Homoleptic and heteroleptic gallium(III) compounds containing monosubstituted cyclopentadienyl ligands: Ga(C5H4Me)3, Ga(C5H4SiMe3)3, and R2Ga(C5H4</sub

Article abstract of DOI:10.1021/om0005304

The new gallium(III) cyclopentadienyl derivatives Ga(C₅H₄Me)₃ and Ga(C₅SiMe₃)₃ have been synthesized by metathetical reactions. Subsequent stoichiometric ligand redistribution reactions wit

Full text of DOI:10.1021/om0005304

4550
Organometallics 2000, 19, 4550-4556
Hom olep tic a n d Heter olep tic Ga lliu m (III) Com p ou n d s
Con ta in in g Mon osu bstitu ted Cyclop en ta d ien yl Liga n d s:
Ga (C5H4Me)3, Ga (C5H4SiMe3)3, a n d R2Ga (C5H4Me)
(R ) Me, Et)
O. T. Beachley, J r.* and Michael T. Mosscrop
Department of Chemistry, University at Buffalo, The State University of New York,
Buffalo, New York 14260-3000
Received J une 21, 2000
The new gallium(III) cyclopentadienyl derivatives Ga(C5H4Me)3 and Ga(C5H4SiMe3)3 have
been synthesized by metathetical reactions. Subsequent stoichiometric ligand redistribution
reactions with GaR3 (R ) Me, Et) were used to prepare R2Ga(C5H4Me) as pure single com-
pounds. However, when the syntheses of RGa(C5H4Me)2 (R ) Me, Et) and MenGa(C5H4SiMe3)3-n
(n )1, 2) by analogous stoichiometric ligand redistribution reactions were investigated,
mixtures of compounds were the isolated products. The heteroleptic organogallium compound
Me2Ga(C5H4Me) has also been prepared in high yields by using metathetical reactions
between Me2GaCl and Li(C5H4Me) in pentane and between Cl2Ga(C5H4Me), formed in-situ
from Ga(C5H4Me)3 and GaCl3 in diethyl ether, and LiMe. All pure compounds have been
characterized by their physical properties, elemental analyses, NMR spectra, and cryoscopic
molecular weight studies.
In tr od u ction
compound in any phase. A benzene solution consisted
of a mixture of MeGa(C5H5)2, Me2Ga(C5H5), and Ga-
(C5H5)3, whereas the product isolated after reacting Ga-
(C5H5)3 and GaMe3 in a 2:1 mol ratio was a mixture of
Me2Ga(C5H5) and Ga(C5H5)3. X-ray structural studies
Whether a heteroleptic organogallium compound of
the type GaR2R′ exists as a single compound or under-
goes a series of ligand redistribution reactions to form
a mixture of GaR2R′, GaR′2R, GaR′3, and GaR3 depends
on the nature of the organic groups and the phase.
When the organic groups are methyl and phenylethnyl
as in Me2Ga(CtCPh),1 a single compound exists in the
solid phase and in benzene solution. Both the X-ray
structural study of a crystal1c and the cryoscopic mo-
lecular weight study of a benzene solution1a identified
the presence of dimers. The structure of the dimer in
the solid phase had phenylethnyl groups bridging four
coordinate gallium atoms.1c In contrast, the character-
ization data for gallium compounds that contained only
methyl and tert-butyl groups as in Me2Ga(t-Bu) were
consistent with the existence of mixtures with GaMe3,
MeGa(t-Bu)2, and Ga(t-Bu)3.2 When the organic sub-
stituents are a methyl or an ethyl group and a cyclo-
pentadienyl group as in Me2Ga(C5H5),3 Et2Ga(C5H5),3b,4
and EtGa(C5H5)2,4 single compounds exist in the solid
phase, but dissolution in benzene produced equilibrium
mixtures of monomeric species including GaR3, R2Ga-
(C5H5), RGa(C5H5)2, and/or Ga(C5H5)3 (R ) Me, Et). In
of Me2Ga(C5H5),3d Et2Ga(C5H5),4 and EtGa(C5H5)2
4
identified polymeric structures with cyclopentadienyl
units bridging four-coordinate gallium in each case.
Even though these isolable solids are polymers, the
parent Ga(C5H5)3 is a monomer in the solid state and
in benzene solution.5 In this paper we describe the
nature of Ga(C5H4Me)3 and Ga(C5H4SiMe3)3 and the
effects of these monosubstituted cyclopentadienyl ligands
on the chemistry of the heteroleptic organogallium
compounds RnGa(C5H4Me)3-n (R ) Me, Et; n ) 1, 2) and
MenGa(C5H4SiMe3)3-n (n )1, 2).
Resu lts a n d Discu ssion
The cyclopentadienyl derivatives Ga(C5H4Me)3 and
Ga(C5H4SiMe3)3 were prepared by reacting GaCl3 with
Li(C5H4R) (R ) Me, SiMe3) (eq 1) in diethyl ether. The
GaCl3 + 3 Li(C5H4R) Et O8 Ga(C5H4R)3 + 3 LiCl (1)
2
0 °C
3a
R ) Me, SiMe3
contrast, MeGa(C5H5)2 cannot be isolated as a pure
(1) (a) J effery, E. A.; Mole, T. J . J . Organomet. Chem. 1968, 11, 393.
(b) Lee, K. E.; Higa, K. T. J . Organomet. Chem. 1993, 449, 53. (c) Tecle,
B.; Ilsley, W. H.; Oliver, J . P. Inorg. Chem. 1981, 20, 2335.
(2) Cleaver, W. M.; Barron, A. R. Chemtronics 1989, 4, 146.
(3) (a) Beachley, O. T., J r.; Royster, T. L., J r.; Arhar, J . R. J .
Organomet. Chem. 1992, 434, 11. (b) Stadelhofer, J .; Weidlein, J .;
Haaland, A. J . Organomet. Chem. 1975, 84, C1. (c) Stadelhofer, J .;
Weidlein, J .; Fischer, P.; Haaland, A. J . Organomet. Chem. 1976, 116,
55. (d) Mertz, K.; Zettler, F.; Hausen, H.-D.; Weidlein, J . J . Organomet.
Chem. 1976, 122, 159.
desired product was separated from the LiCl and excess
Li(C5H4R) by extraction with pentane. Removal of the
pentane by vacuum distillation at room temperature
lead to the isolation of Ga(C5H4Me)3 as a golden-yellow
oil. The trimethylsilyl derivative Ga(C5H4SiMe3)3 was
a golden-brown/amber liquid. Even though both com-
(4) Beachley, O. T., J r.; Rosenblum, D. B.; Churchill, M. R.; Lake,
C. H.; Krajkowski, L. M. Organometallics 1995, 14, 4402.
(5) Beachley, O. T., J r.; Getman, T. D.; Kirss, R; Hallock, R. B.;
Hunter, W. C.; Atwood, J . L. Organometallics 1985, 4, 751.
10.1021/om0005304 CCC: $19.00 © 2000 American Chemical Society
Publication on Web 09/23/2000

Ga(III) Compounds with Cyclopentadienyl Ligands
Organometallics, Vol. 19, No. 22, 2000 4551
pounds are nonvolatile and decompose slowly at room
temperature, they had acceptable elemental analyses
for carbon and hydrogen. The original liquids became
increasingly viscous and darker in color with time.
