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Crystalline Nitrogen OxidesЧCrystal Structure of N2O3 and a Remark Concerning the Crystal Structure of N2O5.

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acetonitrile by addition of lithium tetraphenylborate presumably occurs in other protonatable nitrogen bases as well
and is potentially of biological importance. In ongoing investigations the preparation of single crystals of metal-cation
chelate complexes'' '1 of tetra(2'-pyridyl)pyrazine will be attempted.
Received: November 14, 1991 [Z 5019 IE]
German Version: Angew. Chem. 1992,104, 348
CAS Registry numbers:
tetra(2-pyridy1)pyrazine dihydrochloride, 138901-51-6; tetra(2-pyridy1)pyrazine hrs(tetraphenylborate), 138901-52-7; tetra(2-pyridyljpyrazine 2500597-4.
[l] H. Bock, D. Jaculi, Z. Nuturjorsch. B 1991, 46, 1091.
[2] See: H. Bock. K. Ruppert, C. Niither, Z. Havlas, H.-F. Herrmann, C.
Arad. I. Gobel, A. John, J. Meuret, S. Nick, A. Rauschenbach, W. Seitz,
T. Vaupel. B. Solouki, Angew. Chem. 1992,104, in press; Angeu. Chem. In!.
Ed. Engl. 1992, 31. in press (May issue) and literature cited therein.
[ 3 ] H. A. Staab, T. Saupe, Angew. Chem. 1988, 100,895; Angeu. Chem. In!.
Ed. EngI. 1988, 27, 865; T. Barth, C. Krieger, F. A. Neugebauer, H. A.
Staah, rhid. 1991, 103, 1006 and 1991,30, 1030 and literature cited therein.
(41 Tetra(2-pyridy1)pyrazine (Alpha): 100 mg were recrystallized from 3 mL
dry HCCI, under an atmosphere of n-hexane. Colorless plates; for the
crystal structure analysis we are grateful to Dr. J. W. Bats (Universitlt
Frankfurt); see T. Vaupel, Diplomurbeil, Universitat Frankfurt, 1992. The
molecule is arranged around a crystallographic inversion center. Angle
sum of all six-membered rings 720". bond lengths C-N 134 pm, C-C (ring)
138-139 pm. C-C 149 pm.
[5] Tetra(2-pyridyljpyrazine dihydrochloride: 520 mg (1.3 mmol) tetra(2pyridy1)pyrazine were stirred in 60 mL aqueous 1 N HCI at room temperature for 2 h. The water was then removed under reduced pressure and the
dried residue recrystallized from 200 mL acetonitrile. Single crystals:
70 mg were dissolved in 100 mL boiling acetonitrile and slowly cooled to
room temperature; after 2 d colorless polyhedra had grown. Crystal structure analysis: C,,H,,CI,N,
(461.23) a = 940.5(2), h =771.8(2), c =
1563.2(6) pm, fl =105.13(3)", V =1095.3 x lo6 pm3 (100 K), Z = 2,
pca,c=1.399 gem-', ~(Mo,,) = 0.32 mm-', monoclinic, space group
P2,jn, Siemens-AED 11 four-circle diffractometer. 6843 measured reflections 3' 5 2 H 5 60", of which 2493 are independent with I >2u(f). Structure resolution by direct methods and difference Fourier techniques
(SHELXTL-PIUS),N = 2943, NP =182, R = 0.033. R, = 0.037, M, = 1/u2
( F ) 0.00008 F2. GOOF = 2.864, Shift/Err 5 0.001, residual electron
density +0.43/-0.30 e 0 k 3 . Empirical absorption correction, extinction
correction. all C, N, and CI atoms were anisotropically refined; H atoms
(from difference Fourier analysis) isotropically refined. The dihydrochloride is arranged around a crystallographic inversion center. Angle sums of
all rings 7 2 0 , bond lengths C-N 134 pm. C-C (ring) 139 pm, C-C 149 pm.
b) Further details of the crystal structure determination are available on
request from the Fachinformationszentrum Karlsruhe, Gesellschaft fur
wissenschaftlich-technische Information mbH, D-W-7514 EggensteinLeopoldshafen 2, on quoting the deposit number CSD-56020, the authors,
and the literature citation.
