Synthesis of Indium Amide Compounds

Article abstract of DOI:10.1021/ic971138u

Indium trichloride reacts with 3 equiv of lithium amide in diethyl ether to give In(NRR′)₃ (R = Ph or t-Bu, R′ = SiMe₃; R = t-Bu, R′ = SiHMe₂) and with 3 or 4 equiv of LiNMe(SiMe₃) to yield Li[In{NMe(SiMe₃)}₄]. The chloride also reacts with LiNPh₂ in THF to give the salt Li[In(NPh₂)₃Cl] and with LiNRR′ in pyridine to yield the neutral adduct In(NRR′)₃(py) (R = R′ = Ph; R = Me, R′ = SiMe₃). The volatile liquids In[N(t-Bu)(SiHMe₂)]₃ and In[NMe(SiMe₃)]₃(Py) react with p-Me₂Npy to form the solid compounds In[N(t-Bu)(SiHMe₂)]₃(p-Me₂Npy) and In[NMe(SiMe₃)]₃(p-Me₂Npy), respectively. X-ray crystallographic studies show that In(NPh₂)₃(py), In[N(t-Bu)(SiHMe₂)]3(p-Me₂Npy), and the ether adduct of In[NPh(SiMe₃)]₃ contain nearly planar In(amide)₃ fragments. Crystallographic studies also show that the anion in the salt [Li(THF)₄][In(NPh₂)₃Cl] is nearly tetrahedral and in [Li(p-Me₂Npy)][In{NMe(SiMe₃)}₄] the tetrahedral-like anion is bound to the Li cation via two amide nitrogens. The Li in the latter structure is also bonded to p-Me₂Npy, resulting in a planar three-coordinate geometry for Li. Crystal data are the following, C₃₁H₅₂N₃OSi₃In at -50 °C; P2₁/n (monoclinic), a = 11.003(2) A?, b = 18.678(3) A?, c = 17.618(3) A?, β= 95.42(1)°, and Z = 4. C₄₁H₃₅N₄In·C₇H₈ at -50 °C: P1? (triclinic), a = 10.112(2) A?, b = 12.786(3) A?, c = 15.870(5) A?, α = 87.42(2)°, β = 74.95(2)°, γ = 78.15(2)°, and Z = 2. C₂₅H₅₈N₅Si₃In at -50 °C: P2₁/c (monoclinic), a = 9.797(3) A?, b = 18.203(6) A?, c = 19.592(5) A?, β = 100.27(2)°, and Z = 4. C₅₂H₆₂ClInLiN₃O₄ at 23 °C: P2₁/n (monoclinic), a = 16.076(2) A?, b = 17.185(2) A?, c = 18.447(3) A?, β= 97.41(1)°, and Z =4. C₂₃H₅₈InLiN₆Si₄ at 23 °C: P1 (triclinic), a = 15.792(3) A?, b = 16.345(3) A?, c = 16.678-(3) A?, α = 62.69(1)°, β= 81.00(1)°, γ = 86.94(1)°, and Z = 4.

Full text of DOI:10.1021/ic971138u

Inorg. Chem. 1998, 37, 3835-3841
3835
Synthesis of Indium Amide Compounds
Jungsook Kim, Simon G. Bott, and David M. Hoffman*
Department of Chemistry, University of Houston, Houston, Texas 77204
ReceiVed September 5, 1997
Indium trichloride reacts with 3 equiv of lithium amide in diethyl ether to give In(NRR′)3 (R ) Ph or t-Bu, R′
) SiMe3; R ) t-Bu, R′ ) SiHMe2) and with 3 or 4 equiv of LiNMe(SiMe3) to yield Li[In{NMe(SiMe3)}4]. The
chloride also reacts with LiNPh2 in THF to give the salt Li[In(NPh2)3Cl] and with LiNRR′ in pyridine to yield
the neutral adduct In(NRR′)3(py) (R ) R′ ) Ph; R ) Me, R′ ) SiMe3). The volatile liquids In[N(t-Bu)(SiHMe2)]3
and In[NMe(SiMe3)]3(py) react with p-Me2Npy to form the solid compounds In[N(t-Bu)(SiHMe2)]3(p-Me2Npy)
and In[NMe(SiMe3)]3(p-Me2Npy), respectively. X-ray crystallographic studies show that In(NPh2)3(py), In[N(t-
Bu)(SiHMe2)]3(p-Me2Npy), and the ether adduct of In[NPh(SiMe3)]3 contain nearly planar In(amide)3 fragments.
Crystallographic studies also show that the anion in the salt [Li(THF)4][In(NPh2)3Cl] is nearly tetrahedral and in
[Li(p-Me2Npy)][In{NMe(SiMe3)}4] the tetrahedral-like anion is bound to the Li cation via two amide nitrogens.
The Li in the latter structure is also bonded to p-Me2Npy, resulting in a planar three-coordinate geometry for Li.
Crystal data are the following. C31H52N3OSi3In at -50 °C: P21/n (monoclinic), a ) 11.003(2) Å, b ) 18.678(3)
Å, c ) 17.618(3) Å, â ) 95.42(1)°, and Z ) 4. C41H35N4In‚C7H8 at -50 °C: P1h (triclinic), a ) 10.112(2) Å,
b ) 12.786(3) Å, c ) 15.870(5) Å, R ) 87.42(2)°, â ) 74.95(2)°, γ ) 78.15(2)°, and Z ) 2. C25H58N5Si3In at
-50 °C: P21/c (monoclinic), a ) 9.797(3) Å, b ) 18.203(6) Å, c ) 19.592(5) Å, â ) 100.27(2)°, and Z ) 4.
C52H62ClInLiN3O4 at 23 °C: P21/n (monoclinic), a ) 16.076(2) Å, b ) 17.185(2) Å, c ) 18.447(3) Å, â )
97.41(1)°, and Z ) 4. C23H58InLiN6Si4 at 23 °C: P1h (triclinic), a ) 15.792(3) Å, b ) 16.345(3) Å, c ) 16.678-
(3) Å, R ) 62.69(1)°, â ) 81.00(1)°, γ ) 86.94(1)°, and Z ) 4.
We have reported several examples of using low-temperature
) Ph, L ) py; R ) Me, R′ ) SiMe3, L ) py or p-Me2Npy),
Li[In(NPh2)3Cl] and Li[In{NMe(SiMe3)}4]. Since we began this
study, a new homoleptic compound, In(2,2,6,6-tetramethylpi-
peridino)3, has been reported.8
chemical vapor deposition (CVD) to deposit main group and
transition metal nitride thin films from homoleptic amido
compounds and ammonia precursors.1 With this as background,
we became interested in using homoleptic indium amido
compounds as precursors to indium nitride films.2 Only two
examples of homoleptic indium amido complexes, In[N(SiMe3)2]3
and In(NEt2)3, had been reported in the literature when we began
this study.3-5 The hexamethydisilazane compound, a solid, is
involatile (dec <168 °C) and therefore not suitable for use as
a CVD precursor. The diethylamido complex5 In(NEt2)3 was
particularly attractive to us because we showed earlier that Ga-
(NMe2)3 and ammonia precursors give clean GaN films at very
low temperatures.6,7 We found In(NEt2)3, however, to be
difficult to purify and not very volatile.