These observations are consistent with the occurrence
of prototropic rearrangements of the substituted cyclo-
pentadienide rings (isomerization) and subsequent Di-
els-Alder dimerization reactions.6 Similar conclusions
have been made for other heavy group 13 metal cyclo-
pentadienyl derivatives.5,6-8 The closely related com-
pound Ga(C5H5)3 also decomposes/isomerizes at room
temperature with a change in color from colorless to
yellow.5 Since Ga(C5H4Me)3 and Ga(C5H4SiMe3)3 cannot
be distilled or recrystallized, the isolation of analytically
pure compounds required the use of high-purity re-
agents and the minimization of potential side reactions
that might produce impurities. Full details of the
preparative procedures are described in the Experimen-
tal Section.
faster than the other rearrangements, as the rate of a
sigmatropic rearrangement increases with the metallic
character of the migrating group.6 Thus, the slower
movement of the SiMe3 group leads to two resonances,
an intense line at 0.24 and a smaller line at -0.12 ppm.
These lines may be assigned to the SiMe3 group in
different vinyl positions on the cyclopentadienyl ring.
The methyl-substituted cyclopentadienyl gallium com-
pound Ga(C5H4Me)3 is a Lewis acid, as it formed 1:1
adducts with NMe3 and THF. Both adducts were solids
at room temperature. The NMe3 adduct was colorless,
whereas the THF adduct was pale yellow. Both adducts
were stable to dissociation of the base at room temper-
ature. When sublimation of Ga(C5H4Me)3‚NMe3 was
attempted, only a small quantity of a colorless solid
sublimed at 35 °C. Most of the material did not sublime
but became brown, an indication of isomerization.6 In
contrast, when the THF adduct was heated at its
melting point of 78-81 °C, no color change was ob-
served. Thus, these adducts have less tendency to
decompose and/or isomerize than does Ga(C5H4Me)3.
The heteroleptic organogallium compounds R2Ga-
(C5H4Me) (R ) Me, Et) were prepared by stoichiometric
ligand redistribution reactions3a,4 (eq 2) between Ga-
(C5H4Me)3 and GaMe3 or GaEt3, as appropriate. The
The 1H NMR spectrum of Ga(C5H4Me)3 exhibited
three resonances, one for the ring methyl group and two
for the cyclopentadienide ring protons. A fourth line at
5.99 ppm was observed, but it is believed to be due to
an impurity of C5H5 that probably exists as Ga(C5H4-
Me)2(C5H5). Fractional distillation of the methylcyclo-
pentadiene monomer prior to reaction with the Li(n-
Bu) demonstrated that this impurity originated with the
commercially available methylcyclopentadiene dimer.
Even though this impurity was minimized to the extent
that it did not significantly impact the elemental
analysis of Ga(C5H4Me)3, it could never be eliminated.
The literature7 reveals that the related compound Al-
(C5H4Me)3, a light yellow oil, was also contaminated
with an impurity of C5H5. The 13C NMR spectrum of
Ga(C5H4Me)3 had a total of four resonances with one
for the methyl group and three for ring carbon atoms.
2 GaR3 + Ga(C5H4Me)3 pentane8 3 R2Ga(C5H4Me) (2)
25 °C
compound Me2Ga(C5H4Me) was isolated by vacuum
sublimation at room temperature, whereas Et2Ga(C5H4-
Me) was a mobile liquid that was purified by vacuum
distillation at room temperature. The excellent elemen-
tal analysis and the sharp melting point of Me2Ga(C5H4-
Me) (61.5-62.0 °C) identify the solid as a single com-
pound. Liquid Et2Ga(C5H4Me) was also an analytically
pure, single compound at room temperature. The 1H
NMR spectrum of this neat, colorless liquid exhibited
one set of sharp lines that are consistent with Et2Ga-
(C5H4Me). One set of sharp resonances suggests the
presence of one species, especially since either multiple
sets of lines or line broadening is observed at room
temperature when solutions of multiple species are
formed by a ligand redistribution reaction (eq 3). The
closely related compound Et2Ga(C5H5)4 (mp 35-36 °C)
also exists as a single species in the liquid state at
1
Low-temperature H NMR techniques (-50 °C was the
lowest temperature studied) were unable to sufficiently
slow the migration of the metal about the cyclopenta-
dienyl ring so that the lines for the individual static
structures could be observed. Similar observations have
been made for Ga(C5H5)3,5 In(C5H5)3,8 and In(C5H4Me)3.8
Even though the NMR spectra of Ga(C5H4Me)3 are
consistent with either fluxional or nonfluxional rings to
gallium, the compound is believed to have fluxional
rings with η1-bonding. If the compound were nonflux-
ional and had a “static” structure, the ipso-carbon atom
of each of the three cyclopentadienyl rings would have
to be bonded both to gallium and to a methyl group, a
sterically unfavorable structure.
1
45 °C according to its H NMR spectrum. Conversely,
EtGa(C5H5)2 exists in the solid state as a pure single
compound, but its melt (mp 39.0-39.4 °C) forms mul-
tiple species according to its 1H NMR spectrum at
45 °C.4 As Me2Ga(C5H4Me) was a crystalline solid at
room temperature, an X-ray structural study was at-
tempted. However, the crystals of Me2Ga(C5H4Me) were
twinned and unsuitable for study. Crystals could not
be obtained from either pentane, methylcyclohexane, or
benzene solutions even though the compound was very
soluble. It should be noted that Me2Ga(C5H4Me) was
more stable toward isomerization than was either Et2-
Ga(C5H4Me) or Ga(C5H4Me)3. Crystals of Me2Ga(C5H4-
Me) were stored in sealed ampules at room temperature
for over one year without any evidence of decomposition/
isomerization by 1H NMR spectroscopy. In contrast,
samples of liquid Et2Ga(C5H4Me) in sealed ampules
gradually changed color and became yellow-green and
increasingly viscous with time at room temperature.
1
The resonances in the H and 13C NMR spectrum of
Ga(C5H4SiMe3)3 have chemical shifts that are as ex-
pected for this compound with fluxional cyclopentadi-
enyl rings.6 However, all lines were considerably broader
than those observed for Ga(C5H4Me)3. This increased
line broadening is related to the variety of sigmatropic
rearrangement processes that occur for the molecule,
including metallotropic shifts of the gallium fragment,
silatropic shifts of the SiMe3 group, and prototropic
shifts of ring hydrogen atoms. The rate of the metallo-
tropic shift of the gallium fragment is expected to occur
(6) J utzi, P. Chem. Rev. 1986, 86, 983, and references therein.
(7) Fisher, J . D.; Budzelaar, P. H. M.; Shapiro, P. J .; Staples, R. J .;
Yap, G. P. A.; Rheingold, A. L. Organometallics 1997, 16, 871.
(8) Poland, J . S.; Tuck, D. G. J . Organomet. Chem. 1972, 42, 307.

4552 Organometallics, Vol. 19, No. 22, 2000
Beachley and Mosscrop
Cryoscopic molecular weight studies of benzene solu-
tions of Me2Ga(C5H4Me) identified the presence of
monomeric species. H NMR spectral studies of solu-
tions of Me2Ga(C5H4Me) in d8-THF, d6-benzene, d8-
toluene, d12-cyclohexane, CDCl3, and CD2Cl2 revealed
that Me2Ga(C5H4Me) does not exist as a single com-
pound in solution but forms an equilibrium mixture of
Me2Ga(C5H4Me), MeGa(C5H4Me)2, and GaMe3 (eq 3).
