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Catalytic Oxidation of Partially and Fully Fluorinated Olefins with Osmium Tetroxide.

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6 =146.9 ('J(C.H) =157.2 Hz; C-2,6), 136.4 ('J(C,H) =155.9 Hz; C-3,5),
124.0 ('J(C,H) =158.5 Hz; C-4), AB(C,H,P) = 8.2 (C-2.6). -1.7 (C-3,5),
-5.8 (C-4).
~
Received: May 9, 1992 [Z5333IE]
German version: Angew. Chem. 1992, 104, 1388
CAS Registry numbers:
1 , 1295-35-8; 2, 289-68-9; 3, 143331-78-6.
[l] C. Elschenbroich, M. Nowotny, B. Metz, W. Massa, J. Graulich, K. Biehler. W. Sauer, Angew. Chem. 1991, 103, 601; Angew. Chem. Int. Ed. Engl.
1991, 30. 547.
[2] Comprchenswe Coordination Chemistry (Eds.: G. Wilkinson, R. D.
Gillard, J A. McCleverty), Pergamon, Oxford, 1987, Chap. 50.
[3] The formation of [(C,H,N),Ni] from [Ni(acac),] and C,H,N in toluene
was postulated, the pyridine complex was however neither isolated nor
characterized in solution: a) L. Conoira. J. G. Rodriguez. J. Chem. Res.
Synop. 1988.68. Better documented are however several homoleptic complex cations [(ql-C,H,N),M]"+; b) [(C,H,N),Cr]2+. presumed as the
building block of CrX,.6 py (X = Br. I): D. G. Holah, 1. P. Fackler, Jr.,
Inorx. Chem. 1965,4, 1112; c) [(C,H,N),Cr(PF,),], axial coordination by
two F atoms of the counterions: G. Fochi, J. Strahle, F. Gingl, ibid. 1991,
30,4669; d) [(C,H,N),Fe][Fe,(CO),,1, isolated [Fe(py),]'+ octahedra: R.
J. Doedens, L. E Dahl, J . Am. Chem. Soc. 1966, 88, 4847; e)
[(C,H,N),Co]'+,
proposed to be present in solutions of
[(C,H,N),Co(PF,),] in pyridine: D. W. Herlocker, M. R. Rosenthal,
Inorg. Chini. Acta 1970,4,501; f ) [ (C,H ,N),NiI2 +,
spectroscopically identified in solutions of [(C,H,N),Ni(BF,),] in pyridine: M. R. Rosenthal, R.
S. Drago, Inorg. Chem. 1%5,4,840;g) [(C,H,N),Pd]'+, X-ray structural
analysis, B. Freckmann, K. F. Tebbe, Acts Crystallogr. Sect. A 1981, 37,
C 228; h) [(C,H,N),Pt]Z', X-ray structural analysis, C. H. Wei, B. E.
Hingerty, W. R. Busing, Acta Crystallogr. Sect. C , 1989, 45, 26; i)
[(C,H,N),Cu,Ag]+, X-ray structural analysis. K . Nilsson, A. Oskarsson,
Actu Chem. Scand. Ser. A 1982,36, 605; j) see also: H. Lehmkuhl, R. Paul,
R. Mynott, Liehigs Ann. Chem. 1981, 1139.
H. Behrens, A. Miiller, Z. Anorg. A&. Chem. 1965, 341, 124.
C. Elschenbroich. J. Koch, J. Kroker, M. Wunsch, W. Massa. G. Baum, G.
Stork, Chem. Ber. 1988, 121, 1983.
A. J. Ashe 111, J. C. Colburn, J. Am. Chem. Soc. 1977, 99, 8099.
C. Elschenbroich, J. Kroker, W. MaSSa, M. Wiinsch, A. J. Ashe III, Angew.
Chem. 1986, 98, 562; Angew. Chem. Int. Ed. Engl. 1986, 25, 571.