Expermental Section
General Considerations. All manipulations were carried out in a
glovebox or by using standard Schlenk techniques. Solvents were
purified by using standard techniques, after which they were stored in
the glovebox over 4-Å molecular sieves. HNPh2 was purchased from
Aldrich and H2NMe from Matheson. Me3SiCl, Me2HSiCl, Me2SiCl2,
t-BuNH2, and t-BuNH(SiMe3) were purchased from Aldrich, degassed
with an argon stream, and then stored in the refrigerator over 3-Å
molecular sieves. PhNH(SiMe3) was synthesized by the literature
method.9 Infrared spectra were obtained by using an FTIR instruments
and NMR spectra were collected on a 300-MHz instrument.
HNMe(SiMe3). This compound was prepared by using a modifica-
tion of the literature procedure.10 Methylamine (7.8 g, 0.25 mol) was
added to a frozen solution of ClSiMe3 (11 g, 0.10 mol) in ether (200
mL). A white solid formed while the mixture was being warmed slowly
to room temperature. After warming to room temperature, the reaction
mixture was stirred for an additional 4 h. The mixture was then cold-
filtered (0 °C), and the filtrate was distilled at atmospheric pressure
under argon, giving the product as a colorless liquid (bp 71 °C/760
mmHg; lit.10 bp 71 °C/755 mmHg) (yield 6.0 g, 58%).
Because of potential problems with using the known indium
amido compounds as precursors to InN, we have prepared new
derivatives. Herein we report the syntheses of In(NRR′)3 (R
) Ph or t-Bu, R′ ) SiMe3; R ) t-Bu, R′ ) SiHMe2),
In(NRR′)3L (R ) t-Bu, R′ ) SiHMe2, L ) p-Me2Npy; R ) R′
(1) For a review on the subject, see: Hoffman, D. M. Polyhedron 1994,
13, 1169.
(2) Two reviews on group 13 nitrides are the following: Strite, S.; Morkoc¸,
H. J. Vac. Sci. Technol. B 1992, 10, 1237. Strite, S.; Lin, M. E.;
Morkoc¸, H. Thin Solid Films 1993, 231, 197.
(3) Bu¨rger, H.; Cichon, J.; Goetze, U.; Wannagat, U.; Wismar, H. J. J.
Organomet. Chem. 1971, 33, 1.
(4) Petrie, M. A.; Ruhlandt-Senge, K.; Hope, H.; Power, P. P. Bull. Soc.
Chim. Fr. 1993, 130, 851.
(5) Rossetto, G.; Brianese, N.; Camporese, A.; Porchia, M.; Zanella, P.;
Bertoncello, R. Main Group Met. Chem. 1991, 14, 113.
(6) Gordon, R. G.; Hoffman, D. M.; Riaz, U. Mater. Res. Soc. Symp.
Proc. 1991, 204, 95.
LiNMe(SiMe3). In the glovebox, a solution of n-BuLi (23 mL, 36
mmol; 1.6 M in hexane) was added slowly to a stirred solution of
HNMe(SiMe3) (4.0 g, 39 mmol) in hexane (50 mL) at room temper-
ature. A white solid formed immediately. The reaction mixture was
stirred for 3 h after the addition was completed. The white solid was
(8) Frey, R.; Gupta, V. D.; Linti, G. Z. Anorg. Allg. Chem. 1996, 622,
1060.
(7) Gordon, R. G.; Hoffman, D. M.; Riaz, U. Mater. Res. Soc. Symp.
Proc. 1992, 242, 445.
(9) Anderson, H. H. J. Am. Chem. Soc. 1951, 73, 5802.
(10) Sauer, R. O.; Hasek, R. H. J. Am. Chem. Soc. 1946, 68, 241.
S0020-1669(97)01138-5 CCC: $15.00 © 1998 American Chemical Society
Published on Web 07/07/1998

3836 Inorganic Chemistry, Vol. 37, No. 15, 1998
Kim et al.
filtered off, washed with hexane, and then dried under vacuum for 6 h
(yield 2.0 g, 50%).
Calcd for C18H48N3InSi3: C, 42.49; H, 9.53; N, 8.26. Found: C, 42.99;
H, 9.76; N, 7.98.
1H NMR (CD3CN): δ -0.021 (s, 9, SiMe3), 2.39 (s, 3, NMe).
HN(t-Bu)(SiHMe2). A solution of t-BuNH2 (7.3 g, 0.10 mol) in
ether (10 mL) was added slowly to ClSiHMe2 (4.7 g, 0.05 mol) in
cold (-78 °C) ether (50 mL). A white solid formed immediately. The
reaction mixture was stirred for 4 h while the temperature was allowed
slowly to increase to room temperature. The mixture was filtered, and
the filtrate was distilled at atmospheric pressure under argon, giving
the product as a colorless liquid (bp 105 °C/760 mmHg) (yield 3.9 g,
60%).
1H NMR (C6D6): δ 0.42 (d, JHH ) 3.6 Hz, 18, SiMe2H), 1.40 (s,
27, CMe3), 4.80 (septet, JHH ) 3.0 Hz, 3, SiMe2H). 13C{1H} NMR
(C6D6): δ 3.97 (SiHMe3), 36.8 (CMe3), 54.9 (CMe3). IR (Nujol, CsI,
cm-1): 2075 vs, 1413 w, 1359 vs, 1303 w, 1246 vs, 1230 vs, 1196 vs,
1114 w, 1047 vs, 1020 s, 993 s, 922 vs, 883 vs, 844 vs, 790 vs, 754
vs, 677 m, 651 w, 630 w, 599 w, 524 w, 472 s, 420 w.
In[N(t-Bu)(SiHMe2)]3(p-Me2Npy). In[N(t-Bu)(SiHMe2)]3 (0.20 g,
0.39 mmol) was dissolved in ether (10 mL), and p-(dimethylamino)-
pyridine (0.048 g, 0.39 mmol) was added quickly to the solution,
resulting in a clear solution. The flask was transferred to the freezer
(-35 °C), where it was kept for 48 h. Large, colorless crystals formed
(yield 0.17 g, 69%).
1H NMR (C6D6): δ 0.45 (d, JHH ) 3.3 Hz, 18, SiMe2H), 1.46 (s,
27, CMe3), 2.13 (s, 6, NMe2), 4.82 (septet, JHH ) 3.3 Hz, 3, SiMe2H),
6.03 (d, 2, m-py), 8.51 (d, 2, o-py).
1H NMR (C6D6): δ 0.12 (d, JHH ) 2.7 Hz, 6, SiMe2H), 0.36 (broad,
3
′
1, NH), 1.10 (s, 9, CMe3), 4.82 (octet, JHH
HNSiHMe2).
≈
3JHH ) 3.0, Hz, 1,
LiN(t-Bu)(SiHMe2). In the glovebox, a solution of n-BuLi (7.5 mL,
12 mmol; 1.6 M in hexane) was added slowly to HN(t-Bu)(SiHMe2)
(1.7 g, 13 mmol) in hexane (50 mL) at room temperature. The reaction
mixture was stirred for 3 h after the addition was completed. The
solution was taken to dryness under vacuum, leaving the product as a
white solid. The solid was dried in vacuo for 6 h (yield 1.6 g, 97%).
