Jürgen Kopf

Preparation and characterization of the first triscyclopentadienyl lanthanoid complexes containing two aliphatic nitrile ligands: Crystal and molecular structures of the isomorphous compounds Trans-bis(acetonitrile)tris(η5cyclopentadienyl)lanthanoid(III) (Ln = La, Ce, Pr). A successful confirmation of the solid ‘solid angle sum rule’

Abstract Systematic studies to arrive at some first examples of the sterically congested complex type Cp3Ln(NCR)2 (Cp = η5-C5H5, Ln = lanthanoid element) resulted in the preparation and detailed spectroscopic characterization of analytically pure representatives of this type with Ln = La, Ce and Pr, but not with Nd (R = CH3, and C2H5 for Ln = La only). The crystal and molecular structures of representatives of the isomorphous series Cp3Ln(NCCH3)2, (Ln = La, Ce, Pr) were determined from three-dimensional X-ray diffraction data. The compounds crystallize in the orthorhombic space group Pnca (standard group Pbcn) with: a = 14.940(3), b = 14.074(3), c = 8.596(2)A, Z = 4, R = 0.070, Rw = 0.079 for 1633 intensity data (La derivative, I); a = 14.906(3), b = 13.974(3), c = 8.502(2)A, R = 0.041, Rw = 0.047 for 1378 intensity data (Ce derivative, VII); a = 14.936(3), b = 13.986(3), c = 8.498(2)A, R = 0.031 for 1372 intensity data (Pr derivative, IX). According to the X-ray crystallographic results, the novel complexes are trigonal bipyramidally coordinated with three η5-bonded Cp rings in the equatorial plane (Ln—ring centre distances 2.62, 2.64 for La, 2.58, 2.59Afor Ce and 2.57, 2.57Afor Pr and two acetonitrile groups in the axial positions (Ln N 2.785 for La, 2.749 for Ce, 2.752 for Pr). The range of the distances in the three derivatives is in agreement with the trend in the crystal radii along the lanthanoid series. Pure 1:2 adducts involving any alkyl group larger than R = C2H5 could not be isolated. The relative stabilities of the novel Cp3Ln(NCR)2 systems, with respect to the decreasing ionic radius (i.e. from La to Nd) and to the variable space demanded by the group R, are in excellent accord with independent expectations based on the recently developed cone packing model (‘SAS-rule’) for f-element organometallics.

Crystal structure and propene polymerization characteristics of bridged zirconocene catalysts

Abstract The synthesis, crystal structure and propene polymerization behaviour of four bridged zirconocene dichlorides is presented. All catalysts are capable of isotactic propene polymerization. Methyl substitutions at the 2-, 4- and 7-positions of the bridged bis(indenyl)zirconocene dichlorides were introduced. The methyl substituent in the 7-position of the idenyl ring induces a significant steric interaction with the bridging group. On comparison of the 2,4,7-methyl substituted catalysts with their unsubstituted counterparts, only the ethylidene bridged catalyst rac -1,2-ethylidene-bis(2,4,7-trimethyl-1-indenyl)zirconium dichloride ( 4 ) is forced into the optimum geometry for isotactic propene polymerization. Owing to the steric bulk at the bridge catalyst 4 is very rigid with respect to the movement of the idenyl rings and the metal centre thus produces highly isotacic polypropene even up to high polymerization temperatures. Molecular mechanics calculations and temperature-dependent NMR measurements demonstrate that catalyst 4 is not able to equilibrate between the λ and δ conformational state as the corresponding rac -1,2-ethylidene-bis(-1-indenyl)zirconium dichloride ( 3 ) catalyst does. In the case of the catalyst isopropyliden((3- tert -butyl)cyclopentadienyl-9-fluorenyl)zirconium dichloride ( 6 )_the substitution in the 3-position changes the symmetry from C s to C 1 . This catalyst produces isotactic polypropene but with a decreased polymerization activity.

