‐acetamidoacrylate) was crystallographically characterized as the opposite diastereomer to that expected for productive hydrogenation demonstrating a Curtin–Hammett kinetic regime similar to rhodium catalysis. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Three volatile iridium (I) complexes with cyclooctadiene and acetylacetonate derivatives were synthesized and characterized. • Two complexes contained beta-ketoiminate ligand were obtained for the first time. • Thermal properties of complexes were studied by TG, DSC and tensiometry (transpiration method). • Sublimation and melting enthalpies and entropies were derived. • Effect of donor atom changing (O vs. N) in chelating ligand on volatility and thermal stability of complexes was established. Abstract Three hetero-ligand volatile iridium (I) complexes with β-diketonate derivatives [Ir(cod)(L)] (cod = 1,5-cyclooctadiene, L = CH 3 C(O)CHC(X)CH 3 , X = O (acac) 1 , N–H (i -acac) 2 , N–CH 3 (Me i -acac) 3) have been synthesized, purified and characterized in order to investigate the influence of (O,O) and (O,N) coordination sites in chelate ligand on the thermochemical properties of this type compounds. β-Ketoiminate complexes (L = i -acac, Me i -acac) were prepared for the first time. Thermal behavior of iridium complexes in condensed phase has been studied by differential scanning calorimetry and thermodynamic parameters of melting processes (Δ melt. H m.p. , Δ melt. S ° m.p.) have been determined for the first time. The temperature dependencies of saturated vapor pressures over the solid complexes have been measured by flow (transpiration) method (temperature intervals (363–423) K, (383–431) K and (383–420) K for compounds 1 , 2 and 3 , respectively). Using these data, the thermodynamic parameters of sublimation processes (Δ sub H T , Δ sub S ° T) have been calculated. It has been found that although the ligand modification has a minor effect on the vaporization characteristics of this type complexes, the volatility unexpectedly decreases in the following sequence: L = acac > i -acac > Me i -acac. However, the vapor pressure values in the above-mentioned temperature interval are sufficient to all complexes studied be used as effective volatile precursors to obtain iridium-containing coatings by chemical vapor-phase deposition methods. [ABSTRACT FROM AUTHOR]

This review collects the very recent developments in enantioselective metal‐catalyzed domino reactions published since the beginning of 2016. It illustrates that many types of enantioselective metal‐catalyzed domino processes continue to be developed, allowing an easy one‐pot access to complex molecular architectures from simple starting materials while providing economic advantages, such as avoiding costly protecting groups and time‐consuming purification procedures after each step. Abbreviations: acac: acetylacetonate; Ar: aryl; BINAP: 2,2′‐bis(diphenylphosphino)‐1,1′‐binaphthyl; BINOL: 1,1′‐bi‐2‐naphthol; Bn: benzyl; Boc: tert‐butoxycarbonyl; Box: bisoxazoline; BOXAX: 2,2′‐bis(oxazolyl)‐1,1′‐binaphthyl; Bz: benzoyl; cod: cyclooctadiene; Cy: cyclohexyl; DBDMH: 1,3‐dibromo‐5,5‐dimethylhydantoin; DBU: 1,8‐diazabicyclo[5.4.0]undec‐7‐ene; DCE: dichloroethane; de: diastereomeric excess; DIPEA: diisopropylethylamine; dr: diastereomeric ratio; ee: enantiomeric excess; Hex: hexyl; L: ligand; MTBE: methyl tert‐butyl ether; Naph: naphthyl; Ms: mesyl; M.S.: molecular sieves; NMP: N‐methyl‐2‐pyrrolidone; Ns: nosyl; PG: protecting group; Phos: phosphinyl; PHOX: phosphinooxazoline; Phth: phthaloyl; Pin: pinacolato; Piv: pivaloyl; Pybox: 2,6‐bis(2‐oxazolyl)pyridine; r.t.: room temperature; TBS: tert‐butyldimethylsilyl; Tf: trifluoromethanesulfonyl; TFA: trifluoroacetic acid; THF: tetrahydrofuran; TMS: trimethylsilyl; Tol: tolyl; Ts: 4‐toluenesulfonyl (tosyl). [ABSTRACT FROM AUTHOR]

