New synthesis of polyfluorodiols: Nine new derivatives of HOC(2-OH-C6H4)(CF3)2

Article abstract of DOI:10.1016/S0022-1139(02)00203-8

Nine new polyfluorodiols, HOC(2-OH-3-C₆H₃F)(CF₃)₂, HOC(2-OH-5-C₆H₃F)(CF₃)₂, HOC(2-OH-3,5-C₆H₂F₂)(CF₃) ₂, HOC(2-O

Full text of DOI:10.1016/S0022-1139(02)00203-8

Journal of Fluorine Chemistry 118 (2002) 103–106
New synthesis of polyfluorodiols: nine new derivatives
of HOC(2-OH-C H )(CF )
6
4
3 2
*
Benjamin G. Nolan, Shoichi Tsujioka, Steven H. Strauss
Department of Chemistry, Colorado State University, Fort Collins, CO 80523-1872, USA
Received 12 June 2001; received in revised form 1 August 2002; accepted 9 August 2002
Abstract
Nine new polyfluorodiols, HOC(2-OH-3-C H F)(CF ) , HOC(2-OH-5-C H F)(CF ) , HOC(2-OH-3,5-C H F )(CF ) , HOC(2-OH-4,5-
3 2
6
3
3 2
6
3
3 2
6
2
2
C
6
H
2
F
2
)(CF
)(CF
mass spectrometry.
2002 Elsevier Science B.V. All rights reserved.
3
)
2
, HOC(2-OH-4,6-C
6
H
2
F
2
)(CF
3
)
2
, HOC(2-OH-3,4,5-C
6
HF
3
)(CF
3
)
2
, HOC(2-OH-4,5,6-C
6
HF
3
)(CF
3
)
2
, HOC(2-OH-3-t-Bu-5-
Me-C
6
H
2
3
)
2
, HOC(2-OH-3-I-C
6
H
3
)(CF ) , have been synthesized and characterized by GC, NMR spectroscopy, and high-resolution
3 2
#
Keywords: Gas chromatography; Mass spectrometry; Fluoroalkoxide
1
. Introduction
monodentate fluoroalkoxide ligands. For example, the
ꢀ
ꢀ
in aqueous solution [6], while salts of the B(OCH(CF ) )
3 2 4
sodium salt of the B(OC(CF ) C(CF ) O) anion is stable
3
2
3 2
2
Highly fluorinated alcohols and the metal alkoxides that
can be derived from them are of interest for a number of
reasons [1,2]. In general, they are chemically stable and
resistant to oxidation, enabling the fluoroalkoxides to be
used as ligands to stabilize metal atoms in high oxidation
states. In addition, the high electronegativity of fluorinated
substituents reduces the basicity of the oxygen atom, dis-
favoring the formation of extended alkoxy-bridged species.
This leads to higher solubility in low-dielectric solvents and
higher volatility of complexes with these types of ligands.
Furthermore, the steric and electronic properties can be
readily modified, allowing for a wide variety of possible
ligands. One area where they are important is in the design of
metathesis catalysts, where they are used as components of
complexes based on tungsten and molybdenum [3]. As part
of this research, it was found that varying the character of the
fluoroalkoxide ligand had a significant effect on catalyst
activity. Metal fluoroalkoxides have also found use as pre-
cursors for chemical vapor deposition of metal fluorides [4]
and fluorine-doped metal oxides [5].
anion are readily hydrolyzed [7]. Also, the lithium salt of the
ꢀ
B(O C F ) anion, which is also hydrolytically stable, has
2
6 4 2
been found to be thermally stable to 270 8C [8]. This paper
describes the synthesis of nine new fluorinated diols, all
based on the compound HOC(2-OH-C H )(CF ) (see struc-
6
4
3 2
ture). This diol was first synthesized by Gilbert and co-
workers [9], and numerous derivatives have been reported
since that time. However, the list of halogenated derivatives
is short: HOC(2-OH-4-C H Br)(CF ) ; HOC(2-OH-5-
6
3
3 2
C H Br)(CF ) ; HOC(2-OH-3-C H Cl)(CF ) ; HOC(2-
6
3
3 2
6
3
3 2
OH-4-C H Cl)(CF ) ; and HOC(2-OH-4-C H F)(CF )
3 2
6
3
3 2
6
3
[10]. Note that the last compound in this list is the only
reported diol based on HOC(2-OH-C H )(CF ) in which a
6
4
3 2
fluorine atom has been incorporated into the phenyl ring. No
homologous diols in which iodine atoms have been added
have been reported.
