Syntheses, structure, and properties of mixed Cp-amidinate rare-earth-Metal(III) Complexes

Article abstract of DOI:10.1021/om400856d

A family of mixed Cp-amidinate rare-earth-metal(III) complexes [Cp ₂L¹LnPhCN] (Ln = Y (1), La (2), Sm (3), Eu (4), Gd (5), Tb (6), Dy (7); L¹ = PhC(NSiMe₃)₂), [Cp ₂L¹Ln] (Ln = Er (8), Yb (9)), and [Cp₂L ²Ln] (Ln = Y (10), Eu (11), Gd (12), Tb (13), Dy (14), Er (15); L² = N(t-Bu)C(Ph)N(SiMe₃)) were synthesized by treatment of Cp₃Ln with lithium amidinates. The phase transition has been observed for compounds 5 and 9 at low temperature (200 K). Single-crystal structural analyses reveal that compounds 1, 3, 4, 5b, 6, 7, 9b, and 10-15 contain two staggered Cp rings. In contrast, two eclipsed Cp rings were observed in compounds 2, 5a, 8, and 9a. Moreover, the luminescent properties of complex 6 and magnetic properties of complex 7 were also investigated.

Full text of DOI:10.1021/om400856d

Article
pubs.acs.org/Organometallics
Syntheses, Structure, and Properties of Mixed Cp−Amidinate Rare-
Earth-Metal(III) Complexes
Jun-Feng Liu,†,‡ Fu-Xing Pan,†,‡ Shuang Yao,† Xue Min,†,‡ Dongmei Cui,§ and Zhong-Ming Sun*,†
†State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences,
5625 Renmin Street, Changchun, Jilin 130022, People’s Republic of China
‡University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China
§Changchun Institute of Applied Chemistry, State Key Laboratory of Polymer Physics and Chemistry, Chinese Academy of Sciences,
5625 Renmin Street, Changchun, Jilin 130022, People’s Republic of China
S
* Supporting Information
ABSTRACT: A family of mixed Cp−amidinate rare-earth-
metal(III) complexes [Cp2L1LnPhCN] (Ln = Y (1), La (2),
Sm (3), Eu (4), Gd (5), Tb (6), Dy (7); L1 = PhC-
(NSiMe3)2), [Cp2L1Ln] (Ln = Er (8), Yb (9)), and
[Cp2L2Ln] (Ln = Y (10), Eu (11), Gd (12), Tb (13), Dy
(14), Er (15); L2 = N(t-Bu)C(Ph)N(SiMe3)) were synthe-
sized by treatment of Cp3Ln with lithium amidinates. The
phase transition has been observed for compounds 5 and 9 at
low temperature (200 K). Single-crystal structural analyses
reveal that compounds 1, 3, 4, 5b, 6, 7, 9b, and 10−15 contain
two staggered Cp rings. In contrast, two eclipsed Cp rings
were observed in compounds 2, 5a, 8, and 9a. Moreover, the luminescent properties of complex 6 and magnetic properties of
complex 7 were also investigated.
On the other hand, reactions based on tris(cyclopentadienyl)
rare-earth-metal(III) species Cp3Ln have aroused longstanding
interest in the synthesis of mixed ligand supported organic rare-
earth-metal complexes,13 which often exhibit unique chemical
reactivities and magnetic properties.1b,c,14 Alcohol,15 thiol,15h,16
hydroxylaminato,17 and amino14,18 ligands have been widely
used to prepare new organic rare-earth-metal compound-
s,2a−p,13 in which the cyclopentadienyl Cp ring can be easily
substituted by these ligands mentioned above. Generally, the
majority of the obtained target complexes have di- or trinuclear
frameworks and the O or N atoms in the ligand can serve as
bridging atoms. In addition, various rare-earth/aluminum
heterobimetallic complexes have been reported by Roesky
and co-workers using Cp3Ln and the aluminum monohydr-
oxide L′AlOH(Me) (L′ = CH(CMeNAr)2, Ar = 2,6-iPr2C6H3)
as precursors.19 The new class of rare-earth/aluminum
heterobimetallic compounds as catalysts is very effective for
the polymerization of ε-caprolactone. Recently, the function-
alization of rare-earth metallocenes was investigated through
the reactions of Cp3Ln with various unsaturated molecules.20,21
INTRODUCTION
■
Over the past decades, organolanthanide chemistry has
attracted considerable attention in materials science due to
their unique properties in single-molecule magnets (SMMs),1
catalytic transformations,2,3and atomic layer deposition (ALD)
and metal−organic chemical vapor deposition (MOCVD)
