Trimerization of phenylacetonitrile. InMe3 as a base for C-H acidic nitriles

Article abstract of DOI:10.1021/om0303956

The reaction of phenylacetonitrile with InMe₃ in boiling toluene in a molar ratio of 3:1 leads to a trimerization of the nitrile with evolution of methane. The presence of CsF accelerates the reaction. The colorless product was recrystallized from toluene/TMEDA to give 2-amino-1-[Me₂In(TMEDA)]-4-amino-3,5-diphenyl-6-benzylpyridine (6). A similar reaction of Ph₂CHCN with InMe₃ in boiling toluene gives not the product of a trimerization but a metalla-substituted ketenimine which crystallizes after addition of THF as the dimer [Ph₂C=C=NInMe₂(THF)]₂ (7). The reaction was monitored by ¹H NMR spectroscopy, exhibiting a equilibrium with a 0.5(7) to nitrile ratio of 82:18 mol %. CsF accelerates this reaction as well. Quite similarly, the reaction between GaMe₃ and Ph₂CHCN proceeds to give [Ph₂C=C=NGaMe₂]₂ (8), but the position of the equilibrium 0.5(8):Ph₂CHCN is more unfavorable (34:66 mol %). A complete transfer to 7 or 8 was observed when [Ph₂C=C=NLi(OEt₂)₂]₂ (9) was added to Me₂InCl or Me₂GaCl. 6, 7, 9, and Ph₂CHCN were characterized by NMR and vibrational spectroscopy as well as by X-ray structure analyses. According to these, 6 shows a delocalization of π-electrons over the six-membered ring and the amino/amido functions. The In atom possesses coordination number (CN) 5 with an In-N single bond of 2.180(3) A and two weak donor-acceptor bonds of 2.439(3) A (pyridine) and 2.533(3) A (TMEDA). The ketenimine sequence in 7 shows C=C distances of 1.35 A and C=N distances of 1.20 A (mean values). The unit cell of the dimer 9 consists of two crystallographically unique molecules with almost planar four-membered Li₂N₂ rings.

Full text of DOI:10.1021/om0303956

Organometallics 2003, 22, 4129-4135
4129
Tr im er iza tion of P h en yla ceton itr ile. In Me3 a s a Ba se for
C-H Acid ic Nitr iles
Effat Iravani and Bernhard Neumu¨ller*
Fachbereich Chemie der Universita¨t Marburg, Hans-Meerwein-Strasse,
D-35032 Marburg, Germany
Received May 27, 2003
The reaction of phenylacetonitrile with InMe3 in boiling toluene in a molar ratio of 3:1
leads to a trimerization of the nitrile with evolution of methane. The presence of CsF
accelerates the reaction. The colorless product was recrystallized from toluene/TMEDA to
give 2-amino-1-[Me2In(TMEDA)]-4-amino-3,5-diphenyl-6-benzylpyridine (6). A similar reac-
tion of Ph2CHCN with InMe3 in boiling toluene gives not the product of a trimerization but
a metalla-substituted ketenimine which crystallizes after addition of THF as the dimer
[Ph2CdCdNInMe2(THF)]2 (7). The reaction was monitored by 1H NMR spectroscopy,
exhibiting a equilibrium with a 0.5(7) to nitrile ratio of 82:18 mol %. CsF accelerates this
reaction as well. Quite similarly, the reaction between GaMe3 and Ph2CHCN proceeds to
give [Ph2CdCdNGaMe2]2 (8), but the position of the equilibrium 0.5(8):Ph2CHCN is more
unfavorable (34:66 mol %). A complete transfer to 7 or 8 was observed when [Ph2CdCd
NLi(OEt2)2]2 (9) was added to Me2InCl or Me2GaCl. 6, 7, 9, and Ph2CHCN were characterized
by NMR and vibrational spectroscopy as well as by X-ray structure analyses. According to
these, 6 shows a delocalization of π-electrons over the six-membered ring and the amino/
amido functions. The In atom possesses coordination number (CN) 5 with an In-N single
bond of 2.180(3) Å and two weak donor-acceptor bonds of 2.439(3) Å (pyridine) and
2.533(3) Å (TMEDA). The ketenimine sequence in 7 shows CdC distances of 1.35 Å and
CdN distances of 1.20 Å (mean values). The unit cell of the dimer 9 consists of two
crystallographically unique molecules with almost planar four-membered Li2N2 rings.
In tr od u ction
Recently we were able to elucidate the reaction
between the metalanes MMe3 (M ) Al, Ga, In, Tl) and
acetonitrile.1-4 In the case of Al (1), Ga (2), and In (3)
the generation of a six-membered heterocyle with evolu-
tion of methane was observed (see Figure 1). We could
show that halide ions acting as catalysts by forming
intermediate metalates of the types [XMMe3]- and
[Me3MXMMe3]-,5 especially when cesium salts were
used. Only the metalane TlMe3 acts as a simple Lewis
acid, initiating the well-known nitrile trimerization6 to
a 1,3,5-triazine (4; Figure 1). The NCCCN sequence of
the heterocycle is part of a ligand which recently was
used very often to stabilize organometal fragments or
low-valent metal ions7 and which can be derived from
the acac (acetylacetonate) ligand. The iminium protons
n
in 2 can be abstracted with BuLi, followed by silylation
with Me3SiCl to give the corresponding N-SiMe3 het-
erocycle (5; Figure 1).1 A very recent study of the
(1) Kopp, M. R.; Neumu¨ller, B. Z. Anorg. Allg. Chem. 1999, 625,
739.
(2) Kopp, M. R.; Kra¨uter, T.; Dashti-Mommertz, A.; Neumu¨ller, B.
Organometallics 1998, 17, 4226.
(3) Kopp, M. R.; Neumu¨ller, B. Z. Anorg. Allg. Chem. 1999, 625,
1246.
F igu r e 1. Schematic representation of 1-5.
(4) For reactions of metal-activated organonitrils see: Kukushkin,
interaction of CoIII centers with acetonitrile in the
presence of a tosylamide anion leads to identical trim-
erization.8
Therefore, the question is, which intermediate is
present during the reaction and is it possible to use
V. Y.; Pombeiro, A. J . L. Chem. Rev. 2002, 102, 1771.
(5) (a) Werner, B.; Neumu¨ller, B. Chem. Ber. 1996, 129, 355. (b)
Werner, B.; Kra¨uter, T.; Neumu¨ller, B. Inorg. Chem. 1996, 25, 2977.
(c) Wilson, I. L.; Dehnicke, K. J . Organomet. Chem. 1974, 67, 229.
