Ekkehard Lindner

Coordination chemistry and catalysis with hemilabile oxygen-phosphorus ligands

Classification of O,P ligands: ether-phosphines and furylphosphines, β-ketophosphines, phosphinocarboxylates, α-phosphinosulphoxides and their complexes of chromium group, of ruthenium, of cobalt group, of nickel group. Reactivity: oxidative additions, insertion reactions, metallation and catalytic applications

CHEMISTRY IN INTERPHASES : A NEW APPROACH TO ORGANOMETALLIC SYNTHESES AND CATALYSIS

Combining the advantages of homogeneous and heterogeneous catalysis is still a problem that has not been satisfactorily solved. Chemistry in interphases offers a new approach for overcoming the difficulties, as is described in this article. Owing to the swellable or porous matrix, an interphase represents a state which in the most favorable case is similar to that of a solution. Moreover the proper choice of a mobile hybrid copolymer enables the control of the density and accessibility of the reactive centers, which results in a distinct improvement of the activity of the catalysts (two examples are shown schematically).

Dynamic, reactivity and catalytic behavior of pseudo-undercoordinated ruthenium and rhodium complexes stabilized by intramolecular solvents

Abstract The fluxional behavior of pseudo-undercoordinated ruthenium complexes provided with bifunctional ether-phosphine ligands which compete for a common coordination site at the metal center is reviewed. The quantitative determination of this dynamic exchange by temperature-dependent 31 P NMR spectroscopy and line-shape analyses gives access to kinetic and thermodynamic data. From these, valuable information concerning the different chelating abilities of various ether-phosphines is available in dependence on both O-nucleophilicity and phosphorus basicity. Based on these experimental results, appropriate (ether-phosphine)-ruthenium and rhodium complexes are presented showing high reactivity toward the activation of small molecules like hydrogen, sulfur dioxide, carbon dioxide, carbon disulfide, ethene and phenylacetylene. Moreover, their catalytic properties with respect to hydrogenations, carbonylations and carbon dioxide hydrogenation are discussed.

Catalytic activity of cationic diphospalladium(II) complexes in the alkene/CO copolymerization in organic solvents and water in dependence on the length of the alkyl chain at the phosphine ligands

Abstract A series of diphos ligands CH2(CH2PR2)2 (1a–x) (a–g: R=(CH2)nOH, n=1, 3–8; h–k: R=(CH2)nCH(CH2OH)2, n=3–6; l–u: R=CnH2n+1, n=1–8, 10, 14; v–x: R=CH(CH3)2, (CH2)2CH(CH3)2, (CH2)3CH(CH3)2, ( Scheme 1 Download : Download high-res image (228KB) Download : Download full-size image Scheme 1 . ), provided with functionalities of different polarity, was prepared photochemically by hydrophosphination of the corresponding 1-alkenes with H2P(CH2)3PH2 or reaction of Grignard reagents with Cl2P(CH2)3PCl2. The water-soluble palladium complexes [(R2P(CH2)3PR2)Pd(OAc)2] (2a–k) were obtained by reaction of Pd(OAc)2 with the ligands 1a–k in ethanol–acetonitrile. Treatment of PdCl2(NCC6H5)2 with 1l–x afforded the dichloropalladium(II) complexes [(R2P(CH2)3PR2)PdCl2] (3l–x). Upon chloride abstraction with AgBF4 in dichloromethane–acetonitrile the dicationic palladium(II) complexes [(R2P(CH2)3PR2)Pd(NCCH3)2][BF4]2 (4l–x) are formed. The structure of 4n (R=n-Pr) was investigated by an X-ray structural analysis. In particular the water-soluble complexes 2c–k proved to be highly active in the carbon monoxide/ethene copolymerization under biphasic conditions (water–toluene). In the presence of an emulsifier and methanol as activator the catalytic activity increased by a factor of about three. Also higher olefins could be successfully incorporated into the copolymerization with CO and the terpolymerization with ethene and CO. The catalytic activity of the dicationic complexes 4l–x in the propene or 1-hexene/CO copolymerization strongly depends on the length of the alkyl chain R. At 25°C a maximum is achieved in the case of 4q (R=nHex) which is five times more active than the corresponding catalyst with the dppp-ligand. This maximum is shifted to 4t (R=n-C10H21) if the temperature is raised to 60°C. The 1-alkene/CO copolymers are distinguished by their regioregular microstructure and their ultra high molecular weights. Compared to the sulfonated dppp-SO3 catalyst the water-soluble complexes 2c,e,f,h are responsible for a higher 1-hexene incorporation in the terpolymerization of ethene with 1-hexene and CO.

