Synthesis and characterization of monohaloalkoxyarsoranes bearing a novel tridentate ligand occupying one apical and two equatorial sites

Article abstract of DOI:10.1080/10426501003772003

A series of pentavalent organoarsenic monohalides (F, Cl, and Br) were synthesized using a rigid tridentate ligand with a 2,2,2-trifluoro-1,1- diphenylethanol skeleton. The chloro derivative (4) could not be isolated due to its sensitivity to air, whereas the fluoro (5) and bromo derivatives (6) were isolated as crystalline solids. The X-ray crystallography of 5 and 6 revealed that both compounds adopted a pentacoordination at the arsenic atom with a covalent arsenic-halogen bond rather than the tetracoordinated ionic form. The solid state structures around the arsenic atom of 5 and 6 were almost ideal trigonal bipyramidal (TBP) geometries. The NMR measurements implied that 4, 5, and 6 were in the pentacoordinated state even in solution. Copyright Taylor & Francis Group.

Full text of DOI:10.1080/10426501003772003

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Phosphorus, Sulfur, and Silicon and the
Related Elements
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Synthesis and Characterization of
Monohaloalkoxyarsoranes Bearing a
Novel Tridentate Ligand Occupying One
Apical and Two Equatorial Sites
Hideaki Yamamichi a , Shiro Matsukawa a & Yohsuke Yamamoto a
a Department of Chemistry, Graduate School of Science , Hiroshima
University , Higashi-Hiroshima, Japan
Published online: 27 May 2010.
To cite this article: Hideaki Yamamichi , Shiro Matsukawa & Yohsuke Yamamoto (2010) Synthesis and
Characterization of Monohaloalkoxyarsoranes Bearing a Novel Tridentate Ligand Occupying One Apical
and Two Equatorial Sites, Phosphorus, Sulfur, and Silicon and the Related Elements, 185:5-6, 974-982,
DOI: 10.1080/10426501003772003
To link to this article: http://dx.doi.org/10.1080/10426501003772003
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Phosphorus, Sulfur, and Silicon, 185:974–982, 2010
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426501003772003
SYNTHESIS AND CHARACTERIZATION OF
MONOHALOALKOXYARSORANES BEARING A NOVEL
TRIDENTATE LIGAND OCCUPYING ONE APICAL
AND TWO EQUATORIAL SITES
Hideaki Yamamichi, Shiro Matsukawa, and Yohsuke Yamamoto
Department of Chemistry, Graduate School of Science, Hiroshima University,
Higashi-Hiroshima, Japan
A series of pentavalent organoarsenic monohalides (F, Cl, and Br) were synthesized using
a rigid tridentate ligand with a 2,2,2-trifluoro-1,1-diphenylethanol skeleton. The chloro
derivative (4) could not be isolated due to its sensitivity to air, whereas the fluoro (5) and
bromo derivatives (6) were isolated as crystalline solids. The X-ray crystallography of 5 and
6 revealed that both compounds adopted a pentacoordination at the arsenic atom with a
covalent arsenic-halogen bond rather than the tetracoordinated ionic form. The solid state
structures around the arsenic atom of 5 and 6 were almost ideal trigonal bipyramidal (TBP)
geometries. The NMR measurements implied that 4, 5, and 6 were in the pentacoordinated
state even in solution.
Keywords Arsenic; hypervalent; NMR study; pentacoordinate; X-ray analysis
INTRODUCTION
Hypervalent1 group 15 element compounds, especially the phosphorus compounds,
have attracted significant interests and have been widely investigated because such species
are assumed to be involved as intermediates (or transition states) in the biological phosphoryl
transfer reaction2 as well as in synthetic reactions such as the Wittig olefination.3 Pentaco-
ordinate hypervalent group 15 element compounds generally adopt a trigonal bipyramidal
(TBP) geometry, which has two different types of bonds, i.e., apical and equatorial bonds.
Since the apical (hypervalent) bond is weaker and longer than the equatorial bond, the
former is considered to be involved in the bond formation/cleavage reaction with the pen-
tacoordinate species. Thus, understanding the bonding nature of hypervalent compounds is
very important in order to appreciate the reactions involving such species as intermediates.
