Synthesis and characterization of (4-fluorophenyl)amino-based amino- and iminometallanes of group 13. Crystal structures of (MeAlNRf)4, (MeMNRf)6·nTHF (M = Al, n = 2; M = Ga, n = 7), and (MeIn(THF)NRf)4 (Rf = 4-C6H4F)

Article abstract of DOI:10.1021/om9607457

The novel amino- and iminometallanes (MeAlNR_f)_n (1) (n = 4, la; n = 6, 1b), (Me₂GaN-(H)R_f)₂ (2), (Me₂GaNR_f)₆ (3), (Me₂InN(H)R_f)₂ (4), and (MeIn(THF)NR_f)₄ (5) (R_f = 4-C₆H₄F) have been prepared in high yield by the reaction of AlMe₃, GaMe₃, and InMe₃, respectively, with 4-fluoroaniline. All of the products have been fully characterized by elemental analysis, IR, NMR, and mass spectroscopy. The crystal structures of 1a, 1b·2THF, 3·7THF, and 5 have been determined. For the degree of oligomerization of compound 1 a solvent- and temperature-dependent influence is assumed. (MeGaNR_f)₄ (3) is the first hexameric iminogallane and (MeIn(THF)NR_f)₄ (5) is the second iminoindane described in the literature.

Full text of DOI:10.1021/om9607457

Organometallics 1997, 16, 1197-1202
1197
Syn th esis a n d Ch a r a cter iza tion of
(4-F lu or op h en yl)a m in o-Ba sed Am in o- a n d
Im in om eta lla n es of Gr ou p 13. Cr ysta l Str u ctu r es of
(MeAlNRf)4, (MeMNRf)6‚n THF (M ) Al, n ) 2; M ) Ga , n )
7), a n d (MeIn (THF )NRf)4 (Rf ) 4-C6H4F )†
Christoph Schnitter, Said D. Waezsada, Herbert W. Roesky,* Markus Teichert,
Isabel Uso´n, and Emilio Parisini
Institut fu¨r Anorganische Chemie der Universita¨t Go¨ttingen, Tammannstrasse 4,
D-37077 Go¨ttingen, Germany
Received August 27, 1996X
The novel amino- and iminometallanes (MeAlNRf)n (1) (n ) 4, 1a ; n ) 6, 1b), (Me2GaN-
(H)Rf)2 (2), (MeGaNRf)6 (3), (Me2InN(H)Rf)2 (4), and (MeIn(THF)NRf)4 (5) (Rf ) 4-C6H4F)
have been prepared in high yield by the reaction of AlMe3, GaMe3, and InMe3, respectively,
with 4-fluoroaniline. All of the products have been fully characterized by elemental analysis,
IR, NMR, and mass spectroscopy. The crystal structures of 1a , 1b‚2THF, 3‚7THF, and 5
have been determined. For the degree of oligomerization of compound 1 a solvent- and
temperature-dependent influence is assumed. (MeGaNRf)6 (3) is the first hexameric
iminogallane and (MeIn(THF)NRf)4 (5) is the second iminoindane described in the literature.
In tr od u ction
tures. In order to avoid side chain elimination, a
perfluorinated aromatic amine was used.4b
The reactions of organometallic compounds of group
13 with primary amines have been studied for decades.1
In the first step of the reaction aminometallanes (R2MN-
(H)R′)n (M ) Al, Ga, In; n ) 1, 2, 3)2 are formed.
Generally, the compounds have a core structure of a
four-membered ring with alternating metal and nitro-
gen atoms. The thermolysis of the aminometallanes
proceeds by two different routes. One possible pathway
(a) is the intermolecular reaction of aminometallanes
forming iminometallanes (RMNR′)n.3 The degree of
oligomerization in the resulting cage compounds is
highly dependent on the metal and on the steric demand
of the ligands. The second route (b) of the thermolysis
of the aminometallanes takes place by intramolecular
side chain elimination of hydrocarbons. Especially for
the thermolysis of aminogallanes and -indanes route b
is strongly favored due to the high temperatures needed
for completing hydrocarbon elimination. Therefore only
five iminogallanes4a-d and one iminoindane4b have been
reported in the literature to date.
As the number of electron-withdrawing fluorine atoms
on the nitrogen ligand might affect the temperature of
pyrolysis, we investigated the reactions of the trimeth-
ylmetallanes of aluminum, gallium, and indium using
4-fluoroaniline in which the steric influence of the
fluorine atom is minimized for the degree of oligomer-
ization of the products. In this paper we report the
synthesis and characterization of the aminometallanes
(Me2GaN(H)Rf)2 (2) and (Me2InN(H)Rf)2 (4) and the
iminometallanes (MeAlNRf)4 (1a ), (MeAlNRf)6 (1b),
(MeGaNRf)6 (3), and (MeIn(THF)NRf)4 (5). The molec-
ular structures of 1a , 1b‚2THF, 3‚7THF, and 5 have
been determined by X-ray diffraction studies at low
temperature.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All experiments were per-
formed using standard Schlenk techniques under dry nitrogen
atmosphere due to the extreme sensitivity of reactants and
products toward air and moisture. A Braun MB 150-GI drybox
was used to store the compounds and to prepare the samples
for spectroscopic characterizations. All solvents were dried
over sodium/benzophenone, freshly distilled and degassed prior
to use. Trimethylalane and 4-fluoroaniline were purchased
from Aldrich Chemical Co., and trimethylgallane was pur-
chased from Strem Chemicals. Trimethylindane was prepared
as described in the literature.5a
We have previously reported on the synthesis of the
first iminogallane and -indane with heterocubane struc-
* To whom correspondence should be addressed. Telefax: +49(0)-
551393373. E-mail: hroesky@gwdg.de.
† Dedicated to Professor Leopold Horner on the occasion of his 85th
birthday.
