Dimethylindium hydrazides [Me2In-NH-NHR]2 (R = CMe3, C6H5)

Article abstract of DOI:10.1016/j.jorganchem.2005.12.014

Trimethylindium reacted with phenyl- and tert-butylhydrazine by the release of methane and the formation of the corresponding dimethylindium hydrazides (1 and 2, respectively). Both products form dimers and possess four-membered In₂N₂ heterocycles with two exocyclic N-N bonds in their molecular cores. Interestingly, one compound (1) crystallizes with centrosymmetric molecules in which the N-N bonds are located on different sides of the In₂N₂ ring (C_2h), while both N-N bonds are on the same side in 2 (C_2v). In contrast, the reaction of tri(tert-butyl)indium with tert-butylhydrazine yielded a quite unexpected product. Partial decomposition occurred, and in a low yield the adduct of tribenzylindium with the unchanged tert-butylhydrazine was isolated. In a remarkable reaction, the trialkylindium derivative did not react with the relatively acidic hydrazine, but by the release of the corresponding alkane with the solvent toluene.

Full text of DOI:10.1016/j.jorganchem.2005.12.014

Journal of Organometallic Chemistry 691 (2006) 1382–1388
www.elsevier.com/locate/jorganchem
Dimethylindium hydrazides [Me2In-NH-NHR]2 (R = CMe3, C6H5)
a,
a
b
Werner Uhl *, Christian H. Emden , Werner Massa
a
Institut fu¨r Anorganische und Analytische Chemie, Universita¨t Mu¨nster, Corrensstrasse 30, D-48149 Mu¨nster, Germany
b
Fachbereich Chemie der Philipps-Universita¨t, Hans-Meerwein-Straße, D-35032 Marburg, Germany
Received 5 October 2005; received in revised form 5 December 2005; accepted 9 December 2005
Available online 19 January 2006
Abstract
Trimethylindium reacted with phenyl- and tert-butylhydrazine by the release of methane and the formation of the corresponding
dimethylindium hydrazides (1 and 2, respectively). Both products form dimers and possess four-membered In2N2 heterocycles with
two exocyclic N–N bonds in their molecular cores. Interestingly, one compound (1) crystallizes with centrosymmetric molecules in which
the N–N bonds are located on different sides of the In2N2 ring (C2h), while both N–N bonds are on the same side in 2 (C2v). In contrast,
the reaction of tri(tert-butyl)indium with tert-butylhydrazine yielded a quite unexpected product. Partial decomposition occurred, and in
a low yield the adduct of tribenzylindium with the unchanged tert-butylhydrazine was isolated. In a remarkable reaction, the trialkylin-
dium derivative did not react with the relatively acidic hydrazine, but by the release of the corresponding alkane with the solvent toluene.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Indium; Hydrazides; Adducts
1. Introduction
nated hydrazide groups [7–9], of dimers possessing hetero-
cycles [5,8,10–16], and of oligomeric compounds with a
cage-like arrangement of metal and nitrogen atoms
[5,13,14,17–20]. In the past, most work has been done with
respect to the synthesis and structural characterization of
dialkylelementhydrazides of the elements aluminum and
gallium. Usually, these compounds form dimers possessing
four- (Al2N2, two exocyclic N–N bonds), five- (Al2N3, one
endocyclic N–N bond) or six-membered heterocycles
(Al2N4, two endocyclic N–N bonds) in their molecular cen-
ters. The respective molecular structure seems to be deter-
mined by steric reasons and by the transannular
electrostatic repulsion between the positively charged alu-
minum and gallium atoms or the negatively charged nitro-
gen atoms [16]. Their synthesis succeeds on different routes:
(i) alkane or hydrogen elimination by the reaction of trial-
kylelement derivatives or dialkylelement hydrides with
hydrazines possessing at least one N–H group; (ii) treat-
ment of dialkylelement halides with lithium hydrazides by
salt elimination; (iii) formation of adducts R2ECl-
NH2NHR and their reaction with alkyllithium reagents
by the release of alkane and the precipitation of lithium
The hydrazides of the heavier elements of third main-
group found considerable interest in recent research, which
essentially is caused by two important subjects. These com-
pounds may be suitable to act as starting materials for the
generation of the corresponding element nitrides (e.g., AlN
or GaN) under relatively mild conditions and are, thus, of
interest with some respect for an application in material
science [1]. Indeed, thermal decomposition accompanied
by the formation of the nitrides was observed in some
recent investigations. However, more systematic experi-
ments are required to get a concise impression of the prin-
cipal applicability of these precursors. Secondly, these
hydrazides showed a nice coordination behaviour owing
to their bidentate character with lone electron pairs at
two neighbouring nitrogen atoms [2], and many different
structural motifs were detected with the formation of
adducts [3–6], of monomers containing ‘‘side-on’’ coordi-
*
Corresponding author. Tel.: +49 251 8336610; fax: +49 251 8336660.
