Heterometallic rare-earth metal complexes with imino-functionalized 8-hydroxyquinolyl ligands: Synthesis, characterization and catalytic activity towards hydrophosphinylation of trans-β-nitroalkene

Article abstract of DOI:10.1039/c5nj00409h

Reactions of rare-earth metal amides [(Me₃Si)₂N]₃RE(μ-Cl)Li(THF)₃ with different equiv. of 2-(2,6-diisopropylphenylimino)-8-hydroxyquinoline (1) afforded different heterometallic rare-earth metal complexes, and catalytic activity of the resulting complexes was investigated. Reactions of rare-earth metal amides [(Me₃Si)₂N]₃RE(μ-Cl)Li(THF)₃ (RE = Y, Er, Dy) with 1 equiv. of compound 1 afforded the heterobimetallic rare-earth metal and lithium complexes 2-4 bridged by the oxygen atom of 2-(2,6-diisopropylphenylimino)-8-hydroxyquinoline and the nitrogen atom of N(SiMe₃)₂. However, the treatment of rare-earth metal amides [(Me₃Si)₂N]₃RE(μ-Cl)Li(THF)₃ (RE = Sm, Er, Yb) with 2 equiv. of compound 1 gave different heterobimetallic rare-earth metal and lithium complexes 5-7 bridged by the oxygen atoms of 2-(2,6-diisopropylphenylimino)-8-hydroxyquinoline. Complex 6 can also be prepared by the treatment of 3 with 1 equiv. of 1. Complexes 2-7 were fully characterized using spectroscopic methods, elemental analyses and single crystal X-ray diffraction. Investigation of the catalytic properties of the complexes indicated that all complexes exhibited a high catalytic activity towards the addition of diphenylphosphine oxide to trans-β-nitroalkenes to afford β-nitrophosphonates under mild conditions.

Full text of DOI:10.1039/c5nj00409h

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Heterometallic rare-earth metal complexes with
imino-functionalized 8-hydroxyquinolyl ligands:
synthesis, characterization and catalytic activity
towards hydrophosphinylation of trans-b-
nitroalkene†
Cite this:DOI: 10.1039/c5nj00409h
Qingbing Yuan,a Shuangliu Zhou,*a Xiancui Zhu,a Yun Wei,a Shaowu Wang,*ab
Xiaolong Mu,a Fangshi Yao,a Guangchao Zhanga and Zheng Chena
Reactions of rare-earth metal amides [(Me3Si)2N]3RE(m-Cl)Li(THF)3 with different equiv. of 2-(2,6-diiso-
propylphenylimino)-8-hydroxyquinoline (1) afforded different heterometallic rare-earth metal complexes,
and catalytic activity of the resulting complexes was investigated. Reactions of rare-earth metal amides
[(Me3Si)2N]3RE(m-Cl)Li(THF)3 (RE = Y, Er, Dy) with 1 equiv. of compound 1 afforded the heterobimetallic
rare-earth metal and lithium complexes 2–4 bridged by the oxygen atom of 2-(2,6-diisopropyl-
phenylimino)-8-hydroxyquinoline and the nitrogen atom of N(SiMe3)2. However, the treatment of rare-earth
metal amides [(Me3Si)2N]3RE(m-Cl)Li(THF)3 (RE = Sm, Er, Yb) with 2 equiv. of compound 1 gave different
heterobimetallic rare-earth metal and lithium complexes 5–7 bridged by the oxygen atoms of 2-(2,6-diiso-
propylphenylimino)-8-hydroxyquinoline. Complex 6 can also be prepared by the treatment of 3 with 1 equiv.
of 1. Complexes 2–7 were fully characterized using spectroscopic methods, elemental analyses and single
crystal X-ray diffraction. Investigation of the catalytic properties of the complexes indicated that all complexes
exhibited a high catalytic activity towards the addition of diphenylphosphine oxide to trans-b-nitroalkenes to
afford b-nitrophosphonates under mild conditions.
