Synthesis and catalytic application of magnesium complexes bearing pendant indolyl ligands

Article abstract of DOI:10.1039/c5dt01173f

Three novel indole-based ligand precursors [HIndPh^R, R = methoxy, HIndPh^OMe (2a); thiomethoxy, HIndPh^SMe (2b); and N,N′-dimethylamino, HIndPh^NMe2 (2c)] have been synthesized via Sonogashira and cyclization react

Full text of DOI:10.1039/c5dt01173f

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Synthesis and catalytic application of magnesium
complexes bearing pendant indolyl ligands†
Cite this: DOI: 10.1039/c5dt01173f
Kuo-Fu Peng, Yun Chen and Chi-Tien Chen*
Three novel indole-based ligand precursors [HIndPhR, R = methoxy, HIndPhOMe (2a); thiomethoxy,
HIndPhSMe (2b); and N,N’-dimethylamino, HIndPhNMe2 (2c)] have been synthesized via Sonogashira and
cyclization reactions with moderate to high yield. Reactions of these ligand precursors with 0.6 equivalent
of MgnBu2 in THF afforded the magnesium bis-indolyl complexes 3a–3c, respectively. All the ligand pre-
cursors and related magnesium complexes have been characterized by NMR spectroscopy and elemental
analyses. The molecular structures are reported for compounds 3a and 3b. Under optimized conditions,
compound 3a demonstrates efficient catalytic activities towards the ring opening polymerization of
L-lactide and ε-caprolactone in the presence of BnOH.
Received 25th March 2015,
Accepted 14th April 2015
DOI: 10.1039/c5dt01173f
www.rsc.org/dalton
investigation of organo-catalyzed ROP using indole as the
organocatalyst has been reported;12a,b the indole-containing
Introduction
Environmentally friendly polyesters, such as poly(ε-capro- metal complexes used in the ROP of cyclic esters are rare. Bild-
lactone) (PCL) or polylactide (PLA), are the most important syn- stein’s group reported the enantioselective chiral indole-imino
thetic biodegradable polymers, and these polymers have chromium(III) complexes for the conversion of propylene oxide
attracted great interest for various applications, especially in and CO to enantioenriched β-butyrolactone that is the
the drug delivery or biomedical field based on their biocompa- key monomer for the production of PHB by ring-opening
tible properties.1 The main method to synthesize the poly- polymerization.12c Recently, Lamberti’s group designed anili-
esters is the ring opening polymerization (ROP) reaction using dopyridyl-indolyl yttrium complexes which demonstrated mod-
metal complexes.1c Although a number of excellent catalysts erate stereoselectivity and efficient activities in the ROP of
have been examined for the ROP,2 chemists are still interested rac-lactide.12d Herein, we report the synthesis and characteriz-
in the development of novel efficient metal catalysts to ation of magnesium complexes incorporating pendant
produce polymers which contain the properties of a precise functionalized indolyl ligands. To our knowledge, no
molecular weight, narrow polydispersity index (PDI), efficient analogous magnesium complexes derived from substituted
rate and high enantio- or regio-selectivity under mild con- indolyl ligands have been reported. Their application
ditions. Recently, the metal complexes supported by N-hetero- towards the ROP of L-lactide (L-LA) and ε-caprolactone (ε-CL)
cyclic-containing anionic ligands, such as pyrrole,3 pyridine,3i,4 will be examined.
pyrazole,5 imidazole,3i,6 oxazoline,7 quinoline,4a–d,8 benzotri-
azole,9 and carbazole,10 have been shown to exhibit catalytic
activities towards the ROP of cyclic esters. We also previously
Results and discussion
Preparation of ligand precursors and magnesium complexes
reported some metal complexes bearing pendant mono-
anionic anilido-pyrazolate5m or anilido-oxazolinate7b–d ligands
which worked as catalysts/initiators in catalyzing the ROP of
cyclic esters. Some metal complexes supported by indolyl
ligands have been reported and applied in many catalytic reac-
tions,11 such as olefin polymerization,11a–h hydroarylation,11i–j
cross-coupling reactions11k–l and others.11m–p Although the
The synthesis of indole compounds has been reported
through many strategies, such as Fischer indole synthesis or
Pd/Cu-catalyzed cyclization.13 According to experimental oper-
ation and for a cost-effective procedure, our strategy focused
on the Sonogashira reaction14 and Zn-mediated cyclization,15
as shown in Scheme 1. The acetylene ligand precursors 1a–1c
were prepared via Pd/Cu-catalyzed Sonogashira reaction
[PdCl2(PPh3)2/CuI/HNEt2 for 1a and 1b, and PdCl2/dppf/CuI/
HNEt2 for 1c] from the reactions of 2-ethynylaniline with aryl
halides (2-iodoanisole for 1a, 2-iodothioanisole for 1b and
2-bromo-N,N-dimethylaniline for 1c) under mild conditions,
Department of Chemistry, National Chung Hsing University, Taichung 402, Taiwan.
E-mail: ctchen@dragon.nchu.edu.tw
†Electronic supplementary information (ESI) available. CCDC 1044567–1044568.
For ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/c5dt01173f
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Fig. 1 Molecular structure of one of the crystallographically indepen-
dent molecules of 3a. Hydrogen atoms are omitted for clarity. Selected
bond lengths (Å) and bond angles (°): Mg–N, 2.091(2); Mg–O(1), 2.149(1);
Mg–O(2), 2.228(1); N–C(8), 1.381(2); C(8)–C(9), 1.478(3); C(9)–C(14),
1.400(3); O(1)–C(14), 1.406(2); O(1)–C(15), 1.447(2); O(1)–Mg–O(1A),
180.00(10); O(2)–Mg–O(2A), 180.00(10); N–MgN(0A), 180.00(12); O(1)–
Mg–O(2), 83.98(5); N–Mg–O(2), 86.34(6); N–Mg–O(1), 83.01(6); Mg–N–
C(8), 125.66(13); Mg–O(1)–C(14), 121.67(11).
Scheme 1
respectively.14c Compounds 1a and 1b were prepared in high
yields without further purification for the cyclization.
However, compound 1c had to be purified via column
chromatography before cyclization. For these acetylene com-
pounds, the signals of –NH2 on 1H NMR spectra were found to
be around δ 4.5 ppm (4.50 ppm for 1a and 4.54 ppm for 1b)
and acetylene functionality on 13C{1H} NMR spectra was found
to be between δ 90–93 ppm (90.6 and 91.3 ppm for 1a, and
92.1 and 92.7 ppm for 1b). The NMR spectra of 1a and 1c are
consistent with those reported in the literature.16 Treatment of
acetylene compounds 1a–1c with 0.5 equivalent ZnBr2 in
refluxing toluene resulted in the formation of related indole
ligands 2a–2c in moderate to high yields, respectively. The
signals of –NH on the 1H NMR spectrum for indole 2c were
observed at δ 10.75 ppm. The NMR spectra of 2a and 2b are
consistent with those reported in the literature.17,18 Com-
pounds 1a, 1b and 2c were characterized by elemental analyses
as well.
Treatment of pendant indole ligand precursors 2a–2c with
0.6 equivalent nBu2Mg in THF affords the desired bis-indolyl
magnesium complexes 3a–3c (room temperature for 3a or
60 °C for 3b and 3c) in moderate yields. Compounds 3a–3c
were characterized by NMR spectroscopy as well as by elemen-
tal analyses. The disappearance of the N–H signal of indole
and the appearance of coordinated THF (1.02, 3.23 ppm for
3a, 1.17, 3.35 ppm for 3b and 1.42, 3.57 ppm for 3c in C6D6)
are consistent with the structures proposed in Scheme 1. The
NMR spectroscopy indicates that these compounds are highly
symmetric species in solution. The elemental analysis data are
also consistent with a complex containing two coordinated
THF.