Received 18 November 2008; accepted 19 December 2008.
Dedicated to Professor Naomichi Furukawa on the occasion of his 70th birthday.
This work was supported by a Grant-in-Aid for Scientific Research on Priority Areas (No. 18064013) from
the Ministry of Education, Culture, Sports, Science, and Technology, Japan.
Address correspondence to Yohsuke Yamamoto, Department of Chemistry, Graduate School of Science,
Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan. E-mail: yyama@sci.hiroshima-
u.ac.jp
974

MONOHALOGENATED ALKOXYARSORANES
pentacoordination tetracoordination
975
X
X
X
As
As
As
X
A
B
C
arsorane
arsonium salt
CT complex
Figure 1 Possible structure forms for pentavalent arsenic compounds having halogen atoms.
A pentavalent arsenic compound having one or more halogen atoms can adopt the
following forms: a pentacoordinate arsenic (arsorane) with a covalent arsenic–halogen bond
(A), a tetracoordinate arsonium salt (B), and a charge-transfer (CT) complex (C) (Figure 1).
The arsoranes (A) generally assume a trigonal bipyramidal (TBP) geometry, whereas the
tetracoordinated arsenic compounds (B and C) adopt a tetrahedral geometry at the arsenic
atom. Such structural diversity is found in the crystal structures of the triorganoarsenic
dihalides. For example, in the solid state Ph3AsF2,4 Me3AsCl2,5a and Ph3AsBr2 are
5b
TBP molecules (A), whereas Me3AsBr25 exists as the CT complex, i.e., Me3As···Br—Br
(C). In contrast, the tetraorganoarsenic monohalides, Ph4AsI,6 Me4AsBr,7 and Me4AsI8
exclusively adopt the ionic form (B) in both the solid state and in solution. Furthermore, no
structural insights regarding the haloalkoxyarsoranes (R3As(OR’)X) have been reported.9
In this article, we report the first synthesis of monohalo-alkoxyarsoranes using a novel
tridentate ligand, which occupies one apical and two equatorial sites in a TBP geometry.
The single crystal X-ray analysis of the fluoro and bromo derivatives revealed that both
compounds have TBP structure.
RESULTS AND DISCUSSION
Synthesis
Monohalogenated arsoranes 4, 5, and 6 were synthesized as shown in Scheme 1.
The diiodide 110 was first dilithiated with 2 equivalents of n-BuLi, and then treated with
dichloro(3,5-dimethylphenyl)arsine (XylAsCl2; Xyl = 3,5-Me2C6H3) to afford the triary-
larsine cis-2 in 79% yield as a single stereoisomer. The deprotection of cis-2 with trifluo-
roacetic acid gave the alcohol cis-3 in 95% yield. The oxidative chlorination of cis-3 using
SO2Cl2 gave the moisture-sentitive chloroarsorane 4, which was easily hydrolyzed upon
exposure to air. Thus, in-situ generated 4 was treated with CsF to afford the fluoroarsorane 5
as an air- and moisture-stable crystalline solid in 44% yield (two steps from cis-3) as a single
isomer. Abstraction of the fluorine atom of 5 with trimethylsilyl trifluoromethanesulfonate
(TMSOTf), followed by bromination with MgBr2·OEt2, then afforded the bromoarsorane
6 as a single isomer. Compound 6 was slightly unstable to moisture and contained a small
amount of hydrolyzed compounds.

976
H. YAMAMICHI ET AL.
CF3
RO
F3C
1) n-BuLi (2 eq.)