Received (in Victoria, Australia)
16th February 2015,
Accepted 7th May 2015
DOI: 10.1039/c5nj00409h
www.rsc.org/njc
The Michael addition of phosphorus compounds to nitro-
alkenes provides a practical route to b-nitrophosphonates,
Introduction
Non-Cp ligands based on N and O atoms have been extensively which can be transformed into the corresponding 1,4-addition
applied to stabilize rare-earth metal complexes, due to their products, b-amino phosphonates, through a simple reduction
strong coordinative abilities and finely tuned sizes and electronic of the nitro group.10 Previous studies mainly focus on the
properties of the substituents.1 Rare-earth metal complexes sta- catalytic addition of nucleophiles such as dialkyl phosphites
bilized by b-diketiminates,2 amidinates,3 guanidinates,4 bridged [(RO)2P(O)H]11 and secondary phosphines (R2PH)12 to b-nitro-
bisphenolates,5 diamido ligands,6 and modified pyrrolyl or indolyl alkenes. However, the diarylphosphine oxides [Ar2P(O)H]13 have
ligands7 have been synthesized and applied in various organic been much neglected even though the adducts possess synthetic
transformations. Recently, 8-hydroxy or 8-aminoquinoline deriva- potential and may be used as useful analogues of phosphonates.
tives have been used as ligands for rare-earth metal8 and group 4 In our previous study, we have reported that the lanthanide
metal complexes9 because of their excellent coordination proper- amides displayed high catalytic activities towards hydrophos-
ties and near infrared luminescence.
phonylation of aldehydes, unactivated ketones and imines.14
Recently, we have also developed a series of rare-earth metal
amides as catalysts for the high regioselective addition of
phosphites to a,b-unsaturated carbonyl compounds.15 As our
continuous interest in the development of organo rare-earth
metal amido complexes as catalysts for the C–P formation
reaction, we herein report the synthesis, characterization and
catalytic activity of rare-earth metal complexes with tridentate
imino-functionalized 8-hydroxyquinolyl ligands towards the
addition of diphenylphosphine oxide to trans-b-nitroalkenes.
a Anhui Key Laboratory of Functional Molecular Solids, Institute of Organic
Chemistry, School of Chemistry and Materials Science, Anhui Normal University,
Wuhu, Anhui 241000, P. R. China. E-mail: slzhou@mail.ahnu.edu.cn,
swwang@mail.ahnu.edu.cn
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic
Chemistry, Chinese Academy of Sciences, Shanghai 200032, P. R. China
† Electronic supplementary information (ESI) available. CCDC 1048534–1048539.
For ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/c5nj00409h
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Experimental section
Materials and methods
Synthesis of g :g -[g :g -2-(2,6- Pr2C6H3)N CH-8-OC9H6N]2-
LiRE[N(SiMe3)2]2 (RE = Sm (5), Er (6), Yb (7))
To a toluene (10.0 mL) solution of compound 1 (0.465 g,
1.40 mmol) a toluene (20.0 mL) solution of [(Me3Si)2N]3Sm(m-Cl)-
Li(THF)3 (0.623 g, 0.70 mmol) was added at room temperature.
After the reaction mixture was stirred at room temperature for
6 h, the mixture was then heated at 40 1C for 12 h. The solvent
was evaporated under reduced pressure. The residue was
extracted with n-hexane (15.0 mL). The extractions were combined
and concentrated to about 10.0 mL. The yellow crystals 5 were
obtained by cooling the concentrated solution at 0 1C for several
days (0.456 g, 40%). IR (KBr pellets, cmÀ1): n = 3059, 2961, 2868,
2361, 2342, 1630, 1589, 1551, 1458, 1369, 1341, 1252, 1098, 841,
748. Anal. calc. for C56H81LiN6O2Si4Sm: C, 59.00; H, 7.16; N, 7.37.
Found: C, 58.92; H, 7.20; N, 7.25.