Fig. 2 Molecular structure of one of the crystallographically indepen-
dent molecules of 3b. Hydrogen atoms are omitted for clarity. Selected
bond lengths (Å) and bond angles (°): Mg–N(1), 2.138(2); Mg–N(2),
2.126(2); Mg–O(1), 2.078(2); Mg–O(2), 2.053(2); Mg–S(1), 2.769(1); Mg–
S(2), 2.763(1); N(1)–C(8), 1.398(3); C(8)–C(9), 1.488(4); C(9)–C(14),
1.386(4); S(1)–C(14), 1.777(3); S(1)–C(15), 1.780(3); N(2)–C(23), 1.389(3);
C(23)–C(24), 1.469(3); C(24)–C(29), 1.402(4); S(2)–C(29), 1.778(3); S(2)–
C(30), 1.796(3); O(1)–Mg–O(2), 99.21(8); S(1)–Mg–S(2), 83.76(3), N(1)–
Mg–N(2), 169.17(9); O(1)–Mg–S(1), 164.32(6); O(2)–Mg–S(2), 164.80(6);
N(1)–Mg–O(1), 93.89(8); N(1)–Mg–O(2), 95.65(8); N(1)–Mg–S(1),
72.10(6); N(1)–Mg–S(2), 95.14(7); N(2)–Mg–O(1), 90.96(8); N(2)–Mg–
O(2), 93.12(8); N(2)–Mg–S(1), 101.70(6); N(2)–Mg–S(2), 75.10(6); Mg–
N(1)–C(8), 129.53(17); Mg–S(1)–C(14), 101.86(9); Mg–N(2)–C(23),
133.04(16); Mg–S(2)–C(29), 97.78(8).
Suitable crystals for the structural determination of 3a or
3b were obtained from THF/n-hexane solution. The molecular
structures are depicted in Fig. 1 and 2. The structure of 3a
reveals that the Mg centre adopts an approximate octahedral
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geometry [OTHF–Mg–OTHF ∼ 180°] with the metal centre che- angles between the planes defined by N–Mg–O(1)/N–C(8)–
lated by two nitrogen atoms of the indole ring, two oxygen C(9)–C(14)–O(1), which is 33.1° for 3a, N(1)–Mg–S(1)/N(1)–
atoms of methoxy and two oxygen atoms of coordinated THF. C(8)–C(9)–C(14)–S(1) and N(2)–Mg–S(2)/N(2)–C(23)–C(24)–
The structure of 3b reveals that the Mg centre adopts a dis- C(29)–S(2), which are 55.1° and 51.7° for 3b.
torted octahedral geometry [N(1)–Mg–N(2), 169.17(9)°, O(1)–
Ring-opening polymerization
Mg–S(1), 164.32(6)° and O(2)–Mg–S(2), 164.80(6)°] with the
metal centre chelated by two nitrogen atoms of the indole
ring, two sulfur atoms of thiomethoxy and two oxygen atoms
of coordinated THF. The positions of coordinated THF mole-
cules are different between 3a (trans- configuration) and 3b
(cis-configuration) in the solid state. This difference might
result from the soft properties of the sulfur atoms trans to the
THF molecules. However, only one set of signals corres-
Several magnesium complexes containing auxiliary ligands
have been reported as initiators/catalysts for the ROP of cyclic
esters,4f,5a,g,h,o,s,6e,7c,22 especially for those complexes bearing
β-diketiminate (BDI)22a–d or amino-phenolate22e–l ligands.
Although attempts to synthesize related magnesium benzyl
oxide complexes have been proved unsuccessful, the efficient
catalytic activities demonstrated by magnesium di-substituted
complexes7c,23c–d towards the ROP of cyclic esters encouraged
us to examine the magnesium bis-indolyl complexes 3a–3c in
catalyzing the ROP of cyclic esters. Representative results are
shown in Tables 1 and 2.
The catalytic activities employing these complexes as cata-
lysts are examined under a dry nitrogen atmosphere. The reac-
tions were run in 2.5 mL solvent at 0 °C or 30 °C for the
prescribed time with the prescribed equivalent ratios of the
catalyst (0.0125 mmol), L-LA and alcohol, as shown in Table 1.
Optimized conditions (entry 1) were found to be dichloro-
methane at 0 °C in the presence of benzyl alcohol (BnOH)
after several trials of running the polymerization with various
solvents (dichloromethane, tetrahydrofuran or toluene) and
alcohols [BnOH, 2-propanol (iPrOH) and 9-anthracenemetha-
nol (9-AnOH)] for polymerization of L-LA (entries 1–5). Poor
conversions were observed in the absence of benzyl alcohol or
3a under the optimized conditions (entries 6 and 7). The same
optimized conditions were applied to examine the catalytic
activities of the other two catalysts. Therefore a clear decreas-
ing tendency of catalytic activity was found for these mag-
nesium complexes in the order 3a > 3b > 3c (entries 1, 8 and
9). The interaction between the pendant methoxy group and
1
ponding to THF molecules has been observed on the H NMR
for 3b (Fig. S2†), even though the temperature was cooled
down to 183 K (Fig. S4†). This demonstrates the fluxional be-
haviour of coordinated THF molecules in solution. According
to the coordinated THF positions of related magnesium com-
plexes reported in the literature,19 the trans- and cis-configur-
ations are observed for 3a and 3b [OTHF–Mg–OTHF, 180.00(10)°
for 3a and 99.21(8)° for 3b], respectively. The Mg–OTHF bond
length of 3a [2.228(1) Å] is longer than that of 3b [2.053(2) and
2.078(2) Å], and this tendency is also consistent with the litera-
ture data [Mg–OTHF, 2.141(4)–2.230(4) Å for trans-form19a,b and
2.066(1)–2.136(5) Å for cis-form19c,d]. The Mg–Nindole bond
lengths [2.091(2) Å for 3a, and 2.126(2) and 2.138(2) Å for 3b]
are close to those found in magnesium anilido complexes
[1.994(2)–2.131(2) Å].7c,20 The Mg–Omethoxy bond length
[2.149(1) Å] for 3a is close to that found in magnesium com-
plexes bearing methoxy functionality [2.109(2)–2.239(2) Å].7c,21
The Mg–Sthiomethoxy bond length [2.769(1) and 2.763(1) Å] for
3b is shorter than that for anilido-oxazolinate magnesium
complexes containing thiomethoxy functionality [2.8613(9)
and 2.8215(9) Å].7c The chelate 6-membered rings of 3a and 3b
have a half-chair conformation as evidenced by the dihedral
Table 1 Polymerisation of L-LA using compounds 3a–3c as catalysts in CH2Cl2 if not stated otherwisea
Conv.d (%)
Yielde (%)
Mw/Mn
b
Entry
Catalyst
[LA]0 : [Mg]0 : [ROH]
T (°C)
t (min)
Mn b (obsd)
Mn c (calcd)
1
3a
3a
3a
3a
3a
3a
3a
3b
3c
3a
3a
3a
3a
3a
3a
3a
300 : 1 : 1
300 : 1 : 1
300 : 1 : 1
300 : 1 : 1
300 : 1 : 1
300 : 1 : 0
300 : 0 : 1
300 : 1 : 1
300 : 1 : 1
200 : 1 : 1
300 : 1 : 1
400 : 1 : 1
500 : 1 : 1
600 : 1 : 1
400 : 1 : 2
500 : 1 : 5
0
0
0
0
0
0
0
0
0
30
30
30
30
30
30
30
3
3
3
3
3
3
3
3
3
1
1
1
1
3
1
2
40 300
—
—
40 000
—
—
—
29 800
—
26 600
35 000
43 100
47 400
50 400
35 100
18 900
37 300
—
—
31 600
—
—
—
22 500
—
28 400
41 200
55 500
69 300
81 400
28 400
14 100
86
11
<5
73
12
<5
<5
52
17
98
95
96
96
94
98
97
82
—
—
68
—
—
—
47
—
89
93
94
95
91
94
87
1.35
—
—
1.24
—
—
—
1.91
—
1.31
1.29
1.31
1.23
1.24
1.28
1.13
2f
3g
4h
5i
6
7
8
9
10
11
12
13
14
15
16
a [Mg]0 = [BnOH] = 0.005 M in 2.5 mL CH2Cl2. b Obtained from GPC analysis values time 0.58. c Calculated from [M(monomer) × [LA]0/[Mg]0
conversion yield/([ROH]eq)] + M(ROH). d Obtained from 1H NMR analysis. e Isolated yield. f In toluene. g In THF. h ROH = iPrOH. i ROH = 9-AnOH.
