Trisguanidinate lanthanide complexes: Syntheses, structures, and catalytic activity for mild amidation of aldehydes with amines

Article abstract of DOI:10.1021/om900120v

A series of new trisguanidinate lanthanide complexes including the first THF-solvated trisguanidinate lanthanum complexes were synthesized and fully characterized. The complexes were found to be efficient catalysts for amidation of aldehydes with amines u

Full text of DOI:10.1021/om900120v

3856 Organometallics 2009, 28, 3856–3862
DOI: 10.1021/om900120v
Trisguanidinate Lanthanide Complexes: Syntheses, Structures,
and Catalytic Activity for Mild Amidation of Aldehydes with Amines
Cunwei Qian,† Xingmin Zhang,† Junmei Li,† Fan Xu,† Yong Zhang,† and Qi Shen*,†,‡
†Key Laboratory of Organic Synthesis of Jiangsu Province, Department of Chemistry and Chemical
Engineering, Dushu Lake Campus, Suzhou University, Suzhou 215123, People’s Republic of China, and
‡State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, Shanghai 200032, People’s Republic of China
Received February 16, 2009
A series of new trisguanidinate lanthanide complexes including the first THF-solvated trisguani-
dinate lanthanum complexes were synthesized and fully characterized. The complexes were found to
be efficient catalysts for amidation of aldehydes with amines under mild conditions with a wide scope
of substrates including pyrrolidine, piperidine, and morpholine, and one of the intermediates for
this process, lanthanum amido complex {[(iPrN)CNHiPr(NC6H4p-Cl)]2La(NHC6H5)}2 C7H8, was
3
isolated.
Introduction
ability.1-4 Various lanthanide guanidinate derivatives
have been synthesized including hydride,5 amide,6 alky-
lide,7 and alkoxide8 and found to be efficient catalysts in
homogeneous catalyses such as polymerization of nonpo-
lar and polar monomers, e.g., ethylene, propylene,5b styr-
ene,7c,8 methyl methacrylate,6a and lactones (lactide and ε-
caprolactone),6a,6c,8 as well as hydrosilylation of alkenes.7f
As is well known, the guanidinate anions in these transfor-
mations act as ancillary ligands to stabilize the Ln-active
group bond, and themselves are “inert”. Recently, guani-
dinate anions have proven to serve not only as an
inert ligand but also an active group in some cases. For
example, trisguanidinate lanthanide complexes can be used
as highly active catalysts for homo-polymerization of ε-
caprolactone and trimethylene carbonate, as well as their
copolymerization.9 Very recently, the insertion of phenyl
isocyanate into the lanthanide-guanidinate ligand bond
has also been reported using the guanidinate complexes
[(C5H5)2Ln( μ-η1:η2-NdC(NMe2)2)]2 (Ln = Gd, Er) to
yield the corresponding insertion products [(C5H5)2Ln
( μ-η1:η2-OCNdC(NMe2)2)NPh]2 (Ln = Gd, Er).10 To
assess further the reactivity of the lanthanide-guanidinate
In recent years guanidinate ligands, an alternative to
cyclopentadienyl anions, have attracted increasing atten-
tion in organolanthanide chemistry, as they have the
advantages of tunable steric and electronic effects by
variation of the substituents on the nitrogen atoms and
varied binding modes due to the third nitrogen chelating
*Corresponding author. E-mail: qshen@suda.edu.cn.