[6] Tetraphenylborate salt of diprotonated tetra(2-pyridy1)pyrazine: A suspension of 200 mg (0.04 mmol) dihydrochloride in 20 mL acetonitrile was
dissolved in methanol. On addition of 800mg (2.5mmol) lithium tetraphenylborate in 5 mL acetonitrile a yellow color appeared; after 3 h
yellow cubes had grown. Crystal structure analysis: C,,H,,B,N, (1028.7);
u=11.082(6). b=11.160(7), c =12.366(6)pm. a:=80.98(5), /l=
84.87(4). 7 = 63.68(4)", V =1353 x 46 106pm3 (loOK), Z =1,
1.263 g ~ m - jt(MoKJ
= 0.07 mm-'. triclinic, space group Pi, SiemensAED-II four-circle diffractometer, 5461 measured rellections between
3 s 2H I55'. of which 3833 are independent with I z 1 u(0. Structure
resolution by direct methods and difference Fourier technique
(SHELXTL-PIUS),N = 3833, NP = 478, R = 0.054, R , = 0.040, 1%' = 1/
0 2 ( F ) 0.0002 Fz. GOOF = 1.3660, Shift/Err 5 0.001, residual electron
density 0.40:-0.26 e,.&-3. Empirical absorption correction, extinction
correction, B, C, and N atoms were anisotropically refined; H atoms (from
difference Fourier analysis), isotropically refined. The dication is arranged
around a cryStdllOgrdphiC inversion center. Angle sums of all rings 720.
bond lengths C-N 134pm. C-C(ring) 139 pm, C-C 150 pm. For further
details of the crystal structure see [5 b].
[7] Selected reviews on hydrogen-bridge bonds: a) A. F. Wells, Structurul Inorgunic Chcrnrstry, 5th ed., Clarendon Press, Oxford, 1987, pp. 355-376; b)
J. Elmsley. Chem. SOC.Rev. 1980,Y. 91-24;c) R. Taylor, 0. Kennard, Arc.
Chrm. Rex 1984.17,320:d)G. R. Desiraju, Acc. Chem. Res. 1991,24,290.
e) Among the examples for different hydrogen bridges within one compound. the yellow and white polymorphic modifications of 3,6-dichloro25dihydroxyterephthalic acid dimethyl ester which have different intramolecular bridges 0-H ' ' ' 0 and 0-H . - . C I ,are pointed out (Q.-C.
Yang. M. F. Richardson. J. D. Dunitz. Acta Crystallogr. Sect. B, 1988.45,
Angew. Chrm. I n t . Ed. Engl. 3 / (1992J No. 3
312). f ) For mono- and diprotonation see for example R. Schwesinger, M.
Missfeldt, K. Peters, H. G. von Schnering, Angew.. Chem. 1987, 99, 210;
A n g a t . Chem. Int. Ed. Engl. 1987. 26, 1165.
[XI All quantum chemical calculations were performed at the AM1 level
(M. J. S. Dewar, E. G. Zoebisch, E. F. Healy, J. J. P. Stewart, J. Am. Chem.
Soc. 1985, 107, 3902; program version SCAMP 4.0, T. Clark, Universitlt
Erlangen). a) For the neutral molecule, a complete geometry optimization
starting from standard structural parameters yields AH, = 984 kJmol-I,
C-N 135 pm, C-C (ring) 140 pm, C-C 149 pm. ipso angle in pyridine 117".
twisting angle 54", nonbonding distance N ... N 320 pm; E , = 9.06 eV
(exp. IEY = 8.1 eV; T. Vaupel, Diplomarheit, Universitdt Frankfurt, 1992).
b) The calculations for the diprotonated compounds were based on the
crystal structure data. Dichloride N +-H distance corrected according to
[7c] to 104pm): AHf=1132kJmoI-' ([MH:CI;])
and 2314kJmol-'
(MH:) as well as bis(tetrapheny1borate) AH< = 241 I kJmol-' ([MH;]).