×
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Table 2 Polymerisation of ε-CL using compound 3a as the catalyst in toluene if not stated otherwisea
Conv.d (%)
Yielde (%)
Mw/Mn
b
Entry
[CL]0 : [Mg]0 : [BnOH]
T (°C)
t (min)
Mn b (obsd)
Mn c (calcd)
1f
2g
3
4
5
6
7
8
9
500 : 1 : 1
500 : 1 : 1
500 : 1 : 1
500 : 1 : 0
500 : 0 : 1
100 : 1 : 1
300 : 1 : 1
700 : 1 : 1
100(100) : 1 : 1
250 : 1 : 2.5
500 : 1 : 5
0
0
0
0
0
0
0
0
0
1
1
1
1
—
—
—
—
<5
46
99
81
<5
99
98
97
—
—
90
70
—
91
93
90
92
92
91
—
—
64 800
142 500
—
28 900
49 500
82 300
32 400
20 300
17 400
56 600
46 200
—
11 400
33 700
77 600
22 700
11 400
11 300
1.33
1.14
—
1.27
1.32
1.26
1.29
1.15
1.17
1
0.5
0.75
7
0.5(1)
3
99(99)
99
98
10
11
0
30
7
a [Mg]0 = [BnOH] = 0.0083M in 1.875 mL toluene. b Obtained from GPC analysis values time 0.56. c Calculated from [M(monomer) × [CL]0/[Mg]0 ×
conversion yield/([BnOH]eq)] + M(BnOH). d Obtained from 1H NMR analysis. e Isolated yield. f In CH2Cl2. g In THF.
the magnesium center might affect the activities of this cata- values (comparing with entry 10). The ROP of rac-lactide (rac-
lytic system. The linear relationship (R2 value = 0.957) between LA) employing 3a or 3b at 0 °C under the optimized conditions
1
the number-average molecular weight (Mn) and the monomer- was examined. Based on the homonuclear decoupled H NMR
to-initiator ratio ([L-LA]0/[Mg]0 = 200–600) is demonstrated in spectra, the atactic polylactides (Pr = 0.51 for 3a; Pr = 0.43 for
Fig. 3 (Table 1, entries 10–14, PDIs = 1.23–1.31). The gap 3b) were produced. Comparing with other structure-related
between calculated molecular weight [Mn(calcd)] and observed magnesium complexes, the catalytic activity of 3a was more
molecular weight [Mn(obsd)] was easily obtained with a higher than magnesium complexes bearing anilido-oxazolinate
monomer-to-initiator loading ratio. This means that the cata- ligands,7c benzotriazole phenoxide ligands,9d or amino-
lyst demonstrates poor living and controlled behaviors in cata- phenolate ligands.22c,h
lyzing polymerization reactions. The end group analysis is
Optimized catalyst 3a was introduced for examining the
demonstrated by the 1H NMR spectrum of polylactide catalytic activities in the ROP of ε-CL under a dry nitrogen
(PLA-100), as shown in Fig. 4. Peaks are assignable to the atmosphere. The prescribed equivalent ratios of the catalyst
corresponding protons in the proposed structure. However, the (0.0156 mmol), ε-CL and BnOH were employed in 1.875 mL
ESI-MS spectrum (Fig. S5†) shows that serious trans-esterifica- solvent at 0 °C for the prescribed time, as shown in Table 2.
tion could happen in this system.23a,b With reference to the Toluene seems to be the right choice at 0 °C in the presence of
mechanism reported for magnesium complexes bearing an BnOH for the ROP of ε-CL after running the polymerization
N,N di-anionic ligand or a bis(N,O-chelate) ligand, the active reactions with various solvents (dichloromethane, tetrahydro-
magnesium alkoxide species might form first, followed by the furan or toluene) (entries 1–3). Compound 3a showed efficient
coordination–insertion mechanism.23c,e The immortal behav- activities in the presence of BnOH, however lower activity and
ior was demonstrated using benzyl alcohol as the chain trans- higher molecular weight were observed in the absence of
fer agent (entries 15 and 16) resulting in the reasonable Mn BnOH (entries 3 and 4). The polymerization reaction might be
initiated by a ligand in the absence of BnOH. Trace amount of
polymers was observed in the absence of 3a under the opti-
mized conditions (entry 5). The linear relationship (R2 value =
0.996) between the number-average molecular weight and
monomer-to-initiator ratio ([ε-CL]0/[Mg]0) exhibited by 3a
implies the “living” character of the polymerization process
under optimized conditions (entries 3, 6–8; PDIs = 1.26–1.33).
Representative results catalyzed by 3a are shown in Fig. 5. The
“living” character was also confirmed by the resumption
experiment (entry 9). The end group analysis is demonstrated
by the 1H NMR spectrum of polycaprolactone (PCL-100), as
shown in Fig. 6. Peaks are assignable to the corresponding
protons in the proposed structure, indicating that a similar
mechanism as discussed above might happen in the polymer-
ization of ε-CL. The “immortal” character was examined using
2.5 or 5 equivalents of BnOH as the chain transfer agent to
produce the polymers with a lower molecular weight at 0 °C or
30 °C (entries 10 and 11). Compound 3a showed better cata-
Fig. 3 Polymerization of L-LA catalyzed by 3a in CH2Cl2 at 30 °C.
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Fig. 4 1H NMR spectrum of PLA-100 initiated by 3a in the presence of BnOH in CH2Cl2 at 0 °C.
cing lower molecular weights and moderate PDIs (∼1.3) meaning
in a poorly controlled fashion. The mass spectrum of the pro-
duced polymers reveals that serious trans-esterification could
happen during polymerization. Complex 3a also demonstrated
activities in catalyzing the ROP of ε-CL efficiently, producing
the expected molecular weights and narrow PDIs (∼1.2). Pre-
liminary studies on fine-tuning the modification of indole
ligands with different substituents and their application in the
synthesis of metal complexes are currently underway.
Experimental
General conditions
All manipulations were carried out under an atmosphere of
dinitrogen using standard Schlenk-line or drybox techniques.
Solvents were refluxed over the appropriate drying agent and
distilled prior to use. Deuterated solvents were dried over
Fig. 5 Polymerization of ε-CL catalyzed by 3a in toluene at 0 °C.
lytic activity than that demonstrated by magnesium complexes molecular sieves.
bearing sulfonate phenoxide ligands.22u
1H and 13C{1H} NMR spectra were recorded either on
Varian Mercury-400 (400 MHz) or Varian Inova-600 (600 MHz)
spectrometers in chloroform-d or benzene-d6 at ambient temp-
erature unless stated otherwise and referenced internally to
the residual solvent peak and reported as parts per million
Conclusions
Three novel magnesium bis-indolyl complexes 3a–3c have relative to tetramethylsilane. Elemental analyses were per-
been synthesized and fully characterized. They all show two co- formed by an Elementar Vario ELIV instrument. The GPC
ordinated THF molecules in the NMR spectroscopic studies measurements were performed in THF at 35 °C with a Waters
and elemental analyses. The molecular determination by 1515 isocratic HPLC pump, a Waters 2414 refractive index
single-crystal X-ray crystallography for 3a and 3b is also con- detector, and a Waters styragel column (HR4E). Molecular
sistent with this result. Under optimized conditions, complex weights (Mn) and molecular weight distributions (PDIs) were
3a shows catalytic activities for the ROP of L-LA in the presence calculated using polystyrene as the standard. The electrospray
of benzyl alcohol with “immortal” behaviour, however, produ- ionization mass spectrometry (ESI-MS) analyses were carried
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Fig. 6 1H NMR spectrum of PCL-100 initiated by 3a in the presence of BnOH in toluene at 0 °C.
out with a Thermo Finnigan TSQ Quantum Triple Quadrupole was purified via column chromatography (ethyl acetate :
Mass Spectrometer.
