close

Вход

Забыли?

вход по аккаунту

?

High Molecular Weight Polypropylene through Specifically DesigneZirconocene Catalysts.

код для вставкиСкачать
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
because their activities were less than 5 % of those of the
reference zirconocene catalysts.['] Under these peripheral
make catalyst
conditions,
theproduction
required demand
particularly
for pure
uneconomical.
hafnium would
This
report on the synthesis of polypropylene of molecular mass
far above M , = 100000 gmol-' announces the technical
breakthrough for polymerization with zirconocene catalysts.
A glance at Table 1 shows that for the polymerization of
propylene with the catalysts 2 b and 3b the molecular weight
of the polymers formed at technically acceptable reaction
temperatures are drastically higher than those formed with
the complexes known to date (2 a and 3 a), in spite of the only
slight variation in the catalyst system. In the simplest case the
!$o 0 63
H C t Y ,
~
WoH
?
0-C-OH
0 KtOC&$
CHIOH
R'
R'
R2
(b)
(8)
(C)
I
H2S04
-03
I2fj
CH,
si(?kH9
2)CH3M48r
b) (CH3)2SiCb \
R2
0
b) TosH
(el
R' (d)
(r)
Scheme 1 . Synthesis of the ligand systems of catalysts 2. Yields of the individ.
ual steps: (b) 52%, (c) + (d) 79%, (e) SO%, (f) 91 %. R2 = CH(CH,),.
k2
2a-e
introduction of a methyl group at the indenyl ligand (R' =
CH,; 2b) in the immediate proximity of the silylene bridge
suffices. This change alone increases the molecular weight of
the polymer fivefold and provides distinctly improved tacticity (> 96%; m.p. 145-148°C). Although the same effect
can be achieved with the hafnium derivative 2a', it shows
only a fraction of the activity of the zirconium reference
catalyst 2 a (Table 1;see also [S]). Larger 2-substituents adjacent to the bridge (R' = C,H,, 2c), do not result in improved polymer properties. However, another substituent in
4-position, that is, at the annelated benzene ring, effects a
further increase in molecular weight (R2 = iC,H,, 2d), and
this complex is much more active than the reference catalyst
2 a. Furthermore, the isotacticity also increases (98 YO,m.p.
152 "C). The catalyst 2d is therefore a realistic candidate for
technical applications. Modification of R3on the silyl group
can also be advantageous for high molecular weight polymers, as indicated by the exchange of methyl (2b) by phenyl
(2 e).
The underlying ligand system of those catalysts 2, in which
R' = CH,, was synthesized from the ketoaldehyde (a) according to the new, generalizable sequence outlined in
Scheme 1 l o ]
.c93
The R' effect seems to be of a general nature, since it is
also observed in the tetrahydroindenyl derivatives 3 (Table 1).
Replacing H (3 a) with CH, (3 b) doubles the polypropylene
mass and increases the isotacticity. Nevertheless, the achievable molecular weights are much lower than those of the
analogous systems of 2 with aromatic six-membered rings.
This demonstrates that for technical catalysts for propylene
polymerization not only the 2-alkyl substitution but also the
benzoannelation of the five-membered ring is crucial.
Although our results appeared to be able to be explained
by a distortion of the catalyst framework, this conclusion
proved false, because the molecular structures of the reference catalyst 2 a and its methyl derivative 2b are identical in
all parameters (Table 2, Fig. 1 and 2).["] As may be seen in
Figure 2, right, the methyl groups present in 2 b in 2-position
are turned away from the spatial segment relevant for catalysis. A direct steric influence of this group on the chain
termination reaction and thus on the polymer mass is therefore not expected.[l2. In our opinion an electronic effect is
dominant. It is reasonable to assume[141that a decrease in
the local Lewis acidity at the (cationic) zirconium atom of
the active species[2.15] lowers its tendency to abstract a 8-H
atom. The number of chain terminations thereby decreases
and the molecular mass thus increases (2 a --t 2 b). Additional
alkyl substitution enhances this effect (2d), while loss of
aromaticity of the six-membered ring weakens it drastically
(3b). The alkyl substituents in 2- and 4-position provide in
Table 1. Bulk polymerization of propylene at 50 'C in the presence of zirconocene catalysts of type 2 and 3. PP
Catalyst
( + MAO)
Activity
Indenyl type
2a
2a' [a]
2b
2c
2d
2e
M.p.
