24
1 Organischer Teil (Woche 1-2): 1. Herstellung eines Alkens über die Olefinierung eines Aldehyds nach Wittig oder Wadsworth-Horner-Emmons. Jede Zweiergruppe stellt eines von zwei ausgewählten 2-zweistufigen Präparaten über eine Olefinierungsreaktion her. Alle Einzelversuche sind ausführlich beschrieben im „Praktikum Präparative Organische Chemie“ (s.u.). a) 2-26, dann 11-3: Wittig-Reaktion zu 2,3 trans-4E-5,9-Dimethyldeca-2,4,8- triensäureethylester, ausgehend von Bromessigester. 2 Stufen: Phosphoniumsalz und Ylid, dann Olefin. b) 2-28, dann 11-7: Wadsworth-Horner-Emmons-Olefinierung zu trans-3(4- Bromphenyl)acrylsäureethylester, ausgehend von Bromessigester. 2 Stufen: Arbuzow-Reaktion zum Phosphonat, dann Olefin. In beiden Fällen wird das Zwischenprodukt (Phosphoniumsalz und Ylid bzw. Phosphonat) isoliert. Charakterisierung mit 1 H-NMR und 31 P-NMR-Spektrum. Welche Signale stehen für das Phosphoniumsalz, welche für das Ylid und welche für das Phosphonat? Das Produkt der Olefinierung entsteht prinzipiell als E/Z-Gemisch (besonders bei der Wittig-Olefinierung). Es wird in beiden Fällen mittels Säulenchromatographie gereinigt. Die beiden Diastereomere (Reinprodukt oder eine Mischfraktion) sollen im 1 H-NMR-Spektrum voneinander unterschieden werden, evtl. unterstützt durch ein HPLC-Chromatogramm. Welches E/Z-Verhältnis wurde in der Reaktion insgesamt erreicht? Wie rein sind die erhaltenen Produktfraktionen? Lit.: R. Brückner et al., Praktikum Präparative Organische Chemie, Organisch- Chemisches Grundpraktikum, Spektrum Verlag 2008. Hier findet sich weitere Originalliteratur. 2. Herstellung eines β-Ketiminat-Liganden für die ringöffnende Lactid- polymerisation (integrierter Versuch Woche 5). Jede Zweiergruppe stellt eines von zwei Ketiminaten aus Acetylaceton und einem unsymmetrischen N,N-Dialkyldiamin her.

Organischer Teil (Woche 1-2): 1. Herstellung eines Alkens ... · 1 Organischer Teil (Woche 1-2): 1. Herstellung eines Alkens über die Olefinierung eines Aldehyds nach Wittig oder

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  • 1

    Organischer Teil (Woche 1-2):

    1. Herstellung eines Alkens ber die Olefinierung eines Aldehyds nach Wittig

    oder Wadsworth-Horner-Emmons.

    Jede Zweiergruppe stellt eines von zwei ausgewhlten 2-zweistufigen Prparaten

    ber eine Olefinierungsreaktion her. Alle Einzelversuche sind ausfhrlich

    beschrieben im Praktikum Prparative Organische Chemie (s.u.).

    a) 2-26, dann 11-3: Wittig-Reaktion zu 2,3trans-4E-5,9-Dimethyldeca-2,4,8-

    triensureethylester, ausgehend von Bromessigester.

    2 Stufen: Phosphoniumsalz und Ylid, dann Olefin.

    b) 2-28, dann 11-7: Wadsworth-Horner-Emmons-Olefinierung zu trans-3(4-

    Bromphenyl)acrylsureethylester, ausgehend von Bromessigester.

    2 Stufen: Arbuzow-Reaktion zum Phosphonat, dann Olefin.

    In beiden Fllen wird das Zwischenprodukt (Phosphoniumsalz und Ylid bzw.

    Phosphonat) isoliert. Charakterisierung mit 1H-NMR und 31P-NMR-Spektrum. Welche

    Signale stehen fr das Phosphoniumsalz, welche fr das Ylid und welche fr das

    Phosphonat? Das Produkt der Olefinierung entsteht prinzipiell als E/Z-Gemisch

    (besonders bei der Wittig-Olefinierung). Es wird in beiden Fllen mittels

    Sulenchromatographie gereinigt. Die beiden Diastereomere (Reinprodukt oder eine

    Mischfraktion) sollen im 1H-NMR-Spektrum voneinander unterschieden werden, evtl.

    untersttzt durch ein HPLC-Chromatogramm. Welches E/Z-Verhltnis wurde in der

    Reaktion insgesamt erreicht? Wie rein sind die erhaltenen Produktfraktionen?

    Lit.: R. Brckner et al., Praktikum Prparative Organische Chemie, Organisch-

    Chemisches Grundpraktikum, Spektrum Verlag 2008. Hier findet sich weitere

    Originalliteratur.

    2. Herstellung eines -Ketiminat-Liganden fr die ringffnende Lactid-

    polymerisation (integrierter Versuch Woche 5).

    Jede Zweiergruppe stellt eines von zwei Ketiminaten aus Acetylaceton und einem

    unsymmetrischen N,N-Dialkyldiamin her.

  • 2

    a) Acetylaceton + N,N-Diethyl(ethylendiamin)

    b) Acetylaceton + N,N-Dimethyl(propylendiamin)

    Das Produkt wird ber sein 1H-NMR-Spektrum (evtl. in Einzelfllen ber sein

    Massenspektrum) charakterisiert. Es muss fr die nachfolgende Komplexierung

    sauber und trocken sein.

    Lit.: D. Neculai, H. W. Roesky, A. M. Neculai, J. Magull, H.-G. Schmidt, M.

    Noltemeyer, J. Organomet. Chem. 2002, 634-644, 47-52.

    3. Herstellung eines Bis(cylopentadiens) ber das metallierte Dien

    Ausgangspunkt fr Ansametallocene zur Olefinpolymerisation.

    Jede Zweiergruppe stellt eines von zwei Bis(cyclopentadienen) ber Metallierung und

    Alkylierung des Dienvorlufers her.

    a) Inden + Dibromethan

    b) Cyclopentadien + Dimethyldichlorsilan

    Das Produkt wird ber sein 1H-NMR-Spektrum charakterisiert.

    Lit.: a) H. G. Alt, R. Ernst, I. K. Bhmer, J. Organomet. Chem. 2002, 658, 259-265;

    b) Q. Yang, M. D. Jensen, Synlett 1996, 147-148.

    4. Herstellung eines Tetrapeptids ber Festphasensynthese.

    Jede Zweiergruppe stellt eines von zwei Tetrapeptiden an der festen Phase her.

    a) H-Tyr-Ile-Lys-Leu-OH

    b) H-Lys-Tyr-Lys-Leu-OH

  • 3

    Das Peptid wird aus Fmoc-Aminosuren am Wang-Harz hergestellt. Nach der letzten

    Kupplung und Fmoc-Abspaltung wird das fertige Peptid mit TFA vom Harz

    abgespalten; dabei werden gleichzeitig smtliche Schutzgruppen entfernt. Das

    Peptid wird in Ether gefllt, getrocknet und per 1H-NMR-Spektrum und HPLC auf

    seine Identitt und Reinheit hin berprft.

    Lit.: W. Chan (Autor), W. C. Chan (Herausgeber), Peter D. White. In: Fmoc Solid

    Phase Peptide Synthesis: A Practical Approach (Taschenbuch), Oxford University

    Press Oxford New York 2000, ISBN 0-19-963724-5.

  • 115

    Iceton 11

    ~PPh3 1H190P (318.35)

    9.3 g, 150 mmol, :::Hq (IOOmL)

    ~m Reaktionsgehit und in eisge'gesaugt und mit llorid (95-98%)

    , (375 mL) wird mmol) versetzt.

    is das ablaufenri telverbindung

    3H, eHJ ), 3.74

    eingesetzt.

    3. Praktikumswoche

    2-26 (Triphenyl-..\5_phosphanyliden)essigsureethylester 1)

    NaOH,Et02C'v"Br PPh3. [Et02C'v"~Ph3 Br 8 ] Et02C~PPh3 H20

    C4H7Br02 (167.00) C22H2102P (348.37)

    Durchfhrung der Reaktion

    Im Reaktionskolben wird Triphenylphosphan (26.2 g, 100 mmol, 1.0 quiv.) in getrocknetem Toluol (120 mL) gelst. Unter Rhren wird eine Lsung von Bromessigsureethylester (Prparat 6-12, 16.7 g, 100 mmol) in getrocknetem Toluol (20 mL) zugetropft und danach ber Nacht bei Raumtemp. gerhrt. Der Niederschlag wird abgesaugt, mit etwas Petrolether (Sdp. 30-50C) angefeuchtet und trocken gesaugt. Das rohe Phosphoniumbromid wird in eiskaltem H20 (1 L) gelst und unter Rhren so viel wssrige NaOH-Lsung (2 M) zugetropft, bis ein zuvor hinzugefgter Tropfen ethanolischer Phenolphthalein-Lsung gerade einen Farbumschlag auftreten lsst.

