Room temperature cyclopentadiene elimination reaction for the synthesis of diethylgallium-amides, -phosphides, and -thiolates. Crystal and molecular structures of [Et2GaP(t-Bu)2]2 and [Et2GaS(SiPh3)]<

Article abstract of DOI:10.1021/om960284p

The compounds [Et₂GaNEt₂J₂, [Et₂GaN(H)(Me)]₂, [Et₂GaN(H)(t-Bu)]₂, [Et₂GaP(i-Pr)₂]₂, [Et₂-GaP(t-Bu)₂]₂, and [Et

Full text of DOI:10.1021/om960284p

Organometallics 1996, 15, 3653-3658
3653
Room Tem p er a tu r e Cyclop en ta d ien e Elim in a tion
Rea ction for th e Syn th esis of Dieth ylga lliu m -Am id es,
-P h osp h id es, a n d -Th iola tes. Cr ysta l a n d Molecu la r
Str u ctu r es of [Et2Ga P (t-Bu )2]2 a n d [Et2Ga S(SiP h 3)]2
O. T. Beachley, J r.,* Daniel B. Rosenblum, Melvyn Rowen Churchill,*
Charles H. Lake, and Laurence M. Toomey
Department of Chemistry, State University of New York at Buffalo, Buffalo, New York 14260
Received April 11, 1996X
The compounds [Et2GaNEt2]2, [Et2GaN(H)(Me)]2, [Et2GaN(H)(t-Bu)]2, [Et2GaP(i-Pr)2]2, [Et2-
GaP(t-Bu)2]2, and [Et2GaS(SiPh3)]2 have been prepared in high yields at room temperature
by the elimination of cyclopentadiene from Et2Ga(C5H5) and the corresponding amine,
phosphine, or thiol. The three diethylgallium amides and [Et2GaP(i-Pr)2]2 are liquids,
whereas the other phosphide and the thiolate are crystalline solids at room temperature.
All compounds were fully characterized by elemental analyses, 1H and 31P NMR spectroscopy,
and cryoscopic molecular weight studies in benzene, as appropriate, and are dimeric in
solution. The crystalline compounds [Et2GaP(t-Bu)2]2, and [Et2GaS(SiPh3)]2 were character-
ized by X-ray structural studies. Even though [Et2GaN(H)(t-Bu)]2 and [Et2GaS(SiPh3)]2 were
1
prepared at room temperature and isolated in high yield, H NMR studies revealed that
neither compound was formed in high yield in solution. Removal of the cyclopentadiene by
either dimerization or distillation and/or dimerization of the gallium product are necessary
to prevent the back-reaction to re-form the reactants.
The preparation of electronic materials typically
requires precursors which have an ultrahigh level of
purity. The obvious impurities are those imported with
the reagents used to prepare the precursors and those
which are formed during the synthetic reactions. The
simplest and most direct route to single source precur-
sors R2GaER′2 (E ) N, P) from readily available, high
purity, but simple, reagents which do not involve atoms
from potentially electronically damaging elements is the
hydrocarbon elimination reaction (eq 1). After the
at room temperature, amines with very bulky substit-
uents such as 2,4,6-tri-tert-butylphenylamine, NH2[(t-
Bu3)C6H2], did not give the desired products. The
reactants were recovered. The explanation for this
observation4 was that the elimination reaction actually
occurred but the resulting monomeric gallium-nitrogen
product reacted readily with the cyclopentadiene to re-
form the reactants instead of associating to form gal-
lium-nitrogen dimers or trimers. Association of the
monomer would tie up the lone pair on the group 15
element and, in turn, prevent the back-reaction of
cyclopentadiene as a weak acid.
GaMe3 + HER2 f (1/n)[Me2GaER2]n + CH4 (1)
In this paper we describe the results of our investiga-
tions of the reactions of Et2Ga(C5H5)5 with some primary
and secondary amines, several secondary phosphines,
and a thiol. This study enabled us to learn more about
the nature of the reaction, including the relative ease
of the forward and reverse reactions, the effects of the
multiple gallium reactants which are present in solution
due to the occurrence of the redistribution equilibrium5
(eq 3), and the effects of the ethyl verses the methyl
groups on the nature of this reaction.
impurities associated with the reagents have been
minimized, the second source of impurities originates
with the high temperatures typically needed for the
hydrocarbon elimination reaction. The preparation of
gallium-nitrogen precursors uses temperatures of 100-
150 °C,1,2 whereas gallium-phosphorus derivatives
typically use higher temperatures of 150-250 °C.3
A
goal of our research has been to discover and study
hydrocarbon elimination reactions which occur at or
below room temperature.
One novel reaction which satisfied these criteria is
the cyclopentadiene elimination reaction4 which occurs
between Me2Ga(C5H5) and primary and secondary
amines and phosphines (eq 2). Even though a series of
2Et2Ga(C5H5) h EtGa(C5H5)2 + GaEt3
(3)
Furthermore, this study provided us with a series of
diethylgallium-group 15 and 16 compounds for which
very few other examples are known. The other ex-
amples of which we are aware are Et2GaPEt2,6 Et2GaAs-
(t-Bu)2,7 Et2GaN3,8 Et2GaNH2,9 Et2GaN(C5H10),10
Me2Ga(C5H5) + HERR′ h
(1/n)[Me2GaERR′]n + C5H6 (2)
dimethylgallium amides and phosphides were prepared
(4) Beachley, O. T., J r.; Royster, T. L., J r.; Arhar, J . R.; Rheingold,
A. L. Organometallics 1993, 12, 1976.
(5) Beachley, O. T., J r.; Rosenblum, D. B.; Churchill, M. R., Lake,
C. H., Krajkowski, L. M. Organometallics 1995, 14, 4402.
(6) (a) Maury, F.; Combes, M.; Constant, G.; Carles, R.; Renucci, J .
B. J . Phys. (Paris) 1982, 43, C1-347. (b) Maury, F.; Constant, G.
Polyhedron 1984, 3, 581.
X Abstract published in Advance ACS Abstracts, August 1, 1996.
(1) Coates, G. E. J . Chem. Soc. 1951, 2003.
