Chemistry of In(C5H5)3 and some heteroleptic organoindium(III) derivatives. Crystal and molecular structures of In(C5H5)3, (C5H5)3In·PPh3, and (M

Article abstract of DOI:10.1021/om0202322

Pure In(C₅H₅)₃ has been prepared in high yields from InCl₃ and Li(C₅H₅) in THF solution with the absence of external heating. Neat In(C₅H₅)₃ readily decompo

Full text of DOI:10.1021/om0202322

4632
Organometallics 2002, 21, 4632-4640
Ch em istr y of In (C5H5)3 a n d Som e Heter olep tic
Or ga n oin d iu m (III) Der iva tives. Cr ysta l a n d Molecu la r
Str u ctu r es of In (C5H5)3, (C5H5)3In ‚P P h 3, a n d
(Me3CCH2)2In (C5H5)
O. T. Beachley, J r.,* David J . MacRae, Andrey Yu. Kovalevsky,
Yuegang Zhang, and Xue Li
Department of Chemistry, University at Buffalo, The State University of New York,
Buffalo, New York 14260
Received March 27, 2002
Pure In(C5H5)3 has been prepared in high yields from InCl3 and Li(C5H5) in THF solution
with the absence of external heating. Neat In(C5H5)3 readily decomposes at 150 °C to form
In(C5H5)(s) and cyclopentadiene as the primary products whereas a benzene suspension
decomposes under refluxing conditions. In(C5H5)3 forms an isolable 1:1 adduct with PPh3
but NMe3, THF, and Et2O do not form stable adducts. Ligand redistribution reactions with
InR3 (R ) Me and CH2CMe3) in THF solution provided R2In(C5H5) and RIn(C5H5)2. These
heteroleptic organoindium(III) compounds have been isolated as analytically pure crystalline
solids, but in THF solution they form equilibrium mixtures of the adducts of InR3, R2In-
(C5H5), RIn(C5H5)2, and In(C5H5)3, as appropriate. Crystals of [In(C5H5)3]n, (C5H5)3In‚PPh3,
and [(Me3CCH2)2In(C5H5)]n were characterized by single-crystal X-ray structural studies.
In tr od u ction
solutions were consistent with the presence of mono-
Our recent research has been designed to gain a
fundamental understanding of the detailed nature of
heteroleptic organometallic compounds of the heavier
group 13 elements. The gallium compounds R2GaCp and
RGaCp2 (R ) Me,1,2 Et,3 CH2CMe3;4 Cp ) C5H5,1,2,4
C5H4Me2,3) were prepared in nearly quantitative yields
by ligand redistribution reaction between GaR3 and
GaCp3 (eqs 1 and 2). Many of these heteroleptic com-
2R2GaCp h RGaCp2 + GaR3
2RGaCp2 h R2GaCp + GaCp3
(3)
(4)
mers. To prepare heteroleptic organoindium compounds
and gain an understanding of their chemistry, we
needed pure In(C5H5)3, a necessary starting material
for the preparation of these types of compounds by
ligand redistribution reactions. In this paper, we de-
scribe a reliable procedure for the synthesis of In(C5H5)3
as well as a description of its physical and chemical
properties. This compound was used, in turn, for the
preparation of the heteroleptic derivatives R2In(C5H5)
and RIn(C5H5)2 (R ) Me, CH2CMe3).
2GaR3 + GaCp3 f 3R2GaCp
GaR3 + 2GaCp3 f 3RGaCp2
(1)
(2)
pounds were isolated as analytically pure solids that
were chemically stable at room temperature,1-3 whereas
in other cases pure single compounds could not be
obtained.4 The analytically pure derivatives were crys-
talline solids. In contrast, liquids were typically unstable
at room temperature because their ligands redistributed
to form more symmetrical derivatives. X-ray structural
studies of the crystalline solids revealed linear polymers
with four-coordinate gallium atoms that were bridged
by cyclopentadienide groups through their 1- and 3-po-
sitions. Even though many compounds were isolated as
analytically pure crystalline solids, dissolution always
produced equilibrium mixtures of multiple species (eqs
3 and 4). Cryoscopic molecular weight studies of benzene
Resu lts a n d Discu ssion
The synthesis of analytically pure In(C5H5)3 in high
yields has been achieved by reacting InCl3 with Li(C5H5)
in a 1:3.09 mol ratio in THF solution at room temper-
ature. Since all reactants and products were soluble in
THF, reaction times were kept short. Furthermore, no
external heating was employed during the preparative
reaction or during the isolation and purification of the
product. The initial indium-containing product (C5H5)3-
In‚THF was readily separated from LiCl and excess Li-
(C5H5) by extraction with benzene at room temperature.
The THF was then removed quantitatively from the
unstable adduct by vacuum distillation at room tem-
perature. A final washing of the product with pentane
produced In(C5H5)3 as a bright yellow powder that did
not melt but appeared to decompose at ∼160-164 °C
as shown by a color change from bright yellow to orange
(1) Beachley, O. T., J r.; Royster, T. L.; Arhar, J . R. J . Organomet.
Chem. 1992, 434, 11.
(2) Beachley, O. T., J r.; Mosscrop, M. T. Organometallics 2000, 19,
4550.
(3) Beachley, O. T., J r.; Rosenblum, D. B.; Churchill, M. R.; Lake,
C. H.; Krajkowski, L. M. Organometallics 1995, 14, 4402.
(4) Beachley, O. T., J r.; Maloney, J . P.; Rogers, R. D. Organometallics
1997, 16, 3267.
10.1021/om0202322 CCC: $22.00 © 2002 American Chemical Society
Publication on Web 09/27/2002

In(C5H5)3 and Heteroleptic Organoindium(III) Derivatives
Organometallics, Vol. 21, No. 22, 2002 4633
of In(C5H5)3 was reported previously.5 The space group
for the earlier structure was P212121 whereas the
current structural study has identified the Pbca space
group with a unit cell that is almost twice as large as
the original. The indium atom has a distorted tetrahe-
dral configuration. The largest C-In-C angle occurs
between the two terminal cyclopentadienide groups and
is 129.9(2)° for C(11)-In(1)-C(1) whereas the second
largest angle occurs between the two bridging cyclopen-
tadienide groups, C(6)-In(1)-C(8′) (1.5 - x, y + 0.5, z)
at 99.4(1)°. The terminally coordinated cyclopentadien-
ide rings have largely nonconjugated π-systems with
C(1)-C(3), C(4)-C(5), C(12)-C(13), and C(14)-C(15)
being essentially double bonds. The ipso-carbon atoms
C(1) and C(11) are bonded to In(1) by using almost sp3-
hybridized orbitals as shown by the positions of the
hydrogen atom. These hydrogen atoms are displaced
from the corresponding plane of the cyclopentadienide
ring by 0.23 Å for H(1) and -0.43 Å for H(11). The
bridging cyclopentadienide groups have an allyl-like
conjugated π-system containing C(6)-C(7)-C(8) atoms
and a double bond between C(9) and C(10). Thus, atoms
C(6) and C(8) have close to sp2-hybridization. The
cyclopentadienide ring with atoms C(1) through C(5) is
positioned almost on top of the ring with C(11) through
C(15). The angle between their planes is 17.7°. The
positioning of these two rings results in a short van der
Waals contact between C(4) and C(14) of 3.38 Å. The
sum of the van der Waals radii is 3.42 Å.6 Thus, there
might be some degree of π-π interaction. There are no
short distances that might be indicative of interactions
between the chains.
The preparation of In(C5H5)3 has been described in
two articles. The initial preparation7 utilized the reac-
tion between InCl3 and excess Na(C5H5) in diethyl ether
but the yield was minimal and the elemental analysis
suggested that the sample was impure as the percent
carbon was low (calcd 58.11, found 56.49). The major
indium-containing product, indium(I) cyclopentadienide,
was isolated by sublimation when the crude reaction
product was heated at 150 °C. The second synthesis8 of
In(C5H5)3 had two major modifications to the original
procedure. The reagent Na(C5H5) was replaced with Li-
(C5H5) and the product was isolated with refluxing
benzene. The percent carbon observed for this product
was low also (calcd 58.11, found 57.6). It is noteworthy
that neither of these papers reported a melting point, a
decomposition temperature, or a solubility study of the
compound in any solvent. When we attempted to
prepare In(C5H5)3 using the method described by Poland
and Tuck,8 impure In(C5H5)3 was obtained. Details of
these experiments and the resulting products are pro-
vided with the Supporting Information.
