Bis(2-cycloazylindolyl)titanium Complexes: Synthesis, Characterization, and the Catalytic Behaviors towards Hydroamination and Ring-opening Polymerization of ε-Caprolactone

Article abstract of DOI:10.1002/zaac.201500072

The ligands 2-pyrazol-1-yl-1H-indole (HL1) and 2-1,2,4-triazol-1-yl-1H-indole (HL2) individually reacted with Ti(NMe₂)₄ in tetrahydrofuran to form the corresponding complexes Ti(L1)₂(NMe₂)₂ (1) and Ti

Full text of DOI:10.1002/zaac.201500072

Journal of Inorganic and General Chemistry
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Zeitschrift für anorganische und allgemeine Chemie
DOI: 10.1002/zaac.201500072
Bis(2-cycloazylindolyl)titanium Complexes: Synthesis, Characterization, and
the Catalytic Behaviors towards Hydroamination and Ring-opening
Polymerization of ε-Caprolactone
Jing-Jing Zhao,[a] Hao Pei,[a] Yan-Mei Chen,[a,b] Ning Lu,[a] Jin-Na Liu,[a] Jin-Fa Hu,[a]
Wei Liu,[a] Wu Li,[b] and Yahong Li*[a]
Keywords: Hydroamination; Titanium; Ring-opening polymerization; ε-Caprolactone
Abstract. The ligands 2-pyrazol-1-yl-1H-indole (HL1) and 2-[1,2,4]- as well as the single-crystal X-ray diffraction of 1 and 2. Both 1 and
triazol-1-yl-1H-indole (HL2) individually reacted with Ti(NMe2)4 in
2 exhibit high activities towards intermolecular hydroamination of ter-
tetrahydrofuran to form the corresponding complexes Ti(L1)2(NMe2)2 minal alkynes with high selectivity, and they also efficiently promote
(1) and Ti(L2)2(NMe2)2 (2), respectively. The titanium complexes the ring-opening polymerization of ε-caprolactone.
were fully characterized by NMR measurement and elemental analysis
atoms are good candidates for synthesizing titanium complexes
Introduction
with good catalytic activities and selectivities.
The catalytic addition of N–H bond across a carbon–carbon
In this work, we employ 2-cycloazylindolyl ligands HL1
multiple bond, known as hydroamination, is synthetically the
(HL1 = 2-pyrazol-1-yl-1H-indole) and HL2 (HL2 = 2-
most important approach for the substituted amines and
[1,2,4]triazol-1-yl-1H-indole) to synthesize titanium com-
imines.[1] Since the hydroamination reaction could provide the
plexes. The organometallic chemistry of the titanium com-
targeted products with 100% atom economic efficiency, both
plexes based on these ligands remains unexplored. We antici-
inter- and intramolecular hydroamination have attracted ever-
pated that the donor (N, N) atoms of the ligands are well suited
increasing attention over the past two decades.[1] A plethora of
to bind high valent titanium, giving the titanium complexes
metal-based catalytic systems have been reported to induce the
with high reactivity.
hydroamination of alkynes and alkenes. Group 4 based organo-
The reactions of Ti(NMe2)4 with HL1 and HL2, respec-
metallic complexes have played a prominent role in the field
tively, generated Ti(L1)2(NMe2)2 (1) and Ti(L2)2(NMe2)2 (2).
of catalytic hydroamination, due to their low cost, low toxicity,
Herein, we report the synthesis and characterization of these
and high reactivity.[2] A mechanistic study for the titanium-
complexes. The catalytic activities of 1 and 2 towards intermo-
catalyzed hydroamination of alkynes indicated that the ligand
lecular hydroamination of alkynes and polymerization of ε-
chelating to the central metal atom plays an outstanding role
caprolactone were also investigated.