The product was used without further purification.
1H NMR (CD3CN): δ 0.09 (d, JHH ) 3.0 Hz, 6, SiMe2H), 1.14 (s,
9, CMe3), 4.49 (septet, JHH ) 3.0 Hz, 1, SiMe2H). IR (Nujol, CsI,
cm-1): 2052 vs, 1402 w, 1356 vs, 1303 w, 1246 vs, 1217 vs, 1192 vs,
1124 w, 1041 vs, 1016 s, 995 m, 922 vs, 887 vs, 833 vs, 769 vs, 750
vs, 696 m, 667 w, 623 w, 569 s, 461 w, 422 w.
In[NPh(SiMe3)]3. In the glovebox, a solution of LiNPh(SiMe3) (0.52
g, 3.0 mmol) in ether (5 mL) was added slowly to a suspension of
InCl3 (0.22 g, 1.0 mmol) in ether (25 mL). The reaction mixture was
stirred for 24 h. The mixture was taken to dryness in vacuo and then
held in vacuo for 4 h. The residue was extracted with hexane (10 ×
10 mL), and the extracts were filtered through Celite. The hexane was
removed in vacuo, and the residue was held in vacuo for 24 h, leaving
the product as a viscous liquid (yield 0.55 g, 90%). If the product is
not held under dynamic vacuum for a long time, an ether adduct is
obtained. Crystals of the ether adduct were grown from hexanes at
low temperature (-35 °C). The ether can be removed from the etherate
by dissolution in CH2Cl2 and then immediate removal of the CH2Cl2/
ether in vacuo. A microanalysis was performed for the etherate. A
satisfactory carbon analysis was not obtained. Anal. Calcd for
C31H52N3OInSi3: C, 54.59; H, 7.70; N, 6.16. Found: C, 54.03; H,
7.73; N, 6.00.
1H NMR (C6D6): δ 0.18 (s, 27, SiMe3), 6.80 (t, 3, p-Ph), 6.96 (d,
6, o-Ph), 7.08 (t, 6, m-Ph). 13C{1H} NMR (C6D6): δ 2.35 (SiMe3),
121.3 (Ph), 125.3 (Ph), 130.0 (Ph). IR (Nujol, CsI, cm-1): 1589 vs,
1491 vs, 1423 w, 1248 vs, 996 w, 920 vs, 842 vs, 750 s, 696 s, 634 w,
511 s.
In[N(t-Bu)(SiMe3)]3. In the glovebox, a solution of LiN(t-Bu)-
(SiMe3) (0.47 g, 3.1 mmol) in ether (5 mL) was added slowly to a
suspension of InCl3 (0.22 g, 1.0 mmol) in ether (25 mL). The reaction
mixture was stirred in the glovebox for 24 h. The mixture was taken
to dryness in vacuo and then held in vacuo for 4 h. The residue was
extracted with hexane (5 × 10 mL), and the extracts were filtered
through Celite. The hexane was removed in vacuo from the filtrate,
leaving the product as a white solid (yield 0.43 g, 79%). Anal. Calcd
for C21H54N3InSi3: C, 46.03; H, 9.95; N, 7.67. Found: C, 45.81; H,
9.76; N, 7.49.
In(NPh2)3(py). In the glovebox, a solution of LiNPh2 (0.53 g, 3.0
mmol) in pyridine (10 mL) was added slowly to a suspension of InCl3
(0.22 g, 1.0 mmol) in pyridine (25 mL). The reaction mixture was
stirred for 24 h. The solvent was removed in vacuo, and the residue
was held in vacuo for 12 h. The residue was extracted with toluene (5
× 10 mL), and the extracts were filtered through Celite. The volume
of the filtrate was reduced in vacuo to 20 mL. Cooling of the solution
(-35 °C for 24 h) produced light yellow crystals, which were isolated
by removal of the mother liquid with a pipet and drying in vacuo for
12 h (yield 0.48 g, 70%). Anal. Calcd for C41H35N4In: C, 70.48; H,
5.06; N, 8.02. Found: C, 70.30; H, 4.87; N, 7.81.
1H NMR (C6D6): δ 5.93 (t, 2, m-py), 6.32 (t, 1, p-py), 6.65 (t, 6,
p-Ph), 6.96 (t, 12, m-Ph), 7.11 (d, 12, o-Ph), 7.47 (d, 2, o-py). 13C-
{1H} NMR (C6D6): δ 120.4 (Ph), 122.7 (Ph), 125.1 (py), 129.9 (Ph),
139.9 (py), 148.7 (py), 152.8 (Ph). IR (Nujol, CsI, cm-1): 1584 s,
1524 w, 1491vs, 1338 m, 1296 vs, 1203 s, 1182 m, 1064 m, 1042 w,
989 m, 926 m, 873 m, 862 s, 839 w, 802 w, 779 w, 744 vs, 694 vs,
646 w, 617 w, 578 w, 530 w, 503 s, 447 w, 430 w, 421 s.
In[NMe(SiMe3)]3(py). In the glovebox, a solution of LiNMe(SiMe3)
(0.32 g, 3.0 mmol) in pyridine (10 mL) was added slowly to a
suspension of InCl3 (0.22 g, 1.0 mmol) in pyridine (25 mL). The
reaction mixture was stirred for 24 h. The solvent was removed in
vacuo, and the residue was held in vacuo for 12 h. The residue was
extracted with hexane (3 × 10 mL), and the extracts were filtered
through Celite. Hexane was removed in vacuo from the filtrate, and
the residue, a viscous light red liquid, was held in vacuo for 12 h (yield
0.41 g, 82%). A similar yield is obtained using a 9:1 mixture of ether/
pyridine as the reaction solvent. The compound distills at 70-75 °C,
0.01 mmHg, with some decomposition.
1H NMR (C6D6): δ 0.32 (s, 27, SiMe3), 2.94 (s, 9, NMe), 6.47 (t, 2,
m-py), 6.77 (t, 1, p-py), 8.46 (d, 2, o-py). 13C{1H} NMR (C6D6): 1.23
(SiMe3), 34.7 (NMe), 125, 139, 149 (py). IR (CsI, Nujol, cm-1): 1604
vs, 1562 w, 1535 w, 1487 s, 1448 vs, 1427 s, 1400 s, 1338 w, 1286 s,
1244 vs, 1217 m, 1167 s, 1050 vs, 1012 m, 931 w, 926 s, 891 s, 862
vs, 831 vs, 748 m, 700 m, 677 w, 642 w, 619 w, 596 w, 572 w, 445
w, 420 w.
In[NMe(SiMe3)]3(p-Me2Npy). In[NMe(SiMe3)]3(py) (0.20 g, 0.40
mmol) was dissolved in hexane (10 mL), and p-(dimethylamino)-
pyridine (0.049 g, 0.40 mmol) was added quickly to the solution,
resulting in a clear solution. The flask was transferred to the freezer
(-35 °C), where it was kept for 24 h. Large tan crystals formed (yield
0.18 g, 86%). Anal. Calcd for C19H46N5InSi3: C, 41.96; H, 8.54; N,
12.88. Found: C, 41.67; H, 8.50; N, 12.84.
1H NMR (C6D6): δ 0.40 (s, 27, SiMe3), 1.46 (s, 27, CMe3). 13C-
{1H} NMR (C6D6): δ 6.63 (SiMe3), 36.9 (CMe3), 55.7 (CMe3). IR
(Nujol, CsI, cm-1): 1303 w, 1248 s, 1228 m, 1211 w, 1182 m, 1031
m, 1018 w, 981 m, 910 w, 858 s, 836 s, 775 m, 749 m, 671 w, 630 w,
603 w, 516 w, 470 m.