    Isolierung und Reinigung

    Der Niederschlag wird abgesaugt, mit Hp gewaschen, mit (wenig!) MeOH ~ angefeuchtet, .trocken gesaugt und in einer Trockenpistole bei 50C ber P40,o ,~O eHgetrocknet. Die Tltelverbmdung (85-90%) wird als farbloser Feststoff erhalten 2).

    Charakterisierung

    Schmp. 126-127C. - 'H-NMR (400 MHz, CDCI3) : 8 = 1.25 (t, 3H, CHJ ), 3.34 (d, IH, CH), 4.43 (q, 2H, CH2), 6.95-7.07 (m, 9H, Ar-H), 7.58-7.69 ppm (m, 6H, Ar-H).

    Anmerkungen: I) (Triphenyl-I,S-phosphanyliden)essigsureethylester wird im Versuch 11-3 als Edukt

    eingesetzt. 2) Sollte der Schmelzpunkt nicht im angegebenen Bereich liegen, wird aus Et,O oder

    AcOEt umkri stallisiert.

    M. Hanack, C. 1. Collins, H. Stutz, B. M. Benjamin,J. Am. ehern. Soc. 1981,103,2356--2360.

    http:7.58-7.69http:6.95-7.07
  • 3. Praktikumswoche 117

    2-28 (Diethoxyphosphoryl)essigsureethylester 1)

    P(OEth

    CaH170SP (224.19)

    Durchfhrung der Reaktion 2)

    Im Reaktionskolben wird ein Gemisch aus Triethylphosphit (30.7 g, 185 mmol, 1.23 quiv.) und Bromessigsureethylester (Prparat 6-12,25.1 g, 150 nunol) 8 h unter Rckfluss erhitzt ]).

    Isolierung und Reinigung

    Nach dem Erkalten wird das entstandene Bromethan mit einer Destillationsapparatur bei Atmosphrendruck abdestilliert und der Rckstand im Vakuum fraktionierend destilliert (SdP'IOmbM I44- 146C). Die Titelverbindung (90-95%) wird als farblose Flssigkeit erhalten.

    Charakterisierung

    IH-NMR (250 MHz, CDCI]): /) = 1.33 (me, 9H, 3 x CH3), 2.96 (d, 2H, CH2), 4.17 ppm (me, 6H, 3 x CH2).

    Anmerkungen: I) (Diethoxyphosphoryl)essigsureelhylester wird in den Versuchen 2-30, 11-7 und 11-10

    als Edukt eingesetzt. 2) Vorsicht: Bei der Reaktion wird Bromethan gebildet, das unter den Reaktionsbedin

    gungen entweichen knnte. Daher muss am Blasenzhler ein Gasableirungsschlauch angebracht werden.

    3) Die Reaktion kann auch ber Nacht durchgefilhrt werden.

    Ableitungsschlauch

    Methode: A. van der Klei, R. L. P. de Jong, J. Lugtenburg, A. G. M. Tielens, Eur. J. Org. ehern. 2002, 3015-3023.

  • 296 Kapitel 11 Kondensationen von Phosphor-sta bilisierten C-Nucleophilen

    11-3 2.3trans,4E-5,9-Dimethyldeca-2,4,8- 1 triensureethylester

    ~o

    Durchfhrung der Reaktion

    Im Reaktionskolben wird ein Gemisch aus E-Citral l ) (Geranial, 1.52 g, 10.0 mrnol) Dt und (Triphenyl-A.5-phosphanyliden)essigsureethylester (Prparat 2-26, 3.48 g, Im 10.0 mmol, 1.0 quiv.) in getrocknetem Toluol (35 mL) 5 h bei 40C gerhrt. Das

    Reaktionsgemisch wird danach ber Nacht bei Raumtemp. gerhrt. pal

    5 t Isolierung und Reinigung

    Ra Das Lsungsmittel wird bei vermindertem Druck am Rotationsverdampfer ent

    fernt. Der Rckstand wird mit Petrolether (Sdp. 30-50C, 2 x 5 mL) digeriert und Is( jeweils abgesaugt ' ). Die Filtrate werden vereinigt. Das Lsungsmittel wird bei Da vermindertem Druck am Rotationsverdampfer entfernt und der Rckstand durch fer Sulenchromatographie an Kieselgel (Sulendurchrnesser: 3.0-4.0 cm, Eluens: un< CyclohexanJAcOEt, 95 :5 v:v bis 90: I 0 v:v) gereinigt. (50-55%) wird als farblose Flssigkeit erhalten ).

    Charakterisierung

    Die Titelverbindung bei

    du!

    ens

    (50 n-:J = 1.502. - IH-NMR (250 MHz, CDCI): = 1.30 (t, 3H, CH), 1.61 und 1.69 (s, 2 x 3H, 2 x CH) , 1.90 (s, 3H, CH) , 2.15 (me, 4H, 2 x CH,), 4 .21 (q, 2H, Ch CH,), 5.08 (m, IH, s~-H), 5.79 (m, lH, sp'-H), 6.00 (d, IH, s~-H), 7.55 ppm '1-1 (me, I H, sp' -H). 2 x

    2H, Anmerkungen:

    I) ,,z-Citral" trgt im Gegensatz dazu nur einen Trivialnarnen, nmlich Neral. Am

    2) Diese zweimalige Manahme dient zum Entfernen des Triphenylphosphanoxids. 1 )

    3) Das gereinigte Produkt kann das 2Jcis,4E-Isomer zu 10% enthalten. 2)

    In Anlehnung an: A. Gbler, W. Boland, U. Preiss, H. Simon, Helv. Chim. Acta 1991, 74, In A 1773-1789. 1773

    20

  • 11. Praktikumswoche, 1. Teil

    trans-3-(4-Bromphenyl)acrylsureethylester 1)

    o 11

    (EtOhP""C02Et , ~o

    NaH in MinerallSr ~

    Durchfhrung der Reaktion 2)

    Im Reaktionskolben wird Natriumhydrid (60%ig in Minerall, 780 mg, 20.0 mmol, 1.33 quiv.) vorgelegt und mit getrocknetem THF (20 mL) versetzt. Unter

    Rbren und Eiskhlung wird eine Lsung von (Diethoxyphosphoryl)essigsure

    etbylester (Prparat 2-28, 4.26 g, 19.0 mmol, 1.27 quiv.) in getrocknetem THF

    (10 mL) innerhalb von 10 min zugetropft. Anschlieend wird unter fortgesetztem

    Rbren und Khlen eine Lsung von 4-Brombenzaldehyd (2.78 g, 15 .0 mmol) in

    getrocknetem THF (10 mL) innerhalb von 10 min zugetropft. Dann lsst man das

    Reaktionsgemisch auf Raumtemp. erwrmen und ruhrt noch I h bei Raurntemp.

    Isolierung und Reinigung

    Das Reaktionsgemisch wird mit wssriger N

  • Journal of Organometallic Chemistry 643644 (2002) 4752

    www.elsevier.com/locate/jorganchem

    Synthesis and structure of monomeric and solvent-free LPrX2compounds supported by a new -diketiminato ligand

    [L=Et2NCH2CH2NC(Me)CHC(Me)NCH2CH2NEt2, X=Cl, Br,BH4]

    Dante Neculai, Herbert W. Roesky *, Ana Mirela Neculai, Jorg Magull,Hans-Georg Schmidt, Mathias Noltemeyer

    Institut fur Anorganische Chemie, Uniersitat Gottingen, Tammannstrae 4, D-37077 Gottingen, Germany

    Received 29 May 2001; accepted 6 July 2001

    Dedicated to Professor Francois Mathey on the occasion of his 60th birthday

    Abstract

    Trivalent praseodymium complexes with a new -diketiminato ligand, possessing two pendant arms, LPrX2, (X=Cl (3), Br (4),BH4 (5)), have been prepared by the reactions of the lithium salt of the ligand with the corresponding halides. X-ray structuraland elemental analysis showed that 3, 4, and 5 are neutral, monomeric and solvent-free complexes. These complexes adopt apseudo-octahedral geometry with the two X (X=Cl, Br, BH4) arranged in the trans positions. 2002 Elsevier Science B.V. Allrights reserved.

    Keywords: -Diketiminato ligand; Lanthanide; Halides; Borohydride

    1. Introduction

    Nitrogen-based ligands for preparing lanthanidecomplexes have been used increasingly over the pastfew years [17]. A broad range of chemistry of lan-thanide complexes and important applications havealso been described [810]. Nevertheless, there are onlya few lanthanide complexes known with monoanionic-diketiminato ligands [912]. Our interest in the chem-istry of diorganolanthanide complexes of general for-mula LLnR2 stems from the potential use of thesesystems as novel olefin polymerization catalysts [13],and as -diketiminato-based ligands [1416]. This ledus to prepare some new starting materials. Conse-quently, given the importance of a solvent-free andbifunctional compound such as LLnX2 as precursor forthe synthesis of dialkyllanthanide complexes, we de-signed and synthesized a new -diketiminato ligand

    with two pendant donor arms, which proved to besuitable for our purpose.