Among the many varieties of fluorinated alcohols, one
subset is the fluorinated diols. With two oxygen atoms, these
can act as chelating ligands to form complexes than are
morestable, chemically and thermally, than those with
The nine new diols reported in this paper were chosen as
synthetic targets as an extension of our previous work with
fluoroalkoxyaluminates and borates with formulas (B,
*
Corresponding author. Tel.: þ1-970-491-5104; fax: þ1-970-491-1801.
E-mail address: strauss@lamar.colostate.edu (S.H. Strauss).
0022-1139/02/$ – see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 1 1 3 9 ( 0 2 ) 0 0 2 0 3 - 8

104
B.G. Nolan et al. / Journal of Fluorine Chemistry 118 (2002) 103–106
ꢀ
Al)(ORF)4 [11–14]. These anions were found to be excel-
lent weakly coordinating anions [15], and most were com-
prised of fluoroalkoxides with the general formula
HFA to phenol, but it was subsequently found that a 1:1
molar ratio did not reduce the yield of the fluorodiol.
Therefore, most of the syntheses were carried out with a
1:1 molar ratio. In each case the ꢀ35 8C reaction mixture
was allowed to warm to 24 Æ 1 8C during 30 min and was
stirred until there was no further pressure change (the
pressure was monitored with an electronic manometer
attached to the sealed reaction vessel). In those cases where
HFA remained after the reaction was complete (i.e. no
further pressure drop), it was converted to the hydrate by
bubbling nitrogen through the reaction mixture into a large
volume of water. The HFA-free reaction mixture was opened
to the atmosphere and treated with 50 ml of distilled water,
resulting in the formation of a white precipitate (hydrated
ꢀ
OCR(CF3)2 . As previously mentioned, hydrolysis of the
ꢀ
B–O or Al–O bonds is a serious problem for (B, Al)(ORF)4
anions. Our expectation is that substituting two diolates for
four alkoxides will lead to enhanced stability with respect to
hydrolysis because of the chelate effect. In support of this,
Barthel et al. reported that lithium borates containing two
catecholate or substituted catecholate ligands possessed this
property [8,16].
2
. Experimental
AlCl ). After stirring for 6 h, the organic layer was removed
3
Samples for NMR spectroscopy were solutions in 5-mm
glass tubes. NMR spectra were recorded on a Varian Inova
and the aqueous layer washed twice with 20 ml portions of
fresh 1,2-dichloroethane. The three 1,2-dichloroethane frac-
tions were combined and dried over MgSO for 4 h. After
removing MgSO4 by filtration, 1,2-dichloroethane was
removed using a rotary evaporator. Unless otherwise noted,
the residue was recrystallized and/or sublimed to yield a
white crystalline solid.
1
3
3
00 spectrometer operating at the indicated frequencies: H,
00.1 MHz; 19F, 282.4 MHz. Chemical shifts (d scale) are
4
1
relative to SiMe (d ¼ 0 for H NMR) and CFCl3 (d ¼ 0 for
4
1
9
F 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 5973 N in electron ionization (EI)
mode.
