Bridging and terminal arrangement of alkylperoxo groups in organoindium peroxides

Article abstract of DOI:10.1002/ejic.200900449

Treatment of bis(tert-butyl)-2,2,6,6-tetramethyl-3,5-heptanedionatoindium, [(Me₃C)₂In{Me₃C-C(O)C(H)C(O)-CMe₃}] (1), with oxygen afforded the dinuclear alkylindium peroxide [(Me ₃C-O-O)(Me₃C

Full text of DOI:10.1002/ejic.200900449

FULL PAPER
DOI: 10.1002/ejic.200900449
Bridging and Terminal Arrangement of Alkylperoxo Groups in Organoindium
Peroxides
Werner Uhl*[a] and Barun Jana[a]
Keywords: Indium / Peroxides / Organoelement compounds
Treatment of bis(tert-butyl)-2,2,6,6-tetramethyl-3,5-heptane- C(O)C(H)C(O)-C6H5}] (2), gave by ligand exchange the di-
dionatoindium, [(Me3C)2In{Me3C-C(O)C(H)C(O)-CMe3}] (1),
with oxygen afforded the dinuclear alkylindium peroxide
[(Me3C-O-O)(Me3C)In(µ-OCMe3)2In{Me3C-C(O)C(H)C(O)-
CMe3}2] (3) in moderate yield. Compound 3 has an oxidizing
peroxo group in close proximity to an In–C bond and decom-
poses slowly at room temperature by quenching of these con-
flicting functionalities. The reaction of oxygen with the corre-
sponding dibenzoylmethane derivative, [(Me3C)2In{H5C6-
peroxide
[In2(µ-O-O-CMe3)2{H5C6-C(O)C(H)C(O)-C6H5}4]
(4) in which the indium atoms are terminally coordinated by
chelating ligands and bridged by two peroxo groups. Diper-
oxide 4 does not contain In–C bonds, is thermally quite
stable, and can be handled at room temperature in THF solu-
tion over several hours without decomposition.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
the central aluminum atom. Systematic investigations
should help (i) to find easy preparative access to a broad
variety of these peroxides, (ii) to enhance their thermal sta-
bility, (iii) to study the fascinating coordination behavior of
the peroxo groups, and (iv) to allow their application in
secondary reactions, at least for selected, relatively persist-
ent derivatives. The strategy for the synthesis of such com-
pounds in our group comprises the use of bis(trimethyl-
silyl)methyl groups, which give rise to E–C bonds that are
relatively insensitive towards attack of oxygen. The coordi-
native saturation of the central atoms by chelating ligands
and the formation of ate complexes with Li counteri-
ons[5,6,8] (which by side-on coordination diminish the charge
density of the peroxo ligands) contribute to the stability of
these peroxides. This present report is focused on the gener-
ation of organoindium peroxides.
Introduction
Organoelement peroxides of the elements aluminum, gal-
lium, and indium have the oxidizing function of peroxo
groups in close proximity to reductive E–C bonds. Accord-
ingly, very fast quenching of these functionalities is usually
observed by the insertion of an oxygen atom into the E–
C bonds and formation of the corresponding alkoxides.[1]
Isolated and well characterized compounds of this type are
rare. Gallium and indium peroxides were obtained by the
insertion of an oxygen molecule into one E–C bond of the
corresponding tri(tert-butyl)element compounds.[2,3] We ob-
tained an alkylgallium peroxide by accident when traces of
oxygen came into contact with a solution of [iPr-N-
C(H)=C(H)-N-iPr]GaR [R = C(SiMe3)3].[4] The product
has a singular molecular structure with a peroxo ligand ter-
minally coordinated by two alkylgallium groups. Motivated
by this finding we were able to generate some relatively per-
sistent organoelement peroxides by specific reactions. Treat-
ment of the alkylgallium trihydride Li[H3Ga-CH(SiMe3)2]
with the H2O2–DABCO adduct afforded by the release of
hydrogen a heterocyclic dianion, in which three alkylgal-
lium groups are bridged by three peroxo groups.[5,6] Even
an alkylaluminum peroxide possessing a strongly reducing
Al–C bond besides a peroxo group was accessible by the
reaction of a suitable hydrido species with tert-butyl hydro-
gen peroxide.[7] This compound has a chelating β-diketimin-
ato ligand and a bis(trimethylsilyl)methyl group attached to
Results and Discussion
Synthesis of the Starting Compounds [(Me3C)2In(acac)]