MeGa(C5H4Me)2 and EtGa(C5H4Me)2, but neither could
be isolated as a single compound. Removal of solvent
1
GaR3 + 2 Ga(C5H4Me)3 pentane8 3 RGa(C5H4Me)2 (4)
25 °C
resulted in the isolation of a liquid at room temperature
in each case. Vacuum distillation of the resulting liquid
at room temperature separated a distillate from a
solvent
1
yellow-brown liquid residue. H NMR spectral studies
2 R2Ga(C5H4Me) y
z GaR3 + RGa(C5H4Me)2 (3)
K
of benzene solutions identified the distillate as mixture
of RGa(C5H4Me)2 and R2Ga(C5H4Me) (R ) Me, Et) and
the yellow-brown residue as Ga(C5H4Me)3 with a small
amount of RGa(C5H4Me)2. Thus, the chemistry of RGa-
(C5H4Me)2 (R ) Me, Et) is similar to that of MeGa-
(C5H5)2,3a as none of these compounds can be isolated
The presence of multiple species at the normal operating
temperature of the instrument was evident from the
multiple gallium-methyl lines. When the solvent was
d8-THF, three sharp resonances were observed in the
gallium-methyl region of the spectrum, whereas two
sets of lines were observed for the protons of the C5H4-
Me group. This multiplicity of lines is consistent with
slow exchange between the species in eq 3. When the
solvent was not a Lewis base, exchange was faster. Two
broad lines were observed for the methyl groups bonded
to gallium, and the C5H4Me group exhibited only one
set of lines. The identity of the 1H NMR lines was
confirmed by comparing the observed spectrum with the
spectrum recorded for a mixture of Ga(C5H4Me)3 and
GaMe3 in a 1:1 mol ratio as well as with the spectra for
pure GaMe3 and Ga(C5H4Me)3 in the same solvent. The
equilibrium constant for the redistribution of Me2Ga-
(C5H4Me) in THF solution (eq 3) was estimated to be
4
as pure single compounds. In contrast, EtGa(C5H5)2
is the only dicyclopentadienyl derivative that has been
isolated as a pure single compound, and it has a
polymeric structure in the solid phase.
1
A comparison of the H NMR spectra of solutions of
GaR3 (R ) Me, Et) and Ga(C5H4Me)3 mixed in 2:1 and
1:1 mol ratios in benzene with the spectra of the
products isolated from the reaction designed to prepare
RGa(C5H4Me)2 (eq 4) demonstrated that the isolated
products were mixtures and not originally pure com-
pounds that were undergoing ligand redistribution
reactions (eq 5) when placed in solution. When the
solvent
1
2.3 × 10-2 by using the integration data from the H
2 RGa(C5H4Me)2 y
z R2Ga(C5H4Me) +
K
NMR spectra at the normal operating temperature of
the instrument. The corresponding equilibrium constant
Ga(C5H4Me)3 (5)
for Me2Ga(C5H5) was 1.4 × 10-1 3a
.
The solution chemistry of Et2Ga(C5H4Me) paralleled
that of Me2Ga(C5H4Me). A cryoscopic molecular weight
study demonstrated the presence of monomeric species
reagents were mixed in the stoichiometric ratio of 1:2
mol in C6D6, the resulting 1H NMR spectrum had
relative integrations of lines for the R group to the
methyl line for the C5H4Me group that were consistent
with the formula RGa(C5H4Me)2, whereas the spectra
for the isolated products did not. Second, the spectrum
for the stoichiometric mixture had sharper lines than
those observed in the spectra of either Me2Ga(C5H4Me)
or Et2Ga(C5H4Me). Thus, the ethyl derivative displayed
the expected triplet/quartet signals. Signal averaging
for the C5H4Me group lines in the spectra of samples
dissolved in C6D6 resulted in only one set of lines. The
d8-THF spectra once again showed a reduction in the
rate of ligand exchange, as separate sets of lines were
observed for the multiple C5H4Me groups and alkyl
groups in the multiple species.
1
in benzene solution, whereas H NMR spectral studies
identified multiple species formed by a ligand redistri-
bution reaction (eq 3). Multiple sets of gallium-ethyl
lines were observed for each of the solvents including
d8-THF, C6D6, C6D12, and d8-toluene. When d8-THF was
the solvent, the spectrum displayed three sharp triplets
and three quartets for the ethyl group protons, one for
each of the three species in the equilibrium (eq 3),
GaEt3, Et2Ga(C5H4Me), and EtGa(C5H4Me)2. In addi-
tion, two sets of resonances were observed for the C5H4-
Me ring protons, as observed for Me2Ga(C5H4Me). When
the solvent was not basic, such as C6D6, C6D12, and d8-
toluene, broad singlets were observed in place of the
expected triplets and/or quartets due to more rapid ethyl
group exchange. The NMR spectrum of a d8-toluene
solution at -40 °C displayed only broadening of the lines
for the ethyl groups and a single set of lines for the C5H4-
Me ring. Thus, the rate of the metallotropic shift
remained sufficiently rapid that lines for the static
structure of the C5H4Me ring were not observed.6 The
equilibrium constant for the redistribution reaction (eq
3) in THF at ambient temperature, as calculated by
using the integration values for the methyl, methylene,
and cyclopentadienide ring protons, had a value of 1.5
× 10-2. The equilibrium constant for the redistribution
of Et2Ga(C5H5)4 as calculated from the 1H NMR spectral
Ligand redistribution reactions between Ga(C5H4-
SiMe3)3 and GaMe3 were investigated as potential
routes to Me2Ga(C5H4SiMe3) and MeGa(C5H4SiMe3)2,
but neither could be isolated as single compounds
1
according to the H NMR spectral data. Instead, mix-
tures were formed by ligand redistribution reactions of
the intended products (eqs 3 and 5). The additional
fluxionality of the SiMe3 group combined with the
metallotropic shifts of the gallium probably hinders the
formation of the cyclopentadienyl bridge, which appears
necessary to stabilize these types of compounds in the
condensed state and make them isolable as single
compounds. The steric bulk of the SiMe3 group might
also be a factor to prevent bridging.
data for eq 3 was 1.3 × 10-2
.
Ligand redistribution reactions (eq 4) were used for
the attempted synthesis of the monoalkyl derivatives
The compound Me2Ga(C5H4Me) has also been pre-
pared in ∼85% yield by using a metathetical reaction

Ga(III) Compounds with Cyclopentadienyl Ligands
Organometallics, Vol. 19, No. 22, 2000 4553
between Me2GaCl11 and excess Li(C5H4Me) in pentane
solution (eq 6). The product isolated after removal of
that have been characterized by X-ray structural studies
exist as linear polymers with the cyclopentadienyl
groups bridging four-coordinate MR2 moieties.3d,4,8,9 In
contrast, solutions are composed of monomers according
to cryoscopic molecular weight studies.3,4 Thus, four-
coordinate metal centers formed by bridging cyclopen-
tadienyl groups are necessary for the stabilization of a
compound in the condensed phase, whereas the presence
of monomers permits facile ligand redistribution reac-
tions to form multiple species. As Me2Ga(C5H4Me) and
Et2Ga(C5H4Me) exist as single compounds in the con-
densed state, they probably exist as polymers. The only
dicyclopentadienyl derivative that has been isolated as
Me2GaCl + Li(C5H4Me) pentane8 Me2Ga(C5H4Me) +
25 °C
LiCl (6)
solvent and subsequent sublimation at room tempera-
ture had excellent elemental analyses for C, H, and Ga
and a sharp melting point. All characterization data
were in agreement with those observed for the com-
pound prepared by the ligand redistribution reaction.