processes.2,4 Amidinate ligands [R1NC(R3)NR2]− (L−; R1, R2 =
H, alkyl, cycloalkyl, aryl, trimethylsilyl; R3 = H, alkyl, aryl) are
very popular in the synthesis of lanthanide complexes because
of their versatile steric and electronic properties, which can be
easily tuned by changing various groups on R1, R2, and R3.5
Edelmann and co-workers made pioneering contributions in
the rare-earth-metal chemistry of amidinate ligands.5 In general,
the rare-earth-metal amidinate complexes can be obtained by
the reactions between amidinate ligands and rare-earth-metal
precursors. Alternatively, the Junk group also synthesized rare-
earth-metal amidinate complexes using elemental rare-earth
metals, organomercury reagents, and formamidinate ligands
[R1NC(H)NR2] (LH) as reactants.6 Some of the divalent rare-
earth-metal amidinate complexes have the unique properties of
reduction to cleave the E−E bond in the diaryl dichalcogenides
REER (R = aryl; E = Se, Te),7 activate C−X bonds,6f,h and
reduce carbodiimides.6e In addition, the catalytic activities of
the trivalent rare-earth-metal amidinate complexes were also
studied,5b−d,l,8 such as the Tishchenko reaction,6d polymer-
ization of olefins9 and dienes,10 intramolecular hydroamina-
tion/cyclization reactions,11 and ring-opening polymerization of
rac-lactide.12
i
For example, the reaction of Cp3Y with PrN=CNiPr in
toluene gave rise to an amidino-substituted cyclopentadienyl
yttrium complex, as a result of Ln−Cp bond insertion and
subsequent isomerization.21a
Received: August 26, 2013
Published: March 7, 2014
© 2014 American Chemical Society
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In comparison with the above achievements of rare-earth-
metal complexes, only a few studies on the chemistry of rare-
earth-metal complexes containing a mixed cyclopentadienyl−
amidinate (Cp-amidinate) ligand have been reported,22,23 and
the utilization of the mixed Cp−amidinate rare-earth-metal
complexes in materials chemistry remains unexplored.2a−p,5
Herein, we describe the synthesis and characterization of mixed
Cp−amidinate rare-earth-metal complexes starting from the
simple Cp3Ln and alkali-metal salt of amidinate precursors
(Schemes 1 and 2). Furthermore, a phase transformation
occurring in the crystal structures has been observed when the
temperature is changed. In addition, the luminescent properties
of complex 6 and magnetic properties of complex 7 have also
been investigated in this contribution.
RESULTS AND DISCUSSION
■
Synthesis and Structure of Mixed Cp−Amidinate
Rare-Earth-Metal(III) Complexes 1−9. As shown in Scheme
1, to a solution of LiL1 and PhCN in Et2O was added the
Figure 1. ORTEP representation of complex 1 with the probability
ellipsoids drawn at the 30% level. Hydrogen atoms are omitted for
clarity.
Scheme 1. Synthesis of Mixed Cp−Amidinate Rare-Earth-
Metal(III) Complexes 1−9
Å and N2−C1 1.340(4) Å). The N(1)−Y−N(2) and N(1)−
C(1)−N(2) angles are 57.09(10) and 118.3(3)°, respectively.
Similar to the case for compound 1, compound 2 was also
obtained as colorless crystals in 51% yield. The feature of
compound 2 is that the two cyclopentadienyl rings are arranged
in an eclipsed orientation with respect to each other (Figure S1,
Supporting Information). Unlike the case for compound 1, the
distances of La−N(1) and La−N(2) in compound 2 are equal
(La−N(1) 2.521(3) Å and La−N(2) 2.526(3) Å). The La−
N(3) distance in compound 2 is 2.679(3) Å, which is longer
than the Y−N(3) bond length in compound 1. The N−C
distances of the amidinate ligand in compound 2 are also
similar (N(1)−C(1) 1.327(5) Å and N(2)−C(1) 1.333(4) Å).
The N(1)−La−N(2) bite angle (54.07(10)°) is decreased in
comparison to that in compound 1, but the acute N(1)−C(1)−
N(2) bite angle of the amidimate ligand in compound 2
(119.1(3)°) is slightly larger than that in compound 1.
