Synthesis and structure of novel perfluorinated iodinanes

Article abstract of DOI:10.1016/S0022-2860(00)00502-0

Several novel iodinanes have been prepared and structurally characterized. The structures of all are heavily influenced by secondary bonding involving the iodine(III) center and oxygen or chlorine. The iodonium salt, [Ph(CF₃CH₂)I]CF₃SO₂NSO₂CF₃, has a chain structure with the anion in a transoid conformation, while the diphenyl derivative, [Ph₂I]CF₃SO₂NSO₂CF₃, forms a dimeric structure which stabilizes a cisoid conformation of the anion. In comparison to the known compound, PhICl₂, which has a simple chain structure, perfluoroalkyliodinedichlorides CF₃CH₂ICl₂ and CHF₂(CF₂)₅CH₂ICl₂, have more complicated structures in which weak interactions between chains, coupled with aggregation of perfluoro groups, results in the formation of layers. The dicarboxylate, CF₃CH₂I(O₂CCF₃)₂ has a T-shaped coordination similar to other derivatives, but forms a tetrameric array of molecules not previously seen. (C) 2000 Elsevier Science B.V.

Full text of DOI:10.1016/S0022-2860(00)00502-0

Journal of Molecular Structure 550–551 (2000) 337–348
www.elsevier.nl/locate/molstruc
Synthesis and structure of novel perfluorinated iodinanesଝ
1
*
V. Montanari, D.D. DesMarteau , W.T. Pennington
Department of Chemistry, H.L. Hunter Chemistry Laboratory, Clemson University, Clemson, SC 29634-1905, USA
Received 30 August 1999; accepted 1 December 1999
Abstract
Several novel iodinanes have been prepared and structurally characterized. The structures of all are heavily influenced by
secondary bonding involving the iodine(III) center and oxygen or chlorine. The iodonium salt, [Ph(CF3CH2)I]CF3SO2NSO2CF3,
has a chain structure with the anion in a transoid conformation, while the diphenyl derivative, [Ph2I]CF3SO2NSO2CF3, forms a
dimeric structure which stabilizes a cisoid conformation of the anion. In comparison to the known compound, PhICl2, which has
a simple chain structure, perfluoroalkyliodinedichlorides CF3CH2ICl2 and CHF2(CF2)5CH2ICl2, have more complicated struc-
tures in which weak interactions between chains, coupled with aggregation of perfluoro groups, results in the formation of
layers. The dicarboxylate, CF3CH2I(O2CCF3)2 has a T-shaped coordination similar to other derivatives, but forms a tetrameric
array of molecules not previously seen. ᭧ 2000 Elsevier Science B.V. All rights reserved.
Keywords: Perfluoroalkyliodinedichlorides; Perfluorinated iodinanes; Dimer
1. Introduction
preparation of numerous other iodine (III) compounds
[1,2]. We have recently shown that the novel iodo-
Iodinanes, iodine(III) containing compounds such
as iodonium salts (I) or organic iodosyls (RIO or RIX2
derivatives, II), are valuable reagents for a wide
variety of synthetic applications. Diaryliodonium
salts are efficient arylating agents and have been
used in industry in lithography and as polymerization
initiators [1,2]. Many iodoaryl halides and [bis(acyl-
oxy)iodo]arenes are commercially available; the
former are useful halogenating or oxidizing reagents
of organic substrates and the latter are effective oxidi-
zers and radical initiators and are heavily used for the
nium salt, [Ph(CF3CH2)I]CF3SO2NSO2CF3 is a
powerful alkylating agent which can be utilized in
water, and we have used it for fluoroalkylation of
amino acids and peptides [3]. The CF3CH2– group
and derivatives have also been used to form stable
perfluoroalkyliodine dichlorides, and we have found
them to be very effective chlorinating reagents [4].
Secondary bonding is observed in most iodanes, and
we have found that perfluorinated materials often
have interesting and unusual structures [5–7]. For
this reason, we are reporting the synthesis and struc-
tural characterization of several iodonium salts of
perfluorinated sulfonimide anions and of related
perfluoroalkyliodine dichloride derivatives. Detailed
structural studies may provide insight into the varied
reactivity of these compounds and the unexpected
lack of reactivity of [Ph(CF3CH2)I]CF3SO2NSO2CF3
with water (Scheme 1).
ଝ
Dedicated to Professor James R. Durig on the occasion of his
65th birthday.
* Corresponding author. Tel.: ϩ1-864-656-4200; fax: ϩ1-864-
656-6613.
1
Tel: ϩ1-864-656-4705; fax: ϩ1-864-656-0627.
E-mail addresses: billp@clemson.edu (W.T. Pennington),
fluorin@clemson.edu (D.D. DesMarteau).
0022-2860/00/$ - see front matter ᭧ 2000 Elsevier Science B.V. All rights reserved.
PII: S0022-2860(00)00502-0