Complex 6 was prepared as pink crystals in 41% (0.50 g)
yield by the treatment of compound 1 (0.465 g, 1.40 mmol) with
[(Me3Si)2N]3Er(m-Cl)Li(THF)3 (0.635 g, 0.70 mmol) using the
procedures similar to those described above for the preparation
of 5. IR (KBr pellets, cmÀ1): n = 3059, 2959, 2868, 2361, 1630,
1589, 1553, 1458, 1369, 1341, 1182, 1099, 932, 840, 745. Anal.
calc. for C56H81LiN6O2Si4Er: C, 58.14; H, 7.06; N, 7.26. Found:
C, 57.59; H, 7.09; N, 6.99.
Complex 6 can also be prepared by the treatment of 3 with
1 equiv. of 1 by employing the procedures similar to those used
for the preparation of complex 5.
Complex 7 was prepared as yellow crystals in 43% yield
by the treatment of compound 1 (0.465 g, 1.40 mmol) with
[(Me3Si)2N]3Yb(m-Cl)Li(THF)3 (0.639 g, 0.70 mmol) using the
procedures similar to those described above for the preparation
of 5. IR (KBr pellets, cmÀ1): n = 3059, 2959, 2868, 1630, 1589,
1553, 1458, 1371, 1340, 1182, 1099, 932, 849, 745. Anal. calc. for
All syntheses and manipulations of air- and moisture-sensitive
materials were performed under a dry argon and an oxygen-
free atmosphere using standard Schlenk techniques or in a
glovebox. All solvents were refluxed and distilled over sodium
benzophenone ketyl under argon prior to use unless otherwise
noted. [(Me3Si)2N]3RE(m-Cl)Li(THF)3 (RE = Y, Sm, Dy, Er, Yb)16
and 2-(2,6-diisopropylphenylimino)-8-hydroxyquinoline (1)9
were prepared according to literature methods. Data of elemental
analyses were obtained on a Perkin-Elmer 2400 Series II elemental
analyzer. 1H NMR and 13C NMR spectra for analyses of com-
pounds were recorded on a Bruker AV-300 NMR spectrometer
(300 MHz for 1H; 75.0 MHz for 13C) in C6D6 for lanthanide
complexes and in CDCl3 for organic compounds. Chemical
shifts (d) were reported in ppm. IR spectra were recorded on
a Shimadzu FTIR-8400S spectrometer (KBr pellets).
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Synthesis of g :g -[2-(2,6- Pr2C6H3)N CH]-8-OC9H6N]Li-
[l-N(SiMe3)2]RE[N(SiMe3)2]2 (RE = Y (2), Er (3), Dy (4))
To a toluene (10.0 mL) solution of compound 1 (0.300 g,
0.90 mmol) a toluene (20.0 mL) solution of [(Me3Si)2N]3Y(m-Cl)-
Li(THF)3 (0.746 g, 0.90 mmol) was added at room temperature.
After the reaction mixture was stirred at room temperature for
6 h, the mixture was then heated at 40 1C for 12 h. The solvent
was evaporated under reduced pressure. The residue was
extracted with n-hexane (15.0 mL). The extractions were com-
bined and concentrated to about 10.0 mL. The colorless
crystals 2 were obtained by cooling the concentrated solution at
0 1C for several days (0.345 g, 38% yield). IR (KBr pellets, cmÀ1):
n = 2961, 2868, 2361, 2342, 2170, 1638, 1618, 1560, 1458,
1369, 1341, 1261, 1182, 1098, 932, 841, 745. 1H NMR (300
MHz, C6D6): d 7.62 (s, 1H), 7.31–7.24 (m, 3H), 7.12–7.08
(m, 3H), 6.87–6.84 (m, 2H), 2.97 (s, 2H), 1.41 (s, 12H), 0.35
(s, 36H), 0.18 (s, 9H), 0.05 (s, 9H). 13C NMR (125 MHz, C6D6):
d 162.3, 160.7, 148.1, 142.7, 138.9, 137.3, 131.9, 131.2, 125.5,
123.2, 120.1, 117.3, 115.4, 28.3, 23.5, 5.2, 4.5, 2.6. Anal. calc. for
C
56H81LiN6O2Si4Yb: C, 57.85; H, 7.02; N, 7.23. Found: C, 57.62;
H, 7.09; N, 6.99.