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r
pubs.acs.org/Organometallics
Published on Web 05/20/2009
2009 American Chemical Society

Article
Organometallics, Vol. 28, No. 13, 2009 3857
Table 1. Details of the Crystallographic Data of 1, 2, 6, and 11
1
2
6
11
empirical
formula
fw
C
N9O
43H65Cl3La
C46H75LaN9
N9O
C39H96N9Nd
Si6
1004.03
213(2)
0.71075
monoclinic
P21/n
14.607(2)
23.159(3)
17.262(3)
90.00
97.433(2)
90.00
5790.5(14)
4
1.152
C71H96Cl4La2
N14
1565.24
223(2)
0.71075
triclinic
P1
10.6450(19)
13.7826(19)
15.599(3)
66.180(6)
89.372(7)
69.433(6)
1937.2(5)
1
969.30
223(2)
0.71075
triclinic
P1
10.463(2)
13.118(2)
17.912(3)
80.505(4)
89.947(4)
86.812(5)
2421.0(8)
2
909.06
223(2)
0.71075
monoclinic
C2/c
22.072(6)
10.114(3)
44.341(12)
90
94.846(3)
90
9863(5)
8
1.224
temp (K)
˚
λ (A)
cryst syst
space group
˚
a (A)
˚
b (A)
˚
c (A)
R (deg)
β (deg)
γ (deg)
3
˚
V (A )
Z
Dcalc (g cm-3
)
1.328
1.089
1002
1.342
1.273
802
μ (mm-1
F(000)
)
0.907
3832
1.053
2148
θ range (deg)
no. of rflns
no. of unique rflns
Rint
variables
R[I > 2σ(I)]
wR2
3.00 to 25.5
17 336
8828
0.0384
531
3.14 to 25.5
15 178
7586
0.0583
507
3.00 to 27.5
41 121
10 714
0.0620
527
3.00 to 27.5
13 983
7060
0.0401
380
0.0409
0.0841
0.0668
0.1615
0.0620
0.0594
0.0535
0.1130
˚
Table 2. Selected Bond Distances (A) and Angles (deg) for 1 and 6
due to the relative stability of the guanidinates complexes
formed via rearrangement. The same situation has also been
found in the literature.11
1
6
1
6
Bond Distances
Ln1-N1
Ln1-N2
Ln1-N4
Ln1-N5
Ln1-N7
2.549(3) 2.507(4) Ln1-N8
2.558(3) 2.494(4) N1-C1
2.532(3) 2.496(4) N2-C1
2.525(3) 2.528(4) N3-C1
2.547(3) 2.494(4) La1-O1
2.592(3) 2.463(4)
1.348(4) 1.335(6)
1.330(4) 1.324(6)
1.377(4) 1.450(7)
2.585(3)
Bond Angles
N1-Ln1-N2 52.67(9) 53.47(13) N7-Ln1-N8 51.66(9) 53.68(14)
N4-Ln1-N5 53.37(10) 53.54(14)
bond, we synthesized a series of guanidinate lanthanide
complexes with various central metals and guanidinate
anions and examined their catalytic activity for amidation
of aldehydes with amines. It was found that trisguanidinate
lanthanide complexes are efficient catalysts for amidation
reaction of aldehydes with amines with a wide scope of
amines including secondary cyclic amines. One of the inter-
mediates in the present transformation, bisguanidinate lan-
thanum amido complex {[(iPrN) CNHiPr(NC6H4p-Cl)]2La-
(NHC6H5)}2 C7H8, was also isolated and fully characterized.
Here we would like to report the results.
3
The same reaction with various lithium guanidinates
yielded the trisguanidinate lanthanum complexes 3, 4, and
5 in good yields (eq 2).
The reaction of anhydrous NdCl3 with Na[(TMS)2NC-
(NiPr2)2] in a 1:3 molar ratio was then conducted in THF.
Upon crystallization blue crystals were isolated and char-
acterized to be complex 6 (eq 3).
Results and Discussion
Synthesis and Characterization of Trisguanidinate Lantha-
nide Complexes. First, we tried to prepare a series of trisgua-
nidinate lanthanum complexes, as this class of lanthanum
complex has not been reported until now. Treatment of
anhydrous LaCl3 with 3 equiv of lithium salts Li[(iPrN)-
CNHR(NiPr)] (R = -C6H4p-Cl and -C6H5), which were
freshly prepared in situ by the reaction of Li[NHAr] with N,
N0-diisopropylcarbodiimide in THF, after workup, afforded
the corresponding asymmetric guanidinate lanthanum com-
plexes of 1 and 2 via a 1,3-H shift as shown in eq 1. The
formation of asymmetric guanidinate complexes is expected
All complexes were characterized by elemental analysis and
1
IR spectroscopy, and H NMR for La complexes. The IR
spectra of these complexes exhibit the strong absorptions in
(11) Zhang, J.; Cai, R.-F.; Weng, L.-H.; Zhou, X.-G. Organometal-
lics 2004, 23, 3303.

