The crystal and molecular structures of 1-naphthylphenyliodonium tetrafluoroborate and 1-naphthylphenyliodonium tetrakis(pentafluorophenyl)gallate

Article abstract of DOI:10.1039/b202805k

The X-ray structures of 1-naphthylphenyliodonium tetrafluoroborate 1 and 1-naphthylphenyliodonium tetrakis(pentafluorophenyl)gallate 2 are reported. Crystals of 1 are monoclinic, space group P2(1)/c, with unit cell dimensions a = 11.8914(11), b = 8.8699(9

Full text of DOI:10.1039/b202805k

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The crystal and molecular structures of 1-naphthylphenyliodonium
tetrafluoroborate and 1-naphthylphenyliodonium
tetrakis(pentafluorophenyl)gallate†
Bilal R. Kaafarani,a Haiyan Gu,a A. Alan Pinkertonb and Douglas C. Neckers*a
a Center for Photochemical Sciences, Bowling Green State University, Bowling Green,
Ohio 43403, USA. E-mail: neckers@photo.bgsu.edu
b Department of Chemistry, University of Toledo, Toledo, Ohio, 43606, USA
Received 12th December 2001, Accepted 26th March 2002
First published as an Advance Article on the web 25th April 2002
The X-ray structures of 1-naphthylphenyliodonium tetrafluoroborate 1 and 1-naphthylphenyliodonium
tetrakis(pentafluorophenyl)gallate 2 are reported. Crystals of 1 are monoclinic, space group P2(1)/c, with unit cell
dimensions a = 11.8914(11), b = 8.8699(9), c = 14.4445 (13) Å, β = 90.944(4)Њ, Z = 4, and R = 0.0596 for 8286 unique
observed reflections. Crystals of 2 are monoclinic, space group P2(1)/c, with unit cell dimensions a = 15.003(5),
b = 18.287(6), c = 14.738(6) Å, β = 115.436(13)Њ, Z = 4, and R = 0.0222 for 8063 unique observed reflections.
The iodonium cations of 1 exist as π-stacked dimers; however, those of 2 are monomeric.
1
Introduction
2
Results and discussion
The reaction of diacetoxyiodoarene with metalloarenes was
employed to synthesize these compounds. The X-ray crystal
structures of compounds 1 and 2 are shown in Fig. 2. To the
best of our knowledge, this is the first report of the X-ray struc-
ture of a tetrakis(pentafluorophenyl)gallate iodonium salt
photoinitiator.
Diaryl iodonium salts have been extensively used as cationic
photoinitiators in a wide range of applications because of
their thermal stability and excellent initiating efficiency.1 We
previously reported and compared the photopolymerization of
epoxides using some of these photoinitiators.2a We have also
reported that iodonium tetrakis(pentafluorophenyl)gallates
show the fastest rate of acid release.3 These gallates are advan-
tageous over other iodonium salts because of their excellent
solubility in monomers and high photosensitivity.4
Since diphenyliodonium salts were first used as cationic
photoinitiators in the 1970’s, many studies have focused on the
scope of their photochemistry.5 Most commercial aromatic
iodonium salts are phenyl or substituted phenyl, with absorp-
tions concentrated below 300 nm. Upon laser flash photolysis
of iodonium salts, several transient species formed, but it was
difficult to interpret what they were.6 The introduction of a
naphthyl group will increase the absorption of such iodonium
salts at longer wavelengths making it easier to identify transient
species formed during photolysis. In this paper, we report the
crystal and molecular structures, and packing of the iodonium
salts 1 and 2 (Fig. 1). The photophysical studies of these
compounds will be reported elsewhere.
Alcock7 et al. reported that iodonium salts paired with halide
anions invariably existed as dimers in the crystal, with the
halide anion as the bridge atom. The packings of 1 and 2 are
shown in Fig. 3(a) and (b), respectively. When paired with
tetrafluoroborate, the cation of 1 also dimerized; however, the
interaction in this case is through the naphthyl π-system, as
shown in Fig. 3(c). That was not the case, however, with com-
pound 2. The absence of dimer aggregation in 2 may explain
why iodonium salts paired with this anion have excellent solu-
bility in nonpolar solvents. The two naphthyl rings and the two
phenyl rings are parallel to each other in each case. The distance
between the centers of the naphthyl planes is 3.63 Å. The dis-
tance between the centers of the iodonium cation and the
tetrafluoroborate anion (3.576 Å) in 1 is much shorter than that
between the centers of the iodonium cation and the
tetrakis(pentafluorophenyl)gallate anion (5.57 Å) in 2. Previ-
ously, we reported that the anion has an important effect on the
reactivity of iodonium salts.2 We suggest that it is the distance
between the centers of the cation and the anion that is the key
factor in this effect.
3
Experimental
3.1 X-Ray crystallography
Preliminary examination and data collection were carried out
with Ag-Kα radiation in the case of 1 and Mo-Kα in the case of
2, using a Bruker AXS SMART platform diffractometer.8
Intensity data were collected using three different ꢀ settings and
0.3Њ increment ω scans, 2θ < 60.68Њ for 1 and 2θ < 55.46Њ for 2,
which corresponds to more than a hemisphere of data. Data
integration was carried out with SAINT,9 and corrections for
Fig. 1 Iodonium salts 1 and 2.
† Contribution no. 456 from the Center for Photochemical Sciences.
Electronic supplementary information (ESI) available: colour version
of Fig. 3. See http://www.rsc.org/suppdata/dt/b2/b202805k/
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This journal is © The Royal Society of Chemistry 2002
DOI: 10.1039/b202805k