Schlenk, glovebox, and high-vacuum techniques were
employed, with purified argon used when an inert atmo-
sphere was required [17]. All reagents and solvents were
2.1.1. Preparation of HOC(2-OH-C H )(CF )
3 2
6
4
The reagents were AlCl (0.0947 g, 0.692 mmol), phenol
3
(6.50 g, 69.2 mmol), and HFA (5.74 g, 34.6 mmol) in
120 ml 1,2-dichloroethane (clear, colorless solution; stirred
for 2 days; clear, tan final solution). Purification of the
cloudy oil by sublimation at 60 8C yielded a white crystal-
line solid. Yield of HOC(2-OH-C H )ðCF Þ ¼ 6:01 g
reagent grade or better. The compounds AlCl (Aldrich,
3
6
4
3 2
1
9
(
9%), hexafluoroacetone (Aldrich, 97%), 2-iodophenol
Fluorochem, 98%), phenol (Aldrich, >99%), 2-t-butyl-4-
methylphenol (Aldrich, 99%), 2-fluorophenol (Fluorochem,
8%), 4-fluorophenol (Fluorochem, 99%), 2,4-difluorophe-
nol (Alfa Aesar, >98%), 3,4-difluorophenol (Fluorochem,
9%), 3,5-difluorophenol (Fluorochem, 99%), 2,3,4-trifluor-
(67% based on phenol). H NMR (C D /C F ,): d 7.43 (s,
6
6
6 6
1H), 7.20 (d, 1H, J
7:8 Hz), 6.55 (t, 1H, J
HꢀH
¼ 8:1 Hz), 6.80 (t, 1H, J
HꢀH
¼
¼ 7:8 Hz), 6.13 (d, 1H,
HꢀH
19
9
J
¼ 8:1 Hz), 5.66 (s, 1H), and 5.39 (s, 1H). F NMR
6 6 6
HꢀH
6
(C D /C F ): d ꢀ75.98 (s). GC analysis evidenced a purity
9
of ꢁ99%. HRMS: m/z 260.0265. C H F O requires m/z
9
6 6 2
ophenol (Fluorochem, 97%), 3,4,5-trifluorophenol (Fluor-
ochem, 97%), and MgSO (Fisher, anhydrous) were used as
260.0272.
2.1.2. Preparation of HOC(2-OH-3-C H F)(CF )
3 2
4
received. The solvent 1,2-dichloroethane was purified by
distillation under nitrogen from P O (Fisher).
6
3
The reagents were AlCl (0.616 g, 4.62 mmol), 2-fluor-
3
2
5
ophenol (10.3 g, 92.3 mmol), and HFA (15.3 g, 92.3 mmol)
in 135 ml 1,2-dichloroethane (clear, yellow solution; stirred
for 3 weeks; clear, dark yellow final solution). Purification
by sublimation at 60 8C and recrystallization from hexane/
CHCl (4:1 (v:v)). Yield of HOC(2-OH-3-C H F)ðCF Þ ¼
2
.1. Preparation of fluorodiols
The improved synthesis of HOC(2-OH-C H )(CF ) and
the nine new compounds were prepared using a modified
6
4
3 2
3
6
3
3 2
1
version of the synthesis of HOC(2-OH-C H )(CF )
6
9:15 g (36% based on 2-fluorophenol). H NMR (C D /
6 6
4
3 2
reported by Gilbert and co-workers [9]. In all 10 syntheses,
the phenol and AlCl were dissolved in 1,2-dichloroethane.
C F ): d 7.12 (m, 1H), 6.48 (m, 1H), 6.23 (m, 1H), 6.16 (s,
6
6
1
9
3
1H), and 5.53 (s, 1H). F NMR (C D /C F ): d ꢀ75.35 (s,
6
6
6 6
After degassing the solution, hexafluoroacetone (HFA),
which had been measured out in a calibrated bulb using a
6F) and ꢀ137.53 (m, 1F). GC analysis evidenced a purity of
ꢁ99%. HRMS: m/z 278.0166. C H F O requires m/z
9
5 7 2
ꢀ
5
high-vacuum (10 Torr) line, was then added to the frozen
mixture at ꢀ35 8C. CAUTION: HEXAFLUOROACETONE
IS BOTH TOXIC AND TERATOGENIC AND MUST
BE HANDLED CAREFULLY BY TRAINED PERSON-
NEL. The initial pressure of HFAwas usually 600 Æ 20 Torr.
Two syntheses were carried out with a 2:1 molar ratio of
278.0178.