CF3
MOMO
2) XylAsCl2
SO2Cl2
CH2Cl2
O
As
Cl
As
Et2O
I
Xyl
I
Xyl
cis-2 (R = MOM) 79%
Xyl = 3,5-Me2C6H3
1
4
CF3CO2H
CH2Cl2
cis-3 (R = H)
95%
CsF
THF
F3C
F3C
1) TMSOTf
2) MgBr2·OEt2
O
O
As
As
F
CH2Cl2 / Et2O
Xyl
Xyl
Br
6
5 44%
Scheme 1
Crystal Structures
Single crystals of fluoroarsorane 5 and bromoarsorane 6 were obtained by recrys-
tallization from CH3CN and CH2Cl2/n-hexane, respectively, and were then subjected to
an X-ray crystallographic analysis. The ORTEP drawings of the molecular structures of
these compounds are shown in Figure 2. Selected bond lengths and angles are contained
in Table I. In both cases, the geometry at the arsenic atom is regarded as TBP, and the
halogen atoms are covalently bonded to the corresponding arsenic atom. According to the
apicophilicity rule,11 it is reasonable that the electronegative fluorine and bromine atoms
occupy the apical sites of 5 and 6, respectively. The As–F distance in 5 (1.8099(10) Å)
is close to that of the pentacoordinated Ph3AsF2 (1.834(3) Å for both fluorine atoms).4
Similarly, the As–Br distance in 6 (2.4788(6) Å) is close to those of pentacoordinated
Ph3AsBr2 (2.552(5), 2.441(5) Å),5b and much shorter than that observed in the arsonium
salt Me4As+Br− (4.01(2) Å).7
Figure 2 ORTEP drawings of the structures of compounds 5 and 6 with the thermal ellipsoids shown at the 50%
probability level. All hydrogen atoms are omitted for clarity.

MONOHALOGENATED ALKOXYARSORANES
977
Table I Selected bond lengths and angles for compounds 5 and 6
5 (X = F)
6 (X = Br)
Bond length (Å)
As1–O1
As1–C1
As1–C2
As1–C3
1.9249 (11)
1.9182 (16)
1.9182 (17)
1.9087 (16)
1.8099 (10)
1.889 (2)
1.931 (4)
1.926 (4)
1.909 (4)
2.4788 (6)
As1–X1
Bond angles (deg)
O1–As1–C1
O1–As1–C2
O1–As1–C3
O1–As1–X1
C1–As1–C2
C1–As1–C3
C1–As1–X1
C2–As1–C3
C2–As1–X1
C3–As1–X1
82.64 (6)
82.44 (6)
93.27 (6)
174.76 (5)
101.02 (7)
130.26 (7)
93.80 (6)
127.69 (7)
94.52 (6)
91.97 (6)
83.23 (13)
83.26 (13)
89.34 (13)
177.67 (8)
100.87 (16)
132.14 (15)
94.83 (11)
125.15 (16)
95.86 (11)
92.93 (11)
To evaluate the pentacoordination character, the %TBPe values were calculated.12
The %TBPe values of 5 and 6 are 97% and 94%, respectively. Furthermore, the apical bond
angles (O1–As1–X1, 174.76(5)◦ for 5 and 177.67(8)◦ for 6) are close to the ideal value of
180◦. These values apparently indicate that the compounds adopt the TBP structure. The
reason for adoption of the TBP geometry in 5 and 6 is that the well-designed tridentate
ligand prefers to occupy one apical and two equatorial sites of the TBP geometry rather
than three apices of tetrahedral geometry.
The As1–O1 distance of the fluoro derivative 5 (1.9249(11) Å) is 0.03 Å longer than
that of the bromo derivative 6 (1.889(2) Å). This difference could originate from the degree
of tilt of the monodentate Xyl group, probably due to the difference in the crystal packing
force. The dihedral angle O1–As1–C3–C4 of 5 (31.2◦) is significantly smaller than that of
6 (47.0◦). Therefore, steric repulsion between the oxygen atom (O1) and the ortho proton
at C4 should be greater in 5 than in 6, giving rise to the longer As1–O1 distance in 5. The
fact that the O1–As1–C3 angle of 5 (93.3◦) is larger than that of 6 (89.4◦) is also pertinent
to the greater steric repulsion in 5.
