Palladium‐Catalyzed Suzuki–Miyaura Cross‐Coupling of Secondary α‐(Trifluoromethyl)benzyl Tosylates

A palladium‐catalyzed C(sp³)−C(sp²) Suzuki–Miyaura cross‐coupling of aryl boronic acids and α‐(trifluoromethyl)benzyl tosylates is reported. A readily available, air‐stable palladium catalyst was employed to access a wide range of functionalized 1,1‐diaryl‐2,2,2‐trifluoroethanes. Enantioenriched α‐(trifluoromethyl)benzyl tosylates were found to undergo cross‐coupling to give the corresponding enantioenriched cross‐coupled products with an overall inversion in configuration. The crucial role of the CF₃ group in promoting this transformation is demonstrated by comparison with non‐fluorinated derivatives.     

Pd(II) complexes of Schiff bases and their application as catalysts in Mizoroki–Heck and Suzuki–Miyaura cross‐coupling reactions

Schiff bases of 2‐(phenylthio)aniline, (C₆H₅)SC₆H₄N?CR (R = (o‐CH₃)(C₆H₅), (o‐OCH₃)(C₆H₅) or (o‐CF₃)(C₆H₅)), and their palladium complexes (PdLCl₂) were synthesized. The compounds were characterized using ¹H NMR and ¹³C NMR spectroscopy and micro analysis. Also, electrochemical properties of the ligands and Pd(II) complexes were investigated in dimethylformamide–LiClO₄ solution with cyclic and square wave voltammetry techniques. The Pd(II) complexes showed both reversible and quasi‐reversible processes in the ?1.5 to 0.3 V potential range. The synthesized Pd(II) complexes were evaluated as catalysts in Mizoroki–Heck and Suzuki–Miyaura cross‐coupling reactions. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and X‐ray Crystal Structures of Acenaphthenequinone‐based α‐Diimine Palladium Complexes and a Novel V‐shape Tripalladium Cluster

Partially fluorinated 1,4‐Diazadiene (α‐Diimine) ligand 3,5‐CF₃‐BIAN (1) formed from 3,5‐bis(trifluoromethyl)aniline and acenaphthenequinone was used in the synthesis of palladium dichlorido complex 2 and its mono methyl chlorido palladium complex 3 . Both complexes as well as side products of the reaction with methyl lithium such as trans‐bis(3,5‐bis(trifluoromethyl)aniline complex 4 and an interesting mixed valent trinuclear V‐shaped palladium cluster 5 with two bridging μ²,η³‐N,CN′ non‐innocent BIAN ligands were structurally characterized by the single‐crystal XRD method.     

Cross‐coupling reactions in water using ionic liquid‐based palladium(II)–phosphinite complexes as outstanding catalysts

Two new phosphinite ligands based on ionic liquids [(Ph₂PO)C₇H₁₄N₂Cl]Cl ( 1 ) and [(Cy₂PO)C₇H₁₄N₂Cl]Cl ( 2 ) were synthesized by reaction of 1‐(3‐chloro‐2‐hydoxypropyl)‐3‐methylimidazolium chloride, [C₇H₁₅N₂OCl]Cl, with one equivalent of chlorodiphenylphosphine or chlorodicyclohexylphosphine, respectively, in anhydrous CH₂Cl₂ and under argon atmosphere. The reactions of 1 and 2 with MCl₂(cod) (M = Pd, Pt; cod = 1,5‐cyclooctadiene) yield complexes cis‐[M([(Ph₂PO)C₇H₁₄N₂Cl]Cl)₂Cl₂] and cis‐[M(Cy₂PO)C₇H₁₄N₂Cl]Cl)₂Cl₂], respectively. All complexes were isolated as analytically pure substances and characterized using multi‐nuclear NMR and infrared spectroscopies and elemental analysis. The catalytic activity of palladium complexes based on ionic liquid phosphinite ligands 1 and 2 was investigated in Suzuki cross‐coupling. They show outstanding catalytic activity in coupling of a series of aryl bromides or aryl iodides with phenylboronic acid under the optimized reaction conditions in water. The complexes provide turnover frequencies of 57 600 and 232 800 h^?1 in Suzuki coupling reactions of phenylboronic acid with p‐bromoacetophenone or p‐iodoacetophenone, respectively, which are the highest values ever reported among similar complexes for Suzuki coupling reactions in water as sole solvent in homogeneous catalysis. Furthermore, the palladium complexes were also found to be highly active catalysts in the Heck reaction affording trans‐stilbenes. Copyright © 2014 John Wiley & Sons, Ltd.     

