On the Use of Non‐Symmetrical Mixed PCN and SCN Pincer Palladacycles as Catalyst Precursors for the Heck Reaction

The mixed pincer palladacycles (Me₂NCH₂(Cl)CCCH₂CH₂Y‐κN,κC,κY)PdCl ( 1 , Y=PPh₂; 2 , OPPh₂) and (t‐BuSCH₂CH₂CC(Cl)(o‐NC₅H₄)‐κS,κC,κN)PdCl 3 have been obtained in high yields by chloropalladation of heterosusbstituted alkynes Me₂NCH₂CCCH₂CH₂PPh₂, Me₂NCH₂CCCH₂CH₂OPPh₂ and t‐BuSCH₂CH₂CC(o‐NC₅H₄), respectively. The molecular structures of 1 and 3 have been ascertained by means of X‐ray diffraction analysis. The catalytic properties of these mixed donor group pincer‐type palladacycles have been evaluated in the arylation of olefins (Heck reaction). The pincer palladacycle 1 is highly active for the coupling of aryl iodides and aryl bromides with n‐butyl acrylate. In contrast it is only moderately active for the coupling of aryl chlorides substituted with electron‐withdrawing groups and inactive for the coupling of electron neutral and electron deactivated aryl chlorides.     

Metallkomplexe mit biologisch wichtigen Liganden. CXXIII. Darstellung von Isophthaloyl‐ und Terephthaloyl‐di‐[(β,γ,δ)‐amino‐α‐aminocarboxylat]‐verbrückten zweikernigen Ruthenium‐, Rhodium‐ und Iridium‐Halbsandwich‐Komplexen

The reaction of the Cu(II) bis N,O‐chelate‐complexes of L‐2,4‐diaminobutyric acid, L‐ornithine and L‐lysine {Cu[H₂N–CH(COO)(CH₂)_nNH₃]₂}²⁺(Cl^–)₂ (n = 2–4) with terephthaloyl dichloride or isophthaloyl dichloride gives the polymeric complexes {‐OC–C₆H₄–CO–NH–(CH₂)_n–CH(nh₂)(COO)Cu(OOC)(NH₂)CH–CH₂)_n–NH‐}_x 1 – 5 . From these the metal can be removed by precipitation of Cu(II) with H₂S. The liberated ω,ω′‐N,N′‐diterephthaloyl (or iso‐phthaloyl)‐diaminoacids 6 – 10 react with [Ru(cymene)Cl₂]₂, [Ru(C₆Me₆)Cl₂]₂, [Cp*RhCl₂]₂ or [Cp*IrCl₂]₂ to the ligand bridged bis‐amino acidate complexes [L_n(Cl)M–(OOC)(NH₂)CH–(CH₂)_nNH–CO]₂–C₆H₄ 11 – 14 .     

Efficient Access to Conjugated Dienones and Diene‐diones from Propargylic Alcohols and Enolizable Ketones: A Tandem Isomerization/Condensation Process Catalyzed by the Sixteen‐Electron Allyl‐Ruthenium(II) Complex [Ru(η3‐2‐C3H4Me)(CO)(dppf)] [SbF6]

A large variety of conjugated dienones R¹R²CCHCHC(R³)C(O)R⁴ and diene‐diones R¹R²CCHCHC{C(O)R³}C(O)R⁴ have been synthesized in high yields by reacting terminal propargylic alcohols HCCCR¹R²(OH) with enolizable ketones R³CH₂C(O)R⁴ and β‐dicarbonyl compounds R³C(O)CH₂C(O)R⁴, respectively. The process, which is catalyzed by the 16e^‐ (η³‐allyl)‐ruthenium(II ) complex [Ru(η³‐2‐C₃H₄Me)(CO)(dppf)] [SbF₆] associated with CF₃CO₂H, involves the initial isomerization of the propargylic alcohol into the corresponding α,β‐unsaturated aldehyde R¹R²CCHCHO (Meyer–Schuster rearrangement) and subsequent aldol‐type condensation.     