Structure in Solution
It is interesting whether the haloarsoranes are in pentacoordinated state or not in
solution. The 19F NMR spectrum of fluoroarsorane 5 shows a singlet at −94.6 ppm cor-
responding to the apical fluorine atom attached to the arsenic atom. This chemical shift
is comparable to those of the reported fluoroarsoranes having the apical fluorine atoms,
e.g., −87.3 ppm for Ph3AsF2 and −99.7 ppm for (PhCH2)3AsFCl.13 Thus, 5 should also
maintain the pentacoordination with the apical fluorine atom in solution as well as in the
crystal structure. In the 13C NMR spectrum of fluoroarsorane 5, signals of the ipso-carbon
atoms connected to the arsenic atom are observed as doublets coupled with the apical
2
2
fluorine atom [δ = 147.2 (d, JCF = 2 Hz) and 139.4 (d, JCF = 2 Hz)], thus providing
further evidence for 5 containing a covalent As–F bond also in solution.

978
H. YAMAMICHI ET AL.
H3C CH3
H3C CH3
O
P
Br
O
P
Ph
Ph
Ph
OBn
CH3
H
Br
H3C
7
8
31P NMR: δ –17.8
31P NMR: δ 70.9
1H NMR: δ 8.10-6.75
1H NMR: δ 8.53-8.33
Figure 3 Comparison of NMR chemical shifts between the Martin’s bromophosphorane (left) and phosphonium
bromide (right).
The 1H NMR spectra of arsoranes 4, 5, and 6 are similar. The singlets for the ortho
protons of the Xyl group are observed at δ = 7.82 for 4, 7.97 for 5, and 7.69 for 6
ppm. The ortho protons of the tridentate ligand resonate at δ = 8.21–8.19 for 4, 7.91
for 5, and 8.28–8.26 ppm for 6. As shown by Granoth and Martin, the aromatic protons
ortho to the hypervalent central atom are shifted downfield compared to those of the
1
corresponding onium species.14 For example, the H NMR spectrum of phosphorane 7
shows the downfield-shifted ortho proton of the bidentate ligand at δ = 8.53–8.33, whereas
the ortho protons of phosphonium bromide 8 resonate at δ = 8.10–6.75 (Figure 3). Thus,
the very similar 1H NMR signals of 4, 5, and 6 imply that these monohalides also adopt the
trigonal bipyramidal (TBP) structure in solution.
In conclusion, we successfully synthesized a series of monohalogenated arsoranes
using a novel tridentate ligand, which occupies one apical and two equatorials sites in
a trigonal bipyramidal structure. The solid state structures of the fluoro (5) and bromo
(6) derivatives were unambiguously determined by single crystal X-ray diffraction. NMR
measurements indicate that these haloarsoranes exist in the pentacoordinate state also in
solution.
EXPERIMENTAL
Melting points were measured using a Yanaco micro melting point apparatus. The
1H (400 MHz), 13C (100 MHz), and 19F (376 MHz) NMR spectra were recorded using a
JEOL EX-400 or a JEOL AL-400 spectrometer. The 1H NMR chemical shifts (δ) are given
in ppm downfield from Me4Si, and were determined by referencing to residual chloroform
(δ = 7.26 ppm) and dimethyl sulfoxide (δ = 2.49 ppm). The 13C NMR chemical shifts (δ) are
given in ppm downfield from Me4Si, and were determined by referencing to chloroform-d
(δ = 77.00 ppm). The 19F NMR chemical shifts (δ) are given in ppm downfield from the
external CFCl3. The elemental analyses were performed using a Perkin-Elmer 2400 CHN
elemental analyzer. Tetrahydrofuran (THF) and diethyl ether (Et2O) were freshly distilled
from Na-benzophenone, and the other solvents were distilled from CaH2. Preparative thin
layer chromatography was carried out on Merck silica gel 60GF254 plates. Merck silica gel
60 was used for the column chromatography.

MONOHALOGENATED ALKOXYARSORANES
979
1,1-Bis-(2-iodophenyl)-2,2,2-trifluoroethyl Methoxymethyl Ether (1)
To a mixture of 1,1-bis(2-iodophenyl)-2,2,2-trifluoroethanol10 (6.87 g, 13.6 mmol)
and NaH (60% in oil, 1.09 g, 27.3 mmol) under argon, THF (27 mL) was added at 0◦C,
and the resulting mixture was stirred for 20 min. Methoxymethyl chloride (2.10 mL, 27.6
mmol) was then added at the same temperature. After stirring for 1 h at 0◦C, the reaction
was quenched with H2O at 0◦C, and the mixture was extracted with Et2O (3 × 40 mL).