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V. Montanari et al. / Journal of Molecular Structure 550–551 (2000) 337–348
glass frit, air-dried, then freeze-dried at 5 ×
10Ϫ4 mm Hg: The resulting 1 (30.7 g, 89%) was
recrystallized from dichloromethane (4 ml/g) at
Ϫ20ЊC. The colorless crystals of 1 (27.3 g, 90%
recovery) had m.p. 77–79ЊC (dec 105–120ЊC by
TGA, 5ЊC/min). Crystals are also obtained from
CFC113 in which 1 is sparingly soluble.
Scheme 1.
2.2.2. Preparation of diphenyliodonium (N,N0-bis-
2. Experimental
trifluoromethylsulfonyl) imide (2)
Into
a
solution of (CF3SO2)2NH (5.53 g,
2.1. General
19.7 mmol) in dichloromethane (25 ml), PhI(O-
COCF3)2 (8.47 g, 19.7 mmol) was added in one
portion at 20ЊC. An endothermic reaction ensued,
All starting materials used in this work are commer-
cially available. N,N0-bis-trifluoromethanesulfonyl
imide, (CF3SO2)2NH, is available from 3M Co. as
producing
a
clear yellow solution. Benzene
(2.00 ml, 22.3 mmol) was then added in one portion,
and the reaction mixture was stirred at 20ЊC for 42 h.
The volatiles were evaporated to give a thick reddish
syrup. On addition of ice, this syrup consisting of 2
and residual trifluoroacetic acid solidified. Water
(50 ml) was added and the suspension was stirred
until 2 was finely divided. The resulting off-white
powder was collected on a glass frit, air-dried, then
dried in vacuum over P2O5. The product (9.52 g, 90%)
was pure by NMR analysis. Crystals were obtained
from dichloromethane at Ϫ20ЊC, m.p. 65–66ЊC.
௣
the lithium salt (HQ 115 ), which is an electrolyte
for lithium-ion secondary batteries. The acid was
obtained by vacuum sublimation from 96% H2SO4
according to DesMarteau and Witz [8]. For the
preparation of dichloroiodo compounds 3–5, iodo-
benzene (Aldrich), CF3CH2I (PCR, Inc.) and
H(CF2)6CH2I (PCR, Inc.) were used as received.
Silver trifluoroacetate for the preparation of
CF3CH2I(OCOCF3)2 (6) from 4 was prepared from
equimolar amounts of trifluoroacetic acid and silver
carbonate in deionized water, then dried in vacuum at
100ЊC. (CF3SO2)2NH and CF3CH2I(OCOCF3)2 are
hygroscopic and were handled in a glove box under
dry nitrogen.
2.2.3. Preparation of dichloroiodobenzene (3)
CF3CH2ICl2 (4) (2.81 g, 10 mmol) was added under
nitrogen into an ice-cold solution of iodobenzene
(1.10 ml, 10 mmol) in chloroform (25 ml). The reac-
tion was allowed to return to 22ЊC overnight. After
14 h the yellow precipitate of PhICl2 (3) was rapidly
collected on a glass frit and dried in vacuum. 3 is
much less stable to moisture than 4 and should not
be exposed to the atmosphere for long times. Yield
2.23 g (81%). Recrystallization was not necessary.
2.2. Synthesis of compounds 1–6
2.2.1. Preparation of (1,1,1-trifluoroethyl) phenyl
iodonium (N,N0-bis-trifluoromethylsulfonyl) imide (1)
Under a dry nitrogen atmosphere, CF3CH2I(O-
COCF3)2 (6) (26.50 g, 60.8 mmol) was added in one
portion into a suspension of (CF3SO2)2NH (18.00 g,
64 mmol) in dry CFC 113 (50 ml) (moisture must not
be admitted into the reaction until workup). Into the
resulting solution, dry benzene (6.2 ml, 70 mmol) was
added dropwise under ice-water cooling. The reaction
was allowed to return to 20ЊC over 18 h. The volatiles
were evaporated and the brown residue was pumped
at 5 × 10Ϫ4 mmHg for 2 h. Shaking with ice/water
(ca. 100 ml) produced a white powder (the color is
due to residual CF3COOH from the reaction, which
is extracted by water). This powder was collected on a
2.2.4. Preparation of dichloroiodo-2,2,2-
trifluoroethane (4)
A 100 ml three-necked glass bulb containing 1-
iodo-2,2,2-trifluoroethane (5.0 ml, 51.2 mmol) was
fitted with a nitrogen inlet and connected via FEP
(fluorinated ethylene propylene) tubes to a chlorine
cylinder and to a trap containing aqueous NaOH.
The flask was cooled in ice, and chlorine was passed
through the system at such a rate as to maintain slow
bubbling through the trap (until the end of the reaction