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Fig. 2 ORTEP drawings (50% probability ellipsoids) of 1 (a) and 2 (b). Selected bond lengths (Å) and angles (Њ): I–C(1) 2.109(3), I–C(11) 2.106(2),
C(11)–I–C(1) 97.36(9) in 1. I–C(1) 2.107(2), I–C(11) 2.110(2), Ga–C(17) 2.0095(19), Ga–C(23) 2.0115(19), Ga–C(29) 2.0223(19), Ga–C(35)
2.0197(19), C(1)–I–C(11) 96.26(8), C(17)–Ga–C(23) 112.49(8), C(17)–Ga–C(35) 105.86(7), C(23)–Ga–C(35) 113.36(7), C(17)–Ga–C(29) 113.77(8),
C(23)–Ga–C(29) 101.30(8), C(35)–Ga–C(29) 110.26(7) in 2. Selected dihedral angles (Њ) in 2: the dihedral angle between the mean plane of the ring
containing C(17) [{C(18)C(17)C(22)}] and that including C(23) [{C(24)C(23)C(28)}] is 118.4, {C(18)C(17)C(22)} and {C(30)C(29)C(34)} 67.4,
{C(18)C(17)C(22)} and {C(36)C(35)C(40)} 88.1, {C(30)C(29)C(34)} and {C(24)C(23)C(28)} 75.4, {C(30)C(29)C(34)} and {C(36)C(35)C(40)}
115.1, {C(24)C(23)C(28)} and {C(36)C(35)C(40)} 65.6.
absorption and decay were applied using SADABS.9 The X-ray
structures were determined by direct methods10 and refinement
was by full matrix least squares11 on F 2 using all 8286 (for 1)
and 8063 (for 2) unique data. The final refinement included
anisotropic thermal parameters for non-hydrogen atoms with
isotropic thermal parameters for all hydrogen atoms. The
refinement converged to wR2 = 0.1259 (for F 2, all data), R1 =
0.0454 [F, 8286 reflections with I > 2σ(I )] in the case of 1, and
wR2 = 0.0561, R1 = 0.0237 in the case of 2. The crystal data
and experimental details are listed in Table 1. The molecular
structures of compounds 1 and 2 are shown in Fig. 2.
0.1 mol) was added portionwise over 20 min. After stirring for
8 h, 100 ml water was added. The crude product was filtered off
and washed with diethyl ether. After recrystallization from
acetic acid, pure product was obtained (60%), mp 193 ЊC dec.
1H-NMR (200 MHz, acetone-d6, δ): 8.70 (d, J = 7.4 Hz, 1H, Ar
H), 8.334 (d, J = 8.2 Hz, 1H, Ar H), 8.19 (d, J = 8.0 Hz, 1H, Ar
H), 8.107 (d, J = 8.2 Hz, 1H, Ar H), 7.81–7.63 (m, 3H, Ar H),
1.817 [s, 6H, (CH3CO2)2].
9-Diacetoxyiodophenanthrene. The title compound was syn-
thesized from 9-iodophenanthrene and NaBO3ؒ4H2O by the
same procedure mentioned above. Yield: 68%; mp 199 ЊC dec.
1H NMR (200 MHz, acetone-d6, δ): 8.88 (s, 1H, Ar H), 8.78 (d,
J = 7.4 Hz, Ar H), 8.22–8.17 (m, 1H, Ar H), 8.02 (d, J = 7.6 Hz,
1H, Ar H), 7.85–7.69 (m, 4H, Ar H), 1.94 (s, 6H, (CH3CO2)2).
CCDC reference numbers 178309 and 178310.
See http://www.rsc.org/suppdata/dt/b2/b202805k/ for crystal-
lographic data in CIF or other electronic format.
3.2 Materials
1-Naphthylphenyliodonium tetrafluoroborate (1). The title
compound was synthesized following a literature procedure.13
To a stirred solution of 0.744 g (2 mmol) 1-diacetoxy-
iodonaphthalene and 0.854 g (2 mmol) tetraphenyltin in 20 ml
dichloromethane under argon, 0.51 ml (4 mmol) trifluoroboron
diethyl etherate was added dropwise. The solution was stirred
overnight and filtered. The filtrate was washed with 10 ml water,
and the organic layer was evaporated to give a white solid. After
recrystallization twice from acetone/chloroform, a pure pale
All chemicals and solvents (Spectrophotometric Grade) were
purchased from Aldrich Chemical Co. and used as received,
unless otherwise noted. Lithium tetrakis(pentafluorophenyl)-
gallate was synthesized as previously reported.11
