Synthesis of dihalomethyl compounds of indium, X2InCHX2, and a study of their coordination chemistry

Article abstract of DOI:10.1021/om9506835

Indium(I) halides, InX (X = Cl, Br, I), react with haloforms, CHX₃, to give X₂InCHX₂ derivatives. Treatment of the latter with (C₂H₅)₄N⁺X^- gives the 1:1 electrolytes [(C₂H₅)₄N][X₃-InCHX₂], but with neutral ligands L (L = dimethylsulfoxide (dmso), 1,1,3,3-tetramethyl-2-thiourea (tmtu), triphenylphosphine), the products were the adducts of the corresponding indium trihalide, InX₃L_n (X = Cl, L = tmtu, n = 2; X = Cl, L = Ph₃P, n = 2; X = Cl, L = dmso, n = 3; X = Br, L = dmso, n = 3; X = I, L = Ph₃P, n = 2: X = I, L = tmtu, n = 1). [(C₂H₅)₄N][X₃InCHX₂] (X = Br, I) reacts with InX to give, after the addition of (C₂H₅)₄NX, the salts [(C₂H₅)₄N]₂[X ₃InCHXInX₃].

Full text of DOI:10.1021/om9506835

Organometallics 1996, 15, 2201-2204
2201
Articles
Syn th esis of Dih a lom eth yl Com p ou n d s of In d iu m ,
X2In CHX2, a n d a Stu d y of Th eir Coor d in a tion Ch em istr y
J ose´ Estrela dos Santos and Clovis Peppe*
Departamento de Quimica-CCEN, Universidade Federal da Paraiba, 58.059-900,
J oa˜o Pessoa-PB, Brazil
Martyn A. Brown and Dennis G. Tuck*
Department of Chemistry and Biochemistry, University of Windsor,
Windsor, Ontario, Canada N9B 3P4
Received August 30, 1995X
Indium(I) halides, InX (X ) Cl, Br, I), react with haloforms, CHX3, to give X2InCHX2
derivatives. Treatment of the latter with (C2H5)4N+X- gives the 1:1 electrolytes [(C2H5)4N][X3-
InCHX2], but with neutral ligands L (L ) dimethylsulfoxide (dmso), 1,1,3,3-tetramethyl-2-
thiourea (tmtu), triphenylphosphine), the products were the adducts of the corresponding
indium trihalide, InX3Ln (X ) Cl, L ) tmtu, n ) 2; X ) Cl, L ) Ph3P, n ) 2; X ) Cl, L )
dmso, n ) 3; X ) Br, L ) dmso, n ) 3; X ) I, L ) Ph3P, n ) 2: X ) I, L ) tmtu, n ) 1).
[(C2H5)4N][X3InCHX2] (X ) Br, I) reacts with InX to give, after the addition of (C2H5)4NX,
the salts [(C2H5)4N]2[X3InCHXInX3].
(Aldrich) were used as supplied. (C2H5)4N+X- salts (X ) Cl,
Br, I) (Aldrich) were dried over P2O5; dimethylsulfoxide (dmso)
(Merck) was dried over Linde 4A molecular sieves; triphen-
ylphosphine (Aldrich) was recrystallized from anhydrous di-
ethyl ether. Acetonitrile and CH2Cl2 (ACS grade; Merck) were
refluxed over calcium hydride and distilled before use. Acetone
(ACS grade; Merck) was refluxed over anhydrous calcium
chloride and distilled before use. Toluene (ACS grade; Merck),
diethyl ether (ACS grade; Merck), n-hexane (ACS grade
Merck), and petroleum ether (ACS grade; Merck) were dried
over sodium and distilled before use.