X Abstract published in Advance ACS Abstracts, February 15, 1997.
(1) For reviews see: (a) Downs, A. J ., Ed. Chemistry of Aluminum,
Gallium, Indium and Thallium; Chapmann & Hall: London, 1993.
(b) Cesari, M.; Cucinella, S. In The Chemistry of Inorganic Homo- and
Heterocycles; Haiduc, I., Sowerby, D. B., Eds.; Academic Press: London,
1987; Vol. 1.
Elemental analyses were performed by the Analytisches
Labor des Instituts fu¨r Anorganische Chemie der Universita¨t
Go¨ttingen. As described in the literature5b,c elemental analy-
(2) For examples see: (a) Schauer, S. J .; Pennington, W. T.;
Robinson, G. H. Organometallics 1992, 11, 3287. (b) J anik, J . F.;
Duesler, E. N.; Paine, R. T. Inorg. Chem. 1987, 26, 4341. (c) Zettler,
F.; Hess, H. Chem. Ber. 1977, 110, 3943. (d) Neumu¨ller, B. Chem. Ber.
1989, 122, 2283. (e) Atwood, D. A.; Atwood, V. O.; Carriker, D. F.;
Cowley, A. H.; Gabbai, F. P.; J ones, R. A.; Bond, M. R.; Carrano, C. J .
J . Organomet. Chem. 1993, 463, 29. (f) Atchinson, K. A.; Backer-Dirks,
J . D. J .; Bradley, D. C.; Faktor, M. M.; Frigo, D. M.; Hursthouse, M.
B.; Hussain, B.; Short, R. L. J . Organomet. Chem. 1989, 366, 11.
(3) For a review see: Veith, M. Chem. Rev. 1990, 90, 3.
(4) (a) Amirkhalili, S.; Hitchcock, P. B.; Smith, J . D. J . Chem. Soc.,
Dalton Trans. 1979, 1206. (b) Belgardt, T.; Roesky, H. W.; Noltemeyer,
M.; Schmidt, H.-G. Angew. Chem. 1993, 105, 1101; Angew. Chem., Int.
Ed. Engl. 1993, 32, 1056. (c) Belgardt, T.; Waezsada, S. D.; Roesky,
H. W.; Gornitzka, H.; Ha¨ming, L.; Stalke, D. Inorg. Chem. 1994, 33,
6247. (d) Cordeddu, F.; Hausen, H. D.; Weidlein, J . Z. Anorg. Allg.
Chem. 1996, 22, 573.
S0276-7333(96)00745-5 CCC: $14.00 © 1997 American Chemical Society

1198 Organometallics, Vol. 16, No. 6, 1997
Schnitter et al.
ses of metal-nitrogen compounds of group 13 are often not
exact. Cause for this is an incomplete burning of the samples,
due to the formation of metal carbides and nitrides already at
low temperatures.
toluene (20 mL). The reaction mixture was then heated under
reflux for 3 h. Slowly cooling the mixture to room temperature
yielded product 4 as colorless crystals (4.64 g, 86%), mp 202
°C. 1H NMR (200.13 MHz, THF-d8): δ 6.83-6.79 (m, 8 H,
Ar-H), 4.06 (s (br), 2 H, NH), -0.24 (s, 12 H, In(CH3)2) ppm.
19F NMR (188.32 MHz, THF-d8): δ -127.0 (s, Ar-F) ppm. MS
(70 eV): m/e (%) 510 (M, 15), 495 (M - Me, 12), 400 (M -
HN-4-C6H4F, 40), 255 (M/2, 25), 145 (InMe2, 100), 115 (In, 55).
IR (Nujol mull): 3283 (m, νNH), 1501 (vs), 1462 (s), 1441 (s),
1231 (s), 1203 (vs), 1152 (s), 838 (vs), 763 (vs), 730 (s), 707 (s)
cm-1. Anal. Calcd for C16H22F2In2N2 (510.0): C, 37.7; H, 4.4;
N, 5.5. Found: C, 37.1; H, 4.2; N, 5.4.
