Synthesis of HC[(CBut)(NAr)]2Al (Ar = 2,6-Pr 2iC6H3) and its reaction with isocyanides, a bulky azide, and H2O

Article abstract of DOI:10.1021/om061107j

The reaction of H₂C[(CBu^t)₂(NAr) ₂] (Ar = 2,6-Prⁱ₂C₆H₃) with AlEt₃ in refluxing toluene gave HC[(CBu^t) ₂(NAr)₂]AlEt₂ (1) in high yield. Treatment of 1 with 2 equiv of iodine in toluene yielded HC[(CBu^t) ₂(NAr)₂]AlI₂ (2). Reduction of 2 with potassium resulted in the formation of the tert-buty]-substituted β-diketiminato aluminum(I) compound HC[(CBu^t)₂(NAr)₂]Al (3). Reactions of 3 with isocyanides, H₂O, and a bulky terphenyl azide were investigated. 3 reacted with 2 equiv of CNAr to give two C-C coupling products: in dilute solution, the C-C coupling of two CNAr molecules was followed by the C-H activation of one of the CHMe₂ groups on the Ar ring of CNAr, while in concentrated solution or in the presence of an excess of the isocyanide, the coupling was accompanied by cleavage of one of the C-N bonds of the ligand backbone. Reaction of 3 with the bulky azide 2,6-Ar ₂C₆H₃N₃ yielded the C-H activation product 6. Hydrolysis of 3 in toluene afforded a hydroxyaluminum hydride. Compounds 1 and 3-5 were characterized by X-ray single-crystal analysis.

Full text of DOI:10.1021/om061107j

Organometallics 2007, 26, 1039-1043
1039
Synthesis of HC[(CBut)(NAr)]2Al (Ar ) 2,6-Pri2C6H3) and Its
Reaction with Isocyanides, a Bulky Azide, and H2O
Xiaofei Li, Xiaoyan Cheng, Haibin Song, and Chunming Cui*
State Key Laboratory of Elemento-Organic Chemistry, Nankai UniVersity,
Tianjin 300071, People’s Republic of China
ReceiVed December 6, 2006
The reaction of H2C[(CBut)2(NAr)2] (Ar ) 2,6-Pri2C6H3) with AlEt3 in refluxing toluene gave
HC[(CBut)2(NAr)2]AlEt2 (1) in high yield. Treatment of 1 with 2 equiv of iodine in toluene yielded
HC[(CBut)2(NAr)2]AlI2 (2). Reduction of 2 with potassium resulted in the formation of the tert-butyl-
substituted â-diketiminato aluminum(I) compound HC[(CBut)2(NAr)2]Al (3). Reactions of 3 with
isocyanides, H2O, and a bulky terphenyl azide were investigated. 3 reacted with 2 equiv of CNAr to give
two C-C coupling products: in dilute solution, the C-C coupling of two CNAr molecules was followed
by the C-H activation of one of the CHMe2 groups on the Ar ring of CNAr, while in concentrated
solution or in the presence of an excess of the isocyanide, the coupling was accompanied by cleavage of
one of the C-N bonds of the ligand backbone. Reaction of 3 with the bulky azide 2,6-Ar2C6H3N3 yielded
the C-H activation product 6. Hydrolysis of 3 in toluene afforded a hydroxyaluminum hydride. Compounds
1 and 3-5 were characterized by X-ray single-crystal analysis.
Chart 1
Introduction
The syntheses of the isolable â-diketiminato group 13 element
carbene analogues HC[(CMe)(NAr)]2M (M ) Al, Ga, In, Tl;
Ar ) 2,6-Pri2C6H3) represent interesting achievements in group
13 chemistry.1 Experimental and theoretical work indicated that
they could act as strong σ-donors, as Lewis acids, and as
reducing agents.2 In addition, easily tunable â-diketiminato
ligands may allow access to other members of this series with
modified structures and reactivities. A number of reactions of
HC[(CMe)(NAr)]2Al (3′; Chart 1) with organic functional
groups and Lewis acids have been examined.2b,3 We are
interested in extending this chemistry using the more sterically
demanding â-diketiminato ligand {HC[(CBut)(NAr)]2}-, in
which bulkier tert-butyl groups are present on the ligand
backbone instead of methyl groups.4 It has been demonstrated
that steric manipulations of the â-diketiminato ligand backbone
can have a profound effect on the coordination number and reac-
tivity of the metal complexes.5 Herein we report the synthesis
of the monomeric aluminum(I) species HC[(CBut)(NAr)]2Al (3;
Chart 1) and its reactions with isocyanides, 2,6-Ar2C6H3N3, and
H2O.
Coupling reactions of isocyanides can create new C-C and
C-N bonds and, hence, have attracted widespread interest.6
These reactions usually proceed either by reductive coupling
of isocyanide complexes of transition metals mediated by a
reducing reagent7 or by consecutive insertion into M-C bonds.8
However, reductive coupling of isocyanides promoted by heavier
main-group-element complexes has been less investigated.9 It
has been shown that bulky isocyanides interact with low-valent
heavier main-group-element species to yield donor-acceptor
complexes or ketenimine analogues.10 Insertion of isocyanides
* To whom correspondence should be addressed. E-mail: cmcui@
nankai.edu.cn.
(1) (a) Cui, C.; Roesky, H. W.; Schmidt, H.-G.; Noltemeyer, M.; Hao,
H.; Cimpoesu, F. Angew. Chem., Int. Ed. 2000, 39, 4272. (b) Hardman, N.
