Lanthanide amido complexes incorporating amino-coordinate-lithium bridged bis(indolyl) ligands: Synthesis, characterization, and catalysis for hydrophosphonylation of aldehydes and aldimines

Article abstract of DOI:10.1021/ic300137r

Two series of new lanthanide amido complexes supported by bis(indolyl) ligands with amino-coordinate-lithium as a bridge were synthesized and characterized. The interactions of [(Me₃Si)₂N] ₃Ln^III(μ-Cl)Li(THF)

Full text of DOI:10.1021/ic300137r

Article
pubs.acs.org/IC
Lanthanide Amido Complexes Incorporating Amino-Coordinate-
Lithium Bridged Bis(indolyl) Ligands: Synthesis, Characterization,
and Catalysis for Hydrophosphonylation of Aldehydes and Aldimines
Xiancui Zhu,† Shaowu Wang,*,†,‡ Shuangliu Zhou,† Yun Wei,† Lijun Zhang,† Fenhua Wang,†
Zhijun Feng,† Liping Guo, and Xiaolong Mu†
†Laboratory of Functionalized Molecular Solids, Ministry of Education, Anhui Laboratory of Molecule-Based Materials, Institute of
Organic Chemistry, School of Chemistry and Materials Science, Anhui Normal University, Wuhu, Anhui 241000, People’s Republic
of China
‡State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences,
Shanghai 200032, People’s Republic of China
S
* Supporting Information
ABSTRACT: Two series of new lanthanide amido complexes
supported by bis(indolyl) ligands with amino-coordinate-lithium as a
bridge were synthesized and characterized. The interactions of
[(Me3Si)2N]3LnIII(μ-Cl)Li(THF)3 with 2 equiv of 3-(CyNHCH2)-
C8H5NH in toluene produced the amino-coordinate-lithium bridged
bis(indolyl) lanthanide amides [μ-{[η1:η1:η1:η1-3-(CyNHCH2)-
Ind]2Li}Ln[N(SiMe3)2]2] (Cy = cyclohexyl, Ind = Indolyl, Ln = Sm
(1), Eu (2), Dy (3), Yb (4)) in good yields. Treatment of [μ-
{[η1:η1:η1:η1-3-(CyNHCH2)Ind]2Li}Ln[N(SiMe3)2]2] with THF gave
new lanthanide amido complexes [μ-{[η1:η1-3-(CyNHCH2)Ind]2Li-
(THF)}Ln[N(SiMe3)2]2] (Ln = Eu (5), Dy (6), Yb (7)), which can be
transferred to amido complexes 2, 3, and 4 by reflux the corresponding
complexes in toluene. Thus, two series of rare-earth-metal amides
could be reciprocally transformed easily by merely changing the solvent in the reactions. All new complexes 1−7 are fully
characterized including X-ray structural determination. The catalytic activities of these new lanthanide amido complexes for
hydrophosphonylation of both aromatic and aliphatic aldehydes and various substituted aldimines were explored. The results
indicated that these complexes displayed a high catalytic activity for the C−P bond formation with employment of low catalyst
loadings (0.1 mol % for aldehydes and 1 mol % for aldimines) under mild conditions. Thus, it provides a convenient way to
prepare both α-hydroxy and α-amino phosphonates.
transition metals such as palladium,10 molybdenum,11 man-
INTRODUCTION
Structurally well-defined cyclopentadienyl-free rare-earth-metal
■
ganese,12 platinum,13 copper,14 and lanthanide,15 etc., has been
documented; (2) catalytic activities for the olefins polymer-
ization in the presence of transition-metal complexes bearing
indolide-imine ligands have been reported in the references.
For example, nickel16 and titanium dichloride17 complexes
bearing unsymmetrical bidentate indolide-imine ligands are
reported to display high activities toward ethylene polymer-
ization, and rare-earth-metal alkyl complexes18 incorporating
indolide-imine ligands in combination with aluminum alkyls
and borate generated efficient homogeneous catalysts for the
polymerization of isoprene. However, the syntheses and
catalytic activities for transformation of small molecules in the
presence of lanthanide amido complexes bearing amino-
functionalized indolyl ligands remain to be less investigated.
complexes bearing nitrogen-based supporting ligands have been
a continuous interest, due to easy tailorability of substituents on
the nitrogen atom in consideration of steric demand and
electronic properties in the development of activity controllable
new metal catalysts.1 In view of this point, many nitrogen-based
monodentate or polydentate ligands, such as various modified
amido ligands,2 β-diketiminates,3 amidinates or guanidinates,4
cyclic pyrrolyl,5 aromatic indolyl,6 and carbazolyl7 ligands, as
alternatives to the cyclopentadienyl, have been developed.
Indole or its derivatives are widely distributed in biological
systems as an important constituent of biomolecules and
natural products.8 Indole is an electron-rich aromatic
compound with characteristic properties due to the presence
of an electron-rich pyrrole moiety,9 which makes the indolyl
ligands having plentiful applications in transition-metal
chemistry: (1) Research focused on the syntheses and the
bonding modes of indolyl or substituted indolyl ligands with
Received: January 18, 2012
Published: June 19, 2012
© 2012 American Chemical Society
7134
dx.doi.org/10.1021/ic300137r | Inorg. Chem. 2012, 51, 7134−7143

Inorganic Chemistry
Article
The α-hydroxy or α-amino phosphonic acids and their
derivatives have been recognized as a class of important
bioactive compounds, which have been widely used as
pesticides, antibiotics, anticancer drugs, antiviral agents, enzyme
inhibitors, and HIV protease.19 The addition of dialkyl
phosphites to carbonyl compounds (Pudovik or Abramov
reaction) has been regarded as the most straightforward and
atom-economical pathway for the C−P bond formation in
syntheses of α-hydroxyphosphonates or α-hydroxyphosphonic
acids, and this reaction should be promoted by a base, however,
side reaction, byproduct and harsh reaction conditions cannot
be avoided. In the process of developing a more-convenient
way to synthesize α-hydroxyphosphonates and α-hydroxyphos-
phonic acids, some organic base,20 metal compounds including
rare-earth-metal complexes21−24 as catalysts for promoting the
reaction efficiently were found, but, the drawbacks such as
harsh reaction conditions, high catalyst loading, long reaction
time, and narrow scope of the substrates in most cases remain
to be solved. To meet the growing demands for enantiomeri-
cally pure materials, the synthesis of α-amino phosphonates
asymmetrically has been developed. The first example was
reported by Shibasaki and co-workers25 using the hetero-
metallic lanthanide-potassium-binaphthol complexes for the
preparation of acyclic and cyclic α-amino phosphonates in the
presence of a large catalyst loading (5−20 mol %). The
Al(salalen)26 catalyst and some organocatalysts, such as chiral
thiourea,27 quinine,28 and phosphoric acid29 have been found to
be active in catalyzing the hydrophosphonylation of imines, but
10 mol % catalyst loading and excess dialkyl phosphonates
(1.5−2.0 equiv) were required. Therefore, the development of
a more-efficient catalyst with regard to reducing the catalyst
loading and the amount of phosphonates for the synthesis of α-
amino phosphonate is still strongly required.
[N(SiMe3)2]2] at room temperature, after workup, gave the
corresponding new amino and THF-coordinate-lithium bridged
bis(indolyl) lanthanide amido complexes [μ-{[η1:η1-3-
(CyNHCH2)Ind]2Li(THF)}Ln[N(SiMe3)2]2] (Ln = Eu (5),
Dy (6), Yb (7)) in good yields, which can be transferred to the
amido complexes 2, 3, and 4 by reflux the corresponding
complexes in toluene (Scheme 1). Thus, two series of rare-
Scheme 1. Preparation of Complexes
earth-metal amides could be reciprocally transformed by merely
changing the solvents in the reactions. The complexes are
sensitive to air and moisture, and they are soluble in solvents
such as tetrahydrofuran (THF), toluene, CH2Cl2, and even n-
hexane. All complexes were fully characterized by spectroscopic
methods and elemental analyses. The structures of the
complexes 1−7 were additionally determined by single-crystal
X-ray diffraction (XRD) study.
We herein report the synthesis and structural character-
ization of two series of new lanthanide amides supported by
bis(indolyl) ligands with amino-coordinate-lithium as a bridge,
this kind of complex would possess different sites to be
modified, with regard to an electronic, steric, and even lithium
coordination environment (see Chart 1). The catalytic activity
X-ray analyses revealed that complexes 1−4 were centrosym-
metrical mononuclear structures crystallized in the tetragonal
system with space group P42 c. They are neutral compounds
̅
1
Chart 1
composed of bis(indolyl) ligands with amino-coordinate-
lithium as a bridge, the lanthanide metal is coordinated by
two amino-functionalized indolyl monoanions in an η1 mode
through indolyl nitrogen atom, two amido ligands N(SiMe3)2
(the representative structure of the complexes is shown in
Figure 1 and Scheme 1; figures for complexes 2, 3, and 4 are
given in the Supporting Information). The lithium ion is
of these new lanthanide amido complexes on the hydro-
phosphonylation of both aromatic and aliphatic aldehydes and
substituted imines under mild conditions will be for the first
time reported.