(2) Park, J . T.; Kim, Y.; Kim, J .; Kim, K.; Kim, Y. Organometallics
1992, 11, 3320.
(3) (a) Coates, G. E.; Graham, J . J . Chem. Soc. 1963, 233. (b)
Beachley, O. T., J r.; Coates, G. E. J . Chem. Soc. 1965, 3241.
S0276-7333(96)00284-1 CCC: $12.00 © 1996 American Chemical Society

3654 Organometallics, Vol. 15, No. 17, 1996
Beachley et al.
Et2GaN(C2H4),11 Et2GaN(i-Bu)2,12 Et2GaN(Cy)2,12 Et2-
GaNdC(H)(Ph),13 and Et2GaNdC(H)(t-Bu).13
It is also noteworthy that when direct comparisons are
made between the physical properties of the methyl- and
ethylgallium derivatives, the ethyl compounds have
lower melting points and are typically liquids at room
temperature, whereas the methyl compounds are solids.
The reactions of Et2Ga(C5H5) with HNEt2, HN(H)Me,
HN(H)(t-Bu), HP(i-Pr)2, HP(t-Bu)2, and HS(SiPh3) in
benzene or pentane provide convenient room tempera-
ture routes to the preparation of [Et2GaNEt2]2, [Et2GaN-
(H)(Me)]2, [Et2GaN(H)(t-Bu)]2, [Et2GaP(i-Pr)2]2, [Et2-
GaP(t-Bu)2]2, and [Et2GaS(SiPh3)]2 in high yields (70-
90%). The insolubility of HS(SiPh3) in pentane made
benzene the preferred solvent for the synthesis of [Et2-
GaS(SiPh3)]2. The only direct comparison between the
temperature required for the synthesis of these com-
pounds by the elimination of cyclopentadiene by using
Et2Ga(C5H5) with the temperature necessary for the
elimination of ethane by using GaEt3 has been provided
by this study. When GaEt3 was reacted with the thiol,
a temperature of 70 °C was necessary to eliminate
ethane and form [Et2GaS(SiPh3)]2. Only two other
diethylgallium compounds, Et2GaPEt2 and Et2GaN-
(C2H4), have been prepared by hydrocarbon elimination
reactions, and both preparative reactions required tem-
peratures in the range of 100-150 °C.6,11 However,
elimination reactions have been used for the preparation
of several of the dimethylgallium derivatives of the
amines and phosphines used in this study. For ex-
ample, GaMe3 and HN(H)Me required 125 °C;1 HN(H)-
(t-Bu) needed 110 °C,2 but HP(t-Bu)2 was heated at 220
°C for 10 days for the elimination of methane to form
[Me2GaP(t-Bu)2]2.14
All products prepared during this investigation were
fully characterized by partial elemental analyses (C and
H), cryoscopic molecular weight studies in benzene
solution, and 1H and 31P NMR spectroscopy, as ap-
propriate. All group 13-15 products except [Et2GaP-
(t-Bu)2]2 were liquids at room temperature and were
isolated by vacuum distillation. The solids [Et2GaP(t-
Bu)2]2 and [Et2GaS(SiPh3)]2 were purified by recrystal-
lization and were characterized additionally by their
melting points and by X-ray structural studies.
The characterization data for benzene solutions of all
compounds prepared in this study, cryoscopic molecular
weight and NMR spectral data, confirm the presence
of only dimers. The molecular weight data exhibited
no concentration dependence, and the 31P NMR spectra
of the phosphorus compounds had only single lines.
Thus, it is unlikely that multiple species with different
degrees of association are present in solution. When
the diethylgallium derivatives are compared with the
corresponding dimethyl species, differences in degrees
of association are noted. For example, Me2GaN(H)(Me)
is a trimer15 in benzene solution, and Me2GaP(i-Pr)2 has
been observed as an equilibrium mixture of dimers and
trimers16 by NMR spectroscopy, but Me2GaN(H)(t-
Bu),2,17 Me2GaNEt2,4 and Me2GaP(t-Bu)2 14,18 are dimers.
Proton NMR spectroscopy clearly shows that [Et2-
GaN(H)(t-Bu)]2 and [Et2GaN(H)(Me)]2 exist as mixtures
of cis and trans isomers in benzene solution. The cis
isomer has two magnetically different ethyl groups on
gallium. As a result, two triplets and two quartets of
equal intensity are observed. In contrast, the ethyl
groups in the trans isomer are equivalent but magneti-
cally different from the ethyl protons in the cis isomer.
The methylene protons of the gallium ethyl groups in
the trans isomer are also magnetically nonequivalent,
and therefore their resonance appears as a doublet of
quartets. The methylene protons for both compounds
exhibited the same geminal coupling constant, 13.6 Hz.
The integrations of the two lines for the tert-butyl
groups on nitrogen due to the two isomers suggest
approximately 77% trans and 23% cis isomer. In
contrast, a sample of [Me2GaN(H)(t-Bu)]2 prepared by
either the analogous cyclopentadiene elimination reac-
17
tion4 or a metathesis reaction at -78 °C
had reso-
nances for only the trans isomer (benzene solution),
whereas when the compound was prepared by the
elimination of methane from GaMe3 and HN(H)(t-Bu)
1
at 110 °C,2 the H NMR spectrum of a toluene solution
demonstrated the presence of both isomers (67% trans
and 33% cis). A benzene solution of [Et2GaN(H)(Me)]2
had equal quantities of the cis and trans isomers
according to the intensities of the N-Me resonances.
Since the corresponding methylgallium compound4 is a
trimer [Me2GaN(H)(Me)]3, comparisons are inappropri-
ate.
1
The H and 31P NMR spectra of the two phosphides
prepared in this investigation, [Et2GaP(i-Pr)2]2 and [Et2-
GaP(t-Bu)2]2, are consistent with the presence of only
dimers. The 31P NMR spectrum of each compound
shows a single resonance. The chemical shifts of the
lines are comparable with those observed for the cor-
responding dimeric dimethylgallium derivatives. The
compound [Et2GaP(i-Pr)2]2 has its line at -5.72 ppm,
whereas [Me2GaP(i-Pr)2]2 is at -11.0 ppm.16 Similary,
the chemical shift for [Et2GaP(t-Bu)2]2 is 35.22 ppm,
whereas [Me2GaP(t-Bu)2]2 is 28.41 ppm.14,18 The 1H
NMR spectra of both diethylgallium phosphides exhibit
virtual coupling between the protons of the substituents
on phosphorus and the two ring phosphorus atoms.