    Herein, we report the synthesis of the ligand L=Et2NCH2CH2NC(Me)CHC(Me)NCH2CH2NEt2 (2H) and the preparation of LPrX2, (X=Cl (3), Br (4),BH4 (5)), derivatives. To the best of our knowledge, weobtained and characterized the first nonmetallocene,neutral, monomeric and solvent-free lanthanide com-pounds (LLnCl2, LLnBr2 and LLn(BH4)2) by X-raystructural analysis. Moreover, we demonstrated thatLLnCl2 could be used in metathesis reaction withNaBH4.

    2. Results and discussion

    2.1. Synthesis of LH (2)

    LH was prepared in a two-step synthesis as shown inScheme 1.

    Acetylacetone reacted with N,N-diethyl(ethylenedi-amine) in 1:1 molar ratio giving 1 in a very high yield.

    * Corresponding author. Tel.: +49-551-393001; fax: +49-551-393373.

    E-mail address: [email protected] (H.W. Roesky).

    0022-328X/02/$ - see front matter 2002 Elsevier Science B.V. All rights reserved.PII: S 0 0 2 2 -328X(01 )01107 -X

    mailto:[email protected]
  • D. Neculai et al. / Journal of Organometallic Chemistry 643644 (2002) 475248

    Scheme 1.

    Compound 1 is the intermediary step for the prepara-tion of 2.

    Treatment of 1 with Meerwein salt, [Et3O]BF4, indichloromethane followed by N,N-diethyl(ethylenedi-amine) and NaOH afforded 2 in 52% yield. Compound2 is a yellow oil at room temperature and soluble in anycommon organic solvent. It can be easily transformedinto its lithium salt with LiMe (Eq. (1)), but attempts tosolidify or to crystallize the LiL were unsuccessful.Therefore, every time when LiL was needed, it wasprepared prior to use, and it was used without anyfurther purification.

    LH2

    +LiMe CH4

    LiL (1)

    2.2. Synthesis of LPrX2, (X=Cl (3), Br (4), BH4 (5))

    Treatment of LiL with an equivalent amount ofeither anhydrous PrCl3 or anhydrous PrBr3 in tolueneat refluxing temperature afforded LPrX2 (X=Cl, Br),in good yields (Eq. (2)).

    LiL+PrX3LiX

    LPrX2 X=Cl (3), Br (4) (2)

    Reaction of LPrCl2 with an excess of NaBH4 (1:3) intoluene under reflux afforded compound 5 (Eq. (3)) inmoderate yield.

    LPrCl2+2NaBH4 2NaCl

    LPr(BH4)25

    (3)

    It has to be noticed that compounds 3 and 4 wereprepared using the anhydrous salts, not the THF ad-ducts. Compounds 3, 4, and 5 are well soluble intoluene, acetonitrile and THF. These complexes arethermally very stable, their melting points are in therange of 142188 C. Mass spectroscopy and elementalanalysis showed that compounds 3, 4, and 5 aremonomeric, solvent-free compounds, and contain nolithium halides. The monomeric structures of 3, 4, and5 were confirmed by the single-crystal X-ray structuralanalysis. A 1H-NMR resonance was not observed inevery case due to the paramagnetic nature of thepraseodymium. Compound 5 exhibits a 11B-NMR spec-trum that showed one sharp resonance at room temper-ature. This suggests that there is either a rapid exchangeof the BH4 groups on the NMR timescale, or both BH4groups are equivalent. A temperature-dependent NMRspectrum indicated that both BH4 groups are equivalent

    in solution. Moreover, any coupling between 11B and1H nuclei was not observed in the 11B-NMR spectrum.

    2.3. X-ray structural analysis of LPrX2 (X=Cl (3), Br(4) and BH4 (5))

    Single crystals of 3 and 4 suitable for X-ray structuralanalysis were obtained by recrystallization from tolu-ene, while single crystals of 5 were formed when thesolvent was slowly removed in vacuo. Compounds 3, 4,and 5 crystallize in the monoclinic P21/c space group.X-ray structural analysis revealed that compounds 3, 4,and 5 are monomeric in the solid state. The X-raycrystal structure of 4 resembles that of 3, therefore,only the X-ray crystal structure of 3 is given (Fig. 1).The crystal structure of 5 is given in Fig. 2.

    Selected bond distances and angles for compounds 3,4, and 5 are listed in Table 1. In all compounds, bothpendant arms are coordinated to the metal center andall four nitrogen atoms and the praseodymium atomare in the same plane. Moreover, for compound 4, thepraseodymium atom is arranged in the plane of the

    Fig. 1. Perspective view of molecule 3 in the crystal.

  • D. Neculai et al. / Journal of Organometallic Chemistry 643644 (2002) 4752 49

    Fig. 2. Perspective view of molecule 5 in the crystal.

    in the range of the previously reported PrB bondlengths of related compounds (2.757 A ) [21].

    2.4. Conclusions

    Herein, we have shown that compounds with thegeneral formula LLnX2 are easily available when -diketiminato-based ligands, and metals in the +3 oxi-dation state are used. However, the metathesis to yieldLLnR2 compounds is one of the important challengesin this field. Compounds LLnR2 resemble those of thewell-known catalysts of the titanium congeners. Up tothis date, only aryl [10,11], or alkyl [12,13] groupswithout donor functions were used as substituents atthe nitrogen atoms of the -diketiminato backbone inlanthanide chemistry. Thus, in order to increase theirthermodynamic stability, we designed and obtained aligand that contains two pendant arms on the nitrogenatoms, instead. This results in additional chelates,formed around the metal atom to yield monomeric andsolvent-free complexes.

    3. Experimental

    All operations involving air- and moisture-sensitivecompounds were performed using standard Schlenk lineand dry box techniques under purified nitrogen atmo-sphere. Toluene, Et2O, pentane, and CH2Cl2 were driedfrom appropriate drying agents (Na/K alloy (toluene,pentane), Na/benzophenone (Et2O), CaH2 (CH2Cl2))and distilled under nitrogen prior to use. Benzene andhexane were used as received. N,N-diethyl(ethylenedi-amine) and water-free PrCl3 were purchased fromAldrich and were used as received. Acetylacetone wasdistilled prior to use. [Et3O]BF4 was prepared as de-scribed in the literature and used as solution in CH2Cl2[22]. C6D6 and C7H8 were dried over Na/K alloy anddegassed. 1H-, 13C- and 11B-NMR spectra wererecorded using Bruker AM 200. Chemical shifts arereported in units downfield from Me4Si with thesolvent as the reference signal. Mass spectra wererecorded using a Finnigan MAT 8230 instrument, andelemental analyses were carried out at the AnalyticalLaboratories of the Institute of Inorganic Chemistry ofthe University of Gottingen. Melting points were deter-mined in sealed capillary tubes under nitrogen and areuncorrected.

    3.1. Preparation of LH (2)

    3.1.1. Preparation of 1In a 500 ml round-bottomed flask equipped with a

    condenser, 29.3 g (0.29 mol) of acetylacetone and 34 g(0.29 mol) of N,N-diethylenediamine in 250 ml of ben-zene were refluxed for 2 days. Consequently, the solvent

    Table 1Selected bond lengths (A ) and bond angles () for 3, 4, and 5

    3X 54

    Bond lengths2.442(2) 2.462(2)Pr(1)N(2) 2.421(4)2.448(2)Pr(1)N(1) 2.455(2) 2.430(4)

    Pr(1)N(3) 2.692(2) 2.688(2) 2.739(4)2.694(2) 2.749(5)2.682(2)Pr(1)N(4)2.6836(7)Pr(1)X(1) 2.852(1) 2.644(8)2.6903(7) 2.868(1) 2.824(5)Pr(1)X(2)

    Bond angles75.79(8)N(2)Pr(1)N(1) 77.18(7) 76.66(14)

    67.17(15)69.89(7)N(2)Pr(1)N(4) 67.81(7)126.3(2)Pr(1)N(1)C(1) 130.45(17) 124.7(4)123.9(2)N(1)C(1)C(2) 125.3(2) 124.2(5)

    130.8(5)131.4(2)C(1)C(2)C(3) 130.6(3)124.5(3)C(2)C(3)N(2) 125.2(2) 124.2(5)

    C(3)N(2)Pr(1) 130.32(17)125.6(2) 122.9(4)145.95(7)N(3)Pr(1)N(4) 144.47(6) 146.08(14)

    N(1)Pr(1)N(3) 69.26(8) 70.31(7) 68.57(14)137.080(12)136.42(3) 144.1(2)X(1)Pr(1)X(2)

    ligand framework, C3N2 (see Table 1). For compounds3 and 5, the praseodymium atom is positioned slightlyout of this plane. The coordination number at thepraseodymium atom in 3 and 4 is six and the geometryaround the metal atom is pseudo-octahedral.