in controlling the regioselectivity of the hydroamination prod-
ucts.[3] Thus, the effects of a variety of ligands, e.g., Cp-based
molecules,[4] amidate compounds,[5] pyrrolyl ligands,[6]
guanidinate,[7] imidazole-containing compounds,[8] etc., on the
regioselectivity of the hydroamination products have been
scrutinized. All these results proved that the polydentate li-
gands with several nitrogen donors and deprotonable hydrogen
Results and Discussion
Syntheses of the Ligands and Titanium Complexes
HL1 and HL2 were prepared according to the literature pro-
cedures.[9] The addition of the HL1 ligand in THF to a cold
Ti(NMe2)4 solution (–35 °C) followed by warming to room
temperature afforded the product Ti(L1)2(NMe)2 (1)
(Scheme 1). After recrystallization from Tol/hexane, dark red
* Prof. Dr. Y. Li
Fax: +86-512-65880089
E-Mail: liyahong@suda.edu.cn
1
[a] Key Laboratory of Organic Synthesis of Jiangsu Province
College of Chemistry, Chemical Engineering and Materials Sci-
ence
crystals were obtained. Complex 1 was characterized by H
and 13C NMR spectroscopy and elemental analysis. Compari-
1
son of the H NMR spectrum of 1 with the corresponding li-
Soochow University
Suzhou, 215123, P. R. China
gand revealed that an additional resonance appeared in the
high-field region (δ = 3.46 ppm), which was attributed to the
methyl groups of NMe2, while the N–H signal (single peak
around 9.26 ppm) of the free ligand disappeared.
Complex 2 was prepared by a procedure similar to that of
1. Complex 2 was also characterized by NMR spectroscopy
[b] Key Laboratory of Salt Lake Resources and Chemistry
Qinghai Institute of Salt Lakes
Chinese Academy of Sciences
Xining, 810008, P. R. China
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201500072 or from the au-
thor.
Z. Anorg. Allg. Chem. 2015, 641, (7), 1322–1328
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are summarized in Table 1. The selected bond lengths and
bond angles are given in Table 2.
Table 1. Crystallographic data and structure refinement for complexes
1 and 2.
1
2
Empirical formula
Formula weight
Temperature /K
Wavelength /Å
Crystal system
Space group
a /Å
b /Å
C
26H28N8Ti
C24H26N10Ti
502.42
296(2)
0.71073
monoclinic
C2/c
27.195(3)
9.5168(11)
28.594(3)
90
500.43
296(2)
0.71073
orthorhombic
P212121
10.0801(7)
10.3390(7)
23.9680(17)
90
c /Å
α /°
β /°
90
90
2497.9(3)
4
1.331
94.807(2)
90
7374.4(14)
12
1.358
0.382
Scheme 1. The synthesis of complexes 1 and 2.
γ /°
V /Å3
(1H and 13C) and elemental analysis. The H NMR spectrum
of 2 shows a large and broad singlet for the dimethylamido
protons at δ = 3.50 being assigned to the protons of the methyl
group.
The molecular structures of 1 and 2 in the solid states were
confirmed by single-crystal X-ray analyses. Figure 1 and Fig-
ure 2 show the structures of 1 and 2, respectively. The crystal-
lographic data and experimental details for structural analyses
1
Z
ρ /mg·m–3
μ /mm–1
0.374
1048
F(000)
3144
Crystal size /mm3
Theta range for data collection
Limiting indices
0.60ϫ0.40ϫ0.20 0.60ϫ0.40ϫ0.20
2.15° to 26.99°
–12 Յ h Յ 12,
–13 Յ k Յ 13,
–30 Յ l Յ 20
16160 / 5441
5426 / 1 / 320
1.032
1.99° to 27.45°
–31 Յ h Յ 35,
–11 Յ k Յ 12
–35 Յ l Յ 37
24168 / 8448
8425 / 648 / 480
1.050
Reflections collected / unique
Data / restraints / parameters
GOF
R1, wR2 [I Ͼ 2σ(I)]
R1 = 0.0341,
wR2 = 0.0798
R1 = 0.0437,
wR2 = 0.0851
R1 = 0.0444,
wR2 = 0.1118
R1 = 0.0637,
wR2 = 0.1236
R1,
wR2 (all data)
Largest diff. peak and hole /e·Å–3 0.199 and –0.268 0.439 and –0.435
Table 2. Selected bond lengths /Å and angles /° for 1 and 2.