Thus, the tert-butyl resonance for [Et2GaP(t-Bu)2]2 is
split into an apparent triplet (J P-H ) 7.0 Hz), whereas
the C-H proton for the methine hydrogen of the
isopropyl group in [Et2GaP(i-Pr)2]2 appears as a septet
of triplets (3J P-H ) 7.2 Hz). It is also noteworthy that
the methylene protons for the ethyl groups bound to
gallium in [Et2GaP(i-Pr)2]2 also exhibit virtual coupling
as a quartet of triplets (J P-H ) 2.4 Hz) is observed.
(7) Miller, J . E.; Mardones, M. A.; Nail, J . W.; Cowley, A. H.; J ones,
R. A.; Ekerdt, J . G. Chem. Mater. 1992, 4, 447.
(8) Muller, J .; Dehnicke, K. J . Organomet. Chem. 1968, 12, 37.
(9) Andrews, J . E.; Littlejohn, M. A. J . Electrochem. Soc. 1975, 1274.
(10) Sen, B.; White, L. J . Inorg. Nucl. Chem. 1973, 35, 2207.
(11) Storr, A.; Thomas, B. S. J . Chem. Soc. A 1971, 3850.
(12) Nutt, W. R.; Murray, K. J .; Gulick, J . M.; Odom, J . D.; Dang,
Y.; Lebioda, L. Organometallics 1996, 15, 1728.
(13) J ennings, J . R.; Wade, K. J . Chem. Soc. A 1967, 1222.
(14) Arif, A. M.; Benac, B. L.; Cowley, A. H.; Kidd, K. B.; Nunn, C.
M. New J . Chem. 1988, 12, 553.
The 1H NMR spectrum of [Et2GaS(SiPh3)]2 in benzene
has only one set of lines for the protons of the ethyl
groups. Thus, either the molecule exists only as the
trans isomer or both isomers are present but a rapid
isomerization process with breaking of a gallium-sulfur
(15) Storr, A. J . J . Chem. Soc. A 1968, 2605.
(16) Cowley, A. H.; J ones, R. A.; Mardones, M. A.; Nunn, C. M.
Organometallics 1991, 10, 1635.
(17) Atwood, D. A; J ones, R. A.; Cowley, A. H.; Bott, S. G.; Atwood,
J . L. J . Organometal. Chem. 1992, 434, 143.
(18) Arif, A. M.; Benac, B. L.; Cowley, A. H.; Geerts, R. L.; J ones, R.
A.; Kidd, K. B.; Power, J . M; Schwab, S. T. J . Chem. Soc., Chem.
Commun. 1986, 1543.

Diethylgallium-Amides, -Phosphides, and -Thiolates
Organometallics, Vol. 15, No. 17, 1996 3655
C(31)-P(1)-C(41) ) 110.2(3)°; the distances of the
C-CH3 linkages are in the expected range with C(31)-
Me ) 1.490(11) f 1.517(11) Å and C(41)-Me ) 1.493-
(11) f 1.521(9) Å.
A comparison of the major structural features of [Et2-
GaP(t-Bu)2]2 with other closely related molecules of the
type (R2GaPR′2)2 suggests some differences but also
many similarities. The other molecules [(n-Bu)2GaP-
(t-Bu)2]2,18 [Me2GaP(SiMe3)2]2,20 and [(t-Bu)2GaP(H)-
21
(C5H9)]2
have planar Ga2P2 cores, whereas [(Me3-
22
CCH2)2GaPPh2]2 has a puckered core. Although the
halide derivatives [Cl2GaP(SiMe3)2]2
(SiMe3)2]2
23
and [Br2GaP-
24
contain a planar Ga2P2 core with equal
Ga-P bond lengths, it is noteworthy that [Et2GaP(t-
Bu)2]2 is the only molecule containing two organic
groups bonded to gallium that has both a planar Ga2P2
core and all four gallium-phosphorus distances equal
within experimental error. The angle between the
organic groups bound to gallium is similar to that in
the other structurally characterized di-tert-butylphos-
phide derivative [(n-Bu)2GaP(t-Bu)2]2,18 but it is smaller
than those observed for [Me2GaP(SiMe3)2]2 20 (114.5(3)°),
Figu r e 1. Molecular geometry of [Et2GaP(t-Bu)2]2. ORTEP2
diagram, 30% probability ellipsoids for non-hydrogen atoms
with hydrogen atoms omitted for clarity.
Ta ble 1. Im p or ta n t In ter a tom ic Dista n ces (Å) a n d
An gles (d eg) for [Et2Ga P (t-Bu )2]2
22
[(Me3CCH2)2GaPPh2]2 (124.35(50) and 121.98(49)°),
21
and [(t-Bu)2GaP(H)(C5H9)]2 (121.0(2)°).
(A) Bond Lengths (Å)
The compound [Et2GaS(SiPh3)]2 has also been sub-
jected to an X-ray structural study and is shown in
Figure 2. Interatomic distances and angles are provided
in Table 2. This molecule has precise Ci symmetry
(crystallography required) with a planar Ga2S2 core.
