CNC-pincer rare-earth metal amido complexes with a diarylamido linked biscarbene ligand: synthesis, characterization, and catalytic activity

Article abstract of DOI:10.1021/om500354s

In preparation of CNC-pincer rare-earth metal amido complexes with a diarylamido linked biscarbene ligand, it is found that conditions have a key influence on final products. Reaction of a THF suspension of bis[2-(3-benzylimidazolium)-4-methylphenyl]amine

Full text of DOI:10.1021/om500354s

Article
pubs.acs.org/Organometallics
CNC-Pincer Rare-Earth Metal Amido Complexes with a Diarylamido
Linked Biscarbene Ligand: Synthesis, Characterization, and Catalytic
Activity
Xiaoxia Gu,† Xiancui Zhu,*,† Yun Wei,† Shaowu Wang,*,†,‡ Shuangliu Zhou,† Guangchao Zhang,†
and Xiaolong Mu†
†Laboratory of Functional 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: In preparation of CNC-pincer rare-earth metal amido
complexes with a diarylamido linked biscarbene ligand, it is found that
conditions have a key influence on final products. Reaction of a THF
suspension of bis[2-(3-benzylimidazolium)-4-methylphenyl]amine dichlor-
ides (H3LCl2) with [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 (RE = Yb, Eu, Sm) in
THF at room temperature afforded the only unexpected fused-heterocyclic
compound 8,9-dibenzyl-3,14-dimethyl-8a,9-dihydro-8H-benzo[4,5]imidazo-
[2′,1′:2,3]imidazo[1,2-a]imidazo[2,1-c]quinoxaline (1) containing an imi-
dazolyl ring and a piperidyl ring, which formed through carbene C−C and
C−N coupling. However, the reaction of H3LCl2 with [(Me3Si)2N]3Er(μ-
Cl)Li(THF)3 in toluene afforded the CNC-pincer erbium amido complex
incorporating a diarylamido linked biscarbene ligand LEr[N(SiMe3)2]2 (2)
in low yield and the above fused-heterocyclic compound 1. The stepwise
reaction of H3LCl2 with strong bases (n-BuLi or LiCH2SiMe3) in THF for 4
h, followed by treatment with [(Me3Si)2N]3RE(μ-Cl)Li(THF)3, generated zwitterion complexes [L2RE][RECl{N(SiMe3)2}3] (L
= [4-CH3-2-{(C6H4CH2-[N(CH)2CN]}C6H3]2N; RE = Y (3), Er (4), Yb (5)) in less than 20% yields together with fused-
heterocyclic compound 1. Additionally, the reaction of H3LCl2 with 6 equiv of NaN(SiMe3)2 in THF for 4 h, followed by
treatment with YbCl3, generated a novel discrete complex [L2Yb][{Na(μ-N(SiMe3)2)}5(μ5-Cl)] (6). The one-pot reaction of
H3LCl2 with n-BuLi, followed by reaction with [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 in THF at −78 °C, generated the CNC-pincer
lanthanide bisamido complexes LRE[N(SiMe3)2]2 (RE = Er (2), Y (7), Sm (8), Eu (9)) in moderate yields. These kinds of
biscarbene supported pincer bisamido complexes could also be prepared by a one-pot reaction of bis(imidazolium) salt (H3LCl2)
with 5 equiv of NaN(SiMe3)2, followed by treatment with RECl3, in good yields at −78 °C. Investigation of the catalytic activity
of complexes 2 and 7−9 indicated that all complexes showed a high activity toward the addition of terminal alkynes to
carbodiimides producing propiolimidines, which represents the first example of rare-earth metal CNC-pincer-type catalysts
applied for catalytic C−H bond addition of terminal alkynes to carbodiimides at room temperature.
the precise tailoring of the metal coordination sphere could
provide liable complexes and enable the complexes to be used
as homogeneous catalysis. Transition-metal complexes with
bis(NHC) ligands have been found to be efficient catalysts in
different catalytic reactions.11 However, bis(NHC)-incorpo-
rated tridenate pincer rare-earth metal complexes are quite rare:
Cui et al. reported CCC-pincer 2,6-xylentyl bis(NHC) rare-
earth metal dibromides,12 which exhibited a high activity and
cis-1,4 selectivity for isoprene polymerization in the presence of
cocatalysts;9b Arnold et al. reported the synthesis and reactivity
INTRODUCTION
■
Functionalized N-heterocyclic carbene (NHC) ligands have
attracted an increasing attention in organometallic chemistry
for their strong electron-donating property, easy modification,
and stablility since their first discovery. Thus, different types of
carbene ligands have been developed and applied in organo-
metallic chemistry.1,2 Recently, several examples of rare-earth
metal complexes bearing alkoxo-,3 aryloxo-,4 salicylamido-,5
amido-,6 indenyl-,7 and fluorenyl-8functionalized NHC ligands
and their catalytic activities in lactide polymerization,3a olefin
copolymerization,8a,b and isoprene polymerization9 were
documented. Bis(NHC)-incorporated tridentate CNC-pincer
ligand10 having strong electron-donating ylidene carbons and
Received: April 3, 2014
Published: April 29, 2014
© 2014 American Chemical Society
2372
dx.doi.org/10.1021/om500354s | Organometallics 2014, 33, 2372−2379

Organometallics
Article
of a yttrium complex with a tridentate amino bis(NHC)
ligand.13 The chemistry of rare-earth metal complexes with
bis(NHC) ligands requires to be developed.
Scheme 1. Formation of Fused-Heterocyclic Compound 1
Propiolamidines (RNC(CCR)(NHR)) are important
amidine derivatives not only being applicable in biological and
pharmaceutical systems14 but also being used as heteroallylic
ligands in coordination chemistry and catalysis.15 It is well-
established that the amidines {RNC(R)NHR} can be easily
prepared by the nucleophilic addition of organometallic
reagents RM to carbodiimides, followed by hydrolysis.16
However, the corresponding propiolamidines RNC(C
CR)(NHR), which contain a conjugated CC triple bond,
could hardly be obtained by hydrolysis of the propiolamidinate
precursors because of their high sensitivity to hydrolysis.16h The
addition of C−H bonds of terminal alkynes to carbodiimides
could provide a straightforward and atom-efficient route to
propiolamidines. Hou and co-workers for the first time
developed the half-sandwich yttrium alkyl complex {Me2Si-
(C5Me4)(NPh)}Y(CH2SiMe3)(THF)17 as a catalyst to accom-
plish the catalytic addition of C−H bonds of terminal alkynes
to carbodiimides; we found that the sandwich-type lanthano-
cene amido complexes (EBI)LnN(SiMe3)2 (EBI = ethylenebis-
(η5-indenyl))18a and cyclopentadienyl-free complexes {(CH2-
SiMe2)[(2,6-iPr2C6H3)N]2}LnN(SiMe3)2(THF)18b could cata-
lyze the addition of the terminal alkyne C−H bond to
carbodiimides to produce the corresponding propiolamidines
RNC(CCR)(NHR). However, elevated reaction temper-
atures (for example, 80 or 60 °C) are required to accomplish
the reaction to produce the desired products, so catalysts
operated at room temperature for catalytic addition of terminal
alkynes C−H bonds to carbodiimides are highly required. Here,
we will report the synthesis of CNC-pincer rare-earth metal
complexes bearing a diarylamido linked bis(NHC) ligand, and
their room temperature catalytic application for the addition of
terminal alkynes to carbodiimides. To the best our knowledge,
it represents the first example of CNC-pincer rare-earth metal
amido complexes incorporating a diarylamido linked bis(NHC)
ligand as catalysts for catalytic addition of terminal C−H bonds
of alkynes to carbodiimides for preparation of propiolamidines
at room temperature.