Abstract Reaction of [(η4-COD)Ir(μ 2 -Cl)] 2 (1) with tin CH 2 CRCHCRCH 2 SnR′ 3 (R = H, Me; R' = Me, n -Bu) or lithium pentadienide reagents gives the corresponding acyclic pentadienyl sandwich compounds [(η4-COD)Ir(η5-CH 2 CMeCHCMeCH 2) (2) and [(η4-COD)Ir(η5-CH 2 CHCHCHCH 2) (3). Treatment of 1 with different phosphines affords the well-known mononuclear phosphine complexes [(η4-COD)IrClPR 3 ] [R = Ph, 4 ; i -Pr, 5 ; Me, 6 ] which react with lithium pentadienide to give the exclusive formation of [(η4-COD)Ir(1-3-η-CH 2 CHCHCHCH 2)PR 3 ] [R = Ph, 7 ; P(i -Pr), 8 ], whereas the less steric trimethylphosphine shows an equilibrium mixture of the pseudo iridacyclic [(η4-COD)Ir(1,4-5′-η-CH 2 CHCHCHCH 2)PMe 3 ] (9a) and [(η4-COD)Ir(1-3-η-CH 2 CHCHCHCH 2)PMe 3 ] (9b) in a 2:1 ratio. Additionally, the addition reaction of phosphines to compound 2 gives the dimethyl-pentadienyl complexes [(η4-COD)Ir(1-3-η-CH 2 CMeCHCMeCH 2)PPh 3 ] (10) and the mixture of isomers [(η4-COD)Ir(1,4-5′-η-CH 2 CMeCHCMeCH 2)PMe 3 ] (11a) and [(η4-COD)Ir(1-3-η-CH 2 CMeCHCMeCH 2)PMe 3 ] (11b) in a 2:1 ratio. Compounds 2 , 4 , 5 , 6 , 7 , 8 , 9b , 10 and 11a have been structurally characterized by single-crystal X-ray diffraction studies. The influence of the electronic and steric effects of the different ligands, as well as the preference of the bonding modes in the pentadienyl ligands is analyzed and contrasting to pentadienyl electron rich complexes, derived from IrCl(PR 3) 3 , previously described in the literature. Graphical abstract Image 1 Highlights • Synthesis of iridium sandwich compounds with cyclooctadiene and pentadienyl ligands. • Addition of tertiary phosphines to iridium cyclooctadiene pentadienyl complexes. • Formation of pseudo -iridacycle compounds with cyclooctadiene and PMe 3 ligands. • Influence of electronic contribution by different ligands in pentadienyl bonding modes. • The cone angle of tertiary phosphines dictates the pentadienyl bonding modes. [ABSTRACT FROM AUTHOR]

The first adamantyl platinum complexes were isolated and characterized, namely [(COD)Pt(2‐Ad)Cl], [(dppe)Pt(2‐Ad)Cl], [(COD)Pt(2‐Ad)Me] and, [(dppe)Pt(2‐Ad)Me] {COD = 1,5‐ cyclooctadiene, dppe = 1,2‐bis(diphenylphosphino)ethane, Ad = adamantyl}. These complexes show considerable stability, including resistance to heating to 125° C in solution for several days. It is therefore concluded that previously existing road blocks to synthesizing platinum adamantyls were due to complications in the transmetallation step, and not due to intrinsic instability of the final product. Counterintuitively, the key to successful transmetallation from ZnII onto PtII is imposing slow reaction progress via use of a solvent in which both the platinum chloride precursor and adamantyl anion precursor are poorly soluble. Adamantly adamantyl: The first example of an adamantyl complex of platinum [–(COD)Pt(2‐Ad)Cl]– has been isolated and characterized. The synthesis requires transmetallation from 2‐Ad2Zn with slow reaction progress, and derivatives of the complex are prepared through ligand exchange and further alkylation. [ABSTRACT FROM AUTHOR]

Previously unknown functionally substituted 1,1′-(9-selenabicyclo[3.3.1]nonane-2,6-diyl)dipyridi-nium dibromides were synthesized in 90–98% yields by one-pot condensation of selenium dibromide, cyclo-octa-1,5-diene, and substituted pyridines. [ABSTRACT FROM AUTHOR]