V. Montanari et al. / Journal of Molecular Structure 550–551 (2000) 337–348
339
Scheme 2.
essentially all the chlorine is absorbed). After ca.
2.2.5. Preparation of dichloroiodo-1H,1H,7H-
perfluoroheptane (5)
Similar to 4, 5 was prepared in 70% yield. Crystals
from chloroform at Ϫ20ЊC; m.p. 122–123ЊC.
10 min the product began to form as a yellow solid.
After 2 h the chlorine flow was stopped and the
system was slowly flushed with nitrogen for 30 min.
After standing under a hood in a beaker for 30 min to
evaporate any unreacted 1-iodo-2,2,2-trifluoroethane,
product 4 was obtained as bright yellow leaflets,
greenish in transmitted light, m.p. 111ЊC. Yield
12.18 g (85%). Crystals were obtained by allowing 4
to sublime slowly in the cold inside a sealed, evacu-
ated tube.
2.2.6. Preparation of (bis-trifluoroacetoxy)iodo-2,2,2-
trifluoroethane (6)
Into a suspension of silver trifluoroacetate (4.73 g,
21.5 mmol) in CFC 113 (50 ml) was added 4 (2.81 g,
10 mmol) in one portion at 20ЊC. The suspension
turned from yellow to white in 3 h. The suspension