Figure 1. Structure of fused-heterocyclic compound 1. Hydrogen
atoms were omitted for clarity. Selected bond lengths: N(3)−C(10),
1.489(2) Å; N(2)−C(10), 1.474(2) Å; N(1)−C(10), 1.457(2) Å;
N(27)−C(10), 1.533(2) Å.
RESULTS AND DISCUSSION
■
the corresponding complexes similar to complex 2 could not be
obtained under the same conditions.
Attempts for Synthesis of CNC-Pincer Diarylamido
Linked Bis(NHC) Rare-Earth Metal Amido Complexes. To
synthesize the CNC-pincer diarylamido linked bis(NHC) rare-
earth metal amido complexes, the reaction of [(Me3Si)2N]3-
RE(μ-Cl)Li(THF)3 (RE = Sm, Eu, Yb) with 1 equiv of bis[2-
(3-benzylimidazolium)-4-methylphenyl]amine dichlorides
(H3LCl2) was first run in THF at room temperature; after
work-up, the unexpected novel fused-heterocylclic compound
8,9-dibenzyl-3,14-dimethyl-8a,9-dihydro-8H-benzo[4,5]-
imidazo[2′,1′:2,3]imidazo[1,2-a]imidazo[2,1-c]quinoxaline (1),
instead of the desired CNC-pincer complex (Scheme 1, Figure
1), was isolated (as high as 42% yield). This compound is
believed to form through carbene C−C coupling, followed by
C−N coupling.
When the solvent was changed from THF to toluene, an
equimolar reaction between [(Me3Si)2N]3Er(μ-Cl)Li(THF)3
and H3LCl2 run at room temperature, after work-up, generated
the CNC-pincer erbium bisamido complex LEr[N(SiMe3)2]2
(2) (as low as 13% yield) together with the fused-heterocyclic
compound 1 (Scheme 2). However, for other rare-earth metals,
Next, we tried to prepare the CNC-pincer diarylamido linked
bis(NHC) rare-earth metal amido complexes using the Arnold’s
conditions.13 However, the stepwise treatment of H3LCl2 with
n-BuLi in THF at −30 °C, followed by reaction with
[(Me3Si)2N]3RE(μ-Cl)Li(THF)3, generated the novel zwitter-
ionic complexes [L2RE][RECl{N(SiMe3)2}3] (L = [4-CH3-2-
{(C6H4CH2-[N(CH)2CN]}-C6H3]2N; RE = Y (3), Er (4), Yb
(5)) (less than 20% yields), together with isolation of the
fused-heterocyclic compound 1. Complexes 3−5 could also be
prepared by treatment of H3LCl2 with LiCH2SiMe3, followed
by reaction with [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 (Scheme 3).
Another stepwise reaction that in situ deprotonation of
H3LCl2 with NaN(SiMe3)2 in THF at −78 °C, followed by
treatment with YbCl3, only generated a novel discrete complex
6 that contains cationic [L2Yb]+ with an inverse crown counter
pentagonal anion [{Na(μ-N(SiMe3)2)}5(μ5-Cl)]− (Scheme 4).
No fused-heterocyclic compound 1 was observed, probably for
the reason that low-temperature reaction might prevent the
carbene carbon from coupling.
2373
dx.doi.org/10.1021/om500354s | Organometallics 2014, 33, 2372−2379

Organometallics
Article
diagrams of 4 and 6 are shown in Figures 2 and 3. The
important bond distances and angles are shown in Table 1.
X-ray analyses revealed that complexes 3−6 formulated as
discrete complexes. The central metal ions in complexes 3−6
have the same coordination numbers; the central metal ions of
the cation adopt a distorted octahedral geometry surrounded by
two diarylamido linked bis(NHC) ligands. Complex 6 is a
novel discrete complex containing cationic [L2Yb]+ incorporat-
ing two diarylamido linked bis(NHC) ligands and an inverse
crown counter pentagonal anion [{Na(μ-N(SiMe3)2)}5(μ5-
Cl)]−.19 The average RE−Ccarbene bond lengths, 2.518(3) Å in
3, 2.477(5) Å in 4, 2.461(6) Å in 5, and 2.456(4) Å in 6, are
well-consistent with the trend of ionic radii of the
corresponding lanthanide elements and are distinctly shorter
than those of the previously reported corresponding 6-
coordinated cationic complexes.4d
Scheme 2. Reaction of H3LCl2 and [(Me3Si)2N]3Er(μ-
Cl)Li(THF)3
The above results indicated that the CNC-pincer diarylamido
linked bis(NHC)-ligated bisamido complexes (type of complex
2) could not be satisfactorily synthesized by changing solvents
from THF to toluene, or by lowering preparation reaction
temperatures from room temperature to −30 °C. We were
delighted to find that the CNC-pincer rare-earth amido
complexes LRE[N(SiMe3)2]2 (RE = Er (2), Y (7), Sm (8),
Eu (9)) could be prepared in moderate yields by one-pot
reaction of H3LCl2 with 2 equiv of n-BuLi, followed by
treatment with [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 in THF at
−78 °C (Scheme 5, upper path). These kinds of complexes can
also be prepared in moderate yields by treatment of H3LCl2
with 5 equiv of NaN(SiMe3)2, followed by reaction with 1
equiv of RECl3 in THF at −78 °C (Scheme 5, lower path). The
fused-heterocyclic compound 1 has not been found in both
pathways; the results further indicated that low temperature
could prevent the in situ formed bis(NHC) from coupling.
Scheme 3. Stepwise Reactions of H3LCl2 with Bases,
Followed by Addition to [(Me3Si)2N]3RE(μ-Cl)Li(THF)3
1
The H NMR spectra of 3, 7, and 8 revealed the absence of
the NH, and NC(H)N proton resonances of the bis-
(imidazolium) salt (H3LCl2) at 8.51 and 10.46 ppm. The 13C
NMR spectra of complex 3 showed carbene carbon resonances
at 194.2 and 194.5 ppm. Similarly, complex 7 showed carbene
carbon resonances at 192.0 and 192.5 ppm, and those of
carbene carbons in complex 8 resonate at 152.5 ppm, probably
due to the paramagnetic property of the complex. The
molecular structures of complexes 2 and 7−9 were determined
by single-crystal X-ray analyses. A representative structure
diagram is shown in Figure 4. The selected bond distances and
angles are compiled in Table 2.