F igu r e 1. Molecular geometry and labeling of atoms for
[In(C5H5)3]n (50% probability ellipsoids for non-hydrogen
atoms).
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles
a
(d eg) for In (C5H5)3
(A) Indium-Carbon Distances
In(1)-C(1)
In(1)-C(6)
In(1)#2-C(8)
2.229(4) In(1)-C(11)
2.389(4) In(1)-C(8)#1
2.482(4)
2.229(4)
2.482(4)
(B) Carbon-Carbon Distances for Cyclopentadienide Rings
C(1)-C(2)
C(1)-C(5)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(6)-C(7)
C(6)-C(10)
C(7)-C(8)
1.453(6) C(8)-C(9)
1.461(6) C(9)-C(10)
1.366(6) C(11)-C(15)
1.423(6) C(11)-C(12)
1.358(6) C(12)-C(13)
1.419(6) C(13)-C(14)
1.442(5) C(14)-C(15)
1.408(5)
1.441(5)
1.360(5)
1.458(5)
1.476(5)
1.352(6)
1.438(5)
1.363(6)
(C) Angles around Indium
C(11)-In(1)-C(1)
129.9(2) C(11)-In(1)-C(6)
104.2(1)
C(11)-In(1)-C(8)#1 108.8(1) C(6)-In(1)-C(8)#1 99.4(1)
C(1)-In(1)-C(8)#1
102.0(1)
a
Symmetry transformations used to generate equivalent at-
oms: #1 - x + 3/2, y + 1/2, z; #2 -x + 3/2, y - 1/2, z.
to brown that occurred slowly. Even though the pure
solid appeared to decompose at ∼160-164 °C, heating
of a suspension of In(C5H5)3 in benzene to reflux was
sufficient to induce decomposition as observed by a
change in its color from bright yellow to brownish
orange and a shift of the single resonance in its 1H NMR
spectrum to higher field (see later paragraph). As In-
1
(C5H5)3 does not melt and H NMR spectra of solutions
containing the compound do not identify the presence
of multiple In-C5H5 species due to rapid exchange of
C5H5 substituents, the only tool for evaluating the purity
of In(C5H5)3 is its elemental analysis. The isolation of
pure In(C5H5)3 requires the use of pure reagents and
paying careful attention to the details of the preparative
procedure.
The solubility of In(C5H5)3 in benzene and its proper-
ties after heating in benzene were investigated in order
to learn possible reasons for the poor elemental analyses
for the products isolated by us after using the method
of Poland and Tuck.8 Pure In(C5H5)3 has minimal
solubility in benzene at room temperature. Heating to
60 °C increased the solubility but decomposition also
The structure of In(C5H5)3 (Figure 1) consists of
infinite polymeric chains that are located along the
crystallographic b axis. Each indium is bonded to four
cyclopentadienide groups. Two cyclopentadienide groups
are monohapto or terminal whereas the other two form
bridges between two indium atoms by using the carbon
atoms at the 1- and 3-positions of the rings. Selected
interatomic distances and angles are collected in Table
1. The structure of another polymorphic modification
(5) Einstein, F. W. B.; Gilbert, M. M.; Tuck, D. G. Inorg. Chem. 1972,
11, 2832.
(6) Zefirov, Y. V.; Zorkii, P. M. Russ. Chem. Rev. 1989, 58, 713.
(7) Fischer, E. O.; Hofmann, H. P. Angew. Chem. 1957, 69, 639.
(8) Poland, J . S.; Tuck, D. G. J . Organomet. Chem. 1972, 42, 307.

4634 Organometallics, Vol. 21, No. 22, 2002
Beachley et al.
occurred. All of the originally soluble In(C5H5)3 did not
redissolve upon reheating. The chemical shift of the
resonance for the C5H5 protons moved to higher field
with heating and new resonances for C5H6 and dicyclo-
pentadiene appeared in the spectrum and increased in
intensity as the sample was heated for longer times.
Thus, C5H6 was formed by thermal decomposition, not
hydrolysis.
Pure In(C5H5)3 decomposes readily at 150 °C to form
In(C5H5)7,9 and C5H6 as the isolated products. Heating
for only 15 min was sufficient to completely decompose
a 2.6-mmol sample as ∼81% of the indium was con-
verted to In(C5H5). These observations of the thermal
decomposition of In(C5H5)3 are consistent with our
observations of heating the compound with benzene and
with the observed instability of In(C5Me5)3.9 Thus, the
formation of In(C5H5) from the decomposition of In-
(C5H5)3 does not require Na(C5H5).8
F igu r e 2. Molecular geometry and labeling of atoms for
(C5H5)3In‚PPh3 (50% probability ellipsoids for non-hydro-
gen atoms, hydrogen atoms are omitted for clarity).
When In(C5H5)3 and In(C5H5) were present in a THF
solution, the indium(III) species stabilized In(C5H5). The
solution remained pale yellow for more than 4 months
while being held at ∼20 °C. In contrast, a THF solution
of only In(C5H5) that was initially light yellow after
warming from -196 to ∼20 °C became brown after 20
min and very dark brown, almost black, with a metallic
mirror on the NMR tube after 45 min. The 1H NMR
spectrum of the THF solution of In(C5H5)3 and In(C5H5)
exhibited only a single line for the C5H5 protons.
Exchange of C5H5 moieties through the formation of an
indium(II) species THF‚(C5H5)2In-In(C5H5)2‚THF with
σ-bonded C5H5 moieties is consistent with indium
chemistry11 and with the hypothesis that decomposition
of In(C5H5) in THF involves a transformation from a π-
to a σ-bonded species prior to cleavage of the indium-
carbon bond.9 Thus, the change in chemical shift of the
single resonance for the cyclopentadienide protons to
higher field as samples of In(C5H5)3 are heated in
benzene could be due to the presence of In(C5H5) which,
in turn, is exchanging C5H5 ligands with In(C5H5)3
through the formation of an indium(II) species.
Indium(III) cyclopentadienide is a good Lewis acid to
phosphines but not to amines and ethers. The pale
yellow adduct In(C5H5)3‚PPh3 exists as simple mono-
meric species in the crystalline state and in benzene
solution. No dissociation of the adduct in the concentra-
tion range of 0.07 to 0.03 m was observed during
cryoscopic molecular weight studies. The molecular
geometry of the adduct as determined by an X-ray
structural study and the labeling of the atoms is shown
in Figure 2. The arrangement of the substituents on
indium relative to those on phosphorus is shown in
Figure 3. Selected interatomic distances and angles are
collected in Table 2. The substituents around indium
and phosphorus atoms are arranged in distorted tetra-
hedral environments. The indium-carbon distances of
2.256(2), 2.270(2), and 2.263(2) Å are very similar to the
terminal In-C(C5H5) distances in In(C5H5)3 of 2.229(4)
Å but shorter than the bridging In-C(C5H5) distances
of 2.389(4) and 2.482(4) Å determined in the present
F igu r e 3. Arrangement of atoms about the indium-
phosphorus vector in (C5H5)3In‚PPh3.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for (C5H5)3In ‚P P h 3
(A) Indium-Phosphorus and Indium-Carbon Distances
In(1)-P(1)
In(1)-C(6)
2.6992(4) In(1)-C(1)
2.270(2) In(1)-C(11)
2.256(2)
2.263(2)
(B) Phosphorus-Carbon Distances
P(1)-C(16)
P(1)-C(22)
1.816(2)
1.814(2)
P(1)-C(28)
1.821(2)
(C) Angles around Indium
113.68(6) C(1)-In(1)-P(1)
114.09(7) C(11)-In(1)-P(1)
115.02(7) C(6)-In(1)-P(1)
C(1)-In(1)-C(11)
C(1)-In(1)-C(6)
C(11)-In(1)-C(6)
106.22(5)
102.53(5)
103.57(5)
(D) Angles around Phosphorus
C(22)-P(1)-C(16) 105.10(7) C(16)-P(1)-C(28) 105.46(7)
C(22)-P(1)-C(28) 105.93(7) C(22)-P(1)-In(1)
C(16)-P(1)-In(1) 111.46(5) C(28)-P(1)-In(1)
114.63(5)
113.48(5)
study. The In-C(C5H5) distance in the five-coordinate
adduct Cl2(C5H5)In‚(THF)212 is longer at 2.377(2) Å. The
cyclopentadienide ligands are arranged around the
indium with a propeller-like orientation in an -sc-
conformation with respect to the phenyl substituents
as seen in Figure 3. The phenyl groups are rotated with
respect to each other so that the dihedral angles
between their planes are -81.2°, -52.5°, and 53.1°. The
torsion angles along the indium-phosphorus bond of
C(1)-In(1)-P(1)-C(22), C(6)-In(1)-P(1)-C(16), and
C(11)-In(1)-P(1)-C(28) are -25.29(7)°, -26.56(7)°, and
-27.64(7)°, respectively. The indium-phosphorus bond
(9) Beachley, O. T., J r.; Pazik, J . P.; Glassman, T. E.; Churchill, M.