Crystal structure determination of 3: An orange single crystal of dimensions ca. 0.27 x 0.13 x 0.10 mm3 was measured on a four-circle diffractometer (CAD4, Enraf-Nonius. Mo,. radiation, graphite rnonochromator) at 193 K . I t proved to be tetragonal, space group P42,c. 2 = 2, with
the lattice constants refined from 25 reflections with B z 1 5 O a = 1219.7(2),
c = 686.6(1) pm and a density pEAlrd
= 1.440 Mgm-3. In total 4623 reflections (complete sphere in the reciprocal space up to 0 = 23 ") were collected. After a numerical absorption correction (p = 12.6 cm-', min./max.
transmission 0.85j0.89) there were (R,,, = 0.017) 701 independent reflections. all F > 4o(F). The structure was solved by direct methods and refined with anisotropicic temperature factors for all heavy atoms [9]. The
high quality of the data set allowed all the H atoms to be localized and be
freely refined with isotropic temperature factors. Furthermore, the correct
orientation of the structure to the polar axis could be clearly determined
by refinement of Rogers q parameter [9] (to 1.00(3)). By the use of an
extinction correction and a weighting according to l/u2(Fo)reliability factors of R = 0.013, wR = 0.014 were achieved, whereas for the inverted
structure only R = 0.031 and wR = 0.037 were obtained. Further details
of the crystal structure investigation may be obtained from the Fachinformationszentrum Karlsruhe, Gesellschaft for wissenschaftlich-technische
Information mbH, D-W-7514 Eggenstein-Leopoldshafen 2 (FRG) on
quoting the depository number CSD-56415, the names of the authors, and
the journal citation.
G. M. Sheldrick, SHELXTL-Plus. Release 4.0 for Siemens R3 Crystallographic Research systems, Siemens Analytical X-Ray Instruments, Inc.,
Madison, Wisconsin, USA, 1989.
a) A. Almenningen, B. Andersen, E. E. Astrup, Acta Chem. Scand. 1970,
24.1579: J. C. Marriott, J. A. Salthouse, M. J. Ware, J. M. Freeman, Chem.
Conrmun. 1970. 595; b) G. M. Sheldrick, Acta Crystallogr. Secr. B 1975,
31, 305.
X-ray structural analyses of homoleptic organophosphane-Ni complexes
are, apart from ref. [lob], only known for chelate complexes of the type
[(P-P),Ni]: a) P-P = CH,[P(cyhex),],, Ni-P average 221 pm, C. Kriiger,
Y.-H. Tsay, ACIUCrystallogr. Sect. B 1972, 28, 1941; b) P-P = trans2,3.bis(diphenylphosphino)bicyclo[2.2.1]heptane,renorphos, Ni-P 219.5,
H. Brunner, G. Vitulli, W. Porzio, M. Zocchi, Inorg. Chim. Acra 1985, 96,
67; c) P-P = [Cp,Zr(CH,PMe,),], Ni-P 216.7, H. H. Karsch, G. Miiller,
C. Kriiger, J Organomet. Chem. 1984, 273, 195; d) P-P= Ph,P(CH,),PPh,, Ni-P 216.5, H. Hartung, U. Baumeister, B. Waltber, M.
Maschmeier, Z. Anorg. ANg. Chem. 1989, 578, 177; e) P-P = [(Me,P-q6C,H,),Cr], Ni-P 214.9, C. Elschenbroich, G. Heikenfeld, M. Wunsch, W.
Massa, G. Baum, Angew. Chem. 1988, 100, 397; Angew. Chem. Int. Ed.
-
Angew. Chem lnt. Ed. Engl. 1992, 31, No. 10
Engl. 1988, 27, 414; f ) P-P = MeP(CH,PMe,),, Ni-P 213.8, G. Muller,
H. H. Karsch, Acra Crysrallogr. Sect. C 1987, 43, 663.
1121 Compare [l] Figure 2 and literature cited therein. According to electron
transmission spectroscopy the anionic state 'B,(n*) of C,H,P is binding:
P. D. Burrow, A. J. Ashe Ill, D. J. Belleville, K. D. Jordan, J. Am. Chem.
Soc. 1982, 104, 425.
[I31 From the EPR spectrum of the radical anion C,H,P-' the high n spin
population p , = 0.47 (c:,b,) can be deduced: F. Gerson, G. Plattner, A. J.
Ashe 111, G. Markl, Mol. Phys. 1974, 28, 601.
[14] R. S. Nyholm, Proc. Chem. Soc. 1961, 273.
[15] A. J. Ashe 111, Ace. Chem. Res. 1978, i f , 153.
[16] a) R. V. Hodges, J. L. Beauchamp, A. J. Ashe Ill, W.-T. Chan, Organometallics 1985, 4, 457; b) G. Markl, Lect. Heterocycl. Chem. 1972, 1 , 69.
[17] D. T. Clark, I. W. Scanlan, J. Chem. SOC.Faraday Trans. II 1974, 70, 1222.