J.; Eichler, B. E.; Power, P. P. Chem. Commun. 2000, 1991. (c) Baker, R.
J.; Farley, R. D.; Jones, C.; Kloth, M.; Murphy, D. M. Dalton Trans. 2002,
3844. (d) Hill, M. S.; Hitchcock, P. B. Chem. Commun. 2004, 1818. (e)
Hill, M. S.; Hitchcock, P. B.; Pongtavornpinyo, R. Dalton Trans. 2005,
273. (f) Cheng, Y.; Hitchcock, P. B.; Lappert, M. F.; Zhou, M. Chem.
Commun. 2005, 752. (g) Bourget-Merle, L.; Lappert, M. F.; Severn, J. R.
Chem. ReV. 2002, 102, 3031.
(2) For leading references, see: (a) Zhu, H.; Chai, J, Jancik, V.; Roesky,
H. W.; Merrill, W. A.; Power, P. P. J. Am. Chem. Soc. 2005, 127, 10170.
(b) Zhu, H.; Chai, J.; Chandrasekhar, V.; Roesky, H. W.; Magull, J.; Vidovic,
D.; Schmidt, H.-G.; Noltemeyer, M.; Power, P. P.; Merrill, W. A. J. Am.
Chem. Soc. 2004, 126, 9472. (c) Chen, C.-H.; Tsai, M.-L.; Su, M.-D.
Organometallics 2006, 25, 2766.
(3) (a) For a review, see: Roesky, H. W. Inorg. Chem. 2004, 43, 7284.
(b) Yang, Z.; Ma, X.; Oswald, R. B.; Roesky, H. W.; Noltemeyer, M. J.
Am. Chem. Soc. 2006, 128, 12406. (c) Zhu, H.; Yang, Z.; Magull, J.; Roesky,
H. W.; Schmidt, H.-G.; Noltemeyer, M. Organometallics 2005, 24, 6420.
(d) Peng, Y.; Fan, H.; Jancik, V.; Roesky, H. W.; Herbst-Irmer, R. Angew.
Chem., Int. Ed. 2004, 43, 6190. (e) Peng, Y.; Fan, H.; Zhu, H.; Roesky, H.
W. Magull, J.; Hughes, C. E. Angew. Chem., Int. Ed. 2004, 43, 3443.
(4) Budzelaar, P. H. M.; van Oort, A. B.; Orpen, A. G. Eur. J. Inorg.
Chem. 1998, 1485.
(5) A review: Bourget-Merle, L.; Lappert, M. F.; Severn, J. R. Chem.
ReV. 2002, 102, 3031.
(6) For reviews, see: (a) Carnahan, E. M.; Protasiewicz, J. D.; Lippard,
S. J. Acc. Chem. Res. 1993, 26, 90. (b) Do¨mling, A. Chem. ReV. 2006,
106, 17.
(7) For examples see: (a) Berg, F. J.; Petersen, J. L. Organometallics
1991, 10, 1599. (b) Acho, J. A.; Lippard, S. J. Organometallics 1994, 13,
1294. (c) Rehder, D.; Bottcher, C.; Collazo, C.; Hedelt, R.; Schmidt, H. J.
Organomet. Chem. 1999, 585, 294.
(8) Durfee, L. D.; Rothwell, I. P. Chem. ReV. 1988, 88, 1059.
(9) (a) Uhl, W.; Schuetz, U.; Hiller, W.; Heckel, M. Chem. Ber. 1994,
127, 1587. (b) Uhl, W.; Hahn, I.; Schuetz, U.; Pohl, S.; Saak, W.; Martens,
J.; Manikowski, J. Chem. Ber. 1996, 129, 897. (c) Weidenbruch, M.; Brand-
Roth, B.; Pohl, S.; Saak, W. Angew. Chem., Int. Ed. 1990, 29, 90. (d)
Weidenbruch, M.; Brand-Roth, B.; Pohl, S.; Saak, W. Polyhedron 1991,
10, 1147.
10.1021/om061107j CCC: $37.00 © 2007 American Chemical Society
Publication on Web 01/11/2007

1040 Organometallics, Vol. 26, No. 4, 2007
Li et al.
Figure 2. Thermal-ellipsoid plot (30% probability) of 3. Selected
bond lengths (Å) and angles (deg): Al1-N1 ) 1.9637(15),
Al1-N1* ) 1.9637(15), N1-C2 ) 1.341(2), C1-C2 ) 1.393(2),
N1-C7 ) 1.445(2); N1-Al1-N1* ) 91.85(9), C2-N1-C7 )
125.61(14), C2-N1-Al1 ) 128.14(12), C7-N1-Al1 ) 106.18-
(10), C2-C1-C* ) 131.9(2).
Figure 1. Thermal-ellipsoid plot (30% probability) of 1. Only one
of the two independent molecules in the unit cell is shown.
Hydrogen atoms have been omitted for clarity. Selected bond
lengths (Å) and angles (deg): Al1-C36 ) 1.980(4), Al1-C38 )
1.974(4), Al1-N1 ) 1.945, Al1-N2 ) 1.936(3); N1-Al1-N2
) 99.03(13), N1-Al1-C36 ) 108.43(16), N1-Al1-C38 )
111.47(17), N2-Al1-C36 ) 110.60(17), N2-Al1-C38 ) 110.77-
(16), C36-Al1-C38 ) 115.3(2).