Scheme 4. Synthesis of the Discrete Complex 6
As expected, the diarylamido linked bis(NHC) ligand
coordinates to the central metal ion in a tridenate mode by
the amido nitrogen and the two carbene carbon atoms, forming
a distorted trigonal-bipyramidal geometry with the two
silylamido N″ groups and the amido group occupying the
equatorial positions having the sum of the angles of (N(3)−
RE−N(6), N(6)−RE−N(7), and N(7)−RE−N(3)) of
359.83(9)° for 2, 359.81(11)° for 7, 359.87(9)° for 8, and
359.80(2)° for 9, and the two carbene atoms at the axial sites.
The average RE−Ccarbene bond lengths, 2.525(4) Å in 7,
2.589(3) Å in 8, 2.564(9) Å in 9, and 2.510(3) Å in 2, fall in the
range of the linkage of a lanthanide metal ion and an ylidene
carbon,9 and are well-consistent with the trend of ionic radii of
the corresponding lanthanide elements. The average Y−Ccarbene
bond length of 2.525(4) Å in 7 is both shorter than 2.541(3) Å
in the CCC-pincer bis(NHC)-ligated rare-earth metal
dibromides (PBNHC)YBr2(THF)((PBNHC) = 2,6-(2,4,6-
Me3C6H2NCHCHNCCH2)2C6H3)9b and 2.569(3) Å in the
The molecular structures of complexes 3−6 were determined
by single-crystal X-ray analyses. The representative structure
2374
dx.doi.org/10.1021/om500354s | Organometallics 2014, 33, 2372−2379

Organometallics
Article
Figure 2. Molecular structure of complex 4. Hydrogen atoms were omitted for clarity.
Figure 3. Molecular structure of complex 6. Hydrogen atoms were omitted for clarity.
Table 1. Selected Bond Distances (Å) and Angles (deg) for Complexes 3−6
Y (3)
Er (4)
Yb (5)
Yb (6)
RE(1)−N(3)
RE(1)−N(8)
RE−Nav
RE(1)−C(10)
RE(1)−C(27)
RE(1)−C(44)
RE(1)−C(61)
RE−Cav
N(3)−RE(1)−C(10)
C(10)−RE(1)−N(8)
N(8)−RE(1)−C(27)
C(27)−RE(1)−N(3)
C(44)−RE(1)−C(61)
2.308(2)
2.330(2)
2.319(2)
2.522(3)
2.523(3)
2.511(3)
2.517(3)
2.518(3)
76.13(9)
102.91(10)
104.14(10)
76.84(9)
151.46(11)
2.309(4)
2.305(4)
2.284(4)
2.290(4)
2.278(3)
2.266(3)
2.307(4)
2.287(4)
2.272(3)
2.481(5)
2.457(5)
2.457(4)
2.470(5)
2.461(6)
2.447(4)
2.482(5)
2.462(6)
2.463(4)
2.474(5)
2.463(6)
2.455(4)
2.477(5)
2.461(6)
2.456(4)
76.45(17)
102.89(17)
103.46(16)
77.20(16)
154.45(17)
77.41(16)
102.14(16)
103.25(17)
77.20(17)
155.11(19)
78.80(12)
101.95(12)
100.67(13)
78.58(13)
156.68(14)
2375
dx.doi.org/10.1021/om500354s | Organometallics 2014, 33, 2372−2379

Organometallics
Article
C(27) in 7, 138.3(3)° of C(10)−Eu−C(27) in 9, and
138.01(10)° of C(10)−Sm−C(27) in 8.
Scheme 5. Synthetic Pathways for Preparation of
Diarylamido Linked Bis(NHC) Rare-Earth Metal Amides
Catalytic Activity on Addition of Terminal Alkyne C−
H Bonds to Carbodiimides. The addition of C−H bonds of
terminal alkynes to carbodiimides could provide a straightfor-
ward, atom-efficient route to propiolamidines. Previously
developed rare-earth metal complexes as catalysts for catalytic
addition of terminal C−H bonds of alkynes to carbodiimides
required elevated reaction temperatures at 80 or 60 °C.17,18
The fact that the carbene ligands have a strong electron-
donating property is established, with the CNC-pincer
diarylamido linked bis(NHC) supported rare-earth metal
amido complexes in hand, the catalytic activities of these
complexes on terminal C−H bond addition to carbodiimides
were examined (Table 3).
Table 3. Optimization of the Conditions in the Catalytic
a
Reaction of Terminal Alkynes to Carbodiimides
c
b
entries
cat. (mol %)
solvent
temp (°C)/time (h)
yield (%)
1
2
3
4
5
6
7
8
9 (2%)
9 (3%)
9 (5%)
9 (5%)
9 (5%)
2 (5%)
7 (5%)
8 (5%)
THF
THF
THF
toluene
THF
THF
THF
THF
r.t./12
r.t./12
r.t./12
r.t./12
60/12
r.t./12
r.t./12
r.t./12
64
81
88
82
88
87
87
85
a
Reaction conditions: dicyclohexylcarbodiimide (2.0 mmol), phenyl-
b
c
acetylide (2.1 mmol), solvent (5 mL). Isolated yields. Cat.:
[LREN(SiMe3)2] (RE = Er (2), Y (7), Sm (8), Eu (9)).
Results showed that the yields of the catalytic addition
reaction were raised along with an increase of catalyst loading
(Table 3, entries 1−3) and THF seemed to be a better solvent
than toluene for the reaction (Table 3, entries 3 and 4). The
propiolamidine 10 was obtained in 87, 87, 85, and 88% yields
using the catalysts 2 and 7−9 in 12 h (Table 3, entries 5−8),
respectively, indicating that the central metal ions of the
complexes had little influence on the catalytic activities of the
addition of terminal alkynes to carbodiimides. It was worth
noting that the addition reaction of phenylacetylide to
dicyclohexylcarbodiimide was conducted at room temperature
immediately. The reaction yield of the product was unchanged
Figure 4. Representative molecular structure of complexes 2 and 7−9.
Hydrogen atoms were omitted for clarity.