Rhodium‐Catalyzed Hydrogenation of Alkenes by Rhodium/Tris(fluoroalkoxy)phosphane Complexes in Fluorous Biphasic System

The reaction of [Ir(μ‐Cl)(COD)]₂ with various fluorous derivatives of triphenylphosphane containing a para‐, meta‐, or ortho‐(1H,1H‐perfluoroalkoxy)‐substituted fluorous phosphane P(C₆H₄‐ORf)₃ (Rf=CH₂C₇F₁₅, CH₂CH₂CH₂C₈F₁₇) and CO (1 atm) gives the corresponding trans‐[Ir(μ‐Cl)(CO){P(C₆H₄ORf)₃}₂]. The IR ν_CO values of these complexes give some information on the donor/acceptor properties of the phosphanes. These fluorous derivatives of triphenylphosphane, as well as a phosphane bearing two (1H,1H‐perfluoroalkyloxy) chains at the 3,5‐positions, were used in association with [Rh(μ‐Cl)(COD)]₂ or [Rh(COD)₂]PF₆ in the reduction of methyl cinnamate, 2‐cyclohexen‐1‐one, cinnamaldehyde, and methyl α‐acetamidocinnamate in a two‐phase system D‐100/ethanol under 1 bar hydrogen at room temperature. Some differences in catalytic activity were observed in the reduction of methyl cinnamate, the most active catalyst being the rhodium complex containing the phosphane with the p‐fluorous ponytail. Recycling of the fluorous catalyst was possible, particularly using the p‐substituted phosphane, where no significant loss of catalyst or activity was observed, and generally with very low leaching of rhodium or phosphane in the organic phase.     

Soluble polymers of monosubstituted acetylenes with quaternary ammonium pendant groups: structure and morphology

Soluble conjugated polymers were obtained in the presence of Pd(II), Pt(II) and Rh(I) complexes from monosubstituted acetylene 3‐dimethylamino‐1‐propyne (H? C≡CCH₂N(CH₃)₂, 1 ) and the corresponding hydrochloride (H? C≡CCH₂N(CH₃)₂·HCl, 2 ) and hydrobromide (H? C≡CCH₂N(CH₃)₂·HBr, 3 ) derivatives. A series of reactions were performed to achieve the optimization of the polymerization conditions. The highest yields were found for polymers synthesized using Pd(II) bisacetylides specially prepared, i.e. trans‐[Pd(PPh₃)₂(C≡CCH₂N(CH₃)₂)₂], trans‐[Pd(PPh₃)₂(C≡CCH₂N(CH₃)₂)₂HCl] and trans‐[Pd(PPh₃)₂(C≡CCH₂N(CH₃)₂)₂HBr], respectively. The dimension and size distribution of the polymers were investigated using dynamic light scattering. Polymers containing quaternary ammonium groups showed evidence of a hydrodynamic radius of about 300 nm if prepared with the Rh(I) catalyst and of 160 nm if prepared with the Pd(II) catalysts. Polymers obtained from 1 showed smaller hydrodynamic radius compared to polymers obtained from 2 and 3 , regardless the polymerization catalyst. The ionic polymeric materials were soluble in organic solvents and, more interestingly, in water. The formation of nanoparticles with pearl‐like morphology was achieved using a recently developed osmosis‐based method, with dimensions varying from 60 nm up to micrometres. Copyright © 2011 Society of Chemical Industry     

Anticancer Potential of (Pentamethylcyclopentadienyl)chloridoiridium(III) Complexes Bearing κP and κP,κS‐Coordinated Ph2PCH2CH2CH2S(O)xPh (x=0–2) Ligands

Iridium(III) complexes of the type [Ir(η⁵‐C₅Me₅)Cl₂{Ph₂PCH₂CH₂CH₂S(O)_xPh‐κP}] (x=0–2; 1 – 3 ) and [Ir(η⁵‐C₅Me₅)Cl{Ph₂PCH₂CH₂CH₂S(O)_xPh‐κP,κS}][PF₆] (x=0–1; 4 and 5 ) with 3‐(diphenylphosphino)propyl phenyl sulfide, sulfoxide, and sulfone ligands Ph₂PCH₂CH₂CH₂S(O)_xPh were designed, synthesized, and characterized fully, including X‐ray diffraction analyses for complexes 3 and 4 . In vitro studies against human thyroid carcinoma (8505C), submandibular carcinoma (A253), breast adenocarcinoma (MCF‐7), colon adenocarcinoma (SW480), and melanoma (518A2) cell lines provided evidence for the high biological potential of the neutral and cationic iridium(III) complexes. Neutral iridium(III) complex 5 proved to be the most active, with IC₅₀ values up to about 0.1 μM , representing activities of up to one order of magnitude higher than cisplatin. Using 8505C cells, apoptosis was shown to be the main mechanism through which complex 5 exerts its tumoricidal action. The described iridium(III) complexes represent potential leads in the search for novel metal‐based anticancer agents.     