We intended to generate relatively persistent organoin-
dium peroxides by coordinative saturation of the central in-
dium atoms by a chelating ligand and insertion of intact
oxygen molecules into In–C bonds. Suitable starting com-
pounds like 1 and 2 were easily obtained by the reaction of
tri(tert-butyl)indium with the corresponding acidic neutral
acetylacetone derivatives dipivaloyl- and dibenzoylmethane
[Equation (1)]. Butane was released, and the products were
formed in almost quantitative yields. The dipivaloylmethan-
ide derivative 1 was isolated as a viscous liquid in very high
purity; attempts for crystallisation failed. The phenyl com-
pound 2 gave colorless crystals. NMR spectroscopic data
[a] Institut für Anorganische und Analytische Chemie der Uni-
versität Münster,
Corrensstraße 30, 48149 Münster, Germany
Fax: +49-251-8336660
E-mail: uhlw@uni-muenster.de
3942
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 3942–3947

Alkylperoxo Groups in Organoindium Peroxides
(chemical shifts and integration ratios) are as expected and ported previously, low steric shielding gave dimeric formula
do not need to be discussed. The molecular peak of each units with coordination numbers of five at the indium
compound was detected in the mass spectrum.
atoms.[9]
Synthesis of the Alkylindium Peroxide 3
Treatment of a solution of compound 1 with elemental
oxygen at low temperature (–50 to –30 °C) over 45 min gave
a colorless solution from which the product 3 precipitated
after concentration and storing at –30 °C over several days
[Equation (2)]. The molecular structure of 3 was confirmed
by crystal structure determination [see schematic drawing
in Equation (2)]. Substituent exchange and insertion of an
oxygen molecule into an In–C bond gave a dinuclear peroxo
compound in which one indium atom is coordinated to two
acetylacetonato ligands, while the other one is terminally
coordinated to a tert-butyl and a tert-butylperoxo group.
Both indium atoms are bridged by tert-butoxy groups
which result from the insertion of oxygen atoms into In–C
(1)
The central indium atom of compound 2 (Figure 1) is
coordinated by two carbon atoms of tert-butyl groups and
two oxygen atoms of the chelating ligand. The coordination
sphere is strongly distorted with a very large C–In–C angle
of 148.29(8)° and a relatively small bite angle O–In–O of
84.38(6)°. Obviously, this distortion depends merely on the
chelating coordination and seems not to be influenced by
steric repulsion between the tert-butyl groups because we
did not observe a similar enlargement for other tert-butyl
indium compounds. The In–C bond lengths are quite sim-
ilar [217.6(2) and 218.3(2) pm] and correspond to standard
values. A slightly larger difference resulted for the In–O dis-
tances [215.3(2) and 218.3(2) pm]. The C–O (126.4 pm) and
C–C distances (141.1 pm) reflect the delocalized π-bonding
in the chelate. As observed many times before the metal
atom is 29.3 pm above the average plane of the 1,3-dionato
group. The phenyl groups are almost coplanar with the che-
late (angle between the normals of the planes 14.7 and
17.2°) which may allow for some delocalization. Similar or-
ganoindium acetylacetonato compounds have been re-
1
bonds. Three singlets were detected in the H NMR spec-
trum for the different tert-butyl groups of the peroxo ligand,
the terminal alkyl group attached to indium and the tert-
butoxy bridges. The chelating ligand gave two sets of reso-
nances in the correct integration ratio. NMR spectroscopic
characterization was hindered by partial overlap of reso-
nances and by slow decomposition of 3 in solution even at
low temperature which resulted in the occurrence of several
resonances of unknown secondary products with steadily
increasing intensity. The peroxide content of the solid was
determined by hydrolysis, oxidation of iodide and titration
of the resulting elemental iodine with thiosulfate. By this
relatively simple method 94% of the calculated value was
reproducibly obtained.