R.; Fettinger, J . C.; Blom, R. Organometallics 1988, 7, 1051.
(10) Beachley, O. T., J r.; Blom, R.; Churchill, M. R.; Faegri, K., J r.;
Fettinger, J . C.; Pazik, J . P.; Victoriano, L. Organometallics 1989, 8,
346.
(12) Visona, P.; Benetollo, F.; Rossetto, G.; Zanella, P. Polyhedron
1996, 15, 1743.
(11) Tuck, D. G. Chem. Soc. Rev. 1993, 269.

In(C5H5)3 and Heteroleptic Organoindium(III) Derivatives
Organometallics, Vol. 21, No. 22, 2002 4635
distance of 2.699(2) Å is shorter than the corresponding
distances in both (Me3In)2‚diphos of 2.755(4) Å13 and H3-
In‚[P(C6H11)3]2 of 2.9869(5) Å.14 The cyclopentadienide
groups have the characteristic features of simple σ-bond-
ed monohapto rings.
The possibility of weak intermolecular interactions
between some p-hydrogen atoms on the phenyl rings in
one adduct molecule and a carbon-carbon π-bond of a
cyclopentadienide ring in a neighboring molecule exists.
The distance between the appropriate atoms for this
possible interaction between H(27A)‚‚‚π C(14′)-C(15′)
(2.5 - x, 0.5 + y, 0.5 - z) is 2.62 Å, and the angle
between C(27)-H(27A)‚‚‚π(C(14′)-C(15′) is 162°. The
distance between H(32A)‚‚‚C(7) (1 + x, y, z) is 2.836 Å.
The sum of van der Waals radii for carbon and hydrogen
is 2.870 Å.6 These intermolecular contacts might help
the adduct crystallize by making 3-dimensional net-
works of the molecules.
F igu r e 4. Molecular geometry and labeling of atoms for
[(Me3CCH2)2In(C5H5)]n (50% probability ellipsoids for non-
hydrogen atoms, hydrogen atoms are omitted for clarity).
The heteroleptic organoindium compounds Me2In-
(C5H5) and (Me3CCH2)2In(C5H5) were prepared as color-
less solids in nearly quantitative yields by facile stoich-
iometric ligand redistribution reactions between In-
(C5H5)3 and InR3 (R ) Me and CH2CMe3) in THF
solution (eq 1) at room temperature. The THF was
readily removed from these compounds by vacuum
distillation at ∼20 °C. Each product was purified by
sublimation at 100-110 °C. The physical properties of
Me2In(C5H5) as prepared by the ligand-redistribution
reaction were identical with those previously reported.15
Samples of pure Me2In(C5H5) decompose at ∼200 °C to
an unknown dark brown material. No In(C5H5) was
observed. An analytically pure sample of (Me3CCH2)2-
In(C5H5) also decomposed at 188-190 °C to an unknown
dark brown material. No In(C5H5) was observed.
An X-ray structural study of (Me3CCH2)2In(C5H5)
revealed that the compound exists as a polymer with
cyclopentadienide units bridging In(CH2CMe3)2 moi-
eties. The structure is fully ordered in the monoclinic
cell and the P21 space group. However, as the angle â
in the unit cell is essentially 90°, twinning exists in the
structure. Thus, the absolute configuration of the mol-
ecule could not be determined. The unit cell contains
two asymmetric units, each of which consists of two
(Me3CCH2)2In(C5H5) monomers as depicted in Figure
4. Selected interatomic distances and angles are col-
lected in Table 3. Each asymmetric unit contains two
monomeric segments of the polymeric chain which have
slightly different geometries with respect to the In-
C5H5-In connections. Every indium atom is in contact
with four carbon atoms, two from terminal CH2CMe3
groups and two from bridging C5H5 moieties, in a highly
distorted tetrahedral environment. The C(CH2Me3)-
In-C(CH2Me3) angles are significantly larger than the
angle for an ideal trigonal-planar arrangement of atoms
with values of 150.9(2)° [In(1)], 152.3(2)° [In(2)], 145.8(2)°
[In(3)], and 145.6(2)° [In(1)], while the C(C5H5)-In-
C(C5H5) angle is less than the ideal tetrahedral angle
with values of 91.9(2)° [In(1)], 91.5(2)° [In(2)], 100.8(2)°
[In(3)], and 102.1(2)° [In(4)]. The bridging indium-
Ta ble 3. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for (Me3CCH2)2In (C5H5)a
(A) Indium-Carbon Distances
In(1)-C(1)
In(1)-C(16)
In(1)#2-C(9)
In(2)-C(6)
In(2)-C(26)
In(3)-C(41)
In(3)-C(46)
In(4)-C(33)
In(4)-C(51)
2.517(5) In(1)-C(11)
2.148(5) In(1)-C(9)#1
2.543(5) In(2)-C(3)
2.539(5) In(2)-C(21)
2.190(4) In(3)-C(31)
2.183(4) In(3)-C(39)#2
2.135(5) In(3)#2-C(39)
2.539(5) In(4)-C(36)
2.162(5) In(4)-C(56)
2.180(5)
2.543(5)
2.550(5)
2.160(5)
2.534(4)
2.530(5)
2.530(5)
2.519(4)
2.179(4)
(B) Carbon-Carbon Distances for Cyclopentadienide Ring
C(1)-C(2)
1.418(7) C(1)-C(5)
1.404(7) C(3)-C(4)
1.380(7) C(6)-C(10)
1.436(7) C(7)-C(8)
1.429(6) C(9)-C(10)
1.403(6) C(31)-C(35)
1.397(6) C(33)-C(34)
1.386(6) C(36)-C(37)
1.380(6) C(38)-C(39)
1.418(7) C(36)-C(40)
1.417(7)
1.419(7)
1.401(6)
1.388(7)
1.408(6)
1.426(6)
1.443(6)
1.442(6)
1.438(7)
1.411(7)
C(2)-C(3)
C(4)-C(5)
C(6)-C(7)
C(8)-C(9)
C(31)-C(32)
C(32)-C(33)
C(34)-C(35)
C(37)-C(38)
C(39)-C(40)
(C) Angles around Indium
C(16)-In(1)-C(11)
C(11)-In(1)-C(1)
150.9(2) C(16)-In(1)-C(1)
103.8(2)
100.3(2) C(16)-In(1)-C(9)#1 106.1(2)
C(11)-In(1)-C(9)#1 89.0(2) C(1)-In(1)-C(9)#1
91.9(5)
102.4(2)
105.4(2)
91.5(2)
C(21)-In(2)-C(26)
C(26)-In(2)-C(6)
C(26)-In(2)-C(3)
C(46)-In(3)-C(41)
152.3(2) C(21)-In(2)-C(6)
100.1(2) C(21)-In(2)-C(3)
89.9(2) C(6)-In(2)-C(3)
145.8(2) C(46)-In(3)-C(39)#2 103.1(2)
107.98(16)
98.9(2) C(39)#2-In(3)-C(31) 100.8(2)
145.6(2) C(51)-In(4)-C(36)
98.7(2) C(51)-In(4)-C(33)
91.2(2) C(36)-In(4)-C(33)
C(41)-In(3)-C(39)#2 91.8(2) C(46)-In(3)-C(31)
C(41)-In(3)-C(31)
C(51)-In(4)-C(56)
C(56)-In(4)-C(36)
C(56)-In(4)-C(33)
109.0(2)
102.1(2)
102.1(2)
a
Symmetry transformations used to generate equivalent at-
oms: #1 - x + 1, y, z; #2 - x - 1, y, z.