Ethylene/1‐octadecene copolymerization using [η5:η1‐C5Me4‐4‐R1‐6‐R‐C6H2O]TiCl2 catalysts

Copolymerization of ethylene with 1‐octadecene was studied using [η⁵:η¹‐C₅Me₄‐4‐R₁‐6‐R‐C₆H₂O]TiCl₂ [R₁ = ^tBu (1), H (2, 3, 4); R = ^tBu (1, 2), Me (3), Ph (4)] as catalysts in the presence of Al(i‐Bu)₃ and [Ph₃C][B(C₆F₅)₄]. The effect of the concentration of comonomer in the feed and Al/Ti molar ratio on the catalytic activity and molecular weight of the resultant copolymer were investigated. The substituents on the phenyl ring of the ligand affect considerably both the catalytic activity and comonomer incorporation. The 1 /Al(i‐Bu)₃/[Ph₃C][B(C₆F₅)₄] catalyst system exhibits the highest catalytic activity and produces copolymers with the highest molecular weight, while the 2 /Al(i‐Bu)₃/[Ph₃C][B(C₆F₅)₄] catalyst system gives copolymers with the highest comonomer incorporation under similar conditions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Single‐Pot Ethane Carboxylation Catalyzed by New Oxorhenium(V) Complexes with N,O Ligands

The oxorhenium(V) chelates [ReOCl(N,O‐L)(PPh₃)] [N,O‐L=(OCH₂CH₂)N(CH₂CH₂OH)(CH₂COO) ( 2 ), (OCH₂CH₂)N(CH₂COO)(CH₂COOCH₃) ( 3 )] and [ReOCl₂(N,O‐L)(PPh₃)] [N,O‐L=C₅H₄N(COO‐2) ( 4 ) C₅H₃N(COOCH₃‐2)(COO‐6) ( 5 )] have been prepared by reaction of [ReOCl₃(PPh₃)₂] ( 1 ), in refluxing methanol, with N,N‐bis(2‐hydroxyethyl)glycine [bicine; N(CH₂CH₂OH)₂(CH₂COOH)], N‐(2‐hydroxyethyl)iminodiacetic acid [N(CH₂CH₂OH)(CH₂COOH)₂], picolinic acid [NC₅H₄(COOH‐2)] or 2,6‐pyridinedicarboxylic acid [NC₅H₃(COOH‐2,6)₂], respectively, with ligand esterification in the cases of 3 and 5 . All these complexes have been characterized by IR and multinuclear NMR spectroscopy, FAB⁺‐MS, elemental and X‐ray diffraction structural analyses. They act as catalysts, in a single‐pot process, for the carboxylation of ethane by CO, in the presence of potassium peroxodisulfate K₂S₂O₈, in trifluoroacetic acid (TFA), to give propionic and acetic acids, in a remarkable yield (up to ca. 30%) and under relatively mild conditions, with some advantages over the industrial processes. The picolinate complex 4 provides the most active catalyst and the carboxylation also occurs, although much less efficiently, by the TFA solvent in the absence of CO. The selectivity can be controlled by the ethane and CO pressures, propionic acid being the dominant product for pressures about ca. 7 and 4 atm, respectively (catalyst 4 ), whereas lower pressures lead mainly to acetic acid in lower yields. These reactions constitute an unprecedented use of Re complexes as catalysts in alkane functionalization.     

