New or improved syntheses of the polyfluoroalcohols (see abstract)

Article abstract of DOI:10.1016/S0022-1139(01)00471-7

Five new polyfluoroalcohols, HOC(cyclo-C₆H₁₁)₂(CF₃), HO(cyclo-C₆H₁₁)(CF₃)₂, HOC(2,4,6-C₆H₂(CF₃)₃)(CF ₃)₂

Full text of DOI:10.1016/S0022-1139(01)00471-7

Journal of Fluorine Chemistry 112 ꢀ2001) 335±342
New or improved syntheses of the poly¯uoroalcohols
HOCꢀcyclo-C6H11)2ꢀCF3), HOꢀcyclo-C6H11)ꢀCF3)2, and
HOCꢀAr)ꢀCF3)2 ꢀAr ˆ 4-C6H4ꢀt-Bu), 2,4,6-C6H2ꢀCF3)3,
4-Siꢀi-Pr)3-2,6-C6H2ꢀCF3)2, 3,5-C6H3ꢀCH3)2),
and 2-C6H4ꢀCꢀOH)ꢀCF3)2)$
Thomas J. Barbarich, Benjamin G. Nolan, Shoichi Tsujioka,
Susie M. Miller, Oren P. Anderson, Steven H. Strauss*
Department of Chemistry, Colorado State University, Fort Collins, CO 80523 USA
Received 7 February 2001; accepted 8 August 2001
Abstract
Five new poly¯uoroalcohols, HOCꢀcyclo-C6H11)2ꢀCF3), HOꢀcyclo-C6H11)ꢀCF3)2, HOCꢀ2,4,6-C6H2ꢀCF3)3)ꢀCF3)2, HOCꢀ4-Siꢀi-Pr)3-2,6-
C6H2ꢀCF3)2)ꢀCF3)2, and HOCꢀ3,5-C6H3ꢀCH3)2)ꢀCF3)2, have been synthesized, and new procedures with improved yields for two known
poly¯uoroalcohols ꢀHOCꢀcyclo-C6H11)ꢀCF3)2, HOCꢀ4-C6H4ꢀt-Bu))ꢀCF3)2) have been developed. Variable temperature 19F NMR spectra and
the X-ray structure of one of the new poly¯uoroalcohols, HOCꢀ2,4,6-C6H2ꢀCF3)3)ꢀCF3)2, are also reported. In hydrocarbon solution, the OH
hydrogen atom of this compound interacts with one of the ¯uorine atoms of one of the o-CF3 groups in a manner identical to that previously
reported by us for HOCꢀ4-Siꢀi-Pr)3-2,6-C6H2ꢀCF3)2)ꢀCF3)2. In the solid-state, however, the OH hydrogen atom in HOCꢀ2,4,6-C6H2ꢀCF3)3)-
ꢀCF3)2 appears to interact with one ¯uorine atom from each of the two geminal CF3 groups. # 2001 Elsevier Science B.V. All rights reserved.
Keywords: Poly¯uoroalcohols; Geminal; Fluoroalkoxide; Hydrogen bonding
1. Introduction
Tungsten and molybdenum complexes containing poly¯uor-
oalkoxide ligands are important ole®n metathesis catalysts
[3±6]. It was found that varying the steric and electronic
properties of the ¯uoroalkoxide ligands had a signi®cant
effect on catalyst activity [3±6]. Metal ¯uoroalkoxides have
also found use as precursors for chemical vapor deposition
of metal ¯uorides [7,8] and ¯uorine-doped metal oxides
[9,10].
Our work with poly¯uoroalkoxides involves the synthesis
and use of new weakly coordinating anions [11±13] such
as tetrakis- or hexakisꢀpoly¯uoroalkoxy)metallates [14±22].
Examples include AlꢀOCRꢀCF3)2)4 ꢀR ˆ H [14±19], CH3
[14±19], Cy [14,18,19], Ph [14,17±20], 4-C6H4CH3
[14,18,19], 4-C6H4ꢀt-Bu) [14,18,19], CF3 [14,18,19,21]),
AlꢀOCPh2ꢀCF3))4À [14,16,18], and NbꢀOCHꢀCF3)2)6À [22].
We have synthesized a number of new poly¯uoroalcohols
to make these anionic species, and this paper reports on our
progress in this area. Many abbreviations are used in the
following discussion; Table 1 lists these abbreviations, their
corresponding formulas and structures, as well as the yields
of the preparative reactions.
Highly ¯uorinated alcohols and the metal alkoxides that
can be derived from them are of current interest for a number
of reasons [1,2]. In general, poly¯uoroalkoxides are more
chemically stable and more resistant to oxidation than their
hydrocarbon equivalents, enabling ¯uoroalkoxides to be
used as ligands to stabilize metal atoms in high oxidation
states. In addition, the high electronegativities of the poly-
¯uoro substituents reduce the basicity of the oxygen atom,
which inhibits the formation of extended ±M±OꢀR)±M±
OꢀR)± alkoxy-bridged species. This in turn leads to a higher
solubility in low-dielectric solvents and a higher volatility of
complexes with these types of ligands. Furthermore, the
steric and electronic properties can be readily modi®ed by
À
substitution allowing for a wide variety of ORF ligands.
$ This paper is dedicated to Karl Christe, a true pioneer in the field of
fluorine chemistry.
* Corresponding author. Tel.: ‡1-970-491-5104; fax: ‡1-970-491-1801.
E-mail address: strauss@chem.colostate.edu ꢀS.H. Strauss).