3858 Organometallics, Vol. 28, No. 13, 2009
Qian et al.
the range 1600-1640 cm-1, which are consistent with a partial
CdN double-bond character, indicting the π-electrons being
delocalized within the N-C-N linkage.
Complexes 1-6 are sensitive to air and moisture. They
have good solubility in THF and even in toluene.
The structures of complexes 1, 2, and 6 were further
determined by single-crystal X-ray analysis. The details for
crystal data collections are given in Table 1, and selected
bond lengths and angles for complexes 1 and 6 are listed in
Table 2. Complex 2 has the same structure motif as that of
complex 1 (see Supporting Information), but no detailed
bond angles and lengths could be obtained, as the data were
poor. Thus, only the crystal structures of complexes 1 and 6
are shown in Figures 1 and 2, respectively. As shown in
Figure 1, complex 1 is a THF-solvated monomer, in which
the central metal La ion is ligated by six nitrogen atoms of
three chelating guanidinate ligands and one oxygen atom
from a coordinated THF molecule to form a capped
octahedron. To our best knowledge, this is the first exam-
ple for a THF-solvated trisguanidinate lanthanide com-
plex. The allowance of a coordinated THF molecule in the
coordination sphere around the central metal in this com-
plex may be attributed to the large ionic radius of La and
less bulky guanidate ligand, which provides the space for
the coordination of a THF molecule. Complex 6 is an
unsolvated monomer (Figure 2). The central metal Nd
ion is coordinated by six nitrogen atoms from three ligands
to form an octahedron. The solid state structure of complex
6 is analogous to those for the known homoleptic trisgua-
nidinate lanthanide complexes.9 The four-membered
LnNCN rings in complexes 1 and 6 are essentially planar.
The average bond angle of N-Ln-N, 52.60(9)°, in com-
plex 1 is comparable with 53.56(14)° in complex 6. These
values are also compared to the reported 54.32° in [(iPr2N)-
C(NiPr)2]3Nd.9a The average Ln-N bond lengths, 2.550(3)
Figure 1. Molecular structure of complex 1. Hydrogen atoms
are omitted for clarity, and thermal ellipsoids are drawn at the
30% probability level.
˚
˚
A for complex 1 and 2.497(4) A for complex 6, are
comparable when the difference in ion radius between La
and Nd metals is considered.12 The values are also in the
range for the published analogues.9 The La-O bond length
˚
is 2.585(3) A, which is typical.
Catalytic Activity of Trisguanidinate Lanthanide Com-
plexes for Amidation of Aldehydes with Amines. The synthesis
of aromatic and aliphatic acylamides is of significant im-
portance in organic synthesis, as acylamides are an essential
motif in polymers, natural products, and pharmaceuticals.13
A direct amidation of aldehydes with amines is the most
desired approach to acylamides due to economical and
available starting materials. Very recently, pioneering work
by Seo and Marks showed that homoleptic lanthanide
amides Ln[N(SiMe3)2]3 are efficient catalysts for amidation
of aldehydes with amines under mild conditions without the
use of a peroxide.14 To explore the reactivity of trisguanidi-
nate lanthanide complexes, amidation of aldehydes with
amines was tried using these guanidinate complexes.
Figure 2. Molecular structure of complex 6. Hydrogen atoms
are omitted for clarity, and thermal ellipsoids are drawn at the
30% probability level.
To address the influence of lanthanide metals and guani-
dinate ligands on the activity of trisguanidinate lanthanide
complexes, the following known complexes (Scheme 1) were
also synthesized according to the literature.6a9a,9b,
Scheme 1
With the complexes in hand, the catalytic activity of
complexes 1-10 for the reaction of benzaldehyde 1a with
(12) Shannon, R. D. Acta Crystallogr. 1976, A32, 751.
(13) Humphrey, J. M.; Chanberlin, A. R. Chem. Rev. 1997, 97, 2243.
(14) Seo, S.; Marks, T. J. Org. Lett. 2008, 10, 317.