[I81 a) J. Fischer, A. Mitschler, L. Ricard, F. Mathey, J. Chem. SOC.Dalton
Trans. 1980, 2522; B. Deschamps, F. Mathey, J. Fischer, J. Nelson, Inorg.
Chem. 1984,23,3455; b) T. C. Klebach, R. Lourens, F. Bickelhaupt, C. H.
Stam, A. van Herk, J Organornet. Chem. 1981, 210, 211; c) T. A. van der
Knaap, F. Bickelhaupt, H. van der Poel, G. van Koten, C. H. Stam, J. Am.
Chem. Sor. 1982, 104, 1756.
1191 a) C. A. Tolman, W. C. Seidel, L. W. Gosser, J Am. Chem. Soc. 1974, 96.
53; b) C. A. Tolman, Chem. Rev. 1977, 77, 313.
[20] Compare with [Ni(PPh,),]S[Ni(PPh,),]
PPh,, R. Mynott, A. Mollbach, G. Wilke, J. Organomet. Chem. 1980, 199, 107.
[21] Note added in proof (August 10, 1992): Very recently from bis(2,4dimethylpentadieny1)iron and phosphabenzene we have obtained pentakis(q'-phosphabenzene)iron, spacegroup P2/n, Z = 4, a = 1600.1(2),h =
972.2(1), c = 1618.8 pm, fi = 102.126(5)", mean Fe-P distance = 216 pm.
+
Catalytic Oxidation of Partially and Fully
Fluorinated Olefins with Osmium Tetroxide**
By Wolfgang A . Herrmann,* Stefan J. Eder,
and Wolfgang Scherer
The oxidation of olefins catalyzed by osmium tetroxide is
a reliable method for the synthesis of vicinal cis diols.['I The
catalytic and stereochemical efficiency of this reaction can be
explained by the formation of an intermediate cyclic osmate(VI)ester from the olefin and OsO, in the presence of pyridine bases, which undergoes hydrolytic cleavage. Current
literature is still based on the assumption that very electronpoor olefins do not react with the metal oxide, and thus are
also not oxidizable.['* We report here the contrary, namely,
the formation of cycloadducts of partially and fully fluorinated olefins and their conversion into fluorinated diols and
products of subsequent reactions.
Fluoroalkenes 1a-i including those in which fluorine is
directly bound to the carbon atoms of the double bond
(1e-i), react with osmium tetroxide in hexane in the presence of pyridine and other nitrogen-containing bases at
room temperature without i r r a d i a t i ~ n . ~
In~ ]all cases, the
isolable, thermally stable, cyclic osmate(v1) esters 2 a-i were
obtained quantitatively within minutes or hours according
to Scheme 1. Tetracyanoethylene 1j is converted into the
analogous cycloadduct 2j. In comparison to the known complexes of this type, the fluorinated derivatives 2e-i are extremely sensitive to hydrolysis.
The structure of the new osmate esters was determined by
a single-crystal X-ray diffraction study of 2 h.I4I Complex 2 h
['I Prof. W. A. Herrmann, Dr. S. J. Eder, W. Scherer
Anorganisch-chemisches Institut der Technischen Universitat Miinchen
Lichtenbergstrasse 4, D-W-8046 Garching (FRG)
["I Multiple Bonds between Main-Group Elements and Transition Metals,
Part 107. This research was supported by the Fonds der Chemischen Industrie and the Hauptlaboratorium of Hoechst AG (Frankfurt). - Part
106: R. Buffon, A. Anroux, F. Lefebvre, M. Leconte, A. Choplin, J. M.
Basset, W. A. Herrmann, J Mol. Catal., in press.
Q VCH Verlagsgesellschaft mbH, W-6940 Weinheim. 1992
0570-0833~92/iOl0-1345$3.50+ ,2510
1345
HOJ
1a-c
3a-c
2a-c
H O l
R'
3d
___)
Id, e
2d, e
I
4
If-h, j
2f-h, j
I
5
4-7 I
AT
Fig. 1. SCHAKAL representation of one of the two crystallographically independent molecules of the perfluorinated osmate ester 2h. Selected distances
[pml and angles ['I: Os2-021 173.2(5), Os2-024 172.3(5), Os2-022 199.6(5),
0 ~ 2 - 0 2 3196.9(5), Os2-N21 212.8(7), C21-023 138.6(9). C22-022 132.0(9),
C21-C22 159(1), C22-Fl9 143.9(9); 0 2 2 - 0 ~ 2 - 0 2 3 81.9(2), 0~2-023-C21
116.2(5), 022-C22-C21 112.4(7).
