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  • 11
    Electronic Resource
    Electronic Resource
    The First Titanacyclic Five-Membered Cumulene. Synthesis, Structure, and Reactivity (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 967-971 
    Details
    ISSN: 0009-2940
    Keywords: Titanocene ; Diyne ; Cumulene ; Titanacyclopentadiene ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The first five-membered titanacyclic cumulene (5) was prepared by treatment of the titanocene generator Cp2Ti(Me3SiC2SiMe3) with the di-tert-butylbutadiyne in a molecular one-to-one ratio. The reaction of 5 with “Cp2Zr” or of the analogous complex with “Cp2Ti” leads to cleavage of the central C-C bond in the metallacyclocumulene complexes to afford the same product, the heterodimetallic ρ, π,-alkynyl-bridged titanocene-zirconocene complex Cp2Zr(μ-η1η2-C≡CtBu)Cp2Ti(μ-η1η2-C≡CtBu) (6), in which each alkynyl group is π-bonded to one and π-bonded to the other metal as shown by X-ray diffraction studies. In solution the two alkynyl groups become equivalent. The coupling reaction of “Cp2Ti” with bis(trimethylsilyl)butadiyne in a one-to-two molecular ratio leads to the unsymmetrically substituted titanacyclopentadiene (7).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951281002
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  • 12
    Electronic Resource
    Electronic Resource
    Reactions of Lactams with Titanocene- and Zirconocene-Alkyne Complexes as Elemental Steps in Catalytic Anionic Ring-Opening Polymerization of Lactams (1996)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1281-1285 
    Details
    ISSN: 0009-2940
    Keywords: Zirconocenes ; Titanocenes ; N-Methyl-ε-caprolactam ; β-Propiolactam ; ε-Caprolactam ; Ring-opening polymerization ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Depending on the nature of the metal and the ring size, lactams react with titanocene and zircocene complexes of bis-(trimethylsilyl)acetylene Cp2Ti(Me3SiC2SiMe3) and Cp2Zr-(L)(Me3SiC2SiMe3) (L = Py, THF) to yield different products. In the reaction of Cp2Zr(Py)(Me3SiC2SiMe3) with N-methyl-€-caprolactam a simple ligand exchange reaction occurs and the complex Cp2Zr(Me3SiC2SiMe3)[O=H2)5] (1) was isolated. With β-propiolactam the alkenyl-amido complex Cp2)(SiMe3)][-NH2] (2) was obtained, which indicates that an agostic metal-hydrogen interaction has taken place. The reaction of Cp2Ti(Me3-SiC2SiMe3) with €-caprolactam gives after elimination of the alkyne and molecular hydrogen the first early transition metal complex with a deprotonated coordinated €-caprolactam in a η2-amidate bonding fashion (3). The obtained complexes were characterized by NMR spectra (1, 2) and crystal structure analysis (1-3) and discussed as elemental steps in anionic ring-opening polymerization of lactams catalyzed by metallocene-alkyne complexes.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19961291022
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  • 13
    Electronic Resource
    Electronic Resource
    Ligand- Substrate Communication in Group 4 Aminopyridinato Complexes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 789-794 
    Details
    ISSN: 0009-2940
    Keywords: Agostic interactions ; Ligand effects ; Titanium ; Zirconium ; Aminopyridinato ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tris(aminopyridinato) zirconium and ansa-aminopyridinato titanium complexes have been sythesized. The reaction of (TMS-APy)3-Zr-Cl (4-methyl-2-trimethylsilyl-aminopyridine=TMS-APy-H) with trimethylsilylbutadiynyl lithium generated in situ affords (TMS-APy)3—Zr—C≡C—C≡C—TMS (1). (TMS-apy)3-Zr-Me2 (2). Compound 2 shows an agostic interaction of the dimethylamido moiety. The reaction of Ti(NMe,2),4 with silox(Apy-H)21,3-di(4′-picolin-2′-yl-amino)-1,1,3,3-tetraisopropyldisiloxane=silox (APy-H)2] gives rise to silox(Apy)2-Ti-(NMe2)2-Ti-[NMe,2)2 (3). Complex 3 reacts with ε-caprolactam to form a caprolactamato complex (4). X-ray crystal structure analyses of 1, 2, 3 and 4 are reported. The complexes 1, 2, 3 and 4 may be considered to be strained donor-functionalized amido(metal) complexes due to the η2 binding mode of the ligand cores, TMS-APy and silox(APy)2, to meet the requirements of the ancillary coordinated substrates is observed. Thus, aminopyridinato complexes seem to be valuable model compounds for investigations of ligand-substrate communications in early transition metal chemistry.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300618
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  • 14
    Electronic Resource
    Electronic Resource
    Zur Synthese und Charakterisierung von Platincyclobutadien-Komplexen durch Reduktion von Hexachloroplatinsäure (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2393-2396 
    Details
    ISSN: 0009-2940