(6) March, J . Advanced Organic Chemistry, 3rd ed.; Wiley: New
York, 1985.
10.1021/om0303956 CCC: $25.00 © 2003 American Chemical Society
Publication on Web 09/06/2003

4130 Organometallics, Vol. 22, No. 20, 2003
Iravani and Neumu¨ller
- TMEDA - InMe2 - C7H7 - Ph)+; 235 (76) (InN4C4H16)+;
218 (35) (InN3C4H13)+; 116 (14) (TMEDA)+; 115 (2) (In)+; 91
(12) (C7H7)+; 77 (4) (Ph)+. Anal. Calcd: C, 66.57; H, 7.16; N,
9.95. Found: C, 66.37; H, 6.98; N, 9.91.
other nitriles for this trimerization? To answer the
questions, we decided to use the phenyl-substituted
acetonitriles PhCH2CN and Ph2CHCN. However, if a
oligomerization occurs, the products must be different
now, because those nitriles have less than three acidic
protons for abstraction and H-shift, respectively.
Syn th esis of [P h 2CdCdNIn Me2(THF )]2 (7). Method A
(typical experiment without CsF): 1.76 g (11.0 mmol) of InMe3
was dissolved in 25 mL of toluene. The solution was dropped
into a solution of 2.13 g (11.0 mmol) of Ph2CHCN. A weak gas
evolution was observed (no preceptible warming of the solu-
tion, probably CH4). The mixture was heated under reflux for
48 h. The solvent was removed under vacuum, and the residue
was dissolved in 20 mL of THF. The mixture was filtered, and
the filtrate was stored at -20 °C. After several days colorless
plates of 7 were obtained (2.4 g, 53% yield; in the melting point
determination, crystals of 7 became soft and opaque at ca. 40
°C and the white mass melted at 164 °C). The coordinated
solvent can be removed under vacuum.
Exp er im en ta l Section
Gen er a l P r oced u r es. All experiments were carried out
under an atmosphere of argon using Schlenk techniques.
Purification and drying of the solvents were performed using
standard methods.9 GaMe3 and InMe3 were donated by the
group of Prof. Dr. J . Lorberth. PhCH2CN and Ph2CHCN were
purchased from Aldrich and Merck-Schuchardt (PhCH2CN was
distilled and stored under argon; Ph2CHCN was recrystallized
from THF and stored under argon). Me2GaCl and Me2InCl
were prepared according to literature procedures.10,11
The 1H and 13C NMR spectra were recorded on a Bruker
ARX-200 spectrometer (1H, 200.135 MHz; 13C, 50.324 MHz).
The standard is TMS (external) with δ 0.0 ppm. The IR spectra
were obtained using a Bruker IFS-88 instrument (Nujol mulls,
CsI disks for the range 4000-500 cm-1; polyethylene disks for
the range 500-100 cm-1). The Raman spectra (RE) was
recorded on a J obin Yvon spectrometer (LABRAM HR800; He-
Ne laser; 633 nm). The melting points were measured with a
Dr. Tottoli (Bu¨chi) melting point apparatus in sealed capil-
laries under argon (values not corrected).
If 1 mol % CsF, was added the yield increases to 90% under
the same conditions.
Method B: 1.16 g (5.82 mmol) of Ph2CCNLi was dissolved
in 25 mL of Et2O, and the solution was added at 0 °C to 1.05
g (5.82 mmol) of Me2InCl in 25 mL of Et2O. The reaction is
exothermic, and the precipitation of LiCl was observed. The
mixture was stirred for 10 h. The suspension was filtered, and
the filtrate was evaporated to dryness. The residue was
dissolved in 20 mL of THF and stored at -20 °C. After several
days colorless plates of 7 could be isolated (2.0 g, 87% yield).
1H NMR (THF-d8; ppm): -0.48 (s, 12 H, InCH3), 1.60 (m, 8 H,
CH2CH2, THF), 3.49 (m, 8 H, OCH2, THF), 6.68 (m, pseudo-
Syn th esis of 2-Am in o-1-[Me2In (TMEDA)]-4-a m in o-3,5-
d ip h en yl-6-ben zylp yr id in e (6). A 0.86 g (7.3 mmol) amount
of PhCH2CN in 5 mL of toluene was added dropwise to a
solution of 1.17 g (7.3 mmol) of InMe3 in 40 mL of toluene at
20 °C. The mixture was heated under reflux for 5 days and
then filtered at room temperature. The filtrate was concen-
trated under vacuum, and 10 mL of DME was added. The
solution was covered with a small amount of TMEDA and
stored at -20 °C. Colorless crystals of 6 were obtained during
a period of 6 weeks (0.73 g, 42% yield; in the melting point
determination, crystals of 6 became opaque at ca. 50 °C and
shrank to a white mass which showed no change up to 310
triplet, 4 H, C4-H, phenyl), 7.06 (m, pseudo-triplet, 8 H, C3/5
H, phenyl), 7.25 (m, pseudo-doublet, 8 H, C2/6-H, phenyl). 13
-
C
NMR (THF-d8; ppm): -7.7 (InCH3), 25.1 (CH2CH2, THF), 55.0
(NdCdC), 66.9 (OCH2, THF), 122.0, 128.2 (C2/6, C3/5, phenyl),
129.3 (C4, phenyl), 141.2 (NdCdC), 143.8 (C1, phenyl). IR
(Nujol, cm-1): 2167 m (νas(out-of-phase CdCdN)); 1949 w,
1873 m, 1804 m, 1747 w, 1667 w, 1594 m, 1490 s, 1455 s, 1378
s, 1345 w, 1236 m (νs(out-of-phase CdCdN)), 1178 m, 1032
m, 1006 vw, 972 w, 913 w, 850 m, 811 vw, 753 s, 699 s, 649 m,
628 m, 614 w, 537 s (νas(InC2)), 515 m, 489 w (νs(InC2)), 473
m, 454 w (νring(In2N2)), 406 w, 345 w, 294, 258 vw, 225 w, 200
w, 151 m, 133 m. RE (crystalline; cm-1): 3073 w, 3064 w, 3057
s, 3051 w, 3044 m, 2166 w (νas(in-phase CdCdN)), 1596 m,
1240 w (νs(in-phase CdCdN)), 1199 m, 1167 m, 1157 w, 1034
w, 1027 m, 1010 s, 813 w, 771 m, 703 w, 647 w, 627 s, 613 s,
535 m (νas(InC2)), 493 w (νs(InC2)), 404 s, 298 w (νring(In2N2)),
243 vw, 227 vw, 188 m, 124 s, 116 s. EI-MS (m/z (relative
intensity), fragment): 193 (100) (HNCCPh2)+; 166 (52) (CPh2)+;
115 (10) (In)+; 77 (10) (Ph)+. Anal. Calcd (THF-free material):
C, 57.00; H, 4.78; N, 4.15. Found: C, 57.10; H, 4.94; N, 4.09.