1H NMR (C6D6): δ 0.42 (s, 27, SiMe3), 1.90 (s, 6, NMe2), 3.13 (s,
9, NMe), 5.71 (d, 2, m-py), 8.20 (d, 2, o-py).
In[N(t-Bu)(SiHMe2)]3. LiN(t-Bu)(SiHMe2) (0.42 g, 3.1 mmol) in
ether (5 mL) was added dropwise to a slurry of InCl3 (0.22 g, 1.0 mmol)
in ether (25 mL) at -78 °C. The mixture was stirred while the
temperature was allowed slowly to increase to room temperature over
24 h. A white precipitate formed. The ether was removed by vacuum
distillation, and the residue was extracted with hexane (3 × 10 mL).
The extracts were combined and filtered through Celite. Hexane was
removed in vacuo from the filtrate, and the residue, a viscous light
yellow liquid, was held in vacuo for 24 h (yield 0.28 g, 53%). Anal.
[Li(THF)4][In(NPh2)3Cl]. In the glovebox, a solution of LiNPh2
(0.53 g, 3.0 mmol) in THF (10 mL) was added slowly to a suspension
of InCl3 (0.22 g, 1.0 mmol) in THF (25 mL). The reaction mixture
was stirred for 24 h. The mixture was taken to dryness in vacuo and
then held in vacuo for 8 h. The residue was extracted with benzene (5
× 10 mL), and extracts were filtered through Celite. The benzene was
removed in vacuo, and the residue was held in vacuo for 24 h, leaving
1
a viscous reddish brown liquid that is [Li(THF)][In(NPh2)3Cl] by H
NMR (i.e., one THF). Brownish yellow crystals were grown at low

Synthesis of Indium Amide Compounds
Inorganic Chemistry, Vol. 37, No. 15, 1998 3837
Table 1. Crystal Data for In[NPh(SiMe3)]3(ether), In(NPh2)3(py)‚toluene, In[N(t-Bu)(SiHMe2)]3(p-Me2Npy),
[Li(p-Me2Npy)][In{NMe(SiMe3)}4], and [Li(THF)4][In(NPh2)3Cl]
In[NPh(SiMe3)]3
(ether)
In(NPh2)3(py)‚
In[N(t-Bu)(SiHMe2)]3
(p-Me2Npy)
[Li(p-Me2Npy)]
[In{NMe(SiMe3)}4]
[Li(THF)4]
[In(NPh2)3Cl]
toluene
empirical formula
fw
C31H52N3OSi3In
681.95
C41H35N4In‚C7H8
790.77
C25H58N5Si3In
627.97
C23H58InLiN6Si4
652.86
C52H62ClInLiN3O4
950.31
cryst dimens (mm)
0.66 × 0.38 × 0.30
0.12 × 0.24 × 0.28
0.710 73
P1h (triclinic)
10.112(2)
12.786(3)
15.870(5)
87.42(2)
74.95(2)
78.15(2)
-50
0.30 × 0.45 × 0.55
0.08 × 0.15 × 0.17
0.710 73
P1h (triclinic)
15.792(3)
16.345(3)
16.678(3)
62.69(1)
81.00(1)
86.94(1)
23
0.07 × 0.09 × 0.10
radiation (Mo KR), Å
space group
a, Å
b, Å
c, Å
0.710 73
0.710 73
0.710 73
P21/n (monoclinic)
11.003(2)
18.678(3)
P21/c (monoclinic)
9.797(3)
18.203(6)
P21/n (monoclinic)
16.076(2)
17.185(2)
17.618(3)
19.592(5)
18.447(3)
R, deg
â, deg
γ, deg
temp, °C
Z
95.42(1)
100.27(2)
97.41(1)
-50
4
3605
1.26
-50
4
3438
1.21
23
4
5054
1.25
2
4
3777
1.15
V, Å3
1939
1.35
D
calcd, g/cm3
µ, cm-1
7.68
6.36
7.98
7.59
5.55
R, Rw
0.022, 0.024b
0.032, 0.028b
0.026, 0.027b
0.067, 0.076c
0.057, 0.079c
a
2
a R ) ∑||Fo| - |Fc||/∑|Fo|; Rw ) [∑w(|Fo| - |Fc|)2/∑w|Fo| ]1/2
.
b w ) [σ(F)]-2
.
c w ) [0.04F2 + (σ(F))2]-1
.
temperature (-35 °C) from toluene/THF (9:1). The crystals were then
dried under dynamic vacuum for 12 h (yield 0.45 g, 47%). The
microanalysis for this material suggests the formula [Li(THF)x][In-
(NPh2)3Cl] where x = 4. Anal. Calcd for C52H62N3ClInLiO4: C, 65.71;
H, 6.60; N, 4.40. Found: C, 65.08; H, 6.29; N, 4.23.
(SiMe3)}4], where the θ/2θ method was used. Two standard reflections
were monitored after every 2 h or every 100 data collected for In-
(NPh2)3(py)‚toluene, In[N(t-Bu)(SiHMe2)]3(p-Me2Npy), and In[NPh-
(SiMe3)]3(ether). The data showed no decay. Three standard reflections
were monitored every 1 h of exposure time for [Li(THF)4][In(NPh2)3-
Cl] and [Li(p-Me2Npy)][In{NMe(SiMe3)}4]. The data for the diphe-
nylamido complex showed no significant decay, but the data for [Li(p-
Me2Npy)][In{NMe(SiMe3)}4] showed a linear decay of <5%, which
was corrected for by applying a normalization factor as a function of
X-ray exposure time. In all cases Lorentz and polarization corrections
were applied during data reduction. No absorption correction was
applied for In(NPh2)3(py)‚toluene, In[N(t-Bu)(SiHMe2)]3(p-Me2Npy),
and In[NPh(SiMe3)]3(ether) due to their small absorption coefficients.
Semiempirical absorption corrections for [Li(THF)4][In(NPh2)3Cl] and
[Li(p-Me2Npy)][In{NMe(SiMe3)}4] were applied based on Ψ scans of
10 reflections having ø angles between 70° and 90°. Calculations for
In(NPh2)3(py)‚toluene, In[N(t-Bu)(SiHMe2)]3(p-Me2Npy), and In[NPh-
(SiMe3)]3(ether) were made using Nicolet’s SHELXTL PLUS (1987)
package of programs,11 and those for [Li(THF)4][In(NPh2)3Cl] and [Li-
(p-Me2Npy)][In{NMe(SiMe3)}4] were made using the MolEN pack-
age.12
In[NPh(SiMe3)]3(ether). The Laue symmetry was determined to
be 2/m, and from the systematic absences the space group was shown
unambiguously to be P21/n. The structure was solved by using the
SHELXTL Patterson interpretation program, which revealed the
positions of most of the non-hydrogen atoms. The remaining non-
hydrogen atoms were located in subsequent difference Fourier synthe-
ses. The usual sequence of isotropic and anisotropic refinement
followed. The hydrogen atoms attached to carbon were then entered
in ideal calculated positions and constrained to riding motion with a
single variable isotropic temperature factor for all of them. After all
shift/esd ratios were less than 0.1, convergence was reached at the
agreement factors listed in Table 1. No unusually high correlations
were noted between any of the variables in the last cycle of refinement.