The structures of complexes 3, 4, 5a, 6 and 7 are more
similar to that of complex 1 on account of bearing two
staggered cyclopentadienyl rings. Due to the lanthanide
contraction effect, the corresponding Ln−N(1)/N(2) bond
lengths slightly decrease with the reduction of the metal ion
radius in compounds 3, 4, 5b, 6 and 7 (Figure 2A). On the
other hand, the N(1)−Ln−N(2) angles for compounds 3, 4,
5b, and 7 slightly increase with the reduction of the lanthanide
ion radius (Figure 2B). However, a particular exception occurs
in compound 6, in which the N(1)−Tb−N(2) angle is smaller
than those of compounds 5b and 7 (Figure 2B).
appropriate Cp3Ln species at ambient temperature to give rise
to the corresponding Cp2L1LnPhCN (Ln = Y (1), La (2), Sm
(3), Eu (4), Gd (5), Tb (6), Dy (7)). Interestingly, analogous
reactions led to Cp2L1Ln (Ln = Er (8), Yb (9)) under similar
conditions.
The X-ray diffraction analysis of single crystals of complexes
1−4, 5a, 6−8, and 9a was carried out at room temperature, and
the corresponding data of the compounds 5b and 9b were also
obtained at low temperature (Tables S1 and S2, Supporting
Information) (compound 5 has a phase transition at low
temperature; compounds 5a,b are identical and are obtained at
room and low temperature, respectively; compound 9 is similar
to compound 5). The X-ray structure characterizations for
complexes 1−7 indicate that these compounds are isostructural
and adopt the same triclinic space group P1. The corresponding
̅
data of compounds 8 and 9a show that they are also
isostructural and crystallize in the orthorhombic crystal system
with the space group Pnma, while compound 9b adopts
monoclinic space group C2/c.
Figure 1 shows representative features of the isostructural
complexes 1−7 in which each central metal atom is coordinated
by one amidinate ligand, two cyclopentadienyl rings, and one
neutral benzonitrile molecule. The two cyclopentadienyl rings
of complexes 1, 3, 4, 5b, 6, and 7 were staggered, while an
eclipsed conformation was observed in complexes 2 and 5a.
Compound 1, shown in Figure 1, was collected as colorless
crystals in 46% yield. This complex contains two staggered
cyclopentadienyl rings. The Y−N(2) length is 2.393(3) Å and
is shorter than that of Y−N(1) (2.410(3) Å). As expected, the
distance between the metal center and the nitrogen atom in the
benzonitrile molecule is 2.526(4) Å (Y−N(3)), slightly longer
than those of Y−N(1) and Y−N(2). The C−N distances of the
delocalized N−C−N ligand are similar (N(1)−C(1) 1.333(4)
It is interesting and noteworthy that the two cyclo-
pentadienyl rings of complex 5 adopt a staggered conformation
at low temperature (5b) (Figure S5, Supporting Information),
while they are eclipsed at room temperature (5a) (Figure S4,
Supporting Information). This phenomenon indicates that
compound 5 has a phase transition at low temperature (Figure
3). To the best of our knowledge, this behavior has not been
documented in mixed Cp−amidinate rare-earth-metal com-
plexes. The phase transition phenomenon is also reflected on
the corresponding cell parameters, with the cell volume
reduced at a ratio of 4.2% (Table S1, Supporting Information).
The Ln−N(1)/N(2) distances in compound 5a containing two
staggered rings (Gd−N(1) 2.526(4) Å and Gd−N(2) 2.529(4)
Å) are not only longer than corresponding values of compound
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as multiplets between 10.50 and 6.52 ppm. Moreover, a single
peak at −3.48 ppm is attributed to the characteristic SiMe3
resonance.
In comparison to compounds 1−7, the features of
compounds 8 (Figure S8, Supporting Information), 9a (Figure
S9, Supporting Information) and 9b (Figure 4) are the loss of
Figure 4. ORTEP representation of complex 9b with the probability
ellipsoids drawn at the 30% level. Hydrogen atoms are omitted for
clarity.
benzonitrile ligand and adoption of a more highly symmetric
space group. Obviously, there is not enough room for
compounds 8 and 9 to accommodate the coordination of
other ligands due to the smaller ionic radii of Er3+ and Yb3+.