Amidophosphine‐stabilized palladium complexes catalyse Suzuki–Miyaura cross‐couplings in aqueous media

We report a simple and efficient procedure for Suzuki–Miyaura reactions in aqueous media catalysed by amidophosphine‐stabilized palladium complexes trans‐{L³PPh₂}₂PdCl₂ ( 3 ), trans‐{L³PPhtBu}₂PdCl₂ ( 4 ), [Pd(η³‐C₃H₅)(L³PPh₂)Cl] ( 5 ) and {Pd[2‐(Me₂NCH₂)C₆H₄](L³PPh₂)Cl} ( 6 ). The acidity of the NH proton in complexes 3 , 4 , 5 , 6 plays an important role in their catalytic activity. In addition, the palladium complexes cis‐{L¹PPh₂}PdCl₂ ( 1 ) and trans‐{L²PPh₂}₂PdCl₂ ( 2 ) stabilized by phosphines containing Y,C,Y‐chelating ligands L^1,2 have also been found to be useful catalysts for Suzuki–Miyaura reactions in aqueous media. The method can be effectively applied to both activated and deactivated aryl bromides yielding high or moderate conversions. The catalytic activity of couplings performed in pure water increases when utilizing a Pd complex with more acidic NH protons. A decrease of palladium concentration from 1.0 to 0.5 mol% does not lead to a substantial loss of conversion. In addition, Pd complex 1 can be efficiently recovered using two‐phase system extraction. Copyright © 2016 John Wiley & Sons, Ltd.     

Fluoroborates by Cleavage of Trimethylamine‐bis(trifluoromethyl)boranes with NEt3 × 3 HF. Structures of C6F5(CF3)2B · NMe3, K[C6H5CH2(CF3)2BF], and K[C6H5(CF3)2BF]

Trimethylamine‐bis(trifluoromethyl)boranes R(CF₃)₂B · NMe₃ (R = cis/trans‐CF₃CF=CF ( 1/2 ), HC≡C ( 3 ), H₂C=CH ( 4 ), C₂H₅ ( 5 ), C₆H₅CH₂ ( 6 ), C₆F₅ ( 7 ), C₆H₅ ( 8 )) react with NEt₃ × 3 HF depending on the nature of R at 155–200 °C under replacement of the trimethylamine ligand to form the corresponding fluoro‐bis(trifluoromethyl)borates [R(CF₃)₂BF]^– ( 1 a/2 a – 8 a ). The structures of 7 , K[C₆H₅CH₂(CF₃)₂BF] ( K‐6 a ), and K[C₆H₅(CF₃)₂BF] ( K‐8 a ) have been investigated by single‐crystal X‐ray diffraction. In 7 the CF₃ groups make short repulsive contacts with NMe₃ and C₆F₅ entities – the B–CF₃ bonds being unusually long. The B–F bond lengths of K‐6 a and K‐8 a (1.446(3) and 1.452(2) Å, respectively) are long for a fluoroborate.     

