Structure and reactivity of derivatives of dihalogenomethyl indium(III) halides, X2InCHX2 (X = Cl, Br, I)

Article abstract of DOI:10.1016/j.jorganchem.2004.10.036

The reactions of indium monohalides, InX with haloforms, CHX₃, in 1,4-dioxane (diox), produce the dioxane adducts of dihalogeno- dihalogenomethyl-indium(III), X₂In(diox)_nCHX₂ (X = Cl, Br, n = 1; X = I, n = 2) co

Full text of DOI:10.1016/j.jorganchem.2004.10.036

Journal of Organometallic Chemistry 690 (2005) 925–931
www.elsevier.com/locate/jorganchem
Structure and reactivity of derivatives of dihalogenomethyl
indium(III) halides, X2InCHX2 (X = Cl, Br, I)
a,
b,1
a
c
Clovis Peppe *, Dennis G. Tuck , Fabiano M. de Andrade , Jose A. Nobrega ,
´
´
b
Martin A. Brown , Robert A. Burrow
a
a
´ ´ ˆ
Departamento de Quımica, Laboratorio de Materiais Inorganicos, Universidade Federal de Santa Maria, Campus UFSM,
97105-900 Santa Maria-RS, Brazil
b
Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ont., Canada N9B3P4
´ ˆ
Departamento de Quımica, CCT, Universidade Estadual da Paraiba-UEPb, R. Juvencio Arruda s/n, 58109-790 Campina Grande-PB, Brazil
c
Received 2 October 2004; accepted 19 October 2004
Available online 19 November 2004
Abstract
The reactions of indium monohalides, InX with haloforms, CHX3, in 1,4-dioxane (diox), produce the dioxane adducts of dihalo-
geno–dihalogenomethyl–indium(III), X2In(diox)nCHX2 (X = Cl, Br, n = 1; X = I, n = 2) compounds. The ionic derivative
[(C2H5)4N] [Cl3InCHCl2] was prepared and its crystal structure determined by X-ray means. The reactions of the X2In(diox)nCHX2
compounds are significantly different from those of the related X2InCH2X compounds. The dihalogenomethyl derivatives react with
strong electrophiles suggesting dihalogenomethyl substituents of mild nucleophilic character, while the carbon atoms in the halog-
enomethyl derivatives are electrophilic.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Indium; Organoindium; Carbenoid; Crystal structure; Carbon–carbon bond formation
1. Introduction
(X = Br, I) compounds, 1 and their derivatives with
anionic and neutral donors, L. Adduct formation
may occur at either the metallic center, 1a favored
by hard ligands, or at the halogenomethyl carbon
atom, in which case ylid complexes of InX3, 1b were
identified (Scheme 1) [3].
Related work has shown that the analogous dihalog-
enomethyl compounds X2InCHX2 (X = Cl, Br, I) could
also be prepared by the reaction of InX with CHX3 in
acetonitrile, although the only stable derivatives then
obtained were the salts of the [X3InCHX2]ꢀ anions.
All efforts to obtain adducts with neutral donors such
as dimethylsulfoxide (dmso), triphenyl phosphine and
1,1,3,3-tetramethyl-2-thiourea (tmtu) resulted in the for-
mation of adducts of the corresponding indium(III) ha-
lide, InX3Ln(X = Cl, L = tmtu, n = 2; X = Cl, I,
L = Ph3P, n = 2; X = Cl, Br, L = dmso, n = 3; X = I,
L = tmtu, n = 1) [4]. We now report the isolation of
Metal carbenoids such as the Simmons–Smith re-
agent, iodomethylzinc iodide, IZnCH2I have found
extensive applications in olefin cyclopropanation [1].
More recently, it was determined that they are able to
homologate copper(I) reagents, RCu by adding methy-
lene units to produce new organocopper–zinc reagents
of the type R(CH2)nCu Æ ZnI2 able to react with electro-
philes [2]. The synthesis and structural investigation of
related new metal carbenoids is therefore of great
interest.
Previous papers have investigated the preparation,
crystal structure and reactivity of X2InCH2X
*
Corresponding author. Tel.: +55552208868; fax: +55552208031.
E-mail address: peppe@quimica.ufsm.br (C. Peppe).
1
In memmorian.
