Catalytic Gas‐phase Fluorination of Hexachlorobutadiene to 1,2‐Dichlorotetrafluorocyclobutene over Cr/Zn‐based Catalysts

In this paper, the gas‐phase fluorination of hexachlorobutadiene (HCBD) to synthesize 1,2‐dichlorotetrafluorocyclobutene (DTB) was carried out over a series of Cr/M/Zn catalysts (M = Ni, Co, Cu, In, Al). The influence of prefluorination by different fluorinating agents (HF, 95%HF + 5%Cl₂, 95%HF + 5%O₂, CF₂O, CF₂Cl₂) on catalytic performance of Cr/Co/Zn sample was also investigated. The addition of prompters to the Cr/Zn catalyst improved remarkably its catalytic properties. The Cr/Ni/Zn catalyst exhibited the best catalytic activity (1.318 mmol/h/g) at 390 °C and the Cr/Co/Zn catalyst showed the best DTB selectivity (42.5%) at 350 °C. Compared to that of gaseous HF, the catalytic performance of the Cr/Co/Zn catalyst after treatment by HF + O₂ and CF₂O increased considerably, whereas for HF + Cl₂ and CF₂Cl₂ it showed little effect. In order to identify the different species (Cr─O, Cr─F, CrO _xF _y) present on catalysts’ surface and determine their exact role, these catalysts before and after the reaction were characterized by X‐ray photoelectron spectroscopy. It was found that the concentration of the various species was responsible for the activity and lifetime of catalysts. Moreover, a possible reaction route is proposed based upon the product distribution. The most feasible formation pathway of DTB proceeded via the cyclization of C₄Cl₄F₂ or C₄Cl₃F₃ to yield c‐C₄Cl₄F₂ and c‐C₄Cl₃F₃ followed by further the Cl/F exchange.     

Dismutierungs- und Isomerisierungsreaktionen an C?Cl?F-Verbindungen

Dismutation and Isomerization Reactions of C? Cl? F Compounds Results of dismutation and isomerization reactions of the compounds C₂Cl_6?nF_n (n = 1 to 5) are shown. Chromium oxides and aluminium fluoride are used as catalysts in heterogeneous reactions. Reaction mechanisms are formulated. Under the applied conditions no thermal decompositions occur. Thermal stability of the compounds is described.     

Preparation and properties of perfluorochloromethyl-mercaptophosphoryldichlorides and -chlorophosphanes

In Arbuzov-type reactions CF_nCl_3?nSCl reacts with ROPCl₂ (R = CH₃, C₂H₅) to give CF_nCl_3?nSP(O)Cl₂ (n = 3,2,1,0). The corresponding reaction with CF₃SeX (X = Cl, Br) produces CF₃SeP(O)Cl₂ in good yields only in the presence of catalysts such as SbCl₅ or BCl₃. Reactions between P₄ and the sulfenylchlorides produce (CF_nCl_3?nS)_xPCl_3?n (n = 3,2,1 and x = 1,2). On heating CF_n′ Cl_3?n′ SP(O)Cl₂ (n′ = 2,1,0) decompose to P(O)Cl₃ and SCF_n′ Cl_2?n′. During this process fluorination of P(O)Cl₃ to P(O)F₃ by SCF₂ is observed. A Cl/Br exchange between CF_nCl_3?nSP(O)Cl₂ (n = 3,2) and PBr₃ was proved ¹⁹F? and ³¹P-NMR-spectroscopically.Chemical and physical properties of the newly synthesized compounds will be discussed.     

Reactions of some fluoroaromatics with the ethoxide anion

The reactions of sodium ethoxide in ethanol with various fluoroaromatics, C₆F_6?nH_n, C₆F_5?nH_nNO₂, C₆F₅X (X = CF₃, C₆F₅, COCH₃, CH₂Br), C₆Cl₆ and $\text{m}$H₂C₆Cl₄ have been studied. Partial substitution of the aromatic halogen was observed. The new products have been characterized by elemental analysis, NMR (H?1 and F?19), infrared and mass spectroscopy.     