A halide‐free pyridinium‐substituted η3‐cycloheptatrienide–Pd complex

We report the synthesis and characterization of a novel 4‐(dimethylamino)pyridinium‐substituted η³‐cycloheptatrienide–Pd complex which is free of halide ligands. Diacetonitrile{η³‐[4‐(dimethylamino)pyridinium‐1‐yl]cycloheptatrienido}palladium(II) bis(tetrafluoroborate), [Pd(C₂H₃N)₂(C₁₄H₁₆N₂)](BF₄)₂, was prepared by the exchange of two bromide ligands for noncoordinating anions, which results in the empty coordination sites being occupied by acetonitrile ligands. As described previously, exchange of only one bromide leads to a dimeric complex, di‐μ‐bromido‐bis({η³‐[4‐(dimethylamino)pyridinium‐1‐yl]cycloheptatrienido}palladium(II)) bis(tetrafluoroborate) acetonitrile disolvate, [Pd₂Br₂(C₁₄H₁₆N₂)₂](BF₄)₂·2CH₃CN, with bridging bromide ligands, and the crystal structure of this compound is also reported here. The structures of the cycloheptatrienide ligands of both complexes are analogous to the dibromide derivative, showing the allyl bond in the β‐position with respect to the pyridinium substituent. This indicates that, unlike a previous interpretation, the main reason for the formation of the β‐isomer cannot be internal hydrogen bonding between the cationic substituents and bromide ligands.     

Application of ortho‐palladated homoveratrylamine complex containing mixed phosphorus–nitrogen donors in the Suzuki reaction

The catalytic activity of [Pd{C₆H₂(CH₂CH₂NH₂)‐(OMe)₂,3,4}Br(PPh₃)] monomeric ortho‐palladated complex of homoveratrylamine and triphenylphosphine was investigated in the Suzuki cross‐coupling reaction of various aryl halides with aryl boronic acids. The substituted biaryls were produced in excellent yields using a catalytic amount of this complex in ethanol at 60°C. Copyright © 2012 John Wiley & Sons, Ltd.     

Electrospray ionization collision induced dissociation of thiocarbocyanine and selenocarbocyanine dyes

The effect of the properties of sulphur and selenium atoms, the composition and location of substituents (―CH₃, ―OCH₃, ―C₂H₅, and ―C₃H₆―((N⁺Br^?)C₅H₅)), and the charge state on the collision induced dissociation (CID) behaviour of ions generated by electrospray ionization (ESI) of thiocarbocyanine and selenocarbocyanine dyes have been investigated. The results show that, for of all the examined singly charged ions, the main dissociation channel was related to the formation of distonic ions, generated as a result of cleavages within the dimethine bridge. In the case of doubly charged ions (with propyl‐pyridinium substituents), competition between fragmentation processes related to charges located at different nitrogen atoms has been observed. The S/Se replacement also has an impact on the CID behaviour of the examined carbocyanine dyes. On the basis of the performed CID MS/MS experiments, general rules for the CID of thiocarbocyanine and selenocarbocyanine dyes have been proposed.     

Synthesis of substituted biaryls via Suzuki,Stille and Hiyama cross‐coupling and homo‐coupling reactions by CN‐dimeric and monomeric ortho‐palladated catalysts

The catalytic activity of dimeric [Pd{C₆H₂(CH₂CH₂NH₂)–(OMe)₂,2,3}(μ‐Br)]₂ and monomeric [Pd{C₆H₂(CH₂CH₂NH₂)–(OMe)₂,2,3}Br(PPh₃)] complexes as efficient, stable and air‐ and moisture‐tolerant catalysts was investigated in the Suzuki, Stille and Hiyama cross‐coupling and homo‐coupling reactions of various aryl halides. Substituted biaryls were produced in excellent yields in short reaction times using catalytic amounts of these complexes. The monomeric complex was demonstrated to be more active than the corresponding dimeric catalyst for the cross‐coupling reaction of unreactive aryl bromides and chlorides. The combination of homogeneous metal catalysts and microwave irradiation gave higher yields of products in shorter reaction times. Copyright © 2013 John Wiley & Sons, Ltd.     