The synthesis of Me2Ga(C5H4Me) by a metathetical
reaction is significant because the first reported syn-
thesis of Me2Ga(C5H5) by a metathetical reaction in
cyclohexane gave a low yield (30-60%) of an impure
product.3b,c This original product had an unsatisfactory
elemental analysis, and its melting point was signifi-
cantly lower than that observed for the pure compound
prepared by a ligand redistribution reaction.3a The
difference between the results of the syntheses of Me2-
Ga(C5H4Me) and of Me2Ga(C5H5)3b,c by metathetical
reactions may be attributed to the solubility of these
compounds in the reaction solvent. The product Me2-
Ga(C5H4Me) is soluble in pentane, whereas Me2Ga-
(C5H5)3a is insoluble in cyclohexane. Thus, the reaction
between Me2GaCl and an excess of Li(C5H5) in cyclo-
hexane was probably incomplete, and samples of Me2-
Ga(C5H5) might have been contaminated with Me2GaCl,
a compound with volatility similar to Me2Ga(C5H5).
The third route to Me2Ga(C5H4Me) in high yield
involved a metathetical reaction between Cl2Ga(C5H4-
Me) and LiMe in diethyl ether solution (eq 7). The chloro
4
a single pure compound is EtGa(C5H5)2, and its isola-
tion required shifting the ligand redistribution equilib-
rium to minimize the presence of Et2Ga(C5H5) in the
solution prior to removal of solvent and isolation of the
compound by sublimation. When the equilibrium had
not been shifted, removal of solvent and subsequent
sublimation produced a product with low carbon/
hydrogen analyses, probably a mixture of EtGa(C5H5)2
and Et2Ga(C5H5). Since Et2Ga(C5H5) has weaker Lon-
don dispersion forces and is more volatile than EtGa-
(C5H5)2, Et2Ga(C5H5) sublimed before or with EtGa-
(C5H5)2 contaminated the desired product and produced
low carbon and hydrogen analysis. Thus, EtGa(C5H5)2
is the only example of a gallium or indium dicyclopen-
tadienyl derivative, to date, that has the appropriate
magnitude of the equilibrium constant for the redistri-
bution equilibrium, has sufficiently strong bridges to
stabilize the condensed phase with four-coordinate
gallium and overcome the loss of entropy due to forming
the polymer, but has sufficiently weak London disper-
sion forces and weak bridges to permit sublimation/
distillation prior to decomposition. In the case of the
other gallium or indium dicyclopentadienide derivatives
that have been investigated, two cyclopentadienide
groups prevent formation of the bridge necessary for
stabilization.
Et2O
2 GaCl3 + Ga(C5H4Me)3 + 2 LiMe
8
0 °C
3 Me2Ga(C5H4Me) + 2 LiCl (7)
derivative Cl2Ga(C5H4Me) was formed in-situ by using
a stoichiometric ligand redistribution reaction between
Ga(C5H4Me)3 and GaCl3. Extensive research on these
chlorogallium methylcyclopentadienyl derivatives has
revealed that Cl2Ga(C5H4Me) and ClGa(C5H4Me)2 can-
not be isolated and characterized because of the occur-
rence of facile isomerization/polymerization reactions.
If Cl2Ga(C5H4Me) and ClGa(C5H4Me)2 are to be used
as reagents, best results are obtained if they are reacted
soon after formation in solvents that are Lewis bases,
diethyl ether, or THF.
Five heteroleptic diorganogallium and -indium cyclo-
pentadienyl derivatives, Me2Ga(C5H5),3a Et2Ga(C5H5),4
Me2Ga(C5H4Me), Et2Ga(C5H4Me), and Me2In(C5H5),9
but only one dicyclopentadienyl derivative, EtGa-
(C5H5)2,4 have been prepared and isolated as analyti-
cally pure single compounds in the condensed phase at
room temperature. However, when these compounds are
dissolved, equilibrium mixtures of multiple species are
formed by ligand redistribution reactions.3a,4 All solids
Exp er im en ta l Section
All compounds described in this investigation were exceed-
ingly 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 tech-
niques. All solvents were dried by conventional procedures.
The reagent Li(C5H4Me) was prepared by adding a solution
of Li(n-Bu) in hexane/pentane to an excess of fractionally
distilled C5H5Me at 0 °C. The insoluble product was washed
three times with the reaction solvent and then thoroughly
dried under vacuum. The trimethylsilyl derivative Li(C5H4-
SiMe3) was prepared by the literature method.10 The compound
Me2GaCl11a,b was prepared by a ligand redistribution reaction
between GaMe3 and GaCl3 in pentane at room temperature.11c
Elemental analyses were performed by E&R Microanalytical
Laboratory, Parsippany, NJ . Melting points were determined
with a Mel-Temp by using flame-sealed capillaries filled with
argon and are uncorrected. Infrared spectra of samples as
either neat liquids or Nujol mulls between CsI plates were
recorded by using a Perkin-Elmer 683 spectrometer. 1H NMR
(400 MHz) and 13C NMR (125.7 MHz) spectra were recorded
with Varian VXR-400 and Varian VXR-500 spectrometers,
respectively. Proton chemical shifts are reported in δ (ppm)
units and are referenced to SiMe4 at δ 0.00 ppm and either
C6D5H at δ 7.15 or the residual proton in the other deuterated
solvents, as appropriate. Carbon-13 chemical shifts are refer-
(9) (a) Beachley, O. T., J r.; Robirds, E. S.; Atwood, D. A.; Wei, P.
Organometallics 1999, 18, 2561. (b) Krommes, P.; Lorberth, J . J .
Organomet. Chem. 1975, 88, 329.
(10) Beachley, O. T., J r.; Lees, J . F.; Glassman, T. E.; Churchill, M.
R.; Buttrey, L. A. Organometallics 1990, 9, 2488.
(11) (a) Armer, B.; Schmidbaur, H. Chem. Ber. 1967, 100, 1521. (b)
Magee, C. P.; Sneddon, L. G.; Beer, D. C.; Grimes, R. N. J . Organomet.
Chem. 1975, 86, 159. (c) Rosenblum, D. B. Ph.D. Thesis, State
University of New York at Buffalo, Buffalo, NY, 1997; p 52.

4554 Organometallics, Vol. 19, No. 22, 2000
Beachley and Mosscrop
enced to SiMe4 at δ 0.00 ppm and to C6D6 at δ 128.39 ppm.
All samples for NMR spectra were contained in flame-sealed
NMR tubes. Molecular weights were measured cryoscopically
for benzene solutions by using an instrument similar to that
described by Shriver and Drezdzon.12
2.24 (t, 9.0, ring-CH3), 1.57 (s, 9.6, N-CH3). Anal. Calcd for
C
21H30GaN: C, 68.88; H, 8.26. Found: C, 68.39; H, 8.04.
