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Enantiomer Separation on Immobilized Chirasil-Metal and Chirasil-Dex by Gas Chromatography and Supercritical Fluid Chromatography.

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anion. This increases the water solubility and gives a propensity for ion aggregation.L41
Received: March 13. 1991 [Z 4493 IE]
German version: Angew. Chem. 103 (1991) 1002
c x 10‘
h [nml
Fig. 1. NIR spectra of l’e in 0.5 M aqueous NaCl solution. Concentration of
a) 0.43 mM. b) 2.1 mM. C) 4.3 mM.
When a solution of 1.O in water was slowly evaporated
under vacuum a shiny black film resulted. The ESR spectrum of the film was anisotropic and the line shape depended
on the orientation of the film in the magnetic field (Fig. 2).
[l] J. R. Ferraro, I. M. Williams: Introduction to Synthetic Ekcrrical Conductors, Academic Press, New York, 1987.
[2] R. H. Boyd, W. D. Phillips, J Chem. Phys. 43 (1965) 2927; Z . G. Soos, S. R.
Bondeson in J. S . Miller (Ed.): Extended Linear Chain Compounds, Plenum
Press, New York 1983.193-257; S . Nakayama, K. Suzuki, Bull Chem. Soc
Jpn. 46 (1973) 3694; M. de Sorgo, B. Wasserman, M. Szwarc, J Phys. Chem.
76 (1972) 3468; N. Sakai, I. Shirotani, S . Minomura, Bull. Chern. Sac. Jpn.
44 (1971) 675.
[3] This phenomenon is somewhat analogous to the aggregation of certain dyes
[4], which form stacks and give excitonic bands. Because the dyes are closed
shell molecules the bonding between molecules in the stack, the electronic
structure of the stack, and the nature of the optical transition are somewhat
different. There appear to be no examples of dye aggregates that absorb at
such long wavelengths. There are no long-wavelength bands in aqueous
NaCl solutions of neutral 1.
[4] D. G. Duff, C. H. Giles in F. Franks (Eds.): Water; A Comprehensive Treatise, Val. 4, Plenum Press, New York, 1975, Chap. 3.
[5] J. Fabian, R. Zahradnik, Angew. Chem. I01 (1989) 693; Angew. Chem. Inr.
Ed. Engl. 28 (1989) 677.
[6] T. M. Dietz, B. J. Stallman, W. S. V. Kwan, J. F. Penneau, L. L. Miller,
Chem. Commun. 1990, 367.
[7] J. B. Torrance, B. A. Scott, B. Welber, F. B. Kaufman, P. E. Seiden, Phys.
Rev. B19 (1979) 730.
[8] J. E. Wertz, J. R. Bolton: Eleclron Spin Resonance, Chapman and Hall, New
York, 1986, Chap. 7, 8.
191 G. Heywang, L. Born, H. G. Fitzky, T. Hassel, J. Hocker, H.-K. Muller, B.
Pittel, S. Roth, Angew. Chem. fOf (1989) 462; Angew. Chem. I n l . Ed. Engl.
28 (1989) 483.
Enantiomer Separation on Immobilized ChirasilMetal and Chirasil-Dex by Gas Chromatography
and Supercritical Fluid Chromatography **
By Volker Schurig,* Dieter Schmalzing,
and Michael Schleimer
Dedicated to Professor Michael Hanack
Fig. 2. ESR spectra of l’e. a) 8 mM in 0.5 M aqueous NaCl at 280 K. b) Thin
with thin dimension perpendicular to magnetic field; ( 11) with one long
film, (I)
dimension parallel to magnetic field at 300K. Scale bar corresponds to
0.6 Gauss.
These spectra suggest that the asymmetric solution spectrum
results from unoriented, slowly tumbling aggregated radicals, that are similar to the oriented radicals immobilized in
the film.t81A KBr pellet of the film, like the NaCl solutions
showed an NIR absorption extending into the IR.
The 4-probe conductivity of a pure pressed pellet was
0.1 S cmThus, it has been demonstrated that l-@
assembles into an
aggregate in aqueous NaCl which has similar optical and
magnetic resonance properties as the conducting solid.