1
Ti(1)–N(5)
Ti(1)–N(6)
Ti(1)–N(1)
1.8843(19)
1.8888(17)
2.1148(18)
104.83(8)
97.07(7)
96.66(7)
158.92(7)
88.71(7)
Ti(1)–N(3)
Ti(1)–N(4)
Ti(1)–N(2)
N(5)–Ti(1)–N(1)
N(5)–Ti(1)–N(3)
N(1)–Ti(1)–N(3)
N(6)–Ti(1)–N(4)
N(3)–Ti(1)–N(4)
N(6)–Ti(1)–N(2)
N(3)–Ti(1)–N(2)
2.1157(17)
2.2633(17)
2.2661(16)
99.21(7)
94.25(7)
157.61(7)
93.42(7)
72.88(6)
163.87(8)
88.43(6)
N(5)–Ti(1)–N(6)
N(6)–Ti(1)–N(1)
N(6)–Ti(1)–N(3)
N(5)–Ti(1)–N(4)
N(1)–Ti(1)–N(4)
N(5)–Ti(1)–N(2)
N(1)–Ti(1)–N(2)
N(4)–Ti(1)–N(2)
Figure 1. Molecular structure of 1 (N1, N2, N3, N6 are coplanar).
Hydrogen atoms are omitted for clarity.
89.98(7)
73.84(7)
73.40(7)
2
Ti(2)–N(3)
Ti(2)–N(4)
Ti(2)–N(5)
2.1064(18)
2.3016(18)
2.2654(19)
Ti(2)–N(15)
Ti(2)–N(14)
Ti(2)–N(6)
1.8883(18)
1.8916(19)
2.1178(18)
N(15)–Ti(2)–N(14) 104.16(8)
N(15)–Ti(2)–N(3) 97.83(7)
N(15)–Ti(2)–N(6) 100.51(7)
N(14)–Ti(2)–N(3)
N(14)–Ti(2)–N(6)
N(15)–Ti(2)–N(5)
N(3)–Ti(2)–N(5)
N(15)–Ti(2)–N(4)
N(3)–Ti(2)–N(4)
N(5)–Ti(2)–N(4)
98.30(8)
95.27(8)
93.28(8)
87.46(7)
164.64(8)
73.08(7)
74.29(7)
N(3)–Ti(2)–N(6)
N(14)–Ti(2)–N(5) 160.61(7)
N(6)–Ti(2)–N(5) 72.91(7)
N(14)–Ti(2)–N(4) 89.62(7)
N(6)–Ti(2)–N(4) 84.67(7)
153.73(7)
Symmetry transformations used to generate equivalent atoms: #1 –x,
y, –z+1/2.
Figure 2. Molecular structure of 2 (only one of two molecules is
shown). Hydrogen atoms are omitted for clarity.
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Single crystal X-ray diffraction studies revealed that 1 crys- Table 3. Reaction of 4-chloroaniline with 1-hexyne catalyzed by 1 and
2 under different conditions.a)
tallizes in the orthorhombic crystal system with P212121 space
group. The central metal atom shows a distorted octahedral
arrangement. The L1– ligand adopts a bidentate binding motif.
N1, N2, N3, and N6 atoms occupy equatorial positions about
the titanium atom. The angles between the equatorial nitrogen
atoms add up to 359.98°. Angles of N1–N6–N3, N1–N2–N3,
Entry Catalyst Temperature /°C Time Yieldb) Selectivity
N6–N1–N2, and N2–N3–N6 are 87.538(65)°, 93.322(72)°,
93.483(70)°, 85.638(63)°, respectively (Figure 1). N4 and N5
atoms occupy axial positions, and the N4–Ti–N5 angle is dis-
torted away from the idealized position of 180° to 158.92(7)°.
The two Ti–N(NMe2) bond lengths are nearly identical
[1.8843(19) and 1.8888(17) Å], and remarkably shorter than
the average Ti–N(indolyl) (2.1153 Å) and Ti–N(pyrazolyl)
(2.2647 Å) bond lengths.