Similar to the case for compounds 2 and 5a, compounds 8 and
9a contain two eclipsed cyclopentadienyl rings. The Ln−N
distances of compound 8 (Er−N(1) 2.309(4) Å and Er−N(2)
2.315(5) Å) are slightly longer than those of compound 9a
(Yb−N(1) 2.289(4) Å and Yb−N(2) 2.303(4) Å). Their
N(1)−Ln−N(2) angles are similar (58.96(17)° (8) and
59.75(14)° (9a)). Interestingly, the phase transition phenom-
enon is also observed in compounds 9a,b when the
temperature is changed (Figure 5). In comparison to
Figure 2. Ln−N(1)/N(2) distances (A) and N(1)−Ln−N(2) angles
(B) of compounds 3 (Sm), 4 (Eu), 5b (Gd), 6 (Tb), and 7 (Dy).
Figure 3. Phase transition of complex 5.
Figure 5. Phase transition of complex 9.
5b containing two staggered rings (Figure S8, Supporting
Information) but also longer than those of compound 3 (Sm−
N(1) 2.444(3) Å and Sm−N(2) 2.432(4) Å). However, the
N(1)−Ln−N(2) angle of 53.83(13)° in compound 5a is
smaller than the corresponding angles of compounds 3, 4, 5b,
6, and 7 (Figure 2B). On the other hand, the data of
compounds 2 and 5a with regard to Ln−N(1)/N(2) bond
lengths and N(1)−Ln−N(2) angles are very similar because of
two eclipsed rings exist in both complexes.
compound 9a, compound 9b contains two staggered cyclo-
pentadienyl rings and adopts a lower space group (monoclinic
group C2/c). The bond lengths and bond angle of compound
9b (Yb−N(1) 2.285(4) Å, Yb−N(2) 2.296(4) Å, and N(1)−
Yb−N(2) 59.55(14)°) are similar to those of compound 9a.
Moreover, due to the paramagnetism of the ytterbium atom,
1
only broad signals were observed in the H NMR spectrum of
compound 9.7c,11b
Compound 3 was confirmed by NMR spectroscopy. In the
1H NMR spectrum, only one signal was observed at low field
for the two cyclopentadienyl rings (1H NMR δ 10.72 ppm).
The signals for chemical shifts of the aromatic protons appear
Synthesis and Structure of Mixed Cp−Amidinate
Rare-Earth-Metal(III) Complexes 10−15. As shown in
Scheme 2, treatment of LiL2 and PhCN in Et2O with the
appropriate Cp3Ln species at ambient temperature gave
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Pnma) and lower symmetry space group (monoclinic group
C2/c), respectively.
Scheme 2. Synthesis of Complexes 10−15
Fluorescent Properties. It is well-known that the rare-
earth-metal compounds play an important role in materials
chemistry, due to their distinctive and excellent luminescent
performance. Recently, a few works on the luminescent
properties of rare-earth-metal amidinate complexes have been
documented.28 In 2011, the luminescent properties of a
divalent europium silaamidinate complex were reported by
Pan and co-workers.28 In the divalent lanthanide complex, the
emission peak at 528 nm can be contributed to the 4f−5d
transition of Eu2+. We report here the fluorescent properties of
the mixed Cp−amidinate trivalent terbium complex. The
emission spectrum of [Cp2L1TbPhCN] (6) was measured.
The characteristic transitions for the Tb3+ ion were observed at
Cp2L2Ln (Ln = Y (10), Eu(11), Gd (12), Tb (13), Dy (14), Er
(15)), respectively. The X-ray crystal structures for complexes
10−15 indicate that these compounds are isostructural and
adopt the same monoclinic space group P21 (Tables S2 and
Table S3, Supporting Information).
Figure 6 shows a feature of the isostructural compounds 10−
5
15 in which two atoms (Si and C) of ligand L2 are jointly
493, 547, 590, and 623 nm, which can be attributed to D4
→7FJ (J = 6−3) (Figure 7). Among these transitions, the green
Figure 6. ORTEP representation of complex 10 with the probability
ellipsoids drawn at the 30% level. Partial hydrogen atoms are omitted
for clarity.