0022-328X/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.10.036

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C. Peppe et al. / Journal of Organometallic Chemistry 690 (2005) 925–931
L
L
X2In(L)nCH2X
X2InCH2X
X3InCH2L
1a
1b
1
X= Br, L = diox, n= 2;
X= Br, L = thf, n= 2;
X= Br, L= Br−, n= 1;
X= I, L= I−, n= 1;
X= Br, L = tmen, (C2H5)3N,
(C6H5)3E (E= P, As, Sb), (C6H5CH2)2S,
(C6H5)3PS, [(CH3)2N]2CS; X= I, L = tmen,
(C6H5)3P.
X= Br, L= (C6H5)3PO, n= 2.
Scheme 1. The coordination chemistry of X2InCH2X compounds, 1.
the 1,4-dioxane (diox) adducts, X2In(diox)nCHX2. The
salts [(C2H5)4N] [Cl3InCHCl2] and [(C6H5)4P]
[Br3InCHBr2] were also prepared from X2In(diox)-
CHX2, and the structure of the chlorine derivative
determined by X-ray methods. Further, we have demon-
strated that the dihalogenomethyl substituents on the
X2In(diox)nCHX2 compounds is of a mild nucleophilic
character, reacting only with strong electrophiles, such
as allyl bromide derivatives, carboxylic and mineral
acids.
excess CHI3, leaving I2In(diox)2CHI2 as a yellow pow-
der (0.95 g, 1.32 mmol, 64%). All the X2In(diox)nCHX2
compounds are air sensitive. Spectroscopic studies and
handling for elemental analysis were conducted under
dry nitrogen. Anal. Calc. for Cl2In(diox)CHCl2,
C5H9O2InCl4: In 32.1%. Found: 31.1%. 1H NMR
(CD3CN): d = 5.60 (s, 1H), 3.60 (s, 8H); 13C NMR
(CD3CN): d = 67.58, 46.65. Calc. for Br2In(diox)CHBr2,
C5H9O2InBr4, In 21.5%. Found: 21.2%. 1H NMR
(CD3CN): d = 5.36 (s, 1H), 3.60 (s, 8H); 13C NMR
(CD3CN): d = 67.77, 37.31. Calc. for I2In(diox)2CHI2,
C9H17O4InI4, In 14.1%, I 62.5. Found: 13.9%, 62.4%.
1H NMR (CD3CN): d = 4.30 (s, 1H), 3.59 (s, 16H);
13C NMR (CD3CN): d = 67.50, ꢀ47.75.
2. Experimental
2.1. General
2.3. Preparation of [Q] [X3InCHX2] [Q = (C2H5)4N,
X = Cl; Q = (C6H5)4P, X = Br]
The preparation of InX (X = Cl, Br, I) source and
treatment of starting materials, methods of elemental
analysis, and spectroscopic techniques were those de-
scribed earlier [4]. Allyl bromide and 3-bromo-2-
methyl-prop-1-ene were commercial reagents (Aldrich)
and distilled before used. 1,4-Dioxane was dried over
sodium/benzophenone and distilled before used. Other
reagents and solvents (ACS grade) were used as
supplied.
The salts [Q][X3InCHX2] were prepared from the cor-
responding X2In(diox)CHX2 compounds. Thus, to a
solution of X2In(diox)CHX2 (X = Cl, 2.66 mmol;
X = Br, 2.05 mmol) in 20 mL of dry acetonitrile was
added an equimolar amount of QX [X = Cl,
Q = (C2H5)4N, 2.66 mmol; X = Br, Q = (C6H5)4P, 2.05
mmol]. The mixture was stirred for ca. 2 h. At this point,
any solid impurity was removed by filtration. The salts
[Q] [X3InCHX2]were isolated as described below:
[(C2H5)4N] [Cl3InCHCl2]: Removal of all the volatiles
from the filtrate solution, gave an oil, which was redis-
solved in 20 mL of a mixture (1:1, v/v) of acetoni-
trile:ethanol (95%). Slow evaporation of the solvent in
air deposited colorless crystals of [(C2H5)4N]
[Cl3InCHCl2] (0.70 g, 1.6 mmol, 60%). Anal. Calc. for
C9H21NInCl5: In 26.4%. Found: 25.9%. 1H NMR
[(CD3)2 CO]: d = 5.63 (s, 1H), 3.47 (q, J = 7.5 Hz, 8H);
1.37 (tt, J = 7.5 Hz, J = 2.4 Hz, 12H); 13C NMR
[(CD3)2 CO]: d = 53.01, 46.65, 7.67.