E-mail address: uhlw@uni-muenster.de (W. Uhl).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.12.014

W. Uhl et al. / Journal of Organometallic Chemistry 691 (2006) 1382–1388
1383
halide; (iv) hydroalumination, and (v) amide replacement
reactions. In contrast to the well-known chemistry of alu-
minum and gallium hydrazides, only very few reports on
indium hydrazides can be found in the literature. One
salt-like compound was reported by the group of No¨th
[21], some adducts were published by our group [22], and
only one neutral indium hydrazide was obtained by Glad-
felter with the compound In{N(SiMe3)-NMe2}3 [23]. More
systematic investigations into the applicability of indium
hydrazides for the formation of indium nitride require
the availability of a broader spectrum of corresponding
compounds possessing different properties such as solubil-
ity, volatility or thermal stability. Here, we report on
some attempts on the generation of dimethyl- and di(tert-
butyl)indium hydrazine derivatives.
agreement with the molecular structure schematically
shown in Eq. (1). The expected three signals were observed
for the different protons of the phenyl groups. The chemi-
cally different N–H protons gave two doublets by a cou-
pling across the N–N bond with chemical shifts of
d = 4.75 and 2.85 and a coupling constant of 3.0 Hz. The
resonance of the methyl groups attached to indium
occurred at a relatively high field (d = ꢀ0.18). Compound
1 did not melt until 200 ꢁC, however, the color of the pow-
der changed significantly from colorless over yellow to
brown at temperatures above 80 ꢁC. Attempts for enhanc-
ing the yield by changing the solvent and the reaction con-
ditions (e.g., boiling toluene) failed. Precipitation of
elemental indium occurred in many cases, and compound
1 was isolated in moderate yields only. 1 is rather sensitive
towards traces of oxygen, and the product adopted an
intensive yellow color on contact with air. Single crystals
for a crystal structure determination (see below) were
obtained by recrystallization from 1,2-difluorobenzene.
However, in accordance with the observations reported
before this procedure was accompanied by considerable
decomposition.
2. Results and discussion
2.1. Synthesis of dimethylindium phenylhydrazide and
dimethylindium tert-butylhydrazide
Owing to the instability and non-existence of dialkylin-
dium hydrides one very effective route for the synthesis of
aluminum and gallium hydrazides could not be applied
for the generation of indium hydrazides at all. A second
principal method involved the treatment of adducts formed
by hydrazines and dialkylaluminum or -gallium halides
with n- or tert-butyllithium. However, only substitution
reactions by the replacement of the chlorine atoms were
observed for those compounds bearing small alkyl groups
attached to their aluminum or gallium atoms, and success-
ful deprotonation of the hydrazine ligands and the forma-
tion of hydrazides were achieved with bulky tert-butyl
groups only [6]. Owing to the larger radius of indium atoms
all attempts for the generation of indium hydrazides on
such a route failed even in the case of adducts derived from
di(tert-butyl)indium chloride. Instead, the hydrazine
adducts of the corresponding trialkylindium derivatives
were formed and detected by NMR spectroscopy. Thus,
we decided to continue our efforts to synthesize indium
hydrazides by employing the direct reaction between
hydrazines and trialkylindium compounds.
2 InMe3 + 2 H2N-N(H)R
2 Me3In
NH2-N(H)R
R
N
H
H
N
N
Me
Me
In
In
- 2 CH4
Me
Me
H
N
R
H
1 (R = C6H5); 2 (R = CMe3)
ð1Þ
The reaction of trimethylindium with tert-butylhydra-
zine was different from that described before. When a solu-
tion of the indium compound in n-hexane was treated with
an equimolar quantity of the hydrazine derivative, Eq. (1),
a colorless solid precipitated after a few minutes, and gas
evolution was observed. A small quantity of the product
2 was formed and could be isolated from the solution.
The solid could be dissolved in benzene or toluene, but it
is stable in these solvents for a short period only. 1H
NMR data could be recorded, which verified the formation
of an adduct, Me3In-NH2-N(H)-CMe3 [d = ꢀ0.02 (9H,
InMe3), 0.52 (9H, CMe3), 2.42 (1H, br., NH), 2.53 (2H,
br., NH2)]. We were not able to get further data of charac-
terization owing to the relatively fast decomposition
accompanied by the precipitation of elemental indium.