0022-1139/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 1 1 3 9 ꢀ 0 1 ) 0 0 4 7 1 - 7

336
T.J. Barbarich et al. / Journal of Fluorine Chemistry 112 -2001) 335±342
Table 1
Abbreviations, formulas, structures, and yields
Abbreviation
HꢀHFCP)
Formula
Structure
Yield ꢀ%)
93
HOꢀcyclo-C6H11)ꢀCF3)2
HꢀHFDPP)
HꢀHFBuPP)
HꢀHFTFPP)
HOCꢀ3,5-C6H3ꢀCH3)2)ꢀCF3)2
52
75
16
HOCꢀ4-C6H4ꢀt-Bu))ꢀCF3)2
HOC-2,4,6-C6H2ꢀꢀCF3)3)ꢀCF3)2
HꢀHFSiPP)
HꢀDCTE)
HOCꢀ4-Siꢀi-Pr)3-2,6-C6H2ꢀCF3)2)ꢀCF3)2
9
HOCꢀcyclo-C6H11)2ꢀCF3)
95
H2ꢀ1,2-HFAB)
HOCꢀ2-C6H4ꢀCꢀOH)ꢀCF3)2))ꢀCF3)2
29
2. Experimental
at the end of a glass ®ber and placed in the cold nitrogen
stream of the low-temperature ꢀLT) 2 u of a Siemens
SMART CCD diffractometer system. The diffraction data
collection and subsequent structural computations were
performed using the crystallographic software supplied by
Siemens [23] or by Sheldrick [24]. Lorentz and polarization
corrections were applied to the data. Details of the crystal-
lographic experiment and subsequent computations are
summarized in Table 2 [25,26]. The structure was solved
by direct methods and was re®ned using full-matrix least-
squares procedures on F2 for all data. Non-hydrogen atoms
were re®ned anisotropically. The H1 hydrogen atom was
located in the difference density map and re®ned. The other
hydrogen atoms were placed in calculated positions. The
structure has a disordered CF3 bonded to C7 which was
modeled isotropically as 12 partial ¯uorine atoms, each with
a site occupancy factor equal to 0.25. Crystallographic data
ꢀexcluding structure factors) for this structure have been
2.1. Physical methods
Samples for NMR spectroscopy were solutions in 5 mm
glass tubes. NMR spectra were recorded on a Varian Inova
300 spectrometer operating at the indicated frequencies: 1H,
300.1 MHz; 19F, 282.4 MHz. Chemical shifts ꢀd scale) are
relative to SiMe4 ꢀd ˆ 0 for 1H NMR) and CFCl3 ꢀd ˆ 0 for
19F NMR) external standards. High-resolution mass spectra
ꢀHRMS) were recorded on a Fisons VG AutoSpec spectro-
meter by liquid secondary ion mass spectrometry ꢀLSIMS).
Gas chromatography/mass spectrometry ꢀGC/MS) was per-
formed using an Agilent 5973N in electron ionization ꢀEI)
mode.
Crystals of HOCꢀ2,4,6-C6H2ꢀCF3)3)ꢀCF3)2 were grown
by vacuum sublimation just above room temperature. A
suitable crystal was embedded in Halocarbon-25-5S grease

T.J. Barbarich et al. / Journal of Fluorine Chemistry 112 -2001) 335±342
337
Table 2
ꢀAldrich, 99%), 1,3,5-trisꢀtri¯uoromethyl)benzene ꢀAldrich,
99%), and hexa¯uoro-2-phenyl-2-propanol ꢀCentral Glass
Ê
Co. Ltd., 99%) were dried over 4 A molecular sieves and
X-ray crystal data collection, solution and refinement details for
HOCꢀ2,4,6-C6H2ꢀꢀCF3)3)ꢀCF3)2
Molecular formula
Formula weight ꢀg molÀ1
Space group
C12H3F15
448.14
C2/c
O
vacuum distilled. The following solvents were puri®ed by
distillation under nitrogen or under vacuum from the indi-
cated drying agent: diethyl ether ꢀNa); benzene-d6 ꢀCam-
bridge, >99% D; Na); toluene-d8 ꢀCambridge, >99% D; Na);
methylcyclohexane-d14 ꢀCambridge, >99% D, Na); dichlor-
omethane-d2 ꢀCambridge, >99% D; P2O5); chloroform-d
ꢀCambridge, >99% D, P2O5); hexa¯uorobenzene ꢀP2O5).