2.2. Preparation of X2In(diox)nCHX2(X = Cl, Br, n = 1;
X = I, n = 2)
InX (X = Cl, 0.40 g, 2.66 mmol; X = Br, 0.40 g, 2.05
mmol; X = I, 0.50 g, 2.07 mmol) was suspended in 20
mL of freshly distilled dry 1,4-dioxane (diox). Excess
CHX3 (X = Cl, 1.00 mL, 12.50 mmol; X = Br, 0.55
mL, 6.30 mmol; X = I, 1.63 g, 4.14 mmol) was added
to the suspension and the mixture stirred to complete
dissolution of InX (X = Cl, 6 h; X = Br, 4 h; X = I, 16
h). At this point, any small quantity of solid impurity
was removed by filtration, the volatiles removed from
the filtrate under high vacuum, and the solution held
at low pressure for ca. 3 h. This procedure yields the
chloro and bromo derivatives as white solids (X = Cl,
0.71 g, 2.00 mmol, 75%; X = Br, 0.90 g, 1.68 mmol,
82%). The iodine compound was isolated by adding tol-
uene (10 mL) to the yellow solid obtained; this removes
[(C6H5)4P] [Br3InCHBr2]: Addition of 20 mL of eth-
anol (95%) to the acetonitrile filtrate solution and slow
concentration in air deposited colorless crystals of
[(C6H5)4P] [Br3InCHBr2] (1.45 g, 1.67 mmol, 82%).
Anal. Calc. for C25H21PInBr5: In 13.2%. Found:
1
13.2%. H NMR [(CD3)2CO]: d = 7.87–7.82 (m, 20H),
5.34 (s, 1H); 13C NMR [(CD3)2CO]: d = 136.39, 135.60

C. Peppe et al. / Journal of Organometallic Chemistry 690 (2005) 925–931
927
(d, J = 9.8 Hz), 131.33 (d, J = 12.1 Hz), 118.86 (d,
J = 83.70 Hz), 45.57.
(m, 10H), 3.16 (q, J = 7.5 Hz, 8H), 1.20 (tt, J = 7.5
Hz, J = 2.4 Hz, 12H).
2.6. The reaction of X2In(diox)nCHX2 (X = Br, n = 1;
X = I, n = 2) with HX in the presence of 1,1,3,3-
tetramethyl-2-thiourea (tmtu), [(CH3)2N]2CS, and
InX3
2.4. The thermal decomposition of Br2In(diox)CHBr2
A solution of Br2In(diox)CHBr2 (2.2 g, 4.1 mmol) in
dioxane (10 mL) was heated under reflux for 3 h. After
this period, all the volatiles were removed under vacuum
and condensed in a liquid nitrogen trap; a GC/MS anal-
ysis of the condensed liquid revealed only the solvent,
1,4-dioxane, and residual CHBr3, used in the prepara-
tion of Br2In(diox)CHBr2. The brown solid residue left
in the reaction flask, after pumping, was chromato-
graphed on a silica gel column; initial eluent was n-hex-
ane, then an n-hexane:ethyl acetate mixture with
increasing proportion of the ester up to the pure ester
was used; finally very polar solvents (acetone and etha-
nol) were employed as eluents; no organic derivative
from the initial reagent, Br2In(diox)CHBr2, was
detected.