Crystal structure determination
Suitable crystals of complexes 2–7 were each mounted in a sealed
capillary. Diffraction was performed on a Bruker SMART CCD area
detector diffractometer using graphite-monochromated Mo-Ka
radiation (l = 0.71073 Å). An empirical absorption correction
was applied using the SADABS program. All structures were solved
by direct methods, completed by subsequent difference Fourier
syntheses, refined anisotropically for all nonhydrogen atoms by
full-matrix least-squares calculations on F2 using the SHELXTL
program package. All hydrogen atoms were refined using a riding
model. See Table 4 for crystallographic data.
C
40H77LiN5OSi6Y: C, 52.89; H, 8.54; N, 7.71. Found: C, 53.37;
H,8.40; N, 7.16.
Complex 3 was prepared as pink crystals in 42% (0.414 g)
yield by the treatment of compound 1 (0.300 g, 0.90 mmol) with
[(Me3Si)2N]3Er(m-Cl)Li(THF)3 (0.816 g, 0.90 mmol) using the
procedures similar to those described above for the preparation
of 2. IR (KBr pellets, cmÀ1): n = 3063, 2959, 2868, 2361, 2342,
2185, 1630, 1591, 1553, 1458, 1371, 1341, 1252, 1180, 1099,
1057, 841, 750. Anal. calc. for C40H77LiN5OSi6ErÁC4H8O: C,
49.91; H, 8.09; N, 6.61. Found: C, 50.08; H, 7.92; N, 6.35.
Complex 4 was prepared as colorless crystals in 39% (0.383 g)
yield by the treatment of compound 1 (0.300 g, 0.90 mmol) with
General procedure for hydrophosphination of b-nitroalkene
derivatives (8 as an example)
[(Me3Si)2N]3Dy(m-Cl)Li(THF)3 (0.812 g, 0.90 mmol) using the A 30.0 mL Schlenk tube under dried argon was charged with
procedures similar to those described above for the preparation complex 7 (11.8 mg, 0.05 mmol), diphenylphosphine oxide
of 2. IR (KBr pellets, cmÀ1): n = 3061, 2959, 2868, 2361, 2342, (0.202 g, 1.0 mmol), and 5.0 mL of THF, and then b-nitro-
1630, 1589, 1553, 1460, 1553, 1460, 1369, 1341, 1182, 1099, 932, styrene (0.150 g, 1.0 mmol) was added to the mixture. The
839, 745. Anal. calc. for C40H77LiN5OSi6DyÁC7H8: C, 52.55; H, mixture was stirred at room temperature for 6 hours. After the
7.98; N, 6.52. Found: C, 52.29; H, 7.87; N, 6.46.
reaction was completed, the reaction mixture was hydrolyzed by
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water, extracted with ethyl ether, dried over anhydrous sodium
sulfate, and then filtered. After the solvent was removed under
reduced pressure, the final products were further purified by
recrystallization from ethyl acetate or column chromatography.
Compound 8 was isolated as a white solid (0.332 g, 95%). The
full characterization data for the resulting products can be
found in the ESI.†
Results and discussion
Synthesis of rare-earth metal complexes with imino-
functionalized 8-hydroxyquinolyl ligands
Treatment of rare-earth metal amides [(Me3Si)2N]3RE(m-Cl)Li-
(THF)3 (RE = Y, Er, Dy) with 1 equiv. of 2-(2,6-diisopropylphenyl-
imino)-8-hydroxyquinoline (1) in toluene at 40 1C produced the
heterometallic rare-earth metal complexes 2–4 (Scheme 1). While
reactions of rare-earth metal amides [(Me3Si)2N]3RE(m-Cl)Li(THF)3
(RE = Sm, Er, Yb) with 2 equiv. of compound 1 in toluene at 40 1C
gave the heterometallic rare-earth metal complexes 5–7. Complex 3
further reacted with 1 equiv. of compound 1 to also afford
complex 6 (Scheme 1). Complexes 2–7 are sensitive to air and
moisture, they have a good solubility in either polar solvents or
nonpolar solvents. The complexes were fully characterized by
spectroscopic methods, elemental analyses, and single crystal
X-ray diffraction.