)
Unit cell dimensions
Ê
a ꢀA)
18.851ꢀ2)
8.4164ꢀ9)
Ê
b ꢀA)
Ê
c ꢀA)
17.922ꢀ2)
a ꢀ8)
b ꢀ8)
g ꢀ8)
90.000
92.847ꢀ6)
90.000
Ê 3
2.2.1. Preparation of HOC-3,5-C6H3-CH3)2)-CF3)2
-H-HFDPP))
Unit cell volume ꢀA )
2839.9ꢀ4)
Z
8
2.096
Calculated density ꢀg cmÀ3
)
The compound 5-bromo-m-xylene ꢀ7.93g, 42.8 mmol)
was added as a solution in diethyl ether ꢀ15 ml) to a
suspension of Mg ꢀ1.15 g, 47.1 mmol) in 100 ml ether. This
was stirred at room temperature for 1 h, then at re¯ux for
18 h under Ar purge, after which time the solution turned
brown and cloudy. After degassing the solution, hexa¯uor-
oacetone ꢀ7.1 g, 42.8 mmol), which had been measured out
in a calibrated bulb using a high-vacuum ꢀ10À5 Torr) line,
was added at À1968C. The mixture was warmed to room
temperature and stirred for 18 h. The resulting cloudy yellow
solution was cooled to 08C and an aqueous solution of
sulfuric acid was added. The organic layer was isolated,
and the aqueous layer washed twice with 25 ml portions of
ether. The fractions were combined, washed twice with
30 ml portions of brine, and dried over MgSO4. After
18 h, the suspension was ®ltered, and volatiles removed
to leave an orange oil. This was dissolved in hexane, and
washed with 50 ml distilled water. The aqueous layer was
washed twice with 25 ml portions of hexane. All hexane
fractions were combined, and volatiles removed to yield a
yellow oil. The alcohol was further puri®ed by dissolving the
oil in toluene, and re¯uxing with LiH ꢀ0.50 g, 62.5 mmol
ꢀ1.5 times 5-bromo-m-xylene)) for 18 h. Volatiles were
removed under vacuum, and the yellow solid was kept under
vacuum for 18 h. The lithium salt was protonated with an
aqueous solution of sulfuric acid, and extracted into 50 ml of
hexane. The hexane layer was isolated, and the aqueous
layer washed twice with 25 ml portions of hexane. All
fractions were combined, and volatiles removed to leave
a yellow oil. This was distilled at 358C under vacuum to
yield HOCꢀ3,5-C6H3ꢀCH3)2)ꢀCF3)2 as a clear colorless oil
ꢀ6.11 g, 52% based on 5-bromo-m-xylene). 1H NMR ꢀC6D6/
C6F6) d 7.35 ꢀs, 2H), 6.69 ꢀs, 1H), 2.59 ꢀs, 1H), 1.96 ꢀs, 6H);
19F NMR ꢀC6D6/C6F6) d À75.27 ꢀs). Based on the absence
of other 19F NMR resonances and the signal/noise ratio, the
purity of this compound is ꢀ99%.
Crystal dimensions ꢀmm)
Absorption coefficient ꢀcmÀ1
0.80 Â 0.40 Â 0.40
2.66
)
Fꢀ0 0 0)
y range for data collection ꢀ8)
Limiting indices
1744
2.16±30.00
À1 ꢁ h ꢁ 26
À1 ꢁ k ꢁ 11
À25 ꢁ l ꢁ 25
5003
Reflections collected
Independent corrections
Refinement method
4115
Full-matrix least-squares on F2
4115/1/279
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2sꢀI)]
R indices ꢀall data)
0.871
R1 ˆ 0.0507, wR2 ˆ 0.1257
R1 ˆ 0.0648, wR2 ˆ 0.1416
0.0097ꢀ7)
Extinction coefficient
Ê 3
Largest diffraction peak and hole ꢀA ) 0.465 and À0.542
deposited with the Cambridge Crystallographic Data Center
as supplementary publication numbers.1
2.2. Materials
Schlenk or glovebox techniques were employed, with
puri®ed nitrogen, helium or argon used when an inert atmo-
sphere was required [27]. All reagents and solvents were
reagent grade or better. An aqueous sulfuric acid solution
with a concentration of approximately 1 M was used where
indicated in the experimental details. The term ``brine''
refers to a saturated aqueous solution of sodium chloride.
The compounds LiH ꢀAldrich, 95%), n-BuLi ꢀAldrich,
2.5 M solution in hexane) 4-t-butylmagnesium bromide
ꢀAldrich, 2.0 M solution in diethyl ether), hexa¯uoroacetone
ꢀAldrich, 97%), ethanol ꢀFisher, 90%), hexane ꢀmixture of
isomers, Fisher, 99.9%), hydrogen ꢀꢀ99.9%, Liquid Air
Corp.), and Rh ꢀStrem, 5% on carbon) were used as received.
Magnesium turnings were ground using a mortar and
pestle in a helium-®lled glovebox. Tri-isopropylsilyl tri-
¯uoromethanesulfonate ꢀAldrich, 97%), 5-bromo-m-xylene
ꢀAlfa Aesar, 97%), N,N,N0,N0-tetramethylethylenediamine
ꢀAldrich, 99%), 3,5-bisꢀtri¯uoromethyl)bromobenzene
2.2.2. Preparation of HOC-2,4,6-C6H2-CF3)3)-CF3)2
-H-HFTFPP))
Over the course of 5 min, a 2.5 M hexane solution of n-
BuLi ꢀ3.6 ml, 9.0 mmol) was added dropwise at room
temperature to a stirred solution of 1,3,5-C6H3ꢀCF3)3
ꢀ2.59 g, 9.2 mmol) in diethyl ether ꢀ10 ml) to make a
1 CCDCꢀ#), copies of the data can be obtained, free of charge, on
application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK, fax:
‡44-1223-336033, e-mail: deposit@ccdc.cam.ac.uk.