(2f)
li0l
H20
6
Aside from these exceptional cases, the hydrolysis of osmate esters 2a-d with electron-withdrawing groups such as
CF, and C,F, is synthetically useful. For synthetic application the catalytic variant of this reaction appears to be especially advantageous. Thus the typical fluoroolefins 1 a-d can
be converted under standard conditions into the 1,2-diols
3a-d by treatment with potassium hexacyanoferrate(m),
with hydrogen peroxide as the primary oxidant on free or
supported[81 osmium tetroxide, or with the salt K,[OsO,(OH),]. A representative selection of data on these reactions
is listed in Table 1. When a-fluoroalcohols are formed (e.g.
from 1 e-i), ketones or 1,2-diketones arise after spontaneous
elimination of H F (Table 1). Although this loss of fluorine
2i
li
I
I
a
b
c
d
e
f
CF3 C6F13C6Fs CF3 F
H
H
H
H
H
H
H
H
H
H
F
F
F
g
h
F
CF,
F
F
R3
CF3 C,F,
[a] For the structures of compounds l i and 2i see above
$
Scheme 1. py
=
i
j
[dl
CN
CN
CN
Table 1. Catalytic oxidation of selected fluoroolefins with H,O, or K,[Fe(CN),I.
Pyridine. *) Liberation of HX. a) Vacuum
Oxidation
product
H,O,
cat.
la
lb
lc
3a
3b
3c
3d
HOOC-C0-CF3
67 ?4
68%
85 %
48%
80%
87%
95%
>99%
88%
83%
Id
Ig
lh
has a trans-configurated linear osmyl group (OSO,)~+with
octahedral geometry about the osmium center (Fig. 1). A
comparison with the structures of non-fluorinated osmate
esters shows that the numerous electron-withdrawing groups
d o not affect the structural parameters of 2 h.[,]
The thermolysis and hydrolysis of the new osmate esters
are dependent upon their constitution : hydrolysis of the
fluoro- and cyano-substituted osmate esters occurs primarily
on the ring systems. Hydrolysis of 2e and 2f, j, for example,
provides the respective isolable hydroxyacetato and oxalato
complexes 4 and 5 . Continued hydrolysis yields the corresponding osmium-free hydroxycarboxylic acid and dicarboxylic acids (Scheme 1). Of the series of osmate esters examined, 2f, derived from tetrafluoroethylene 1 f, is most
thermally
when 2f is heated under vacuum at
I50 "C, the previously unknown difluoride 6 is obtained as a
stable pyridine complex in 80 % yield by elimination of oxalyl fluoride. Esters 2a-e and 2g-i are thermally stable to at
least 110 "C, 2h to approximately 190 "C.
1346
YCH l'e r lu~ sg~~el l . ~eha~i
mbH. W-6940 Wemheini, 1992
Oxidant
Fe"")
cat.
Fluoroolefin
li
0
0
u
/
\
98%
299%
63%
70%
stoichiometric
299%
>99%
>99%
>99%
80%
80%
>90%
F,C,
,CFZ.
F,C-CF,
appears to be a drawback, this method holds promise for the
preparation of fluorinated mono- and diketones in special
cases, since fully fluorinated olefins are often more easily
accessible than their partially fluorinated congeners.
0570-0833/92!1010-134hS 3.50f.25/0
Angew. Chem. Ini. Ed. Engl. 1992, 31, N o . 10
We demonstrate here that even the most electron-poor
olefins undergo Os0,-catalyzed oxidations. The reduced reactivity of chloroolefins relative to their fluorine counterparts is explained by a size effect; in all other respects the
chloroolefins behave a n a l o g ~ u s l y . The
~ ~ ] procedure is also
applicable to strained fluoroolefins, for example norbornene
derivatives.
Our results cannot be rationalized with the frequently held
conception of the mechanism of the osmylation as the electrophilic attack of osmium tetroxide on the olefin. The pyridine base effect discussed by Corey et al. and Hoffmann et
al.['] is more applicable. According to this mechanistic description, the polarized cis-OsO, group reacts by a [2 31
cycloaddition (trans influence of the pyridine base). The
remarkable reactivity of polar fluoroolefins such as
vinylidene fluoride F,C=CH, (1 f), (CF,),C=CF,, and
F(CF,)C=C(OC,H,), supports this interpretation.
