Synthesis of substituted aminogallanes by alkyltrimethyltin elimination

Article abstract of DOI:10.1021/om950812h

Alkyltrimethyltin elimination reactions of R₃Ga (R = Me, Et) with R″R′NSnMe₃ (R″ = i-Bu, SnMe₃, C₆H₁₁ and R′ = i-Bu, i-Pr, C₆H₁₁) have been investigated. The aminogallanes [Me

Full text of DOI:10.1021/om950812h

1728
Organometallics 1996, 15, 1728-1733
Syn th esis of Su bstitu ted Am in oga lla n es by
Alk yltr im eth yltin Elim in a tion
W. Rodger Nutt,*,1a Kelly J . Murray,1a J ames M. Gulick,1b J erome D. Odom,1b
Yan Ding,1b and Lukasz Lebioda1b
Departments of Chemistry, Martin Chemical Laboratory, Davidson College,
Davidson, North Carolina 28036, and University of South Carolina,
Columbia, South Carolina 29208
Received October 13, 1995X
Alkyltrimethyltin elimination reactions of R3Ga (R ) Me, Et) with R′′R′NSnMe3 (R′′ )
i-Bu, SnMe3, C6H11 and R′ ) i-Bu, i-Pr, C6H11) have been investigated. The aminogallanes
[Me2GaN(i-Bu)2]2, [Et2GaN(i-Bu)2]2, [Me2GaN(i-Pr)SnMe3]2, [Me2GaN(C6H11)2]2, and [Et2GaN-
(C6H11)2]2 were isolated in 88.6, 68.6, 69.1, 81.0, and 80.4% yields, respectively. X-ray
crystallographic studies of [Et2GaN(i-Bu)2]2, [Me2GaN(i-Pr)SnMe3]2, [Me2GaN(C6H11)2]2, and
[Et2GaN(C6H11)2]2 indicate that the four aminogallanes are dimeric in the solid state. The
four-membered (Ga-N)2 rings in [Et2GaN(i-Bu)2]2 and [Et2GaN(C6H11)2]2 (molecules 1 and
2) are nonplanar with fold angles on the Ga‚‚‚Ga diagonals of 148.7(3) and 146.3(3), 147.7
1
(3)°. All five aminogallanes exist as dimers in benzene solutions. The H and 13C NMR
spectra are reported and discussed.
In tr od u ction
evolution had ceased. The product [(PhMe2CCH2)2-
GaN(H)Pr]2 was obtained in 83% yield. In the case of
the Bu3Ga/HNEt2 reaction, the reactants were heated
to boiling for 1.5 h. Interestingly, the reactions of (c-
C3H5)3Ga with ethyleneimine and (i-Pr)3Ga‚OEt2 with
HN(i-Pr)2 in benzene proceeded at or below room
temperature and the aminogallanes were isolated in 85
and 90% yields. Also, Me2Ga{2-[N(CH2C6H5)]NC5H4}-
(OEt2) was obtained in 73% yield from the reaction of
Me3Ga (prepared in situ) with 2-(benzylamino)pyridine
in diethyl ether at room temperature.2n The alkane
elimination reaction offers a simple, single-step syn-
thetic route to aminogallanes. Generally, this synthetic
procedure does not require a solvent and the yields are
high. However, in most cases temperatures above 100
°C are needed to effect the formation of the aminogal-
lane.
Traditionally, the alkane elimination (eq 1) reaction
has been utilized to prepare the substituted aminogal-
lanes R2GaNR′R′′ (R and R′′ ) alkyl or aryl and R′ )
H, alkyl, or aryl). Elimination reactions between Me3-
R3Ga + HNR′R′′ f R2GaNR′R′′ + RH
(1)
Ga and 10 different primary amines have been re-
ported.2a-f Typically, toluene solutions of the reactants,
the reactants in sealed tubes, or the Lewis acid-base
adducts of the reactants were heated at temperatures
from 100 to 160 °C for periods of 7-24 h and the
resulting aminogallanes were isolated in yields that
varied from 67 to 100%. Reactions of Me3Ga with
secondary2f,g or heterocyclic2h amines also have been
found to proceed under similar reaction conditions with
comparable yields. Examples of elimination reactions
that have involved trialkylgallium compounds other
than Me3Ga include those of Et3Ga with ethyleneimine,2g
(PhMe2CCH2)3Ga with H2NPr,2i Et3Ga or (i-Bu)3Ga with
piperidine,2j Bu3Ga with HNEt2,2k (c-C3H5)3Ga with
ethyleneimine,2l and (i-Pr)3Ga‚OEt2 with HN(i-Pr)2.2m
The first three reactions required temperatures of 120
°C or above for a period of several days or until gas
A number of monomeric3ab and dimeric3c-g aminogal-
lanes have been prepared by LiCl elimination (eqs 2 and
3). In these examples hexane, diethyl ether, or hexane/
R2GaCl + LiNR′R′′ f R2GaNR′R′′ + LiCl (2)
Cl2GaNR′2 + 2LiMe f Me2GaNR′2 + 2LiCl (3)
diethyl ether solutions of the reactants were mixed at
or below 0 °C and the resulting mixtures were stirred
at room temperature or heated for a period of 4-18 h.
The yields varied from 52 to 86%. This synthetic
method offers the advantage of a facile, low-temperature
pathway to the preparation of aminogallanes with bulky
X Abstract published in Advance ACS Abstracts, February 15, 1996.
(1) (a) Davidson College. (b) University of South Carolina.
(2) (a) Waggoner, K. M.; Power, P. P. J . Am. Chem. Soc. 1991, 113,
3393. (b) Byers, J . J .; Lee, B.; Pennington, W. T.; Robinson, G. H.
Polyhedron 1992, 11, 967. (c) Lee, B.; Pennington, W. T.; Robinson, G.