Chemie in Interphasen – ein neuer Weg für die metallorganische Synthese und Katalyse

Wie lassen sich die Vorteile homogener und heterogener Katalyse vereinen? Darauf gibt es noch keine zufriedenstellende Antwort. Ein erfolgversprechender neuer Ansatz wird hier vorgestellt: die Chemie in Interphasen. Die quellbare oder porose Matrix als stationare Phase macht die Interphase zu einem Zustand, der im gunstigsten Fall dem in Losung ahnlich ist. Daruber hinaus last sich uber ein mobiles Hybridcopolymer die Dichte und die Zuganglichkeit der reaktiven Zentren einstellen, was eine gezielte Beeinflussung der Katalysatoraktivitat ermoglicht. Zwei Komplexe, die erfolgreich als Hybridkatalysatoren eingesetzt werden konnten, sind gezeigt.

New Inorganic–Organic Hybrid Materials for HPLC Separation Obtained by Direct Synthesis in the Presence of a Surfactant

Nanostructured, mesoporous inorganic–organic hybrid xerogels were reproducibly synthesized by a sol–gel procedure. For the introduction of long alkyl chains into inorganic polymers, trifunctional n-alkyltrialkoxysilanes of the type CH3(CH2)nSi(OR)3 (n = 7, 11, 17; R = CH3, C2H5) were co-condensed with Si(OEt)4 (TEOS). The synthetic pathway involves the employment of n-hexadecylamine as template and catalyst. The xerogels obtained by the present procedure consist of uniform spherical particles with a diameter of about 1 μm. The composition of the new materials was determined by 13C and 29Si cross polarization magic angle spinning (CP/MAS) NMR spectroscopy. In addition, the degree of organization was investigated by small angle X-ray and electron diffraction. In accordance with 13C CP/MAS NMR spectroscopic measurements, the alkyl chains form a crystalline arrangement within the silica polymer. Brunauer–Emmett–Teller (BET) adsorption measurements confirm specific surface areas of up to 1400 m2/g. The material properties prove the xerogels to be suitable as stationary phases in high-performance liquid chromatography (HPLC). These novel mesoporous, nanostructured materials have been successfully employed in HPLC for the first time. Different standard reference materials (SRMs) containing polycyclic aromatic hydrocarbons have been separated with the xerogels described in the present work.

Neuartige basische Liganden für die homogenkatalytische Methanolcarbonylierung X. Synthese, eigenschaften und komplexchemie mehrzähniger alkoxyethylphosphane und ihr verhalten als steuerliganden bei der methanolhydrocarbonylierung

Abstract Bi-, tri-, and quadridentate alkoxyethylphosphanes of the type RI1nP(CH2CH2-OR2)3-n are obtained from the correspon R1 = Ph, Cy (= cyclo-C6H11)) and 1,2-alkoxychloroethanes ClCH2CH2OR2 (R2 = Me, i-Pr). It was demonstrated using the following examples, Ph2PCH2CH2OMe, Cy2PCH2CH2OMe, and Cy2PCH2CH2O(i-Pr), that these ligands lead to the chelate complexes (OC)4 WPR 1 2 CH 2 CH 2 O R2 with (OC)5WTHF. The complexes (OC)5WPR12CH2CH2OR2 occur as intermediates, which upon irradiation are transformed to (OC)4 WPR 1 2 CH 2 CH 2 O R2 with elimination of CO. The process is reversible in the presence of carbon monoxide. The influence of different ether phosphane ligands on the methanol conversion and the selectivity to ethanol and acetaldehyde is discussed in relation to different parameters upon application of Co(OAc)2/I2 and CoI2 as components of the catalyst. CoI2 proves to be superior to the Co(OAc)2/I2 system.