carbon(C5H5) bond distances (Å) of 2.517(5) for In(1)-
C(1), 2.543(5) for In(1)-C(9, #1), 2.550(5) for In(2)-C(3),
2.530(5) for In(3)-C(39, #2), 2.534(4) for In(3)-C(31),
2.539(5) for In(4)-C(33), and 2.519(4) for In(4)-C(36)
are slightly longer than those in In(C5H5)3 at 2.389(4)
and 2.482(4) Å and in Me2In(C5H5) at 2.457(12) and
2.484(12) Å.15 The In-C(CH2CMe3) bond distances are
similar to the In-Me distances of 2.118(14) and 2.129(13)
Å in Me2In(C5H5)15 and the In-C(CH2Me3) distance of
2.12(2) Å in [In(CH2CMe3)Cl2]x.16 The In-C bond vectors
are almost parallel in the asymmetric unit for indium-
(13) Bradley, D. C.; Chudzynska, H.; Faktor, M. M.; Frigo, D. M.;
Hursthouse, M. B.; Hussain, B.; Smith, L. M. Polyhedron 1988, 7, 1289.
(14) Cole, M. L.; Hibbs, D. E.; J ones, C.; Smithies, N. A. J . Chem.
Soc., Dalton Trans. 2000, 545.
(15) Beachley, O. T., J r.; Robirds, E. S.; Atwood, D. A.; Wei, P.
Organometallics 1999, 18, 2561.

4636 Organometallics, Vol. 21, No. 22, 2002
Beachley et al.
(1) and -(2) with the angles between these vectors being
177.5° and 176.6°. These vectors are slightly bent in the
asymmetric unit for indium(3) and -(4) where the angles
are 169.7° and 169.3°. The planes of the C5H5 rings are
slightly tilted with respect to the C-In bonds by 12.2°
and 11.3° for C1‚‚‚C5, 13.6° and 11.2° for C6‚‚‚C10, 6.2°
and 13.5° for C31‚‚‚C35, and 15.9° and 13.5° for C36‚‚
‚C40. The carbon-carbon distances within each C5H5
ring are appropriate for a delocalized allyl-type bonding
between the carbon atoms at the 1, 2, and 3 positions
of the ring whereas the carbon-carbon distance between
the atoms at the 4 and 5 positions is shorter and
representative of a double bond. Thus, each indium(III)
atom can be considered to have two normal σ-bonds to
the neopentyl carbon atoms and a three-centered two-
electron bond across the C(C5H5)-In-C(C5H5) system.
mixture of (Me3CCH2)2In(C5H5) and In(C5H5)3 (eq 5 ).
2(Me3CCH2)In(C5H5)2(melt) 150 °C8 In(C5H5)3 +
(Me3CCH2)2In(C5H5)(s) (5)
The homoleptic derivative In(C5H5)3 then decomposed
to In(C5H5) and C5H6 (eq 6 ) whereas the (Me3CCH2)2-
In(C5H5)3 150 °C8 In(C5H5)(s) + C5H6 +
organic produce(s) (6)
In(C5H5) sublimed without decomposition to the cooler
walls of the apparatus.
Even though all of the heteroleptic organoindium
derivatives of the types R2In(C5H5) and RIn(C5H5)2 (R
) Me, CH2CMe3) can be isolated as pure compounds in
the solid state, they dissolve in THF to form adducts
that redistribute their ligands to form equilibrium
mixtures of InR3‚THF, R2In(C5H5)‚THF, RIn(C5H5)2‚
THF, and In(C5H5)3‚THF, as appropriate (eqs 3 and 4).
Dissolution of all known organoindium(III) cyclopenta-
dienide derivatives at room temperature requires the
use of a Lewis base with significant donor ability. The
cyclopentadienide bridges in the polymer must be
broken for dissolution to occur. Thus, these compounds
are exceedingly soluble in THF, a strong base, but are
essentially insoluble in nonbasic solvents and in weakly
basic solvents such as C5H12, C6H6, Et2O, HCCl3, and
CCl4. In contrast, the cyclopentadienide bridges in the
related gallium derivatives are weaker as Me2Ga(C5H4-
The first examples of heteroleptic organoindium
compounds that incorporate two cyclopentadienide groups
MeIn(C5H5)2 and (Me3CCH2)In(C5H5)2 have been pre-
pared as analytically pure yellow solids by ligand
redistribution reactions (eq 2) in THF solutions. The
preparative reactions utilized excess In(C5H5)3. The
equilibrium in which the ligands of RIn(C5H5)2 redis-
tribute to form R2In(C5H5) and In(C5H5)3 in THF solu-
tion (eq 4) must be shifted to minimize the amount of
R2In(C5H5), a potential impurity that has a sublimation
temperature that is similar to or slightly less than that
of RIn(C5H5)2. Analytically pure MeIn(C5H5)2 was iso-
lated easily by sublimation at 110-120 °C. Decomposi-
tion, rather than melting, occurred at 150-160 °C but
only very small amounts of In(C5H5) were formed.
Analytically pure, yellow (Me3CCH2)In(C5H5)2 was also
isolated by sublimation at 90-95 °C but it was neces-
sary to remove a small amount of (Me3CCH2)2In(C5H5)
that sublimed as a colorless solid prior to the sublima-
tion of (Me3CCH2)In(C5H5)2. The two compounds (Me3-
CCH2)2In(C5H5) and (Me3CCH2)In(C5H5)2 are readily
distinguished by their color. Careful control of the
temperature during sublimation is necessary for the
isolation of analytically pure (Me3CCH2)In(C5H5)2. It is
of interest that (Me3CCH2)In(C5H5)2 sublimed at a lower
temperature than MeIn(C5H5)2. This observation sug-
gests that the cyclopentadienide bridge bonds that
stabilize the compounds as solids appear to be weaker
in (Me3CCH2)In(C5H5)2 than in MeIn(C5H5)2. X-ray
structural studies of (Me3CCH2)In(C5H5)2 and MeIn-
(C5H5)2 were prevented by severe twining of the crystals.
Me),2 Et2Ga(C5H4Me),2 Et2Ga(C5H5),3 and EtGa(C5H5)2
3
dissolve in benzene and form monomers in solution. The
1H NMR spectrum of (Me3CCH2)2In(C5H5) in THF
solution at ∼20 °C clearly demonstrates the occurrence
of the ligand redistribution equilibria and the presence
of (Me3CCH2)2In(C5H5)‚THF, (Me3CCH2)In(C5H5)2‚THF,
In(CH2CMe3)3‚THF, and In(C5H5)3‚THF (eqs 3 and 4).
Six resonances are observed for the methyl and meth-
ylene protons for the neopentyl groups. However, only
one resonance for the cyclopentadienide protons can be
seen. Cooling of the solution to -60 °C, the lowest
temperature studied, did not change the spectrum. The
cyclopentadienide protons for the three different species
were not resolved. The resonances for the neopentyl
substituents associated with each of the three com-
pounds in the solution were identified by comparing the
chemical shifts of each line with the resonances for the
independent species.