338
T.J. Barbarich et al. / Journal of Fluorine Chemistry 112 -2001) 335±342
yellow-orange solution. This was stirred for 2 h with no
change in appearance. The solution was degassed, and
hexa¯uoroacetone ꢀ1.43g, 8.59 mmol), which had been
measured out in a calibrated bulb using a high-vacuum
ꢀ10À5 Torr) line, was then added at À1968C. After warming
to room temperature, the reaction mixture was stirred for
18 h. After this time there was still no change in appearance,
and volatiles were removed to leave a yellow solid. Con-
centrated sulfuric acid was added to this, and the resulting
mixture distilled under vacuum through 0 and À1968C cold
traps. HOCꢀ2,4,6-C6H2ꢀCF3)3)ꢀCF3)2 was collected in the
08C trap as clear colorless crystals ꢀ0.662 g, 16% based on
1,3,5-C6H3ꢀCF3)3). 1H NMR ꢀC6D6) d 7.80 ꢀs, 1H), 7.00 ꢀs,
1H), 3.13 ꢀs, 1H); 19F NMR ꢀC6D6, 258C) d À53.05 ꢀm, 3F),
À54.78 ꢀseptet, JFÀF ˆ 15 Hz, 3F), À63.63 ꢀs, 3F), À69.31
ꢀq, JFÀF ˆ 15 Hz, 6F); 19F NMR ꢀCD2Cl2/toluene-d8 1:1
ꢀv:v),À988C)dÀ47.40ꢀt,JFÀF ˆ 127 Hz,1F),À54.17ꢀs,6F),
À55.59 ꢀd, JFÀF ˆ 111 Hz, 2F), À62.89 ꢀs, 3F), À68.64 ꢀm,
3F). Based on the absence of other 19F NMR resonances and
the signal/noise ratio, the purity of this compound is ꢀ99%.
ꢀ0.63ml, 1.58 mmol) was added to a solution of 1 ꢀ0.58 g,
1.57 mmol)in diethyletherꢀ40 ml)atÀ788C. After15 minof
stirring the solution became pink, and was warmed to room
temperature. After 5 h the solution became orange. After
degassing the solution, hexa¯uoroacetone ꢀ0.322 g, 1.94
mmol), which had been measured out in a calibrated bulb
using a high-vacuum ꢀ10À5 Torr) line, was added at À1968C.
As the solution thawed, it became yellow. The reaction
mixture was stirred for 12 h, after which time there was no
change in appearance. After this time, CF3CO2H ꢀ1 ml) was
added. Volatiles were then removed under vacuum, during
which time the solution remained yellow until only a small
amount was left, upon which time thecolor changed to purple.
When almost no liquid was remaining, hexane was added and
the resulting suspension ®ltered. Volatiles were removed from
the ®ltrate under vacuum to yield an oily yellow solid. Several
recrystallizations from 5 to 10 ml hexane at À788C yielded
HOCꢀ4-Siꢀi-Pr)3-2,6-C6H2ꢀCF3)2)ꢀCF3)2 as a slightly yellow
solid ꢀ0.078 g, 9% based on 1). 1H NMR ꢀCDCl3) d 8.01 ꢀs,
1H), 7.87 ꢀs, 1H), 3.70 ꢀs, 1H), 1.37 ꢀseptet, JHÀH ˆ 7 Hz,
3H), 1.01 ꢀd, JHÀH ˆ 7 Hz, 18H); 19F NMR ꢀCDCl3, 258C) d
À53.11 ꢀm, 3F); À54.87 ꢀseptet, JFÀF ˆ 15 Hz, 3F), À70.17
ꢀq of m, JFÀF ˆ 15 Hz, 6F); 19F NMR ꢀmethylcyclohexane-
d14, À968C) d À48.79 ꢀt, JFÀF ˆ 126 Hz), 1F), À54.83ꢀs,
3F), À56.04 ꢀd, JFÀF ˆ 124 Hz, 2F), À70.36 ꢀs, 6F)). GC/MS
analysis evidenced a purity of ꢀ99%.
2.2.3. Preparation of 1-Si-i-Pr)3-3,5-C6H3-CF3)2 -1)
A 2.5 M hexane solution of n-BuLi ꢀ4.8 ml, 12.0 mmol)
was added to a solution of 1-Br-3,5-C6H3ꢀCF3)2 ꢀ3.61 g,
12.3mmol) in diethyl ether ꢀ40 ml) at À788C. After 5 min
the solution became yellow and a white precipitate formed.
The solution was slowly warmed to room temperature, and
after 20 min, it had become a wine red color. After an
additional 60 min, it became brown. The reaction mixture
was frozen at À1968C, and a solution of CF3SO3Siꢀi-Pr)3
ꢀ3.70 g, 12.1 mmol) in ether ꢀ10 ml) was added. As the
reaction thawed the solution became purple, then violet-
black with white and black solids. The volatile material was
removed under vacuum, and hexane was added to the
resulting solid, making a black solution. This was ®ltered,
and volatiles removed from the red ®ltrate under vacuum to
leave a red liquid. Distillation at 488C under vacuum yielded
a clear colorless liquid which contained the desired product
1 and a small amount of CF3SO3Siꢀi-Pr)3 starting material.
This was removed by stirring an ether solution of the liquid
with LiH ꢀ0.038 g, 4.8 mmol) for 15.5 h at room temperature
followed by ®ltration, and then removal of volatiles ꢀether
and HSiꢀi-Pr)3) under vacuum. Hexane was added to the
remaining solid to make a suspension. This was ®ltered, and
volatiles removed from the ®ltrate under vacuum to yield
3,5-ꢀCF3)2C6H3Siꢀi-Pr)3 as a white solid ꢀ2.43g, 53% based
on 1-Br-3,5-C6H3ꢀCF3)2). 1H NMR ꢀCDCl3) d 7.87 ꢀs, 1H),
1.43ꢀseptet, JHÀH ˆ 7 Hz, 3H), 1.06 ꢀd, JHÀH ˆ 7 Hz,
18H); 19F NMR ꢀCDCl3) d À63.33 ꢀs). Based on the absence
of other 19F NMR resonances and the signal/noise ratio, the
purity of this compound is ꢀ99%.