In tr od u ction
We have demonstrated that halomethyl complexes of
indium(III), X2InCH2X (X ) Br, I), can be prepared by
the oxidative insertion of an indium monohalide, InX,
into the carbon-halogen bond of the appropriate meth-
ylene dihalide.1 The addition of halide anions X- to
these species yields the corresponding salt of [X3In-
CH2X]-, but on treatment with neutral ligands, L (L )
Ph3P2,1 tmen,1 or tmtu2 ), the corresponding phosphorus,
nitrogen, or sulfur ylides X3InCH2L were obtained. We
now report the reactions of indium monohalides, InX,
with haloforms, CHX3 (X ) Cl, Br, I), and again we find
that InX inserts oxidatively into one carbon-halogen
bond of CHX3 to give X2InCHX2 derivatives. Some of
chemical properties of these compounds have been
investigated, especially their coordination chemistry
with anionic and neutral ligands and their reaction with
InX leading to halo-dimetallo-methane derivatives X2-
InCHXInX2, isolated and structurally characterized as
the salts [(C2H5)4N]2[X3InCHXInX3] (X ) Br, I).
Indium analysis involved back-titration of excess EDTA with
thorium nitrate. In a typical analysis, ca. 50 mg of the
compound was destroyed in nitric acid, the resultant solution
neutralized with sodium hydroxide, and the pH adjusted to 3
using a buffer of potassium hydrogen phthalate (0.1 M) and
HCl (0.1 M). Excess EDTA (10-2 M) was then added, and the
mixture was titrated with a standard solution (10-2 M) of
thorium(IV) nitrate, using xylenol orange as indicator. Halide
analysis was by the Volhard method, involving silver halide
precipitation and back-titration with potassium thiocyanate
solution. Microanalysis was by Canadian Microanalytical
Services Ltd. Conductivities were measured in a standard
platinum electrode cell, standardized with 1 M aqueous KNO3.
Proton NMR were recorded on a Varian EM 360 spectrometer,
and 13C NMR on a Bruker AC300L Instrument.
Exp er im en ta l Section
Gen er a l Da ta . Indium monohalides were prepared by
heating metal and trihalide together in a sealed tube.3 CHCl3
(Merck) was refluxed over anhydrous calcium chloride and
distilled before used; CHBr3, CHI3, N,N,N′,N′-tetramethyl-
ethanediamine (tmen), and 1,1,3,3-tetramethyl-2-thiourea (tmtu)
All preparative work was conducted under a dry nitrogen
atmosphere, using standard vacuum line techniques up to the
isolation of the products, which are air stable.
P r ep a r a tion of [(C2H5)4N][Cl3In CHCl2]. Indium mono-
chloride (0.30 g, 2.00 mmol) and CHCl3 (3.00 mL, 4.38 g, 37.5
mmol) were stirred together in acetonitrile (15 mL) until the
monochloride was consumed (ca. 48 h). A white precipitate,
an impurity resulting from the oxidation of InCl, was filtered
off and discarded. All the volatiles were removed from the
solution under vacuum to give an oil, which was redissolved
in acetonitrile (15 mL); tetraethylammonium chloride (0.33 g,
2.0 mmol) was added, and volatiles again were removed under
X Abstract published in Advance ACS Abstracts, April 1, 1996.
(1) Annan, T. A.; Tuck, D. G.; Khan, M. A.; Peppe, C. Organome-
tallics 1991, 10, 2159.
(2) Souza, A. C.; Peppe, C.; Tian, Z.; Tuck, D. G. Organometallics
1993, 12, 3354.
(3) Contreras, J . G. Ph.D. Thesis, Simon Fraser University, 1972.
(4) Weast, R. C. Handbook of Chemistry and Physics, 57th ed.; CRC
Press: Boca Raton, FL, 1976.
S0276-7333(95)00683-2 CCC: $12.00 © 1996 American Chemical Society

2202 Organometallics, Vol. 15, No. 9, 1996
dos Santos et al.