Although Me2In(C5H5) is isolable as an analytically
pure solid, it exists in THF solution as a mixture of Me2-
In(C5H5)‚THF, MeIn(C5H5)2‚THF, InMe3‚THF, and In-
(C5H5)3‚THF according to NMR spectroscopy. Even
though four compounds are present in THF solution,
only three resonances, two for In-Me protons and one
for C5H5 protons, are observed at ∼20 °C. As the
solution was cooled to -40 °C, one of the original In-
Me resonances moved from -0.52 ppm to slightly higher
field and split into two lines at -0.53 and -0.56 ppm.
The second In-Me resonance at -1.10 ppm shifted to
higher field also. The new line at -0.53 ppm is assigned
to Me2In(C5H5)‚THF whereas the one at -0.56 ppm is
for InMe3‚THF on the basis of their relative intensities.
Pure InMe3‚THF dissolved in THF has a single reso-
nance at -0.55 ppm. The second In-Me resonance that
The neopentyl derivative (Me3CCH2)In(C5H5)2 melts
at 126.4-126.9 °C. If heating is immediately quenched
after the compound melts, the observed melting point
is reproducible. However, the melt does decompose.
When a sample of pure (Me3CCH2)In(C5H5)2 was heated
at 150 °C in a sealed, evacuated tube, pale yellow
crystals of In(C5H5) collected in the coolest part of the
tube whereas colorless needles of (Me3CCH2)2In(C5H5)
formed on the warmer walls. A condensable gaseous
product was identified as C5H6 with a trace of CMe4.
These data suggest that (Me3CCH2)In(C5H5)2 melted
and then redistributed its ligands to form initially a
(16) Beachley, O. T., J r.; Spiegel, E. F.; Kopasz, J . P.; Rogers, R. D.
Organometallics 1989, 8, 1915.

In(C5H5)3 and Heteroleptic Organoindium(III) Derivatives
Organometallics, Vol. 21, No. 22, 2002 4637
shifted from -1.10 to -1.64 ppm over the temperature
range of 20 to -90 °C may be assigned to the In-Me
group in MeIn(C5H5)2‚THF. The resonance correspond-
ing to the C5H5 protons shifted from 6.04 to 5.97 ppm
over the temperature range of 20 to -90 °C. Conforma-
tion of these assignments for the various In-Me reso-
nances was obtained by preparing a THF solution of
Me2In(C5H5) with one small crystal of InMe3. The
resonances for the In-Me groups occurred at -0.55 and
-0.56 ppm at -90 °C whereas the resonance at higher
field disappeared because the equilibrium had been
shifted. These temperature-dependent NMR spectro-
scopic data are consistent with the occurrence of ligand
redistribution equilibria (eqs 3 and 4) and with the
exchange of methyl groups and cyclopentadienide groups
between the different species. The resonances of the
cyclopentadienide ligands for the different species could
not be resolved at any temperature studied.
and (Me3CCH2)In(C5H5)‚THF at 0.61 and 0.37 ppm,
respectively, moved to 0.54 and 0.25 ppm at -50 °C.
The single resonance associated with the C5H5 protons
appeared at 6.03 ppm at 20 °C but was broader and
slightly shifted to 6.04 ppm at -30 °C. At -40 °C the
resonance split into two lines at 5.95 and 6.05 ppm. The
resonance at 6.05 ppm may be assigned to the C5H5
protons for the cyclopentadienide groups for both (Me3-
CCH2)In(C5H5)2‚THF and (Me3CCH2)2In(C5H5)‚THF
whereas the resonance at 5.95 ppm may be assigned to
In(C5H5)3‚THF. The chemical shift of the resonance at
6.05 ppm remained constant to -60 °C, whereas the
resonance at 5.95 assigned to In(C5H5)3‚THF shifted to
5.93 ppm at -60 °C, the lowest temperature studied.
The equilibrium constants for the ligand redistribu-
tion reactions for THF solutions of Me2In(C5H5) (eq 3),
(Me3CCH2)2In(C5H5) (eq 3), MeIn(C5H5)2 (eq 4), and
(Me3CCH2)In(C5H5)2 (eq 4) have calculated values of 3.9
× 10-3, 3.2 × 10-3, 0.15, and 2.0 × 10-2, respectively,
at the normal operating temperature of the instrument.
The equilibrium constants for the methyl derivatives
were calculated on the basis of the integrations of the
methyl resonances whereas the equilibrium constants
for the neopentyl derivatives were based on the integra-
tions for the methyl protons for the tert-butyl groups
on the neopentyl substituents. More accurate, detailed,
and complete thermodynamic data results could not be
obtained for these systems as the resonances were not
resolved fully.
The monomethyl derivative MeIn(C5H5)2 exists as a
mixture of MeIn(C5H5)2‚THF, Me2In(C5H5)‚THF, In-
(C5H5)3‚THF, and possibly InMe3‚THF in THF solution.
Two In-Me lines and one C5H5 line are observed at ∼20
°C. Thus, the methyl groups are exchanging between
the different species as are the cyclopentadienide groups.
When the temperature was lowered from 20 to -80 °C,
the most intense In-Me resonance shifted from -1.09
to -1.49 ppm whereas the smaller line moved from
-0.37 to -0.03 ppm. The resonance corresponding to
the C5H5 protons broadened and shifted from 5.98 to
5.85 ppm between 20 and -40 °C. At -60 °C the C5H5
protons exhibited lines at 6.06 and 5.72 ppm. Additional
lowering of the temperature to -80 °C caused the
cyclopentadienide resonances to shift to 6.02 and 5.71
ppm. The presence of an In-Me resonance associated
with Me2In(C5H5)‚THF at a chemical shift other than
at 0.53 ppm suggests that InMe3‚THF is present in
solution. Even though no resonance for InMe3‚THF was
observed, its presence is required by the balanced
chemical equation for the ligand redistribution reaction
of Me2In(C5H5)‚THF (eq 3).
1H NMR spectroscopy suggests that (Me3CCH2)In-
(C5H5)2 exists in THF solution as an equilibrium mix-
ture of (Me3CCH2)In(C5H5)2‚THF, (Me3CCH2)2In(C5H5)‚
THF, (Me3CCH2)3In‚THF, and In(C5H5)3‚THF (eqs 3
and 4). The resonances for the methyl protons associated
with the neopentyl groups for all three species were
observed at 20 °C. However, only two of the three
resonances for the methylene protons for the neopentyl
groups could be observed. The line for the methylene
protons for (Me3CCH2)3In‚THF was not observed, pos-
sibly because its intensity is expected to be extremely
low and/or the resonance is masked by other resonances.