The adduct decomposes on evacuation by the release of
methane and the formation of the hydrazide 2. However,
that reaction is not quantitative and selective enough to
offer a reasonable method for the synthesis of 2. The best
results were obtained by heating the suspension of the
A solution of trimethylindium in cyclopentane or n-hex-
ane was treated with an equimolar quantity of phenylhydra-
zine at room temperature. Two phases are formed owing to
the low solubility of phenylhydrazine in hydrocarbons.
After few minutes the second phase disappeared, and a col-
orless solid precipitated accompanied by gas evolution. The
solid was filtered off and cautiously dried in vacuum over a
short period only to yield a colorless powder of product 1 in
59% yield. Longer evacuation caused some significant alter-
ations, which subsequently resulted in the insolubility of the
product in organic solvents. The product (1) is relatively
unstable in aromatic solvents such as benzene or toluene,
so that the characterization by 13C NMR spectroscopy suc-
1
ceeded with some difficulties only. The H NMR spectro-
scopic data including the integration ratio are in clear

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W. Uhl et al. / Journal of Organometallic Chemistry 691 (2006) 1382–1388
adduct in toluene under reflux for 3 h, Eq. (1). Elemental
indium precipitated, which was removed by filtration.
The product (2) is highly soluble in non-polar solvents such
as cyclopentane or n-hexane, thus, all attempts of recrystal-
lization from these solvents failed. It was obtained as a col-
orless waxy solid from the solvent 1,2-difluorobenzene.
Partial decomposition occurred, and the solvent could
not be removed completely from the solid without initiat-
ing secondary processes. Thus, owing to decomposition
and the particular consistence of the product a reasonable
figure for the yield could not be detected. The NMR spec-
troscopic investigations gave similar results as described for
compound 1.
Single crystals of compound 1 were obtained by recrys-
tallization from 1,2-difluorobenzene (20/+8 ꢁC) as
described before. It possesses a four-membered In2N2
heterocycle in its molecular center with two exocyclic
N–N bonds (Fig. 1). With only one exception, similar
structures were observed for dimeric organoelement
hydrazides of gallium [2,5,6,11,12,14], while a broader var-
iability of structural motifs was determined for the corre-
sponding aluminum derivatives [2,4,10,16]. The only
neutral indium hydrazide published so far, In{N(SiMe3)-
NMe2}3, formed a monomer in the solid state [23]. Two
dimers were detected in the cell of 1, both reside on crystal-
lographic centers of symmetry and possess ideally planar
In2N2 rings. The In–N bond lengths (223.2–224.4 pm) are
almost indistinguishable and are in the normal range of
In–N–In groups with nitrogen bridging two indium atoms
[24]. Expectedly, the larger angle in the heterocycles is
found at the nitrogen atoms (96.6ꢁ vs. 83.4ꢁ on average).
The N–N distances (143.9 pm on average) are in the usual
range observed for aluminum and gallium hydrazides [2].
The inner nitrogen atoms attached to indium possess a dis-
torted tetrahedral coordination sphere, while the exo nitro-
gen atoms have a trigonal pyramidal surrounding (sum of
the angles 339.9ꢁ).
The growing of single crystals of compound 2 proved to
be extremely difficult. In one case only relatively small crys-
tals were obtained, which, however, were twinned. Never-
theless, refinement of the structure to reasonable R-values
succeeded. 2 forms dimers with an inner In2N2 heterocycle
and two exocyclic N–N bonds as often observed before for
dimeric aluminum and gallium hydrazides. However, for
the first time a cis-arrangement of the hydrazido ligands
was determined (Fig. 2). Schematic drawings of the differ-
ent structures of both indium hydrazides (approximately
C2h for 1 and C2v for 2) are shown in Scheme 1. Owing
to the twin problem the standard deviations of the struc-
tural data of 2 are relatively high, thus, the discussion is
restricted to a few features only. The In–C distances differ
(213.2 vs. 218.2 pm on average) compared to the narrow
range observed for the centrosymmetric compound 1.
The shorter ones were detected for those bonds which are
on the same side of the In2C2 heterocycle as the N–N
bonds. The N–N bonds are little lengthened compared to
those of 1 (143.9 vs. 149 pm on average), but the In–N
bond lengths are in the same range. Owing to the particular
molecular symmetry of 2 the central In2N2 heterocycle is
not planar, but folded across the Inꢁ ꢁ ꢁIn axis by 18.7ꢁ.
Fig. 2. Molecular structure of 2. The thermal ellipsoids are drawn at the
40% probability level. Hydrogen atoms of methyl groups are omitted.