CNC-pincer bis(NHC)-ligated rare-earth metal monoamido
complex {CH2CH2(1-C[NCHCHNMes])}2NY(Cl)N-
(SiMe3)2.13 In contrast, the C(10)−Er−C(27) bond angle of
141.39(10)° in 2 is larger than 141.07(13)° of C(10)−Y−
Table 2. Selected Bond Distances (Å) and Angles (deg) for Complexes 2 and 7−9
Er (2)
Y (7)
Sm (8)
Eu (9)
RE(1)−N(3)
RE(1)−N(6)
RE(1)−N(7)
RE−Nav
RE(1)−C(10)
RE(1)−C(27)
RE−Cav
N(3)−RE(1)−N(6)
N(3)−RE(1)−N(7)
N(6)−RE(1)−N(7)
C(10)−RE(1)−C(27)
2.321(2)
2.246(3)
2.288(2)
2.267(3)
2.511(3)
2.509(3)
2.510(3)
103.32(9)
137.88(9)
118.63(9)
141.39(10)
2.340(3)
2.261(3)
2.395(2)
2.318(3)
2.338(3)
2.328(3)
2.593(3)
2.584(3)
2.589(3)
104.18(9)
135.09(9)
120.60(9)
138.01(10)
2.389(6)
2.317(7)
2.312(7)
2.315(7)
2.552(9)
2.575(8)
2.564(9)
104.0(2)
136.5(2)
119.3(2)
138.3(3)
2.296(3)
2.279(3)
2.529(4)
2.521(4)
2.525(4)
103.53(11)
137.56(11)
118.72(12)
141.07(13)
2376
dx.doi.org/10.1021/om500354s | Organometallics 2014, 33, 2372−2379

Organometallics
Article
by elevating the reaction temperature to 60 °C (Table 3, entry
5).
Under the optimized reaction conditions, we next examined
the substrate scope of the catalytic addition of the terminal
alkynes to carbodiimides in the presence of the complex 9
(Table 4). It is found that the catalyst displayed a high catalytic
EXPERIMENTAL SECTION
■
General Procedure. All manipulations were carried out under a
dry oxygen-free argon atmosphere using standard Schlenk techniques
or in a glovebox unless otherwise stated. All solvents (toluene, hexane,
THF, diethyl ether) were refluxed and distilled over sodium
benzophenone ketyl under argon prior to use unless otherwise
noted. RECl3,20 [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 (RE = Y, Sm, Eu,
Er, Yb),21 and bis[2-(3-benzylimidazolium)-4-methylphenyl]amine
dichlorides (H3LCl2)11c were prepared according to literature
methods. Elemental analyses data were obtained on a macro-elemental
Table 4. Addition of Various Terminal Alkynes to
a
Carbodiimides Catalyzed by Catalyst 9
1
analyzer. H NMR and 13C NMR spectra for analyses of compounds
were recorded on a 300/500 NMR spectrometer (300 MHz for 1H; 75
1
MHz for 13C; 500 MHz for H; 126 MHz for 13C), and all chemical
shift values refer to δ TMS 0.00 ppm, CDCl3 (δ (1H), 7.26 ppm; δ
(13C), 77.16 ppm), C6D6 (δ (1H), 7.15 ppm; δ (13C), 128.06 ppm),
and C4D8O (δ (1H), 1.72, 3.58 ppm; δ (13C), 25.31, 67.21 ppm). J
values are reported in Hz. IR spectra were recorded on an FT-IR
spectrometer (KBr pellet). Mass spectra were performed on a
Micromass GCT-MS spectrometer. Crystallographic X-ray data were
collected on a SMART 1000 CCD area detector diffractometer.
Preparation of 8,9-Dibenzyl-3,14-dimethyl-8a,9-dihydro-
8H-benzo[4,5]imidazo[2′,1′:2,3]imidazo[1,2-a]imidazo[2,1-c]-
quinoxaline (1). [(Me3Si)2N]3Yb(μ-Cl)Li(THF)3 (1.616 g, 1.77
mmol) was added to H3LCl2 (1.031 g, 1.77 mmol) in THF (30 mL),
and the mixture was stirred for 12 h at room temperature. The solvent
was removed under reduced pressure to afford a yellow solid, which
was recrystallized from hexane to yield colorless crystals of 1 (379 mg,
42% yield): C34H31N5. 1H NMR (300 MHz, C6D6, ppm): δ 7.45−7.42
(d, 2H, J = 7.3 Hz, Ar-H), 7.32−7.30 (d, 1H, J = 8.0 Hz, Ar-H), 7.26−
7.05 (m, 9H, Ar-H), 7.08−7.05 (d, 1H, J = 9.0 Hz, Ar-H), 6.70−6.68
(d, 1H, J = 6.0 Hz, Ar-H), 6.61−6.59 (d, 1H, J = 6.0 Hz, Ar-H), 6.29
(s, 1H, Ar-H), 5.76−5.76 (d, 1H, J = 2.4 Hz, NCH2), 5.59−5.58 (d, J =
2.4 Hz, NCH2), 5.53−5.52 (d, J = 2.1 Hz, NCH2), 5.47−5.46 (d, 1H, J
= 2.4 Hz, NCH2), 4.63 (s, 1H, NCHN), 4.44−4.34 (d, 1H, J = 13.2
Hz, NCHCHN), 4.22−4.18 (d, 1H, J = 13.7 Hz, NCHCHN), 3.86−
3.82 (d, 1H, J = 13.9 Hz, NCHCHN), 3.72−3.68 (d, 1H, J = 13.2 Hz,
NCHCHN), 2.18−2.16 (d, 6H, J = 5.0 Hz, Ar−CH3). 13C NMR (75
MHz, C6D6, ppm): δ 19.9 (Ar-CH3), 20.2 (Ar-CH3), 50.1 (NCH2),
56.1 (NCH2), 79.4 (NCHN), 96.2 (NCN), 106.6 (NCHCHN), 107.7
(NCHCHN), 110.6 (NCHCHN), 111.2 (NCHCHN), 114.2, 117.6,
118.7, 119.8, 121.8, 122.6, 125.8, 126.3, 126.5, 126.8, 127.1, 127.4,
127.6, 128.2, 128.7, 129.2, 131.3, 137.2, 137.5, 138.2, 139.27 (Ar-C).
HRMS (ESI): calcd for C34H32N5: m/z 510.2652 ([M + 1]+), Found:
510.2651. Anal. Calcd for C34H31N5: C, 80.13; H, 6.13; N, 13.74.
Found: C, 80.66; H, 6.70; N, 13.12. mp: 92 °C. IR (KBr pellets,
cm−1): ν 3064 (w), 2953 (w), 2918 (w), 2862 (w), 1666 (m), 1606
(m), 1514 (m), 1454 (m), 1307 (m), 1249 (w), 1180 (w), 1029 (w),
1012 (w), 933 (w), 881 (s), 840 (s), 731 (s), 700 (s).
When [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 (RE = Eu, Sm) were used
instead of [(Me3Si)2N]3Yb(μ-Cl)Li(THF)3, the fused-heterocyclic
compound 1 could also be isolated in 34% and 36% yield, respectively.