Figure 7. Excitation (black, λem 547 nm) and emission spectra (green,
λex 341 nm) of complex 6 as solid samples.
occupied. Similar to the case for compounds 8 and 9,
compounds 10−15 also have no benzonitrile ligand. Moreover,
although the two cyclopentadienyl rings in compounds 10−15
are staggered, they are very close to eclipsed. Similar to the case
for compound 1, the Y−N(1) length (2.315(4) Å) is longer
than that of Y−N(2) (2.305(5) Å) in compound 10. The Y−N
distances in compound 10 are shorter than those in compound
1, but the N(1)−Y−N(2) bite angle (58.4(2)°) in compound
10 is larger than that of compound 1. Additionally, the Ln−
N(1) distances and the N(1)−Ln−N(2) bite angles for
compounds 11−15 display the trends similar to those found
in compounds 3, 4, 5a, 6, and 7. However, the Tb−N(2) bond
length (2.354(5) Å) is the longest in compounds 11−15.
Phase Transition Behavior. Thirty years ago, some rare-
earth-metal complexes bearing two eclipsed cyclopentadienyl-
s,13,15a,b,16a,18c,21c,23a,24 pentamethylcyclopentadienyls
(C5Me5),13,25 and other substituted cyclopentadienyls13,26
have been observed previously by different research groups.
However, the eclipsed ring phenomenon occurring in rare-
earth-metal complexes has been almost entirely attributed to
the result of steric hindrance. In our investigation of the mixed
Cp−amidinate rare-earth-metal(III) complexes, the phase
transition of eclipsed cyclopentadienyl rings and staggered
cyclopentadienyl rings depend on the temperature, which is
similar to the case for ferrocene.27 For example, the eclipsed
cyclopentadienyl rings in compound 5a are observed at
ambient temperature; in contrast, compound 5b with staggered
cyclopentadienyl rings is more stable at low temperature.
Interestingly, as the phase transition occurs, compounds 9a,b
adopt a higher symmetry space group (orthorhombic group
7
emission at 547 nm (5D4 → F5) is the most prominent.
Unfortunately, in contrast to compound 6, the characteristic
transitions for the Tb3+ and Eu3+ ions were not observed in the
compounds [Cp2L2Tb] (13), [Cp2L1EuPhCN] (4), and
[Cp2L2Eu] (11).29
Magnetic Properties. Considering the magnetic properties
of Ln3+ ions,1 the temperature dependence of the magnetic
susceptibility χmT for compound 7 were measured in the
temperature range 2−300 K under an applied field of 1000 Oe
using polycrystalline samples (Figure S21, Supporting
Information). For compound 7, the value of χmT is 14.51
cm3 K mol−1 at 300 K, which is close to the expected value of
14.17 cm3 K mol−1 for a single Dy3+ ion (6H15/2, S = 5/2, L = 5,
30
4
g = /3). Upon cooling, the value of χmT for compound 7
slowly increases to reach a maximum of 14.99 cm3 K mol−1 at
50 K and then rapidly decreases to a minimum value of 11.60
cm3 K mol−1 at 2 K. These magnetic behaviors are attributed to
crystal-field effects such as thermal depopulation of the Dy3+
Stark sublevels.30 Alternating current (ac) susceptibility
measurements for compound 7 were carried out under zero
direct current (dc) field with an ac field of 3 Oe with oscillating
frequencies. As shown in Figure S23 (Supporting Information),
compound 7 exhibits frequency-dependent out-of-phase signals
without maxima, suggesting the presence of slow magnetic
relaxation at low temperature, which is due to extremely
efficient quantum tunneling of the magnetization within the
lowest Kramers doublet.
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(w), 2896 (w), 2254 (m),1642 (m), 1608 (w),1596 (m), 1565 (m),
1489 (w), 1446 (m), 1408 (s), 1247 (s), 1013 (w), 1003 (w), 988
(m), 951 (w), 918 (w), 825 (s), 745 (s), 697 (w), 681 (w).
CONCLUSION
■
A family of mixed Cp−amidinate rare-earth-metal(III)
complexes were prepared in a one-step reaction using Cp3Ln
and lithium salts of the amidinate ligands as precursors. There
are two staggered Cp rings in compounds 1, 3, 4, 5b, 6, 7, 9b,
and 10−15, whereas compounds 2, 5a, 8, and 9a contain two
eclipsed Cp rings. Interestingly, a phase transformation
occurring in the crystal structures for compounds 5 and 9
has been observed when the temperature is changed. Moreover,
the luminescent and magnetic properties of compounds 6 and
7 were also investigated.