Helical and random coil conformations of N‐propargylamide polymer and copolymers

An N‐propargylamide monomer, CH?CCH₂NHCOC(CH₃)₂CH₂CH₃ (monomer 9), was polymerized in the presence of (nbd)Rh⁺B^?(C₆H₅)₄ (nbd represents norbornadiene) in CH₂Cl₂, CHCl₃, tetrahydrofuran or dimethylformamide, to provide polymers with moderate number‐average molecular weights (M_n = 8700–12 100 g mol^?1) in high yields (≥92%). The resulting poly(N‐propargylamide) (polymer 9) dissolves almost completely in CHCl₃ (>95%). According to the UV‐visible spectra, measured at various temperatures, polymer 9 forms relatively stable helices over a wide temperature range (35–65 °C). Moreover, it exhibits reversible conformational transitions from an ordered helix to a random coil. On copolymerization of monomer 9 with CH?CCH₂NHCO(CH₂)₃CH₃ (monomer 4) or CH?CCH₂NHCO(CH₂)₇CH₃ (monomer 8), the solubility of polymer 9 improves noticeably. All the copolymers form helices under the experimental conditions. From the viewpoint of monomers 4 and 8, copolymerization with monomer 9 is favorable in terms of the copolymers forming helices. These findings reveal that the helical content and thermodynamic stability of the helices formed in the copolymers are likely to be controlled by selecting a suitable comonomer and by adjusting the composition of the copolymer. Copyright © 2007 Society of Chemical Industry     

Dimerization of Terminal Arylalkynes in Aqueous Medium by Ruthenium and Acid Promoted (RAP) Catalysis: Acetate‐ Assisted (sp)C?(sp2)C Bond Formation

The hexamethylbenzene ruthenium(II) dimer [{RuCl(μ‐Cl)(η⁶‐C₆Me₆)}]₂ (5 mol%), tested among a series of ruthenium(II) and ruthenium(IV) complexes, represents an efficient precatalyst source for the dimerization of terminal arylalkynes ArCCH [Ar=C₆H₅, 3,4,5‐(OMe)₃C₆H₂, 4‐MeOC₆H₄, 2‐MeOC₆H₄, 4‐MeC₆H₄, 2,4,5‐Me₃C₆H₂, 4‐BrC₆H₄, 4‐ClC₆H₄, 4‐FC₆H₄, 4‐HC(O)C₆H₄, 4‐CH₂CHC₆H₄, 3‐NCC₆H₄, 4‐O₂NC₆H₄, 4‐EtO₂C‐(CH₂)₃OC₆H₄, 4‐HO(CH₂CH₂O)₃C₆H₄, 3‐HO(CH₂CH₂O)₃‐C₆H₄] in acetic acid/water mixture (1:1, v/v). The reactions proceed for 24 h at room temperature under heterogeneous conditions and afford the dimeric enyne derivatives (E)‐Ar CHCH CC Ar in high yields and stereoselectivity. The preformed acetato complex [RuCl(η⁶‐C₆Me₆)(κ²‐OAc)] catalyzes the dimerization of phenylacetylene under analogous conditions, with rapid substrate conversion. The presence of cosolvents of acetic acid different from water reduces dramatically the efficiency and selectivity of the reaction. The aqueous medium facilitates the activation stage of the precatalyst by assisting the splitting of the ruthenium dimer. The addition or generation in situ of acetate salts results in shorter reactions times (0.5–3 h) and excellent yields, due to the rapid formation of active acetato complexes. Circumstantial evidence indicates that the π‐bound alkyne molecule is activated by intramolecular proton abstraction. This is currently the most efficient, E‐selective and wide‐scope catalytic system for the alkyne dimerization reaction in protic aqueous media.     

Towards near-IR emissive rhenium tricarbonyl complexes: Synthesis and characterisation of unusual 2,2′-biquinoline complexes

Diethyl-2,2′-biquinoline-4,4′-dicarboxylate (debq) reacts with pentacarbonylbromorhenium in toluene to give fac-[Re(CO)₃(debq)Br]; subsequent reaction with AgOTf in MeCN affords the cationic complex fac-[Re(CO)₃(debq)(MeCN)]OTf. X-ray crystallographic data on fac-[Re(CO)₃(debq)Br] show that the debq ligand is coordinated in a bidentate fashion at an angle of 32° from the equatorial plane of the complex: DFT calculations confirm this as the lowest energy conformation. fac-[Re(CO)₃(debq)Br] and fac-[Re(CO)₃(debq)(MeCN)]OTf both possess ¹MLCT absorptions in the visible region, the former most red-shifted to ca. 465 nm. Both complexes demonstrated unusual luminescent properties: in solution, emission appears to be dominated by ligand-centred processes, whereas only ³MLCT emission, tailing into the near-IR, was observed in the solid state at 671 (τ = 59 ns) and 711 nm (τ = 19 ns) for fac-[Re(CO)₃(debq)(MeCN)]OTf and fac-[Re(CO)₃(debq)Br], respectively. However, the debq ligand is not labile in these complexes, which are robust to competing ligands and coordinating solvents.     