Article
Organometallics, Vol. 28, No. 13, 2009 3859
aniline 2a was examined at 25 °C. As shown in Table 3,
complexes 1-9 can serve as the catalysts for this transforma-
tion, yielding the desired product 3aa in moderate to excellent
yields after 3 h. However, bisguanidinate neodymium chloride
10 is not so activel; the same reaction with 10 afforded 3aa in
only 10% yield. The much higher yield obtained with the
corresponding homoleptic complex 6 compared to that ob-
tained with 10 (Table 3, entries 11 and 12) may be attributed to
the third Nd-guanidate bond being activated by the other two
guanidinate ligands around the Nd metal. The substituents on
the guanidinate anions exert an influence on the activity. For
the same La complexes the active sequence for guanidinate
anions is NiPr2 < NHC6H5 < N(C6H5)2 < NHC6H4p-Clπ
(Table 3, entries 6-10) and Cy < iPr (Table 3, entries 6 and 8).
The activity of the central metals follows the trend Yb < Sm <
Nd < La (Table 3, entries 3-6). The same activity trend is
also found for the Tishchenko reaction with homoleptic
lanthanide amides.15
Table 3. Amidation of a Benzaldehyde 1a with an Aniline 2a
Catalyzed by Complexes 1-10a
cat. (amt
(mol %))
cat. (amt
(mol %))
entry
yield (%)b
entry
yield (%)b
1
2
3
4
5
6
7
8 (1%)
8 (2%)
8 (5%)
7 (5%)
9 (5%)
3 (5%)
5 (5%)
28
42
70
60
76
81
72
8
9
10
11
12
13
4 (5%)
2 (5%)
1 (5%)
6 (5%)
10 (5%)
11 (2.5%)
85
77
89
50
10
90
With optimized reaction conditions (Table 3, entry 10), we
then screened the scope of amidation with selected aldehydes
and amines. The results are listed in Table 4. All the reactions
proceeded smoothly to afford the corresponding acylamides
in good to excellent yields. The aromatic aldehydes with an
electron-withdrawing group at the p-position on the phenyl
a Starting amine, aldehyde, and catalyst concentrations are 0.02
mmol/mL in each experiment; amine/aldehyde = 1:3. b Isolated yields
based on aniline.
Table 4. Catalytic Amidation of Various Aldehydes with Aminesa
a Starting amine, aldehyde, and catalyst concentrations are identical in each experiment; amine/aldehyde = 1:3. bIsolated yields based on amine.

3860 Organometallics, Vol. 28, No. 13, 2009
Qian et al.
Scheme 2. Proposed Catalytic Cycle for Amidation of Aldehydes with Amines Catalyzed by Trisguanidine Lanthanide
ring give higher yields relative to the aldehydes with an
electron-donating group. The reaction with a primary aro-
matic amine (aniline) proceeded smoothly to give the acyla-
mide in good yields (Table 4, entries 1-4). It is worth noting
that the amidation of aldehydes with secondary cyclic amines
such as pyrrolidine, piperidine, and morpholine proceeded
well with the present catalyst to afford the corresponding
acylamides in good to excellent yields (Table 4, entries
8-16). The reactions of aldehydes with a pyrrolidine give
the products in 62-81% yields. The value (62%) for the
reaction of 1a with pyrrolidine is much higher than that
obtained by homoleptic lanthanide amides.14
According to the catalytic cycle proposed by Seo and
Marks,13 the two byproducts, alcohol and ester, should be
produced in this process. We have detected the two bypro-
ducts by 1H NMR (Supporting Information). The Tishchenko
reaction of benzaldehyde was further examined by use of
complex 1 as the catalyst. The reaction at room temperature
using 1.7 mol % of 1 afforded the ester in 73% yield after 3 h,
indicating triguanidinate lanthanide complexes can also serve
as catalysts for the Tishchenko reaction. Therefore, it is
reasonable to propose a mechanism similar to that suggested
by Seo and Marks for the amidation of aldehydes with amines
by trisguanidinate lanthanide complexes. In our case the
triguanidinate lanthanide complex reacts first with an amine
to afford the guanidinate amido complex 11, which then reacts
with an aldehyde to yield the active species A. A reacts further
with a second aldehyde to produce an acylamide and to release
B (Scheme 2).