(b) THF . A solution of 0.631 g of Ga(C5H4Me)3 (2.06 mmol)
in THF (approximately 10 mL) was stirred for 2 h. Then the
excess THF was removed from the resulting yellow solution
by vacuum distillation to afford Ga(C5H4Me)3‚THF (0.668 g,
1.76 mmol, 85.6% yield) as a pale yellow solid. Ga(C5H4Me)3‚
THF: mp 78-81 °C; 1H NMR (C6D6, δ) 6.06 (s, 0.2, C5H5), 5.99
(s, 4.0, ring-H), 5.39 (s, 4.9, ring-H), 3.46 (m, 3.9, THF), 2.15
(s, 9.0, CH3), 1.28 (m, 3.2, THF).
Syn th esis of Ga (C5H4Me)3. A Solv-Seal flask, charged with
6.31 g of Li(C5H4Me) (73.4 mmol) and approximately 125 mL
of diethyl ether, was connected to a sidearm dumper that
contained 4.07 g of freshly sublimed GaCl3 (23.1 mmol)
dissolved in approximately 50 mL of ether. After the Li(C5H4-
Me)/Et2O slurry was cooled to 0 °C, the GaCl3/Et2O solution
was slowly added over a period of 1 h. The resulting mixture
was stirred overnight while warming to room temperature. The
Et2O was then removed by vacuum distillation, and ap-
proximately 50 mL of pentane was added to the two-necked
Schlenk flask. The product, Ga(C5H4Me)3, was isolated by
three extractions. The remaining LiCl was a colorless solid.
The pentane was then removed from the apparatus by vacuum
distillation followed by overnight pumping to leave 6.15 g (20.0
mmol, 86.7% yield, based on GaCl3) of a pale golden-yellow
liquid. Since Ga(C5H4Me)3 decomposes slowly at room tem-
perature as demonstrated by the original liquid becoming
increasingly viscous and darker in color with time, it was
stored under vacuum in sealed ampules at -20 °C. Ga(C5H4-
Me)3: 1H NMR (C6D6, δ) 5.99 (s, 0.2, C5H5, see Discussion),
5.82 (s, 4.2, ring-H), 5.46 (s, 4.6, ring-H), 2.08 (s, 9.0, ring-
CH3); (d8-THF, δ): 5.95 (s, 4.6, ring-H), 5.85 (s, 0.2, C5H5), 5.01
(s, 5.1, ring-H), 2.08 (s, 9.0, ring-CH3); (neat liquid, capillary
of C6D6 for reference, δ): 5.79 (s, 0.2, C5H5), 5.58 (s, 6.5, ring-
H), 5.22 (s, 6.5, ring-H), 1.95 (s, 9.0, ring-CH3); 13C NMR (C6D6,
δ) 139.56 (s, ring-C), 114.26 (s, ring-C), 112.72 (s, -C5H5),
103.05 (s, ring-C), 15.53 (s, -CH3). Anal. Calcd for C18H21Ga:
C, 70.40; H, 6.90. Found: C, 69.97; H, 6.88. Cryoscopic
molecular weight, benzene solution, fw 307.08 (molality, obsd
mol wt, assoc): 0.0868, 343, 1.12; 0.0695, 345, 1.12; 0.0458,
356, 1.16.
Syn th esis of Me2Ga (C5H4Me) by a Liga n d Red istr ibu -
tion Rea ction . A flask containing Ga(C5H4Me)3 (0.476 g, 1.55
mmol) was connected to a 90° elbow and a Schlenk flask. Then,
0.361 g of GaMe3 (3.14 mmol) and 25 mL of pentane were
vacuum distilled onto the Ga(C5H4Me)3 and the solution was
allowed to stir overnight at room temperature. Removal of the
pentane by vacuum distillation produced a colorless solid that
was transferred by vacuum sublimation at room temperature
to the attached Schlenk flask held at -196 °C and identified
as Me2Ga(C5H4Me) (0.700 g, 3.91 mmol, 84.1% yield based on
Ga(C5H4Me)3). Large colorless, hexagonal shaped crystalline
plates were obtained by heating a sample under vacuum in a
sealed tube at 35 °C. The crystals were twinned and were
unsuitable for an X-ray structural study. Attempts to grow
X-ray quality crystals of Me2Ga(C5H4Me) by recrystallization
from pentane, methylcyclohexane, and toluene solutions were
unsuccessful. Me2Ga(C5H4Me): mp 61.5-62 °C; 1H NMR
(C6D6, δ) 5.98 (s, 1.1, ring-H), 5.80 (s, 1.1, ring-H), 2.11 (s, 3.0,
ring-CH3), -0.43 (s br, 4.8, Me3Ga/Me2GaCp), -1.04 (s br, 0.3,
MeGaCp2); (d8-THF, δ): 5.84 (s, 0.3, MeGaCp2 ring-H), 5.75
(s, 0.9, Me2GaCp ring-H), 5.52 (s, 1.0, Me2GaCp ring-H), 5.40
(s, 0.3, Me2GaCp ring-H), 2.06 (s, 3.0, ring-CH3), -0.49 (s, 0.9,
Me3Ga), -0.65 (s, 4.1, Me2GaCp), -1.08 (s, 0.3, MeGaCp2).
Anal. Calcd for C8H13Ga: C, 53.71; H, 7.32. Found: C, 53.91;
H, 7.48. Cryoscopic molecular weight, benzene solution, fw
178.91 (molality, obsd mol wt, assoc): 0.0711, 189, 1.06; 0.0578,
190, 1.06; 0.0400, 198, 1.10.
Syn th esis of Ga (C5H4SiMe3)3. The synthesis of Ga(C5H4-
SiMe3)3 was identical to that previously described for Ga(C5H4-
Me)3. A diethyl ether solution of GaCl3 (3.53 g, 20.1 mmol) was
added to an ether slurry of Li(C5H4SiMe3) (8.73 g, 60.5 mmol)
at -78 °C over a 30 min period. The reaction mixture was
stirred overnight at -78 °C, and the Et2O was removed by
vacuum distillation. The product Ga(C5H4SiMe3)3 was isolated
by three extractions with 50 mL of pentane. The pentane was
then removed by vacuum distillation. Overnight pumping at
-78 °C left 7.77 g (16.1 mmol, 80.3% yield based on GaCl3) of
Ga(C5H4SiMe3)3 as a golden-brown liquid. Ga(C5H4SiMe3)3: 1H
NMR (C6D6, δ) 6.25 (s br, 5.2, ring-H), 5.96 (s, 1.4, C5H5, see
Discussion), 5.76 (s br, 52.3, ring-H), 0.24 (s, 27, SiMe3), -0.12
(s, 1.0, SiMe3); 13C NMR (C6D6, δ) 120.19 (br, ring-C), 113.45
(br, ring-C), 108.12 (br, ring-C), 1.74 (SiMe3), 0.42 (SiMe3),
-1.68 (SiMe3). Soluble in pentane, ether, and benzene. Anal.
Calcd for C24H39GaSi3: C, 59.86; H, 8.16. Found: C, 60.10; H,
7.22.