N‐Heterocyclic carbene‐phosphinidene adducts of the type (IDipp)PR [R = Ph (5), SiMe3 (6); IDipp = 1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene] were used as ligands for the preparation of rhodium(I) and iridium(I) complexes. Treatment of (IDipp)PPh (5) with the dimeric complexes [M(μ‐Cl)(COD)]2 (M = Rh, Ir; COD = 1,5‐cyclcooctadiene) afforded the corresponding metal(I) complexes [M(COD)Cl{(IDipp)PPh}] [M = Rh (7) or Ir (8)] in moderate to good yields. The reaction of (IDipp)PSiMe3 (6) with [Ir(μ‐Cl)(COD)]2 did not yield trimethylsilyl chloride elimination product, but furnished the 1:1 complex, [Ir(COD)Cl{(IDipp)PSiMe3}] (9). Additionally, the rhodium‐COD complex 7 was converted into the corresponding rhodium‐carbonyl complex [Rh(CO)2Cl{(IDipp)PPh}] (10) by reaction with an excess of carbon monoxide gas. All complexes were fully characterized by NMR spectroscopy, microanalyses, and single‐crystal X‐ray diffraction studies. [ABSTRACT FROM AUTHOR]

Abstract The reactions of [RhCl(cod)] 2 and Ph 2 P(CH 2 CH 2 O) n CH 2 CH 2 PPh 2 P (n = 3, 4, 5) under a CO atmosphere yield [RhCl(CO){(Ph 2 P(CH 2 CH 2 O) n CH 2 CH 2 Ph 2 -P,P′)}] m monocarbonyl metallacrown ethers. These complexes are mixtures of cyclic n -mers and monomers with trans coordination geometries at the rhodium. The monocarbonyl rhodium metallacrown ethers reversibly react with CO at atmospheric pressure to form [RhCl(CO) 2 {(Ph 2 P(CH 2 CH 2 O) n CH 2 CH 2 Ph 2 -P,P′)}] m dicarbonyl metallacrown ethers. These complexes are only stable under a CO atmosphere as demonstrated by 31P{1H} NMR spectroscopy. Upon prolonged exposure to the atmosphere, all the monocarbonyl metallacrown ethers lose CO and undergo phosphine ligand oxidation to form [RhCl(H 2 O){Ph 2 P(O)(CH 2 CH 2 O) n CH 2 CH 2 P(O)Ph 2 -O,O'}] metallacrown ethers. These are the first examples of metallacrown ethers in which the transition metal is coordinated via phosphine oxide donors. Graphical abstract Image 1 Highlights • Metallacrown ethers with RhCl centers are mixtures of trans monomers and oligomers. • Reactions with CO yield metallacrown ethers with RhCl(CO) 2 centers. • Exposure to air results in oxidation of the phosphines in complexes. • Complexes are first examples of metallacrown ethers with phosphine oxide donors. [ABSTRACT FROM AUTHOR]

A new dibenzocyclooctadiene lignan, longipedunin E (1), and a new natural product, benzoyl oxokadsuranol (2), together with seven known compounds 3-9, were isolated from the methanol extract of the stems of Kadsura longipedunculata. The structure elucidation of the new compound was primarily based on spectroscopic analyses including HR-ESI-MS, IR, UV, 1D and 2D NMR. [ABSTRACT FROM AUTHOR]

The cod ligand (cis,cis‐1,5‐cyclooctadiene) can be superficially considered to mimic similarities in spatial behavior of a leaf of the Venus fly‐trap (Dionaea muscipula). Thus, the synthesis of an unsymmetrical bidentate trans ligand (N,O‐donor atoms) based on the β‐enaminonate backbone is introduced to evaluate the electronic and steric influence on the structural behavior of the cod ligand when coordinated to a square planar transition metal. A range of platinum(II) / palladium(II) complexes of the type [M(cod)(N,O‐Bid)]A (M = PtII, PdII; β‐enaminonato ligand (N,O‐Bid) = NH‐acac, NMe‐acac, NPh‐acac; A = BF4–, PF6–) is reported. The complexes were fully characterized, including by detailed X‐ray structural investigations. Theoretical calculations on the [M(cod)(N,O‐Bid)]+ complexes for the complete nickel triad are also described and the structural behavior of the cod ligand critically evaluated. The influence of the variation of the β‐enaminonato ligands on the coordination arrangement of the cod was investigated and found that no significant changes to the M–C and C=C bond lengths were observed. The Venus fly‐trap jaw angle (ψ), however, varies by ca. 8° and the twist angle (τ) by ca. 10°, whereas the cod bite angle (χ), as well as the β‐enaminonato ligand bite angle (N–M–O; θ) both remain virtually constant. Calculated spectroscopic tendencies within the Ni‐triad are also included. [ABSTRACT FROM AUTHOR]