Most other structurally characterized molecules of this
type, including [(t-Bu)2GaS(H)]2,25 [Ph2GaSEt]2,26 and
{Ph2GaS[Sn(c-C6H11)3]}2,27 are also planar, but [Me2-
GaS(C6F5)]2 28 and [I2GaS(i-Pr)]2 29 are puckered. Bond
lengths within the planar Ga2S2 core of [Et2GaS(SiPh3)]2
alternate in length, Ga(1)-S(1) ) Ga(1a)-S(1a) )
2.450(2) Å and Ga(1)-S(1a) ) Ga(1a)-S(1) ) 2.396(2)
Å. Angles within this system are S(1)-Ga(1)-S(1a) )
88.1(1)° and Ga(1)-S(1)-Ga(1a) ) 91.9(1)°. The ethyl
ligands are associated with bond lengths of Ga(1)-C(1)
) 1.934(14) Å and Ga(1)-C(3) ) 1.971(11) Å and a large
interligand angle C(1)-Ga(1)-C(3) ) 125.1(4)°. Similar
large interligand angles have been observed for the
other thiolate derivatives. The angles at the R-carbon
atoms for [Et2GaS(SiPh3)]2 are Ga(1)-C(1)-C(2) )
119.6(8)° and Ga(1)-C(3)-C(4) ) 114.4(8)°, while the
C(R)-C(â) bond lengths are C(1)-C(2) ) 1.437(14) Å
and C(3)-C(4) ) 1.446(11) Å. Libration is not as large
a problem as in the previous structure. The largest
relevant Uii values are U33 ) 0.143(10) Å2 for C(1)
versus U33 ) 0.186(13) Å2 for C(2), and U22 ) 0.140(10)
Å2 for C(3) versus U22 ) 0.115(9) Å2 for C(4).
Ga(1)-P(1)
Ga(1)-C(21)
P(1)-C(31)
P(1)-Ga(1A)
C(21)-C(22)
2.482(2)
1.998(6)
1.904(6)
2.483(2)
1.418(13)
Ga(1)-C(11)
Ga(1)-P(1A)
P(1)-C(41)
C(11)-C(12)
1.999(6)
2.483(2)
1.900(6)
1.380(12)
(B) Bond Angles (deg)
114.8(2) P(1)-Ga(1)-C(21)
P(1)-Ga(1)-C(11)
117.3(2)
86.9(1)
C(11)-Ga(1)-C(21) 107.1(3) P(1)-Ga(1)-P(1A)
C(11)-Ga(1)-P(1A) 117.1(2) C(21)-Ga(1)-P(1A) 113.1(2)
Ga(1)-P(1)-C(31)
C(31)-P(1)-C(41)
114.2(2) Ga(1)-P(1)-C(41)
110.2(3) Ga(1)-P(1)-Ga(1A)
113.2(2)
93.1(1)
C(31)-P(1)-Ga(1A) 113.2(2) C(41)-P(1)-Ga(1A) 112.1(2)
Ga(1)-C(11)-C(12) 119.9(6) Ga(1)-C(21)-C(22) 118.0(6)
ring bond is occurring. Similar observations were
recently reviewed by Oliver.19
The crystal and molecular structure of [Et2GaP(t-
Bu)2]2 is consistent with the observations for solutions.
The molecular geometry for [Et2GaP(t-Bu)2]2 is shown
in Figure 1. Interatomic distances and angles are
collected in Table 1. The molecule has precise Ci
symmetry and a planar Ga2P2 core in which Ga(1)-P(1)
) Ga(1A)-P(1A) ) 2.482(2) Å and Ga(1)-P(1A) ) Ga-
(1A)-P(1) ) 2.483(2) Å. The P-Ga-P angles are 86.9-
(1)°, while the Ga-P-Ga angles are 93.1(1)°. Each
gallium(III) atom is linked to two ethyl groups with Ga-
(1)-C(11) ) 1.999(6) Å and Ga(1)-C(21) ) 1.998(6) Å
and an interligand angle of C(11)-Ga(1)-(C21) ) 107.1-
(3)°. The angles at the R-carbon atoms of the ethyl
groups are larger than the normal tetrahedral value of
109.5°, with Ga(1)-C(11)-C(12) ) 119.9(6)° and Ga-
(1)-C(21)-C(22) ) 118.0(6)°. The carbon-carbon dis-
tances within the ethyl groups are anomalously short
as a result of artificial librational contraction, with
C(11)-C(12) ) 1.380(12) Å and C(21)-C(22) ) 1.418-
(13) Å. Note that there are large anisotropic displace-
ment coefficients for these atoms (viz., U22 for C(11) is
0.125(7) Å2, while U22 for C(12) is 0.228(12) Å2; U22 for
C(21) is 0.113(6) Å2, while U22 for C(22) is 0.285(15) Å2).
The bridging di-tert-butylphosphide ligands are associ-
ated with bond lengths of P(1)-C(31) ) 1.904(6) Å and
P(1)-C(41) ) 1.900(6) Å and an interligand angle of
(20) Dillingham; M. D. B.; Burns, J . A.; Byers-Hill, J ; Gripper, K.
D.; Pennington, W. T.; Robinson, G. H. Inorg. Chem. Acta 1994, 216,
267.
(21) Heaton, D. E.; J ones, R. A.; Kidd, K. B.; Cowley, A. H.; Nunn,
C. M. Polyhedron 1988, 7, 1901.
(22) Banks, M. A.; Beachley, O. T., J r.; Buttrey, L. A.; Churchill,
M. R.; Fettinger, J . C. Organometallics 1991, 10, 1901.
(23) Wells, R. L.; Self, M. F.; McPhail, A. T.; Aubuchon, S. R.
Organometallics 1993, 12, 2832.
(24) Aubuchon, S. R.; McPhail, A. T.; Wells, R. L.; Giambra, J . A.;
Bowser, J . R. Chem. Mater. 1994, 6, 82.
(25) Power, M. B.; Barron, A. R. J . Chem. Soc., Chem. Commun.
1991, 1315.
(26) Hoffman, G. G.; Burschka, C. J . Organomet. Chem. 1984, 267,
229.
(27) Ghazi, S. U.; Heeg, M. J .; Oliver, J . P. Inorg. Chem. 1994, 33,
4517.
(28) Hendershot, D. G.; Kumar, R.; Barber, M.; Oliver, J . P.
Organometallics 1991, 10, 1917.
(19) Oliver, J . P. J . Organometal. Chem. 1995, 500, 269 (see
references cited therein).
(29) Hoffman, G. G.; Burschka, C. Angew. Chem., Int. Ed. Engl.
1985, 24, 970.

3656 Organometallics, Vol. 15, No. 17, 1996
Beachley et al.
F igu r e 2. Molecular geometry of [Et2GaS(SiPh3)]2. ORTEP2 diagram, 30% probability ellipsoids for non-hydrogen atoms
with hydrogen atoms artificially reduced.