Heteronukleare Metallatomcluster der Typen X4−n[SnM(CO)4P(C6H5)3]n und M2(CO)8 [μ-Sn(X)M (CO)4P(C6H5)3]2 aus Umsetzungen von SnX2 mit M2(CO)8[P(C6H5)3]2 (X = Halogen; M = Mn,Re; n = 2, 3)

Heteronuclear Metal Atom Clusters of the Types X_4?n[SnM(CO)₄P(C₆H₅)₃]_n and M₂(CO)₈[μ-Sn(X)M(CO)₄P(C₆H₅)₃]₂ by Reaction of SnX₂ with M₂(CO)₈[P(C₆H₅)₃]₂ (X = Halogene; M = Mn, Re; n = 2, 3) The compounds of the both types X_4?n[SnM(CO)₄P(C₆H₅)₃]_n (n = 3; M = Mn; X = F, Cl, Br, I. n = 2: M = Mn, Re; X = Cl, Br, I) and M₂(CO)₈[μ-Sn(X)M(CO)₄P(C₆H₅)₃]₂ (M = Mn; X = Cl, I. M = Re; X = Cl, Br, I) are prepared by reaction of SnX₂ with M₂(CO)₈[P(C₆H₅)₃]₂ (M = Mn, Re). Their IR frequencies are assigned. In Re₂(CO)₈[μ-Sn(Cl)Re(CO)₄P(C₆H₅)₃]₂ the central molecule fragment contains a planar Re₂Sn₂ rhombus with a transannular Re? Re bond of 316.0(2) pm. Each of the Sn^IV atoms is connected with the terminal ligands Cl and Re(CO)₄P(C₆H₅)₃. These ligands are in transposition with respect to the Re₂Sn₂ ring. The mean values for the remaining bond distances (pm) are: Sn? Re = 274.0(3); Sn? Cl = 243(1), Re? C = 176(5), Re? P = 242.4(9), C? O = 123(5). The factors with an influence on the geometrical shape of such M₂Sn₂ rings (M = transition metal) are discussed.     

Effect of catalysts on the reaction of allyl esters with hydrosilanes

The reaction of hydrosilylation of allyl esters XOCH₂CH=CH₂ (X = MeCO, CF₃CO, C₃F₇CO) and PhOCH₂CH=CH₂ with hydrosilanes HSiY₃ (Y = Cl, OEt) in the presence of the Speier catalyst, the Speier catalyst with additives, and of various nickel complexes was studied. The catalytic hydrosilylation reaction in the presence of the Speier catalyst is accompanied by the reduction. Additives to the Speier catalyst (vinyltriethoxysilane and some ethers) allow to suppress considerably the reduction reaction. In the presence of the studied nickel complexes mainly reduction and isomerization reactions occurred. The best nickel catalysts of hydrosilylation were the mixtures of NiCl₂ or Ni(acac)₂ with phosphine oxides. In contrast to allyl esters, the hydrosilylation of simple olefins proceeds easier, the content of the product of hydrosilylation in the reaction mixture reaches 94.3%.     

A DFT study of Lp···π/halogen bond competition in complexes of perhalogenated alkenes with oxygen/nitrogen containing simple molecules

The possible noncovalent lone pair‐π/halogen bond (lp···π/HaB) complexes of perhalogenated unsaturated C₂Cl_nF_4?n (n = 0–4) molecules with four simple molecules containing oxygen or nitrogen as electron donor, formaldehyde (H₂CO), dimethyl ether (DME), NH₃, and trimethylamine (TMA), have been systematically examined at the M062X/aug‐cc‐pVTZ level. Natural bond orbital (NBO) analysis at the same level is used for understanding the electron density distributions of these complexes. The progressive introduction of Cl atom on C₂Cl_nF_4?n influences more on the lp···π complexes over the corresponding HaB ones. Within the scope of this study, gem‐C₂Cl₂F₂ is the best partner molecule for lp···π interaction with the simple molecules, coupled with the greatest interaction energy (IE) and second‐order orbital interaction [E(2) value], whereas C₂F₄ is the poorest one. The C₂Cl₃F·H₂CO and C₂Cl₄·H₂CO complexes exhibit reverse lp···π bonding, while the Z/E‐C₂Cl₂F₂·NH₃, C₂Cl₃F·NH₃ and C₂Cl₄·NH₃ complexes perform half‐lp···π bonding according to the NBO analysis. The lp···π interaction involving the oxygen/nitrogen and the π‐hole of C₂Cl_nF_4?n overwhelms the HaB involving the oxygen/nitrogen and the σ‐hole of the Cl atom. The electron‐donating methyl groups contribute significantly to the two competitive interactions, therefore, DME and TMA engage stronger in the partner molecules than H₂CO and NH₃. Our theoretical study would be useful for future experimental investigation on noncovalent complexes. © 2016 Wiley Periodicals, Inc.     