Structural characterization and thermal behaviour of block copolymers of polydimethylsiloxane and polyamide having trichlorogermyl pendant groups

Block copolymers having a pendant trichlorogermyl group as a part of polyamide segment? (CO? R′? CO? NH? Ar? NH? )_xCO? R′? CO? and polydimethylsiloxane of general formula [(? CO? R′? CO? HN? Ar? NH)_x? CO? R′? CO? NH(CH₂)₃SiO(CH₃)₂ ((CH₃)₂SiO)_ySi(CH₃)₂(CH₂)₃ NH? ]_n (where R′ = CH₂CH(GeCl₃), CH(CH₃)CH(GeCl₃), CH(GeCl₃)CH(CH₃); Ar = C₆H₄, (? C₆H₃? CH₃)₂, (? C₆H₃? OCH₃)₂, 2,5‐(CH₃)₂? C₆H₂, C₆H₄? O? C₆H₄) were prepared by a polycondensation reaction and characterized using CHN and Ge analysis, Fourier transform infrared (FTIR) and ¹H NMR spectroscopy, thermogravimetric analysis (TGA) and molecular weight determination. They have a lamellar structure with weight‐average molecular weight in the range 1.21 × 10⁵–4.79 × 10⁵ g mol^?1. These copolymers display two glass transition temperatures and have an average decomposition temperature of 489 °C. TGA, FTIR and gas chromatography/mass spectrometry studies indicate that degradation of these block copolymers results in carbon monoxide, oligomeric siloxanes and polyamide fragments. They are thermally stable due to the hydrogen bonded interlinked chains of polyamide, while they absorb water due to the presence of Ge? Cl bonding. Copyright © 2010 Society of Chemical Industry     

Ethylene polymerization by 3‐oxa‐pentamethylene bridged asymmetric dinuclear titanocene/MAO system

An asymmetric 3‐oxa‐pentamethylene bridged dinuclear titanocenium complex (CpTiCl₂)₂(η⁵‐η⁵‐C₉H₆(CH₂CH₂OCH₂CH₂)C₅H₄) ( 1 ) has been prepared by treating two equivalents of CpTiCl₃ with the corresponding dilithium salts of the ligand C₉H₇(CH₂CH₂OCH₂ CH₂)C₅H₅. The complex 1 was characterized by ¹H‐, ¹³C‐NMR, and elemental analysis. Homogenous ethylene polymerization catalyzed using complex 1 has been conducted in the presence of methylaluminoxane (MAO). The influences ofreaction parameters, such as [MAO]/[Cat] molar ratio, catalyst concentration, ethylene pressure, temperature, and time have been studied in detail. The results show that the catalytic activity and the molecular weight (MW) of polyethylene produced by 1 /MAO decrease gradually with increasing the catalyst concentration or polymerization temperature. The most important feature of this catalytic system is the molecular weight distribution (MWD) of polyethylene reaching 12.4, which is higher than using common mononuclear metallocenes, as well as asymmetric dinuclear titanocene complexes like [(CpTiCl₂)₂(η⁵‐η⁵‐C₉H₆(CH₂)_nC₅H₄)] (n = 3, MWD = 7.31; n = 4, MWD = 6.91). The melting point of polyethylene is higher than 135°C, indicating highly linear and highly crystalline polymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Highly Stereoselective Synthesis of Arylene‐Silylene‐Vinylene Polymers