Scheme 1. Reaction of 3 with CNAr
into Al-C bonds has also been reported.11 Compound 3 reacts
with CNAr, leading to the C-C coupling of the isocyanide
molecules accompanied by the respective C-N and C-H bond
cleavages. These kinds of isocyanide-coupling reactions medi-
ated by a mononuclear main-group-metal complex that do not
contain metal-alkyl groups and carried out without additional
reagents are unprecedented.
N-Al-N angle (91.85(9)°) is larger by 2° compared to that
found in the methyl-substituted derivative,1a probably caused
by the increasing repulsion of the two flanking Ar groups in
the tert-butyl-substituted species.
Results and Discussion
Synthesis of HC[(CBut)(NAr)]2Al. Reaction of the free
diimine H2C[(CBut)NAr]]2 with AlEt3 in refluxing toluene for
8 h and subsequent crystallization from n-hexane afforded
HC[(CBut)(NAr)]2AlEt2 (1) as pale yellow crystals in high yield.
The diiodide precursor HC[(CBut)(NAr)]2AlI2 (2) was prepared
in excellent yield by the reaction of 1 with 2 equiv of iodine.
Reduction of 2 with 2 equiv of potassium in toluene at room
temperature followed by crystallization from toluene gave red
crystals of the tert-butyl-substituted (â-diketiminato)aluminum-
(I) species HC[(CBut)(NAr)]2Al (3). Compound 3 has a limited
solubility in toluene and is very thermally stable in solution.
No decomposition was observed after it had been heated at
reflux in toluene for 2 h.
Reaction of 3 with Isocyanides. Reactions of 3 with
isocyanides were performed with the expectation that a donor-
acceptor or an allenic species would result, analogous to the
reactions of the isolable silylenes with bulky isocyanides.10
Reaction of 3 with CNBut resulted in the formation of a
complicated mixture under various conditions. Many attempts
to isolate pure products were unsuccessful. Therefore, we used
the sterically more demanding aryl isocyanide CNAr for the
reaction. Reaction of CNAr with 1 equiv of 3 was conducted
in toluene from -78 °C to room temperature. The proton NMR
study of the crude product indicates the formation of multiple
products, which could not be identified. Nevertheless, yellow
crystals of 4 were obtained in 30% yield by crystallization from
n-hexane (Scheme 1). Attempts to isolate the other products
were unsuccessful. Since 3 is poorly soluble in toluene, the
reaction was carried out at room temperature. Upon addition
of 2 equiv of CNAr in toluene to a dilute toluene solution of 3,
an immediate color change to dark pink was observed and,
surprisingly, compound 5 was isolated in high yield. However,
when 2 equiv of neat CNAr (or an excess) was added to a
suspension of 3 in a small amount of toluene, compound 4 was
obtained selectively in good yield. Compounds 4 and 5 are
thermally stable, and rearrangements of one to the other were
not observed under various conditions, suggesting that they are
very likely generated by different mechanisms.
1
Compounds 1-3 have been characterized by their H and
13C NMR and IR spectra and elemental analysis. The NMR
spectra of these complexes show the expected patterns. The
UV-vis spectrum of 3 in n-hexane shows a maximum at 364
nm (ꢀ ) 13 000 M-1 cm-1). The structures of 1 and 3 were
determined by X-ray single-crystal analysis (Figures 1 and 2).
The structure of 3 (Figure 2) contains a planar AlN2C3 six-
membered ring similar to that of HC[(CMe)(NAr)]2Al.1a The
(10) (a) Gru¨tzmacher, H.; Freitag, S.; Herbst-Irmer, R.; Sheldrick, G. S.
Angew. Chem., Int. Ed. Engl. 1992, 31, 437. (b) Takeda, N.; Suzuki, H.;
Tokitoh, N.; Okazaki, R.; Nagase, S. J. Am. Chem. Soc. 1997, 119, 1456.
(c) Takeda, N.; Kajiwara, T.; Suzuki, H.; Okazaki, R.; Tokitoh, N. Chem.
Eur. J. 2003, 9, 3530. (d) Cui, C.; Olmstead, M. M.; Fettinger, J. C.; Spikes,
G. H.; Power, P. P. J. Am. Chem. Soc. 2005, 127, 17530. (e) Abe, T.;
Iwamoto, T.; Kabuto, C.; Kira, M. J. Am. Chem. Soc. 2006, 128, 4228. (f)
Uhl, W.; Hannemann, F.; Wartchow, R. Organometallics 1998, 17, 3822.
(g) Escudie´, J.; Ranaivonjatovo, H.; Rigon, L. Chem. ReV. 2000, 100, 3639.
(11) (a) Li, X.; Ni, C.; Song, H.; Cui, C. Chem. Commun. 2006, 1763.
(b) Shapiro, P. J.; Vij, A. Yap, G. P. A.; Rheingold, A. L. Polyhedron
1995, 12, 203.
