Nickel-catalyzed reaction of highly fluorinated epoxides with halogens

Full text of DOI:10.1021/ja961408s

8140
J. Am. Chem. Soc. 1996, 118, 8140-8141
Nickel-Catalyzed Reaction of Highly Fluorinated
A 400-mL stainless steel shaker tube was charged with 3 g
of Ni powder (Aldrich, 99.99%, 100 mesh) and 127 g of I2 and
cooled to -78 °C. After evacuating, 90 g of HFPO was added
and the tube was vigorously shaken at 185 °C for 8 h. Gas
⊥
Epoxides with Halogens
Zhen-Yu Yang
(
CF3COF) was transferred into a -78 °C trap and 146.3 g of
crude liquid product was distilled to give 116.8 g (78%) of a
4.3:1:4.7 (GC area) mixture of CF2I2, I(CF2)2I, and I(CF2)3I .
Other catalysts containing nickel such as Ni/Zn (Urushibara
DuPont Central Research & DeVelopment
Experimental Station, Wilmington, Delaware 19880-0328
6
7,8
catalyst) and Ni/Cu/Zn also catalyze the reaction. The success
in the reaction with Ni alloys prompted us to use a vessel with
high nickel content as a reactor. Indeed, the reaction proceeded
well in a Hastelloy C reactor to give greater than 85% of CF2I2
ReceiVed April 29, 1996
Transition metal catalyzed reactions have been widely used
in hydrocarbon transformations, but the analogous chemistry
in perfluorocarbons is largely unexplored. Although huge
numbers of transition metal complexes containing fluorinated
ligands have been reported, these complexes usually lack the
catalytic activity necessary for useful transformations of fluo-
rocarbons. That is due to the fact that they exhibit dramatically
different structural and bonding characteristics with enhanced
thermal stability in comparison with their hydrocarbon coun-
9
in the absence of added nickel catalyst.
Reaction of HFPO with bromine under similar conditions
gave CF2Br2 and CF3COF with traces of Br(CF2)nBr (n ) 2,
3
). The reaction proceeded in a Hastelloy C vessel or in a
stainless steel vessel with Ni powder, but only a very low yield
<5%) of CF2Br2 was observed in the absence of nickel powder
(
in a stainless steel tube. Since this is a heterogeneously
catalyzed reaction, vigorous shaking or agitating is critical to
achieve high yields of the desired products. The reaction could
also be carried out in inert solvents such as fluorochlorocarbons
or perfluorocarbons, but the absence of solvent greatly simplified
the workup process and minimized waste with similar yields
and selectivites compared to the reaction in solvents.
1
terparts. Fluorinated organometallic reagents have recently
received much attention, but catalytic reactions are much more
attractive for the synthesis of fluorocarbons.2 Although transi-
tion metal complex catalyzed defluorinations of perfluorocarbons
have been reported very recently, other useful metal catalyzed
reactions under conventional conditions remain unknown to the
best of our knowledge.3 We report here the first example of a
transition metal catalyzed reaction of highly fluorinated epoxides
with halogens, which may involve the metal CF2 complex, to
give dihalodifluoromethanes and fluorinated acyl fluorides in
good yields.
The nickel catalyzed reaction also can be carried out with
interhalogens such as I-X (X ) Br, Cl). With I-Br and HFPO
at 190 °C in a Hastelloy C shaker tube, a 1:1:0.29 (mol) mixture
of CF2I2, CF2Br2, and CF2IBr was isolated in 74% total yields.
Similarly, the major product with I-Cl was CF2I2 (58% yield
base on I-Cl) along with CF2ICl (9% yield based on I-Cl)
Difluorocarbene and its precursors react with iodine to give
very poor yields of CF2I2.4 Reaction of hexafluoropropylene
oxide (HFPO), a well-known difluorocarbene precursor, with
I2 in a stainless steel tube or in a glass tube affords only less
1
0
and CF2Cl2.
In both cases, traces of higher homologues
X(CF2)nY (X, Y ) halogen and n ) 2, 3) were also detected
1
9
by GC-MS and F NMR analysis.
5,6
than 15% yield of CF2I2. We discovered that the reaction of
HFPO with I2 in the presence of 3-10 mol % of Ni powder in
a stainless steel shaker tube or a glass tube resulted in high
yields of CF2I2 and CF3COF, along with small amounts of
I(CF2)nI (n ) 2, 3).
The nickel catalyzed reaction is general and works well with
other fluorinated epoxides. The perfluorophenyl, perfluorosul-
fonyl fluoride, and chlorofluorocarbon groups in the epoxides
did not interfere with the reaction. The reaction of these
fluorinated functionalized epoxides with I2 in the presence of
Ni powder in a sealed glass tube with vigorous shaking at 190
°
C afforded good yields (68-81%) of CF2I2 and the corre-
⊥
Publication No. 7414.
sponding fluorinated acyl fluorides.