c) For the model calculations of H,C,N+-H ... NC,H,, the starting point
was the structure determined by neutron diffraction [9] with the six-meinbered rings perpendicular to each other and the N . . . N distance varied
between 280 pin and 240 pm. For the individual potential curves AAH,/Ar
(Scheme 1). the bridge proton is moved in 5 pm steps along the N-N axis
and the geometry of thecomplete system including both pyridine rings was
optimized. Additional calculations for coplanar pyridine rings yield similarpotentialcurves, theAAH,valuesofwhichare higher by 2-3 kJmol-'
It has been pointed out that semiempirical calculation procedures often
exaggerate N/N repulsion relative to the H+-bridge attraction due to insufficient N+-H '.. N parametrization. d) For the calculations of diprotonated tetra(2-pyridy1)pyrazine with two intramolecular H + bridges. the
simulation of the "flip-flop" molecular dynamics started with the Cartesian
coordinates of the experimental structure (Fig. 1 bottom), transforming
the latter structure in ten equally weighted steps into that of its mirror
image. In the fifth step the enthalpy of formation increased from
2410 kJmo1-I to 2414 kJmol-'. The structural parameters given correspond to interpolation values.
[9] J. Roziere, J. M. Williams, E. Grech, Z. Malarski, L. Sohzyzk, J. Chem.
P h w . 1980. 72, 61 17; see also P. Tenlon, R. G. Delaplane. I. Olovson, J.
Reziere, Actu Crystallogr. Sect. 1985, C41. 479.
[lo] An extensive literature search, although still incomplete with respect to the
multitude of publications [7c], yields a comparably short N+-H .-.N
bridge of 252.6 pm for 1,6-diazabicyclo[4.4.4]tetradecane hydrochloride
(R. W. Alder, A. G. Orpen, R. B. Sessions, J. Chem. Soc. Chem. Commun.
1983, 999); the position of the H + center is not reported. The shortest
N " . N distance found so Par (247pm) i s found in syn-1,6:8,13-diimino[l4]annulene perchlorate (R. Sestro, T. Pilati, M. Simonetta. E. Vogel,
J. Am. Chem. Soc. 1985, 107, 3185).
(111 See for example: S. Hunig, H. Quast, Neuere Furbige Systeme (Abstr. 11.
Int. Farbensymposium, Elmau. 1964) Verlag Chemie, Weinheim, 1964,
pp. 17-19 and 35-43; T. Vaupel, Diplomurbeit, Universitat Frankfurt
1992; see also H. A. Goodwin, F. Lions, J. Am. Chrm. SOC.1959.8/,6415.
Crystalline Nitrogen Oxides-Crystal Structure
of N,O, and a Remark Concerning the Crystal
Structure of N,O,
By Arndt Simon,* Jorg Horakh, Axel Obermeyer,
and Horsf Borrrnann
Our knowledge of the crystal structures of nitrogen oxides, N,O, N,O,, N,O,, N,O,, and N,O,, is still rather
incomplete. The structure determinations of N,O['] and
N,0,[21 were complicated by the static disorder of the molecules. Raman spectrat3'contradict the linearity of the NO:
ion in NOlNO; as determined in the crystal structure of
N,O, .[41 In the course of a structure determination of N,O,
only a possible unit cell could be proposed.[51
Our results on the structure of the stable cubic and the
metastable monoclinic forms of N,04 have already been
published.[61Here we report on phase transformations in
crystalline N 2 0 3 / N 2 0 4samples, a single-crystal structure
determination of N,O,, and indications of the existence of
[*] Prof. Dr. A. Simon, J. Horakh, A. Obermeyer, H. Borrmann
Max-Planck-Institut fur Festkorperforschung
Heisenbergstrasse 1, D-W-7000 Stuttgart 80 (FRG)
Verlugsgesellsrhajt mbH, W-6940 Wrinheim, 1992
0570-0833~92jO303-03013 3.50+ .25/0
hitherto unknown nitrogen oxides. In addition, we describe
preliminary results, which prove that the crystal structure of
N,O, needs to be revised.