Orthopalladated complexes of phosphorus ylide: Poly(N‐vinyl‐2‐pyrrolidone)‐stabilized palladium nanoparticles as reusable heterogeneous catalyst for Suzuki and Heck cross‐coupling reactions

The phosphorus ylide [Ph₃PCHC(O)C₆H₄‐NO₂–4] reacted with Pd(OAc)₂ to give the C,C‐orthometallated complex [Pd{κ²(C,C)‐C₆H₄PPh₂C(H)CO(C₆H₄‐NO₂–4)}(μ‐OAc)]₂, which underwent bridge exchange reaction with NaN₃, NaCl, KBr and KI, respectively, to afford the binuclear C,C‐orthopalladated complexes [Pd{κ²(C,C)‐C₆H₄PPh₂C(H)CO(C₆H₄‐NO₂–4)}(μ‐X)]₂ (X = N₃ ( 1 ), Cl ( 2 ), Br ( 3 ) and I ( 4 )). The complexes were identified using spectroscopy (infrared and NMR), CHNS technique and single‐crystal X‐ray structure analysis. Thereafter, palladium nanoparticles with narrow size distribution were easily prepared using the refluxing reaction of iodo‐bridged orthopalladated complex 4 with poly(N ‐vinyl‐2‐pyrrolidone) (PVP) as the protecting group. The PVP‐stabilized palladium nanoparticles were characterized using a variety of techniques including X‐ray diffraction, transmission and scanning electron microscopies, energy‐dispersive X‐ray spectroscopy, inductively coupled plasma analysis and Fourier transform infrared spectroscopy. The catalytic activity of the PVP‐stabilized palladium nanoparticles was evaluated in the Suzuki reaction of phenylboronic acid and the Heck reaction of styrene with aryl halides of varying electron densities. This catalyst exhibited excellent catalytic activity for Suzuki cross‐coupling reactions in ethanol–water. Notably, aryl chlorides which are cheaper and more accessible than their bromide and iodide counterparts also reacted satisfactorily using this catalyst. After completion of reactions, the catalyst could be separated using a simple method and used many times in repeat cycles without considerable loss in its activity.     

Highly efficient orthopalladated complexes of second and third benzyl amine for catalyzing the Suzuki cross‐coupling reaction

In this work, ortho‐palladated complexes [Pd(µ‐Cl)(C₆H₄CH₂ NRR′‐κ²‐C,N)]₂ and [Pd(C₆H₄CH₂NH₂‐2‐C,N)Cl(Y)] were tested in the Suzuki–Miyaura cross‐coupling reaction. Cyclopalladated Pd(II) complexes as thermally stable catalysts can activate aryl bromides and chlorides. These complexes were active and efficient catalysts for the Suzuki–Miyaura reaction of aryl bromides and even less reactive aryl chlorides. The cross‐coupled products of a variety of aryl bromides and aryl chloride with phenylboronic acid in methanol as solvent at 60 °C were produced in excellent yields. Copyright © 2010 John Wiley & Sons, Ltd.     

Mono‐ and dinuclear oxime palladacycles bearing diphosphine ligands: An unusual coordination mode for dppe

Three new oxime‐based palladacycles, namely [Pd{C,N‐C₆H₄{C(Me)?NOH}‐2}(dppm)]ClO₄ ( 1 ), [Pd₂{C,N‐C₆H₄{C(Me)?NOH}‐2}₂(dppe)₂(μ‐dppe)](ClO₄)₂ ( 2 ) and [Pd{C,N‐C₆H₄{C(Me)?NOH}‐2}(dppmS₂)]ClO₄ ( 3 ), were synthesized by the reaction of dinuclear oxime complex [Pd{C,N‐C₆H₄{C(Me)?NOH}‐2}(μ‐Cl)]₂ with different diphosphine ligands (dppm, dppe and dppmS₂). The synthesized complexes were characterized using Fourier transform infrared, ³¹P NMR, ¹H NMR and ¹³C NMR spectroscopic methods and elemental analyses, and their molecular structures were elucidated using X‐ray crystallography. The structure of 2 is worthy of note as it is the first oxime palladacycle where there are both bridging (P–) and chelating (P^P) dppe ligands, giving rise to a dinuclear complex. The palladium atom is in a five‐coordinate, square pyramidal P₃NC environment, while in 3 the palladium atom is in a distorted square planar environment, coordinated by the oxime ligand and a chelating (S^S) dppmS₂ ligand. These complexes were employed as efficient catalysts for the Suzuki–Miyaura cross‐coupling reaction of several aryl bromides with phenylboronic acid. The in vitro cytotoxicity of the compounds was also evaluated against human tumour cell lines (HT29, A549 and HeLa) using the MTT assay method. The results indicate that the dinuclear complex 2 has greater catalytic and anticancer activity in comparison with the mononuclear complexes 1 and 3 .     