For complex 2, there are two independent molecules in the
cell (Figure S2, Supporting Information). Only one of two is
shown (Figure 2.). The central titanium atom adopts a distorted
octahedral arrangement. The titanium atom is surrounded by
four nitrogen atoms from two chelating ligands, and two nitro-
gen atoms from two dimethyamidos with one triazole nitrogen
atom (N5) and one dimethylamido (N14) nitrogen atom occu-
/h
/%
(M:anti-M)c)
1
2
3
4
5
6
7
8
1
2
1
2
1
2
1
2
1
2
1
2
80
12
59
35
70
42
90
45
86
72
80
61
44
60
86:14
87:13
75:25
92:8
89:11
96:4
86:14
99:1
74:26
97:3
80
24
12
24
12
24
100
100
120
120
9
10
11
12
94:6
94:6
a) Reaction conditions: 1-hexyne (1 mmol), 4-chloroaniline
(1.5 mmol), catalyst (10 mol-%), toluene (4 mL). b) Isolated yield after
reduced by LiAlH4 and purified by column chromatography. c) Ratio
of the Markovnikov and anti-Markovnikov products determined by
pying the axial positions and the other four nitrogen atoms GC-MS.
(N3, N4, N6, N15) occupying equatorial positions. Angles be-
tween equatorial nitrogen atoms (N6–N15–N3: 84.838(67)°;
N15–N3–N4: 94.507(73)°; N3–N4–N6: 94.150(78)°; N4–N6–
N15: 86.435(66)°.) add up to 359.93°. The bond lengths be-
tween the titanium atom and donor nitrogen atoms [Ti(2)–N(5)
= 2.2654(19) Å, Ti(2)–N(4) = 2.3016(18) Å] are apparently
for the hydroamination catalysed by both 1 and 2. Complex 1
gave better yields than 2. However, 2 can catalyse the hydro-
amination with formation of almost exclusively Markovnikov
imines.
Table 4. Intermolecular hydroamination of various alkynes with 4-
chloroaniline catalyzed by 1 and 2.a)
longer than Ti–N (indole) distances [Ti(2)–N(3)
2.1064(18) Å, Ti(2)–N(6) = 2.1178(18) Å].
=
Hydroamination of Alkynes Catalyzed by 1 and 2
The successful determination of the crystal structures of the
complexes prompted us to explore the catalytic activities of
1 and 2. Subsequently, the intermolecular hydroamination of
alkynes catalysed by 1 and 2, respectively, were investigated.
Firstly, the reaction conditions were optimized. The reaction
was performed between 1-hexyne and 4-chloroaniline in tolu-
ene by using 1 or 2 as the catalyst. The reactions were carried
out at different temperature with a ratio of 2:3 of alkyne and
amine. The hydroamination products were directly reduced to
the secondary amines by LiAlH4 in toluene. The final products
were isolated by flash chromatography.
Entry
Catalyst
1
R1
Isolated yieldb)
/%
Selectivity
(M:anti-M)c)
1
2
3
Ph
nBu
nHex
26
90
86
20:80
86:14
62:38
4
5
6
2
Ph
nBu
nHex
18
72
55
83:17
97:3
81:19
As shown in Table 3, when 1 was used as catalyst, 10 mol%
catalyst loading at 100 °C in toluene gave a good yield within
12 h. However, complex 2 was found to be less active:
10 mol% at 100 °C in toluene gave lower yield within 12 h,
and a moderate yield could be achieved by prolonging the re-
action time to 24 h.
a) Reaction conditions: 1-hexyne (1 mmol), 4-chloroaniline
(1.5 mmol), catalyst (10 mol-%), toluene (4 mL), 12 h, 100 °C for 1;
24 h, 100 °C for 2. b) Isolated yield after reduced by LiAlH4 and
purified by column chromatograph. c) Ratio of the Markovnikov and
anti-Markovnikov products determined by GC-MS.
