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  • 1
    Electronic Resource
    Electronic Resource
    Di-tert-butyl(N-pyrrolyl)phosphane,-sulfide, and-selenide, studied by multinuclear magnetic resonance (1997)
    Springer
    Fresenius' journal of analytical chemistry 357 (1997), S. 489-493 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  Di-tert-butyl(N-pyrrolyl)phosphane (1),-sulfide (2) and-selenide (3) were studied by 1H, 13C, 15N, 31P and 77Se NMR spectroscopy in solution. Restricted rotation about the P–N bond was observed for 1 (ΔG≠ C≈58.5 kJ/mol) and 2, 3 (ΔG≠ C≈45 kJ/mol) by 1H and 13C NMR at variable temperature. The fairly high pyrrolyl rotation barrier in 1 is ascribed to the expected steric effects exerted by the tert-butyl groups and to repulsion between the lone pairs of electrons at the phosphorus and nitrogen atoms. These repulsive forces are reduced in 2 or 3, or in di-tert-butyl(phenyl) phosphane (ΔG≠ C≈44 kJ/mol). Signs of coupling constants nJ(31P, 13C) and n+1J(31P, 1H) (n=2, 3) were determined by two-dimensional (2D) 13C/1H heteronuclear shift correlations. The preferred orientation of the pyrrolyl group in 1 is evident from the coupling constants 2J(31P, 13C(2))=+35.4 Hz and 2J(31P, 13C(5))=−9.3 Hz, typical of C(2) in syn and C(5) in anti position with respect to the assumed axis of the phosphorus lone pair. Hahn-echo extended (HEED) polarization transfer pulse sequences served for measuring 1J(31P, 15N) and isotope induced chemical shifts 1Δ15/14N(31P) from 31P NMR spectra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050198
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  • 2
    Electronic Resource
    Electronic Resource
    Novel rearrangements and formation of 2,5-dihydro-1,2,5-oxoniastannaboratolesvia methanolysis of zwitterionic η2-(alkyn-1-yl-borate)alkenyltin compounds (1999)
    Springer
    Chemistry of heterocyclic compounds 35 (1999), S. 1041-1051 
    Details
    ISSN: 1573-8353
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Organo-substituted 2,5-dihydro-1,2,5-oxoniastannaboratoles3 were prepared by methanolysis of zwitterionic η2-(alkyn-l-ylborate)alkenyltin compounds1. Analogously, the bis[η2-(alkyn-l-yl-borate)alkenyltin derivative2 reacts with an excess of methanol to give a dimeric MeO-bridged 2,5-dihydro-1,2,5-oxoniastannaboratole (10a)2. Various intermediates could be identified by NMR spectroscopy, and the molecular structure of(10a) 2 was determined by X-ray analysis. The structures of several products of the methanolysis indicate that protolysis of an Sn-C=bond occurs first, followed by an MeO/alkenyl exchange reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02251795
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  • 3
    Electronic Resource
    Electronic Resource
    Group 5 Metal Complexes with Cyclooctatetraene: Formation and Characterization of (Butadiene)(cyclooctatetraene)(cyclopentadienyl)tantalum Systems (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1461-1466 
    Details
    ISSN: 1434-1948
    Keywords: Diene complexes ; η3-Cyclooctatetraene metal complex ; B(C6F5)3 addition ; Tantalum ; Bicyclo[5.1.0]octadienyl metal complex ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The [(η4-diene)(η5-RCp)TaCl2] complexes 6a-e (diene = butadiene, isoprene or 2,3-dimethylbutadiene; RCp = pentamethylcyclopentadienyl, methylcyclopentadienyl or cyclopentadienyl) react with cyclooctatetraene dianion (employed as [(cot)Li2]) to yield the (η4-diene)(η3-cyclooctatetraene)(η5-RCp)tantalum complexes 7. The η3-cot coordination was confirmed by an X-ray crystal structure analysis of the compound [(supine-s-cis-η4-C4H6)(η3-cot)(η5-Cp*)Ta] 7a. In solution, the cot ligand of all the complexes 7 is fluxional. Two isomers [supine and proneorientation of the (diene)CpTa subunit] were found for the (η4-butadiene)(η3-cot)CpTa system (7e/7e′ = 95:5). Complex 7e cleanly adds the organometallic Lewis acid B(C6F5)3 to yield the betaine system [(η4-C4H6){C8H8B(C6F5)3}Cp*Ta] 8, which contains a substituted bicyclo[5.1.0]octadienyl ligand.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Reactions of Functional Groups at the Periphery of Group 4 Metallocene Frameworks: Selective Formation of a Cp-Bonded Azaboretidine Derivative by a Hydroboration Route (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 409-416 
    Details
    ISSN: 1434-1948