The compound (Me3CCH2)3In‚THF will be formed by the
redistribution of (Me3CCH2)2In(C5H5)‚THF, a product
of the initial redistribution reaction (eq 3). Only minor
changes for the chemical shifts for the resonances of the
neopentyl methyl protons were observed as the tem-
perature was lowered. Thus, the resonances at 0.99,
0.83, and 1.10 ppm for (Me3CCH2)2In(C5H5)‚THF, (Me3-
CCH2)In(C5H5)2‚THF, and (Me3CCH2)3In‚THF, respec-
tively, at 20 °C were observed at 1.00, 0.84, and 1.10
ppm, respectively, at -50 °C. In contrast, the methylene
protons on the neopentyl substituents shifted more
significantly as the lines for (Me3CCH2)2In(C5H5)‚THF
Exp er im en ta l Section
All compounds described in this investigation were sensitive
to oxygen and moisture and were manipulated either under a
purified argon atmosphere in a Vacuum Atmospheres drybox
or by using standard vacuum line techniques. The starting
16
materials Li(C5H5),9 InMe3,17 and In(CH2CMe3)3 were pre-
pared by literature methods whereas InCl3 was purchased
from Strem Chemicals, Inc. and was used as received. Special
care was taken during the preparation of Li(C5H5) to ensure
its purity.9 All solvents were carefully dried by using conven-
tional procedures. Elemental analyses were performed by
either E&R Microanalytical Laboratory, Parsippany, NJ , or
Oneida Research Services, Whitesboro, NY. Melting points
were determined with a Mel-Temp by using flame-sealed
capillaries filled with argon and are uncorrected. 1H NMR (400
MHz) spectra were recorded with a Varian Unity-Nova 400
spectrometer whereas 13C NMR (125.7 MHz) spectra were
recorded with a Varian Unity-Nova 500 spectrometer. Proton
chemical shifts are reported in δ (ppm) units and are refer-
enced to SiMe4 at δ 0.00 ppm and C6D5H at δ 7.15 ppm or the
proton impurities in d8-THF at 1.73 and 3.58 ppm. Carbon
chemical shifts are referenced to SiMe4 at δ 0.00 and to d8-
THF at δ 67.40 and 25.27 ppm. All samples for NMR spectra
were contained in flame-sealed NMR tubes. Deuterated sol-
vents, benzene-d6 and THF-d8, were purchased from Aldrich
Chemical Co. and Cambridge Isotopes, Inc., respectively, dried
with P4O10, and vacuum distilled into tubes coated with sodium
mirrors. The benzene-d6 was purchased as 99.6% atom percent
deuterated. Molecular weights were measured cryoscopically
in benzene solution by using an instrument similar to that
described by Shriver and Drezdon.18
Syn th esis of In (C5H5)3 in THF Solu tion . A three-necked
Solv-Seal flask that contained 2.19 g (30.4 mmol) of Li(C5H5)
(17) Bradley, D. C.; Chudzynska, H. C.; Harding, I. S. Inorganic
Syntheses; Cowley, A. H., Ed.; J ohn Wiley and Sons Inc.: New York,
1997; Vol. 31, p 67.
(18) Shriver, D. F.; Drezdon, M. A. The Manipulation of Air-Sensitive
Compounds; Wiley: New York, 1986; p 38.

4638 Organometallics, Vol. 21, No. 22, 2002
Beachley et al.
and 75 mL of THF was connected to a sidearm dumper charged
with 2.17 g (9.81 mmol) of InCl3 and to a medium porosity
frit. A THF solution of InCl3 was added to the Li(C5H5)/THF
solution over a period of 1 h and then the resulting solution
was stirred for 3 h at room temperature. Flask-to-flask vacuum
distillation at room temperature was used to remove most of
the THF. The color changed from colorless to orange/yellow.
When a thick, viscous material was present, it was dynami-
cally evacuated for an additional 2 h until a thick paste
remained. Then approximately 75 mL of benzene was added
by vacuum distillation to the resulting mixture of In(C5H5)3‚
THF, LiCl, and excess Li(C5H5). The resulting solution of In-
(C5H5)3‚THF was separated from the insoluble material by
filtration. The benzene and the remaining THF were removed
by flask-to-flask vacuum distillation and then by dynamic
evacuation for ∼4 h. Finally, approximately 75 mL of pentane
was added to the product and the resulting suspension was
stirred for 2 h. The pentane was removed rapidly by vacuum
distillation to produce a dry powder that was dynamically
evacuated for an additional 4 h. The final product In(C5H5)3
was a bright yellow powder that weighed 2.36 g (7.61 mmol,
77.6% yield based on InCl3). In (C5H5)3: Mp: color change from
C5H5, 5.00 H), 2.932 (s, C5H6, 0.41 H). 13C NMR (THF-d8) 4
months after solution preparation, δ 106.82 (s, C5H5).
Stu d ies of Lew is Acid ity of In (C5H5)3. (a ) NMe3. A flask
was charged with 0.052 g (0.017 mmol) of In(C5H5)3, 0.020 g
(0.085 mmol) of NMe3, and 5 mL of C6H6. The resulting cloudy
yellow suspension was maintained at room temperature for 2
h. The material, volatile at room temperature, was removed
by trap-to-trap vacuum distillation to leave a cream-colored
product. Finally, the flask was dynamically evacuated for an
additional 24 h and the product turned yellow. The final
product weighed 0.050 g. Thus, the In(C5H5)3 retained only a
very small amount of NMe3. Mp: 121 °C (sample began to turn
tan), 136 °C (sample turned brown), 141 °C (apparent melting).
Crystals of In(C5H5) were observed in the cooler part of the
melting point capillary at the conclusion of the melting point
1
experiment. H NMR (THF-d8): δ 5.85 (s, C5H5, 15.0 H), 1.12
(s, NCH3, 1.8 H). (b) P P h 3. A flask was charged with 0.805 g
(2.59 mmol) of In(C5H5)3 and 0.525 g (2.00 mmol) of PPh3 and
approximately 10 mL of C6H6. The resulting bright-yellow
suspension in C6H6 was stirred for 1 h and filtered through a
medium porosity frit. The benzene was removed by vacuum
distillation and replaced with 10 mL of C5H12. Washing of the
product with cold pentane provided 1.02 g (1.79 mmol, 89.5%
yield based on PPh3) of In(C5H5)3‚PPh3 as pale yellow crystals.
In (C5H5)3‚P P h 3: Mp 159 °C (sample began to turn orange),
169 °C (sample suddenly melted and became orange red), 180
°C (sample turned brown). Crystals of In(C5H5) were observed
in the cooler part of the melting point capillary at the
conclusion of the melting point experiment. Anal. Calcd for
1
bright yellow to orange at ∼160-164 °C dec. H NMR (THF-
d8): δ 5.90 (s, C5H5). 13C NMR (THF-d8) δ 111.09 (s, C5H5).
Anal. Calcd for C15H15In: C, 58.10; H, 4.88; In, 37.03. Found:
C, 58.06; H, 4.87; In, 36.96. Solubility: soluble in THF; no
appreciable solubility in Et2O, C6H6, C5H12, or CHCl3.
Th er m a l Decom p osition of In (C5H5)3. An evacuated
break-seal tube that contained 0.803 g (2.59 mmol) of In(C5H5)3
was placed halfway into a 150 °C oven. After ∼1 min of heating
pale yellow crystals began to collect at the cool end of the tube
and a brown solid was observed in the bottom of the tube. A
total of 15 min of heating was used to completely decompose
the sample. The tube was opened and the volatile, condensable
material was transferred to an NMR tube and identified as
C5H6. The pale, yellow crystalline solid was identified as In-
(C5H5) (0.379 g, 2.11 mmol, 81.3% yield based on In(C5H5)3).
The unidentified brown residue that was insoluble in common
organic solvents weighed 0.392 g. P a le yellow cr ysta ls: In-
(C5H5). Mp 168.6-169.7 °C dec (lit.9 mp 169.3-171 °C dec).
1H NMR (THF-d8): δ 5.99 (s, C5H5). Vola tile liqu id (C5H6
a n d C10H12): 1H NMR (C6D6): δ 6.49 (m, 27.99 H, C5H6), 6.29
(m, 29.37 H, C5H6), 5.93 (m, 1.01 H, C5H6), 5.48 (m, 0.97 H,
C5H6), 3.57 (m, 0.73 H, C10H12), 3.12 (m, 0.82 H, C10H12), 2.70
(m, 34.27 H, C10H12), 2.59 (m, 1.02 H, C10H12), 2.11 (m, 1.06
H, C10H12), 1.58 (m, 1.76 H, C10H12), 1.18 (s, 0.57 H, C10H12),
1.16 (s, 0.43 H, C10H12).
C
33H30InP: C, 69.25; H, 5.28. Found: C, 68.83; H, 5.24.
Solubility: soluble in THF and C6H6; no appreciable solubility
in pentane. 1H NMR (THF-d8): δ 5.95 (s, C5H5, 15H), 7.30 (br
m, PPh, 15H). 1H NMR (C6D6): δ 6.20 (s, C5H5, 15H), 7.00 (m,
PPh), 7.43 (m, PPh). 31P{1H} NMR (THF-d8): δ -3.08 (s).