    The PrN bond lengths of the pendant arm arelonger than those of the backbone, due to the coordina-tive and covalent character involved in different bond-ing modes. The PrX (X=Cl, Br) bond length issimilar to those found in the literature (X=Cl, 2.896,2.872 A ) [6,1720], (X=Br, 2.877, 2.897 A ) [19,20].The coordination number of the praseodymium atomin 5 is 10. Each BH4 group is coordinated via threehydrogen atoms to the praseodymium atom. The PrBbond lengths are different (Table 1). However, they are

  • D. Neculai et al. / Journal of Organometallic Chemistry 643644 (2002) 475250

    was removed and 1 distilled, as yellowish oil underdynamic vacuum (4.2 mbar). Yield 54.7 g (95%). 1H-NMR (C6D6, 200 MHz): 11.1 (s, 1H), 4.86 (s, 1H),2.8 (q, 2H, J=5 Hz), 2.2 (m, 6H), 1.97 (s, 3H), 1.51 (s,3H), 0.86 (t, 6H, J=7 Hz). 13C-NMR (C6D6, 125MHz): 193.71, 161.54, 95.19, 53.19, 47.55, 41.80,28.90, 18.70, 12.37. Anal. Found: C, 66.53; H, 11.21; N,14.59. Calc. for C11H22N2O: C, 66.62; H, 11.18; N,14.13%. EIMS; m/z (relative intensity): 198 ([M+], 4),112 ([M+C5H12N], 2), 86 ([C5H12N], 100).

    3.1.2. Preparation of 2A 500 ml Schlenk flask topped with a 100 ml addi-

    tion funnel was charged with 30 g (0.15 mol) of 1 in dryCH2Cl2 (150 ml). A solution of [Et3O]BF4 (54.1 g,53.2%) in CH2Cl2 was transferred by a cannula to theaddition funnel and was added dropwise to the stirringreaction mixture over a period of 1 h. Then, the reac-tion was allowed to proceed for one additional hour atroom temperature (r.t.). Consequently, 17.58 g of N,N-diethylenediamine in 50 ml CH2Cl2 was syringed intothe reaction mixture over a period of 30 min. Further-more, stirring was continued overnight to ensure com-plete reaction. The solvent was removed and 6.05 g(0.15 mol) of NaOH in water (150 ml) and hexane (250ml) was added. Using a separating funnel, the organicpart was separated, washed with water (150 ml), driedover MgSO4, concentrated and distilled under dynamicvacuum (4.2 mbar) to give 2 as yellow oil. Yield 23.3 g(52%). 1H-NMR (C6D6, 200 MHz): 11.3 (s, 1H), 4.55(s, 1H), 3.28 (t, 4H, J=6.7 Hz), 2.63 (t, 4H, J=6.7Hz), 2.45 (q, 8H, J=7 Hz), 1.73 (s, 6H), 0.97 (t, 12H,J=7.1 Hz). 13C-NMR (C6D6): 159.78, 95.04, 55.07,47.84, 45.97, 19.44, 12.59. Anal. Found: C, 68.82; H,12.23; N, 19.58. Calc. for C17H36N4: C, 68.87; H, 12.24;N, 18.90%. EIMS; m/z (relative intensity): 296 ([M+],7), 210 ([M+C5H12N], 36), 114 ([C6H14N2], 100), 86([C5H12N], 78).

    3.2. Preparation of 3

    Dry Et2O (50 ml) was added to 3.0 g (10.1 mmol) of2 in a 100 ml Schlenk flask. The mixture was cooled to78 C and a solution of 6.32 ml (1.6 M, 10.1 mmol)LiMe in Et2O was added dropwise. The reaction wasstirred for 2 h at 78 C, and then stirred overnight atr.t. till the methane evolution had ceased. The solventwas removed and toluene (30 ml) was added. Finally,the solution was added dropwise to a suspension of2.50 g (10.1 mmol) PrCl3 in toluene (30 ml) in a 100 mlSchlenk flask. Then, the reaction mixture was refluxedovernight. The suspension was filtered, concentrateduntil crystals are formed. Finally, the resulting solutionwas warmed and it was left undisturbed for severalhours at r.t. The large yellow crystals that formed wereseparated by filtration, washed with pentane (50 ml),

    and dried in vacuo. Yield 7.61 g (88.2%). M.p. 164 C.Anal. Found: C, 40.53; H, 6.95; N, 11.04. Calc. forC17H35Cl2N4Pr: C, 40.25; H, 6.95; N, 11.04%. EIMS;m/z (relative intensity): 506 ([M+], 12), 471 ([M+Cl],7), 420 ([M+, C5H12N], 100).

    3.3. Preparation of 4

    Compound 4 was obtained by a method analogousto the preparation of 3. Dry Et2O (20 ml) was added to0.58 g (1.98 mmol) of 2 in a 25 ml Schlenk flask. Themixture was cooled to 78 C and a solution of 1.3ml (1.6 M, 2 mmol) LiMe in Et2O was added dropwise.The reaction was stirred for 2 h at 78 C and thenstirred overnight at r.t. Then, the volatiles were re-moved in vacuo and toluene (15 ml) was added. Thissolution was added dropwise to a suspension of 0.75 g(1.98 mmol) PrBr3 in toluene (20 ml). Finally, thereaction mixture was refluxed overnight. The suspen-sion was filtered, concentrated until crystals wereformed. The resulting solution was warmed and it wasleft undisturbed for several hours at 26 C. Theyellow crystals that formed were recovered by filtration,washed with pentane, and dried in vacuo. Yield 0.89 g(75.4%). M.p. 188 C. Anal. Found: C, 34.25; H, 5.93;N, 8.86. Calc. for C17H35Br2N4Pr: C, 34.25; H, 5.92; N,9.40%. EIMS; m/z (relative intensity): 596 ([M+], 5),515 ([M+Br], 3), 510 ([M+C5H12N], 30), 86([C5H12N], 100).

    3.4. Preparation of 5

    A mixture of 0.5 g (0.98 mmol) 3 and 0.112 g (2.96mmol) NaBH4 in a 50 ml Schlenk flask equipped witha condenser was refluxed in toluene (35 ml) overnight.The suspension was filtered. The resulting clear solutionwas concentrated under reduced pressure to obtainyellow crystals of 5, which were collected by filtrationand washed with pentane (10 ml). Yield 0.31 g (68%).M.p. 142 C. 11B-NMR (C7D8/ext. BF3OR2, 25 C): 67.2 (s). Anal. Found: C, 43.56; H, 9.08; N, 11.47. Calc.for C17H43B2N4Pr: C, 43.81; H, 9.30; N, 12.02%. EIMS;m/z (relative intensity): 466 ([M+], 4), 451 ([M+BH4], 76), 366 ([M+ (C5H12N+BH3)], 100).

    4. X-ray crystallography

    Data for crystal structures of 3 and 5 were collectedon a StoeSiemens four-circle diffractometer, and datafor the crystal structure of 4 were collected on a Stoeimage plate IPDS II-system.

    All structures were solved by direct methods(SHELXS-97) and refined against F2 using SHELXS-97[23]. The heavy atoms were refined anisotropically.Hydrogen atoms were included using the riding model

  • D. Neculai et al. / Journal of Organometallic Chemistry 643644 (2002) 4752 51

    Table 2Crystal data and structure refinement parameters for compounds 3, 4, and 5

    3 4 5

    C17H35Br2N4PrEmpirical formula C17H43B2N4PrC17H35Cl2N4Pr507.30Formula weight 596.22 466.08

    14070 73Temperature (C)0.71073Wavelength (A ) 0.71073 0.71073YellowColor Yellow Yellow

    MonoclinicMonoclinic MonoclinicCrystal systemSpace group P21/nP21/n P21/nUnit cell dimensions

    a (A ) 10.8486(18)11.865(2) 11.9164(12)b (A ) 11.5807(10) 7.9520(9) 12.4611(16)c (A ) 16.085(3) 25.792(5) 15.949(3)

    9090 90 () () 90.898(15)95.86(2) 96.843(13)

    9090 90 ()2198.6(6)V (A 3) 2224.7(6) 2351.4(6)4Z 4 4

    1.7801.533 1.317Dcalc (g cm3)

    5.789 2.078Absorption coefficient (mm1) 2.4660.500.600.500.900.500.50 0.600.500.30Crystal size (mm)1.8824.80Theta range for data collection () 3.5122.513.5225.04

    Index ranges 14h14, 12k13, 12h12, 8k9, 12h12, 11k13,17l19 15l1730l30

    43 720/38064804 3680Reflections collected/uniqueReflections observed [I2(I)] 3560 [Rint=0.0794]3891 [Rint=0.0300] 3680 [Rint=0.0384]

    3806/0/2233889/0/224 3062/396/247Data/restraints/parametersR1=0.0215, wR2=0.0561Final R indices [I2(I)] R1=0.0182, wR2=0.0451 R1=0.0342, wR2=0.0826R1=0.0222, wR2=0.0579R indices (all data) R1=0.0202, wR2=0.0458 R1=0.0421, wR2=0.0880

    1.0711.158 1.059Goodness-of-fit on F2

    1.145 and 0.712 0.718 and 1.039Largest difference peak and hole 0.859 and 1.029(e A 3)

    with Uiso tied to Uiso of the parent atoms. Crystal datacollection details, and the solution and refinement pro-cedures are summarized in Table 2.