X2In(diox)nCHX2 (X = Br, n = 1, 1.65 g, 3.08 mmol;
X = I, 2.01 g, 2.48 mmol) and two molar equivalents of
tmtu were stirred in 1,4-dioxane (10 mL) for 2 h. An ex-
cess of gaseous HX was passed through the solution, fol-
lowed by addition of solid InX3 (X = Br, 3.08 mmol;
X = I, 2.48 mmol). After 1 h of continuous stirring, all
the volatiles were removed under high vacuum. This
treatment produced an oily material. Stirring this oil
in ethanol 95% (10 mL) caused the precipitation of
[{[(CH3)2N]2CS}2CH2] [InX4]2 [X = Br, 3.12 g (colorless
crystals), 2.71 mmol, 88%; X = I, 3.42 g (yellow solid),
2.24 mmol, 90%]. Analytical and spectroscopic data
for these compounds are as follows:
In a parallel experiment, the brown solid residue, ob-
tained by removal of the solvent was partitioned in a
separation funnel with water and toluene; to the aque-
ous phase was added (C2H5)4NBr (0.86 g, 4.1 mmoles)
leading to the precipitation of [(C2H5)4N] (InBr4) (1.69
g, 3.0 mmol, 73%). Anal. Calc. for C8H20InBr4: In,
20.4%; Br, 56.4%. Found: In, 20.1%; Br, 56.6%. 1H
NMR [(CD3)2CO]: d = 3.50 (q, J = 7.5 Hz, 2H), 1.43
(tt, J = 7.5 Hz, J = 2.4 Hz, 3H).
[{[(CH3)2N]2CS}2CH2] [InBr4]2: Anal. Calc. for
C11H14N4S2In2Br8: In, 20.02%; Br, 55.72%; C, 11.49%;
H, 2.26%; N, 4.87%. Found: In, 19.96%; Br, 55.52%;
C, 11.36%; H, 2.21%; N, 4.72%. Molar conductivity (1
mmol Lꢀ1, CH3CN): 249 Xꢀ1 cm2 molꢀ1 1H NMR
.
(CDCl3): d = 3.55 (s, 12H), 5.15 (s, 2H); 13C NMR
(CDCl3): d = 38.29, 44.72, 173.88.
[{[(CH3)2N]2CS}2CH2] [InI4]2: Anal. Calc. for
C11H14N4S2In2I8: In, 15.11%; I, 66.64%; C, 8.66%; H,
1.70%; N, 3.67%. Found: In, 15.07%; I, 66.33%; C,
8.63%; H, 1.66%; N, 3.52%. Molar conductivity (1
2.5. The reaction of Br2In(diox)CHBr2 with benzoic acid
mmol Lꢀ1, CH3CN): 258 Xꢀ1 cm2 molꢀ1 1H NMR
.
Br2In(diox)CHBr2 (1.65 g, 3.08 mmol) and benzoic
acid (0.37 g, 3.08 mmol) were stirred in 1,4-dioxane
(10 mL) for 16 h and then heated under reflux for addi-
tional 3 h. All the volatiles were removed under high
vacuum and condensed in a trap cooled by liquid nitro-
gen; this solution revealed the presence of CH2Br2 by
GC/MS. After pumping, a solid residue is left in the
flask; this solid was re-dissolved in 20 mL of an etha-
nol:acetone (1:1, v/v) solution containing (C2H5)4NBr
(0.64 g, 3.08 mmol); a tedious recrystallization process
by reduction of the solution volume by slow evaporation
open to the atmosphere leads first to the deposition of
[(C2H5)4N] (InBr4) (0.76 g, 1.35 mmol), 44% based on
initial Br2In(diox)CHBr2 as colorless needles. Anal.
Calc. for C8H20InBr4: In, 20.4%; Br, 56.4%. Found:
(CDCl3): d = 3.55 (s, 12H), 5.15 (s, 2H); 13C NMR
(CDCl3): d = 38.29, 44.72, 173.88.
2.7. The reaction of I2In(diox)2CHI2 with allyl bromide:
the preparation of 4,4-diiodo-but-1-ene
To a solution of I2In(diox)2CHI2 prepared from equi-
molar amounts (0.82 mmol) of InI (0.20 g) and CHI3
(0.33 g) in 1,4-dioxane (10 mL) was added allyl bromide
(0.14 mL, 1.64 mmol). The mixture stirred for 4 h. After
this time, diethyl ether (40 mL) was added to the solu-
tion and the reaction was quenched with water (10
mL). The organic phase was extracted and washed with
additional 10 mL of water. The organic phase was dried
(MgSO4), filtered and concentrated under vacuum. The
oily residue was purified in a silica gel column with hex-
ane as eluent to yield 4,4-diiodo-but-1-ene (173 mg, 0.56
mmol, 68% based on initial I2In(diox)2CHI2). It is
important to note that the column chromatography
must be carried out as quickly as possible to avoid
light-induced decomposition of the product, 4,4-dii-
1
In, 20.1%; Br, 56.5%. H NMR [(CD3)2CO]: d = 3.50
(q, J = 7.5 Hz, 2H), 1.43 (tt, J = 7.5 Hz, J = 2.4 Hz,
3H). Ceased the deposition of [(C2H5)4N] (InBr4) oc-
curred the precipitation of colorless plates of
[(C2H5)4N] [Br2In(O2CC6H5)2] (0.78 g, 1.20 mmol),
39% based on initial Br2In(diox)CHBr2. Anal. Calc.