These spectral qualities are characteristic of radical anion
stacks. Indeed, an X-ray crystal structure of a conducting
naphthalene dianhydride salt has shown x-stacks of radical
anions.[g1Whether the stacks in solution are composed of
Oare doped with another redox state is not known.
only l mor
It does seem important, however, that laeis actually a tri-
Angew. Chem. I n l . Ed. Engl. 30 (1991) No. 8
The development of surface-bonded stationary phases by
cross-linking and/or chemical binding (“immobilization”)
represented a breakthrough in high-resolution capillary
chromatography.[’’ The resulting merits are stable films, low
bleeding of the stationary phase, high washout stability, and
hence use in splitless and on-column sampling. To achieve
universal physico-, chemo-, and enantioselective stationary
phases based on chemically modified chiral polysiloxanes,
e.g. Chirasil-Val,[’I Chira~il-Metal[~I
and Chira~il-Dex,~~.
an immobilization on the glass surface is desirable.
We describe here the immobilization of enantioselective
metal chelate and cyclodextrin phases. Chiral polysiloxanes
can be immobilized thermally or radically.L6- The nickel@)
Chirasil-Metal 1 prepared by us according to Scheme 1 and
the octanyl Chirasil-Dex 2c obtained according to Scheme 2
can be immobilized thermally on the fused silica surface with
The thermal immobilization
binding rates of up to 75 %.I1’
does not lead to any decomposition and/or epimerization,
[*] Prof. Dr. V. Schurig, Dipl.-Chem. D. Schmalzing
DipL-Chem. M. Schleimer
Institut fur Organische Chemie der Universitat
Auf der Morgenstelle 18. W-7400 Tubingen (FRG)
[**I This work was supported by the Deutsche Forschungsgemeinschaft, the
Fonds der Chemischen Industrie und Chrompack International, Middelburg (The Netherlands) (supply of fused-silica capillary columns). We
thank G. J. Nicholson, U . Miihleck and Professor E. Boyer, Tubingen, for
valuable discussions.
Verlagsgesellschaft mbH, W-6940 Weinheim, 1991
OS70-0833/91/0808-0987 $3.50+ .25/0
6. Polysiloxane.H2PtC16 1111
Fig. 1. Enantiomer separation by complexation GC (1.5 m x 0.05 mm (I. D.)
fused silica capillary column, coated with immobilized 1 [12]). Left: 2-methyltetrahydrofuran, l 5
2.0 bar N 2 . Right 2-methy10xetane, 140"c, 2.0 bar
Scheme 1 . Synthesis ofthe chemica~~y
modified &iral po~ysi]oxanes~ i I l / c h i rasil-Metal 1 [12]. LDA = lithium diisopropylamide. The polysiloxane used in
step 6 was a 10-13 :90-87 mixture of methylhydro/dimethylpolysiloxane.
either in the case of the metal chelates or in the case of the
cyclodextrin derivatives; this is confirmed by the decrease in
the separation factor tl, which does not exceed 5 to 10%
(depending upon the racemate checked). Typical gas-chromatographic enantiomer separations are shown in Figures 1
(immobilized 1) and 2 (immobilized 2c). As can be seen from
Figure 1 , in particular, the use of shorter columns having
small internal diameters (I. D.) enables very short analysis
times. The capillary column immobilized with chemically
bonded Chirasil-Metal 1 exhibits a markedly higher temperature stability than the previously described physical mixtures of Chirasil-Metal phases and polysil~xanes,~'
31 and
thus extends the scope of complexation gas chromatography
The capillary columns immobilized with chemically
bound Chirasil-Dex 2c show none of the disadvantages of
j tio
Palysiloxone. H2P1CI,
I \
Scheme 2. Synthesis of the chemically modified chiral polysiloxanes ChirasilDex 2s-c [4]. DMSO = dimethyl sulfoxide, DMF = dimethylformamide,
polysiloxane = methylhydro/dimethylpolysiloxane5/95. Za, x = 3 (Dex 1);
Zb, x = 5 (Dex 2); Zc, x = 8 (Dex 3).