The NMR and IR spectra of 7 isolated from method A (with
or without CsF) were identical; all the reactions were moni-
tored in sealed NMR tubes as well.
1
°C). H NMR (THF-d8; ppm): 0.01 (s, 6 H, InCH3), 1.64 (s, 2
H, CH2Ph), 2.50 (s, br, 12 H, CH3, TMEDA), 3.11 (m, 4 H, CH2,
TMEDA), 4.40 (s, 2 H, NH2), 5.71 (s, br, 1 H, NH), 6.93-7.37
(m, 15 H, H phenyl). 13C NMR (THF-d8; ppm): 0.69 (InCH3),
41.3 (s, CH2, TMEDA), 42.5 (s, CH2), 47.1 (s, CH3, TMEDA),
125.9, 127.7, 128.0 (C4, phenyl), 128.2, 129.4, 129.6, 130.2,
131.6, 132.1 (C2/6, C3/5, phenyl), 129.5, 136.9, 138.5, (C1, phenyl),
141.9 (H2NCC(Ph)CCH2Ph, pyridine), 150.2 (H2NCCCNH,
pyridine), 155.5 (NC, pyridine), 156.4 (H2NC, pyridine), 238.2
(HNC, pyridine). IR (Nujol, cm-1): 3478 (w, ν(NH2)), 3438 (w,
ν(NH2)), 3384 (w, ν(NH)), 2724 (vw), 1621 (m, ν(NdC), HNC),
1602 (m, ν(NdC), H2NC), 1582 (m), 1560 (m), 1307 (m), 1260
(m), 1152 (w), 1073 (m), 1026 (m), 938 (m), 800 (m), 764 (m),
704 (m), 513 (m, ν(InC2)), 451 (m, ν(InN)), 400 (m, ν(InN)),
243 (vw), 129 (vw). EI-MS (m/z (relative intensity), frag-
ment): 351 (100) (M - TMEDA - InMe2 - C7H7)+; 274 (4) (M
Syn th esis of [P h 2CdCdNGa Me2]2 (8). Method B: 2.58 g
(13.0 mmol) of Ph2CCNLi was dissolved in 25 mL of Et2O and
given at 0 °C to 1.75 g (12.9 mmol) of Me2GaCl in 25 mL of
Et2O. The reaction was exothermic, and LiCl precipitated. The
mixture was stirred for 15 h and filtered. The filtrate was
evaporated to dryness. The residue was dissolved in THF and
stored at -20 °C. After several days colorless crystals of 8 could
be isolated (3.4 g, 73% yield; mp 154 °C). 1H NMR (THF-d8;
ppm): -0.32 (s, 12 H, GaCH3), 6.86 (m, pseudo-triplet, 4 H,
C4-H, phenyl), 7.31 (m, pseudo-triplet, 8 H, C3/5-H, phenyl),
7.56 (m, pseudo-doublet, 8 H, C2/6-H, phenyl). 13C NMR (THF-
(7) See for example: (a) Kuhn, N.; Kuhn, A.; Speis, M.; Bla¨ser, D.;
Boese, R.; Chem. Ber. 1990, 123, 1301. (b) Kuhn, N.; Kuhn, A.;
Lewandowski, J .; Speis, M. Chem. Ber. 1991, 124, 997. (c) Cui, C.;
Roesky, H. W.; Schmidt, H.-G.; Noltemeyer, M. Angew. Chem., Int. Ed.
2000, 39, 4531. (d) Hardman, N. J .; Cui, C.; Roesky, H. W.; Fink, W.
H.; Power, P. P. Angew. Chem., Int. Ed. 2001, 40, 2172. Review: (e)
Bourget-Merk, L.; Lappert, M. F.; Severn, J . R. Chem. Rev. 2002, 102,
3031.
(8) Duran, M. L.; Garcia-Vazquez, J . A.; Gomez, C.; Sousa-Pedrares,
A.; Romero, J .; Sousa, A. Eur. J . Inorg. Chem. 2002, 2348.
(9) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of
Laboratory Chemicals, 2nd ed.; Pergamon Press: Oxford, U.K., 1980.
(10) Gmelin Handbook of Inorganic Chemistry; Springer-Verlag:
Berlin, New York, 1987; Gallium, Organogallium Compounds, Part 1.
(11) Weidlein, J . In Gmelin Handbook of Inorganic Chemistry;
Springer-Verlag: Berlin, New York, 1991; Indium, Organoindium
Compounds, Part 1.
d8; ppm): -4.1 (GaCH3), 55.1 (NdCdC), 122.4, 128.6 (C2/6, C3/5
,
phenyl), 128.0 (C4, phenyl), 140.0 (br, NdCdC), 143.2 (C1,
phenyl). IR (Nujol; cm-1): 2188 (νas(out-of-phase CdCdN)),
1952 m, 1873 m, 1804 m, 1748 m, 1652 m, 1597 s, 1493 vs,
1344 s, 1322 s, 1281 s, 1262 vs, 1224 m (νs(out-of-phase Cd
CdN)), 1207 vs (br), 1179 vs, 1079 vs, 1053 vs (br), 973 m,
944 vw, 905 vs, 888 vs, 803 vs, 703 vs, 616 vs (νas(GaC2)), 575
vs (νs(GaC2)), 534 vs, 457 s (νring(Ga2N2)), 395 s (νring(Ga2N2)),

Trimerization of Phenylacetonitrile
Organometallics, Vol. 22, No. 20, 2003 4131
Ta ble 1. Cr ysta llogr a p h ic Da ta for 6, 7, 9, a n d P h 2CHCN
6
7
9
Ph2CHCN
IPDS II
instrument
radiation
formula
fw
IPDS I (Stoe)
IPDS II
IPDS II
Mo KR
Mo KR
C40H48In2N2O2
818.47
Mo KR
C44H60N2O4Li2
694.85
Mo KR
C
39H50InN5
C14H11N
703.68
193.25
cryst size (mm)
a (Å)
b (Å)
0.52 × 0.11 × 0.06
11.065(1)
12.786(2)
14.356(2)
65.98(1)
81.43(1)
77.94(1)
1809.6(4)
triclinic
P1h
0.43 × 0.24 × 0.06
10.288(1)
12.973(2)
15.105(2)
75.30(1)
73.56(1)
83.82(1)
1868.9(4)
triclinic
P1h
0.2 × 0.15 × 0.06
13.790(2)
15.279(3)
22.582(4)
100.32(1)
107.05(1)
101.77(1)
4306(1)
triclinic
P1h
0.71 × 0.15 × 0.07
10.720(2)
6.297(1)
c (Å)
16.385(2)
R (deg)
â (deg)
107.28(1)
γ (deg)
V (Å3)
1056.1(3)
monoclinic
P21/c
cryst syst
space group
No.28
2
2
2
14
Z
2
2
4
4
Fcalcd (g/cm3)
temp (K)
1.291
193
6.9
52.63
-13 e h e 13
-15 e k e 15
-17 e l e 17
15 960
7130 (0.0647)
6136
1.454
193
12.7
52.62
-12 e h e 11
-16 e k e 15
-18 e l e 18
21 410
7531 (0.0846)
6033
1.072
193
0.7
52.83
-17 e h e17
-19 e k e19
-27 e l e28
63 273
17 410 (0.1698)
3367
1.214
193
0.7
52.54
-13 e h e 13
-7 e k e 7
-20 e l e 20
13 704
2133 (0.0592)
1456
µ (cm-1
)
2θmax (deg)
h, k, l values
no. of rflns
no. of unique rflns (Rint
no. of rflns with Fo > 4σ(Fo)
no. of params
)
426
421
845
181
a
R1
0.0465
0.0431
0.0775
0.0361
wR2 (all data)b
0.1252c
1.00/-1.17
0.1145d
0.72/-0.98
0.2557e
0.26/-0.26
0.089f
max/min resid electron density (e/Å3)
0.17/-0.14
R1 ) ∑||Fo| - |Fc||/∑|Fc|. wR2 ) {∑[w(Fo - Fc2)2]/∑[w(Fo2)2]}1/2
.