Ta ble 2. Im p or ta n t In ter a tom ic Dista n ces (Å) a n d
An gles (d eg) for [Et2Ga S(SiP h 3)]2
are well-behaved with all 18 C-C bonds in the range
1.353(16)-1.392(13) Å. One point worthy of note is a
consistent reduction from the ideal trigonal value for
the internal angles at the ipso carbon atoms (viz.,
C(12)-C(11)-C(16) ) 115.2(8)°, C(22)-C(21)-C(26) )
115.4(10)°, and C(32)-C(31)-C(36) ) 116.7(6)°).
(A) Bond Lengths (Å)
Ga(1)-S(1)
Ga(1)-C(3)
S(1)-Si(1)
Si(1)-C(11)
Si(1)-C(31)
C(3)-C(4)
2.450(2)
1.971(11)
2.148(3)
1.861(9)
1.864(6)
1.446(11)
Ga(1)-C(1)
Ga(1)-S(1A)
S(1)-Ga(1A)
Si(1)-C(21)
C(1)-C(2)
1.934(14)
2.396(2)
2.396(2)
1.864(11)
1.437(14)
The reagents Et2Ga(C5H5) and HN(H)(t-Bu) or HS-
SiPh3 have been used to synthesize [Et2GaN(H)(t-Bu)]2
and [Et2GaSSiPh3]2 in high yields of the isolated
products at room temperature. In order to learn more
(B) Bond Angles (deg)
S(1)-Ga(1)-C(1)
C(1)-Ga(1)-C(3)
C(1)-Ga(1)-S(1A)
Ga(1)-S(1)-Si(1)
112.3(3)
125.1(4)
108.8(2)
124.0(1)
S(1)-Ga(1)-C(3)
102.1(3)
88.1(1)
113.8(3)
91.9(1)
107.1(3)
109.8(4)
110.9(3)
119.6(8)
122.7(8)
S(1)-Ga(1)-S(1A)
C(3)-Ga(1)-S(1A)
Ga(1)-S(1)-Ga(1A)
S(1)-Si(1)-C(11)
C(11)-Si(1)-C(21)
C(11)-Si(1)-C(31)
Ga(1)-C(1)-C(2)
Si(1)-C(11)-C(12)
1
about the nature of these reactions, H NMR spectros-
copy was used to probe the relative rates of the cyclo-
pentadiene elimination reaction and to measure the
extent of the overall reaction in solution with time.
Stoichiometric quantities of the reagents were combined
in sufficient C6D6 to form solutions with concentrations
which were comparable to those used in the synthetic
Si(1)-S(1)-Ga(1A) 114.8(1)
S(1)-Si(1)-C(21)
S(1)-Si(1)-C(31)
115.3(2)
105.2(3)
C(21)-Si(1)-C(31) 108.5(4)
Ga(1)-C(3)-C(4)
114.4(8)
Si(1)-C(11)-C(16) 122.0(7)
Si(1)-C(21)-C(22) 121.6(8)
C(12)-C(11)-C(16) 115.2(8)
Si(1)-C(21)-C(26)
1
122.9(6)
122.9(6)
reactions. When the H NMR spectrum of the reagents
C(22)-C(21)-C(26) 115.4(10) Si(1)-C(31)-C(32)
upon mixing was observed, the only observed lines were
those of the adducts of Et2Ga(C5H5), EtGa(C5H5)2, and
GaEt3 with either the amine or the thiol. The spectrum
was qualitatively similar to that observed when pure
Et2Ga(C5H5) was dissolved in benzene,5 but the chemi-
cal shifts were different due to the formation of adducts.
Lines for products were not observed. These observa-
tions confirm the occurrence of the ligand redistribution
reaction5 (eq 3) and the presence of multiple gallium
species when solutions of Et2Ga(C5H5) are in the pres-
ence of Lewis bases with acidic protons but also dem-
onstrate that the elimination reaction with this base is
either suprisingly slow or the equilibrium constant for
the reaction is very small. In the case of the reaction
with HN(H)(t-Bu), evidence of product formation was
Si(1)-C(31)-C(36) 120.4(5)
C(32)-C(31)-C(36) 116.7(6)
The two SiPh3 substituents in [Et2GaS(SiPh3)]2 take
up the same mutually trans configuration as has been
observed for other gallium-thiolate derivatives.19 Each
S(SiPh3) ligand is associated with a S(1)-Si(1) bond
length of 2.148(3) Å and Si-Ph distances of Si(1)-C(11)
) 1.861(9) Å, Si(1)-C(21) ) 1.864(11) Å, and Si(1)-
C(31) ) 1.864(11) Å. Angles about silicon range from
105.2(3)° to 115.3(2)°. The S-Si-Ph angles are rather
irregular (S(1)-Si(1)-C(31) ) 105.2(3)°, S(1)-Si(1)-
C(11) ) 107.1(3)°, and S(1)-Si(1)-C(21) ) 115.3(2)°),
while the Ph-Si-Ph angles are closer in value (C(21)-
Si(1)-C(31) ) 108.5(4)°, C(11)-Si(1)-C(21) ) 109.8(4)°,
and C(11)-Si(1)-C(31) ) 110.9(3)°). The phenyl groups

Diethylgallium-Amides, -Phosphides, and -Thiolates
Organometallics, Vol. 15, No. 17, 1996 3657
noted only after 31/2 h at room temperature by the
occurrence of lines for the t-Bu groups of the cis and
trans isomers of [Et2GaN(H)(t-Bu)]2, 1.02 and 1.00 ppm,
respectively. The lines for the gallium-nitrogen prod-
ucts continued to grow such that the reaction was
approximately 37% complete after 2 days at room
temperature, 43% complete after 3 days, and 49%
complete after 4 days. Then, heating of the NMR tube
at 65 °C was initiated. After approximately 15 h of
heating, the spectrum was consistent with the presence
of only two gallium species, the cis and trans isomers
of the dimeric product. The chemical shifts of all lines
were identical with those observed for the product
isolated from the synthetic experiment. All lines for the
three initial gallium species had disappeared. In the
case of the thiol with the bulky SiPh3 group, the Lewis
base with the more acidic proton, the spectrum did not
change from that initially observed, even after heating
at 45 °C for 2 weeks. Proton NMR lines for the product
were not observed. Thus, since [Et2GaN(H)(t-Bu)]2 and
[Et2GaS(SiPh3)]2 can be isolated in high yield after
cyclopentadiene elimination reactions at room temper-
ature, removal of the cyclopentadiene monomer by
either dimerization or distillation and/or dimerization
of the gallium product to prevent the back-reaction of
the cyclopentadiene must be necessary to produce the
observed high yields of products.