2.2.5. Preparation of HOC-4-C6H4-t-Bu))-CF3)2
-H-HFBuPP))
Hexa¯uoroacetone ꢀ5.58 g, 33.6 mmol), which had been
measured out in a calibrated bulb using a high-vacuum
ꢀ10À5 Torr) line, was added to a degassed solution of 4-t-
butylphenylmagnesium bromide ꢀ16.8 ml of a 2 M diethyl
ethersolution,33.6 mmol)in40 mldiethylether.Afterstirring
the resulting yellow solution for 18 h, volatiles were removed
under vacuum to leave a yellow solid. Sulfuric acid was added
as an aqueous solution, which turned the solid into an oil. This
was isolated, and the aqueous phase was extracted three times
with 20 ml portions of hexane. The organic fractions ꢀoil and
hexane) were combined and dried over MgSO4 followed by
Ê
4 A molecular sieves. After ®ltering this solution, volatiles
were removed from the ®ltrate to yield a solid, which was
Ê
dissolvedinpentaneanddriedagainover4 Amolecularsieves.
After ®ltering this solution, volatiles were removed from the
®ltrate under vacuum to yield HOCꢀ4-C6H4ꢀt-Bu))ꢀCF3)2 as a
white crystalline solid ꢀ7.55 g, 75% based on 4-t-butylphe-
nylmagnesium bromide). 1H NMR ꢀC6D6) d 7.95 ꢀd, JHÀH
ˆ
8:1 Hz, 8H), 7.23ꢀd, JHÀH ˆ 8:7 Hz, 8H); 19F NMR ꢀC6D6) d
À75.52 ꢀs). GC/MS analysis evidenced a purity of ꢀ99%.
HRMS: found 300.0944. C13H14OF6 requires 300.0949.
2.2.6. Preparation of HOC-cyclo-C6H11)-CF3)2
-H-HFCP))
2.2.4. Preparation of HOC-4-Si-i-Pr)3-2,
6-C6H2-CF3)2)-CF3)2 -H-HFSiPP))
The compound HOCꢀC6H5)ꢀCF3)2 ꢀ19.1 g, 78.3mmol)
and rhodium on carbon ꢀ0.167 g 5% Rh/C, 0.081 mmol Rh)
were combined to make a suspension. This mixture was
The synthesis of this compound was described brie¯y in
an earlier report [28]. A 2.5 M hexane solution of n-BuLi

T.J. Barbarich et al. / Journal of Fluorine Chemistry 112 -2001) 335±342
339
stirred at room temperature under 80 psi H2 for 4 days. After
this time there was no change in appearance, and the
suspension was ®ltered through Celite to yield HOCꢀcy-
clo-C6H11)ꢀCF3)2 as a clear colorless liquid ꢀ18.2 g, 93%
based on HOCꢀC6H5)ꢀCF3)2). 1H NMR ꢀC6D6) d 2.12
ꢀs, 1H), 0.86±1.83ꢀ1H); 19F NMR ꢀC6D6/C6F6) d À72.72
ꢀs). GC/MS analysis evidenced a purity of ꢀ99%.
reactions. Alcohols of the type HOCRꢀCF3)2 ꢀR ˆ H, non-
¯uorinated alkyl, aryl) may be prepared by addition of
hexa¯uoroacetone ꢀHFA) to the appropriate Grignard or
organolithium reagent [1] followed by protonation:
‡
H
MR ‡ ꢂCF3†2CO ! MOCRꢂCF3†2!HOCRꢂCF3†
2
where, M ˆ Li, MgX ꢀX ˆ Cl, Br, I)
2.2.7. Preparation of HOC-cyclo-C6H11)2-CF3)
-H-DCTE))
Using the appropriate Grignard reagents, this method was
used to synthesize the new alcohol HꢀHFDPP), and to
improve the yield of the previously reported compound
HꢀHFBuPP). The reported synthesis for the latter com-
pound, for which the puri®ed yield was only 43%, consisted
of electrophilic aromatic substitution of HFA on t-butylben-
zene catalyzed by AlCl3 [30]. Using the Grignard reagent 4-
t-butylphenylmagnesium bromide, our yield of puri®ed
alcohol was increased to 75%.
The compound HOCꢀC6H5)2ꢀCF3) ꢀ2.00 g, 7.93mmol)
was dissolved in 25 ml of ethanol, and Rh ꢀ0.2 g 5% Rh/C,
0.097 mmol Rh) was added to make a suspension. This
mixture was stirred at room temperature under 80 psi H2 for
4 days. After this time there was no change in appearance,
and the suspension was ®ltered through Celite and ethanol
removed under vacuum to yield HOC-cyclo-C6H11)2ꢀCF3)
as a clear colorless liquid ꢀ1.98 g, 95% based on
The yield of the new compound HꢀHFDPP) was not as
high as for HꢀHFBuPP), which was most likely due to the
longer puri®cation process. The crude product ꢀorange oil)
was ®rst dissolved in hexane and washed with water to
remove any hexa¯uoroacetone trihydrate. Deprotonation by
LiH was then performed to facilitate the removal of diethyl
ether and other volatile impurities under vacuum. These
impurities proved to be dif®cult to separate from the alcohol
by distillation or column chromatography. Reprotonation
with sulfuric acid followed by vacuum distillation resulted in
a 52% yield of puri®ed HꢀHFDPP).