The final difference map showed a maximum peak of about 0.25 e/Å3.
1H NMR (CD3CN): δ 0.18 (m, 8, THF), 3.64 (m, 8, THF), 6.62 (t,
6, p-Ph), 6.80 (d, 12, o-Ph), 6.96 (t, 12, m-Ph). 13C{1H} NMR (CD3-
CN): δ 26.6 (THF), 68.7 (THF), 119.7 (Ph), 123.7 (Ph), 129.9 (Ph),
154.8 (Ph). IR (Nujol, CsI, cm-1): 1581 m, 1340 m, 1288 s, 1207 m,
1166 m, 1041 m, 989 w, 887 s, 868 w, 852 s, 787 w, 744 s, 725 m,
692 m, 578 w, 515 w, 501 w, 470 w, 428 w.
Li[In{NMe(SiMe3)}4]. In the glovebox, a solution of LiNMe-
(SiMe3) (0.44 g, 4.0 mmol) in ether (5 mL) was added slowly to a
suspension of InCl3 (0.22 g, 1.0 mmol) in ether (25 mL). The reaction
mixture was stirred for 24 h. The ether was removed in vacuo, and
the residue was then held in vacuo for 4 h. The residue was extracted
with hexane (10 × 10 mL), and the extracts were filtered through Celite.
The hexane was removed in vacuo from the filtrate, and the residue
was held in vacuo for 24 h. The dried residue, a white solid, is the
monoetherate by 1H NMR (yield 0.44 g, 72%). The ether can be
removed by dissolution of the etherate in CH2Cl2 and then immediate
vacuum distillation to remove the CH2Cl2/ether. Anal. Calcd for
C16H48N4InLiSi4: C, 36.20; H, 9.13; N, 10.56. Found: C, 36.07; H,
9.53; N, 10.24.
1H NMR (C6D6): δ 0.29 (s, 36, SiMe3), 2.75 (s, 12, NMe). 13C-
{1H} NMR (C6D6): δ 1.74 (SiMe3), 35.5 (NMe). IR (Nujol, CsI, cm-1):
1246 vs, 1153 m, 1068 s, 1018 s, 956 w, 893 s, 854 s, 833 s, 769 s,
738 s, 678 w, 667 m, 580 w, 439 s.
[Li(p-Me2Npy)][In{NMe(SiMe3)}4]. This compound was prepared
by dissolving the etherate (0.10 g, 0.17 mmol) in toluene, adding
p-(dimethylamino)pyridine (0.020 g, 0.17 mmol) to the solution, and
keeping the mixture at -35 °C for 48 h. Light yellow crystals were
obtained (yield 0.090 g, 81%).
1H NMR (C6D6): δ 0.38 (s, 36, SiMe3), 2.08 (s, 6, NMe2), 3.10 (s,
12, NMe) 5.83 (d, 2, m-py), 7.77 (d, 2, o-py).
X-ray Crystallography. Crystal data are presented in Table 1.
Crystals of In(NPh2)3(py)‚toluene and [Li(p-Me2Npy)][In{NMe-
(SiMe3)}4] are yellow plates, and crystals of In[N(t-Bu)(SiHMe2)]3(p-
Me2Npy), In[NPh(SiMe3)]3(ether), and [Li(THF)4][In(NPh2)3Cl] are
colorless blocks. The crystals of In(NPh2)3(py)‚toluene, In[N(t-Bu)-
(SiHMe2)]3(p-Me2Npy), and In[NPh(SiMe3)]3(ether) were handled under
mineral oil. For each of these compounds the crystal chosen for analysis
was transferred to a cold nitrogen stream for data collection on a Nicolet
R3m/V diffractometer. Crystals of [Li(THF)4][In(NPh2)3Cl] and [Li-
(p-Me2Npy)][In{NMe(SiMe3)}4] were mounted in capillaries, and the
data were collected at room temperature on an Enraf-Nonius CAD-4F
(κ geometry) diffractometer. Intensities were measured using the
ω-scan technique except in the case of [Li(p-Me2Npy)][In{NMe-
In(NPh2)3(py)‚toluene. The Laue symmetry was determined to be
1h, and the space group was shown to be P1 or P1h. Because the unitary
structure factors displayed centric statistics, space group P1h was
assumed to be correct. The structure was solved by using the
SHELXTL Patterson interpretation program, which revealed the position
of the In atom. The remaining non-hydrogen atoms were located in
subsequent difference Fourier syntheses. The usual sequence of
(11) Sheldrick, G. M. SHELXTL PLUS, Release 3.4 for the Nicolet R3m/V
Crystallographic System; Nicolet Instrument Corp.: Madison, WI,
1987.
(12) MolEN, An InteractiVe Structure Solution Program; Enraf-Nonius:
Delft, The Netherlands, 1990.

3838 Inorganic Chemistry, Vol. 37, No. 15, 1998
Kim et al.
isotropic and anisotropic refinement followed. Hydrogen atoms
attached to carbon were then entered in ideal calculated positions and
constrained to riding motion with a single variable isotropic temperature
factor for the nonsolvent hydrogens and a separate variable for the
toluene hydrogens. The toluene methyl group was treated as an ideal
rigid body and allowed to refine independently. After all shift/esd ratios
were less than 0.2, convergence was reached at the agreement factors
listed in Table 1. No unusually high correlations were noted between
any of the variables in the last cycle of full-matrix least-squares
refinement, and the final difference map showed a maximum peak of
about 0.5 e/Å3.
Scheme 1
In[N(t-Bu)(SiHMe2)]3(p-Me2Npy). The Laue symmetry was de-
termined to be 2/m, and from the systematic absences the space group
was shown unambiguously to be P21/n. The structure was solved by
using the SHELXTL Patterson interpretation program, which revealed
the position of the In atom. The remaining non-hydrogen atoms were
located in subsequent difference Fourier syntheses. The usual sequence
of isotropic and anisotropic refinement followed. The hydrogen atoms
attached to carbon were then entered in ideal calculated positions and
constrained to riding motion with a single variable isotropic temperature
factor for all of them. The hydrogens attached to Si were located in
difference maps and allowed to refine independently. The two methyl
groups attached to N5 were refined as ideal rigid bodies and allowed
to rotate independently. After all shift/esd ratios were less than 0.1,
convergence was reached at the agreement factors listed in Table 1.
No unusually high correlations were noted between any of the variables
in the last cycle of refinement. The final difference map showed a
maximum peak of about 0.5 e/Å3.