(
1) (a) Kiplinger, J. L.; Richmond, T. G.; Osterberg, C. E. Chem. ReV.
1
994, 94, 373. (b) Hughes, R. AdV. Organomet. Chem. 1990, 31, 183. (c)
(7) New Hydrogenation Catalysts: Urushibara Catalysts; Hata, K.; John
Wiley & Son, Inc.: New York, 1972; pp 29-60.
Stone, F. G. A. Pure Appl. Chem. 1972, 30, 5451. (d) Bruce, M. I.; Stone,
F. G. A. Prep. Inorg. React. 1968, 4, 177. (e) Treichel, P. M.; Stone, F. G.
A. AdV. Organomet. Chem. 1964, 1, 143.
(8) (a) Ni/Cu/Zn catalyst was prepared by reaction of NiCl2/CuSO4 with
Zn in water. To a stirred solution of 13.0 g of NiCl2 and 16.0 g of CuSO4
in 100 mL of water was slowly added 13.0 g of Zn at room temperature.
Solids were filtered and poured into 10% HCl, and the resulting mixture
was stirred for 30 min. After filtration, the solids were washed with water
and acetone and dried under vacuum at 60 °C to give 11.3 g of Ni/Cu/Zn
catalyst. (b) A 0.4-L stainless steel Shaker tube was charged with 127 g of
iodine and 5.0 g of Ni/Cu catalyst and then evacuated at low temperature.
After 90 g of HFPO was added, the resulting mixture was heated at 185 °C
for 8 h. 112.0 g of dark liquid was obtained which was distilled to give
79.3 g of a mixture of CF2I2, ICF2CF2I, and ICF2CF2CF2I in a ratio of
39.3:1:3 (GC area).
(
2) (a) Burton, D. J.; Yang, Z. Y.; Morken, P. A. Tetrahedron 1994, 50,
2
993. (b) Burton, D. J.; Yang, Z. Y. Tetrahedron 1992, 48, 189. (c)
Chemistry of Organic Fluorine Compounds II. A Critical ReView; Hudlicky,
M., Pavlath, A. E., Eds.; ACS Monograph 187; American Chemical
Society: Washington, DC, 1995.
(
3) (a) Aizenberg, M.; Milstein, D. Science 1994, 265, 359. (b) Kiplinger,
J. L.; Richmond, T. G. J. Am. Chem. Soc. 1996, 118, 1805. (c) Burdeniuc,
J.; Crabtree, R. H. J. Am. Chem. Soc. 1996, 118, 2525.
(
4) (a) Mahler, W. Inorg. Chem. 1963, 2, 230. (b) Mitsh, R. A. J.
Heterocycl. Chem. 1964, 1, 233; (c) Kesling, H. S.; Burton, D. J.
Tetrahedron Lett. 1975, 3358; (d) Wheaton, G. A.; Burton, D. J. J. Org.
Chem. 1978, 43, 3643.
(9) (a) Hastelloy C alloy contains 56.43% Ni, 15.5% Cr,16% Mo, and
small amounts of other elements while stainless steel 316 alloy contains
only 12% Ni. (b) A 1-L Hastelloy autoclave was charged with 381 g (1.5
mol) of I2 and cooled to -78 °C. After evacuating, 266 g (1.6 mol) of
HFPO was added and the autoclave was heated at 185 °C for 10 h. After
cooling to 0 °C, gas (CF3COF) was vented and 458 g of liquid was washed
with aqueous Na2SO3 solution and distilled to give 395 g of a 240:1:4.8
(
5) HFPO as a CF2 precursor: (a) Sargeant, P. B.; Krespan, C. G. J. Am
Chem. Soc. 1969, 91, 415. (b) Sargeant, P. B. J. Org. Chem. 1970, 35,
78. (c) Chepik, S. D.; Petrov, V. A.; Galakhov, M. V.; Belen’kii, G. G.;
Mysov, E. I.; German, L. S. IzV. Akad. Nauk SSSR, Seri. Khim. 1990, 8,
844. (d) Millauer, H.; Schwertfeger, W.; Siegemund, G. Angew. Chem.,
Int. Ed. Engl. 1985, 24, 161.
6
1
1
9
(mol) mixture of CF2I2, I(CF2)2I, and I(CF2)3I, bp 106-107 °C. F NMR
for CF2I2: +18.6 ppm (s). HRMS: calcd for CF2I2 303.8057; found
303.8065.