Then, approximately 50 mL of pentane was distilled onto the
Et2Ga(C5H5) at -196 °C. The amine or phosphine was then
vacuum distilled onto the Et2Ga(C5H5)-solvent mixture. Fi-
nally, the flask was warmed from -196 °C to ambient
temperature and stirred overnight. The reactions of Et2Ga-
(C5H5) with HS(SiPh3), HP(i-Pr)2, and HP(t-Bu)2 were carried
out in benzene rather then pentane for reaction times of 2 h,
2 weeks, and 2 days, respectively. Liquid products were
quantitatively transferred to small flasks with stir bars by
washing with pentane, and then the flask was attached to a
short-path still connected to a preweighed receiving flask. The
pentane was removed by vacuum distillation at room temper-
ature, and then heat was applied by means of an oil bath to
distill the product.
[Et2Ga N(H)(t-Bu )]2. Product purified by vacuum distilla-
tion, oil bath at 90 °C; bp, 70 °C (<10-3 mmHg); yield 95%;
mp, 17-20.5 °C. 1H NMR (C6D6): δ 1.36 (t, CH2CH3, cis), 1.30
(t, CH2CH3, trans), 1.27 (t, CH2CH3, cis), 1.02 (s, C(CH3)3, cis,
2.0H), 1.00 (s, C(CH3)3, trans, 6.4H), 0.68 (dq, J ) 12Hz, CH2-
CH3, trans), 0.43 (dq, J ) 12 Hz, CH2CH3, trans), 0.66 (q, CH2-
CH3, cis), 0.41 (q, CH2CH3, cis). Anal. Calcd for C8H20GaN:
C, 48.05%; H, 10.08%. Found: C, 48.11%; H, 10.11%. Cryo-
scopic molecular weight, benzene solution, fw 200 (obsd
molality, obsd mol wt, association): 0.090, 384, 1.93; 0.068,
377, 1.88, 0.041, 344, 1.73.
[Et2Ga N(H)(Me)]2. Product purified by vacuum distilla-
tion, oil bath at 125 °C; bp, 45 °C (<10-3 mmHg); yield, 85%.
1H NMR (C6D6): δ 2.12 (d, NCH3, cis), 2.10 (d, NCH3, trans),
1.28 (t, CH2CH3, cis), 1.23 (t, CH2CH3, trans), 1.19 (t, CH2CH3,
cis), 0.38 (dq, J ) 12 Hz, CH2CH3, trans), 0.55 (q, CH2CH3,
cis), 0.52 (dq, J ) 12 Hz, CH2CH3, trans), 0.35 (q, CH2CH3,
cis). Approximate equal molar quantities of cis and trans
isomers were observed. Anal. Calcd for C5H14GaN: C,
38.04%; H, 8.94%. Found: C, 38.56%; H, 8.62%. Cryoscopic
molecular weight, benzene solution, fw 158 (obsd molality, obsd
mol wt, association): 0.126, 327, 2.08; 0.098, 310, 1.97, 0.072,
316, 2.00; 0.063, 312, 1.98; 0.047, 314, 1.99.
[Et2Ga NEt2]2. Product purified by vacuum distillation, oil
bath at 100 °C; bp, 70 °C (<10-3 mmHg); yield, 90%. 1H NMR
(C6D6): δ 2.72 (q, NCH2CH3, 2H), 1.31 (t, GaCH2CH3, 3H), 0.78
(t, NCH2CH3, 3H), 0.55 (q, GaCH2CH3, 2H). Mass spectrum
(m/e, relative intensity): 371 (dimer - Et+), 91; 198 (monomer
- H+), 43; 170 (monomer - Et+), 91; 127 (Et2Ga+), 93; 100
(EtGa+), 66; 69 (Ga+), 100. Anal. Calcd for C4H20GaN: C,
48.05%; H, 10.08%; N, 7.00%. Found: C, 48.52%; H, 9.76%;
N, 7.39%. Cryoscopic molecular weight, benzene solution, fw
200 (obsd molality, obsd mol wt, association): 0.086, 424, 2.12;
0.053, 414, 2.07, 0.034, 422, 2.11.
Exp er im en ta l Section
All compounds described in this investigation were ex-
tremely sensitive to oxygen and moisture and were manipu-
lated in a standard vacuum line or in a purified argon
atmosphere. The starting compound Et2Ga(C5H5) was pre-
pared and purified by the literature method.5 Amines were
dried over KOH and distilled prior to use. Phosphines were
vacuum distilled prior to use. The compound HS(SiPh3) was
purchased from Aldrich Chemical Co. and used as received.
Solvents were dried by conventional procedures. Elemental
analyses were performed by E+R Microanalytical Laborato-
1
ries, Inc., Corona, NY. The H NMR spectra were recorded at
400 MHz by using a Varian VXR-400 spectrometer. Proton
chemical shifts are reported in δ units (ppm) and are refer-
enced to SiMe4 at δ 0.00 and C6H6 at δ 7.15. The 31P NMR
spectra were recorded at 161.9 MHz by using a Varian VXR-
400 spectrometer and are referenced to 85% H3PO4 at δ 0.00.
The following abbreviations are used to report the multiplici-
ties of lines: s (singlet), d (doublet), t (triplet), q (quartet), br
(broad), st (septet of triplets), dq (doublet of quartets), qt
(quartet of triplets). All samples for NMR spectra were
contained in sealed NMR tubes. Infrared spectra were re-
corded for either neat liquids, Nujol solutions of liquids, or as
Nujol mulls for solids by using CsI plates and a Perkin-Elmer
Model 683 spectrometer. Absorption intensities are reported
with abbreviations w (weak), m (medium), s (strong), vs (very
strong), and sh (shoulder). The spectroscopic data are avail-
able with the Supporting Information. Melting points were
observed in sealed capillaries and are uncorrected. Molecular
weights were measured cryoscopically in benzene by using an
instrument similar to that described by Shriver.30 Mass
spectra were obtained by Electron Impact with a VG Model
70-SE high-resolution mass spectrometer.