(2)
Crystal structure determination verified the formation of
an organoindium peroxide in which an oxidizing peroxo
group is in close proximity to a reducing In–C bond (Fig-
ure 2). This unusual structural motif may cause the facile
decomposition by quenching of these conflicting properties.
Figure 1. Molecular structure and numbering scheme of 2; the ther-
mal ellipsoids are drawn at the 40% probability level; hydrogen
atoms are omitted. Selected bond lengths [pm] and angles [°]: In1–
C4 218.3(2), In1–C5 217.6(2), In1–O1 215.3(2), In1–O2 218.3(2),
O1–In1–O2 84.38(6), C4–In1–C5 148.29(8).
Eur. J. Inorg. Chem. 2009, 3942–3947
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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3943

W. Uhl, B. Jana
FULL PAPER
Ligand exchange gives a dinuclear compound in which the gen. A clear solution was obtained in diethyl ether from
indium atoms possess different coordination spheres. The which the product 4 crystallized upon cooling to –15 °C. In
atom In1 has a coordination number of six in a distorted n-hexane compound 4 precipitated directly as a colorless
octahedral surrounding and is coordinated by two chelating powder with high purity. Crystal structure determination of
ligands and two oxygen atoms of the bridging alkoxy 4 revealed a dimeric constitution with two indium atoms
groups. The indium atoms are located 43.6 and 59.6 pm bridged by two tert-butylperoxo groups and two chelating
above the average planes of the 1,3-dionato moieties. The ligands coordinated to each metal atom [Equation (3)].
bridging alkoxy groups and the indium atoms form a four- Hence, an intact In–C bond was not found. Compound 4
membered In2O2 heterocycle which deviates from planarity is relatively stable in THF solutions at room temperature.
(fold angle across the In–In axis 17.2°) and has the tert- NMR spectra revealed essentially the resonances expected
butyl groups on different sides. The atom In2 has a dis- for the acetylacetonato ligands, the tert-butyl peroxo groups
torted tetrahedral coordination sphere and is terminally co- and the diethyl ether molecules which are enclosed in the
ordinated by peroxo and alkyl groups. Despite the different crystals. In addition, all spectra showed an impurity of
coordination numbers of the metal atoms the In–O bonds Ͻ5% of an unknown product which had a particularly
in the In2O2 ring are quite similar (212.4 to 214.0 pm). The characteristic resonance at δ = 10.1 ppm. The supernatant
1
In–O bond to the terminal peroxo group is shorter [202.8(5) solutions after separation of 4 showed the H NMR reso-
pm]. The In–C bond length [221.0(7) pm] corresponds to nances of the peroxide [(Me3C)2InOOCMe3]2 (δ = 1.50 and
standard values. The O–O distance [149.0(7) pm] is similar 1.16), which has been reported several years ago,[2] and of
to the O–O distances in other terminal alkylperoxo the alkoxide [(Me3C)2InOCMe3]2 (δ = 1.39 and 1.24). In
groups.[3,7,8,10] In contrast to hydrogen peroxide, which has particular the first compound is the expected by-product of
the gauche arrangement of the terminal hydrogen atoms,[11] a ligand exchange reaction leading to the formation of 4.
an almost ideally planar surrounding is detected for the per-
oxo group of 3 with an In–O–O–C torsion angle of 179°.
This particular conformation may be favored by a mini-
mum steric repulsion between the substituents and has been
observed before.[4,7] A strongly related dinuclear indium
compound with a tetra- and a hexacoordinate indium atom
bridged by tert-butoxy ligands has been reported.[12] But it
had two terminal tert-butoxy instead of the tert-butyl and
tert-butylperoxy groups of 3.
(3)
The indium atoms of the centrosymmetric compound 4
(Figure 3) are coordinated by six oxygen atoms of two che-
lating ligands and two bridging tert-butylperoxo groups.