With the optimized reaction conditions in hand, we further
Under the optimized reaction conditions, we investigated the investigated the scope of the reaction by screening a large se-
reactions of 4-chloroaniline with several alkynes. As seen in lection of amines. The results are listed in Table 5 and Table 6.
Table 4, the reaction of 4-chloroaniline with phenylacetylene In all cases, the Markovnikov products were favored.
gave the corresponding anti-Markovnikov imine in low yield
As can be seen from Table 5 and Table 6, the halo-substitu-
(entry 1, Table 4). Both the yield and selectivity of the reaction tions on phenyl ring provided the corresponding imines in
of 1-octyne with 4-chloroaniline were inferior to that of 1- moderate yields. The position of the substituent seemed to in-
hexyne with 4-chloroaniline. So 1-hexyne was a good substrate fluence the results greatly, as the ortho-substituted anilines
Z. Anorg. Allg. Chem. 2015, 1322–1328
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Table 5. Intermolecular hydroamination of 1-hexyne with various anil-
ines catalyzed by 1.a)
Table 6. Intermolecular hydroamination of 1-hexyne with various anil-
ines catalyzed by 2.a)
Selectivity
Selectivity
Entry
Amine
Isolated yieldb) /%
Entry
Amine
Isolated yieldb) /%
(M:anti-M)c)
(M:anti-M)c)
1
92
98:2
1
81
99:1
99:1
2
31
86:14
2
70
3
4
88
90
99:1
3
4
5
6
57
72
31
78
100:0
97:3
86:14
5
6
48
80
95:5
96:4
100:0
97:3
7
72
93:7
7
32
99:1
8
9
70
93
94:6
92:8
8
9
71
92
92:8
86:14
10
12
65:35
10
46
70:30
11
12
97
60
92:8
96:4
11
12
95
80
100:0
100:0
a) Reaction conditions: 1-hexyne (1 mmol), anilines (1.5 mmol), cata-
lyst (10 mol-%), toluene (4 mL), 12 h, 100 °C for 1. b) Isolated yield
after reduced by LiAlH4 and purified by column chromatography. c)
Ratio of the Markovnikov and anti-Markovnikov products determined
by GC-MS.
a) Reaction conditions: 1-hexyne (1 mmol), anilines (1.5 mmol), cata-
lyst (10 mol-%), toluene (4 mL), 24 h, 100 °C for 2. b) Isolated yield
after reduced by LiAlH4 and purified by column chromatography. c)
Ratio of the Markovnikov and anti-Markovnikov products determined
by GC-MS.
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Table 7. Polymerization of ε-caprolactone initiated by 1 and 2 (conditions: [ε-CL]: [initiator] = 200:1).
b)
c)
d)
Entry Initiators Solvent
Time /h T /°C
Mn (calc)(104)
Mn (104)
Mn (104)
PDI
Efficiency /% Yielda) /%
1
2
3
4
5
6
7
8
1
1
1
1
1
1
2
2
2
2
2
2
THF
THF
Tol
3
1
3
1
3
2
3
2
60
80
60
80
60
80
60
80
60
80
60
80
2.07
1.89
2.01
1.98
1.23
1.50
1.05
1.19
1.44
1.73
1.09
2.07
3.79
2.77
2.44
2.00
2.35
2.34
2.95
2.92
3.29
2.88
3.07
2.70
2.12
1.55
1.37
1.12
1.32
1.31
1.65
1.64
1.84
1.61
1.72
1.51
1.37
1.46
1.28
1.24
1.27
1.38
1.35
1.39
1.35
1.48
1.33
1.37
55
68
82
99
52
64
36
41
44
60
36
77
91
83
88
87
54
66
46
52
63
76
48
91
Tol
DME
DME
THF
THF
Tol
Tol
DME
DME
9
3
1.5
3
10
11
12
1.5
b
a) Yield: weight of polymer obtained/weight of monomer used. [M/I] = 200. Efficiency: the calculated average molecular weight [Mn (calc)]/
c
the experimentally measured value (Mn ). b) Mn(calc) = M monoϫ[M]/[I]ϫconv. c) Measured by GPC relative to polystyrene standards. d)
Measured by GPC relative to polystyrene standards with Mark-Houwink corrections[13] for Mn (obsd) = 0.56 Mn (GPC) for ε-caprolactone.