Although a-hydroxyfluorides react further by elimination
of HF, the catalytic variant of the reaction sequence described here provides a new, convenient route to oxygenated
organofluorine compounds. Osmium tetroxide can now be
considered a universal oxidizing agent for olefins. The optimization of the less toxic, immobilized variantsf8]is thus of
even greater importance.
+
correction, empirical absorption correction ( p = 62.9 cm-'), R =
R, = [Xw(lF,/- ~ ~ ~ ) z / Z ~ ~ F=
o~z]''z
C(llF'I - ~ ~ l l ) / X I F=o 0.035;
~
0.035, residual electron density + 1.18/-0.93e;A3. Figure 1 shows one of
the two crystallographically independent molecules. Further details of the
crystal structure investigation may be obtained from the Fachinformationszentrum Karlsruhe, Gesellschaft fur wissenschaftlich-technischeInformation mbH, D-W-7514 Eggenstein-Leopoldshafen 2 (FRG), on quoting the depository number CSD-56416, the names of the authors, and the
journal citation.
[5] B. A. Cartwright, W. P. Griffith, M. Schroder, A. C. Skapski, Inorg. Chim.
Acfa 1981, 53, L129-Ll30.
[6] The osmate ester [(py),O~(OCCl,CCI,O)] obtained from CI,C=CCI, is
thermally also not very stable; nevertheless, it could be characterized.
171 S. J. Eder, Dissertation, Technische Universitit Miinchen, 1992.
[8] W A. Herrmann, G. Weichselbaumer (Hoechst AG), WO 91/00143 from
January 10, 1991.
[9] K. A. Jvrgensen, R. Hoffmann, J. Am. Chem. SOC.1986,108,1867- 1876;
b) E. J. Corey, P. D. Jardine, S . Virgil, P.-W. Yuen, R. D. Connell, ibid.
1989, 111, 9243-9244; c) E. J. Corey, G. I. Lotto, Tetrahedron Lett. 1990,
31, 2665-2668.
[lo] a) 19FNMR (235.3 MHz, CD,CN, vs. CF,CO,H): 6 = -17.34 (s);
"CNMR (100.5 MHz, CD,CN): b = 128.8 (tt, 'J(C,F) = 263, 'J(C,F)
= 47 Hz, CF,), 151.46 (0, 'J(C,H) = 186, C,H,N), 144.03 @, 'J(C,H)
168). 127.99 ( m , 'J(C,H) = 172 Hz); IR (KBr): v(Os0) = 857 cm-' (st).
Correct C, H, N. F analyses. - b) l9FNMR (see above, CH,C12):
b = -31.06 (s, OsF); IR (KBr): v(Os0) = 855 cm-'. Correct C. H, N, F
analyses.
[ l l ] K. B. Sharpless, W. Amberg, M. Beller, H. Chen, J. Hartung, Y Kawanami, D. Liibben, E. Manoury, Y. Ogino, T. Shibata, T. Ukita, 1. Org.
Chem. 1991,56,4585-4588.
Experimental Procedure
Zf: C,F, was separated from the stabilizing agent a-pinene by cooling to
- 35 "C, and was then passed through a solution of OsO, (2.00 g, 7.9 mmol) in
toluene (80 mL) and pyridine (1.3 mL) at 25 "C. After a few minutes 2 f separated as an ochre precipitate. The reaction mixture was concentrated and the
residue dried under vacuum to give analytically pure Zf. Yield 4.0g (99%).
M.p. 143°C (decomp)[lOa]. After compound 2f was heated for 6 h at 135"C/
10- Torr, the residue was recrystallized from CH,CI, (- 30°C) to give analytically pure [(py),OsO,F,] in 80% yield[lOb].
Catalytic oxidation with hexacyanoferrate(rI1): K,[OsO,(OH),] (100 mg,
0.27 mmol), pyridine (0.36 mL), K,[Fe(CN),] (14.7 g, 45 mmol), and K,CO,
(6.2g) were dissolved in a mixture of H,O (100mL) and t-C,H,OH
(100 mL)[11]. This solution was vigorously stirred while 15-20 mmol of the
olefin was added. The reaction mixture was stirred for 24h, Na,SO3.7H,O
(1 1.4 g) was added, and the mixture stirred an additional 1h. The organic phase
was separated, the aqueous phase washed with CH,CI, (2 x 50 mL), the collected organic layers dried over MgSO,, and concentrated. For yields see Table 1.
