Aryl(dimethyl)gallium compounds and methyl(diphenyl)gallium: Synthesis, structure, and redistribution reactions

Article abstract of DOI:10.1021/om701055a

Treatment of diphenylmercury with an excess of trimethylgallium at higher temperatures resulted in the formation of dimethyl(phenyl)gallium (1). Similarly, reaction of 1-chloromercurio(4-methylbenzene) and 1-chloromercurio(4-tert-butylbenzene) with an excess of trimethylgallium gave dimethyl(4methylphenyl)gallium (2) and dimethyl(4-tert-butylphenyl)gallium (3), respectively. Treatment of diphenylmercury with an equivalent amount of trimethylgallium resulted in the formation of methyl(diphenyl)gallium (4). The X-ray crystallographic studies of compounds 1, 2, 3, and 4 revealed the presence of trigonal planar coordinate gallium atoms in monomeric molecules, which associate to polymeric strands by additional intermolecular gallium π-aryl contacts, thus leading to an overall trigonal bipyramidal coordination geometry at gallium. Compounds 1-4 are stable in the solid state and in solution. Substituent redistribution reactions take place at higher temperatures and at room temperature in the presence of THF. Compound 1 could also be prepared by the reaction of triphenylgallium with an excess of trimethylgallium at higher temperatures.

Full text of DOI:10.1021/om701055a

Organometallics 2008, 27, 4565–4571
4565
Aryl(dimethyl)gallium Compounds and Methyl(diphenyl)gallium:
Synthesis, Structure, and Redistribution Reactions
Peter Jutzi,* Joseph Izundu, Beate Neumann, Andreas Mix, and Hans-Georg Stammler
Fakulta¨t fu¨r Chemie, UniVersita¨t Bielefeld, UniVersita¨tstrasse 25, 33615 Bielefeld, Germany
ReceiVed October 19, 2007
Treatment of diphenylmercury with an excess of trimethylgallium at higher temperatures resulted in
the formation of dimethyl(phenyl)gallium (1). Similarly, reaction of 1-chloromercurio(4-methylbenzene)
and 1-chloromercurio(4-tert-butylbenzene) with an excess of trimethylgallium gave dimethyl(4-
methylphenyl)gallium (2) and dimethyl(4-tert-butylphenyl)gallium (3), respectively. Treatment of
diphenylmercury with an equivalent amount of trimethylgallium resulted in the formation of methyl-
(diphenyl)gallium (4). The X-ray crystallographic studies of compounds 1, 2, 3, and 4 revealed the presence
of trigonal planar coordinate gallium atoms in monomeric molecules, which associate to polymeric strands
by additional intermolecular gallium π-aryl contacts, thus leading to an overall trigonal bipyramidal
coordination geometry at gallium. Compounds 1-4 are stable in the solid state and in solution. Substituent
redistribution reactions take place at higher temperatures and at room temperature in the presence of
THF. Compound 1 could also be prepared by the reaction of triphenylgallium with an excess of
trimethylgallium at higher temperatures.
ordinary conditions might have prevented the isolation of
such compounds. The diaryl(methyl)gallium compound (2,6-
MesC6H3)2GaMe, which contains bulky aryl substituents, is
described as a stable species.14 The comparable diaryl-
(methyl)gallium compound {2,6-(4-tBuC6H4)2C6H3}2GaMe
is an unstable species due to redistribution reactions.15
Comparable observations have been described by Beachley
et al. for some dialkylgallyl-substituted cyclopentadienes.16
In this report, we describe the preparation of dimethyl(phe-
nyl)gallium (1), dimethyl(4-methylphenyl)gallium (2), dimethyl-
(4-tert-butylphenyl)gallium (3), and methyl(diphenyl)gallium
(4), following the Hg/Ga metathesis strategy introduced by
Oliver et al. for the preparation of some group 13 element
organic compounds.4 The preparation of poly(dimethylgallyl)-
substituted benzene derivatives will be presented in a forthcom-
ing paper. The compounds 1-4 are characterized by their NMR
spectroscopic and X-ray crystallographic data and by their
stability with respect to redistribution reactions.
1. Introduction
Organogallium(III) compounds are important tools in orga-
nometallic chemistry. Many homoleptic and heteroleptic com-
pounds have already been synthesized and structurally charac-
terized during the last century.1 The interest in such molecules
is based on their Lewis acid properties and on their potential
use as precursors in CVD processes.2-4 The synthesis as well
as structural studies of simple homoleptic organogallium(III)
compounds such as triphenylgallium 5-9 and trimethylgallium10-12
have been reported. In the context of our investigations of
substituent redistribution reactions in dialkylgallyl-substituted
ferrocene derivatives,13 we became interested in the properties
of the corresponding benzene derivatives. Surprisingly, het-
eroleptic organogallium(III) compounds such as dimeth-
yl(phenyl)gallium and methyl(diphenyl)gallium, which con-
tain simple aryl and alkyl groups in the same molecule, are
so far unknown. Redistribution reactions taking place under
* Corresponding author. Phone: +49-5211066163. E-mail: peter.jutzi@
uni-bielefeld.de.
2. Results and Discussion
(1) Tuck, D. G. Gallium and Indium. In ComprehensiVe Organometallic
Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon
Press: Oxford, 1982; Vol. 1, pp 683-724.
Synthesis and Characterization. For the synthesis of di-
methyl(phenyl)gallium (1), diphenylmercury was treated with
an excess of trimethylgallium according to eq 1a. The original
colorless suspension was heated at 100 °C to afford a clear
solution. On cooling to room temperature, a fine precipitate
separated from the solution. The volatile components consisting
of dimethylmercury and trimethylgallium were removed in
vacuo. The residue was washed with n-hexane and dried to give
compound 1 as an amorphous, colorless solid in 90% yield. 1
was crystallized from trimethylgallium as solvent in 83% yield.
(2) Lee, K. E.; Higa, K. T. J. Organomet. Chem. 1993, 449, 53.
(3) Miehr, A.; Mattner, M. R.; Fischer, R. A. Organometallics 1996,
15, 2053.
(4) Beachley, O. T., Jr.; Rosenblum, D. B.; Churchill, M. R.; Lake, C. H.;
Krajkowski, L. M. Organometallics 1995, 14, 4402.
(5) Gilman, H.; Jones, R. G. J. Am. Chem. Soc. 1940, 62, 980.