Reaction of the thallium salt Tl[7,8-Me 2 -10-SMe 2 -7,8- nido -C 2 B 9 H 8 ] with [(cod)RhCl] 2 in THF furnishes new rhodacarborane 1,2-Me 2 -3,3-(cod)-8-SMe 2 -3,1,2 -closo -RhC 2 B 9 H 8 ( 1 ). The latter undergoes 1,2 → 1,7 carbon atom isomerization upon reflux in o -xylene for 5 h producing complex 1,8-Me 2 -2,2-(cod)-11-SMe 2 -2,1,8- closo -RhC 2 B 9 H 8 ( 2 ). Reaction of complex 2 with 1 equiv of I 2 in benzene results in a loss of the cod ligand and formation of product 3 , consisting of cationic [(1,8-Me 2 -11-SMe 2 - closo -2,1,8-RhC 2 B 9 H 8 ) 2 I 3 ] + ( 3a + ) and anionic [(1,8-Me 2 -11-SMe- closo -2,1,8-RhC 2 B 9 H 8 ) 2 I 3 ] − ( 3b – ) iodide species. In contrast, unisomerized analog 3,3-(cod)-8-SMe 2 - closo- 3,1,2-RhC 2 B 9 H 10 reacts with I 2 affording dimeric iodide [3,3-I 2 -8-SMe 2 - closo- 3,1,2-RhC 2 B 9 H 10 ] 2 ( 5 ). The structures of 2 and 5 were determined by a single crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

Compound [Ir(C8H12)(C51H45P4)](Cl)2 or [Ir(cod)(CH(dppm)2-κ3P,C,P)](Cl)2 (1a), was obtained from [IrCl(cod)]2 and the carbodiphosphorane (CDP) salt [CH(dppm)2]Cl [where cod = cycloocta-1,5-diene and dppm = bis(diphenylphosphino) methane]. Treatment of 1a with thallium(I) trifluoromethanesulfonate [Tl(OTf)] and subsequent crystallization gave complex [Ir(C8H12)(C51H45P4)](OTf)2·CH3CO2C2H5·CH2Cl2 or [Ir(cod)(CH(dppm)2-κ3P,C,P)](OTf)2·CH3CO2C2H5·CH2Cl2 (1b) [systematic name: (cycloocta-1,5-diene)(1,1,3,3,5,5,7,7-octaphenyl-1,7-diphospha-3,5-diphosphoniaheptan-4-yl)-iridium(I) bis(trifluoromethanesulfonate)-ethyl acetate-dichloromethane (1/1/1)]. This five-coordinate iridium(I) complex cation adopts a trigonal-bipyramidal geometry with the CDP carbon and one cod double bond in axial sites. Compound 1b represents the first example of a non-meridional coordination of the PCP pincer ligand [CH(dppm)2]+ with a P-Ir-P angle of 98.08 (2)°. Compound 2, [Ir(Cl)2(H)(C51H44P4)]·(CH3)2CO or [Ir(Cl)2(H)(C(dppm)2-κ3P,C,P)]·(CH3)2CO [systematic name: dichloridohydrido(1,1,3,3,5,5,7,7-octaphenyl-1,5λ5,7-triphospha-3-phosphoniahept-4-en-4-yl)iridium(III) acetone monosolvate], crystallizes as an acetone monosolvate. It is a six-coordinate IrIII coordination compound. Here, the PCP pincer ligand is coordinated in a meridional manner; one chlorido ligand is positioned trans to the carbon donor, the remaining two coordination sites being occupied by the second chlorido and a hydrido ligand trans to each other. Complex 3, [Ir(Cl)2(H)(C51H45P4)]Cl·5H2O or [Ir(Cl)2(H)(CH(dppm)2-κ3P,C,P)]Cl·5H2O [systematic name: dichloridohydrido(1,1,3,3,5,5,7,7-octaphenyl-1,7-diphospha-3,5-diphosphoniaheptan-4-yl)iridium(III) chloride pentahydrate], represents the conjugate CH acid of 2. The ligand [CH(dppm)2]+ is coordinated in a meridional manner. In the cationic six-coordinate IrIII complex 4, [Ir(Cl)(H)-(CO)(C51H44P4)]Cl·2CH3OH·H2O or [Ir(Cl)(H)(CO)(C(dppm)2-κ3P,C,P)]Cl^#183;- 2CH3OH·H2O [systematic name: carbonylchloridohydrido(1,1,3,3,5,5,7,7-octaphenyl- 1,5λ5,7-triphospha-3-phosphoniahept-4-en-4-yl)iridium(III) chloride-methanol-water (1/2/1)], the chlorido ligand is found in the plane defined by the Ir center and the meridional PCP ligand; the H and CO ligands are positioned axially to this plane and trans to each other. [ABSTRACT FROM AUTHOR]