The X-ray structure of 4 (Figure 3) shows of the presence of
an AlC2N four-membered ring and a C4N heterocycle, most
likely formed via C-C coupling of the two CNAr molecules
and C-H addition of one of the CHMe2 groups to the â-C of
the AlC2N ring. The AlC2N cycle is almost planar (∆ ) 0.0363

Synthesis of HC[(CBut)(NAr)]2Al
Organometallics, Vol. 26, No. 4, 2007 1041
Figure 3. Thermal-ellipsoid plot (30% probability) of 4. Selected
bond lengths (Å) and angles (deg): Al1-N1 ) 1.909(3), Al1-N2
) 1.899(4), Al1-N3 ) 1.818(4), Al1-C49 ) 2.003(5), N3-C48
) 1.511(6), N4-C49 ) 1.278(5), C48-C49 ) 1.556(6): N1-
Al1-N2 ) 122.27(16), N3-Al-C49 ) 75.19(18), N3-C48-C49
) 99.2(3).
Figure 4. Thermal-ellipsoid plot (30% probability) of 5. Selected
bond lengths and angles (deg): Al1-N1 ) 1.9795(18), Al1-N3
) 1.8559(17), Al1-C3 ) 1.969(2), Al1-C25 ) 2.020(2), N1-
C1 ) 1.313(3), C1-C2 ) 1.471(3), C2-C3 ) 1.342(3), N3-C24
) 1.412(2), C24-C25 ) 1.528(3); N1-Al1-C3 ) 86.71(8), N1-
Al1-N3 ) 112.69(7), N3-Al1-C25 ) 72.38(7), N3-C24-C25
) 102.37(16).
Scheme 2. Proposed Mechanisms for CNAr Coupling
length (1.528(3) Å) is indicative of a C-C single bond. The
NMR spectra of 5 are in agreement with the structure. The
proton resonance of the γ-CH for the â-diketiminato ligand does
1
not appear in the H NMR spectrum. The 13C NMR spectrum
shows two broad singlets at δ 204.66 and 197.26 ppm, attributed
to the resonances of the two carbon atoms attached to the
aluminum atom, respectively.
Å), while the C4N ring adopts a puckered conformation with
the C24 atom bent out of the C3N quasi-plane (∆ ) 0.0595 Å).
The N3-C48 and C48-C49 bond lengths are 1.511(6) and
1.556(16) Å and are typical of C-N and C-C single bonds,
Because the reactions proceed instantaneously, the mecha-
nisms are subject to speculation. The reactions might involve
initial coordination of the isocyanide to 3 to form a donor-
acceptor or zwitterionic species (A), which could either undergo
migration-insertion of CNAr into one of the Al-N bonds or
couple with another molecule of CNAr. In the dilute solution,
the former pathway might dominate and subsequent double
insertion and reductive cleavage of the C-N bond14 by the
aluminum atom would lead to the formation of 5. However,
high concentration or an excess of CNAr in the system may
favor isocyanide coupling prior to the insertion followed by the
C-H addition to yield 4 (Scheme 2).
1
respectively. The H NMR spectrum of 4 shows a singlet at δ
3.61 ppm, attributed to the resonance due to the â-CH in the
AlC2N ring, and the 13C resonance appears at δ 85.9 ppm. We
reason that the reaction may proceed by way of reductive
coupling of two CNAr molecules to form a four-membered
AlC2N carbene intermediate (Scheme 2; B), which subsequently
undergoes intramolecular C-H addition13 to yield 4. However,
we were unable to isolate the intermediate or to trap it with
alkynes and alkenes.
Deep pink crystals of 5 suitable for an X-ray diffraction study
were obtained from diethyl ether at -20 °C. The molecular
structure of 5 is shown in Figure 4. The molecular array shows
that one of the C-N bonds in the ligand backbone has been
cleaved and a new C-N bond has been formed. This kind of
cleavage has been reported for divalent (â-diketiminato)-
zirconium intermediates and postulated to be a reductive
process.14 The Al1-C3 (1.969(2) Å) and Al1-C25 (2.020(2)
Å) bond lengths are in the reported range for Al-C single bonds.
The Al-N3 bond distance (1.8559(17) Å) is consistent with a
Al-N single bond, while the Al1-N1 bond distance (1.9795-
(18) Å) is slightly longer than those found in trivalent (â-
diketiminato)aluminum compounds.15 The C24-C25 bond
Reaction of 3 with 2,6-Ar2C6H3N3. It has been shown that
reaction of the methyl-substituted (â-diketiminato)aluminum-
(I) species HC[(CMe)(NAr)]2Al with a bulky terphenyl azide
gives two types of intramolecular addition products, and an
aluminum imide species was assumed as an intermediate.2b We
reason that the tert-butyl-substituted â-diketiminato ligand would
provide more efficient protection and thus stabilize the mono-
meric imide species. Therefore, the reaction of 3 with 2,6-
Ar2C6H3N3 was performed analogously as reported. The isolable
yellow crystalline product was identified as 6 on the basis of
1
the H and 13C NMR and IR spectra and elemental analysis
(Scheme 3). The 1H NMR spectrum showed a broad singlet at
δ 3.37 ppm, and the IR spectrum displayed an absorption
centered at 3238 cm-1, suggesting the presence of an N-H
group. The spectroscopic data of 6 are similar to those of one
of the two products generated by the reaction of HC[(CMe)-
(NAr)]2Al with 2,6-Ar2C6H3N3. The formation of 6 may also
result from an monomeric imide species, as proposed.2b
(12) (a) Sheldrick, G. M. SHELXS-90/96, Program for Structure Solution.
Acta Crystallogr., Sect. A 1990, 46, 467. (b) Sheldrick, G. M. SHELXL-
97, Program for Crystal Structure Refinement; University of Go¨ttingen,
Go¨ttingen, Germany, 1997.