(6) Oliver, J. P.; Stevens, L. G. J. Inorg. Nucl. Chem. 1962, 24, 953.
(7) Malone, J. F.; McDonald, W. S. J. Chem. Soc 1970, 3362.
(8) Perkins, P. G.; Twentyman, M. E. J. Chem. Soc. 1965, 1038.
(9) Miller, S. B.; Jelus, B. L.; Smith, J. H.; Munson, B.; Brill, T. B. J.
Organomet. Chem. 1979, 170, 9.
(10) Kraus, C. A.; Toonder, F. E. Proc. Nat. Acad. Sci. U.S.A. 1933,
19, 298. ; , J. Am. Chem. Soc. 1933, 55, 3547.
(11) Mitzel, N. W.; Lustig, C.; Berger, R. J. F.; Runeberg, N. Angew.
Chem. 2002, 114, 2629.; Angew. Chem., Int. Ed. 2002, 41, 2519.
(12) Boese, R.; Downs, A. J.; Greene, T. M.; Wall, A. W.; Morrison,
C. A.; Parsons, S. Organometallics 2003, 22, 2450.
(14) Wehmschulte, R. J.; Steele, J. M.; Khan, M. A. Organometallics
2003, 22, 4678.
(15) Young, J. D.; Khan, M. A.; Powell, D. R.; Wehmschulte, R. J.
Eur. J. Inorg. Chem. 2007, 1671.
(16) (a) Beachley, O. T., Jr.; Mosscrop, M. T. Organometallics 2000,
19, 4550. (b) Beachley, O. T.; Royster, T. L.; Arhar, J. R. J. Organomet.
Chem. 1992, 434, 11.
(13) Althoff, A.; Eisner, D.; Jutzi, P.; Lenze, N.; Neumann, B.; Schoeller,
W. W.; Stammler, H. G. Chem. Eur. 2006, 12, 5471.
10.1021/om701055a CCC: $40.75
2008 American Chemical Society
Publication on Web 08/27/2008

4566 Organometallics, Vol. 27, No. 18, 2008
Jutzi et al.
A possible alternative strategy for the synthesis of mono-
dialkylgallyl-substituted benzene derivatives, but not for poly-
dialkylgallyl-substituted ones, is given by the reaction of
triphenylgallium with the corresponding trialkylgallium com-
pound. This route has been checked only for the preparation of
1. Thus, triphenylgallium was treated with an excess of
trimethylgallium in n-hexane according to eq 1b. The colorless
solution was heated at 100 °C for 2 h. After cooling to room
temperature, the volatile components consisting of n-hexane and
trimethylgallium were removed in vacuo. Compound 1 was
obtained as an amorphous, colorless solid in 97% yield, which
was crystallized from trimethylgallium in 91% yield.
to give the redistribution products trimethylgallium, methyl-
(diphenyl)gallium (4), and triphenylgallium.
A rapid methyl group exchange already at room temperature
was observed upon addition of trimethylgallium to a benzene
solution of 1, as indicated by the presence of an averaged methyl
1
group signal at δ ) -0.15 ppm in the H NMR spectrum and
at δ ) 1.1 ppm in the 13C NMR spectrum of the reaction
mixture.
The compounds dimethyl(4-methylphenyl)gallium (2) and
dimethyl(4-tert-butylphenyl)gallium (3) were synthesized by
treating 1-chloromercurio(4-methylbenzene) and 1-chloromer-
curio(4-tert-butylbenzene),19 respectively, with an excess of
trimethylgallium (eq 2).
excess GaMe3
Ph2Hg + 2 GaMe3
8 2 PhGaMe2 + HgMe2
100 °C
(1)
(1a)
GaPh3 + 2 GaMe3 excess GaMe , n-hexane8 2 PhGaMe2 (1b)
3
100 °C
(1)
Compound 1 is very sensitive to air and moisture, readily
soluble in aromatic solvents such as benzene, but only sparingly
soluble in aliphatic hydrocarbons.
Contrary to the preparation of compounds 1 and 2, compound
3 separated already in a crystalline form and nearly quantita-
tively from the hot reaction mixture on cooling. The remaining
solution contained trimethylgallium, chlorodimethylgallium,
dimethylmercury, and small amounts of 3.
The compounds 2 and 3 are more sensitive to air and moisture
than 1. They are readily soluble in aromatic solvents such as
benzene, but sparingly soluble in hydrocarbons. In their 1H and
13C NMR spectra, the expected resonance signals were observed
(see Experimental Section).
Compounds 2 and 3 showed long-term stability at room
temperature in the solid state and in benzene solution. Redis-
tribution reactions were investigated in more detail only with
compound 3. As with 1, addition of THF to a benzene solution
of 3 promoted substituent exchange reactions. The formation
of the THF adducts of 3 and of the redistribution products di-
(4-tert-butylphenyl)(methyl)gallium and trimethylgallium in a
ratio of 1:3:5, respectively, was detected by NMR spectroscopy.
In the solid state, 3 decomposed at elevated temperatures under
reduced pressure to give trimethylgallium, di(4-tert-butylphe-
nyl)(methyl)gallium, and tri(4-tert-butylphenyl)gallium, as con-
cluded from the NMR spectroscopic data.
Methyl(diphenyl)gallium (4) was prepared by treating diphe-
nylmercury with a nearly stoichiometric amount of trimethyl-
gallium (eq 3). Crystals of 4 were obtained in 98% yield. The
1H and 13C NMR spectra showed the expected resonance signals
(see Experimental Section).
The 1H NMR spectrum of 1 measured in benzene-d6 at room
temperature revealed a singlet at δ ) -0.13 ppm for the two
methyl groups, a multiplet at δ ) 7.27 ppm for three protons
in para- and meta-positions, and a multiplet at δ ) 7.62 ppm
for two protons in ortho-postion of the phenyl ring. The 13C
NMR spectrum in benzene-d6 showed expected signals at δ )
-2.9 (methyl), 128.2 (C-3/5) 129.8 (C-4), 137.2 (C-2/6), and
148.2 (C-1) ppm.17
Compound 1 is monomeric in benzene-d6 solution, as proven
by its diffusion coefficient (D ) 1.56 × 10-9 m2 s-1) compared
with that of 2-phenylpropane (D ) 1.70 × 10-9 m2 s-1). The
diffusion coefficients were determined by pulsed field gradient
NMR experiments (see Experimental Section).18 The monomeric
structure of 1 in aromatic solvents is in accordance with the
low-temperature 1H NMR data. In toluene-d8, the methyl group
signal remained a sharp singlet at 275, 245, and 220 K,
respectively, with a nearly unchanged chemical shift. The
monomeric molecules presumably are weakly stabilized by
π-contacts with the aromatic solvent.