["C]
Isotacticity
[%I
Proportion of
isotact. pentads
mmmm [Ye]
141
138
148
145
152
148
94.2
94.6
96.8
96.4
98.0
82.2
82.7
90.2
90.1
91.6
35
60
350
340
370
460
450
PI
M
35
10
32
65
147
153
94.0
96.0
85.8
90.2
R2
RS
mmol cat. h
H
H
CH3
CZH,
CH3
CH,
H
H
H
H
i-C,H,
H
CH3
60
2
40
30
CH3
CH,
CH3
C6H5
105
Teirahydroindenyl type
3a
H
3b
CH 3
polypropylene
[ l o 3gmol-'1
R'
H
=
M w
[a] For comparison with 2a, the hafnocene derivative with the same structural formula, 2a', has been listed. [b] Not determined.
1348
8 VCH
Verlagsgesellschaft mhH, W-6940 Weinherm, 1992
0570-0833/92/10i0-f348
$3.50+ ,2510
Angew. Chem. Ini. Ed. Engl. 1992, 31,No. I0
Our interpretation of these results suggests that another
optimization of the catalysts derived from the indenyl complex 2 a would be possible if the effects of the 2- and 4substituents can be combined in a way to avoid steric hindrance at the active site. Modified CVFF force field calculations have shown that all these derivatives should have the
same framework structures as 2 a and 2b within experimental
C24
Experimental Procedure
Fig. 1, Crystal structure and molecular structure of the ansu-zirconocene catalyst Zb (R1 = R' = CH,; R 2 = H). The ellipsoids represent 50% probability;
hydrogen atoms are omitted.
2d the currently optimal catalyst by increasing the basicity of
the aromatic ligand without placing a steric obstacle in the
path of the growing polymer chain.
In accord with this interpretation, electron-withdrawing
substituents lower the molecular mass. A 5-chloro substituent
in the catalyst yields molecular weight of M , = 9900 gmolfor polypropylene;['6a1similar effects are known for bridged
and nonbridged indenyl complexes of the same type.['6b3
Fig. 2. Comparison of the structure of the catalysts 2a (left) and 2b (right);
view onto the edge of the Zr plane (ORTEP drawing).
The higher stereospecificity (higher proportion of isotactic
pentads, polymer's higher melting point) observed with all
these new complexes 2b-d compared with the parent catalyst 2 a is striking. A subordinate spatial effect of the substituents on the exact position of the reactant at the active
site must therefore be assumed.
Table 2. Comparison of the structure of the unsubstituted and methyl-substituted zirconocene catalysts 2 a and Zb.
Zr-CI [pm]
CI-Zr-CI ["I
C-Si-C I"]
CP-Z~
fbl I P ~ I
Cp-Zr-Cp [b] ["I
El-E2 [c] ["I
Zr-C [pm]
[dl ["I
B [cl ["I
2a
2b
A
243.14(2)
98.76(1)
94.57(6)
224.13(1)
127.81(1)
61.94
247.0(1)-265.9(1)
110
0
241.9 [a]
99.06
94.3(1)
224.4 [a]
128.11(1)
61.39
246.2(3)-266.3(5)
110
0
1.2
0.3
0.3
0.3
0.3
0.6
-
0
0
[a] Average value. [b] Centers of the five-membered rings of the indenyl ligands. [c] Interplanar angle between the two indenyl ligands. [d] Aperture gap
according to [12b]. [el Obliquity angle according to [12b].
Angen. Chem. I n [ . E d Engl. 1992, 31, N o . 10
0 VCH Veriagsgesellschaft mbH,
All manipulations were conducted in an inert argon atmosphere.
Ligand systems: A solution of the relevant indene [9,18a] (30 mmol) in THF
(30 mL) was slowly treated with a solution of hutyllithium (12 mL, 30 mmol,
2 . 5 ~ in
) n-hexane at 25 "C and heated for 1 h under reflux. The solution was
then added dropwise to a solution of dimethyl- or methylphenyldichlorosilane
(15mmol) in TH F (10mL) at 25°C and stirred for 15h. The mixture was
poured onto ice water and extracted with diethyl ether. The residue remaining
after removal of the solvent was chromatographed on silica gel 60. The unchanged starting material for the ligand was eluted with solvent mixtures of
n-hexane/CH,CI, (between 20: I and 10: 1); yield 35-60%.