    Keywords: Functionalized zirconocenes ; Half-sandwich complexes ; Hydroboration ; Propene polymerization/Homogeneous catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 6-Amino-6-methylfulvene has been coupled with benzoic acid by treatment with 7-azahydroxybenzotriazole and DCC. Subsequent two-fold deprotonation, at the NH and 6-methyl groups, generated the vinylidene-bridged Cp/benzoylamido ligand 5. Treatment of 5 with ZrCl4(THF)2 gave the spiro-metallocene complex 3a (characterized by X-ray crystal structure analysis), while reaction of 5 with (Et2N)2ZrCl2(THF)2 yielded the bridged half-sandwich complex 3b. Treatment of 3a with two molar equivalents of the strongly electrophilic borane HB(C6F5)2 resulted in hydroboration of the exocyclic C=C double bond with concomitant intramolecular N-B adduct formation to yield the azaboretidine-type systems 7 (three diastereoisomers, one of which has been characterized by X-ray diffraction analysis). Similarly, hydroboration of 3b with HB(C6F5)2 yielded the azaboretidine derivative 9. Activation of the complexes 7 and 9 with methylalumoxane led to active homogeneous Ziegler-type propene polymerization catalysts.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Organotin cations stabilized by π coordination - synthesis and NMR studies in solution and in the solid state (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1597-1603 
    Details
    ISSN: 0009-2940
    Keywords: Organoboration ; Tin compounds ; NMR, multinuclear ; NMR, 119Sn ; NMR, solid-state ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The organoboration of tetraalkynyltin compounds [Sn-(C≡CR1)4 (1): R1 = Me (a), Et (b), Pr (c), iPr (d), tBu (e)] with triethylborane (2) proceeds stepwise. Intermediates with a cationic triorganotin (3, 5) and a dicationic diorganotin fragment (4), stabilized by intramolecular coordination of one and two alkynyl moieties, respectively, were isolated (3e, 4a) and/or identified by multinuclear NMR in solution (1H, 11B, 13C, 119Sn) and in the solid state (13C and 119Sn CP/MAS) (3e, 4a). The magnitude of 1J(13C≡13C) in 4a (101.0 Hz) is significantly smaller than that for sodium triethyl-1-propynylborate (7) (119.2 Hz), proving the weak coordination of the C≡C bond to the dicationic tin fragment. The final products of the organoboration, 1,4,6,9-tetraalkyl-2,7-bis(diethylboryl)-3,8-diethyl-5-stannaspiro[4.4]nona-1,3,6,8-tetraenes (6b-6e) were obtained in high yield.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250714
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  • 6
    Electronic Resource
    Electronic Resource
    Trimethylsilylierte 1,4-Diborinane und 1,3-Diborolane - Bildung, Isomeren-Trennung und Charakterisierung (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 813-820 
    Details
    ISSN: 0009-2940
    Keywords: Hydroboration of 1-alkinylsilanes ; Ethyldiboranes(6) ; Alkyl substituent exchanges ; BH-borane-catalysed ; 1,4-Diborinanes, trimethylsilyl-substituted, isomers of ; Lewisbase - 1,4-Diborinanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Trimethylsilylated 1,4-Diborinanes and 1,3-Diborolanes - Formation, Isomer Separation, and CharacterisationMe3SiC≡CH (A) reacts with excess (Et2BH)2 via the compounds 1, 1′ and 2, 2′ to yield a mixture of four regio- and stereoisomeric 1,4-diethyl-2,5(6)-bis(trimethylsilyl)-1,4-diborinanes (3a-d) and minor amounts of 1,3-diethyl-2-methyltrans-2,5-bis(trimethylsilyl)-1,3-diborolane (4a). The 2,5-ee-(Me3Si)2 compound 3d is isolated as the adduct 3d(Pic)2 (X-ray structure analysis), from which pure 3d is obtained with Et2O-BF3. 3d and Me3P form equilibria of the 1:1 and 1:2 addition compounds 3d(Me3P)n (n = 1,2) at room temperature. Me3SiC≡CMe (B) reacts with (Et2BH)2 via 5 to give 6-10, and Me3SiC≡CSiMe3 (C) reacts with (Et2BH)2 to form the ring compounds 12 and 13 via the presumably threo/erythro mixture of 11a and b.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270504
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  • 7
    Electronic Resource
    Electronic Resource
    Organoborierung von Tetrakis(trimethylsilylethinyl)stannan - Röntgenstrukturanalyse eines 5-Stannaspiro[4.4]nona-1,3,6,8-tetraen-Derivates[1] (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 643-650 
    Details
    ISSN: 0009-2940
    Keywords: Organoboration ; Tin, alkynyl compounds ; Spiro-tetraorganotin compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organoboration of Tetrakis(trimethylsilylethynyl)stannane - X-ray Structure of a 5-Stannaspiro[4.4]nona-1,3,6,8-tetraene DerivativeTetrakis(trimethylsilylethynyl)stannane (1) reacts with non-cyclic trialkylboranes BR3 [2, R = Me (a), Et (b), Pr (c), iPr (d)] and 9-alkyl-9-borabicyclo[3.3.1]nonanes[2e (alkyl = Et), 2f (alkyl = neopentyl)] to give the 3,8-dialkyl-2,7-bis(dialkylboryl)-1,4,6,9-tetrakis(trimethylsilyl)-5-stannaspiro[4.4]nona-1,3,6,8-tetraenes 5a to f in high yield. The reaction proceeds stepwise, and intermediates as well as final products were characterized by 1H, 11B, 13C, 29Si, 119Sn NMR spectroscopy. According to an X-ray structure analysis of 5f · 0.5 CH2Cl2 (space group P2/c) the endocyclic CSnC bond angles are small [84.9(2) and 84.2(2)°] and the two five-membered rings are not exactly planar. Steric crowding causes a strong twist of the skeleton of the other ring systems. The agreement between solid-state and liquid-phase NMR data shows that main structural features are retained in solution.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250316