(
6) (a) John, E. O.; Kirchmeier, R. L.; Shreeve, J. M. Inorg. Chem. 1992,
3
3
1. 329. (b) We repeated the reaction of HFPO with I2 in a stainless steel
16 tube to give less than 15% yield of CF2I2. In a glass tube, no yield was
(10) CF2ICl, bp 31-34 °C, 19F NMR: +8.2 ppm (s) and CF2Cl2 is too
volatile to be isolated.
improved.
S0002-7863(96)01408-4 CCC: $12.00 © 1996 American Chemical Society

Communications to the Editor
J. Am. Chem. Soc., Vol. 118, No. 34, 1996 8141
Scheme 1
The precise mechanism for this nickel catalyzed reaction is
II
unclear. Initially, Ni I2 generated from the reaction of iodine
with nickel powder was suspected as a catalytic species.
However, the recovered dark powder after reaction was a
II
11
mixture of Ni(0) and Ni I2 as determined by X-ray diffraction.
II
As a control experiment, we carried out the reaction with Ni I2
(
Aldrich, 99.99%) as a catalyst under identical conditions; no
I
desired CF2I2 was obtained. Subhalide Ni I has also been
considered as a catalytic species, since Ni(I) complexes in either
homogeneous solution or on silica support were formed by
reaction of Ni(0) and Ni(II) complexes or by reduction of Ni-
In conclusion, we have discovered an unprecedented nickel
catalyzed reaction of highly fluorinated epoxides with halogens
at elevated temperatures. Since HFPO is a readily available
material, the reaction provides the first useful synthesis of CF2I2
which is an important building block for the preparation of other
12
(II). Such a possibility may not be the case in this reaction
II
because when a mixture of powdered nickel and Ni I2 was
heated at above 180 °C, even in the molten state, no evidence
I
for the formation subhalide NiI was observed; thus, Ni I seems
fluorinated compounds, but heretofore has been extremely
unlikely to be the catalytic species.13 We propose that nickel
atoms are the catalytic center where the fluorinated epoxide first
adsorbs and then undergoes oxidative addition to give fluori-
4,5,16,19
difficult to obtain.
In addition, the high value of by-
product, fluoroacyl fluoride, the absence of solvent, and high
yields make this reaction more attractive for the synthesis of
functional fluorocarbons on a large scale. Mechanistic studies
and further applications of the novel chemistry are currently in
progress.
nated oxanickel cyclobutane A and/or B, which rapidly decom-
pose to CF3COF and nickel difluorocarbene C.1
4-16
The
formation of NidCF2 C may alter the reactivity of the carbene
carbon from electrophilic to nucleophilic, resulting in facile
reaction with halogens to give intermediate D.17 Finally,
reductive elimination could give CF2X2 and regenerated nickel
Acknowledgment. We wish to thank Drs. R. R. Burch, C. G.
Krespan, P. A. Morken, and B. E. Smart for valuable discussion and
R. E. Smith for technical assistance.
(Scheme 1). The formation of small amounts of higher
homologues X(CF2)nX (n ) 2, 3) is consistent with reaction of
18
halogens with the dimer or trimer of CF2.
Supporting Information Available: Experimental details and
characterization of all products (5 pages). See any current masthead
page for ordering and Internet access instructions.
(
11) Nickel powder is not completely converted into NiI2 upon reaction
with iodine in the solid phase. When a large excess of I2 (20 g) and nickel
powder (3.0 g) was heated in an evacuated sealed glass tube at 180 °C for
1
0 h, the dark powder obtained after removing excess I2 was a mixture of
JA961408S
Ni and NiI2 as determined by powder X-ray diffraction. The X-ray
diffraction pattern of this mixture is almost identical to that of recovered
catalyst.
(15) The thermal stability of transition metal complexes containing
fluorocarbon groups strongly depends on the ligands. The coordinatively
unsaturated complexes are much less stable than coordinatively saturated
ones. For example, (PPh3P)2NiICF3 is a highly thermally stable complex
and melts above 200 °C without decomposition, see: Ashley-Smith, J.;
Green, M.; Stone, F. G. A. J. Chem. Soc. A 1969, 3019. However, CF3-
NiBr is much less stable and only 1% CF3NiBr could be trapped with Et3P
at -78 °C. See: Klabunde, K. J. Angew. Chem., Int. Ed. Engl. 1975, 14,
287. We believe that the intermediates A and/or B are highly reactive.
(16) An alternative mechanism for the formation of complex C is the
reaction of :CF2 with Ni atoms rather than through intermediates A and B.
However, reaction of other :CF2 precursors such as ClCF2CO2K with I2
and catalytic nickel powder at 180 °C gave no CF2I2 in the absence of
solvent and low yield of CF2I2 in DMF as reported, although I2 reacted
with the salt in the presence of equimolar amounts of KI and CuI to give
good yields of CF2I2. See: Su, D. B.; Duan, J. X.; Chen. Q. C. J. Chem.