Fig. 1 Representative molecular structure of complex 3. Hydrogen atoms
were omitted for clarity.
X-ray diffraction analyses revealed that complexes 2–4 were
isostructural heterometallic rare-earth metal and lithium com-
plexes bridged by the oxygen atom of 2-(2,6-diisopropylphenyl-
imino)-8-hydroxyquinolyl and the nitrogen atom of N(SiMe3)2.
Rare-earth metal adopted a four-coordinated distorted tetra-
hedral configuration, and lithium adopted a three-coordinated
distorted trigonal configuration. A representative structure
diagram of complex 3 is shown in Fig. 1. Complexes 5–7 were
another type of heterometallic rare-earth metal and lithium
bridged by the oxygen atoms of the 2-(2,6-diisopropylphenyl-
imino)-8-hydroxyquinolyl ligand, and a representative structure
diagram of complex 6 is shown in Fig. 2. In complexes 5–7,
rare-earth metal and lithium all adopted a four-coordinated
Fig. 2 Representative molecular structure of complex 6. Hydrogen atoms
and isopropyl groups were omitted for clarity.
distorted tetrahedral configuration. The selected bond lengths
and angles were listed in Table 1.
In Table 1, the bond length of the corresponding RE(1)–N(5)
is slightly longer than RE(1)–N(3) and RE(1)–N(4) in complexes
2–4, due to the different coordination environment. The bond
lengths of Li(1)–N(2) in complexes 2 (2.649(7) Å), 3 (2.656(10) Å),
4 (2.672(18) Å) are dramatically longer than the corresponding
bond lengths of Li(1)–N(1) and Li(1)–N(5) ranging from 2.029(6) Å
to 2.236(9) Å. Therefore, lithium metals were thought to adopt a
three-coordinated distorted trigonal configuration. The average
RE–N bond lengths of 2.280(3) Å in 2, 2.266(3) Å in 3, and
2.289(6) Å in 4 are well consistent with their ionic radii
sequence. The average Y–N bond length of 2.280(3) Å in 2 is
shorter than that of 2.456 (4) Å found in [2-(2,6-iPr2C6H3NC(H)-
C6H4-C9H6N)Y(CH2SiMe3)2(THF),8a probably due to the bulkiness
of the ligand and different coordinated number of rare-earth
metal. In complexes 5–7, RE(1), Li(1), O(1), and O(2) are nearly
coplanar to form a square plane with a sum of the bond angles of
359.291 for 5, 359.241 for 6 and 359.261 for 7. The average RE–N
bond lengths of 2.287(3) Å in 5, 2.214(3) Å in 6, and 2.188(6) Å in 7
are well consistent with their ionic radii sequence due to the
lanthanide contraction. The average RE–N bond lengths of
2.287(3) Å in 5, and 2.188(6) Å in 7 are compared with the
Scheme 1 Synthesis of heterometallic rare-earth metal complexes 2–7.