Several experiments were performed with compound 1 to
check substituent redistribution reactions. A solution of 1 in
benzene remained unchanged after 1 week at room temperature,
1
as checked by H NMR spectroscopy, but very slight changes
were observed after heating for 2 h at 80 °C. A toluene solution
of 1 heated at 120 °C for 4 h decomposed into a mixture of
1
products that could not be individually characterized by H
NMR spectroscopy. Addition of THF to a benzene-d6 solution
of 1 at room temperature promoted substituent exchange
reactions. The formation of the THF adducts of methyl(diphe-
nyl)gallium (compound 4, vide infra), of trimethylgallium, and
of 1 in a ratio of 1:1:4, respectively, was proven by H NMR
spectroscopy.
Substituent exchange reactions of 1 have been observed not
only in solution but also in the solid state. Whereas 1 remained
unchanged under reduced pressure (10 mbar) for about 3 h and
under normal pressure (1 bar) for over 18 months, the compound
decomposed at elevated temperatures under reduced pressure
Ph2Hg + GaMe3 100 °C8 Ph2GaMe+ HgMe2
(3)
(4)
1
Compound 4 is rather air and moisture sensitive. It showed
long-term stability at room temperature in the solid state as well
as in solution. It liberated no trimethylgallium when heated at
70 and 120 °C in vacuo (10 mbar) each for a period of 30 min,
but when heated at 150 °C in vacuo (10 mbar) for a period of
30 min, it decomposed to give triphenylgallium and trimethyl-
gallium.
(17) Jennings, J. R.; Pattison, I.; Wade, K.; Wyatt, B. K. J. Chem. Soc.
A 1967, 1608.
(18) Cohen, Y.; Avram, L.; Frish, L. Angew. Chem. 2005, 117, 524.;
Angew, Chem, Int. Ed. 2005, 44, 520.
(19) (a) Barleunga, J.; Campos, P. J.; Roy, M. A.; Asensio, G. J. Chem.
Soc., Perkin Trans. 1 1980, 1420. (b) Odom, J. D.; Ellis, P. D.; Wilson,
N. K.; Sens, M. A. J. Magn. Reson. 1975, 19, 323. (c) Lattes, A.; Perie, J.
J. Organomet. Chem. 1981, 204, 1.

Aryl(dimethyl)gallium Compounds
Organometallics, Vol. 27, No. 18, 2008 4567
Table 1. X-ray Crystal Structural Data for 1
empirical formula
fw
temperature (K)
wavelength (Å)
cryst syst
space group
unit cell dimensions
a (Å)
C8H11Ga
176.89
100(2)
0.71073
monoclinic
P2/c
color
index range
colorless
-23 e h e 23
-10 e k e 9
-17 e l e 18
50 739/4547/3398
99.4%
no. of reflns coll/unique/>2σ(I)
completeness
transmision:
∆FMax
16.8630(4)
7.2520(2)
12.8280(5)
90
95.6040(14)
90
1561.24(8)
0.5468
0.4257
4547/0/167
1.055
b (Å)
c (Å)
∆FMin
no. of data/restraints/params
R (deg)
goodness-of-fit on F2
ꢀ (deg)
R factor [I > 2σ(I)]
R1
wR2
γ (deg)
0.0355
0.0796
3
V (Å
)
Z
8
R factor (all data)
R1
wR2
F (Mg/m3)
F(000)
1.505
720
0.30 × 0.30 × 0.20
0.0559
0.0862
cryst size (mm3)
Table 2. Selected Bond Lengths [Å] and Bond Angles [deg] for
Compounds 1A and 1B
Both molecules exhibit comparable mean gallium-carbon bond
lengths (LGa-C). The bond angles within the trigonal plane
in 1A differ slightly from those in 1B (see Table 2). The sum
of the bond angles at the three-coordinate gallium centers in
1A and 1B is 360°, in accordance with the presence of sp2-
1A
1B
Ga(1)-C(1)
Ga(1)-C(8)
Ga(1)-C(7)
LGa-C
Ga(1) · · · C(6a)
Ga(1) · · · C(5b)
1.972(2)
1.967(2)
1.962(2)
1.97
3.11
3.25
Ga(2)-C(9)
Ga(2)-C(16)
Ga(2)-C(15)
LGa-C
Ga(2) · · · C(14a)
Ga(2) · · · C(14b)
1.982(2)
1.965(2)
1.959(2)
1.97
3.16
3.30
C(7)-Ga(1)-C(8) 124.03(10) C(15)-Ga(2)-C(16) 124.38(10)
C(7)-Ga(1)-C(1) 119.24(9)
C(15)-Ga(2)-C(9)
120.22(10)
115.39(10)
360.0
116.7(2)
123.55(17)
119.74(17)
C(8)-Ga(1)-C(1) 116.48(10) C(16)-Ga(2)-C(9)
∑C-Ga-C
C(2)-C(1)-C(6)
359.8
116.8(2)
∑C-Ga-C
C(14)-C(9)-C(10)
C(2)-C(1)-Ga(1) 120.63(17) C(14)-C(9)-Ga(2)
C(6)-C(1)-Ga(1) 122.14(17) C(10)-C(9)-Ga(2)
X-ray Structural Data. The solid state structures of 1-4
were determined by single-crystal X-ray diffraction analysis.
Suitable crystals were prepared in a glovebox to avoid contact
with air or moisture. The crystals of compounds 1 and 4 were
coated with a viscous oil to prevent decomposition before the
measurement, whereas the crystals of 2 and 3 were coated with
silicon vacuum grease, because they decomposed readily in the
viscous oil before the measurement. X-ray structural parameters
of 1 are listed in Table 1, and the parameters for 2-4 are given
as Supporting Information. Selected bond lengths and bond
angles of 1 are presented in Table 2, while those of 2-4 are
collected as Supporting Information. The molecular structure
of 1 is presented in Figure 1, whereas those of 2-4 are given
in the Supporting Information. Typical motifs of the solid state
structures of 1-4 are given in Figures 2, 3, 4, and 5.