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V. Montanari et al. / Journal of Molecular Structure 550–551 (2000) 337–348
Table 1
Crystallographic details
(a) For compounds 1–3
1
2
3
Formula
C10H7NO4F9S2I
567.19
158
C14H10NO4F6S2I
561.25
293
C6H5Cl2I
274.90
153
Formula weight (amu)
Temperature (K)
Crystal color; habit
Crystal size (mm)
Crystal system
Space group
Colorless; parallelepiped
0:21 × 0:27 × 0:36
Monoclinic
P21/n (No. 14)
8.467(3)
19.514(5)
10.824(4)
90
95.28(3)
90
1780.9(8)
4
Colorless; plate
0:10 × 0:30 × 0:45
Orthorhombic
Pbca (No. 61)
19.036(4)
22.720(3)
8.917(2)
90
90
90
3856.6(9)
8
1.93
Yellow; needle
0:08 × 0:10 × 0:28
Monoclinic
P21/n (No. 14)
12.150(3)
5.352(1)
12.437(4)
90
102.05(2)
90
790.9(4)
4
˚
a (A)
˚
b (A)
˚
c (A)
a (Њ)
b (Њ)
g (Њ)
˚
V (A3)
Z
Dcalc (g cmϪ3
)
2.12
2.14
2.31
4.63
m (mmϪ1
)
1.95
Transmission factors
2u Range
0.88–1.00
5.0–50.0
3429
3093 (0.061)
2678
0.69–1.00
5.0–50.0
3389
3389
2079
0.94–1.00
5.0–45.0Њ
1234
1037 (0.040)
866
Reflections collected
Reflections unique (Rint)
Reflections observed ꢀI Ͼ 2sꢀI††
R; Rw (observed data)
R; Rw (all data)
0.047; 0.065
0.054; 0.066
0.029; 0.031
0.067; 0.041
0.045; 0.056
0.054; 0.057
(b) For compounds 4–6
4
5
6
Formula
C2H2F3Cl2I
280.84
123
C7H3F12Cl2I
512.89
173
C6H2O4F9I
435.98
133
Formula weight (amu)
Temperature (K)
Crystal color; habit
Crystal size (mm)
Crystal system
Space group
Yellow; plate
0.07 × 0.24 × 0.26
Monoclinic
C2/m (No. 12)
7.203(5)
8.079(5)
11.277(4)
90
92.92(4)
90
655.4(6)
4
Colorless; plate
0.03 × 0.10 × 0.18
Monoclinic
P21/c (No. 14)
25.282(8)
5.381(3)
10.521(5)
90
98.36(4)
90
1416(1)
4
Colorless; parallelepiped
0.18 × 0.28 × 0.46
Triclinic
P-1 (No. 2)
9.958(3)
12.606(3)
9.847(2)
94.87(2)
103.33(2)
103.18(2)
1158.8(6)
4
˚
a (A)
˚
b (A)
˚
c (A)
a (Њ)
b (Њ)
g (Њ)
˚
V (A3)
Z
Dcalc (g cmϪ3
)
2.85
5.65
2.41
2.76
2.50
2.90
m (mmϪ1
)
Transmission factors
2u Range
0.50–1.00
5.0–50.0
679
631 (0.045)
603
0.65–1.00
5.0–50.0
2903
2463 (0.071)
1319
0.71–1.00
5.0–50.0Њ
4311
4055 (0.049)
3612
Reflections collected
Reflections unique (Rint)
Reflections observed ꢀI Ͼ 2sꢀI††
R; Rw (observed data)
R; Rw (all data)
0.023; 0.036
0.024; 0.037
0.078; 0.093
0.140; 0.106
0.045; 0.062
0.050; 0.063