P r ep a r a tion of (MeIn (THF )N-4-C6H4F )4 (5). Compound
4 (1.85 g, 3.63 mmol) was heated in an oil bath to 220 °C. After
ca. 3 h gas evolution ceased and the reaction mixture resolidi-
fied. The yellow residue was washed with n-hexane (50 mL)
and recrystallized from toluene (5 mL)/THF (5 mL) to give
colorless crystals of product 5, which were suitable for an X-ray
diffraction analyses. These crystals partially lose the coordi-
nated THF by removal of the solvent in vacuo, yielding
(MeInN-4-C6H4F)4‚THF (1.25 g, 72%), mp 232 °C. 1H NMR
(200.13 MHz, THF-d8): δ 6.76-6.69 (m, 16 H, Ar-H), 0.15 (s,
12 H, InCH3) ppm. 19F NMR (188.32 MHz, THF-d8): δ -128.4
(s, Ar-F) ppm. MS (70 eV) m/e (%): 956 (M, 100), 115 (In, 66).
IR (Nujol mull): 1487 (s), 1467 (s), 1200 (s), 832 (s), 781 (s)
cm-1. Anal. Calcd for C28H28F4In4N4‚C4H8O (1027.9): C, 37.4;
H, 3.5; N, 5.5. Found: C, 36.9; H, 3.5; N, 5.6.
NMR spectra were recorded on a Bruker AM 250 and were
externally referred to tetramethylsilane or CFCl3, respectively.
FT-IR spectra were measured on a Bio-Rad FTS-7 as Nujol
mulls between KBr plates in the range 4000-400 cm-1 (only
strong absorptions are given), and EI mass spectra, on
Finnigan MAT 8230 or Varian MAT CH 5 instruments.
P r ep a r a tion of (MeAlN-4-C6H4F )4 (1a ) a n d (MeAlN-4-
C6H4F )6 (1b). 4-Fluoroaniline (2.22 g, 20.0 mmol) in toluene
(30 mL) was slowly added to a solution of trimethylalane (1.44
g, 20.0 mmol) in toluene (50 mL) at 0 °C. The reaction mixture
was refluxed until gas evolution was finished (2 h). After
removal of the solvent under reduced pressure the white solid
was heated at 130 °C for 2 h. The residue was dissolved in
n-hexane (100 mL) and filtered. Removal of the solvent in
vacuo gave product 1 (2.16 g, 72%), mp 179 °C. 1H NMR
(250.13 MHz, THF-d8): δ 7.35-6.65 (m, Ar-H), -0.94 (s, Al-
(CH3)) ppm. 19F NMR (235.32 MHz, THF-d8): δ -121.3 (s,
Ar-F) ppm. MS (70 eV): m/e (%) 906 ((MeAlN-4-C6H4F)6, 100),
891 ((MeAlN-4-C6H4F)6 - Me, 82), 604 ((MeAlN-4-C6H4F)4, 4),
589 ((MeAlN-4-C6H4F)4 - Me, 6), 453 ((MeAlN-4-C6H4F)3, 10),
302 ((MeAlN-4-C6H4F)2, 20). IR (Nujol mull): 1506 (s), 1465
(s), 1232 (s), 1201 (s), 1158 (s), 1099 (s), 872 (s), 861 (s), 835
(s), 785 (s), 732 (s), 701 (s), 680 (s), 535 (s), 511 (s), 410 (s)
cm-1. Anal. Calcd for (C7H7AlFN)x (151.1): C, 55.6; H, 4.7;
N, 9.3. Found: C, 53.7; H, 4.8; N, 8.9.
Crystals of the tetrameric product 1a were obtained from
n-hexane at -20 °C, whereas the crystallization in THF at
room temperature afforded the hexameric compound 1b‚2THF.
P r ep a r a tion of (Me2Ga N(H)-4-C6H4F )2 (2). 4-Fluoro-
aniline (2.51 g, 22.6 mmol) dissolved in toluene (20 mL) was
slowly added dropwise to a solution of trimethylgallane (2.59
g, 22.6 mmol) in toluene (20 mL) at room temperature. The
reaction mixture was heated for 3 h under reflux. The solution
was concentrated under reduced pressure (20 mL) and cooled
overnight in a freezer (2 °C) to yield product 2 (4.07 g, 86%)
as colorless crystals, mp 194 °C. 1H NMR (200.13 MHz, THF-
d8): δ 6.94-6.90 (m, 8 H, Ar-H), 4.70 (s (br), 2 H, NH), -0.31
(s, 12 H, Ga(CH3)2) ppm. 19F NMR (188.32 MHz, THF-d8): δ
-123.8 (s, Ar-F) ppm. MS (70 eV): m/e (%) 420 (M, 10), 405
(M - Me, 15), 209 (M/2 - H, 100), 99 (GaMe2, 90). IR (Nujol
mull): 3287 (m, νNH), 1235 (s), 1226 (vs), 1209 (vs), 1197 (vs),
1154 (s), 871 (s), 836 (vs), 757 (vs), 739 (s), 705 (s), 584 (s),
546 (s), 538 (s), 462 (s) cm-1. Anal. Calcd for C16H22F2Ga2N2
(419.8): C, 45.8; H, 5.3; N, 6.7. Found: C, 45.9; H, 5.3; N,
6.5.