    5. Supplementary material

    Crystallographic data for the structural analysis havebeen deposited with the Cambridge CrystallographicData Centre, CCDC nos. 164078, 163836, and 164079for compounds 3, 4 and 5, respectively. Copies of thisinformation may be obtained free of charge from TheDirector, CCDC, 12 Union Road, Cambridge CB21EZ, UK (Fax: +44-1223-336033; e-mail: [email protected] or www: http://www.ccdc.cam.ac.uk).

    Acknowledgements

    We are thankful to the Deutsche Forschungsgemein-schaft for financial support. Moreover, we thank UlrichSchaller for a sample of PrBr3.

    References

    [1] F.T. Edelmann, Angew. Chem. 107 (1995) 2647 (Angew. Chem.Int. Ed. Engl. 34 (1995) 2466).

    [2] J.A.R. Schmidt, J. Arnold, J. Chem. Soc. Chem. Commun.(1999) 2149.

    [3] P.W. Roesky, Inorg. Chem. 37 (1996) 4507.[4] T. Dubbe, S. Gambarotta, G. Yap, Organometallics 17 (1998)

    3967.[5] J.R. Hagadorn, J. Arnold, Organometallics 15 (1996) 984.[6] C. Apostolidis, A. Carvalho, A. Domingos, B. Kanellakopulos,

    R. Maier, N. Marques, A.P. de Matos, J. Rebizant, Polyhedron18 (1999) 263.

    [7] S. Bambirra, M.J.R. Brandsma, E.A.C. Brussee, A. Meetsma, B.Hessen, J.H. Teuben, Organometallics 19 (2000) 3197.

    [8] R. Duchateau, C.T. Van Wee, A. Meetsma, J.H. Teuben, J. Am.Chem. Soc. 115 (1993) 4931.

    [9] L.W.M. Lee, W.E. Piers, M.R.J. Elsegood, W. Clegg, M. Parvez,Organometallics 18 (1999) 2947.

    [10] D. Dress, J. Magull, Z. Anorg. Allg. Chem. 621 (1995) 948.[11] P.B. Hitchcock, M.F. Lappert, S. Tian, J. Chem. Soc. Dalton

    Trans. (1997) 1945.[12] D. Dress, J. Magull, Z. Anorg. Allg. Chem. 620 (1994) 814.[13] G.J.P. Britovsek, V.C. Gibson, D.F. Wass, Angew. Chem. 111

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    [15] C.M Cui, H.W. Roesky, H.-G. Schmidt, M. Noltemeyer,Angew. Chem. 112 (2000) 4705 (Angew Chem. Int. Ed. 39 (2000)4531).

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    [17] Q. Shen, M. Qi, S. Song, L. Zhang, Y. Lin, J. Organomet.Chem. (1997) 549.

    [18] S.W.A. Bligh, N. Choi, H.R. Hudson, C.M. McGrath, M.McPartlin, J. Chem. Soc. Dalton Trans. (1994) 2335.

    [19] K. Kramer, G. Meyer, P. Fischer, A.W. Hewat, H.U. Gudel, J.Solid State Chem. 95 (1991) 1.

    [20] U. Schaller, Dissertation, Universitat Gottingen, 2000.[21] D. Deng, X. Zheng, C. Qian, J. Sun, L. Zhang, J. Organomet.

    Chem 466 (1994) 95.[22] C.T. Goralski, W. Chrisman, D.L. Hasha, L.W. Nicholson, P.R.

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    [23] G.M. Sheldrick, SHELXL: Program for Crystal Structure Refine-ment, University of Gottingen, Gottingen, Germany, 1997.

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  • Dinuclear ansa zirconocene complexes containing a sandwich and ahalf-sandwich moiety as catalysts for the polymerization of ethylene

    Helmut G. Alt *, Rainer Ernst, Ingrid K. Bohmer

    Laboratorium fur Anorganische Chemie der Universitat Bayreuth, Lehrstuhl fur Anorganische Chemie II, Universitat Bayreuth, Postfach 10 12 51,

    Universitaetsstrasse 30, NW I, D-95440 Bayreuth, Germany

    Received 16 May 2002; received in revised form 5 June 2002; accepted 14 June 2002

    Abstract

    Dinuclear ansa zirconocene complexes containing a half-sandwich and a sandwich moiety and their ligand precursors have been

    synthesized and characterized. After activation with methylalumoxane (MAO), these catalysts produce polyethylenes with bimodal

    molecular weight distributions in homogeneous and heterogeneous media. The catalyst performances and the polymer properties

    were compared with mono nuclear reference catalysts. # 2002 Elsevier Science B.V. All rights reserved.

    Keywords: Ansa zirconocene; Half-sandwich complexes; Dual site catalysts; Dinuclear complexes; Homogeneous and heterogeneous ethylene

    polymerization

    1. Introduction

    In the last decade metallocene complexes have been

    established as excellent catalysts for the polymerization

    of ethylene and propylene [1/5]. The produced poly-olefins have narrow molecular weight distributions due

    to identical active sites of the catalyst. However, this can

    be disadvantageous for industrial processing. In order to

    obtain broader molecular weight distributions, cumber-

    some or costly approaches, like the blending of different

    resins, are necessary. On the other side, in most cases, it

    is not possible to obtain the desired multi modal resins

    by mixing individual mono nuclear catalysts (averaging

    effect). Therefore, it was the intention to solve this

    problem with dinuclear complexes as catalyst precur-

    sors. Two different active sites in one molecule should be

    able to produce two different polymer chains with

    different molecular weights. Other known dinuclear

    complexes do not unify two different catalytic centers

    [6/13]. The model compounds presented in this papershould provide the advantages of both the half-sand-

    wich (high molecular mass) [14,15] and the sandwich

    catalysts (low molecular mass) [5,16,17] and thus have

    the potential of dual site catalysts.

    2. Results and discussion

    2.1. Synthesis of the ligand precursors

    For the preparation of asymmetric dinuclear metallo-

    cene complexes, a ligand precursor with an v-alkenylfunctionality is reacted catalytically with dichloro-

    methylsilane in a hydrosilylation reaction [18]. This

    chlorosilane intermediate then reacts in an SN2 reaction

    [19/23] with two equivalents of sodium cyclopentadie-nide to form the ligand precursor (Scheme 1).

    In the same manner, the following intermediates and

    ligand precursors were synthesized:

    * Corresponding author. Tel.: /49-921-552555; fax: /49-921-552157

    E-mail address: [email protected] (H.G. Alt).

    Journal of Organometallic Chemistry 658 (2002) 259/265

    www.elsevier.com/locate/jorganchem

    0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 6 7 3 - X

    mailto:[email protected]
  • 2.2. Synthesis of the dinuclear complexes 7/9

    The reaction of such a ligand precursor with four

    equivalents of butyllithium and two equivalents of

    zirconium tetrachloride leads to the dinuclear complexes

    7/9 (Scheme 2).The following complexes were synthesized in the same

    manner:

    For comparison purposes, the already known silyl

    bridged sandwich complex 10 [20,23] (Scheme 3) and the

    half-sandwich complex 11 [14,15] (Scheme 4) were

    synthesized.

    2.3. Polymerization of ethylene

    Half-sandwich catalysts of titanium and zirconium

    are known to produce polyethylenes of very high

    molecular masses (/106 g mol1) [13,14]. In contrast,silyl bridged bis(cyclopentadienyl) catalysts produce

    resins with a significantly lower molecular mass (B/5/105 g mol1) [20,23]. The polymerization propertiesof the asymmetric dinuclear complexes 7/9 meet theexpectations (Table 1).

    Compounds 7/9 showed mid range activities in thehomogeneous polymerization which varied around the

    value for reference catalyst 11/methylalumoxane

    (MAO). The homogeneous polymerization with 9/

    MAO exceeded the activity of the reference catalyst

    11/MAO by ca. 50%. The activities from the hetero-

    geneous experiments were generally lower than those

    from the homogeneous series. This result confirms the

    observations from other metallocene catalysts [17,20,23]

    where heterogenization on silica gel causes decreasing

    activities (Scheme 5). The lowest decrease is observed in

    the case of the half-sandwich reference catalyst 11/

    MAO.