V. Montanari et al. / Journal of Molecular Structure 550–551 (2000) 337–348
341
Table 2
˚
Selected distances (A) and angles (Њ) (see table footnotes for atom generated by the following symmetry operator)
(a) Compounds 1 and 2
1
2
I–Cphenyl
I···Oanion
2.114(6)
2.112(5), 2.113(5)
2.923(3), 2.926(3)b
2.922(4), 2.945(4)a
I–Calkyl
C–I–C
2.144(7)
95.5(3)
97.1(2)
Calkyl–I···O
172.4(2), 72.4(2)a
83.5(2), 167.8(2)a
Cphenyl–I···O
173.2(1)b, 83.0(1)b
O···I···O
82.6(1), 176.0(1)
96.8(1)
108.6(2)
(b) Compounds 3–5
3
4
5
I–Cl
I···Cl
2.478(3), 2.502(3)
3.426(3)c
2.107(9)
2.484(2) × 2
2.469(5), 2.511(5)
3.566(2)d
3.322(5)e
I–Cphenyl
I–Calkyl
Cl–I–Cl
Cl–I···Cl
Cl–I–C
C–I···Cl
I–Cl···I
2.140(6)
2.15(2)
175.0(2)
176.7(1)
171.0(1)f
82.8(1)c, 100.4(1)c
88.3(3), 88.7(3)
166.7(3)
68.5(1)d, 120.5(1)g
85.5(1) × 2
152.4(1) × 2
111.5(1)
94.4(2)e, 90.4(2)e
87.7(5), 87.5(5)
174.5(5)
100.4(3)
143.0(5)
(c) Compound 6h
6
I–O
I···O
2.127(5), 2.156(4) 2.139(4), 2.113(4)
3.240(5) 3.022(4)i, 3.149(4)i
2.124(7) 2.138(6)
I–Calkyl
O–I–O
O–I···O
O–I–C
C–I···O
C–O···I
168.1(2) 163.6(2)
84.4(2), 107.4(2) 68.1(2)i, 128.3(2)i, 124.6(2)i, 70.4(2)i
88.0(2), 80.3(2) 81.4(2), 82.6(2)
165.4(2) 146.7(2), 151.3(2)
131.5(5) 138.8(5)i, 148.0(5)i
a
1=2 ϩ x; 1=2 Ϫ y; 1=2 ϩ z:
b
c
d
e
f
1 Ϫ x; 1 Ϫ y; Ϫz.
1=2 Ϫ x; Ϫ1=2 ϩ y; 1=2 Ϫ z:
1=2 Ϫ x; 1=2 Ϫ y; Ϫz.
Ϫ x, Ϫ1=2 ϩ y; z.
x, Ϫy, z.
1=2 Ϫ x; Ϫ1=2 ϩ y; Ϫz.
Second line of data corresponds to additional molecule in the asymmetric unit.
1 Ϫ x; Ϫy, 2 Ϫ z:
g
h
i
was filtered through a Schlenck tube under nitrogen
2.3. X-ray crystallography
and the volatiles were evaporated into a cold trap. The
residual syrup was allowed to stand at Ϫ20ЊC for
several hours. The resulting white crystalline solid
was dried at 5 × 10Ϫ4 mm Hg: Yield 3.76 g (86%);
m.p. 37–39ЊC (Scheme 2).
Intensity data for compounds 1–6 were measured
with graphite-monochromated MoKa radiation ꢀl ˆ
ꢀ
0:71073 A† by using v/2u scans on a Rigaku
AFC7R diffractometer. An empirical absorption