for C22H30NO4InBr2: In, 17.8%; Br, 24.7%. Found: In,
17.3%; Br, 24.5%. 1H NMR (CD3CN): d = 7.40–8.10
1
odo-but-1-ene. H NMR (CDCl3): d = 3.12 (triplet of
multiplets, 3J = 6.6Hz, 4J = 1.3 Hz, 4J = 1.0 Hz, 2H),

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C. Peppe et al. / Journal of Organometallic Chemistry 690 (2005) 925–931
3
4.90 (t, J = 6.6 Hz, 1H), 5.18 (doublet of multiplets,
Table 1
Crystal data and structural refinement of [(C2H5)4N][Cl2CHInCl3]
2
4
3J = 16.9 Hz, J = 1.3 Hz, J = 1.3 Hz, 1H), 5.28 (dou-
blet of multiplets, 3J = 10.2 Hz, 2J = 1.7 Hz, 4J = 1.0
Empirical formula
C9H21Cl5InN
3
3
3
Hz, 1H), 5.68 (m, J = 16.9 Hz, J = 10.2 Hz, J = 6.6
Hz, 1H); 13C NMR (CDCl3): d = ꢀ27.42, 51.64,
119.29, 136.34; MS (70 eV, EI): m/z (%): 308 (M, 25),
267 (5), 183(100).
Formula weight
Temperature (K)
Crystal system
435.36
298(2)
Monoclinic
P21/c
Space group
Unit cell dimensions
˚
a (A)
13.421(19)
16.377(35)
˚
2.8. The reaction of I2In(diox)2CHI2 with 3-bromo-2-
methyl-prop-1-ene: the preparation of 4,4-diiodo-2-
methyl-but-1-ene
b (A)
˚
c (A)
16.289(17)
92.045(10)
3578(9)
b (°)
3
˚
V (A )
Z
8
1.62
Dcalc (Mg/m3)
To a solution of I2In(diox)2CHI2 prepared from equi-
molar amounts of InI (0.20 g, 0.82 mmol) and CHI3
(0.33 g, 0.82 mmol) in 1,4-dioxane (10 mL) was added
3-bromo-2-methyl-prop-1-ene (0.16 mL, 1.64 mmol).
The mixture was kept under stirring for 1 h at room
temperature and at 60 °C for one additional hour. An
identical work up to that described for the reaction with
allyl bromide (Section 2.7) afforded 4,4-diiodo-2-methyl-
but-1-ene (143 mg, 0.44 mmol, 54% based on initial
Absorption coefficient (mmꢀ1
F(0 0 0)
)
2.047
1728
2.0–25.0
Theta range for data collection (°)
Index ranges
0 6 h 6 15, 0 6 k 6 19,
0 6 l 6 19
6813
Reflections collected
Independent reflections
Absorption correction
Max. and min. transmission
Refinement method
6517 [Rint = 0.12]
u-scan
1.000 and 0.738
Full-matrix least-squares on F
2765/0/290
1
I2In(diox)2CHI2). H NMR (CDCl3): d = 1.73 (s, 3H),
3.19 (d, J = 7.6 Hz, 2H), 4.87 (d, J = 1.5 Hz, 1 H),
Data/restraints/parameters
Goodness-of-fit on F
3
2
1.92
R1 = 0.050, wR2 = 0.044
1.20 and ꢀ1.02
2
3
5.05 (d, J = 1.5 Hz, 1 H), 5.10 (t, J = 7.6, 1H); MS
(70 eV, EI): m/z (%): 322 (M, 4), 195 (47), 67(100).