    The molecular masses of these polyethylenes pro-

    duced with the dinuclear catalysts 7/9/MAO aresignificantly higher than those of the reference catalyst

    10/MAO; the trend of the molecular weights by hetero-

    genization was not found to follow a certain rule

    (Scheme 6).

    The polymer produced with catalyst 11/MAO shows

    the highest Mn of the complete series both under homo-

    and heterogeneous conditions. All other polymers vary

    around Mn/80 kg mol1 under homogeneous condi-

    H.G. Alt et al. / Journal of Organometallic Chemistry 658 (2002) 259/265260

  • tions. Silica supported catalysts develop molecular

    masses that are in the range of the homogeneously

    produced polymers or below (Scheme 6).

    Polymerization with the dinuclear complexes/MAO

    gave resins with a broader molecular mass distribution

    width HI than with mononuclear complexes. The

    polydispersities observed were between HI/6.2 and

    Table 1

    Polymerization data

    Catalyst Activity g (PE)/g (Zr) h Mn TmMw DHmMh Crystallinity a

    MzPolydispersity HI

    Homogeneous conditions

    7 51,000 81,210 138.1

    505,500 147.3

    1,654,000 50.8

    406,400

    6.2

    8 102,000 85,230 139.3

    614,800 145.8

    2,098,000 50.3

    498,900

    7.5

    9 146,000 70,400 140.9

    578,600 175.6

    2,983,000 60.6

    446,100

    8.2

    10 109,000 95,120 n.d.

    266,400

    851,600

    217,200

    2.8

    11 89,000 261,500 n.d.

    737,200

    1,981,000

    717,200

    2.8

    Heterogeneous conditions (supported on silica gel )

    7 42,000 33,400 139.3

    406,950 147.8

    1,679,990 50.9

    316,000

    12.2

    8 77,000 91,060 140.1

    710,200 149.1

    2,417,000 51.4

    577,100

    7.8

    9 102,000 45,140 136.5

    357,450 155.6

    1,329,840 53.7

    284,090

    7.9

    10 102,000 104,000 n.d.

    271,200

    1,075,000

    258,900

    2.6

    11 88,000 196,100 n.d.

    488,300

    2,008,000

    416,900

    2.5

    n.d., not determined.

    Scheme 1. Synthesis of the intermediate 1 and the ligand precursor 2.

    Scheme 2. Synthesis of the dinuclear complex 7.

    Scheme 3. Synthesis of the mono nuclear silyl bridged metallocene

    complex 10.

    Scheme 4. Synthesis of the mono nuclear amido silyl half-sandwich

    complex 11.

    H.G. Alt et al. / Journal of Organometallic Chemistry 658 (2002) 259/265 261

    DominikHervorheben
  • 12.2 under homo- and heterogeneous conditions. They

    exceeded the values of the reference polymers of 10/

    MAO (homogeneous: HI/2.8; heterogeneous: HI/2.6) and 11/MAO (homogeneous: HI/2.8; heteroge-neous: HI/2.5) by more than 100% (Scheme 7).

    This width increase is especially pronounced with the

    polyethylene produced from 7/MAO where two relative

    maxima can be seen in the HT-GPC plot (Scheme 8).

    It is well known from former results that half-

    sandwich catalysts produce polyethylenes with high

    molecular masses (/106 g mol1) [13,14]. The amidosilyl compounds are sterically not very demanding and

    the active center of the catalysts is easily accessible for

    the addition of the monomer. Polymer growth occurs

    stress free, termination reaction only starts at high

    molecular weight. It can be postulated that the fraction

    with a maximum at 700,000 g mol1 is produced by the

    half-sandwich component, the fraction with a maximum

    at 25,000 g mol1 by the sandwich component of

    catalyst 7. This conclusion can be derived from the

    properties of the monomeric reference catalysts and the

    produced polymers.The HT-GPC curve does not always show two

    separate maxima but a distinct broadening of the

    molecular mass distribution relative to the mononuclear

    catalysts.

    Polymerization with a 1:1 mixture of 10 /MAO and

    11 /MAO does not give the same bimodal molecular

    weight distribution as with 9 /MAO. The 1:1 mixture of

    10 /MAO and 11 /MAO produces a mononuclear resinwith only a slightly broadened molecular weight. We

    assume that in the mixture, the two originally different

    active sites communicate with each other, eventually

    via the cocatalyst MAO to give an averaged molecular

    weight.

    In the dinuclear catalysts, the active sites are sepa-

    rated from each other and cannot undergo such a

    reaction. This behavior is the major justification forthe preparation of such dual site catalysts.

    3. Experimental

    All experimental work was routinely carried out using

    Schlenk technique. Dried and purified Ar was used as

    inert gas. Toluene, pentane, diethylether and tetrahy-

    drofuran were purified by distillation over Na/K alloy.

    Ether was additionally distilled over LiAlH4. Methylene

    chloride was dried with CaH2. Deuterated solvents suchas CHCl3-d1 and C6H6-d6 were dried over molecular

    sieves (300 pm), degassed and stored under inert gas

    atmosphere.

    Commercially available indene was distilled and

    stored at /28 8C. Cyclopentadiene was freshly distilledfrom the dimer. MAO (30% in C6H5CH3) was supplied

    by Witco Company, Bergkamen. All the other starting

    materials were commercially available and were usedwithout further purification.

    3.1. NMR spectroscopy

    The spectrometer Bruker ARX 250 was available for

    the recording of the NMR spectra. The organometallic

    compounds were prepared under inert gas atmosphere

    (Ar). The spectra were recorded at 25 8C. The chemicalshifts in the 1H-NMR spectra are referred to the residual

    proton signal of the solvent (d/7.24 ppm for CHCl3,d/7.15 ppm for C6H6) and in the

    13C-NMR spectra to

    the solvent signal (d/77.0 ppm for CHCl3-d1, d/128.0ppm for C6H6-d6). Tetramethylsilane (d/0.0 ppm) wasused as external reference for 29Si-NMR spectra.

    Scheme 5. Activities of the catalysts 7/11/MAO in the homogeneousand heterogeneous polymerization reactions of ethylene.

    Scheme 6. Molecular weights Mn of the polyethylenes obtained from

    7/11/MAO.

    Scheme 7. Polydispersities HI of the polyethylenes obtained from 7/11/MAO.

    H.G. Alt et al. / Journal of Organometallic Chemistry 658 (2002) 259/265262

  • 3.2. GC/MS and mass spectroscopy

    GC/MS spectra were performed with a HP5971Amass detector in combination with a HP5890 gaschromatograph. Helium was applied as carrier gas, a

    12 m J&W Fused Silica column (DB 1, film 0.25 mm wasused. The measuring program was: 3 min at 70 8C(starting phase); 20 8C min1 (heating phase); variabletime at 210 8C (final phase).

    The mass spectra were recorded with a VARIAN

    MAT CH7 instrument, GC/MS with a VARIAN 3700gas chromatograph in combination with a VARIANMAT 312 mass spectrometer.

    3.3. Gas chromatography

    Gas chromatograms were recorded using a Perkin/Elmer Auto System gas chromatograph with flame

    ionization detector (FID) and He as carrier gas (1 ml

    min1).Temperature program:

    Starting phase: 3 min at 50 8CHeating phase: 5 8C min1 (15 min)Plateau phase: 310 8C (15 min)

    3.4. High temperature gel permeation chromatography

    (HT-GPC)

    A Waters HT-GPC 150C instrument was applied tomeasure the mass distributions of the polymer samples.

    Four columns filled with cross-linked polystyrene were

    used for separation of the fractions. The pore diameters

    of the styragels were 500, 1000, 10,000 and 100,000 A in

    the individual columns. A RI Waters 401 refractometer

    was used for detection. The polymer samples were

    dissolved in boiling 1,2,4-trichlorobenzene that wasalso used as eluent. The measurements were carried

    out at 150 8C. The apparatus was calibrated with aninternal polystyrene standard.

    3.5. Synthesis of the chlorosilane precursors

    3.5.1. General procedure

    v-Alkenyl substituted half-sandwich ligand precursor(10 mmol) in 10 ml of C5H12 and ca. 50 mg of

    hexachloroplatinic acid hydrate were given to a Schlenk

    vessel at room temperature (r.t.). Methyldichlorosilane(1.15 g, 10 mmol) was added and the mixture was stirred

    for 40 h. Then the suspension was filtered through

    Na2SO4 and the solvent was removed in vacuo. Yields:

    90/95%.

