Werner Röll

Synthesis and properties of elastomeric poly(propylene)

Elastomeric poly(propylene) with low percentages of isotactic pentads and high molecular weight was synthesized using unbridged “oscillating” metallocenes. The polymer sample with the highest [mmmm] content (22%) shows a small amount of crystallinity, which is highly influenced by the thermal history, and differs significantly in stress-strain and dynamic mechanical properties from all other samples. Polymers with lower isotacticity index, although lacking crystallinity in thermal analysis, differ in their viscoelastic behaviour from those of atactic poly(propylene). In dynamic mechanical analysis the γ relaxation at low temperature shows high sensitivity to low isotactic contents.

Highly isotactic polypropene prepared with rac-dimethylsilyl-bis (2-methyl-4-t-butyl-cyclopentadienyl) zirconiumdichloride: An NMR investigation of the polymer microstructure

Abstract Isotactic polypropene was prepared using rac-dimethyl-silylbis(2-methyl-4-t-butyl-cyclopentadienyl) zirconiumdichloride (1) and methylalumoxane (MAO) at temperatures between 0 and 80°C and with Al/Zr ratios of 300 and 1500. The polymers, prepared at temperatures below 30°C had melting points of 162°C and above. The chain ends were determined by means of distortionless enhancement by polarization transfer (DEPT)-NMR spectroscopy. The pentad intensities were corrected according to the chemical shifts of the end groups. The intensity distributions are shown to arise from enantiomorphic site control of the chiral catalyst species.

ansa-Metallocene derivatives XXXIII. 2-Dimethylamino-substituted bis-indenyl zirconium dichloride complexes with and without a dimethylsilyl bridge: syntheses, crystal structures and properties in propene polymerization catalysis

Abstract Bis(2-N,N-dimethylamino-indenyl) zirconium dichloride, (2-(CH 3 ) 2 N-C 9 H 6 ) 2 ZrCl 2 , and dimethylsilyl-bridged bis(2-N,N-dimethylamino-indenyl) zirconium dichloride, (CH 3 ) 2 Si(2-(CH 3 ) 2 N-C 9 H 5 ) 2 ZrCl 2 , were prepared by reaction of the corresponding ligand lithium salts with ZrCl 4 in toluene. Diffractometric structure determinations reveal C 2 -symmetric complex geometries for both complexes. An increased electron density at the Zr center of the dimethylamino-substituted complexes is indicated by reduction potentials which are 0.3–0.4 V more negative than those of their unsubstituted analogs. When activated with methyl aluminoxane in toluene solution, (CH 3 ) 2 Si(2-(CH 3 ) 2 N-C 9 H 5 ) 2 ZrCl 2 catalyzes the polymerization of propene to polymers with a microstructure comparable with that of polymers produced with other Me 2 Si-bridged bis(indenyl)ZrCl 2 complexes, but with a substantially increased fraction of i-propyl end groups derived from alkyl exchange between Zr-polymer and AlMe species.

Etude par spectroscopies vibrationnelles des complexes phenyle bistrans-halogenotetracarbonyl) metallocarbyniques et de leurs derives perdeuteries

Abstract Phenylbis(trans-halotetracarbonyl)carbynemetal complexes and their deuterated species [Br(CO)4WC]2C6H4(I), [Br(CO)4WC]2C6D4(II), [Br(CO)4CrC]2C6H4(III) and [Br(CO)4CrC]2C6D4(IV) have been synthesised and their IR and Raman spectra recorded. The ν±(MC) signals at 1372 cm−1 for I and 1352 cm−1 for III are in the same region as those for single carbyne complexes. Investigation of some of the vibrational modes of the phenyl ring shows that the carbyne fragment influences the π-electronic distribution of the ring by localising the π-electrons on the bonds parallel to the axis of the complex molecule.

Strukturen zweier (CO)4-Cr-biscarben-komplexe mit teilweise ungewöhnlichen bindungsverhlätnissen an den carbenkohlenstoffatomen

Abstract X-ray structure analyses of (CO)4 CrC(OEt)C 6 H 4 C (OEt) (I) and (CO)4 CrC(OEt)CHPhCHPhC (OEt) (II) are presented. In I the five-membered chelate ring is planar and the complex is symmetrically built, both carbene moieties showing the same bonding parameters (CrC(carbene): 200.0(6) and 200.4(7) pm; C(carbene)O: 131.8(8) and 130.8(8) pm). In II the C(carbene)Cr bond lengths differ from each other: 198(1) and 202(1) pm. Electronic adjustment results from the corresponding alkoxy group (C(carbene)O: 134(1) and 127(1) pm). The reason for this difference seems to be the sterically-induced twist of the five-membered chelate ring. Complex II is unsymmetrically distorted.

Übergangsmetall-Carbin-Komplexe, LXXII [1]. Reaktionen von trans-Bromotetracarbonyl(phenylcarbin)chrom mit Lithiumthiokresolat und Lithiumselenophenolat / Transition Metal Carbyne Complexes, LXXII [1]. Reactions of trans-Bromotetracarbonyl(phenylcarbyne)chromium with Lithium Thiocresolate and Lithium Phenylselenolate

The reaction of trans-bromotetracarbonyl(phenylcarbyne)chromium (1) with lithium phenylselenolate and subsequent protonation with aqueous hydrochloric acid leads to (CO)5Cr[Se2(C6H5)2] (3) and (CO)4Cr(μ-SeC6H5)2Cr(CO)4 (4). From 1 and lithium 4-methylphenylthiolate (CO)5CrC(C6H5)SC6H4CH3 (5) and (CO)5CrS(C2H5)(4-CH3C6H4) (6) are obtained, if triethyloxonium tetrafluoroborate is used instead of hydrochloric acid. The analoguous reaction of 1 with lithium phenylselenolate yields the seleno ether complex (7). Reaction conditions, properties, spectroscopic data and the results of an X-ray structure determination of the binuclear complex (4) are reported.