X-r a y St r u ct u r e Det er m in a t ion s for 1a , 1b‚2THF ,
3‚7THF , a n d 5. The highly unstable crystals of 3‚7THF and
5 were mounted in an oil drop on a glass fiber at low
temperature.6 Data for 1b‚2THF were collected at -80 °C on
a Stoe-Siemens-Huber diffractometer with monochromated Mo
KR radiation (λ ) 0.710 73 Å) using a SMART-CCD area
detector. For the integration of intensities the program SAINT
was used. Data for 1a , 3‚7THF, and 5 were collected at low
temperatures on a Stoe-Siemens-AED diffractometer with
monochromated Mo KR radiation (λ ) 0.710 73 Å) using the
learnt profile method.7 A semiempirical absorption correction
based on ψ-scans was employed for structure 3‚7THF. Due
to the small number of strong reflections at a suitable ø angle,
no ψ-scan absorption correction was possible in the case of 5.
All the structures were solved by direct methods using
SHELXS-90/96.8 All non-hydrogen atoms were refined aniso-
tropically. For the hydrogen atoms a riding model was used.
The structures were refined against F2 with a weighting
2
scheme of w-1 ) σ2(Fo2) + (g1P)2 + g2P with P ) (Fo + 2Fc2)/3
using SHELXL-93/96.9 The R values are defined as R1 )
2
4
∑||Fo| - |Fc||/∑|Fo| and wR2 ) [∑w(Fo - Fc2)2/∑wFo
]
1/2. The
crystals of compound 1b‚2THF contain two disordered THF
molecules per asymmetric unit. The crystals of compound 3‚-
7THF contain THF solvent in two different situations: One
molecule occupies a general position within the asymmetric
unit, showing discrete disorder among two partially occupied
sites. The other THF molecule is disordered over a 3h axis,
whose symmetry it is unable to fulfill. Thus, the asymmetric
unit contains 7/6 THF molecules plus one-sixth of compound
3. In both cases, the refinement of the disordered solvent was
carried out using distance and ADP restraints.
P r ep a r a tion of (MeGa N-4-C6H4F )6 (3). Compound 2
(2.10 g, 5.0 mmol) was heated for 3 h to 205 °C for a
quantitative elimination of methane. The pale yellow residue
was washed with n-hexane (30 mL) and recrystallized from
THF at -26 °C to yield product 3‚7THF. Removal of the
solvent in vacuo gave the THF-free product 3 (1.24 g, 64%),
mp 320 °C. 1H NMR (200.13 MHz, THF-d8): δ 6.98-6.82 (m,
24 H, Ar-H), -0.47 (s, 18 H, GaCH3) ppm. 19F NMR (188.32
MHz, THF-d8): δ -122.3 (s, Ar-F) ppm. MS (70 ev): m/e (%)
1163 (M, 28), 776 ([MeGaN-4-C6H4F]4, 10), 388 (M/3, 100), 194
(M/6, 10). IR (Nujol mull): 1499 (vs), 1467 (vs), 1378 (s), 1367
Resu lts a n d Discu ssion
(s), 1200 (vs), 1153 (s), 839 (s), 790 (s), 780 (s) cm-1
. Anal.
Addition of trimethylalane to 4-fluoroaniline leads to
the formation of the iminoalane (MeAlNRf)n (1) (Scheme
1). The intermediate aminoalane could not be isolated,
possibly due to the electron-withdrawing properties of
the fluorine atom as observed in the reaction of tri-
Calcd for C42H42F6Ga6N6 (1163.2): C, 43.4; H, 3.6; N, 7.2.
Found: C, 42.3; H, 3.8; N, 7.2.
P r ep a r a tion of (Me2In N(H)-4-C6H4F )2 (4). 4-Fluoro-
aniline (2.34 g, 21.1 mmol) in toluene (20 mL) was slowly
added to a solution of trimethylindane (3.37 g, 21.1 mmol) in
(5) (a) Brauer, G. Handbuch der pra¨parativen Anorganischen Che-
mie Bd. II; Ferdinand Enke Verlag: Stuttgart, Germany, 1978; p 864.
(b) Paciorek, K. J . L.; Nakahara, J . H.; Hoferkamp, L.; George, C.;
Flippen-Anderson, J . L.; Gilardi, R.; Schmidt, W. R. Chem. Mater. 1991,
3, 82. (c) Interrante, L. V.; Sigel, G. A.; Garbauskas, M.; Hajna, C.;
Slack, G. A. Inorg. Chem. 1989, 28, 252.
(6) Kottke, T.; Stalke, D. J . Appl. Crystallogr. 1993, 26, 615.
(7) Clegg, W. Acta Crystallogr., Sect. A 1983, 39, 158.
(8) Sheldrick, G. M. SHELXS-90/96. Acta Crystallogr., Sect. A 1990,
46, 467.
(9) Sheldrick, G. M. SHELXL-93/96, program for crystal structure
refinement, University of Go¨ttingen, 1996.

Amino- and Iminometallanes
Sch em e 1
Organometallics, Vol. 16, No. 6, 1997 1199
F igu r e 1. Packing diagram of 3‚7THF (view down the
c-axis). One of the THF molecules is disordered on a 3h-
axis.