31P{1H} NMR (C6D6) δ 5.95 (s). Cryoscopic molecular weight,
benzene solution, formula weight 572 (observed molality,
observed molecular weight, association): 0.0688, 582, 1.02;
0.0406, 588, 1.03; 0.0274, 584, 1.02.
Syn th esis of Me2In (C5H5) by a Liga n d Red istr ibu tion
Rea ction . A THF solution of 0.655 g (4.10 mmol) of InMe3
was allowed to react with 0.636 g (2.05 mmol) of In(C5H5)3 at
room temperature for 1 h. After the THF was removed by
vacuum distillation, the flask was dynamically evacuated for
an additional 3 h. The resulting colorless solid was sublimed
at 100-110 °C to produce 1.19 g (5.67 mmol, 92.2% yield) of
Me2In(C5H5). Me2In (C5H5): Colorless solid. Mp 190-196 °C
dec (color change to dark brown) (lit.15 mp 195-200 °C dec).
Solubility: soluble in THF; no appreciable solubility in Et2O,
Rea ction of In (C5H5)3 w ith In (C5H5). A sidearm dumper
was charged with 0.15 g (0.48 mmol) of In(C5H5)3 and con-
nected to a reaction vessel charged with 0.086 g (0.48 mmol)
of In(C5H5) and a magnetic stir bar. Solvent (1 mL of THF-d8)
was added by vacuum distillation, the reactants were mixed,
and the resulting solution was poured into the NMR tube. The
NMR tube was flame-sealed and maintained at -196 °C until
the 1H NMR spectrum was recorded. Solvent (THF-d8) was
vacuum distilled into a second NMR tube that contained 0.126
g (0.700 mmol) of In(C5H5). This NMR tube was flame-sealed
C6H6, or C5H12.
1H NMR (THF-d8): δ 6.04 (s, C5H5, 5.00H),
-0.52 (s, Me2In(C5H5)‚THF and InMe3)‚THF, 5.78H), -1.10 (s,
1
MeIn(C5H5)2‚THF, 0.22 H) (lit. H NMR (d8-THF): δ 6.05 (s,
C5H5, 2.19H), 0.11 (s, InMe3)‚THF, 0.48H), -0.52 (s, Me2In-
(C5H5)‚THF, 6.0H), -1.11 (s, MeIn(C5H5)2)‚THF, 0.11H).
Syn th esis of (Me3CCH2)2In (C5H5) by a Liga n d Red is-
tr ibu tion Rea ction . A THF solution of 1.42 g (4.33 mmol) of
freshly sublimed In(CH2CMe3)3 was allowed to react with 0.672
g (2.17 mmol) of In(C5H5)3 dissolved in THF. After the THF
was removed by vacuum distillation, the product was sublimed
at 100-110 °C to produce 1.923 g (5.97 mmol, 91.7% yield) of
(Me3CCH2)2In(C5H5). (Me3CCH2)2In (C5H5): Colorless solid.
Mp 188-190 °C dec (color change to brown). Anal. Calcd for
1
and maintained at -196 °C until the H NMR spectrum was
recorded. In (C5H5)3 a n d In (C5H5): 1H NMR (THF-d8): initial
spectrum, 20 min after warming, pale yellow solution, δ 5.940
(s, C5H5), 4 months after solution preparation, pale yellow
solution, δ 5.934 (s, C5H5). 13C NMR (THF-d8): 4 months after
1
solution preparation, δ 108.07 (s, C5H5). In (C5H5): H NMR
(THF-d8): initial spectrum, 10 min after warming, brown
solution, δ 5.985 (s, C5H5), C5H6 negligible; 20 h after warming,
black precipitate, δ 6.500 (m, C5H6, 0.21 H), 6.407 (m, C5H6,
0.23 H), 5.986 (s, C5H5, 5.00 H), 2.935 (s, C5H6, 0.35 H); 72 h
after warming, black precipitate, δ 6.503 (m, C5H6, 0.20 H),
6.403 (m, C5H6, 0.23 H), 5.986 (s, C5H6, 5.00 H), 2.934 (s, C5H6,
0.37 H); 4 months after solution preparation, black precipitate,
δ 6.503 (m, C5H6, 0.20 H), 6.404 (m, C5H6, 0.23 H), 5.985 (s,
C
15H27In: C, 55.92; H, 8.45. Found: C, 55.91; H, 8.33. Solubil-
ity: soluble in THF; no appreciable solubility in Et2O, C6H6,
1
or C5H12. H NMR (THF-d8): δ 6.07 (s, C5H5, 4.78H), 0.99 (s,
(Me3CCH2)2In(C5H5), 15.81H), 0.61 (s, (Me3CCH2)2In(C5H5),
3.76H), 0.82 (s, (Me3CCH2)In(C5H5)2, 0.47H), 0.49 (s, (Me3-
CCH2)In(C5H5)2, 0.01H), 1.11 (s, (Me3CCH2)3In, 1.83H), 0.81
(s, (Me3CCH2)3In, 0.35H).

In(C5H5)3 and Heteroleptic Organoindium(III) Derivatives
Organometallics, Vol. 21, No. 22, 2002 4639
Ta ble 4. Da ta for X-r a y Cr ysta llogr a p h ic Stu d ies of [In (C5H5)3]n , (C5H5)3In ‚P P h 3, a n d [(Me3CCH2)2In (C5H5)]n
[In(C5H5)3]n
(C5H5)3In‚PPh3
[(Me3CCH2)2In(C5H5)]n
molec. formula
Mr
cryst shape
cryst syst
space group
a, Å
C
15H15In
310.09
yellow plate
orthorhombic
Pbca
C33H30InP
572.36
yellow brick
monoclinic
P21/n
11.0573(2)
15.3171(3)
16.8052(3)
90
108.559(1)
90
2698.21(9)
1.409
C15H27In
322.19
colorless brick
monoclinic
P21
9.7386(1)
14.9887(2)
20.7791(3)
90
90.0068(4)
90
9.8029(3)
9.5808(3)
24.6957(7)
90
90
90
2319.4(1)
1.776
8
2.005
90(1)
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
3033.10(7)
1.411
4
D
Z
calcd, g/cm3
4
µ(Mo KR), mm-1
T (K)
0.954
1.535
90.0(1)
60.0
90.0(1)
58.5
max. 2θ, deg
absorp. corr. meth.
reflns measd
unique reflns (Rint
reflns I > 4σ(I)
refined parameters
R [I > 2σ(I)]
wR2
50.0
SADABS19
21659
2039(0.067)
1526
SADABS19
48046
SADABS19
32340
)
7876 (0.059)
6571
406
0.028
0.065
14405 (0.047)
13854
629
0.026
0.061
190
0.028
0.065
goodness-of-fit
extinction coeff.
1.028
None
1.204
None
1.013
0.0068(1)
Syn th esis of MeIn (C5H5)2 by a Liga n d Red istr ibu tion
Rea ction w ith Excess In (C5H5)3. The same procedure as
described for the preparation of Me2In(C5H5) was used to
prepare MeIn(C5H5)2. Reagents: 0.164 g (1.02 mmol) of freshly
sublimed InMe3, 0.953 g (3.07 mmol) of In(C5H5)3, and 10 mL
of THF. The resulting yellow solid was sublimed at 110-120
°C to produce 0.649 g (2.497 mmol, 81.6% yield based on
InMe3) of MeIn(C5H5)2. MeIn (C5H5)2: Yellow solid. Mp 150.7-
160.2 °C dec (gradual change from yellow to viscous brown
liquid). Anal. Calcd for C11H13In: C, 50.81; H, 5.04; In, 44.15.
Found: C, 50.57; H, 5.32; In, 44.03. Solubility: soluble in THF;
no appreciable solubility in Et2O, C6H6, or C5H12. Attempts to
grow crystallographic quality crystals by slow sublimation at
130-140 °C produced severely twinned crystals that were not
residue was observed at the bottom of the tube. The tube was
opened and the condensable gases transferred to an NMR tube.