Preparation of [LEr{[N(SiMe3)2]2}] (2). Reaction between-
[(Me3Si)2N]3Er(μ-Cl)Li(THF)3 (1.098 g, 1.21 mmol) and H3LCl2
(705 mg, 1.21 mmol) in toluene was stirred for 12 h at room
temperature and, after work-up, generated pink crystals of the CNC-
pincer bis(NHC)-ligated erbium complex LEr[N(SiMe3)2]2 (2) (157
mg, 13% yield) and fused-heterocyclic compound 1 (217 mg, 35%
yield). Complex LEr[N(SiMe3)2]2 (2) can also be prepared in 22%
yield (317 mg) by treatment of H3LCl2 (848 mg, 1.46 mmol) with a
solution of 2 M NaN(SiMe3)2 in THF (3.6 mL, 7.28 mmol), followed
by treatment with a suspension of ErCl3 (398 mg, 1.46 mmol). Anal.
Calcd for C46H66N7Si4Er(C6H14)0.5: C, 56.60; H, 7.08; N, 9.43. Found:
C, 56.78; H, 6.74; N, 10.01. mp: 134 °C. IR (KBr pellets, cm−1): ν
3061 (w), 2862 (w), 1604 (m), 1546 (m), 1508 (m), 1483 (w), 1365
(w), 1307 (w), 1251 (w), 1180 (w), 1138 (w), 933 (w), 883 (s), 837
(s), 682 (s), 657 (s).
b
entries
R
Ar
product
yield (%)
1
2
Cy
iPr
Cy
iPr
Cy
iPr
Cy
iPr
Cy
iPr
Cy
iPr
Cy
iPr
Ph
Ph
10
11
12
13
14
15
16
17
18
19
20
21
22
23
88
90
73
79
70
81
92
95
90
93
89
91
68
72
3
4-MeOC6H4
4-MeOC6H4
4-MeC6H4
4-MeC6H4
4-FC6H4
4
5
6
7
8
4-FC6H4
9
4-ClC6H4
4-ClC6H4
4-BrC6H4
4-BrC6H4
n-C5H11
10
11
12
13
14
n-C5H11
a
Reaction conditions: carbodiimides (2.0 mmol), terminal alkynes (2.1
mmol), catalyst loading (5 mol %), THF (5 mL), room temperature,
b
reaction time (12 h). Isolated yields.
activity on addition of terminal alkyne C−H bonds to
carbodiimides with substrates of aromatic alkynes or aliphatic
alkynes at room temperature. The substituents on the phenyl
ring of the aromatic alkynes can be electron-donating groups,
such as CH3O− and CH3−, or electron-withdrawing groups,
such as F−, Cl−, and Br−. However, reactions of alkynes with
electron-withdrawing substituted groups (Table 4, entries 7−
12) afforded much more better results than those of alkynes
with electron-donating groups on the phenyl ring with
carbodiimides (Table 4, entries 3−6), probably owing to the
stronger acidity of the former, which may favor the alkyne−
amido exchange process in the catalytic initation step; this
result is parallel to the previous results.18 In the case of alkyl
alkynes (Table 4, entries 13 and 14), the reaction can go
smoothly, but gives results a bit poorer than those of aromatic
alkynes performed, probably owing to their weaker acidity.
CONCLUSION
■
In summary, we have demonstrated that a variety of the CNC-
pincer diarylamido bis(NHC)-ligated rare-earth metal com-
plexes can be synthesized and characterized. Results indicated
that conditions play a key role in the formation of final
products. The diarylamido linked bis(NHC) rare-earth metal
amides can be used as catalysts to accomplish the catalytic
addition of terminal C−H bonds of alkynes to carbodiimides at
room temperature with a high catalytic activity, which
represents the first example of organo rare-earth metal
complexes as catalysts applied for catalytic addition of C−H
bonds of alkynes to carbodiimides at room temperature.
Further studies on the reactivity and catalytic reactivities of
these kinds of complexes are in progress.
Preparation of [L2Y][YCl{[N(SiMe3)2]3}] (3). A solution of
H3LCl2 (926 mg, 1.59 mmol) in THF (30 mL) was cooled to −30
°C, and a solution of n-BuLi (2.50 mL, 3.18 mmol) in hexane was
added dropwise with stirring for 4 h at −30 °C. [(Me3Si)2N]3Y(μ-
2377
dx.doi.org/10.1021/om500354s | Organometallics 2014, 33, 2372−2379

Organometallics
Article
Cl)Li(THF)3 (1.318 g, 1.59 mmol) was then added to the mixture,
and the mixture was allowed to warm slowly to room temperature
overnight. The solvent was removed under reduced pressure to afford
a yellow solid, which was washed with hexane to yield colorless crystals
of 1 (324 mg, 40% yield), and recrystallization of the remaining solid
from diethyl ether afforded yellow crystals of 3 (466 mg, 19% yield).
1H NMR (500 MHz, C4D8O): δ 7.69 (s, 4H, imi-H), 7.22−7.16 (m,
12H, imi-H and Ar-H), 7.05−6.99 (d, J = 7.0 Hz, 8H, Ar-H), 6.70−
6.68 (d, J = 6.6 Hz, 8H, Ar-H), 6.49−6.48 (d, J = 7.8 Hz, 4H, Ar-H),
6.37−6.35 (d, J = 8.0 Hz, 4H, Ar-H), 4.91−4.88 (d, J = 14.7 Hz, 4H,
NCH2), 4.06−4.03 (d, J = 14.8 Hz, 4H, NCH2), 2.10 (s, 12H, ArCH3),
0.17 (s, 36H, Si(CH3)3), 0.04 (s, 18H, Si(CH3)3). 13C NMR (126
MHz, C4D8O): δ 2.1(Si(CH3)3), 6.2 (Si(CH3)3), 20.0 (ArCH3), 52.7
(NCH2), 120.7, 121.8, 124.8 (imi-C), 127.9, 128.2, 128.6, 129.2, 132.6,
136.7, 147.0 (Ar-C), 194.2 (carbene-C), 194.5 (carbene-C). Anal.
Calcd for C86H114ClN13Si6Y2: C, 60.35; H, 6.71; N, 10.64. Found: C,
60.67; H, 6.20; N, 10.28. mp: 150 °C. IR (KBr pellets, cm−1): ν 2963
(w), 2351 (m), 2318 (m), 1672 (s), 1632 (s), 1580 (s), 1454 (m),
1373 (m), 1261 (m), 1105 (m), 1018 (m), 966 (m), 935 (s), 881 (s),
802 (s), 691 (vs).
Preparation of [L2Er][ErCl{[N(SiMe3)2]3}] (4). Following the
procedure similar to that described for the preparation of 3, 1 (268
mg, 35% yield) and 4 (420 mg, 15% yield) were isolated from a
reaction of a solution of H3LCl2 (874 mg, 1.50 mmol) and n-BuLi (3.4
mL, 3.0 mmol) at −30 °C for 4 h, followed by reaction with
[(Me3Si)2N]3Er(μ-Cl)Li(THF)3 (1.361 g, 1.50 mmol) at −30 °C.