0 VCH Verlagsgeselischaji mbH. W-6940
the columns coated with neat (pentylated/acylated) cyclodextrin derivatives, such as tendency to formation of
droplets, sensitivity towards thermal shock, long conditioning times, low tolerance towards solvent introduction upon
direct injection (splitless, on-~olumn),['~1
and limited lifeBy quantitative immobilization of 1 in a capillary column
with small internal diameter (1.5 m x 0.05 mm) it was possible for the first time to extend complexation chromatography to supercritical fluid chromatography. The enantiomers
of 1-(2-naphthyl)ethanol and I-phenylethanol could already
be separated quantitatively in a 1.5-m column in less than 10
minutes at 80 "C with carbon dioxide as supercritical mobile
phase (ci in each case 1.4, R, in each case 1.65; Fig. 3). Remarkably, the mobile phase carbon dioxide apparently has
too low a Lewis basicity to block free coordination sites on
the metal ion for enantioseiective complexation of the alcohols. Together with immobilized octanyl Chirasil-Dex 212,
which is also suitable for the separation of enantiomers in
Fig. 2. Enantiomer separation of cis-pinane, (1 -chloroethyl)benzene, pulegone, isomenthol, and ethyl mandelate by inclusion GC (10m x 0.1 mm
(I. D.) fused silica capillary column, coated with immobilized Z c [12]). 1 min
isothermally at 8 0 ° C then with 3 Kmin-' up to 140°C, 1 bar H , .
t [mid
H,C: CH-(CH,);&
x = 1. 3. 6
t Is1
t IS1
Angen'. Chem. Int. Ed. Engl. 30 (1991) No. 8
gen!). Capillary columnscoated statically with 2 were conditioned for 36 h
at 230°C in a weak stream of hydrogen. In all cases the columns were
washed with ten column volumes each of methanol followed by methanol/
dichloromethane and dichloromethane. The binding rate was determined
as 75% by comparison of the capacity factor for n-tridecane before and
after the washing at 130°C.
[13] V. Schurig, L Chromarogr. 441 (1988) 135.
1141 W.-Y. Li, H. L. Jin, D. W. Armstrong, J. Chromarogr. 509 (1990) 303.
[15] W. Meltzow, lecture note at the I n l . Symp. fnstrum. Anal. Chrm. Compur.
Techno/., InCom 1991, Dusseldorf, 22 February 1991.
[I61 V. Schurig, Z. Juvancz, G. J. Nicholson, D. Schmalzing, J. High Resolur.
Chromatogr. 14 (1991) 58.
[I71 V. Schurig, J. Ossig, R. Link, Angew. Chem. 101 (1989) 197; Anxew. Chem.
Int. Ed. Engl. 28 (1989) 194.
Syndiotactic Poly(1-0x0-2-phenyltrimethylene):
On the Mode of the Chain Growth under
Palladium Catalysis
By Marc0 Barsacchi, Giambattista Consiglio,*
Lorenzo Medici, Giorgio Petrucci, and Ulrich W Suter
Palladiumlcontaining catalytic systems modified by phosphorus or nitrogen ligands and having anions that coordinate weakly or not at all display different chemoselectivity in
carbonylation reactions of olefins, depending on the nature
of the ligand or the anion or both. Thus, when styrene is the
substrate and methanol the solvent, the catalytic system
formed in situ from Pd(CH3C00),/1 ,lo-phenanthroline(phen)/p-CH,C,H,SO,H in the absence of hydrogen
and in the presence of an oxidant such as 1,4-benzoquinone
catalyzes the chemo- and regioselective formation of a new
interesting polymeric material, poly( 1-oxo-2-phenyltrimethylene),''] which is the strictly alternating copolymer of carbon
monoxide and styrene (Scheme 1). The preformed complex
Fig. 3. Enantiomer separation by complexation SFC (1.5 m x 0.05 mm (I. D.)
fused silica capillary column, coated with immobilized 1). Left: 1phenylethanol, SOT, 100 atm CO,. Right: 1-(2-naphthyl) ethanol, SOT,
130atm C 0 2 .