Syn th esis of Me2Ga (C5H4Me) by a Meta th etica l Rea c-
11c
tion . A pentane solution of Me2GaCl
(1.15 g, 8.54 mmol)
was combined with 0.755 g of Li(C5H4Me) (8.77 mmol) in 25
mL of pentane at 0 °C and stirred overnight. The pentane was
removed by vacuum distillation to leave a colorless solid.
Sublimation of the resulting solid at room temperature under
static vacuum to a Schlenk flask maintained at -196 °C
produced Me2Ga(C5H4Me) (1.29 g, 7.20 mmol, 84.4% yield
based on Me2GaCl) as a colorless crystalline solid. The product
tested negative for chloride ion (addition of Ag+ to a hydrolyzed
solution). Colorless crystals of Me2Ga(C5H4Me) were grown by
sublimation at 35 °C in a sealed and evacuated tube placed at
a 45° angle over a drying oven, but they proved unsuitable
for an X-ray structural study. Me2Ga(C5H4Me): mp (sublimed
solid) 60-62 °C; (crystals) 62-63.5 °C. All spectral data were
identical to that previously described for the compound
prepared by a ligand redistribution reaction. Anal. Calcd for
C8H13Ga: C, 53.71; H, 7.32; Ga, 38.97. Found (sublimed
solid): C, 53.42; H, 7.46. Found (crystals): C, 53.49; H, 7.49;
Ga, 39.24.
Syn th esis of Me2Ga(C5H4Me) fr om Ga(C5H4Me)3, GaCl3,
a n d LiMe. Two tubes with one containing 0.899 g (5.10 mmol)
of GaCl3 dissolved in 10 mL of Et2O and the second containing
11.0 mL of a solution of LiMe in OEt2 (1.4 M, 15.4 mmol) were
attached to a round-bottomed flask charged with 0.785 g (2.56
mmol) of Ga(C5H4Me)3 dissolved in 25 mL of Et2O. First, the
colorless GaCl3/Et2O solution was added to the pale yellow Ga-
(C5H4Me)3/Et2O solution at 0 °C. After the resulting solution
was allowed to stir for 30 min, the LiMe/Et2O solution was
added. A colorless precipitate formed immediately. This mix-
ture was warmed to room temperature and stirred overnight.
The ether was removed by vacuum distillation while holding
the reaction flask at 0 °C until the pressure of the volatile
components in the flask at room temperature was less than 2
Syn th esis of Lew is Ad d u cts of Ga (C5H4Me)3. (a ) NMe3.
The Lewis acid Ga(C5H4Me)3 (1.402 g, 4.565 mmol) was
combined with NMe3 (0.371 g, 6.28 mmol) in approximately
30 mL of pentane to form a slightly soluble yellow solid at room
temperature. The yellow solid was separated by extraction
with pentane (four times) to leave a small amount of an
unknown insoluble tan solid. The yellow solid was sublimed
at 35 °C to a -78 °C coldfinger to give Ga(C5H4Me)3‚NMe3 as
a colorless solid. A brown solid remained at the bottom of the
sublimator. Prolonged heating of colorless Ga(C5H4Me)3‚NMe3
at 50 °C produced a brown solid that appeared identical to
the unsublimed material. Ga(C5H4Me)3‚NMe3: mp 72-73 °C
1
melts with decomposition to a brown liquid; H NMR (C6D6,
δ) 6.37 (s, 5.1, ring-H), 6.13 (s, 0.3, C5H5), 5.19 (s, 5.7, ring-H),
(12) Shriver, D. F.; Drezdzon, M. A. The Manipulation of Air-
Sensitive Compounds; Wiley: New York, 1968; p 38.

Ga(III) Compounds with Cyclopentadienyl Ligands
Organometallics, Vol. 19, No. 22, 2000 4555
mmHg. Then, a colorless solid was sublimed at room temper-
ature from the reaction flask through an elbow into an
attached Schlenk flask maintained at -196 °C. If the vapor
pressure of the sublimed solid at room temperature was
measurable, i.e., greater than about 2 mm, the volatile
material (ether) was removed by vacuum distillation and
discarded. The sublimed, colorless solid was identified as Me2-
Ga(C5H4Me) (0.970 g, 5.42 mmol, 70.9% based on GaCl3) by
of this yellow-green liquid with a short path still afforded pure
Et2Ga(C5H4Me) as a colorless liquid (1.04 g, 5.00 mmol, 93.1%
yield based on Ga(C5H4Me)3). Samples were stored in sealed
ampules at -20 °C. Et2Ga(C5H4Me): colorless liquid at ambi-
ent temperature; 1H NMR (C6D6, δ) 6.07 (s, 1.3, ring-H), 5.90
(t, 1.3, ring-H), 2.15 (s, 3.0, ring-CH3), 1.02 (s br, 5.2, Et3Ga/
Et2GaCp-CH3), 0.82 (t, 0.2, EtGaCp2-CH3), 0.21 (s br, 3.5, Et3-
Ga/Et2GaCp-CH2), -0.20 (q, 0.1, EtGaCp2-CH2); (d8-THF,
δ): 5.92 (s, 0.2, EtGaCp2 ring-H), 5.87 (s, 1.1, Et2GaCp
ring-H), 5.52 (s, 1.2, Et2GaCp ring-H), 5.34 (s, 0.2 EtGaCp2
ring-H), 2.08 (s, 3.0, ring-CH3), 1.07 (t, 1.4, GaEt3-CH3), 0.99
(t, 4.5, Et2GaCp-CH3), 0.84 (t, 0.3, EtGaCp2-CH3), 0.27 (q, 1.0,
GaEt3-CH2), 0.12 (q, 3.3, Et2GaCp-CH2), -0.13 (q, 0.1,
EtGaCp2-CH2); (neat liquid, capillary of C6D6 for reference,
δ): 6.14 (s, 0.04, -C5H5), 5.85 (s, 2.1, ring-H), 5.80 (s, 2.1, ring-
H), 2.10 (s, 3.0, ring-CH3), 0.94 (t, J HH ) 8.0 Hz, 7.1, Et2GaCp-
CH3), 0.05 (q, J HH ) 8.0 Hz, 4.3, Et2GaCp-CH2); 13C NMR
(C6D6, δ) 139.14 (s, ring-C), 112.35 (s, ring-C), 103.54 (s,
ring-C), 15.71 (s, ring-Me), 10.72 (s, Et2GaCp-CH2), 6.38 (s,
Et2GaCp-CH3). Anal. Calcd for C10H17Ga: C, 58.04; H, 8.28.
Found: C, 58.11; H, 8.13. Cryoscopic molecular weight,
benzene solution, fw 206.96 (molality, obsd mol wt, assoc):
0.0825, 177, 0.85; 0.0593, 173, 0.84; 0.0383, 167, 0.81.
1
its melting point and H NMR spectrum. The nonvolatile off-
white solid, presumably LiCl, that remained in the reaction
flask weighed 0.8542 g. Thus, 90% of the mass of the starting
materials was accounted for by the masses of Me2Ga(C5H4-
Me) and the insoluble solid (LiCl). Me2Ga(C5H4Me): mp 58-
61.5 °C. All spectral data were identical to that previously
described for the compound prepared by a ligand redistribution
reaction.