RESULTS AND DISCUSSION
■
Synthesis and Characterization of the Rare-Earth-
Metal Complexes. Treatment of [(Me3Si)2N]3LnIII(μ-Cl)Li-
(THF)3 with 2 equiv of 3-(CyNHCH2)C8H5NH in toluene,
after workup, produced the lanthanide complexes [μ-
{[η1:η1:η1:η1-3-(CyNHCH2)Ind]2Li}Ln[N(SiMe3)2]2] (Cy =
cyclohexyl, Ind = indolyl, Ln = Sm (1), Eu (2), Dy (3), Yb
(4)) in good isolated yields. The addition of THF to the
toluene solution of [μ-{[η1:η1:η1:η1-3-(CyNHCH2)Ind]2Li}Ln-
Figure 1. ORTEP diagram of the molecular structure of complex 1. All
hydrogen atoms are omitted for clarity.
7135
dx.doi.org/10.1021/ic300137r | Inorg. Chem. 2012, 51, 7134−7143

Inorganic Chemistry
Article
Table 1. Selected Bond Length (Å) and Bond Angle (deg) of Complexes 1−7
1
2
3
4
5
6
7
Bond Distance (Å)
2.328(6)
Ln(1)−N(1)
Ln(1)−N(3)
Ln(1)−N(5)
Ln(1)−N(6)
Ln−Nav.
Li(1)−N(2)
Li(1)−N(4)
Li(1)−C(2)
Li(1)−O(1)
2.381(2)
2.294(2)
2.372(5)
2.283(5)
2.266(4)
2.197(4)
2.424(6)
2.376(7)
2.301(6)
2.278(5)
2.345(7)
2.065(15)
2.042(15)
2.322(2)
2.301(2)
2.253(2)
2.241(2)
2.279(2)
2.094(4)
2.074(4)
2.264(4)
2.234(6)
2.246(3)
2.212(3)
2.204(3)
2.232(4)
2.080(9)
2.087(9)
2.338(2)
2.027(3)
2.328(5)
2.029(6)
2.281(6)
2.023(7)
2.232(4)
2.018(5)
2.531(4)
2.522(9)
2.534(11)
2.528(8)
1.932(15)
1.968(4)
1.970(9)
Bond Angle (deg)
110.3(2)
N(3)−Ln(1)−N(1A)
N(3)−Ln(1)−N(1)
N(1)−Ln(1)−N(1A)
N(3)−Ln(1)−N(3A)
N(6)−Ln(1)−N(5)
N(6)−Ln(1)−N(3)
N(5)−Ln(1)−N(3)
N(6)−Ln(1)−N(1)
N(5)−Ln(1)−N(1)
N(3)−Ln(1)−N(1)
N(2)−Li(1)−N(2A)
N(2)−Li(1)−N(4)
N(2)−Li(1)−O(1)
N(4)−Li(1)−O(1)
111.99(7)
109.24(7)
82.39(11)
124.21(12)
109.54(17)
110.84(16)
82.5(3)
110.34(16)
109.05(17)
84.5(2)
109.5(2)
83.1(3)
125.4(3)
125.9(3)
125.8(2)
113.9(2)
117.5(2)
101.4(2)
103.6(2)
131.0(2)
87.1(2)
122.97(6)
112.07(6)
108.29(6)
105.92(6)
116.16(6)
85.15(6)
121.70(12)
112.14(13)
109.18(12)
107.49(12)
114.74(13)
85.99(13)
147.2(3)
146.7(8)
147.4(10)
148.0(7)
126.4(7)
120.0(7)
110.2(7)
118.19(19)
111.9(2)
127.2(2)
117.0(4)
113.5(5)
127.5(5)
coordinated by a carbon atom of β-position of the indolyl
ligands as compared Li−C distances (2.531(4) Å in 1, 2.522(9)
Å in 2, 2.534(11) Å in 3, 2.528(8) Å in 4) with those of Li−C5
ring distances found in CpLi(solvent)x and IndLi(solvent)x
(here, Ind = indenyl),30 and amino nitrogen atoms, thus
formed the amino-coordinate-lithium bridged bis(indolyl)
ligands. It is found that the protons on nitrogen atoms of the
substituent amino groups have not been removed. Comparison
of the Ln−N bond distances of the same molecule indicated
that they are not identical, and also N(1)−Ln−N(1A), N(3)−
Ln−N(3A) are far from the ideal tetrahedral angles (see Table
1), so the coordination geometry of the central metal can be
described as distorted tetrahedral. The geometry of central
lanthanide metals in complexes 1−4 is very similar to the
racemic-bis(indenyl) group IV metal complexes.31 From Figure
2 and Table 1, we could see that the coordinate mode of
lithium ion was changed from coordinated by carbon atom of
indolyl ligand and the amino nitrogen atoms to coordinated by
the amino nitrogen atoms and THF molecule, and the
molecular symmetry found in complexes 1−4 was also
completely changed (the representative structure of the
complex 7 is shown in Figure 2 and Scheme 1; figures for
complexes 5 and 6 are shown in the Supporting Information).
From Table 1, we can see that the usual consequences of the
contraction of the ionic radius of the Ln3+ ions when moving
from Sm3+ to Yb3+ are clearly reflected by the average Ln−N
distances of 2.338(2) Å in 1, 2.328(5) Å in 2, 2.281(6) Å in 3,
and 2.232(4) Å in 4. The similar results can be found in the
average Ln−N distances of complexes 5−7. From Table 1, we
can also find that the Ln−N bond distances from the metal to
the indolyl ligand are generally longer than those from the
metal to the N(SiMe3)2. For example, the Sm(1)−N(1)
distances are 2.381(2) Å in 1, which are longer than the
Sm(1)−N(3) distances of 2.294(2) Å. The similar results can
also be found in other lanthanide metal complexes 2 to 4. This
may be attributable to the steric effect of indolyl ligands. From
Table 1, we can find that the average Eu−N bond distance of
2.345(7) Å found in 5 is a slightly longer than that of 2.328(5)
Å found in 2. But, the average Dy−N and Yb−N distances
found in 3 or 6, and 4 or 7 are almost identical regardless of a
THF molecule coordinated to a lithium ion. The average Sm−
N bond distance found in 1 (2.338(2) Å), and the average Yb−
N bond distance found in 4 and 7 (2.232(4) Å), are longer than
the corresponding Ln−N distances of 2.268(3) Å found in the
mononuclear complex {(Me2Si)[(2,6-iPr2C6H3)N]2}SmN-
(SiMe3)2(THF)2e and 2.181(4) Å found in {(Me2Si)-
[(2,6-iPr2C6H3)N]2}YbN(SiMe3)2(THF),2e probably due to
the steric effect of indolyl ligands. The average Sm−N bond
distance of 2.338(2) Å found in 1 is comparable to the Sm−N
distance of 2.399(4) Å found in the samarium(III) complex
Figure 2. ORTEP diagram of the molecular structure of complex 7. All
hydrogen atoms are omitted for clarity.
7136
dx.doi.org/10.1021/ic300137r | Inorg. Chem. 2012, 51, 7134−7143

Inorganic Chemistry
Article
(C5Me5)2Sm(DMI) (DMI = Me2C8H4N),32 but the average
Sm−N distance in 1 is shorter than those of 2.610(4) Å and
2.601(4) Å in (DMI)2Sm(THF)4.32 The Eu−N bond distance
for the metal to the indolyl nitrogen atom of 2.372(5) Å in
complex 2 is also shorter than that of 2.633(7) Å in the
binuclear complex [Eu2(Ind)4(NH3)6] (Ind = Indolyl).33 The
Yb−N bond distance of 2.266(4) Å in 4 is comparable with
2.262(2) Å found in L1Lu(CH2SiMe3)2(THF) (L1 = 7-(2,6-
(99% yield, entry 5). However, no product was observed when
the reaction was carried out in the absence of catalyst under the
same conditions (entry 6). Then, the reaction conditions were
selected as 0.1 mol % of rare-earth-metal complexes at room
temperature under solvent-free conditions for 20 min for the
following studies. Examinations of the catalytic activity of other
amino-coordinate-lithium bridged bis(indolyl) rare-earth-metal
amides under the selected conditions also provided high
isolated yields of products. The result indicated that the ionic
radii of the rare-earth metals or solvated lanthanide amido
complexes have little influence on the catalytic activity of those
catalysts (entries 7−12).
With the optimized reaction conditions in hand, all the
complexes exhibited similar catalytic activity. So, the ytterbium
complex 4 was selected as the catalyst for the following
experiments to study the electronic effects and steric effects of
the substrates and the scope of the hydrophosphonylation
reaction. A variety of aromatic and aliphatic aldehydes were
evaluated under the optimized reaction conditions, and the
results are presented in Table 3.