2.1.3. Preparation of HOC(2-OH-5-C H F)(CF )
3 2
6
3
The reagents were AlCl (0.616 g, 4.62 mmol), 4-fluor-
3
ophenol (4.43 g, 39.6 mmol), and HFA (6.57 g, 39.6 mmol)
in 100 ml 1,2-dichloroethane (clear, orange solution; stirred

B.G. Nolan et al. / Journal of Fluorine Chemistry 118 (2002) 103–106
105
1
for 2 days; no color change). Purification by sublimation at
5 8C and recrystallization from hexane/CHCl (5:1 (v:v)).
ophenol). H NMR (C D /C F ): d 6.94 (t, 1H, J
¼
6
6
6
6
HꢀF
6
1
9
5
9:52 Hz), 5.46 (s, 1H), and 4.85 (s, 1H). F NMR (C D /
6
3
Yield of HOC(2-OH-5-C H F)ðCF3Þ ¼ 6:00 g (54% based
C F ): d ꢀ75.75 (m, 6F), ꢀ142.40 (m, 1F), ꢀ153.50 (m,
6 6
6
3
2
1
on 4-fluorophenol). H NMR (C D /C F ): d 7.31 (m, 1H),
1H), and ꢀ154.30 (m, 1F). GC analysis evidenced a purity of
ꢁ99%. HRMS: m/z 313.9978. C H F O requires m/z
6
6
6 6
6
.46 (m, 1H), 5.93 (m, 1H), 5.57 (s, 1H), and 5.48 (s, 1H).
F NMR (C D /C F ): d ꢀ75.51 (s, 6F) and ꢀ120.74 (m,
9
3 9 2
1
9
313.9989.
6
6
6 6
1
F). GC analysis evidenced a purity of ꢁ99%. HRMS: m/z
78.0167. C H F O requires m/z 278.0178.
2
2.1.8. Preparation of HOC(2-OH-4,5,6-C HF )(CF )
3 2
9
5
7
2
6
3
The reagents were AlCl (0.211 g, 1.60 mmol), 3,4,5-
3
2
.1.4. Preparation of HOC(2-OH-3,5-C H F )(CF )
3 2
trifluorophenol (3.25 g, 21.9 mmol), and HFA (6.45 g,
38.9 mmol) in 40 ml 1,2-dichloroethane (clear, yellow solu-
tion; stirred for 3.5 days; clear, dark yellow final solution).
6
2
2
The reagents were AlCl (0.383 g, 2.87 mmol), 2,4-difluor-
3
ophenol (7.47 g, 57.5 mmol), and HFA (6.39 g, 38.5 mmol) in
25 ml 1,2-dichloroethane (clear, dark amber solution; stirred
for 2 days; no color change). Purification by sublimation at
0 8C. Yield of HOC(2-OH-3,5-C H F )ðCF3Þ ¼ 8:04 g
1
Purification by recrystallization from hexane/CHCl (5:1
3
(v:v)). Yield of HOC(2-OH-4,5,6-C HF )ðCF3Þ ¼ 4:02 g
6
3
2
1
7
(59% based on 3,4,5-fluorophenol). H NMR (C D /C F ):
6 6 6 6
6
1
2 2
2
(47% based on 2,4-difluorophenol). H NMR (C D /C F ):
d 7.36 (s, 1H), 5.88 (m, 1H), and 4.00 (s, 1H). 19F NMR
(C D /C F ): d ꢀ75.71 (m, 6F), ꢀ128.64 (m, 1F), ꢀ129.07
6 6 6 6
d 7.04 (m, 1H), 6.18 (m, 1H), 5.75 (s, 1H), and 5.03 (s, 1H). 19F
NMR (C D /C F ): d ꢀ75.43 (s, 6F), ꢀ117.39 (m, 1F), and
6
6
6 6
(m, 1H), and ꢀ169.09 (m, 1F). Based on the absence of other
6
6
6 6
1
9
ꢀ
ꢁ
132.22 (m, 1F). GC/MS analysis evidenced a purity of
99%. HRMS: m/z 296.0078. C H F O requires m/z
F NMR resonances and the signal/noise ratio, the purity of
this compound is ꢁ99%. HRMS: m/z 313.9996. C H F O
9 3 9 2
9
4 8
2
296.0084.
requires m/z 313.9989.