Complex 6. Yield: 67 mg (51%) as yellowish crystals. Anal. Calcd
for 6, C30H38N3Si2Tb (Mr = 655.73): C, 54.95; H, 5.85; N, 6.41.
Found: C, 54.87; H, 5.90; N, 6.45. IR data (cm−1): 3062 (w), 2950
(w), 2896 (w), 2229 (w),1640 (m), 1594 (w),1565 (m), 1492 (w),
1451 (m), 1430 (m), 1366 (w), 1242 (m), 1051 (w), 1014 (w), 952
(w), 921 (w), 892 (w), 825 (m), 750 (m), 698 (m), 666 (w).
Complex 7. Yield: 75 mg (57%) as yellow crystals. Anal. Calcd for
7, C30H38N3Si2Dy (Mr = 659.31): C, 54.65; H, 5.82; N, 6.37. Found:
C, 54.68; H, 5.86; N, 6.41. IR data (cm−1): 3065 (w), 2952 (w), 2895
(w), 2250 (w),1643 (m), 1597 (w),1567 (w), 1498 (w), 1446 (w),
1401 (m), 1364 (w), 1245 (s), 1050 (w), 1014 (w), 1002 (w), 988
(w), 954 (w), 917 (w), 891 (w), 826 (s), 745 (m), 698 (m), 681 (w).
Complex 8. Yield: 51 mg (45%) as yellow-brown crystals. Anal.
Calcd for 8, C23H33N2Si2Er (Mr = 560.95): C, 49.24; H, 5.94; N, 5.00.
Found: C, 49.30; H, 5.84; N, 5.11. IR data (cm−1): 3082 (w), 2950
(w), 2893 (w), 1645 (m), 1594 (w), 1563 (w), 1499 (w), 1409 (s),
1261 (w), 1242 (s), 1072 (w), 1032 (w), 1005 (s), 995 (m), 963 (w),
918 (w), 888 (w), 827 (s), 751 (s), 701 (m), 685 (w).
EXPERIMENTAL SECTION
■
Materials, Syntheses, and Characterization. All manipulations
were carried out under a purified nitrogen atmosphere using modified
Schlenk techniques or in a N2 gas glovebox unless otherwise indicated.
Et2O, n-hexane, and THF were distilled under a nitrogen atmosphere
from sodium benzophenone prior to use. Cp3Ln (Ln = Y, La, Sm, Eu,
Gd, Tb, Dy, Er, Yb),31 Li[CPh(NSiMe3)2],5a,32 and Li[N(t-Bu)C-
(Ph)N(SiMe3)]33 were prepared by literature methods. Benzonitrile
and lithium bis(trimethylsilyl)amide were purchased from Alfa Aesar
and Sigma-Aldirich, respectively. They were directly used without
further purification. The deuterated solvent C6D6 was dried over
activated molecular sieves (4 Å) and vacuum-transferred before use.
NMR spectra were recorded on a Bruker 400 MHz spectrometer at
298 K. The elemental analyses of C, H, and N in the solid samples
were carried out on a VarioEL analyzer. IR spectra were obtained on a
Nicolet 6700 instrument in the range 4000−650 cm−1. The
luminescence spectra were recorded on a Hitachi F-4500 fluorescence
spectrophotometer. The photomultiplier tube (PMT) voltage was 400
V, the scan speed was 1200 nm/min, and the slit width of excitation
and emission is 5.0 nm. Temperature-dependent magnetic suscepti-
bility data were recorded on a Quantum Design MPMS-XL SQUID
magnetometer under an applied field of 1 kOe over the temperature
range 2−300 K.
Complex 9. Yield: 71 mg (63%) as yellow-brown crystals. Anal.
Calcd for 9, C23H33N2Si2Yb (Mr = 566.73): C, 48.74; H, 5.88; N, 4.94.
Found: C, 48.80; H, 5.84; N, 4.87. IR data (cm−1): 3082 (w), 2953
(w), 2894 (w), 1644 (m), 1593 (w),1562 (w), 1498 (w), 1420 (s),
1409 (s), 1262 (w), 1242 (s), 1073 (w), 1032 (w), 1004 (m), 993
(m), 959 (w), 918 (w), 828(m), 742 (m), 702 (w), 686 (w).