Figure 2. ORTEP representation of gallium-arene intermolecular
contacts in 1. The broken lines represent intermolecular distances:
Ga(1)C(6a) 3.11 Å; Ga(1)C(5b) 3.25 Å in 1A and Ga(2)C(14a)
3.16 Å; Ga(2)C(14b) 3.30 Å in 1B.
Dimethyl(phenyl)gallium (1). Compound 1 crystallizes in
the form of colorless plates in the space group P2/c. The
structural investigation revealed the presence of two independent
monomers, 1A and 1B (Figure 1), with slightly different bond
lengths and bond angles. The gallium aryl-carbon bonds in
1A and in 1B are longer than the gallium methyl-carbon bonds.
Figure 3. ORTEP representation of the solid state structure of
compound 2 with the thermal ellipsoids given at the 50% probability
level. Hydrogen atoms are omitted for clarity. The broken lines
represent intermolecular distances; Ga(1)C(6) and Ga(1)C(2) 3.12
Å. Intramolecular distances (Å) and angles (deg): Ga(1)-C(9)
1.959(2);Ga(1)-C(8)1.961(2);Ga(1)-C(1)1.975(2);C(9)Ga(1)-C(1)
117.06(10); C(8)-Ga(1)-C(1) 117.63(10); C(9)-Ga(1)-C(8)
125.31(11).
Figure 1. ORTEP representation of the molecular structures of 1A
and 1B with the thermal ellipsoids given at the 50% probability
level. Hydrogen atoms are omitted for clarity.

4568 Organometallics, Vol. 27, No. 18, 2008
Jutzi et al.
coordination behavior of 1A and 1B presumably is a result of
crystal-packing effects.
Dimethyl(4-methylphenyl)gallium (2). A part of the solid
state structure of 2 is presented in Figure 3. As observed for
compound 1, the gallium aryl-carbon distance is slightly longer
than each of the gallium methyl-carbon distances. The three-
coordinate gallium atom is characterized by the bond angle sum
of 360°. The planes [C(2)C(6)Ga(1)] and [C(1)C(8)C(9)] are
inclined at an angle of 13.8°. The gallium-ipso-carbon-para-
carbon vector deviates from a linear arrangement to give a
[C(4)C(1)Ga(1)] dip angle of 0.7°. As in 1, the coordination
sphere of the gallium atom in 2 is completed by two π-contacts
to give an overall five-coordinate gallium atom exhibiting a
trigonal-bipyramidal coordination geometry. Comparable gal-
lium-π-arene contacts [Ga(1)C(6) and Ga(1)C(2): 3.12 Å] are
observed. In the resulting polymeric strand structure, the gallium
atoms are coordinated to ortho-carbon atoms of the neighboring
phenyl groups.
Dimethyl(4-tert-butylphenyl)gallium (3). A part of the solid
state structure of 3 is presented in Figure 4. The structural
features of 3 are comparable to those of 1 and 2. The
coordination sphere of the trigonal planar gallium atom is
completed by two π-contacts to ortho-carbon atoms of neigh-
boring phenyl groups [Ga(1)C(2a) 3.17 Å and Ga(1)C(6a) 3.11
Å] to give a trigonal-bipyramidal coordination geometry at
gallium in the resulting polymeric strand structure.
Figure 4. ORTEP representation of the solid state structure of
compound 3 with the thermal ellipsoids given at the 50% probability
level. Hydrogen atoms are omitted for clarity. The broken lines
represent intermolecular distances: Ga(1)C(2a) 3.17 Å and Ga(1)C(6a)
3.11 Å. Intramolecular distances (Å) and angles (deg): Ga(1)-C(1)
1.9808(11); Ga(1)-C(7) 1.9641(12); Ga(1)-C(8) 1.9630 (12);
C(8)-Ga(1)-C(7)126.13(5);C(8)-Ga(1)-C(1)116.92(5);C(7)-Ga(1)-C(1)
116.95(5).
Methyl(diphenyl)gallium (4). A part of the solid state
structure of 4 is presented in Figure 5. The three-coordinate
gallium atom is characterized by the bond angle sum of 360°.
Each gallium aryl-carbon distance is slightly longer than the
gallium methyl carbon distance. The phenyl groups are arranged
in a propeller form, with the plane [C(2)C(6)Ga(1)] inclined at
31.4°totheplane[C(8)C(12)Ga(1)]andtheplane[C(1)C(7)C(13)]
inclined at 18.8° to the plane [C(2)C(6)Ga(1)] and at 16.6° to
the plane [C(8)C(12)Ga(1)]. The gallium-ipso-carbon-para-
carbon vectors deviate from linearity to give a C(4)C(1)Ga(1)
dip angle of 5.3° and a C(10)C(7)Ga(1) dip angle of 3.1°. The
coordination sphere of the gallium atom is completed by two
π-contacts to give an overall five-coordinate gallium atom
exhibiting a trigonal-bipyramidal coordination geometry. Gal-
lium-π-arene intermolecular contacts [Ga(1)C(12a) 2.99(2) Å
and Ga(1) C(6a) 3.08(2) Å] gave a polymeric strand structure,
in which the gallium atoms are coordinated to the ortho-carbon
atoms of the neighboring phenyl groups.
Figure 5. ORTEP representation of the solid state structure of
compound 4 with the thermal ellipsoids given at the 50% probability
level. Hydrogen atoms are omitted for clarity. The broken lines
represent intermolecular distances: Ga(1)C(12a) 2.99(2) Å and
Ga(1) C(6a) 3.08(2) Å. Intramolecular distances (Å) and angles
(deg): Ga(1)-C(13) 1.949(2); Ga(1)-C(1) 1.976(2); Ga(1)-C(7)
1.976(2); C(13)-Ga(1)-C(1) 118.65(10); C(13)-Ga(1)-C(7)
121.84(10); C(1)-Ga(1)-C(7) 119.46(8).
3. Conclusion
hybridized atoms. In 1A as well as 1B, the gallium-bound
methyl groups and the phenyl carbon atoms are not aligned in
the same plane. The planes [C(2)C(6)Ga(1)] and [C(1)C(7)C(8)]
in 1A are inclined at an angle of 8.7°, whereas the planes
[C(10)C(14)Ga(2)] and [C(9)C(15)C(16)] in 1B are inclined at
12.1°. Furthermore, the gallium-ipso-carbon-para-carbon vec-
tor deviates from a linear arrangement to give a [C(4)C(1)Ga(1)]
dip angle of 6.6° in 1A and a [C(12)C(9)Ga(2)] dip angle of
2.1° in 1B.