Palladium(II)‐N‐heterocyclic carbene complexes: synthesis,characterization and catalytic application

N‐Heterocyclic carbenes (NHCs) are of great importance and are powerful ligands for transition metals. A new series of sterically hindered benzimidazole‐based NHC ligands (LHX) ( 2a , 2b , 2c , 2d , 2e , 2f ), silver–NHC complexes ( 3a , 3b , 3c , 3d , 3e , 3f ) and palladium–NHC complexes ( 4a , 4b , 4c , 4d , 4e , 4f ) have been synthesized and characterized using appropriate spectroscopic techniques. Studies have focused on the development of a more efficient catalytic system for the Suzuki coupling reaction of aryl chlorides. Catalytic performance of Pd–NHC complexes and in situ prepared Pd(OAc)₂/LHX catalysts has been investigated for the Suzuki cross‐coupling reaction under mild reaction conditions in aqueous N,N‐dimethylformamide (DMF). These complexes smoothly catalyzed the Suzuki–Miyaura reactions of electron‐rich and electron‐poor aryl chlorides. Copyright © 2014 John Wiley & Sons, Ltd.     

Mixed bis(morpholine‐4‐dithiocarbamato‐S,S′)antimony(III) complexes: synthesis,characterization and biological studies

Some mixed bis(morpholine‐4‐dithiocarbamato‐S,S′)antimony(III) complexes [(OC₄H₈NCS₂)₂SbL] with oxygen or sulfur donor ligands [L = ―OOCCH₃ ( 1 ), ―OOCC₆H₅ ( 2 ), ―SOCCH₃ ( 3 ), ―SCH₂COOH ( 4 ), ―OOCC₆H₄(OH) ( 5 ), ―SCH₂CH₂CH₃ ( 6 ), ―OC₆H₅ ( 7 ), ½ ―SCH₂CH₂S― ( 8 )] have been synthesized by reacting the chloro‐bis(morpholine‐4‐dithiocarbamato‐S,S′)antimony(III) with corresponding oxygen or sulfur donor ligands in 1:1 or 2:1 stoichiometries. These have been characterized by melting point, molecular weight determination (cryoscopically), antimony (iodometrically) and sulfur (gravimetrically) estimation, elemental analyses (C, H and N), UV–visible, FT‐IR, far IR, multinuclear NMR (¹H and ¹³C)], TG/DTA analysis, ESI–mass and powder X‐ray diffraction studies. The splitting of the strong band observed at 1046–1066 cm^?1 due to υ(C―S) indicated anisobidentate mode of binding of the dithiocarbamate group, which was further supported by a ¹³C NMR signal appearing at around δ 200 due to NCS₂ moiety. The base peak observed at m/z 444.9 supports the strong chelating nature of the morpholine‐4‐dithiocarbamate compared to the other hetero ligands used. TGA revealed that, complexes 21 and 4 were decomposed in three steps; also 6 was decomposed in two steps, followed by the formation of Sb₂S₃. The results obtained by antimicrobial screening tests indicate that complex 3 showed a maximum zone of inhibition (20 mm) against Trichoderma ressie at a concentration of 200 µg ml^?1. Complexes 2 , 3 and 8 are most active (zone of inhibition (ZI) 17–20 mm) against both of the fungal species Aspergillus niger and Trichoderma ressie as well as complex 4 (ZI 17 mm) and 6 (ZI 18 mm) against Trichoderma ressie. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and Characterization of m‐Terphenyl (1,3‐Diphenylbenzene) Compounds Containing Trifluoromethyl Groups