gave the corresponding amines with relatively lower yields for the ROP of ε-CL, forming poly(ε-CL) with a relatively
(entries 2, 7, and 10 in Table 5 and Table 6). Lower yield of narrow PDI and high molar mass (Mn Ͼ 20000).
imine for the hydroamination of 1-hexyne with 2,4-dichloroan-
As can be seen from Table 7, complex 1 exhibits good ac-
iline is attributable to the bulky hindrance of aniline. Notably, tivity toward the ROP of ε-CL. Two polymerization experi-
exclusive regioselectivity for the Markovnikov products were ments carried out at 60 and 80 °C in toluene demonstrated that
achieved in the presence of 2 when 2,4-dichloroaniline and 3- the conversion increased significantly with the increase of re-
chloroaniline were reacted with 1-hexyne (entries 3 and 5 in action temperature (entries 3 and 4). At 60 °C, full conversion
Table 6).
was obtained in 180 min, and the initiation efficiency was
When 4-methoxyaniline was used as aniline source (entry 9 82%. When the same experiment was performed at 80 °C, the
in Table 5 and Table 6), good yield was obtained. However, as polymerization finished in 60 min with a higher efficiency
2-methoxyaniline was used as substrate, both 1 and 2 are not (99%). Moreover, the solvent also affected the polymerization
effective catalysts under the conditions employed, and low results. Toluene was found to be the better solvent. It is be-
yields and poor regioselectivity are obtained (entry 10 in cause the coordination of ethereal solvents DME and THF
Table 5 and Table 6). It is possible that the ortho-methoxy molecules to the central metal atom may hinder the attack of
group of 2-methoxyaniline coordinates to the central titanium ε-caprolactone to the same metal atom.
atom, leading to the low yield.
Complex 2 showed lower activity compared with 1. When
When naphthalene-1-amine was employed as the amine the polymerization was carried out in DME at 80 °C, full con-
source, complexes 1 and 2 showed higher activity with higher versions could be achieved within 1.5 h with an efficiency of
yields (entry 11 in Table 5 and Table 6). Complex 2 was found 77%. Poor yields were afforded at 60 °C. Increasing of the
to be more selective with respect to the Markovnikov products. polymerization temperature led to higher efficiency and
broader molecular weight distribution. The reactions per-
formed in THF gave lower efficiencies (entries 7 and 8).
Ring-Opening Polymerization of ε-Caprolactone Initiated by
The catalytic activities of 1 and 2 are much higher than
1 and 2
those of sulfonamide-supported titanium complexes.[12a]
Ring-opening polymerization (ROP) of ε-caprolactone initi-
ated by transition metal catalysts is a very effective method
Conclusions
for producing PCL, which is an important biodegradable and
Two new complexes were synthesized and characterized.
biocompatible polymer. Such polymer is an important building
The catalytic activities toward intermolecular hydroamination
block for the production of segmented copolymers and poly-
reactions of alkynes were studied. Both 1 and 2 can catalyze
mer networks.[10] Among the various catalytic processes, tita-
the hydroamination reactions with selective Markovnikov
nium and zirconium compounds were proved to be effective
products. Ring-opening polymerization of ε-caprolactone in
initiators for the polymerization of lactones. However, only
different solvents and at different temperatures initiated by 1
very few group 4 metal complexes was reported to initiate the
and 2 were also carried out. The results show that both of them
polymerization of lactones,[11] and the examples for employing
can initiate the polymerization to give polyesters with high
titanium amides[12] as the initiators for the polymerization of
molecular weights and low poly-disperisities.
ε-caprolactone are very rare. Therefore, we studied the ring-
opening polymerization of ε-caprolactone initiated by 1 and 2.