c w ) 1/[σ2(Fo2) + (0.0862P)2]; P ) [max(Fo2, 0) + 2Fc2]/3. w )
a
b
2
d
1/[σ2(Fo2) + (0.0763)2]. e w ) 1/[σ2(Fo2) + (0.0931P)2]. f w ) 1/[σ2(Fo2) + (0.0583P)2].
325 s, 248 s, 155 m. EI-MS (m/z (relative intensity), frag-
ment): 317 (8) (Me2GaNCCPh2(CN))+; 193 (100) (HNCCPh2)+;
178 (7) (CCPh2)+; 166 (34) (CPh2/Ga2N2)+; 77 (13) (Ph)+; 69
(1) (Ga)+. Anal. Calcd: C, 65.81; H, 5.52; N, 4.80. Found: C,
65.94; H, 6.62; N, 4.91.
phenyl), 128.6 (2/6C, 3/5C, phenyl), 137.5 (1C, phenyl). IR (Nujol,
cm-1): 2724 w, 2673 w, 2242 m (ν(CtN)), 1950 w, 1873 w,
1803 w, 1747 w, 1656 w, 1596 m, 1492 s, 1345 m, 1291 w,
1221 w, 1178 m, 1159 m, 1098 w, 1078 m, 1031 w, 1005 m,
971 m, 915 m, 850 m, 812 m, 744 vs, 697 vs, 649 s, 628 s, 539
s, 455 s. RE (crystalline, cm-1): 3078 vw, 3062 s,3054 s, 3042
vw, 2986 vw, 2978 vw, 2936 w, 2247 s (ν(CtN)), 2235 m (ν-
(CtN), Fermi resonance), 2191 vw, 1608 m, 1590 w, 1457 vw,
1267 w, 1226 vw, 1198 s, 1189 s, 1181 s, 1161 w, 1156 vw,
1035 s, 1010 vs, 975 m, 814 s, 758 s, 652 s, 632 vw, 620 m,
543 vw, 460 vw, 400 m, 347 m, 279 vw, 260 m, 206 vw, 162 w,
149 m, 136 m.
X-r ay Str u ctu r e Deter m in ation of 6, 7, 9, an d P h2CHCN.
The crystals were covered with a perfluorinated polyether and
mounted at the top of a glass capillary under a flow of cold
gaseous nitrogen. The measured intensities were corrected for
Lorentz and polarization and by a numerical absorption
correction (for cell parameters, instruments, and radiation see
Table 1). The structures were solved by direct methods (6, SIR-
92;12 7, 9, and Ph2CHCN, SHELXS-9713). Refinement was
performed against F2 by full-matrix least squares with the
program SHELXL-97.14 The positions of the H atoms were
calculated for ideal positions and refined with a common
displacement parameter. A free refinement was used for the
amino/amido H atoms of 6 (H1, H2, H3) and for all H atoms
in Ph2CHCN. The calculation of the bond lengths, bond angles,
and Ueq values was performed with the program PLATON.15
The molecules of 9 show disorder behavior for one phenyl ring
C(91)-C(141)/C(92)-C(142) (occupation parameters 0.7/0.3; all
phenyl rings are refined as rigid groups) and several coordi-
Syn th esis of [P h 2CdCdNLi(OEt2)2]2 (9). A 7.0 g portion
(36.2 mmol) of Ph2CHCN was dissolved in 50 mL of Et2O and
cooled to -78 °C. A 22.6 mL (36.2 mmol) of a 1.6 M solution of
nBuLi in n-hexane was added dropwise over 30 min. The
mixture was warmed to 20 °C and stirred for an additional 5
h. After 1 h of heating under reflux conditions the solvent was
evaporated under vacuum. The residue was dissolved in a
small portion of Et2O and stored at -20 °C. After 1 day
colorless crystals of 9 could be isolated (11.6 g, 92.2% yield; in
the melting point determination, crystals of 9 were carefully
dried under a stream of argon, the material became soft and
opaque at ca. 30 °C, and the white mass melted at 152 °C).
The coordinated solvent can be removed under vacuum to give
a colorless powder. 1H NMR (THF-d8; ppm): 1.00 (t, 24 H,
OCH2CH3), 3.25 (q, 16 H, OCH2CH3), 6.25 (m, pseudo-triplet,
4 H, C4-H, phenyl), 6.80 (m, pseudo-triplet, 8 H, C3/5-H,
phenyl), 7.10 (m, pseudo-doublet, 8 H, C2/6-H, phenyl). 13C
NMR (THF-d8; ppm): 15.2 (CH3, Et2O), 54.0 (NdCdC), 65.8
(OCH2, Et2O), 116.0 (C4, phenyl), 121.5, 127.7 (C2/6, C3/5), 139.8
(br, NdCdC), 144.3 (C1). IR (Nujol, cm-1): 2726 vw, 2023 vs,
br (νas(out-of-phase)), 1652 w, 1586 s, 1334 m, 1306 m, 1261
m (νs(out-of-phase)) 1184 m, 1154 m, 1108 m, 1093 m, 1062 s,
1028 m, 993 m, 944 vw, 916 w, 884 w, 839 w, 795 w, 756 vs,
740 s, 693 vs, 668 m, 658 w, 639 vw, 619 vw, 585 w, 510 s, 457
s, 374 s, 348 s, br (νring(Li2N2)). EI-MS (m/z (relative intensity),
fragment): 193 (100) (HNCCPh2)+; 178 (2) (C2Ph2)+; 166 (17)
(CPh2)+; 77 (39) (Ph)+. Anal. Calcd: C, 76.05; H, 8.70; N, 4.03.