Synthesis of Complexes 10−15. To a mixture of Li[N(t-
Bu)C(Ph)N(SiMe3)] (LiL2; 0.25 mmol) and benzonitrile (PhCN;
0.25 mmol) in 5 mL of Et2O was added Cp3Ln (0.20 mmol) at room
temperature, and the mixture was stirred for 24 h. After filtration, the
resulting solution was stored at ambient temperature for several days
to obtain the desired compounds.
1
Complex 10. Yield: 40 mg (43%) as colorless crystals. H NMR
(400 MHz, C6D6): δ 7.04−6.99 (m, 3H, Ph), 6.92−6.90 (m, 2H, Ph),
6.27 (s, 10H, Cp), 0.90 (s, 9H, CMe3), −0.17 (s, 9H, SiMe3). Anal.
Calcd for 10, C24H33N2SiY (Mr = 466.52): C, 61.79; H, 7.14; N, 6.01.
Found: C, 61.56; H, 7.23; N, 6.08.
Complex 11. Yield: 54 mg (51%) as red crystals. Anal. Calcd for 11,
C24H33N2SiEu (Mr = 529.57): C, 54.43; H, 6.29; N, 5.29. Found: C,
54.39; H, 6.31; N, 5.33. IR data (cm−1): 3083 (w), 2955 (w), 2897
(w), 1612 (w), 1599 (w), 1572 (w), 1525 (w), 1489 (w), 1452 (w),
1368 (m), 1241 (m), 1076 (w), 1038 (w), 1011 (w), 962 (w), 914
(w), 829 (m), 746 (m), 700 (w), 667 (w).
Complex 12. Yield: 60 mg (56%) as yellowish crystals. Anal. Calcd
for 12, C24H33N2SiGd (Mr = 534.86): C, 53.89; H, 6.23; N, 5.24.
Found: C, 53.85; H, 6.27; N, 5.28. IR data (cm−1): 3082 (w), 2953
(w), 2899 (w), 1611 (w), 1599 (w), 1574 (w), 1524 (m), 1492 (w),
1463 (w), 1450 (m), 1369 (m), 1244 (m), 1154 (w), 1076 (w), 1042
(w), 1011 (m), 919 (w), 870 (w), 827 (w), 754 (m), 703 (w), 668
(w).
Complex 13. Yield: 58 mg (54%) as yellowish crystals. Anal. Calcd
for 13, C24H33N2SiTb (Mr = 536.53): C, 53.72; H, 6.21; N, 5.22.
Found: C, 53.68; H, 6.24; N, 5.27. IR data (cm−1): 3085 (w), 2959
(m), 2899 (w), 1611 (w), 1596 (w), 1574 (w), 1528 (m), 1491 (w),
1465 (w), 1451 (m), 1382 (m), 1244 (m), 1155 (w), 1075 (w), 1040
(w), 1011 (m), 984 (w), 921 (w), 870 (w), 828 (m), 757 (m), 703
(m), 666 (w).
Complex 14. Yield: 64 mg (59%) as yellowish crystals. Anal. Calcd
for 14, C24H33N2SiDy (Mr = 540.11): C, 53.37; H, 6.17; N, 5.19.
Found: C, 53.31; H, 6.20; N, 5.23. IR data (cm−1): 3081 (w), 2956
(m), 2899 (w), 1612 (m), 1600 (m), 1574 (w), 1524 (m), 1490 (w),
1460 (w), 1444 (w), 1392 (w), 1365 (m), 1238 (m), 1127 (w), 1050
(w), 1013 (w), 988 (w), 920 (w), 825 (m), 748 (m), 701 (m), 666
(w).
Complex 15. Yield: 40 mg (37%) as yellow-brown crystals. Anal.
Calcd for 15, C24H33N2SiEr (Mr = 544.87): C, 52.90; H, 6.12; N, 5.14.
Found: C, 52.85; H, 6.16; N, 5.19.
Synthesis of Complexes 1−9. To a mixture of Li[CPh-
(NSiMe3)2] (LiL1; 0.25 mmol) and benzonitrile (PhCN; 0.25
mmol) in 5 mL of Et2O was added Cp3Ln (0.20 mmol) at room
temperature, and the mixture was stirred for 24 h. After filtration, the
resulting solution was stored at ambient temperature for several days
to obtain the desired compounds.