Attem p ted Syn th esis of MeGa (C5H4Me)2 by Liga n d
Red istr ibu tion Rea ction . The reagents 0.850 g of Ga(C5H4-
Me)3 (2.77 mmol) and 0.155 g of GaMe3 (1.35 mmol) were
combined in approximately 25 mL of pentane and allowed to
stir overnight at room temperature. The pentane was then
removed by vacuum distillation to leave a yellow-brown liquid,
from which a colorless liquid was transferred by vacuum
distillation at ambient temperature to an attached Schlenk
flask. A yellow-brown liquid remained in the original round-
Attem p ted Syn th esis of EtGa (C5H4Me)2 by Liga n d
Red istr ibu tion Rea ction . A solution prepared from Ga(C5H4-
Me)3 (0.922 g, 3.00 mmol), GaEt3 (0.210 g, 1.34 mmol), and 25
mL of pentane was allowed to stir overnight at room temper-
ature. Then the pentane was removed by vacuum distillation
to leave a yellow liquid, which was vacuum distilled at room
temperature. A yellow-green liquid distilled through a 90°
elbow attached to a Schlenk flask held at -196 °C, whereas a
yellow-brown liquid remained in the original reaction flask.
1H NMR spectroscopy identified the yellow-brown liquid as
predominantly Ga(C5H4Me)3 with a trace of EtGa(C5H4Me)2,
while the distilled liquid was identified as a mixture of
Et(C5H4Me)2 and Et2Ga(C5H4Me). Yellow-brown liquid: 1H
NMR (C6D6, δ) 5.84 (s, 2.6, ring-H), 5.49 (s, 3.0, ring-H), 2.08
(s, 6.0, ring-CH3), 0.83 (t, 0.4, EtGaCp2-CH3), -0.20 (q, 0.1,
EtGaCp2-CH2). Yellow-green distilled liquid: 1H NMR (C6D6,
δ) 6.01 (s, 2.4, ring-H), 5.77 (t, 2.6, ring-H), 2.12 (s, 6.0, ring-
CH3), 1.02 (t, 3.5, Et2GaCp-CH3), 0.82 (t, 2.2, EtGaCp2-CH3),
0.22 (q, 2.5, Et2GaCp-CH2), -0.21 (q, 1.4, EtGaCp2-CH2).
1H NMR Sp ectr a l Stu d y of Ga Et3 a n d Ga (C5H4Me)3 in
a 1:2 m ol Ra tio. An NMR tube was attached to a small
reaction vessel that contained 0.128 g of Ga(C5H4Me)3 (0.417
mmol). After the solvent C6D6 was added by vacuum distilla-
tion, 0.0334 g of GaMe3 (0.213 mmol) was distilled into the
vessel. The resulting solution was warmed from -196 °C to
room temperature, stirred, and then poured into the NMR
tube. The NMR tube was flame sealed. An identical procedure
1
bottomed flask. H NMR spectra identified the distillate as a
mixture of MeGa(C5H4Me)2 and Me2Ga(C5H4Me), whereas the
yellow-brown liquid was found to be predominantly Ga(C5H4-
Me)3 with a trace of MeGa(C5H4Me)2. Similar results were
obtained when the mol ratio of Ga(C5H4Me)3 to GaMe3 was
increased to 2.8:1. Colorless liquid distillate: 1H NMR (C6D6,
δ) 5.97 (m, 2.2, ring-H), 5.375 (t, 2.3, ring-H), 2.09 (s, 6.0, ring
-CH3), -0.44 (s, 4.8, Me2GaCp), -1.04 (s, 1.4, MeGaCp2); (d8-
THF, δ): 5.84 (s, 1.2, MeGaCp2 ring-H), 5.75 (s, 1.3, Me2GaCp
ring-H), 5.52 (s, 1.4, Me2GaCp ring-H), 5.40 (s, 1.3, MeGaCp2
ring-H), 2.06 (s, 6.0, ring-CH3), -0.49 (s, 0.6, GaMe3), -0.65
(s, 5.4, Me2GaCp), -1.08 (s, 1.3, MeGaCp2). Yellow-brown
residue: 1H NMR (C6D6, δ) 5.85 (s, 3.2, ring-H), 5.51 (s, 3.3,
ring-H), 2.08 (s, 6.0, ring-CH3), -1.04 (s, 0.3, MeGaCp2).
1H NMR Sp ectr a l Stu d y of Ga Me3 a n d Ga (C5H4Me)3 in
a 1:2 m ol Ra tio. An NMR tube was attached to a very small
reaction vessel that contained 0.128 g of Ga(C5H4Me)3 (0.418
mmol). Then C6D6 followed by 0.0242 g of GaMe3 (0.211 mmol)
was added by vacuum distillation. The resulting solution was
stirred and then poured into the NMR tube. The NMR tube
was flame sealed. A second solution with d8-THF as solvent
was prepared by using the identical procedure. 1H NMR (C6D6,
δ): 5.95 (s, 3.4, ring-H), 5.69 (s, 3.4, ring-H), 2.08 (s, 6.0,
ring-CH3), -0.44 (s, 1.1, Me2GaCp), -1.05 (s, 1.9, MeGaCp2);
(d8-THF): 5.94 (s, 0.9, GaCp3 ring-H), 5.83 (s, 2.1, MeGaCp2
ring-H), 5.75 (s, -, Me2GaCp ring-H), 5.52 (s, -, Me2GaCp
ring-H), 5.39 (s, 2.2, MeGaCp2 ring-H), 5.01 (s, 0.7, GaCp3
ring-H), 2.06 (s, 6.0, ring-CH3), -0.50 (s, -, GaMe3), -0.65 (s,
0.4, Me2GaCp), -1.08 (s, 1.5, MeGaCp2).
1
was carried out with d8-THF as solvent. The H NMR spectra
were indicative of an equilibrium mixture of species formed
by a ligand redistribution reaction. 1H NMR (C6D6, δ): 5.98
(s, 2.4, ring-H), 5.70 (s, 2.5, ring-H), 2.11 (s, 6.0, ring-CH3),
1.02 (t, 0.8, Et2GaCp-CH3), 0.83 (t, 2.6, EtGaCp2-CH3), 0.22
(q, 0.6, Et2GaCp-CH2), -0.21 (q, 1.8, EtGaCp2-CH2);
(d8-THF): 5.94 (s, 1.3, GaCp3 ring-H), 5.92 (s, 1.5, EtGaCp2
ring-H), 5.87 (s, 0.4, Et2GaCp ring-H), 5.52 (s, 0.4, Et2GaCp
ring-H), 5.34 (s, 1.3 EtGaCp2 ring-H), 5.01 (s, 1.6, GaCp3 ring-
H), 2.08 (s, 6.0, ring-CH3), 0.99 (t, 1.4, Et2GaCp-CH3), 0.84
(t, 1.0, EtGaCp2-CH3), 0.11 (q, 1.0, Et2GaCp-CH2), -0.14 (q,
1.7, EtGaCp2-CH2).