2a-2e: A solution of the appropriate indene (10 mmol) in TH F (30 mL) was
) n-hexane at
treated with a solution of butyllithium (8 mL, 22 mmol, 2 . 5 ~ in
25 "C and stirred for 15 h. The solvent was removed, and the solid residue
washed with n-hexane and dried in vacuum (oil pump) for 5 h. The powdered
dilithium salt was added to a suspension of ZrCI, (2.33 g, 10 mmol) in CH,CI,
at -78°C. The mixture was allowed to warm to 25°C (15 h) and was then
evaporated to dryness under vacuum. The process yielded a 1 : 1 mixture of the
ruc and meso isomer. The residue was dried at
Torr and extracted with
toluene. The pure racemate (an orange-yellow crystalline powder) was recovered from the extract by crystallization (- 35°C); further recrystallization is
possible from CH,CI, or THF; yield of pure compound 10-25% (rac).
3a, b: The aromatic analogues Za, b were hydrogenated according to [18 b].
Yield 50%.
Propylene polymerization: A dry 16-L, thermostatable steel reactor was
charged with nitrogen and 10 L of liquid propylene at 30°C. Then a solution
of methylalumoxane in toluene (30 mL, 40 mmol Al; average molar mass
950 gmol-') was added. Simultaneously, 0.02 mmol of metallocene was dissolved in an identical solution of methylalumoxane in toluene (20 mL) and left
to stand for 15 min to be "activated. The orange-red solution was then added
to the reactor. The reactor was heated to 50°C and kept at this temperature for
1 h. The reaction was stopped by the addition of isopropanol(10 mL), cooled,
the pressure released, and the product dried in vacuum. The yield was determined by weighing.
Polymer analysis: Molecular masses were determined by gel permeation chromatography (as solution in 1,2-dichlorobenzene at 135 "C; molar mass distribution MJM, in total i3), melting points by DSC, triad isotaxies and proportion of isotactic pentades by "C NMR spectroscopy [18c] (Bruker WP 300,
110"C, hexachlorobutadiene/CDCI,CDCI,).
Received: May 16, 1992 [Z5355IE]
German version: Angew. Chem. 1992, 104,1373
CAS Registry numbers:
t a , 119821-97-5; Za', 124684-46-4; 2b, 143278-86-8; 2c, 143278-92-6; 2d,
143346-94-3; 2e, 143346-95-6; 3a, 115701-70-7;3b, 143346-96-7; polypropyl-
ene (isotactic homopolymer), 25085-53-4.
[I] a) W. Kaminsky, K. Kiilper, H. H. Brintzinger, F. R. W. P. Wild, Angew.
Chem. 1985, 97, 507; Angew. Chem. Int. Ed. Engl. 1985, 24, 507; b) W.
Kaminsky, Angew. Makromol. Chem. 1986,145/146,149.
[2] P. Pino, P. Ciani, M. Galimberti, J. Wei, N. Piccolrovazzi in Transition
Metals and Orguno-Metallics as Catalysts f o r Olefin Polymerization (Eds.:
W. Kaminsky, H. Sinn), Springer, Berlin, 1988.
[3] W. Kaminsky, K. Kiilper, S . Niedoha, Makromol. Chem. Macromol.
Symp. 1986, 3, 377.
[4] W. A. Herrmann, J. Rohrmann, E. Herdtweck, W Spaleck, A. Winter,
Angew. Chem. 1989,101,1336; Angew. Chem. Int. Ed. Engl. 1989,28,1511.
[5] T. Mise, S. Miya, H. Yamazaki, Chem. Lett. 1989, 1853.
[6] J. W. Roll, H.-H. Brintzinger, B. Rieger, R. Zolk, Angew. Chem. 1990,102,
339; Angew. Chem. Int. Ed. Engl. 1990, 29, 219.
[7] J. A. Ewen, L. H. Haspeslagh, J. L. Atwood, H. Zhang, J. Am. Chem. SOC.
1987, 109, 6544.
[XI W. Spaleck, M. Antberg, V. Dolle, R. Klein, J. Rohrmann, A. Winter, New
J. Chem. 1990,14,499.
[9] a) G. Erker, D. Reuschling, J. Rohrmann, R. Nolte, M. Aulhach, A. WeiB
(Hoechst AG), DE-OS 4104931 of February 18,1991; b) J. Rohrmann, M.
Antberg, W. Spaleck (Hoechst AG), DE-OS 4128238 of August 26, 1991.