H. Inorg. Chim. Acta 1991, 190, 173. (d) Park, J . T.; Kim, Y.; Kim, J .;
Kim, Y. Organometallics 1992, 11, 3320. (e) Ferry, J . M.; Cole-
Hamilton, D. J .; Mullin, J . B. Chemtronics 1989, 4, 141. (f) Coates, G.
E. J . Chem. Soc. 1951, 2003. (g) Storr, A.; Thomas, B. S. J . Chem.
Soc. (A) 1971, 3850. (h) Beachley, O. T., J r.; Bueno, C.; Churchill, M.
R.; Hallock, R. B.; Simmons, R. G. Inorg. Chem. 1981, 20, 2423. (i)
Beachley, O. T., J r.; Noble, M. J .; Churchill, M. R.; Lake, C. H.
Organometallics 1992, 11, 1051. (j) Sen, B.; White, L. J . Inorg. Nucl.
Chem. 1973, 35, 2207. (k) Haran, R.; J ouany, C.; Laurent, J . P. Bull.
Soc. Chem. Fr. 1968, 457. (l) Mu¨ller, J .; Margiolis, K.; Dehnicke, K. J .
Organomet. Chem. 1972, 46, 219. (m) Hoffmann, G. G.; Fischer, R. Z.
Anorg. Allg. Chem. 1990, 590, 181. (n) Zhou, Y.; Richeson, D. S.
Organometallics 1995, 14, 3558.
(3) (a) Waggoner, K. M.; Ruhlandt-Senge, K.; Wehmschulte, R. J .;
He, X.; Olmstead, M. M.; Power, P. P. Inorg. Chem. 1993, 32, 2557.
(b) Brothers, P. J .; Wehmschulte, R. J .; Olmstead, M. M.; Ruhlandt-
Senge, K.; Parkin, S. R.; Power, P. P. Organometallics 1994, 13, 2792.
(c) Bradley, D. C.; Dawes, H. M.; Hursthouse, M. B.; Smith, L. M.;
Thornton-Pett. M. Polyhedron 1990, 9, 343. (d) Atwood, D. A.; J ones,
R. A.; Cowley, A. H.; Bott, S. G.; Atwood, J . L. J . Organomet. Chem.
1992, 434, 143. (e) Atwood, D. A.; J ones, R. A.; Cowley, A. H.; Bott, S.
G.; Atwood, J . L. Polyhedron 1991, 10, 1897. (f) Atwood, D. A.; Atwood,
V. O.; Carriker, D. E.; Cowley, A. H.; Gabbai, F. P.; J ones, R. A.; Bond,
M. R.; Carrano, C. J . J . Organomet. Chem. 1993, 463, 29. (g) Herberich,
G. E.; Englert, U.; Posselt, D. J . Organomet. Chem. 1993, 461, 21.
0276-7333/96/2315-1728$12.00/0 © 1996 American Chemical Society

Synthesis of Substituted Aminogallanes
Organometallics, Vol. 15, No. 6, 1996 1729
benzophenone, calcium hydride, and sodium, respectively, and
distilled into storage flasks. Toluene-d8 (Aldrich Chemical Co.)
was refluxed over calcium hydride and distilled into a storage
flask. All experiments were performed under an oxygen-free,
dry nitrogen or argon atmosphere by using Schlenk and
glovebox techniques.10
The 1H and 13C NMR spectra were obtained from toluene-
d8 solutions with a Bruker AC-300 or AM-500 spectrometer.
The 1H and 13C chemical shifts are reported in parts per million
(ppm) with respect to Me4Si at 0.0 ppm. The 1H chemical
shifts were referenced to the 1H resonance of the residual
CHD2C6D5 (δ 2.09) solvent impurity, and the chemical shifts
in the 13C spectra were referenced to the methyl 13C resonance
of toluene-d8 (δ 20.4). The molecular weights were determined
cryoscopically in benzene with an apparatus similar to that
described by Dilts and Shriver.11 Melting points were obtained
in sealed tubes on an Electrothermal IA 6304 melting point
apparatus and are uncorrected. All elemental analyses were
performed by E + R Microanalytical Laboratory, Corona, NY.
substituents on both the gallium and nitrogen atoms.
The monomeric aminogallanes (t-Bu)2GaN(1-Ad)SiPh3
and Trip2GaNPh2 (1-Ad ) 1-adamantyl; Trip ) 2,4,6-
triisopropylphenyl) were isolated in 67 and 62% yields.3a
However, the procedure requires several steps, the
yields are usually lower than the yields in alkane
elimination reactions, and solvents are needed.
Recently, Me2Ga(C5H5) has been found to undergo a
cyclopentadiene elimination reaction (eq 4) with several
primary and secondary amines.4 These elimination
Me2Ga(C5H5) + HNR′R′′ f Me2GaNR′R′′ + C5H6
(4)
reactions occurred overnight at or below room temper-
ature in benzene or pentane solutions, and the resulting
aminogallanes were obtained in yields of 63-90%. Like
the alkane elimination reaction, the cyclopentadiene
elimination reaction provides a simple, single-step
synthetic route to aminogallanes. Unlike the alkane
elimination reaction, however, reaction temperatures
above 100 °C are not required. However, the elimina-
tion of cyclopentadiene appears to be inhibited when the
amine has bulky substituents. No reaction was ob-
served between Me2Ga(C5H5) and dicyclohexylamine,
2,4,6-tri-tert-butylaniline, or 2,2,4,4-tetramethylpiperi-
dine.