Final R indices [I > 2r(I)]
Largest diff. peak and hole (e A
ꢀ3
˚
)
2.9. Crystallographic measurements
coordinate to the metal atom, while soft ligands (phos-
phines, arsines, sulfides, selenides) were found bonded
to the halomethylic carbon. The molecules X2InCHX2
demonstrate very different pattern of Lewis acid behav-
ior, the essence of which is that they give stable adducts
only with ligands such as halides by coordination at the
indium atom, as described previously [4]. The dioxane
adducts synthesized in this study also involve coordina-
tion at the metallic center, as revealed by NMR spectro-
scopic data displayed in Table 2, which summarizes the
chemical shifts associated to the dihalomethyl substitu-
A suitable crystal of [(C2H5)4N][Cl3InCHCl2] was
mounted on a glass fiber, and X-ray diffraction data
was collected on a Rigaku AFC65 instrument with
graphite monochromated Mo Ka radiation (0.71073
˚
A). Cell constants and orientation matrices for data col-
lection were obtained using 25 reflections in the range
8.59 6 2h 6 16.07. The space group was identified from
the systematic absences as P21/c, and this was subse-
quently confirmed by the successful structure refine-
ment. Corrections were applied for decay, absorption
(semi-empirical using psi-scans), Lorentz and polariza-
tion effects. The structure was solved by direct methods.
All non-hydrogen atoms were refined anisotropically.
Hydrogen atoms were included initially in ideal posi-
tions, and subsequently refined isotropically. Other de-
tails of the data collection and structure refinement are
given in Table 1. Programs used in solving the structure
are in [5–10].
Table 2
1H and 13C Resonances of the dihalomethyl substituent on the
X2In(diox)nCHX2 compounds and related molecules
Compound
1H
13C
46.6
Cl2In(diox)CHCl2
Br2In(diox)CHBr2
I2In(diox)2CHI2
[Cl3InCHCl2]ꢀ
[Br3InCHBr2]ꢀ
[I3InCHI2]ꢀa
CH2Cl2
5.60
5.36
4.30
5.63
5.34
3.95
5.32
5.00
3.34
7.27
6.84
5.00
37.3
ꢀ47.8
46.6
45.6
3. Results and discussion
ꢀ23.2
54.0
20.3
We have demonstrated in previous papers that the
molecule Br2InCH2Br contains two electron deficient
sites, the metallic center and the halomethylic carbon
atom [3]. Accordingly, it forms stable adducts with the
ligand attached at either the In or C atoms (see Scheme
1). Hard ligands such as halides and oxygen donors
CH2Br2
CH2I2
ꢀ62.5
77.5
12.1
CHCl3
CHBr3
CHI3
ꢀ139.9
a
Data from [4].

C. Peppe et al. / Journal of Organometallic Chemistry 690 (2005) 925–931
929
ent attached to indium together with the parent CHX3
reagents and related molecules.
the crystal structure of [(C2H5)4N] [Cl3InCHCl2]. The
refinement showed the presence of two independent
ion pairs in the unit cell. The compound crystallizes in
alternate layers of both types of anions, with the cations
between these layers. Fig. 1 shows a cross-section of the
layers; crystallographic symmetry generates equivalent
ions stacked down the z-axis. The two corresponding
anions are identical within the experimental error, and
are so treated in this discussion. The two cations differ
only by the conformation of the ethyl groups.
The structure of one anion is shown in Fig. 2. The
other is identical as mentioned above and selected dis-
tances are listed in Table 3. The structure of the [Cl3In-
CHCl2]ꢀ anion clearly establishes the four-coordinate
indium(III) species. The stereochemistry around the in-
dium atom is slightly distorted tetrahedral (sum of all
angles at In 656(3)°).
The most fundamental chemical properties of the
X2In(diox)nCHX2 compounds are depicted at Scheme
2. The compounds are of marginal stability. The bro-
mine derivative decomposes in refluxing dioxane to
InBr3, the trihalide was isolated as the tetrabromoin-
date(III) following reaction with tetraethylammonium
bromide; but we were not able to detect any identifiable
product derived from the organyl substituent after care-
ful GC/MS analysis; it is possible that gaseous products
were formed and lost before product analysis.