342
V. Montanari et al. / Journal of Molecular Structure 550–551 (2000) 337–348
Fig. 1. Thermal ellipsoid plot (50% probability) of 1, showing the chain structure of the ion pairs.
correction based on azimuthal scans of several moder-
ately intense reflections was applied to the data, as
were Lorentz and polarization corrections. The inten-
sities of three check reflections measured periodically
throughout data collection fluctuated by only ^1–2%
for each of the compounds except 6, indicating crystal
and electronic stability. For 6, the intensities of the
standard reflections declined by 5.6%, presumably
due to crystal decomposition; a linear correction was
applied to the data to account for this phenomenon.
The structures were solved by direct methods and
refined by using full-matrix least-squares techniques.
All non-hydrogen atoms were refined anisotropically;
hydrogen atoms were placed in optimized positions
types of compounds (for example see Refs. [12–
20]), significant secondary interactions between ions
or between molecules for 1–6, indicated by intera-
tomic contacts shorter than the sum of van der Waal’s
˚
˚
radii for the atoms involved (I: 1.98 A; Cl: 1.75 A; O:
˚
1.52 A) [21], were observed. The compounds fall into
two categories (in the N–X–L Martin–Arduengo
classification systems [22], where N represents the
number of valence electrons formally associated
with a central atom, represented by X, and L gives
the number of ligands directly bonded to X): (1) 8-I-2
species represented by the iodonium salts, 1 and 2; (2)
10-I-3 species represented by the aryl-and alkyliodine
dichlorides, 3–5, and the alkyliodine dicarboxylate, 6.
ꢀ
ꢀdC–H ˆ 0:96 A† with a refined group thermal para-
meter. Structure solution, refinement and the calcula-
tion of derived results were performed with the
Shelxtl package of computer programs [9]. Neutral
atom scattering factors were those of Cromer and
Waber [10, Table 2.2B], and the real and imaginary
anomalous dispersion corrections were those of
Cromer [11, Table 2.3.1]. Relevant crystallographic
data is given in Table 1.
3.1.1. Structures of iodonium salts, 1 and 2
The cations in 1 and 2 have the expected bent coor-
dination of covalently bonded ligands. The I–C bond
distance for the perfluorinated alkyl ligand is some-
what longer than that to the phenyl groups (2.144(7)
˚
˚
versus 2.114(6) A for 1 and 2.112(5)–2.113(5) A for
2). This relative elongation is presumably due to stabi-
lization of the cation by the phenyl group through a
resonanace effect, and destabilization of the cation by
the presence of fluorine in the beta position for the
alkyl group.
3. Results and discussion
For both compounds, a distorted square planar
coordination about the iodine is completed by reason-
ably strong interactions to sulfonyl oxygen atoms of
3.1. Structural studies
˚
Selected distances and angles for compounds 1–6
are given in Table 2. Distances and angles within the
anions or the ligands attached to iodine were all within
previously reported ranges. As expected for these
the anion (I···O: 2.922(4)–2.945(4) A for 1;
˚
2.923(3)–2.926(3) A for 2). These distances are
within the range observed for similar compounds
[12,15–17,19]. In 1, the I···O interactions link ions

V. Montanari et al. / Journal of Molecular Structure 550–551 (2000) 337–348
343
Fig. 2. Thermal ellipsoid plot (50% probability) of a centrosym-
metric dimer of ion pairs for 2.
into infinite chains running parallel to the ac-diagonal
of the cell (see Fig. 1); adjacent ion pairs in a chain are
related by n-glide symmetry. As opposed to the
extended structure of 1, the I···O interactions in 2
link ions into a dimer of ion pairs (see Fig. 2); the
dimer is situated about an inversion center (at 1/2 1/2
0).
The I···O interactions for 1 involve sulfonyl oxygen
atoms on separate sulfur atoms of an anion, but the
interactions in 2 involve oxygen atoms bonded to the
same sulfur atom. The former leads to the extended
chain structure observed, while the latter favors a
closed “molecular dimer” structure. Whether the
observed structures are due to differences in the steric
requirements of the perfluoroalkyl ligand versus the
phenyl group, or may represent alternative structures
possible for either compound (i.e. potential poly-
morphs) is unknown.
An additional interesting feature of structures 1 and 2
is the conformation of the anion. In previously reported
structures of this anion [23–25], a transoid conforma-
tion is observed in which the F3C–S···S–CF3 pseudo-
torsion angle approaches 180Њ. In two of these structures
[23,24], there are only relatively weak interactions
between the anion and cation, involving hydrogen
Fig. 3. 3a Perfluorosulfonimide anion in 1, with transoid conforma-
tion. (b) Perfluorosulfonimide anion in 2, with cisoid conformation.
bonding, while in the third the anion is strongly
coordinated to a lithium ion [25]. We have found
that in many metal salts of this anion, strong
cation–anion coordination of a multidentate nature
usually favors a cisoid conformation, and leads to
many novel and unusual layered and zeolitic-style
structures [26,27].2 In 1, the anion has the transoid
2
We have observed the following conformations: Li[CF3SO2N-
SO2CF3]·H2O, cisoid; Na[CF3SO2NSO2CF3]·H2O·MeOH, cisoid;
K[CF3SO2NSO2CF3],
cisoid;
Rb[CF3SO2NSO2CF3]·C4H8O2,
transoid; Rb[CF3SO2NSO2CF3]·H2O, transoid; Cs[CF3SO2N-
SO2CF3]·H2O, cisoid.