(13) Bourissou, D.; Guerret, O.; Gabba¨ı, F. P.; Bertrand, G. Chem. ReV.
2000, 100, 39.
(14) (a) Basuli, F.; Kilgore, U. J.; Brown, D.; Hoffman, J. C.; Mindiola,
D. J. Organometallics 2004, 23, 6166. (b) Hamaki, H.; Takeda, N.; Tokitoh,
N. Organometallics 2006, 25, 2457. (c) Bai, G.; Wei, P.; Stephan, D. W.
Organometallics 2006, 25, 2649.
(15) Stender, M.; Eichler, B. E.; Hardman, N. J.; Power, P. P.; Prust, J.;
Noltemeyer, M.; Roesky, H. W. Inorg. Chem. 2001, 40, 2794.

1042 Organometallics, Vol. 26, No. 4, 2007
Li et al.
Scheme 3. Reaction of 3 with 2,6-Ar2C6H3N3 and H2O
was kept at -25 °C overnight to yield light yellow crystals of 2
(12.3 g, 83.0%). Mp: 252 °C. Anal. Calcd for C35H53AlI2N2
(782.58): C, 53.72: H, 6.83; N, 3.58. Found: C, 53.95; H, 6.70;
N 3.65. 1H NMR (CDCl3, 400 MHz): δ 1.16 (s, 18H, CMe3), 1.28
(d, 24H, CHMe2), 3.53 (sept, 4H, CHMe2), 6.25 (s, 1H, γ-CH),
7.13 (d, 4H, Ar H), 7.23 (d, 2H, Ar H). 13C NMR (CDCl3): δ
24.24 (CH3), 27.31 (CHMe2), 28.97 (CH), 32.00 (CH3), 43.79
(CMe3), 103.04 (γ-C), 124.48, 127.43, 140.36, 145.12 (Ar C),
181.66 (CN). IR (cm-1): 2968, 2868, 1655, 1622, 1498, 1466, 1352,
1314, 1260, 1180, 1103, 1018, 934, 795, 757, 599.
Hydrolysis of 3. Since aluminum hydroxides are important
precursors for the preparation of oxo-bridged bimetallic sys-
tems,16 we were interested in the reaction of 3 with H2O,
expecting to generate a hydroxyaluminum hydride. Indeed,
reaction of 3 with 1 equiv of H2O in toluene afforded colorless
crystals of 7 in high yield (Scheme 3). The 1H NMR spectrum
of 7 showed a singlet at δ 0.37 ppm, attributed to the resonance
arising from the hydroxy proton. The OH absorption is also
Synthesis of HC[(CBut)(NAr)]2Al (3). A solution of LAlI2 (3.2
g, 6.0 mmol) in 50 mL of toluene was added to a suspension of
finely divided potassium (0.56 g, 14.4 mmol) in toluene (10 mL).
The mixture was vigorously stirred at room temperature for 5 days.
The solution became red, and all of the potassium appeared to be
consumed. The solution was filtered, and the residue was extracted
with toluene (80 mL). The red-brown filtrate was concentrated (to
15 mL) and stored at -35 °C overnight, affording red crystals of
3 (0.62 g, 20%). The remaining solid could not be identified, due
to its poor solubility in organic solvents. Mp: 172 °C dec. Anal.
Calcd for C35H53AlN2 (528.77): C, 79.50; H, 10.10; N, 5.30.
observed in the IR spectrum as a sharp band at 3715 cm-1 17
.
The IR spectrum also showed a strong absorption at 1857 cm-1
,
indicating the presence of an Al-H moiety.18 Unfortunately,
we were unable to obtain single crystals of 7 suitable for X-ray
analysis, since it is not stable in solution and slowly underwent
ligand cleavage even at low temperature.
1
Found: C, 79.32; H, 10.23; N, 5.52. H NMR (C6D6): δ 1.13 (s,
18H, CMe3), 1.26 (d, 12H, CHMe2), 1.43 (d, 12H, CHMe2), 3.21
(sept, 4H, CHMe2), 5.88 (s, 1H, γ-CH), 6.95 (br s, 1H), 7.06 (d,
4H, Ar H), 7.34 (br s, 1H, Ar H). 13C NMR (CDCl3): δ 23.40
(CH3), 25.68 (CHMe2), 28.96 (CH), 32.96 (CH3), 42.61 (CMe3),
100.57 (γ-C), 123.76, 127.11, 143.74, 144.26 (Ar C), 173.36 (CN).
UV-vis (n-hexane; λmax (nm) (ꢀ (mol-1 L cm-1))): 285 (2900),
364 (13 000). IR (cm-1): 3061, 2977, 2867, 1624, 1547, 1501,
1392, 1358, 1304, 1273, 1217, 1100, 759.