Against our misgivings based on the literature information
about the stability of aryl(dialkyl)gallium species, the
compounds dimethyl(phenyl)gallium (1), dimethyl(4-meth-
ylphenyl)gallium (2), dimethyl(4-tert-butylphenyl)gallium (3),
and methyl(diphenyl)gallium (4) are stable under ordinary
conditions of temperature and pressure in the solid state and
in solution. In the crystalline solids, the structural motifs
found in triphenylgallium7 are preserved: molecular units with
trigonal-planar gallium atoms are connected to strand-like
coordination polymers by π-contacts, leading to an overall
trigonal-bipyramidal geometry at gallium. The (aryl)C-Ga
distances in 1-4 are longer than the (methyl)C-Ga distances
and thus exclude a pronounced intramolecular aryl gallium
back-bonding. Redistribution reactions are observed at higher
temperatures and at room temperature after the addition of
THF. Several experiments have shown that reaction temper-
atures of about 100 °C are necessary for the synthesis of
1-4. In most cases, trimethylgallium is required as solvent
The coordination sphere of the gallium atoms in 1A and 1B
is completed by two π-contacts to phenyl systems of neighboring
molecules to finally give five coordinate gallium atoms exhibit-
ing a trigonal bipyramidal coordination geometry (Figure 2).
In the formed strand structures, the gallium atoms form
π-contacts in the range 3.11-3.25 Å with an ortho-carbon atom
and with a meta-carbon atom from adjacent phenyl groups in
1A and in the range 3.16-3.30 Å with two ortho-carbon atoms
from adjacent phenyl groups in 1B. The difference in the

Aryl(dimethyl)gallium Compounds
Organometallics, Vol. 27, No. 18, 2008 4569
colorless crystals separated. Trimethylgallium was removed through
a syringe, and the crystals were washed with 3 mL of n-hexane
and dried in vacuo (10 mbar) for 1 h to give 1 (2.40 g, 13.57 mmol)
to shift the equilibrium to the product side. It should be
emphasized that easy to perform substituent exchange reac-
tions are a prerequisite for the application of the synthetic
concept of dynamic covalent chemistry.20
1
in 83% yield. Compound 1: H NMR (benzene-d6): δ -0.13 (s,
6H, methyl), 7.27 (m, 3H, para- and meta-phenyl), 7.62 (m, 2H,
ortho-phenyl). 13C NMR (benzene-d6): δ -2.9 (methyl), 128.2 (C-
3/5), 129.8 (C-4), 137.2 (C-2), 148.2 (C-1). The NMR spectrum
of the amorphous solid corresponded to that of crystalline 1. Anal.
Found: C: 54.11; H: 5.23. Calcd: C: 54.32; H: 6.27.14,16,26 MS
m/z (%): [Ph2Ga+],27 223/225 (35/24); [PhGaMe+], 161/163 (86/
55); [PhGa+], 146/148 (6/4); [GaMe2+], 99/101 (44/28); [Ga+],
69/71 (44/28).
(b) By Substituent Redistribution. To a suspension of tri-
phenylgallium (1.00 g, 3.32 mmol) in 10 mL of n-hexane was added
through a syringe trimethylgallium (1.00 g, 8.71 mmol). The
colorless solution was heated at 100 °C for 2 h. After cooling to
room temperature, the volatile components consisting of n-hexane
and trimethylgallium were removed under reduced pressure (10
mbar). Compound 1 was obtained as an amorphous, colorless solid
(1.70 g, 9.61 mmol, 97%). 1 was suspended in 0.5 mL of
trimethylgallium and heated at 100 °C for 1 h to give a colorless
solution. On cooling, the temperature was maintained at 40 °C
without stirring for 15 h. Colorless crystals of 1 separated from
the solution, trimethylgallium was removed through a syringe, and
the crystals were washed with 2 mL of n-hexane and dried in vacuo
(10 mbar) for 1 h to give 1 in 91% yield. The cell parameters of
the crystals and the NMR spectra in benzene-d6 were identical to
those of 1 prepared by route (a).
4. Experimental Section
General Comments. All experiments were conducted under a
purified argon atmosphere using standard Schlenk techniques. All
solvents were commercially available, purified by conventional
means, distilled, and stored under argon prior to use. The NMR
spectra were recorded on a Bruker Avance DRX 500 spectrometer
at 300 K (1H NMR, 500.1 MHz, 600.13 MHz; 13C NMR, 125.8
MHz, 150.9 MHz). The chemical shift values are reported in ppm,
and the reference solvent was calibrated benzene-d6 (1H: δ ) 7.15,
13C: δ ) 128.0 ppm). The diffusion coefficient NMR experiments
were performed on a Bruker Avance DRX 600 FT-NMR spec-
trometer (600.13 MHz) at 294.7 K using a Bruker 5 mm TBI
z-gradient probe and the longitudinal eddy current delay sequence
(ledbpgp2s). The diffusion constants were calculated using the
SIMFIT program package. The Microanalytical Laboratories of the
University of Bielefeld and Beller & Matthies, Goettingen, per-
formed the CH elemental analyses. Mass spectrometric measure-
ments were performed at the University of Bielefeld on a VG
Autospec spectrometer (EI; 70 eV; 200 µA emission). X-ray crystal
structure data were collected at the University of Bielefeld on a
Nonius Kappa CCD X-ray equipment.
Starting Materials. Diphenylmercury was purchased from
Aldrich Chemicals. 1-Chloromercurio(4-methylbenzene) and 1-chlo-
romercurio(4-tert-butylbenzene)19 were prepared using a literature
procedure.
Diffusion Coefficient of 1. A NMR tube charged with 1 (3.5
mg, 0.02 mmol) and benzene-d6 (0.45 mL) was carefully closed,
and the diffusion coefficient of the sample was measured as
described below. The same parameters were used for 1 and for the
reference sample (3.5 mg of 2-phenylpropane in 0.45 mL of C6D6).