Me2C6H3NCH)Ind), and 2.274(3) Å found in L2 Lu[iPr2NC-
2
(CH2SiMe3)NiPr2] (L2 = 7-(2,6-iPr2C6H3NCH)Ind) (Ind =
Indolyl),18 even if the ionic radii differences between these
types of complexes were taken into account.34 The average
Dy−N bond distance of 2.281(6) Å found in 3, 2.279(2) Å in
6, is longer than the average Dy−N bond distance of 2.219(3)
Å found in the complex {(CH2SiMe2)[(2,6-iPr2C6H3)N]2}-
DyN(SiMe3)2(THF).2d The corresponding average Yb−N
distances of 2.232(4) Å found in 4 and 7, are longer than
that of 2.181(4) Å found in {(CH2SiMe2)[(2,6-iPr2C6H3)N]2}-
YbN(SiMe3)2(THF).2d
Catalytic Activities of the Complexes on Hydro-
phosphonylation of Aldehydes. During the study of the
catalytic reactivity of the above complexes, it is found that the
above complexes can function as efficient catalysts for
hydrophosphonylation of aldehydes with a high activity and
compatibility with a wide range of substrates under an
environmentally benign solvent-free conditions.
Ytterbium complex 4 was employed as a catalyst for selecting
the favorable catalytic reaction conditions for hydrophospho-
nylation of aldehydes, and the results are listed in Table 2.
As shown in Table 3, a wide range of substituted aromatic
aldehydes are suitable for the catalytic addition of diethyl or
diphenyl phosphite. The substituents on the phenyl ring of
aldehydes could be either electron-donating groups, such as
CH3, CH3O, and (CH3)2N, or electron-withdrawing groups,
such as Cl, Br, and NO2, and excellent yields (97−99%) of the
products can be isolated (entries 1−9). Next, the scope of the
substrates were expanded to various aliphatic aldehydes. The
results showed that the steric effects of aldehydes have little
influence on the outputs of the reaction (entries 10−14). For
example, when the more sterically hindered aldehydes such as
2,2-dimethyl-propionaldehyde or the less bulky propionalde-
hyde was employed in the reactions, the outputs of the reaction
still remained at 96%−97% yields (entries 10−14). Comparison
the results of hydrophosphonylation of aldehydes with diethyl
phosphite, hydrophosphonylation of aldehydes with dipheyl
phosphite also gave excellent results, regardless of the electronic
effects of the substituents, but the reaction required for 12 h for
completion (entries 15−19). These results further suggested
that these lanthanide complexes supported by amino-
coordinate-lithium bridged bis(indolyl) ligands exhibited a
high catalytic activity for the C−P bond formation than the
Table 2. Catalytic Reaction of Benzaldehyde with Diethyl
Phosphite
a
entry
cat
loading (mol %)
solvent
toluene
yield (%)
1
complex 4
complex 4
complex 4
complex 4
complex 4
none
1
99
98
98
51
99
0
2
0.5
0.1
0.05
0.1
toluene
3
toluene
4
toluene
5
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
solvent-free
24a
prevous lanthanide amides [(Me3Si)2N]3La(μ-Cl)Li(THF)3
6
and {(μ-η5:η1):η1-2-[(2,6-Me2C6H3)NCH2](C4H3N)SmN-
(SiMe3)2}2,24c including the scope of the substituents both
aldehydes and phosphites, the ratio of aldehydes to phosphites,
and the solvent in the reaction.
7
complex 1
complex 2
complex 3
complex 5
complex 6
complex 7
0.1
0.1
0.1
0.1
0.1
0.1
97
98
99
97
98
97
8
9
10
11
12
Catalytic Activities of the Complexes on Hydro-
phosphonylation of Aldimines. Given the proven bio-
activity of the α-amino phosphonates, we try to explore the
application of the above complexes in the synthesis of α-amino
phosphonates via catalytic additions of diethyl phosphite to
aldimines. Ytterbium complex 4 was employed as a catalyst for
selecting the optimized reaction conditions for hydrophospho-
nylation of aldimines. An excellent yield of product (99%)
could be isolated for the catalytic addition of diethyl phosphite
to benzylideneaniline in the presence of 3 mol % of the
ytterbium complex 4 as a catalyst in THF at 40 °C for 6 h
(Table 4, entry 1). Decreasing catalyst loading from 3 mol % to
2 mol % and then to 1 mol % did not affect the yields of the
product (Table 4, entries 2 and 3). While the catalyst loading
was reduced from 1 mol % to 0.5 mol %, the yield of the
product decreased dramatically from 99% to 64% (entry 4). A
a
Benzaldehyde and diethyl phosphite (1:1 equiv).
From the table (entry 1), it is found that the hydro-
phosphonylation of benzaldehyde could be accomplished in
toluene at room temperature within 20 min, producing the
product in 99% yield in the presence of 1 mol % of catalyst. It is
found that the outputs of the catalytic reactions were not
affected by the catalyst loadings when the catalyst loadings were
changed from 1 mol % to 0.5 mol % and to 0.1 mol % (entries
1−3), but further decreasing the catalyst loadings to 0.05 mol %
led to a dramatically low yield of product (entry 4). When the
reaction was carried out under solvent-free conditions, it was
surprising to find that the output of the product remained high
7137
dx.doi.org/10.1021/ic300137r | Inorg. Chem. 2012, 51, 7134−7143

Inorganic Chemistry
Article
Table 3. Results of Phosphonylation Reaction of Aldehydes
with Diethyl Phosphites or Diphenyl Phosphites
Table 4. Catalytic Reaction of Benzylideneaniline with
Diethyl Phosphite
a
b
Catalyzed by Complex 4
a
entry cat (mol %)
solvent
temp (°C) time (h) yield (%)
1
2
4 (3)
4 (2)
4 (1)
4 (0.5)
4 (1)
4 (1)
4 (1)
4 (1)
4 (1)
4 (1)
4 (1)
4 (0.5)
4 (0.5)
1 (1)
2 (1)
3 (1)
5 (1)
6 (1)
7 (1)
8 (1)
9 (1)
10 (1)
11 (1)
THF
40
40
40
40
40
40
40
40
rt
6
6
99
99
99
64
98
97
98
99
76
99
98
65
65
97
99
98
98
97
98
70
72
80
82
THF
3
THF
6
4
THF
6
5
toluene
n-hexane
Et2O
6
6
6
7
6
8
CH2Cl2
THF
6
9
6
10
11
12
13
14
15
16
17
18
19
20
21
22
23
THF
rt
12
2
toluene
toluene
toluene
THF
80
80
80
40
40
40
40
40
40
40
40
40
40
6
12
6
THF
6
THF
6
THF
6
THF
6
THF
6
THF
6
THF
6
THF
6
THF
6
a
Aldimine and diethyl phosphite (1:1.2 equiv); 8 = [(Me3Si)2N]3Yb-
(μ-Cl)Li(THF)3;35 9 = [(Me3Si)2N]3Sm(μ-Cl)Li(THF)3;35 10 = {(μ-
η5:η1):η1-2-[(2,6-Me2C6H3)NCH2](C4H3N)SmN(SiMe3)2}2;24d 11 =
(η5:η1:η5:η1-Et8-calix[4]-pyrrolyl){SmN(SiMe3)2}2.24c
Examination of the catalytic activity of the different lanthanide
amides on hydrophosphonylation of benzylideneaniline also
produced high yields of product, indicating that the ionic radii
of the rare-earth metals or coordination on the lithium of the
complexes have little influence on the catalytic activities on the
hydrophosphonylation of benzylideneaniline (entries 14−19).
Notably, other lanthanide complexes only displayed moderate
activities of hydrophosphonylation of benzylideneaniline in
comparative experiments on catalytic activity of different
lanthanide complexes,24 suggesting the ligands’ effect on the
catalytic activity for hydrophosphonylation of benzylideneani-
line and the advantages of the present catalysts (entries 20−
23).
The scope of substrates for the catalytic hydrophosphony-
lations of aldimines was then investigated using 1 mol % of
complex 4 as a catalyst in THF at 40 °C for 6 h. The results are
presented in Table 5. It is found that the electronic nature of
the substituents on C-terminal of the imines had little effect on
the activity of hydrophosphonylation of aldimines (except for
−NO2, only 42% yield, entry 7), regardless of the electron-
donating groups or electron-withdrawing groups (entries 1−6).
When the electron-donating substituents were used, such as
Me, OMe, on N-terminal of the imines, good to high yields of
products 12h and 12i were isolated (entries 8 and 9). It was
also found that the electronic and steric nature have some
effects on the activities of the hydrophosphonylation of
a
b
Aldehyde and diethyl phosphite (1:1 equiv) for 20 min. Aldehyde
and diphenyl phosphite (1:1 equiv) for 12 h.
survey of the solvents indicated that the catalysts were
compatible with a variety of solvents with isolation of excellent
yields of product (entries 5−8). When the reaction was carried
out at room temperature for 6 h in the presence of 1 mol % of
complex 4 as a catalyst, a 76% yield of product was obtained; by
prolonging the reaction time to 12 h, a 99% yield of product
could be obtained (entries 9 and 10). A 98% yield of product
could be obtained when the catalytic addition of diethyl
phosphite to benzylideneaniline was carried out at 80 °C in
toluene for 2 h (entry 11). However, the results were still
dissatisfactory when the catalytic reaction was carried out at 80
°C in the presence of 0.5 mol % of the catalyst, even the
reaction time was prolonged to 12 h (entries 12 and 13).