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Table 1 Selected bond lengths (Å) and bond angles (1)
Table 2 Optimizations for the addition of diphenylphosphine oxide to
b-nitrostyrenea
2 (Y)
2.149(2)
3 (Er)
2.142(3)
4 (Dy)
2.172(5)
RE(1)–O(1)
RE(1)–N(3)
RE(1)–N(4)
RE(1)–N(5)
Li(1)–N(1)
Li(1)–N(2)
Li(1)–N(5)
Li(1)–O(1)
2.259(3)
2.242(3)
2.338(3)
2.029(6)
2.649(7)
2.232(7)
2.221(7)
2.229(3)
2.241(3)
2.327(3)
2.030(9)
2.656(10)
2.236(9)
2.213(9)
2.260(6)
2.251(6)
2.357(6)
2.049(17)
2.672(18)
2.222(17)
2.208(18)
Entry
Cat. (mol%)
Solvent
Time (h)
Yieldb (%)
1
2
3
4
5
6
7
8
2 (1)
2 (3)
2 (5)
2 (5)
2 (5)
2 (5)
2 (5)
2 (5)
3 (5)
4 (5)
5 (5)
6 (5)
7 (5)
THF
THF
THF
THF
24
24
24
6
1
6
6
6
6
6
51
78
95
95
42
90
92
25
94
93
90
91
93
O(1)–RE(1)–N(3)
O(1)–RE(1)–N(4)
O(1)–RE(1)–N(5)
N(3)–RE(1)–N(4)
N(3)–RE(1)–N(5)
N(4)–RE(1)–N(5)
O(1)–Li(1)–N(1)
O(1)–Li(1)–N(5)
N(1)–Li(1)–N(5)
Li(1)–N(5)–RE(1)
RE(1)–O(1)–Li(1)
82.53(9)
117.11(9)
100.89(9)
113.23(10)
123.36(10)
113.23(10)
78.5(2)
83.4(2)
158.8(4)
88.78(19)
94.05(17)
82.57(11)
117.22(13)
100.88(13)
113.19(12)
123.00(12)
114.12(12)
78.0(3)
83.2(3)
157.3(5)
88.5(3)
93.9(2)
82.5(2)
117.6(2)
99.8(2)
113.8(2)
123.9(2)
112.9(2)
77.8(6)
84.9(6)
158.7(9)
88.2(5)
93.4(4)
THF
Toluene
Et2O
n-Hexane
THF
THF
THF
9
10
11
12
13
6
6
6
THF
THF
a
Reactions were performed with 1.0 mmol of diphenylphosphine oxide
and 1.0 mmol of b-nitrostyrene, solvent (5 mL), room temperature.
Isolated yield.
5 (Sm)
6 (Er)
7 (Yb)
b
RE(1)–O(1)
RE(1)–O(2)
RE(1)–N(5)
RE(1)–N(6)
Li(1)–O(1)
Li(1)–O(2)
Li(1)–N(1)
Li(1)–N(3)
2.287(2)
2.208(2)
2.288(3)
2.285(3)
1.989(6)
2.281(7)
2.043(7)
2.009(6)
2.201(2)
2.129(2)
2.215(3)
2.212(3)
1.978(7)
2.276(8)
2.041(7)
2.004(7)
2.178(2)
2.107(2)
2.193(3)
2.182(3)
1.978(6)
2.243(7)
2.037(7)
2.008(6)
Table 3 Addition of diphenylphosphine oxide to b-aryl nitroalkene cat-
alyzed by complex 7a
O(1)–RE(1)–O(2)
N(5)–RE(1)–N(6)
O(1)–RE(1)–N(5)
O(1)–RE(1)–N(6)
O(2)–RE(1)–N(5)
O(2)–RE(1)–N(6)
O(1)–Li(1)–O(2)
N(1)–Li(1)–N(3)
O(1)–Li(1)–N(1)
O(1)–Li(1)–N(3)
O(2)–Li(1)–N(1)
O(2)–Li(1)–N(3)
RE(1)–O(1)–Li(1)
RE(1)–O(2)–Li(1)
82.29(8)
118.72(11)
128.65(10)
102.46(9)
96.44(10)
124.87(11)
87.4(3)
128.8(3)
84.0(2)
145.7(4)
102.3(3)
76.8(2)
84.64(9)
118.31(13)
128.42(11)
103.23(10)
97.75(11)
120.82(12)
86.2(3)
127.1(3)
84.8(3)
145.8(4)
100.7(3)
76.7(2)
84.35(8)
117.91(11)
129.58(10)
102.09(9)
97.58(10)
122.30(11)
85.7(2)
126.7(3)
85.0(2)
146.3(3)
102.1(3)
77.3(2)
Entry
1
Substrate
Product
Yieldb (%)
95
8
2
3
9
85
93
10
97.7(2)
91.91(18)
97.4(2)
91.00(18)
97.4(2)
91.81(18)
4
11
96
corresponding RE–N bond lengths of 2.319(6) Å in [(Me3Si)2N]3Sm-
(m-Cl)Li(THF)316a and 2.211(5) Å in [(Me3Si)2N]3Yb(m-Cl)Li(THF)3.16b