Found: C, 75.95; H, 8.86; N, 3.93.
(12) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.;
Burla, M. C.; Polidori, G.; Camalli, M. SIR-92; Universities of Bari,
Perugia, and Rome, Bari, Perugia, and Rome, Italy, 1992.
(13) Sheldrick, G. M. SHELXS-97; University of Go¨ttingen, Go¨ttin-
gen, Germany, 1997.
(14) Sheldrick, G. M. SHELXL-97; University of Go¨ttingen, Go¨ttin-
gen, Germany, 1997.
P h 2CHCN. For comparison the nitrile was recrystallized
from THF and investigated by NMR, IR, and RE spectroscopy
as well as by X-ray structure analysis. 1H NMR (THF-d8,
ppm): 5.60 (s, 1 H, CHCN), 7.17 (m, 10 H, H phenyl). 13C NMR
(THF-d8; ppm): 42.2 (CHCN), 113.4 (CHCN), 122.4, 128.2 (4C,
(15) Spek, A. L. PLATON-98; University of Utrecht, Utrecht, The
Netherlands, 1998.

4132 Organometallics, Vol. 22, No. 20, 2003
Iravani and Neumu¨ller
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles (d eg) of 6, 7, 9, a n d P h 2CHCN
Compound 6
In(1)-N(1)
In1(1)-N(3)
In(1)-N(4)
In(1)-C(7)
In(1)-C(8)
2.180(3)
2.439(3)
2.523(3)
2.160(5)
2.148(4)
N(1)-C(1)
N(2)-C(3)
N(3)-C(1)
N(3)-C(5)
1.342(4)
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
1.412(5)
1.401(4)
1.426(4)
1.378(5)
C(2)-C(21)
C(4)-C(41)
C(5)-C(6)
C(6)-C(61)
1.489(5)
1.502(4)
1.517(5)
1.509(5)
1.375(4)
1.370(4)
1.349(4)
N(1)-In(1)-N(3)
N(1)-In(1)-N(4)
N(1)-In(1)-C(7)
N(1)-In(1)-C(8)
N(3)-In(1)-N(4)
N(3)-In(1)-C(7)
N(3)-In(1)-C(8)
N(4)-In(1)-C(7)
N(4)-In(1)-C(8)
57.72(9)
90.01(9)
112.6(1)
114.5(2)
147.37(9)
102.2(1)
93.1(1)
C(7)-In(1)-C(8)
In(1)-N(1)-C(1)
In(1)-N(3)-C(1)
N(1)-C(1)-N(3)
In(1)-N(3)-C(5)
C(1)-N(3)-C(5)
In(1)-N(4)-C(9)
In(1)-N(4)-C(10)
131.5(2)
101.7(2)
89.2(2)
111.4(3)
150.7(2)
119.9(3)
108.1(2)
109.5(2)
In(1)-N(4)-C(11)
N(1)-C(1)-C(2)
N(3)-C(1)-C(2)
C(1)-C(2)-C(3)
C(1)-C(2)-C(21)
C(3)-C(2)-C(21)
N(2)-C(3)-C(2)
N(2)-C(3)-C(4)
111.8(2)
C(2)-C(3)-C(4)
C(3)-C(4)-C(5)
C(3)-C(4)-C(41)
C(5)-C(4)-C(41)
N(3)-C(5)-C(4)
N(3)-C(5)-C(6)
C(4)-C(5)-C(6)
C(5)-C(6)-C(61)
120.2(3)
117.7(3)
120.2(3)
122.1(3)
123.0(3)
113.8(3)
123.2(3)
113.8(3)
127.6(3)
121.0(3)
118.1(3)
119.9(3)
122.1(3)
120.2(3)
119.5(3)
94.4(1)
96.8(2)
Compound 7
Molecule I
2.131(4)
In(1)-O(1)
In(1)-N(1)
In(1)-N(1a)
2.451(3)
2.252(3)
2.458(3)
In(1)-C(15)
In(1)-C(16)
N(1)-C(1)
C(1)-C(2)
1.188(5)
1.358(5)
C(2)-C(3)
C(2)-C(9)
1.479(5)
1.459(6)
2.119(4)
O(1)-In(1)-N(1)
O(1)-In(1)-C(15)
O(1)-In(1)-C(16)
O(1)-In(1)-N(1a)
86.1(1)
91.9(1)
90.8(1)
160.05(9)
N(1)-In(1)-C(15)
N(1)-In(1)-C(16)
N(1)-In(1)-N(1a)
C(15)-In(1)-C(16)
112.2(2)
108.2(2)
73.9(1)
C(15)-In(1)-N(1a)
C(16)-In(1)-N(1a)
In(1)-N(1)-C(1)
In(1)-N(1)-In(1a)
96.1(2)
94.9(2)
129.2(3)
106.1(1)
C(1)-N(1)-In(1a)
N(1)-C(1)-C(2)
C(1)-C(2)-C(3)
C(1)-C(2)-C(9)
124.6(3)
179.4(4)
115.9(4)
117.9(4)
139.6(2)
Molecule II
In(2)-O(2)
In(2)-N(2)
In(2)-(N2a)
2.456(3)
2.242(3)
2.435(3)
In(2)-C(35)
In(2)-C(36)
2.140(4)
2.143(4)
N(2)-C(21)
C(21)-C(22)
1.201(5)
1.350(5)
C(22)-C(23)
C(22)-C(29)
1.489(5)
1.477(5)
O(2)-In(2)-N(2)
O(2)-In(2)-C(35)
O(2)-In(2)-C(36)
O(2)-In(2)-N(2a)
83.7(1)
95.7(1)
89.8(1)
159.81(9)
N(2)-In(2)-C(35)
N(2)-In(2)-C(36)
N(2)-In(2)-N(2a)
C(35)-In(2)-C(36)
104.9(2)
109.4(1)
76.6(1)
C(35)-In(2)-N(2a)
C(36)-In(2)-N(2a)
In(2)-N(2)-C(21)
In(2)-N(2)-In(2a)
93.7(1)
92.4(1)
127.8(3)
103.4(1)
C(21)-N(2)-In(2a)
N(2)-C(21)-C(22)
C(21)-C(22)-C(23)
C(21)-C(22)-C(29)
126.8(3)
178.5(4)
118.2(3)
118.6(3)
145.7(2)
Compound 9
Molecule I
1.401(6)
2.06(1)
2.03(1)
N(1)-C(1)
C(1)-C(2)
N(2)-C(15)
1.184(6)
1.379(6)
1.180(6)
C(15)-C(16)
Li(1)-N(1)
Li(1)-N(2)
Li(2)-N(1)
Li(2)-N(2)
Li(1)-O(1)
2.05(1)
2.07(1)
1.95(1)
Li(1)-O(2)
Li(2)-O(3)
Li(2)-O(4)
1.97(1)
1.90(1)
1.98(1)
Li(1)-N(1)-Li(2)
Li(1)-N(2)-Li(2)
N(1)-Li(1)-N(2)
N(1)-Li(2)-N(2)
C(1)-N(1)-Li(1)
84.2(4)
84.4(4)
96.1(5)
95.2(5)
141.2(5)
C(1)-N(1)-Li(2)
Li(1)-N(2)-C(15)
C(15)-N(2)-Li(2)
N(1)-C(1)-C(2)
N(2)-C(15)-C(16)
133.6(5)
142.6(5)
132.9(5)
178.6(6)