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V. Montanari et al. / Journal of Molecular Structure 550–551 (2000) 337–348
3.1.2. Structures of iodine dichlorides, 3–5
All three of the iodine dichloride compounds have
the expected T-shaped coordination, with chlorine
atoms occupying axial positions and the carbon
atom of the ligand in an equatorial position. As
observed for compound 1, the I–C distance for the
perfluoroalkyl group in 4 is somewhat longer than
for the phenyl group in
2.107(9) A). Similar elongation is seen for the longer
perfluorinated alkyl chain in 5 (2.15(2) A), but the
3 (2.140(6) versus
˚
˚
difference is not considered significant, here, due to
the higher uncertainty in this parameter.
The structure of dichloroiodobenzene, 3, has been
previously determined [28,29], but is included here to
facilitate comparison with the other compounds. In
addition to the three ligands bonded to the iodine
˚
atom, an I···Cl interaction of 3.426(3) A joins mole-
cules related by 21 symmetry to complete a distorted
square planar coordination about the central atom and
to link molecules into chains running parallel to the b-
axis (see Fig. 4). Additional longer I···Cl interactions
Fig. 4. Thermal ellipsoid plot (50% probability) of 3, showing the
chain structure of the molecules.
˚
(3.913(3)–3.975(3) A) complete a very distorted octa-
hedral coordination about the iodine atom.
conformation (Fig. 3a) with a C–S···S–C torsion angle
of 169.1Њ, but in 2 the anion has a cisoid conformation
(Fig. 3b) with a C–S···S–C angle of Ϫ38.2Њ. The latter
conformation is apparently due to steric constraints of
the dimeric cation–anion structure.
The structure of 4 is very different than that of the
phenyl derivative, 3, in that I···Cl interactions
(3.566(2) A) link molecules into unusual, planar
ribbons of iodine and chlorine, with alkyl groups
extending outward (see Fig. 5); the coordination
˚
Fig. 5. Thermal ellipsoid plot (50% probability) of 4, showing the planar ribbon structure of the molecules.

V. Montanari et al. / Journal of Molecular Structure 550–551 (2000) 337–348
345
Fig. 6. Layered structure of 4.
about the iodine atom has a very distorted pentagonal
geometry. Additional longer I···Cl interactions
˚
(3.871(2)–3.990(2) A) join ribbons related by C-
centering to form loosely associated layers (Fig. 6)
which stack in the a-direction of the unit cell.
The structure of 5 bears similarity to both 3 and 4.
Fig. 7. Thermal ellipsoid plot (50% probability) of 5, showing the
chain structure of the molecules.
˚
As in 3, I···Cl interactions (3.322(5) A) link mole-
˚
cules into a zig-zag chain, with adjacent molecules
in the chain related by 21 symmetry (see Fig. 7).
However, packing of the chains is dominated by
aggregation of the perfluorinated groups, which brings
ICl2 units of chains related by inversion symmetry (at
the origin) into close contact. Including longer I···Cl
PhI(CO2CF3)2 (I···O ˆ 3.000(4)–3.133(7) A) [32],
˚
PhI(O2CCHCl2)2 (I···O ˆ 2.936(10) A) [30], and
˚
F5PhI(O2CCF3)2 (I···O ˆ 3.075(8)–3.120(10) A) [33].
The arrangement of the molecules of 6 and the inter-
molecular interactions that occur are quite different,
however. PhI(O2CCH3)2 is a molecular species, with
no significant intermolecular interaction. PhI(CO2CF3)2
and the isomorphous PhI(O2CCHCl2)2 form centro-
symmetric dimers across an inversion center through
intermolecular I···O contacts of 3.038(3) and
˚
contacts, ranging from 3.699(5) to 3.915(5) A, the
iodine atom can be considered eight-coordinate, and,
as in 4, these additional contacts link chains into
layers which stack parallel to the a-axis of the unit
cell (see Fig. 8a and b for comparison of the crystal
packing in 3 and 5, respectively). The packing of
chains in 5 is very similar to that seen in numerous
metal derivatives of perfluorsulfonimides [5–7].
˚
3.049(10) A, respectively. And, F5PhI(O2CCF3)2
which also forms a centrosymmetric dimer through
˚
I···O contacts (2.955(11) and 2.918(9) A for two
unique molecules in the asymmetric unit), but also
has an additional intermolecular I···O contact
˚
(3.190(9) and 3.322(8) A) which link dimers into infi-
3.1.3. Structure of iodine dicarboxylate, 6
nite chains. In 6, one of the unique molecules in the
Compound 6 has a T-shaped coordination (Fig. 9)
with secondary intramolecular I···O interactions
cell forms a centrosymmetric dimer with an I···O
˚
˚
distance of 3.022(4) A, while the other molecule and
(2.955(5)–3.185(4) A) completing a nearly planar
˚
its inversion related partner interact with the dimer
through three I···O contacts of 3.022(4), 3.240(4),
(mean deviation ϳ0.5 A) pentagonal coordination,
very similar to other dicarboxylates, such as
˚
˚
and 3.457(4) A to form a tetrameric structure (see
PhI(O2CCH3)2 (I···O ˆ 2.817(5)–2.850(5) A) [30,31],