Figure 2. Molecular structure and numbering scheme of 3; the ther-
mal ellipsoids are drawn at the 40% probability level; hydrogen
The formation of 4 may be described by ligand exchange
and insertion of a complete oxygen molecule into an In–C
bond. The In–O distances differ slightly with 212.6 pm on
average to the oxygen atoms of the chelating ligands and
216.2 pm to the bridging peroxo groups. The O–O bond
length [147.0(3) pm] corresponds to standard values. The
acetylacetonato ligands exhibit the expected bond param-
eters. The terminal phenyl groups deviate slightly from a
coplanar arrangement with the 1,3-dionato groups (angles
atoms and the methyl groups of the tert-butoxy bridges and acetyl-
acetonato ligands are omitted. Selected bond lengths [pm] and
angles [°]: In1–O1 213.2(4), In1–O2 215.1(4), In1–O3 214.8(4), In1–
O4 216.0(4), In1–O5 213.3(4), In1–O6 214.0(4), In2–O5 213.0(4),
In2–O6 212.4(4), In2–O7 202.8(5), In2–C9 221.0(7), O7–O8
149.0(7), In2–O7–O8 102.2(3), O7–O8–C81 107.9(5).
Synthesis of the Peroxide 4
A different reaction course was observed upon treatment between the normals of the planes 11.1°, 14.6°, 23.0° and
of the dibenzoylmethane derivative 2 with elemental oxy- 32.5°) which may indicate some delocalization of electron
3944
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Eur. J. Inorg. Chem. 2009, 3942–3947

Alkylperoxo Groups in Organoindium Peroxides
pentane was treated with solid dibenzoylmethane (0.853 g,
3.81 mmol) in small portions. The mixture was rigorously stirred
and slowly warmed to room temperature. A clear brown solution
resulted after stirring for 4 h. The mixture was cooled to –15 °C to
get brown crystals of 2; yield 1.44 g (84%), m.p. (argon; sealed
density. The indium atoms are 44.8 (O11, O12, C11, C12,
C13) and 20.7 pm (O21, O22, C21, C22, C23) above the
average planes of the corresponding O2C3 moieties.
1
capillary) 137 °C. H NMR (400 MHz, C6D6): δ = 1.45 (s, 18 H,
InCMe3), 6.70 (s, 1 H, CH of chelate), 7.18 (m, 6 H, meta- and
para-H of phenyl), 7.96 (pseudo-d, 4 H, ortho-H of phenyl) ppm.
13C NMR (100 MHz, C6D6): δ = 31.9 (In-CMe3), 36.8 (In-C), 94.9
(C-H of chelate), 127.8 (ortho-C of phenyl), 128.6 (meta-C of
phenyl), 131.6 (para-C of phenyl), 140.6 (ipso-C of phenyl), 187.9
(C-O) ppm. IR (CsI, paraffin): ν = 1593 (vs), 1548 (vs), 1520 [s,
˜
ν(CO), ν(CC)] 1452 (vs), 1377 [vs, paraffin] 1304 [m, δ(CH3)] 1229
(m), 1182 (w), 1157 (m), 1099 (w), 1089 (m), 1055 (m), 1015 (m),
1000 (w), 970 (vw), 935 (m), 839 (w), 810 (s), 785 (w), 752 [s, ν(CC)]
719 [vs, paraffin] 687 (s), 623 (s), 613 (sh), 530 (s), 517 (s), 455 [m,
ν(InC), ν(InO), δ(CC3), phenyl] cm–1. MS (EI, 20 eV, 310 K): m/z
(%) = 452 (3), 453 (0.5) [M+]; 395 (38), 396 (8) [M+ – CMe3]; 339
(100), 340 (16) [M+ – CMe3 – butene]. C23H29InO2 (452.3): calcd.
C 61.1, H 6.5; found C 61.0, H 6.5.