179.0(6)
O(1)-Li(1)-O(2)
O(1)-Li(1)-N(1)
O(1)-Li(1)-N(2)
O(2)-Li(1)-N(1)
O(2)-Li(1)-N(2)
114.8(6)
110.3(5)
114.9(5)
109.1(4)
110.0(5)
O(3)-Li(2)-O(4)
O(3)-Li(2)-N(1)
O(3)-Li(2)-N(2)
O(4)-Li(2)-N(1)
O(4)-Li(2)-N(2)
110.5(6)
110.5(6)
121.4(6)
110.6(6)
107.6(5)
Molecule II
N(3)-C(45)
C(45)-C(46)
N(4)-C(59)
1.181(7)
1.376(8)
1.191(6)
C(59)-C(60)
Li(3)-N(3)
Li(3)-N(4)
1.385(7)
2.07(1)
2.02(1)
Li(4)-N(3)
Li(4)-N(4)
Li(3)-O(5)
2.05(1)
2.07(1)
1.95(1)
Li(3)-O(6)
Li(4)-O(7)
Li(4)-O(8)
1.94(1)
1.96(1)
1.95(1)
Li(3)-N(3)-Li(4)
Li(3)-N(4)-Li(4)
N(3)-Li(3)-N(4)
N(3)-Li(4)-N(4)
C(45)-N(3)-Li(3)
83.0(5)
83.6(4)
97.0(5)
96.0(5)
138.0(6)
C(45)-N(3)-Li(4)
C(59)-N(4)-Li(3)
C(59)-N(4)-Li(4)
N(3)-C(45)-C(46)
N(4)-C(59)-C(60)
138.7(6)
152.4(6)
123.6(6)
179.7(7)
177.3(6)
O(5)-Li(3)-O(6)
O(5)-Li(3)-N(3)
O(5)-Li(3)-N(4)
O(6)-Li(3)-N(3)
O(6)-Li(3)-N(4)
112.5(6)
108.9(5)
109.0(5)
115.0(6)
113.3(6)
O(7)-Li(4)-O(8)
O(7)-Li(4)-N(3)
O(7)-Li(4)-N(4)
O(8)-Li(4)-N(3)
O(8)-Li(4)-N(4)
116.6(6)
109.6(5)
110.6(5)
110.7(6)
111.5(6)
Ph2CHCN
C(1)-N(1)
1.147(2)
177.9(1)
C(1)-C(2)
1.470(2)
C(2)-C(3)
1.525(2)
111.6(1)
C(2)-C(4)
1.527(2)
112.4(1)
N(1)-C(1)-C(2)
C(1)-C(2)-C(3)
109.4(1)
C(1)-C(2)-C(4)
C(3)-C(2)-C(4)
nated Et2O molecules (for occupation parameters see the
Supporting Information).
toluene. The reaction can be described as trimerization
of PhCH2CN with evolution of one molecule of methane
(eq 1).
Selected bond lengths and angles of 6, 7, 9, and Ph2CHCN
are given in Table 2.
However, it was not possible to follow our reactions
to the metal-containing heterocycles by NMR spectros-
copy; only the starting materials and products were
observed. We assumed that in all cases the initial step
is a deprotonation by a metalane or the more basic
metalates [XMMe3]- and [Me3MXMMe3]-, followed by
the attack of the formed anion on further nitrile
molecules. This combination of deprotonated nitrile in
Resu lts a n d Discu ssion
The reaction of PhCH2CN with InMe3 in a molar ratio
of 3:1 gave under reflux conditions in toluene a product
which can be derived from 2,4-diaminopyridine. Color-
less crystals of 6 were formed from DME/TMEDA/

Trimerization of Phenylacetonitrile
Organometallics, Vol. 22, No. 20, 2003 4133
the presence of a hard Lewis acid seems to be necessary
for this type of trimerization. The six methylene protons
from the three benzylnitrile molecules in eq 1 undergo
different reaction pathways. One proton was abstracted
for the formation of methane, three protons were used
in hydrogen shifts for the generation of NH2 and NH
functions, and two protons are still present in a meth-
ylene group. All carbon atoms of the pyridine ring are
substituted.
A mixture of Ph2CHCN with MMe3 (molar ratio 1:1;
CsF as catalyst) in boiling THF lead in a slow reaction
to a equilibrium. The educt Ph2CHCN and the product
1/2[Ph2CdCdNMMe2(THF)]2 (7, 8) form a ratio of 18:
82 mol % (7, M ) In) and 64:36 mol % (8, M ) Ga; ratios
determined in all cases by 1H NMR spectroscopy in
sealed NMR tubes and d8-THF as solvent), respectively
(eq 2). However, the coupling product Ph2(CN)C-C(CN)-
analysis. The exocyclic NH2 and NH functions give
singlet signals at 4.40 and 5.71 ppm in the 1H NMR
spectrum. The short H2N-C and HN-C bonds can be
interpreted as a partly iminium character and should
lead to downfield shifts of the corresponding 13C NMR
signals. Especially the HN-C carbon atom acts as a
bridge between the pyridine nitrogen atom and the In-
(H)N function is a good probe because of the downfield
signal at 238.2 ppm. The C atom adjacent to the NH2
group shows a resonance at 156.4 ppm. In crystalline 6
the two hydrogen atoms in the NH2 function are
different. Therefore, two stretching vibrations at 3478
and 3438 cm-1 were observed in the IR spectrum. The
corresponding band ν(NH) was measured at 3384 cm-1
.