As an extension of our studies of metathetical reac-
tions between substituted gallanes and substituted
aminosilanes,5 the alkyltrimethyltin elimination reac-
tions of Me3Ga or Et3Ga with R′′R′NSnMe3 were inves-
tigated. Exothermic reactions of (n-Bu)3B, Ph3B, or
Et3Al with Me2NSnMe3 in diethyl ether, light petroleum
ether, or benzene solvents have been reported, and the
products (n-Bu)2BNMe2, Ph2BNMe2, and (Et2AlNMe2)2
were isolated in 86, 59, and 50% yields.6 In addition,
t-Bu(H)NSi(Me2)N(t-Bu)GaMe2 was prepared in 94%
yield by allowing GaMe3 to react with t-Bu(H)NSi-
(Me2)N(t-Bu)SnMe3 in benzene at 40 °C.7 These results
suggest that the alkyltrimethyltin elimination reaction
may afford a simple, single-step, low-temperature path-
way to substituted aminogallanes.
Rea ction s of Me3Ga or Et3Ga w ith R′′R′NSn Me3
.
R′′R′NSnMe3 was syringed into a 25 mL ampule that was
equipped with a Teflon valve. The Me3Ga or Et3Ga was trap-
to-trap distilled onto the aminostannane, and the ampule was
allowed to stand at room temperature or was heated. Subse-
quently the volatile components were trap-to-trap distilled
from the reaction solution or mixture and a solid remained.
The composition of the distillate (Me4Sn or EtSnMe3 and
1
unreacted trialkylgallium) was characterized by H NMR.
[Me2Ga N(i-Bu )2]2. A solution of Me3Ga (1.40 g, 12.2 mmol)
and (i-Bu)2NSnMe3 (1.91 g, 6.53 mmol) was heated at 55-56
°C for 6 h. Recrystallization of the solid from pentane gave
[Me2GaN(i-Bu)2]2 (1.32 g, 88.6% yield): mp 72-74 °C; 1H NMR
(500.138 MHz) δ 2.78 (d, NCH2, 4.0H), 1.95 (m, NCH2CH(CH3)2,
2.0H), 0.86 (d, NCH2CH(CH3)2, 12.0H), -0.02 (s, (CH3)2Ga,
5.5H); 13C NMR (125.759 MHz) δ 58.1 (NCH2), 27.1 (NCH2-
CH(CH3)2), 22.5 (NCH2CH(CH3)2), -4.8 ((CH3)2Ga). Anal.
Calcd for C20H48Ga2N2: C, 52.67; H, 10.61; N, 6.14. Found:
C, 52.89; H, 10.81; N, 6.21. Molecular weight for C20H48
-
Ga2N2: calcd, 456; found, 4.5 × 102 (calculated molality
0.0346).
[Et2Ga N(i-Bu )2]2. A solution of Et3Ga (1.81 g, 11.5 mmol)
and (i- Bu)2NSnMe3 (1.74 g, 5.96 mmol) was heated at 56-57
°C for 6 h. Recrystallization of the solid from pentane gave
[Et2GaN(i-Bu)2]2 (1.05 g, 68.6% yield): mp 97-98 °C; 1H NMR
(500.138 MHz) δ 2.87 (d, NCH2, 4.1H), 1.96 (m, NCH2CH(CH3)2,
2.0H), 1.37 (t, (CH3CH2)2Ga, 6.1H), 0.91 (d, NCH2CH(CH3)2,
12.0H), 0.74 (q, (CH3CH2)2Ga, 4.2H); 13C NMR (125.759 MHz)
δ 58.4 (NCH2), 27.5 ((NCH2CH(CH3)2), 22.7 (NCH2CH(CH3)2),
11.2 ((CH3CH2)2Ga), 5.0 ((CH3CH2)2Ga). Anal. Calcd for
Exp er im en ta l Section
C
24H56Ga2N2: C, 56.28; H, 11.02; N, 5.47. Found: C, 56.27;
Ma ter ia ls a n d Gen er a l P r oced u r es. Trimethylgallium,
triethylgallium, and trimethyltin chloride were purchased from
Strem Chemicals and used without further purification. Di-
isobutylamine, isopropylamine, and dicyclohexylamine (Ald-
rich Chemical Co.) were distilled from calcium hydride prior
to use. The compounds (i-Bu)2NSnMe3, i-PrN(SnMe3)2, and
(C6H11)2NSnMe3 were prepared by published procedures.8
Note: trimethyltin compounds are toxic.9 The solvents diethyl
ether, benzene, and pentane were refluxed over sodium/
H, 10.89; N, 5.47. Molecular weight for C24H56Ga2N2: calcd,
512; found, 5.3 × 102 (calculated molality 0.0311).
[Me2Ga N(i-P r )Sn Me3]2. A solution of Me3Ga (1.38 g, 12.0
mmol) and i-PrN(SnMe3)2 (2.04 g, 5.31 mmol) was heated at
44-45 °C for 15.5 h. Recrystallization of the solid from
pentane (2.0 mL)/diethyl ether (1.5 mL) gave [Me2GaN(i-Pr)-
SnMe3]2 (1.18 g, 69.1% yield): mp 151-152 °C; 1H NMR
(300.133 MHz) δ 3.78 (sept, NCH, 1.1H), 1.02 (d, NCH(CH3)2,
2
6.8H), 0.38 (s, (CH3)3Sn, 8.7H, J Sn-H ) 52.7 Hz), -0.09 (s,
(CH3)2Ga, 6.0H); 13C NMR (75.469 MHz) δ 53.6 (NCH, J Sn-C
2
(4) Beachley, O. T., J r.; Royster, T. L.; Arhar, J . R.; Rheingold, A.
L. Organometallics 1993, 12, 1976.
3
) 19.5 Hz), 29.3 (NCH(CH3)2, J Sn-C ) 14.8 Hz), 2.4 ((CH3)3-
(5) (a) Nutt, W. R.; Blanton, J . S.; Boccanfuso, A. M.; Silks, L. A.;
Garber, A. R.; Odom, J . D. Inorg. Chem. 1991, 30, 4136. (b) Nutt, W.