The diffusion experiments were performed at room temperature (T
) 294.7 K) without heating the sample. The air flow was switched
off and no spinning was applied to the NMR tube. Prior to the
measurement the sample was left for 4 h in the magnet in order to
assume a constant temperature condition. The diffusion delay (big
delta) was set to 50 ms, and the length of the gradient (little delta)
was optimized to 3 and 3.2 ms, respectively, and was incremented
linearly in 16 steps per experiment. Diffusion coefficients: 1 ) 1.56
Caution! Trimethylgallium is a pyrophoric liquid and should
be handled with care. Dimethylmercury is poisonous to the central
nervous system and has a long latency period before the charac-
teristic symptoms appear. Its characteristic volatility allows trans-
dermal absorption and inhalation of the vapors, which must certainly
be avoided.21-23 It is therefore necessary to use a combination of
gloves as suggested by Blayney et al.24 Dimethylmercury was
decomposed by treating with aqua regia. The resulting mercury
dichloride was precipitated under basic conditions before it was
appropriately disposed.
Dimethyl(phenyl)gallium (1). (a) By Hg/Ga Exchange. In a
Schlenk flask, trimethylgallium (3.87 g, 33.70 mmol) was added
via septum with a syringe to freshly sublimed diphenylmercury
(2.92 g, 8.20 mmol). The septum was replaced with a glass stopper,
and the vessel was tightly closed.25 The colorless suspension was
heated at 100 °C for 5 h. A fine precipitate separated from the
solution on cooling to room temperature. The volatile components
were removed under reduced pressure (10 mbar) and proven by
1H NMR spectroscopy to consist of HgMe2 (δ ) 0.12 ppm) and
GaMe3 (δ ) -0.15 ppm). The residue was washed twice with 5
mL of n-hexane at -70 °C to give 1 as a colorless, amorphous
solid (2.60 g, 14.70 mmol, 90%). This solid was suspended in
trimethylgallium (1.70 g, 15.30 mmol) and heated at 100 °C for
1 h. The formed clear solution was cooled to 40 °C and maintained
at this temperature without stirring for 15 h. After this period,
× 10-9 m2 s-1; 2-phenylpropane ) 1.70 × 10-9 m2 s-1
.
Low-Temperature 1H NMR Data of 1. A NMR tube was
charged with 1 (8.00 mg, 0.05 mmol) and toluene-d8 (0.45 mL). The
1H NMR data were measured at different temperatures. 1H NMR (300
K): δ -0.16 (s, 6H), 7.23 (m, 3H), 7.55 (m, 2H). 1H NMR (275 K):
1
δ -0.20 (s, 6H), 7.27 (m, 3H), 7.57 (m, 2H). H NMR (245 K): δ
-0.22 (s, 6H), 7.30 (m, 3H), 7.59 (m, 2H). 1H NMR (220 K): δ -0.25
(s, 6H), 7.32 (m, 3H), 7.60 (m, 2H).
Thermal Stability of 1 in Benzene-d6. A NMR tube was charged
with compound 1 (64.0 mg, 0.40 mmol) and 0.6 mL of benzene-d6
and tightly closed. Identical NMR spectra were obtained before
and after heating at 80 °C for 2 h. 1H NMR (benzene-d6): δ -0.12
(s, 6H, methyl), 7.30 (m, 3H, meta/para-phenyl), 7.65 (m, 2H,
ortho-phenyl). 13C NMR (benzene-d6): δ -2.9 (methyl), 128.2 (C-
3/5), 129.7 (C-4), 137.0 (C-2/6), 148.6 (C-1).
Redistribution Reactions in Benzene-d6 Solution of
1
Promoted by THF. A NMR tube was charged with 1 (64.0 mg,
0.40 mmol), benzene-d6 (0.4 mL), and THF (0.2 mL, 178 mg, 2.46
(20) Rowan, S. T.; Cantrill, S. J.; Cousins, G. R. L.; Sanders, J. K. M.;
Stoddart, J. F. Angew. Chem. 2002, 114, 938. ; , Angew. Chem., Int. Ed.
2002, 41, 898.
(21) Nierenberg, D. W.; Nordgren, R. E.; Chang, M. B.; Siegler, R. W.;
Blayney, M. B.; Hochberg, F.; Toribara, T. Y.; Cernichiari, E.; Clarkson,
T. New Engl. J. Med. 1998, 338 (23), 1672.
(22) Blayney, M. B. Appl. Occup. EnViron. Hyg. 2001, 16 (2), 233.
(23) (a) Florea, A.; Buesselberg, D. BioMetals 2006, 19 (4), 419. (b)
Lockwood, A. H.; Landrigan, P. J. New Engl. J. Med. 1998, 339 (17), 1243.
(24) Blayney, M. B.; Winn, J. S.; Nierenberg, D. W. Chem. Eng. News
1997, 7.
(26) (a) The novel compounds are extremely air-sensitive; deviations
from the calculated CH values may be due to partial oxidation of the crystals
or to the presence of traces (not detectable by NMR) of chemisorbed
trimethylgallium. Deviations from calculated CH values in group 13 element
organic compounds have already been reported, for instance in: Long, L. H.;
Sackmann, J. F. Trans. Faraday Soc. 1958, 54, 1797. (b) Beachley, O. T.,
Jr.; Hallock, R. B.; Zhang, H. M.; Atwood, J. L. Organometallics 1985, 4,
1675.
(25) A Schlenk flask and a glass stopper are tightly secured with a
screwed on bracket.
(27) Result of substituent redistribution reactions.

4570 Organometallics, Vol. 27, No. 18, 2008
Jutzi et al.
mmol). The formation of the THF adducts of methyl(diphenyl)gal-
lium, of trimethylgallium, and of 1 in the ratio of 1:1:4, respectively,
was proven by NMR spectroscopy. The ratio was established from
δ -5.2 (methyl), 21.7 (Ar-Me), 129.0 (C-3/5), 137.8 (C-2/6), 139.2
(C-4), 143.6 (C-1). Anal. Found: C: 54.97; H: 6.13. Calcd: C: 56.61;
H: 6.86.14,16a,26 MS data: The MS data of compound 2 were not
conclusive due to the substituent exchange reactions at elevated
temperature.
1
the intensity of the H NMR signals in relation to the respective
Ga-methyl group signals. The THF signals are broadened due to
exchange reactions between coordinated and free THF molecules.