To further confirm the suggestion, the isolation of amido
complex 11 was tried. Treatment of complex 1 with aniline in
a 1:20 molar ratio, which is the same molar ratio for the
catalytic reaction, in THF, after workup, afforded white
crystals suitable for X-ray analysis in 40% yield. The crystals
were further characterized to be the expected amido complex
Figure 3. Molecular structure of complex 11. Hydrogen atoms
are omitted for clarity, and thermal ellipsoids are drawn at the
30% probability level.
11. The molecular structure of 11 is shown in Figure 3. The
details for crystal data collection are shown in Table 1, and
selected bond lengths and angles for complex 11 are listed in
Table 5. Complex 11 is a central symmetric dimer linked by
two symmetric nitrogen bridges. Each La metal ion is ligated
by four nitrogen atoms from two guanidinate ligands and
two bridging-nitrogen atoms in an octahedral arrangement.
The two four-membered LaNCN rings are essentially pla-
nar. The average La-N (guanidinate ligand) bond length is
(15) (a) Berberich, H.; Roesky, P. W. Angew. Chem., Int. Ed. 1998, 37,
1569. (b) Zuyls, A.; Roesky, P. W.; Deacon, G. B.; Konstas, K.; Junk, P.
C. Eur. J. Org. Chem. 2008, 693.
˚
2.527(4) A, which is comparable with that in 1 when the
difference in ionic radius for the La ions with different

Article
Organometallics, Vol. 28, No. 13, 2009 3861
Synthesis of [iPrNHCNiPr(NC6H4p-Cl)]3La THF (1). A
˚
Table 5. Selected Bond Distances (A) and Angles (deg) for 11
3
Schlenk flask was charged with p-ClC6H4NH2 (1.905 g,
15.0 mmol), THF (30 mL), and a stir bar. The solution was
cooled to 0 °C, and n-BuLi (8.6 mL, 15.0 mmol, 1.75 M in
hexane) was added. The solution was then slowly warmed to
room temperature and stirred for 1 h. To this solution was added
N,N0-diisopropylcarbodiimide (2.4 mL, 15.3 mmol) at 0 °C. The
resulting solution was slowly warmed to room temperature,
stirred for 1 h, and then added slowly to a pale gray slurry of
LaCl3 (1.22 g, 5.0 mmol) in 20 mL of THF. The color of the
solution immediately changed to yellow. The resulting solution
was then stirred for another 24 h and evaporated to dryness in
vacuo. The residue was extracted with Et2O, and LiCl was
removed by centrifugation. The extracts were concentrated
and cooled to 0 °C for crystallization, to afford colorless
crystals. Yield: 2.47 g (51%) Mp: 185-186 °C. 1H NMR
(400 MHz, C6D6): δ 7.23-7.21 (d, 6H, m-H-Ph), 6.93-6.91
(m, 6H, o-H-Ph), 3.66-3.58 (m, 7H, R-H-THF and N-H) 3.35-
3.33 (m, 6H, H-C(N)Me2), 1.43-1.46 (m, 4H, β-H, THF), 0.90-
0.88 (d, 36H, CH3) ppm. Anal. Calcd for C43H65Cl3LaN9O
(969.30): C, 53.28; H, 6.76; N, 13.01; La, 14.33. Found: C, 53.05;
H,6.08; N, 13.51; La, 15.00. IR (KBr pellet): 3316 (s), 3076 (s),
2973 (s), 2925 (s), 2870 (s), 1640 (s), 1580 (s), 1520 (s), 1416 (s),
Bond Distance
La1-N1
La1-N4
La1-N7
N1-C1
N3-C1
2.553(4)
2.580(4)
2.538(4)
1.353(6)
1.376(6)
La1-N2
La1-N5
N7-La1#1
N2-C1
2.478(4)
2.488(4)
2.587(4)
1.311(6)
3.035(7)
La1-C27
Bond Angles
N1-La1-N2
C14-N5-La1
53.05(13)
99.0(3)
N4-La1-N5
La1 - N7 - C27
52.61(13)
94.5(3)
coordination number is considered.12 The length of La-μ2-N
˚
˚
bond is 2.538(4) A, which is longer than 2.458(9) A in Cp2La-
(NPh2)2Li.16 This is reasonable, because a bridging Ln-N
bond length is normally longer than that of a terminal Ln-N
bond. It was noticed that the distance of La to Cipso (an
aromatic carbon atom on the aniline group), La1-C27, is
˚
3.035(7) A. Such a short distance and the small angle
La-N7-C27 (94.5°) indicate the presence of a weak bond-
ing of the La-C (aromatic carbon) bond. The bond distance
is in the same range as those found in the other known
complexes with a lanthanide metal-π-arene interaction.