Stereoregular trans‐arylene‐silylene‐vinylene polymers of M_w=13100–34800 and PDI=1.6–2.9 of the general formulas CH₂CH [ SiMe₂C₆H₄‐SiMe₂CHCH ] ( 16, 17, 18 ) and CH₂CH [ (R)CHCHC₆H₄CHCH ] (where R= Me₂Si‐p C₆H₄‐ SiMe₂ ,  Me₂Si‐m C₆H₄SiMe₂ and  Me₂SiC₆H₄C₆H₄SiMe₂ ) ( 19, 20, 21 ) have been effectively synthesized via silylative coupling (SC) homopolycondensation of bis(vinyldimethylsilyl)arenes ( 10, 12, 14 ) and cross‐polycondensation of 4‐(vinyldimethylsilyl)styrene ( 11 ) as well as cross‐copolycondensation of bis(vinyldimethylsilyl)arenes ( 10, 12 and 14 ) with 1,4‐divinylbenzene ( 9 ) catalyzed by [RuH(Cl)(CO)(PCy₃)₂] ( 7 ). Such highly stereoregular products cannot be synthesized via ADMET polycondensation or ring opening metathesis ROM or polyaddition of hydridosilanes to acetylenes.     

Rhenium(I) complexes with aliphatic Schiff bases appended to bio-active moieties

Novel facial tricarbonylrhenium(I) complexes, fac-[Re(urca)₂(CO)₃Cl] (1) and fac-[Re(bzta)(CO)₃Cl] (2) were isolated from the coordination reactions of 5-((5-hydroxypentylimino)methyl)uracil (urca) and 2-((5-hydroxypentylimino)methyl)benzothiazole (bzta) with [Re(CO)₅Cl], respectively. Spectral characterization of metal complexes 1 and 2 were supported by their X-ray crystal structures. DNA interactions were assessed via UV–Vis calf-thymus (CT)-DNA binding titrations and gel electrophoresis. Redox properties of the metal complexes were probed using voltammetry.     

Nickel(II) Chloride‐Catalyzed Regioselective Hydrothiolation of Alkynes

Regioselective Markovnikov‐type addition of PhSH to alkynes (HC≡C‐R) has been performed using easily available nickel complexes. The non‐catalytic side reaction leading to anti‐Markovnikov products was suppressed by addition of γ‐terpinene to the catalytic system. The other side reaction leading to the bis(phenylthio)alkene was avoided by excluding phosphine and phosphite ligands from the catalytic system. It was found that catalytic amounts of Et₃N significantly increased the yield and selectivity of the catalytic reaction. Under optimized conditions high product yields of 60–85% were obtained for various alkynes [R=n‐C₅H₁₁, CH₂NMe₂, CH₂OMe, CH₂SPh, C₆H₁₁(OH), (CH₂)₃CN]. The X‐ray structure of one of the synthesized products is reported.     

Atom Economic Ruthenium‐Catalyzed Synthesis of Bulky β‐Oxo Esters

Ruthenium complexes with the formulae Ru(CO)₂(PR₃)₂(O₂CPh)₂ [ 6a – h ; R=n‐Bu, p‐MeO‐C₆H₄, p‐Me‐C₆H₄, Ph, p‐Cl‐C₆H₄, m‐Cl‐C₆H₄, p‐CF₃‐C₆H₄, m,m′‐(CF₃)₂C₆H₃] were prepared by treatment of triruthenium dodecacarbonyl [Ru₃(CO)₁₂] with the respective phosphine and benzoic acid or by the conversion of Ru(CO)₃(PR₃)₂ ( 8e – h ) with benzoic acid. During the preparation of 8 , ruthenium hydride complexes of type Ru(CO)(PR₃)₃(H)₂ ( 9g , h ) could be isolated as side products. The molecular structures of the newly synthesized complexes in the solid state are discussed. Compounds 6a – h were found to be highly effective catalysts in the addition of carboxylic acids to propargylic alcohols to give valuable β‐oxo esters. The catalyst screening revealed a considerably influence of the phosphine′s electronic nature on the resulting activities. The best performances were obtained with complexes 6g and 6h , featuring electron‐withdrawing phosphine ligands. Additionally, catalyst 6g is very active in the conversion of sterically demanding substrates, leading to a broad substrate scope. The catalytic preparation of simple as well as challenging substrates succeeds with catalyst 6g in yields that often exceed those of established literature systems. Furthermore, the reactions can be carried out with catalyst loadings down to 0.1 mol% and reaction temperatures down to 50 °C.