Ta ble 1. An a lytica l Resu lts
g, 0.66 mmol, 33.1% based on InCl) deposited as a white
powder, which was collected and dried.
indium, %
halogen, %
Rea ction of Br 2In CHBr 2 w ith d m so. This reaction was
investigated in two different ways:
compd
found
calcd
found
calcd
(C2H5)4N[Cl3InCHCl2]
(C2H5)4N[Br3InCHBr2]b
(C2H5)4N[I3InCHI2]
InCl3(tmtu)2
InCl3(Ph3P)2
InCl3(dmso)3
26.2
17.2
12.8
22.8
15.7
25.0
18.7
11.1
18.3
21.4
16.4
26.4
17.5
12.9
23.7
15.4
25.2
19.5
11.3
18.3
21.7
16.5
28.5a
55.3a
70.0
21.5
14.8
23.0
40.2
38.0
62.0
52.0
63.5
40.8
60.8
71.1
21.9
14.3
23.6
40.7
37.3
60.6
52.6
63.8
Meth od i. Rea ction w ith Equ im ola r Qu a n tities of
In Br a n d CHBr 3. Indium monobromide (0.89 g, 4.56 mmol)
and CHBr3 (0.40 mL, 1.16 g, 4.58 mmol) were stirred in
acetonitrile (15 mL) until the monobromide dissolved (ca. l h).
Small traces of residual solids were removed, and dmso (0.98
mL, 1.07 g, 13.7 mmol) was added to the filtrate. The solution
was pumped under vacuum to yield an oil, which was redis-
solved in hot ethanol (40 mL); after storage at -18 °C, InBr3-
(dmso)3 (1.53 g, 2.60 mmol, 57% based on InBr) precipitated
and was collected by filtration and dried.
InBr3(dmso)3
InI3(Ph3P)2
InI3(tmtu)
[(C2H5)4N]2[(Br3In)2CHBr]c
[(C2H5)4N]2[(I3In)2CHI]
a
Halide bonded to carbon may not be completely detected by
Meth od ii. Rea ction w ith Excess CHBr 3. Indium mono-
bromide (0.51 g, 2.62 mmol) and CHBr3 (2.00 mL, 5.78 g, 22.9
mmol) were stirred in acetonitrile (15 mL) until the monobro-
mide dissolved. Small traces of residual solids were removed,
and dmso (2.40 mL, 2.64 g, 33.8 mmol) was added to the
filtrate. The solution was pumped under vacuum to yield an
oil; addition of diethyl ether again led to the precipitation of
InBr3(dmso)3 (0.90 g, l.53 mmol, 58% based on InBr) as a white
powder.
b
the Volhard method. Found: C, 6.56; H, 3.35; N, 2.13. Calcd:
C, 16.44; H, 3.22; N, 3.13. c Found: C, 18.60; H, 3.77; N, 2.69.
Calcd: C, 19.20; H, 3.89; N, 2.64.
vacuum. Addition of 10 mL of ethanol caused the precipitation
of [(C2H5)4N][Cl3InCHCl2] as colorless crystals (0.60 g, 1.38
mmol, 69% based on InCl). Analytical results for this and
other compounds are collected in Table 1.
P r ep a r a tion of [(C2H5)4N][Br 3In CHBr 2]. Indium mono-
bromide (1.03 g, 5.28 mmol) and CHBr3 (2.0 mL, 5.79 g, 22.9
mmol) were stirred in acetonitrile (15 mL) until all the
monobromide dissolved (ca. 2 h). Small traces of residual solid
were removed by filtration, and tetraethylammonium bromide
(1.11 g, 5.29 mmol) was added to the filtrate. All the volatile
materials were removed from the solution to give an oil, which
was redissolved in 20 mL of acetone/ethanol (1:1, v/v); on
standing, this solution deposited colorless crystals of [(C2H5)4-
N][Br3InCHBr2] (2.74 g, 4.16 mmol, 79% based on InBr).