7138
dx.doi.org/10.1021/ic300137r | Inorg. Chem. 2012, 51, 7134−7143

Inorganic Chemistry
Article
of C6H5CHNC6H5 at 8.50 ppm with the addition of
C6H5CHNC6H5 to the mixture of intermediate A within
10 min can be observed. This imine proton disappeared upon
heating the reaction mixture at 40 °C for 6 h in THF-d8;
instead, the characteristic resonances at 4.88 and 4.80 ppm for
the (EtO)2P(O)−PhCH−NHPh, which was formed via the
addition of a phosphorus atom to the imine carbon appeared,
suggesting that the intermediate C produced. The intermediate
C was also obtained through the reaction of 12a with complex
1, and was characterized by 1H NMR, infrared (IR), and
Table 5. Results of Hydrophosphonylation Reaction of
Aldimines with Diethyl Phosphite Catalyzed by Complex 4
a
entry
R1
C6H5
R2
product
yield (%)
1
1
2
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
12a
12b
12c
12d
12e
12f
99
98
97
96
96
95
42
90
83
84
80
92
89
84
97
98
81
90
78
92
elemental analyses. H NMR spectrum of the intermediate C
4-MeC6H4
4-MeOC6H4
2-MeOC6H4
4-ClC6H4
4-BrC6H4
4-O2NC6H4
C6H5
shown identical resonances as those obtained by reaction of
intermediate A with the imine C6H5CHNC6H5 in NMR
probing process (see page 54 of the Supporting Information).
Several attempts to grow crystals of A and C failed, but
intermediates A and C were fully characterized. On the basis of
these experimental results, the catalytic mechanism is proposed
as follows (Scheme 2): interaction of catalyst with diethyl
phosphite produced the intermediate A, which coordinates with
aldehydes or aldimines to afford intermediate B of which O or
N atom may have a weak coordination with lithium, resulting in
greater electron deficiency on the carbon atom of aldehydes or
aldimines. The addition of the phosphorous atom of the diethyl
phosphite to the carbon atom of aldehydes or aldimines gave
intermediate C, which then interacted with diethyl phosphite to
produce the final products.
3
4
5
6
7
12g
12h
12i
8
4-MeC6H4
4-MeOC6H4
4-MeC6H4
4-MeOC6H4
4-MeC6H4
4-MeOC6H4
4-MeOC6H4
tBu
9
C6H5
10
11
12
13
14
15
16
17
18
19
20
4-MeOC6H4
4-MeOC6H4
4-ClC6H4
4-ClC6H4
4-BrC6H4
2-pyrrolyl
2-pyrrolyl
3-indolyl
3-indolyl
3-indolyl
C6H5
12j
12k
12l
12m
12n
12o
12p
12q
12r
12s
12t
C6H5
tBu
4-tBuC6H4
cyclohexyl
4-MeC6H4SO2
CONCLUSION
■
New lanthanide amides [μ-{[η1:η1:η1:η1-3-(CyNHCH2)-
Ind]2Li}Ln[N(SiMe3)2]2] bearing amino-coordinate-lithium
bridged bis(indolyl) ligands were synthesized in good isolated
yields via reactions of [(Me3Si)2N]3LnIII(μ-Cl)Li(THF)3 (Ln =
Sm, Eu, Dy, Yb) with the amino-substituted indolyl ligand 3-
(CyNHCH2)C8H5NH. These complexes can be transferred to
[μ-{[η1:η1-3-(CyNHCH2)Ind]2Li(THF)}Ln[N(SiMe3)2]2]
(Ln = Eu, Dy, Yb) via the addition of THF to [μ-{[η1:η1:η1:η1-
3-(CyNHCH2)Ind]2Li}Ln[N(SiMe3)2]2] at room temperature.
Reflux complexes [μ-{[η1:η1-3-(CyNHCH2)Ind]2Li(THF)}Ln-
[N(SiMe3)2]2] in toluene resulted in the isolation of [μ-
{[η1:η1:η1:η1-3-(CyNHCH2)Ind]2Li}Ln[N(SiMe3)2]2]. Thus,
two different rare-earth-metal amides could be reciprocally
transferred easily by merely changing the solvents. These new
lanthanide complexes were found to exhibit an excellent
catalytic activity on the hydrophosphonylation of aldehydes and
aldimines. These catalysts have the advantages of easy
preparation, compatibility with a wide range of substrates
(aldehydes and aldimines) and solvents, high yield of products,
and proceeding under an environmentally benign condition for
aldehydes. High catalytic activity catalysts with a low catalyst
loading (1 mol %) for hydrophosphonylation of aldimines are
for the first time to be reported in this field. These advantages
of these complexes imply the potential applications of other
rare-earth metal amides in this field. Using NMR technique, the
intermediates of the catalytic reaction can be observed, thus, the
mechanism of the catalytic reaction was proposed. Further
works on this field are now under investigation in our
laboratory.
a
Aldimine and diethyl phosphite (1:1.2 equiv); complex 4 as a catalyst.
aldimines when the substituents existed on both the N-terminal
and the C-terminal (entries 10−14). Heteroaromatic aldimines,
such as 2-(tBuNCH)C4H3NH, 2-(PhNCH)C4H3NH, also
worked well, and 97% and 98% yields of products could be
isolated, respectively (entries 15 and 16). When the indolyl
imines were used in the reaction, product yields of 78%−90%
could be obtained, depending on the electronic and steric
nature of the substrates (entries 17−19). The N-benzylidene-
benzenesulfonamide can also be hydrophosphonylated under
the same conditions, using complex 4 as a catalyst (entry 20).
In order to understand the mechanism of the catalytic
reaction, several experiments were probed by the NMR
technique, and the catalytic reaction was probed stepwise
1
with H NMR spectra. First, the stoichiometric reaction of
1
complex 1 with diethyl phosphite was monitored by H NMR
1
spectrum. H NMR spectra clearly indicated the equilibium
process of HP(O)(OCH2CH3)2 and HOP(OCH2CH3)2, and
the resonances of the protons of the HP(O)(OCH2CH3)2 and
HOP(OCH2CH3)2 at 7.81 ppm, 5.53 ppm. These resonances
disappeared when the diethyl phosphite was treated with
complex 1; instead, the protons of the OCH2CH3 of the diethyl
1
phosphite appeared in the H NMR spectrum (see page 54 of
the Supporting Information), suggesting the reaction of
complex 1 with diethyl phosphite produced the active species
of A (as indicated in Scheme 2). The solid state of the
suggested A exihited a catalytic activity on reaction of
C6H5CHNC6H5 with diethyl phophite, producing the
hydrophosphonylation product 12a with 90% isolated yield,
almost a similar catalytic activity to that of complex 1. Then, the
interaction of the intermediate A with C6H5CHNC6H5 was
EXPERIMENTAL SECTION
■
Materials and Methods. All syntheses and manipulations of air-
and moisture-sensitive materials were performed under dry argon and
oxygen-free atmosphere, using standard Schlenk techniques or a
glovebox. All solvents were refluxed and distilled over sodium
1
probed by H NMR spectrum. The resonance of imine proton
7139
dx.doi.org/10.1021/ic300137r | Inorg. Chem. 2012, 51, 7134−7143

Inorganic Chemistry
Article
Scheme 2. Proposed Mechanism for the Catalytic Reactions
benzophenone ketyl under argon prior to use unless otherwise noted.
[(Me3Si)2N]3LnIII(μ-Cl)Li(THF)3 (Ln = Sm, Eu, Dy, and Yb),35 3-
(CyNHCH2)C8H5NH,36 aldimines were prepared according to
literature methods.37 Elemental analyses data were obtained on a
Perkin−Elmer Model 2400 Series II elemental analyzer. 1H NMR and
13C NMR spectra for analyses of compounds were recorded on a
C42H74LiN6Si4Sm: C, 54.08; H, 8.00; N, 9.01. Found: C, 54.32; H,
8.23; N, 8.82.