Indigo-blue N'O, exists in its pure form only in the solid
state, melting at about - 100 0C.[71Reed and Lipscomb discovered that single crystals become polycrystalline due to a
phase transformation when cooled below - 125 0C.[51Therefore we first performed extensive powder diffraction experiments, using the modified Guinier technique,L8]in order to
optimize conditions for crystal growth. The samples, prepared from NO, and NO,['] showed a very complex behavior
(Fig. 1). Depending on temperature and thermal treatment
we were able to identify six different diffraction patterns
besides those of N,O, .[lo]
I l3
, k+B
. k+D
I _____(
Fig. 1 . Results of the investigation with the modified Guinier technique [8]of
samples of N,O, which were sealed in X-ray capillaries under vacuum (I) and
1 bar N O (11). respectively [9]. Arrows indicate directions of temperature
changes (values in [ "C h-'1, dotted lines for temperature changes without Xray observations, full lines for temperature changes with simultaneous X-ray
diffraction). Cooling always began at room temperature with cooling rates of
approxiinately 10' or 10' 'C h - '. The diagrams of cubic and monoclinic N,O,
are denoted with k and m, respectively. Diagrams A through D were observed
together with those of N,O, in contrast to diagrams E and F[10].
Above approximately - 150 "C the intense lines of the
cubic diagram k of N,O, are observed with all samples.
After being shock-cooled to - 190 "C the amorphous sample I was slowly heated up; at - 160 "C diagram k was observed first. At slightly higher temperature, diagram A of
N,O, was also observed. Obviously, N,O, crystallizes more
readily than N,O, . Therefore it is very surprising that after
crystallization of the amorphous phase from either a shockcooled or a slowly cooled sample 11, the diagrams E and F
did not show any lines for N,O,. At - 150 "C in both cases
the cubic line pattern of N,O, together with diagram B of
N,O, developed. These results are best explained with the
existence of at least one new oxide below - 150 "C, the composition of which must be between N,O, and N,O,. We
believe that diagrams A through D belong to distinctly different modifications of N,O,.
A single crystal of N,O, was grown after the compound
had been enriched locally in the sample by zone melting.
Probably this is the reason why a crystal of phase B grew, in
spite of the fact that in powder diagrams phaseA was reproducibly observed in the same temperature range.[' ',''] Fig302
Fig. 2. Projection of the orthorhombic unit cell of N,O, (phase B). The distances [pm] and angles ["I are: Nl-N2 189.06(6). N1-01 111.96(6), N2-02
120.87(6), N2-03 120.57(5); 01-Nl-N2 105.12(4), 02-N2-03 128.61(5), 0 2 N2-NI 119.55(4). 03-N2-N1 111.84(3).
k+A k+B
ure 2 shows a projection of the structure onto (100) of the
orthorhombic unit cell.['31As was proposed in 1920['4] and
supported later by IR,[''] Raman,["] and NMR experiments," 71 N,O, must be described as a "nitroso-nitro'' compound. There are only slight changes in geometric details
~ , r l u ~ s ~ e . ~ e l l s mbH,
c ~ i a f iW-6940 Wernherm, 1992
determined in the solid state compared to the molecular
shape as revealed from microwave spectra in the gas
phase.[lB1Especially the very long N-N distance (189.1 pm)
is rather close to the value (186.4 pm) in the gas phase and
represents a Pauling bond-order of about 0.2. A formal description as nitrosyl nitrite is also supported by the N-0
distances and the 0 - N - 0 angle (Nl -01 1 12 pm compared to
121 pm
and 0 - N - 0 128.6 ' in comparison with 118 pm and 134.3 in
N204[61or 124pm and 115" in NO;["]). The N,O, molecule is almost planar; on the average the atoms deviate only
1.5 pm from the least-squares plane. However, because the
angles around N2 add up to exactly 360.0 this deviation is
mainly due to the position of 01, which lies 7.8 pm above the
plane through NI, N2,02, and 0 3 (mean deviation 0.3 pm).