1 · THF: 1H NMR (benzene-d6): δ -0.06 (s, methyl), 1.47 (THF),
3.52 (THF), 7.30 (m, para- and meta-protons), 7.68 (m, ortho-
protons). 13C NMR (benzene-d6): δ -8.9 (methyl), 25.3 (THF),
67.3 (THF), 134.6 (C-3/5), 136.0 (C-4), 137.3 (C-2/6), 150.9 (C-
Dimethyl(4-tert-butylphenyl)gallium (3). Trimethylgallium (5.95
g, 51.80 mmol) was added through a syringe to 1-chloromercurio(4-
tert-butylbenzene) (3.19 g, 8.60 mmol). The resulting colorless
suspension was heated at 100 °C for 5 h in a closed vessel to give
a colorless solution. The solution was cooled to 30 °C without
stirring and kept at this temperature for 15 h. During this period,
colorless crystals of 3 separated from the solution (1.9 g, 8.20 mmol,
95%). Compound 3: 1H NMR (benzene-d6): δ -0.09 (s, 6H,
1
1). Methyl(diphenyl)gallium (4 · THF): H NMR (benzene-d6): δ
0.08 (s, methyl), 1.47 (THF), 3.52 (THF), 7.30 (m, para- and meta-
protons), 7.77 (m, ortho-protons). 13C NMR (benzene-d6): δ -11.0
(methyl), 25.3 (THF), 67.3 (THF). The aromatic 13C resonances
of 1 · THF and of 4 · THF were overlapped with one another.
Trimethylgallium · THF: 1H NMR (benzene-d6): δ -0.23 (s, meth-
yl), 1.47 (THF), 3.52 (THF). 13C NMR (benzene-d6): δ -5.4
(methyl), 25.3 (THF), 67.3 (THF).28
3
methyl), 1.30 (s, 9H, t-Bu), 7.43 (d, 2H, meta-protons, JHH ) 8
Hz), 7.73 (d, 2H, ortho-protons, 3JHH ) 8 Hz). 13C NMR (benzene-
d6): δ -2.8 (methyl), 31.4 (Ar-Me), 34.7 (C-Me3), 125.2 (C-3/5),
137.5 (C-2/6), 144.7 (C-1), 152.6 (C-4). Anal. Found: C, 58.96;
H, 8.31. Calcd: C, 61.85; H, 8.22.14,16a,26 MS m/z (%): [M+], 233/
235 (10/7); [t-BuC6H4GaMe+], 218/220 (11/7); [t-BuC6H4Ga+],
203/205 (13/8); [t-BuC6H4Me+], 150 (7); [t-BuC6H5+], 135 (34);
[Me2CC6H5+],27 119 (100); [GaMe2+], 99/101 (70/48); [C6H4Me+],
91 (60); [Ga+], 69/71 (18/12).
Thermally Induced Redistribution Reactions of 1. Two
Schlenk flasks, A and B, were connected by a bent ground-glass
joint. Flask A was charged with compound 1 (500.0 mg, 2.80 mmol)
and the system was evacuated (10 mbar). Flask B was then cooled
with liquid nitrogen. Flask A was heated in three subsequent steps
to 70, 120, and 150 °C, respectively, each for a period of 30 min.
After each heating period, flask A was reweighed and thereafter
the system was reassembled for the next reaction step. After this
procedure, colorless crystals had deposited on the cooler region of
Redistribution Reactions in Benzene-d6 Solution of 3 Pro-
moted by THF. An NMR tube was charged with compound 3
(32.40 mg, 0.10 mmol), benzene-d6 (0.4 mL), and THF (0.2 mL,
0.18 g, 2.46 mmol). The formation of the THF adducts of di(tert-
butylphenyl)(methyl)gallium, trimethylgallium, and 3 in a ratio of
1:3:5, respectively, was proven by NMR spectroscopy. The ratio
was concluded from the intensity of the respective methyl group
signal at gallium. The THF signals were broadened due to exchange
reactions between coordinated and free THF molecules. 3 · THF:
1H NMR (benzene-d6): δ -0.02 (s, methyl), 1.29 (s, tBu), 1.45
(THF), 3.52 (THF), 7.40 (m, meta-protons), 7.69 (d, ortho-protons).
13C NMR (benzene-d6): δ -8.1 (methyl), 25.8 (THF), 31.4 (Me),
34.6 (C-Me3) 67.8 (THF), 124.4 (C-3/5), 137.2 (C-2/6), 145.7 (C-
1), 149.9 (C-4). Di(tert-butylphenyl)(methyl)gallium · THF: 1H
NMR (benzene-d6): δ 0.13 (s, methyl), 1.28 (s, tBu), 1.45 (THF),
3.52 (THF), 7.41 (m, meta-protons), 7.79 (d, ortho-protons). 13C
NMR (benzene-d6): δ -10.2 (methyl), 25.8 (THF), 31.5 (Me), 34.6
(C-Me3), 67.8 (THF). The aryl-group 13C resonances of 3 · THF
and of di(tert-butylphenyl)(methyl)gallium · THF were overlapped
with one another. Trimethylgallium · THF: 1H NMR (benzene-d6):
δ -0.20 (s, methyl) 1.47 (THF), 3.52 (THF). 13C NMR (benzene-
d6): δ -4.8 (methyl), 25.8 (THF), 67.8 (THF). For comparison
GaMe3 · THF: 1H NMR (benzene-d6); δ -0.17 (s, methyl) 1.39
(THF), 3.46 (THF). 13C NMR (benzene-d6): δ -4.7 (methyl), 25.6
(THF), 68.2 (THF).
1
flask A. The H and 13C NMR spectra of the deposited crystals
indicated the formation of methyl(diphenyl)gallium (4) (∼8%) and
of triphenylgallium. Compound 1 liberated 135.0 mg (1.20 mmol),
168.70 mg (1.50 mmol), and 194.5 mg (1.70 mmol) of trimethyl-
gallium at 70, 120, and 150 °C, respectively. Methyl(diphenyl)gal-
lium (4) (vide infra): 1H NMR, (benzene-d6): δ -0.09 (s, methyl),
7.29 (m, para-and meta-protons), 7.70 (m, ortho-protons). The 13
C
NMR signals of 4 overlapped with those of triphenylgallium.
Triphenylgallium: 1H NMR (benzene-d6): δ 7.29 (m, 3H), 7.74 (m,
2H). 13C NMR (benzene-d6): δ 128.2 (C-3/5), 129.6 (C-4), 138.1
(C-2), 145.1 (C-1).