The average Yb–O bond length of 2.143(2) Å in 7 is compared
with 2.179(8) Å in L2YbN(TMS)2 (L = 3,5-tBu2-2-(O)-C6H2CHQN-8-
C9H6N).8b
5
6
7
8
12
13
14
89
87
90
Catalytic addition of diphenylphosphine oxide to trans-b-
nitroalkenes
With above complexes in hand, the catalytic addition of diphenyl-
phosphine oxide to the trans-b-nitrostyrene was examined,
and results were summarized in Table 2. Complex 2 was first
employed as a catalyst for the hydrophosphination of b-nitro-
styrene. Results showed that 5 mol% of the catalyst 2 could
efficiently catalyze the hydrophosphination of b-nitrostyrene to
afford the product 8 as the only regioselective product. It was
found that running the reactions in solvents such as toluene,
THF, and diethyl ether afforded the product 8 in high yields
15
16
90
89
9
a
Reaction conditions: substrate (1.0 mmol), Ph2P(O)H (1.0 mmol),
b
reaction time: 6 hour. Isolated yield.
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Table 4 Crystallographic data for complexes 2–7
2
3
4
5
6
7
Formula
Formula weight
Cryst system
Space group
a (Å)
b (Å)
c (Å)
C40H77YLiN5OSi6 C40H77ErLiN5OSi6 C40H77DyLiN5OSi6 C56H81LiN6O2Si4Sm C56H81LiN6O2Si4Er C56H81LiN6O2Si4Yb
908.46
Orthorhombic
Pbca
986.81
Orthorhombic
Pbca
982.05
Orthorhombic
Pbca
1140.93
Monoclinic
P21/n
1156.83
Monoclinic
P21/n
1162.61
Monoclinic
P21/n
15.529(1)
23.551(1)
33.002(2)
90
12069.7(11)
293(2)
15.531(1)
23.556(2)
32.975(2)
90
12063.7(13)
293(2)
15.561(1)
23.561(2)
33.081(3)
90
12128.4(19)
293(2)
16.567(1)
17.468(1)
22.508(2)
104.071(1)
6318.1(8)
293(2)
16.457(2)
17.610(2)
22.508(2)
104.279(1)
6265.4(10)
293(2)
16.489(1)
17.569(1)
22.319(1)
104.437(1)
6261.4(6)
293(2)
b (deg)
V (Å3)
T (K)
Z
8
8
8
4
8
4
Dcalcd (g cmÀ3
)
1.000
1.114
3888
1.087
1.539
4120
1.076
1.379
4104
1.199
1.046
2388
1.227
1.457
2412
1.234
1.611
2416
m (mmÀ1
F(000)
)
y range (deg)
Reflns collected
Unique reflns
1.69 to 27.50
101 453
13 849
1.69 to 27.45
99 412
13 766
1.68 to 27.69
99 998
14 131
1.49 to 27.80
54 457
14 810
1.39 to 25.00
44 071
11 042
1.49 to 27.59
53 755
14 452
(Rint = 0.1617)
509
0.0564
0.1075
1.069
(Rint = 0.0673)
509
0.0420
0.1063
1.059
(Rint = 0.1144)
509
0.0689
0.2024
0.998
(Rint = 0.0405)
651
0.0442
0.0982
1.022
(Rint = 0.0386)
651
0.0363
0.1034
1.071
(Rint = 0.0432)
651
0.0394
0.0661
1.009
Parameters
R1 (I 4 2s(I))
wR2 (I 4 2s(I))
Goodness of fit
Largest diff peak/hole (e ÅÀ3) 0.335 and À0.409 1.033 and À0.616 1.601 and À1.061 1.523 and À0.714 1.337 and À0.988 1.187 and À1.124
(Table 2, entries 1–7), while running the reaction in n-hexane
afforded the product 8 in a low yield (Table 2, entry 8). When
the reaction was conducted in the absence of a catalyst, no
addition product 8 was isolated under the same conditions.