Preparation of [μ-{[η1:η1:η1:η1-3-(CyNHCH2)Ind]2Li}Eu[N-
(SiMe3)2]2] (2). This compound was isolated as red crystals in 60%
yield by treatment of [(Me3Si)2N]3EuIII(μ-Cl)Li(THF)3 (1.01 g, 1.13
mmol) with 3-(CyNHCH2)C8H5NH (0.51 g, 2.26 mmol) following
the procedures similar to those used for the preparation of 1. Because
1
Bruker Model AV-300 NMR spectrometer (300 MHz for H; 75.0
1
MHz for 13C) in C6D6 for lanthanide complexes and in CDCl3 for
organic compounds. Chemical shifts (δ) were reported in ppm. J
values are reported in Hz. IR spectra were recorded on a Shimadzu
Model FTIR-8400s spectrometer (KBr pellet). HRMS measurements
were conducted with an Agilent Model 6220 ESI-TOF mass
spectrometer.
of significant paramagnetic shifts and broadening effects, the H and
13C NMR spectra are not informative. IR (KBr pellet, cm−1): ν 2926
(s), 2850 (m), 1635 (s), 1577 (w), 1533 (w), 1454 (s), 1357 (m),
1350 (w), 1217 (m), 1184 (m), 1095 (w), 1010 (w), 964 (m), 891
(m), 837 (w), 740 (m). Anal. Calc. for C42H74LiN6Si4Eu: C, 53.99; H,
7.98; N, 8.99. Found: C, 53.76; H, 8.02; N, 8.65.
Preparation of [μ-{[η1:η1:η1:η1-3-(CyNHCH2)Ind]2Li}Dy[N-
(SiMe3)2]2] (3). This compound was isolated as colorless crystals in
64% yield by treatment of [(Me3Si)2N]3DyIII(μ-Cl)Li(THF)3 (0.99 g,
1.10 mmol) with 3-(CyNHCH2)C8H5NH (0.50 g, 2.20 mmol)
following the procedures similar to those used for the preparation of 1.
Because of significant paramagnetic shifts and broadening effects, the
1H and 13C NMR spectra are not informative. IR (KBr pellet, cm−1): ν
Preparation of [μ-{[η1:η1:η1:η1-3-(CyNHCH2)Ind]2Li}Sm[N-
(SiMe3)2]2] (1). To a toluene (10.0 mL) solution of 3-(CyNHCH2)-
C8H5NH (0.63 g, 2.76 mmol) was added a toluene (20.0 mL) solution
of [(Me3Si)2N]3SmIII(μ-Cl)Li(THF)3 (1.23 g, 1.38 mmol) at room
temperature. After the reaction mixture was stirred at room
temperature for 6 h, the mixture was then heated at 80 °C for 24 h
and the color of the solution was gradually changed from colorless to
yellow. The solvent was evaporated under reduced pressure. The
residue was extracted with n-hexane (2 × 10 mL). The combined
extractions were concentrated to ∼10.0 mL. The yellow crystals were
2922 (s), 2848 (m), 1618 (w), 1552 (w), 1498 (w), 1450 (s), 1357
(m), 1338 (w), 1261 (m), 1238 (m), 1207 (m), 1180 (m), 1134 (m),
1031 (w), 966 (m), 889 (m), 846 (w), 829 (m), 779 (w). Anal. Calc.
for C42H74LiN6Si4Dy: C, 53.39; H, 7.89; N, 8.89. Found: C, 53.54; H,
7.81; N, 8.69.
1
obtained at 0 °C for several days (0.75 g, 58% yield). H NMR (300
MHz, C6D6, ppm): δ 13.02 (d, 2H, J = 7.50 Hz, C8H5), 8.56 (s, 2H,
C8H5), 7.89−7.77 (m, 6H, C8H5), 3.60 (d, 4H, J = 8.40 Hz, −CH2),
2.46−1.66 (m, 22H, C6H11), −1.34 (s, 36H, Si(CH3)3). 13C NMR (75
MHz, C6D6, ppm): δ 150.4 (C8H5), 135.9 (C8H5), 125.3 (C8H5),
122.6 (C8H5), 122.3 (C8H5), 119.9 (C8H5), 115.8 (C8H5), 106.1
(C8H5), 57.7 (−CH2), 40.6 (C6H11), 34.0 (C6H11), 26.1 (C6H11), 25.4
(C6H11), 2.9 (Si(CH3)3). IR (KBr pellet, cm−1): ν 2941 (w), 2846
(m), 1618 (m), 1552 (m), 1498 (m), 1450 (s), 1357 (s), 1338 (w),
1265 (m), 1207 (m), 1180 (s), 1134 (m), 1031 (m), 966 (m), 918
(w), 889 (m), 846 (w), 788 (w), 648 (w). Anal. Calc. for
Preparation of [μ-{[η1:η1:η1:η1-3-(CyNHCH2)Ind]2Li}Yb[N-
(SiMe3)2]2] (4). This compound was isolated as yellow crystals in
60% yield by treatment of [(Me3Si)2N]3YbIII(μ-Cl)Li(THF)3 (1.29 g,
1.41 mmol) with 3-(CyNHCH2)C8H5NH (0.64 g, 2.82 mmol)
following the procedures similar to those used for the preparation of 1.
Because of significant paramagnetic shifts and broadening effects, the
1H and 13C NMR spectra are not informative. IR (KBr pellet, cm−1): ν
2922 (s), 2846 (w), 2360 (s), 2341 (m), 1577 (w), 1550 (w), 1498
(w), 1373 (m), 1357 (m), 1238 (m), 1207 (w), 1180 (m), 1031 (m),
7140
dx.doi.org/10.1021/ic300137r | Inorg. Chem. 2012, 51, 7134−7143

Inorganic Chemistry
Article
Table 6. Crystallographic Data for Complexes 1−7
1
2
3
4
5
6
7
formula
mol wt
T (K)
C42H74SmLiN6Si4
932.72
C42H74EuLiN6Si4
934.33
C42H74DyLiN6Si4
944.87
C42H74YbLiN6Si4
955.41
C46H82EuLiN6OSi4
1006.44
113(2)
C46H82DyLiN6OSi4
1016.98
C46H82YbLiN6OSi4
1027.52
113(2)
293(2)
113(2)
113(2)
113(2)
293(2)
λ (Å)
0.71073
0.71073
0.71073
0.71073
0.71073
monoclinic
P21/c
0.71073
0.71073
cryst syst
space group
a (Å)
tetragonal
tetragonal
tetragonal
tetragonal
triclinic
triclinic
P42 c
P42 c
P42 c
P42 c
P1
P1
̅
̅
̅
̅
̅
̅
1
1
1
1
12.050(4)
12.050(4)
34.797(12)
90
12.1994(7)
12.1994(7)
34.813(3)
90
12.1877(7)
12.1877(7)
34.665(2)
90
12.2057(3)
18.343(5)
17.565(4)
17.537(4)
90
11.7126(13)
15.2595(19)
15.9326(19)
81.424(7)
70.535(5)
81.591(7)
2640.6(5)
2
11.7254(7)
15.3734(9)
16.1586(9)
81.8810(10)
70.4730(10)
81.5320(10)
2702.0(3)
2
b (Å)
12.2057(3)
c (Å)
34.5086(18)
α (deg)
β (deg)
χ (deg)
V (Å3)
Z (Å3)
Dcalcd
90
90
90
90
90
97.687(5)
90
90
90
90
90
5053(3)
4
5181.1(6)
4
5149.1(5)
4
5141.1(3)
4
5600(2)
4
1.226
1.198
1.219
1.234
1.194
1.279
1.263
(g cm−3
)
μ (mm−1
)
1.290
1.335
1.576
1.944
1.241
1.543
1.856
F (000)
1956
1960
1972
1988
2120
1066
1074
θ range
(deg)
1.79−27.87
1.77−27.72
1.77−27.52
1.77−27.54
1.61−26.00
1.36−27.84
1.34−27.58
reflcns
collcd/
unique
32477/6032
43489/6045
42058/5934,
43498/5930
49680/11011
33526/12491
23610/12178
Rint
0.0400
0.0297
0.0510
0.0678
0.0610
0.0345
0.0298
GOF
1.075
1.094
1.189
1.016
1.337
1.020
1.018
R1, wR2 (I >
2σ(I))
0.0288, 0.0545
0.0477, 0.1213
0.0471, 0.0693
0.0376, 0.0626
0.0833, 0.1597
0.0259, 0.0608
0.0399, 0.0777
R1, wR2 (all
0.0319, 0.0559
0.0573, 0.1272
0.0813, 0.0781
0.0898, 0.0743
0.0904, 0.1627
0.0288, 0.0617
0.0645, 0.0879
data)
largest diff
0.315 and −0.739
0.574 and −0.554
0.809 and −1.104
0.648 and −0.516
1.116 and −1.301
1.266 and −0.723
0.867 and −0.862
peak/hole
(e Å−3
)
966 (m), 933 (m), 889 (w), 869 (w), 738 (m). Anal. Calc. for
C42H74LiN6Si4Yb: C, 52.80; H, 7.81; N, 8.80. Found: C, 53.17; H,
7.79; N, 8.48.