Experimental Section
All experiments were carried out under an argon atmosphere
using Schlenk line and glovebox techniques. Solvents were dried
over sodium and freshly distilled and degassed prior to use. The
NMR spectra were recorded at room temperature on a Bruker AMX
400 spectrometer. Infrared spectra were recorded on a Bio-Rad FTS
6000 FT IR spectrophotometer. UV-vis spectra were measured
with a Shimadzu UV-2401PC spectrometer. The free ligand
H2C[(CBut)(NAr)]2 was prepared as described in the literature.4
Synthesis of HC[(CBut)(NAr)]2AlEt2 (1). A solution of AlEt3
(2.8 g, 24.0 mol) in n-hexane (12 mL) was added with rapid stirring
to a solution of H2C[(CBut)(NAr)]2 (10.0 g, 20.0 mmol) in n-hexane
(70 mL). The colorless solution was heated at reflux for 24 h to
yield a yellow solution. This was concentrated (to ca. 25 mL) and
kept at -25 °C overnight. Yellow crystals of 1 formed (11.1 g,
94.7%). Mp: 169 °C. Anal. Calcd for C39H63AlN2 (586.89): C,
79.81; H, 10.82; N, 4.77. Found: C, 79.54; H, 11.07; N, 4.62. 1H
NMR (CDCl3): δ 0.27 (br s, 4H, Al-CH2), 0.73 (br, 6H, Al-
CH2CH3), 1.13 (s, 18H, CMe3), 1.26 (d, 12H, CHMe2), 1.32 (d,
12H, CHMe2), 3.34 (sept, 4H, CHMe2), 5.66 (s, 1H, γ-CH), 7.09
(d, 4H, Ar H), 7.17 (m, 2H, Ar H). 13C NMR (CDCl3): δ 9.67
(Al-C), 24.69 (CH3), 26.66 (CHMe2), 27.87 (CH), 32.66 (CH3),
43.21 (CMe3), 100.60 (γ-C), 124.00, 126.02, 142.44, 144.42 (Ar
C), 179.10 (CN). IR (cm-1): 3061, 2980, 2855, 1536, 1490, 1387,
1359, 1312, 1270, 1218, 1182, 1134, 1102, 990, 933, 787, 758,
691, 626.
Synthesis of 4. To a suspension of 3 (0.21 g, 0.40 mmol) in
toluene (2 mL) was added 2,6-diisopropylphenyl isocyanide (0.16
g, 0.82 mmol) at room temperature. The originally red solution
became black immediately. The solution was stirred at room
temperature for 15 min, and then all volatiles were removed under
vacuum. The residue was extracted with n-hexane (20 mL). The
extract was filtered, and the black filtrate was concentrated (to ca.
3 mL). After it stood overnight at -35 °C, the solution afforded
yellow crystals of 4 (0.26 g, 72%). Mp: 80 °C dec. Anal. Calcd
for C61H87AlN4: C, 81.10; H, 9.71; N, 6.20. Found: C, 80.97; H,
9.57; N, 6.08. 1H NMR (CDCl3): δ 0.01, 0.08 (s, 6H, CMe2), 0.33,
0.59, 0.78, 0.87, 0.90, 1.04, 1.15, 1.25, 1.27, 1.28, 1.30, 1.35, 1.61
(d, 42H, CHMe2), 1.21, 1.24 (s, 18H, CMe3), 2.29, 3.02, 3.19, 3.66
(sept, 7H, CHMe2), 3.61 (s, 1H, CH), 5.89 (s, 1H, γ-CH), 6.36 (m,
1H, Ar H), 6.45 (m, 1H, Ar H), 6.79-6.85 (m, 2H, Ar H), 6.98
(m, 1H, Ar H), 7.15-7.21 (m, 4H, Ar H), 7.21-7.28 (m, 2H, Ar
H). 13C NMR (CDCl3): δ 14.12, 20.59, 22.18, 22.66, 23.00, 23.37,
24.41, 24.75, 25.06, 25.29, 25.80, 25.85, 25.92, 26.63, 26.69, 26.84,
27.18, 27.35, 27.73, 28.23, 28.54, 28.62, 29.44, 29.80, 31.60
(CHMe2, CMe2), 32.47, 32.87 (CMe3), 43.46, 43.76, 45.01 (CMe3,
CMe2), 85.95 (CH), 99.20 (γ-C), 116.98, 119.40, 121.11, 123.09,
123.75, 123.96, 124.50, 124.59, 125.23, 126.92, 127.56, 129.41,
133.73, 138.54, 140.31, 140.77, 143.97, 144.14, 145.08, 145.80,
149.88, 151.60 (Ar C), 179.60, 180.58 (CN). UV-vis (n-hexane;
Synthesis of HC[(CBut)(NAr)]2AlI2 (2). A hot (80 °C) solution
of LAlEt2 (11.1 g, 18.9 mmol) in toluene (60 mL) was added rapidly
to a stirred solution of iodine (12.1 g, 47.3 mmol) in toluene (20
mL) at 80 °C. The mixture turned from purple to bright yellow
after the addition was complete. The solution was stirred for 2 h at
room temperature and then concentrated (to 25 mL). The solution
λ
max (nm) (ꢀ (mol-1 L cm-1))): 354 (shoulder). IR (cm-1): 3059,
2964, 2867, 1621, 1538, 1492, 1435, 1387, 1359, 1311, 1265, 1189,
1103, 1030, 927, 792, 749.
Synthesis of 5. To a solution of 3 (0.21 g, 0.40 mmol) in toluene
(40 mL) was slowly added a solution of 2,6-diisopropylphenyl
isocyanide (0.15 g, 0.80 mmol) in toluene (10 mL) at room
temperature. Upon addition, the solution turned from red to purple.
After the addition was complete in 15 min, the solution was stirred
for an additional 2 h. The solution was concentrated (to ca. 10 mL)
and then kept at -35 °C overnight to give purple crystals of 5
(0.22 g, 61%). Mp: 208 °C dec. Anal. Calcd for C61H87AlN4: C,
(16) For examples, see: (a) Bai, G.; Singh, S.; Roesky, H. W.;
Noltemeyer, M.; Schmidt, H.-G. J. Am. Chem. Soc. 2005, 127, 3449. (b)
Jancik, V.; Roesky, H. W. Angew. Chem., Int. Ed. 2005, 44, 6016.
