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:6.95-7.073. 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.
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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
DominikHervorheben12.2 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
DominikHervorheben3.7. 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
DominikHervorhebenmmol) 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.
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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#