Anal. Calcd for C86H114ClN13Si6Er2: C, 55.28; H, 6.15; N, 9.75.
Found: C, 55.16; H, 6.15; N, 9.88. mp: 153 °C. IR (KBr pellets,
cm−1): ν 2954 (w), 2358 (w), 2342 (w), 1657 (m), 1647 (m), 1549
(m), 1510 (m), 1452 (s), 1400 (s), 1311 (m), 1250 (m), 1173 (m),
1138 (m), 1113 (m), 1011 (m), 934 (m), 839 (m), 714 (m), 669 (m).
Preparation of [L2Yb][YbCl{[N(SiMe3)2]2}3] (5). Following the
procedure similar to that described for the preparation of 3, 1 (209
mg, 37% yield) and 5 (385 mg, 16% yield) were isolated from a
reaction of a solution of H3LCl2 (747 mg, 1.28 mmol) and n-BuLi (1.4
mL, 2.56 mmol) at −30 °C for 4 h, followed by reaction with
[(Me3Si)2N]3Yb(μ-Cl)Li(THF)3 (1.170 g, 1.28 mmol) at −30 °C.
Anal. Calcd for C86H114ClN13Si6Yb2(C6H14): C, 56.20; H, 6.56; N,
9.26. Found: C, 56.31; H, 6.37; N, 9.64. mp: 156 °C. IR (KBr pellets,
cm−1): ν 2959 (w), 2378 (m), 2320 (m), 1647 (w), 1632 (w), 1549
(m), 1508 (m), 1400 (m), 1339 (m), 1312 (m), 1254 (m), 1180 (m),
1138 (s), 1115 (s), 1013 (m), 935 (s), 885 (s), 839 (m), 750 (m), 669
(m).
C6D6, ppm): δ 4.7 (SiC(CH3)3), 6.7 (SiC(CH3)3), 20.3 (ArCH3)),
55.3 (NCH2), 119.2, 120.0, 123.4 (imi-C), 127.0, 127.5, 127.8, 128.1,
128.3, 128.3, 128.8, 129.0, 129.1, 132.2, 135.0, 147.0 (Ar-C), 192.0
(carbene-C), 192.5 (carbene-C). Anal. Calcd for C46H66N7Si4Y: C,
60.16; H, 7.24; N, 10.68. Found: C, 60.32; H, 7.30; N, 10.39. mp: 146
°C. IR (KBr pellets, cm−1): ν 3030 (w), 2962 (w), 2926 (w), 2858
(w), 1662 (w), 1608 (w), 1548 (w), 1512 (w), 1452 (w), 1400 (w),
1261 (s), 1095 (s), 1022 (s), 925 (w), 802 (s), 700 (w), 669 (w).
Preparation of [LSm{[N(SiMe3)2]2}] (8). This complex was
prepared as yellow crystals in 27% yield (331 mg) following the
procedure similar to that described for the preparation of 7 by
treatment of a THF suspension of H3LCl2 (664 mg, 1.14 mmol) with
a solution of 2 M NaN(SiMe3)2 in THF (2.8 mL, 5.69 mmol),
followed by reaction with a THF suspension of SmCl3 (293 mg, 1.14
mmol). 1H NMR (300 MHz, C6D6, ppm): δ 8.81−8.79 (d, J = 8.2 Hz,
2H, imi-H), 7.71−7.70 (d, J = 7.0 Hz, 2H, imi-H), 7.59−7.56 (dd, J =
8.3, 1.7 Hz, 2H, Ar-H), 6.92−6.90 (m, 8H, Ar-H), 6.64 (d, J = 1.7 Hz,
2H, Ar-H), 6.65−6.47 (dd, J = 7.5, 1.9 Hz, 4H, Ar-H), 5.29−5.29 (d, J
= 1.7 Hz, 2H, NCH2), 4.75−4.70 (d, J = 14.9 Hz, 2H, NCH2), 2.60 (s,
6H, ArCH3), 1.04 (s, 18H, Si(CH3)3), 1.03 (s, 18H, Si(CH3)3). 13C
NMR (75 MHz, C6D6, ppm): δ 1.9 (SiC(CH3)3), 6.0 (SiC(CH3)3),
19.9 (ArCH3), 51.7 (NCH2), 115.2, 115.3, 117.0, 117.1 (imi-C), 124.2,
126.5, 126.8, 127.0, 127.2, 127.6, 127.8, 128.0, 129.4, 133.0, 133.1,
133.2 (Ar-C), 152.5 (carbene-C). Anal. Calcd for C46H66N7Si4Sm: C,
56.39; H, 6.79; N, 10.01. Found: C, 56.24; H, 6.78; N, 9.81. mp: 140
°C. IR (KBr pellets, cm−1): ν 3084 (w) 3024 (w), 2945 (w), 2910 (w),
2837 (w), 1666 (m), 1610 (m), 1566 (m), 1517 (s), 1492 (w), 1454
(w), 1404 (w), 1373 (w), 1350 (s), 1325 (s), 1296 (w), 1180 (w),
1130 (w), 1026 (w), 939 (w), 860 (s), 842 (s), 758 (s), 696 (s), 669
(s).
Preparation of [LEu{[N(SiMe3)2]2}] (9). This complex was
prepared as yellow crystals in 30% yield (981 mg) following a
procedure similar to that described for the preparation of 7 by
treatment of a THF suspension of H3LCl2 (1.078 g, 1.85 mmol) with a
solution of 2 M NaN(SiMe3)2 in THF (4.6 mL, 9.24 mmol), followed
by reaction with EuCl3 (478 mg, 1.85 mmol). Anal. Calcd for
C46H66N7Si4Eu: C, 56.30; H, 6.78; N, 9.99. Found: C, 56.02; H, 6.56;
N, 9.72. mp: 168 °C. IR (KBr pellets, cm−1): ν 3061 (w), 3028 (w),
2954 (w), 2918 (w), 2862 (w), 1604 (m), 1585 (m), 1514 (m), 1398
(w), 1309 (w), 1247 (w), 1180 (w), 1138 (w), 1028 (w), 983 (w), 933
(w), 840 (s), 817 (s), 702 (s), 650(s).
Complexes 2 and 7−9 can also be prepared in 25, 28, 31, and 36%
yield, respectively, by a one-pot reaction of H3LCl2 (1 equiv) with n-
BuLi (2 equiv), followed by reaction with 1 equiv of [(Me3Si)2N]3-
RE(μ-Cl)Li(THF)3 (RE = Er, Y, Sm, Eu) in THF at −78 °C for 4 h.
General Experimental Procedure for the Catalytic Addition
of Terminal Alkynes to Carbodiimides (10 as an example). In
the glovebox, a Schlenk tube was charged with complex 9 (98 mg, 0.10
mmol), phenylacetylide (214 mg, 2.10 mmol), and THF (5 mL).