Important bond lengths (pm) and angles (ꢁ): In1–C11 212(2), In1–C12
220(1), In1–N11 223(1), In1–N21 225(1), In2–C21 214(2), In2–C22 217(2),
In2–N11 225(1), In2–N21 222(1), N11–N12 149(2), N21–N22 148(2),
In1ꢁ ꢁ ꢁIn2 328.8(1), N11–In1–N21 83.9(5), In1–N11–In2 94.5(4), N11–
In2–N21 84.0(4), In1–N21–In2 94.8(4).
Me
Me
Me
Me
CMe3
N
CMe3
N
C6H5
N
In
In
In
In
Fig. 1. Molecular structure of 1. The thermal ellipsoids are drawn at the
40% probability level. Methyl and phenyl hydrogen atoms are omitted.
Only one dimer is depicted. Important bond lengths (pm) and angles (ꢁ):
In1–C1 214.7(3), In1–C2 215.5(3), In1–N11 223.2(2), In1–N110 224.4(2),
N11–N12 143.9(3), In1ÆIn10 335.51(4), C1–In1–C2 130.2(1), N11–In1–
N110 82.88(8), In1–N11–In10 97.13(8) [second molecule: In2–C3 215.6(2),
In2–C4 215.2(3), In2–N21 223.4(2), In2–N2100 223.9(2), N21–N22
143.8(3), In2–In200 332.79(5), C3–In2–C4 133.8(1), N21–In2–N2100
83.86(9), In2–N21–In200 96.14(9)]. N110 and In10 generated by ꢀx,
ꢀy + 2, ꢀz + 1; N2100 and In200 generated by ꢀx, ꢀy + 1, ꢀz + 2.
H
H
H
H
N
H
N
N
N
H
H
H
N
C6H5
Me Me
Me Me
1 (C2h
)
2 (C2v)
Scheme 1.

W. Uhl et al. / Journal of Organometallic Chemistry 691 (2006) 1382–1388
1385
The occurrence of cis/trans isomers of dimeric gallium
2.2. Reaction of tri(tert-butyl)indium with tert-
butylhydrazine
hydrazides in solution was derived from some temperature
dependent NMR spectroscopic investigations several times
before [5,6,11,12]. However, structural evidence was miss-
ing, and the trans isomers crystallized in all cases and were
detected by crystal structure determinations. Thus, the
molecular structure of 2 represents the singular case where
the cis isomer could be isolated in the solid state. It strongly
supports the existence of that particular molecular form in
solution. However, NMR spectra of 2 are quite simple and
in absolute agreement with a centrosymmetric molecule. In
order to get a better insight into the dynamic behaviour of
the molecules in solution NMR experiments at low temper-
ature were conducted in toluene. A general and significant
low-field shift was detected with decreasing temperature
(e.g., for In–Me: d = 0.08 at room temperature to
d = 0.27 at ꢀ70 ꢁC). Coalescence of the NH and Me–In
resonances with very broad signals seem to occur at about
ꢀ75 ꢁC. Below that temperature (ꢀ80 ꢁC) two sets of reso-
nances were observed for each kind of N–H protons
(d = 2.79/2.53 and 2.71/2.41, pairs of resonances with
equal intensity) and for the methyl groups attached to
indium (d = 0.41 and 0.32). Thus, it seems to be clear that
two different molecular forms exist at low temperature. But
a concise interpretation of these observations is prevented
by decomposition and by the occurrence of resonances
which were caused by secondary products. As mentioned
before, similar equilibria were detected for dimeric gallium
hydrazides. However, the equilibration of their isomeric
forms was observed at relatively high temperatures
(>50 ꢁC).
Tri(tert-butyl)indium did not react with tert-butylhydra-
zine by the release of methylpropane in n-pentane or n-hex-
ane even after prolonged stirring of solutions at room
temperature. Reaction was observed in boiling toluene over
several hours. However, considerable quantities of elemen-
tal indium precipitated as a grey powder. After filtration all
volatile components were removed in vacuum. A colorless
solid remained which was recrystallized from cyclopentane.
Surprisingly, the NMR spectroscopic characterization of
the product (3) revealed a resonance of one sort of tert-
butyl groups only, and benzyl groups could be identified
by the signals of their phenyl and methylene protons. The
hydrazine molecule seemed to be intact, and two reso-
nances of N–H protons were detected in an integration
ratio of 2 to 1. A coupling across the N–N bond was
detected with a relatively large coupling constant of
5.8 Hz. In accordance with the results of a crystal structure
determination an adduct of tert-butylhydrazine with tri-
benzylindium was formed in the course of that reaction,
Eq. (2). Thus, interestingly the hydrazine molecule was
not affected here, instead toluene was attacked, and a ben-
zyl compound resulted by the probable release of methyl-
propane. It seems that caused by the influence of the
alkyl group the acidity of the hydrazine molecule is consid-
erably decreased [25]. Furthermore, steric shielding of the
indium compound In(CMe3)3 may influence the particular
course of this reaction. The yield of the finally isolated
product 3 is 13% only. But no further compound could
be identified by NMR spectroscopy, and the rough product
after filtration showed only the resonances of 3. Volatile
products may be formed by the homolytic cleavage of
In–C bonds, which were removed together with the solvent.