R.; Blanton, J . S.; Kroh, F. O.; Odom, J . D. Inorg. Chem. 1989, 28,
2224. (c) Nutt, W. R.; Anderson, J . A.; Odom, J . D.; Williamson, M.
M.; Rubin, B. H. Inorg. Chem. 1985, 24, 159. (d) Nutt, W. R.; Stimson,
R. E.; Leopold, M. F.; Rubin, B. H. Inorg. Chem. 1982, 21, 1909.
(6) (a) George, T. A.; Lappert, M. F. Chem. Commun. 1966, 463. (b)
George, T. A.; Lappert, M. F. J . Chem. Soc. A 1969, 992.
(7) Veith, M.; Lange, H.; Belo, A.; Recktenwald, O. Chem. Ber. 1985,
118, 1600.
1
Sn, J Sn-C ) 365, 349 Hz), -0.8 ((CH3)2Ga). Anal. Calcd for
C
16H44Ga2N2Sn2: C, 29.96; H, 6.92; N, 4.37. Found: C, 30.13;
H, 7.11; N, 4.44. Molecular weight for C16H44Ga2N2Sn2: calcd,
641; found, 6.3 × 102 (calculated molality 0.0296).
[Me2Ga N(C6H11)2]2. After the ampule had been warmed
to room temperature, the solution of Me3Ga (0.425 g, 3.70
mmol) and (C6H11)2NSnMe3 (0.936 g, 2.72 mmol) slowly
(8) J ones, K.; Lappert, M. F. J . Chem. Soc. 1965, 1944.
(9) Davies, A. G.; Smith, P. J . In Comprehensive Organometallic
Chemistry; Wilkinson, G., Ed.; Pergamon Press: Oxford, U.K., 1982;
Vol. 2, p 608.
(10) Shriver, D. F.; Drezdzon, M. A. The Manipulation of Air-
Sensitive Compounds, 2nd ed.; Wiley-Interscience: New York, 1986.
(11) Dilts, J . A.; Shriver, D. F. J . Am. Chem. Soc. 1968, 90, 5769.

1730 Organometallics, Vol. 15, No. 6, 1996
Ta ble 1. Exp er im en ta l Da ta fr om th e X-r a y Diffr a ction Stu d y
Nutt et al.
[Et2GaN(i-Bu)2]2
[Me2Ga(i-Pr)SnMe3]2
[Me2GaN(C6H11)2]2
[Et2GaN(C6H11)2]2
cryst syst
space group
cell dimensa
a, Å
b, Å
c, Å
monoclinic
P21/n (No. 14)
monoclinic
P21/n (No. 14)
monoclinic
P21/c (No. 14)
triclinic
P1h (No. 2)
10.252(4)
24.129(8)
12.086(5)
8.770(2)
15.124(3)
9.622(1)
11.560(6)
9.537(2)
13.509(7)
19.024(6)
19.325(8)
10.158(2)
100.17(3)
102.25(2)
109.83(3)
3305(61)
4
R, deg
â, deg
101.75(3)
94.82(1)
107.14(4)
γ, deg
V, Å3
2927(21)
4
1271(2)
2
1423(19)
2
Z
mol wt
512.2
1.16
641.4
1.68
560.2
1.31
Mo KRj (0.71069Å)
616.3
1.24
F(calcd), g cm-3
radiation
monochromator
2θ range, deg
scan type
scan speed, deg min-1
scan width, deg
no. of unique data
graphite
4-46
ω/2θ
1-3 (in ω)
0.8 + 0.35 tan θ
4406
3716
0.0655
0.0574
1768
2158
1840
0.0613
0.0685
9179
2
2
no. of unique data with F0 > 3σ(F0
)
Rb
Rw
0.0326d
0.0799e
0.0824d
0.1495e
c
a
Unit cell parameters were derived from a least-squares refinement of 25 reflections: 11.63° e θ e 13.78°, 9.31° e θ e 12.31°, 10.01°
e θ e 13.99°, 9.47° e θ e 12.05°. R ) ∑||Fo| - |Fc||/∑|Fo|. c Rw ) [∑||Fo| - |Fc||w1/2/∑|Fo|w1,2]. R1 for all reflection data in SHELXL-93.
b
d
e wR2 ) [∑w(Fo - Fc2)/∑w(Fo2)2]1/2 for all reflection data in SHELXL-93.
2
converted to a waxy, white solid over a period of 1.2 h. The
ampule was allowed to stand at room temperature for 20.3 h,
and a powdery, white solid along with a liquid formed.
Recrystallization of the solid from pentane gave [Me2GaN-
(C6H11)2]2 (0.617 g, 81.0% yield): mp 190-191 °C; 1H NMR
H, 10.74; N, 4.67. Molecular weight for C32H64Ga2N2: calcd,
616; found, 5.9 × 102 (calculated molality 0.0277).
X-r a y Cr ysta llogr a p h ic An a lysis. Colorless crystals of
[Et2GaN(i-Bu)2]2, [Me2GaN(i-Pr)SnMe3]2, [Me2GaN(C6H11)2]2,
and [Et2GaN(C6H11)2]2 were mounted in capillary tubes under
a nitrogen atmosphere. The determination of the unit cell and
the collection of the intensity data were made on a CAD-4
diffractometer equipped with a graphite monochromator. Unit
cell parameters and details of the data collection are given in
Table 1. The positions of the C, N, Ga, and Sn atoms were
taken from Patterson maps. After several cycles of a full-
matrix least-squares refinement with all non-hydrogen atoms
anisotropic, the hydrogen atoms were generated at calculated
positions (C-H ) 0.96 Å; H-C-H ) 109.5°) with rigid
geometry. Additional cycles of refinement led to convergence.