The yellow crystalline solid was collected in the drybox and
identified as In(C5H5) (0.211 g, 1.17 mmol, 76% yield based
on eqs 5 and 6) by its physical properties and 1H NMR
spectrum. The colorless needles were identified as (Me3CCH2)2-
In(C5H5) (0.452 g, 1.40 mmol, 91% based on eqs 5 and 6). P a le
1
yellow cr ysta ls: In(C5H5). Mp 169.8-170.4 °C dec. H NMR
(THF-d8): δ 5.99 (s, C5H5). Color less n eed les: (Me3CCH2)2-
1
In(C5H5). Mp 188.2-191.4 °C dec. H NMR (THF-d8): δ 6.08
(s, C5H5, 4.89H), 0.99 (s, (Me3CCH2)2In(C5H5), 15.75H), 0.61
(s, (Me3CCH2)2In(C5H5), 3.74H), 0.82 (s, (Me3CCH2)In(C5H5)2,
0.51H), 0.49 (s, (Me3CCH2)In(C5H5)2, 0.01H), 1.11 (s, (Me3-
CCH2)3In, 1.79H), 0.82 (s, (Me3CCH2)3In, 0.31H). Vola tile
liqu id : C5H6 and CMe4. 1H NMR (C6D6): δ 6.48 (m, C5H6,
15.13 H), 6.29 (m, C5H6, 16.25 H), 3.58 (m, C5H6, 1.22 H), 2.68
1
useful. H NMR (THF-d8): δ 5.98 (s, C5H5, 10.7H), -0.37 (s,
Me2In(C5H5), 0.23H), -1.09 (s, MeIn(C5H5)2, 2.06H).
Syn th esis of (Me3CCH2)In (C5H5)2 by a Liga n d Red is-
tr ibu tion Rea ction w ith Excess In (C5H5)3. The same
procedure as described for the preparation of Me2In(C5H5) was
used to prepare (Me3CCH2)In(C5H5)2. Reagents: 0.282 g (0.859
mmol) of freshly sublimed In(CH2CMe3)3, 0.799 g (2.58 mmol)
of In(C5H5)3, and 10 mL of THF. The resulting yellow solid
was heated at 90-95 °C to isolate the product by sublimation.
A small amount of a colorless solid identified as (Me3CCH2)2-
In(C5H5) that sublimed initially was removed. Then the sample
was reheated and 0.766 g (2.42 mmol, 94% yield based on In-
(CH2CMe3)3) of (Me3CCH2)In(C5H5)2 as a yellow solid was
isolated from the coldfinger of the sublimator. (Me3CCH2)In -
(C5H5)2: Yellow solid. Mp 126.4-126.9 °C dec (gradual change
(m, C10H12, 27.78 H), 1.41 (m, C10H12, 1.28 H), 1.24 (m, C10H12
1.20 H), 0.91 (s, CMe4, 12 H), 0.86 (m, C10H12, 1.35 H), 0.39 (s,
0.38 H).
,
Collection of X-r a y Diffr a ction Da ta a n d Str u ctu r a l
Solu tion s for [In (C5H5)3]n , In (C5H5)3‚P P h 3, a n d [(Me3C-
CH2)2In (C5H5)]n : Gen er a l F ea tu r es. Well-defined crystals
of the title compounds were covered with Infineum V8512 oil
(Infineum USA L. P., 1900 East Linden Avenue, Linden, NJ
07036) and mounted on a Bruker SMART1000 CCD diffrac-
tometer equipped with the rotating anode (Mo KR radiation,
λ ) 0.71073 Å). X-ray diffraction data were collected at 90 K.
Details for all compounds are provided in Table 4. Data
collection for each compound involved four sets of frames (600
frames in each set) and covered half-reciprocal space using the
ω-scans technique (0.3° frame width) with different æ angles.
Reflection intensities were integrated by using the SAINT-
PLUS program.19 The solution and refinement of the struc-
tures were performed by use of the SHELXTL program
package.20 The structures were refined by full-matrix least
squares against F2. Non-hydrogen atoms were refined in
anisotropic approximation. The hydrogen atoms were located
from yellow to viscous brown liquid). Anal. Calcd for C15H21
-
In: C, 56.99; H, 6.70. Found: C, 56.86; H, 6.69. Solubility:
soluble in THF; no appreciable solubility in Et2O, C6H6, or
C5H12.
1H NMR (THF-d8): δ 6.03 (s, C5H5, 10.14H), 0.99 (s,
(Me3CCH2)2In(C5H5), 0.91H), 0.61 (s, (Me3CCH2)2In(C5H5),
0.19H), 0.83 (s, (Me3CCH2)In(C5H5)2, 7.87H), 0.37 (s, (Me3-
CCH2)In(C5H5)2, 1.77H), 1.10 (s, (Me3CCH2)3In, 0.11H).
Th er m a l Decom p osit ion of (Me3CCH2)In (C5H5)2. A
break-seal tube that contained 0.972 g (3.07 mmol) of (Me3-
CCH2)In(C5H5)2 was evacuated and flame sealed. The tube was
placed halfway into a 150 °C oven. Immediately, the (Me3-
CCH2)In(C5H5)2 began to melt and pale yellow crystals col-
lected at the coolest end of the tube while colorless needles
formed on the walls of the tube immediately above the oven.
After the tube was heated for 15 min, a trace of a brown
(19) SMART and SAINTPLUS, Area detector control and integra-
tion software, Ver. 6.0 1; Bruker Analytical X-ray Systems: Madison,
WI, 1999.
(20) SHELXTL, Ver. 5.10; An integration system for solving, refin-
ing, and displaying crystal structures from diffraction data; Bruker
Analytical X-ray Systems: Madison, WI, 1997.

4640 Organometallics, Vol. 21, No. 22, 2002
Beachley et al.
from difference electron density Fourier syntheses and refined
in isotropic approximation for [In(C5H5)3]n, with Uiso ) 1.2Ueq
of the preceding carbon atom for In(C5H5)3‚PPh3, or as idealized
CH3 groups with Uiso ) 1.5Ueq and by using the riding model
with Uiso ) 1.2Ueq of the preceding carbon atom for [(Me3-
CCH2)2In(C5H5)]n. Data were corrected for absorption by using
the Bruker AXS SADABS program that is a part of the
SAINTPLUS package.19
The structure of (Me3CCH2)2In(C5H5) provides an example
of twinning by pseudo-merohedry,21,22 which occurs when the
metric symmetry is higher than the symmetry of the structure.
The structure appeared to be orthorhombic with all angles in
the unit cell of exactly 90°. Although the |E2 - 1| value of 0.867
was close to that for the centrosymmetric space group, the
systematic absences only for three mutually orthogonal 21
screw axes were found giving only one acceptable space group
P212121 and indicating the presence of both racemic twinning
and general twinning in the structure. The structure could
then be solved in the monoclinic space group P21, which
requires the transformation of the unit cell. The Rint value for
the orthorhombic space group was 0.083, significant but just
slightly higher than that for the monoclinic space group
(0.047). The structure was solved by the Patterson method,
which gave the positions of the indium atoms. Structural
refinement was completed by using the twining law (1 0 0;
0 -1 0; 0 0 -1) for the generation of the unequal components,
which were doubled to satisfy the racemic twining. The three
scale factors for twin components were refined to values
0.20385, 0.35935, and 0.16834.
Su p p or tin g In for m a tion Ava ila ble: Experimental de-
tails for the attempted synthesis of In(C5H5)3 by the literature8
method; variable-temperature NMR spectral data for hetero-
leptic organoindium cyclopentadienide compounds; solubility
and stability of In(C5H5)3 in benzene; and complete tables of
positional parameters, interatomic distances and angles,
anisotropic thermal parameters, and positions for hydrogen
atoms and packing diagrams for the three compounds studied.
This material is available free of charge via the Internet at
http://pubs.acs.org.
(21) Giacovazzo, C. Fundamentals of Crystallography; Oxford Uni-
versity Press: Oxford, UK, 1992.
(22) Herbst-Irmer, R.; Sheldrick, G. M. Acta Crystallogr. 1998, B54,
443.
OM0202322