The new alcohols HꢀHFSiPP) and HꢀHFTFPP) were
prepared in a similar manner to HꢀHFBuPP) and HꢀHFDPP),
but the appropriate organolithium reagents were used instead
of the corresponding Grignard reagents. For HꢀHFSiPP),
the silyl arene ꢀ1) was lithiated with n-BuLi and then treated
with HFA. Puri®cation by successive recrystallizations from
hexane at À788C resulted in a yield of 9%. To make
HꢀHFTFPP), 1,3,5-trisꢀtri¯uoromethyl)benzene was lithiated
with n-BuLi and then treated with HFA. Distillation of
the crude product resulted in puri®ed HꢀHFTFPP) in a yield
of 16%.
The known compound HꢀHFCP) and the new ¯uoroalco-
hol HꢀDCTE) were synthesized by catalytic hydrogenation
of HOCꢀC6H5)ꢀCF3)2 and HOCꢀC6H5)2ꢀCF3), respectively,
over Rh/C. Alcohol/Rh ratios of 966:1 and 326:1 were used
to prepare HꢀHFCP) and HꢀDCTE), respectively. Higher
ratios were found to work as well, but reaction times were
longer. Overall, this method was very ef®cient: the only
puri®cation necessary was ®ltration to remove Rh/C and
removal of ethanol in the case of HꢀDCTE). Isolated yields
were very high, 95% for HꢀDCTE) and 93% for HꢀHFCP).
The previously reported method for synthesizing HꢀHFCP)
consisted of a free radical-initiated reaction between
cyclohexane and HFA [31], resulting in an isolated yield
of only 69%.
1
HOCꢀC6H5)2ꢀCF3)). H NMR ꢀC6D6/C6F6) d 1.55 ꢀs, 1H),
0.99±1.86 ꢀ22H); 19F NMR ꢀC6D6/C6F6) d À68.97 ꢀs). GC/
MS analysis evidenced a purity of ꢀ99%.
2.2.8. Preparation of HOC-2-C6H4-C-OH)-CF3)2))-CF3)2
-H2-1,2-HFAB))
The compound Li2ꢀOCꢀC6H4)ꢀCF3)2) was generated fol-
lowing the procedure of Barbarich et al. [28]. A 2.5 M
hexane solution of n-BuLi ꢀ34.8 ml, 86.9 mmol) and
TMEDA ꢀ1.01 g, 8.69 mmol) were dissolved in 50 ml
diethyl ether and stirred for 30 min to make a cloudy white
mixture. After degassing, the solution and cooling to 08C,
HOCꢀC6H5)ꢀCF3)2 ꢀ9.634 g, 39.5 mmol) was added dropwise
over 15 min as a solution in ether ꢀ15 ml). This mixture was
stirred at 08C for 30 mm, then at room temperature for 20 h.
After this time, it was cloudy and yellow. The mixture was
cooled to 08C and hexa¯uoroacetone ꢀ6.56 g, 39.5 mmol),
which had been measured out in a calibrated bulb using a
high-vacuum ꢀ10À5 Torr) line, was added. The mixture was
warmed to room temperature, and stirred for 2 days. After this
time it was still cloudy and yellow, and an aqueous solution of
sulfuric acid was added. The yellow organic layer was iso-
lated, and the aqueous layer washed twicewith 20 ml portions
of ether. The organic fractions were combined, and washed
twice with brine. Volatiles were then removed to leave a
yellow oil. This was recrystallized from hexane/CHCl3 ꢀ20:1
ꢀv:v)) to yield HOCꢀ2-C6H4ꢀCꢀOH)ꢀCF3)2))ꢀCF3)2 as a
slightly yellow solid ꢀ4.65 g, 29% based on HOCꢀC6H5)-
ꢀCF3)2). 1H NMR ꢀC6D6) d 7.69 ꢀm, 2H), 6.72 ꢀm, 2H), 5.50
ꢀs, 2H); 19F NMR ꢀC6D6/C6F6) d À72.81 ꢀs). GC/GS analysis
evidenced a purity of ꢀ99%.
3. Results and discussion
3.1. Synthesis of new polyfluoroa!cohols
The synthesis of H2ꢀ1,2-HFAB) completes the series of
bisꢀ2-hydroxyhexa¯uoro-2-propyl)benzene derivatives. The
1,3- and 1,4- varieties have been reported, and were made by
Table 1 lists the compounds discussed below with their
abbreviations, structures, and yields of the preparative

340
T.J. Barbarich et al. / Journal of Fluorine Chemistry 112 -2001) 335±342
Table 3
AlCl3-catalyzed electrophilic aromatic substitution of ben-
zene with HFA [32]. The 1,2-isomer was not formed in this
reaction, presumably due to steric hindrance considerations.
The ®rst attempt to synthesize a 1,2-diol consisted of the
reaction of HꢀHFBuPP) with HFA in the presence of AlCl3.
It was hoped that the t-butyl group would favor substitution
of HFA in the ortho-position by ꢀa) blocking the para-site,
and ꢀb) effectively blocking the meta-site by steric hin-
drance. However, no reaction was observed. This could
be due to excessive steric hindrance at both the ortho-
and meta-sites. The successful synthesis of H2ꢀ1,2-HFAB)
resulted from the reaction of the dilithiated LiOCꢀ2-
C6H4Li)ꢀCF3)2 with HFA in diethyl ether. Adding two
equivalents of n-BuLi to HOCꢀC6H5)ꢀCF3)2 in the presence
of TMEDA leads to an ortho-lithiated dianion ꢀafter depro-
tonation of the alcohol) [29]. The carbanion then reacts with
HFA, overcoming the steric hindrance barrier to form
Li2ꢀ1,2-HFAB). Protonation with H2SO4 followed by
recrystallization yielded H2ꢀ1,2-HFAB) in 29% yield. This
diol may be useful as a bidentate ligand: both oxygen atoms
are weak donors, but can form stable complexes with a
central atom by virtue of its chelating nature.