Catalytic oxidation with hydrogen peroxide: OsO, (80 mg, 0.315 mmol) was
dissolved in T H F (30 mL) and immobilized on cross-linked poly(4-vinylpyridine) (Reillex 402, 1 g)[8]. An "oxidation solution" made from tert-butanol
(100 mL) and 30% H,O, (25 mL) and dried over aqueous MgSO, was used
along with the heterogeneous catalyst to oxidize the olefins listed in Table 1
(25-100 mmol). Standard workup, for yields see Table 1.
Received: May 13, 1992 [Z5345IE]
German version: Angew. Chem. 1992, 104,1371
[l] Reviews: a) M. Schroder, Chem. Rev. 1980,80,187-213; b) W. P. Griffith
in Gmelins Handbuch der Anorganischen Chemie, Band Osmium, Suppl.
Vol. 1 (Eds.: K. Swars), Springer, Berlin, 1980, p. 1848; c) J. L. Courtney
in Organic Syntheses by Oxidation with Metal Compounds (Eds.: W. J. Mijs,
C. R. H. I. de Jonge), Plenum, New York, 1986, Chapter 8, p. 449; d) H.
Waldmann, Nachr. Chem. Techn. Lab. 1992,40,702-708; e) A. H. Haines,
Methodsfor the Oxidation of Organic Compounds, Academic Press, New
York, 1985, pp. 280-285.
[2] a) H. B. Henbest, W. R. Jackson, B. C. G. Robb, J. Chem. Soc ( B ) 1966,
803-807; b) D. G. Lee in Techniques and Applications in Organic Synthesis, Yo/.1 (Ed.: R. L. Augustine), Dekker, New York, 1969, p. 11ff; c) M.
Hudlicky, Chemistry of Organic Fluorine Compounds, 2nd ed., E. Horwood. London 1976.
131 Cf. J. M. Wallis, J. K. Kochi, J. Am. Chem. SOC.1988, 110, 8207-8223.
[4] Complex 2h crystallized from toluene/CH,CI, at -20 "C in the monoclinic space group P2,/c with a = 1548.1(9), b = 1769.7(4), c = 1519.2(9)pm,
= 94.85(3)", Z = 8, V = 4147 x lo6 pm3, S = 2.282 g ~ m - F(000)
~,
=
2688; Mo,, radiation, CAD-4 Enraf-Nonius diffractometer, w scan, maximum 90 s. 7846 measured reflections 1 i0 < 25" (OjlS), (0/21), (-IS/
18), 6477 independent reflections, of these 5516 with I 3.0a(Z) were used
for refinement, structure solution by the Patterson method, no intensity
Angew. Chem. Znt. Ed. Engl. 1992, 31, No. 10
High Molecular Weight Polypropylene through
Specifically Designed Zirconocene Catalysts
By Walter Spaleck,* Martin Antberg, Jiirgen Rohrmunn,
Andreas Winter, Bernd Bachmann, Paul Kiprof,
Joachim Behm, and Worfgang A . Herrmann*
Only a few years after the discovery of the isotactic polymerization of propylene with zirconocene catalysts,''
more
than 250 patents and numerous original publications document a fascinating, rapid development. Nevertheless, all variants of these "stereorigid' zirconocene/methylalumoxane
catalysts remained merely of academic interest. Practical application failed because of the insufficient molecular mass of
the polymeric products. For instance, the catalyst 1 described
first gave only polymeric waxes with M , < 30000 gmol-'
under technically reasonable conditions ( > 40 "C) in the presence of methylalumoxane (MAO) as cocatalyst.['. 31 Modification of the zirconocene complexes brought only gradual
improvement^.[^-^] The structurally analogous hafnium
derivatives['] could also not solve the technical problems,
1
[*] Prof. Dr. W A. Herrmann, Dr. P. Kiprof, Dr. J. Behm
Anorganisch-chemisches Institut der Technischen Universitat Munchen
Lichtenbergstrasse 4, D-W-8046 Garching (FRG)
Dr. W Spaleck, Dr. M. Antberg, Dr. J. Rohrmann, Dr. A. Winter,
Dr. B. Bachmann
Hoechst AG
Briiningstrasse 50, D-W-6230 Frankfurt am Main 80 (FRG)
0 VCH Verlagsgesellschafi mbH, W-6940 Weinheim, 1992
0570-0833~92/10l0-1347
d 3.50f .25/0
1347
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