(17) (a) Li, X.; Song, H.; Duan, L.; Cui, C.; Roesky, H. W. Inorg. Chem.
2006, 45, 1912. (b) Bai, G.; Roesky, H. W.; Li, J.; Noltemeyer, M.; Schmidt,
H.-G. Angew. Chem., Int. Ed. 2003, 42, 5502. (c) Bai, G.; Peng, Y.; Roesky,
H. W.; Li, J.; Schmidt, H.-G.; Noltemeyer, M. Angew. Chem., Int. Ed. 2003,
42, 1017.
1
81.10; H, 9.71; N, 6.20. Found: C, 80.92; H, 9.92; N, 5.98. H
(18) Cui, C.; Roesky, H. W.; Hao, H.; Schmidt, H.-G.; Noltemeyer, M.
Angew. Chem., Int. Ed. 2000, 39, 1815.
NMR (CDCl3): δ 0.03, 0.07, 0.46, 1.01, 1.03, 1.08, 1.43, 1.54 (d,

Synthesis of HC[(CBut)(NAr)]2Al
Organometallics, Vol. 26, No. 4, 2007 1043
3H, CHMe2), 0.24 (br, 3H, CHMe2), 1.02, 1.14, 1.24 (d, 42H,
CHMe2), 0.76, 0.97 (s, 18H, CMe3), 2.32, 2.51, 2.72, 2.88, 3.13,
3.23, 3.43, 3.48 (sept, 8H, CHMe2), 6.61-7.26 (m, 13H, CCHCN
and Ar H). 13C NMR (CDCl3): δ 14.12, 21.20, 22.23, 23.01, 23.62,
23.84, 24.21, 24.34, 24.78, 25.22, 25.31, 25.47, 25.67, 26.08, 27.46,
28.07, 28.35, 28.45, 28.67, 28.96, 29.32 (CHMe2), 29.03, 31.29
(CMe3), 36.83, 42.85 (CMe3), 119.49, 121.33, 121.98, 122.15,
122.43, 122.77, 123.08, 123.26, 123.52, 123.80, 124.43, 124.58,
124.71, 128.59, 133.76, 136.44, 138.01, 138.57, 139.94, 140.98,
141.68, 142.52, 143.75, 146.26, 146.68, 146.99 (Ar C), 157.62
(CCHdC), 194.21 (NCBut), 197.26 (ArNdCAl), 204.66 (ButCAl).
UV-vis (n-hexane; λmax (nm) (ꢀ (mol-1 L cm-1))): 274 (10 800),
352 (2500). IR (cm-1): 3381, 2963, 2867, 1642, 1615, 1465, 1322,
1261, 1184, 757.
with n-hexane (20 mL). The extract was concentrated (to ca. 10
mL) and stored at -20 °C for 2 days to give white crystals of 7
(0.17 g, 78%). Mp: 108 °C dec. 1H NMR (CDCl3): δ 0.38 (s, 1H,
OH), 1.13 (s, 18H, CMe3), 1.24, 1.29 (d, 24H, CHMe2), 3.41 (sept,
4H, CHMe2), 5.80 (s, 1H, γ-CH), 7.10 (m, 4H, Ar H), 7.18 (m,
2H, Ar H). 13C NMR (CDCl3): δ 24.10, 26.53, 28.08 (CHMe2,
CMe3), 32.38, 43.09 (CMe3, CHMe2), 98.73 (γ-C), 124.03, 126.62,
140.57, 144.66 (Ar C), 197.59 (CN). IR (cm-1): 3744, 3715 (AlO-
H), 3055, 2963, 2869, 1857 (Al-H), 1538, 1506, 1465, 1437, 1389,
1364, 1316, 1277, 1262, 1219, 1197, 1157, 1101, 1028, 933, 851,
820, 792, 758, 693, 448.
X-ray Structural Determination. Data were collected at
294(2) K on a Bruker Smart-Apex II diffractometer using graphite-
monochromated Mo KR (λ ) 0.710 73 Å) radiation. All structures
were solved by direct methods (SHELXS-97)12a and refined by full-
matrix least squares on F2. All non-hydrogen atoms were refined
anisotropically, and hydrogen atoms were refined by a riding
model (SHELXL-97).12b Crystallographic data for 1: C39H63AlN2,
Mr ) 586.89, triclinic, space group P1h, a ) 12.511(3) Å, b )
18.267(4) Å, c ) 18.810(4) Å, R ) 77.870(4)°, â ) 70.988(3)°,
Reaction of 3 with 2,6-Ar2C6H3N3. To solution of 3 (0.21 g,
0.40 mmol) in toluene (20 mL) at -78 °C was slowly added a
solution of 2,6-Ar2C6H3N3 (0.18 g, 0.40 mmol) in toluene (10 mL)
at -78 °C. The color changed from red to black immediately. The
mixture was slowly warmed to room temperature, during which
time the color changed from black to bright yellow. After all
volatiles were removed under vacuum, the residue was extracted
with n-hexane (20 mL). The extract was concentrated (to 10 mL)
and stored at -20 °C for 2 days to give yellow crystals of 6 (0.21
g, 55%). Mp: 148-151 °C dec. Anal. Calcd for C65H97AlN3: C,
γ ) 70.924(3)°, V ) 3815.4(13) Å3, Z ) 4, Dc ) 1.022 g cm-3
,
F(000) ) 1296, 19 416 reflections measured (13 332 unique).