Catalysis of dimerization and oligomerization reactions of lower alkenes by systems based on Ni(PPh3)2(C2H4) and Ni(PPh3) n Cl (n = 2 or 3)

The catalytic characteristics of the individual complex Ni(PPh₃)₂(C₂H₄) and Ni(PPh₃) _n Cl (n = 2 or 3) and those of systems based on these complexes in combination with Brönsted and Lewis acids in ethylene and propylene oligomerization have been determined. A correlation between the BF₃ · OEt₂ solution storage time and the catalytic properties of the nickel systems has been established for the reactions of the lower alkenes. The observed increase in the turnover frequency and turnover number of the catalyst is due to the increase in the Brörsted acid concentration as a result of irreversible conversions of BF₃ · OEt₂ caused by its interaction with impurity water in the solvent. The formation of the Ni(PPh₃)₂(C₂H₄)-BF₃ · OEt₂ catalytic system in the presence of a substrate dramatically extends the system’s service life. The interaction of the nickel precursors with boron trifluoride etherate has been investigated using a complex of physical methods, and the main reactions yielding catalytically active species have been revealed.     

RUTHENIUM (II) COMPLEXES IN CATALYTIC OXIDATION

Abstract

Ruthenium (II) complexes of the type RuL(CO)₂Cl₂, [RuL(CO)₂L^? ₂]²⁺ and [RuL(CO)₂Cl L′]⁺ [L = bipyridine (bpy), phenanthroline (phen), biquinoline (biq) and L′ = pyridine (py), 4-chloropyridine (Cl-py), 4-methoxypyridine (MeO-py)] were synthesized from [Ru(CO)₂Cl₂]_n and L, to produce the intermediate RuL(CO)₂Cl₂ followed by hydrolysis and reaction with L′. The catalytic activity of these complexes in epoxidation of olefins with iodosylbenzene under ambient conditions was investigated. A possible mechanism of these reactions, explaining the effects of the ligands on the reaction was explored. At least one carbonyl ligand remained bound to the metal through the reaction. The formation of an oxo intermediate was inferred from spectroscopic detection of bridged oxygen Ru—O—Ru and Ru=O species.     

Über Chalkogenolate. 139. Untersuchungen über Dialkylester von Chalkogenokohlensäuren. 2. O,Se- und S,Se-Dialkylmonothiomonoselenocarbonate

On Chalcogenolates. 139. Studies on Dialkyl Esters of Chalcogenocarbonic Acids. 2. O,Se- and S, Se-Dialkyl Monothiomonoselenocarbonates The hitherto unknown esters RSe? CS? OR′, where R = C₂H₅, ⁿC₃H₇ and R′ = C₂H₅, ⁿC₃H₇, are formed by reaction of NaSeR with Cl? CS? OR′ and of RSe? CS? Cl with HOR′. At the first time, the esters RSe? CO? SR′ with R = R′ = C₂H₅, ⁿC₃H₇ have been prepared by reaction between NaSeR and Cl? CO? SR′. The compounds have been characterized by means of diverse spectroscopic methods.     

Preparation and structures of a series of phosphorus‐free Nickel(II) diamine complexes and their applications in hydrogenation of acetophenone