The precipitate of elemental indium may be taken as an
indication of such a decomposition reaction.
1
Low temperature H NMR data of the indium hydra-
zide 1 show, however, that these equilibria may indeed
involve more complicated mixtures of compounds and
that the description by simple cis/trans isomers may be
an oversimplification. At room temperature the expected
simple spectrum resulted with a singlet for the methyl
groups attached to indium and a singlet for each of the
chemically different N–H protons. Coalescence of the
methyl resonance occurred at about ꢀ25 ꢁC. Below that
In(CMe3)3
+
H2N-N(H)-CMe3
+
3 H5C6-CH3
temperature
a
splitting into five signals resulted
CH2-C6H5
(d = 0.14, 0.11, ꢀ0.03, ꢀ0.12 and ꢀ0.23) with temperature
dependent intensity ratios of about 1.0/1.2/2.0/1.1/1.0 at
ꢀ33 ꢁC and 1.0/0.6/2.0/0.6/1.0 at ꢀ83 ꢁC. Two methyl res-
onances are to be expected for the cis isomer, while the
trans form should give one resonance only. Thus, it seems
to be clear that further species are present here, which,
however, could not be identified unambiguously, and all
attempts to assign particular structures would be rather
speculative. Same holds for the hydrazine resonances.
The two signals observed at room temperature gave seven
resonances at ꢀ23 ꢁC [d = 5.09 (d, JH–H = 4.8 Hz), 4.73,
4.42, 3.03, 2.92 (d, JH–H = 4.8 Hz), 2.83 and 2.71]. Further
cooling to ꢀ83 ꢁC gave a completely different spectrum
with eight resonances (d = 5.32, 4.85, 4.66, 4.57, 2.84,
2.71, 2.66, 2.65 and 2.52), the last six ones of which are
of equal intensity.
ð2Þ
C6H5-H2C
In
NH2-N(H)-CMe3
- 3 HCMe3
CH2-C6H5
3
Crystal structure determination verified the unexpected
structure of 3 (Fig. 3). Three benzyl groups are attached
to the central indium atom, which is further coordinated
by the NH2-nitrogen atom of a tert-butylhydrazine ligand.
The molecules are located on crystallographic mirror
planes. The methylene carbon atoms of the benzyl groups
are almost ideally in a plane with the indium atom (sum
of the C–In–C angles 358.2ꢁ). The hydrazine moiety is
almost perpendicular to that group with C–In–N angles
between 93.6ꢁ and 94.8ꢁ. This particular bonding situation

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W. Uhl et al. / Journal of Organometallic Chemistry 691 (2006) 1382–1388
cyclopentane over LiAlH4, 1,2-difluorobenzene over
˚
molecular sieves (4 A). Trimethylindium and tri(tert-
butyl)indium were obtained according to the literature
procedures [27,28]. Commercially available phenylhydra-
zine (Aldrich) was degassed, stored over molecular sieves
and distilled in vacuum prior to use. MOCHEM GmbH
(Marburg, Germany) kindly supported us with tert-butyl-
hydrazine.
3.1. Synthesis of dimethylindium phenylhydrazide 1
Trimethylindium (0.895 g, 5.60 mmol) was dissolved in
45 ml of n-hexane and treated with 550 ll (0.605 g,
5.60 mmol) of phenylhydrazine at room temperature.
Two liquid phases were formed owing to the insolubility
of the hydrazine in n-hexane. The reaction started by gas
evolution and precipitation of the colorless product after
a few minutes. The suspension was stirred at room temper-
ature for 1 h. Compound 1 was isolated in a pure form by
filtration and short evacuation of the residue (maximum
10ꢀ2 Torr, 1 min). Yield: 0.835 g (59%), colorless powder,
which adopts an intense yellow color on contact with traces
of air. The melting point could not be determined; the color
of the powder changed to brown at about 80 ꢁC under
Fig. 3. Molecular structure of 3. The thermal ellipsoids are drawn at the
40% probability level. Methyl groups of the tert-butyl group and hydrogen
atoms of the benzyl groups are omitted. Important bond lengths (pm) and
angles (ꢁ): In1–C11 220.2(2), In1–C21 220.8(2), In1–N1 235.1(2), N1–N2
143.3(3), C11–In1–C21 114.27(5), C11–In1–C110 129.66(9), C11–In1–N1
94.76(6), C21–In1–N1 93.63(7). C110 generated by x, ꢀy + 1/2, z.