346
V. Montanari et al. / Journal of Molecular Structure 550–551 (2000) 337–348
Fig. 8. 8a Packing diagram of 3, shown down the y-axis. (b) Packing diagram of 5, shown down the y-axis.

V. Montanari et al. / Journal of Molecular Structure 550–551 (2000) 337–348
347
features. Although differing only in the nature of
one side chain, the iodonium salts, 1 and 2, have
very different structures and stabilize different
conformations of the perfluorosulfonimide anion.
Likewise, the presence of a perfluoroalkyl chain
in 4 and 5 results in aggregation of hydrophobic
side groups and leads to assembly of chains into
weakly interacting layers. Recently, fluorine and
perfluorinated groups have gained attention for
crystal engineering applications [34–40], but
none of these have focused on the role of hydro-
phobic/hydrophilic aggregation as a driving force
for structure design. We have found this phenomenon
to be very important for the production of novel and
unusual structures with great potential for application.
In addition to our continued efforts to produce synthe-
tically useful perfluorinated materials, we will also
continue to explore the interplay of secondary
bonding to iodine(III) with pefluoroalkyl aggregation
for structure design.
Fig. 9. Thermal ellipsoid plot (50% probability) of 6.
It was hoped that the structural information
obtained on these compounds would explain their
unusual reactivity and behavior, but no obvious
conclusions can be made at this time. In a recent
review Umemoto suggested that ionization in a series
of (perfluoralkyl)aryliodonium salts was incomplete,
and that the increased reactivity observed for triflates
relative to the other members of the series was due to
its greater polarization [2]. As yet, there is no conclu-
sive structural information available on these
compounds, but when obtained and combined with
Fig. 10). Formation of additional I···O interactions to
extend the structure of 6 may be prevented by the
presence of the additional CF3 group of the side chain.
4. Conclusion
Secondary bonding occurs in all the compounds
1–6, yet they display a wide diversity of structural
Fig. 10. Tetrameric structure of 6.

348
V. Montanari et al. / Journal of Molecular Structure 550–551 (2000) 337–348
P.J. Stang, C.M. Crittell, B.L. Williamson, Tetrahedron 48
(1992) 3527.
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Acknowledgements
Financial support of this research by the National
Science Foundation is gratefully acknowledged. The
authors thank Dr George L. Schimek, Dr Lixin Xue
and Ms Rosa D. Bailey for assistance with the crystal-
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