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  • 8
    Electronic Resource
    Electronic Resource
    1,1-Organoboration of Di-1-alkynylsilanes with Alkynyl Groups of Different Reactivity: New Organometallic-Substituted Siloles (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2221-2226 
    Details
    ISSN: 0009-2940
    Keywords: Silanes, alkynyl[(trimethylstannyl)ethynyl]- ; 1,1-Ethyloboration, intermolecular ; 1,1-Vinyloboration, intramolecular ; Siloles ; Protodeborylation ; Protodestannylation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of alkynyl[(trimethylstannyl)ethynyl]dimethylsilanes 4 [alkynyl R1 - C≡C: R1 = Bu (b), tBu (c), iPent (d), Ph (e), SiMe3 (f)] is reported. The intermolecular 1,1-ethyloboration of 4 with triethylborane takes place selectively at the Sn - C≡ bond to give first the alkenyl(alkynyl)dimethylsilanes 5 and 6. There exists an equilibrium between 5 and 6, and compound 6 has the suitable stereochemistry for the final intramolecular 1,1-vinyloboration to form the 4-(diethylboryl)-2-(trimethylstannyl)siloles 7. Protodeborylation of 7 with water gives the 2-(trimethylstannyl)siloles 8, and protodeborylation and protodestannylation with an excess of acetylacetone affords the siloles 9. Multinuclear NMR (1H-, 11B-, 13C-, 29Si-, and 119Sn-) serves for monitoring the reactions and for the characterization of the products.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261009
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  • 9
    Electronic Resource
    Electronic Resource
    Organosubstituierte 1,1′-Spirobisilole und 1,1′-Spirobigermole durch vierfache Organoborierung von Tetra-1-alkinylsilanen und -germanen (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1385-1396 
    Details
    ISSN: 0009-2940
    Keywords: Silanes, tetra-1-alkynyl- ; Germanes, tetra-1-alkynyl- ; 1,1-Ethyloboration, intermolecular ; 1,1-Vinyloboration, intramolecular ; Spirosilanes ; Spirogermanes ; Protodeborylation ; Transition metals, η41-complexes of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organosubstituted 1,1′-Spirobisiloles and 1,1′-Spirobigermoles by Fourfold Organoboration of Tetra-1-alkynylsilanes and -germanes[1]Si(C≡CR)4 [R=Me (A), R=Ph (B), R=SiMe3 (C)] and Ge(C≡CR)4 [R=Me (D), R=Ph (E)] react with Et3B by twofold intermolecular ethyloboration and twofold intramolecular vinyloboration to form the organo-substituted 5-sila(germa)spiro[4.4]nonatetraenes , R=Me: 1a, R=Ph: 1b; M=Ge, R=Me: 2d, R=Ph: 2e] via the mono-and bisethyloboration compounds 3 or 4 (e.g. 3b, 4c) with different rates: Ge 〉 Si; Me 〉 Ph. For comparison, compounds Sn(C≡CR)4 [R=Me (F), R=Ph (G)] react with Et3B in the absence of a solvent to mixtures of various spirotin compounds (5f, 5g, 6f, 8f, 9g, 10g, 11g) of which only 9g (R=Ph) corresponds to the spirosilanes and -germanes. This is the result of effective competition between intramolecular and intermolecular organoboration in the case of the tetra-1-alkynyltin compounds. The protodeborylation of 1a, b and 2d, e with MeCO2H leads to 12a, b and 13d, e, respectively. 12a isomerises by UV irradiation to allyl isomers 12a′. From 12a with 2 equiv. of maleic anhydride the 1:2 addition compound 14a is obtained, the autaddition of 12a, d leads to 15a, d. Spiro compound 12a reacts with (OC)5Fe or CpCo(C2H4)2 to give the cyclodiastereomeric η41-complexes [(OC)3Fe]2-12a (16a1-a4; X-ray structure analysis of meso- 16a1), (OC)3Fe-12a (17a) and (CpCo)2-12a (18a1-a4). - All products were characterized by multinuclear NMR, including measurements of the coupling constants 1J(13C13C), 2J(29Si29Si), nJ(29Si13C) and nJ(119Sn13C).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260617
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  • 10
    Electronic Resource
    Electronic Resource
    π-Koordination an Diorganozinn-DikationenDiese Arbeit wurde von der Deutschen Forschungsgemeinschaft, dem Fonds der Chemischen Industrie und der Volkswagen-Stiftung gefördert. (1991)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 103 (1991), S. 1374-1376 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19911031030
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