To develop economical and phosphorus‐free catalysts for hydrogenation of ketones, three new complexes, [Ni(1R,2R‐dpen)₂(H₂O)Cl]₂Cl₂· 2Et₂O (1), [Ni(1R,2R‐dpen)(phen)(CH₃OH)₂]Cl₂·2CH₃OH (2) and [Ni(1,8‐dan)₂(DMF)Cl]₂Cl₂· 3H₂O (3), and three reported compounds, [Ni(opda)(phen)Cl₂]·CH₃OH (4), [Ni(opda)₂Cl₂] (5) and [Ni(1,2‐dach)₂]Cl₂ (6), were prepared and the structures of new compounds were determined by single crystal X‐ray diffraction analysis, in which 1R,2R‐dpen, phen, 1,8‐dan, opda and 1,2‐dach denote 1R,2R‐1,2‐diphenylethylenediamine, 1,10‐phenanthroline, 1,8‐diaminonaphthalene, o‐phenylenediamine and 1,2‐diaminocyclohexane, respectively. The catalytic effects for hydrogenation of acetophenone of these compounds were tested. This revealed very poor or no catalytic effects of these complexes in transfer hydrogenation of acetophenone using isopropanol or HCOOH? NEt₃ as hydrogen source. However, they presented much better catalytic effects in ionic hydrogenation of acetophenone using H₂ gas as hydrogen source with a dependence of the catalytic effects on the base used in the hydrogenation reactions. The complexes represent a kind of green hydrogenation catalyst, although the conversion in the hydrogenation reactions is not as high as expected. Copyright © 2010 John Wiley & Sons, Ltd.     

Carbon monoxide poisoning as a probe for the active site(s) of a nickel-based olefin oligomerization catalyst

The interaction of the olefin oligomerization catalyst system derived from [Ni(sacsac)(PBu₃)Cl] (sacsac = pentane-2,4-dithionate = dithioacetylacetonate) with carbon monoxide (CO) has been examined by a combination of ³¹P NMR and FTIR spectroscopy. The catalyst is rapidly and completely inhibited by CO; however, removal of the CO restores catalytic activity. A CO-adduct of the active catalyst has a characteristic CO stretching frequency of 2042 cm^?1, and δ³¹P 9.9 ppm. Carbon monoxide does not react with [Ni(sacsac)(PBu₃)Cl], but [Ni(sacsac)(PBu₃)(Cl)] reacts with any of Et₂AlCl, BuLi, Li[Et₃BH] or K[(s-Bu)₃BH] under an atmosphere of carbon monoxide in the presence or absence of olefin to produce [Ni(PBu₃)(CO)₃], which has been identified by FTIR and ³¹P NMR. [Ni(sacsac)(PBu₃)Cl] reacts completely with BuLi or K[(s-Bu)₃BH] to form catalytically inactive species which yield active catalysts on addition of Et₂AlCl.     

Oxidative addition of different electrophiles with rhodium(I) carbonyl complexes of unsymmetrical phosphine–phosphine monoselenide ligands

Dimeric chlorobridge complex [Rh(CO)₂Cl]₂ reacts with two equivalents of a series of unsymmetrical phosphine–phosphine monoselenide ligands, Ph₂P(CH₂)_nP(Se)Ph₂ {n = 1( a ), 2( b ), 3( c ), 4( d )}to form chelate complex [Rh(CO)Cl(P∩Se)] ( 1a ) {P∩Se = η²‐(P,Se) coordinated} and non‐chelate complexes [Rh(CO)₂Cl(P～Se)] ( 1b–d ) {P～Se = η¹‐(P) coordinated}. The complexes 1 undergo oxidative addition reactions with different electrophiles such as CH₃I, C₂H₅I, C₆H₅CH₂Cl and I₂ to produce Rh(III) complexes of the type [Rh(COR)ClX(P∩Se)] {where R = ? C₂H₅ ( 2a ), X = I; R = ? CH₂C₆H₅ ( 3a ), X = Cl}, [Rh(CO)ClI₂(P∩Se)] ( 4a ), [Rh(CO)(COCH₃)ClI(P～Se)] ( 5b–d ), [Rh(CO)(COH₅)ClI‐(P～Se)] ( 6b–d ), [Rh(CO)(COCH₂C₆H₅)Cl₂(P～Se)] ( 7b–d ) and [Rh(CO)ClI₂(P～Se)] ( 8b–d ). The kinetic study of the oxidative addition (OA) reactions of the complexes 1 with CH₃I and C₂H₅I reveals a single stage kinetics. The rate of OA of the complexes varies with the length of the ligand backbone and follows the order 1a > 1b > 1c > 1d . The CH₃I reacts with the different complexes at a rate 10–100 times faster than the C₂H₅I. The catalytic activity of complexes 1b–d for carbonylation of methanol is evaluated and a higher turnover number (TON) is obtained compared with that of the well‐known commercial species [Rh(CO)₂I₂]^?. Copyright © 2006 John Wiley & Sons, Ltd.     