with a high s-character in the In–C bonds has been
observed several times before, e.g., in adducts of gallane,
GaH3 [26]. Further narrow contacts to the indium atoms
could not be detected, so that a higher coordination num-
ber with a trigonal bipyramidal geometry at the indium
atoms can be excluded. The In–N bond of 3 (235.1 pm) is
little lengthened by about 5 pm compared to those of
adducts between dimethylindium chloride and hydrazines.
This may be caused by the enhanced bulkiness of the ben-
zyl groups compared to the methyl substituents and by the
influence of the electronegative chlorine atom in the chloro
compounds. The N–N bond length (143.3 pm) is in the
normal range. The phenyl groups are oriented to the same
side of the molecule and form a hollow in which the hydra-
zine ligand in enclosed. The N–N bond bisects the angle
C11–In1–C110, which is relatively large (129.7ꢁ) compared
to the remaining two C–In–C angles (114.3ꢁ).
1
argon, but the solid did not melt until 200 ꢁC. H NMR
(C6D6, 300 MHz, 298 K): d = 7.11 (4H, pseudo-t, m-H of
phenyl), 6.74 (2H, pseudo-t, p-H of phenyl), 6.40 (4H,
3
pseudo-d, o-H of phenyl), 4.75 (2H, d, JHꢁ ꢁ ꢁH = 3.0 Hz,
3
N–H), 2.85 (2H, d, JHꢁ ꢁ ꢁH = 3.0 Hz, N–H), ꢀ0.18 (12H,
s, InMe2). 13C NMR (C6D6, 100 MHz, 298 K): d = 152.1
(N–C), 129.4, 119.5, 112.5 (all phenyl), ꢀ4.4 (InMe2). IR
(cmꢀ1; paraffin; CsBr): 3301 w br., 3256 w br., 3187 w br.
mNH; 2954 vs, 2923 vs, 2853 vs (paraffin); 1699 vw, 1599
s, 1580 m, 1495 s (phenyl); 1462 vs, 1377 s (paraffin);
1306 w, 1263 w, 1207 w, 1177 w, 1156 w, 1074 w, 1023
w, 953 w, 881 w dCH3, mCC, mNN, mNC; 799 s, 754 sh,
694 vs (phenyl); 676 sh, 615 w, 517 m, 467 m mInC, mInN.
3.2. Synthesis of dimethylindium tert-butylhydrazide 2
In summary, the synthesis of dialkylindium hydrazides
seems to be rather difficult compared to the relatively facile
syntheses of the aluminium or gallium analogues. The
indium compounds could be isolated in low yields only.
They tend to decompose in solution or in vacuum, and
redox processes with the precipitation of elemental indium
were observed in all synthetic procedures. This is in
remarkable contrast to the properties of the aluminum or
gallium hydrazides, which are accessible on high yield
routes and can be sublimed in vacuum in many cases with-
out decomposition. Furthermore, we did not observe the
preferred attack of an E–C bond on solvent molecules in
the presence of hydrazine molecules before.
Trimethylindium (0.779 g, 4.875 mmol) was dissolved in
25 ml of n-hexane and treated with 521 ll (0.429 g,
4.875 mmol) of tert-butylhydrazine at room temperature.
A solid precipitated which probably consists of the adduct
Me3InÆNH2N(H)-CMe3. It was filtered off, dissolved in
25 ml of toluene and heated under reflux for 3 h. Elemental
indium precipitated, which was filtered off. The solvent was
removed in vacuum, and the residue was recrystallized with
partial decomposition from 1,2-difluorobenzene (20/
ꢀ15 ꢁC). A colorless waxy solid resulted, which even after
prolonged evacuation included a considerable quantity of
the solvent. Owing to the viscidity of the product the
determination of a reasonable yield and the determination
of the melting point failed. 1H NMR (C6D6, 200 MHz,
3. Experimental
3
298 K): d = 2.65 (2H, d, JHꢁ ꢁ ꢁH = 1.5 Hz, N–H), 2.52
3
All procedures were carried out under purified argon.