n-hexane = 1 : 5). Yield, 1.12 g, 99%. 1H NMR (400 MHz):
2-Bromo-N,N-dimethylaniline (TCI), 2-iodoanisole (Alfa δ(ppm) 3.89 (s, –OCH3, 3H), 4.50 (b, –NH, 2H), 6.67–6.72
Aesar), 2-iodothioanisole (Alfa Aesar), bis(triphenylphosphine)- (overlap, Ar-H, 2H), 6.90 (d, J = 8.4 Hz, Ar-H, 1H), 6.94 (td, J =
palladium(II)chloride (Acros), copper(I) iodide (Strem), palla- 7.6 & 0.8 Hz, Ar-H, 1H), 7.12 (m, Ar-H, 1H), 7.29 (m, Ar-H, 1H),
dium(II) chloride (UR Chemical), 1,1′-bis(diphenylphosphino)- 7.45 (dd, J = 7.6 & 1.6 Hz, Ar-H, 1H), 7.36 (dd, J = 7.6 & 1.6 Hz,
ferrocene (Strem), diethylamine (Acros), zinc(II) bromide Ar-H, 1H). 13C{1H} NMR (100 MHz): δ(ppm) 52.6 (–OCH3),
(Acros), 9-anthracenemethanol (Acros) and di-n-butyl mag- 110.4, 114.0, 117.5, 120.5, 129.4, 129.5, 131.2, 132.3 (Ar-C),
nesium (1.0 M in heptane, Aldrich) were used as supplied. 90.6, 91.3, 108.0, 112.6, 148.1, 159.6 (tert-C). Anal. Calc. for
N,N-Dimethylforamide (TEDIA) was dried over molecular C15H13NO (M.W. 239.34): C, 80.69; H, 5.87; N, 6.27. Found: C,
sieves before use. Benzyl alcohol (TEDIA) and ε-caprolactone 80.50; H, 5.90; N, 6.30%. The NMR spectra are consistent with
(Acros) were dried over CaH2 and distilled before use. L- or rac- the literature report.16
lactide (Bio Invigor) were recrystallized from dry toluene prior
2-[(2-Thiomethoxyphenyl)ethynyl]aniline (1b). The pro-
to use. 2-Ethynylaniline was prepared by the modification of cedure for the preparation of 1b was similar to that used for
methods reported in the literature.14
1a, using PdCl2(PPh3)2 (0.0175 g, 2.5 mol%), CuI (0.0095 g,
5 mol%), 2-iodothioanisole (1.25 g, 5.0 mmol), and 2-ethynyl-
aniline (0.703 g, 6 mmol), 5 mL DMF and HNEt2 (4.14 mL,
40 mmol) for 2.5 hours. The crude product was pumped to
dryness to afford a green oil, 1b. Compound 1b was pure
enough without the need for further purification for the next
step, otherwise it was purified via column chromatography
(ethyl acetate : n-hexane = 1 : 5). Yield, 1.20 g, 99%. 1H NMR
(400 MHz): δ(ppm) 2.49 (s, –SCH3, 3H), 4.54 (b, –NH, 2H),
6.68–6.71 (overlap, Ar-H, 2H), 7.09–7.14 (overlap, Ar-H, 2H),
7.18 (d, J = 8.0 Hz, Ar-H, 1H), 7.28 (td, J = 7.6 & 1.1 Hz, Ar-H,
1H), 7.38 (dd, J = 8.0 & 1.6 Hz, Ar-H, 1H), 7.48 (dd, J = 7.6 & 0.8
Hz, Ar-H, 1H). 13C{1H} NMR (100 MHz): δ (ppm) 15.1 (–SCH3),
114.1, 117.5, 124.3, 124.4, 128.4, 129.8, 131.7, 131.7 (Ar-C),
92.1, 92.7, 107.4, 121.6, 148.1, 140.4 (tert-C). Anal. Calc. for
C15H13NS (M.W. 239.34): C, 75.28; H, 5.47; N, 5.85. Found: C,
75.70; H, 5.84; N, 6.05%.
Preparations
2-[(2-Methoxyphenyl)ethynyl]aniline (1a). To a flask con-
taining PdCl2(PPh3)2 (0.0175 g, 2.5 mol%), CuI (0.0095 g,
5 mol%), 2-iodoanisole (1.17 g, 5 mmol) and 2-ethynylaniline
(0.703 g, 6 mmol), 5 mL DMF and HNEt2 (4.14 mL, 40 mmol)
were added at room temperature under nitrogen. The reaction
mixture was heated at 50 °C for 14 hours and the conversion
was monitored by 1H NMR spectrum. The reaction mixture
was allowed to cool to room temperature. Then the mixture
was extracted with a mixed solution of 20 mL ethyl acetate and
50 mL de-ionized water. The organic layer was separated and
dried over magnesium sulphate. The solution was passed
through a pad of silica gel. The filtrate was pumped to dryness
to afford green oil, 1a. Compound 1a was pure enough without
the need for further purification for the next step, otherwise it
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2-{[2-(N,N-dimethylamino)phenyl]ethynyl}aniline (1c). The
Bis[2-(2-methoxyphenyl)indolyl]magnesium·2THF (3a). To a
procedure for the preparation of 1c was similar to that used flask containing 2a (0.893 g, 4.0 mmol) in 6 mL THF, di-n-
for 1a, using PdCl2 (0.0177 g, 10.0 mol%), DPPF (0.111 g, butyl magnesium (2.4 mL, 2.4 mmol) was added at 0 °C. The
20 mol%), CuI (0.038 g, 20 mol%), 2-bromo-N,N-dimethyl- reaction mixture was allowed to warm up to room temperature.
aniline (0.800 g, 4 mmol) and 2-ethynylaniline (0.609 g, After 1 hour of stirring, a pale-orange suspension was formed.
5.2 mmol), 5 mL DMF and HNEt2 (3.30 mL, 32 mmol) for Then the orange solution was removed by filtration and the
24 hours at 80 °C. The conversion of 1H NMR spectrum was off-white solid obtained was washed with 3 mL cool THF
monitored up to about 70%. The crude product was purified twice. The residue was pumped to dryness to afford a
by column chromatography (ethyl acetate : n-hexane = 1 : 5) to white solid. Yield, 0.90 g, 74%. 1H NMR (C6D6, 600 MHz):
afford a pale-yellow solid, 1c. Yield, 0.60 g, 63%. 1H NMR δ (ppm) 1.02 (b, –CH2–, 8H), 2.99 (s, –OCH3, 6H), 3.23
(400 MHz): δ(ppm) 2.94 (s, –N(CH3)2, 6H), 4.43 (b, –NH, 2H), (b, –OCH2–, 8H), 6.79 (d, J = 7.8 Hz, Ar-H, 1H), 6.96 (td, J = 7.8
6.68–6.72 (overlap, Ar-H, 2H), 6.91–6.98 (overlap, Ar-H, 2H), & 1.6 Hz, Ar-H, 1H), 7.01 (m, Ar-H, 1H), 7.26 (s, Ar-H, 1H),
7.12 (td, J = 7.8 & 1.2 Hz, Ar-H, 1H), 7.25 (td, J = 7.8 & 1.6 Hz, 7.32–7.38 (overlap, Ar-H, 2H), 7.46 (d, J = 7.8 Hz, Ar-H, 1H),
Ar-H, 1H), 7.35 (m, Ar-H, 1H), 7.48 (dd, J = 7.8 & 1.6 Hz, Ar-H, 8.06 (dd, J = 7.8 & 1.8 Hz, Ar-H, 1H), 8.13 (d, J = 7.2 Hz, Ar-H,
1H). The NMR spectrum is consistent with literature reports.16
1H). 13C{1H} NMR (C6D6, 150 MHz): δ(ppm) 25.2 (–CH2–),
2-(2-Methoxyphenyl)-1H-indole (2a). To a flask containing 59.9 (–OCH3), 68.7 (–OCH2–), 101.3, 114.5, 116.7, 118.1,
ZnBr2 (0.563 g, 2.5 mmol), a toluene solution of 1a (1.12 g, 120.0, 120.8, 125.0, 127.0, 130.76 (Ar-C), 129.1, 132.5, 143.8,
5.0 mmol) was added at room temperature under nitrogen. 147.0, 153.5 (tert-C). Anal. Calc. for C38H40MgN2O4
The reaction mixture was heated at 100 °C for 1.5 hours. After (M.W. 613.04): C, 74.45; H, 6.58; N, 4.57. Found: C, 73.99; H,
cooling, the mixture was passed through a pad of silica gel 6.49; N, 4.39%.
and the filtrate was pumped to dryness to afford a dark brown
Bis[2-(2-thiomethoxyphenyl)indolyl]magnesium·2THF (3b).