The nitrosyl group and the nitrite unit are therefore twisted
3.7" about the N-N bond. The planarity of N,O, was explained as a consequence of bonding interaction between the
a, orbitals of the NO, fragments. These orbitals have significant oxygen character.["] A similar explanation seems also
reasonable for N,O,, since the 0-0 distance in N,O, is even
shorter than that in N,O,, despite the longer N-N distance.
This particular geometry is also reflected in the smaller N I N2-03 angle relative to that of NI-N2-02 and in the small
0 1 -N1-N2 angle. Recently published ab initio calculations
of the electronic structure of N,O, were obviously performed only for the planar geometry without further explanation.[231 The calculated N-N distances are 10-15 %
shorter than the experimental value for all basis sets tested.
The redetermination of the structure of N,0,[41 from dif251 led to a surprising result. The (pseufractometer data
do-)hexagonal structure was confirmed in the first instance,
and the refinement converged at R = 0.028. The N-0 distance in the NO: ion is 3.6 pm shorter and in the NO; ion
1.5 pm longer than the values obtained from the earlier
structure refinement. Refinements with data sets collected at
different temperatures between 0 "C and - 168 "C did not
give any hint for disorder or an erroneous description of the
structure. However, a careful inspection of Guinier photo-
0570-0833/92j0303-0302$3.50+ ,2510
Angew. Chmni. Inl. Ed. Engl. 31 (1992j N o . 3
graphs showed very slight but systematic line splittings.
Therefore the symmetry needs to be reduced from hexagonal
to orthorhombic,[261resulting in a very small deviation of
0.3 Yo from the ideal a : b ratio o f the (ortho-)hexagonal system (1
The structural consequences of this result are
under investigation.
Received: October 8, 1991 [Z 49591E.3
German version: Angeii. Chem. 1992, 104, 325
[I] W. C. Hamilton, M. Petrie, J. Phys. Chrm. 1961, 65, 1453.
[2] W. J. Dulmage. F. A. Meyers, W. N. Lipscomb, J. Chem. Phjs. 1951, 19,
1432: Arlo Cry.srallogr. 1953, 6. 760; W
. N. Lipscomb, F. E. Wang.
W. R.May. E. L. Lippert, Arta Crystdlogr. 1961, 14. 1100.
[3] W. W. Wilson, K. 0. Christe, Inorg. Chem. 1987, 26, 1631.
[4] E. Grison, K. Erics, J. L. De Vries, Act4 CrystaNogr. 1950, 3, 290.
[ 5 ] T. B. Reed. W. N. Lipscomb, Acta Crystallogr. 1953, 6, 781.
[6] A. Obermeyer, H. Borrmann. A. Simon, Z. KristuNogv. 1991, 196. 129.
[7] I. R. Beattie, S. W. Bell, A. J. Vosper, J. Chem. Soc. 1960,4796.
[XI A. Simon, J. Appl. Crystallogr. 1970. 3, 11; ibid. 1971, 4, 138.
191 I : N,O, was condensed at - 78 "C and allowed to react with gaseous NO
by slowly raising the temperature. At approximately -50°C a deep blue
= 0.2 mm) was
liquid separated from the N,O,. An X-ray capillary (0
filled to a height of 2 cm. cooled to roughly -100'C (ethanol/N,(liq)),
evacuated, and sealed. 11: A gaseous mixture of NO, and NO was condensed into an X-ray capillary at -78 "C. The NO pressure in the apparatus was kept at about I bar to maximize the amount of N,O, in the
reaction product. After "annealing" at - 50 "C for several hours with
intermittant warming to room temperature, the sample had changed color
from greenish blue to dark blue. The capillary was sealed at approximately
- 100 C under 1 bar NO.
[lo] The different powder diagrams in Figure 1 are characterized by the followingdvalues[pm]:A(-IIO'C): 557,406,401,360, 349.299,290.286.281.