    3.6. Synthesis of the ligand precursors 1/6

    3.6.1. General procedure

    The corresponding chlorosilane presursor (5 mmol) in

    100 ml of Et2O was treated with 0.88 g (10 mmol)

    sodium cyclopentadienide dissolved in 10 ml of THF.The mixture was stirred for 8 h at r.t. The suspension

    was filtered through Na2SO4 and the solvent was

    removed in vacuo. Yields: 90/95%.

    Scheme 8. Molecular weight distribution of the polyethylene produced with 7/MAO under homogeneous conditions.

    H.G. Alt et al. / Journal of Organometallic Chemistry 658 (2002) 259/265 263

    DominikHervorheben
  • 3.7. Synthesis of the dinuclear complexes 7/9

    3.7.1. General procedure

    The ligand precursor (5 mmol) was dissolved in 400

    ml of Et2O and 12.5 ml (20 mmol) of n-butyllithium (1.6

    M in C6H14) were added. The reaction mixture was

    stirred for a minimum of 8 h at r.t.

    The solution was cooled to /78 8C. Then 2.33 g (10mmol) of ZrCl4 was added. The reaction mixture was

    brought to r.t. within 6 h and stirred for another 6 h.

    The solvent was removed in vacuo, the residue sus-

    pended in CH2Cl2 and the suspension filtered through

    Na2SO4. The CH2Cl2 phase was removed in vacuo, the

    residue washed with C5H12 and the product crystallized

    from CH2Cl2/C5H12. Yields: 60/70% (Table 2).

    3.8. Synthesis of the ligand precursors for the mono

    nuclear complexes

    3.8.1. General procedure

    Dichlorodimethylsilane (2.58 g, 20 mmol) in 200 ml of

    Et2O and 10 mmol of sodium cyclopentadienide (or 10

    mmol of fluorenyllithium) were mixed at r.t. in a

    Schlenk vessel. The mixture was stirred for 8 h, then

    filtered through Na2SO4 and silica gel. The solvent was

    removed in vacuo. Yield: 95%.

    3.9. Preparation of the indenyl chlorosilane precursor

    Indene (80 mmol) in 150 ml of Et2O was treated with50 ml (80 mmol) of butyllithium (1.6 M solution in

    C6H14). The solution was stirred for 4 h at r.t. Then it

    was cooled to /78 8C. Dichlorodimethyl silane (80

    Table 2

    NMR data of compounds 1/9

    Compound 1H-NMR 13C-NMR 29Si-NMR

    1 7.59/7.19 (m, 5H, ar H, Ind), 6.61 (s, 1H, ar H, Ind), 3.79(s, 1H, al H, Ind), 2.03/0.57 (m, 12H, bridge), 0.91 (s, 3H,NSiCH3), 0.78 (s, 9H,

    t Bu), 0.14 (s, 3H, ClSiCH3)

    144.7, 143.1 (Cq, Ind), 131.5, 129.9, 126.6, 124.6, 122.6

    (CH, Ind), 44.9 (CH, al, Ind), 32.1, 30.0, 22.5, 21.8, 18.2,

    14.2 (CH2, bridge), 4.2 (CH3,t Bu), 0.9, 0.2 (SiCH3)

    33.1 (ClSi),4.2 (IndSi)

    2 7.50/7.22 (m, 12H, ar H, Ind), 6.95/6.47 (m, 8H, ar H,Cp), 3.52 (s, 2H, al H, Ind), 3.06/3.00 (m, 2H, al H, Cp),1.26/0.45 (m, 12H, bridge), 1.21 (m, 9H, t Bu), 0.02/0.10 (s, 6H, SiCH3)

    144.6, 143.9 (Cq, Ind, Cp), 138.5, 132.9, 129.6, 126.2,

    124.5, 122.3 (CH, ar, Ind, Cp), 47.3 (CH, al, Ind, Cp),

    33.1, 29.9, 23.9, 22.9 (CH2, bridge), 3.2, 4.5(SiCH3)

    5.5, 7.3

    3 7.67/7.31 (m, 4H, ar H, Ind), 6.41 (s, 1H, ar H, Ind), 3.72(s, al H, Ind), 2.76/2.71, 1.87/1.23 (m, 12H, bridge), 1.33(s, 3H, NSiCH3), 0.84 (s, 9H,

    t Bu), 0.29 (s, 6H,

    ClSiCH3)

    144.8, 143.9 (Cq, Ind), 127.8, 125.8, 124.6, 123.7, 119.5

    (CH, ar, Ind), 45.7 (CH, al, Ind), 33.5, 33.1 (CH3,t Bu),

    31.9, 27.5, 23.6, 19.9 (CH2, bridge), 5.4, 0.3, 90.0(SiCH3)

    32.8 (ClSi),7.3 (IndSi)

    4 7.63/7.22 (m, 4H, ar H, Ind), 6.34 (s, 1H, ar H, Ind), 3.69(s, 1H, al H, Ind), 2.68/0.54 (m, 20 H, bridge, pentyl-substituent), 0.91 (s, 3H, NSiCH3), 0.79 (s, 9H,

    t Bu),

    0.18 (s, 6H, ClSiCH3)

    145.1, 144.6, 143.8 (Cq, Ind), 127.5, 125.6, 124.4, 123.6,

    119.5 (CH, ar, Ind), 44.9 (CH, al, Ind), 32.5, 32.1, 28.4,

    27.9, 22.7, 22.4, 21.7, 16.6 (CH2, bridge, pentyl-sub-

    stituent), 15.8 (CH3,t Bu), 14.3 (CH3), 1.4, 1.9

    (SiCH3)

    33.1 (ClSi),5.4 (IndSi)

    5 7.52/7.19 (m, 12H, ar H, Ind), 6.93/6.23 (m, 8H, ar H,Cp), 3.54 (s, 2H, al H, Ind), 3.02 (m, 2H, al H, Cp), 1.77/0.13 (m, 8H, bridge), 1.23 (s, 9H, t Bu), 0.07/0.26 (s,9H, SiCH3)

    145.7, 144.8 (Cq, Ind, Cp), 132.9, 129.3, 125.1, 124.1,

    123.2, 119.4 (CH, ar, Ind, Cp), 46.3 (CH, al, Cp), 32.5,

    29.9, 27.6, 23.4 (CH2, bridge), 4.6, 5.9 (SiCH3)

    7.0

    6 7.53/7.26 (m, 12H, ar H, Ind), 6.98/6.33 (m, 8H, ar H,Cp), 3.68 (s, 2H, al H, Ind), 3.01 (m, 2H, al H, Cp), 1.34/0.55 (m, 20H, bridge), 1.19/1.17 (m, 9H, t Bu), 0.05/0.13 (s, 6H, SiCH3)

    144.9, 144.3 (Cq), 137.3, 133.2, 127.8, 125.4, 124.7, 122.6

    (CH, ar, Ind, Cp), 46.4 (CH, al, Cp), 35.4, 32.6, 29.6,

    24.3, 23.6, 22.8 (CH2, bridge), 4.2, 5.9 (SiCH3)

    4.9, 7.5

    7 7.55/6.38 (m, 14H, ar H), 2.72/0.46 (m, 23H, bridge,pentyl-substituent), 1.33 (s, 9H, t Bu), 0.03, 0.15 (s,6H, SiCH3)

    145.8, 145.1 (Cq, Ind, Cp), 138.3, 132.9, 130.9, 129.4,

    125.1, 123.9, 119.5 (CH, Ind, Cp), 45.9 (Cq,t Bu), 33.2,

    32.2, 29.9, 28.6, 27.6, 24.2, 24.1, 22.8, 13.4, 13.3 (CH2,

    bridge, pentyl-substituent), 14.3 (CH3,t Bu), 5.8, 6.7

    (SiCH3)

    7.5 (CpSi),9.5 (IndSi)

    8 7.64/6.61 (m, 14H, ar H), 2.30/0.41 (m, 12H, bridge),1.41 (s, 9H, t Bu), 0.11/0.01 (s, 6H, SiCH3)

    145.6, 143.9 (Cq, Ind, Cp), 131.0, 128.3, 126.4, 123.9,

    121.4 (CH, Ind, Cp), 32.2, 29.7, 27.1, 26.5, 24.3, 22.9

    (CH2, bridge), 4.5 (CH3,t Bu), 1.9, 6.5 (SiCH3)

    7.6 (CpSi),8.1 (IndSi)

    9 7.62/6.67 (m, 14H, ar H), 2.74/0.47 (m, 8H, bridge), 1.05(s, 9H, t Bu), 0.21, 0.19, 0.01 (s, 9H, SiCH3)

    145.8, 144.6 (Cq, Ind, Cp), 130.7, 128.6, 127.5, 124.7,

    119.8 (CH, Ind, Cp), 33.2, 32.9 (t Bu), 30.8, 30.7, 27.4,

    26.2, 19.8, 14.1 (CH2, bridge), 0.3, 0.2, 6.5 (SiCH3)

    7.8 (CpSi),12.9 (IndSi)

    H.G. Alt et al. / Journal of Organometallic Chemistry 658 (2002) 259/265264

    DominikHervorheben
  • mmol) was added, slowly warmed to r.t. and stirred for

    12 h. The suspension was filtered through Na2SO4 and

    the solvent was removed in vacuo. Yield: 95%.