Rea ction of I2In CHI2 w ith tm tu . Indium monoiodide
(0.36 g, l.49 mmol) and CHI3 (0.58 g, 1.49 mmol) were stirred
in acetonitrile (15 mL) until the monoiodide dissolved (ca. 4
h). Small traces of residual solids were removed by filtration,
and tmtu (0.40 g, 3.03 mmol) was added to the filtrate;
evaporation to 50% of the initial volume led to the deposition
of 0.40 g of a solid, which was filtered off and dried under
vacuum. It was shown by GC/MS to be a mixture of CHI3 and
tmtu. The volatiles were removed from the filtrate to leave
an oil; addition of petroleum ether (10 mL) led to the precipita-
tion of InI3(tmtu) (0.33 g, 0.53 mmol, 35% based on InI) as a
white powder, which was collected and dried.
P r ep a r a tion of [(C2H5)4N][I3In CHI2]. Indium monoio-
dide (0.51 g, 2.10 mmol) and CHI3 (0.83 g, 2.10 mmol) were
stirred in acetonitrile (10 mL) until the monoidide dissolved
(ca. 4 h). Small traces of residual solid were removed by
filtration, and tetraethylammonium iodide (0.54 g, 2.10 mmoles)
was added to the filtrate. The solution was reduced in volume
by ca. 30% in vacuo, at which point yellow crystals of CHI3
(0.38 g, 0.96 mmol) (1H NMR in CDCl3: 5.00 ppm) precipitated
and were removed by filtration. Additional concentration of
the solution lead to by precipitation of [(C2H5)4N][I3InCHI2]
as yellow crystals (0.90 g, 1.00 mmol, 48% based on InI).
Rea ction of I2In CHI2 w ith P h 3P . Indium monoiodide
(0.51 g, 2.10 mmol) and CHI3 (0.83 g, 2.10 mmol) were stirred
in acetonitrile (15 mL) until the monoiodide dissolved (ca. 4
h), and small traces of residual solids were removed by
filtration. Ph3P (1.10 g, 4.20 mmol) was added to the filtrate,
which was concentrated to 50% of its initial volume. The
yellow solid (0.24 g) which deposited was discarded since it
contained no indium. When the filtrate was kept at -18 °C,
InI3(Ph3P)2 precipitated as a white powder, which was collected
and dried (1.10 g, 1.10 mmol, 52% based on InI).
Rea ction s of Cl2In CHCl2 w ith Neu tr a l Liga n d s. In-
dium monochloride (0.30 g, 2.00 mmol) and CHCl3 (3.00 mL,
4.48 g, 37.5 mmol) were stirred in acetonitrile (15 mL) until
the monochloride dissolved (ca. 48-72 h). A white precipitate
was filtered off and discarded, the volatiles were removed from
the solution under vacuum, and the residue so obtained was
redissolved in acetonitrile (15 mL). The ligand L (L ) Ph3P,
dmso, tmtu) was added to the solution, and the reactions were
worked up as follows:
Rea ction of I2In CHI2 w ith d m so. Indium monoiodide
(0.30 g, 1.24 mmol) and CHI3 (0.49 g, 1.24 mmol) were stirred
in acetonitrile (15 mL) until the monoiodide dissolved (ca. 4
h), traces of residual solids were removed, and dmso (0.30 mL,
0.33 g, 4.23 mmol) was added to the filtrate. The filtrate was
concentrated under vacuum to 50% and cooled to -18 °C,
which led to the precipitation of yellow crystals (0.60 g), which
were filtered off and dried under vacuum. The analytical
results for this material (C, 8.66; H, 2.02; In, 13.2; 1 59.0) are
not those for InI3(dmso)2 or I2InCHI2(dmso)n, and the formula-
tion of this product is not possible at this point (see below).
1,1,3,3-Tetr a m eth yl-2-th iou r ea . tmtu (0.53) 4.02 mmol)
was added and the mixture stirred for 30 min; all the volatiles
were removed under vacuum to leave an oil, which on
treatment with toluene (10 mL) precipitated InCl3(tmtu)2 (0.44
g, 0.91 mmol, 45% based on InCl) as a white powder, which
was filtered off and dried under vacuum.