SFC,['6] two further systems, based on complementary
methods are now available for the separation of enantiomers
with supercritical gases. These systems combine the advantages of capillary GC (high efficiency and speed, universal
detection) and high-pressure liquid chromatography (no
limitation to volatile and thermally stable components). The
supercritical mobile phase used, carbon dioxide, is compatible with the universal flame ionization detector and with
mass spectrometric coupling. Because of the good solvating
properties of the supercritical gases, SFC enantiomer separations are achieved already at low temperature. Since the separation factors c[ increase with decreasing temperature in the
region of enthalpy-control of the enantiomer separation," '1
the lower efficiency of SFC compared to GC can thus be
largely compensated.
Received: March 25, 1991 [Z 4545 IE]
German version: Angew. Chem. 103 (1991) 994
[l] K. Grob: Making and Manipulating Capillary Columns for Gas Chromatography, Huthig, Heidelberg 1986.
[2] H. Frank, G. J. Nicholson, E. Bayer, J. Chromatogr. Sci. 15 (1977) 174;
Angew. Chem. 90 (1978) 396; Angew. Chem. Int. Ed. Engl. 17(1978) 363.
131 V. Schurig, R. Link in D. Stevenson, I. D. Wilson (Eds.): Chii-d Separations, Proceedings of rhe International Meeting on Chromatography 1987,
Plenum, New York 1988, p. 91.
[4] V. Schurig, D. Schmalzing, U. Muhleck, M. Jung, M. Schleimer, P. Mussche, C . Duvekot, J. C. Buyten, J. High Resolut. Chromatogr. 13 (1990)
[5] P. Fischer, R. Aichholz, U. Bolz, M. Juza, S . Krimmer, Angew. Chem. 102
(1990) 439; Angew. Chem. fnt. Ed. Engl. 29 (1990) 427.
[6] G. Lai, G. Nicholson, E. Bayer, Chromatographia 26 (1988) 229; G. Lai,
U. Muhleck, G. Nicholson, E. Bayer, J. Chromatogr. 540 (1991) 217.
[7] X. Lou, Y. Sheng, L. Zhou, J. Chromatogr. 514 (1990) 253.
[8] W. Roder, F.-J. Ruffing, G. Schomburg, W. H. Pirkle, HRC & CC J. High
Resolur. Chromarogr. Chromatogr. Commun. 10 (1987) 665.
S. Bradshaw, S . K. Aggarwal, C. A. Rouse, B. J. Tarbet, K. E. Markides,
[9] .I.
M. L. Lee, J. Chromatogr. 405 (1987) 169.
[lo] G . Opitz, N. Fischer, Angew. Chem. 77(1965) 41; Angew. Chem. Int. Ed.
Engl. 4 (1965) 70.
[ l l ] S. A. M a t h , W. J. Lough, L. Chan, D. M. H. Abram, Z. Zhou, J. Chem.
SOC.Chem. Commun. 1984, 1038.
1121 Immobilization conditions: capillary columnscoated statically with J were
conditioned for 100 h at 180°C in a weak stream of nitrogen (no hydro
Angew. Chem. Ini. Ed. Engl. 30 (1991) No. 8
Scheme 1
[(I ,10-phen)Pd(p-CH3C6H.S0,),1 behaves similarly.[21By
contrast, in nonprotic solvents [(dppp)Pd(p-CH ,C,H,SO,),]
(dppp = 1,3-bis(diphenylphosphino)propane) brings about
selective carbonylation to E-l,5-diphenylpent-l-en-3-one
even under high hydrogen partial pressure.t31Steric discrimination is evident for these reactions. The formation of
imdiastereomerically pure E-I ,5-diphenylpent-l-en-3-one
plies a complete discrimination between the two diastereotopic hydrogen atoms during p elimination from the inter[*] Prof. Dr. G. Consiglio, L. Medici
Eidgenossische Technische Hochschule
Technisch-Chemisches Laboratorium
ETH-Zentrum, Universitatsstrasse 6, CH-8092 Zurich (Switzerland)
Prof. Dr. U. W Suter, Dr. M. Barsacchi, Dr. G. Petrucci
Eidgenossische Technische Hochschule, Institut fur Polymere
Zurich (Switzerland)
Verlagsgesellschaft mbH. W-6940 Weinheim. 1991
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enantiomers, separating, immobilized, supercritical, chirasil, metali, dex, chromatography, gas, fluid
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