Preparation of [μ-{[η1:η1-3-(CyNHCH2)Ind]2Li(THF)}Yb[N-
(SiMe3)2]2] (7). This compound was isolated as yellow crystals in
39% yield by treatment of [μ-{[η1:η1:η1:η1-3-(CyNHCH2)Ind]2Li}-
Yb[N(SiMe3)2]2] (4) (0.63 g, 0.66 mmol) with 10 mL THF following
the procedures similar to those used for the preparation of 5. Because
Preparation of [μ-{[η1:η1-3-(CyNHCH2)Ind]2Li(THF)}Eu[N-
(SiMe3)2]2] (5). A toluene solution of [μ-{[η1:η1:η1:η1-3-(CyNHCH2)-
Ind]2Li}Eu[N(SiMe3)2]2] (2) (0.51 g, 0.55 mmol) was treated with 10
mL of THF at room temperature (rt) for 5 h. The solvent was
evaporated under reduced pressure, and the residue was extracted with
10 mL of n-hexane. Red rectangular crystals were obtained upon
allowing the extraction to stand at room temperature for several days
(0.26 g, 53% yield). Because of significant paramagnetic shifts and
1
of significant paramagnetic shifts and broadening effects, the H and
13C NMR spectra are not informative. IR (KBr pellet, cm−1): ν 2922
(m), 2848 (w), 1917 (w), 1880 (w), 1620 (w), 1452 (s), 1357 (m),
1238 (m), 1180 (m), 1031 (m), 1008 (m), 933 (m), 829 (w), 738
(m), 586 (w). Anal. Calc. for C46H82LiN6OSi4Yb·THF: C, 54.61; H,
8.25; N, 7.64. Found: C, 54.85; H, 7.74; N, 7.89. Complex 4 was
obtained again in 47% yield by refluxing 7 in toluene, following the
procedures similar to those described above for transferring 5 to 2.
1
broadening effects, the H and 13C NMR spectra are not informative.
IR (KBr pellet, cm−1): ν 2922 (s), 2848 (m), 1637 (s), 1581 (w), 1500
(w), 1448 (s), 1390 (w), 1357 (m), 1232 (s), 1207 (m), 1182 (m),
1134 (w), 1056 (w), 968 (m), 889 (m), 846 (w), 738 (m). Anal. Calc.
for C46H82LiN6OSi4Eu·THF: C, 55.73; H, 8.33; N, 7.80. Found: C,
55.65; H, 8.12; N, 7.85. A toluene (10 mL) solution of complex 5
(0.22 g, 0.22 mmol) was refluxed at 100 °C temperature for 5 h. The
solvent was evaporated under reduced pressure and the residue was
extracted with 10 mL n-hexane. Complex 2 was obtained again upon
allowing the extraction at room temperature (0.13 g, 61% yield).
Preparation of [μ-{[η1:η1-3-(CyNHCH2)Ind]2Li(THF)}Dy[N-
(SiMe3)2]2] (6). This compound was isolated as colorless crystals in
45% yield by treatment of [μ-{[η1:η1:η1:η1-3-(CyNHCH2)Ind]2Li}-
Dy[N(SiMe3)2]2] (3) (0.42 g, 0.44 mmol) with 10 mL THF following
the procedures similar to those used for the preparation of 5. Because
1
Experiments for Tracking the Intermediates with H NMR.
All manipulations of air- and moisture-sensitive materials were
performed under dry argon and oxygen-free atmosphere in a glovebox
or under argon with exclusion of air and moisture. The catalytic
reaction was probed by NMR stepwise. Diethyl phosphite (2.0 mg,
1
14.5 μmol) was dissolved in THF-d8, which was characterized by H
NMR. First, the addition of complex 1 (13.5 mg, 14.5 μmol) to the
mixture of diethyl phosphite and THF-d8; the mixture was monitored
1
by H NMR. The disappearance of resonances of the protons of the
HP(O)(OCH2CH3)2 and HOP(OCH2CH3)2 at 7.81 ppm, 5.53 ppm,
and appearance of protons of ethyl suggested the formation of
intermediate A. Then, to the above solution was added C6H5CH
NC6H5 (2.6 mg, 14.5 μmol) at rt, and the reaction mixture was probed
1
1
of significant paramagnetic shifts and broadening effects, the H and
by H NMR. The disappearance of resonance of the imines proton
13C NMR spectra are not informative. IR (KBr pellet, cm−1): ν 2922
(s), 2846 (w), 1658 (w), 1618 (w), 1450 (s), 1373 (m), 1238 (m),
1180 (s), 1131 (m), 1111 (w), 1008 (s), 966 (m), 829 (w), 738 (m),
586 (w). Anal. Calc. for C46H82LiN6OSi4Dy·0.5THF: C, 54.75; H,
8.23; N, 7.98. Found: C, 54.97; H, 7.78; N, 7.78. Complex 3 was
obtained again in 50% yield by refluxing 6 in toluene, following the
procedures similar to those described above for transferring 5 to 2.
C6H5CHNC6H5, and appearance of the resonance of the −CHN−
proton at 4.88 and 4.80 ppm suggested the formation of intermediate
C.
Experiments for Identification of the Intermediates A and C.
A mixture of complex 1 with dialkyl phosphite in a 1:1 molar ratio was
stirred in 10 mL of THF at room temperature for 30 min. The solvent
was evaporated under reduced pressure and the residues were washed
7141
dx.doi.org/10.1021/ic300137r | Inorg. Chem. 2012, 51, 7134−7143

Inorganic Chemistry
Article
with 5 mL of n-hexane. The volatiles were removed under reduced
pressure. The isolated white solid was characterized as intermediate A.
IR (KBr pellet, cm−1): ν 2927 (m), 2854 (m), 2393 (m), 1454 (s),
1352 (w), 1261 (s), 1101 (w), 1051 (w), 802 (s), 740 (s), 424 (w).
Anal. Calc. for C40H66LiN5O3PSi2Sm: C, 52.83; H, 7.31; N, 7.70.
Found: C, 52.79; H, 7.78; N, 7.77.
A mixture of the intermediate A with 1 equiv of PhNCHPh was
heated to 40 °C for 6 h in 10 mL of THF. The solvent was evaporated
under reduced pressure, and the residues were washed with 5 mL of n-
hexane. The volatiles were removed under reduced pressure. The
isolated solid material was characterized as intermediate C.
128.8, 128.3, 128.2, 118.5, 114.1, 63.5 (d, J = 6.7 Hz), 57.2 (d, J =
149.7 Hz), 16.8 (d, J = 5.7 Hz), 16.5 (d, J = 5.6 Hz). HRMS (ESI) m/
z: calcd for C17H22NO3P [M+H]+: 320.1416; Found: 320.1416.
The solid of the suggested active species A was isolated and was
used for the catalytic reaction of C6H5CHNC6H5 with diethyl
phosphite with isolation of product 12a in 90% yield under the
reaction conditions.
ASSOCIATED CONTENT
■
S
* Supporting Information
Characterization data and spectra for compounds, and figures
for 1−7 with bond distances and angles. X-ray crystallographic
files, in CIF format, for structure determination of complexes
1−7. This material is available free of charge via the Internet at
http://pubs.acs.org.
Alternative route to intermediate C: Reaction of the complex 1 with
12a in a 1:1 molar ratio, after workup using the procedures similar to
those for reaction of intermediate A with imine PhNCHPh. The
isolated solid material was characterized as intermediate C. IR (KBr
pellet, cm−1): ν 2922 (s), 2848 (m), 2384 (w), 1498 (m), 1452 (s),
1357 (m), 1238 (m), 1207 (w), 1116 (w), 1058 (w), 829 (m), 738 (s),
1
428 (w). H NMR (300 MHz, C6D6, ppm): δ 8.13 (1H), 7.92−7.80
AUTHOR INFORMATION
■
(m, 2H), 7.54 (s, 3H), 7.18−7.00 (m, 10H), 6.64 (s, 4H), 5.67 (s,
1H), 4.91 (d, 1H, J = 20.6 Hz), 4.06 (d, 4H, J = 6.4 Hz), 3.57 (s, 4H),
2.52−0.82 (m, 28H), 0.09 (s, 18H). Anal. Calc. for
C53H77LiN6O3PSi2Sm: C, 58.37; H, 7.12; N, 7.71. Found: C, 58.43;
H, 7.65; N, 7.28.
Corresponding Author
*E-mail: swwang@mail.ahnu.edu.cn.
Notes
The authors declare no competing financial interest.
Crystal Structure Determinations. A suitable crystal of
complexes 1−7 was each mounted in a sealed capillary. Diffraction
was performed on a Bruker SMART CCD area detector diffractometer
using graphite-monochromated Mo Kα radiation (λ = 0.71073 Å). An
empirical absorption correction was applied using the SADABS
program.38 All structures were solved by direct methods, completed by
subsequent difference Fourier syntheses, and refined anisotropically for
all non-hydrogen atoms by full-matrix least-squares calculations on F2
using the SHELXTL program package.39 All hydrogen atoms were
refined using a riding model. Crystal data and details of the data
collection are given in Table 6. Further details are included in the
Supporting Information.
ACKNOWLEDGMENTS
■
This work is supported by the National Natural Science
Foundation of China (Nos. 20832001, 20802001, 21072004),
the National Basic Research Program of China (No.
2012CB821604), the grant from the Ministry of Education
(No. 20103424110001), and Anhui Province (Nos. 2007Z016,
KJ2012A138). The help for this work from Prof. Dr. Hai-bin
Song from Nankai University is acknowledged.