2
.1.5. Preparation of HOC(2-OH-4,5-C H F )(CF )
3 2
2.1.9. Preparation of HOC(2-OH-3-t-Bu-5-Me-
C H )(CF )
The reagents were AlCl (0.152 g, 1.14 mmol), 2-t-butyl-4-
6
2
2
The reagents were AlCl (0.341 g, 2.60 mmol), 3,4-difluor-
3
6
2
3 2
ophenol (4.43 g, 39.6 mmol), and HFA (6.39 g, 38.5 mmol) in
0 ml 1,2-dichloroethane (clear, pink solution; stirred for 3.5
days; clear, dark pink final solution). Purification by recrys-
3
4
methylphenol (4.63 g, 28.3 mmol), and HFA (5.74 g,
34.6 mmol) in 120 ml 1,2-dichloroethane (clear, red solution;
stirred for 50 h; clear, dark red final solution). Purification by
sublimation at 60 8C. Yield of HOC(2-OH-3-t-Bu-5-Me-
C H )ðCF3Þ ¼ 5:94 g (64% based on 2-t-butyl-4-methyl-
tallization from hexane/CHCl (5:1 (v:v)). Yield of HOC(2-
3
OH-4,5-C H F )ðCF3Þ ¼ 7:07 g (62% based on 3,4-difluor-
6
1
2
2
2
ophenol). H NMR (C D /C F ): d 7.16 (m, 1H), 5.90 (s, 1H),
6
6
6
6
6
2
2
19
1
5.85 (m, 1H), and 4.82 (s, 1H). F NMR (C D /C F ): d
phenol). H NMR (C D /C F ): d 8.07 (s, 1H), 7.20 (s,
6
6
6
6
6
6
6 6
ꢀ
75.76 (s, 6F), ꢀ131.33 (m, 1F), and ꢀ145.05 (m, 1F). GC
1H), 7.12 (m, 1H), 3.84 (s, 1H), 2.00 (s, 3H), and 1.42
(s, 9H). 19F NMR (C D /C F ): d ꢀ75.60 (s). GC analysis
analysis evidenced a purity of ꢁ99%. HRMS: m/z 296.0081.
C H F O requires m/z 296.0084.
6
6
6 6
evidenced a purity of ꢁ99%. HRMS: m/z 330.1054.
C14H16F6O2 requires m/z 330.1054.
9
4 8 2
2
.1.6. Preparation of HOC(2-OH-4,6-C H F )(CF )
6 2 2 3 2
The reagents were AlCl3 (0.260 g, 1.94 mmol), 3,5-
difluorophenol (5.05 g, 38.9 mmol), and HFA (6.45 g,
8.9 mmol) in 40 ml 1,2-dichloroethane (clear, tan solution;
stirred for 36 h; white solid suspended in tan final solution).
Purification by sublimation at 55 8C and recrystallization
2.1.10. Preparation of HOC(2-OH-3-C H I)(CF )
3 2
6
3
The reagents were AlCl (0.095 g, 0.71 mmol), 2-iodo-
3
3
phenol (3.11 g, 14.2 mmol), and HFA (2.35 g, 14.2 mmol) in
45 ml 1,2-dichloroethane (clear, purple solution; stirred for
45 h; white precipitate in clear purple final solution). Pur-
ꢀ
3
from hexane/CHCl (4:1 (v:v)). Yield of HOC(2-OH-4,6-
3
ification by fractional vacuum distillation (10 Torr; the
product distilled at 100 8C). Yield of HOC(2-OH-3-
C H F )ðCF Þ ¼ 7:68 g (67% based on 3,5-difluorophe-
6
2
2
3 2
1
1
nol). H NMR (C D /C F ): d 7.71 (s, 1H), 6.09 (m, 1H),
C H I)ðCF Þ ¼ 2:71 g (50% based on 2-iodophenol). H
6
6
6
6
6
3
3 2
5
.92 (m, 1H), and 3.87 (s, 1H). 19F NMR (C6D6/C6F6): d
NMR (C D /C F ): d 7.31 (d, J
HꢀH
¼ 9 Hz, 1H), 7.18 (d,
19
6
6
6
6
ꢀ
75.76 (m, 6F), ꢀ102.81 (m, 1F), and ꢀ105.60 (m, 1F). GC
JHꢀH ¼ 9 Hz, 1H), and 6.05 (t, JHꢀH ¼ 9 Hz, 1H). F NMR
(C D /C F ): d ꢀ75.56 (s). GC analysis evidenced a purity
analysis evidenced a purity of ꢁ99%. HRMS: m/z 296.0078.
C H F O requires m/z 296.0084.
6
6
6 6
of 96%. HRMS: m/z 385.9223. C H F IO requires m/z
9
9
4
8
2
5
6
2
385.9239.