Koordinationsverhältnisse in basenfreien tricyclopentadienyl-lanthanoid(III)-komplexen: IV. Die röntgenstrukturen von tricyclopentadienyl-erbium(III) und -thulium(III)☆

Abstract The single crystal X-ray analyses of sublimated (C5H5)3Er (6) and (C5H5)3Tm (7) confirm, for the first time, the existence of coordinatively well-saturated molecules containing just three η5-C5H5 ligands per metal ion (formal coordination number: 9, space group: Pna21, lattice parameters: a 1972.1(3), b 1389.4(1), c 862.4(3) pm for 6, and a 1999.1(3), b 1379.8(4), c 1379.8(4), c 857.8(3) pm for 7; R = 0.076 and 0.047, respectively). Individual molecules align themselves into chains by Van der Waals interactions. The structures of 6 and 7 show a marked contrast to those of their La und Pr homologues on the one hand, and with the structure of (C5H5)3Lu on the other.

Über metallalkyl- und -arylverbindungen : XXV. Die kristallstruktur von dimethyl(N,N,N′,N′-tetramethylethylendiamin)magnesium

Abstract Dimethyl(N,N,N′,N′-tetramethylethylenediamine)magnesium is prepared from Me2Mg and N,N,N′,N′-tetramethylethylenediamine (TMEDA), it has been investigated by X-ray diffraction methods (orthorhombic space group Cmca, Z = 8, 879 reflections, R = 0.076). Similarly to Ph2Mg · TMEDA the Mg atom is fourfold coordinated by two methyl groups and the chelate ligand. MgC and MgN distances are very similar in both compounds. Compared to polymeric Me2Mg and Et2Mg the MgC distances in Me2Mg · TMEDA are significantly shorter.

Metallorganische Verbindungen des Kupfers. V: Synthese und Struktur von Komplexen des 3,3,6,6-tetramethyl-1-thia-4-cycloheptins mit Kupfer(I)-Bromid, -Iodid und -Cyanid

Abstract Due to ring strain in the cycloalkyne 3,3,6,6-tetramethyl-1-thia-4-cycloheptyne (TMTCH, C10H16S), the CC group shows unusual coordinating properties towards CuI. Thus copper(I)bromidedimethylsulfide reacts with half a mole of TMTCH in dimethylsulfide (DMS/THF) with formation of the polymeric complex [(CuBr)2(dms)(η2-tmtch)]n (2b). Using [Cul(dms)] an analogous iodo compound was not obtained. However, [CuI(η2-tmtch)]2 (1c) reacts with dimethylsulfide under formation of monomeric [CuI(dms)(η2-tmtch)] (3). The reaction of coppercyanide with an excess of TMTCH yields the first example of an alkyne cyano copper complex [CuCN(η2-tmtch)]4 (4); it contains a slightly puckered Cu4(CN)4 ring. Hitherto no structures of (η2-alkyne)CuX complexes with X = I or CN have been described.

Über Metallalkyl- und Aryl-Verbindungen: Organonatrium-Verbindungen mit Benzyl-, Xylyl-, Diphenylmethyl- und 1-Phenyl-Ethyl-Carbanionen☆

Abstract Several organosodium compounds with the carbanions benzyl (phenylmethadine), diphenylmethyl (diphenylmethadine), o -xylyl ( o -methylphenylmethadine) and 1-phenyllethyl (1-phenylethadine) have been synthesized as base adducts with TMEDA (tetramethylethylenediamine) or PMDTA (pentamethyldiethylenetriamine) and studied by X-ray diffraction methods. Their structures are the result of ionic interactions between solvated Na ions and carbanions in combination with steric effects. Always a maximum number of shorter (ca. 260 pm) and longer (up to 300 pm) NaC contacts is achieved, often by formation of cyclic tetramers or polymer chains. The following compounds have been investigated in detail: [benzylsodium(PMDTA)] n ( 3 ), [ o -xylysodium(TMEDA)] 4 ( 4 ), [diphenylmethylsodium(TMEDA)] 4 , ( 5 ), diphenylmethylsodium(PMDTA) (monomer) ( 6 ) and [1-phenylethylsodium(TMEDA)] 4 ( 7 ).