All calculations were performed on a DEC VAX 8530 or IBM
PS/2 Model 90 computer using ORFFE4,12 SHELXS-86,13 a and
SHELX-7613b or SHELXL-93.13c Scattering factors for all
atoms included real and imaginary anomalous dispersion
components.14 Selected bond lengths and angles are given in
Tables 2-5.
3
(500.138 MHz) δ 3.08 (triplet of triplets, J ax-ax ) 11.6 Hz,
3J ax-eq ) 2.1 Hz, NCHCH2CH2CH2CH2CH2, 2.0H), 1.95 (d,
2J ax-eq ≈ 12.1 Hz, NCHC(Heq)HCH2CH2CH2C(Heq)H, 4.2H),
2
1.74 (d, J ax-eq ≈ 12.8 Hz, NCHCH2C(Heq)HCH2C(Heq)HCH2,
2
4.2H), 1.57 (d, J ax-eq ≈ 13.0 Hz, NCHCH2CH2C(Heq)HCH2-
2
3
CH2, 2.3H), 1.47 (quartet of doublets, J ax-eq ≈ J ax-ax ≈ 12.0
Hz, 3J ax-eq ) 2.7 Hz, NCHC(Hax)HCH2CH2CH2C(Hax)H, 3.7H),
2
3
3
1.25 (quartet of triplets, J ax-eq ≈ J ax-ax ≈ 12.8 Hz, J ax-eq
)
3.1 Hz, NCHCH2C(Hax)HCH2C(Hax)HCH2, 4.0H), 1.04 (quartet
2
3
of triplets, J ax-eq
≈
3J ax-ax ≈ 13.0 Hz, J ax-eq ) 4.1 Hz,
NCHCH2CH2C(Hax)HCH2CH2, 1.9H), 0.01 (s, (CH3)2Ga, 6.1H);
13C NMR (75.469 MHz) δ 64.9 (NCHCH2CH2CH2CH2CH2), 38.3
(NCHCH2CH2CH2CH2CH2), 28.5 (NCHCH2CH2CH2CH2CH2),
26.7 (NCHCH2CH2CH2CH2CH2), -1.9 ((CH3)2Ga). Anal. Cal-
cd for C28H56Ga2N2: C, 60.03; H, 10.08; N, 5.00. Found: C,
60.13; H, 10.19, N, 5.06. Molecular weight for C28H56Ga2N2:
calcd, 560; found, 5.5 × 102 (calculated molality 0.0267).
Resu lts a n d Discu ssion
[Et2Ga N(C6H11)2]2. A solution of Et3Ga (1.51 g, 9.64 mmol)
and (C6H11)2NSnMe3 (3.24 g, 9.40 mmol) was heated at 52-
53 °C for 10.9 days. Clear, colorless crystals slowly precipi-
tated during this period. The crystalline [Et2GaN(C6H11)2]2
(2.33 g, 80.4% yield) was washed four times with pentane: mp
142-143 °C; 1H NMR (500.138 MHz) δ 3.03 (triplet of triplets,
The alkyltrimethyltin elimination reaction (eq 5) of
R3Ga (R ) Me, Et) with R′′R′NSnMe3 (R′′ ) i-Bu,
SnMe3, C6H11 and R′ ) i-Bu, i-Pr, C6H11) in the absence
of a solvent gave [Me2GaN(i-Bu)2]2, [Et2GaN(i-Bu)2]2,
[Me2GaN(i-Pr)SnMe3]2, [Me2GaN(C6H11)2]2, and [Et2-
GaN(C6H11)2]2 in 88.6, 68.6, 69.1, 81.0, and 80.4% yields.
3
3J ax-ax ) 11.7 Hz, J ax-eq ) 2.1 Hz, NCHCH2CH2CH2CH2CH2,
2
2.0H), 1.94 (d, J ax-eq ≈ 12.1 Hz, NCHC(Heq)HCH2CH2CH2C-
2
(Heq)H, 4.2H), 1.76 (d, J ax-eq ≈ 12.8 Hz, NCHCH2C(Heq)-
HCH2C(Heq)HCH2, 4.2H), 1.57 (d, 2J ax-eq ≈ 12.9 Hz, NCHCH2-
2R3Ga + 2R′′R′NSnMe3 f
2
CH2C(Heq)HCH2CH2, 2.3H), 1.52 (quartet of doublets, J ax-eq
[R2GaNR′R′′]2 + 2RSnMe3 (5)
3
3
≈ J ax-ax ≈ 12.0 Hz, J ax-eq ) 2.7 Hz, NCHC(Hax)HCH2CH2-
3
CH2C(Hax)H, 4.0H), 1.37 (t, J H-H ) 8.0 Hz, (CH3CH2)2Ga,
6.2H), 1.26 (quartet of triplets, J ax-eq
3J ax-eq ) 3.0 Hz, NCHCH2C(Hax)HCH2C(Hax)HCH2, 4.2H), 1.04
2
In all cases except one, the neat reactants were heated
≈
3J ax-ax ≈ 12.9 Hz,
(12) Busing, W. R.; Martin, K. O.; Levy, H. A. ORFFE (revised by
F. M. Brown, C. K. J ohnson, and W. E. Thiessen); Oak Ridge National
Laboratory: Oak Ridge, TN, 1985.
(13) (a) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467. (b)
Sheldrick, G. M. SHELX-76 Program for Crystal Structure Determi-
nation; Cambridge University Press: New York, 1975. (c) Sheldrick,
G. M. SHELXL-93; University of Go¨ttingen, Go¨ttingen, Germany, 1993.
(14) Cromer, D. T.; Waber, J . T. International Tables for X-Ray
Crystallography; Kynoch Press: Birmingham, England, 1974; Vol. IV.