Abstract: Reaction of [U{C(SiMe3)(PPh2)}(BIPM)(μ‐Cl)Li(TMEDA)(μ‐TMEDA)0.5]2 (BIPM=C(PPh2NSiMe3)2; TMEDA=Me2NCH2CH2NMe2) with [Rh(μ‐Cl)(COD)]2 (COD=cyclooctadiene) affords the heterotrimetallic UIV−RhI2 complex [U(Cl)2{C(PPh2NSiMe3)(PPh[C6H4]NSiMe3)}{Rh(COD)}{Rh(CH(SiMe3)(PPh2)}]. This complex has a very short uranium–rhodium distance, the shortest uranium–rhodium bond on record and the shortest actinide–transition metal bond in terms of formal shortness ratio. Quantum‐chemical calculations reveal a remarkable Rh I → → UIV net double dative bond interaction, involving RhI 4d z 2 ‐ and 4dxy/xz‐type donation into vacant UIV 5f orbitals, resulting in a Wiberg/Nalewajski–Mrozek U−Rh bond order of 1.30/1.44, respectively. Despite being, formally, purely dative, the uranium–rhodium bonding interaction is the most substantial actinide–metal multiple bond yet prepared under conventional experimental conditions, as confirmed by structural, magnetic, and computational analyses. [ABSTRACT FROM AUTHOR]

The indirect detection of CO by using impregnated paper strips is reported. The ligand‐substitution reaction of cod by CO in an organometallic complex leads to the liberation of 1,5‐cyclooctadiene (cod), which can be smelled by the human olfactory system with very high sensitivity. Azolium salts tagged with methoxy polyethylene glycols (MeOPEG; 136, 750, and 2000 g/mol) were converted to the respective [IrCl(cod)(MeOPEG‐NHC)] complexes (NHC = N‐heterocyclic carbene). On reaction with CO, [IrCl(CO)2(MeOPEG‐NHC)] and 1,5‐cyclooctadiene are rapidly formed in virtually quantitative yield. Paper strips were coated with a thin film (1–10 µm) of an [IrCl(cod)(MeOPEG‐NHC)] complex. Exposure of the paper to low concentrations of CO (100 ppm) leads to rapid evolution of the strongly smelling olefin. [ABSTRACT FROM AUTHOR]

Pseudohalogenogermylenes [(iBu)2ATI]GeY (Y = NCO 4, NCS 5) show different coordination behavior towards group 6 metal carbonyls in comparison to the corresponding halogenogermylenes [(iBu)2ATI]GeX (X = F 1, Cl 2, Br 3) (ATI = aminotroponiminate). The reactions of compounds 4-5 and 1-3 with cis-[M(CO)4(COD)] (M = Mo, W, COD = cyclooctadiene) gave trans-germylene metal complexes {[(iBu)2ATI]GeY}2M(CO)4 (Y = NCO, M = Mo 6, W 11; Y = NCS, M = Mo 7) and cis-germylene metal complexes {[(iBu)2ATI]GeX}2M(CO)4 (M = Mo, X = F 8, Cl 9, Br 10; M = W, X = Cl 12), respectively. Theoretical studies on compounds 7 and 9 reveal that donor-acceptor interactions from Mo to Ge atoms are better stabilized in the observed trans and cis geometries than in the hypothetical cis and trans structures, respectively. [ABSTRACT FROM AUTHOR]