Sch em e 2
Further thermolysis of compound 2 and recrystalli-
zation from THF afford the hexakis(µ3-((4-fluorophenyl)-
imino)methylgallane) 3‚7THF (Scheme 2), the first
hexameric iminogallane characterized by X-ray diffrac-
tion. As in the case of the homologous aluminum
compound 1 the EI mass spectrum shows also fragment
ions of the tetrameric and dimeric iminometallanes. But
in contrast to compound 1, crystallization from solvents
other than THF did not yield suitable crystals for an
X-ray diffraction analysis. The crystals of 3 contain
seven solvent molecules for each iminogallane molecule
in the lattice, which are readily dissociated if the solvent
is removed in vacuo. The packing diagram of compound
3 (view down the c-axis) is shown in Figure 1. One of
the THF molecules is disordered on a 3h-axis. Due to
their high solvent content, the crystals immediately
decay if allowed to warm above -20 °C. The temper-
methylalane with pentafluoroaniline.4c In the mass
spectra of (MeAlNRf)n (1) fragment ions for the species
with n ) 1 to n ) 6 could be detected. Crystallization
of compound 1 afforded crystals of either tetrameric 1a
(hexane, -20 °C) or hexameric 1b‚2THF (THF, room
temperature), depending on the temperature and sol-
vent used (Scheme 1). When the solvent is removed
from the crystals in vacuo, both compounds have identi-
cal spectroscopic data. We are currently studying
whether the control of the oligomerization in the crystals
is dependent on the crystallization temperature or the
donor properties of the solvent used.
Interestingly, the formation of the iminoalane (MeAlN-
4-C6H4F)n is complete within only 2 h, occurring at a
low thermolysis temperature (130 °C), while the prepa-
ration of the analogous non-fluorine-containing com-
pound (MeAlNC6H5)6 requires 180 °C for 24 h.10
Reaction of trimethylgallane and -indane with 4-fluo-
roaniline in toluene leads to the formation of the
corresponding dimeric aminometallanes (Me2GaN(H)-
4-C6H4F)2 (2) and (Me2InN(H)-4-C6H4F)2 (4) in high
yield (Scheme 2). The compounds are air- and moisture-
sensitive white solids.
1
ature-dependent H NMR spectra show no evidence for
an equilibrium of different oligomers in solution.
Heating of the aminoindane 4 in an oil bath to 220
°C for 3 h and subsequent recrystallization from THF
at -26 °C yields the tetrakis(µ3-((4-fluorophenyl)imino)-
methylindane) tetrakis(tetrahydrofuran) adduct
5
(Scheme 2). However, the THF molecules are not
strongly bonded, since the removal of the solvent in
vacuo at room temperature leaves only one THF mol-
ecule in the compound as shown by elemental analysis
1
and H NMR spectroscopy. In the mass spectrum the
molecular ion of the tetrameric iminoindane without
THF was detected with an intensity of 100%, showing
a high stability of this species even in the gas phase.
Suitable crystals for an X-ray diffraction analysis of
compound 5 could be obtained after 2 months at -26
°C from toluene/THF.
Cr ysta l Str u ctu r es of 1a , 1b‚2THF , 3‚7THF , a n d
5. The experimental details of the crystallographic
study are summarized in Table 9. The crystal structure
of 1a contains two independent molecules in the asym-
metric unit (Figure 2). The cage formed by the four
aluminum and the four nitrogen atoms describes an
almost perfect heterocubane, the largest deviation from
the ideal 90° angle being 1.1°.
The EI mass spectra of 2 and 4 show the molecular
ions of the dimeric species and their characteristic
fragments. In the IR spectra the N-H vibrations are
observed as sharp bands (3287 cm-1 for compound 2,
3283 cm-1 for compound 4). Only one sharp signal is
1
observed in the H NMR spectra for the methyl groups
at the metal indicating that there is no cis/trans
isomerization in solution as observed for other amino-
metallanes.11
(11) For examples see: (a) Neumu¨ller, B. Chem. Ber. 1989, 122,
2283. (b) Amirkhalili, S.; Hitchcock, P. B.; J enkins, A. D.; Nyathi, J .
Z.; Smith, J . D. J . Chem. Soc., Dalton Trans. 1981, 377. (c) Neumu¨ller,
B. Z. Naturforsch. 1991, 46B, 753.
(10) Al-Wassil, A. A. I.; Hitchcock, P. B.; Sarisaban, S.; Smith, J .
D.; Wilson, C. L. J . Chem. Soc., Dalton Trans. 1985, 1929.

1200 Organometallics, Vol. 16, No. 6, 1997
Schnitter et al.