Soc., Chem. Commun. 1992, 807.
(12) Ni(I) complexes: (a) Heimbach, P. Angew. Chem., Int. Edi. Engl.
1
964, 3, 648. (b) Nilges, M. J.; Barefield, E. K.; Belford, R. L.; Davis, P.
H. J. Am. Chem. Soc. 1977, 99, 755. (c) Tsou, T. T.; Kochi, J. K. J. Am.
Chem. Soc. 1979, 101, 6319. (d) Ratliff, K. S.; Broeker, G. K.; Fanwick,
P. E.; Kubiak, C. P. Angew. Chem. 1990, 102, 405. (e) Morgenstern, D.
A.; Wittrig, R. E.; Fanwick, P. E.; Kubiak, C. P. J. Am. Chem. Soc. 1993,
1
15, 6470. (f) Cai, F. X.; Lepetit, C.; Kermarec, M.; Olivier, D. J. Mol.
Catal. 1987, 43, 93. (g) Sibille, S.; Coulombeix, J.; Perichon, J.; Fuchs, J.
Mortreux, A.; Petit, F. J. Mol. Catal. 1985, 32, 239. (h) Bonneviot, L.;
Olivier, D.; Che. M. J. Mol. Catal. 1983, 21, 415.
(13) Upon heating Ni/NiI2 powder at 185 °C in He for 1, 2, and 3 h, no
changes of X-ray diffraction patterns were observed. A neutron diffraction
investigation also indicated no evidence for the formation of subhalide NiI
in 9% Ni in molten nickel(II) iodide, see: Allen, A. D.; Howe, R. A. J.
Phys.: Condens. Matter 1991, 3, 97. Little reaction of Ni-Cr alloys
(
Hastelloy) with I2 was observed at or below 250 °C, see: Ginzburg, V. I.;
(17) Difluorocarbene is the most electrophilic carbene known and is a
ground state singlet, see: (a) Carter, E. A.; Goddard, W. A., III J. Chem.
Phys. 1988, 88, 1752. (b) Dixon, D. A. J. Phys. Chem. 1986, 90, 54. (c)
Bauschlicher, C. W., Jr.; Schaefer, H. F., III; Bagus, P. S. J. Am. Chem.
Soc. 1977, 99, 7106. The metal complexes with singlet carbene give relative
weak donor/acceptor bonds rather than strong covalent bonds, see: Brothers,
P. J.; Roper, W. R. Chem. ReV. 1988, 88., 1293. Ion beam studies on Ni-C
bond strength have demonstrated that the bond strength is 40 kcal/mol less
Kabakova, O. I. Zashch. Met. 1969, 5, 672.
14) The oxidative additions of hydrocarbon epoxides to nickel complexes
(
in homogeneous solution and to Ni ion beams in the gas phase were
proposed. The oxidative addition product in gas phase decomposes to give
Ni carbene complex, see: (a) De Pasquale, R. J. J. Chem. Soc., Chem.
Commun. 1973, 157. (b) Halle, L. F.; Armentrout, P. B.; Beauchamp, J. L.
Organometallics, 1983, 2, 1829. For carbon-oxygen bond activation of
epoxides by other transition metal complexes, see: (c) Walter, D. Cood.
Chem. ReV. 1987, 79, 135. (d) Backvall, J. E.; Karlsson, O.; Ljunggren, S.
O. Tetrahedron Lett. 1980, 21, 4985. (e) Trost, B. M.; Angle, S. R. J. Am.
Chem. Soc. 1985, 107, 6123. (f) Aye, K.-T.; Gelmini, L.; Payne, N. C.;
Vittal, J. J.; Puddephatt, R. J. J. Am. Chem. Soc. 1990, 112, 2464.
Intermediate B may also be possible in this reaction since the C-O bond
is stronger than the C-C bond in perfluoroethers, see: Molecular Structure
and Energetics; Liebman, J. F., Green berg, A., Eds.; VCH Publishers:
Deerfield Beach, FL, 1986; Vol. 3, Chapter 4.
+
+ 14b
for NiCF2 than NiCH2 . The donor/acceptor bonds have significantly
reduced electrophilicity of carbon center of CF2 in low valent later transition
metal and CF2 complexes, see: (d) Clark, G. R.; Hoskins, S. V.; Jones, T.
C.; Roper, W. R. J. Chem. Soc., Chem. Commun. 1983, 719. (e) Gallop,
M. A.; Roper, W. R. AdV. Organomet. Chem. 1986, 25, 121.
(18) Yang, Z. Y.; Krusic, P. J.; Smart, B. E. J. Am. Chem. Soc. 1995,
117, 5397.
(19) Elsheimer, S.; Dolbier, W. R.; Murla, M. J. Org. Chem. 1984, 49,
205