Stepwise interaction of first row transition metal atoms with 1,5-cyclooctadiene to give (C8H12)2M complexes is studied using the M06-L/DZP density functional method. The experimentally known (C8H12)2Ni is the thermodynamically most favorable complex, with a predicted geometry consistent with its experimental structure as determined by X-ray crystallography. The other transition metal atoms from scandium to zinc also interact exothermically with 1,5-cyclooctadiene to give (C8H12)2M derivatives, but these exhibit lower symmetry than the S4 symmetry exhibited by (C8H12)2Ni. Carbon-hydrogen activation of CH2 groups in a C8H12 ligand is predicted for most systems. Thus, conversion of (η2,2-C8H12)2M to (η3,2-C8H11)(η2,1-C8H13)M, through a hydride intermediate (η3,2-C8H11)(η2,2-C8H12)MH, is predicted for scandium, vanadium, chromium, manganese, and cobalt. For titanium with a low-lying empty orbital, further C-H activation through a hydride intermediate (η6-C8H10)(η2,1-C8H13)TiH is predicted, leading ultimately to (η6-C8H10)(η1,1-C8H14)Ti, in which the hexahapto η6-C8H10 ligand is shown by NICS to be aromatic. These two C-H activation processes on a titanium center represent the dehydrogenation of 1,5-cyclooctadiene to 1,3,5-cyclooctatriene with the second 1,5-cyclooctadiene ligand as the hydrogen acceptor. For zinc C-H activation terminates at (η1-C8H11)(C8H12)ZnH, which has a C-Zn-H three-center bond. No energetically favorable C-H activation processes are predicted for the iron, nickel, and copper (η2,2-C8H12)2M derivatives. [ABSTRACT FROM AUTHOR]

Abstract: Dibenzocyclooctadiene lignans are an interesting class of molecules because of their unique structure based on an axially chiral biaryl moiety as well as their significant biological activity. Herein, we describe the development of a palladium‐catalyzed atroposelective C−H alkynylation and its application in gram‐scale, stereocontrolled formal syntheses of (+)‐isoschizandrin and (+)‐steganone. tert‐Leucine was identified as an efficient, catalytic transient chiral auxiliary. A wide range of enantiomerically enriched biaryl compounds were prepared by this approach in good yields (up to 99 %) with excellent enantioselectivity (up to >99 % ee). [ABSTRACT FROM AUTHOR]

Abstract: This work describes the results from the studies on the potential of [Ir(μ‐Cl)(cod)]2 (cod=1,5‐cyclooctadiene) as metallic precursor for the preparation of Ir(NSiN) complexes (NSiN=fac‐bis‐(pyridine‐2‐yloxy)methylsilyl). The reaction of [Ir(μ‐Cl)(cod)]2 with bis‐(pyridine‐2‐yloxy)methylsilane enabled the synthesis of [Ir(H)(Cl)(NSiN)(η2‐cod)] with an uncommon η2‐coordination mode for the cod ligand. The application of Ir–NSiN species as catalysts precursors for the dehydrogenative silylation of carboxylic acids was also explored. The outcomes from these catalytic studies revealed a clear influence of the ancillary ligand on the catalytic activity of Ir–NSiN species. Thus, whereas [Ir(H)(CF3SO3)(NSiN)(coe)] shows poor catalytic activity, the related complex [Ir(H)(CF3CO2)(NSiN)(coe)] with a trifluoroacetate ligand was demonstrated to be a highly active catalyst precursor. [ABSTRACT FROM AUTHOR]

Brookhart-type catalytic systems based on zero-valent nickel complexes Ni(COD)2 and Ni(COD)L [where COD is cyclooctadiene and L is bis-2,6-diisopropylphenyl-diazabutadiene (DPP-DAB) or N,N′-bis-2,6- diisopropylphenyl-bis-iminoacenaphthene (DPP-BIAN)] activated with Lewis acids such as methylaluminoxane (MAO) and boron trifluoride etherate BF3·OEt2 were investigated via electron spin resonance (ESR) spectrometry, revealing that presence of diimine ligand results in Lewis acids, formally oxidating Ni(0) to Ni(I). An oxidation mechanism is proposed. [ABSTRACT FROM AUTHOR]

The asymmetric unit of the title compound, C12H12Cl4O2, contains two crystallographically independent molecules with almost identical conformations (r.m.s. overlay fit for the non-hydrogen atoms = 0.059 Å). In each molecule, the central eight-membered ring has a distorted boat configuration, and two non-planar four-membered rings are fused on either side of the eight-membered ring. A weak C—H...O hydrogen bond links the two independent molecules. In the crystal, weak C—H...O hydrogen bonds link the molecules into a two-dimensional network parallel to (001).

A reaction between [(COD)IrCl]2 (COD is cycloocta-1,5-diene), HCl and indene failed to provide the hoped for chloridoindenyliridium dimer, but instead produced the title compound, [IrCl3(CH3CN)(C8H12)], which is an octahedral complex of iridium(III) with a chelating cycloocta-1,5-diene ligand, three chloride ligands in a fac arrangement, and one acetonitrile ligand. Attempts to devise a rational synthesis for the title compound were unsuccessful.