272, 258. 257, 236, 235, 198.1. 194.1. 185.2. B ( - 1 3 0 T ) : 523, 440, 402,
362, 331, 295. 275, 262, 261. 255. 252, 238. 235, 233, 209, 182.6. C
( - 145 C): 599,461,351,336,280,269. D ( - 180 "C): 420,378, 347,322.
297, 286. 274, 273, 258, 251. 249, 242, 231. 226, 213, 211, 197.6, 189.1,
17X.5.173.5. E(-155'C):511,479,40X,349,348,312,282,277,264,257,
256. 242, 229. 225, 193.1. F (-l50'C): 600, 426, 407, 404, 369, 353, 348,
300. 275. 256. 254. k (-170°C): 548.3, 387.7, 316.6. 245.2, 207.3, 182.8,, 133.0, 129.2.m ( - 1 1 2 T ) : 517.362, 351. 322,285.266,259,
244. 235, 217. 194.7, 192.6. 181.5. 149.7, 148.0, 131.0.
[ I l l From the structure factors given by Reed and Lipscomb 151 a powder
diagram can be calculated which is very similar to diagram A.
[12] Sample 11 completely crystallized at -115 "C to form a light blue solid. A
small part of the sample was kept solid and the rest was melted. At
- 106 C a crystal started growing from the solid and became deeper in
color as was observed with the microscope. Rotation photographs showed
the crystal to be mainly cubic N,O,. At the end of the solid column a
separated section (0.5 mm length) remained; this was very dark blue and
solidified at - 108 "C. I t was almost completely melted at -104.5"C and
recrystallized when cooled at a rate of 1 "C per h. According to rotation
and oscillation photographs, few crystallites of different sizes formed at
- 106.5"C. During the two days measurements of a data set, a perfect
single crystal formed which could be cooled to - 160°C without destruction. [13]
[I31 a) Crystal data of N,O,: u = 506.86(4), b = 647.96(5). c = 863.26(6) pm
at -160"C;y,~,,,, =1.781 gcm-',Z=4,spacegroupP2,2,2, (No. 19),
R = 0.022 and wR = 0.021 for 1352 reflections and 47 refined parameters.
b) Further details of the crystaI structure investigation are available on
request from the Fachinformationszentrum Karlsruhe, Gesellschaft fur
wissenschaftlich-technische Information mbH. D-W-7514 EggensteinLeopoldshafen 2 (FRG) on quoting the depository number CSD-55934,
the names of the authors, and the journal citation.
1141 H. Wieland, Berichre 1921, 54, 1781.
[I51 W. A. Yeranos, M. J. Joncich, Mol. Phys. 1967, 13. 263.
[16] 1. C. Hisatsune, J. P. Devlin. Spectrochim. Acta 1960, 16, 401.
[17] H. Schultheiss, E. Fluck. Z. Naturforsch. B 1977, 32, 257; L.O.
Andersson, J. Mason. Chem. Commun. 1968, 99.
[I81 A. H. Brittain, A. P. COX,R. L. Kuczkowski. Trans. Faraday Soc. 1969,
65, 1963.
[I91 D. B. Keck. C. D. Hause, J. Mol. Spectroscopy 1968. 26, 163.
[20] J. Laane. J. R. Ohlsen. Prog. Inorg. Chem. 1980, 27, 473.
[21] M. 1. Kay, B. C. Frazer, Acra Crysrallogr. 1961, / 4 , 56.
[22] R. Ahlrichs, F. Keil. 1 Am. Cliem. Soc. 1974, 96,761 5 ; B. M. Gimarc. S. A.
Khan, M. C. Kohn, J. Am. Chem. Soc. 1978, 100, 1996.
I231 S. A. Maluendes. A. H. Jubert, E. A. Castro, 1 Mol. Struct. (Theorhem)
1990. 204. 145.