[lo] 'H NMR (I00 MHz, CDCI,, 25 "C) 2a: 6 = 6.9-7.7 (m, 5H, arom. H),
6.S5(s,2H,3-H),2.2-2.8(m,4H,CH2),
1.30(s,6H, SiCH,), l.lO(t, 6H,
CH,).-2b:S=6.92-7.75(m,8H.arom.H),6.80(s,2H,~-H),2.18(~,
6H, CH,), 1.25 (s, 6H, SiCH,). - 2 c : b = 7.0-8.2 (m, 13H, arom. H), 6.90
W-6940 Weinheim, 1992
0570-0833/92/10tO-l349 3 3.50+.25/0
1349
(s, 2H, B-H), 2.67 (s, 3H, CH,), 2.45 ( s , 3H, CH,), 1.50 (s, 3H, SiCH,).
-2d: S = 6.7-7.5 (m, 6H, arom. H), 6.85 (s, 2H, 8-H), 3.0 (m. 2H, CH),
2.23 (s, 6H, CH,), 1.17-1.37 (m, 12H, CH,), 1.27 ( s , 6H, SiCH,). - 3 b :
S = 6.05 ( s , 2H, 8-H), 2.44-3.37 (m, 8H, CH,), 2.10 (s, 6H, CH,), 1.431.93 (m, 8H , CH,), 0.90 ( s . 6 H, SiCH,).
Ill] 2b: monoclinic (space group P2,/c, no. 14), u = 878.2(2), b = 2668.8(2),
c = 921.9(2) pm, 8 = 112.24(1)", V =1999 x lo6 pm3, Z = 4, psalGd
=
1.583 gcm-', A4 = 476.6. Lattice parameters from 25 reflections at high
diffraction angles (33.2" < 20 < 44.8 "). Data collection on a CAD4 single
crystal diffractometer (Enraf-Nonius), Mo,, radiation (2. = 71.07 pm,
graphite monochromator) at room temperature in w scan to Om,, = 25"
(I,,, = 90 s, scan width: 1.2 + 0.3 tan8). Intensity data from 3837 observed reflections h(- lO/O), k(0/31), I( - lO/lO), of 2969 independent reflections 576 reflections with I/.([) < 0.01 suppressed, 2704 with I > lu(1)
used, structure solution through direct methods with subsequent difference Fourier syntheses; no absorption correction ( p = 8.7 cm-'), observed decomposition (5.7% in 107 h) not corrected; H atoms calculated
in ideal positions, included in the calculation of the structure factors, but
not refined. Refinement according to the least-squares method, R =
XI IFo I - IEII)/CIFol = 0.046;
R, = I X w ( I Sl - IEl),/Z wI F,2 II"' =
0.029; GOF = [ X w ( [ F o l- IF,l)'/(NO-NV)]''2 = 1.993. Residual electron
density 0.51 e k ' 121 pm beside Z r l and -0.45 e k 3 88 pm beside
Zr 1. Further details of the crystal structure investigation may be obtained
from the Fachinformationszentrum Karlsruhe, Gesellschaft for wissenschaftlich-technische Information mhH, D-W-7514 Eggenstein-Leopoldshafen 2 (FRG) on quoting the depository numbers CSD-53960 (Za)
and 56457 (2b), the names of the authors, and the journal citation.
1121 a) L. Cavallo, P. Corradini, G. Guerra, M. Vacatello, Polymer 1991, 32,
1329; b) K. Hortmann, H.-H. Brintzinger, New J. Chem. 1992, 16, 51.
1131 A theoretical consideration of the problem leads to the conclusion that
methyl substitution at the 2-position does not influence the transition state
of the polymerization reaction [12a]. This statement seems to be substantiated since the quoted loss of stereospecificity is actually observed o n
3-methyl substitution. The + I effect of the methyl substituents, which
improves the molecular mass of polypropylene, is also seen in the series of
(CH,),Si-bridged cyclopentadienyl complexes; cf. 151.
1141 J. A. Ewen, M. J. Elder, R. L. Jones, S. Curtis, H. N. Cheng in Calalylic
Oiefn Poiymerizaiion (Eds.: T. Keii, K. Soga), Tokio, 1990.
1151 R. F. Jordan, R. E. La Pointe, C. S. Bajgur, R. Willet, B. Scott, J. Am.
Chem. SOC.1986, i08,7410.
1161 a) H. M. Riepl, Dissertation, TechnischeUniversitat Munchen 1992; b) W.
Spaleck, J. Rohrmann, M. Antberg, unpublished; c) N. Piccolrovazzi, P.
Pino, G. Consiglio, A. Sironi, M. Moret, Organomefuks 1990, 9, 3098.
[17] W. A. Herrmann, J. Behm, unpublished, 1992.