The organic layer was washed with brine (100 mL), dried over anhydrous K2CO3, and
the solvent was evaporated. The crude product was purified by column chromatography on
silica gel (n-hexane:CH2Cl2 = 1:1, Rf = 0.30), followed by recrystallization from n-hexane
to afford a white solid of 1 (7.10 g, 13.0 mmol, 95%). 1H NMR (CDCl3): δ = 8.2–7.9 (br
s, 2H), 8.07 (d, J = 8 Hz, 1H), 7.96 (d, J = 8 Hz, 1H), 7.47 (t, J = 8 Hz, 1H), 7.34 (br
s, 1H), 7.03 (t, J = 8 Hz, 2H), 4.74 (d, J = 6 Hz, 1H, OCH2O), 4.66 (d, J = 6 Hz, 1H,
OCH2O), 3.60 (s, 3H, OCH3). 13C NMR (CDCl3): δ = 143.7 (CH), 143.3 (CH), 137.7 (C),
133.5 (C), 130.0 (CH), 127.2 (CH), 124.6 (q, 1JCF = 291 Hz, CF3), 93.4 (OCH2O, CH2),
85.2 (q, 2JCF = 28 Hz, CCF3), 57.4 (OCH3, CH3). 19F NMR (CDCl3): δ = −69.0 (br s).
Mp: 45.0–49.0◦C. Elemental analysis: Calcd for C16H13F3I2O2: C 35.06, H 2.39. Found:
C 35.18, H 2.35%.
Dichloro(3,5-dimethylphenyl)arsine (XylAsCl2)
XylAsCl2 was prepared in a manner similar to the synthesis of acenaphthene-5-
dichloroarsine.15 To a suspension of 3,5-dimethylaniline (5.00 mL, 40.1 mmol) in H2O
(225 mL), conc. aq. HCl (25 mL) was added at room temperature. To the mixture cooled
to 0◦C, NaNO2 (2.50 g, 36.2 mmol) in H2O (20 mL) was added dropwise. The resulting
mixture was then stirred for 1 h at 0◦C to generate a diazonium salt. The solution of the
diazonium salt kept at 0◦C was added dropwise to a mixture of As2O3 (6.99 g, 36.2 mmol),
NaHCO3 (7.01 g, 83.5 mmol), KOH (24.0 g, 428 mmol), and CuSO4 · 5 H2O (1.50 g,
6.02 mmol) in H2O (200 mL) at room temperature, and the resulting mixture was stirred
overnight at room temperature. The mixture was filtered to remove the solid materials, and
the filtrate was condensed to ca. 200 mL by boiling. To the resulting solution, 6M aq. HCl
(300 mL) was added, and the mixture was cooled to 0◦C to give a white precipitate, which
was collected by filtration to afford a white powder of 3,5-dimethylphenylarsonic acid (4.91
g, 21.3 mmol, 59%). 1H NMR (DMSO-d6): δ = 7.34 (s, 2H), 7.29 (s, 1H), 2.33 (s, 6H).
To a suspension of 3,5-dimethylphenylarsonic acid (1.66 g, 7.19 mmol) in n-hexane
(16 mL), PCl3 (2.4 mL, 34 mmol) was added dropwise under argon at room temperature,
and the mixture was refluxed for 1 h. The supernatant was then transferred to another
flask, and the solvent was evaporated in vacuo to afford a colorless crystalline solid of
1
dichloro(3,5-dimethylphenyl)arsine (502 mg, 2.00 mmol, 28%). H NMR (CDCl3): δ =
7.46 (s, 2H), 7.16 (s, 1H), 2.39 (s, 6H).
Synthesis of cis-2
To a solution of 1 (548 mg, 0.999 mmol) in Et2O (10 mL), n-BuLi (1.66 M solution
in n-hexane, 1.21 mL, 2.01 mmol) was added under argon at 0◦C, and the mixture was
stirred for 15 min at the same temperature. To the mixture, a solution of XylAsCl2 (252 mg,
0.995 mmol) in Et2O (10 mL) at 0◦C was added, then the resulting mixture was stirred for
2 h at room temperature. The reaction was then quenched with H2O at room temperature.