2
3
3
(quartet of triplets, J ax-eq ≈ J ax-ax ≈ 13.0 Hz, J ax-eq ) 4.0
3
Hz, NCHCH2CH2C(Hax)HCH2CH2, 2.0H), 0.72 (q, J H-H ) 8.0
Hz, (CH3CH2)2Ga, 4.0H); 13C NMR (75.469 MHz) δ 64.4
(NCHCH2CH2CH2CH2CH2), 38.2 (NCHCH2CH2CH2CH2CH2),
28.5 (NCHCH2CH2CH2CH2CH2), 26.6 (NCHCH2CH2CH2CH2-
CH2), 11.1 ((CH3CH2)2Ga), 7.2 ((CH3CH2)2Ga). Anal. Calcd
for C32H64Ga2N2: C, 62.36; H, 10.47; N, 4.54. Found: C, 62.48;

Synthesis of Substituted Aminogallanes
Organometallics, Vol. 15, No. 6, 1996 1731
Ta ble 2. Selected In tr a m olecu la r Dista n ces (Å)
(molecules 1 and 2) are nonplanar with fold angles on
the Ga‚‚‚Ga diagonals of 148.7(3) and 146.3(3),
147.7(3)°. These angles are smaller than the fold angles
of 154.2 and 171.8(2)° that were observed in the only
other reported aminogallanes [Me2GaN(H)Dipp]2 (Dipp
a n d Bon d An gles (d eg) for [Et2Ga N(i-Bu )2]2
Distances
Ga(1)‚‚‚Ga(2)
Ga(1)-N(1)
Ga(2)-N(1)
Ga(1)-C(1)
Ga(2)-C(5)
N(1)-C(9)
2.864(1)
2.061(6)
2.053(6)
2.010(8)
1.975(8)
1.484(10)
1.494(10)
N(1)‚‚‚N(2)
Ga(1)-N(2)
Ga(2)-N(2)
Ga(1)-C(3)
Ga(2)-C(7)
N(1)-C(13)
N(2)-C(21)
2.837(9)
2.068(6)
2.035(6)
1.983(9)
1.993(9)
1.495(10)
1.489(10)
3g
) 2,6-i-Pr2C6H3)2a and [(2,3-Me2C4H4)GaNEt2]2 with
nonplanar (Ga-N)2 rings. The Ga-methylated ami-
nogallanes and all other substituted dimeric amino-
gallanes2a,i,3-f for which structural data are known
contain planar (Ga-N)2 rings. Steric overcrowding
between substituents on neighboring atoms in the
(Ga-N)2 ring and packing forces are probably respon-
sible for the distortion of the (Ga-N)2 rings in the
Ga-ethylated aminogallanes.
N(2)-C(17)
Angles
N(1)-Ga(1)-N(2)
C(1)-Ga(1)-C(3)
C(1)-Ga(1)-N(1)
C(1)-Ga(1)-N(2)
C(3)-Ga(1)-N(1)
C(3)-Ga(1)-N(2)
Ga(1)-N(1)-Ga(2)
C(9)-N(1)-C(13)
C(9)-N(1)-Ga(1)
C(9)-N(1)-Ga(2)
C(13)-N(1)-Ga(1)
C(13)-N(1)-Ga(2)
86.8(2) N(1)-Ga(2)-N(2)
123.2(4) C(5)-Ga(2)-C(7)
110.2(3) C(7)-Ga(2)-N(1)
109.4(3) C(7)-Ga(2)-N(2)
111.2(4) C(5)-Ga(2)-N(1)
110.0(4) C(5)-Ga(2)-N(2)
87.9(2)
112.7(4)
107.4(3)
109.4(3)
120.4(4)
116.3(3)
The C-Ga bond lengths (Tables 4 and 5) in [Et2GaN-
(C6H11)2]2 (average 1.996(7), 1.996(7) Å) are slightly
longer than the corresponding bond lengths in [Me2-
GaN(C6H11)2]2 (average 1.980(9) Å). The longer C-Ga
bonds in the former aminogallane probably result from
an increase in substitution on the carbon atoms bonded
to the gallium atoms. A similar trend is found in the
C-Ga bond distances for [(t-Bu)2GaN(H)Ph]2 (2.006(9)
and 2.18(2) Å)3e and [Me2GaN(H)Ph]2 (1.954(6) and
1.936(6) Å).2a Despite significant variations in the
N-Ga bond lengths in molecule 1 of [Et2GaN(C6H11)2]2,
the average N-Ga bond distances in molecules 1 and 2
(2.070(5), and 2.069(5) Å) are nearly identical with the
average N-Ga bond length (2.068(5) Å) found in [Me2-
GaN(C6H11)2]2. By comparison, the average N-Ga
distances in [Et2GaN(i-Bu)2]2 (2.054(6) Å) and trans-
[Me2GaN(i-Pr)SnMe3]2 (2.034(4) Å) are shorter. The
small decrease in the average N-Ga bond length within
the series [R2GaN(C6H11)2]2, [Et2GaN(i-Bu)2]2, and trans-
[Me2GaN(i-Pr)SnMe3]2 can be attributed to the decrease
in the steric requirements of nitrogen substituents in
the series.