The catalytic activities of the above different rare-earth metal
complexes towards hydrophosphination of b-nitrostyrene
were investigated with 5 mol% of catalyst loading using THF
as a solvent. It is found that all complexes 2–7 exhibited a high
catalytic activity on the hydrophosphination of b-nitrostyrene
(Table 2, entries 9–13), indicating that the ionic radii of the
lanthanide metals and coordination modes of the central
metal have little influence on the catalytic activities of the
catalysts.
Evidence that different lanthanide metal complexes exhi-
bited a similar catalytic activity. Next, we examined the substrate
scope of the catalytic addition of diphenylphosphine oxide to
different b-nitroalkene employing complex 7 as a catalyst, and
the results were listed in Table 3. From Table 3, we can see that
complex 7 exhibited a high catalytic activity on the catalytic
addition for different b-nitroalkene despite the electronic nature
and the steric effect of the substituents on the aryl groups
(Table 3, entries 1–9). When the substituents on the phenyl ring
are the electron-donating groups such as CH3O–, CH3–, products
9–11 can be isolated in high yields (Table 3, entries 2–4). When
the substituents on the phenyl ring are the electron-withdrawing
ones such as Cl–, Br–, products 12–15 can also be isolated in
satisfactory yields (Table 3, entries 5–8). For (E)-2-(2-nitrovinyl)-
naphthalene, product 16 was also obtained in a good yield of
89% (Table 3, entry 9).
Scheme 2 Proposed mechanism of the addition of diphenylphosphine
oxide to trans-b-nitroalkenes catalyzed by rare-earth metal complexes.
addition of phosphorous to the coordinated C–C double bond of
nitroalkene and finally protonolysis of the intermediate by
diphenylphosphine oxide to release the addition product with
a completion of the catalytic cycle (Scheme 2).
Conclusions
Two series of novel heterometallic rare-earth metal complexes
Based on the previous mechanism on hydrophosphination bearing imino-functionalized 8-hydroxyquinolyl ligands were
of phosphinoalkenes catalyzed by lanthanide amides,17 the synthesized via reactions of [(Me3Si)2N]3RE(m-Cl)Li(THF)3 with
catalytic addition pathway of diphenylphosphine oxide to different equiv. of 2-(2,6-diisopropylphenylimino)-8-hydroxy-
trans-b-nitroalkene is proposed involving the initial Ln-N(SiMe3)2 quinoline. X-ray diffraction analyses revealed that complexes
protonolysis to generate Ln-OPPh2, followed by the intramolecular 2–4 were isostructural heterometallic rare-earth metal and lithium
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complexes bridged by the oxygen atom of 2-(2,6-diisopropyl-
phenylimino)-8-hydroxyquinoline and the nitrogen atom of
N(SiMe3)2. However, complexes 5–7 were another type of hetero-
metallic rare-earth metal and lithium bridged by the oxygen
atoms of 2-(2,6-diisopropylphenylimino)-8-hydroxyquinoline. All
complexes exhibited an excellent catalytic activity on the hydro-
phosphinylation of b-nitroalkene derivatives.
Acknowledgements
Financial support for this work from the National Natural
Science Foundation of China (21432001, 21372010, 21172003),
the National Basic Research Program of China (2012CB821600)
is acknowledged, and grant from Anhui Normal University is
also acknowledged.
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