    Keywords: Platinum complexes ; Cyclobutadiene complexes ; Alkyne dimerization ; Catalysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Characterization of Platinumcyclobutadiene Complexes by the Reduction of Hexachloroplatinic AcidHexachloroplatinic acid is reduced in 1-butanol in the presence of an alkyne R-C≡C-R′ (R, R′ = Me, Et, nPr) to give platinumcyclobutadiene complexes [PtCl2(C4R2R2′)] (1). H[PtCl3(CH3CH2CH=CH2)] (2) is an intermediate which is isolated as bis(triphenylphosphoranylidene)ammonium salt (PPN-salt) [PPN][PtCl3(CH3CH2CH=CH2)] (3). The molecular structure of [PtCl2(C4Et4)] (1b) shows in the solid state a planar cyclobutadiene ring with internal bond angles of 93(3) and 87(2)°. The Pt-C bond lengths are 208(2) and 210(2) pm. The ethyl groups are pushed out of the ring plane, away from the Pt atom, with an angle of 7(2)°.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261108
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  • 15
    Electronic Resource
    Electronic Resource
    β-Alkoxy- and β-Hydroxyalkylphosphanes as Ligands in the Stereoselective Hydrogenation  -  A Comparison (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 767-773 
    Details
    ISSN: 0009-2940
    Keywords: Ether phosphanes ; Hydroxyalkylphosphanes ; Rhodium ; Asymmetric hydrogenation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optically pure 1,4-bis(diphenylphosphanyl)-2-hydroxy-butane (2) and its methyl ether 1 can be conveniently prepared by starting from chiral pool substances such as malic or L-ascorbic acid. Different pathways to these compounds were elucidated. In one case an interesting migration of an acetalic OH-protective group was observed. The reaction of the bisphosphanes with Rh1 or PdII gave uniform metal complexes. On the basis of X-ray structural analysis, NMR and IR data it was concluded that in the investigated precatalysts of the type [Rh(COD)(bisphosphane)]BF4 a coordination of the alkoxy or hydroxy oxygen to the metal does not take place. Nevertheless, significant differences in enantioselectivity and activity could be observed when several prochiral substrates were hydrogenated.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280805
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  • 16
    Electronic Resource
    Electronic Resource
    Ring-Enlargement and Ring-Opening Reactions of Benzoxazole, Thiazoles, and Benzisoxazole by Zirconocene-Alkyne Complexes (1996)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 207-211 
    Details
    ISSN: 0009-2940
    Keywords: Zirconocene ; Titanocene ; Benzoxazoles ; Thiazoles ; Benzisoxazoles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Zirconocene alkyne complexes Cp2Zr(L)(Me3SiC2R) (L = Py, THF; R = SiMe3 tBu) react with heterocyclic compounds like benzoxazole and related thiazoles to yield ring-expanded adducts (1-3) and (4, 5) by formal C-X (X = O, S) bond cleavage and coupling with the coordinated alkyne. In the case of benziso-xazole, the alkyne is not coupled but eliminated, and with ring-enlargement of the benzisoxazole a N-bridged dimer (6) is formed. The obtained complexes 1, 3, and 6 were characterized by NMR spectra and crystal structure analysis.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19961290214
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  • 17
    Electronic Resource
    Electronic Resource
    Synthesis and Structure of Mononuclear Titanium Complexes Containing ansa-Aminopyridinato Ligands (1996)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1087-1091 
    Details
    ISSN: 0009-2940
    Keywords: ansa-Aminopyridinato ligands ; Strained amido ligands ; Titanium complexes ; Olefin polymerization ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of siloxane-bridged bis(2-aminopyridines) were synthesized from dichlorosiloxanes and 2-aminopyridines in the presence of a base via nucleophilic substitution reactions. They were used, after deprotonation, as dianionic (ansa-aminopyridinato) ligands to stabilize mononuclear titanium complexes with unusual coordination geometries. An X-ray crystal structure analysis of one of the ligands and of a titanium complex proved mononuclearity and provided information about the binding mode of this novel type of ligands. Ethylene polymerization studies showed low activity, remarkable differences between structurally related complexes, and broad molecular weight distributions. Sterically less demanding substituents and a high basicity of the ligand increase polymerization activity.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19961290917
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  • 18
    Electronic Resource
    Electronic Resource