In diethyl ether, InCl3 reacts with 3 equiv of lithium amide
to give In(NRR′)3 (R ) Ph or t-Bu, R′ ) SiMe3; R ) t-Bu, R′
) SiHMe2). The ether adduct of the phenyl silyl amide
derivative, In[NPh(SiMe3)]3(ether), a colorless crystalline solid,
can be isolated from the synthesis if the product is held under
vacuum only briefly. The ether can also be removed from the
etherate by dissolution in CH2Cl2 and then removal of the CH2-
Cl2/ether in vacuo. In[N(t-Bu)(SiMe3)]3 is a volatile white solid
(subl 70 °C, 10-2 Torr, with some decomposition) while In-
[NPh(SiMe3)]3 is a yellow-orange liquid that decomposes at ≈70
°C under vacuum and In[N(t-Bu)(SiHMe2)]3 is a light yellow
liquid that distills at 30 °C, 10-2 Torr. In[N(t-Bu)(SiHMe2)]3
reacts with p-(dimethylamino)pyridine to form the adduct In-
[N(t-Bu)(SiHMe2)]3(p-Me2Npy), a colorless crystalline solid.
This compound was prepared to have a solid sample for an
X-ray crystallographic analysis (see below). Attempted reac-
tions of InCl3 with LiN(SiHMe2)2 in ether and pyridine solvents
produced copious amounts of a gray insoluble precipitate that
is presumably In metal.
When less sterically encumbered amides are reacted with
indium chloride in weakly coordinating ether solvents, salts are
isolated. Thus, indium trichloride reacts with 3 equiv of LiNMe-
(SiMe3) in diethyl ether to give [Li(ether)][In{NMe(SiMe3)}4]
instead of the intended tris(amide) product. The yield of the
salt is nearly doubled (to 72%) by carrying out the reaction
with the correct 1:4 stoichiometry. Similarly, InCl3 reacts with
3 equiv of LiNPh2 in THF to give [Li(THF)4][In(NPh2)3Cl],
which forms yellow crystals upon low-temperature crystalliza-
tion from toluene/THF. Both [Li(ether)][In{NMe(SiMe3)}4] and
[Li(THF)4][In(NPh2)3Cl] show moderate solubility in benzene.
To have a sample of Li[In{NMe(SiMe3)}4] suitable for X-ray
analysis, the p-(dimethylamino)pyridine adduct [Li(p-Me2Npy)]-
[In{NMe(SiMe3)}4] was prepared by reacting the etherate with
p-Me2Npy and crystallizing from toluene.
[Li(p-Me2Npy)][In{NMe(SiMe3)}4]. The Laue symmetry was
determined to be 1h, and the space group was shown to be P1 or P1h.
Because the unitary structure factors displayed centric statistics, the
space group P1h was assumed to be the correct setting. The structure
was solved by using the MolEN Patterson interpretation program, which
revealed the position of the In atoms. The remaining non-hydrogen
atoms were located in subsequent difference Fourier syntheses.
A
disorder observed for one of the N(Me)SiMe3 groups resolved as two
Si and four Me positions with site occupancies refined to 0.5. The In,
N, and full-occupancy Si atoms were refined with anisotropic thermal
parameters. Hydrogen atoms attached to carbon were then entered in
ideal calculated positions and constrained to riding motion such that
U(H) ) 1.3U(attached C). After all shift/esd ratios were less than 0.01,
convergence was reached at the agreement factors listed in Table 1.
No unusually high correlations were noted between any of the variables
in the last cycle of full-matrix least-squares refinement, and the final
difference map showed a maximum peak of about 1.0 e/A3 located
near In(1).
[Li(THF)4][In(NPh2)3Cl]. The Laue symmetry was determined to
be 2/m, and from the systematic absences the space group was shown
unambiguously to be P21/n. The structure was solved by using the
MolEN Patterson interpretation program, which revealed the position
of the In atom. The remaining non-hydrogen atoms were located in
subsequent difference Fourier syntheses, but due in part to the weak
scattering by the crystal, the phenyl groups and THF molecules were
difficult to locate and refine. Attempts to model both either as rigid
groups or with bond length and angle restraints led to unreasonable
geometries and/or thermal parameters. The disorder for only one THF
molecule was eventually resolved. For all the THF molecules, the best
refinements were obtained by assigning a common thermal parameter
to each residue. Due to the paucity of data, only the In atom was refined
with anisotropic thermal parameters. The hydrogen atoms attached to
carbon were entered in ideal calculated positions and constrained to
riding motion such that U(H) ) 1.3U(attached C). After all shift/esd
ratios were less than 0.1, convergence was reached at the agreement
factors listed in Table 1. No unusually high correlations were noted
between any of the variables in the last cycle of refinement. The final
difference map showed a maximum peak of about 0.5 e/A3.
The isolation of the salt compounds from reactions carried
out in ether solvents contrasts with the results of reactions
between InCl3 and 3 equiv of LiNRR′ (R ) R′ ) Ph; R ) Me,
R′ ) SiMe3) carried out in pyridine, which produce the neutral
complexes In(NRR′)3(py). In[NMe(SiMe3)]3(py) can also be
prepared by carrying out the reaction in a 9:1 mixture of ether/
Results and Discussion
Syntheses and Spectroscopic Characterization. A sum-
mary of our synthetic results is presented in Scheme 1.

Synthesis of Indium Amide Compounds
Inorganic Chemistry, Vol. 37, No. 15, 1998 3839
Figure 1. View of In[NPh(SiMe3)]3(ether) showing the atom-number-
ing scheme (50% probability ellipsoids).
Figure 3. View of In[N(t-Bu)(SiHMe2)]3(p-Me2Npy) showing the
atom-numbering scheme (40% probability ellipsoids).
Figure 4. View of [Li(p-Me2Npy)][In{NMe(SiMe3)}4] showing the
atom-numbering scheme for one of the two independent molecules in
the unit cell (50% probability ellipsoids).
Figure 2. View of In(NPh2)3(py) showing the atom-numbering scheme
(40% probability ellipsoids).
pyridine. In(NPh2)3(py) is a yellow crystalline solid, and In-
[NMe(SiMe3)]3(py) is a viscous light red liquid that distills at
70-75 °C with decomposition. The py ligand in In[NMe-
(SiMe3)]3(py) is displaced by p-(dimethylamino)pyridine, a
better donor than unsubstituted pyridine, to yield In[NMe-
(SiMe3)]3(p-Me2Npy) as a crystalline light tan solid after
workup.
We considered the possibility that in the reactions described
in the previous paragraph the pyridine solvent prevents forma-
tion of [In{NMe(SiMe3)}4]- and [In(NPh2)3Cl]- by blocking
open coordination sites. To test this idea, we reacted In[NMe-
(SiMe3)]3(py) with excess LiNMe(SiMe3) (4-5 equiv) in neat
pyridine. After stirring for 24 h, the pyridine was removed in
vacuo, and the residue was extracted with benzene-d6 (some
Figure 5. View of [In(NPh2)3Cl]- from [Li(THF)4][In(NPh2)3Cl]
showing the atom-numbering scheme (50% probability ellipsoids).