1365 (s), 1327 (s), 1162 (m), 1123 (m), 1034 (m), 939 (m) cm-1
Synthesis of [iPrNHCNiPr(NC6H5)]3La THF 1/2C6H14 (2).
Following the procedure similar to that for the synthesis of 1,
.
˚
The value can also be compared to 2.75 A of Y-Cipso
3
3
in {[6,60-Me2-(C6H3)2](2,20-NSiMet3Bu)2}YCl(THF)2
and
17a
complex Li[iPrNHCNiPr(NC6H5)] (15.0 mmol), which was
2.841 A of Nd-Cipso in [ μ2-p-(Me2SiN)2C6H4]Nd( μ2-Cl)-
˚
i
(THF)4 2PhMe17b when the differences in ionic radius be-
formed in situ by the reaction of LiNHC6H5 with PrN=
3
CdNiPr, reacted with LaCl3 (1.22 g, 5.0 mmol) in THF
(60 mL) to yield colorless crystals (2) upon crystallization from
a mixture of ether and n-hexane. Yield: 2.45 g (54%). Mp: 138-
139 °C. 1H NMR (400 MHz, C6D6): δ 7.33-7.29 (t, 6H, m-H-
C6H5-), 7.24-7.21 (m, 6H, o-H, -C6H5), 6.88-6.84 (t, 3H,
p-H-C6H5-), 3.57-3.37 (brm, 7H, R-H-THF and H-N), 3.35-
3.33 (m, 6H, H-C(N)Me2), 1.28-0.88 (d, 47H, CH3, -CH2-,
overlap) ppm. Anal. Calcd for C46H75LaN9O (909.06): C, 60.71;
N, 13.85; H, 8.42; La,15.26. Found: C, 59.98; N, 14.99; H,
7.94; La, 15.84. IR (KBr pellet): 3298 (s), 3072 (s), 2967 (s),
2930 (s), 2868 (s), 1646(s), 1619 (s), 1591 (s), 1511 (s), 1441 (s),
1363 (s), 1326 (s), 1164 (m), 1123 (m), 1067 (m), 952 (m), 865 (m),
tween La and Y, and La and Nd were considered, respectively.
The amido complex 11 can also serve as the precatalyst for
amidation of aldehydes with amines. The reaction of 1a with 2a
using 2.5 mol % 11 afforded the acylamide 3aa in 90% yield,
which is almost the same as that obtained by complex 1
(Table 2, entry 10). The result demonstrates that amido
complex 11 formed in situ is one of the intermediates in the
amidation catalyzed by a trisguanidinate lanthanide complex.
Conclusion
694 (m) cm-1
.
Synthesis of [(CyN)2CN(C6H5)2]3La 2C7H8 (3). Following
A series of asymmetric and symmetric trisguanidinate
lanthanide complexes were synthesized, and the first THF-
solvated trisguanidinate lanthanum complex was structu-
rally characterized. All these trisguanidinate complexes serve
as efficient catalysts for amidation of aldehydes with amines
including secondary cyclic amines. The isolation of a bisgua-
nidinate lanthanum amido complex demonstrates that the
reaction of a trisguanidinate lanthanum complex with an
amine is the first step in the present process. Further study on
the reactivity of the Ln-guanidinate ligand bond is ongoing
in our laboratory.
3
the procedure for the synthesis of 2, the reaction of
Li[(CyN)2C(N(C6H5)2)] (15.0 mmol) in THF (20 mL) with
LaCl3 (1.22 g, 5.0 mmol) in THF (60 mL) afforded 3 as colorless
crystals after crystallization in toluene. Yield: 4.41 g (61%).