Toluene was dried over Na/benzophenone, n-hexane and
(2H, d, JHꢁ ꢁ ꢁH = 1.5 Hz, N–H), 0.82 (18H, s, CMe3),
0.10 (6H, s, InMe2). 13C NMR (C6D6, 50 MHz, 298 K):

W. Uhl et al. / Journal of Organometallic Chemistry 691 (2006) 1382–1388
1387
d = 53.8 (N–C), 26.8 (Me of CMe3), ꢀ8.8 (InMe2). IR
(cmꢀ1; paraffin; CsBr): 3331 w, 3165 w mNH; 2954 vs,
2923 vs, 2853 vs, 1459 s, 1377 s (paraffin); 1305 w, 1229
w, 1211 w, 1174 w, 1109 vw, 1076 m, 1036 m, 954 w, 865
vw dCH3, mCC, mNN, mNC; 720 sh, 691 s, 519 m, 442 m
mInC, mInN, dC3C.
m, 3017 m (phenyl); 2955 vs, 2924 vs, 2854 vs (paraffin);
1937 vw, 1864 vw, 1806 vw, 1594 m, 1487 m (phenyl);
1455 s, 1377 m (paraffin); 1305 vw qCH3; 1207 m, 1178
w, 1151 w, 1038 s, 995 w, 899 w, 846 vw, 795 w mCC,
mNN, mNC; 752 m, 698 m (phenyl); 536 vw, 520 vw, 463
m mInC, mInN, dC3C.
3.3. Synthesis of tribenzylindium(tert-butylhydrazine) 3
3.4. Crystal structure determinations of compounds 1–3
Tri(tert-butyl)indium (1.079 g, 3.78 mmol) was dissolved
in 50 ml of toluene and treated with 404 ll (0.333 g,
3.78 mmol) of tert-butylhydrazine at room temperature.
The yellow color of the trialkylindium compound disap-
peared immediately. The solution was heated under reflux
for 18 h, which resulted in the precipitation of a finely
divided grey powder of probably elemental indium. Filtra-
tion and evaporation of the solvent yielded a colorless solid
residue, which was recrystallized from cyclopentane. Yield:
0.239 g (13%), colorless crystals of 3. 1H NMR (C6D6,
200 MHz, 298 K): d = 7.03 (6H, pseudo-t, meta-H of phe-
nyl), 6.92 (6H, pseudo-d, ortho-H of phenyl), 6.77 (3H,
pseudo-t, para-H of phenyl), 2.38 (2H, d, 3JHꢁ ꢁ ꢁH = 5.8 Hz,
NH2), 2.18 (6H, s, CH2 of benzyl), 1.68 (1H, t,
3JHꢁ ꢁ ꢁH = 5.8 Hz, NH), 0.43 (9H, s, CMe3). 13C NMR
(C6D6, 75 MHz, 298 K): d = 148.7 (ipso-C of phenyl),
128.9 and 126.3 (ortho- and meta-C of phenyl), 121.5
(para-C of phenyl), 53.1 (NC), 25.4 (CMe3), 23.0 (In-
CH2). IR (cmꢀ1; paraffin; CsBr): 3311 m br. mNH; 3062
Single crystals were obtained on cooling of saturated
solutions in different solvents (compounds 1, 1,2-difluoro-
benzene, 20/+8 ꢁC; compound 2, pentafluorobenzene,
20/+8 ꢁC; compound 3, cyclopentane, +8 ꢁC). The crystal-
lographic data were collected with a STOE IPDS diffrac-
tometer. The structures were solved by direct methods
and refined with the program SHELXL-97 [29] by a full-
matrix least-squares method based on F2. Crystal data,
data collection parameters and structure refinement details
are given in Table 1. The crystal of compound 2 proved to
be a reflection twin in (001). Owing to the approach of the
monoclinic angle to 90ꢁ, the small ratio of the twin
domains of about 0.2, and the weak overall intensities, twin
integration and refinement gave poor results only. Thus,
reflection data integrated with the orientation matrix of
the stronger domain only were used, and the 14 most
impaired reflections were omitted. A possible additional
inversion twinning could not be confirmed significantly
(Flack parameter 0.34(11)). Due to remarkable deviations
Table 1
Crystal data and structure refinement for 1, 2, and 3a
1
2
3
Formula
Temperature (K)
Crystal system
Space group [30]
a (pm)
b (pm)
c (pm)
a (ꢁ)
C
193(2)