1
insoluble material remained). The H NMR specrum of the
extract showed only the presence of the salt [Li(pyridine)][In-
{NMe(SiMe3)}4]. Because the pyridine did not prevent forma-
tion of the salt in the aforementioned experiment, we also
examined the possibility that the neutral In(NRR′)3(py) com-
pounds are formed via [In(NRR′)4]- intermediates. To test this
idea, we reacted preformed [Li(ether)][In{NMe(SiMe3)}4] with
1/3 equiv of InCl3 in neat pyridine under the same reaction
conditions (23 °C/24 h) used to prepare In[NMe(SiMe3)]3(py)
from LiNMe(SiMe3) and InCl3. After the specified time the
pyridine solvent was removed in vacuo. The 1H NMR spectrum
of the residue (benzene-d6) revealed the soluble components to
be a 60:40 mixture of [Li(py)x][In{NMe(SiMe3)}4] and In[NMe-
(SiMe3)]3(py). This result suggests that the formation of In-
[NMe(SiMe3)]3(py) from InCl3/LiNMe(NSiMe3) in pyridine is
not entirely through an anion intermediate. On the basis of these
two sets of experiments, the role pyridine solvent plays to allow
isolation of the neutral adducts In[NMe(SiMe3)]3(py) and In-
(NPh2)3(py) rather than the anions [In{NMe(SiMe3)}4]- and
[In(NPh2)3Cl]- is not clear. It is reasonable to suggest, however,

3840 Inorganic Chemistry, Vol. 37, No. 15, 1998
Kim et al.
Table 2. Selected Bond Distances (Å) and Angles (deg) for In[NPh(SiMe3)]3(ether), In(NPh2)3(py)‚toluene, In[N(t-Bu)(SiHMe2)]3(p-Me2Npy),
[Li(p-Me2Npy)][In{NMe(SiMe3)}4], and [Li(THF)4][In(NPh2)3Cl]
In[NPh(SiMe3)]3
(ether)
In(NPh2)3(py)‚
In[N(t-Bu)(SiHMe2)]3
(p-Me2Npy)
[Li(p-Me2Npy)]
[Li(THF)4]
[In(NPh2)3Cl]
toluene
[In{NMe(SiMe3)}4]a
Distances
In-N1
2.098(2)
2.103(2)
2.083(2)
2.283(2) (Z ) O)
2.079(3)
2.072(3)
2.099(3)
2.264(4) (Z ) N4)
2.130(3)
2.124(3)
2.122(3)
2.327(3) (Z ) N4)
2.17(1)
2.05(1)
2.08(1)
2.17(2) (Z ) N4)
2.02(4)
1.98(4)
1.99(4)
2.02(2)
2.11(1)
2.15(1)
2.384(6) (Z ) Cl)
In-N2
In-N3
In-Z
Li1-N1
Li1-N4
Li1-N106
Angles
119.3(1)
115.0(1)
114.8(1)
100.7(1)
92.4(1)
110.4(1)
121.4(3)
(X ) Si1, Y ) C3)
117.4(1)
121.0(2)
123.2(2)
(X ) Si2, Y ) C9)
114.9(1)
121.1(2)
124.4(2)
N1-In-N2
N1-In-N3
N2-In-N3
Z-In-N1
Z-In-N2
Z-In-N3
X-N1-Y
117.3(1)
121.4(1)
115.9(1)
90.0(1)
106.3(1)
97.3(1)
120.8(2)
(X ) Si1, Y ) C4)
123.3(1)
115.8(2)
120.1(2)
(X) Si2, Y ) C13)
122.8(1)
117.0(2)
116.2(2)
128.0(1)
111.3(1)
109.5(1)
99.0(1)
100.0(1)
105.3(1)
119.5(3)
(X ) C1, Y ) C7)
127.5(3)
113.0(2)
117.2(3)
(X ) C13, Y ) C19)
114.7(3)
127.1(3)
118.8(3)
119.9(5)
107.2(6)
110.7(5)
89.9(6)
109.4(6)
118.7(5)
111.(1)
(X ) Si1, Y ) C1)
128.3(6)
112.(1)
113.(1)
(X ) Si2, Y ) C2)
125.7(7)
120.(1)
115.(1)
(X ) Si3, Y ) C3)
122.7(5)
122.(1)
107.(1)
(X ) Si4, Y ) C4)
129.7(9)
109.(1)
100.(2)
114.9(6)
109.6(6)
113.2(5)
100.9(4)
106.8(4)
110.7(4)
110.(2)
((X ) C1, Y ) C7)
123.(1)
127.(1)
121.(1)
((X ) C13, Y ) C19)
117.(1)
121.(1)
123.(2)
In-N1-X
In-N1-Y
X-N2-Y
In-N2-X
In-N2-Y
X-N3-Y
(X ) Si3, Y ) C22)
128.6(1)
115.2(2)
(X ) C25, Y ) C31)
121.6(3)
119.0(2)
(X ) Si3, Y ) C15)
115.3(1)
119.9(2)
(X ) C25, Y ) C31)
124.(1)
113.(1)
In-N3-X
In-N3-Y
X-N4-Y
In-N4-X
In-N4-Y
N1-Li1-N4
N1-Li1-N106
N4-Li1-N106
131.(2)
128.(2)
a Distances and angles for only one of the two independent molecules in the asymmetric unit are presented. See the Supporting Information for
full details.
that the pyridine slows formation of the anions, thereby allowing
isolation of the neutral complexes.
The overall geometries of the four-coordinate In atoms can
be loosely described as severely distorted tetrahedral with the
exception of [In(NPh2)3Cl]-, which approaches an ideal tetra-
hedral geometry. In In[NPh(SiMe3)]3(ether), In(NPh2)3(py), and
In[N(t-Bu)(SiHMe2)]3(p-Me2Npy), the amide nitrogens and the
In atoms are close to planar, with the sum of the N-In-N
angles being 355°, 350° and 349°, respectively (Table 2). The
N-In-N angles associated with the amide ligands in the neutral
compounds vary widely, with the biggest difference found in
In(NPh2)3(py), where N1-In-N2 is more than 17° larger than
N2-In-N3 and N1-In-N3. On the other hand, the N-In-N
angles in In[N(t-Bu)(SiHMe2)]3(p-Me2Npy) fall in a narrow 4°
range. The amide nitrogen coordination geometries are all
planar with the exception of N1 and N4 in [Li(p-Me2Npy)][In-
{NMe(SiMe3)}4], which show slight pyramidalization (≈10°)
because they are bound to the Li cation. The X-N-Y angles
at the amide nitrogens in the neutral compounds are all within
4° of 120°, but the associated In-N-X,Y angles span a large
range, 113-129°, suggesting that the energy barrier for bending
is low and the angle is set by steric factors.
There is no evidence to suggest the existence of dimer
solution structures in room temperature 1H NMR spectra of In-
[N(t-Bu)(SiMe3)]3, In[NPh(SiMe3)]3, and In[N(t-Bu)(SiHMe2)]3
or in low-temperature spectra of In[NPh(SiMe3)]3 (toluene-d8,
down to -60 °C). A molecular weight determination of In-
[NPh(SiMe3)]3 gave a mass of 710 ( 40 g/mol (isothermal
distillation, pentane solvent, Ta[N(SiMe3)2]2Cl3 standard), which
is about 17% higher than the monomer molecular weight of
608 g/mol.
In the 1H NMR spectra of In[N(t-Bu)(SiHMe2)]3 and In(N(t-
Bu)(SiHMe2))3(p-Me2Npy) the Si-H protons appear as septets
due to coupling with the methyl groups attached to Si.