R1 ) 0.0628 (I > 2σ(I)), wR2 ) 0.1968 (all data), GOF ) 1.009
for 757 parameters and 0 restraints. Crystallographic data for 3:
C35H53AlN2, Mr ) 528.77, monoclinic, space group C2/c, a )
23.748(4) Å, b ) 8.5153(15) Å, c ) 17.376(3) Å, â ) 108.731-
(3)°, V ) 3327.7(10) Å3, Z ) 4, Dc ) 1.055 g cm-3, F(000) )
1160, 8178 reflections measured (2910 unique). R1 ) 0.0438 (I >
2σ(I)), wR2 ) 0.1435 (all data), GOF ) 1.042 for 180 parameters
and 0 restraints. Crystallographic data for 4: C61H87AlN4, Mr )
903.33, triclinic, space group P1h, a ) 12.544(2) Å, b ) 14.444(3)
Å, c ) 18.624(3) Å, R ) 73.795(3)°, â ) 108.731(3)°, γ ) 83.397-
(3)°, V ) 3218.6(9) Å3, Z ) 2, Dc ) 0.932 g cm-3, F(000) ) 988,
16 271 reflections measured (11 213 unique). R1 ) 0.0909 (I >
2σ(I)), wR2 ) 0.2997 (all data), GOF ) 1.041 for 621 parameters
and 1 restraint. Crystallographic data for 5: C61H87AlN4, Mr )
903.33, monoclinic, space group P21/n, a ) 14.255(2) Å, b )
18.737(3) Å, c ) 21.076(3) Å, â ) 91.189(2)°, V ) 5628.2(13)
Å3, Z ) 4, Dc ) 1.066 g cm-3, F(000) ) 19 076, 46 034 reflections
measured (11 046 unique). R1 ) 0.0673 (I > 2σ(I)), wR2 ) 0.1878
(all data), GOF ) 1.085 for 619 parameters and 0 restraints.
1
82.93; H, 9.74; N, 4.46. Found: C, 82.85; H, 9.69; N, 4.40. H
NMR (C6D6): δ -0.17 (m, 2H, AlCH2), 0.60, 0.86 (s, 18H, CMe3),
0.73, 0.79, 0.90 (d, 3 × 3H, CHMe2), 1.03 (m, 12H, CHMe2), 1.17,
1.19 (d, 2 × 3H, CHMe2), 1.27 (d, 3H, CHMe2), 1.34 (d, 3H,
CHMe2), 1.42 (t, 6H, CHMe2), 1.49, 1.52 (d, 2 × 3H, CHMe2),
2.41, 2.82, 2.95, 3.05, 3.13, 3.17, 3.86 (sept, 7 × 1H, CHMe2),
2.66 (m, 1H, CHMeCH2), 3.37 (s, 1H, NH), 5.90 (s, 1H, γ-CH),
6.59 (m, 1H, Ar H), 6.92 (m, 1H, Ar H), 6.99 (m, 1H, Ar H), 7.02-
7.10 (m, 2H, Ar H), 7.18-7.21 (m, 2H, Ar H), 7.28 (m, 1H, Ar
H). 13C NMR (C6D6): δ 22.12, 23.44, 23.54, 23.63, 24.09, 24.26,
25.24, 25.44, 25.91, 26.05, 26.25, 26.33, 26.51, 26.72, 26.87, 27.04,
27.22, 27.61, 28.60, 30.04, 30.22, 30.32, 30.57, 30.67, 31.00, 32.69
(AlCH2, CHMe2, CHMeCH2), 30.81, 31.59, 41.73, 41.92 (CMe3),
107.55 (γ-C), 114.40, 122.62, 022.88, 123.08, 123.31, 123.79,
124.80, 127.20, 128.30, 128.37, 129.07, 132.71, 136.29, 139.71,
141.07, 142.94, 144.04, 144.32, 145.46, 146.77, 147.51, 147.82,
148.28, 148.71, 150.80 (Ar C), 172.59 (CN). UV-vis (n-hexane;
λ
max (nm) (ꢀ (mol-1 L cm-1))): 302 (580), 390 (1177). IR (cm-1):
Acknowledgment. This work was supported by the National
Natural Science Foundation of China (No. 20421202) and the
Program for New Century Excellent Talents in University
(NCET).
3238 (N-H), 3058, 2963, 2868, 1923, 1698, 1575, 1542, 1461,
1435, 1403, 1386, 1362, 1321, 1253, 1203, 1101, 1030, 931, 867,
804, 758, 730, 692, 663, 556, 506, 447.
Reaction of 3 with H2O. To a solution of 3 (0.21 g, 0.40 mmol)
in toluene (20 mL) cooled to -78 °C was slowly added a solution
of H2O (0.007 g, 0.40 mmol) in toluene (10 mL). The mixture was
slowly warmed to room temperature, during which time the color
changed from red to bright yellow. After all volatiles were removed
under vacuum, a yellow solid remained. The residue was extracted
Supporting Information Available: CIF files giving X-ray
crystallographic data files for compounds 1 and 3-5. This material
is available free of charge via the Internet at http://pubs.acs.org.
OM061107J