Präparative und ir-spektroskopische untersuchungen über die zweikernigen dinatrium-dekacarbonyl-dimetallate(-I), Na2[M2(CO)10], des chroms (M=Cr), molybdäns (M=Mo) und wolframs (M=W)

Abstract Following a new method very pure sodium salts Na 2 [M 2 (CO) 10 ] (M=Cr, Mo, W) are obtained by reduction of the group VI metal carbonyls with an excess of sodium and catalytic amounts of 2,2′-bipyridine. The IR spectra of these compounds are recorded in CH 3 CN (in the range of 4000-200 cm −1 ) and are discussed. According to these results the anions [M 2 (CO) 10 2− have D 4 d symmetery and no bridging carbonyl groups. 1 H-NMR investigations exclude the presence of hydrogen-bridged complexes.

Supported organometallic complexes Part XXXV. Synthesis, characterization, and catalytic application of a new family of diamine(diphosphine)ruthenium(II) complexes

The novel diamine(dppp)ruthenium(II) complexes 3L1 � /3L12 have been obtained by reaction of equimolar amounts of Cl2Ru(dppp)2 (2) with the diamines L1 � /L12 in excellent yields. Within a few minutes one of the diphosphine ligands was quantitatively exchanged by the corresponding diamine. X-ray structural investigations of 3L1, 3L2, and 3L8 show triclinic unit cells with the space groups P/ ¯ 1 (3L1, 3L2) and P 1( 3L8). Whereas in solution all these complexes prefer a trans -RuCl2 configuration, in the solid state cis -(3L1, 3L2) and trans -isomers (3L8) were observed. With the exception of 3L5, 3L6, and 3L12 all mentioned ruthenium complexes are highly catalytically active in the hydrogenation of the a,b-unsaturated ketone trans -4-phenyl-3-butene-2one. In most cases the conversions and selectivities toward the formation of the unsaturated alcohol trans -4-phenyl-3-butene-2-ol were � /99% with high turnover frequencies (TOFs) under mild conditions. # 2002 Elsevier Science B.V. All rights reserved.

Asymmetric hydrogenation of an α,β-unsaturated ketone by diamine(ether–phosphine)ruthenium(II) complexes and lipase-catalyzed kinetic resolution: a consecutive approach

Abstract The RuCl2(η1-Ph2PCH2CH2OCH3)2(diamine) complexes 2L1–2L5 have been prepared in high yields from the reaction of equimolar amounts of RuCl2(η2-Ph2PCH2CH2OCH3)2 1 with various kinds of chelating diamines L1–L5 to form five-membered chelates with ruthenium. These novel ruthenium(II) complexes have been used as catalysts in the asymmetric hydrogenation of the prochiral ketone trans-4-phenyl-3-butene-2-one 3, using 2-propanol and different types of cocatalysts. Whereas complexes with achiral diamines afforded the racemic alcohols, complexes with chiral diamines (R,R or S,S) allowed the formation of the corresponding enantiomerically enriched secondary alcohol (S or R) with ee values of 45%. In order to obtain the secondary alcohol with ee of >99%, the kinetic resolution of enantiomerically enriched trans-4-phenyl-3-butene-2-ol 3 was performed in a consecutive approach using either the lipase-catalyzed enantioselective transesterification of the alcohol with isopropenyl acetate as the acyl donor in toluene or the enantioselective hydrolysis of the corresponding acetate in buffer. The determination of the enantiomeric excess (ee) of the resulting enantiomerically enriched secondary alcohols was performed by gas chromatography using heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin as the chiral stationary phase.