oil. The crude product was purified by column chromato- To a flask containing 2b (0.359 g, 1.5 mmol) in 2 mL THF, di-
graphy (ethyl acetate : n-hexane = 1 : 3) to afford the product as n-butyl magnesium (0.9 mL, 0.9 mmol) was added at 0 °C. The
1
a pale-yellow solid. Yield, 1.05 g, 94%. H NMR (400 MHz): δ reaction mixture was allowed to warm up to room temperature
(ppm) 3.98 (s, –OCH3, 3H), 6.89 (b, Ar-H, 1H), 6.99–7.11 and reacted at 60 °C. After 1 hour of stirring, the volatiles were
(overlap, Ar-H, 3H), 7.17 (t, J = 7.2 Hz, Ar-H, 1H), 7.26 (t, J = 7.8 removed under reduced pressure. The residue was washed
Hz, Ar-H, 1H), 7.40 (d, J = 7.6 Hz, Ar-H, 1H), 7.63 (d, J = 7.2 Hz, with 3 mL cool THF three times and pumped to dryness to
Ar-H, 1H), 7.83 (d, J = 7.6 Hz, Ar-H, 1H), 9.64 (b, –NH, 1H). The afford a pale-yellow solid. Yield, 0.23 g, 48%. 1H NMR
NMR spectrum is consistent with the literature.17
(C6D6, 600 MHz): δ(ppm) 1.17 (b, –CH2–, 8H), 1.62 (s, –SCH3,
2-(2-Thiomethoxyphenyl)-1H-indole (2b). The procedure for 6H), 3.35 (b, –OCH2–, 8H), 6.69–6.70 (overlap, Ar-H, 4H),
the preparation of 2b was similar to that used for 2a with 1b 6.93 (m, Ar-H, 2H), 7.03 (s, Ar-H, 1H), 7.22 (m, Ar-H, 2H),
(1.20 g, 5.0 mmol) and ZnBr2 (0.563 g, 2.5 mmol). The reaction 7.31 (t, J = 6.9 Hz, Ar-H, 2H), 7.52 (d, J = 8.4 Hz, Ar-H, 2H),
mixture was heated at 100 °C for 1 hour. The crude product 7.59 (d, J = 7.2 Hz, Ar-H, 2H), 8.05 (d, J = 7.8 Hz, Ar-H, 2H).
was purified by column chromatography (ethyl acetate : 13C{1H} NMR (C6D6, 150 MHz): δ(ppm) 16.2 (–SCH3), 25.3
n-hexane = 1 : 6) to afford the product as a pale-brown solid. (–CH2–), 68.7 (–OCH2–), 103.5, 114.9, 118.2, 120.2,
Yield, 1.13 g, 94%. 1H NMR (400 MHz): δ (ppm) 2.38 (s, –SCH3, 120.8, 126.4, 128.4, 129.5, 131.6 (Ar-C), 129.8, 132.4, 139.2,
3H), 6.79 (d, J = 2.0 Hz, Ar-H, 1H), 7.12 (t, J = 7.8 Hz, Ar-H, 1H), 145.9, 147.2 (tert-C). Anal. Calc. for C38H40MgN2O2S2
7.18–7.33 (overlap, Ar-H, 3H), 7.40 (m, Ar-H, 1H), 7.58 (dd, J = (M.W. 645.17): C, 70.74; H, 6.25; N, 4.34. Found: C, 70.43;
7.8 & 1.8 Hz, Ar-H, 1H), 7.65 (d, J = 8.0 Hz, Ar-H, 1H), 9.09 (b, H, 6.25; N, 4.29%.
–NH, 1H). The NMR spectrum is consistent with the literature
Bis{2-[2-(N,N-dimethylamino)phenyl]indolyl}magnesium·2THF
(3c). To a flask containing 2c (0.226 g, 1.0 mmol) in 10 mL
report.18
2-[2-(N,N-Dimethylamino)phenyl]-1H-indole (2c). The pro- THF, di-n-butyl magnesium (0.6 mL, 0.6 mmol) was added at
cedure for the preparation of 2c was similar to that used for 2a 0 °C. The reaction mixture was allowed to warm up to room
with 1c (0.853 g, 3.6 mmol) and ZnBr2 (0.406 g, 1.8 mmol). temperature and reacted at 60 °C for 2 hours. After cooling,
The reaction mixture was heated at 100 °C for 14 h. The crude the orange solution was stirred at room temperature for
product was purified by column chromatography (ethyl further 12 hours to form a suspension. The reaction mixture
acetate : n-hexane = 1 : 8) to afford the product as a pale-yellow was filtered and the residue was washed with 5 mL cool THF
1
1
solid. Yield, 0.52 g, 61%. H NMR (400 MHz): δ (ppm) 2.65 (s, twice to afford a pale-yellow solid. Yield, 0.11 g, 35%. H NMR
–N(CH3)2, 6H), 6.80 (m, Ar-H, 1H), 7.07–7.25 (overlap, Ar-H, (C6D6, 600 MHz): δ (ppm) 1.42 (p, J = 2.9 Hz, –CH2–, 8H), 1.81
5H), 7.38 (dd, J = 8.0 & 0.8 Hz, Ar-H, 1H), 7.62 (d, J = 7.6 Hz, (b, –N(CH3)2, 12H), 3.57 (t, J = 6.0 Hz, –OCH2–, 8H), 6.35 (m,
Ar-H, 1H), 7.73 (dd, J = 7.6 & 1.6 Hz, Ar-H, 1H), 10.75 (b, –NH, Ar-H, 2H), 6.82 (m, Ar-H, 2H), 7.00 (td, J = 7.5 & 1.0 Hz, Ar-H,
1H). 13C{1H} NMR (100 MHz): δ (ppm) 44.5 (s, –N(CH3)2), 99.6, 2H), 7.15–7.16 (overlap with C6D6, Ar-H, 2H), 7.30–7.36
110.9, 119.5, 119.6, 120.2, 121.7, 123.2, 128.2, 129.3 (Ar-C), (overlap, Ar-H, 4H), 7.57 (d, J = 8.4 Hz, Ar-H, 2H), 7.89
126.0, 128.3, 136.1, 137.8, 150.5 (tert-C). Anal. Calc. for (m, Ar-H, 2H), 8.07 (dd, J = 7.2 & 0.6 Hz, Ar-H, 2H). 13C{1H}
C16H16N2 (M.W. 236.31): C, 81.32; H, 6.82; N, 11.85. Found: C, NMR (C6D6, 150 MHz): δ(ppm) 25.8 (–CH2–), 44.1 (b,
81.14; H, 6.93; N, 11.54%.
–N(CH3)2), 67.9 (–OCH2–), 103.4, 115.7, 118.2, 119.0, 120.6,
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121.3, 126.86, 126.9, 132.6 (Ar-C), 132.2, 132.8, 144.4, lected at 100 K using an Oxford Gemini S diffractometer.
144.6, 147.7 (tert-C). Anal. Calc. for C40H46MgN4O2 Empirical absorption correction was based on spherical har-
(M.W. 639.12): C, 75.17; H, 7.25; N, 8.77. Found: C, 75.29; monics, implemented in the SCALE3 ABSPACK scaling algor-
H, 7.72; N, 9.06%.
ithm from CrysAlis RED, Oxford Diffraction Ltd. The space
Polymerization procedure of L- or rac-lactide. Typically, to a group determination was based on a check of the Laue sym-
flask containing the prescribed amount of monomers (L- or metry and systematic absences and was confirmed using the
rac-lactide) and 0.0125 mmol catalyst, was added 2.5 mL structure solution. The structure was solved by direct methods
solvent containing 0.0125 mmol alcohol. The reaction mixture using a SHELXTL package.24 All non-H atoms were located
was stirred at the prescribed temperature for the prescribed from successive Fourier maps, and hydrogen atoms were
time. After the reaction was quenched by the addition of refined using a riding model. Anisotropic thermal parameters
1.5 mL acetic acid solution (0.35 N), the resulting mixture was were used for all non-H atoms, and fixed isotropic parameters
poured into 15 mL n-hexane to precipitate polymers. Crude were used for H atoms. Some details of the data collection and
products were recrystallized from THF/hexane and dried refinement are given in Table 3. CCDC reference numbers
in vacuo up to a constant weight.
1044567–1044568 for 3a and 3b.