     

Dinuclear Rhodium Complexes Containing the Diyne 1,4-C6H4(C≡CH)2 and the Isomeric Bisvinylidene 1,4-C6H4(CH=C:)2 as Bridging Units

The reaction of [RhCl(PiPr₃)₂] ( 1 ) with 1,4-C₆H₄(C≡CH)₂ at 0°C leads almost quantitatively to the formation of the bis(alkyne) complex [(PiPr₃)₂ClRh-(HC≡C₆H₄-C≡CH)RhCl(PiPr₃)₂] (2). At elevated temperatures (THF, 60°C) it rearranges to give the isomeric bis(vinylidene) complex [(PiPr₃)₂ClRh-(=C=CH-C₆H₄-CH=C=)RhCl(PiPr₃)₂] (3). A one-pot synthesis of 3 is also described. Treatment of either 2 or 3 with pyridine affords the bis(alkynyl)dihydrido compound [(PiPr₃)₂(py)Cl(H)Rh(-C≡C-C₆H₄-C≡C-)Rh(H)Cl(py)(PiPr₃)₂] ( 4 ) in which both metal centers are octahedrally coordinated. Whereas the reaction of 2 with NaC₅H₅ produces the complex C_sH₅(PiPr₃)Rh(HC≡C-C₆H₄-C≡CH)Rh(PiPr₃)C₅H₅ ( 7 ), the bis(vinyl-idene) isomer C₅H₅(PiPr₃)Rh(=C=CH-C₆H₄-CH=C=)Rh(PiPr₃)C₅H_s ( 8 ) is obtained from 4 and NaC₅H₅. Electrophiles preferably attack the Rh=C bonds of 8 and thus on protonation with CF₃CO₂H the bis(vinyl) complex C₅H₅(PiPr₃)(CF₃CO₂)-Rh(Z,Z-CH=CH-C₆H₄-CH=CH)Rh(O₂CCF₃)(PiPr₃)C₅H_s ( Z-9 ) is formed. In acetone solution, it rearranges to give the E isomer. Reaction of 8 with sulfur affords the bis(thioketene) complex C₅H₅(PiPr₃)Rh(≡²-C,S; η²-C,S-S=C=CH-C₆H₄-CH=C=S)-Rh(PiPr₃)C₅H₅ ( 12 ), for which only one diastereomer is observed. All attempts to prepare mononuclear rhodium compounds containing the diyne HC≡C-C₆H₄-G≡CH or the isomeric vinylidene: C=CH-C₆H₄-G≡CH as ligand failed.     

Copolymerization of ethylene and 1‐decene by metallocenes: Direct comparison of Me2C(Cp)(Flu)ZrMe2 with Et(Cp)(Flu)ZrMe2

Copolymerizations of ethylene with 1‐decene have been carried out by using two syndiospecific metallocenes synthesized by modifying the bridge: highly syndiospecific isopropylidene(1‐η⁵‐cyclopentadienyl)(1‐η⁵‐fluorenyl)‐dimethylzirconium (Me₂C(Cp)(Flu)ZrMe₂, 1 ) and less syndiospecific (1‐fluorenyl‐2‐cyclopentadienylethane)‐dimethylzirconium (Et(Cp)(Flu)ZrMe₂, 2 ), in the presence of [Ph₃C][B(C₆F₅)₄] as a cocatalyst. The ethano bridged 2 compound of smaller dihedral angle showed much higher activity than 1 compound. The catalytic activities of the two compounds were enhanced about twice when a suitable amount of 1‐decene comonomer is present in the feed. The compound 1 showed better comonomer reactivity than 2 . The properties (T_m, density, and crystallinity) of copolymers seem not to be affected by the type of bridge of the metallocenes, and mainly depend on 1‐decene content in the copolymer.     

Kupfer,Silber, Gold; fixiert in metallorganischen π-Pinzetten

Alkinyl functionalized titanocenes of general type RC≡C-[Ti]-C≡CR and Cl-[Ti]-C≡CR {[Ti] = (η⁵-C₅H₄-SiMe₃)₂Ti}; R = singly bonded organic ligand} can successfully be used as organometallic π-tweezers to stabilize numerous mononuclear MX/R¹ species (M = Cu, Ag, Au; X = singly bonded inorganic group; R¹ = singly bonded organic ligand). The synthesis, manifold reaction chemistry as well as bonding and spectroscopy of {[Ti](C≡CR)₂}MX/R¹ and {[Ti] (C≡CR)(Cl)}CuX complexes is described