Complex 1. Yield: 54 mg (46%) as colorless crystals. 1H NMR (400
MHz, C6D6): δ 7.01−6.98 (m, 5H, Ph), 6.89−6.87 (m, 2H, Ph), 6.80
(t, JH−H = 7.6 Hz, 1H, Ph), 6.64 (t, JH−H = 8.0 Hz, 2H, Ph), 6.25 (s,
10H, Cp), −0.14 (s, 18H, SiMe3). Anal. Calcd for 1, C30H38N3Si2Y
(Mr = 585.72): C, 61.51; H, 6.55; N, 7.18. Found: C, 61.45; H, 6.60;
N, 7.20.
Complex 2. Yield: 65 mg (51%) as colorless crystals. Anal. Calcd for
2, C30H38N3Si2La (Mr = 635.72): C, 56.68; H, 6.04; N, 6.61. Found: C,
56.61; H, 6.10; N, 6.65. IR data (cm−1): 3060 (w), 2952 (w), 2893
(w), 2229 (w), 1634 (m), 1567 (m), 1498 (w), 1450 (m), 1428 (w),
1363 (w), 1321 (w), 1251 (m), 1237 (m), 1209 (m), 1122 (w), 950
(m), 892 (w), 823 (m), 779 (w), 750 (m), 699 (m), 664 (m).
1
Complex 3. Yield: 84 mg (65%) as yellow crystals. H NMR (400
MHz, C6D6): δ 10.72 (s, 10H), 10.49 (d, JH−H = 7.2 Hz, 2H, Ph), 8.11
(t, JH−H = 7.2 Hz, 2H, Ph), 7.91 (t, JH−H = 7.2 Hz, 1H, Ph), 6.73−6.63
(m, 5H, Ph), −3.478 (s, 18H, SiMe3). Anal. Calcd for 3,
C30H38N3Si2Sm (Mr =647.16): C, 55.67; H, 5.93; N, 6.49. Found:
C, 55.27; H, 5.97; N, 6.53. IR data (cm−1): 3071 (w), 2937 (w), 2853
(w), 1627 (m), 1607 (m), 1590 (m), 1566 (m), 1449 (m), 1439 (m),
1363 (w), 1247 (w), 1237 (m), 1128 (w), 1012 (w), 946 (w), 889
(w), 842 (m), 825 (m), 748 (m), 725 (w), 701 (m), 666 (w).
Complex 4. Yield: 86 mg (66%) as red crystals. Anal. Calcd for 4,
C30H38N3Si2Eu (Mr = 648.77): C, 55.54; H, 5.92; N, 6.49. Found: C,
55.49; H, 5.95; N, 6.53.
Complex 5. Yield: 80 mg (61%) as yellowish crystals. Anal. Calcd
for 5, C30H38N3Si2Gd (Mr = 654.06): C, 55.09; H, 5.87; N, 6.43.
Found: C, 55.02; H, 5.90; N, 6.46. IR data (cm−1): 3061 (w), 2950
X-ray Crystal Structure Determination. Suitable crystals of
compounds 1−15 were covered in mineral oil (Aldrich). Crystallo-
1378
dx.doi.org/10.1021/om400856d | Organometallics 2014, 33, 1374−1381

Organometallics
Article
graphic data were collected at 200 or 293 K on a Bruker Apex II CCD
diffractometer with graphite-monochromated Mo Kα radiation (λ =
0.71073 Å). Data processing was accomplished with the SAINT
program.34 The structure was solved by direct methods and refined on
F2 by full-matrix least squares using SHELXTL-97.35 All non-hydrogen
atoms were refined with anisotropic displacement parameters during
the final cycles. All hydrogen atoms of the organic molecule were
placed by geometrical considerations and were added to the structure
factor calculations. A summary of the crystallographic data for
complexes 1−15 is given in the Supporting Information.
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ASSOCIATED CONTENT
* Supporting Information
■
S
Figures, tables, and CIF files giving X-ray crystallographic data,
a summary of crystal data for compounds 1−15, ORTEP
representation of compounds 3−8, 9a, and 11−15, lumines-
cence measurements of compounds 4, 11, and 13, magnetic
measurements of compound 7, and 1H NMR spectra of
compounds 1, 3 and 10. This material is available free of charge
via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail for Z.-M.S.: szm@ciac.ac.cn.
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We acknowledge the support of this work by the National
Nature Science Foundation of China (21171662), Jilin
Province Youth Foundation (20130522132JH), and SRF for
ROCS (State Education Ministry).
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