In accord with compound 7 a general reaction mech-
anism for the trimerization of the nitriles could be the
creation of a ketenimine in the first step, followed by
nucleophilic attack of the metal-substituted ketenimine
on another molecule of nitrile. This is even more likely,
since the deprotonation of PhCH2CN with nBuli in the
presence of TMEDA gives the lithiated dimeric keten-
iminate [{(TMEDA)Li}{NCC(H)Ph}]2.17 Very recent
studies of the diprotonation of CH3CN in solution arrive
at the same conclusion, the generation of the ketenimi-
nate [H2CdCdN]-.18 It is known that reaction with a
electrophile then leads to substituted ketenimines.19
Therefore, reaction 3 is no surprise. The concept of a
nucleophilic attack of a strong base on one or two nitrile
molecules was realized by the work of M. F. Lappert
16
Ph2 was formed when the reaction mixture to 8 was
heated for 14 days, indicating a slow radical process
occurring under these conditions.
To achieve a complete transfer in 7 and 8, we decided
to synthesize the lithiated ketenimine [Ph2CdCdNLi(O2-
Et)2]2 (9) on the basis of the reaction of Ph2CHCN with
nBuLi in Et2O (eq 3). 9 was added to solutions of Me2-
MCl in Et2O to give depending on the metal M in a
metathesis reaction 7 or 8 (eq 4) after recrystallization
from THF.
(17) Boche, G.; Marsch, M.; Harms, K. Angew. Chem., Int. Ed. Engl.
1986, 4, 373.
(18) Scott, R.; Granander, J .; Hilmersson, G. Chem. Eur. J . 2002,
8, 2081.
(19) (a) Daly, J . J . J . Chem. Soc. 1961, 2801. (b) Hagvi, R. R.;
Wheatley, P. J . J . Chem. Soc. A 1970, 2053. (c) Lambrecht, J .; Gambke,
B.; von Seyerl, G.; Huttner, G.; Kollmannsberger-von Nell, G.; Herzberg-
er, S.; J oachims, J . C. Chem. Ber. 1981, 114, 3751. (d) Syntheses and
reactions of ketenimines: Perst, H. In Methoden der organischen
Chemie (Houben-Weyl), 4th ed.; G. Thieme Verlag: Stuttgart, New
York, 1993; Vol. E15/3.
The H and 13C NMR spectra of 6 show characteristic
resonances, confirming the structure found by X-ray
1
(16) Lam, L.; Lee, G.-H.; Liang, E. Bull. Chem. Soc. J pn. 2001, 74,
1033.

4134 Organometallics, Vol. 22, No. 20, 2003
Iravani and Neumu¨ller
over the last few years, leading to a variety of interest-
ing chelating ligands with CCN or C(CN)2 backbones.6e,20
These results support our imaginations about the reac-
tion mechanism.
The first strong indicator of a ketenimine in solution
are the 1H and 13C NMR spectra. If the reaction is
carried out according to (2), there is still a resonance
1
for the methine proton in the H NMR spectrum of Ph2-
CHCN because of the equilibrium between InMe3 and
Ph2CHCN. The ratio Ph2CHCN:[NCCPh2]- was deter-
mined (sealed NMR tubes) to be 18:82 (7) and 64:36 (8),
respectively. Reaction 4 gave pure 7 with 13C NMR
parameters of 55.0 and 141.2 ppm for the phenyl-
substituted and nitrogen-substituted carbon atoms. The
corresponding values for 8 are 55.1 and 137.0 ppm.
The second probe is vibrational spectroscopy. The
most characteristic vibrational mode of a ketenimine is
the asymmetrical valence vibration νas(CdCdN), usu-
ally found between 2000 and 2200 cm-1. In the case of
the centrosymmetrical dimer 7 (see eq 2), the IR
spectrum shows the out-of-phase absorption at 2167
cm-1 and the Raman spectrum (RE) the in-phase
emission at 2166 cm-1. The symmetrical modes are not
very significant, because of their position of ca. 1200
cm-1 (see the Experimental Section). For the educt Ph2-
CHCN ν(CN) was found at 2242 (IR), 2247, and 2235
cm-1 (RE; Fermi resonance). Two bands of the four
In2N2 ring vibrations21 were measured. Because of the
rule of mutual exclusion only two ring vibrations (with
mainly stretching character) were expected in the IR
spectrum (observed 454 cm-1) and two in the RE
spectrum (observed 298 cm-1). The values for the
probably likewise centrosymmetrical dimer 8 are some-
what different and signify another electronic situation
(2188 cm-1; νas(out-of-phase CdCdN)). The more ionic
character of the Li-N bonds in 9 compared with In-
(Ga)-N bonds in 7 and 8 leads to a better coupling of
the CdC and CdN parts of the ketenimine sequence
CdCdN, indicated by a shift of νas(out-of-phase) to lower
wavenumbers, in this case 2023 cm-1. Both 7 and 8
fragment under EI-MS conditions in such a way that
only for 8 could a metal atom in a heavier fragment be
detected (m/z 317; (Me2GaNCCPh2(CN))+).
Figure 2 shows a molecule of 6 with a central planar
six-membered pyridine ring. The amino and amido
functions are included in the π-electron system of the
pyridine ring. Clear hints of this are the short N-C
distances N(1)-C(1) (1.342(4) Å) and N(2)-C(3) (1.375
Å), which are in the same range as the bond lengths
N(3)-C(1) (1.370(4) Å) and N(3)-C(5) (1.349(4) Å) of the
central ring. The bond In(1)-N(1) at 2.180(3) Å can be
described as an In-N single bond, while In(1)-N(3)
(2.439(3) Å) and In(1)-N(4) (2.523(3) Å) have the
character of weak donor-acceptor interactions. In-N
distances in organometalllic amides of the type [Me2-
InNR′2]2 are typically between 2.22 and 2.28 Å.22 A good
comparison is 3, at 2.20 Å for the In-N bond lengths.3
The axial In-N bonds in the related complex [(DMF)-
F igu r e 2. Molecular structure of 6 (ellipsoids at the 50%
probability level; only H(1), H(2), and H(3) are drawn).