    3.10. Preparation of the indenyl ligand precursor

    The indenyl chlorosilane precursor (80 mmol) in 200

    ml of CH2Cl2 was treated with 200 mmol of t -

    butylamine at r.t. The mixture was stirred for 12 h,

    then the solvent was removed in vacuo. The residue was

    suspended in 200 ml of C5H12 and the suspension was

    filtered through Na2SO4. The solvent was removed invacuo. Yield: 95%.

    3.11. Preparation of the mono nuclear zirconocene

    complex 10

    The ligand precursor (10 mmol) was dissolved in 200

    ml of Et2O. Butyllithium solution (12.5 ml, 1.6 M in

    C6H14; 20 mmol) was added. The mixture was stirred for

    at least 8 h at r.t. Then the solution was cooled to/78 8C and 2.33 g (10 mmol) of ZrCl4 was added. Themixture was brought to r.t. within 6 h and stirred for

    another 6 h. The solvent was removed in vacuo, the

    residue was suspended in CH2Cl2 and the suspension

    was filtered through Na2SO4. The solvent of the CH2Cl2phase was removed in vacuo, the residue was washed

    with C5H12 and Et2O several times, dissolved in CH2Cl2and the solution was crystallized at /28 8C. Yields:50/70%.

    3.12. Synthesis of the amidosilyl zirconium complex 11

    The ligand precursor (20 mmol) was dissolved in 400

    ml of Et2O. Butyllithium solution (12.5 ml, 1.6 M in

    C6H14; 20 mmol) was added at /78 8C. The mixturewas stirred for 12 h at r.t. Then the solution was cooledto /78 8C again and 4.66 g (20 mmol) of ZrCl4 wasadded. The mixture was brought to r.t. within 10 h and

    stirred for another 10 h. The solvent was removed in

    vacuo, the residue was suspended in C5H12 and the

    suspension was filtered through Na2SO4. The solvent

    was removed in vacuo, the residue was suspended in

    C5H12 and the LiCl containing solution was filtered. The

    solution was stored for 24 h at /28 8C. The yellowishcomplex precipitated. Yield: 35%.

    3.13. Polymerization reactions

    An amount of 20/25 mg of the correspondingcomplex was dissolved in 50 ml of C6H5CH3. A volume

    of the solution containing 1/2 mg of complex was takenand activated with MAO (30% in C6H5CH3; Al/Zr/2500:1).

    For heterogeneous polymerizations silica gel was

    added (1 g SiO2 mmol1 (Zr)) to this solution and the

    suspension was stirred for 3 min. Both for homogeneous

    and heterogeneous polymerizations, the catalyst suspen-

    sion was diluted with 250 ml of C5H12 and injected to a 1

    l Buchi laboratory autoclave thermostated at 60 8C. Anethylene pressure of 10 bar was applied to the reactor

    and the catalyst was polymerized for 30 min at 60 (9/3) 8C. The obtained polymer was dried in air for at least60 h. The polymerization results and the physical data of

    the polymers are presented in Table 1.

    Acknowledgements

    We thank the Deutsche Forschungsgemeinschaft

    (DFG) and Phillips Petroleum Company (Bartlesville,

    OK, USA) for the financial support and Witco company

    (Bergkamen) for the donation of methylalumoxane.

    References

    [1] (a) H.-H. Brintzinger, D. Fischer, R. Mulhaupt, B. Rieger, R.

    Waymouth, Angew. Chem. 107 (1995) 1255;

    (b) H.-H. Brintzinger, D. Fischer, R. Mulhaupt, B. Rieger, R.

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    [2] M. Bochmann, J. Chem. Soc. Dalton Trans. (1996) 255.

    [3] F. Kuber, Chem. Unserer Zeit 28 (1994) 197.

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    [5] H.G. Alt, A. Koppl, Chem. Rev. 100 (2000) 1205 (and references

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    Atovmyan, Organometallics 11 (1992) 3942.

    [12] W. Abriel, G. Baum, H. Burdorf, J. Heck, Z. Naturforsch. Teil. B

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    H.G. Alt et al. / Journal of Organometallic Chemistry 658 (2002) 259/265 265

  • Festphasensynthese

    Theorie

    - Prinzip der Festphasensynthese - Schutzgruppenstrategien - Mechanismen Peptidkupplung und Nebenreaktionen - Vor- und Nachteile der Festphasensynthese

    Techniken

    - Schttler - Zentrifugieren - Arbeiten in Spritzen mit Fritte - Arbeiten mit Aminosuren

    Reagenzien und Lsungsmittel

    - Fmoc-Leu-Wang Harz - Fmoc-Tyr(tBu)-OH - Fmoc-Lys(Boc)-OH - Fmoc-Ile-OH - O-(Benzotriazol-1-yl)-N,N,N,N-tetramethyluroniumtetrafluoroborat (TBTU) - N,N-DImethylformamid (DMF) - Dichlormethan (DCM) - Diisopropylethylamin (DIPEA) - Trifluoressigsure (TFA) - Triisopropylsilan (TIS) - Diethylether - Piperidin

    Vorschrift

    Ziel des Versuches ist die Darstellung der beiden Tetrapeptide H-Tyr-Ile-Lys-Leu-OH und H-Lys-Tyr-Lys-Leu-OH.

  • Durchfhrung: In zwei 5 ml Spritzen mit Fritte werden jeweils 100 mg des Fmoc-Leu-Wang Harz eingewogen. 1) Quellen: Es werden 2 ml DMF in die Spritze gegeben und das Harz fr 2 Stunden bei RT auf dem Shaker geschttelt. Das Lsungsmittel wird nach dem Quellen mit Hilfe einer Wasserstrahlpumpe abgesaugt und die Fmoc-Schutzgruppe wie folgt entfernt: 2) Fmoc-Entschtzung Zum Harz in der Spritze werden 2 ml 20% Piperidin gegeben (in DMF) und fr 3 Minuten bei RT geschttelt. Die Lsung wird abgesaugt, es werden 0,680 ml DMF und 1,320 ml 20% Piperidin in die Spritze gegeben und fr 10 Minuten bei RT erneut geschttelt. Nach Entfernung des Lsungsmittels wird das Harz 5x mit jeweils 2 ml DMF gewaschen. 3) Peptidkupplung: Zuerst werden 4 q. der zu kuppelnden Aminosure und 4 q. TBTU in 1 ml DMF in einem Schnappdeckelglas gelst und zum Harz gegeben. Anschlieend werden 10 q. DIPEA hinzugegeben und die Reaktionslsung wird 60 Minuten bei RT geschttelt. Das Lsungsmittel wird entfernt und das Harz 5x mit jeweils 2 ml DMF gewaschen. Die Arbeitsschritte 2) und 3) werden fr jede zu kuppelnde Aminosure wiederholt. Nach Kupplung und Fmoc-Entschtzung der letzten Aminosure wird zuerst 5x mit jeweils 2 ml DMF, 5x mit jeweils 2 ml DCM und 5x mit jeweils 2 ml Diethylether gewaschen. Das Harz wird an der Luft getrocknet. Harz-Abspaltung: Zu dem Harz werden 2 ml Abspaltlsung (93% TFA, 5% TIS und 2% bidest. Wasser) gegeben und 3 Stunden bei RT geschttelt. Anschlieend wird die Reaktionslsung in ein 50 ml Zentrifugenrhrchen gespritzt und mit eisgekhltem Diethylether auf 35 ml aufgefllt. Die Reaktionslsung wird ca. 30 Minuten gekhlt, zentrifugiert und der Ether abdekantiert. Das ausgefallene Peptid wird noch zwei Mal mit eiskaltem Diethylether gewaschen und erneut zentrifugiert. Anschlieend wird das Peptid ber Nacht im Exsikkator getrocknet.

    Analytik

    - ESI, 1H NMR in DMSO-d6

    Skript OC-Teil SynthesepraktikumV2-26V2-28V11-3V11-7Ketiminato LigandsSynthesis and structure of monomeric and solvent-free LPrX2 compounds supported by a new beta-diketiminato ligIntroductionResults and discussionSynthesis of LH (2)Synthesis of LPrX2, (X=Cl (3), Br (4), BH4 (5))X-ray structural analysis of LPrX2 (X=Cl (3), Br (4) and BH4 (5))ConclusionsExperimentalPreparation of LH (2)Preparation of 1Preparation of 2Preparation of 3Preparation of 4Preparation of 5X-ray crystallographySupplementary materialAcknowledgementsReferencesBisindene Synthesis#