General Experimental Procedure for Hydrophosphonylation
of Aldehydes. A mixture of complex 4 (9.55 mg, 0.01 mmol) and
dialkyl phosphite (10 mmol) was stirred for 5 min. Benzaldehyde (10
mmol) was then added, and the resulting mixture was stirred under
solvent-free conditions for 20 min. After 20 min, the temperature of
the exothermic reaction returned to room temperature. Water was
added, and the mixture was extracted with ethyl acetate (3 × 10 mL).
The combined organic layers were dried over anhydrous MgSO4, after
filtration, the solvent was evaporated under reduced pressure.
Recrystallization of the crude product from hexane and diethyl ether
gave the desired product 10a (2.41 g, 99% yield) as white crystals.
Diethyl(hydroxy(phenyl)methyl)phosphonate (10a). Melting
REFERENCES
■
(1) (a) Zimmermann, M.; Anwander, R. Chem. Rev. 2010, 110, 6194.
(b) Nishiura, M.; Hou, Z. Nature Chem. 2010, 2, 257. (c) Kempe, R.
Angew. Chem., Int. Ed. 2000, 39, 468. (d) Armelao, L.; Quici, S.;
Barigelletti, F.; Accorsi, G.; Bottaro, G.; Cavazzini, M.; Tondello, E.
Coord. Chem. Rev. 2010, 254, 3029. (e) Garnovskii, A. D.;
Vasil’chenko, I. S.; Garnovskii, D. A.; Burlov, A. S.; Uraev, A. I. Russ.
J. Gen. Chem. 2009, 79, 2776. (f) Wong, W. K.; Zhu, X. J.; Wong, W.
Y. Coord. Chem. Rev. 2007, 251, 2386. (g) Han, F.; Zhang, Y.; Sun, X.;
Li, B.; Guo, Y.; Tang, Y. Organometallics 2008, 27, 1924. (h) Xie, Z.
Coord. Chem. Rev. 2006, 250, 259. (i) Edelmann, F. T.; Freckmann, D.
M. M.; Schumann, H. Chem. Rev. 2002, 102, 1851. (j) Bourget, M. L.;
Lappert, M. F.; Severn, J. R. Chem. Rev. 2002, 102, 3031. (k) Gibson,
V. C.; Spitzmesser, K. Chem. Rev. 2003, 103, 283. (l) Britovsek, G. J.
P.; Gibson, V. C.; Wass, D. F. Angew. Chem., Int. Ed. 1999, 38, 428.
(2) (a) Wang, J.; Zhang, Y.; Shen, Q. Inorg. Chem. 2009, 48, 744.
(b) Zhang, Z.; Xu, X.; Li, W.; Yao, Y.; Zhang, Y.; Shen, Q.; Luo, Y.
Inorg. Chem. 2009, 48, 5715. (c) Venugopal, A.; Fegler, W.; Spaniol, T.
P.; Maron, L.; Okuda, J. J. Am. Chem. Soc. 2011, 44, 17574. (d) Wu, Y.;
Wang, S.; Zhu, X.; Yang, G.; Wei, Y.; Zhang, L.; Song, H. Inorg. Chem.
2008, 47, 5503. (e) Zhu, X.; Fan, J.; Wu, Y.; Wang, S.; Zhang, L.;
Yang, G.; Wei, Y.; Yin, C.; Zhu, H.; Wu, S.; Zhang, H. Organometallics
2009, 28, 3882.
(3) (a) Zeimentz, P. M.; Arndt, S.; Elvidge, B. R.; Okuda, J. Chem.
Rev. 2006, 106, 2404. (b) Jiao, R.; Shen, X.; Xue, M.; Zhang, Y.; Yao,
Y.; Shen, Q. Chem. Commun. 2010, 46, 4118. (c) Hitchcock, P. B.;
Khvostov, A. V.; Lappert, M. F.; Protchenko, A. V. Dalton Trans. 2009,
13, 2383. (d) Shang, X.; Liu, X.; Cui, D. J. Polym. Sci., Part A: Polym.
Chem. 2007, 45, 5662. (e) Lazarov, B. B.; Hampel, F.; Hultzsch, K. C.
Z. Anorg. Allg. Chem. 2007, 633, 2367. (f) Yao, Y.; Zhang, Z.; Peng, H.;
Zhang, Y.; Shen, Q.; Lin, J. Inorg. Chem. 2006, 45, 2175. (g) Knight, L.
K.; Piers, W. E.; McDonald, R. Organometallics 2006, 25, 3289.
(h) Bourget-Merle, L.; Lappert, M. F.; Severn, J. R. Chem. Rev. 2002,
102, 3031.
1
point (mp) 81−82 °C; H NMR (300 MHz, CDCl3, ppm): δ 7.42−
7.40 (d, 2H, J = 6.0 Hz, ArH), 7.30−7.28 (d, 3H, J = 7.8 Hz, ArH),
4.98 (d, J = 10.5 Hz, 1H, CH), 4.00−3.93 (m, 4H, CH2), 2.72 (s, 1H,
OH), 1.22−1.13 (m, 6H, CH3). 13C NMR (75 MHz, CDCl3, ppm): δ
136.6, 128.2, 128.0, 127.1 (d, J = 5.7 Hz), 71.8 (d, J = 157.9 Hz), 63.3
(d, J = 6.9 Hz), 63.0 (d, J = 7.4 Hz), 16.3. HRMS (ESI) m/z: calcd for
C11H17O4P [M+H]+: 245.0943; Found: 245.0941.
General Experimental Procedure for Hydrophosphonylation
of Aldimines. A mixture of complex 4 (9.55 mg, 0.01 mmol),
aldimines (10 mmol) and dialkyl phosphite (12 mmol) was stirred in 2
mL of THF. The resulting mixture was heated to 40 °C for 6 h. After
the reaction was completed, water was added, and the mixture was
extracted with ethyl acetate (3 × 10 mL). The combined organic layers
were dried over anhydrous MgSO4, and filtered, the solvent was
evaporated under reduced pressure. Recrystallization of the crude
product from hexane and ethyl acetate gave the desired product.
Diethyl (N-phenylamino)(phenyl)methylphosphonate (12a).
Melting point (mp) 86−87 °C; 1H NMR (300 MHz, CDCl3, ppm): δ
7.48 (d, J = 7.2 Hz, 2H), 7.35−7.28 (m, 3H), 7.13−7.08 (m, 2H),
6.71−6.67 (m, 1H), 6.60 (d, J = 7.9 Hz, 2H), 4.84 (d, J = 12.8 Hz,
1H), 4.73 (d, J = 7.6 Hz, 1H), 4.14−4.05 (m, 2H), 3.97−3.86 (m,
1H), 3.72−3.61 (m, 1H), 1.31−1.26 (m, 3H), 1.13−1.08 (m, 3H). 13C
NMR (75 MHz, CDCl3, ppm): δ 146.8 (d, J = 14.7 Hz), 136.3, 129.4,
7142
dx.doi.org/10.1021/ic300137r | Inorg. Chem. 2012, 51, 7134−7143

Inorganic Chemistry
Article
(4) (a) Edelmann, F. T. Chem. Soc. Rev. 2009, 38, 2253.
(b) Edelmann, F. T. Adv. Organomet. Chem. 2008, 57, 183.
(c) Trifonov, A. A.; Lyubov, D. M.; Fedorova, E. A.; Skvortsov, G.
G.; Fukin, G. K.; Kurskii, Yu. A.; Bochkarev, M. N. Russ. Chem. Bull.
Int. Ed. 2006, 55, 435. (d) Yao, Y.; Luo, Y.; Chen, J.; Zhang, Z.; Zhang,
Y.; Shen, Q. J. Organomet. Chem. 2003, 679, 229. (e) Giesbrecht, G. R.;
Whitener, G. D.; Arnold, J. J. Chem. Soc., Dalton Trans. 2001, 6, 923.
(f) Lu, Z.; Yap, G. P. A.; Richeson, D. S. Organometallics 2001, 20, 706.
(g) Zhang, Z.; Zhang, L.; Li, Y.; Hong, L.; Chen, Z.; Zhou, X. Inorg.
Chem. 2010, 49, 5715.
(5) (a) Yang, Y.; Li, S.; Cui, D.; Chen, X.; Jing, X. Organometallics
2007, 26, 671. (b) Yang, Y.; Liu, B.; Lv, K.; Gao, W.; Cui, D.; Chen,
X.; Jing, X. Organometallics 2007, 26, 4575. (c) Liu, C.; Zhou, S.;
Wang, S.; Zhang, L.; Yang, G. Dalton Trans. 2010, 39, 8994. (d) Li, Q.;
Rong, J.; Wang, S.; Zhou, S.; Zhang, L.; Zhu, X.; Wang, F.; Yang, S.;
Wei, Y. Organometallics 2011, 30, 992. (e) Zhou, S.; Yin, C.; Wang, H.;
Zhu, X.; Yang, G.; Wang, S. Inorg. Chem. Commun. 2011, 14, 1196.