Then, dicyclohexylcarbodiimide (413 mg, 2.00 mmol) was added to
the mixture. The mixture was stirred at room temperature for 12 h.
After the solvent was removed under reduced pressure, the residue was
extracted with hexane and filtered to give a clean solution. The solvent
was evaporated under vacuum, and the residue was recrystallized from
hexane to afford the N,N′-dicyclohexyl-3-phenylpropiolamidine 10
(543 mg, 88% yield).
Crystal Structure Determination. Suitable crystals of fused-
heterocyclic compound 1 and complexes 2−9 were each mounted in a
sealed capillary. Diffraction was performed on a 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.22 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 SHELXTL-97.23 All hydrogen
atoms were refined using a riding model. Crystal and refinement data
can be read in the Supporting Information.
Preparation of [L2Yb][{Na(μ-N(SiMe3)2)}5(μ5-Cl)] (6). To a
solution of H3LCl2 (1.403 g, 1.79 mmol) in THF (30 mL) at −78
°C was dropwise added a solution of 2 M NaN(SiMe3)2 in THF (5.4
mL, 10.74 mmol) with stirring for 4 h; a THF suspension of YbCl3
(250 mg, 0.895 mmol) was then added to the mixture. The reaction
mixture was allowed to slowly warm to room temperature overnight.
The solvent was removed under reduced pressure to yield a yellow
solid that was recrystallized from hexane/toluene to afford yellow
crystals of 6 (959 mg, 25% yield) for X-ray analysis. Anal. Calcd for
C98H150N15Si10ClNa5Yb(C7H8)0.5: C, 55.70; H, 7.09; N, 9.60. Found:
C, 55.56; H, 6.58; N, 9.28. mp: 200 °C. IR (KBr pellets, cm−1): ν 3061
(w), 3030 (w), 2954 (w), 1664 (m), 1618 (m), 1514 (m), 1454 (m),
1398 (w), 1309 (w), 1242 (w), 1182 (w), 983 (w), 933 (w), 839 (s),
813 (s),744 (s), 711 (s).
Preparation of [LY{[N(SiMe3)2]2}] (7). To a suspension of H3LCl2
(1.132 g, 1.94 mmol) in THF (30 mL) was added a solution of 2 M
NaN(SiMe3)2 in THF (4.9 mL, 9.72 mmol)) dropwise with stirring for
8 h at −78 °C; then a THF suspension of YCl3 (379 mg, 1.94 mmol)
was added to the mixture. The mixture was allowed to slowly warm to
room temperature overnight. The solvent was removed under reduced
pressure to afford a yellow solid, which was recrystallized from hexane
to yield yellow crystals of 7 in 20% yield (389 mg) for X-ray analysis.
1H NMR (300 M Hz, C6D6, ppm): δ 7.31−7.29 (d, J = 6.0 Hz, 4H,
imi-H), 7.18−7.05 (m, 8H, Ar-H), 6.94−6.84 (dd, J = 19.6, 11.0 Hz,
6H, Ar-H,), 6.30 (s, 2H, Ar-H), 6.13−6.08 (d, J = 14.9 Hz, 2H,
NCH2), 5.59−5.54 (d, J = 14.9 Hz, 2H, NCH2), 2.21 (s, 6H, ArCH3),
0.41 (s, 18H, Si(CH3)3), 0.09 (s, 18H, Si(CH3)3). 13C NMR (75 MHz,
2378
dx.doi.org/10.1021/om500354s | Organometallics 2014, 33, 2372−2379

Organometallics
Article
Organometallics 2008, 27, 2268−2272. (d) Bauer, E. B.; Senthil
Andavan, G. T.; Hollis, T. K.; Rubio, R. J.; Cho, J.; Kuchenbeiser, G.
R.; Helgert; Christopher, T. R.; Letko, S.; Tham, F. S. Org. Lett. 2008,
10, 1175−1178. (e) Edworthy, I.; Blake, A.; Wilson, C.; Arnold, P. L.
Organometallics 2007, 26, 3684−3689. (f) Tulloch, A.; Danopoulos,
A.; Tizzard, G. J.; Coles, S.; Hursthouse, M.; Hay-Motherwell, R.;
Motherwell, W. Chem. Commun. 2001, 1270−1271.
(12) Lv, K.; Cui, D. M. Organometallics 2008, 27, 5438−5440.
(13) Edworthy, I.; Blake, A.; Wilson, C.; Arnold, P. L. Organometallics
2007, 26, 3684−3689.
ASSOCIATED CONTENT
* Supporting Information
■
S
Characterization data and spectra for compounds, tables of
crystallographic data and structure refinement for 1−9, and X-
ray crystallographic files, in CIF format, for structure
determination of fused-heterocyclic 1 and complexes 2−9.
This material is available free of charge via the Internet at
http://pubs.acs.org.
(14) (a) Sienkiewich, P.; Bielawski, K.; Bielawska, A.; Palka, J.
Environ. Toxicol. Pharmacol. 2005, 20, 118−124. (b) Sielecki, T. M.;
Liu, J.; Mousa, S. A.; Racanelli, A. L.; Hausner, E. A.; Wexler, R. R.;
Olson, R. E. Bioorg. Med. Chem. Lett. 2001, 11, 2201−2204.
(c) Stephens, C. E.; Tanious, E.; Kim, S.; Wilson, D. W.; Schell, W.
A.; Perfect, J. R.; Franzblau, S. G.; Boykin, D. W. J. Med. Chem. 2001,
44, 1741−1748. (d) Rowley, C. N.; DiLabio, G. A.; Barry, S. T. Inorg.
Chem. 2005, 44, 1983−1991.
AUTHOR INFORMATION
Corresponding Author
*E-mail: swwang@mail.ahnu.edu.cn (S. Wang); zxc5872271@
126.com (X. Zhu).
■
Notes
The authors declare no competing financial interest.
(15) (a) Cole, M. L.; Deacon, G. B.; Forsyth, C. M.; Junk, P. C.;
ACKNOWLEDGMENTS
■
́
Ceron, D. P.; Wang, J. Dalton Trans. 2010, 39, 6732−6738.
This work was cosupported by the National Natural Science
Foundation of China (Grants 21372010, 21172003) and the
National Basic Research Program of China (2012CB821600).
(b) Edelmann, F. T. Chem. Soc. Rev. 2012, 41, 7657−7672.
(16) (a) Ong, T. G.; O’Brien, J. S.; Korobkov, I.; Richeson, D. S.
Organometallics 2006, 25, 4728−4730. (b) Brown, D. J.; Chisholm, M.
H.; Gallucci, J. C. Dalton Trans. 2008, 1615−1624. (c) Drose, P.; Hrib,
̈
C. G.; Edelmann, F. T. J. Organomet. Chem. 2010, 695, 1953−2051.
(d) Casely, I. J.; Ziller, J. W.; Evans, W. J. Organometallics 2011, 30,
4873−4881. (e) Yi, W.; Zhang, J.; Li, M.; Chen, Z.; Zhou, X. G. Inorg.