Polymerization procedure of ε-caprolactone. Typically, to a
flask containing the prescribed amount of monomers (ε-capro-
lactone) and 0.015625 mmol catalyst was added 1.875 mL
solvent containing 0.015625 mmol alcohol. The reaction
Acknowledgements
mixture was stirred at the prescribed temperature for the pre- We would like to thank the Ministry of Science and Technology
scribed time. After the reaction was quenched by the addition of the Republic of China for financial support (grant number
of 1.5 mL acetic acid solution (0.35 N), the resulting mixture NSC 98-2113-M-005-002-MY3 and NSC 101-2113-M-005-012-
was poured into 15 mL n-hexane to precipitate polymers. MY3).
Crude products were recrystallized from THF/hexane and dried
in vacuo up to a constant weight.
References
Crystal structure data
1 (a) K. E. Uhrich, Chem. Rev., 1999, 99, 3181;
Crystals were grown from a THF/hexane solution for 3a or 3b,
and isolated by filtration. Suitable crystals were mounted onto
Mounted CryoLoop (HAMPTON RESEARCH, size: 0.5–0.7 mm)
using perfluoropolyether oil (Aldrich, FOMBLIN®Y) and
cooled rapidly in a stream of cold nitrogen gas using an
Oxford Cryosystems Cryostream unit. Diffraction data were col-
(b) A.-C. Albertsson and I. K. Varma, Biomacromolecules, 2003,
4, 1466; (c) O. Dechy-Cabaret, B. Martin-Vaca and
D. Bourissou, Chem. Rev., 2004, 104, 6147; (d) C. K. Williams,
Chem. Soc. Rev., 2007, 36, 1573; (e) R. Tong and J. Cheng,
Angew. Chem., Int. Ed., 2008, 47, 4803.
2 (a) B. J. O’Keefe, M. A. Hillmyer and W. B. Tolman, J. Chem.
Soc., Dalton Trans., 2001, 2215; (b) J. Wu, T.-L. Yu,
C.-T. Chen and C.-C. Lin, Coord. Chem. Rev., 2006, 250, 602;
(c) R. H. Platel, L. M. Hodgson and C. K. Williams, Polym.
Rev., 2008, 48, 11; (d) M. Labet and W. Thielemans, Chem.
Soc. Rev., 2009, 38, 3484; (e) C. A. Wheaton, P. G. Hayes and
B. J. Ireland, Dalton Trans., 2009, 4832; (f) M. J. Stanford
and A. P. Dove, Chem. Soc. Rev., 2010, 39, 486;
(g) A. K. Sutar, T. Maharana, S. Dutta, C.-T. Chen and
C.-C. Lin, Chem. Soc. Rev., 2010, 39, 1724; (h) A. Arbaoui
and C. Redshaw, Polym. Chem., 2010, 1, 801; (i) N. Ajellal,
J.-F. Carpentier, C. Guillaume, S. M. Guillaume, M. Helou,
V. Poirier, Y. Sarazin and A. Trifonov, Dalton Trans., 2010,
39, 8363.
3 (a) P.-C. Kuo, J.-C. Chang, W.-Y. Lee, H. M. Lee and
J.-H. Huang, J. Organomet. Chem., 2005, 690, 4168;
(b) K.-C. Hsieh, W.-Y. Lee, L.-F. Hsueh, H. M. Lee and
J.-H. Huang, Eur. J. Inorg. Chem., 2006, 2306; (c) I.-P. Hsieh,
C.-H. Huang, H. M. Lee, P.-C. Kuo, J.-H. Huang, H.-I. Lee,
J.-T. Cheng and G.-H. Lee, Inorg. Chim. Acta, 2006, 359, 497;
(d) Y. Yang, S. Li, D. Cui, X. Chen and X. Jing, Organometal-
lics, 2007, 26, 671; (e) G. Zi, Q. Wang, L. Xiang and H. Song,
Dalton Trans., 2008, 5930; (f) L. M. Broomfield, J. A. Wright
and M. Bochmann, Dalton Trans., 2009, 8269; (g) S.-M. Ho,
Table 3 Summary of crystal data for compounds 3a and 3b
3a
3b
Formula
Fw
T, K
C38H40MgN2O4
613.03
100(2)
C38H40MgN2O2S2
645.15
100(2)
Crystal system
Space group
a, Å
b, Å
c, Å
α, °
Monoclinic
C2/c
21.2856(16)
7.6356(6)
18.3690(12)
90
Monoclinic
P2(1)/n
14.9449(4)
14.0155(3)
15.4168(4)
90
β, °
93.092(6)
90
2981.1(4)
4
1.366
0.107
6238
205
0.0527
0.1489
1.000
93.830(2)
90
3221.99(14)
4
1.330
0.223
12 852
406
0.0555
0.1571
γ, °
V, Å3
Z
ρcalc, Mg m−3
μ(Mo Kα), mm−1
Reflections collected
No. of parameters
a
R1
a
wR2
GoFb
1.000
a R1 = [∑(|F0| − |Fc|]/ ∑|F0|]; wR2 = [∑w(F0 − Fc2)2/ ∑w(F02)2]1/2, w =
2
0.10. b GoF = [∑w(F02 − Fc2)2/(Nrflns − Nparams)]1/2
.
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C.-S. Hsiao, A. Datta, C.-H. Hung, L.-C. Chang, T.-Y. Lee
and J.-H. Huang, Inorg. Chem., 2009, 48, 8004; (h) H. Du,
A. H. Velders, P. J. Dijkstra, Z. Zhong, X. Chen and
J. Feijen, Macromolecules, 2009, 42, 1058; (i) V. Katiyar and
H. Nanavati, Polym. Chem., 2010, 1, 1491; ( j) S. Qiao,
W.-A. Ma and Z.-X. Wang, J. Organomet. Chem., 2011, 696,
2746; (k) W.-Y. Huang, S.-J. Chuang, N.-T. Chunag,
C.-S. Hsiao, A. Datta, S.-J. Chen, C.-H. Hu, J.-H. Huang,
T.-Y. Lee and C.-H. Lin, Dalton Trans., 2011, 40, 7423;
(l) L.-F. Hsueh, N.-T. Chuang, C.-Y. Lee, A. Datta,
J.-H. Huang and T.-Y. Lee, Eur. J. Inorg. Chem., 2011, 5530.
4 (a) D. J. Darensbourg, W. Choi, O. Karroonnirun and
N. Bhuvanesh, Macromolecules, 2008, 41, 3493;
(b) J. Börner, U. Flörke, K. Huber, A. Döring, D. Kuckling
and S. Herres-Pawlis, Chem. – Eur. J., 2009, 15, 2362;
(c) M. Shen, W. Huang, W. Zhang, X. Hao, W.-H. Sun and
C. Redshaw, Dalton Trans., 2010, 39, 9912; (d) J. Börner,
I. dos Santos Vieira, M. D. Jonrs, A. Döring, D. Kuckling,
U. Flörke and S. Herres-Pawlis, Eur. J. Inorg. Chem., 2011,
4441; (e) Z. Zheng, G. Zhao, R. Fablet, M. Bouyahyi,
C. M. Thomas, T. Roisnel, O. Casagrande, Jr. and
J.-F. Carpentier, Dalton Trans., 2008, 2279; (f) Y. Huang,
W.-C. Hung, M.-Y. Liao, T.-E. Tsai, Y.-L. Peng and C.-C. Lin,
J. Polym. Sci., Part A: Polym. Chem., 2009, 47, 2318;
(g) E. Grunova, E. Kirillov, T. Roisnel and J.-F. Carpentier,
Dalton Trans., 2010, 39, 6739.
5 (a) M. H. Chisholm, N. W. Eilerts, J. C. Huffman, S. S. Iyer,
M. Pacold and K. Phomphrai, J. Am. Chem. Soc., 2000, 122,
11845; (b) M. H. Chisholm, J. Gallucci and K. Phomphrai,
Chem. Commun., 2003, 48; (c) M. H. Chisholm,
J. C. Gallucci and K. Phomphrai, Inorg. Chem., 2004, 43,
6717; (d) S. Milione, F. Grisi, R. Centore and A. Tuzi,
Organometallics, 2006, 25, 266; (e) B. Lian, C. M. Thomas,
O. L. Casagrande, Jr., C. W. Lehmann, T. Roisnel and
J.-F. Carpentier, Inorg. Chem., 2007, 46, 328;
(f) M. H. Chisholm, J. C. Gallucci and G. Yaman, Inorg.