2
.1.7. Preparation of HOC(2-OH-3,4,5-C HF )(CF )
6 3 3 2
The reagents were AlCl (0.217 g, 1.63 mmol), 2,3,4-
3
trifluorophenol (4.81 g, 32.5 mmol), and HFA (5.40 g,
2.5 mmol) in 100 ml 1,2-dichloroethane (clear, yellow
solution; stirred for 53 h; clear, dark yellow final solution).
3. Results and discussion
With the exception of HOC(2-OH-C H )(CF ) , all of the
3
6
4
3 2
Purification by sublimation at 65 8C. Yield of HOC(2-OH-
diols described in the experimental section are new.
The synthetic method is very similar to that developed by
3
,4,5-C HF )ðCF3Þ2 ¼ 7:01 g (69% based on 2,3,4-trifluor-
6
3

106
B.G. Nolan et al. / Journal of Fluorine Chemistry 118 (2002) 103–106
Gilbert and co-workers, which consists of mixing a phenol
with hexafluoroacetone in the presence of a catalyst (5 mol%
based on phenol), using xylene as the solvent. In that work,
three catalysts were studied: AlCl , BF , and p-toluenesul-
distillation. Other than for the preparation of HOC(2-OH-
3-C H F)(CF ) , the reaction times ranged from 30 to 66 h.
The synthesis of HOC(2-OH-3-C H F)(CF ) was unusual
in that even after 3 weeks of stirring, the pressure of
hexafluoroacetone had not decreased enough to account
for the amount of phenol starting material. As a result,
the isolated yield was the lowest observed. This behavior
was reproducible. The reason for the slow reactivity of
2-fluorophenol under these reaction conditions is not known
at this time.
6
2
3 2
6
2
3 2
3
3
fonic acid. It was found that the regiochemistry of the
reaction depended on the nature of the catalyst: using
BF yielded primarily para-substituted phenols, while AlCl
3
3
and p-toluenesulfonic acid generally produced ortho-sub-
stituted products. The desired ligands for this work are the
ortho isomers, as they form a stable six-membered chelate
ring with a central atom such as boron. Of the two catalysts
that give rise to these forms, it was found by Gilbert et al.
References
that AlCl catalysis resulted in a higher yield of substituted
3
phenol, and required less time to do so. Therefore, this
catalyst was chosen to synthesize the new diols in this work.
The amount used was generally 5 mol% based on phenol.
The other modification on the original procedure was the
solvent: 1,2-dichloroethane was used instead of xylene.
Xylene has been shown to react with hexafluoroacetone
[
[
1] C.J. Willis, Coord. Chem. Rev. 88 (1988) 133.
2] A.P. Purdy, C.F. George, in: J.S. Thrasher, S.H. Strauss (Eds.),
Proceedings of the ACS Symposium Series 555 on Inorganic
Fluorine Towards the 21st Century, American Chemical Society
Washington, DC, 1994, p. 405.
[
3] (a) J.H. Freudenberger, R.R. Schrock, M.R. Churchill, A.L.
Rheingold, J.W. Ziller, Organometallics 3 (1984) 1563;
in the presence of AlCl [18], creating the possibility for
3
(
b) R.R. Schrock, R.T. DePue, J. Feldman, C.J. Schaverien, J.C.
Dewan, A.H. Liu, J. Am. Chem. Soc. 110 (1988) 1423;
c) R.R. Schrock, J.S. Murdzek, G.C. Bazan, J. Robbins, M. DiMare,
M. O’Regan, J. Am. Chem. Soc. 112 (1990) 3875;
d) L.K. Johnson, S.C. Virgil, R.H. Grubbs, J. Am. Chem. Soc. 112
1990) 5384.
4] (a) L.J. Lingg, A.D. Berry, A.P. Purdy, K.J. Ewing, Thin Solid Films
09 (1992) 9;
b) J.A. Samuels, W.-C. Chiang, C.-P. Yu, E. Apen, D.C. Smith, D.V.
an undesired side reaction to occur when it is used as the
solvent.