Ta ble 8. Selected Bon d An gles (d eg) for
Ta ble 1. Selected Bon d Len gth s (Å) for (MeAlNRf)4
(1a )
(MeIn (THF )NRf)4 (5)
Al(1)-N(1)
Al(1)-N(2)
Al(1)-N(3)
Al(1)-C(1)
1.922(2)
1.947(2)
1.938(2)
1.931(3)
N(4)-Al(2)
N(4)-Al(3)
N(4)-Al(4)
N(4)-C(41)
1.951(2)
1.951(2)
1.918(2)
1.435(3)
N(1)-In(1)-N(1A)
N(1A)-In(1)-N(1B)
In(1)-N(1)-In(1C)
C(1)-N(1)-In(1)
C(1)-N(1)-In(1C)
C(1)-In(1)-N(1A)
83.7(2) N(1)-In(1)-N(1B)
85.8(2) In(1)-N(1)-In(1B)
93.7(2) In(1B)-N(1)-In(1C)
123.8(4) C(1)-N(1)-In(1B)
125.3(4) C(7)-In(1)-N(1)
143.6(3) C(7)-In(1)-N(1B)
85.2(2)
94.6(2)
96.3(2)
115.9(4)
111.9(3)
126.7(3)
Ta ble 2. Selected Bon d An gles (d eg) for
(MeAlNRf)4 (1a )
N(1)-Al(1)-N(3)
N(1)-Al(1)-N(2)
N(3)-Al(1)-N(2)
89.32(10)
89.71
90.00(10)
Al(2)-N(4)-Al(4)
Al(3)-N(4)-Al(4)
Al(2)-N(4)-Al(3)
90.06(10)
90.72(10)
90.00(10)
Ta ble 3. Selected Bon d Len gth s (Å) for
(MeAlNRf)6‚2THF (1b)
Al(1)-N(1)
Al(1)-N(2)
Al(1)-N(3)
Al(1)-C(10)
1.909(3)
1.907(3)
1.952(3)
1.942(4)
N(3)-Al(2)
N(3)-Al(3)
N(3)-C(31)
1.905(3)
1.913(3)
1.455(4)
Ta ble 4. Selected Bon d An gles (d eg) for
(MeAlNRf)6‚2THF (1b)
N(1)-Al(1)-N(2) 113.28(11) Al(2)-N(3)-Al(3) 126.22(13)
N(1)-Al(1)-N(3)
N(2)-Al(1)-N(3)
90.59(11) Al(1)-N(3)-Al(2)
90.06(11) Al(1)-N(3)-Al(3)
89.55(11)
89.11(11)
Ta ble 5. Selected Bon d Len gth s (Å) for
(MeGa NRf)6‚7THF (3)
Ga(1)-N(1)
Ga(1)-N(1C)
N(1)-Ga(1D)
N(1)-C(1)
1.967(43)
1.971(3)
1.971(3)
1.452(6)
Ga(1)-N(1A)
N(1)-Ga(1B)
Ga(1)-C(10)
F(1)-C(4)
2.033(4)
2.033(4)
1.943(5)
1.368(7)
F igu r e 2. Crystal structure of 1a , with anisotropic
displacement parameters depicting 50% probability. All the
hydrogen atoms of the molecule have been omitted for
clarity.
Ta ble 6. Selected Bon d An gles (d eg) for
(MeGa NRf)6‚7THF (3)
and structurally characterized. The structure of com-
pound 1b is shown in Figure 3. The N6Al6 core is a
distorted hexagonal prism with approximate D3d point
group symmetry. The asymmetric unit contains two
half-molecules, the other halves being generated by
inversion centers. The N3Al3 rings are slightly bent into
a chair conformation (mean torsion angle 8.3°). The
N-Al-N angles within the six-membered ring vary
between 112.8(1) and 113.7(1)° and within the four-
membered ring between 90.1(1) and 90.9(1)°. The
corresponding Al-N-Al angles are in the ranges 125.9-
(2)-127.3(2)° and 88.8(1)-89.6(1)°.
Ga(1)-N(1)-Ga(1B) 90.42(14) Ga(1)-N(1)
125.87(18)
Ga(1B)-N(1)-Ga(1D) 90.30(14) N(1)-Ga(1)-N(1A) 89.41(15)
N(1)-Ga(1)-N(1C) 114.05(18) N(1A)-Ga(1)-N(1C) 89.28(15)
C(1)-N(1)-Ga(1)
112.1(3) C(1)-N(1)-Ga(1B) 125.8(3)
C(1)-N(1)-Ga(1D) 110.8(3) C(10)-Ga(1)-N(1) 117.8(2)
C(10)-Ga(1)-N(1A) 124.9(2) C(10)-Ga(1)-N(1C) 116.0(2)
Ta ble 7. Selected Bon d Len gth s (Å) for
(MeIn (THF )NRf)4 (5)
In(1)-C(7)
In(1)-N(1A)
N(1)-C(1)
F(1)-C(4)
2.117(7)
2.136(5)
1.415(8)
1.363(8)
In(1)-N(1)
In(1)-N(1B)
In(1)-O(1)
2.279(5)
2.191(5)
2.732(3)
The mean Al-N bond distance within the six-
membered ring is 1.913 Å, whereas that in between the
six-membered rings is 1.954 Å. This distortion can be
explained as an effect of the repulsion between the
aluminum centers, which thus is minimized for an
Al‚‚‚Al distance of 3.40 Å, whereas the undistorted
structure would impose a shorter distance (3.31 Å). This
accounts also for the 0.04 Å longer Al-N bond distance
between the six-membered rings, where the resulting
mean Al‚‚‚Al distances are 2.71 Å.