The dioxane ligand attached to the metallic center is
easily replaced by halide anions. Thus, crystalline
[(C2H5)4N] [Cl3InCHCl2] and [(C6H5)4P] [Br3InCHBr2]
were prepared from the corresponding X2In(diox)n-
CHX2 compounds. Crystals of both compounds were
examined by single crystal X-ray methods. In the case
of the bromine derivative, the diffraction data were re-
corded satisfactorily but it proved impossible to refine
the structure beyond R < 15%, and the analysis was
abandoned; disorder in the anion seems the most likely
explanation for this failure. We successfully determined
The Cl(3,4,5)–In–C1 angles (mean value 111.6° for In1
and 111.3° for In2) are larger than the ideal value for a tet-
rahedron, and this is presumably imposed by the size of
the CHCl2 substituent. The In–Cl distances (mean value
˚
2.371 A for both anions) are slightly greater than those
in InClꢀ4 for which the In–Cl distances are in the range
QX, CH3CN, r.t.
[Q] [X3InCHX2]
X= Cl, Q= (C2H5)4N, 60%
X= Br, Q= (C6H5)4P, 81%
diox.
[(C2H5)4N] [InX4] + [CHX]
X= Br, 73%
,
1.∆
2. (C2H5)4NX
[(CH3)2N]2CS, HX, InX3, diox
[{[(CH3)2N]2CS}2CH2] [InX4]2
X= Br, 88%; X= I, 90%
X2In(diox)nCHX2
C6H5CO2H, diox
- CH2X2
[X2In(O2CC6H5)]
(C2H5)4NX, acetone:EtOH
[(C H ) N][X In(O C H ) ]
[(C2H5)4N] [InX4] +
X= Br, 44%
2
5 4
2
2 6 5 2
39%
X
Br
, diox
X
R
R
X= I, R= H, 68%; X= I, R= CH3, 54%
Scheme 2. Fundamental chemical properties of X2In(diox)nCHX2 compounds.

930
C. Peppe et al. / Journal of Organometallic Chemistry 690 (2005) 925–931
effect imposes a closing in the Cl–In–Cl angles followed
by the increasing of the Cl–In–C angles at the anion.
The constrained Cl–In–Cl angles forces the increasing
‘‘p’’ orbital contribution in the sp3 hybrids direct toward
the In–Cl bonds, and this effect is responsible for the
slightly longer In–Cl distances. In consequence of this,
the sp3Hybrid toward the In–C bond contains a higher
‘‘s’’ character, causing a shorter In–C bond distance
a
In1
In1
N1
N2
N2
In2
In2
ꢀ
˚
[2.17(1) A for both In1 aꢀnd In2] in [Cl3InCHCl2] when
˚
compared to [CH3InCl3] (2.213 A) [13].
N2
N2
The X2In(diox)nCHX2 compounds react with selected
electrophiles. Both, mineral (HX, X = Br,I) and benzoic
acid provoked the hydrolysis of the In–C bonds in the
molecules. From the reaction of Br2In(diox)CHBr2
and benzoic acid, organic product analysis by GC/MS
revealed the production of CH2 Br2 (M, 172/174/176).
The inorganic products isolated after reaction with
(C2H5)4NBr were the salts [(C2H5)4N] [InBr4] and
[(C2H5)4N] [Br2In(O2CC6H5)2], which come from ligand
redistribution reaction of the primary Br2In(O2C6H5)
formed by the hydrolysis (Eq. (1)). Ligand redistribution
is a common process in indium(III) chemistry and in fact
mixed bromide and benzoate ligands complexes of in-
dium(III) are known to redistribute [14].
N1
In1
In1
b
c
O
Fig. 1. Layers arrangement in the crystal structure of [(C2H5)4N]
[Cl3InCHCl2].
Cl4
Cl2
Cl3
C1
In 1
2Br2InðO2CC6H5Þ ! InBr3 þ BrInðO2CC6H5Þ
ð1Þ
Cl1
2
Hydrolysis of X2In(diox)nCHX2 (X = Br, I) with the
corresponding mineral HX acid follows a similar path-
way. Hydrolysis in the presence of 1,1,3,3-tetramethyl-
2-thiourea and InX3 yields the ionic species
[{[(CH3)2N]2CS}2CH2][InX4]2, which we have reported
before [15]. The reaction leading to these salts seems a
double nucleophilic displacement at the CH2 site of
CH2X2, the primary product of hydrolysis.