Ê
Selected interatomic distances ꢀA) and angles ꢀ8) for HOCꢀ2,4,6-
C6H2ꢀꢀCF3)3)ꢀCF3)2
O±H1
O±C1
0.76ꢀ4)
1.407ꢀ2)
1.566ꢀ3)
C1±C4±C5
C1±C4±C9
C5±C4±C9
118.5ꢀ2)
125.4ꢀ2)
115.7ꢀ2)
C1±C2
)
C1±C31.5C745±ꢀC35±C6
C1±C4
C4±C5
120.9ꢀ2)
1.553ꢀ2)
1.442ꢀ2)
1.391ꢀ2)
1.383ꢀ3)
1.375ꢀ3)
1.393ꢀ2)
1.413ꢀ2)
1.528ꢀ3)
1.522ꢀ2)
C5±C6±C7
C6±C7±C8
C7±C8±C9
C8±C9±C4
C4±C5±C10
C6±C5±C10
C4±C9±C11
C8±C9±C11
120.7ꢀ2)
119.2ꢀ2)
122.8ꢀ1)
121.2ꢀ2)
126.3ꢀ2)
112.5ꢀ2)
126.4ꢀ2)
112.1ꢀ2)
C5±C6
C6±C7
C7±C8
C8±C9
C9±C4
C5±C10
C9±C11
H1±O±C1
O±C1±C4
O±C1±C2
O±Cꢀ21)±C3110.3
C2±C1±C3111.7ꢀ2)
C2±C1±C4
C3±C1±C4
109.3ꢀ2)
104.54ꢀ14)
101.5ꢀ2)
113.1ꢀ2)
114.6ꢀ2)
Ê
distance of 0.76ꢀ4) A is considerably shorter than the value
3.2. Structure and 19F NMR spectra of H-HFTFPP)
of 0.967 A typically found for alcohols by neutron diffrac-
tion [33,34]. For this reason, inter- and intramolecular
contacts involving H1 were normalized by ®xing the O±
Ê
The structure of this compound, shown in Fig. 1, consists
of discrete HOC-2,4,6-C6H2ꢀꢀCF3)3)ꢀCF3)2 molecules.
Selected interatomic bond distances and angles are listed
in Table 3. The hydrogen atoms were placed in calculated
positions except for the hydroxyl group proton ꢀH1), which
was located in the Fourier maps and re®ned. The O±H1
Ê
H1 distance at 0.967 A along the re®ned H1 vector, a
procedure commonly used when evaluating X-ray-derived
results involving hydrogen atoms [33±37]. The p-CF3 is
disordered and was modeled isotropically as 12 partial
¯uorine atoms, each with a site occupancy factor equal to
Fig. 1. Drawing of HOCꢀ2,4,6-C6H2ꢀCF3)3)ꢀCF3)2 with 50% probability thermal ellipsoids. The disordered CF3 group bonded to C7 was modeled
isotropically as 12 partial fluorine atoms, each with a site occupancy factor equal to 0.25 ꢀonly three of the partial fluorine atoms are shown). The two
hydrogen atoms bonded to C6 ꢀH2) and C8 ꢀH3) have been omitted for clarity.

T.J. Barbarich et al. / Journal of Fluorine Chemistry 112 -2001) 335±342
341
Table 4
Many chemists and biochemists believe that the formation
of intermolecular H Á Á Á FC and NÀH Á Á Á FC hydrogen bonds
may be important in the binding of ¯uorinated substrates to
enzyme active sites [39±44]. Nevertheless, bona®de exam-
ples of OÀH Á Á Á FC and NÀH Á Á Á FC hydrogen bonding in
the absence of stronger OÀH Á Á Á X and NÀH Á Á Á X hydrogen
bonds ꢀX ˆ O, N) are rare. In a 1997 study, Dunitz and
Taylor concluded that ``organic ¯uorine hardly ever accepts
hydrogen bonds'' [45]. In a 1996 study, Howard et al. found
only 12 compounds in the CSD containing OH Á Á Á FC inter-
Ê
Interatomic distances ꢀA) and angles ꢀ8) involving the hydroxyl group in
HOCꢀ2,4,6 C6H2ꢀꢀCF3)3)ꢀCF3)2
a
OÀH1
0.76ꢀ4)
2.37ꢀ4)
2.17ꢀ4)
[0.967]
[2.35]
[2.11]
H1 Á Á Á F3
H1 Á Á Á H4
.0O) ÀH1 Á Á Á F396.6 ꢀ3 [91.7]
OÀH1 Á Á Á F4
O Á Á Á F32.570ꢀ2)
O Á Á Á F4
110.3ꢀ3.3)
2.535ꢀ2)
[104.8]
a The values in square brackets were calculated after the O±H bond was
Ê
extended to 0.967 A along the X-ray derived bond vector.
Ê
actions of 2.35 A or less ꢀcompounds containing CF2 or CF3
groups were excluded from their study) [46]. In a 1994 study,
Shimoni and Glusker found that the mean XH Á Á Á FC dis-
tance ꢀX ˆ N, O) for all relevant compounds in the CSD was
0.25. The aromatic ring is distorted from planarity, a feature
commonly observed in the 2,4,6-trisꢀtri¯uoromethyl)phenyl
substituent [38].