Mp: 156-158 °C. 1H NMR (400 MHz, C6D6): δ 7.28-6.86 (m,
40H, Ph), 3.63-3.33 (m, 6H, unique H-Cy), 2.11 (s, 6H,
CH3), 1.69-0.84 (m, 60H, C6H10) ppm. Anal. Calcd for
C89H112N9La(1445.81): C, 73.88; N, 8.71; H, 7.80; La, 9.60.
Found: C, 73.25; H, 7.66; La, 9.55; N, 8.92. IR (KBr pellet):
3440 (s), 3240 (m), 3230 (m), 2944 (m), 1628 (m), 1400 (w),
1267 (m), 1017 (s), 1072 (s), 908 (w), 870 (w), 800 (s) cm-1
.
Experimental Section
Synthesis of [(iPrN)2CN(C6H5)2]3La (4). Following the pro-
cedure for the synthesis of 2, the reaction of Li[(iPrN)2C(N-
(C6H5)2)] (15.0 mmol) in THF (20 mL) with LaCl3 (1.22 g,
5.0 mmol) in THF (60 mL) afforded 4 as colorless crystals upon
crystallization from toluene. Yield: 2.60 g (51%). Mp: 142-
143 °C. 1H NMR (400 MHz, C6D6): δ 7.39-6.89 (m, 30H,
Ph-H), 3. 97-3.91 (m, 6H, CHMe2), 1.44-1.18 (m, 36H, CH3)
ppm. Anal. Calcd for C57H72N9La (1021.5): C, 66.98; H, 7.10;
La, 13.59; N, 12.33. Found: C, 66.02; H, 7.24; La, 14.05; N,
12.04. IR (KBr pellet): 3056 (m), 2983 (m), 1640 (s), 1577 (m),
1498 (s), 1452 (m), 1384 (m), 1311 (m), 1243 (m), 1177 (m),
All syntheses and manipulations of air- and moisture-sensi-
tive materials were performed under a dry argon atmosphere
using standard Schlenk techniques or in a glovebox. All solvents
were refluxed and distilled over sodium benzophenone ketyl
prior to use. C6D6 was distilled under argon from Na/K alloy.
N,N0-Diisopropylcarbodiimide was used without further puri-
fication. All aldehydes and amines were predried, recrystallized,
or distilled before use. Complexes 7-10 was synthesized accord-
ing to the literature.6a,9 Melting points were determined in sealed
1
1056 (w), 753 (m) cm-1
.
Ar-filled capillary tube and are uncorrected. H NMR spectra
were recorded on a Unity Inova-400 spectrometer. Chemical
shifts (δ) are reported in ppm.
Synthesis of [(CyN)2CNiPr2]3La (5). Following the procedure
for the synthesis of 2, the reaction of Li[(CyN)2CNiPr2] (15.0
mmol) in THF (20 mL) with LaCl3 (1.22 g, 5.0 mmol) in THF
(60 mL) afforded 5 as colorless crystals. Yield: 2.96 g (56%).
Mp: 218-219 °C. 1H NMR (400 MHz, C6D6): δ 3.60-3.44
(16) Guan, J.-W.; Jin, S.-C.; Lin, Y.-H.; Shen, Q. Organometallics
1992, 11, 2483.

3862 Organometallics, Vol. 28, No. 13, 2009
Qian et al.
(m, 12H, CH, overlap), 2.13-1.28 (m, 60H, C6H10), 1.16-0.93
(m, 36H, CH3) ppm. Anal. Calcd for C57H108N9La (1058.43): C,
64.68; N, 11.91; H, 10.28; La, 13.12. Found: C, 64.47; H, 10.01;
N, 10.62; La, 13.01. IR (KBr pellet): 3185 (m), 2928 (s), 2851 (s),
1631 (s), 1550 (s), 1450 (s),1338 (m), 1246 (m), 1149 (m),
and a stir bar. The solution was stirred for 0.5 h; then benzalde-
hyde was added (0.30 mL, 3.00 mmol). The resulting mixture
was stirred at 25 °C for 3 h and filtered through a small plug of
silica gel to remove the catalyst. The crude product was purified
by column chromatography (ethyl acetate/petroleum ether,
1:8), yielding acylamide, 175.3 mg (89%).
1099 (m), 885 (m) cm-1
.