The recently published purely metallo-organic NiI salt [Ni(cod)2][Al(ORF)4] (1, cod=1,5-cyclooctadiene, RF= C(CF3)3) provides a starting point for a new synthesis strategy leading to NiI phosphine complexes, replacing cod ligands by phosphines. Clearly visible colour changes indicate reactions within minutes, while quantum chemical calculations (PBE0-D3(BJ)/def2-TZVPP) approve exergonic reaction enthalpies in all performed ligand exchange reactions. Hence, [Ni(dppp)2][Al(ORF)4] (2, dppp=1,3-bis(diphenylphosphino) propane), [Ni(dppe)2][Al(ORF)4] (3, dppe=1,3-bis(diphenyl- phosphino)ethane), three-coordinate [Ni(PPh3)3] [Al(ORF)4] (4) and a remarkable two-coordinate NiI phosphine complex [Ni(PtBu3)2][Al(ORF)4] (5) were characterised by single crystal X-ray structure analysis. EPR studies were performed, confirming a nickel d9 -configuration in complexes 2, 4 and 5. This result is supported by additional magnetization measurements of 4 and 5. Further investigations by cyclic voltammetry indicate relatively high oxidation potentials for these NiI compounds between 0.7 and 1.7 V versus Fc/Fc+. Screening reactions with O2 and CO gave first insights on the reaction behaviour of the NiI phosphine complexes towards small molecules with formation of mixed phosphine- CO-NiI complexes and oxidation processes yielding new NiI and/or NiII derivatives. Moreover, 4 reacted with CH2Cl2 at RT to give a dimeric NiII ylide complex (4c). As CH2Cl2 is a rather stable alkyl halide with relatively high C@Cl bond energies, 4 appears to be a suitable reagent for more general C@Cl bond activation reactions. [ABSTRACT FROM AUTHOR]

To provide a better understanding of the recently published pure metalorganic NiI species, [Ni(cod)2][Al(ORF)4] (1) [cod = 1,5- cyclooctadiene, RF = C(CF3)3], further characterizations were performed and analyzed. Thus, the solvation of 1 in THF was examined by EPR, surprisingly disclosing the initiation of a disproportionation reaction to [NiII(THF)6][Al(ORF)4]2 (3) and Ni0. Further studies con- cerning the ability of 1 to activate small molecules exhibit the formation of a remarkable [Ni3S2(cod)3]2+ cluster (5) in an oxidation reaction with S8, while EPR measurements of the resulting product in a reaction with oxygen indicate a possible coordination of O2. Single crystal X-ray structures as well as spectroscopic analyses of 3 and 5 are described. [ABSTRACT FROM AUTHOR]

Dibenzocyclooctadiene lignans are a specific group of secondary metabolites that occur solely in Schisandra chinensis. The aim of the presented work was to boost the accumulation of lignans in the agitated microshoot cultures of S. chinensis, using different elicitation schemes. The experiments included testing of various concentrations and supplementation times of cadmium chloride (CdCl), chitosan (Ch), yeast extract (YeE), methyl jasmonate (MeJa), and permeabilizing agent-dimethylsulfoxide (DMSO). After 30 days, the microshoots were harvested and evaluated for growth parameters and lignan content by LC-DAD method. The analyses showed enhanced production of lignans in the elicited S. chinensis microshoots, whereas the respective media samples contained only trace amounts of the examined compounds (< 5 mg/l). Elicitation with CdCl caused up to 2-fold increase in the total lignan content (max. ca. 730 mg/100 g DW after the addition of 1000 μM CdCl on the tenth day). Experiments with chitosan resulted in up to 1.35-fold increase in lignan concentration (max. ca. 500 mg/100 g DW) after the supplementation with 50 mg/l on the first day and 200 mg/l on the tenth day. High improvement of lignan production was also recorded after YeE elicitation. After the elicitation with 5000 mg/l of YeE on the first day of the growth period, and with 1000 and 3000 mg/l on the 20th day, the lignan production increased to the same degree-about 1.8-fold. The supplementation with 1000 mg/l YeE on the 20th day of the growth cycle was chosen as the optimal elicitation scheme, for the microshoot cultures maintained in Plantform temporary immersion system-the total content of the estimated lignans was equal to 831.6 mg/100 g DW. [ABSTRACT FROM AUTHOR]