P r ep a r a tion of [(C2H5)4N]2 [Br 3In CHBr In Br 3]. [(C2H5)4-
N][Br3InCHBr2] (0.53 g, 0.80 mmol) and InBr (0.16 g, 0.80
mmol) were stirred in acetonitrile (15 mL) until the monobro-
mide dissolved (ca. 2 h); (C2H5)4NBr (0.17 g, 0.80 mmol) was
added to the solution, and residual solids were removed. The
filtrate was pumped to dryness to yield an oil, which was
redissolved in 20 mL of acetone/ethanol (1:1/v:v); on standing,
this solution yielded [(C2H5)4N]2[Br3InCHBrInBr3] (0.61 g, 0.57
mmol, 71.1% based on InBr) as colorless crystals, which were
filtered off and dried.
Tr ip h en ylp h osp h in e. Triphenylphosphine (0.52 g, 2.00
mmol) was added and the solution concentrated to 50% of its
initial volume. The colorless crystals which precipitated, and
which were removed, were shown to be Ph3P (0.29 g, 1.11
mmol; mp ) 81-82 °C, lit.3 mp 80 °C). Volatiles were removed
under vacuum to yield an oil; addition of n-hexane (10 mL)
led to the precipitation of InCl3(Ph3P)2 (0.34 g, 0.46 mmol, 34%
based on InCl) as a white powder, which was collected and
dried.
P r ep a r a tion of [(C2H5)4N]2[I3In CHIIn I3]. [(C2H5)4N][I3-
InCHI2] (1.02 g, 1.14 mmol) and InI (0.28 g, 1.14 mmol) were
stirred in acetonitrile (15 mL) until the monoiodide dissolved;
(C2H5)4NI (0.29 g, 1.14 mmol) was added to the solution,
residual solids were removed, and the filtrate was concentrated
Dim eth yl Su lfoxid e. In the case of X ) Cl, dmso (0.43
mL, 0.47 g, 6 mmol) was added to the solution, which was
concentrated to half its initial volume, when InCl3(dmso)3 (0.30

X2InCHX2 Compounds
Ta ble 2. Mola r Con d u ctivitiesa
Organometallics, Vol. 15, No. 9, 1996 2203
proved impossible to detect the resonance of the chloride
compound in a 200 MHz instrument, due to the breadth
of the resonance signal, and it was necessary to use an
unusually large line-sharpening parameter in recording
the spectra. This is no doubt the result in part of the
presence of neighboring atoms with high nuclear spin
molar conductivity
compd
(Ω-1 cm2 mol-1
)
(C2H5)4N[Cl3InCHCl2]
(C2H5)4N[Br3InCHBr2]
(C2H5)4N[I3InCHI2]
138
166
157
a
(
115In, I ) 9/2; 35,37Cl, I ) 3/2; 79,81Br, I ) 3/2;127I, I ) 9/2).
All measurements in CH3CN solution at concentrations of ca.
1mM; standard value10 for 1:1 electrolytes in CH3CN 120-160 Ω-1
cm2 mol-1
We also note significant deshielding of the carbon
resonances of the InCHX2 compounds relative to CHX3,
which is probably due to the higher polar character of
the Inδ+-Cδ- bond in the organoindium relative to the
parent CHX3 compounds.
.
Ta ble 3. 1H a n d 13C NMR Sp ectr a of X2In CHX2
Der iva tives
compd
1Ha
13Ca
assgnt
Rea ction of th e X2In CHX2 Sp ecies w ith Neu tr a l
Don or s. The reactions of acetonitrile solutions of X2-
InCHX2 species with neutral ligands were investigated.
In almost every case, the product was an adduct of
corresponding indium(III) halide; the individual com-
pounds isolated are as follows: X ) Cl, L ) tmtu, n )
2; X ) Cl, L ) Ph3P, n ) 2; X ) Cl, L ) dmso, n ) 3; X
) Br, L ) dmso, n ) 3; X ) I, L ) Ph3P, n ) 2; X ) I,
L ) tmtu, n ) 1. The formation of adducts of InX3
adducts is apparent from both the analytical results
(Table 1) and from NMR studies (Table 3). The products
are in general conventional neutral derivatives of the
trihalides, which have been discussed elsewhere.5,6
The product of the reaction between dmso and I2-
InCHI2 is clearly different from those identified above.