Kristall- und molekülstruktur von p-phenylen-bis{ethinylisothiocyanato-trans-bis(triethyl-phosphin)platin(II)}, [Pt(NCS)(PEt3)2]2-p-C6H4(CC)2

Abstract A single-crystal X-ray diffraction study of the title compound has been carried out. The molecule has a center of symmetry. Coordination around the platinum atoms is approximately square planar. The two planes of coordination run parallel and form an angle of 53.4° with the phenylene ring. The Ptligand bond lengths are: PtP 2.304(4), PtN 2.024(9), and PtC 1.921(12) ». The PtC distance is 0.09 » shorter than a single bond. Crystal data: space group P21/c; a = 9.136(2), b = 13.888(8), c = 19.394(18) », β = 109.05(2)°; Z = 2. With 1954 reflections for which FO τ 3σ(FO), the structure has been refined anisotropically to R = 0.051.

cis-dicarbonyl-η5-cyclopentadienyl -1,1,4,4-tetraphenyl-1,4-diphosphabutane-vanadium(+I)cis-[η5-CpV(CO)2{Ph2P(CH2)2PPh2}]

Abstract The crystal and molecular structures of the title compound have been determined. The compound crystallizes in the monoclinic space group P 2 1 c with a = 1228.6 (6), b = 846.0 (4), c = 2771.1 (9) pm, β = 103.94 (3) and Z = 4. The vanadium atom is centred almost exactly between the two best planes spanning the cyclopentadienyl ring-atoms and C1C2P1P2, respectively. The Vanadium-phosphorus distances are longer and PVP-bond angles smaller than in most of the corresponding compounds throughout the periodic table, the data of which are tabulated.

Die Kristall- und Molekülstrukturen von einem Nitropentitol und von vier Nitrohexitolen

Abstract The crystal structures of 1-deoxy-1-nitro- d -arabino-pentitol, and 1-deoxy-1-nitro- d -galacto-, 1-deoxy-1-nitro- l -manno-, 1-deoxy-1-nitro- l -gluco-, and 1-deoxy-1-nitro- d -ido-hexitol were resolved by X-ray diffraction using direct methods. In all compounds, the oxygen atoms of the nitro group show a preference in their orientations to H-1 and H-2, one being in a position synclinal to H-12 and the other 1,3-synclinal to H-2. All molecules adopt the extended, planar, zig-zag conformation which is remarkable for the l -gluco and d -ido isomers, as both thus tolerate parallel 1,3-interactions (O//O) that are avoided in the parent hexitols by a bending into a sickle conformation.

2-chloro-2-cyclopropylidenacetate in synthesis. II: Facile construction of various spirocyclopropane anellated heterocycles

Abstract Methyl 2-chloro-2-cyclopropylidenacetate (1a) reacts with 1,2- and 1,3-bidentate nucleophiles in a heterogeneous system of solid base and dichloromethane under phase transfer catalysis. Spirocyclopropane anellated heterocyclic carboxylates 7, 9, 14, 10, 11 were obtained with KOH from 2-aminothiophenol, 1,2-dihydroxybenzene, 1,3-propanedithiol and with K2CO3 from 2-aminophenol and 2-aminoethanethiol respectively. With KOH the latter gave the seven-membered lactam 13 and 2-aminophenol led to methyl 4-benzoxazolylbutyrate 12. The adduct of benzylamine to the t-butyl ester 1b in a three-step sequence yielded the β-lactame 24 and an isomeric compound, probably the imido-β-lactone E/Z-25. Following a similar strategy, i.e. a sequence of Mukaiyama type alkylation, substitution, functional group interconversion and cyclization, 1a was converted to the cyclic imine 29a which served as a precursor to the carbapenam derivative 31. Finally, a few examples of 1,3-dipolar cycloaddition onto 1a are reported. Diazomethane added regioselectively in the “normal”, diphenyl-diazomethane in the opposite mode to yield pyrazolines 33a and 34a respectively; 2-diazopropane gave both regioisomeric pyrazolines. The primary cycloadduct of nitrilylid 35 and 1a could not be isolated but rather the pyrrole derivative 38 derived by ring-opening rearrangement.