[18] a) M . Adamczyk, D. S. Watt, D. A. Netzel, J. Org. Chem. 1984,49,4226;
b ) E R. W. P. Wild, L. Zsolnai, G. Huttner, H. H. Brintzinger, J.
Organomet. Chem. 1982, 232, 233; c) A. Zambelli, P. Locatelli, A. Provasoli, D. F. Ferro, Macromolecules, 1980, f3, 267.
+
lated as the reactive species for the OjS exchange with
Lawesson reagent"] or for the AlC1, catalyzed electrophilic
substitution with thiophosphinoyl chlorides.t31
For Y = S the monomers 1 with R = Me, Et could be
detected as the products of the gas-phase thermolysis of 2.f4]
In the condensed phase so far only one representative of 1,
namely with the large 2,4,6-tri-tert-butylphenyl
substituent,
has been described and structurally
the correTo our
sponding compound with Y = Se is also
knowledge there is so far not sufficient evidence for 3.
Both of the above equilibria are shifted to the left with
ylide substituents R. Monomeric dithioxo- and diselenoxoi5-phosphanes1 and ionic selenophosphonium halides 3 can
be isolated because of the stabilizing effects of these R
groups.
Dichloro[organo(triphenylphosphonio)methanidyl]phosphanes 5['l react smoothly with sodium diselenide in THF to
give the corresponding ylide-substituted diselenoxo-,I5phosphanes 7, which can be isolated as orange-yellow crystals.
The reaction comprises a reduction of the diselenide and
an oxidation of the phosphorus. The ylide-substituted diselenaphosphirane 6 assumed as intermediate, however, cannot
be observed. Compound 7 is formed by cleavage of the S e S e
bond and flattening of the coordination environment of the
phosphorus. In the case of S instead of Se, and H instead of
the ylide substituent, a value of - 9 kcalmol- is calculated
for the corresponding ring opening.[*]In view of the comparable electronegativities of S and Se, a similar value is to be
expected for the selenium compound ; however, because of
the ylide substituent the formation of 7 should be considerably more favorable energetically.
R'
5
6
P
Phosphorus(v) Selenides with Phosphorus in a
Trigonal-Planar Environment**
R'
Se-
In phosphorus(v) chalcogenides the phosphorus atom is
generally tetracoordinated: dichalcogeno(organo)-15-phosphanes 1, Y = S, Se, form dimers 2J1,21and phosphinoyl
halides 4 show no tendency to dissociate with the formation
of a chalcogeno(diorgano)phosphonium ion 3.
The tricoordinate phosphorus atom in 1 and 3 should be
highly electrophilic. Compounds 1 and 3 are therefore postu-
2
3
4
[*] Prof. Dr. A. Schmidpeter, Dip1.-Chem. G. Jochem, Dr. K. Karaghiosoff,
Priv.-Doz. Dr. C. Rob1
Institut fur Anorganische Chemie der Universitat
Meiserstrasse 1, D-W-8000 Munchen 2 (FRG)
[*"I This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie.
1350
0 VCH
Se
Ph3P
By Alfed Schmidpeter,* Georg Jochem,
Konstantin Karaghiosofl, and Christian Rob1
1
R'
Verlagsgesellschaft mbH, W-6940 Weinheim, 1992
7 , R ' - Me.Et, Ph, m-MeC6H,
The structure of compounds 7 follows from their NMR
spectra. The most important information is the nonequivalence of the two selenium atoms. This shows that the two
parts of the molecule (ylide and PSe, moiety) are planar and
lie in a common plane and cannot easily be twisted against
each other, and that thus the 1,4-dipolar resonance formulas
are of great importance. In contrast to this, the planes of the
aryl group and of the PS, moiety in the aforementioned
compound 1 with R = 2,4,6-tri-tert-butylphenyland Y = S
lie almost perpendicular to each other (dihedral angle =
80 ').rsl Thus, the phosphorus atom is sterically protected
and remains trigonal planar coordinated. In contrast, tricoordination is electronically stabilized by the ylide substituent in 7.
The 31P NMR spectra of 7 (at 25°C) show doublets at
6 x 2 1 and 214 for the PPh, and PSe, group, respectively,
with 2J(P,P) about 40 Hz. Thus, the PSe, signal of 7 lies in
OS70-0833/92/10!0-~350
$3.50+ ,2510
Angew. Chem. Int. Ed. Engl. 1992, 31, No. 10
Документ
Категория
Без категории
Просмотров
1
Размер файла
499 Кб
Теги
molecular, high, weight, polypropylene, designezirconocene, catalyst, specifically
1/--страниц
Пожаловаться на содержимое документа