Similarly, the Si-H proton in the parent amine HN(t-Bu)-
(SiHMe2) gives rise to an “octet” due to coupling with SiMe2
3
3
′
and NH (i.e., JHH ≈ JHH ≈ 3 Hz). The IR spectrum of In-
[N(t-Bu)(SiHMe2)]3 has a strong band at 2075 cm-1 that can
be assigned to the Si-H stretch.
X-ray Crystallographic Studies. X-ray crystal structure
determinations of In[NPh(SiMe3)]3(ether) (Figure 1), In(NPh2)3-
(py)‚toluene (Figure 2), In[N(t-Bu)(SiHMe2)]3(p-Me2Npy) (Fig-
ure 3), [Li(p-Me2Npy)][In{NMe(SiMe3)}4] (Figure 4), and
[Li(THF)4][In(NPh2)3Cl] (Figure 5) were carried out. The
results of the analyses for the two salt compounds are poor
because of the crystal quality.
The In-N(amide) distances in In[N(t-Bu)(SiHMe2)]3(p-Me2-
Npy) (average 2.125(3) Å) are significantly longer than those
in In[NPh(SiMe3)]3(ether) (average 2.095(2) Å) and In(NPh2)3-
(py) (average 2.083(3) Å). The In-N(amide) distances in the
new compounds can be compared to those found in In-
[N(SiMe3)2]3 (2.049(1) Å),4 In(2,2,6,6-tetramethylpiperidino)3
(average 2.078(5) Å),8 (Me3C)2In[N(SiPh3)(2,6-i-PrPh)] (2.104(3)

Synthesis of Indium Amide Compounds
Inorganic Chemistry, Vol. 37, No. 15, 1998 3841
Å),4 and Et2In(NC5H4) (2.166(4) Å).13 In In[NPh(SiMe3)]3-
(ether) the In-O distance (2.283(2) Å) is in the range of dative
In-O bond distances found in In(mesityl)3(THF) (2.414(4) Å),14
In(SC6(CF3)3H2)3(ether) (2.224(6) Å),15 and InCl3(THF)2 (2.265-
(5) Å),16 and the In-N(py) bond lengths in In(NPh2)3(py)
(2.264(4) Å) and In[N(t-Bu)(SiHMe2)]3(p-Me2Npy) (2.327(3)
Å) are close to the corresponding distances found in InX3(py)3
where X ) Cl or Br (2.28(3)-2.38(2) Å)17,18 and InCl2(1,3-
diphenyltriazide)(3,5-dimethylpyridine)2 (average 2.307(7) Å).19
In [Li(THF)4][In(NPh2)3Cl], the [Li(THF)4]+ fragment is not
close to the anion, but in [Li(p-Me2Npy)][In{NMe(SiMe3)}4],
the lithium cation interacts with two of the amide nitrogens (N1
and N4) and p-Me2Npy (N106), giving lithium a planar, three-
coordinate geometry. The N-Li-N angle associated with the
two amide ligands is nearly 30° smaller than the other two
angles, and the three Li-N bond distances are the same within
experimental error. The Li coordination geometry in [Li(p-
Me2Npy)][In{NMe(SiMe3)}4] is similar to that found in [Li-
(py)]2[Cr(NEt2)4].20
carried out in the presence of pyridine yield the neutral
adducts In(NPh2)3(py) and In[NMe(SiMe3)]3(py). In the latter
reactions the role pyridine plays to prevent formation of
[In{NMe(SiMe3)}4]- and [In(NPh2)3Cl]- is not clear. The result
suggests, however, that other neutral In(amide)3L compounds
may be accessible by using similar coordinating solvents, such
as liquefied NMe3, or by using preformed InCl3Ln (L ) amine)
complexes as starting materials. In[N(t-Bu)(SiHMe2)]3 and In-
[NMe(SiMe3)]3(py) react with the strong donor p-(dimethyl-
amino)pyridine to give In(NRR′)3(p-Me2Npy) compounds.
In the solid state, In[NPh(SiMe3)]3(ether), In(NPh2)3(py), and
In[N(t-Bu)(SiHMe2)]3(p-Me2Npy) have nearly planar In(amide)3
cores. The anion in [Li(THF)4][In(NPh2)3Cl] is separated from
the cation in the solid state, but in [Li(p-Me2Npy)][In{NMe-
(SiMe3)}4], the tetrahedral-like anion is bound to the Li cation
via two amide nitrogens. In the latter compound, the Li is also
bonded to p-Me2Npy, resulting in a planar three-coordinate
geometry for Li.
A goal of this study was to prepare CVD precursors for use
in combination with ammonia to give InN. Of the new
compounds, In[N(t-Bu)(SiHMe2)]3 is the most promising pre-
cursor candidate because it is a liquid and it can be volatilized
without appreciable decomposition, two essential attributes of
a CVD precursor.
Conclusion
In(NRR′)3 (R ) Ph or t-Bu, R′ ) SiMe3; R ) t-Bu, R′ )
SiHMe2) compounds are synthesized by reacting InCl3 with
lithium amides in diethyl ether. In contrast, InCl3 reacts with
the less sterically demanding amides LiNPh2 and LiNMe(SiMe3)
in ether solvents to give the salt compounds Li[In(NPh2)3Cl]
and Li[In{NMe(SiMe3)}4], respectively. Similar reactions
Acknowledgment for support is made to the Robert A. Welch
Foundation, Texas Advanced Research Program, and the Energy
Laboratory at UH. We thank Dr. James Korp for his technical
assistance with the crystal structure determinations of In[NPh-
(SiMe3)]3(ether), In(NPh2)3(py), and In[N(t-Bu)(SiHMe2)]3(p-
Me2Npy).
(13) Porchia, M.; Benetollo, F.; Brianese, N.; Rossetto, G.; Zanella, P.;
Bombieri, G. J. Organomet. Chem. 1992, 424, 1.
(14) Rossetto, G.; Brianese, N.; Camporese, A.; Casellato, U.; Ossola, F.;
Porchia, M.; Zanella, P. Gazz. Chim. Ital. 1990, 120, 805.
(15) Bertel, N.; Noltemeyer, M.; Roesky, H. W. Z. Anorg. Allg. Chem.
1990, 588, 102.
(16) Whittlesey, B. R.; Ittycheriah, I. P. Acta Crystallogr. C 1994, 50, 693.
(17) Jeffs, S. E.; Small, R. W. H.; Worrall, I. J. Acta Crystallogr. C 1984,
40, 1329.
(18) Small, R. W. H.; Worrall, I. J. Acta Crystallogr. C 1982, 38, 932.
(19) Leman, J. T.; Roman, H. A.; Barron, A. R. J. Chem. Soc., Dalton
Trans. 1992, 2183.
Supporting Information Available: Complete tables of crystal
data, atomic coordinates, thermal parameters, and bond distances and
angles for In[NPh(SiMe3)]3(ether), In(NPh2)3(py), In[N(t-Bu)(SiHMe2)]3(p-
Me2Npy), [Li(THF)4][In(NPh2)3Cl], and [Li(p-Me2Npy)][In{NMe-
(SiMe3)}4] (44 pages). Ordering information is given on any current
masthead page.
(20) Edema, J. J. H.; Gambarotta, S.; Meetsma, A.; Spek, A. L.; Smeets,
W. J. J.; Chiang, M. Y. J. Chem. Soc., Dalton Trans. 1993, 789.
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