[(Me3C-O-O)(Me3C)In(µ-O-CMe3)2In{Me3C-C(O)C(H)C(O)-
CMe3}2] (3): Dry oxygen was bubbled through a cooled solution
(–50 °C) of compound 1 (1.21 g, 2.93 mmol) in 10 mL of n-pentane
for 45 min. In this period the solution warmed to –30 °C. The mix-
ture was concentrated at this temperature to about 3 mL and stored
at –30 °C for 5 d to yield colorless crystals of 3. Compound 3 de-
composes slowly at room temperature in solution and in the solid
state. Its peroxide content was determined by hydrolysis with 1 
acetic acid, treatment of the solution with potassium iodide and
titration of the resulting iodine with thiosulfate. By this relatively
simple procedure 94% of the calculated peroxide content was re-
producibly determined; yield 0.74 g (57%). 1H NMR (400 MHz,
[D8]toluene, 250 K): δ = 1.12 and 1.23 (s, each 18 H, CMe3 of the
chelate), 1.47 (s, 9 H, In-O-O-CMe3), 1.54 (s, 18 H, µ-O-CMe3),
1.61 (s, 9 H, InCMe3), 5.75 (s, 2 H, CH of chelate) ppm. 13C NMR
(100 MHz, [D8]toluene): δ = 26.9 (In-O-O-CMe3), 28.4 (CMe3 of
chelate), 32.8 (In-CMe3), 32.9 (µ-O-CMe3), 34.5 (In-CMe3), 41.8
(CMe3 of chelate), 72.4 (µ-O-CMe3), 78.0 (In-O-O-CMe3), 90.2 and
90.1 (C-H of chelate), 204.2 and 202.0 (C-O of the chelate) ppm.
Figure 3. Molecular structure and numbering scheme of 4; the ther-
mal ellipsoids are drawn at the 40% probability level; hydrogen
atoms and phenyl groups are omitted. Selected bond lengths [pm]
and angles [°]: In1–O11 213.1(2), In1–O12 211.7(2), In1–O21
213.1(2), In1–O22 212.3(2), In1–O1 217.3(2), In1–O1Ј 215.1(2),
O1–O2 147.0(3), In1–O1–O2 119.3(2), In1Ј–O1–O2 109.2(2), O1–
O2–C1 109.3(3), In1–O1–In1Ј 104.3(1), O1–In1–O1Ј 75.8(1); In1Ј
and O1Ј generated by –x + 1, –y, –z + 1.
Experimental Section
General: All procedures were carried out under an atmosphere of
purified argon in dried solvents (n-hexane and n-pentane with
LiAlH4; diethyl ether with Na/benzophenone). Tri(tert-butyl)in-
dium was obtained according to a literature procedure.[13] Com-
mercially available dipivaloyl- and dibenzoylmethane were dried in
vacuo prior to use.
IR (CsI, paraffin): ν = 1591 (vs), 1575 (vs), 1504 [m, ν(CO), ν(CC)]
˜
[(Me3C)2In{Me3C-C(O)C(H)C(O)-CMe3}] (1): A solution of dipiv-
aloylmethane (0.56 mL, 0.491 g, 2.67 mmol) in 10 mL of n-pentane
was added dropwise to a cooled solution (–40 °C) of tri(tert-butyl)-
indium (0.763 g, 2.67 mmol) in 10 mL of n-hexane. The mixture
was warmed slowly to room temperature and stirred for 14 h. All
volatiles were removed in vacuo to isolate compound 1 as a color-
less viscous liquid in a very high purity. All attempts of crystalli-
zation failed, and 1 was directly applied for secondary reactions
without further purification; yield 1.10 g (100%). 1H NMR
(400 MHz, C6D6): δ = 1.15 (s, 18 H, CMe3 of the chelate), 1.35 (s,
18 H, InCMe3), 5.70 (s, 1 H, CH of chelate) ppm. 13C NMR
(100 MHz, C6D6): δ = 28.4 (CMe3 of chelate), 31.8 (In-CMe3), 42.0
(CMe3 of chelate), 90.2 (C-H of chelate), 202.9 (C-O), In-C not
1460 [vs, paraffin] 1400 [s, δ(CH3)] 1375 [s, paraffin] 1303 (vw),
1246 [m, δ(CH3)] 1225 (s), 1188 (s), 1138 (s), 1028 (w), 955 (m),
930 (m), 916 (m), 872 (s), 843 (w), 815 (w), 793 (m), 762 (m), 739
[s, ν(CC)] 721 [vs, paraffin] 623 (w), 592 (w), 559 (w), 478 [s, ν(InC),
ν(InO), δ(CC3)] cm–1.