The 1H and 13C NMR spectra (in CDCl3) confirm the
presence of dmso (1H, 2.57 ppm, s; 13C, 40.4 ppm), but
the analytical results do not correspond to the adduct
InI3(dmso)2 (calc: C, 7.37; H, 1.86; In, 17.6). Resonances
at 4.84, s (1H), and -39.3 ppm (13C) may indicate the
presence of a CH group (cf results for I3InCHI2-, Table
3), but again no sensible formula can be written on the
basis of the analytical data. The crystals were not
suitable for X-ray crystallography. The tentative con-
clusion is that the product is the result of attack by a
halomethylene group (see eq 1 below) on dmso, but we
have at present no structural data on which to formulate
the processes involved.
Rea ction of [X3In CHX2]- Sp ecies w ith In X. Tet-
raethylammonium salts of [X3InCHX2]- react with
equimolar quantities of InX (X ) Br, I) by dissolution
of the monohalides, and subsequent addition of equimo-
lar quantities of (C2H5)4NX allowed the isolation of
[(C2H5)4N]2[X3InCHXInX3]. The analytical results ob-
tained (Table 1) are in good agreement with the molec-
ular formulae. The solution chemistry of these com-
pounds suggests that complex and interesting decom-
position processes occur in basic solvents, and this
aspect of the problem will be discussed elsewhere.7
Mech a n istic Asp ects. The dihalomethyl compounds
of indium(III), X2InCHX2, synthesized by the insertion
of InX into the carbon-halogen bond of the correspond-
ing haloform, are close analogues of the halomethyl
compounds reported recently.1 A study of the coordina-
tion chemistry of the latter showed that there are two
electron acceptor sites in such molecules, namely the
indium atom and the CH2 group, and that coordination
may occur at either or both of these. Anionic ligands
coordinate to the metal center, while neutral ligands (L),
[(C2H5)4N][Cl3InCHCl2]b 5.63, s (1)
3.13, q (8)
c
InCHCl2
51.4 NCH2CH3
7.2 NCH2CH3
36.3 InCHBr2
52.9 NCH2CH3
7.7 NCH2CH3
-23.2 InCHI2
51.6 NCH2CH3
7.3 NCH2CH3
1.20, tt (12)
[(C2H5)4N[Br3InCHBr2]d 5.41, s (1)
3.51, q (8)
1.39, tt (12)
[(C2H5)4][I3InCHI2]c
3.95, s (1)
3.17 q, (8)
1.15, tt (12)
3.20, s
7.44, s, br
f
2.70, s
7.5, m
3.44, s
7.27
d
InCl3(tmtu)2
SdC[N(CH3)2]2
PC6H5
c
InCl3(Ph3P)2
InCl3(dmso)3
d
InBr3(dmso)3
OS(CH3)2
PC6H5
SdC[N(CH3)2]2
g
InI3(Ph3P)2
InI3(tmtu)d
CHCl3
77.5
12.1
-139.9
CHBr3
CHI3
6.84
5.00
a
ppm from δ(Me4Si) ) 0. s ) singlet, t ) triplet, q ) quartet,
m ) multiplet, br ) broad, tt ) triplet of triplets. Numbers in
b
parentheses show relative integrated intensities. In CD3CN.
d
c Not recorded. In (CD3)2CO. e In (CD3)2SO. f Too insoluble for
g
NMR studies. In CDCl3.
to 50%, when yellow crystals of [(C2H5)4N]2[I3InCHIInI3] (1.12
g, 0.81 mmol, 71%) precipitated.