The bis(silyl)triazene compound 2,6‐(Me₃Si)₂‐4‐Me‐1‐(N?N? NC₄H₈)C₆H₂ ( 4 ) was synthesized by double lithiation/silylation of 2,6‐Br₂‐4‐Me‐1‐(N?N? NC₄H₈)C₆H₂ ( 1 ). Furthermore, 2,6‐bis[3,5‐(CF₃)₂‐C₆H₃]‐4‐Me‐C₆H₂‐1‐(N?N? NC₄H₈)C₆H₂ derivative 6 can be easily synthesized by a C,C‐bond formation reaction of 1 with the corresponding aryl‐Grignard reagent, i.e., 3,5‐bis[(trifluoromethyl)phenyl]magnesium bromide. Reactions of compound 4 with KI and 6 with I₂ afforded in good yields novel phenyl derivatives, 2,6‐(Me₃Si)₂‐4‐MeC₆H₂? I and 2,6‐bis[3,5‐(CF₃)₂? C₆H₃]‐4‐MeC₆H₂? I ( 5 and 7 , resp.). On the other hand, the analogous m‐terphenyl 1,3‐diphenylbenzene compound 2,6‐bis[3,5‐(CF₃)₂? C₆H₃]C₆H₃? I ( 8 ) could be obtained in moderate yield from the reaction of (2,6‐dichlorophenyl)lithium and 2 equiv. of aryl‐Grignard reagent, followed by the reaction with I₂. Different attempts to introduce the ^tBu (Me₃C) or neophyl (PhC(Me)₂CH₂) substituents in the central ring were unsuccessful. All the compounds were fully characterized by elemental analysis, melting point, IR and NMR spectroscopy. The structure of compound 6 was corroborated by single‐crystal X‐ray diffraction measurements.     

(Z)‐2‐Methylbuten‐1‐yl(aryl)iodonium trifluoromethanesulfonates containing electron‐withdrawing groups on the aryl moiety

The crystal structures of [(Z)‐2‐methyl­but‐1‐en‐1‐yl]­[4‐(tri­fluoro­methyl)­phenyl]­iodo­nium tri­fluoro­methane­sulfonate, C₁₂H₁₃F₃I⁺·CF₃O₃S^?, (I), (3,5‐di­chloro­phenyl)­[(Z)‐2‐methyl­but‐1‐en‐1‐yl]­iodo­nium tri­fluoro­methane­sulfonate, C₁₁H₁₂­Cl₂I⁺·CF₃O₃S^?, (II), and bis{[3,5‐bis­(tri­fluoro­methyl)­phenyl][(Z)‐2‐methyl­but‐1‐en‐1‐yl]­iodo­nium} bis­(tri­fluoro­methane­sulfonate) di­chloro­methane solvate, 2C₁₃H₁₂F₆I⁺·­2CF₃­O₃S^?·CH₂Cl₂, (III), are described. Neither simple acyclic β,β‐di­alkyl‐substituted alkenyl­(aryl)­idonium salts nor a series containing electron‐deficient aryl rings have been described prior to this work. Compounds (I)–(III) were found to have distorted square‐planar geometries, with each I atom interacting with two tri­fluoro­methane­sulfonate counter‐ions.     