Chem., 2007, 46, 8676; (g) L. F. Sánchez-Barba, A. Garcés,
M. Fajardo, C. Alonso-Moreno, J. Fernández-Baeza,
A. Otero, A. Antiñolo, J. Tejeda, A. Lara-Sánchez and
M. I. López-Solera, Organometallics, 2007, 26, 6403;
(h) B. Lian, C. M. Thomas, O. L. Cassgrande, Jr., T. Roisnel
and J.-F. Carpentier, Polyhedron, 2007, 26, 3817;
(i) C. Zhang and Z.-X. Wang, J. Organomet. Chem., 2008,
693, 3151; ( j) Z. Zheng, G. Zhao, R. Fablet, M. Bouyahyi,
C. M. Thomas, T. Roisnel, O. Casagrande, Jr. and
J.-F. Carpentier, New J. Chem., 2008, 32, 2279; (k) C. Alonso-
Moreno, A. Gracés, L. F. Sánchez-Barba, M. Fajardo,
J. Fernández-Baeza, A. Otero, A. L. Sánchez, A. Antiñolo,
L. Broomfield, M. I. López-Solera and A. M. Rodríguez,
(o) A. Garcés, L. F. Sánchez-Barba, C. Alonso-Moreno,
M. Fajardo, J. Fernández-Baeza, A. Otero, A. Lara-Sánchez,
I. López-Solera and A. M. Rodríguez, Inorg. Chem., 2010, 49,
2859; (p) A. Silvestri, F. Grisi and S. Milione, J. Polym. Sci.,
Part A: Polym. Chem., 2010, 48, 3632; (q) C.-Y. Tsai, C.-Y. Li,
C.-H. Lin, B.-H. Huang and B.-T. Ko, Inorg. Chem.
Commun., 2011, 14, 271; (r) A. Otero, A. Lara-Sánchez,
J. Fernández-Baeza, C. Alonso-Moreno, J. A. Castro-Osma,
I. Márquez-Segovia, L. F. Sánchez-Barba, A. M. Rodríguez
and J. C. Garcia-Martinez, Organometallics, 2011, 30, 1507;
(s) L. F. Sánchez-Barba, A. Garcés, J. Fernández-Baeza,
A. Otero, C. Alonso-Moreno, A. Lara-Sánchez and
A. M. Rodríguez, Organometallics, 2011, 30, 2775.
6 (a) M. K. Samantaray, V. Katiyar, D. Roy, K. Pang,
H. Nanavati, R. Stephen, R. B. Sunoj and P. Ghosh,
Eur. J. Inorg. Chem., 2006, 2975; (b) L. Ray, V. Katiyar,
M. J. Raihan, H. Nanavati, M. M. Shaikh and P. Ghosh,
Eur. J. Inorg. Chem., 2006, 3724; (c) M. K. Samantaray,
V. Katiyar, K. Pang, H. Nanavati and P. Ghosh, J. Organomet.
Chem., 2007, 692, 1672; (d) L. Ray, V. Katiyar, S. Barman,
M. J. Raihan, H. Nanavati, M. M. Shaikh and P. Ghosh,
J. Organomet. Chem., 2007, 692, 4259; (e) P. L. Arnold,
I. J. Casely, Z. R. Turner, R. Bellabarba and R. B. Tooze,
Dalton Trans., 2009, 7236.
7 (a) A. Alaaeddine, A. Amgoung, C. M. Thomas, S. Dagorne,
S. Bellemin-Laponnaz and J.-F. Carpentier, Eur. J. Inorg.
Chem., 2006, 3652; (b) C.-T. Chen, C.-Y. Chan, C.-A. Huang,
M.-T. Chen and K.-F. Peng, Dalton Trans., 2007, 4073;
(c) M.-T. Chen, P.-J. Chang, C.-A. Huang, K.-F. Peng and
C.-T. Chen, Dalton Trans., 2009, 9068; (d) C.-T. Chen,
H.-J. Weng, M.-T. Chen, C.-A. Huang and K.-F. Peng,
Eur. J. Inorg. Chem., 2009, 2129.
8 (a) Z.-X. Wang and C.-Y. Qi, Organometallics, 2007, 26, 2243;
(b) M. Shen, W. Zhang, K. Nomura and W.-H. Sun, Dalton
Trans., 2009, 9000; (c) B. Li, Y. Wang, Y. Yao, Y. Zhang and
Q. Shen, J. Organomet. Chem., 2009, 694, 2409;
(d) J. Börner, U. Flörke, A. Döring, D. Kuckling and
S. Herres-Pawlis, Macromol. Symp., 2010, 296, 354;
(e) W.-A. Ma and Z.-X. Wang, Dalton Trans., 2011, 1778;
(f) S. Qiao, W.-A. Ma and Z.-X. Wang, J. Organomet. Chem.,
2011, 696, 2746; (g) W.-A. Ma and Z.-X. Wang, Organometal-
lics, 2011, 30, 4364.
9 (a) C.-Y. Li, C.-Y. Tsai, C.-H. Lin and B.-T. Ko, Dalton Trans.,
2011, 40, 1880; (b) J. Y. Li, C.-Y. Li, W.-J. Tai, C.-H. Lin and
B.-T. Ko, Inorg. Chem. Commun., 2011, 14, 1104;
(c) Y.-E. Tai, C.-Y. Li, C.-H. Lin, Y.-C. Liu, B.-T. Ko and
Y. S. Sun, J. Polym. Sci., Part A: Polym. Chem., 2011, 49,
4027; (d) C.-Y. Li, J.-K. Su, C.-J. Yu, Y.-E. Tai, C.-H. Lin and
B.-T. Ko, Inorg. Chem. Commun., 2012, 20, 60.
Organometallics, 2008, 27, 1310; (l) A. D. Schofield, 10 L. Wang, D. Cui, Z. Hou, W. Li and Y. Li, Organometallics,
M. L. Barros, M. G. Cushion, A. D. Schwarz and 2011, 30, 760.
P. Mountford, Dalton Trans., 2009, 85; (m) K.-F. Peng and 11 (a) T. Matsugi, S. Matsui, S.-i. Kojoh, Y. Takagi, Y. Inoue,
C.-T. Chen, Dalton Trans., 2009, 9800; (n) A. Otero,
J. Fernández-Baeza, A. Lara-Sánchez, C. Alonso-Moreno,
T. Fujita and N. Kashiwa, Chem. Lett., 2001, 566;
(b) T. Matsugi, S. Matsui, S.-i. Kojoh, Y. Takagi, Y. Inoue,
T. Nakano, T. Fujita and N. Kashiwa, Macromolecules, 2002,
35, 4880; (c) M. R. Mason, B. N. Fneich and K. Kirschbaum,
I.
Márquez-Segovia,
L.
F.
Sánchez-Barba
and
A. M. Rodríguez, Angew. Chem., Int. Ed., 2009, 48, 2176;
This journal is © The Royal Society of Chemistry 2015
Dalton Trans.

View Article Online
Paper
Dalton Transactions
Inorg. Chem., 2003, 42, 6592; (d) J. Li, T. Gao, W. Zhang and
2002, 648, 176; (b) J. M. Fritsch, K. A. Thoreson and
K. McNeill, Dalton Trans., 2006, 4814; (c) M. Gärtner,
R. Fischer, J. Langer, H. Görls, D. Walther and
M. Westerhausen, Inorg. Chem., 2007, 46, 5118.
W.-H. Sun, Inorg. Chem. Commun., 2003, 6, 1372;
(e) W. Zuo, W.-H. Sun, S. Zhang, P. Hao and A. Shiga,
J. Polym. Sci., Part A: Polym. Chem., 2007, 45, 3415;
(f) W. Zuo, M. Zhang and W.-H. Sun, J. Polym. Sci., Part A: 21 (a) S. Blair, K. Izod, W. Clegg and R. W. Harrington,
Polym. Chem., 2009, 47, 357; (g) M. Zimmermann,
K. W. Törnroos, R. M. Waymouth and R. Anwander,
Organometallics, 2008, 27, 4310; (h) Y. Yang, Q. Wang and
Eur. J. Inorg. Chem., 2003, 3319; (b) G. W. Rabe, M. Zhang-
Preβe, F. A. Riederer and A. L. Rheingold, Inorg. Chim. Acta,
2010, 363, 2341.