Rea ction of (C2H5)4N[CI3In CHCl2] w ith In Cl. When
[(C2H5)4N][CI3InCHCl2] (0.40 g, 0.92 mmol) and InCl (0.14 g,
0.92 mmol) were stirred in acetonitrile (15 mL), dispropor-
tionation led to deposition of indium metal. This was collected,
and volatiles were removed from the filtrate under vacuum to
leave an oil, which on treatment with ethanol (10 mL) gave a
white solid shown to be unreacted [(C2H5)4N][CI3InCHCl2]
(0.26 g, 0.58 mmol).
Resu lts a n d Discu ssion
P r ep a r a tion of X2In CHX2 Sp ecies a n d Th eir
Rea ction s w ith Ha lid e. The reaction of InX (X ) Cl,
Br, I) with CHX3, which involves the oxidative addition
to one C-X bond of the haloform to give X2InCHX2
species, is very similar to that between InX and CH2X2,
which yielded the halomethyl complexes of indium X2-
InCH2X (X ) Br, I).1 Attempts to isolate the X2InCHX2
compounds formed in acetonitrile gave oily materials,
probably because of solvation of the indium center by
the donor solvent, but addition of (C2H5)4NX (X ) Cl,
Br, I) to these solutions caused precipitation of the
crystalline [(C2H5)4N][[X3InCHX2] salts. Elemental
analysis (Table 1), and the molar conductivities (Table
2), show that these compounds are 1:1 electrolytes in
acetonitrile. Additional structural information can be
obtained from their NMR spectra (Table 3). We first
note significant changes between CHX3 and the [X3In-
CHX2]- anions, corresponding to increased shielding of
protons relative to those in CHX3. The 13C resonances
of the InCHX2 group were difficult to detect; in fact, it
(5) Carty, A. J .; Tuck, D. G. Prog. Inorg. Chem. 1975, 19, 143.
(6) Carty, A. J .; Tuck, D. G. J . Chem. Soc. A. 1966, 1081.
(7) Santos, J . D.; Maurera, M. A. M. A.; Longo, E.; Peppe, C.
Unpublished results.

2204 Organometallics, Vol. 15, No. 9, 1996
dos Santos et al.
Sch em e 1
methyl complex of indium and carbene elimination:
X2InCH2X f InX3 + [:CHX]
(1)
This process has been verified in the case of the
bromomethyl analogue, Br2InCH2Br, and we have been
able to identify methylene transfer reactions such as
olefination of acetone8 and the esterification of benzoic
acid.9 These reactions clearly show the possibility of
using halomethyl compounds of indium as methylene
transfer reagents. The use of the new dihalomethyl
complexes, X2InCHX2, as reagents for transference of
halomethylene is also being investigated, and we will
deal with these results elsewhere.
such as Ph3P, tmen, tmtu,2 and dmso,8 prefer to attack
the CH2 group yielding nonelectrolyte adducts whose
structure (e.g. Br3InCH2L) indicates that the reaction
results in nucleophilic substitution of the halide at the
CH2X group by the corresponding ligand, accompanied
by halide transfer to the indium atom.
The new X2InCHX2 compounds behave analogously
only in their reactions with anionic ligands, where the
corresponding salts of [X3InCHX2]- were isolated. In
contrast, reaction with neutral ligands leads to isolation
of the corresponding adduct of InX3 (Scheme 1). The
adduct formation implies decomposition of the dihalo-
Ack n ow led gm en t. This work was supported in part
by Operating Grants (to C.P.) from the Conselho Na-
cional de Desenvolvimento Cientifico e Tecnolo´gico,
CNPQ, Brazil. J .E.S. thanks the CNPQ for the award
of a scholarship. The Natural Sciences and Engineering
Research Council of Canada is also thanked for Operat-
ing Grants (to D.G.T.).
OM9506835
(9) Ferreira, J . M. M.Sc. Thesis, Universidade Federal de Paraiba,
1994.
(10) Geary, W. J . Coord. Chem. Rev. 1971, 7, 81.
(8) Maurera, M. A. M. A. M.Sc. Thesis, Universidade Federal da
Paraiba, 1993.