Attem pted Syn th esis of Me2Ga(C5H4SiMe3) by a Ligan d
Red istr ibu tion Rea ction . After a solution of Ga(C5H4SiMe3)3
(1.08 g, 2.25 mmol)) and GaMe3 (0.520 g, 4.53 mmol) in 30
mL of pentane was allowed to stir for 16 h at room tempera-
ture, the pentane was removed at 0 °C to leave a yellow-orange
viscous liquid and a small amount of a colorless solid. The
pentane that had been removed was observed to “smoke” upon
exposure to air due to the presence of GaMe3 formed by a
ligand redistribution reaction of the proposed product. Vacuum
1H NMR Sp ectr a l Stu d y of Ga Me3 a n d Ga (C5H4Me)3 in
a 1:1 m ol Ra tio. An NMR tube was attached to a small
reaction vessel that contained 0.0847 g of Ga(C5H4Me)3 (0.276
mmol). The solvent, d8-THF, followed by 0.0327 g of GaMe3
(0.285 mmol) was added by vacuum distillation. The resulting
solution was stirred and poured into the NMR tube. The tube
was flame sealed. 1H NMR (d8-THF, δ): 5.83 (s, 2.3, MeGaCp2
ring-H), 5.74 (s, 1.6, Me2GaCp ring-H), 5.51 (s, 1.8, Me2GaCp
ring-H), 5.39 (s, 2.6, MeGaCp2 ring-H), 2.06 (s, 4.5, ring-CH3),
-0.50 (s, 0.3, GaMe3), -0.65 (s, 6.2, Me2GaCp), -1.08 (s, 2.3,
MeGaCp2).
Syn th esis of Et2Ga (C5H4Me) by Liga n d Red istr ibu tion
Rea ction . A solution that was prepared on the vacuum line
by combining 0.549 g of Ga(C5H4Me)3 (1.79 mmol), 0.588 g of
GaEt3 (3.75 mmol), and approximately 25 mL of pentane was
allowed to stir overnight. The pentane was removed by vacuum
distillation to leave a yellow-green liquid. Vacuum distillation

4556 Organometallics, Vol. 19, No. 22, 2000
Beachley and Mosscrop
distillation of the yellow-orange viscous liquid at room tem-
perature for 3 h through a 90° elbow connected to a Schlenk
flask that had been cooled to -196 °C produced a colorless
liquid (0.307 g) and a small amount of a colorless goo in the
neck of the Schlenk flask. A golden-brown liquid (0.619 g)
remained in the original distillation flask. Colorless liquid
(mostly Me2Ga(C5H4SiMe3)): soluble in pentane and benzene;
1H NMR (C6D6, δ) 6.47 (s br, 1.1, ring-H), 6.35 (s br, 1.2, ring-
H), 6.16 (s br, 0.1, C5H5), 0.18 (s, 9.0, SiMe3), 0.12 (s, 0.1,
SiMe3), -0.04 (s, 0.4, SiMe3), -0.13 (s, 0.2, SiMe3), -0.38 (s
br, 1.9, GaMe2), -0.95 (s br, 1.0, GaMe). Colorless goo in neck
of flask (mixture of Me2Ga(C5H4SiMe3) with impurity of Me2-
Ga(C5H5)): 1H NMR (C6D6, δ) 6.53 (s br, 1.3, ring-H), 6.43 (s
br, 1.5, ring-H), 6.19 (s br, 3.4, C5H5), 0.19 (s, 9.0, SiMe3), -0.03
(s, 0.9, SiMe3), -0.13 (s, 0.7, SiMe3), -0.44 (s br, 2.7, GaMe2),
-1.03 (s br, 1.4, GaMe). Golden-brown liquid (mixture of
MeGa(C5H4SiMe3)2 and Ga(C5H4SiMe3)3): soluble in pentane
1H NMR Spectr al Stu dies of GaMe3 an d Ga(C5H4SiMe3)3
in Va r iou s Mola r Ra tios. A small reaction vessel connected
to an NMR tube was charged with Ga(C5H4SiMe3)3, and then
C6D6 followed by the appropriate stoichiometric amount of
GaMe3 was added by vacuum distillation. The resulting
solution was stirred and poured into the NMR tube, and then
the NMR tube was flame sealed. (a) Reagents in 2:1 mol
ratio: 0.125 g (0.259 mmol) of Ga(C5H4SiMe3)3 and 0.0592 g
1
(0.516 mmol) of GaMe3; H NMR (C6D6, δ) 6.51 (s, 1.2, ring-
H), 6.43 (s br, 1.1, ring-H), 6.19 (s, 0.2, C5H5), 0.22 (s, 0.4,
SiMe3), 0.18 (s, 9.0, SiMe3), -0.12 (s, 0.5, SiMe3), -0.32 (s br,
7.4, GaMe2/GaMe3), -0.93 (br, 0.03 GaMe). (b) Reagents in 1:2
mol ratio: 0.0668 g (0.139 mmol) of Ga(C5H4SiMe3)3 and 0.0079
1
g (0.069 mmol) of GaMe3of GaMe3; H NMR (C6D6, δ) 6.45 (s,
2.5, ring-H), 6.33 (s, 2.5, ring-H), 6.15 (s, 0.4, C5H5), 0.17 (s,
18, SiMe3), -0.13 (s, 0.6, SiMe3), -0.28 (s br, 0.5, Me2Ga(C5H4-
SiMe3), -0.94 (s br, 3.0, GaMe, MeGa(C5H4SiMe3)2). (c) Re-
agents in 1:1 mol ratio: 0.265 g (0.550 mmol) of Ga(C5H4-
SiMe3)3 and 0.0636 g (0.554 mmol) of GaMe3; 1H NMR (C6D6,
δ) 6.47 (s br, 2.1, ring-H), 6.35 (s br, 1.6, ring-H), 6.17 (br, 0.4,
C5H5), 0.17 (s, 13.5, SiMe3), -0.34 (s br, 3.7, GaMe2, Me2Ga-
(C5H4SiMe3), -0.96 (s br, 1.3, MeGa(C5H4SiMe3)2).
1
and benzene; H NMR (C6D6) 6.44 (s br, 2.1, ring-H), 6.32 (s
br, 2.1, ring-H), 6.15 (s br, 0.2, C5H5), 0.18 (s, 9.0, SiMe3), -0.04
(s, 0.3, SiMe3), -0.12 (s, 0.4, SiMe3), -0.38 (s br, 0.7, GaMe2),
-0.94 (s br, 1.4, GaMe).
Attem p ted Syn th esis of MeGa (C5H4SiMe3)2 by Liga n d
Red istr ibu tion Rea ction . The reagents GaMe3 (0.0764 g,
0.665 mmol) and Ga(C5H4SiMe3)3 (0.640 g, 1.33 mmol) were
combined in 15 mL of pentane at room temperature for 2 h.
Then the material volatile at room temperature was removed
by vacuum distillation to leave a golden-brown liquid (0.612
g, 85.4% by mass of starting materials). Golden-brown liquid:
1H NMR (C6D6, δ) 6.40 (s br, 1.9, ring-H), 6.30 (s br, 3.4,
ring-H), 6.09 (s br, 0.4, C5H5), 0.23 (s, 2.0, SiMe3, Ga(C5H4-
SiMe3)3), 0.17 (s, 18, SiMe3, MeGa(C5H4SiMe3)2), -0.12 (s, 0.1,
vinyl SiMe3), -0.94 (s br, 3.0, GaMe, MeGa(C5H4SiMe3)2).
Ack n ow led gm en t. This work was supported in part
by the Office of Naval Reasearch (O.T.B.).
1
Su p p or tin g In for m a tion Ava ila ble: Additional H and
13C NMR spectral data as well as infrared spectral data for
the pure compounds are provided. This material is available
free of charge via the Internet at http://pubs.acs.org.
OM0005304