Chem. 2011, 50, 11813−11824. (f) Zhang, W. X.; Hou, Z. M. Org.
Biomol. Chem. 2008, 6, 1720. (g) Ryan, J. S.; Martyn, P. C.
Organometallics 2013, 32, 5277−5280. (h) Fujita, H.; Endo, R.;
Aoyama, A.; Ichii, T. Bull. Chem. Soc. Jpn. 1972, 45, 1846−1852.
(17) Zhang, W. X.; Nishiura, M.; Hou, Z. M. J. Am. Chem. Soc. 2005,
127, 16788−16789.
(18) (a) Zhou, S. L.; Wang, S. W.; Yang, G. S.; Li, Q. H.; Zhang, L. J.;
Yao, Z.; Zhou, H.; Song, H. Organometallics 2007, 26, 3755−3761.
(b) Wu, Y. J.; Wang, S. W.; Zhang, Z.; Yang, G.; Zhu, X.; Zhou, Z.;
Zhu, H.; Wu, S. Eur. J. Org. Chem. 2010, 326−332.
(19) Daniel, W.; Michael, B.; Daniel, O. S.; Richard, E. P. W.;
Richard, A. L. Dalton Trans. 2011, 40, 10918−10923.
(20) (a) Taylor, M. D.; Carter, C. P. J. Inorg. Nucl. Chem. 1962, 24,
387−391. (b) Edleman, N. L.; Marks, T. J.; et al. Inorg. Chem. 2002,
41, 5005−5023. (c) Huang, W.; Upton, B. M.; Khan, S. I.; Diaconescu,
P. L. Organometallics 2013, 32, 1379−1386.
(21) Zhou, S. L.; Wang, S. W.; Yang, G. S.; Liu, X.; Sheng, E.; Zhang,
K.; Cheng, L.; Huang, Z. Polyhedron 2003, 22, 1019−1024.
(22) Sheldrick, G. M. SADABS: Program for Empirical Absorption
REFERENCES
■
(1) Arduengo, A. J.; Tamm, M.; McLain, S. J.; Calabrese, J. C.;
Davidson, F.; Marshall, W. J. J. Am. Chem. Soc. 1994, 116, 7927−7928.
(2) (a) Arnold, P. L.; Liddle, S. T. Chem. Commun. 2006, 3959−
3971. (b) Liddle, S. T.; Edworthy, I. S.; Arnold, P. L. Chem. Soc. Rev.
2007, 36, 1732−1744. (c) Arnold, P. L.; Casely, I. J. Chem. Rev. 2009,
109, 3599−3611.
(3) (a) Patel, D.; Liddle, S. T.; Mungur, S. A.; Rodden, M.; Blake, A.
J.; Arnold, P. L. Chem. Commun. 2006, 1124−1126. (b) Arnold, P. L.;
Casely, I. J.; Turner, Z. R.; Carmichael, C. D. Chem.Eur. J. 2008, 14,
10415−10422. (c) Turner, Z. R.; Bellabarba, R.; Tooze, R. P.; Arnold,
P. L. J. Am. Chem. Soc. 2010, 132, 4050−4051. (d) Arnold, P. L.;
Turner, Z. R.; Bellabarba, R.; Tooze, R. P. J. Am. Chem. Soc. 2011, 133,
11744−11756.
(4) (a) Yao, H. S.; Zhang, Y.; Sun, H. M.; Shen, Q. Eur. J. Inorg.
Chem. 2006, 1124−1126. (b) Wang, Z. G.; Sun, H. M.; Yao, H. S.;
Yao, Y. M.; Shen, Q.; Zhang, Y. J. Organomet. Chem. 2006, 691, 3383−
3390. (c) Wang, Z. G.; Sun, H. M.; Yao, H. S.; Yao, Y. M.; Shen, Q.;
Zhang, Y. Organometallics 2006, 25, 4436−4438. (d) Yao, H. S.;
Zhang, J. G.; Zhang, Y.; Sun, H. M.; Shen, Q. Organometallics 2010,
29, 5841−5846.
(5) Zhang, J. G.; Yao, H. S.; Zhang, Y.; Sun, H. M.; Shen, Q.
Organometallics 2008, 27, 2672−2675.
Correction of Area Detector Data; University of Gottingen: Gottingen,
̈
̈
Germany, 1996.
(6) (a) Arnold, P. L.; McMaster, J.; Liddle, S. T. Chem. Commun.
2009, 818−820. (b) Liddle, S. T.; Arnold, P. L. Organometallics 2005,
24, 2597−2605. (c) Arnold, P. L.; Mungur, S. A.; Blake, A. J.; Wilson,
C. Angew. Chem., Int. Ed. 2003, 42, 5981−5984.
(23) SHELXTL Program, version 5.1; Siemens Industrial Automa-
tion, Inc.: Madison, WI, 1997.
(7) Wang, B. L.; Wang, D.; Cui, D. M.; Gao, W.; Tang, T.; Chen, X.
S.; Jing, X. B. Organometallics 2007, 26, 3167−3172.
(8) (a) Wang, B. L.; Tang, T.; Li, Y.; Cui, D. M. Dalton Trans. 2009,
38, 8963−8969. (b) Yao, C. G.; Wu, C. J.; Wang, B. L.; Cui, D. M.
Organometallics 2013, 32, 2204−2209.
(9) (a) Wang, B. L.; Cui, D. M.; Lv, K. Macromolecules 2008, 41,
1983−1988. (b) Lv, K.; Cui, D. M. Organometallics 2010, 29, 2987−
2993.
(10) (a) Moulton, C. J.; Shaw, B. L. J. Chem. Soc., Dalton Trans. 1976,
1020−1024. (b) Pugh, D.; Danopoulos, A. Coord. Chem. Rev. 2007,
251, 610−641. (c) Mata, J.; Poyatos, M.; Peris, E. Coord. Chem. Rev.
2007, 251, 841−859. (d) Mas-Marza, E.; Poyatos, M.; Sanau, M.;
Peris, E. Organometallics 2004, 23, 323−325. (e) Han, V. H.; Dan, Y.;
Yuan, H. Dalton Trans. 2009, 7262−7268.
(11) (a) Huckaba, A. J.; Hollis, T. K.; Howell, T. O.; Valle, H. U.;
Wu, Y. S. Organometallics 2013, 32, 63−69. (b) Zuo, W. W.;
Braunstein, P. Organometallics 2012, 31, 2606−2615. (c) Wei, W.;
Qin, Y. C.; Luo, M. M.; Xia, P. F.; Shing, M.; Wong, M.
2379
dx.doi.org/10.1021/om500354s | Organometallics 2014, 33, 2372−2379