Conformational studies on heteroleptic trifluoromethyl‐substituted phenylboranes

Organoboranes carrying electron‐withdrawing substituents are commonly used as Lewis acidic catalysts or cocatalysts in a variety of organic processes. These Lewis acids also became popular through their application in `frustrated Lewis pairs', i.e. combinations of Lewis acids and bases that are unable to fully neutralize each other due to steric or electronic effects. We have determined the crystal and molecular structures of four heteroleptic arylboranes carrying 2‐(trifluoromethyl)phenyl, 2,6‐bis(trifluoromethyl)phenyl, 3,5‐bis(trifluoromethyl)phenyl or mesityl substituents. [3,5‐Bis(trifluoromethyl)phenyl]bis[2‐(trifluoromethyl)phenyl]borane, C₂₂H₁₁BF₁₂, (I), crystallizes with two molecules in the asymmetric unit which show very similar geometric parameters. In one of the two molecules, both trifluoromethyl groups of the 3,5‐bis(trifluoromethyl)phenyl substituent are disordered over two positions. In [3,5‐bis(trifluoromethyl)phenyl]bis[2,6‐bis(trifluoromethyl)phenyl]borane, C₂₄H₉BF₁₈, (II), only one of the two meta‐trifluoromethyl groups is disordered. In [2,6‐bis(trifluoromethyl)phenyl]bis[3,5‐bis(trifluoromethyl)phenyl]borane, C₂₄H₉BF₁₈, (III), both meta‐trifluoromethyl groups of only one 3,5‐bis(trifluoromethyl)phenyl ring are disordered. [3,5‐Bis(trifluoromethyl)phenyl]dimesitylborane, C₂₆H₂₅BF₆, (IV), carries only one meta‐trifluoromethyl‐substituted phenyl ring, with one of the two trifluoromethyl groups disordered over two positions. In addition to compounds (I)–(IV), the structure of bis[2,6‐bis(trifluoromethyl)phenyl]fluoroborane, C₁₆H₆BF₁₃, (V), is presented. None of the ortho‐trifluoromethyl groups is disordered in any of the five compounds. In all the structures, the boron centre is in a trigonal planar coordination. Nevertheless, the bond angles around this atom vary according to the bulkiness and mutual repulsion of the substituents of the phenyl rings. Also, the ortho‐trifluoromethyl‐substituted phenyl rings usually show longer B—C bonds and tend to be tilted out of the BC₃ plane by a higher degree than the phenyl rings carrying ortho H atoms. A comparison with related structures corroborates the conclusions regarding the geometric parameters of the boron centre drawn from the five structures in this paper. On the other hand, CF₃ groups in meta positions do not seem to have a marked effect on the geometry involving the boron centre. Furthermore, it has been observed for the structures reported here and those reported previously that for CF₃ groups in ortho positions of the aromatic ring, disorder of the F atoms is less probable than for CF₃ groups in meta or para positions of the ring.     

Reactions of Ru3(CO)12 with Diphosphenes — A New Route to 50‐Electron Ru3P2 nido‐Clusters

The reaction of the symmetric diphosphene 2, 4, 6‐(CF₃)₃‐C₆H₂‐P=P‐C₆H₂‐2, 4, 6‐(CF₃)₃ 4 with Ru₃(CO)₁₂ led to the 50‐electron Ru₃P₂ nido‐cluster Ru₃(CO)₉[μ‐P‐C₆H₂‐2, 4, 6‐(CF₃)₃]₂ 5 , which in solution at room temperature displays hindered rotation of the aromatic rings about the C(aryl)—P bonds. The structure of 5 was determined by X‐ray crystal structure analysis; its Ru₃P₂ centre forms a distorted square pyramid with one ruthenium atom at the apex. One of the two C₆H₂(CF₃)₃ groups is also appreciably distorted. Temperature‐dependent ¹⁹F NMR studies of the [A₃M₃X]₂ spin system (A = M = CF₃, X = ³¹P) of 5 indicated a rotational barrier ΔG^≠ of 82.3 kJ mol^‐1 at 141 °C. The same Ru₃P₂ core was obtained by the reaction of the unsymmetric diphosphene Mes*‐P=P‐Mes 11 with Ru₃(CO)₁₂; hindered rotation about the C(aryl)—P bonds was also observed, in this case.     

Palladium‐Catalyzed Cascade CH Trifluoroethylation of Aryl Iodides and Heck Reaction: Efficient Synthesis of ortho‐Trifluoroethylstyrenes

A palladium‐catalyzed selective C? H bond trifluoroethylation of aryl iodides has been explored. The reaction allows for the efficient synthesis of a variety of ortho‐trifluoroethyl‐substituted styrenes. Preliminary mechanistic studies indicate that the reaction might involve a key Pd^IV intermediate, which is generated through the rate‐determining oxidative addition of CF₃CH₂I to a palladacycle; the bulky nature of CF₃CH₂I influences the reactivity. Reductive elimination from the Pd^IV complex then leads to the formation of the aryl–CH₂CF₃ bond.