[Et2Ga P (i-P r )2]2. Viscous product purified by first washing
with pentane at -78 °C and then vacuum distillation, oil bath
at 72 °C; bp, 70 °C (<10-3 mmHg); yield, 72%. 1H NMR (C6D6):
δ 2.18 (st, J P-H ) 2Hz, J H-H ) 7.2Hz, PC(CH3)2H, 1H), 1.40
(t, GaCH2CH3, 3H), 1.16 (q, J ) 7.2 Hz, PC(CH3)2H, 6H), 0.84
(qt, 3J P-H ) 2.4 Hz, J H-H ) 8.4 Hz, GaCH2CH3, 2H). 31P{1H};
NMR: δ -5.72 (s); Mass Spectrum (m/e, relative intensity):
461 (dimer - Et+), 11; 373 (dimer - P(i-Pr)2+), 14; 303 (dimer -
GaP(i-Pr)2+), 6; 215 (EtGaP(i-Pr)2+), 35; 127 (Et2Ga+), 70; 118
(P(i-Pr)2+), 21; 99 (GaP+), 10; 69 (Ga+), 93. Anal. Calcd for
C
10H24GaP: C, 49.03%; H, 9.87%. Found: C, 48.97%; H,
9.83%. Cryoscopic molecular weight, benzene solution, fw 245
(obsd molality, obsd mol wt, association): 0.076, 505, 2.06;
0.061, 497, 2.03, 0.040, 497, 2.03.
[Et2Ga P (t-Bu )2]2. Product purified by recrystallization
from pentane at -40 °C; 64% yield; mp 160.8-162 °C (dec.).
1H NMR (C6D6): δ 1.43 (t, GaCH2CH3, 3H), 1.33 (t, J ) 7.0
Hz, PC(CH3)3, 9H), 1.00 (q, GaCH2CH3, 2H). 31P{1H} NMR:
δ 35.22 (s). Anal. Calcd for C12H28GaP: C, 52.79%; H, 10.34%.
Found: C, 52.84%; H, 10.41%. Insufficient solubility in
benzene for cryoscopic molecular weight studies.
Rea ction of Et2Ga (C5H5) w ith HERR′ a n d HE′R (E )
N, P ; E′ ) S). In a typical experiment, a quantity (1-8 mmol)
of the appropriate amine or phosphine was vacuum distilled
into a tared tube equipped with a Teflon valve and standard
taper joint. Next, a stoichiometric quantity of Et2Ga(C5H5) was
placed in a Schlenk flask equipped with a magnetic stir bar.
[Et2Ga S(SiP h 3)]2. Product purified by recrystallization
from methylcyclohexane at -40 °C; 81% yield; mp 157.8-158.1
°C. 1H NMR (C6D6): δ 7.75-7.78 (m, o-Ph-H, 6H), 7.10-7.12
(m, m,p-Ph-H, 9H), 1.07 (t, CH2CH3, 6H), 0.68 (q, CH2CH3,
(30) Shriver, D. F. The Manipulations of Air-Sensitive Compounds;
McGraw-Hill: New York, 1968; p 38.

3658 Organometallics, Vol. 15, No. 17, 1996
Beachley et al.
Ta ble 3. Da ta for X-r a y Str u ctu r a l Stu d ies of
[Et2Ga P (t-Bu )2]2 a n d [Et2Ga S(SiP h 3)]2
4H). Anal. Calcd for C22H25GaSSi: C, 63.02%; H, 6.01%.
Found: C, 62.98%; H, 6.11%. Cryoscopic molecular weight,
benzene solution, fw 419 (obsd molality, obsd mol wt, associa-
tion): 0.049, 811, 1.93; 0.038, 812, 1.94, 0.026, 833, 1.99.
[Et2GaP(t-Bu)2]2
[Et2GaS(SiPh3)]2
mol formula
cryst syst.
space group
a, Å
C24H56Ga2P2
monoclinic
P21/n (No. 14)
8.8379(11)
11.5032(19)
14.6460(28)
90.000
91.010(10)
90.000
1488.2(4)
2
C44H50Ga2S2Si2
triclinic
Rea ction of Ga Et3 a n d HS(SiP h 3) in a 1:1 Mole Ra tio.
A break-seal tube, which was charged with 0.23 g (0.78 mmol)
of HS(SiPh3) and 0.12 g (0.78 mmol) of GaEt3, was sealed by
fusion and then warmed from -196 °C to room temperature.
The tube which initially contained a light yellow solid was
gradually heated to 70 °C over the period of 2 h. The resulting
colorless solid and condensible gas, presumed to be ethane by
its physical properties (0.025 g, 0.83 mmol, 100% yield) and
1H NMR spectrum (1H NMR (C6D6): δ 0.80 (s)) were separated
by vacuum distillation. The crude solid was identified as [Et2-
GaS(SiPh3)]2 (0.28 g, 0.67 mmol, 87% yield) by comparison of
its properties with those for the compound prepared by the
other route; mp 155.2-155.7 °C. 1H NMR (C6D6): δ 7.77-7.79
(m, o-Ph-H, 6H), 7.12-7.14 (m, m,p-Ph-H, 9H), 1.09 (t,
CH2CH3, 6H), 0.70 (q, CH2CH3, 4H).