    Synthese neuer N-Aroylisothiazol-2-imine und N-Aroylamino-isothiazoliumsalze durch Cyclisierung von thiocyanato-substituierten HydrazonenHerrn Prof. Dr. M. Mühlstedt zum 65. Geburtstag gewidmet (1994)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 336 (1994), S. 115-120 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of New N-Aroylisothiazole-2-imines and N-Aroylaminoisothiazolium Salts by Cyclisation of Thiocyanato-substituted HydrazonesThe synthesis of new N-aroylisothiazole-2-imines (4g-n) as well as the corresponding acceptor-substituted 2-amino-isothiazolium salts (6f-n) by cyclocondensation of thiocyanatovinylaldehyde hydrazones (3) is reported. The structure of these N-imines was proved by spectroscopic methods. The alternative cyclization route to 1,2,3-thiadiazines (8) is not observed. The hydrazones (3a-e) could not be cyclized to N-imines, only sulfides (5a-c) were obtained. The reaction of 2-thiocyanatomethylen-cycloheptan-2-one (9) with benzhydrazides gave the same ring closure to the salts (10a,b). The structure of the N-imine 11b has been confirmed unequivocally by X-ray structure analysis.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19943360204
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  • 19
    Electronic Resource
    Electronic Resource
    Stability of Bridged and Unbridged η2-Alkyne-titanocene and -zirconocene Complexes - Influence of Metals, Alkyne Substituents, Cp Substitution and Additional Ligands (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 419-424 
    Details
    ISSN: 1434-1948
    Keywords: Alkyne complexes ; Titanium ; Zirconium ; Coordination mode ; Metallacycles ; Cyclopentadienes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of metals, alkyne substituents, Cp substitution and additional ligands on the stability of bridged and unbridged η2-alkyne-titanocene and -zirconocene complexes has been investigated. The reduction of the complex [(η5-C5H4)-SiMe2-(η5-C5H4)]TiCl2 with magnesium in the presence of tolan (PhC2Ph) does not give the expected alkyne-titanocene complex [(η5-C5H4)-SiMe2-(η5-C5H4)]Ti(η2-PhC2Ph) but by coupling of two tolan molecules the corresponding titanacyclopentadiene [(η5-C5H4)-SiMe2-(η5-C5H4)]TiC4Ph4 (1) was obtained. In the analogous reaction with Me3SiC2SiMe3 the stable η2-alkyne complex without additional ligands [(η5-C5H4)-SiMe2-(η5-C5H4)]Ti(η2-Me3SiC2SiMe3) (2) was formed, due to the sterical influence of the alkyne substituents. The compounds without additional ligands (thi)2Ti(η2-PhC2Ph) (3) and (thi)2Ti(η2- Me3SiC2SiMe3) (5) were isolated from the unbridged titanocene complex (thi)2TiCl2 (thi = tetrahydroindenyl). Two equivalents of complex 3 reacted with one equivalent of water to yield the dimeric alkylidene-μ-oxo complex [(thi)2Ti(CPh=CHPh)]2(μ-O) (6). The reaction of the unbridged zirconocene compound (thi)2ZrCl2 gave the alkyne complex (thi)2Zr(THF)(η2-Me3- SiC2SiMe3) (7) which is stabilized by THF. At higher temperature THF was eliminated from the orange complex 7 forming the green complex (thi)2Zr(η2-Me3SiC2SiMe3). This behaviour was investigated in detail using NMR spectroscopy and compared to similar complexes such as Cp2Zr(η2-Me3SiC2SiMe3) (not stable without THF), (ebthi)2Zr(η2-Me3SiC2SiMe3) (ebthi = ethylenebistetrahydroindenyl; stable without THF) and Cp*2Zr(η2-Me3SiC2SiMe3) (Cp* = pentamethyl-Cp, stable without THF). All complexes were characterized by spectroscopic methods. X-ray structural determinations were conducted for the complexes 1, 3 and 7. Compound 3 is the first example of a structurally characterized tolan-titanocene complex without additional ligands.
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    Reactions of ε-Caprolactone with (Alkyne)zirconocene Complexes: Investigation of Elemental Steps in Catalytic Ring-Opening Polymerization of Lactones (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1351-1357 
    Details
    ISSN: 1434-1948
    Keywords: ε-Caprolactone complexes ; Zirconocene ; Ring-opening polymerization ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of Cp2Zr(L)(η2-Me3SiC2SiMe3) (L = THF, pyridine) with ε-caprolactone, cyclohexanone and cycloheptanone result in an insertion of the carbonyl group into the zirconacyclopropene ring system of the alkyne complexes to yield the five-membered metallacyclic spiro-zirconadihydrofurane complexes 1, 3, 4. The product with ε-caprolactone is not stable at room temperature and was identified only by NMR spectra and chemical reactions. Starting from rac-(ebthi)Zr(η2-Me3SiC2SiMe3) with ε-caprolactone and ethylene carbonate under analogous conditions more stable complexes (2, 5) were obtained. Complexes 2 and 3 were characterized by X-ray crystal-structure analysis. Complexes 1 and 2 react with further ε-caprolactone in a catalytic ring-opening polymerization. The polymerization reactions were monitored by NMR spectroscopy.
    Type of Medium: Electronic Resource
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