(
Since the goal of this work was to synthesize new ligand
precursors that could be used to make weakly coordinating
anions, new diols were designed with this in mind. One
important criterion for a weakly coordinating anion is a high
degree of charge dispersal; that is, there are no points of high
charge density located on the anion. Considering HOC(2-
OH-C H )(CF ) , the phenoxy oxygen atom is presumably
(
(
[
[
2
(
Baxter, K.G. Caulton, Chem. Mater. 6 (1994) 1684.
5] (a) S. Suh, D.M. Hoffman, Inorg. Chem. 35 (1996) 6164;
b) L. M ˆı inea, S. Suh, S.G. Bott, J.-R. Liu, W.-K. Chu, D.M.
6
4
3 2
(
the point of highest charge density on the ligand. To decrease
this, one or more fluorine atoms were incorporated into the
phenyl ring. Fluorine is highly electronegative, and should
withdraw charge density away from the phenoxy oxygen
atom, thereby enhancing the degree of charge dispersal in
the overall anion. Iodine was also incorporated in one case
HOC(2-OH-3-C H I)(CF ) , to study the effect of halogen
Hoffman, J. Mater. Chem. 9 (1999) 929.
[
[
6] M. Allan, A.F. Janzen, C.J. Willis, Can. J. Chem. 46 (1968) 3671.
7] T.J. Barbarich, S. Tsujioka, unpublished results, Colorado State
University.
[
[
8] J. Barthel, R. Buestrich, E. Carl, H.J. Gores, J. Electrochem. Soc. 143
(
1996) 3572.
9] B.S. Farah, E.E. Gilbert, M. Litt, J.A. Otto, J.P. Sibilia, J. Org. Chem.
0 (1965) 1003.
6
2
3 2
3
substitution. The compound HOC(2-OH-3-t-Bu-5-Me-
C H )(CF ) was designed according to a different strategy:
[
[
[
[
[
[
10] V.I. Dyachenko, A.F. Kolomiets, A.V. Fokin, Izv. Akad. Nauk SSSR,
Ser. Khim. 11 (1988) 2557.
6
2
3 2
11] S.M. Ivanova, B.G. Nolan, Y. Kobayashi, S.M. Miller, O.P.
Anderson, S.H. Strauss, Chem. Eur. J. 7 (2001) 503.
12] T.J. Barbarich, S.M. Miller, O.P. Anderson, S.H. Strauss, J. Mol.
Catal. 128 (1998) 289.
it is hoped that by sterically blocking the phenoxy oxygen
atom, its nucleophilicity will decrease, thereby making the
anion more weakly coordinating. The results of the work
focusing on the relative weakly coordinating abilities of the
anions that correspond to these diols will be reported in a
subsequent paper.
13] J.J. Rockwell, G.M. Kloster, W.J. Dubay, P.A. Grieco, D.F. Shriver,
S.H. Strauss, Inorg. Chem. Acta 263 (1997) 195.
14] T.J. Barbarich, S.T. Handy, S.M. Miller, O.P. Anderson, P.A. Grieco,
S.H. Strauss, Organometallics 15 (1996) 3776.
The isolated yields ranged from 36 to 69%, and the
modified procedure resulted in a 67% yield for HOC(2-
OH-C H )(CF ) , a modest increase from the 62% yield
15] (a) A.J. Lupinetti, S.H. Strauss, Chemtracts–Inorg. Chem. 11 (1998)
565;
(b) S.H. Strauss, Chem. Rev. 93 (1993) 927.
[16] (a) J. Barthel, M. W u¨ hr, R. Buestrich, H.J. Gores, J. Electrochem.
6
4
3 2
reported by Gilbert. Not all impurities were identified, but
the major component was found to be the para-substituted
isomer. Purification was performed by recrystallization from
a mixture of hexane and chloroform or by sublimation under
reduced pressure. The only exception was HOC(2-OH-3-
C H I)(CF ) , which was a liquid and was purified by
Soc. 142 (1995) 2527;
(
b) J. Barthel, R. Buestrich, E. Carl, H.J. Gores, J. Electrochem. Soc.
43 (1996) 3565.
1
[
17] D.F. Shriver, M.A. Drezdzon, The Manipulation of Air-Sensitive
Compounds, 2nd ed., Wiley/Interscience, New York, 1986.
[18] B.S. Farah, E.E. Gilbert, J.P. Sibilia, J. Org. Chem. 30 (1965) 998.
6
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