Ê
2.5 A whether the acceptor ¯uorine atom was part of a CF3
Ê
group or not ꢀthe median distance was also 2.5 A) [47].
There are two relatively short intramolecular OH Á Á Á FC
contacts involving one ¯uorine atom from each of the two
geminal CF3 groups. Relevant bond distances and angles are
listed in Table 4. The H1 Á Á Á F3and H1 Á Á Á F4 distances are
In dilute hydrocarbon solution at À968C, the 19F NMR
spectrum of HOCꢀ4-Siꢀi-Pr)3-2,6-C6H2ꢀCF3)2)ꢀCF3)2)
revealed that one of the o-CF3 groups experienced slow
rotation [28]. The single resonance for this group at 258C
decoalesced into a doublet ꢀintensity ˆ 2) and a triplet
ꢀintensity ˆ 1) at À968C, and this was attributed to intra-
molecular OH Á Á Á FC hydrogen bonding involving one of the
¯uorine atoms of this CF3 group. It was also found that the
average JC±F value for the doublet and triplet was equal to
the JC±F value for this CF3 group at 258C and that
JCÀF ꢂdoublet† > JCÀF ꢂtriplet†.
Ê
2.35 and 2.11 A, respectively, and the OÀH1 Á Á Á F3and
OÀH1 Á Á Á F3angles are 91.7 and 104.8 8, respectively.
The distances are certainly short enough for the OH Á Á Á F
interactions to be considered as weak hydrogen bonds. In a
previous paper [28], we reported a pair of intermolecular
OH Á Á Á FC contacts in the structure of HOCꢀ4-Siꢀi-Pr)3-2,6-
C6H2ꢀCF3)2)ꢀCF3)2), which exists in the solid state as a
centrosymmetric dimer apparently held together by the pair
of symmetry related OH Á Á Á FC contacts. In that structure,
the distance H Á Á Á F and OÀH Á Á Á F angle were found to be
We now report that HOCꢀ2,4,6-C6H2ꢀꢀCF3)3)ꢀCF3)2
behaves similarly in dilute hydrocarbon solution. The
low-temperature ꢀÀ988C) 19F NMR spectrum of this com-
pound dissolved in a 1:1 ꢀv:v) mixture of toluene-d8 and
Ê
2.01 A and 1718.
Fig. 2. A portion of the 19F NMR spectrum of HOCꢀ2,4,6-C6H2ꢀCF3)3)ꢀCF3)2 at À988C ꢀ1:1 toluene-d8/CD2Cl2). The singlet ꢀ‡) corresponds to the o-CF3
group distal to the hydroxyl group, and the doublet ꢀÃ) and triplet ꢀÃ) correspond to the o-CF3 group proximal to the hydroxyl group ꢀinvolved in
ꢂO†H Á Á Á FꢂC† hydrogen bonding). The single resonance for the geminal CF3 groups is not shown ꢀd À54.17).

342
T.J. Barbarich et al. / Journal of Fluorine Chemistry 112 -2001) 335±342
[16] S.H. Strauss, Fluorocarboranes and Fluoroalkoxyborates and Alumi-
nates, 218th ACS National Meeting, New Orleans, LA, August 1999
ꢀabstract FLUO 1).
dichloromethane-d2 is shown in Fig. 2. The relative d
values of the doublet and the triplet, and the JF±F value,
are nearly the same as those reported for HOCꢀ4-Siꢀi-Pr)3-
2,6-C6H2ꢀCF3)2)ꢀCF3)2). Therefore, we conclude that
HOCꢀ2,4,6-C6H2ꢀꢀCF3)3)ꢀCF3)2, like HOCꢀ4-Siꢀi-Pr)3-2,6-
C6H2ꢀCF3)2)ꢀCF3)2), exhibits intramolecular OH Á Á Á FC
hydrogen bonding involving one of the ¯uorine atoms of
one of the o-CF3 groups.
[17] T.J. Barbarich, S.M. Miller, O.P. Anderson, S.H. Strauss, J. Mol.
Catal. 128 ꢀ1998) 289.
[18] B.G. Nolan, T.J. Barbarich, S. Tsujioka, S.M. Ivanova, B.P. Fauber,
J.C Brady, C.E. Kriley, S.M. Miller, O.P Anderson, A. Bell, S.H.
Strauss, in preparation.
[19] T.J. Barbarich, B.G. Nolan, S.M. Ivanova, S. Tsujioka, S.M. Miller,
O.P. Anderson, S.H. Strauss, in preparation.
[20] T.J. Barbarich, S.T. Handy, S.M. Miller, O.P. Anderson, P.A. Grieco,
S.H. Strauss, Organometallics 15 ꢀ1996) 3776.
[21] T.J. Barbarich, Ph.D. Dissertation, Colorado State University, 1997.
[22] J.J. Rockwell, G.M. Kioster, W.J. Dubay, P.A. Grieco, D.F. Slrriver,
S.H. Strauss, Inorg. Chim. Acta 263ꢀ1997) 195.
Acknowledgements
This research was supported by grants from the NSF
ꢀCHE-9628769 and CHE-9818263) and the NIH ꢀshared
instrument grant 1 Sb RR010547). We thank Central Glass
Co. Ltd., for a gift of HOCꢀC6H5)ꢀCF3)2. TJB thanks the US
Department of Education for fellowship support under the
Graduate Assistance in Areas of National Need Program
ꢀGrant no. P200A10210).
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