F igu r e 3. One of the unique centrosymmetric molecules
in 7 (ellipsoids at the 40% probability level; without H
atoms).
Cl2InNPPh3]2 have been determined to be 2.179(2) Å,
whereas the In center also adopts a distorted-trigonal-
bipyramidal geometry.23 According to the C-C distances
of the pyridine ring, the delocalization of the π-electron
density is typical for a pyridine system (see Table 2).
The pyridine ring and the planes of the adjacent phenyl
rings C(21)-C(26), C(41)-C(46), and C(61)-C(66) en-
close angles of 69, 71, and 90°. This leads to intra-
molecular N-H‚‚‚π-electron hydrogen bonds involving
all three imine H atoms. The closest contacts of H(1),
H(2), and H(3) to the carbon atoms of the phenyl rings
are between 2.51(4) and 2.90(4) Å.
The crystals of compound 7 contain two crystallo-
graphically unique centrosymmetrical molecules with
a four-membered In2N2 ring, one of which is shown in
Figure 3. Two attributes are important for a hetero-
allene such as a ketenimine: the planes C(phenyl ring)/
C/C(phenyl ring)//N/In/In should be more or less per-
pendicular, and the sequence NCC should be linear with
short N-C and C-C bonds. Both criteria are fulfillled.
The average value for the dihedral angle is 85°, and the
mean N-C and C-C distances are 1.20 and 1.35 Å,
respectively. The angle of the CCN sequence has been
(20) (a) Lappert, M. F.; Liu, D.-S. J . Organomet. Chem. 1995, 500,
203. (b) Hitchcock, P. B.; Lappert, M. F.; Leung, W.-P.; Liu, D.-S.; Mak,
T. C. M.; Wang, Z.-X. J . Chem. Soc., Dalton Trans. 1999, 1263.
(21) Weidlein, J .; Mu¨ller, U.; Dehnicke, K. Schwingungsspektrosko-
pie, 2nd ed.; G. Thieme Verlag: Stuttgart, New York, 1988.
(22) For a review on amido compounds of Ga and In see: Carmalt,
C. J . Coord. Chem. Rev. 2001, 223, 217.
(23) Roesky, H. W.; Seseke, U.; Noltemeyer, M.; Sheldrick, G. M. Z.
Naturforsch. 1998, 43b, 1130.

Trimerization of Phenylacetonitrile
Organometallics, Vol. 22, No. 20, 2003 4135
F igu r e 4. One of the unique molecules in 9 (ellipsoids at
the 30% probability level, without H atoms; only one of the
disordered positions of the phenyl rings and Et2O molecules
is given).
F igu r e 5. Graphic representation of Ph2CHCN (ellipsoids
at the 40% probability level).
measured to be 179°. The structure of [{(TMEDA)Li}-
{NdCdC(H)Ph}]‚C6H6 exhibits comparable lengths of
1.15(3) and 1.38(2) Å as well as an angle of 178(1)°.17
The distances in the CCN sequence of the aryl-
substituted 4-Br-C6H4NdCdCPh2 are closer to the
values of 7 (1.24 and 1.33 Å).19 A distorted-trigonal-
bipyramidal environment around the In atoms in 7
leads to two very different In-N bond lengths. N(1)
occupies the equatorial position in the first trigonal
bipyramid, leading to a value of 2.25 Å and a axial
position in the adjacent polyether with 2.44 Å. There-
fore, 7 can also be described as a [Me-In-Me]+ ion,
coordinated by ketenimido and THF ligands. A nondis-
turbed [R-In-R]+ unit is electronically isovalent with
R-Mg-R or R-Hg-R and is linear. This is approxi-
mately realized in Me2InBr,24 [iPr2In(THF)2][BF4],25 and
[Mes2In][BF4].26
The difference is obvious (Figure 5). The core CCN in
Ph2CHCN shows the typical values for CtN triple
bonds (C(1)-N(1) ) 1.147(2) Å) and a C(sp3)-C(sp)
single bond (C(1)-C(2) ) 1.470(2) Å).
Con clu sion
From the results of the presented reactions, every-
thing seems to point to the formation of a ketenimine
species as the first intermediate. Depending on their
basicity and steric bulk, the further attack of nitrile
molecules followed by proton shifts is possible. Notably,
the trimerization leads to the formation of six-π-electron
systems either in the well-known open form27 shown for
1-3 or in a classical Hu¨ckel aromatic species as in 6.
When the metalates [FMMe3]- and [Me3MFMe3]- are
not basic enough for the initial step, only the regular
trimerization to 1,3,5-triazines was observed (M ) Tl).
Surprisingly, our trimerizations were not detected in the
reactions of a nitrile such as PhCH2CN with lithium
reagents, presumably because only equimolar mixtures
of the starting material leading directly to the corre-
sponding ketenimines were investigated. In addition, no
strong Lewis acids such as M3+ (M ) earth metal) and
Co3+ were present. It may be worthwhile to reconceive
this reaction, because highly substituted aromatic sys-
tems would be accessible in one-pot reactions.
The unit cell of 9 consists of two crystallographically
unique molecules with almost planar Li2N2 four-
membered rings (largest deviation of an atom from the
“best plane” 5 pm; molecule I is shown in Figure 4).
Interestingly, the environments of the three N atoms
are strongly distorted. N(1), N(2), and N(4) are the
center of very asymmetrical Li2NC2 sequences. The
angle pairs Li(1)-N(1)-C(1)/Li(2)-N(1)-C(1) (141.2(5),
133.6(5)°),
Li(2)-N(2)-C(15)/Li(3)-N(2)-C(15)
(142.6(5), 132.9(5)°), and Li(3)-N(4)-C(59)/Li(4)-N(4)-
C(59) (152.4(6), 123.6(6)°) are the result of the steric
interactions of the CPh2 units with the Et2O molecules.
Two things are responsible for this behavior. The Li-N
bond lengths are significiantly shorter than the corre-
sponding In-N bonds in 7, and the Li2N2 planes are
not perpendicular to the CPh2 units. The mean dihedral
angles in molecules I and II are 65 and 76°, respectively.
To illustrate the difference in the bond lengths in the
sequence CCN between 7 and Ph2CHCN, we investi-
gated the nitrile by a X-ray structure determination.
Ack n ow led gm en t. This work was supported by the
Deutsche Forschungsgemeinschaft. We thank Prof. Dr.
J . Lorberth for donation of starting material.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data, atomic coordinates, and bond lengths and angles as well
as isotropic or anisotropic displacement parameters for all
atoms in 6, 7, 9, and Ph2CHCN; these data are also available
as CIF files. This material is available free of charge via the
Internet at http://pubs.acs.org.
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