P1h (No. 2)
9.2715(15)
9.5413(13)
14.1872(22)
71.135(11)
89.409(13)
65.247(10)
1067.0(3)
1
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
mol wt
546.1
1.219
1.918
838.6
1.305
1.435
0.8527/0.9445
5.0-45.0
D(calc), g cm-3
µ(Mo KR), mm-1
transm coeff., min/max 0.3808/0.5013
2θ range, deg
index ranges
5.0-45.0
h
k
l
-9 to +9
-12 to +12
-15 to +0
4075
1960 (Rint
1170
0 to +9
Stu d ies of Rela tive Ra tes of Rea ction by NMR Sp ec-
tr oscop y. (a ) Et2Ga (C5H5) a n d HS(SiP h 3). An NMR tube
was charged with 0.024 g (0.08 mmol) of HSSiPh3, 0.016 g (0.08
mmol) of Et2Ga(C5H5), and approximately 1 mL of C6D6 at
-196 °C and then sealed by fusion. The tube was used for an
1H NMR study as described in the Results and Discussion.
-10 to +10
-15 to +15
no. of reflns collecd
no. of unique reflns
no. of reflns > 6σ
R indices (6σ data)
R, %
3002
) 2.45%) 2793 (Rint ) 1.70%)
1261
4.33
4.96
4.36
3.29
(b) Et2Ga (C5H5) a n d HN(H)(t-Bu ). An NMR tube was
charged with 0.049 g (0.26 mmol) of Et2Ga(C5H5), 0.037 g (0.26
mmol) of HN(H)(t-Bu), and approximately 1 mL of C6D6 in
order to investigate the relative rate of formation of [Et2GaN-
(H)(t-Bu)]2 (see Results and Discussion).
Rw, %
R indices (all data)
R, %
7.16
7.66
11.56
4.27
0.35
Rw, %
largest diff peak, e/Å3 0.80
deepest diff peak, e/Å3 -0.48
-0.30
Collect ion of X-r a y Diffr a ct ion Da t a . In each case
crystals were sealed into thin-walled glass capillaries in an
argon atmosphere inside a drybox kept under strictly anaero-
bic and moisture-free conditions. The crystals were inspected
under a binocular polarizing microscope to ensure that they
were single; they were then centered accurately on a Siemens
R3m/V automated four-circle diffractometer. The unit cell
parameters and Laue symmetry were determined as described
previously.31 Intensity data (Mo KR, λh ) 0.710 730 Å) were
collected at ambient temperatures (23-25 °C) with graphite-
monochromatized radiation. Data were corrected for absorp-
tion and for Lorentz and polarization factors. Details are
provided in Table 3.
dispersion.34 The structures were solved by direct methods
and difference-Fourier syntheses. All non-hydrogen atoms
were located, and their positional and anisotropic thermal
parameters were refined. Hydrogen atoms were included in
calculated positions based upon d(C-H) ) 0.96 Å and the
appropriate idealized trigonal or tetrahedral geometry.35 Re-
finement was continued until ∆/σ < 0.003 for each parameter.
The correctness of each structure was confirmed by means of
a final difference-Fourier synthesis.
(a ) [Et2Ga P (t-Bu )2]2. The molecule is centered on the
inversion center at 0, 0, 1/2. The Ga2P2 ring is therefore
required to be planar. Final discrepancy indices are R ) 4.33%
for those 1170 data with Fo > 6σ(Fo) and R ) 7.16% for all
1960 reflections. (Note that only 59.7% of the data are above
6σ(Fo).)
(b) [Et2Ga S(SiP h 3)]2. The molecule lies about the inver-
sion center at 0, 0, 1/2. The Ga2S2 ring is required, by
symmetry, to be strictly planar. The final discrepancy indices
are R ) 4.36% for those 1261 reflections with Fo > 6σ(F) and
R ) 11.56% for all 2793 reflections. (The unattractively high
R-value for all data simply reflects the problem of a very weak
data setsonly 45.1% of the data are above 6σ(Fo).)
(a ) [Et2Ga P (t-Bu )2]2. The crystal was of dimensions 0.35
× 0.30 × 0.30 mm. The crystal belonged to the monoclinic
system (2/m diffraction symmetry); the systematic absences
h0l for h + l ) 2n + 1 and 0k0 for k ) 2n + 1 uniquely define
the centrosymmetric monoclinic space group P21/n (No. 14
var.). One hemisphere of data, (i.e., two equivalent forms, hhkhl
) hhkhhl and hkhl ) hkhhl) was collected. The 4075 reflections thus
collected were merged to 1960 independent, space-group
allowed data with Rint ) 2.45%.
(b) [Et2Ga S(SiP h 3)]2. The crystal was rather small but
equidimensional (0.2 × 0.2 × 0.2 mm). It was found to belong
to the triclinic system (1h diffraction symmetry). Possible space
groups are the noncentrosymmetric space group P1 (No. 1) and
the centrosymmetric space group P1h (No. 2). The centrosym-
metric possibility is far more probable,32 particularly for
synthetic materials; the space group P1h was thus assumed and
was confirmed by the successful solution of the structure.
Ack n ow led gm en t. This work was supported in part
by the Office of Naval Research (O.T.B.). The upgrading
of the X-ray diffractometer was made possible by Grant
89-13733 from the Chemical Instrumentation Program
of the National Science Foundation.
Deter m in a tion of th e Cr ysta l Str u ctu r es. All crystal-
lographic calculations were carried out on a VAXstation 3100
computer with use of the Siemens SHELXTL PLUS (Release
4.11 (VMS)) program package.33 The scattering factors used
were the analytical values for neutral atoms; these were
corrected for both components (∆f′ and i∆f′′) of anomalous
Su p p or tin g In for m a tion Ava ila ble: Complete tables of
positional parameters, interatomic distances and angles,
anisotropic thermal parameters, and calculated positions for
hydrogen atoms, and infrared absorptions for each compound
(15 pages). For ordering information see any current mast-
head page.
(31) Churchill, M. R.; Lashewycz, R. A.; Rotella, F. J . Inorg. Chem.
1977, 16, 265.
OM960284P
(32) Nowacki, W.; Matsumato, T.; Edenharter, A. Acta Crystallogr.
1967, 22, 935.
(33) Sheldrick, G. M. SHELXTL PLUS, Release 4.11 (VMS), Si-
emens Analytical Instrument Corp.; Madison, WI, 1989.
(34) International Tables for X-Ray Crystallography; Kynoch
Press: Birmingham, England, 1974, Vol. 4, pp 99-101 and 149-150.
(35) Churchill, M. R. Inorg. Chem. 1973, 12, 1213.