980
H. YAMAMICHI ET AL.
The mixture was next extracted with Et2O, the organic layer was washed with brine, dried
over MgSO4, and the solvent was evaporated. The crude mixture was purified by column
chromatography (SiO2, CH2Cl2:n-hexane = 1:3, Rf = 0.30) to give a white powder of cis-2
(345 mg, 0.790 mmol, 79%). 1H NMR (CDCl3): 8.09 (d, J = 8 Hz, 2H), 7.43 (t, J = 8 Hz,
2H), 7.31–7.24 (m, 4H), 6.97 (s, 1H), 6.96 (s, 2H), 4.66 (s, 2H), 3.69 (s, 3H), 2.23 (s, 6H).
13C NMR (CDCl3): δ = 142.3 (C), 139.7 (C), 138.2 (C), 133.1 (CH), 132.6 (CH), 132.1
1
(CH), 131.1 (CH), 130.1 (CH), 128.9 (CH), 127.9 (CH), 124.3 (q, JCF = 283 Hz, CF3),
2
93.4 (CH2), 81.8 (q, JCF = 29 Hz, CCF3), 57.4 (CH3), 21.2 (CH3). 19F NMR (CDCl3):
δ = −78.8 (s). Mp: 134.9–138.5◦C (dec.). Elemental analysis: Calcd for C24H22AsF3O2:
C 60.77, H 4.67. Found: C 60.45, H 4.54%.
Synthesis of cis-3
To a solution of cis-2 (23 mg, 0.048 mmol) in CH2Cl2 (1.0 mL), CF3CO2H (0.075
mL, 1.0 mmol) was added at room temperature, and the mixture was stirred for 2.5 h. The
mixture was then evaporated to dryness to give a white powder of cis-3 (20 mg, 0.046
1
mmol, 95%). H NMR (CDCl3): δ = 8.13 (d, J = 8 Hz, 2H), 7.45 (t, J = 8 Hz, 2H),
7.30–7.22 (m, 4H), 6.99 (s, 1H), 6.96 (s, 2H), 3.04 (s, 1H), 2.22 (s, 6H). 13C NMR (CDCl3):
δ = 142.7 (q, 3JCF = 3 Hz, C), 140.1 (C), 138.1 (C), 135.3 (C), 132.9 (CH), 132.8 (CH),
131.2 (CH), 128.6 (CH), 128.2 (CH), 127.4 (CH), 124.9 (q, 1JCF = 286 Hz, CF3), 76.7 (q,
2JCF = 30 Hz, CCF3), 21.1 (CH3). 19F NMR (CDCl3): δ = −79.0 (s). Mp: 188.2–191.1◦C.
Elemental analysis: Calcd for C22H18AsF3O: C 61.41, H 4.22. Found: C 61.09, H 3.98%.
Chloroarsorane 4
To a solution of cis-3 (84 mg, 0.195 mmol) in CH2Cl2 (1.0 mL) under argon, SO2Cl2
(0.080 mL, 1.0 mmol) was added at room temperature and the mixture was stirred for
1
20 min. The solvent was then removed in vacuo to give a white powder of 4. H NMR
(CDCl3): δ = 8.21–8.19 (m, 2H), 7.82 (s, 2H), 7.70 (br s, 2H), 7.42–7.40 (m, 4H), 7.20 (s,
1H), 2.40 (s, 6H). 19F NMR (CDCl3): δ = −72.1 (br s).