88.2(2) Ga(1)-N(2)-Ga(2) 88.5(2)
112.1(7) C(17)-N(2)-C(21)
118.5(5) C(17)-N(2)-Ga(1)
110.3(5) C(17)-N(2)-Ga(2)
111.1(5) C(21)-N(2)-Ga(1)
114.7(5) C(21)-N(2)-Ga(2)
111.5(7)
118.3(4)
109.8(5)
110.3(5)
116.9(5)
Ta ble 3. Selected In tr a m olecu la r Dista n ces (Å)
a n d Bon d An gles (d eg) for [Me2Ga N(i-P r )Sn Me3]2
Distances
Ga‚‚‚Ga′
Ga-N
Ga-C(1)
N-C(3)
Sn-C(6)
Sn-C(8)
2.892(1)
2.039(4)
1.984(5)
1.513(6)
2.135(6)
2.148(6)
N‚‚‚N′
2.859(7)
2.028(4)
1.975(5)
2.112(4)
2.143(7)
Ga-N′
Ga-C(2)
N-Sn
Sn-C(7)
Angles
N-Ga-N′
89.3(2)
110.0(3)
124.4(2)
114.4(2)
113.0(2)
122.4(3)
111.9(3)
112.6(2)
Ga-N-Ga′
C(1)-Ga‚‚‚Ga′
C(1)-Ga-N
C(1)-Ga-N′
C(3)-N-Sn
Sn-N‚‚‚N′
90.7(2)
125.6(2)
113.4(2)
115.6(2)
114.0(3)
123.6(2)
112.4(3)
113.2(2)
C(1)-Ga-C(2)
C(2)-Ga‚‚‚Ga′
C(2)-Ga-N
C(2)-Ga-N′
C(3)-N‚‚‚N′
C(3)-N-Ga
Sn-N-Ga
C(3)-N-Ga′
Sn-N-Ga′
Cryoscopic molecular weight measurements indicate
that all five aminogallanes are dimers in benzene
solutions. trans-[Me2GaN(i-Pr)SnMe3]2 appears to be
the only isomer present in a toluene solution at room
temperature. The 1H NMR spectrum of [Me2GaN(i-Pr)-
SnMe3]2 in toluene exhibited only one Ga-CH3 reso-
nance. Two additional Ga-CH3 resonances of equal
intensity would be expected if the cis isomer were also
present in the solution.2d,4
Ta ble 4. Selected In tr a m olecu la r Dista n ces (Å)
a n d Bon d An gles (d eg) for [Me2Ga N(C6H11)2]2
Distances
Ga‚‚‚Ga′
Ga-N
Ga-C(1)
N-C(3)
2.911 (2)
2.070 (5)
1.981 (9)
1.499 (7)
N‚‚‚N′
2.938 (9)
2.066 (4)
1.978 (8)
1.498 (9)
Ga-N′
Ga-C(2)
N-C(9)
Angles
N-Ga-N′
90.5 (2)
116.1 (5)
122.0 (3)
112.2 (3)
111.7 (3)
121.0 (4)
112.3 (3)
110.3 (4)
Ga-N-Ga′
89.5 (2)
121.9 (4)
111.7 (4)
111.9 (3)
118.3 (5)
120.7 (4)
110.7 (4)
112.2 (3)
C(1)-Ga-C(2)
C(2)-Ga‚‚‚Ga′
C(2)-Ga-N
C(2)-Ga-N′
C(3)-N‚‚‚N′
C(3)-N-Ga
C(9)-N-Ga
C(1)-Ga‚‚‚Ga′
C(1)-Ga-N
C(1)-Ga-N′
C(3)-N-C(9)
C(9)-N‚‚‚N′
C(3)-N-Ga′
C(9)-N-Ga′
The nonplanar (Ga-N)2 rings in [Et2GaN(i-Bu)2]2 and
[Et2GaN(C6H11)2]2 render the two ethyl groups on a
gallium atom and the two substituents on a nitrogen
atom magnetically nonequivalent in the solid state.
1
However, the H NMR spectrum of each Ga-ethylated
aminogallane in toluene solution exhibited only one
signal for the methyl protons and one signal for the
methylene protons in the ethyl group at room temper-
ature. At -68 °C the width of the bands at half-height
increased to 5 Hzsprobably due to the increase in
viscosity of the toluene solutionsbut only one quartet
and one triplet were observed for the methyl and
methylene protons in the spectra of [Et2GaN(i-Bu)2]2
and [Et2GaN(C6H11)2]2. Either the rate of inversion of
the (Ga-N)2 rings in both aminogallanes is very fast in
comparison to the NMR time scale or the rings are
planar in solution.
at temperatures between 44 and 57 °C for periods of 6
h to 10.9 days. The exception is the reaction of Me3Ga
with (C6H11)2NSnMe3, in which the reaction mixture
was allowed to stand at room temperature for 20.3 h.
All five aminogallanes are colorless crystalline solids at
room temperature.
The X-ray crystallographic study of [Et2GaN(i-Bu)2]2,
[Me2GaN(i-Pr)SnMe3]2, [Me2GaN(C6H11)2]2, and [Et2-
GaN(C6H11)2]2 reveals that the four aminogallanes are
dimeric in the solid state (Figures 1-4). The narrow
melting point range for [Me2GaN(i-Pr)SnMe3]2 indicates
that only one isomer is present in the solid state, and it
is the trans isomer (Figure 2). The four-membered
(Ga-N)2 rings in [Et2GaN(i-Bu)2]2 and [Et2GaN(C6H11)2]2
The signals associated with the axial and equatorial
protons on the cyclohexyl groups are well-resolved in
the 1H NMR spectra of [Me2GaN(C6H11)2]2 and [Et2GaN-

1732 Organometallics, Vol. 15, No. 6, 1996
Nutt et al.