[In2(µ-O-O-CMe3)2{H5C6-C(O)C(H)C(O)-C6H5}4] (4): Dry oxygen
was bubbled through a cooled solution (0 °C) of compound 2
(0.73 g, 1.61 mmol) in 20 mL of diethyl ether for 2 min. The color
of the solution changed from dark yellow to colorless. The mixture
was cooled to –15 °C to yield colorless crystals of the product 4,
which enclosed two molecules of diethyl ether per one dimeric for-
mula unit of 4. Compound 4 is insoluble in hydrocarbons such as
n-pentane or benzene. It can be handled in THF solution at room
temperature over many hours without decomposition. It is rela-
tively stable in the solid state, but decomposes slowly upon warm-
ing. The peroxide content was determined as described above (syn-
thesis of 3). This procedure gave reproducibly 92% of the calculated
detected ppm. IR (CsI, paraffin): ν = 1576 (vs), 1558 (sh), 1502 [m,
˜
ν(CO), ν(CC)] 1462 [vs, paraffin] 1402 [s, δ(CH3)] 1377 [s, paraffin]
1358 (s), 1282 (vw), 1247 [m, δ(CH3)] 1226 (m), 1188 (m), 1163
(m), 1134 (s), 1014 (w), 952 (m), 934 (w), 872 (s), 810 (m), 792 (m),
739 [w, ν(CC)] 721 [m, paraffin] 617 (m), 588 (vw), 561 (vw), 475
[m, ν(InC), ν(InO), δ(CC3)] cm–1. MS (EI, 20 eV, 300 K): m/z (%)
= 412 (3), 413 (0.5) [M+], 355 (74), 356 (11) [M+ – CMe3], 299
(100), 300 (45) [M+ – CMe3 – butene]. C19H37InO2 (412.3): calcd.
C 55.4, H 9.0; found C 56.0, H 9.3.
1
value; yield 0.54 g (92%). H NMR (400 MHz, [D8]THF, 250 K):
δ = 1.11 (t, 12 H, CH3 of ether), 1.16 (s, 18 H, O-O-CMe3), 3.40
(q, 8 H, OCH2 of ether), 6.92 (s, 4 H, CH of chelate), 7.25 (pseudo-
t, 16 H, para-H of phenyl), 7.40 (pseudo-t, 8 H, para-H of phenyl),
8.12 (pseudo-d, 16 H, ortho-H of phenyl) ppm. 13C NMR
(100 MHz, [D8]THF, 250 K): δ = 27.0 (CMe3), 81.7 (O-O-C), 94.7
[(Me3C)2In{H5C6-C(O)C(H)C(O)-C6H5}] (2): A cooled solution
(–78 °C) of tri(tert-butyl)indium (1.09 g, 3.81 mmol) in 20 mL of n-
Eur. J. Inorg. Chem. 2009, 3942–3947
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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3945

W. Uhl, B. Jana
FULL PAPER
Table 1. Crystal data and structure refinement for compounds 2, 3, and 4·2Et2O.[a,b]
2
3
4·2Et2O
Empirical formula
Temperature /K
Crystal system
Space group[14]
a /pm
b /pm
c /pm
C23H29O2In
153(2)
C38H74O8In2
153(2)
C76H82O14In2
153(2)
monoclinic
P21/c (no. 14)
1605.0(3)
845.0(2)
1627.0(3)
90
98.47(3)
90
2.1825(8)
4
orthorhombic
triclinic
Pna21[c] (no. 33)
P1 (no. 2)
¯
1924.41(5)
1181.45(3)
1997.77(6)
90
90
90
4.5421(2)
4
1.299
1193.7(2)
1268.9(2)
1387.0(2)
113.772(2)
111.232(2)
91.625(2)
1.7544(5)
1
α /°
β /°
γ /°
V /nm3
Z
Dcalcd. /gcm–3
1.376
1.096
1.372
0.720
µ /mm–1
1.057
Crystal size /mm
Radiation
Θ range for data collection /°
Index ranges
0.34ϫ0.16ϫ0.02
0.15ϫ0.11ϫ0.10
Mo-Kα, graphite monochromator
2.00 Յ 27.91
–25ՅhՅ25,