The mean Al-N bond distance of 1.925 Å is in line
with those found in other hexameric iminoalanes
{HAlNCH(Me)(C6F5)}6 (1.923 Å)14 and (HAlNiPr)6 (1.917
Å).15
The crystal structure of 3 (Figure 4) shows also a
hexagonal prismatic Ga6N6 core. The asymmetric unit
contains one-sixth of the iminogallane, along with a
complete tetrahydrofuran molecule and one-sixth of a
second one disordered on a 3h-axis.
The main difference between the two molecules is the
orientation of the aromatic rings, which form two almost
coplanar pairs in the first molecule, whereas only one
pair of rings is coplanar in the other one.
Only in the first molecule, a contraction of the four
Al-N bond distances between two of the four-membered
Al2N2 rings can be noticed (average 1.918 Å, while the
mean distance within the ring is 1.943 Å). This could
be due to interactions with the π-electron system of the
aromatic rings. The mean Al-N bond distance of 1.934
Å can be described in terms of the resonance hybrid be-
tween two covalent Al-N bonds, as found in monomeric
12a
three-coordinated aluminum amides Al[N(i-Pr)2]3 and
(tBu)2AlNMes212b (1.81 Å, mean values) and as found in
the pure donor bond compound Me3Al‚NMe3 (2.10 Å).13
The hexameric compound 1b, which is formed along
with the tetrameric species, has been also crystallized
(12) (a) Brothers, P. J .; Wehmschulte, R. J .; Olmstead, M. M.;
Ruhland-Senge, K.; Parker, S. R.; Power, P. P. Organometallics 1994,
13, 2792. (b) Petrie, M. A.; Ruhland-Senge, K.; Power, P. P. Inorg.
Chem. 1993, 32, 1135.
(14) Del Piero, G.; Cucinella, S.; Cesari, M. J . Organomet. Chem.
1979, 173, 263.
(13) Anderson, G. A.; Forgaard, F. R.; Haaland, A. Acta Chem.
Scand. 1973, 13, 1947.
(15) Cesari, M.; Perego, G.; Del Piero, G.; Cucinella, S.; Cernia, E.
J . Organomet. Chem. 1974, 78, 203.

Amino- and Iminometallanes
Organometallics, Vol. 16, No. 6, 1997 1201
Ta ble 9. Cr ysta llogr a p h ic Da ta for 1a , 1b‚2THF , 3‚7THF , a n d 5
compound
1a
1b‚2THF
3‚7THF
5
empirical formula
fw
C28H28Al4F4N4
604.5
153(2)
0.40 × 0.35 × 0.35
monoclinic
P21/n
14.263(1)
18.803(2)
23.450(2)
90(0)
106.91(1)
90(0)
6017(1)
8
1.335
0.205
C42H42Al6F6N6 + 2C4H8O
906.7 + 2 × 72.1
193(2)
C42H42Ga6F6N6 + 7C4H8O C44H60F4In4N4O4
1163.2 + 7 × 72.1
1244.2
temp (K)
cryst size (mm)
cryst system
space group
a (Å)
193(2)
193(2)
0.40 × 0.40 × 0.40
0.50 × 0.50 × 0.50
rhombohedral
R3h
20.946(1)
20.946(1)
14.933(2)
90(0)
0.40 × 0.20 × 0.20
tetragonal
P4h21c
15.031(2)
15.031(2)
10.932(2)
90(0)
triclinic
P1h
12.155(3)
12.397(3)
19.270(4)
94.64(3)
b (Å)
c (Å)
R (deg)
â (deg)
107.04(3)
100.52(3)
2702(1)
90(0)
90(0)
γ (deg)
120(0)
90(0)
cell vol V (Å3)
Z
5674(1)
3
2470(1)
2
2
Fc (g‚mm-3
)
1.292
0.183
1096
1.464
1.673
µ (mm-1
F(000)
)
2.174
1.901
2496
2568
1232
2θ range (deg)
5-45
4-50
5-45
8-50
data measd, unique
R,a wR2b (I > 2σ(I))
R, wR2 (all data)
12 145, 7873 (Rint ) 0.028) 21 632, 8648 (Rint ) 0.044) 1909, 1644 (Rint ) 0.020)
1352, 1229 (Rint ) 0.066)
0.031, 0.067
0.036, 0.070
1.082
0.039, 0.086
0.055, 0.095
1.066
0.036, 4.993
729
0.056, 0.136
0.070, 0.144
1.064
0.046, 4.019
729
0.039, 0.104
0.049, 0.112
1.093
0.059, 12.541
219
c
goodness of fit S
weight factors a, bd
refined params
0.034, 0.253
137
min/max transm factors
restraints
0.808/0.955
230
0
466
0
largest diff peak/hole
0.251/-0.268
0.425/-0.337
0.353/-0.323
0.595/-0.563
(e Å-3
)
a
b
2
2
d
R ) ∑||Fo| - |Fc||/∑|Fo|. wR2 ) [∑w(Fo - Fc2)2]/[∑w(Fo2)2]1/2
.
c S ) [∑w(Fo - Fc2)2]/∑(n - p)]1/2
.
w-1 ) σ2(Fo2) + (aP)2 + bP; P )
2
[Fo + 2Fc2]/3.