1-Diacetoxyiodonaphthlene. The title compound was syn-
thesized from 1-iodonaphthalene and sodium peroxyborate-
tetrahydrate (NaBO3ؒ4H2O) following a literature procedure.12
To a stirred solution of 1-iodonaphthalene (2.54 g, 10 mmol) in
90 ml acetic acid held at 40–45 ЊC, NaBO3ؒ4H2O (15.4 g,
1
yellow crystal was obtained (54%), mp 186–187 ЊC. H-NMR
(200 MHz, acetone-d6, δ): 8.83 (d, J = 7.8 Hz, 1H), 8.32–8.25
J. Chem. Soc., Dalton Trans., 2002, 2318–2321
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Table 1 Crystal data and experimental details
Empirical formula
Formula weight
Temperature/K
C16H12BF4I
417.97
150(1)
C40H12F20GaI
1069.12
120(1)
Wavelength/Å
Crystal system, space group
Unit cell dimensions
0.56086
0.71073
Monoclinic, P2(1)/c
a = 11.8914(11) Å, α = 90Њ
b = 8.8699(9) Å, β = 90.944(4)Њ
c = 14.4445(13) Å, γ = 90Њ
1523.3(3)
4, 1.822
1.138
Monoclinic, P2(1)/c
a = 15.003(5) Å, α = 90Њ
b = 18.287(6) Å, β = 115.436(13)Њ
c = 14.738(6) Å, γ = 90Њ
3651(2)
4, 1.945
1.734
Volume/Å3
Z, Calculated density/Mg mϪ3
Absorption coefficient/mmϪ1
F(000)
808
2064
Crystal size/mm
θ range for data collection/Њ
Limiting indices
Reflections collected/unique
Refinement method
0.20 × 0.25 × 0.18
1.35 to 30.24
Ϫ20 ≤ h ≤ 20, Ϫ15 ≤ k ≤ 14, Ϫ24 ≤ l ≤ 15
24408/8286 [R(int) = 0.0596]
Full matrix least squares on F 2
8286/0/231
0.48 × 0.45 × 0.25
4.07 to 27.73
Ϫ17 ≤ h ≤ 18, Ϫ22 ≤ k ≤ 23, Ϫ18 ≤ l ≤ 18
34816/8063 [R(int) = 0.0222]
Full matrix least squares on F 2
8063/0/607
Data/restraints/parameters
Goodness-of-fit on F 2
Final R indices [I > 2σ(I )]
R indices (all data)
1.007
1.101
R1 = 0.0454, wR2 = 0.1083
R1 = 0.1193, wR2 = 0.1259
2.004 and Ϫ1.173
R1 = 0.0237, wR2 = 0.0561
R1 = 0.0250, wR2 = 0.0568
0.350 and Ϫ0.682
Largest diff. peak and hole/e ÅϪ3
Fig. 3 (a) Packing of 1; (b) packing of 2; (c) dimerization of the cation of 1 as revealed by the X-ray measurements.
(m, 3 H), 8.05 (d, J = 8.2 Hz, 1H), 7.85–7.58 (m, 5H), 7.47 (t,
J = 7.2 Hz, 1H). 13C-NMR (acetone-d6 50 MHz, δ): 137.5 (CH),
134.0 (CH), 133.5 (CH), 131.5 (CH), 131.1 (CH), 130.5 (C),
129.2 (CH), 128.7 (CH), 127.5 (CH), 127.2 (CH), 126.7 (CH),
115.4 (C), 112.4 (C). Anal. calcd for C16H12IBF4: C, 45.98;
H, 2.89; found: C, 46.04; H, 3.00%.
dichloromethane. A white precipitate formed immediately.
After stirring for 1 h, the solution was filtered and concentrated
to yield crude product. After passage through a short silica gel
column and recrystallization from chloroform–hexane, a pale
1
yellow crystal was obtained (60%), mp 117–118 ЊC. H-NMR
(200 MHz, acetone-d6, δ): 8.93 (d, J = 7.8 Hz, 1H), 8.43–8.37
(m, 4H), 8.15 (d, J = 8.2 Hz, 1H), 7.91–7.54 (m, 6H). 19F-NMR
(CDCl3, δ): Ϫ118.9 (sm, 8F), Ϫ155.1(m, 4F), Ϫ160.6 (sm, 8F).
Anal calcd. for C40H12IGaF20 C, 44.94; H, 1.13; found: C, 44.86;
H, 1.02%.
1-Naphthylphenyliodonium tetrakis(pentafluorophenyl)gallate
(2). Compound 1 (0.21 g, 0.5 mmol) was mixed with lithium
tetrakis(pentafluorophenyl)gallate (0.46 g, 0.5 mmol) in 10 ml
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Chichester, 1995, ch. 21, pp. 1173; (b) P. J. Stang and V. V. Zhdankin,
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Zhurova for the valuable comments during X-ray measure-
ments. Fellowships from the McMaster Endowment to two of
the authors (B. R. K. and H. G.) are also gratefully acknow-
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