H1
Cl5
Fig. 2. Molecular structure of the [Cl2CHInCl3]ꢀ anion and number-
ing scheme.
The acid hydrolysis of the X2In(diox)nCHX2 mole-
cules suggests a nucleophilic electronic character of the
dihalomethyl substituent attached to the metal. Accord-
ingly, we attempted to react the X2In(diox)nCHX2 spe-
cies with selected organic electrophiles. They failed to
react with carbonyl compounds, but they react with allyl
bromide derivatives. Thus, 4,4-diiodo-but-1-ene and 4,4-
diiodo-2-methyl-but-1-ene were prepared from allyl bro-
mide and 3-bromo-2-methyl-prop-1-ene, respectively.
The scope of this coupling reaction is limited, since reac-
tions with 4-bromo-2-methyl-buten-2-ene, 2-bromo-1-
phenyl-propen-1-ene and 3-bromo-cyclohexen-1-ene
afforded a complex mixture of products. A plausible
intermediate to accommodate these results is depicted
at Fig. 3, that shows the interaction of the allylic sub-
strate with the organoindium compound to produce a
6-membered ring intermediate, with the coupling of
the CHXꢀ2 nucleophile to the c carbon following a SN0
mechanism. Further, allyl halides containing substitu-
ents R1 and R2 different of hydrogen will inhibit the car-
bon–carbon coupling reaction, presumably by steric
hindrance.
Table 3
Selected bond lengths (A) and angles (°) for the [Cl2CHInCl3]ꢀ anions
˚
In1–Cl3
2.376(4)
In2–Cl8
2.372(4)
In1–Cl4
In1–Cl5
In1–C1
Cl1–C1
Cl2–C1
2.371(4)
2.366(4)
2.17(1)
1.80(1)
1.76(1)
In2–Cl9
In2–Cl10
In2–C2
Cl6–C2
Cl7–C2
2.368(4)
2.374(3)
2.17(1)
1.77(1)
1.76(1)
Cl3–In1–Cl4
Cl3–In1–Cl5
Cl3–In1–C1
Cl4–In1–Cl5
Cl4-In1–C1
Cl5–In1–C1
In1–C1–Cl1
In1–C1–Cl2
Cl1–C1–Cl2
107.0(1)
107.9(1)
110.2(3)
106.9(1)
109.7(3)
114.8(3)
110.8(6)
110.1(6)
109.9(6)
Cl8–In2–Cl9
Cl8–In2–Cl10
Cl8–In2–C2
In2–C2–Cl6
Cl9–In2–Cl10
In2–C2–Cl7
Cl9–In2–C2
Cl6–C2–Cl7
Cl10–In2–C2
108.7(2)
107.2(1)
114.8(4)
110.8(6)
106.6(1)
110.2(6)
108.9(3)
110.1(7)
110.3(3)
ꢀ
˚
2.345–2.355 A [11,12], and in the [CH3InCl3] containing
˚
In–Cl distances in the range 2.394–2.409 A [13]; this is as-
cribed by repulsion between the bulky CHCl2 substituent
and the chloride ligands bonded to the metal atom. This

C. Peppe et al. / Journal of Organometallic Chemistry 690 (2005) 925–931
931
R1
mation may be obtained free of the charge from The
Director, CCDC, 12 Union Road, Cambridge, CB2 1
EZ, UK (fax: +44 1223 336033; email: deposit@ccdc.ca-
m.ac.uk or http://www.ccd.cam.ac.uk).
X
Br
X
R2
In
X
X
R3
Acknowledgements
Fig. 3. Proposed intermediate for the reaction of X2In(diox)nCHX2
with allyl bromide derivatives
C.P. thanks FAPERGS-Brazil for financial support.
F.M.A. thanks CNPq for the award of a scholarship.
4. Conclusion
References
The oxidative insertion of indium monohalides into
the carbon–halogen bonds of methylene trihalides affords
dihalogeno–dihalogenomethyl–indium(III) organomet-
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tion of the Lewis bases to the metallic center. Structural
information about the organoindium compounds was
obtained by solving the crystal structure of the ionic
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electron pair of suitable Lewis bases to generate organo-
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have isolated in previous works [3].
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5. Supporting material
´
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Crystallographic data for the structural analysis have
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Data Centre; CCDC No. 248952. Copies of this infor-
´
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