To our delight, it is found that both 1 and 2 can initiate the
Experimental Section
polymerization of ε-caprolactone effectively. The preliminary
results are summarized in Table 7. Both 1 and 2 were active pounds were carried out with a Mikrouna glovebox in a purified nitro-
General Considerations: All manipulations of air-sensitive com-
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gen atmosphere. Ti(NMe2)4 was purchased from Acros and used with- and ε-caprolactone (1.14 g, 10 mmol, [M] / [I]) = 200) was added to
out further purification. Amines were distilled from CaH2. Tetra- a 35 mL pressure tube. A stirring bar was added to the pressure tube.
hydrofuran, toluene, and hexane were heated to reflux over sodium The tube was taken out from the glovebox. The reaction mixture was
benzophenoneketyl for at least 4 d. CDCl3 was distilled from P2O5 in heated at the chosen temperature and terminated by addition of a mix-
a nitrogen atmosphere. Elemental analyses (C, H, N) were performed
ture of conc. HCl / EtOH (1:5; v/v) (2 mL). The resulting polymers
were precipitated from methanol (150 mL), filtered, and dried in a
vacuum. The solids were dissolved in THF (10 mL), column
1
with a Carlo-Erba EA 1110 CHNO-S microanalyser. H and 13C spec-
tra were recorded with an Innova-400 spectrometers at ambient tem-
perature using TMS as an internal standard, and chemical shifts were chromatography on Al2O3 to give a white solid.
reported in ppm. GC/MS spectra were recorded with a GCMS-
Crystallographic data (excluding structure factors) for the structures in
QP2010.
this paper have been deposited with the Cambridge Crystallographic
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK.
Copies of the data can be obtained free of charge on quoting
the depository numbers CCDC-990887 (1) and CCDC-990888 (2)
(Fax: +44-1223-336-033; E-Mail: deposit@ccdc.cam.ac.uk, http://
www.ccdc.cam.ac.uk).
X-ray Crystallography: Crystals grown from concentrated solutions
at room temperature were quickly selected and mounted on a glass
fiber in wax. The data collections were carried out on a Mercury CCD
detector equipped with graphite-monochromated Mo-Kα radiation by
using the φ/ω scan technique at room temperature. The structures were
solved by direct methods with SHELXS-97.[14] The hydrogen atoms
were assigned with common isotropic displacement factors and in-
cluded in the final refinement by use of geometrical restraints. A full-
matrix least-squares refinement on F2 was carried out using SHELXL-
97.
Supporting Information (see footnote on the first page of this article):
1H and 13C NMR spectra of complexes 1 and 2 and the hydroamination
products.
Acknowledgements
Synthesis of Ti(L1)2(NMe2)2 (1): To a solution of Ti(NMe2)4
(0.224 g, 1 mmol) in THF (2 mL) was added a solution of HL1
(0.3364 g, 2 mmol) in THF (4 mL) at –35 °C. After being stirred at
room temperature overnight, the solution was evaporated to dryness to
give a red solid. Crystals of 1 were obtained from Tol/hexane. Yield:
0.380 g (76%). 1H NMR (400 MHz, CDCl3, 25 °C): δ = 7.74–7.71
(m, 2 H, indole and ph), 7.64 (d, 1 H, ph), 7.21 (t, 1 H, ph), 7.13 (t,
1 H, ph), 6.69 (s, 1 H, py), 6.34 (s, 1 H, py), 6.08 (s, 1 H, py), 3.46
(s, 6 H, NMe2). 13C NMR (100 MHz, CDCl3, 25 °C): δ = 142.59,
141.93, 137.50, 130.90, 125.03, 120.26, 119.53, 119.19, 116.55,
107.80, 83.32, 77.48, 77.16, 76.84, 47.95(N-CH3). C26H28N8Ti
(500.43): calcd. C 62.40, H 5.64, N 22.39%; found, C 62.23, H 5.67,
N 21.92%.
The authors appreciate the financial support of Natural Science Foun-
dation of China (21272167 and 21201127), A Project Funded by the
Priority Academic Program Development of Jiangsu Higher Education
Institutions and KLSLRC (KLSLRC-KF-13-HX-1).
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Received: February 8, 2015
Published Online: May 6, 2015
Z. Anorg. Allg. Chem. 2015, 1322–1328
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