F igu r e 4. Crystal structure of 3‚7THF, with anisotropic
displacement parameters depicting 50% probability. All the
hydrogen atoms of the molecule have been omitted for
clarity.
F igu r e 3. Crystal structure of 1b‚2THF, with anisotropic
displacement parameters depicting 50% probability. All the
hydrogen atoms of the molecule have been omitted for
clarity.
The longer M-N bond lengths between six-membered
rings in 1b and 3 are also consistent with a less effective
overlap of the sp3 hybridized orbitals, imposed by the
more strained geometry, leading to weaker and thus
longer bonds as compared to those within the six-
membered rings.
The core of compound 5 consists of a distorted cube
with In and N atoms at alternating corners. A methyl
group and a THF molecule coordinate to each In atom,
thus resulting in a 5-fold coordination of the metals
(distorted trigonal bipyramid). The angle between the
methyl group, the In atom, and the nitrogen trans to
the THF molecule is 111.9(3)°. The 4-fold-coordinated
N atoms bind a 4-fluorophenyl ligand each. The average
In-N-In and N-In-N angles within the cube are 94.9
The molecule fulfills the S6 point group symmetry,
as imposed by the space group, with the 4-fluorophenyl
ligands deviating from the higher D3d symmetry. The
same kind of distortion as in 1b can be observed; the
bond angles N-Ga-N and Ga-N-Ga within the six-
membered ring are 114.1(2) and 125.9(2)°, respectively.
This leads to Ga‚‚‚Ga distances of 3.507(2) Å. The
Ga-N distance between both six-membered rings is
0.064 Å longer than within the ring, with an average
value of 1.990 Å, slightly shorter than in the reported
tetrameric iminogallane{MeGaNC6F5}4 (2.008 Å).4c
There are no reported hexameric iminogallanes to date.

1202 Organometallics, Vol. 16, No. 6, 1997
Schnitter et al.
acterized compounds showing In-THF interactions
{2.257(9) Å in InCl3‚2THF,16 2.414(4) Å in InMes3‚THF,17
and 2.309(5) and 2.416(5) Å in [iPr2In(THF)2][BF4]}.18
Con clu sion s a n d Rem a r k s
The introduction of fluorine into the 4-position of the
phenyl ring resulted in new amino-based amino- and
iminometallanes of group 13 that have unusual proper-
ties. Due to the lower basicity of the amine, the
elimination of hydrocarbons occurred at lower temper-
atures giving products without major impurities. How-
ever, to our surprise, the stronger basic solvent (THF)
gave hexameric 1b‚2THF while recrystallization from
n-hexane afforded tetrameric 1a . Obviously, in the
more polar solvent (THF) the solubiltiy of the hexamer
is less compared to the tetramer. It has to be taken in
consideration however that the crystallization is a
nonequilibrium process. The influence of the solvent
has been nicely demonstrated by isolating the THF
adduct of (MeIn(THF)NRf)4 (5).
F igu r e 5. Crystal structure of 5, with anisotropic dis-
placement parameters depicting 50% probability. All the
hydrogen atoms of the molecule have been omitted for
clarity.
Ack n ow led gm en t. This work has been financially
supported by the BMBF, the Deutsche Forschungsge-
meinschaft, and the Hoechst AG. E.P. and I.U. are
grateful to the EU for an European Union HCM Fel-
lowship (ERB CHBG CT 940731 and ERB CHBG
930338).
and 84.9°, respectively. These values are in good agree-
ment with those observed for the related ((pentafluoro-
phenyl)imino)methylindane4b (95.5 and 84.3°). The
increased radius and soft character of the In atoms with
respect to the Al ones account for the enhanced distor-
tion of the cage with respect to that observed in
compound 1a . The In-N distances range from 2.136-
(5) to 2.279(5) Å. This difference is consistently bigger
than that observed in the pentafluorophenyl analogue
[In-N bond lengths in the range 2.167(1)-2.227(1) Å].4b
This is most likely due to the presence of the coordinated
THF molecule on each In atom. In fact of the three
In-N bonds, the one trans to the THF molecule is the
longest.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data, non-hydrogen fractional coordinates and U values, bond
lengths and angles, anisotropic displacement parameters, and
hydrogen atom coordinates and U values of the structures 1a ,
1b‚2THF, 3‚7THF, and 5 (31 pages). Ordering information
is given on any current masthead page.
OM9607457
(16) Self, M. F.; McPhail, T. A.; Wells, R. L. Polyhedron 1993, 12,
455.
(17) Rosetto, G.; Brianese, N.; Camporese, A.; Casellato, U.; Ossola,
F.; Porchia, M.; Zanella, P.; Graziani, R. Gazz. Chim. Ital. 1990, 120,
805.
The In-O distance is 2.732(3) Å, which is relatively
longer than those observed in other structurally char-
(18) Neumu¨ller, B.; Gahlmann, F. J . Organomet. Chem. 1991, 414,
271.