Reaction mechanism of the preferential oxidation of the CO reaction in an H<Subscript>2</Subscript> stream over Cu–Ni bimetallic catalysts: A computational study

The preferential oxidation (PROX, CO + H₂ + O₂ → CO₂ + H₂O) of the CO reaction in an H₂ stream is the simplest and most cost-effective method to remove CO gas to less than 10 ppm in reformed fuel gas. We study the mechanism of PROX of the CO reaction in the H₂ stream catalyzed by Cu _n Ni (n = 3-12) clusters using a density functional theory (DFT) calculation to investigate bimetallic effects on the catalytic activation. Our results indicate that the Cu₁₂Ni cluster is the most efficient catalyst for H₂ dissociation and the Cu₆Ni cluster is the most efficient catalyst for CO-PROX in excess hydrogen among Cu _n Ni (n = 3-12) clusters. To gain insight into the adsorption and dissociation of the H₂ molecule effect in the catalytic activity over the Cu₁₂Ni cluster and the potential energy surfaces about PROX of CO oxidation on the Cu₆Ni cluster, the nature of the interaction between the adsorbate and substrate is analyzed by detailed electron local densities of states (LDOS) as well as molecular structures.     

Aryl- and acetylene-nickel(I) complexes

Reduction of various pentafluorophenylnickel(II) complexes in the presence of phosphines gives unstable nickel(I) compounds but Ni(C₆F₅)(CO)₂(PPh₃)₂ is isolated in the presence of CO. Similar NiR(CO)₂(PPh₃)₂ (R = C₆F₅,C₆Cl₅, 2,3,5,6-C₆Cl₄H) are obtained by reaction of the halogenonickel(I) complex with MgRBr or LiR. Reduction of NiX₂L₂ in the presence of acetylenes gives [NiXL₂]₂(μ-PhCCR) (R = H, X = Cl and R = Ph, X = Cl, Br) when L = P-n-Bu₃ but only NiX(PPh₃)₃ are recovered when L = PPh₃. No reaction with the alkyne is observed for [NiX(PPh₃)₂]_n but [NiCl(PPh₃)]_n reacts with RCCR′ to give paramagnetic NiCl(PPh₃)(CRCR′) (R = Ph, R′= H, COOEt), diamagnetic [NiCl(PPh₃)]₂(μ-PhCCPh) and cyclotrimerization when R = R′ = COOMe. Chemical and structural behaviour of the new nickel(I) complexes is described.     

Decomposition and byproducts from reactions involving pentafluorophenyl-grignard and lithium reagents. a GC/MS study

Decomposition and side reactions of pentafluorophenylmagnesium bromide and pentafluorophenyllithium, when used in syntheses, have been investigated using GC/MS techniques. Reactions with reagents such as C₆F₅X (X = H, F, Cl, Br, I), C₆F₄X₂ (X = H, Cl), C₆F₃Cl₃, C₆H₆, (C₆X₅)₃P (X = H, F), (C₆X₅)₃P=O (X = H, F), (C₆X₅)Si(CH₃)₃ (X = H, F) and (CH₃)_4-nSiCl_n, n = 1, 2, in ether or ether/n-hexane were studied.In addition to the principal reaction of synthetic use, namely the replacement of a halogen by a pentafluorophenyl group, two types of side reactions were observed. These were (i) intermolecular loss of LiF via a nucleophilic substitution, and (ii) intramolecular loss of LiF, followed by the addition of either, inorganic salts such as lithium or magnesium halides, or organometal compounds such as organolithium or Grignard reagent present in the system. GC/MS proved to be an ideal method of monitoring such organometallic reaction systems, although it was sometimes not possible to identify byproducts as a particular isomer.     