D. Cui, J. Polym. Sci., Part A: Polym. Chem., 2008, 46, 5251; 22 (a) B. M. Chamberlain, M. Cheng, D. R. Moore, T. M. Ovitt,
(i) D. Karshtedt, A. T. Bell and T. D. Tilley, Organometallics,
2004, 23, 4169; ( j) D. Karshtedt, J. L. McBee, A. T. Bell and
T. D. Tilley, Organometallics, 2006, 25, 1801; (k) G. Cravotto,
F. Demartin, G. Palmisano, A. Penoni, T. Radice and
S. Tollari, J. Organomet. Chem., 2005, 690, 2017;
(l) A. Bonet, H. Gulyás, I. O. Koshevoy, F. Estevan,
M. Sanaú, M. A. Ubeda and E. Fernández, Chem. – Eur. J.,
2010, 16, 6382; (m) R. Anod, H. Inden, M. Sugino, H. Ono,
D. Sakaeda, T. Yagyu and M. Maeda, Inorg. Chim. Acta,
2004, 357, 1337; (n) D. Karshtedt, A. T. Bell and T. D. Tilley,
Organometallics, 2006, 25, 4471; (o) J. H. H. Ho,
D. S. C. Balck, B. A. Messerle, J. K. Clegg and P. Turner,
Organometallics, 2006, 25, 5800; (p) S. Taubmann and
H. G. Alt, J. Organomet. Chem., 2008, 693, 1808.
E. B. Lobkovsky and G. W. Coates, J. Am. Chem. Soc., 2001,
123, 3229; (b) M. H. Chisholm, J. Gallucci and
K. Phomphrai, Inorg. Chem., 2002, 41, 2785; (c) A. P. Dove,
V. C. Gibson, E. L. Marshall, A. J. P. White and
D. J. Williams, Dalton Trans., 2004, 570; (d) X. Xu, Y. Chen,
G. Zou, Z. Ma and G. Li, J. Organomet. Chem., 2010, 695,
1155; (e) J. Ejfler, M. Kobyłka, L. B. Jerzykiewicz and
P. Sobota, Dalton Trans., 2005, 2047; (f) L. E. Breyfogle,
C. K. Williams, V. C. Young, Jr., M. A. Hillmyer and
W. B. Tolman, Dalton Trans., 2006, 928; (g) Y. Sarazin,
V. Poirier, T. Roisnel and J.-F. Carpentier, Eur. J. Inorg.
Chem., 2010, 3423; (h) J. Ejfler, K. Krauzy-Dziedzic,
S. Szafert, L. B. Jerzykiewicz and P. Sobota, Eur. J. Inorg.
Chem., 2010, 3602; (i) L. Wang and H. Ma, Macromolecules,
2010, 43, 6535; ( j) V. Poirier, T. Roisnel, J.-F. Carpentier
and Y. Sarazin, Dalton Trans., 2011, 40, 523; (k) A. Grala,
J. Ejfler, L. B. Jerzykiewicz and P. Sobota, Dalton Trans.,
2011, 40, 4042; (l) H.-J. Chuang, S.-F. Weng, C.-C. Chang,
C.-C. Lin and H.-Y. Chen, Dalton Trans., 2011, 40, 9601;
(m) T.-L. Yu, C.-C. Wu, C.-C. Chen, B.-H. Huang, J. Wu and
C.-C. Lin, Polymer, 2005, 46, 5909; (n) J.-C. Wu,
B.-H. Huang, M.-L. Hsueh, S.-L. Lai and C.-C. Lin, Polymer,
2005, 46, 9784; (o) H.-Y. Tang, H.-Y. Chen, J.-H. Huang and
C.-C. Lin, Macromolecules, 2007, 40, 8855; (p) J. Wu,
Y.-Z. Chen, W.-C. Hung and C.-C. Lin, Organometallics,
2008, 27, 4970; (q) M.-Y. Shen, Y.-L. Peng, W.-C. Hung and
C.-C. Lin, Dalton Trans., 2009, 9906; (r) I. L. Fedushkin,
A. G. Morozov, V. A. Chudakova, G. K. Fukin and
V. K. Cherkasov, Eur. J. Inorg. Chem., 2009, 4995;
(s) W.-C. Hung and C.-C. Lin, Inorg. Chem., 2009, 48, 728;
(t) Y.-H. Tsai, C.-H. Lin, C.-C. Lin and B.-T. Ko, J. Polym.
Sci., Part A: Polym. Chem., 2009, 47, 4927; (u) P.-S. Chen,
Y.-C. Liu, C.-H. Lin and B.-T. Ko, J. Polym. Sci., Part A:
Polym. Chem., 2010, 48, 3564; (v) Y. Wang, W. Zhao, D. Liu,
S. Li, X. Liu, D. Cui and X. Chen, Organometallics, 2012, 31,
4182.
12 (a) S. Koeller, J. Kadota, A. Deffieux, F. Peruch, S. Massip,
J.-M. Léger, J.-P. Desvergne and B. Bibal, J. Am. Chem. Soc.,
2009, 131, 15088; (b) S. Koeller, J. Kadota, F. Peruch,
A. Deffieux, N. Pinaud, I. Pianet, S. Massip, J.-M. Léger,
J.-P. Desvergne and B. Bibal, Chem. – Eur. J., 2010, 16, 4196;
(c) H. Wölfle, H. Kopacka, K. Wurst, P. Preishuber-Pflügl
and B. Bildstein, J. Organomet. Chem., 2009, 694, 2493;
(d) G. Li, M. Lamberti, M. Mazzeo, D. Pappalardo,
G. Roviello and C. Pellecchia, Organometallics, 2012, 31,
1180.
13 (a) S. Cacchi and G. Fabrizi, Chem. Rev., 2011, 111, PR215;
(b) D. F. Taber and P. K. Tirunahari, Tetrahedron, 2011, 67,
7159.
14 (a) H. Doucet and J.-C. Hierso, Angew. Chem., Int. Ed., 2007,
46, 834; (b) R. Chinchilla and C. Nájera, Chem. Rev., 2007,
107, 874; (c) C. Peng, Y. Wang, L. Liu, H. Wang, J. Zhao and
Q. Zhu, Eur. J. Org. Chem., 2010, 818.
15 K. Okuma, J.-i. Seto, K.-i. Sakaguchi, S. Ozaki, N. Nagahora
and K. Shioji, Tetrahedron Lett., 2009, 50, 2943.
16 H. Li, H. Yang, J. L. Petersen and K. K. Wang, J. Org. Chem.,
2004, 69, 4500.
17 C. M. So, C. P. Lau and F. Y. Kwong, Org. Lett., 2007, 9, 2795.
18 D. M. Mckinnon and K. R. Lee, Can. J. Chem., 1988, 66, 23 (a) H. Ma and J. Okuda, Macromolecules, 2005, 38, 2665;
1405.
(b) S. Song, H. Ma and Y. Yang, Dalton Trans., 2013, 42,
14200; (c) C. Gallegos, V. Tabernero, F. M. Garcia-Valle,
M. E. G. Mosquera, T. Cuenca and J. Cano, Organometallics,
2013, 32, 6624; (d) J. Wojtaszak, K. Mierzwicki, S. Szafert,
N. Gulia and J. Ejfler, Dalton Trans., 2014, 43, 2424;
(e) B. Gao, D. Zhao, X. Li, Y. Cui, R. Duan and X. Pang, RSC
Adv., 2015, 5, 440.
19 (a) B. Srinivas, C.-C. Chang, C.-H. Chen, M. Y. Chiang,
I. T. Chen, Y. Wang and G.-H. Lee, J. Chem. Soc., Dalton
Trans., 1997, 957; (b) A. Shafir, D. Fiedler and J. Arnold,
J. Chem. Soc., Dalton Trans., 2002, 555; (c) A. S. Pedrares,
W. Teng and K. Ruhlandt-Senge, Chem. – Eur. J., 2003, 9,
2019; (d) R. K. J. Bott, M. Schormann, D. L. Hughes,
S. J. Lancaster and M. Bochmann, Polyhedron, 2006, 25, 387. 24 G. M. Sheldrick, SHELXTL-97, Program for refinement of
20 (a) K.-C. Yang, C.-C. Chang, J.-Y. Huang, C.-C. Lin,
G.-H. Lee, Y. Wang and M. Y. Chiang, J. Organomet. Chem.,
crystal structures, University of Göttingen, Germany,
1997.
Dalton Trans.
This journal is © The Royal Society of Chemistry 2015