Synthesis of [(iPrN)2CN(TMS)2]3Nd (6). As described for 2, a
solution of Na[(iPrN)2CN(TMS)2] (15.0 mmol) was added to a
suspension of NdCl3 (1.30 g, 5.0 mmol) in 60 mL of THF. Blue-
purple crystals (6) were isolated from dimethoxyethane. Yield:
3.3 g (66%). Mp: 231-232 °C. Anal. Calcd for C39H96N9NdSi6
(1004.03): C, 46.66; N, 12.56; H, 9.64; Nd, 14.37. Found: C,
45.74; H, 8.94; N, 11.99; Nd, 14.34. IR (KBr pellet): 2969 (s),
2870 (s), 1622 (s), 1455 (s), 1387 (s), 1327 (s), 1162 (m), 1123 (m),
Procedure for the Tishchenko Reaction of Benzaldehyde. A
30 mL Schlenk flask was charged with a solution of complex 1
(0.05 mmol), THF (2.2 mL), and benzaldehyde (0.30 mL,
3.00 mmol) and a stir bar. The resulting mixture was stirred at
25 °C for 3 h and filtered through a small plug of silica gel to
remove the catalyst. The crude product was purified by column
chromatography (ethyl acetate/petroleum ether, 1:20), yielding
benzyl benzoate, 232 mg (73%).
1034 (m), 939 (m), 860 (m), 698 (m), 575 (m) cm-1
.
X-ray Structural Determination of 1, 2, 3, and 11. A suitable
crystal was mounted in a thin-walled glass capillary for X-ray
structural analysis. Diffraction data were collected on a Rigaku
Mercury CCD equipped with graphite-monochromated Mo KR
Synthesis of {[iPrNHCNiPr(NC6H4p-Cl)]2La(C6H5NH)}2
3
C7H8 (11). A Schlenk flask was charged with [iPrNHCNiPr-
(NC6H4p-Cl)]3La THF (2.9 g, 3.0 mmol), C6H4NH2 (6 mL,
3
˚
60 mmol), THF (30 mL), and a stir bar. The solution was stirred
for 3 h at room temperature and evaporated to dryness in vacuo.
Toluene (20 mL) was added to the residue and then heated until
the solution became clear. The solution was cooled to room
temperature for crystallization, and colorless crystals (11) were
isolated. Yield: 0.94 g (40%). Mp: 206-207 °C. 1H NMR
(400 MHz, C6D6): δ 7.27-6.36 (m, 31H, H-Ph, overlap),
4.11-4.06 (s, 2H, HN-Ph); 3.46-3.19 (br m, 12H, CHMe2
and H-N); 2.13 (S, 3H, CH3-Ph); 1.13-0.86 (m, 48H,
CH3) ppm. Anal. Calcd for C71H96Cl4La2N14 (1565.24): C,
54.48; N, 12.53; H, 6.18; La, 17.75. Found: C, 54.98; N, 12.40;
H, 6.00; La, 18.25. IR (KBr pellet): 3489(s), 3072 (s), 2967 (s),
2974 (s), 1636 (s), 1609 (s), 1585 (s), 1497 (s), 1462 (s), 1377 (s),
1327 (s), 1164 (m), 1125 (m), 1091 (m), 859 (m), 807 (m), 698 (m),
(λ = 0.71070 A) radiation. The structures were solved by direct
methods and expanded by Fourier techniques. Atomic coordi-
nates and thermal parameters were refined by full-matrix least-
squares procedures based on F2. All non-hydrogen atoms were
refined with anisotropic displacement coefficients. Hydrogen
atoms were treated as idealized contributions. The structures
were solved and refined using the SHELXL-97 programs.
Acknowledgment. Financial support by the National
Natural Science Foundation of China (grant no.
20632040) and the Department of National Education
Doctoral Foundation is gratefully acknowledged.
597 (m) cm-1
.
Supporting Information Available: Experimental details and
characterization data for complexes and all acylamides.
This material is available free of charge via the Internet at
http://pubs.acs.org.
Typical Procedure for the Amidation Reaction. A 30 mL
Schlenk flask was charged with a solution of complex 1
(0.05 mmol), aniline (0.09 mL, 1.00 mmol), and THF (2.1 mL)