(6) (a) Tanski, J. M.; Parkin, G. Inorg. Chem. 2003, 42, 264.
(b) Imhof, W. J. Organomet. Chem. 1997, 533, 31. (c) Bowyer, P. K.;
Black, D. S.; Craig, D. C.; Rae, A. D.; Willis, A. C. J. Chem. Soc., Dalton
Trans. 2001, 13, 1948. (d) Carpita, A.; Ribecai, A.; Stabile, P.
Tetrahedron 2010, 66, 7169.
(7) (a) Deacon, G. B.; Forsyth, C. M.; Gatehouse, B. M.; White, A.
H. Aust. J. Chem. 1990, 43, 795. (b) Abrahams, C. T.; Deacon, G. B.;
Forsyth, C. M.; Patalinghug, W. C.; Skelton, B. W.; White, A. H. Acta
Crystallogr., Sect. C: Cryst. Struct. Commun. 1994, 50, 504. (c) Evans,
W. J.; Rabe, G. W.; Ziller, J. W. Organometallics 1994, 13, 1641.
(8) (a) Bartoli, G.; Bencivenni, G.; Dalpozzob, R. Chem. Soc. Rev.
2010, 39, 4449. (b) Jafarpour, M.; Rezaeifard, A.; Gorzin, G. Inorg.
Chem. Commun. 2011, 14, 1732. (c) Husain, K.; Abid, M.; Azam, A.
Eur. J. Med. Chem. 2007, 42, 1300.
(24) (a) Wu, Q.; Zhou, J.; Yao, Z.; Xu, F.; Shen, Q. J. Org. Chem.
2010, 75, 7498. (b) Zhou, X.; Liu, Y.; Chang, L.; Zhao, J.; Shang, D.;
Liu, X.; Lin, L.; Feng, X. Adv. Synth. Catal. 2009, 351, 2567. (c) Zhou,
S.; Wang, H.; Wang, S.; Zhang, L.; Zhu, X.; Wei, Y.; Wang, F.; Feng,
Z.; Gu, X.; Yang, S.; Miao, H. Organometallics 2012, 31, 1696.
(d) Zhou, S.; Wu, Z.; Rong, J.; Wang, S.; Yang, G.; Zhu, X.; Zhang, L.
Chem.Eur. J. 2012, 18, 2653.
(25) (a) Sasai, H.; Arai, S.; Tahara, Y.; Shibasaki, M. J. Org. Chem.
1995, 60, 6656. (b) Groger, H.; Saida, Y.; Sasai, H.; Yamaguchi, K.;
̈
Martens, J.; Shibasaki, M. J. Am. Chem. Soc. 1998, 120, 3089.
(c) Schlemminger, I.; Saida, Y.; Groger, H.; Maison, W.; Durot, N.;
̈
Sasai, H.; Shibasaki, M.; Martens, J. J. Org. Chem. 2000, 65, 4818.
(26) Saito, B.; Egami, H.; Katsuki, T. J. Am. Chem. Soc. 2007, 129,
1978.
(27) Joly, G. D.; Jacobsen, E. N. J. Am. Chem. Soc. 2004, 126, 4102.
(28) Pettersen, D.; Marcolini, M.; Bernardi, L.; Fini, F.; Herrera, R.
P.; Sgarzani, V.; Ricci, A. J. Org. Chem. 2006, 71, 6269.
(29) Akiyama, T.; Morita, H.; Itoh, J.; Fuchibe, K. Org. Lett. 2005, 7,
2583.
(30) Michel, R.; Herbst-Irmer, R.; Stalke, D. Organometallics 2011,
30, 4379.
(31) Brintzinger, H. H.; Fischer, D.; Mulhaupt, R.; Rieger, B.;
̈
Waymouth, R. M. Angew. Chem., Int. Ed. 1995, 11, 1143.
(32) Evans, W. J.; Brady, J. C.; Ziller, J. W. Inorg. Chem. 2002, 41,
3340.
(33) Muller-Buschbaum, K. Z. Anorg. Allg. Chem. 2004, 630, 895.
̈
(34) Shannon, R. D. Acta Crystallogr., Sect. A: Cryst. Phys., Diffr.,
Theor. Gen. Crystallogr. 1976, A32, 751.
(35) (a) Zhou, S.; Wang, S.; Yang, G.; Liu, X.; Sheng, E.; Zhang, K.;
Cheng, L.; Huang, Z. Polyhedron 2003, 22, 1019. (b) Sheng, E.; Wang,
S.; Yang, G.; Zhou, S.; Zhang, K.; Cheng, L.; Huang, Z. Organometallics
2003, 22, 684.
(9) Shimazaki, Y.; Yajimab, T.; Takani, M.; Yamauchi, O. Coord.
Chem. Rev. 2009, 253, 479.
(10) Takani, M.; Takeda, T.; Yajima, T.; Yamauchi, O. Inorg. Chem.
2006, 45, 5938.
(11) Zhu, G.; Tanski, J. M.; Churchill, D. G.; Janak, K. E.; Parkin, G.
(36) Walker, G. N.; Moore, M. A. J. Org. Chem. 1961, 26, 432.
(37) (a) Neuvonen, H.; Neuvonen, K.; Fulop, F. J. Org. Chem. 2006,
̈
̈
71, 3141. (b) García Ruano, J. L.; Aleman
́
, J.; Alonso, I.; Parra, A.;
Marcos, V.; Aguirre., J. Chem.Eur. J. 2007, 13, 6179. (c) Bennett, J.
S.; Charles, K. L.; Miner, M. R.; Heuberger, C. F.; Spina, E. J.; Bartels,
M. F.; Foreman, T. Green Chem. 2009, 11, 166.
J. Am. Chem. Soc. 2002, 124, 13658.
(12) Jeffreys, J. A. D.; Metters, C. J. Chem. Soc., Dalton Trans. 1977,
17, 1624.
(13) Karshtedt, D.; McBee, J. L.; Bell, A. T.; Tilley, T. D.
(38) Sheldrick, G. M. SADABS: Program for Empirical Absorption
Correction of Area Detector Data; University of Gottingen: Gottingen,
̈
̈
Germany, 1996.
(39) Sheldrick, G. M. SHELXTL 5.10 for Windows NT: Structure
Determination Software Programs; Bruker Analytical X-ray Systems,
Inc.: Madison, WI, 1997.
Organometallics 2006, 25, 1801.
(14) Shimazaki, Y.; Yokoyama, H.; Yamauchi, O. Angew. Chem., Int.
Ed. 1999, 38, 2401.
(15) Wu, S.; Wu, Y.; Yang, Y. J. Alloy. Compd. 1992, 180, 391.
(16) (a) Li, J.; Gao, T.; Zhang, W.; Sun, W. Inorg. Chem. Commun.
2003, 6, 1372. (b) Zuo, W.; Sun, W.; Zhang, S.; Hao, P.; Shiga, A. J.
Polym. Sci., Part A: Polym. Chem. 2007, 45, 3415.
(17) (a) Matsugi, T.; Matsui, S.; Kojoh, S.; Takagi, Y.; Inoue, Y.;
Fujita, T.; Kashiwa, N. Chem. Lett. 2001, 30, 566. (b) Matsugi, T.;
Matsui, S.; Kojoh, S.; Takagi, Y.; Inoue, Y.; Nakano, T.; Fujita, T.;
Kashiwa, N. Macromolecules 2002, 35, 4880.
(18) Yang, Y.; Wang, Q.; Cui, D. J. Polym. Sci., Part A: Polym. Chem.
2008, 46, 5251.
(19) (a) Hilderbrand, R. L. The Role of Phosphonates in Living
Systems; CRC Press: Boca Raton, FL, 1983. (b) Patel, D. V.; Rielly-
Gauvin, K.; Ryono, D. E.; Free, C. A.; Rogers, W. L.; Smith, S. A.;
DeForrest, J. M.; Oehl, R. S.; Petrillo, E. W. J. Med. Chem. 1995, 38,
4557. (c) Shibasaki, M.; Yoshikawa, N. Chem. Rev. 2002, 102, 2187.
(d) Demmer, C. S.; Krogsgaard-Larsen, N.; Bunch, L. Chem. Rev.
2011, 111, 7981−8006. (e) Zhao, D.; Wang, R. Chem. Soc. Rev. 2012,
41, 2095−2108 and references therein..
(20) Li, C.; Yuan, C. Tetrahedron Lett. 1993, 34, 1515.
(21) Gawron, O.; Grelecki, C.; Reilly, W.; Sands, J. J. Am. Chem. Soc.
1953, 75, 3591.
(22) (a) Texier-Boullet, F.; Foucaud, A. Synthesis 1982, 165, 916.
(b) Jung, M. E.; Cordova, J.; Murakami, M. Org. Lett. 2009, 11, 3882.
(23) de Noronha, R. G.; Costa, P. J.; Romao, C. C.; Calhorda, M. J.;
Fernandes, A. C. Organometallics 2009, 28, 6206.
7143
dx.doi.org/10.1021/ic300137r | Inorg. Chem. 2012, 51, 7134−7143