Redistribution Reaction between 1 and Trimethylgallium. A
NMR tube was charged with 1 (64.0 mg, 0.40 mmol) and with a
mixture of benzene-d6 (0.5 mL) and trimethylgallium (0.2 mL, 170.0
mg, 1.50 mmol). The NMR tube was closed and allowed to stand
at room temperature for a period of 30 min. Complete equilibration
of 1 and trimethylgallium was proven by averaged Ga-Me group
1
signals in the NMR spectra. H NMR (benzene-d6): δ -0.15 (s,),
7.24 (m, 3H), 7.56 (m, 2H). 13C NMR (benzene-d6): δ 1.1, 128.2
(C-3/5), 129.8 (C-4), 137.2 (C-2), 148.2 (C-1). For comparison:
GaMe3: 1H NMR (benzene-d6): δ 0.15. 13C NMR (benzene-d6): δ
) 1.5.
Thermal Decomposition of 3. Analogously to the procedure
used in the thermal decomposition of 1, 256.0 mg (1.10 mmol) of
3 was heated in three subsequent steps to 70, 120, and 150 °C in
vacuo (10 mbar), for a period of 30 min each. Upon heating, 3
liberated 20.60 mg (0.20 mmol), 67.0 mg (0.60 mmol), and 84.0
mg (0.70 mmol) of trimethylgallium at 70, 120, and 150 °C,
respectively. The 1H and 13C NMR data of the remaining colorless,
amorphous solid material indicated the formation of tri(4-tert-
butylphenyl)gallium and di(4-tert-butylphenyl)(methyl)gallium (∼3%).
These compounds were not isolated in the pure form. Tri(tert-
Dimethyl(4-methylphenyl)gallium (2). Trimethylgallium (4.34
g, 37.80 mmol) was added through a syringe to 1-chloromercurio(4-
methylbenzene) (2.06 g, 6.40 mmol). The resulting colorless
suspension was heated at 110 °C for 5 h in a closed vessel to give
a colorless solution. After the solution was cooled to room
temperature, the volatile components were removed under reduced
pressure. The residue was washed with n-hexane (5 mL) and dried
in vacuo (10 mbar) for 3 h to give compound 2 as an amorphous,
colorless solid (0.92 g, 4.80 mmol, 75%). Trimethylgallium (1.15
g, 10.0 mmol) was added to the solid (0.92 g), and the resulting
colorless suspension was heated at 80 °C for 1 h in a closed vessel
to give a colorless solution. After 3 days at room temperature,
colorless crystals of 2 (0.80 g, 4.17 mmol, 65%) separated from
the solution. Compound 2: 1H NMR, (benzene-d6): δ -0.05 (s,
6H, methyl), 2.20 (s, 3H, Ar-Me), 7.17 (d, 2H, meta-Ar, 3JHH ) 8
Hz), 7.73 (d, 2H, ortho-Ar, 3JHH ) 8 Hz). 13C NMR (benzene-d6):
1
butylphenyl)gallium: H NMR (benzene-d6): δ 1.29 (s, tBu) 7.43
(d, meta-protons), 7.84 (d, ortho-protons). 13C NMR (benzene-d6):
δ 31.4 (Me), 34.7 (CMe3), 125.4 (C-3/5), 138.0 (C-2/6), 142.9 (C-
1
1), 152.3 (C-4). Di(4-tert-butylphenyl)(methyl)gallium: H NMR
(benzene-d6): δ -0.04 (Me), 1.25 (s, tBu), 7.41 (d, meta-protons),
7.83 (d, ortho-protons). The aryl-group 13C resonances of di(4-
tert-butylphenyl)(methyl)gallium overlapped with those of tri(tert-
butylphenyl)gallium.
Methyl(diphenyl)gallium (4). Trimethylgallium (0.28 g, 2.40
mmol) was added to freshly sublimed diphenylmercury (0.75 g,
(28) Jones, A. C.; Cole-Hamilton, D. J.; Holliday, A. K.; Ahmad, M. M.
J. Chem. Soc., Dalton Trans. 1983, 1047.

Aryl(dimethyl)gallium Compounds
Organometallics, Vol. 27, No. 18, 2008 4571
2.10 mmol). The resulting colorless suspension was heated at 100
°C in a closed vessel for 3 h to give a colorless solution. Upon
cooling to room temperature without stirring, compound 4 separated
from the solution as colorless crystals. All volatiles were removed
in vacuo (10-2 mbar), and the remaining crystals (0.49 g, 2.0 mmol,
98%) were washed with n-hexane (0.5 mL) and dried in vacuo
(10-2 mbar) for 2 h. Compound 4: 1H NMR (benzene-d6): δ -0.09
(s, 3H, methyl), 7.29 (m, 2H para- and 4H meta-protons), 7.69
(m, 4H ortho-protons). 13C NMR (benzene-d6): δ -4.6 (methyl),
128.5 (C-3/5), 129.6 (C-4), 137.4 (C-2), 147.4 (C-1). Anal. Found:
C: 63.44; H: 5.21. Calcd: C: 65.34; H: 5.48.14,16a,26 The MS data
of compound 4 were not conclusive due to substituent exchange
reactions at elevated temperature.
flask, a crystalline material deposited, consisting of triphenylgallium
and 4 (∼5%) as proven by NMR spectroscopy. Triphenylgallium:
1H NMR (benzene-d6): δ 7.30 (m, meta-protons), 7.74 (m, ortho-
protons).17 13C NMR (benzene-d6): δ 128.5 (C-3/5), 129.6 (C-4),
137.9 (C-2), 145.4 (C-1). Methyl(diphenyl)gallium (4): H NMR
(benzene-d6): δ -0.09 (s, methyl), 7.29 (m), 7.73 (m).
1
Acknowledgment. We thank Professor Lorberth, Univer-
sity of Marburg, Germany, for a gift of trimethylgallium.
The financial support of the University of Bielefeld and the
“DeutscheForschungsgemeinschaft”isgratefullyacknowledged.
Thermal Decomposition of 4. The experimental setup was the
same as that already described for the thermal decomposition of 1
and 3. Compound 4 (92.40 mg, 0.40 mmol) was heated at 70, 120,
and 150 °C in three subsequent steps in vacuo (10 mbar) for a
period of 30 min each. Compound 4 liberated on heating at 70 and
120 °C no trimethylgallium, but on heating at 150 °C it liberated
trimethylgallium (9.0 mg, 0.08 mmol). On the cooler region of the
Supporting Information Available: The crystallographic data
for compounds 1-4 are deposited, including the intramolecular
distances, bond angles, and the calculated positions of hydrogen
atoms. This information is available free of charge via the Internet
at http://pubs.acs.org.
OM701055A