Mechanism and characterization of alkylene‐ and p‐ethylenebenzylene‐spaced polycarbosilanes ceramic precursor synthesized by electropolymerization

An electropolymerization of haloalkylhalosilanes (Cl? R? SiCH₃Cl₂) that possess two types of electroactive sites, that is, the C? Cl and Si? Cl bond is described. The one‐pot synthesis method is shown to yield branched polycarbosilanes having a regular carbon block‐spaced silicon backbone structure. A series of branched polycarbosilanes, [? R? SiCH₃? ]_n with R being ? CH₂? , ? C₂H₄? , ? C₃H₆? , and ? CH₂? C₆H₄? C₂H₄? , have been successfully electropolymerized with M_n up to 42,600 Dalton. Experimental and simulation cyclic voltammetry of these monomers and the computational examination of their LUMOs are applied to study the electropolymerization mechanism. The results suggest that polymerization proceeds by iterating steps involving (1) electroreduction of a C? Cl bond to a carbanion, which is catalyzed by silylanion radical [Cl SiCl(CH₃)RCl] and/or Ni(0)/TDA‐1; and (2) nucleophilic attack of carbanions to Si? Cl bonds of a second monomer or oligomer to extend the polymer chain. The investigation reveals that the R spacer has a considerable impact on the polymerizability of the corresponding monomer. Such interfacial polymerization resembles a template polymerization, leading to unique microstructures that were preserved even after converted to silicon carbide ceramics at high temperatures. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7677–7689, 2008     

Pentafluorophenyl derivatives of chlorine trifluoride

A reaction between C₆F₅Cl and elemental fluorine under pressure produced pentafluorophenylchlorine(III)difluoride⁽¹⁾ and 1,2-difluoro-1,2-bis(pentafluorophenyl)dichlorane, C₆F₅Cl(F)Cl(F)C₆F₅.The dichlorane was a stable colorless liquid with a boiling point of 121 – 123°. Its characterization by elemental analysis, IR, NMR and Mass Spectra will be presented. It is believed to be the first stable compound with a chlorine-chlorine bond and may be considered to be a derivative of the unknown Cl₂F₄.     

Silicon–oxygen bonding on diphenylsilane through palladium(II)‐catalysed reactions

The reactions of phenols with diphenylsilane are catalysed by palladium(II) catalysts such as Pd(TMEDA)Cl₂ (TMEDA = tetramethylethylenediamine), Pd(DEED)Cl₂ (DEED = N,N′‐diethylethylenediamine), Pd(TEEDA)Cl₂ (TEEDA = N,N′‐tetraethylethylenediamine) or PdCl₂ to form hydrated silanols with molecular formula Ph₂Si(OR)OH·nH₂O (when R = C₆H₅, n = 3; when R = p‐CH₃C₆H₄ or o‐CH₃C₆H₄, n = 1). The reaction of hydroquinone with diphenylsilane in the presence of catalytic amounts of Pd(TMEDA)Cl₂ forms an Si–O‐bonded hydrated aggregate of composition [(C₆H₅)₂Si(OC₆H₄O).0.5H₂0] _n. p‐Benzoquinone reacted with diphenylsilane in the presence of a catalytic amount of Pd(TMEDA)Cl₂ and the reaction proceeded via a multiple pathway involving quinhydrone as an intermediate charge‐transfer complex which reacted further with diphenylsilane to give a linear siloxane. Copyright ­© 2000 John Wiley & Sons, Ltd.     

Effect of collision gas pressure and collision energy on reactions between oxygen and the negative molecular ion of tetrachlorodibenzo-p-dioxins in the collision cell of a triple -quadrupole mass spectrometer

Low-energy reactive collisions between the negative molecular ion of a tetrachlorodibenzo-p-dioxin (TCDD) and oxygen inside the collision cell of a triple-stage quadrupole mass spectrometer produce a substitution ion [M ? Cl + O]^?, a phenoxide ion [C₆H_4-nO₂Cl_n]^?·, [M ? HCl]^?·, and Cl^? by which 1,2,3,4-, 1,2,3,6/1,2,3,7- and 2,3,7,8-TCDD isomers can be distinguished either directly or on the basis of intensity ratios. The collision conditions have an important effect on the relative abundances. Energy- and pressure-resolved curves show that the ions formed by a collisionally activated reaction (CAR) process, i.e. [M ? Cl + O]^? and [C₆H_4-n,O₂Cl_n]^?·, are favoured by a high pressure of oxygen (3-6 mTorr) (1 Torr = 133.3 Pa) and a low collision energy (0.1-7 eV), whereas the ions formed by a collisionally activated dissociation (CAD) process, i.e. [M ? HCl]^?· and Cl^?, are favoured by high pressure and high energy. By choosing a relatively low collision energy (5 eV) and high pressure (4 mTorr), the CAR and CAD ions can be clearly detected.