Triclinic
16H26In2N4
C12H34In2N4
193(2)
C25H33InN2
193(2)
Monoclinic
P21 (no. 4)
686.81(7)
1215.7(2)
1164.6(1)
90
Orthorhombic
Pnma (no. 62)
915.99(4)
1345.99(7)
1894.0(1)
90
ꢀ
P1 ðno. 2Þ
888.34(8)
999.02(9)
1258.40(1)
70.776(7)
b (ꢁ)
84.632(7)
65.699(7)
959.9(1)
2
1.744
2.404
90.80(1)
90
972.3(2)
2
1.585
2.365
90
90
2335.1(2)
4
1.355
c (ꢁ)
V (10ꢀ30 m3)
Z
Dcalc (g cmꢀ3
)
l (mmꢀ1
)
1.024
Crystal size (mm)
Radiation
h Range for data collection (ꢁ)
Index ranges
0.36 · 0.18 · 0.06
Mo Ka; graphite-monochromator
1.72 6 h 6 26.06
ꢀ10 6 h 6 10
ꢀ12 6 k 6 12
ꢀ15 6 l 6 15
3065
3779 [Rint = 0.0353]
219
0.0201
0.24 · 0.05 · 0.04
0.24 · 0.10 · 0.04
1.75 6 h 6 25.91
ꢀ8 6 h 6 8
ꢀ14 6 k 6 14
ꢀ14 6 l 6 14
2554
3513 [Rint = 0.0610]
174
0.0571
1.86 6 h 6 26.19
ꢀ11 6 h 6 11
ꢀ16 6 k 6 16
ꢀ23 6 l 6 23
2191
2441 [Rint = 0.0356]
149
0.0201
Reflections observed
Independent reflections
Parameters
P
P
R = ||Fo| ꢀ |Fc||/ |Fo| [I > 2r(I)]
P
P
wR2 = { w(|Fo|2 ꢀ |Fc|2)2/ |Fo|2}1/2 (all data)
0.0479
0.404/ꢀ0.705
0.1418
3.751b/ꢀ1.530
0.0541
0.322/ꢀ0.821
Max./min. residual electron density (1030 e mꢀ3
)
a
Program SHELXL-97 [29]; solutions by direct methods, full matrix refinement with all independent structure factors.
Near the indium atoms.
b

1388
W. Uhl et al. / Journal of Organometallic Chemistry 691 (2006) 1382–1388
[9] R.J. Wehmschulte, P.P. Power, Inorg. Chem. 35 (1996) 2717.
[10] W. Uhl, J. Molter, B. Neumuller, Inorg. Chem. 40 (2001) 2011.
¨
[11] Y. Kim, J.H. Kim, J.E. Park, H. Song, J.T. Park, J. Organomet.
Chem. 545–546 (1997) 99.
[12] D. Cho, J.E. Park, B.J. Bae, K. Lee, B. Kim, J.T. Park, J.
Organomet. Chem. 592 (1999) 162.
of the dimer 2 from pseudo-symmetry C2v, there is no
choice to use the centrosymmetric space group P21/m.
4. Supplementary material
[13] D.W. Peters, M.P. Power, E.D. Bourret, J. Arnold, Chem. Commun.
(1998) 753.
[14] (a) B. Luo, W.L. Gladfelter, Chem. Commun. (2000) 825;
(b) B. Luo, W.L. Gladfelter, J. Organomet. Chem. 689 (2004) 666.
[15] D.A. Neumayer, A.H. Cowley, A. Decken, R.A. Jones, V. Lakhotia,
J.G. Ekerdt, Inorg. Chem. 34 (1995) 4698.
[16] W. Uhl, J. Molter, R. Koch, Eur. J. Inorg. Chem. (2000) 2255.
[17] V.C. Gibson, C. Redshaw, A.J.P. White, D.J. Williams, Angew.
Chem. (1999);
Crystallographic data for the structural analyses have
been deposited with the Cambridge Crystallographic Data
Centre, CCDC nos. 281041 (1), 281042 (2) and 281043 (3).
Copies of this information may be obtained free of charge
from The Director, CCDC, 12 Union Road, Cambridge
CB1 1EZ, UK (fax: +44 1233 336033; e-mail: depos-
it@ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
Angew. Chem. Int. Ed. 38 (1999) 961.
[18] J.S. Silverman, C.D. Abernethy, R.A. Jones, A.H. Cowley, Chem.
Commun. (1999) 1645.
Acknowledgement
[19] W. Uhl, J. Molter, R. Koch, Eur. J. Inorg. Chem. (1999) 2021.
[20] W. Uhl, J. Molter, B. Neumuller, Chem. Eur. J. 7 (2001) 1510.
¨
[21] H. No¨th, T. Seifert, Eur. J. Inorg. Chem. (2002) 602.
[22] W. Uhl, C.H. Emden, G. Geiseler, K. Harms, Z. Anorg. Allg. Chem.
629 (2003) 2157.
We are grateful to the Deutsche Forschungsgemeins-
chaft and the Fonds der Chemischen Industrie for generous
financial support.
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