[24] NO, was purified by repeated sublimation of (colorless) N,O,, diluted
with argon, and allowed to react with ozone (approx. 20% 0, in 0,)in an
Angew. Clmi. Int. Ed. Engl. 31 (1992) No. 3
apparatus based on the principle of Daniell's burner. The ratio was such
that the gas phase was colorless. The product, N,O,, was condensed at
-78 "C in a trap and further purified by sublimation in ozone containing
0,.The X-ray capillary was filled at -78 "C and sealed under vacuum. At
- 25 "C the sample slowly recrystallized, and at slightly higher temperature
one of the crystallites grew to a size sufficient for measurement.
[25] Crystal structure of N,O,: Measurements and calculations were performed based on the (pseudo-)hexagonal cell (see text). u = b = 540.19(9),
c =652.68(13)pmat -16XoC.p, , ~ y= 2 . 1 7 5 g ~ m - ~ , Z2,spacegroup
P 6Jm m c (No. 194). 3674 measured reflections averaged to 189 independent ones (R,",.= 0.042) R = 0.028 and W R = 0.029 for all 189 reflections
and 12 refined parameters [I 3 b).
1261 Least-squares refinement with 34 reflections of the completely indexed
diagram leads to the lattice constants ( - 179 "C) u = 541.07(6), h =
934.20(8) and c = 653.22(8) pm.
Regioselectivity Control in the PalladiumCatalyzed Copolymerization of Propylene with
Carbon Monoxide **
By Antonio Batistini, Giambattista Consiglio,*
and Ulrich W Suter
The control of regioselectivity is exceedingly important in
the carbonylation of olefins.['321The archetype of this reaction is the hydroformylation of propylene. Even 50years
after the discovery of the reaction, the control of regioselectivity is still a
Better results have been obtained
in the carbonylation of aromatic or functionalized olefinic
substrates.[4- For instance in the hydroalkoxycarbonylation of styrene catalyzed by L,PdC1,[91the use of monophosphine or chelating diphosphine ligands results in a very good
control of the regioselectivity, yielding the branched or the
straight-chain ester.[4- 'I For aliphatic olefins such as propylene such regiochemical control has never been achieved.
In the copolymerization of olefins with carbon monoxide
control of the regioselectivity is even more important. The
regioselective linkage of the olefinic monomer is a general
prerequisite for the production of stereoregular polymers.[t01
The copolymerization of styrene with carbon monoxide
(phen = 1,lOcatalyzed by [Pd(p-CH,C,H,SO,),(phen)]
phenanthroline) provides poly(1-0x0-2-phenyltrimethylene)I1' with considerable stereochemical control: The
content of racemic dyads is higher than 90 YO,
and the stereochemistry is probably controlled by the end of the growing
chain. The related catalyst precursor [Pd(CF,COO),(dppp)]
(dppp = 1,3-propanediyIbis(diphenylphosphine)) is able to
promote not only the strictly alternating copolymerization
of ethylene but also that of aliphatic cr-olefins like propylene.[l4-l6I However, a sample of the propylene-carbon
monoxide copolymer prepared under conditions similar to
those reported in the patent
and recovered
by precipitation with methanol shows poor constitutional
regularity. In fact, the 13CNMR spectrum of the recovered
material exhibits three broad groups of signals in the carbony1 region (6 = 217-207) which are centered at about
6 = 215.5, 212.0, and 207.8 and have an intensity ratio of
[*] Prof. Dr. G. Consiglio
Eidgenossische Technische Hochschule
Laboratorium fur Technische Chemie, ETH-Zentrum
UniversitPtstrasse 6, CH-8092 Zurich (Switzerland)
Dr. A. Batistini, Prof. Dr. U. W. Suter
Eidgenossische Technische Hochschule, Institut fur Polymere
ETH Zurich (Switzerland)
We thank Prof. Dr. D. Milstein (The Weizman Institute of Science, Rehovot, Israel) for the ligand 1.3-propanediylbis(diisopropylphosphine)as
well as for suggestions related to its synthesis.
Verlagsge.wl1schaft mbH, W-6940 Weinheim, 1992
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crystals, structure, crystalline, remarks, nitrogen, oxidesчcrystal, concerning, n2o3, n2o5
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