a
Ta ble 5. Selected In tr a m olecu la r Dista n ces (Å) a n d Bon d An gles (d eg) for [Et2Ga N(C6H11)2]2
Distances
Ga(1)‚‚‚Ga(2)
Ga(1)-N(1)
Ga(2)-N(1)
Ga(1)-C(1)
Ga(2)-C(5)
N(1)-C(9)
2.878(1), 2.872(1)
2.049(5), 2.069(5)
2.086(5), 2.072(5)
1.990(6), 1.992(7)
2.004(7), 1,994(8)
1.496(8), 1.531(8)
1.521(8), 1.518(8)
N(1)‚‚‚N(2)
Ga(1)-N(2)
Ga(2)-N(2)
Ga(1)-C(3)
Ga(2)-C(7)
N(1)-C(15)
N(2)-C(27)
2.849(8), 2.862(9)
2.086(5), 2.064(5)
2.061(5), 2.072(5)
1.999(7), 2,002(7)
1.993(7), 1.996(7)
1.519(8), 1.491(8)
1.483(8), 1.534(8)
N(2)-C(21)
Angles
N(1)-Ga(1)-N(2)
Ga(1)-N(1)-Ga(2)
C(1)-Ga(1)-C(3)
C(1)-Ga(1)-N(1)
C(3)-Ga(1)-N(1)
C(1)-Ga(1)-N(2)
C(3)-Ga(1)-N(2)
C(9)-N(1)-C(15)
C(9)-N(1)-Ga(1)
C(15)-N(1)-Ga(1)
C(9)-N(1)-Ga(2)
C(15)-N(1)-Ga(2)
87.1(2), 87.7(2)
88.2(2), 87.8(2)
N(1)-Ga(2)-N(2)
Ga(1)-N(2)-Ga(2)
C(5)-Ga(2)-C(7)
C(5)-Ga(2)-N(1)
C(7)-Ga(2)-N(1)
C(5)-Ga(2)-N(2)
C(7)-Ga(2)-N(2)
C(21)-N(2)-C(27)
C(21)-N(2)-Ga(1)
C(27)-N(2)-Ga(1)
C(21)-N(2)-Ga(2)
C(27)-N(2)-Ga(2)
86.8(2), 87.4(2)
87.9(2), 88.0(2)
110.4(3), 113.2(3)
114.6(2), 113.7(3)
112.9(3), 111.7(3)
121.1(3), 117.7(3)
108.9(3), 119.2(3)
117.7(5), 118.0(5)
113.4(4), 110.7(4)
108.9(4), 112.2(4)
109.8(4), 109.7(4)
115.1(4), 114.5(4)
113.1(3), 112.6(4)
120.3(3), 118.2(3)
109.4(3), 108.9(3)
112.9(3), 115.6(3)
111.6(3), 111.7(3)
118.5(5), 116.5(5)
115.8(4), 116.6(4)
109.0(4), 109.0(4)
107.8(4), 112.4(4)
113.8(4), 111.0(4)
a
Data are given the order molecule 1, molecule 2.
F igu r e 1. ORTEP diagram of [Et2GaN(i-Bu)2]2.
F igu r e 3. ORTEP diagram of [Me2GaN(C6H11)2]2.
F igu r e 2. ORTEP diagram of [Me2Ga(i-Pr)SnMe3]2.
F igu r e 4. ORTEP diagram of [Et2GaN(C6H11)2]2 (molecule
1).
(C6H11)2]2. The three doublets in the region from 2.0 to
1.57 ppm were assigned to the equatorial protons on
the â-, γ-, and δ-carbon atoms, and the three quartets
of doublets or triplets in the region from 1.52 to 1.0 ppm
were assigned to the axial protons on the â-, γ-, and
δ-carbon atoms. These assignments are consistent with
the COSY contour plots of the aminogallanes and
spectral features distinctive to cyclohexyl groups.15
The alkyltrimethyltin elimination reaction (eq 5)
affords a convenient, single-step, low-temperature path-
way to substituted Ga-methylated or Ga-ethylated ami-
nogallanes. With the exception of the reaction of Et3Ga
with (C6H11)2NSnMe3, which required 10.9 days, the
elimination reactions that were investigated proceeded
readily in the absence of a solvent at or below 57 °C.
Even when the substituents on the nitrogen atom were
the bulky cyclohexyl groups, the aminogallanes [Me2-
GaN(C6H11)2]2 and [Et2GaN(C6H11)2]2 were obtained in
(15) Morelle, N.; Gharbi-Benarous, J .; Acher, F.; Valle, G.; Crisma,
M.; Toniolo, C.; Azerad, R.; Girault, J . J . Chem. Soc., Perkin Trans. 2
1993, 525.

Synthesis of Substituted Aminogallanes
Organometallics, Vol. 15, No. 6, 1996 1733
good yields. Attempts to prepare [Me2GaN(C6H11)2]2 by
cyclopentadiene elimination (eq 4) were unsuccessful,4
and the adduct Me3Ga‚N(H)(C6H11)2 has been found to
be stable to methane elimination (eq 1) during sublima-
tion at 40-60 °C and 0.01 Torr.3c It should be noted
that, at least in the case of the reactions of Me3Ga or
Et3Ga with (C6H11)2NSnMe3, higher reaction tempera-
tures and longer reaction times were required to effect
the formation of [Et2GaN(C6H11)2]2 than [Me2GaN-
(C6H11)2]2.
Research Fund, administered by the American Chemi-
cal Society, is gratefully acknowledged. J .M.G., J .D.O.,
Y.D., and L.L. gratefully acknowledge financial support
from the NSF/EPSCoR (Grant ESR-9108772).
Su p p or tin g In for m a tion Ava ila ble: Listings of bond
lengths, bond angles, selected dihedral angles, hydrogen
coordinates, anisotropic temperature factors, and final posi-
tional parameters for [Et2GaN(i-Bu)2]2, [Me2GaN(i-Pr)SnMe3]2,
[Me2GaN(C6H11)2]2, and [Et2GaN(C6H11)2]2 and COSY plots for
[Me2GaN(C6H11)2]2 and [Et2GaN(C6H11)2]2 (40 pages). Order-
ing information is given on any current masthead page.
Ack n ow led gm en t. The support of this research by
the Research Corp. and the donors of the Petroleum
OM950812H