–15ՅkՅ15, –26ՅlՅ26
10865 (Rint = 0.0425)
452
0.09ϫ0.06ϫ0.04
2.53 Յ 31.08
–23ՅhՅ23, –11ՅkՅ12,
–22ՅlՅ23
6691 (Rint = 0.0382)
272
1.76 Յ 27.14
–15ՅhՅ15,
–16ՅkՅ16, –17ՅlՅ17
7693 (Rint = 0.0460)
420
Independent reflections
Parameters
R1 = Σ|| Fo | – | Fc ||/Σ| Fo | [IϾ2σ(I)]
0.0305 (5212)
0.0486 (9220)
0.1415
0.0428 (6019)
0.1148
2 2
wR2 = {Σ[w(Fo2 – Fc2)2]/ Σ[w(Fo ) ]}1/2 (all data)[b] 0.0740
Max./min. residual electron density [1030 em–3]
+0.764/–1.004
+3.807[d]/–0.782
+1.920[d]/–1.301
[a] Programme SHELXL-97,[15] solutions by direct methods, full-matrix refinement with all independent structure factors. [b] See ref.[16]
for CCDC reference numbers. [c] Flack parameter: 0.01(3). [d] Close to indium.
Peroxides (Ed.: S. Patai), Wiley, London, 1983, p. 807–828; c)
Y. A. Aleksandrov, N. V. Chikinova, J. Organomet. Chem. 1991,
418, 1–59.
(C-H of chelate), 128.7 (meta-C of phenyl), 128.9 (ortho-C of
phenyl), 131.9 (para-C of phenyl), 140.9 (ipso-C of phenyl), 188.7
(C-O of the chelate) ppm. IR (CsI, paraffin): ν = 1593 (m), 1554
˜
[2] a) W. M. Cleaver, A. R. Barron, J. Am. Chem. Soc. 1989, 111,
8966–8967; b) M. B. Power, W. M. Cleaver, A. W. Apblett,
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[m, ν(CO), ν(CC)] 1454 (vs), 1375 [s, paraffin] 1304 [m, δ(CH3)]
1227 (w), 1080 (vs, br.), 1024 (m), 1000 (w), 970 (vw), 937 (m), 889
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Crystal Structure Determinations: Single crystals were obtained di-
rectly from the reaction mixtures as described before. The crystallo-
graphic data were collected with a Bruker APEX diffractometer
with graphite-monochromated Mo-Kα radiation. The crystals were
coated with a perfluoropolyether, picked up with a glass fiber and
immediately mounted in the cooled nitrogen stream of the dif-
fractometer. The crystallographic data and details of the final R
values are provided in Table 1.[16] All non-hydrogen atoms were re-
fined with anisotropic displacement parameters; hydrogen atoms
were calculated on ideal positions and allowed to ride on the
bonded atom with U = 1.2Ueq(C). One tert-butyl group of the com-
pounds 2 (C4) and 3 (C11) shows disorder, the atoms were refined
on split positions. The dimeric molecules of 4 reside on crystallo-
graphic centers of symmetry. Two ether molecules are enclosed per
one dimeric formula unit.
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Acknowledgments
We are grateful to the Deutsche Forschungsgemeinschaft (DFG)
and the Fonds der Chemischen Industrie for generous financial
support.
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[16] CCDC-724557 (for 2), -724558 (for 3), and -724559 (for
4·2Et2O) contain the supplementary crystallographic data for
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