Fluoroarsorane 5
To a solution of cis-3 (84 mg, 0.195 mmol) in CH2Cl2 (1.0 mL) under argon, SO2Cl2
(0.080 mL, 1.0 mmol) was added at room temperature. After stirring for 1 h at ambient
temperature, the mixture was evaporated in vacuo to give a white solid of 4. To the solid
was added CsF (62 mg, 0.49 mmol) and THF (2.0 mL). The resulting mixture was stirred
overnight at room temperature and the reaction was then quenched with H2O. The mixture
was then extracted with Et2O, the organic layer was washed with brine, dried over MgSO4,
and evaporated. The residue was recrystallized from CH3CN to afford colorless plate-like
1
crystals of 5 (39 mg, 0.086 mmol, 44%). H NMR (CDCl3): δ = 7.97 (s, 2H), 7.91 (d,
J = 8 Hz, 2H), 7.72 (d, J = 8 Hz, 2H), 7.38 (t, J = 8 Hz, 2H), 7.32 (t, J = 8 Hz, 2H),
2
7.26 (s, 1H), 2.41 (s, 6H). 13C NMR (CDCl3): δ = 147.2 (d, JCF = 2 Hz, C), 139.4 (d,
3
2JCF = 2 Hz, C), 137.9 (C), 137.7 (C), 134.8 (CH), 131.4 (d, JCF = 7 Hz, CH), 130.5
(CH), 129.7 (CH), 128.0 (CH), 125.5 (q, 1JCF = 282 Hz, C), 122.4 (q, 4JCF = 3 Hz, CH),
2
80.7 (q, JCF = 33 Hz, C), 21.4 (CH3). 19F NMR (CDCl3): δ = −72.0 (br s, 3F), −94.6
(s, 1F). Mp: 216.0–217.5◦C. Elemental analysis calcd for C22H17AsF4O: C 58.94, H 3.82.
Found: C 58.72, H 3.78%.

MONOHALOGENATED ALKOXYARSORANES
981
Bromoarsorane 6
To a solution of 5 (13 mg, 0.029 mmol) in CH2Cl2 (1.0 mL) under argon, TMSOTf
(0.010 mL, 0.055 mmol) was added at room temperature, and the mixture was stirred for
40 min. The volatiles were then removed in vacuo. To the residue, Et2O (1.0 mL) was
added. To the resulting suspension, a suspension of MgBr2 · OEt2 (10 mg, 0.040 mmol) in
Et2O (4.0 mL) was added at room temperature, and the mixture was stirred overnight. The
solvents were removed in vacuo, and the residue was dissolved in CH2Cl2. The resulting
solution was filtered through Celite, and the solvent was evaporated in vacuo to give a white
powder of 6 (15 mg), which contained a small amount of hydrolyzed compounds. 1H NMR
(CDCl3): δ = 8.28–8.26 (m, 2H), 7.69 (s, 2H), 7.69–7.67 (m, 2H), 7.45–7.40 (m, 4H), 7.17
(s, 1H), 2.39 (s, 6H). 19F NMR (CDCl3): δ = −72.1 (br s).
Single Crystal X-Ray Analysis of 5 and 6
Single crystals suitable for X-ray diffraction were mounted on a Rigaku SCXmini
diffractometer and irradiated with graphite monochromated Mo-Kα radiation (λ = 0.71073
Å) at 173 K for the data collection. The data were processed using the Rigaku SCXmini pro-
gram. The structure was solved by a direct method using the SHELXS-97 program.16 Refine-
ment on F2 was carried out using the full-matrix least-squares method of the SHELXL-97
program.16 All nonhydrogen atoms were refined using the anisotropic thermal parameters.
The hydrogen atoms were included in the refinement along with the isotropic thermal pa-
rameters. Crystallographic data for 5: monoclinic system, space group P21/c (no. 14), a =
9.0281(4) Å, b = 12.8285(6) Å, c = 16.1043(8) Å, β = 93.8790(10)◦, V = 1860.88(15)
Å3, Z = 4, Dcalc = 1.600 g cm−3, data/param = 4278/255, R1 (I > 2σ(I)) = 0.0241, wR2
(all data) = 0.0648, GOF = 1.011. 6: monoclinic system, space group P21/n (no. 14),
a = 8.7858(17) Å, b = 7.7016(15) Å, c = 27.834(5) Å, β = 96.097(5)◦, V = 1872.7(6)
Å3, Z = 4, Dcalc = 1.806 g cm−3, data/param = 4274/255, R1 (I > 2σ(I)) = 0.0435, wR2
(all data) = 0.1077, GOF = 1.056.
CCDC-708805 (5) and CCDC-708806 (6) contain the supplementary crystallographic
data for this article. These data can be obtained free of charge from the Cambridge Crys-
tallographic Data Centre via www.ccdc.cam.ac.uk/data request/cif.
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